A slice of PAI.

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D J Loskutoff

Beta-adrenergic receptors in heart failure.

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P A Insel, H K Hammond

Heavy traffic at a dual-purpose human mitochondrial tRNA gene.

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D A Clayton

In vivo gene transfer, Koch's postulates, and renal disease.

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R J Johnson, D Lovett

A major advance in the use of growth factors to enhance wound healing.

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M B Sporn, A B Roberts

Anti-transforming growth factor (TGF)-beta antibodies inhibit breast cancer cell tumorigenicity and increase mouse spleen natural killer cell activity. Implications for a possible role of tumor cell/host TGF-beta interactions in human breast cancer progression.

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TGF-beta effects on angiogenesis, stroma formation, and immune function suggest its possible involvement in tumor progression. This hypothesis was tested using the 2G7 IgG2b, which neutralizes TGF-beta 1, -beta 2, and -beta 3, and the MDA-231 human breast cancer cell line. Inoculation of these cells in athymic mice decreases mouse spleen natural killer (NK) cell activity. Intraperitoneal injections of 2G7 starting 1 d after intraperitoneal inoculation of tumor cells suppressed intraabdominal tumor and lung metastases, whereas the nonneutralizing anti-TGF-beta 12H5 IgG2a had no effect. 2G7 transiently inhibited growth of established MDA-231 subcutaneous tumors. Histologically, both 2G7-treated and control tumors were identical. Intraperitoneal administration of 2G7 resulted in a marked increase in mouse spleen NK cell activity. 2G7 did not inhibit MDA-231 primary tumor or metastases formation, nor did it stimulate NK cell-mediated cytotoxicity in beige NK-deficient nude mice. Finally, serum-free conditioned medium from MDA-231 cells inhibited the NK cell activity of human blood lymphocytes. This inhibition was blocked by the neutralizing anti-TGF-beta 2G7 antibody but not by a nonspecific IgG2. These data support a possible role for tumor cell TGF-beta in the progression of mammary carcinomas by suppressing host immune surveillance.

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C L Arteaga, S D Hurd, A R Winnier, M D Johnson, B M Fendly, J T Forbes

The effects of 2-year treatment with the aminobisphosphonate alendronate on bone metabolism, bone histomorphometry, and bone strength in ovariectomized nonhuman primates.

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This study examined the effect of 2 yr of treatment with the aminobisphosphonate alendronate (ALN) (0.05 or 0.25 mg/kg i.v. ALN every 2 wk) on estrogen deficiency bone loss and bone strength changes in ovariectomized (OVX) baboons (n = 7 per group) and the ALN mode of action at the tissue level. Biochemical markers of bone turnover increased in OVX animals and were maintained by ALN treatment at non-OVX levels (low dose) or below (high dose). 2 yr of treatment produced no cumulative effects on bone turnover markers. Histomorphometry showed a marked increase in cancellous bone remodeling in OVX animals. Activation frequency increased from 0.48 to 0.86 per yr (L5 vertebra), and the osteoid surfaces from 9 to 13.5% (P < 0.05). No changes were observed in eroded and osteoclast surfaces. ALN treatment decreased activation frequency and indices of bone formation to control levels (low dose) or below (high dose), did not change indices of mineralization, and increased bone mineral density (BMD) in the lumbar vertebrae (L2-L4) by 15% at 0.25 mg/kg (P < 0.05), relative to vehicle-treated animals. The mean strength of cancellous bone (L4) increased by 44% (low ALN dose) and 100% (high dose), compared with vehicle. The strength of individual bones correlated with the square of the L2-L4 BMD (r = 0.91, P < 0.0034). In conclusion, ALN treatment reversed the effects of ovariectomy on cancellous bone turnover and increased bone mass and bone strength in baboons.

Authors

R Balena, B C Toolan, M Shea, A Markatos, E R Myers, S C Lee, E E Opas, J G Seedor, H Klein, D Frankenfield

Human and murine dermis contain dendritic cells. Isolation by means of a novel method and phenotypical and functional characterization.

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Dendritic cells (DC) comprise a system of cells in lymphoid and nonlymphoid organs that are specialized to present antigens and to initiate primary T cell responses. The Langerhans cell of the epidermis is used as a prototype for studies of DC in the skin. We have characterized a population of DC in human dermis, one of the first examples of these cells in nonlymphoid organs other than epidermis. To identify their distinct functions and phenotype, we relied upon the preparation of enriched populations that emigrate from organ explants of dermis. The dermal cells have the following key features of mature DC: (a) sheet-like processes, or veils, that are constantly moving; (b) very high levels of surface MHC products; (c) absence of markers for macrophages, lymphocytes, and endothelium; (d) substantial expression of adhesion/costimulatory molecules such as CD11/CD18, CD54 (ICAM-1), B7/BB1, CD40; and (e) powerful stimulatory function for resting T cells. Dermal DC are fully comparable to epidermis-derived DC, except for the lack of Birbeck granules, lower levels of CD1a, and higher levels of CD36. DC were also detected in explants of mouse dermis. We conclude that cutaneous DC include both epidermal and dermal components, and suggest that other human nonlymphoid tissues may also serve as sources of typical immunostimulatory DC.

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A Lenz, M Heine, G Schuler, N Romani

Glomerulosclerosis induced by in vivo transfection of transforming growth factor-beta or platelet-derived growth factor gene into the rat kidney.

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Glomerulosclerosis, a final common lesion of various glomerular diseases, is characterized by mesangial cell proliferation and extracellular matrix (ECM) expansion. TGF-beta and PDGF are known to play a critical role in the regulation of ECM metabolism and mesenchymal cell proliferation, respectively. However, there is little evidence to demonstrate the direct role of each of these growth factors in the pathogenesis of glomerulosclerosis. Using an in vivo transfection technique, we could realize the selective overexpression of single growth factor in the kidney. The introduction of either TGF-beta or PDGF-B gene alone into the kidney induced glomerulosclerosis, although the patterns of action of these growth factors were different; TGF-beta affected ECM accumulation rather than cell proliferation and PDGF affected the latter rather than the former.

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Y Isaka, Y Fujiwara, N Ueda, Y Kaneda, T Kamada, E Imai

Reactivity to myelin antigens in multiple sclerosis. Peripheral blood lymphocytes respond predominantly to myelin oligodendrocyte glycoprotein.

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Although T cell responses to the quantitatively major myelin proteins, myelin basic protein (MBP) and proteolipid protein (PLP), are likely to be of importance in the course of multiple sclerosis (MS), cell-mediated autoimmune responses to other myelin antigens, in particular quantitatively minor myelin antigens, such as myelin-associated glycoprotein (MAG) and the central nervous system-specific myelin oligodendrocyte glycoprotein (MOG), could also play a prevalent role in disease initiation or progression. Highly purified myelin antigens were used in this study to assess cell-mediated immune response to MOG in MS patients, in the context of the reactivity to other myelin antigens, MBP, PLP, and MAG. The greatest incidence of proliferative response by MS peripheral blood lymphocytes was to MOG, as 12 of 24 patients tested reacted and, of these, 8 reacted to MOG exclusively. In contrast, only 1 control individual of 16 tested reacted positively to MOG. The incidence of responses to MBP, PLP, and MAG did not differ greatly between MS patients and control individuals. A predominant T cell reactivity to MOG in MS suggests an important role for cell-mediated immune response to this antigen in the pathogenesis of MS.

Authors

N Kerlero de Rosbo, R Milo, M B Lees, D Burger, C C Bernard, A Ben-Nun

Release of ceramide after membrane sphingomyelin hydrolysis decreases the basolateral secretion of triacylglycerol and apolipoprotein B in cultured human intestinal cells.

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The effect of sphingomyelin hydrolysis on triacylglycerol-rich lipoprotein secretion was examined in the human intestinal cell line, CaCo-2. Addition of sphingomyelinase decreased sphingomyelin and phosphatidylethanolamine by 60 and 20%, respectively. Sphingomyelin hydrolysis decreased the basolateral secretion of triacylglycerol mass, newly synthesized triacylglycerol, and apo B mass. Pulse-chase experiments with [35S]methionine demonstrated a decrease in apo B synthesis and a marked decrease in apo B100 and apo B48 secretion without altering apo A1 secretion. Sphingomyelin hydrolysis did not change apo B mRNA levels nor apo B turnover. Phosphatidylcholine-specific phospholipase C did not decrease apo B synthesis or its basolateral secretion. Membrane protein kinase C (PKC) activity was decreased twofold after sphingomyelin hydrolysis. The PKC inhibitor staurosporine decreased apo B mass and newly synthesized apo B secretion. Sphingomyelinase and staurosporine together caused an additional decrease in apo B secretion suggesting that sphingomyelin hydrolysis decreased apo B secretion independently of its effect on PKC activity. Moreover, conditions that increase PKC activity did not increase apo B secretion. Cell-permeable analogs of ceramide decreased immunoreactive apo B secretion. Sphingosine was without effect. The hydrolysis of membrane sphingomyelin by intestinal or pancreatic neutral sphingomyelinase may lead to the accumulation of cellular ceramide, which, in turn, could inhibit triacylglycerol-rich lipoprotein secretion.

Authors

F J Field, H Chen, E Born, B Dixon, S Mathur

Vitreous levels of the insulin-like growth factors I and II, and the insulin-like growth factor binding proteins 2 and 3, increase in neovascular eye disease. Studies in nondiabetic and diabetic subjects.

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Retinal capillary nonperfusion results in neovascularization of the eye, which is restricted to the retina in less severe cases and progresses to the anterior chamber and the iris angle in the most advanced case, called rubeosis. This angioneogenesis may be induced by the release of retinal growth factors into the vitreous. This study compared levels of the IGF-I and IGF-II, and of the IGF binding protein-2 (IGFBP-2) and IGFBP-3 in vitreous from three groups with different degrees of retinal ischemia, as judged by the extent of neovascularization: a control group without new vessel formation, retinal neovascularization in patients with proliferative diabetic retinopathy, and massive ischemia of various causes resulting in rubeosis. IGF-I and IGFBP-3 were increased 10- and 13-fold in rubeosis (P << 0.01) compared with no ischemia (n = 10), while IGF-II and IGFBP-2 were elevated 2.7- and 4.3-fold (P < 0.01). Within the rubeosis group similar changes were observed independently of the cause of ischemia, which was central vein occlusion, ischemic ophthalmopathy, or intraocular tumor in seven cases and diabetic retinopathy in three samples from two patients. Vitreous from patients with proliferative diabetic retinopathy but without rubeosis (n = 16) contained 2.5- and 2.2-fold elevated levels of IGF-I and of IGFBP-2 (P < 0.05), while IGF-II and IGFBP-3 were increased 1.4- and 1.6-fold, which was not significant. We conclude that: (a) ischemia appears to be a strong stimulus for the local production of IGF-I and -II and of IGFBP-2 and -3 in the eye. (b) Changes in IGF-I and IGFBP-2 in proliferative diabetic retinopathy may be secondary to local ischemia rather than being specific for diabetic retinopathy. (c) IGF-I and IGFBP-3 may play a role in mediating angioneogenesis in the eye.

Authors

R Meyer-Schwickerath, A Pfeiffer, W F Blum, H Freyberger, M Klein, C Lösche, R Röllmann, H Schatz

Potential role for interleukin-10 in the immunosuppression associated with kala azar.

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Patients with acute kala azar are generally nonreactive in a number of immunologic assays, including T cell proliferation and generation of macrophage-activating cytokines, principally IFN-gamma, in response to leishmania antigens in vitro. To test for potential immunosuppressive factors, a series of T cell lines and clones were established from patients with acute kala azar, from patients after chemotherapy for kala azar, and from skin test-positive adults from the same endemic region. Although CD4+ T cell lines and clones could be readily established from the skin test-positive adults, lines and clones from acute or treated patients were heavily biased in expression of CD8+. The CD8+ cells from acute patients did not themselves release cytokines in response to leishmania antigens in vitro, but markedly affected the cytokine profile of peripheral blood mononuclear cells isolated 1 yr later after recovery. Addition of the CD8+ cells caused inhibition of lymphoproliferation and IFN-gamma release, with augmentation of IL-6 and IL-10 release. The inhibitory effects of the CD8+ cells could be partially abrogated by antibodies to IL-10 but not by antibodies to IL-4. Analysis of four patients with acute kala azar demonstrated release of IL-10 that could not be demonstrated in supernatants from asymptomatic skin test-positive individuals. Generation of IL-10 may contribute to the profound suppression of IFN-gamma release that occurs during kala azar due to Leishmania chagasi.

Authors

B J Holaday, M M Pompeu, S Jeronimo, M J Texeira, A de A Sousa, A W Vasconcelos, R D Pearson, J S Abrams, R M Locksley

Myelin basic protein-specific T lymphocyte repertoire in multiple sclerosis. Complexity of the response and dominance of nested epitopes due to recruitment of multiple T cell clones.

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The human T cell response to the myelin basic protein (MBP) has been studied with respect to T cell receptor (TCR) usage, HLA class II restriction elements, and epitope specificity using a total of 215 long-term MBP-specific T cell lines (TCL) isolated from the peripheral blood of 13 patients with multiple sclerosis (MS) and 10 healthy donors. In most donors, the anti-MBP response was exceedingly heterogeneous. Using a panel of overlapping synthetic peptides spanning the entire length of human MBP, at least 26 epitopes recognized by human TCL could be distinguished. The MBP domain most commonly recognized was sequence 80-105 (31% of MS TCL, and 24% of control TCL). Sequence 29-48 was recognized more frequently by control-derived TCL (24%) than by TCL from MS patients (5%). The MBP epitopes were recognized in the context of DRB1 *0101, DRB5*0101, DRB1*1501, DRB1*0301, DRB1*0401, DRB1*1402, and DRB3*0102, as demonstrated using a panel of DR gene-transfected L cells. The TCR gene usage was also heterogeneous. V beta 5.2, a peptide of which is currently being used in a clinical trial for treatment of MS patients, was expressed by only one of our TCL. However, within this complex pattern of MBP-specific T cell responses, a minority of MS patients were found to exhibit a more restricted response with respect to their TCL epitope specificity. In these patients 75-87% of the TCL responded to a single, patient-specific cluster of immunodominant T cell epitopes located within a small (20-amino acid) domain of MBP. These nested clusters of immunodominant epitopes were noted within the amino acids 80-105, 108-131, and 131-153. The T cell response to the immunodominant epitopes was not monoclonal, but heterogeneous, with respect to fine specificity, TCR usage, and even HLA restriction. In one patient (H.K.), this restricted epitope profile remained stable for > 2 yr. The TCR beta chain sequences of TCL specific for the immunodominant region of HK are consistent with an oligoclonal response against the epitopes of this region (80-105). Further, two pairs of identical sequences were established from TCL generated from this patient at different times (June 1990 and June 1991), suggesting that some TCL specific for the immunodominant region persisted in the peripheral repertoire. The possible role of persistent immunodominant epitope clusters in the pathogenesis of MS remains to be established.

Authors

E Meinl, F Weber, K Drexler, C Morelle, M Ott, G Saruhan-Direskeneli, N Goebels, B Ertl, G Jechart, G Giegerich

Regional myocardial downregulation of the inhibitory guanosine triphosphate-binding protein (Gi alpha 2) and beta-adrenergic receptors in a porcine model of chronic episodic myocardial ischemia.

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Regional myocardial ischemia is associated with increased levels of adenosine and norepinephrine, factors that may alter activation of the beta-adrenergic receptor (beta AR)-G protein-adenylyl cyclase pathway in the heart. We have used the ameroid constrictor model to determine whether alterations in myocardial signal transduction through the beta AR-G protein-adenylyl cyclase pathway occur in the setting of chronic episodes of reversible ischemia. Pigs were instrumented with ameroid occluders placed around the left circumflex coronary artery. 5 wk later, after ameroid closure, flow and function were normal in the ischemic bed, but flow (P = 0.001) and function (P < 0.03) were abnormal when metabolic demands were increased. The ischemic bed showed a reduction in myocardial beta AR number (P < 0.005). Despite regional downregulation of myocardial beta AR number, adenylyl cyclase activity was similar in the ischemic and control beds. Quantitative immunoblotting showed that the cardiac inhibitory GTP-binding protein, Gi alpha 2, was decreased in the ischemic bed (P = 0.02). In contrast, the cardiac stimulatory GTP-binding protein, Gs alpha, was increased in endocardial sections from the ischemic bed (P = < 0.05). Decreased Gi alpha 2 content was associated with decreased inhibition of adenylyl cyclase. Reduced Gi alpha 2 content, in conjunction with increased Gs alpha content in the endocardium, may provide a means by which adrenergic activation is maintained in the setting of chronic episodic myocardial ischemia.

Authors

H K Hammond, D A Roth, M D McKirnan, P Ping

Potent aquaretic agent. A novel nonpeptide selective vasopressin 2 antagonist (OPC-31260) in men.

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Solute-free water diuretics (aquaretics) by antagonizing hydrosmotic vasopressin receptors (V2) may be useful in treating water-retaining diseases. The effects of intravenous administration of a newly developed nonpeptide, selective V2 antagonist, OPC-31260, at doses ranging from 0.017 to 1.0 mg/kg to groups of healthy, normally hydrated men were compared with those of 0.33 mg/kg furosemide and placebo. OPC-31260 increased the hypotonic urine volume dose dependently for the first 4 h, while furosemide induced sodium diuresis for 2 h. The absolute increase in the cumulative response in the urine to the highest doses of OPC-31260 was not significantly different from that to furosemide. The higher doses of OPC-31260 rapidly lowered urine osmolality for 2 h, particularly between minutes 15 and 45 (e.g., 1.0-mg/kg dose: 63 +/- 2 mOsm/kg in urine collected between minutes 30 and 45). In a marked hypotonic diuresis, mean free water clearance of the 4-h urine increased dose proportionally into the positive range, reaching 1.80 +/- 0.21 ml/min at 1.0 mg/kg. Whereas furosemide induced marked Na and K diuresis, OPC-31260 increased urinary Na excretion only slightly. At 4 h, 0.75 and 1.0 mg/kg of OPC-31260 almost doubled the plasma arginine vasopressin; and the higher doses increased plasma osmolality and plasma Na slightly, but did not alter plasma K, blood pressure, or heart rate. OPC-31260 thus safely induced a potent aquaretic effect in men.

Authors

A Ohnishi, Y Orita, R Okahara, H Fujihara, T Inoue, Y Yamamura, Y Yabuuchi, T Tanaka

Mitochondrial myopathy with succinate dehydrogenase and aconitase deficiency. Abnormalities of several iron-sulfur proteins.

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Recently, we described a patient with severe exercise intolerance and episodic myoglobinuria, associated with marked impairment of succinate oxidation and deficient activity of succinate dehydrogenase and aconitase in muscle mitochondria (1). We now report additional enzymatic and immunological characterization of mitochondria. In addition to severe deficiency of complex II, manifested by reduction of succinate dehydrogenase and succinate:coenzyme Q oxidoreductase activities to 12 and 22% of normal, respectively, complex III activity was reduced to 37% and rhodanese to 48% of normal. Furthermore, although complex I activity was not measured, immunoblot analysis of complex I showed deficiency of the 39-, 24-, 13-, and 9-kD peptides with lesser reductions of the 51- and 18-kD peptides. Immunoblots of complex III showed markedly reduced levels of the mature Rieske protein in mitochondria and elevated levels of its precursor in the cytosol, suggesting deficient uptake into mitochondria. Immunoreactive aconitase was also low. These data, together with the previous documentation of low amounts of the 30-kD iron-sulfur protein and the 13.5-kD subunit of complex II, compared to near normal levels of the 70-kD protein suggest a more generalized abnormality of the synthesis, import, processing, or assembly of a group of proteins containing iron-sulfur clusters.

Authors

R E Hall, K G Henriksson, S F Lewis, R G Haller, N G Kennaway

Impaired hormonal responses to hypoglycemia in spontaneously diabetic and recurrently hypoglycemic rats. Reversibility and stimulus specificity of the deficits.

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To evaluate the roles of iatrogenic hypoglycemia and diabetes per se in the pathogenesis of defective hormonal counterregulation against hypoglycemia in insulin-dependent diabetes mellitus (IDDM), nondiabetic, and spontaneously diabetic BB/Wor rats were studied using a euglycemic/hypoglycemic clamp. In nondiabetic rats, recurrent (4 wk) insulin-induced hypoglycemia (mean daily glucose, MDG, 59 mg/dl) dramatically reduced glucagon and epinephrine responses by 84 and 94%, respectively, to a standardized glucose fall from 110 to 50 mg/dl. These deficits persisted for > 4 d after restoring normoglycemia, and were specific for hypoglycemia, with normal glucagon and epinephrine responses to arginine and hypovolemia, respectively. After 4 wk of normoglycemia, hormonal counterregulation increased, with the epinephrine, but not the glucagon response reaching control values. In diabetic BB rats (MDG 245 mg/dl with intermittent hypoglycemia), glucagon and epinephrine counterregulation were reduced by 86 and 90%, respectively. Chronic iatrogenic hypoglycemia (MDG 52 mg/dl) further suppressed counterregulation. Prospective elimination of hypoglycemia (MDG 432 mg/dl) improved, but did not normalize hormonal counterregulation. In diabetic rats, the glucagon defect appeared to be specific for hypoglycemia, whereas deficient epinephrine secretion also occurred during hypovolemia. We concluded that both recurrent hypoglycemia and the diabetic state independently lead to defective hormonal counterregulation. These data suggest that in IDDM iatrogenic hypoglycemia magnifies preexisting counterregulatory defects, thereby increasing the risk of severe hypoglycemia.

Authors

A M Powell, R S Sherwin, G I Shulman

The antiinflammatory mechanism of methotrexate. Increased adenosine release at inflamed sites diminishes leukocyte accumulation in an in vivo model of inflammation.

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Methotrexate, a folate antagonist, is a potent antiinflammatory agent when used weekly in low concentrations. We examined the hypothesis that the antiphlogistic effects of methotrexate result from its capacity to promote intracellular accumulation of 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) that, under conditions of cell injury, increases local adenosine release. We now present the first evidence to establish this mechanism of action in an in vivo model of inflammation, the murine air pouch model. Mice were injected intraperitoneally with either methotrexate or saline for 3-4 wk during induction of air pouches. Pharmacologically relevant doses of methotrexate increased splenocyte AICAR content, raised adenosine concentrations in exudates from carrageenan-inflamed air pouches, and markedly inhibited leukocyte accumulation in inflamed air pouches. The methotrexate-mediated reduction in leukocyte accumulation was partially reversed by injection of adenosine deaminase (ADA) into the air pouch, completely reversed by a specific adenosine A2 receptor antagonist, 3,7-dimethyl-1-propargylxanthine (DMPX), but not affected by an adenosine A1 receptor antagonist, 8-cyclopentyl-dipropylxanthine. Neither ADA nor DMPX affected leukocyte accumulation in the inflamed pouches of animals treated with either saline or the potent antiinflammatory steroid dexamethasone. These results indicate that methotrexate is a nonsteroidal antiinflammatory agent, the antiphlogistic action of which is due to increased adenosine release at inflamed sites.

Authors

B N Cronstein, D Naime, E Ostad

Nonsense mutation R1162X of the cystic fibrosis transmembrane conductance regulator gene does not reduce messenger RNA expression in nasal epithelial tissue.

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Cystic fibrosis (CF) patients bearing the premature translation termination mutation (nonsense mutation) W1282X present severe pulmonary and pancreatic disease, whereas patients carrying other nonsense mutations such as G542X, R553X, S1255X, R1162X, and W1316X show a severe pancreatic but mild pulmonary illness. CF gene expression was found absent in respiratory tissues with mutations R553X and W1316X, which led to the hypothesis that the absence of the gene product in the lung is more favorable than the presence of an altered one. We asked whether or not all the nonsense mutations characterized by mild pulmonary disease phenotypes do present the absence of CF gene expression. We therefore investigated gene expression at the mRNA level in respiratory cells obtained from nasal polyps from a patient homozygous for the R1162X mutation. Gene expression was studied by amplification with polymerase chain reaction of segments of the CF transmembrane conductance regulator cDNA that was obtained by reverse transcription of RNA. Semiquantitative analysis was performed by Northern analysis. By comparing the data obtained from polyps deriving from non-CF subjects and a CF patient homozygous for dF508 mutation, it is shown that no reduction of CF gene expression is evident in R1162X respiratory tissue. We conclude that CF nonsense mutations have heterogeneous mechanisms of gene expression.

Authors

R Rolfini, G Cabrini

T cell receptor V beta gene bias in rheumatoid arthritis.

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Polymerase chain reaction (PCR) technology was employed to examine peripheral blood and synovial T cells in patients with rheumatoid arthritis (RA) for biased utilization of T cell receptor (TCR) variable region (V) genes. Oligonucleotide primers specific for individual TCR V beta gene families were used to amplify TCR gene products in a semiquantitative assay of their relative utilization in unselected T cell populations. Mean V beta expression in 24 RA peripheral blood samples was very similar to that in a panel of 15 normal subjects, except for a slight decrease in V beta 13.2 expression. V beta utilization in 8 RA synovial tissue samples and 13 synovial fluid samples was compared to simultaneously obtained blood samples. Although heterogeneous patterns of skewed V beta utilization were observed, several significant trends emerged. By a number of approaches to data analysis, a statistically significant increase in expression of V beta 6 and V beta 15 in synovial T cells was documented. In addition, increased synovial expression of V beta 14 was found, but only in the synovial fluid samples. Reduced expression of V beta 1, V beta 4, V beta 5.1, V beta 10, V beta 16, and V beta 19 was also observed in synovial T cells. These results indicate that biased V beta gene utilization in different peripheral compartments of RA patients can be observed in unselected T cell populations, and are consistent with the conclusion that populations of T cells expressing these V beta gene products may be involved in the pathogenesis of the disease.

Authors

R N Jenkins, A Nikaein, A Zimmermann, K Meek, P E Lipsky

Differential regulation of natriuretic peptide receptor messenger RNAs during the development of cardiac hypertrophy in the rat.

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The heart expresses the three natriuretic peptide receptors (NPR), namely NPR-A, NPR-B, and NPR-C. We have examined the temporal relationship between the expression of mRNA transcripts for atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) and their receptors in the heart during the development of cardiac hypertrophy in the aortovenocaval fistula rat. Messenger RNAs were measured by cDNA amplification. Progressive cardiac hypertrophy was accompanied by increased ANP mRNA prevalence throughout the heart and increased BNP mRNA in the left atrium. The most striking observation was the gradual disappearance of NPR-C transcripts (the putative "clearance" receptor) in all chambers; this was in marked contrast to the increase in mRNA levels for NPR-A and NPR-B (the guanylyl cyclase-linked receptors). Our observations have important therapeutic implications if the transcript changes are mirrored at the receptor protein level because (a) the apparent down-regulation of NPR-C may enhance the local action of natriuretic peptides on the heart, and (b) the loss of NPR-C, particularly if it is widespread, may reduce the rate of elimination of the natriuretic peptides, restricting the therapeutic potential of specific NPR-C ligands designed to reduce peptide clearance.

Authors

L A Brown, D J Nunez, M R Wilkins

A splice junction mutation causes deletion of a 72-base exon from the mRNA for lysosomal acid lipase in a patient with cholesteryl ester storage disease.

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The genetic defect leading to cholesteryl ester storage disease (CESD) has been determined in a 12-yr-old patient. Lysosomal acid lipase (LAL) activity in cultured skin fibroblasts was reduced to approximately 9% of control fibroblasts. Plasma cholesterol (255 mg/dl) and LDL-cholesterol (215 mg/dl) were elevated whereas HDL-cholesterol was reduced (19 mg/dl). Triglycerides were moderately elevated (141 mg/dl). There were no clinical abnormalities with the exception of hepatosplenomegaly. Both parents have reduced LAL activity in white blood cells. PCR analysis of the LAL mRNA from the propositus revealed a single slightly smaller mRNA species in skin fibroblasts as well as in leukocytes. The mother of the patient and his older brother had two mRNA species: one of normal size and one of the same size as the propositus. The father has a LAL mRNA of normal size only. Sequence analysis of a PCR-amplified cDNA fragment showed a 72-bp in-frame deletion resulting in the loss of the codons for amino acids 254-277. Analysis of genomic DNA revealed that the 72 bp represent an exon, indicating that the deletion in the mRNA is caused by defective splicing. Sequence analysis of the patient's genomic DNA revealed a G-->A substitution in the last nucleotide of the 72-bp exon in one of his alleles. The mutant allele was shown to cosegregate with the truncated mRNA in the pedigree, providing further evidence that the G-->A substitution causes aberrant splicing and exon skipping. No normal-sized mRNA is detectable in the propositus even though he is not homozygous for the splice site mutation. This can be only accounted for by assuming that he is a compound heterozygote with a null allele inherited from his father. In summary, the data presented provide evidence that deletion of the codons for amino acids 254-277 in the LAL mRNA in combination with a null allele cause the clinical expression of CESD in our patient.

Authors

H Klima, K Ullrich, C Aslanidis, P Fehringer, K J Lackner, G Schmitz

E-selectin supports neutrophil rolling in vitro under conditions of flow.

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E-selectin was evaluated for its ability to support neutrophil adhesion under conditions of flow. At a wall shear stress of 1.85 dyn/cm2, neutrophils were found to attach to E-selectin expressed on the apical surface of L cell monolayers. The initial intercellular contact was most often evidenced by neutrophils rolling on the monolayer at a mean rate of congruent to 10 microns/s. Anti-E-selectin monoclonal antibody, CL2/6, inhibited this interaction by > 90%. Rolling neutrophils often transiently stopped, but in contrast to the behavior on stimulated endothelial cells, they remained spherical in shape and did not migrate on or beneath the monolayer. A possible contribution of neutrophil L-selectin to this interaction was indicated by the findings that anti-L-selectin monoclonal antibody, DREG-56, inhibited E-selectin-dependent adhesion under flow by > 65%, and there was a highly significant correlation between surface levels of L-selectin and E-selectin-dependent adhesion under flow. E-selectin also appeared to support neutrophil adhesion to IL-1 beta-stimulated endothelial cells under conditions of flow, but it accounted for only congruent to 30% of the level of adherence, in contrast to L-selectin which accounted for > 65%. Thus, both L-selectin and E-selectin can support neutrophil adhesion at wall shear stresses that preclude intercellular adhesion molecule-1-dependent adhesion, and they participate in neutrophil adherence to stimulated endothelial cells under conditions of flow.

Authors

O Abbassi, T K Kishimoto, L V McIntire, D C Anderson, C W Smith

Patch-clamp evidence for calcium channels in apical membranes of rabbit kidney connecting tubules.

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To test the hypothesis that Ca channel plays a role in renal epithelial Ca transport, we exposed and patched apical membranes of freshly microdissected rabbit connecting tubules (CNTs). Single channel Ca currents were recorded with Ba as the charge carrier. In the cell-attached mode, 8-Br-cAMP increased the open-state probability (Po) to 0.6%. In excised, inside-out patches, Po was low spontaneously and remained low during either bath protein kinase A catalytic subunit (PKAcs) or Bay K 8644. Exposure to both agonists, however, unmasked Ca channels previously latent with only one, raising Po by 1.05% at membrane potential of -70 mV. Mean Po for 14 seals (2.57%) peaked at -70 mV, declining with either hyperpolarization or depolarization. The slope conductance was 25 pS. The extrapolated reversal potential (138 mV) agrees with the calculated equilibrium potential for Ca (158 mV). The Ca to Na permeability ratio exceeded 2,800. In four patches stimulated by Bay K 8644 and PKAcs, bath nifedipine reduced Po from 1.03 to 0.15% at -63 mV. These patch-clamp data demonstrate a selective, 25-pS, cAMP/PKAcs-sensitive Ca channel in apical membranes of CNT. Po is stimulated by PKAcs and dihydropyridine (DHP) agonist, but inhibited by DHP antagonist and by depolarization. The data are consistent with the potential role of apical membrane Ca channel in epithelial Ca transport.

Authors

S Tan, K Lau

Reduced beta 1 receptor messenger RNA abundance in the failing human heart.

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Abstract

Heart failure in humans is characterized by alterations in myocardial adrenergic signal transduction, the most prominent of which is down-regulation of beta 1-adrenergic receptors. We tested the hypothesis that down-regulation of beta 1-adrenergic receptors in the failing human heart is related to decreased steady-state levels of beta 1 receptor mRNA. Due to the extremely low abundance of beta 1 receptor mRNA, measurements were possible only by quantitative polymerase chain reaction (QPCR) or by RNase protection methods. Because the beta 1 receptor gene is intronless and beta 1 receptor mRNA abundance is low, QPCR yielded genomic amplification in total RNA, and mRNA measurements had to be performed in poly (A)(+)-enriched RNA. By QPCR the concentration of beta 1 receptor mRNA varied from 0.34 to 7.8 x 10(7) molecules/microgram poly(A)(+)-enriched RNA, and the assay was sensitive to 16.7 zeptomol. Using 100-mg aliquots of left ventricular myocardium obtained from organ donors (nonfailing ventricles, n = 12) or heart transplant recipients (failing ventricles, n = 13), the respective beta 1 mRNA levels measured by QPCR were 4.2 +/- 0.7 x 10(7)/micrograms vs. 2.10 +/- 0.3 x 10(7)/micrograms (P = 0.006). In these same nonfailing and failing left ventricles the respective beta 1-adrenergic receptor densities were 67.9 +/- 6.9 fmol/mg vs. 29.6 +/- 3.5 fmol/mg (P = 0.0001). Decreased mRNA abundance in the failing ventricles was confirmed by RNase protection assays in total RNA, which also demonstrated a 50% reduction in beta 1 message abundance. We conclude that down-regulation of beta 1 receptor mRNA contributes to down-regulation of beta 1 adrenergic receptors in the failing human heart.

Authors

M R Bristow, W A Minobe, M V Raynolds, J D Port, R Rasmussen, P E Ray, A M Feldman

Plasminogen activator inhibitor-1 gene-deficient mice. I. Generation by homologous recombination and characterization.

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Abstract

Homozygous plasminogen activator inhibitor-1 (PAI-1)-deficient (PAI-1-/-) mice were generated by homologous recombination in D3 embryonic stem cells. Deletion of the genomic sequences encompassing the transcription initiation site and the entire coding regions of murine PAI-1 was demonstrated by Southern blot analysis. A 3.0-kb PAI-1-specific mRNA was identified by Northern blot analysis in liver from PAI-1 wild type (PAI-1+/+) but not from PAI-1-/- mice. Plasma PAI-1 levels, measured 2-4 h after endotoxin (2.0 mg/kg) injection were 63 +/- 2 ng/ml, 30 +/- 10 ng/ml, and undetectable (< 2 ng/ml) in PAI-1+/+, heterozygous (PAI-1+/-) and PAI-1-/- mice, respectively (mean +/- SEM, n = 4-11). PAI-1-specific immunoreactivity was demonstrable in kidneys of PAI-1+/+ but not of PAI-1-/- mice. SDS-gel electrophoresis of plasma incubated with 125I-labeled recombinant human tissue-type plasminogen activator revealed an approximately 115,000-M(r) component with plasma from endotoxin-stimulated (0.5 mg/kg) PAI-1+/+ but not from PAI-1-/- mice, which could be precipitated with a polyclonal anti-PAI-1 antiserum. PAI-1-/- mice were viable, produced similar sizes of litters as PAI-1+/+ mice, and showed no apparent macroscopic or microscopic histological abnormalities.

Authors

P Carmeliet, L Kieckens, L Schoonjans, B Ream, A van Nuffelen, G Prendergast, M Cole, R Bronson, D Collen, R C Mulligan

Plasminogen activator inhibitor-1 gene-deficient mice. II. Effects on hemostasis, thrombosis, and thrombolysis.

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Abstract

The effects of plasminogen activator inhibitor-1 (PAI-1) gene inactivation on hemostasis, thrombosis and thrombolysis were studied in homozygous PAI-1-deficient (PAI-1-/-) mice, generated by homologous recombination in D3 embryonic stem cells. Diluted (10-fold) whole blood clots from PAI-1-/- and from PAI-1 wild type (PAI-1+/+) mice underwent limited but significantly different (P < 0.001) spontaneous lysis within 3 h (6 +/- 1 vs 3 +/- 1%, respectively). A 25-microliters 125I-fibrin-labeled normal murine plasma clot, injected into a jugular vein, was lysed for 47 +/- 5, 66 +/- 3, and 87 +/- 7% within 8 h in PAI-1+/+, heterozygous PAI-1-deficient (PAI-1+/-), and PAI-1-/- mice, respectively (P = 0.002 for PAI-1+/+ vs PAI-1-/- mice). Corresponding values after pretreatment with 0.5 mg/kg endotoxin in PAI-1+/+ and PAI-1-/- mice, were 35 +/- 5 and 91 +/- 3% within 4 h, respectively (P < 0.001). 11 out of 26 PAI-1+/+ but only 1 out of 25 PAI-1-/- mice developed venous thrombosis (P = 0.004) within 6 d after injection of 10 or 50 micrograms endotoxin in the footpad. Spontaneous bleeding or delayed rebleeding could not be documented in PAI-1-/- mice after partial amputation of the tail or of the caecum. Thus, disruption of the PAI-1 gene in mice appears to induce a mild hyperfibrinolytic state and a greater resistance to venous thrombosis but not to impair hemostasis.

Authors

P Carmeliet, J M Stassen, L Schoonjans, B Ream, J J van den Oord, M De Mol, R C Mulligan, D Collen

Glutathione, cell proliferation, and 1,3-bis-(2-chloroethyl)-1-nitrosourea in K562 leukemia.

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Abstract

We have pursued our findings of glutathione reductase (GSSG-R) deficiency and disturbed glutathione in cancer patients treated with 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU), by investigating how thiol metabolism, cell proliferation, and the nitrosourea interact in human K562 leukemia. Fasting cells arrested in G greatly increased their reduced glutathione (GSH) in response to growth factors. The rise in thiol began after several hours, peaked before DNA synthesis, and resulted from increased production. BCNU inactivated GSSG-R rapidly, and later retarded, doubled, and greatly prolonged GSH formation before stopping DNA synthesis. Pretreatment unlike post treatment with buthionine-S-R-sulfoximine (BSO) diminished BCNU's ability to block GSSG-R. Enzyme inhibition decreased with falling cellular GSH. In the leukemia system as in vivo, sequential BCNU-induced thiol alterations heralded delayed antiproliferative effects. Drug timing markedly affected both thiol and DNA syntheses. By destroying GSSG-R and delaying the upregulation of thiol synthesis while escalating GSH utilization and requirements, the nitrosourea created a striking and previously unrecognized window of vulnerability for GSH-dependent processes. During this period, altered GSH metabolism could contribute indirectly to BCNU's pleiotropic effects by interfering with DNA alkylation repair, glucose decarboxylation, deoxyribose formation, and possibly by influencing other aspects of proliferation. Acquired GSSG-R deficiency was also an early and sensitive marker for prodrug breakdown and activation.

Authors

H Frischer, E J Kennedy, R Chigurupati, M Sivarajan

VLA-4 integrin can mediate CD11/CD18-independent transendothelial migration of human monocytes.

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Abstract

The migration of human monocytes across unactivated and activated human umbilical vein endothelium (HUVE) in response to chemotactic factors was studied, and the adhesion molecules involved were characterized. Migration of blood monocytes or U937 cell line-derived monocytes across unactivated HUVE induced by C5a, was partially inhibited (by 75%) by mAbs (R15.7 or 60.3) to CD18 of the CD11/CD18 complex on the monocyte. However, when the HUVE was pretreated for 5 h with IL-1 alpha (0.1 ng/ml), TNF-alpha (100 U/ml), or LPS (1 ng/ml), migration induced by C5a was no longer inhibited; i.e., migration became CD18 independent. The monocyte CD18-independent migration was completely blocked by mAbs against alpha 4 or beta 1 integrin chains of VLA-4. This migration was also partially inhibited by mAbs against vascular cell adhesion molecule-1 (VCAM-1), a major counter-receptor on HUVE for VLA-4, but not by mAbs to E-selectin or intercellular adhesion molecule-1. The significant CD18-independent migration across "unactivated" HUVE was also inhibited by mAbs against alpha 4 or beta 1 chains of VLA-4, although mAbs against VCAM-1 did not inhibit under these conditions. Finally, considerable VLA-4-dependent transendothelial migration to C5a was also observed with monocytes from a patient with CD18 deficiency (leukocyte adhesion deficiency). These results suggest that (a) there is a major CD18-independent component in monocyte chemotactic factor-dependent migration across activated and unactivated endothelium; (b) that VLA-4 integrin on the monocyte has a major role in this migration; and (c) that VCAM-1 on activated endothelium functions as a counter-receptor in this process, but other ligands for VLA-4, especially on unactivated endothelium, may also be involved.

Authors

H E Chuluyan, A C Issekutz

Regulation of surfactant phosphatidylcholine secretion from alveolar type II cells during Pneumocystis carinii pneumonia in the rat.

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Abstract

We used an immunosuppressed rat model to test the hypothesis that normal mechanisms regulating surfactant phosphatidylcholine synthesis and secretion in alveolar type II cells are aberrant in Pneumocystis carinii pneumonia. Animal groups included: group 1, healthy controls; group 2, immunosuppressed, without pneumocystosis; group 3, immunosuppressed with pneumocystosis; group 4, immunosuppressed with well-established pneumocystosis treated with trimethoprim-sulfamethoxazole (TMP-SMX). Type II cells were isolated from rats in each group and compared for [3H]choline incorporation into phospholipid and response of the type II cells to secretagogues. Incorporation of [3H]choline into phospholipid subclasses exhibited significant differences. Incorporation into phosphatidylcholine fell from 89.3 +/- 2.2% of total incorporation in group 1 control rats to 79.6 +/- 3.1% in group 3 rats with P. carinii pneumonia, while incorporation into sphingomyelin rose from 5.6 +/- 1.2% in group 1 animals to 15.2 +/- 2.7% in group 3 rats. Incorporation of [3H]choline into phospholipid subclasses in cells from group 2 and group 4 animals was not different from incorporation for group 1 animals. Type II cells from group 1 and group 2 (immunosuppressed control) rats responded appropriately to the secretagogues ATP, TPA, and terbutaline with a marked increase in surfactant phosphatidylcholine secretion; the effect of ATP was also blocked by the lectin, concanavalin A. In contrast, type II cells from group 3 rats failed to respond to the secretagogues with a significant increase in phospholipid secretion. Although treatment of group 4 rats with TMP-SMX markedly reduced the P. carinii organism burden, type II cells from these animals also responded poorly to the secretagogues. The depressed type II cell function described here provides a mechanism for the observed decrease in surfactant phospholipids from bronchoalveolar lavage fluid of experimental animals and patients with P. carinii pneumonia. The data also suggest this defect may become irreversible with advanced disease.

Authors

W R Rice, F M Singleton, M J Linke, P D Walzer

Tumor necrosis factor-alpha mediates changes in tissue protein turnover in a rat cancer cachexia model.

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Abstract

Rats bearing the Yoshida AH-130 ascites hepatoma showed enhanced fractional rates of protein degradation in gastrocnemius muscle, heart, and liver, while fractional synthesis rates were similar to those in non-tumor bearing rats. This hypercatabolic pattern was associated with marked perturbations of the hormonal homeostasis and presence of tumor necrosis factor in the circulation. The daily administration of a goat anti-murine TNF IgG to tumor-bearing rats decreased protein degradation rates in skeletal muscle, heart, and liver as compared with tumor-bearing rats receiving a nonimmune goat IgG. The anti-TNF treatment was also effective in attenuating early perturbations in insulin and corticosterone homeostasis. Although these results suggest that tumor necrosis factor plays a significant role in mediating the changes in protein turnover and hormone levels elicited by tumor growth, the inability of such treatment to prevent a reduction in body weight implies that other mediators or tumor-related events were also involved.

Authors

P Costelli, N Carbó, L Tessitore, G J Bagby, F J Lopez-Soriano, J M Argilés, F M Baccino

Corticotropin-releasing hormone, proopiomelanocortin, and glucocorticoid receptor gene expression in adrenocorticotropin-producing tumors in vitro.

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Abstract

To differentiate between ectopic ACTH syndrome and Cushing's disease, gene expression of corticotropin-releasing hormone (CRH), proopiomelanocortin (POMC), and glucocorticoid receptor was examined in 10 pituitary adenomas (Cushing's disease) and in 10 ectopic ACTH-producing tumors. CRH increased plasma ACTH levels in all patients with Cushing's disease and in five patients with ectopic ACTH syndrome whose tumors contained CRH and CRH mRNA. In five CRH nonresponders, CRH was not detected in tumors that contained no CRH mRNA or that contained only long-size CRH mRNA. Dexamethasone (Dex) decreased plasma ACTH levels in all patients with Cushing's disease and in three patients with ectopic ACTH-producing bronchial carcinoid. These tumors contained glucocorticoid receptor mRNA. CRH increased and Dex decreased ACTH release and POMC mRNA levels in pituitary adenoma and bronchial carcinoid cells. PMA increased POMC mRNA levels only in carcinoid cells. These results reveal characteristics of ectopic ACTH-producing tumors: long-size CRH mRNA and PMA-induced POMC gene expression. In addition, there are two ectopic ACTH syndrome subtypes: tumors containing ACTH with CRH (CRH responder) and tumors without CRH. Dex decreases ACTH release and POMC mRNA levels in some bronchial carcinoids. Therefore, CRH and Dex tests have limited usefulness in differentiating between Cushing's disease and ectopic ACTH syndrome.

Authors

T Suda, F Tozawa, I Dobashi, N Horiba, N Ohmori, M Yamakado, M Yamada, H Demura

Studies of activated GPIIb/IIIa receptors on the luminal surface of adherent platelets. Paradoxical loss of luminal receptors when platelets adhere to high density fibrinogen.

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Abstract

The accessibility of activated GPIIb/IIIa receptors on the luminal surface of platelets adherent to damaged blood vessels or atherosclerotic plaques is likely to play a crucial role in subsequent platelet recruitment. To define better the factors involved in this process, we developed a functional assay to assess the presence of activated, luminal GPIIb/IIIa receptors, based on their ability to bind erythrocytes containing a high density of covalently coupled RGD-containing peptides (thromboerythrocytes). Platelets readily adhered to wells coated with purified type I rat skin collagen and the adherent platelets bound a dense lawn of thromboerythrocytes. With fibrinogen-coated wells, platelet adhesion increased as the fibrinogen-coating concentration increased, reaching a plateau at about 11 micrograms/ml. Thromboerythrocyte binding to the platelets adherent to fibrinogen showed a paradoxical response, increasing at fibrinogen coating concentrations up to approximately 4-6 micrograms/ml and then dramatically decreasing at higher fibrinogen-coating concentrations. Scanning electron microscopy demonstrated that the morphology of platelets adherent to collagen was similar to that of platelets adherent to low density fibrinogen, with extensive filopodia formation and ruffling. In contrast, platelets adherent to high density fibrinogen showed a bland, flattened appearance. Immunogold staining of GPIIb/IIIa receptors demonstrated concentration of the receptors on the filopodia, and depletion of receptors on the flattened portion of the platelets. Thus, there is a paradoxical loss of accessible, activated GPIIb/IIIa receptors on the luminal surface of platelets adherent to high density fibrinogen. Two factors may contribute to this result: engagement of GPIIb/IIIa receptors with fibrinogen on the abluminal surface leading to the loss of luminal receptors, and loss of luminal filopodia that interact with thromboerythrocytes. These data provide insight into the differences in thrombogenicity between surfaces, and may provide a mechanism for purposefully passivating platelet-reactive artificial surfaces.

Authors

B S Coller, J L Kutok, L E Scudder, D K Galanakis, S M West, G S Rudomen, K T Springer

Familial hypertrophic cardiomyopathy. Microsatellite haplotyping and identification of a hot spot for mutations in the beta-myosin heavy chain gene.

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Abstract

Familial hypertrophic cardiomyopathy (FHC) is a clinically and genetically heterogeneous disease. The first identified disease gene, located on chromosome 14q11-q12, encodes the beta-myosin heavy chain. We have performed linkage analysis of two French FHC pedigrees, 720 and 730, with two microsatellite markers located in the beta-myosin heavy chain gene (MYO I and MYO II) and with four highly informative markers, recently mapped to chromosome 14q11-q12. Significant linkage was found with MYO I and MYO II in pedigree 720, but results were not conclusive for pedigree 730. Haplotype analysis of the six markers allowed identification of affected individuals and of some unaffected subjects carrying the disease gene. Two novel missense mutations were identified in exon 13 by direct sequencing, 403Arg-->Leu and 403Arg-->Trp in families 720 and 730, respectively. The 403Arg-->Leu mutation was associated with incomplete penetrance, a high incidence of sudden deaths and severe cardiac events, whereas the consequences of the 403Arg-->Trp mutation appeared less severe. Haplotyping of polymorphic markers in close linkage to the beta-myosin heavy chain gene can, thus, provide rapid analysis of non informative pedigrees and rapid detection of carrier status. Our results also indicate that codon 403 of the beta-myosin heavy chain gene is a hot spot for mutations causing FHC.

Authors

E Dausse, M Komajda, L Fetler, O Dubourg, C Dufour, L Carrier, C Wisnewsky, J Bercovici, C Hengstenberg, S al-Mahdawi

Osteopontin mRNA is expressed by smooth muscle-derived foam cells in human atherosclerotic lesions of the aorta.

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Abstract

Osteopontin is a phosphorylated, sialic acid-rich, noncollagenous bone matrix protein containing the Arg-Gly-Asp-Ser amino acid sequence responsible for cell adhesion. The protein strongly binds to hydroxyapatite and play an important role in calcification. Expression of osteopontin mRNA was analyzed in human aortic atherosclerotic lesion by Northern blot hybridization, as well as by in situ hybridization. The expression of osteopontin mRNA was detected in 24 out of 25 samples of aorta obtained from 17 autopsy cases, but not in one normal aortic sample. The magnitude of expression was proportional to the stage of atherosclerosis. In situ hybridization revealed that the cells expressing osteopontin mRNA were detected in the wall surrounding atheroma and closely associated with calcification. They were morphologically identified as foam cells and immunohistologically positive with HHF35, appearing to be derived from smooth muscle cells. These findings have suggested that smooth muscle cell-derived foam cells express osteopontin mRNA and play an important role in calcification of the atherosclerotic lesions.

Authors

T Ikeda, T Shirasawa, Y Esaki, S Yoshiki, K Hirokawa

Naturally occurring anti-i/I cold agglutinins may be encoded by different VH3 genes as well as the VH4.21 gene segment.

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Abstract

In the current study, we wished to determine if the V regions encoding the naturally occurring anti-i/I Cold Agglutinins (anti-i/I CA) differ from pathogenic anti-i/I CA that are exclusively encoded by the VH4.21 gene. After EBV transformation of B lymphocytes, we generated one anti-I secreting clone from each of two individuals; clone 4G (individual CM, PBL) and clone Sp1 (individual SC, spleen). Clone 4G expresses a VH3 gene sequence that is 92% homologous to the germline gene WHG26. Clone Sp1 also expresses a VH3 gene that is 98% homologous to the fetally rearranged M85/20P1 gene. Another clone, Sp2 (anti-i specificity), from individual SC is 98% homologous to the germline gene VH4.21. For correlation, we studied anti-i/I CA fractions purified from 15 normal sera and found no or relatively small amounts of 9G4 (VH4.21 related idiotype) reactive IgM. Five cold agglutinin fractions contained large amounts of VH3-encoded IgM (compared to pooled normal IgM) by virtue of their binding to modified protein Staph A (SPA), and absorption of three CA fractions with modified SPA specifically removed anti-i/I binding specificity entirely. Collectively, the data indicate that naturally occurring anti-i/I CA may be encoded to a large extent by non-VH4.21-related genes, and that the VH4.21 gene is not uniquely required for anti-i/I specificity.

Authors

L C Jefferies, C M Carchidi, L E Silberstein

Renal ammonia and glutamine metabolism during liver insufficiency-induced hyperammonemia in the rat.

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Abstract

Renal glutamine uptake and subsequent urinary ammonia excretion could be an important alternative pathway of ammonia disposal from the body during liver failure (diminished urea synthesis), but this pathway has received little attention. Therefore, we investigated renal glutamine and ammonia metabolism in midly hyperammonemic, portacaval shunted rats and severely hyperammonemic rats with acute liver ischemia compared to their respective controls, to investigate whether renal ammonia disposal from the body is enhanced during hyperammonemia and to explore the limits of the pathway. Renal fluxes, urinary excretion, and renal tissue concentrations of amino acids and ammonia were measured 24 h after portacaval shunting, and 2, 4, and 6 h after liver ischemia induction and in the appropriate controls. Arterial ammonia increased to 247 +/- 22 microM after portacaval shunting compared to controls (51 +/- 8 microM) (P < 0.001) and increased to 934 +/- 54 microM during liver ischemia (P < 0.001). Arterial glutamine increased to 697 +/- 93 microM after portacaval shunting compared to controls (513 +/- 40 microM) (P < 0.01) and further increased to 3781 +/- 248 microM during liver ischemia (P < 0.001). In contrast to controls, in portacaval shunted rats the kidney net disposed ammonia from the body by diminishing renal venous ammonia release (from 267 +/- 33 to -49 +/- 59 nmol/100 g body wt per min) and enhancing urinary ammonia excretion from 113 +/- 24 to 305 +/- 52 nmol/100 g body wt per min (both P < 0.01). Renal glutamine uptake diminished in portacaval shunted rats compared to controls (-107 +/- 33 vs. -322 +/- 41 nmol/100 g body wt per min) (P < 0.01). However, during liver ischemia, net renal ammonia disposal from the body did not further increase (294 +/- 88 vs. 144 +/- 101 nmol/100 g body wt per min during portacaval shunting versus liver ischemia). Renal glutamine uptake was comparable in both hyperammonemic models. These results indicate that the rat kidney plays an important role in ammonia disposal during mild hyperammonemia. However, during severe liver insufficiency induced-hyperammonemia, ammonia disposal capacity appears to be exceeded.

Authors

C H Dejong, N E Deutz, P B Soeters

One systemic administration of transforming growth factor-beta 1 reverses age- or glucocorticoid-impaired wound healing.

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Abstract

The role of intravenously administered recombinant human transforming growth factor-beta 1 (rhTGF-beta 1) on the healing of incisional wounds in rats with impaired healing due to age or glucocorticoid administration was investigated. The administration of methylprednisolone to young adult rats decreased wound breaking strength to 50% of normal control. Breaking strength of incisional wounds from 19-mo-old rats was decreased approximately 27% compared with wounds from normal healing young adult rats. A single intravenous administration of rhTGF-beta 1 (100 or 500 micrograms/kg) increased wound breaking strength from old rats or young adult rats with glucocorticoid-induced impaired healing to levels similar to normal healing control animals when determined 7 d after injury. Even though the circulating half-life of systemically administered rhTGF-beta 1 is < 5 min, a sustained stimulatory effect on extracellular matrix secretion was evident in glucocorticoid-impaired rats when rhTGF-beta 1 was administered at the time of wounding, 4 h after wounding, or even 24 h before wounding. These observations indicate a previously unrecognized potential for the active form of TGF-beta 1 to profoundly influence the wound healing cascade after brief systemic exposure.

Authors

L S Beck, L DeGuzman, W P Lee, Y Xu, M W Siegel, E P Amento

Expression of parathyroid hormone-related protein in the rat glomerulus and tubule during recovery from renal ischemia.

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Abstract

Parathyroid hormone-related protein (PTHrP) is widely expressed in normal adult and fetal tissues, where it acts in an autocrine/paracrine fashion, stimulates growth and differentiation, and shares early response gene characteristics. Since recovery from renal injury is associated with release of local growth factors, we examined the expression and localization of PTHrP in normal and ischemic adult rat kidney. Male Sprague-Dawley rats underwent complete bilateral renal artery occlusion for 45 min, followed by reperfusion for 15 min, and 2, 6, 24, 48, and 72 h. Renal PTHrP mRNA levels, when compared with sham-operated animals, increased twofold after ischemia, and peaked within 6 h after reperfusion. PTH receptor, beta-actin, and cyclophilin mRNA levels all decreased after ischemia. PTHrP immunohistochemical staining intensity increased in proximal tubular cells after ischemia, changing its location from diffusely cytoplasmic to subapical by 24 h after reperfusion. In addition, PTHrP localized to glomerular epithelial cells (visceral and parietal), but not to mesangial cells. PTHrP and PTH stimulated proliferation two- to threefold in cultured mesangial cells. We conclude that PTHrP mRNA and protein production are upregulated after acute renal ischemic injury, that PTHrP is present in glomerulus and in both proximal and distal tubular cells, and that PTHrP stimulates DNA synthesis in mesangial cells. The precise functions of PTHrP in normal and injured kidney remain to be defined.

Authors

N E Soifer, S K Van Why, M B Ganz, M Kashgarian, N J Siegel, A F Stewart

Cell-matrix interactions modulate interstitial collagenase expression by human keratinocytes actively involved in wound healing.

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Abstract

We reported that interstitial collagenase is produced by keratinocytes at the edge of ulcers in pyogenic granuloma, and in this report, we assessed if production of this metalloproteinase is a common feature of the epidermal response in a variety of wounds. In all samples of chronic ulcers, regardless of etiology, and in incision wounds, collagenase mRNA, localized by in situ hybridization, was prominently expressed by basal keratinocytes bordering the sites of active re-epithelialization indicating that collagenolytic activity is a characteristic response of the epidermis to wounding. No expression of mRNAs for 72- and 92-kD gelatinases or matrilysin was seen in keratinocytes, and no signal for any metalloproteinase was detected in normal epidermis. Immunostaining for type IV collagen showed that collagenase-positive keratinocytes were not in contact with an intact basement membrane and, unlike normal keratinocytes, expressed alpha 5 beta 1 receptors. These observations suggest that cell-matrix interactions influence collagenase expression by epidermal cells. Indeed, as determined by ELISA, primary cultures of human keratinocytes grown on basement membrane proteins (Matrigel; Collaborative Research Inc., Bedford, MA) did not express significant levels of collagenase, whereas cells grown on type I collagen produced markedly increased levels. These results suggest that migrating keratinocytes actively involved in re-epithelialization acquire a collagenolytic phenotype upon contact with the dermal matrix.

Authors

U K Saarialho-Kere, S O Kovacs, A P Pentland, J E Olerud, H G Welgus, W C Parks

Endothelium-dependent hyperpolarization caused by bradykinin in human coronary arteries.

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Abstract

The present study was designed to determine whether bradykinin induces endothelium-dependent hyperpolarization of vascular smooth muscle in human coronary arteries, and if so, to define the contribution of this hyperpolarization to endothelium-dependent relaxations. The membrane potential of arterial smooth muscle cells (measured by glass microelectrodes) and changes in isometric force were recorded in tissues from six patients undergoing heart transplantation. In the presence of indomethacin and NG-nitro-L-arginine (NLA), the membrane potential was -48.3 +/- 0.6 and -46.9 +/- 0.6 mV, in preparations with and without endothelium, respectively, and was not affected by treatment with perindoprilat, an angiotensin-converting enzyme inhibitor. In the presence of both indomethacin and NLA, bradykinin evoked transient and concentration-dependent hyperpolarizations only in tissues with endothelium, which were augmented by perindoprilat and mimicked by the calcium ionophore A23187. Glibenclamide did not inhibit membrane hyperpolarization to bradykinin. In rings contracted with prostaglandin F2 alpha, the cumulative addition of bradykinin caused a concentration-dependent relaxation during contractions evoked by prostaglandin F2 alpha, which was not abolished by NLA and indomethacin. The present findings demonstrate the occurrence of endothelium-dependent hyperpolarization, and its contribution to endothelium-dependent relaxations, in the human coronary artery.

Authors

M Nakashima, J V Mombouli, A A Taylor, P M Vanhoutte

Vasodilation of rat retinal microvessels induced by monobutyrin. Dysregulation in diabetes.

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1-Butyryl-glycerol (monobutyrin) is a simple lipid product of adipocytes with angiogenic activity. Recent studies have shown that the biosynthesis of this compound is tightly linked to lipolysis, a process associated with changes in blood flow. We now present data indicating that monobutyrin is an effective vasodilator of rodent blood vessels using a fluorescent retinal angiogram assay. The vasodilatory activity of monobutyrin is potent (ED50 = 3.3 x 10(-7) M), dose dependent, and stereospecific. Because diabetes represents a catabolic, lipolytic state with numerous vascular complications, we examined the action and regulation of monobutyrin in insulin-deficient diabetic rats. Serum levels of monobutyrin in streptozotocin-induced diabetic rats were greatly elevated compared to normal animals. At the same time, the retinal vessels of the diabetic animals develop a resistance to the vasodilatory activity of monobutyrin. These results demonstrate a role for monobutyrin in the control of vascular tone and suggest a possible involvement in the pathology of diabetes.

Authors

Y D Halvorsen, S E Bursell, W O Wilkison, A C Clermont, M Brittis, T J McGovern, B M Spiegelman

Cardiac alpha-myosin heavy chains differ in their induction of myocarditis. Identification of pathogenic epitopes.

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Abstract

BALB/c mice develop autoimmune myocarditis after immunization with mouse cardiac myosin, whereas C57B/6 mice do not. To define the immunogenicity and pathogenicity of cardiac myosin in BALB/c mice, we immunized mice with different forms of cardiac myosin. These studies demonstrate the discordance of immunogenicity and pathogenicity of myosin heavy chains. The cardiac alpha-myosin heavy chains of BALB/c and C57B/6 mice differ by two residues that are near the junction of the head and rod in the S2 fragment of myosin. Myosin preparations from both strains are immunogenic in susceptible BALB/c as well as in nonsusceptible C57B/6 mice; however, BALB/c myosin induces a greater incidence of disease. To further delineate epitopes of myosin heavy chain responsible for immunogenicity and disease, mice were immunized with fragments of genetically engineered rat alpha cardiac myosin. Epitopes in the region of difference between BALB/c and C57B/6 (residues 735-1032) induce disease in both susceptible and nonsusceptible mice. The data presented here demonstrate that pathogenic epitopes of both mouse and rat myosin residue in the polymorphic region of the S2 subunit. In addition, these studies suggest that polymorphisms in the autoantigen may be part of the genetic basis for autoimmune myocarditis.

Authors

L Liao, R Sindhwani, L Leinwand, B Diamond, S Factor

The reovirus M1 gene determines the relative capacity of growth of reovirus in cultured bovine aortic endothelial cells.

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Abstract

Since blood-borne viruses often interact with endothelial cells before tissue invasion, the interaction between viruses and endothelial cells is likely to be important in viral pathogenicity. Two reovirus isolates (type 1 Lang and type 3 Dearing) differ in their capacity to grow in cultured bovine aortic endothelial cells. The mammalian reoviruses have 10 double-stranded RNA gene segments in their genome. By using 24 reassortant viruses, observed differences in the capacity of different strains to grow in cultured endothelial cells were mapped to the M1 gene (P = 0.00019), which encodes the viral core protein mu 2. No differences were detected in binding or proteolytic processing of viral outer capsid proteins of parental virions between the two reovirus isolates. Northern blot analysis showed a decreased production of viral mRNA in endothelial cells infected with type 3 Dearing reovirus, but not type 1 Lang. Thus, we have identified a viral gene (the M1 gene) responsible for determining the difference in growth capacity of the two reovirus isolates in cultured endothelial cells. Reovirus is an attractive model in which to study the interaction of viruses with endothelial cells at a molecular genetic level.

Authors

Y Matoba, W S Colucci, B N Fields, T W Smith

Glucose-induced protein kinase C activity regulates arachidonic acid release and eicosanoid production by cultured glomerular mesangial cells.

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Abstract

Changes in glomerular eicosanoid production have been implicated in the development of diabetes-induced glomerular hyperfiltration and glomerular mesangial cells (GMC) are major eicosanoid-producing cells within the glomerulus. However, the mechanism for the effect of diabetes mellitus on glomerular mesangial eicosanoid production is unknown. The present study therefore examined whether elevated glucose concentrations activate protein kinase C (PKC) in GMC and whether this PKC activation mediates an effect of elevated glucose concentrations to increase the release of arachidonic acid and eicosanoid production by GMC. The percentage of [3H]arachidonic acid release per 30 min by preloaded GMC monolayers was significantly increased after 3-h exposure to high glucose (20 mM) medium (177% vs control medium) and this increase was sustained after 24-h exposure to high glucose concentrations. 3-h and 24-h exposure to high glucose medium also increased PGE2, 6-keto-PGF1 alpha, and thromboxane (TXB2) production by GMC. High glucose medium (20 mM) increased PKC activity in GMC at 3 and 24 h (168% vs control). In contrast, osmotic control media containing either L-glucose or mannitol did not increase arachidonic acid release, eicosanoid production, or PKC activity in GMC. Inhibiting glucose-induced PKC activation with either H-7 (50 microM) or staurosporine (1 microM) prevented glucose-induced increases in arachidonic acid release and eicosanoid production by GMC. These data demonstrate that elevated extracellular glucose concentrations directly increase the release of endogenous arachidonic acid and eicosanoids by GMC via mechanisms dependent on glucose-induced PKC activation.

Authors

B Williams, R W Schrier

Platelet-derived growth factor inhibits bone regeneration induced by osteogenin, a bone morphogenetic protein, in rat craniotomy defects.

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Abstract

Platelet-derived growth factor (PDGF) is a potent moderator of soft tissue repair through induction of the inflammatory phase of repair and subsequent enhanced collagen deposition. We examined the effect of recombinant BB homodimer PDGF (rPDGF-BB) applied to rat craniotomy defects, treated with and without bovine osteogenin (OG), to see if bone regeneration would be stimulated. Implants containing 0, 20, 60, or 200 micrograms rPDGF-BB, reconstituted with insoluble rat collagenous bone matrix containing 0, 30, or 150 micrograms OG, were placed into 8-mm craniotomies. After 11 d, 21 of the 144 rats presented subcutaneous masses superior to the defect sites. The masses, comprised of serosanguinous fluid encapsulated by fibrous connective tissue, were larger and occurred more frequently in rats treated with 200 micrograms rPDGF-BB, and were absent in rats not treated with rPDGF-BB. The masses underwent resorption within 28 d after surgery. OG (2-256 micrograms) caused a dose-dependent increase in radiopacity and a marked regeneration of calcified tissue in a dose-dependent fashion within defect sites. However, OG-induced bone regeneration was inhibited 17-53% in the presence of rPDGF-BB. These results suggest that rPDGF-BB inhibited OG-induced bone regeneration and stimulated a soft tissue repair wound phenotype and response.

Authors

L J Marden, R S Fan, G F Pierce, A H Reddi, J O Hollinger

Two novel pathogenic mitochondrial DNA mutations affecting organelle number and protein synthesis. Is the tRNA(Leu(UUR)) gene an etiologic hot spot?

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Abstract

We identified two patients with pathogenic single nucleotide changes in two different mitochondrial tRNA genes: the first mutation in the tRNA(Asn) gene, and the ninth known mutation in the tRNA(Leu(UUR)) gene. The mutation in tRNA(Asn) was associated with isolated ophthalmoplegia, whereas the mutation in tRNA(Leu(UUR)) caused a neurological syndrome resembling MERRF (myoclonus epilepsy and ragged-red fibers) plus optic neuropathy, retinopathy, and diabetes. Both mutations were heteroplasmic, with higher percentages of mutant mtDNA in affected tissues, and undetectable levels in maternal relatives. Analysis of single muscle fibers indicated that morphological and biochemical alterations appeared only when the proportions of mutant mtDNA exceeded 90% of the total cellular mtDNA pool. The high incidence of mutations in the tRNA(Leu(UUR)) gene suggests that this region is an "etiologic hot spot" in mitochondrial disease.

Authors

C T Moraes, F Ciacci, E Bonilla, C Jansen, M Hirano, N Rao, R E Lovelace, L P Rowland, E A Schon, S DiMauro

Mithramycin selectively inhibits collagen-alpha 1(I) gene expression in human fibroblast.

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Abstract

The products of the collagen-alpha 1(I) and -alpha 2(I) genes form the triple helical molecule collagen type I, which constitutes the major ECM protein in tissue fibrosis. The collagen-alpha 1(I) gene is mainly transcriptionally regulated, and its promoter activity depends on the interaction of the transcription factors NF-I and Sp1 with a tandem repeat of evolutionary conserved NF-I/Sp1 switch elements. An increased affinity of Sp1 to these elements has been observed in experimental liver fibrosis. Here, we demonstrate that the DNA binding drug mithramycin displays a high affinity binding to the GC-rich elements in the collagen-alpha 1(I) promoter as measured by DNAse I protection and gel retardation assays. Mithramycin interferes with Sp1 but not with NF-I binding to these sites. At a concentration of 100 nM, mithramycin efficiently reduces basal and TGF-beta-stimulated alpha 1(I) gene expression in human primary fibroblasts. The transcriptional activity and mRNA steady state levels of other genes, including the collagenase gene, as well as the growth rate of fibroblasts remained unchanged on exposure to this drug. Taken together, our results indicate that the transcriptional activity of the type I collagen gene highly depends on its GC-rich regulatory elements, and further, that these elements can be differentially blocked, thereby changing the balance between ECM structural and degrading gene activities in human fibroblasts.

Authors

M C Nehls, D A Brenner, H J Gruss, H Dierbach, R Mertelsmann, F Herrmann

Accumulation of "small dense" low density lipoproteins (LDL) in a homozygous patients with familial defective apolipoprotein B-100 results from heterogenous interaction of LDL subfractions with the LDL receptor.

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Abstract

The interaction of LDL and LDL subfractions from a patient homozygous for familial defective apoB-100 (FDB) has been studied. His LDL cholesterol ranged from 2.65 to 3.34 g/liter. In cultured fibroblasts, binding, internalization, and degradation of the patient's LDL was diminished, but not completely abolished. The patient's apolipoprotein E concentration was low, and the amount of apolipoprotein E associated with LDL was not elevated over normal. LDL were separated into six subfractions: LDL-1 (1.019-1.031 kg/liter), LDL-2 (1.031-1.034 kg/liter), LDL-3 (1.034-1.037 kg/liter), LDL-4 (1.037-1.040 kg/liter), LDL-5 (1.040-1.044 kg/liter), and LDL-6 (> 1.044 kg/liter). LDL-5 and LDL-6 selectively accumulated in the patient's plasma. Concentrations of LDL-1 to 3 were normal. The LDL receptor-mediated uptake of LDL-1 and LDL-2 could not be distinguished from normal LDL. LDL-3 and LDL-4 displayed reduced uptake; LDL-5 and LDL-6 were completely defective in binding. When apolipoprotein E-containing particles were removed by immunoabsorption before preparing subfractions, LDL-3 and LDL-4, but not LDL-1 and LDL-2, retained some receptor binding activity. We conclude that in FDB, LDL-1 and LDL-2 contain sufficient apolipoprotein E to warrant normal cellular uptake. In LDL-3 and LDL-4, the defective apoB-100 itself displays some receptor binding; LDL-5 and LDL-6 are inable to interact with LDL receptors and accumulate in plasma.

Authors

W März, M W Baumstark, H Scharnagl, V Ruzicka, S Buxbaum, J Herwig, T Pohl, A Russ, L Schaaf, A Berg

Impairment of cardiac function and energetics in experimental renal failure.

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Abstract

Cardiac function and energetics in experimental renal failure in the rat (5/6 nephrectomy) have been investigated by means of an isolated perfused working heart preparation and an isometric Langendorff preparation using 31P nuclear magnetic resonance (31P NMR). 4 wk after nephrectomy cardiac output of isolated hearts perfused with Krebs-Henseleit buffer was significantly lower (P < 0.0001) at all levels of preload and afterload in the renal failure groups than in the pair-fed sham operated control group. In control hearts, cardiac output increased with increases in perfusate calcium from 0.73 to 5.61 mmol/liter whereas uremic hearts failed in high calcium perfusate. Collection of 31P NMR spectra from hearts of renal failure and control animals during 30 min normoxic Langendorff perfusion showed that basal phosphocreatine was reduced by 32% to 4.7 mumol/g wet wt (P < 0.01) and the phosphocreatine to ATP ratio was reduced by 32% (P < 0.01) in uremic hearts. During low flow ischemia, there was a substantial decrease in phosphocreatine in the uremic hearts and an accompanying marked increase in release of inosine into the coronary effluent (14.9 vs 6.1 microM, P < 0.01). We conclude that cardiac function is impaired in experimental renal failure, in association with abnormal cardiac energetics and increased susceptibility to ischemic damage. Disordered myocardial calcium utilization may contribute to these derangements.

Authors

A E Raine, A M Seymour, A F Roberts, G K Radda, J G Ledingham

Entry of cholera toxin into polarized human intestinal epithelial cells. Identification of an early brefeldin A sensitive event required for A1-peptide generation.

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Abstract

The effect of brefeldin-A (BFA), a reversible inhibitor of vesicular transport, on cholera toxin (CT)-induced Cl- secretion (Isc) was examined in the polarized human intestinal cell line, T84. Pretreatment of T84 monolayers with 5 microM BFA reversibly inhibited Isc in response to apical or basolateral addition of 120 nM CT (2.4 +/- 0.5 vs. 68 +/- 3 microA/cm2, n = 5). In contrast, BFA did not inhibit Isc responses to the cAMP agonist VIP (63 +/- 7 microA/cm2). BFA had no effect on cell surface binding and endocytosis of a functional fluorescent CT analog or on the dose dependency of CT induced 32P-NAD ribosylation of Gs alpha in vitro. In contrast, BFA completely inhibited (> 95%) the ability of T84 cells to reduce CT to the enzymatically active A1-peptide. BFA had to be added within the first 10 min of CT exposure to inhibit CT-elicited Isc. The early BFA-sensitive step occurred before a temperature-sensitive step essential for apical CT action. These studies show that sequential steps are required for a biological response to apical CT: (a) binding to cell surfaces and rapid endocytosis; (b) early, BFA-sensitive vesicular transport essential for reduction of the A1-peptide; and (c) subsequent temperature-sensitive translocation of a signal (the A1-peptide or possibly ADP-ribose-Gs alpha) to the basolateral domain.

Authors

W I Lencer, J B de Almeida, S Moe, J L Stow, D A Ausiello, J L Madara

Infusion of platelet-derived growth factor or basic fibroblast growth factor induces selective glomerular mesangial cell proliferation and matrix accumulation in rats.

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Abstract

Mesangial cell (MC) proliferation and extracellular matrix expansion are involved in the pathogenesis of glomerulosclerosis and renal failure. In vitro, PDGF and basic fibroblast growth factor (bFGF) regulate MC proliferation and/or matrix production. To elucidate the role of PDGF and bFGF in vivo, equimolar concentrations of recombinant PDGF-BB or bFGF or vehicle were infused intravenously into rats over a 7-d period. Rats were either nonmanipulated ("normals") or had received a subnephritogenic dose of anti-MC antibody ("anti-Thy 1.1 rats") before the infusion period. Glomerular cell proliferation (anti-proliferating cell nuclear antigen immunostaining) on days 2, 4, and 7 was unchanged in vehicle-infused normals or anti-Thy 1.1 rats. PDGF infusion increased glomerular cell proliferation 32-fold in anti-Thy 1.1 rats and an 11-fold in normals on day 2. bFGF increased glomerular cell proliferation fourfold in anti-Thy 1.1 rats but was ineffective in normals. Induction of cell proliferation in all kidneys was limited to the glomerulus. The majority of proliferating cells were identified as MC by double immunolabeling. No significant proteinuria, glomerular leukocyte, or platelet influx developed in any group. Glomerular matrix expansion with increased deposition of type IV collagen, laminin, and fibronectin, as well as upregulated laminin and collagen IV mRNA expression was confined to PDGF-infused anti-Thy 1.1 rats. These results show that PDGF and, to a lesser degree, bFGF are selective MC mitogens in vivo and that previous subclinical injury can enhance this MC response. The data thereby support a role of these cytokines in the pathogenesis of glomerulosclerosis.

Authors

J Floege, E Eng, B A Young, C E Alpers, T B Barrett, D F Bowen-Pope, R J Johnson

Skeletal muscle glycogenolysis is more sensitive to insulin than is glucose transport/phosphorylation. Relation to the insulin-mediated inhibition of hepatic glucose production.

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Abstract

The effects of minimal increments in plasma insulin concentrations on hepatic glucose production and glucose uptake, skeletal muscle net glycogen synthesis and glycogenolysis, glycogen synthase and phosphorylase activity, glucose-6-phosphate and uridinediphosphoglucose (UDPG) concentrations were examined in 24-h and in 6-h fasted conscious rats. Insulin was infused for 120 min at rates of 1.5, 3, 6, 12, 24, and 108 pmol/kg per min in 24-h fasted rats and at rates of 3, 6, 9, 12, 36, and 108 pmol/kg per min in 6-h fasted rats while endogenous insulin release was inhibited by SRIF infusion and plasma glucose was maintained at the basal level. All rats received an infusion of [3-3H]glucose. The portion of the muscle glucose-6-phosphate (G6P) pool derived from net glycogenolysis was estimated from the ratio of specific activities of muscle UDPG and plasma glucose. Minimal increments in the circulating insulin levels, which did not stimulate glucose uptake, caused: (a) the increase in skeletal muscle glycogen synthase activity and the decrease in the rate of muscle glycogenolysis and in the G6P concentration; (b) the inhibition of hepatic glucose production. Net muscle glycogen synthesis was not stimulated despite submaximal activation of glycogen synthase, and its onset correlated with the rise in muscle G6P levels. Thus, insulin's inhibition of muscle glycogenolysis is the most sensitive insulin action on skeletal muscle and its dose-response characteristics resemble those for the inhibition of hepatic glucose production. These findings indicate that skeletal muscle glycogen synthase may play a major role in carbohydrate homeostasis even under postabsorptive (basal insulin) conditions and support the notion that insulin may exert some of its effects on the liver through an indirect or peripheral mechanism.

Authors

L Rossetti, M Hu

Bence Jones proteins bind to a common peptide segment of Tamm-Horsfall glycoprotein to promote heterotypic aggregation.

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Abstract

Bence Jones proteins (BJPs) are the major pathogenic factor causing cast nephropathy ("myeloma kidney") by coaggregation with Tamm-Horsfall glycoprotein (THP). Understanding the interaction between these proteins is therefore important in developing treatment strategies to prevent renal failure from cast formation in multiple myeloma. We developed an enzyme-linked immunoassay to examine this phenomenon. Five different human BJPs (four kappa and one lambda immunoglobulin light chains) were used in this assay that demonstrated these proteins bound THP with different affinity. BJPs competed among themselves for binding to THP. The binding site was a peptide portion of THP since these proteins also bound deglycosylated THP. Also, one monoclonal antibody directed against a peptide segment of human THP prevented binding of THP to BJPs. By altering the conformation of THP, reducing agents decreased binding between these two proteins in concentration-dependent fashion. In turbidity studies, the monoclonal antibody that prevented binding and a reducing agent, dithiothreitol, decreased coaggregation. Deglycosylated THP did not coaggregate with BJPs. We concluded that ionic interaction between BJPs and a specific peptide binding site on THP promoted heterotypic coaggregation. The carbohydrate moiety of THP was also essential for coaggregation, perhaps by facilitating homotypic aggregation of THP.

Authors

Z Q Huang, K A Kirk, K G Connelly, P W Sanders

Tauroursodeoxycholic acid stimulates hepatocellular exocytosis and mobilizes extracellular Ca++ mechanisms defective in cholestasis.

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Abstract

To assess the effects of tauroursodeoxycholic acid (TUDCA) on bile excretory function, we examined whether TUDCA modulates vesicular exocytosis in the isolated perfused liver of normal rats in the presence of high (1.9 mM) or low (0.19 mM) extracellular Ca++ and in cholestatic rats 24 h after bile duct ligation. In addition, the effects of TUDCA on Ca++ homeostasis were compared in normal and in cholestatic hepatocytes. In the isolated perfused rat liver, TUDCA (25 microM) stimulated a sustained increase in the biliary excretion of horseradish peroxidase, a marker of the vesicular pathway, in the presence of high, but not low extracellular Ca++ or in the cholestatic liver. In contrast, TUDCA stimulated bile flow to the same extent regardless of the concentration of extracellular Ca++ or the presence of cholestasis. In indo-1-loaded hepatocytes, basal cytosolic free Ca++ ([Ca++]i) levels were not different between normal and cholestatic cells. However, in cholestatic cells [Ca++]i increases induced by TUDCA (10 microM) and its 7 alpha-OH epimer taurochenodeoxycholic acid (50 microM) were reduced to 22% and 26%, respectively, compared to normal cells. The impairment of TUDCA-induced [Ca++]i increase in cholestatic cells could be mimicked by exposing normal cells to low extracellular Ca++ (21%) or to the Ca++ channel blocker NiCl2 (23%). These data indicate that (a) dihydroxy bile acid-induced Ca++ entry may be of functional importance in the regulation of hepatocellular vesicular exocytosis, and (b) this Ca++ entry mechanism across the plasma membrane is impaired in cholestatic hepatocytes. We speculate that the beneficial effect of ursodeoxycholic acid in cholestatic liver diseases may be related to the Ca+(+)-dependent stimulation of vesicular exocytosis by its conjugate.

Authors

U Beuers, M H Nathanson, C M Isales, J L Boyer

Restoration of the cAMP second messenger pathway enhances cardiac preservation for transplantation in a heterotopic rat model.

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Abstract

Current organ preservation strategies subject graft vasculature to severe hypoxia (PO2 approximately 20 Torr), potentially compromising vascular function and limiting successful transplantation. Previous work has shown that cAMP modulates endothelial cell (EC) antithrombogenicity, barrier function, and leukocyte/EC interactions, and that hypoxia suppresses EC cAMP levels. To explore the possible benefits of cAMP analogs/agonists in organ preservation, we used a rat heterotopic cardiac transplant model; dibutyryl cAMP added to preservation solutions was associated with a time- and dose-dependent increase in the duration of cold storage associated with successful graft function. Preservation was also enhanced by 8-bromo-cAMP, the Sp isomer of adenosine 3',5'monophosphorothioate, and types III (indolidan) and IV (rolipram) phosphodiesterase inhibitors. Neither butyrate alone nor 8-bromoadenosine were effective, and the cAMP-dependent protein kinase antagonist Rp isomer of adenosine 3',5'monophosphorothioate prevented preservation enhancement induced by 8-bromo-cAMP. Grafts stored with dibutyryl cAMP demonstrated a 5.5-fold increase in blood flow and a 3.2-fold decreased neutrophil infiltration after transplantation. To explore the role of cAMP in another cell type critical for vascular homeostasis, vascular smooth muscle cells were subjected to hypoxia, causing a time-dependent decline in cAMP levels. Although adenylate cyclase activity was unchanged, diminished oxygen tensions were associated with enhanced phosphodiesterase activity (59 and 30% increase in soluble types III and IV activity, respectively). These data suggest that hypoxia or graft ischemia disrupt vascular homeostasis, at least in part, by perturbing the cAMP second messenger pathway. Supplementation of this pathway provides a new approach for enhancing cardiac preservation, promoting myocardial function, and maintaining vascular homeostatic properties.

Authors

D Pinsky, M Oz, H Liao, S Morris, J Brett, R Sciacca, M Karakurum, M Van Lookeren Campagne, J Platt, R Nowygrod

Mechanical strain and collagen potentiate mitogenic activity of angiotensin II in rat vascular smooth muscle cells.

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Abstract

The effects of extracellular matrix proteins and mechanical strain on the mitogenic activity of angiotensins I and II (AI and AII) were examined in cultured rat vascular smooth muscle (VSM) cells. VSM cells on various extracellular matrices were exposed to AII (1 microM) for 48 h. On plastic, AII induced only a 1.6-fold increase in [3H]thymidine incorporation, but on fibronectin- or type I collagen-coated plastic, the response to AII was enhanced from two- to fourfold. On a type I collagen-coated silicone elastomer, to which mechanical strain was applied, [3H]thymidine incorporation dramatically increased to a maximum of 53-fold. Dup 753 (10(-5) M) blocked the AII-induced increase in DNA synthesis. AI also increased DNA synthesis in VSM cells, and this response was also enhanced by mechanical strain. Mitogenic activity of AI was blocked by ramiprilat (10(-5) M), indicating that its mitogenic activity was via conversion to AII. The synergy between AII and strain was completely eliminated by neutralizing antibodies to PDGF AB (3 micrograms/ml). Furthermore, the mitogenic effect of AII in unstrained cells was also synergistic with submaximal concentrations of PDGF AB (1 ng/ml). Thus, the synergy between AII and mechanical strain probably results from synergism between AII and PDGF secreted in response to strain.

Authors

K Sudhir, E Wilson, K Chatterjee, H E Ives

Upregulated expression and function of integrin adhesive receptors in systemic lupus erythematosus patients with vasculitis.

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Abstract

Upregulation of integrin adhesive receptors has been implicated in various pathological conditions. We examined expression and function of integrin adhesive receptors on peripheral blood lymphocytes from patients with systemic lupus erythematosus (SLE), particularly those with the complication of vasculitis, and found that VLA-4 and LFA-1 expression was increased in SLE patients with vasculitis, while LFA-1 but not VLA-4 expression was increased in those without vasculitis. These results suggested a role of VLA-4 in the pathogenesis of vasculitis in SLE. Functional studies further demonstrated that adhesion to cytokine-activated human umbilical cord vein endothelial cells and to the CS-1 alternatively spliced domain of fibronectin was significantly increased in SLE patients with vasculitis. Analysis of the functional epitopes on the alpha 4 chain demonstrated that antigen densities of all the functional epitopes were increased in those with vasculitis, indicating that the increased expression of VLA-4 resulted from the increased number of VLA-4 molecules, and was not secondary to an increase in one particular functional epitope. Immunoprecipitation studies further support these results. Interestingly, high molecular weight bands associated with VLA-4 were observed in about half of the SLE patients with vasculitis. These results introduce a possibility that upregulation of integrin adhesive receptors has a potential role in the pathogenesis of vasculitis in SLE.

Authors

T Takeuchi, K Amano, H Sekine, J Koide, T Abe

Endothelial cell Ca2+ increases upon tumor cell contact and modulates cell-cell adhesion.

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Abstract

The signal transduction mechanisms involved in tumor cell adhesion to endothelial cells are still largely undefined. The effect of metastatic murine melanoma cell and human prostate carcinoma cell contact on cytosolic [Ca2+] of bovine artery endothelial cells was examined in indo-1-loaded endothelial cell monolayers. A rapid increase in endothelial cell [Ca2+] occurred on contact with tumor cells, but not on contact with 8-microns inert beads. A similar increase in endothelial cell [Ca2+] was observed with human neutrophils or monocyte-like lymphoma cells, but not with endothelial cells, red blood cells, and melanoma cell-conditioned medium. The increase in endothelial cell [Ca2+] was not inhibited by extracellular Ca2+ removal. In contrast, endothelial cell pretreatment with thapsigargin, which releases endoplasmic reticulum Ca2+ into the cytosol and depletes this Ca2+ store site, abolished the cytosolic [Ca2+] rise upon melanoma cell contact. Endothelial cell pretreatment with the membrane-permeant form of the Ca2+ chelator bis-(O-aminophenoxyl)ethane-N,N,N',N'-tetraacetic acid blocked the increase in cytosolic [Ca2+]. Under static and dynamic flow conditions (0.46 dyn/cm2) bis-(O-aminophenoxyl)ethane-N,N,N',N'-tetraacetic acid pretreatment of bovine pulmonary artery endothelial cell monolayers inhibited melanoma cell adhesion to the endothelial cells. Thus, tumor cell contact with endothelial cells induces a rapid Ca2+ release from endothelial intracellular stores, which has a functional role in enhancing cell-cell adhesion.

Authors

R Pili, S Corda, A Passaniti, R C Ziegelstein, A W Heldman, M C Capogrossi

Gray platelet syndrome. Dissociation between abnormal sorting in megakaryocyte alpha-granules and normal sorting in Weibel-Palade bodies of endothelial cells.

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Abstract

The gray platelet syndrome (GPS) is a rare congenital bleeding disorder in which megakaryocytes and platelets are deficient in alpha-granule secretory proteins. Since the Weibel-Palade bodies (WPB) of endothelial cells as well as the alpha-granules contain the von Willebrand Factor (vWF) and P-selectin, we examined by transmission electron microscopy the dermis capillary network of two patients with GPS. Endothelial cells showed the presence of normal WPB with typical internal tubules. Using single and double immunogold labeling for vWF and P-selectin, we detected vWF within WPB, where it was codistributed with the tubules, whereas P-selectin delineated the outline of WPB. Therefore, the fundamental targeting defect in GPS is specific to the megakaryocytic cell line.

Authors

J Gebrane-Younès, E M Cramer, L Orcel, J P Caen

Transgenic mice expressing high plasma concentrations of human apolipoprotein B100 and lipoprotein(a).

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Abstract

The B apolipoproteins, apo-B48 and apo-B100, are key structural proteins in those classes of lipoproteins considered to be atherogenic [e.g., chylomicron remnants, beta-VLDL, LDL, oxidized LDL, and Lp(a)]. Here we describe the development of transgenic mice expressing high levels of human apo-B48 and apo-B100. A 79.5-kb human genomic DNA fragment containing the entire human apo-B gene was isolated from a P1 bacteriophage library and microinjected into fertilized mouse eggs. 16 transgenic founders expressing human apo-B were generated, and the animals with the highest expression had plasma apo-B100 levels nearly as high as those of normolipidemic humans (approximately 50 mg/dl). The human apo-B100 in transgenic mouse plasma was present largely in lipoproteins of the LDL class as shown by agarose gel electrophoresis, chromatography on a Superose 6 column, and density gradient ultracentrifugation. When the human apo-B transgenic founders were crossed with transgenic mice expressing human apo(a), the offspring that expressed both transgenes had high plasma levels of human Lp(a). Both the human apo-B and Lp(a) transgenic mice will be valuable resources for studying apo-B metabolism and the role of apo-B and Lp(a) in atherosclerosis.

Authors

M F Linton, R V Farese Jr, G Chiesa, D S Grass, P Chin, R E Hammer, H H Hobbs, S G Young

Rolling and adhesion of human tumor cells on vascular endothelium under physiological flow conditions.

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Abstract

We investigated the interaction of different human tumor types with resting and IL-1-activated human umbilical vein endothelial cells under laminar flow conditions using a parallel plate flow chamber. Three tumor cell lines (the HT-29M colon carcinoma, the OVCAR-3 ovarian carcinoma, and the T-47D breast carcinoma) showed limited adhesion to unstimulated endothelial cells at any of the shear stress levels tested, while rolling and massive adhesion of tumor cells were observed on IL-1-activated endothelial cells. Three other tumor cell lines (the A375M and A2058 melanomas and the MG-63 osteosarcoma) did not adhere on resting endothelial cells at high shear stress (> 1.5 dyn/cm2) and started to adhere with decreasing shear stress; the number of adherent cells increased steeply on IL-1-activated endothelial cells, but no cell rolling was observed even at the highest shear stress. These mechanisms of tumor cell interaction with endothelial cells were analyzed in detail using the HT-29M colon carcinoma and the A375M melanoma. Incubation of activated endothelial cells with a monoclonal antibody against E-selectin inhibited rolling and adhesion of HT-29M, but had no effect on the adhesion of A375M cells; monoclonal antibody against vascular cell adhesion molecule-1 reduced the adhesion of A375M cells and had no effect on HT-29M. The selective interaction of these two molecules with tumor cells was confirmed by measuring the adhesion of tumor cells on immobilized soluble proteins. On E-selectin-coated surfaces, HT-29M cells rolled during perfusion experiments without subsequent adhesion, while A375M cells did not adhere. On vascular cell adhesion molecule-1-coated surfaces, HT-29M cells neither adhered nor rolled, while A375M cells adhered massively without rolling. Under flow conditions, therefore, cells from different tumor types interact with the endothelial surface by different mechanisms, depending on adhesion molecules expressed on the tumor and endothelial cell surface.

Authors

R Giavazzi, M Foppolo, R Dossi, A Remuzzi

Nonenzymatic glycosylation-induced modifications of intact bovine kidney tubular basement membrane.

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Abstract

We examined structural changes in bovine kidney tubular basement membrane (TBM) following in vitro nonenzymatic glycosylation (NEG). Isolated TBM was incubated for 2 wk at 37 degrees C in the absence of sugar or in the presence of either glucose or ribitol under conditions that minimized degradation and oxidative damage. NEG and crosslink formation in glycated TBM were confirmed by decreased solubility, increased amounts of low mobility material by SDS-PAGE, and increased specific fluorescence compared to controls. Morphological analysis using high resolution, low voltage scanning electron microscopy (LV-SEM) revealed a complex three-dimensional meshwork of interconnecting strands with intervening openings. Glycated TBM underwent distinct morphological changes, including a 58% increase in the amount of image surface area occupied by openings. This was due to an apparent increase in the number of large openings (diameters > 12.5 nm), whereas the number of small openings (diameters < 12.5 nm) remained unchanged. These findings corroborate earlier physiological studies, which established that the loss of glomerular permselectivity seen in patients with diabetic nephropathy is due to the formation of large pores in the kidney filtration barrier of which the BM is a major component. We conclude that NEG and crosslink formation among BM components lead to modifications of BM ultrastructure, which could play a role in loss of barrier function in diabetic microangiopathy and nephropathy.

Authors

S S Anderson, E C Tsilibary, A S Charonis

Nitric oxide mediates interleukin-1-induced cellular cytotoxicity in the rat ovary. A potential role for nitric oxide in the ovulatory process.

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Abstract

Treatment of primary cultures of rat ovarian dispersates with IL-1 beta results in morphologic and cytotoxic changes, thought to reflect tissue remodeling events associated with ovulation. We examined the role that the free radical nitric oxide plays in this process and report that IL-1 beta induces expression of the inducible isoform of nitric oxide synthase in ovarian cells as demonstrated by immunoprecipitation. We show that IL-1 beta treatment results in the formation of nitric oxide (as measured by accumulation of nitrite and cGMP) in both a time- and concentration-dependent manner that is prevented by aminoguanidine, a selective inhibitor of the inducible isoform of nitric oxide synthase. Aminoguanidine also inhibits IL-1-induced ovarian cellular cytotoxicity. These results suggest that nitric oxide is an important mediator of cell death and may act as a physiologically significant mediator of tissue remodeling events that occur in vivo during the ovulatory process.

Authors

C Ellman, J A Corbett, T P Misko, M McDaniel, K P Beckerman