Probing the depths of degradation: matrix metalloproteinase-2 and endometrial menstrual breakdown.

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Authors

L A Liotta

Biological insights through genomics: mouse to man.

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Authors

E M Rubin, G S Barsh

Role of transiently altered sarcolemmal membrane permeability and basic fibroblast growth factor release in the hypertrophic response of adult rat ventricular myocytes to increased mechanical activity in vitro.

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One of the trophic factors that has been implicated in initiating or facilitating growth in response to increased mechanical stress in several tissues and cell types is basic fibroblast growth factor (bFGF; FGF-2). Although mammalian cardiac muscle cells express bFGF, it is not known whether it plays a role in mediating cardiac adaptation to increased load, nor how release of the cytosolic 18-kD isoform of bFGF would be regulated in response to increased mechanical stress. To test the hypothesis that increased mechanical activity induces transient alterations in sarcolemmal permeability that allow cytosolic bFGF to be released and subsequently to act as an autocrine and paracrine growth stimulus, we examined primary isolates of adult rat ventricular myocytes maintained in serum-free, defined medium that were continually paced at 3 Hz for up to 5 d. Paced myocytes, but not nonpaced control cells, exhibited a "hypertrophic" response, which was characterized by increases in the rate of phenylalanine incorporation, total cellular protein content, and cell size. These changes could be mimicked in control cells by exogenous recombinant bFGF and could be blocked in continually paced cells by a specific neutralizing anti-bFGF antibody. In addition, medium conditioned by continually paced myocytes contained significantly more bFGF measured by ELISA and more mitogenic activity for 3T3 cells, activity that could be reduced by a neutralizing anti-bFGF antibody. The hypothesis that transient membrane disruptions sufficient to allow release of cytosolic bFGF occur in paced myocytes was examined by monitoring the rate of uptake into myocytes from the medium of 10-kD dextran linked to fluorescein. Paced myocytes exhibited a significantly higher rate of fluoresceinlabeled dextran uptake. These data are consistent with the hypothesis that nonlethal, transient alterations in sarcolemmal membrane permeability with release of cytosolic bFGF is one mechanism by which increased mechanical activity could lead to a hypertrophic response in cardiac myocytes.

Authors

D Kaye, D Pimental, S Prasad, T Mäki, H J Berger, P L McNeil, T W Smith, R A Kelly

Regulation of rat hepatic low density lipoprotein receptors. In vivo stimulation by growth hormone is not mediated by insulin-like growth factor I.

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Growth hormone (GH) has an important role in the regulation of hepatic LDL receptor expression and plasma lipoprotein levels. This investigation was undertaken to evaluate if these effects of GH on hepatic LDL receptors are direct or mediated by insulin-like growth factor I (IGF-I). Two models were studied in which substitution with GH is important for the regulation of hepatic LDL receptors: hypophysectomized rats receiving high-dose ethynylestradiol or challenge with dietary cholesterol. The hypophysectomized rats were hormonally substituted by infusion with dexamethasone and L-thyroxine, and either GH or IGF-I. In both models, GH was essential for maintaining normal expression of LDL receptors. In contrast, despite fully normalized plasma levels, IGF-I did not support the expression of hepatic LDL receptors. Analysis of plasma lipoproteins revealed that substitution with GH, but not with IGF-I, reduced LDL and intermediate density lipoproteins. In addition, determination of hepatic mRNA levels for apo B-100 and apo B-48 indicated that GH may be more effective than IGF-I in the promotion of apo B mRNA editing. In conclusion, GH has specific effects on hepatic LDL receptor expression and plasma lipoprotein levels that are not mediated by IGF-I.

Authors

M Rudling, H Olivecrona, G Eggertsen, B Angelin

Insulin-like growth factor-1 is a potent neuronal rescue agent after hypoxic-ischemic injury in fetal lambs.

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This study was designed to determine the potential of IGF-1 as a neuronal rescue agent after cerebral ischemia. Unanesthetized late gestation fetal sheep were subjected to 30-min cerebral ischemia by inflation of carotid artery occluder cuffs. 2 h later either 0.1 microgram rhIGF-1, 1 microgram rhIGF-1, 10 micrograms rhIGF-1, or vehicle was infused into a lateral cerebral ventricle over 1 h. Histologic outcome was assessed 5 d later. Overall neuronal loss was reduced with 0.1 microgram (P < 0.05) and 1 microgram (P < 0.002) rhIGF-1, but treatment with 10 micrograms was not effective. With 1 microgram rhIGF-1 neuronal loss scores were significantly lower in brain regions examined including cortex, hippocampus, and striatum, whereas with 0.1 microgram rhIGF-1 the parietal cortex and thalamus were not improved and the improvement seen in other regions was less than with 1 microgram rhIGF-1. Treatment with 1 microgram rhIGF-1 also delayed the onset of seizures and reduced their incidence. Moreover, the secondary phase of cytotoxic edema was reduced and delayed in onset. We conclude that low dose rhIGF-1 therapy promotes neuronal rescue after cerebral hypoxic-ischemic injury in utero, but the effect is dose dependent. Importantly, rhIGF-1 is effective and nontoxic when administered 2 h after the hypoxic ischemic insult. This distinguishes IGF-1 from most other neuroprotective therapies and suggests clinical application may be possible.

Authors

B M Johnston, E C Mallard, C E Williams, P D Gluckman

Recombinant interferon-alpha selectively inhibits the production of interleukin-5 by human CD4+ T cells.

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The effects of recombinant IFN-alpha on the production of IL-5 by human CD4+ T cells were first analyzed on resting CD4+ T cells purified from normal PBMC and stimulated either with a combination of PMA and anti-CD28 mAb or anti-CD3 mAb cross-linked on B7-1/CD32-transfected mouse fibroblasts. We found that IFN-alpha profoundly inhibited in a dose-dependent manner IL-5 production by resting CD4+ T cells whereas IL-10 was upregulated in both systems. The addition of a neutralizing anti-IL-10 mAb to PMA and anti-CD28 mAb upregulated IL-5 production by resting CD4+ T cells but did not prevent IFN-alpha-induced IL-5 inhibition. We then analyzed the effect of IFN-alpha on the production of cytokines by differentiated type 2 helper (Th2) CD4+CD3- cells isolated from peripheral blood of two patients with the hypereosinophilic syndrome. In both cases, IFN-alpha markedly inhibited IL-5 production while it induced mild upregulation of IL-4 and IL-10. Finally, the inhibitory effect of IFN-alpha on IL-5 production was confirmed on a panel of Th2 and Th0 clones generated in vitro. In 2 out of 6 clones, IL-5 inhibition was associated with upregulation of IL-4 and IL-10. We conclude that IFN-alpha selectively downregulates IL-5 synthesis by human CD4+ T cells.

Authors

L Schandené, G F Del Prete, E Cogan, P Stordeur, A Crusiaux, B Kennes, S Romagnani, M Goldman

Functional expression of Fas and Fas ligand on human gut lamina propria T lymphocytes. A potential role for the acidic sphingomyelinase pathway in normal immunoregulation.

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The expression and function of Fas (CD95/APO-1), a cell surface receptor directly responsible for triggering cell death by apoptosis, was investigated on human T lymphocytes resident within the intestinal lamina propria, a major site of antigen challenge and persistent lymphocyte activation. Three color immunofluorescence and FACS analysis indicated that virtually all freshly isolated human gut lamina propria T lymphocytes (T-LPL) express Fas, together with the marker of progress activation CD45R0. A discrete fraction of freshly isolated T-LPL also constitutively expressed Fas ligand (FasL), perhaps as a result of recent in vivo activation. Importantly, whereas Fas cross-linking did not result in apoptosis induction in peripheral blood T lymphocytes (T-PBL), Fas was found to be fully effective in generating the apoptotic signal in T-LPL. This was associated with the activation of an acidic sphingomyelinase and with ceramide generation, early events known to be involved in Fas-mediated apoptotic signaling. By contrast, acidic sphingomyelinase activation and ceramide production were not detectable in T-PBL after Fas cross-linking. However C2-ceramide, a cell permeant synthetic analog of ceramide, could efficiently induce apoptosis in T-LPL and T-PBL when added exogenously. These data indicate that T-LPL constitutively express both Fas and FasL and that Fas cross-linking generates signals resulting in sphingomyelin hydrolysis and apoptosis, outlining a potential mechanism involved in intestinal tolerance. Moreover, they provide the first evidence of a role for ceramide-mediated pathways in normal immunoregulation.

Authors

R De Maria, M Boirivant, M G Cifone, P Roncaioli, M Hahne, J Tschopp, F Pallone, A Santoni, R Testi

Dynamics of viral replication in infants with vertically acquired human immunodeficiency virus type 1 infection.

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About one-third of vertically HIV-1 infected infants develop AIDS within the first months of life; the remainder show slower disease progression. We investigated the relationship between the pattern of HIV-1 replication early in life and disease outcome in eleven infected infants sequentially studied from birth. Viral load in cells and plasma was measured by highly sensitive competitive PCR-based methods. Although all infants showed an increase in the indices of viral replication within their first weeks of life, three distinct patterns emerged: (a) a rapid increase in plasma viral RNA and cell-associated proviral DNA during the first 4-6 wk, reaching high steady state levels (> 1,000 HIV-1 copies/10(5) PBMC and > 1,000,000 RNA copies/ml plasma) within 2-3 mo of age; (b) a similar initial rapid increase in viral load, followed by a 2.5-50-fold decline in viral levels; (c) a significantly lower (> 10-fold) viral increase during the first 4-6 wk of age. All infants displaying the first pattern developed early AIDS, while infants with slower clinical progression exhibited the second or third pattern. These findings demonstrate that the pattern of viral replication and clearance in the first 2-3 mo of life is strictly correlated with, and predictive of disease evolution in vertically infected infants.

Authors

A De Rossi, S Masiero, C Giaquinto, E Ruga, M Comar, M Giacca, L Chieco-Bianchi

Antigen targeting to myeloid-specific human Fc gamma RI/CD64 triggers enhanced antibody responses in transgenic mice.

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Besides their phagocytic effector functions, myeloid cells have an essential role as accessory cells in the induction of optimal humoral immune responses by presenting captured antigens and activating lymphocytes. Antigen presentation by human monocytes was recently found to be enhanced in vitro through the high-affinity Fc receptor for IgG (Fc gamma RI; CD64), which is exclusively present on myeloid cells. To evaluate a comparable role of Fc gamma RI in antigen presentation in vivo, we generated human Fc gamma RI transgenic mice. Under control of its endogenous promoter, human Fc gamma RI was selectively expressed on murine myeloid cells at physiological expression levels. As in humans, expression was properly regulated by the cytokines IFN-gamma, G-CSF, IL-4, and IL-10, and was up-regulated during inflammation. The human receptor expressed by murine macrophages bound monomeric human IgG and mediated particle phagocytosis and IgG complex internalization. To evaluate whether specific targeting of antigens to Fc gamma RI can induce enhanced antibody responses, mice were immunized with an anti-human Fc gamma RI antibody containing antigenic determinants. Transgenic mice produced antigen-specific antibody responses with high IgG1 titers and substantial IgG2a and IgG2b responses. These data demonstrate that human Fc gamma RI on myeloid cells is highly active in mediating enhanced antigen presentation in vivo, and show that anti-Fc gamma RI mAbs are promising vaccine adjuvants.

Authors

I A Heijnen, M J van Vugt, N A Fanger, R F Graziano, T P de Wit, F M Hofhuis, P M Guyre, P J Capel, J S Verbeek, J G van de Winkel

Energy-ubiquitin-dependent muscle proteolysis during sepsis in rats is regulated by glucocorticoids.

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Recent studies suggest that sepsis-induced increase in muscle proteolysis mainly reflects energy-ubiquitin-dependent protein breakdown. We tested the hypothesis that glucocorticoids activate the energy-ubiquitin-dependent proteolytic pathway in skeletal muscle during sepsis. Rats underwent induction of sepsis by cecal ligation and puncture or were sham-operated and muscle protein breakdown rates were measured 16 h later. The glucocorticoid receptor antagonist RU 38486 or vehicle was administered to groups of septic and sham-operated rats. In other experiments, dexamethasone (2.5 or 10 mg/kg) was injected subcutaneously in normal rats. Total and myofibrillar proteolysis was determined in incubated extensor digitorum longus muscles as release of tyrosine and 3-methylhistidine, respectively. Energy-dependent proteolysis was determined in incubated muscles depleted of energy with 2-deoxyglucose and 2,4-dinitrophenol. Levels of muscle ubiquitin mRNA and free and conjugated ubiquitin were determined by Northern and Western blot, respectively. RU 38486 inhibited the sepsis-induced increase in total and myofibrillar energy-dependent protein breakdown rates and blunted the increase in ubiquitin mRNA levels and free ubiquitin. Some, but not all, sepsis-induced changes in ubiquitin protein conjugates were inhibited by RU 38486. Injection of dexamethasone in normal rats increased energy-dependent proteolysis and ubiquitin mRNA levels. The results suggest that glucocorticoids regulate the energy-ubiquitin-dependent proteolytic pathway in skeletal muscle during sepsis.

Authors

G Tiao, J Fagan, V Roegner, M Lieberman, J J Wang, J E Fischer, P O Hasselgren

Modifications of myelin basic protein in DM20 transgenic mice are similar to those in myelin basic protein from multiple sclerosis.

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Transgenic mice containing different numbers of transgenes (2-70) of the myelin proteolipid protein DM20 were phenotypically normal up to 3 mo of age, after which the mice containing 70 copies of the transgene spontaneously demyelinated and died at 10-12 mo. Since we demonstrated that demyelination in multiple sclerosis involved specific chemical changes in myelin basic protein (MBP), we investigated the MBP in our transgenic line for similar changes. Both the total amount of MBP in brain and the MBP mRNA levels were unaffected at the different ages. All the isoforms (14-21 kD) of MBP were present, but the microheterogeneity (a posttranslational event) was changed resulting in a higher proportion of the less cationic components reminiscent of the changes in MBP found in multiple sclerosis. An increased amount of the citrullinated form of MBP was found by Western blot analysis. Immunogold labeling of cryosections of brain revealed a greater density of particles with the anticitrulline antibody at 10 mo and that the levels of peptidylarginine deiminase (which deiminates protein-bound arginine to citrulline) were increased. This stable transgenic line represents a useful animal model for the human disease multiple sclerosis.

Authors

F G Mastronardi, B Mak, C A Ackerley, B I Roots, M A Moscarello

A novel Escherichia coli lipid A mutant that produces an antiinflammatory lipopolysaccharide.

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A unique screen was used to identify mutations in Escherichia coli lipid A biosynthesis that result in a decreased ability to stimulate E-selectin expression by human endothelial cells. A mutation was identified in the msbB gene of E. coli that resulted in lipopolysaccharide (LPS) that lacks the myristoyl fatty acid moiety of the lipid A. Unlike all previously reported lipid A mutants, the msbB mutant was not conditionally lethal for growth. Viable cells or purified LPS from an msbB mutant had a 1000-10,000-fold reduction in the ability to stimulate E-selectin production by human endothelial cells and TNF alpha production by adherent monocytes. The cloned msbB gene was able to functionally complement the msbB mutant, restoring both the LPS to its native composition and the ability of the strain to stimulate immune cells. Nonmyristoylated LPS acted as an antagonist for E-selectin expression when mixed with LPS obtained from the parental strain. These studies demonstrate a significant role for the myristate component of LPS in immune cell activation and antagonism. In addition, the msbB mutant allowed us to directly examine the crucial role that the lipid A structure plays when viable bacteria are presented to host defense cells.

Authors

J E Somerville Jr, L Cassiano, B Bainbridge, M D Cunningham, R P Darveau

Endothelin-3 induces hypertrophy of cardiomyocytes by the endogenous endothelin-1-mediated mechanism.

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We have recently reported that endothelin-1 (ET-1) mediates angiotensin II-induced hypertrophy of cardiomyocytes as an autocrine/paracrine factor. In the present study, we examined whether endothelin-3 (ET-3) induces hypertrophy of cultured neonatal rat cardiomyocytes and whether endogenous ET-1 mediates this effect. ET-3 (10(-7) M) increased the cell surface area of cardiomyocytes after 48 h. ET-3 dose dependently (10(-9)-10(-7) M) stimulated protein synthesis as evaluated by [3H]leucine incorporation; the maximum response was 1.4-fold increase over the control at 10(-7) M. Since the response of cardiac hypertrophy is characterized by enhanced expression of fetal isoforms of muscle specific genes, the effect of ET-3 on steady state levels of mRNA for skeletal alpha-actin was evaluated by Northern blot analysis. ET-3 (10(-9)-10(-7) M) increased mRNA level for skeletal alpha-actin with a maximum response after 6 h. ET-3-induced [3H]leucine incorporation, skeletal alpha-actin mRNA and cell surface area were inhibited by a synthetic ETB receptor antagonist (BQ788). Interestingly, ET-3-induced skeletal alpha-actin gene expression and [3H]leucine incorporation were inhibited by a synthetic ETA receptor antagonist (BQ123) as well as by antisense oligonucleotides against peproET-1 mRNA. ET-3 (10(-7) M) transiently increased mRNA levels for ET-1 peaking at 30 min and stimulated the release of immunoreactive ET-1 from cardiomyocytes. These results suggest that endogenous ET-1 locally generated and secreted by cardiomyocytes may contribute to ET-3-induced cardiac hypertrophy as an autocrine/paracrine factor.

Authors

M Tamamori, H Ito, S Adachi, H Akimoto, F Marumo, M Hiroe

A nonsense mutation in the erythrocyte band 3 gene associated with decreased mRNA accumulation in a kindred with dominant hereditary spherocytosis.

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We studied a French kindred with typical hereditary spherocytosis (HS). Studies of erythrocytes and erythrocyte membranes from HS individuals revealed abnormal erythrocyte membrane mechanical stability as well as 15-20% deficiency of band 3, the anion transporter. Anion transport studies of red cells from two affected individuals revealed decreased sulfate flux. Nucleotide sequence of cDNA encoding the distal third of the cytoplasmic domain and the entire transmembrane domain of band 3 obtained by RT-PCR of reticulocyte RNA of an affected family member was normal. Sequence analysis of genomic DNA from an HS individual identified a nonsense mutation of the band 3 gene, Q330X, near the end of the band 3 cytoplasmic domain. This mutation was present in genomic DNA of all HS family members and absent in DNA of unaffected family members. Using an RT-PCR-based assay, a marked quantitative decrease in accumulation of the mutant band 3 RNA was detected. Thus the codon 330 nonsense mutation is responsible for the decreased accumulation of mutant band 3 RNA and the deficiency of band 3 protein in this kindred. These results have important implications for the role of band 3 defects in the membrane pathobiology of HS as well as for the techniques used in detection of HS mutations.

Authors

P B Jenkins, G K Abou-Alfa, D Dhermy, E Bursaux, C Féo, A L Scarpa, S E Lux, M Garbarz, B G Forget, P G Gallagher

In vitro and in vivo effects of leukotriene B4 antagonism in a primate model of asthma.

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To test the hypothesis that leukotriene (LT) B4 antagonists may be clinically useful in the treatment of asthma, CP-105,696 was evaluated in vitro, using chemotaxis and flow cytometry assays, and in vivo, using a primate asthma model. CP-105,696 inhibited LTB4-mediated monkey neutrophil chemotaxis (isolated cells, LTB4 = 5 nM) and CD11b upregulation (whole blood, LTB4 = 100 nM) with IC50 values of 20 nM and 16.5 microM, respectively. Using a modification of a previously described in vivo protocol (Turner et al. Am. J. Respir. Crit. Care Med. 1994. 149: 1153-1159), we observed that treatment with CP-105,696 inhibited the acute increase in bronchoalveolar lavage (BAL) levels of IL-6 and IL-8 by 56.9 +/- 13.2% and 46.9 +/- 14.5%, respectively, 4 h after challenge with Ascaris suum antigen (Ag). CP-105,696 tended to reduce the increase in BAL protein levels 0.5 h after Ag challenge by 47.5 +/- 18.3%, but this was not statistically significant. In addition, CP-105,696 prevented the significant 11-fold increase in airway responsiveness to methacholine after multiple Ag challenge. These results suggest that LTB4 partially mediates acute and chronic responses to antigen in an experimental primate asthma model and support the clinical evaluation of LTB4 antagonists in human asthma.

Authors

C R Turner, R Breslow, M J Conklyn, C J Andresen, D K Patterson, A Lopez-Anaya, B Owens, P Lee, J W Watson, H J Showell

Regulation of transforming growth factor-beta 1 expression by the hepatitis B virus (HBV) X transactivator. Role in HBV pathogenesis.

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TGF-beta 1 has been implicated in the pathogenesis of liver disease. The high frequency of detection of the hepatitis B virus X (HBx) antigen in liver cells from patients with chronic hepatitis, cirrhosis, and liver cancer suggested that expression of HBx and TGF-beta 1 may be associated. To test this possibility, we examined the expression of TGF-beta 1 in the liver of transgenic mice expressing the HBx gene. We show that the patterns of expression of TGF-beta 1 and Hbx protein are similar in these mice and that HBx activates transcription of the TGF-beta 1 gene in transfected hepatoma cells. The cis-acting element within the TGF-beta 1 gene that is responsive to regulation by Hbx is the binding site for the Egr family of transcription factors. We further show that the Egr-1 protein associates with the HBx protein, allowing HBx to participate in the transcriptional regulation of immediate-early genes. Our results suggest that expression of Hbx might induce expression of TGF-beta 1 in the early stages of infection and raise the possibility that TGF-beta 1 may play a role in hepatitis B virus pathogenesis.

Authors

Y D Yoo, H Ueda, K Park, K C Flanders, Y I Lee, G Jay, S J Kim

Bone mineralization in an osteogenesis imperfecta mouse model studied by small-angle x-ray scattering.

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We have studied the size and orientation of mineral crystals in cortical bone of oim/oim mice, which are known to produce only alpha 1(I) collagen homotrimers and which may serve as a model for human osteogenesis imperfecta. Long bones (femur and tibia) from young (5 wk old) oim/oim mice and from unaffected heterozygous counterparts were investigated by small-angle x-ray scattering (SAXS), which is sensitive to structures smaller than 50 nm. Mineral crystals were compared in terms of their thickness and their alignment with respect to the long bone axis. While electron microscopic tomography has recently shown the existence of large mineral blocks (with all dimensions typically exceeding 50 nm) in mineralized tendons of oim/oim mice, SAXS revealed a family of thin, possibly needle-like, crystals in cortical bone. These crystals were similar in shape to those observed previously in normal mice, but they were thinner and less well aligned in oim/oim mice relative to heterozygotes. Moreover, the crystal thickness and their alignment with the bone axis were more variable in oim/oim bone, with a close correlation (r = 0.94, P < 0.001) between the two parameters. The presence of smaller crystals with more variable alignment in corticalis of oim/oim mice may contribute to the brittleness of their bone, similar to that of human osteogenesis imperfecta.

Authors

P Fratzl, O Paris, K Klaushofer, W J Landis

Thrombospondin-1, an inhibitor of angiogenesis, is regulated by progesterone in the human endometrium.

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Thrombospondin-1 (TSP1), a multifunctional extracellular matrix glycoprotein, has been shown to suppress the angiogenic response in vivo and in vitro. We hypothesized that TSP1 might play a role in the inhibition of capillary morphogenesis during the endometrial cycle and examined its expression in 46 human endometrial specimens. Our results show that the expression of TSP1 in the endometrium is (a) cycle-dependent, (b) associated with periods of low capillary growth, and (c) regulated by progesterone. TSP1 protein was identified in the basement membrane of capillaries of the functional endometrium during the secretory phase. Abundant expression of TSP1 mRNA in the secretory phase was also detected by in situ hybridization, in contrast to the low levels seen in the proliferative phase. These findings were confirmed by Northern analysis of proliferative and secretory endometrium. Transcripts for TSP1 were observed predominantly in stromal cells, but signal was also detected in some endothelial and smooth muscle cells. Since the proliferation of endometrial tissue is regulated by steroid hormones, we tested the effects of estrogen and progesterone on TSP1 expression by stromal cells isolated from human endometrium. We found that levels of TSP1 mRNA and protein were increased after incubation with progesterone. Maximal stimulation of mRNA was observed after 8 h of treatment with 10-50 microM progesterone, and the effect was suppressed by the progesterone antagonist RU-486. Induction by progesterone was cell-specific and equivalent to the stimulation mediated by PDGF. Finally, the levels of TSP1 present in progesterone-stimulated cultures were sufficient to inhibit the migration of endothelial cells in vitro; this effect was nullified by anti-TSP antibodies. We therefore propose that the production of TSP1 at later stages of the endometrial cycle is linked to the inhibition of vessel formation and that TSP1 expression is progesterone-dependent in this tissue.

Authors

M L Iruela-Arispe, P Porter, P Bornstein, E H Sage

Agmatine, a bioactive metabolite of arginine. Production, degradation, and functional effects in the kidney of the rat.

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Until recently, conversion of arginine to agmatine by arginine decarboxylase (ADC) was considered important only in plants and bacteria. In the following, we demonstrate ADC activity in the membrane-enriched fraction of brain, liver, and kidney cortex and medulla by radiochemical assay. Diamine oxidase, an enzyme shown here to metabolize agmatine, was localized by immunohistochemistry in kidney glomeruli and other nonrenal cells. Production of labeled agmatine, citrulline, and ornithine from [3H]arginine was demonstrated and endogenous agmatine levels (10(-6)M) in plasma ultrafiltrate and kidney were measured by HPLC. Microperfusion of agmatine into renal interstitium and into the urinary space of surface glomeruli of Wistar-Frömter rats produced reversible increases in nephron filtration rate (SNGFR) and absolute proximal reabsorption (APR). Renal denervation did not alter SNGFR effects but prevented APR changes. Yohimbine (an alpha 2 antagonist) microperfusion into the urinary space produced opposite effects to that of agmatine. Microperfusion of urinary space with BU-224 (microM), a synthetic imidazoline2 (I2) agonist, duplicated agmatine effects on SNGFR but not APR whereas an I1 agonist had no effect. Agmatine effects on SNGFR and APR are not only dissociable but appear to be mediated by different mechanisms. The production and degradation of this biologically active substance derived from arginine constitutes a novel endogenous regulatory system in the kidney.

Authors

M J Lortie, W F Novotny, O W Peterson, V Vallon, K Malvey, M Mendonca, J Satriano, P Insel, S C Thomson, R C Blantz

Rhinovirus stimulation of interleukin-6 in vivo and in vitro. Evidence for nuclear factor kappa B-dependent transcriptional activation.

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To further understand the biology of rhinovirus (RV), we determined whether IL-6 was produced during RV infections and characterized the mechanism by which RV stimulates lung cell IL-6 production. In contrast to normals and minimally symptomatic volunteers, IL-6 was detected in the nasal washings from patients who developed colds after RV challenge. RV14 and RV1A, major and minor receptor group RVs, respectively, were potent stimulators of IL-6 protein production in vitro. These effects were associated with significant increases in IL-6 mRNA accumulation and gene transcription. RV was also a potent stimulator of IL-6 promoter-driven luciferase activity. This stimulation was modestly decreased by mutation of the nuclear factor (NF)-IL-6 site and abrogated by mutation of the NF-kappa B site in this promoter. An NF-kappa B-DNA binding activity, mediated by p65, p50, and p52 NF-kappa B moieties, was rapidly induced in RV-infected cells. Activator protein 1-DNA binding was not similarly altered. These studies demonstrate that IL-6 is produced during symptomatic RV infections, that RVs are potent stimulators of IL-6 elaboration, and that RV stimulation IL-6 production is mediated by an NF-kappa B-dependent transcriptional stimulation pathway. IL-6 may play an important role in the pathogenesis of RV infection, and NF-kappa B activation is likely to be an important event in RV-induced pathologies.

Authors

Z Zhu, W Tang, A Ray, Y Wu, O Einarsson, M L Landry, J Gwaltney Jr, J A Elias

Detection of receptors for interleukin-6, interleukin-11, leukemia inhibitory factor, oncostatin M, and ciliary neurotrophic factor in bone marrow stromal/osteoblastic cells.

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The functional receptor complexes assembled in response to interleukin-6 and -11 (IL-6 and IL-11), leukemia inhibitory factor (LIF), oncostatin M (OSM), and ciliary neurotrophic factor (CNTF), all involve the signal transducer gp130: IL-6 and IL-11 induce homodimerization of gp130, while the rest heterodimerize gp130 with other gp130-related beta subunits. Some of these cytokines (IL-6, IL-11, and CNTF) also require a specificity-determining alpha subunit not directly involved in signaling. We have searched for functional receptor complexes for these cytokines in cells of the bone marrow stromal/osteoblastic lineage, using tyrosine phosphorylation of the beta subunits as a detection assay. Collectively, murine calvaria cells, bone marrow-derived murine cell lines (+/+LDA11 and MBA13.2), as well as murine (MC3T3-E1) and human (MG-63) osteoblast-like cell lines displayed all the previously recognized alpha and beta subunits of this family of receptors. However, individual cell types had different constellations of alpha and beta subunits. In addition and in difference to the other cell types examined, MC3T3-E1 cells expressed a heretofore unrecognized form of gp130; and MG-63 displayed an alternative form (type II) of the OSM receptor. These findings establish that stromal/osteoblastic cells are targets for the actions of all the members of the cytokine subfamily that shares the gp130 signal transducer; and suggest that different receptor repertoires may be expressed at different stages of differentiation of this lineage.

Authors

T Bellido, N Stahl, T J Farruggella, V Borba, G D Yancopoulos, S C Manolagas

Human endometrial matrix metalloproteinase-2, a putative menstrual proteinase. Hormonal regulation in cultured stromal cells and messenger RNA expression during the menstrual cycle.

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Proteinases are likely effectors of endometrial menstrual breakdown. We have investigated proteinase production by human endometrial stromal cells subjected in vitro to progesterone (P) withdrawal, the physiologic stimulus for menstruation. Culture media of cells exposed to estradiol, P, or estradiol plus P had low levels of proteolytic activity similar to cultures maintained in the absence of steroids. P withdrawal, or addition of RU486 to P-treated cultures, stimulated proteinase secretion. The stromal cell proteinase was characterized by gelatin zymography, inhibitor profile, and organomercurial activation, as a metalloproteinase present mostly as a 66-kD proenzyme with lower levels of a 62-kD active form. The P withdrawal-induced metalloproteinase was identified as matrix metalloproteinase-2 (MMP-2) by Western blotting. The increase of MMP-2 induced by P withdrawal was associated with the metalloproteinase-dependent breakdown of stromal cultures, involving dissolution of extracellular matrix and dissociation of stromal cells. Northern analysis showed the differential expression of MMP-2 mRNA in late secretory phase endometrium. These findings are consistent with the involvement of stromal cell-derived MMP-2 in the proteolysis of extracellular matrix promoting cyclic endometrial breakdown and the onset of menstrual bleeding.

Authors

J C Irwin, D Kirk, R B Gwatkin, M Navre, P Cannon, L C Giudice

Antisense oligodeoxynucleotides selectively suppress expression of the mutant alpha 2(I) collagen allele in type IV osteogenesis imperfecta fibroblasts. A molecular approach to therapeutics of dominant negative disorders.

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We are investigating the use of antisense oligodeoxynucleotides to selectively suppress expression of the mutant type I collagen allele in osteogenesis imperfecta (OI). In this report, we target a human collagen mutation in its natural cellular context. We used cultured fibroblasts from a case of type IV OI, in which the mutant alpha 2(I) allele produces mRNA with exon 16 deleted due to a point mutation in the splice donor site. Lipid-mediated transfection was used to deliver antisense, sense and missense phosphorothioates targeted to both the abnormal mRNA exon 15/17 junction and the nuclear level point mutation. Significant suppression of the mutant protein chain and mRNA was achieved with antisense oligonucleotide to both mRNA and nuclear levels. Mutant protein was suppressed to 44-47% and mutant alpha 2(I) mRNA to 37-43% of their levels in control cells, indicating decreased mRNA as the basis for suppression. Selectivity of mutant allele suppression was better with an mRNA target: suppression was sequence specific and normal mRNA was expressed at 79% of its level in untreated cells. With a nuclear target, significant suppression of mutant mRNA occurred not only with antisense and sense, but also with missense oligonucleotide, which suppressed mutant mRNA to 60% of its level in untreated cells. We also investigated the time course of suppression of protein and mRNA in response to a 4 h transfection of antisense oligonucleotide. From 24-72 h after transfection, mutant protein was suppressed to approximately 50% of its untreated level and suppression of mutant message was significantly greater than that of normal message. The suppression achieved in these studies is insufficient for clinical intervention, but our results provide support for further development of antisense therapy as an approach to the treatment of dominant negative disorders.

Authors

Q Wang, J C Marini

Hyperproinsulinemia is associated with increased beta cell demand after hemipancreatectomy in humans.

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Abstract

The cause of disproportionate hyperproinsulinemia in patients with type II diabetes is controversial. To examine whether increased beta cell demand might contribute, we measured proinsulin and insulin concentrations in clinically healthy humans who had undergone hemipancreatectomy for the purpose of organ donation, a procedure previously demonstrated to increase beta cell demand and diminish insulin secretory reserve capacity. Subjects were studied at least 1 yr after hemipancreatectomy. Seven donors were followed prospectively and serves as their own controls. Nine additional donors were matched with normal controls (cross-sectional group). Fasting serum concentrations of intact proinsulin and conversion intermediates (total) were measured by a two-step radioimmunoassay; independent determinations of intact proinsulin and 32,33 split proinsulin were performed using an immunoradiometric assay. Serum total proinsulin values were significantly greater in hemipancreatectomized groups than controls (prospective group: predonation = 6.24 +/- 1.14 pM, postdonation = 34.63 +/- 17.47 pM, P < 0.005; cross-sectional group: controls = 5.78 +/- 1.12 pM, donors = 15.22 +/- 5.20 pM, P < 0.025). The ratio of total proinsulin to immunoreactive insulin was directly correlated with fasting plasma glucose and showed a significant inverse relationship to secretory reserve capacity. Both absolute and relative hyperproinsulinemia is found in hemipancreatectomized donors. These data demonstrate that partial pancreatectomy with its associated increase in beta cell demand raises measures of proinsulin in humans.

Authors

E R Seaquist, S E Kahn, P M Clark, C N Hales, D Porte Jr, R P Robertson

Oxysterols present in atherosclerotic tissue decrease the expression of lipoprotein lipase messenger RNA in human monocyte-derived macrophages.

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Abstract

The presence of oxysterols in macrophages isolated from atherosclerotic tissue and the effect of oxysterols on the regulation of lipoprotein lipase (LPL) mRNA were studied. Both rabbit and human macrophages, freshly isolated from atherosclerotic aorta, show about the same distribution of oxysterols, analyzed by isotope dilution mass spectrometry, except that all three preparations of human arterial-derived macrophages contained high levels of 27-hydroxycholesterol, which was not found in rabbit macrophages. To determine if oxysterols regulate LPL expression, human monocyte-derived macrophages were incubated with different oxysterols. Incubation with 7 beta-hydroxycholesterol and 25-hydroxycholesterol resulted in a 70-75% reduction of LPL mRNA, analyzed by quantitative RT-PCR. Cholesterol and other tested oxysterols showed no effect on macrophage LPL mRNA expression compared with control. LPL activity in the medium was also reduced after exposure of the macrophages to 7 beta-hydroxycholesterol and 25-hydroxycholesterol. In conclusion, we have demonstrated accumulation of oxysterols in macrophage-derived foam cells isolated from atherosclerotic aorta. There was suppression of LPL mRNA in human monocyte-derived macrophages after incubation with 7 beta-hydroxycholesterol and 25-hydroxycholesterol. It is tempting to suggest that an exposure to oxysterols may explain our earlier observation of a low level of LPL mRNA in arterial foam cells.

Authors

L M Hultén, H Lindmark, U Diczfalusy, I Björkhem, M Ottosson, Y Liu, G Bondjers, O Wiklund

Hypoxia-induced paracrine regulation of vascular endothelial growth factor receptor expression.

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Abstract

Vascular endothelial growth factor (VEGF)/vascular permeability factor (VPF), an endothelial cell (EC)-specific mitogen, stimulates angiogenesis in vivo, particularly in ischemic regions. VEGF/VPF expression by cells of hypoxic tissues coincides with expression of its two receptors, KDR and flt-1, by ECs in the same tissues. We investigated whether hypoxia or hypoxia-dependent conditions operate in coordinating this phenomenon. Human umbilical vein and microvascular ECs were exposed to direct hypoxia or to medium conditioned (CM) by myoblasts maintained in hypoxia for 4 d. Control ECs were maintained in normoxia or normoxia-CM. Binding of 125I-VEGF to ECs was then evaluated. Hypoxic treatment of ECs had no effect on 125I-VEGF binding. However, treatment of ECs with hypoxia-CM produced a threefold increase in 125I-VEGF binding, with peak at 24 h (P < 0.001, ANOVA). Scatchard analysis disclosed that increased binding was due to a 13-fold increase in KDR receptors/cell, with no change in KDR affinity (Kd = 260 +/- 51 pM, normoxia-CM versus Kd = 281 +/- 94 pM, hypoxia-CM) and no change in EC number (35.6 +/- 5.9 x 10(3) ECs/cm2, normoxia-CM versus 33.5 +/- 5.5 x 10(3) ECs/cm2, hypoxia-CM). Similar results were obtained using CM from hypoxic smooth muscle cells. KDR upregulation was not prevented by addition to the hypoxia-CM of neutralizing antibodies against VEGF, tumor necrosis factor-alpha, transforming growth factor beta 1 or basic fibroblast growth factor. Similarly, addition of VEGF or lactic acid to the normoxia-CM had no effect on VEGF binding. We conclude that mechanism(s) initiated by hypoxia can induce KDR receptor upregulation in ECs. Hypoxic cells, normal or neoplastic, not only can produce VEGF/VPF, but can also modulate its effects via paracrine induction of VEGF/VPF receptors in ECs.

Authors

E Brogi, G Schatteman, T Wu, E A Kim, L Varticovski, B Keyt, J M Isner

IgA class switch in I alpha exon-deficient mice. Role of germline transcription in class switch recombination.

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Abstract

Studies have implicated defective Ig class switch in the pathogenesis of IgA deficiency. To understand better the molecular events that regulate IgA class switch, a 1.4-kb region of the IgA locus containing the I alpha exon was replaced with a human hypoxanthine phosphoribosyltransferase minigene by gene targeting in murine embryonic stem cells. The I alpha exon-deficient mice derived from these embryonic stem cells had normal IgA levels in serum and secretions and normal numbers of IgA B cells in Peyer's patches and spleen. Further, I alpha exon-deficient B cells efficiently underwent IgA class switch in vitro, despite the absence of I alpha exon-containing germline transcripts. Notably, I alpha exon-deficient B cells did not require TGF-beta for IgA class switch since stimulation with LPS alone led to IgA expression. Nonetheless, whereas I alpha exon-deficient B cells constitutively expressed human hypoxanthine phosphoribosyltransferase transcripts, they did not produce IgA in the absence of LPS stimulation. These results demonstrate that the I alpha exon or transcripts containing the I alpha exon are not required for IgA class switch. Further, the effects of TGF-beta on I alpha locus transcription can be supplanted by expression of a heterologous minigene at that locus, but a second signal is required for the induction of IgA class switch.

Authors

G R Harriman, A Bradley, S Das, P Rogers-Fani, A C Davis

Murine V lambda x and V lambda x-containing antibodies bind human myelin basic protein.

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Abstract

Myelin basic protein (MBP) is highly immunogenic and a known autoantigen capable of inducing experimental allergic encephalomyelitis (EAE), the animal model of multiple sclerosis. We have previously described a murine monoclonal antibody (mAb), F28C4, directed against the encephalitogenic MBP peptide acetyl (Ac) 1-9, which contains a V lambda x light chain. Considering the rarity of V lambda x usage, we determined whether other Abs having V lambda x light chains shared similar antigen (Ag) specificity. We screened a panel of V lambda x-containing monoclonal and polyclonal Abs, of unknown specificity for reactivity with MBP. All such Ab, but not heavy chain isotype matched controls, bound MBP but were not polyreactive with other potential self Ags. The binding of a recombinant form of V lambda x alone to MBP demonstrated the important contribution of the V lambda x light chain to the reaction. With the exception of mAb F28C4 which recognizes MBP Ac1-9, the epitope specificity of all other V lambda x-bearing Abs was localized to MBP residues 25-34. These results demonstrate a unique association between V lambda x expression and MBP reactivity. Given that V lambda x shares sequence homology with T cell receptors (TCR) from encephalitogenic T lymphocytes, these results imply a potential role for V lambda x in the pathogenesis of EAE.

Authors

F S Galin, C C Maier, S R Zhou, J N Whitaker, J E Blalock

Hypoxia-induced exocytosis of endothelial cell Weibel-Palade bodies. A mechanism for rapid neutrophil recruitment after cardiac preservation.

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Abstract

The period of hypoxia is an important priming event for the vascular dysfunction that accompanies reperfusion, with endothelial cells (ECs) and neutrophils (PMNs) playing a central role. We hypothesized that EC Weibel-Palade (WP) body exocytosis during the hypoxic/ischemic period during organ preservation permits brisk PMN recruitment into postischemic tissue, a process further amplified in an oxidant-rich milieu. Exposure of human umbilical vein ECs to a hypoxic environment (pO2 approximately 20 torr) stimulated release of von Willebrand factor (vWF), stored in EC WP bodies, as well as increased expression of the WP body-derived PMN adhesion molecule P-selectin at the EC surface. Increased binding of 111In-labeled PMNs to hypoxic EC monolayers (compared with normoxic controls) was blocked with a blocking antibody to P-selectin, but was not affected by a nonblocking control antibody. Although increased P-selectin expression and vWF release were also noted during reoxygenation, hypoxia alone (even in the presence of antioxidants) was sufficient to increase WP body exocytosis. To determine the relevance of these observations to hypothermic cardiac preservation, during which the pO2 within the cardiac vasculature declines to similarly low levels, experiments were performed in a rodent (rat and mouse) cardiac preservation/transplantation model. Immunodepletion of recipient PMNs or administration of a blocking anti-P-selectin antibody before transplantation resulted in reduced graft neutrophil infiltration and improved graft survival, compared with identically preserved hearts transplanted into control recipients. To establish the important role of endothelial P-selectin expression on the donor vasculature, murine cardiac transplants were performed using homozygous P-selectin deficient and wild-type control donor hearts flushed free of blood/platelets before preservation/transplantation. P-selectin-null hearts transplanted into wild-type recipients demonstrated a marked (13-fold) reduction in graft neutrophil infiltration and increased graft survival compared with wild-type hearts transplanted into wild-type recipients. To determine whether coronary endothelial WP exocytosis may occur during cardiac preservation in humans, the release of vWF into the coronary sinus (CS) was measured in 32 patients during open heart surgery. CS samples obtained at the start and conclusion of the ischemic period demonstrated an increase in CS vWF antigen (by ELISA) consisting of predominantly high molecular weight multimers (by immunoelectrophoresis). These data suggest that EC WP exocytosis occurs during hypothermic cardiac preservation, priming the vasculature to recruit PMNs rapidly during reperfusion.

Authors

D J Pinsky, Y Naka, H Liao, M C Oz, D D Wagner, T N Mayadas, R C Johnson, R O Hynes, M Heath, C A Lawson, D M Stern

The effect of insulin dose on the measurement of insulin sensitivity by the minimal model technique. Evidence for saturable insulin transport in humans.

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Abstract

Administration of exogenous insulin during an intravenous glucose tolerance test allows the use of the minimal model technique to determine the insulin sensitivity index in subjects with reduced endogenous insulin responses. To study the effect of different insulin administration protocols, we performed three intravenous glucose tolerance tests in each of seven obese subjects (age, 20-41 yr; body mass index, 30-43 kg/m2). Three different insulin administration protocols were used: a low-dose (0.025 U/kg) infusion given over 10 min, a low-dose (0.025 U/kg) bolus injection, and a high-dose (0.050 U/kg) bolus injection, resulting in peak insulin concentrations of 1,167 +/- 156, 3,014 +/- 483, and 6,596 +/- 547 pM, respectively. The mean insulin sensitivity index was 4.80 +/- 0.95 x 10(-5), 3.56 +/- 0.53 x 10(-5), and 2.42 +/- 0.40 x 10(-5) min-1/pM respectively (chi +/- SEM; P = 0.01). The association of higher peak insulin concentrations with lower measured insulin sensitivity values suggested the presence of a saturable process. Because results were not consistent with the known saturation characteristics of insulin action on tissue, a second saturable site involving the transport of insulin from plasma to interstitium was introduced, leading to a calculated Km of 807 +/- 165 pM for this site, a value near the 1/Kd of the insulin receptor. Thus, the kinetics of insulin action in humans in these studies is consistent with two saturable sites, and supports the hypothesis for transport of insulin to the interstitial space. Saturation may have an impact on minimal model results when high doses of exogenous insulin are given as a bolus, but can be minimized by infusing insulin at a low dose.

Authors

R L Prigeon, M E Røder, D Porte Jr, S E Kahn

Acute hypertension activates mitogen-activated protein kinases in arterial wall.

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Abstract

Mitogen-activated protein (MAP) kinases are rapidly activated in cells stimulated with various extracellular signals by dual phosphorylation of tyrosine and threonine residues. They are thought to play a pivotal role in transmitting transmembrane signals required for cell growth and differentiation. Herein we provide evidence that two distinct classes of MAP kinases, the extracellular signal-regulated kinases (ERK) and the c-Jun NH2-terminal kinases (JNK), are transiently activated in rat arteries (aorta, carotid and femoral arteries) in response to an acute elevation in blood pressure induced by either restraint or administration of hypertensive agents (i.e., phenylephrine and angiotensin II). Kinase activation is followed by an increase in c-fos and c-jun gene expression and enhanced activating protein 1 (AP-1) DNA-binding activity. Activation of ERK and JNK could contribute to smooth muscle cell hypertrophy/hyperplasia during arterial remodeling due to frequent and/or persistent elevations in blood pressure.

Authors

Q Xu, Y Liu, M Gorospe, R Udelsman, N J Holbrook

In vivo trafficking of adoptively transferred interleukin-2 expanded tumor-infiltrating lymphocytes and peripheral blood lymphocytes. Results of a double gene marking trial.

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Abstract

Adoptive immunotherapy with tumor-infiltrating lymphocytes (TIL) and IL-2 appears to produce dramatic regressions in patients with metastatic melanoma and renal cancer. However, the in vivo mechanism of TIL function is not known. We conducted an UCLA Human Subject Protection Committee, Recombinant DNA Advisory Committee, and FDA-approved clinical trial using genetically-marked TIL to test the hypothesis that these cells have unique, tumor-specific in vivo trafficking patterns. TIL and PBL (as a control effector cell population) were isolated and expanded in parallel in vitro in IL-2-containing medium for 4-6 wk. During the expansion, TIL and PBL were separately transduced with the amphotropic retroviral vectors LNL6 and G1Na. Transduced TIL and PBL were coinfused into patients and their respective numbers measured in tumor, peripheral blood, and normal tissues; integrated provirus could be quantitated and distinguished by DNA PCR. Nine patients were treated (six melanoma, three renal) and received between 4.5 x 10(8) and 1.24 x 10(10) total cells. Both "marked" TIL and PBL could be detected circulating in the peripheral blood, in some patients for up to 99 d after infusion. Marked TIL and/or PBL could be detected in tumor biopsies in six of nine patients as early as day 6 and as late as day 99 after infusion. No convincing pattern of preferential trafficking of TIL vs. PBL to tumor was noted. Moreover, concurrent biopsies of muscle, fat, and skin demonstrated the presence of TIL/PBL in comparable or greater numbers than in tumor in five patients. The results of this double gene marking trial provide interesting insights into the life span and trafficking of adoptively transferred lymphocytes, but do not support the hypothesis that TIL specifically traffic to tumor deposits.

Authors

J S Economou, A S Belldegrun, J Glaspy, E M Toloza, R Figlin, J Hobbs, N Meldon, R Kaboo, C L Tso, A Miller, R Lau, W McBride, R C Moen

Effects of renin gene transfer on blood pressure and renin gene expression in a congenic strain of Dahl salt-resistant rats.

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Abstract

To investigate whether a BP-regulatory locus exists in the vicinity of the renin locus on rat chromosome 13, we transferred this chromosome segment from the Dahl salt-sensitive (S) rat onto the genetic background of the Dahl salt-resistant (R) rat. In congenic Dahl R rats carrying the S renin gene and fed an 8% salt diet, systolic BP was significantly lower than in progenitor Dahl R rats: 127 +/- 1 mmHg versus 138 +/- 4 mmHg, respectively (P < 0.05). Moreover, the decreased BP in the congenic Dahl R strain was associated with decreased kidney renin mRNA and decreased plasma renin concentration. These findings demonstrate that the Dahl S strain carries alleles in or near the renin locus that confer lower plasma renin concentration and lower BP than the corresponding alleles in the Dahl R strain, at least when studied on the genetic background of the Dahl R rat and in the environment of a high salt diet. The occurrence of coincident reductions in kidney renin mRNA, plasma renin concentration, and BP after interstrain transfer of naturally occurring renin gene variants strongly suggests that genetically determined variation in renin gene expression can affect BP.

Authors

E M St Lezin, M Pravenec, A L Wong, W Liu, N Wang, S Lu, H J Jacob, R J Roman, D E Stec, J M Wang, I A Reid, T W Kurtz

Mapping a cardiomyopathy locus to chromosome 3p22-p25.

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Abstract

Dilated cardiomyopathy (DCM) is a common disorder characterized by cardiac dilation and reduced systolic function. To identify a cardiomyopathy gene, we studied a family with DCM associated with sinus node dysfunction, supraventricular tachyarrhythmias, conduction delay, and stroke. A general linkage approach was used to localize the disease gene in this family. Linkage to D3S2303 was identified with a two-point lod score of 6.09 at a recombination fraction of 0.00. Haplotype analyses mapped this locus to a 30 cM region of chromosome 3p22-p25, excluding candidate genes encoding a G-protein (GNAI2), calcium channel (CACNL1A2), sodium channel (SCN5A), and inositol triphosphate receptor (ITPR1). These data indicate that a gene causing DCM associated with rhythm and conduction abnormalities is located on chromosome 3p, and represent the first step toward disease gene identification.

Authors

T M Olson, M T Keating

Cardiac-specific overexpression of phospholamban alters calcium kinetics and resultant cardiomyocyte mechanics in transgenic mice.

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Abstract

Phospholamban is the regulator of the cardiac sarcoplasmic reticulum (SR) Ca(2+)-ATPase activity and an important modulator of basal contractility in the heart. To determine whether all the SR Ca(2+)-ATPase enzymes are subject to regulation by phospholamban in vivo, transgenic mice were generated which overexpressed phospholamban in the heart, driven by the cardiac-specific alpha-myosin heavy chain promoter. Quantitative immunoblotting revealed a twofold increase in the phospholamban protein levels in transgenic hearts compared to wild type littermate hearts. The transgenic mice showed no phenotypic alterations and no changes in heart/body weight, heart/lung weight, and cardiomyocyte size. Isolated unloaded cardiac myocytes from transgenic mice exhibited diminished shortening fraction (63%) and decreased rates of shortening (64%) and relengthening (55%) compared to wild type (100%) cardiomyocytes. The decreases in contractile parameters of transgenic cardiomyocytes reflected decreases in the amplitude (83%) of the Ca2+ signal and prolongation (131%) in the time for decay of the Ca2+ signal, which was associated with a decrease in the apparent affinity of the SR Ca(2+)-ATPase for Ca2+ (56%), compared to wild type (100%) cardiomyocytes. In vivo analysis of left ventricular systolic function using M mode and pulsed-wave Doppler echocardiography revealed decreases in fractional shortening (79%) and the normalized mean velocity of circumferential shortening (67%) in transgenic mice compared to wild type (100%) mice. The differences in contractile parameters and Ca2+ kinetics in transgenic cardiomyocytes and the depressed left ventricular systolic function in transgenic mice were abolished upon isoproterenol stimulation. These findings indicate that a fraction of the Ca(2+)-ATPases in native SR is not under regulation by phospholamban. Expression of additional phospholamban molecules results in: (a) inhibition of SR Ca2+ transport; (b) decreases in systolic Ca2+ levels and contractile parameters in ventricular myocytes; and (c) depression of basal left ventricular systolic function in vivo.

Authors

V J Kadambi, S Ponniah, J M Harrer, B D Hoit, G W Dorn 2nd, R A Walsh, E G Kranias

Hypoxia alters early gestation human cytotrophoblast differentiation/invasion in vitro and models the placental defects that occur in preeclampsia.

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Abstract

During normal human pregnancy a subpopulation of fetal cytotrophoblast stem cells differentiate and invade the uterus and its arterioles. In the pregnancy disease preeclampsia, cytotrophoblast differentiation is abnormal and invasion is shallow. Thus, the placenta is relatively hypoxic. We investigated whether lowering oxygen tension affects cytotrophoblast differentiation and invasion. Previously we showed that when early gestation cytotrophoblast stem cells are cultured under standard conditions (20% O2) they differentiate/invade, replicating many aspects of the in vivo process. Specifically, the cells proliferate at a low rate and rapidly invade extracellular matrix (ECM) substrates, a phenomenon that requires switching their repertoire of integrin cell-ECM receptors, which are stage-specific antigens that mark specific transitions in the differentiation process. In this study we found that lowering oxygen tension to 2% did not change many of the cells' basic processes. However, there was a marked increase in their incorporation of [3H]thymidine and 5-bromo-2'-deoxyuridine (BrdU). Moreover, they failed to invade ECM substrates, due at least in part to their inability to completely switch their integrin repertoire. These changes mimic many of the alterations in cytotrophoblast differentiation/invasion that occur in preeclampsia, suggesting that oxygen tension plays an important role in regulating these processes in vivo.

Authors

O Genbacev, R Joslin, C H Damsky, B M Polliotti, S J Fisher

Imogen 38: a novel 38-kD islet mitochondrial autoantigen recognized by T cells from a newly diagnosed type 1 diabetic patient.

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Abstract

Cell-mediated autoimmune attack directed against islet proteins of approximately 38 kD in size has been associated with type 1 diabetes. A novel murine cDNA encoding an antigen of this size was cloned using a screening procedure based on the proliferative response of a human diabetic T cell clone (1C6) to a recombinant antigen epitope library. Membrane preparations from COS 7 cells transfected with the full-length 1,267-bp cDNA elicited a proliferative response from the reporter T cells comparable to that of the defined peptide epitope and native insulinoma antigen. In vitro translation and transfection experiments suggested that the protein is initially synthesized as a 44-kD protein and then processed to the native 38-kD form through the proteolytic removal of a 54-aa NH2-terminal mitochondrial targeting sequence. Differential centrifugation, Percoll density gradient centrifugation, and immunofluorescence studies confirmed localization of the antigen to mitochondria. Northern blot, Western blot, and 1C6 T cell proliferation assays showed that, although imogen 38 was more highly expressed in beta cell than alpha cell lines, it was also present in other tissues. It is concluded that imogen 38 may be a target for bystander autoimmune attack in diabetes rather than a primary autoantigen.

Authors

S D Arden, B O Roep, P I Neophytou, E F Usac, G Duinkerken, R R de Vries, J C Hutton

Evidence for an essential role of reactive oxygen species in the genesis of late preconditioning against myocardial stunning in conscious pigs.

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Abstract

Conscious pigs underwent a sequence of 10 2-min coronary occlusions, each separated by 2 min of reperfusion, for three consecutive days (days 1, 2, and 3). On day 1, pigs received an i.v. infusion of a combination of antioxidants (superoxide dismutase, catalase, and N-2 mercaptopropionyl glycine; group II, n = 9), nisoldipine (group III, n = 6), or vehicle (group I [controls], n = 9). In the control group, systolic wall thickening (WTh) in the ischemic-reperfused region on day 1 remained significantly depressed for 4 h after the 10th reperfusion, indicating myocardial "stunning." On days 2 and 3, however, the recovery of WTh improved markedly, so that the total deficit of WTh decreased by 53% on day 2 and 56% on day 3 compared with day 1 (P < 0.01), indicating the development of a powerful cardioprotective response (late preconditioning against stunning). In the anti-oxidant-treated group, the total deficit of WTh on day 1 was 54% less than in the control group (P < 0.01). On day 2, the total deficit of WTh was 85% greater than that observed on day 1 and similar to that observed on day 1 in the control group. On day 3, the total deficit of WTh was 58% less than that noted on day 2 (P < 0.01). In the nisoldipine-treated group, the total deficit of WTh on day 1 was 53% less than that noted in controls (P < 0.01). On days 2 and 3, the total deficit of WTh was similar to the corresponding values in the control group. These results demonstrate that: (a) in the conscious pig, antioxidant therapy completely blocks the development of late preconditioning against stunning, indicating that the production of reactive oxygen species (ROS) on day 1 is the mechanism whereby ischemia induces the protective response observed on day 2; (b) antioxidant therapy markedly attenuates myocardial stunning on day 1, indicating that ROS play an important pathogenetic role in postischemic dysfunction in the porcine heart despite the lack of xanthine oxidase; (c) although the administration of a calcium-channel antagonist (nisoldipine) is as effective as antioxidant therapy in attenuating myocardial stunning on day 1, it has no effect on late preconditioning on day 2, indicating that the ability of antioxidants to block late preconditioning is not a nonspecific result of the mitigation of postischemic dysfunction on day 1. Generation of ROS during reperfusion is generally viewed as a deleterious process. Our finding that ROS contribute to the genesis of myocardial stunning but, at the same time, trigger the development of late preconditioning against stunning supports a complex pathophysiological paradigm, in which ROS play an immediate injurious role (as mediators of stunning) followed by a useful function (as mediators of subsequent preconditioning).

Authors

J Z Sun, X L Tang, S W Park, Y Qiu, J F Turrens, R Bolli

Purification and characterization of a naturally processed hepatitis B virus peptide recognized by CD8+ cytotoxic T lymphocytes.

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Abstract

In vitro studies in patients with hepatitis B virus (HBV) infection have suggested that hepatocytolysis induced by CD8+ cytotoxic T lymphocytes (CTLs) is the most important effector pathway in eliminating infected cells. The recognition is implicated in the endogenously processed HBV antigens in the context of HLA class I molecules presented on the liver cell membrane. However, the naturally occurring HBV peptide antigens have not yet been demonstrated. We report here that a naturally processed peptide antigen P2 was isolated from HLA class I molecules of HBV-infected liver cell membrane. The P2 peptide exhibited the activity of sensitizing target cells for lysis by CD8+ CTLs. The P2 sequence (YVNVNMGLK) purified from liver tissue was in concordance with that encoded by the viral genome for the HBV nucleocapsid antigen or HBcAg 88-96. P2 peptide could also be isolated from the EBV-transformed B cells that were transfected by HBcAg-expressing vector. The P2 epitope, sharing the HLA-A11 binding motifs, was recognized by HLA-A11-restricted CD8+ CTLs. The data provided direct evidence that, in hepatitis B patients, antigenic peptides of HBV were processed by hepatocytes, presented with the class I MHC molecules, and recognized by CD8+ CTLs.

Authors

S L Tsai, M H Chen, C T Yeh, C M Chu, A N Lin, F H Chiou, T H Chang, Y F Liaw