Hyperproliferation of bile duct epithelial cells due to cell-cycle dysregulation is a key feature of cystogenesis in polycystic liver diseases (PCLDs). Recent evidence suggests a regulatory role for microRNAs (miRNAs) in a variety of biological processes, including cell proliferation. We therefore hypothesized that miRNAs may be involved in the regulation of selected components of the cell cycle and might contribute to hepatic cystogenesis. We found that the cholangiocyte cell line PCK-CCL, which is derived from the PCK rat, a model of autosomal recessive polycystic kidney disease (ARPKD), displayed global changes in miRNA expression compared with normal rat cholangiocytes (NRCs). More specific analysis revealed decreased levels of 1 miRNA, miR15a, both in PCK-CCL cells and in liver tissue from PCK rats and patients with a PCLD. The decrease in miR15a expression was associated with upregulation of its target, the cell-cycle regulator cell division cycle 25A (Cdc25A). Overexpression of miR15a in PCK-CCL cells decreased Cdc25A levels, inhibited cell proliferation, and reduced cyst growth. In contrast, suppression of miR15a in NRCs accelerated cell proliferation, increased Cdc25A expression, and promoted cyst growth. Taken together, these results suggest that suppression of miR15a contributes to hepatic cystogenesis through dysregulation of Cdc25A.
Seung-Ok Lee, Tatyana Masyuk, Patrick Splinter, Jesús M. Banales, Anatoliy Masyuk, Angela Stroope, Nicholas LaRusso
Phenylketonuria (PKU) is an inborn error of metabolism caused by mutations in phenylalanine hydroxylase (PAH). Over 500 disease-causing mutations have been identified in humans, most of which result in PAH protein misfolding and increased turnover in vivo. The use of pharmacological chaperones to stabilize or promote correct folding of mutant proteins represents a promising new direction in the treatment of misfolding diseases. We performed a high-throughput ligand screen of over 1,000 pharmacological agents and identified 4 compounds (I–IV) that enhanced the thermal stability of PAH and did not show substantial inhibition of PAH activity. In further studies, compounds III (3-amino-2-benzyl-7-nitro-4-(2-quinolyl)-1,2-dihydroisoquinolin-1-one) and IV (5,6-dimethyl-3-(4-methyl-2-pyridinyl)-2-thioxo-2,3-dihydrothieno[2,3- d]pyrimidin-4(1H)-one) stabilized the functional tetrameric conformation of recombinant WT-PAH and PKU mutants. These compounds also significantly increased activity and steady-state PAH protein levels in cells transiently transfected with either WT-PAH or PKU mutants. Furthermore, PAH activity in mouse liver increased after a 12-day oral administration of low doses of compounds III and IV. Thus, we have identified 2 small molecules that may represent promising alternatives in the treatment of PKU.
Angel L. Pey, Ming Ying, Nunilo Cremades, Adrian Velazquez-Campoy, Tanja Scherer, Beat Thöny, Javier Sancho, Aurora Martinez
Primary biliary cirrhosis (PBC) is a cholestatic disease associated with autoimmune phenomena and alterations in both biliary bicarbonate excretion and expression of the bicarbonate carrier AE2. The bile acid ursodeoxycholic acid (UCDA) is currently used in treatment of cholestatic liver diseases and is the treatment of choice in PBC; however, a subset of PBC patients respond poorly to UDCA monotherapy. In these patients, a combination of UDCA and glucocorticoid therapy appears to be beneficial. To address the mechanism of this benefit, we analyzed the effects of UDCA and dexamethasone on AE2 gene expression in human liver cells from hepatocyte and cholangiocyte lineages. The combination of UDCA and dexamethasone, but not UDCA or dexamethasone alone, increased the expression of liver-enriched alternative mRNA isoforms AE2b1 and AE2b2 and enhanced AE2 activity. Similar effects were obtained after replacing UDCA with UDCA conjugates. In in vitro and in vivo reporter assays, we found that a UDCA/dexamethasone combination upregulated human AE2 alternate overlapping promoter sequences from which AE2b1 and AE2b2 are expressed. In chromatin immunoprecipitation assays, we demonstrated that combination UCDA/dexamethasone treatment induced p300-related interactions between HNF1 and glucocorticoid receptor on the AE2 alternate promoter. Our data provide a potential molecular explanation for the beneficial effects of the combination of UDCA and glucocorticoids in PBC patients with inadequate response to UDCA monotherapy.
Fabián Arenas, Isabel Hervias, Miriam Úriz, Ruth Joplin, Jesús Prieto, Juan F. Medina
Transgenic mice expressing HCV core protein develop hepatic steatosis and hepatocellular carcinoma (HCC), but the mechanism underlying this process remains unclear. Because PPARα is a central regulator of triglyceride homeostasis and mediates hepatocarcinogenesis in rodents, we determined whether PPARα contributes to HCV core protein–induced diseases. We generated PPARα-homozygous, -heterozygous, and -null mice with liver-specific transgenic expression of the core protein gene (Ppara+/+:HCVcpTg, Ppara+/–:HCVcpTg, and Ppara–/–:HCVcpTg mice. Severe steatosis was unexpectedly observed only in Ppara+/+:HCVcpTg mice, which resulted from enhanced fatty acid uptake and decreased mitochondrial β-oxidation due to breakdown of mitochondrial outer membranes. Interestingly, HCC developed in approximately 35% of 24-month-old Ppara+/+:HCVcpTg mice, but tumors were not observed in the other genotypes. These phenomena were found to be closely associated with sustained PPARα activation. In Ppara+/–:HCVcpTg mice, PPARα activation and the related changes did not occur despite the presence of a functional Ppara allele. However, long-term treatment of these mice with clofibrate, a PPARα activator, induced HCC with mitochondrial abnormalities and hepatic steatosis. Thus, our results indicate that persistent activation of PPARα is essential for the pathogenesis of hepatic steatosis and HCC induced by HCV infection.
Naoki Tanaka, Kyoji Moriya, Kendo Kiyosawa, Kazuhiko Koike, Frank J. Gonzalez, Toshifumi Aoyama
Niemann-Pick C1–like 1 (NPC1L1) is required for cholesterol absorption. Intestinal NPC1L1 appears to be a target of ezetimibe, a cholesterol absorption inhibitor that effectively lowers plasma LDL-cholesterol in humans. However, human liver also expresses NPC1L1. Hepatic function of NPC1L1 was previously unknown, but we recently discovered that NPC1L1 localizes to the canalicular membrane of primate hepatocytes and that NPC1L1 facilitates cholesterol uptake in hepatoma cells. Based upon these findings, we hypothesized that hepatic NPC1L1 allows the retention of biliary cholesterol by hepatocytes and that ezetimibe disrupts hepatic function of NPC1L1. To test this hypothesis, transgenic mice expressing human NPC1L1 in hepatocytes (L1-Tg mice) were created. Hepatic overexpression of NPC1L1 resulted in a 10- to 20-fold decrease in biliary cholesterol concentration, but not phospholipid and bile acid concentrations. This decrease was associated with a 30%–60% increase in plasma cholesterol, mainly because of the accumulation of apoE-rich HDL. Biliary and plasma cholesterol concentrations in these animals were virtually returned to normal with ezetimibe treatment. These findings suggest that in humans, ezetimibe may reduce plasma cholesterol by inhibiting NPC1L1 function in both intestine and liver, and hepatic NPC1L1 may have evolved to protect the body from excessive biliary loss of cholesterol.
Ryan E. Temel, Weiqing Tang, Yinyan Ma, Lawrence L. Rudel, Mark C. Willingham, Yiannis A. Ioannou, Joanna P. Davies, Lisa-Mari Nilsson, Liqing Yu
LIGHT is an important costimulatory molecule for T cell immunity. Recent studies have further implicated its role in innate immunity and inflammatory diseases, but its cellular and molecular mechanisms remain elusive. We report here that LIGHT is upregulated and functions as a proinflammatory cytokine in 2 independent experimental hepatitis models, induced by concanavalin A and Listeria monocytogenes. Molecular mutagenesis studies suggest that soluble LIGHT protein produced by cleavage from the cell membrane plays an important role in this effect through the interaction with the lymphotoxin-β receptor (LTβR) but not herpes virus entry mediator. NK1.1+ T cells contribute to the production, but not the cleavage or effector functions, of soluble LIGHT. Importantly, treatment with a mAb that specifically interferes with the LIGHT-LTβR interaction protects mice from lethal hepatitis. Our studies thus identify a what we believe to be a novel function of soluble LIGHT in vivo and offer a potential target for therapeutic interventions in hepatic inflammatory diseases.
Sudarshan Anand, Pu Wang, Kiyoshi Yoshimura, In-Hak Choi, Anja Hilliard, Youhai H. Chen, Chyung-Ru Wang, Richard Schulick, Andrew S. Flies, Dallas B. Flies, Gefeng Zhu, Yanhui Xu, Drew M. Pardoll, Lieping Chen, Koji Tamada
Aniela Jakubowski, Christine Ambrose, Michael Parr, John M. Lincecum, Monica Z. Wang, Timothy S. Zheng, Beth Browning, Jennifer S. Michaelson, Manfred Baetscher, Bruce Wang, D. Montgomery Bissell, Linda C. Burkly
Progenitor (“oval”) cell expansion accompanies many forms of liver injury, including alcohol toxicity and submassive parenchymal necrosis as well as experimental injury models featuring blocked hepatocyte replication. Oval cells can potentially become either hepatocytes or biliary epithelial cells and may be critical to liver regeneration, particularly when hepatocyte replication is impaired. The regulation of oval cell proliferation is incompletely understood. Herein we present evidence that a TNF family member called TWEAK (TNF-like weak inducer of apoptosis) stimulates oval cell proliferation in mouse liver through its receptor Fn14. TWEAK has no effect on mature hepatocytes and thus appears to be selective for oval cells. Transgenic mice overexpressing TWEAK in hepatocytes exhibit periportal oval cell hyperplasia. A similar phenotype was obtained in adult wild-type mice, but not Fn14-null mice, by administering TWEAK-expressing adenovirus. Oval cell expansion induced by 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) was significantly reduced in Fn14-null mice as well as in adult wild-type mice with a blocking anti-TWEAK mAb. Importantly, TWEAK stimulated the proliferation of an oval cell culture model. Finally, we show increased Fn14 expression in chronic hepatitis C and other human liver diseases relative to its expression in normal liver, which suggests a role for the TWEAK/Fn14 pathway in human liver injury. We conclude that TWEAK has a selective mitogenic effect for liver oval cells that distinguishes it from other previously described growth factors.
Aniela Jakubowski, Christine Ambrose, Michael Parr, John M. Lincecum, Monica Z. Wang, Timothy S. Zheng, Beth Browning, Jennifer S. Michaelson, Manfred Baestcher, Bruce Wang, D. Montgomery Bissell, Linda C. Burkly
Nonalcoholic fatty liver disease (NAFLD) is characterized by the accumulation of excess liver triacylglycerol (TAG), inflammation, and liver damage. The goal of the present study was to directly quantify the biological sources of hepatic and plasma lipoprotein TAG in NAFLD. Patients (5 male and 4 female; 44 ± 10 years of age) scheduled for a medically indicated liver biopsy were infused with and orally fed stable isotopes for 4 days to label and track serum nonesterified fatty acids (NEFAs), dietary fatty acids, and those derived from the de novo lipogenesis (DNL) pathway, present in liver tissue and lipoprotein TAG. Hepatic and lipoprotein TAG fatty acids were analyzed by gas chromatography/mass spectrometry. NAFLD patients were obese, with fasting hypertriglyceridemia and hyperinsulinemia. Of the TAG accounted for in liver, 59.0% ± 9.9% of TAG arose from NEFAs; 26.1% ± 6.7%, from DNL; and 14.9% ± 7.0%, from the diet. The pattern of labeling in VLDL was similar to that in liver, and throughout the 4 days of labeling, the liver demonstrated reciprocal use of adipose and dietary fatty acids. DNL was elevated in the fasting state and demonstrated no diurnal variation. These quantitative metabolic data document that both elevated peripheral fatty acids and DNL contribute to the accumulation of hepatic and lipoprotein fat in NAFLD.
Kerry L. Donnelly, Coleman I. Smith, Sarah J. Schwarzenberg, Jose Jessurun, Mark D. Boldt, Elizabeth J. Parks
The inhibitor of NF-κB (I-κB) kinase (IKK) complex consists of 3 subunits, IKK1, IKK2, and NF-κB essential modulator (NEMO), and is involved in the activation of NF-κB by various stimuli. IKK2 or NEMO constitutive knockout mice die during embryogenesis as a result of massive hepatic apoptosis. Therefore, we examined the role of IKK2 in TNF-induced apoptosis and ischemia/reperfusion (I/R) injury in the liver by using conditional knockout mice. Hepatocyte-specific ablation of IKK2 did not lead to impaired activation of NF-κB or increased apoptosis after TNF-α stimulation whereas conditional NEMO knockout resulted in complete block of NF-κB activation and massive hepatocyte apoptosis. In a model of partial hepatic I/R injury, mice lacking IKK2 in hepatocytes displayed significantly reduced liver necrosis and inflammation than wild-type mice. AS602868, a novel chemical inhibitor of IKK2, protected mice from liver injury due to I/R without sensitizing them toward TNF-induced apoptosis and could therefore emerge as a new pharmacological therapy for liver resection, hemorrhagic shock, or transplantation surgery.
Tom Luedde, Ulrike Assmus, Torsten Wüstefeld, Andreas Meyer zu Vilsendorf, Tania Roskams, Mark Schmidt-Supprian, Klaus Rajewsky, David A. Brenner, Michael P. Manns, Manolis Pasparakis, Christian Trautwein
Increasing evidence demonstrates that IL-6 has a protective role during liver injury. IL-6 activates intracellular pathways via the gp130 receptor. In order to identify IL-6–gp130 pathways involved in mediating liver protection, we analyzed hepatocyte-specific gp130 knockout mice in a concanavalin A–induced (Con A–induced) model of immune-mediated hepatitis. We demonstrated that IL-6–gp130–dependent pathways in hepatocytes alone are sufficient for triggering protection in Con A–induced hepatitis. gp130-STAT3 signaling in hepatocytes mediates the IL-6–triggered protective effect. This was demonstrated by analysis of IL-6–induced protection in mice selectively deficient for gp130-dependent STAT1/3 or gp130-SHP2-RAS signaling in hepatocytes. To identify IL-6–gp130–STAT1/3 dependently expressed liver-protective factors, we performed gene array analysis of hepatic gene expression in hepatocyte-specific gp130–/– mice as well as in gp130-STAT1/3– and gp130-SHP2-RAS-MAPK–deficient mice. The mouse IL-8 ortholog KC (also known as Gro-α) and serum amyloid A2 (SAA2) was identified as differentially IL-6–gp130–STAT3–regulated genes. Hepatic expression of KC and SAA2 mediate the liver-protective potential of IL-6, since treatment with recombinant KC or serum SAA2 effectively reduced liver injury during Con A–induced hepatitis. In summary, this study defines IL-6–gp130–STAT3–dependent gene expression in hepatocytes that mediates IL-6–triggered protection in immune-mediated Con A–induced hepatitis. Additionally, we identified the IL-6–gp130–STAT3–dependent proteins KC and SAA2 as new candidates for therapeutic targets in liver diseases.
Christian Klein, Torsten Wüstefeld, Ulrike Assmus, Tania Roskams, Stefan Rose-John, Michael Müller, Michael P. Manns, Mattias Ernst, Christian Trautwein
Cholecystokinin (CCK) modulates contractility of the gallbladder, the sphincter of Oddi, and the stomach. These effects are mediated through activation of gastrointestinal smooth muscle as well as enteric neuron CCK-1 receptors (CCK-1Rs). To investigate the potential physiological and pathophysiological functions linked to CCK-1R–mediated signaling, we compared male WT and CCK-1R–deficient mice (129/SvEv). After 12 weeks on either a standard mouse chow or a lithogenic diet (containing 1% cholesterol, 0.5% cholic acid, and 15% dairy fat), small-intestinal transit time, intestinal cholesterol absorption, biliary cholesterol secretion, and cholesterol gallstone prevalence were compared in knockout versus WT animals. Analysis of mice on either the chow or the lithogenic diet revealed that CCK-1R–/– animals had larger gallbladder volumes (predisposing to bile stasis), significant retardation of small-intestinal transit times (resulting in increased cholesterol absorption), and increased biliary cholesterol secretion rates. The elevation in bile cholesterol, coupled with a tendency toward gallbladder stasis (due to the absence of CCK-induced contraction), facilitates nucleation, growth, and agglomeration of cholesterol monohydrate crystals; this sequence of events in turn results in a significantly higher prevalence of cholesterol gallstones in the CCK-1R–null mice.
David Q.-H. Wang, Frank Schmitz, Alan S. Kopin, Martin C. Carey
The etiology and pathogenesis of bile duct obstruction in children with biliary atresia are largely unknown. We have previously reported that, despite phenotypic heterogeneity, genomic signatures of livers from patients display a proinflammatory phenotype. Here, we address the hypothesis that production of IFN-γ is a key pathogenic mechanism of disease using a mouse model of rotavirus-induced biliary atresia. We found that rotavirus infection of neonatal mice has a unique tropism to bile duct cells, and it triggers a hepatobiliary inflammation by IFN-γ–producing CD4+ and CD8+ lymphocytes. The inflammation is tissue specific, resulting in progressive jaundice, growth failure, and greater than 90% mortality due to obstruction of extrahepatic bile ducts. In this model, the genetic loss of IFN-γ did not alter the onset of jaundice, but it remarkably suppressed the tissue-specific targeting of T lymphocytes and completely prevented the inflammatory and fibrosing obstruction of extrahepatic bile ducts. As a consequence, jaundice resolved, and long-term survival improved to greater than 80%. Notably, administration of recombinant IFN-γ led to recurrence of bile duct obstruction following rotavirus infection of IFN-γ–deficient mice. Thus, IFN-γ–driven obstruction of bile ducts is a key pathogenic mechanism of disease and may constitute a therapeutic target to block disease progression in patients with biliary atresia.
Pranavkumar Shivakumar, Kathleen M. Campbell, Gregg E. Sabla, Alexander Miethke, Greg Tiao, Monica M. McNeal, Richard L. Ward, Jorge A. Bezerra
Ali Canbay, Maria Eugenia Guicciardi, Hajime Higuchi, Ariel Feldstein, Steven F. Bronk, Robert Rydzewski, Makiko Tanai, Gregory J. Gores
We recently showed that antigen-nonspecific inflammatory cells are recruited into the liver when hepatitis B virus (HBV)-specific CTLs are injected into HBV transgenic mice, and that this process amplifies the severity of liver disease. We also showed that the severity of CTL-induced liver disease is ameliorated by the depletion of Gr-1+ cells (Gr-1 is an antigen highly expressed by neutrophils), which, secondarily, abolishes the intrahepatic recruitment of all antigen-nonspecific Gr-1– mononuclear cells (NK and NKT cells, T and B lymphocytes, monocytes, macrophages, dendritic cells) despite the strong induction of chemokine gene expression. Those results suggested that in addition to chemokine expression, CTL-induced functions are necessary for mononuclear cell recruitment to occur. We now report that MMPs known to be produced by Gr-1+ cells are rapidly induced in the livers of CTL-injected mice. The inhibition of MMP activity reduced the intrahepatic recruitment of antigen-nonspecific mononuclear cells and much of the attending liver disease without affecting the migration or antiviral potential of antigen-specific CTLs. The notion that the inhibition of MMP activity is associated with maintenance of antiviral effects but diminished tissue damage may be significant for the development of immunotherapeutic approaches for the treatment of chronic HBV infection.
Giovanni Sitia, Masanori Isogawa, Matteo Iannacone, Iain L. Campbell, Francis V. Chisari, Luca G. Guidotti
Yin Zhi Huang, a decoction of Yin Chin (Artemisia capillaris) and three other herbs, is widely used in Asia to prevent and treat neonatal jaundice. We recently identified the constitutive androstane receptor (CAR, NR1I3) as a key regulator of bilirubin clearance in the liver. Here we show that treatment of WT and humanized CAR transgenic mice with Yin Zhi Huang for 3 days accelerates the clearance of intravenously infused bilirubin. This effect is absent in CAR knockout animals. Expression of bilirubin glucuronyl transferase and other components of the bilirubin metabolism pathway is induced by Yin Zhi Huang treatment of WT mice or mice expressing only human CAR, but not CAR knockout animals. 6,7-Dimethylesculetin, a compound present in Yin Chin, activates CAR in primary hepatocytes from both WT and humanized CAR mice and accelerates bilirubin clearance in vivo. We conclude that CAR mediates the effects of Yin Zhi Huang on bilirubin clearance and that 6,7-dimethylesculetin is an active component of this herbal medicine. CAR is a potential target for the development of new drugs to treat neonatal, genetic, or acquired forms of jaundice.
Wendong Huang, Jun Zhang, David D. Moore
Farnesoid X receptor (FXR) is a bile acid–activated transcription factor that is a member of the nuclear hormone receptor superfamily. Fxr-null mice exhibit a phenotype similar to Byler disease, an inherited cholestatic liver disorder. In the liver, activation of FXR induces transcription of transporter genes involved in promoting bile acid clearance and represses genes involved in bile acid biosynthesis. We investigated whether the synthetic FXR agonist GW4064 could protect against cholestatic liver damage in rat models of extrahepatic and intrahepatic cholestasis. In the bile duct–ligation and α-naphthylisothiocyanate models of cholestasis, GW4064 treatment resulted in significant reductions in serum alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase, as well as other markers of liver damage. Rats that received GW4064 treatment also had decreased incidence and extent of necrosis, decreased inflammatory cell infiltration, and decreased bile duct proliferation. Analysis of gene expression in livers from GW4064-treated cholestatic rats revealed decreased expression of bile acid biosynthetic genes and increased expression of genes involved in bile acid transport, including the phospholipid flippase MDR2. The hepatoprotection seen in these animal models by the synthetic FXR agonist suggests FXR agonists may be useful in the treatment of cholestatic liver disease.
Yaping Liu, Jane Binz, Mary Jo Numerick, Steve Dennis, Guizhen Luo, Bhasha Desai, Kathleen I. MacKenzie, Traci A. Mansfield, Steven A. Kliewer, Bryan Goodwin, Stacey A. Jones
Stem cell factor (SCF) is a molecule with known proliferative effects on hematopoietic cells. More recent studies suggest that this molecule may also have effects on cellular differentiation and proliferation in other types of cells. The current investigations demonstrate that there is a large reservoir of SCF in the liver, that hepatic SCF levels change dramatically following partial hepatectomy in mice, and that SCF blockade, either by administration of anti-SCF antibodies or by using genetically altered, SCF-deficient mice, inhibits hepatocyte proliferation after partial hepatectomy; if SCF is replaced in the genetically SCF-deficient mice after partial hepatectomy, hepatocyte proliferation is restored to that seen in WT animals. Furthermore, SCF administration to IL-6 knockout mice also restores hepatocyte proliferation to normal. In vitro studies using primary mouse hepatocytes demonstrate that SCF causes hepatocyte proliferation and is induced by IL-6 and that treatment with anti-SCF antibodies inhibits IL-6–induced hepatocyte proliferation. Further in vivo studies in IL-6 knockout mice demonstrate that SCF administration to these animals increases p-stat3 levels, suggesting that the SCF-induced increase in hepatocyte proliferation in this system is stat3-mediated.
Xiaodan Ren, Cory Hogaboam, Audra Carpenter, Lisa Colletti
Angiotensin II (Ang II) is a pro-oxidant and fibrogenic cytokine. We investigated the role of NADPH oxidase in Ang II–induced effects in hepatic stellate cells (HSCs), a fibrogenic cell type. Human HSCs express mRNAs of key components of nonphagocytic NADPH oxidase. Ang II phosphorylated p47phox, a regulatory subunit of NADPH oxidase, and induced reactive oxygen species formation via NADPH oxidase activity. Ang II phosphorylated AKT and MAPKs and increased AP-1 DNA binding in a redox-sensitive manner. Ang II stimulated DNA synthesis, cell migration, procollagen α1(I) mRNA expression, and secretion of TGF-β1 and inflammatory cytokines. These effects were attenuated by N-acetylcysteine and diphenylene iodonium, an NADPH oxidase inhibitor. Moreover, Ang II induced upregulation of genes potentially involved in hepatic wound-healing response in a redox-sensitive manner, as assessed by microarray analysis. HSCs isolated from p47phox–/– mice displayed a blunted response to Ang II compared with WT cells. We also assessed the role of NADPH oxidase in experimental liver fibrosis. After bile duct ligation, p47phox–/– mice showed attenuated liver injury and fibrosis compared with WT counterparts. Moreover, expression of smooth muscle α-actin and expression of TGF-β1 were reduced in p47phox–/– mice. Thus, NADPH oxidase mediates the actions of Ang II on HSCs and plays a critical role in liver fibrogenesis.
Ramón Bataller, Robert F. Schwabe, Youkyung H. Choi, Liu Yang, Yong Han Paik, Jeffrey Lindquist, Ting Qian, Robert Schoonhoven, Curt H. Hagedorn, John J. Lemasters, David A. Brenner
Although a lysosomal, cathepsin B–dependent (Ctsb-dependent) pathway of apoptosis has been described, the contribution of this pathway to tissue damage remains unclear. Our aim was to ascertain if Ctsb inactivation attenuates liver injury, inflammation, and fibrogenesis after bile duct ligation (BDL). In 3-day BDL mice, hepatocyte apoptosis, mitochondrial cytochrome c release, and serum alanine aminotransferase (ALT) values were reduced in Ctsb–/– versus Ctsb+/+ animals. Likewise, R-3032 (a Ctsb inhibitor) also reduced these parameters in BDL WT mice. Both genetic and pharmacologic inhibition of Ctsb in the BDL mouse reduced (a) hepatic inflammation, as assessed by transcripts for CXC chemokines and neutrophil infiltration, and (b) fibrogenesis, as assessed by transcripts for stellate cell activation and sirius red staining for hepatic collagen deposition. These differences could not be ascribed to alterations in cholestasis. These findings support a prominent role for the lysosomal pathway of apoptosis in tissue injury and link apoptosis to inflammation and fibrogenesis. Ctsb inhibition may be therapeutic in liver diseases.
Ali Canbay, Maria Eugenia Guicciardi, Hajime Higuchi, Ariel Feldstein, Steven F. Bronk, Robert Rydzewski, Makiko Taniai, Gregory J. Gores