Modulation of hepatic fibrosis by c-Jun-N-terminal kinase inhibition.
ABSTRACT: c-Jun N-terminal kinase (JNK) is activated by multiple profibrogenic mediators; JNK activation occurs during toxic, metabolic, and autoimmune liver injury. However, its role in hepatic fibrogenesis is unknown.JNK phosphorylation was detected by immunoblot analysis and confocal immunofluorescent microscopy in fibrotic livers from mice after bile duct ligation (BDL) or CCl(4) administration and in liver samples from patients with chronic hepatitis C and non-alcoholic steatohepatitis. Fibrogenesis was investigated in mice given the JNK inhibitor SP600125 and in JNK1- and JNK2-deficient mice following BDL or CCl(4) administration. Hepatic stellate cell (HSC) activation was determined in primary mouse HSCs incubated with pan-JNK inhibitors SP600125 and VIII.JNK phosphorylation was strongly increased in livers of mice following BDL or CCl(4) administration as well as in human fibrotic livers, occurring predominantly in myofibroblasts. In vitro, pan-JNK inhibitors prevented transforming growth factor (TGF) beta-, platelet-derived growth factor-, and angiotensin II-induced murine HSC activation and decreased platelet-derived growth factor and TGF-beta signaling in human HSCs. In vivo, pan-JNK inhibition did not affect liver injury but significantly reduced fibrosis after BDL or CCl(4). JNK1-deficient mice had decreased fibrosis after BDL or CCl(4), whereas JNK2-deficient mice displayed increased fibrosis after BDL but fibrosis was not changed after CCl(4). Moreover, patients with chronic hepatitis C who displayed decreased fibrosis in response to the angiotensin receptor type 1 blocker losartan showed decreased JNK phosphorylation.JNK is involved in HSC activation and fibrogenesis and represents a potential target for antifibrotic treatment approaches.
Project description:Hepatocyte apoptosis and activation of hepatic stellate cells (HSC) are critical events in fibrogenesis. We previously demonstrated that phagocytosis of apoptotic hepatocytes by HSC is profibrogenic. Based on this, as well as the observation that reduced nicotinamide adenine dinucleotide phosphate oxidase (NADPH) oxidase induction is central to fibrogenesis, our aim was to study the phagocytic NADPH oxidase NOX2.An in vivo phagocytosis model was developed by injecting wild type (wt) or NOX2(-/-) mice with lentiviral-green fluorescence protein (GFP) containing a hepatocyte-specific promoter, and adeno-tumor necrosis factor-related apoptosis-inducing ligand (ad-TRAIL). Fibrosis was evaluated in bile duct ligated (BDL) wt and NOX2(-/-) mice with or without gadolinium treatment. NOX2 expression was studied in human liver samples and in HSC isolated from fibrotic livers. The fibrogenic activity of NOX2 was assessed by collagen reporter assays.In the phagocytosis model, engulfment of GFP-labeled apoptotic bodies was seen, and the expression of ?-smooth muscle actin (?-SMA) and collagen I increased significantly in the wt but not in the NOX2(-/-) mice. Inhibiting apoptosis decreased the profibrogenic response. NOX2(-/-) animals exhibited significantly less fibrosis following BDL. Inactivating macrophages in wt BDL mice did not lower collagen production to the level observed in NOX2(-/-) mice, suggesting that NOX2-expressing HSC are important in fibrogenesis. NOX2 was up-regulated in HSC from fibrotic livers, and phagocytosis-induced NOX2 expression and activity were demonstrated. Based on reporter assays, production of NOX2-mediated reactive oxygen species directly induced collagen promoter activity in HSC.Apoptosis and phagocytosis of hepatocytes directly induce HSC activation and initiation of fibrosis. NOX2, the phagocytic NADPH oxidase, plays a key role in this process and in liver fibrogenesis in vivo.
Project description:<h4>Background and purpose</h4>Oxidative stress plays a critical role in liver fibrogenesis. Reactive oxygen species (ROS) stimulate hepatic stellate cells (HSCs), and ROS-mediated increases in calcium influx further increase ROS production. Azelnidipine is a calcium blocker that has been shown to have antioxidant effects in endothelial cells and cardiomyocytes. Therefore, we evaluated the anti-fibrotic and antioxidative effects of azelnidipine on liver fibrosis.<h4>Experimental approach</h4>We used TGF-?1-activated LX-2 cells (a human HSC line) and mouse models of fibrosis induced by treatment with either carbon tetrachloride (CCl(4) ) or thioacetamide (TAA).<h4>Key results</h4>Azelnidipine inhibited TGF-?1 and angiotensin II (Ang II)-activated ?1(I) collagen mRNA expression in HSCs. Furthermore, TGF-?1- and Ang II-induced oxidative stress and TGF-?1-induced p38 and JNK phosphorylation were reduced in HSCs treated with azelnidipine. Azelnidipine significantly decreased inflammatory cell infiltration, pro-fibrotic gene expressions, HSC activation, lipid peroxidation, oxidative DNA damage and fibrosis in the livers of CCl(4) - or TAA-treated mice. Finally, azelnidipine prevented a decrease in the expression of some antioxidant enzymes and accelerated regression of liver fibrosis in CCl(4) -treated mice.<h4>Conclusions and implications</h4>Azelnidipine inhibited TGF-?1- and Ang II-induced HSC activation in vitro and attenuated CCl(4) - and TAA-induced liver fibrosis, and it accelerated regression of CCl(4) -induced liver fibrosis in mice. The anti-fibrotic mechanism of azelnidipine against CCl(4) -induced liver fibrosis in mice may have been due an increased level of antioxidant defence. As azelnidipine is widely used in clinical practice without serious adverse effects, it may provide an effective new strategy for anti-fibrotic therapy.
Project description:Liver fibrogenesis is associated with the transition of quiescent hepatocytes and hepatic stellate cells (HSCs) into the cell cycle. Exit from quiescence is controlled by E-type cyclins (cyclin E1 [CcnE1] and cyclin E2 [CcnE2]). Thus, the aim of the current study was to investigate the contribution of E-type cyclins for liver fibrosis in man and mice. Expression of CcnE1, but not of its homolog, CcnE2, was induced in fibrotic and cirrhotic livers from human patients with different etiologies and in murine wild-type (WT) livers after periodical administration of the profibrotic toxin, CCl(4). To further evaluate the potential function of E-type cyclins for liver fibrogenesis, we repetitively treated constitutive CcnE1(-/-) and CcnE2(-/-) knock-out mice with CCl(4) to induce liver fibrosis. Interestingly, CcnE1(-/-) mice were protected against CCl(4)-mediated liver fibrogenesis, as evidenced by reduced collagen type I ?1 expression and the lack of septum formation. In contrast, CcnE2(-/-) mice showed accelerated fibrogenesis after CCl(4) treatment. We isolated primary HSCs from WT, CcnE1(-/-), and CcnE2(-/-) mice and analyzed their activation, proliferation, and survival in vitro. CcnE1 expression in WT HSCs was maximal when they started to proliferate, but decreased after the cells transdifferentiated into myofibroblasts. CcnE1(-/-) HSCs showed dramatically impaired survival, cell-cycle arrest, and strongly reduced expression of alpha smooth muscle actin, indicating deficient HSC activation. In contrast, CcnE2-deficient HSCs expressed an elevated level of CcnE1 and showed enhanced cell-cycle activity and proliferation, compared to WT cells.CcnE1 and CcnE2 have antagonistic roles in liver fibrosis. CcnE1 is indispensable for the activation, proliferation, and survival of HSCs and thus promotes the synthesis of extracellular matrix and liver fibrogenesis.
Project description:<h4>Background & aims</h4>The vitronectin receptor integrin αvβ3 drives fibrogenic activation of hepatic stellate cells (HSCs). Molecular imaging targeting the integrin αvβ3 could provide a non-invasive method for evaluating the expression and the function of the integrin αvβ3 on activated HSCs (aHSCs) in the injured liver. In this study, we sought to compare differences in the uptake of [<sup>18</sup>F]-Alfatide between normal and injured liver to evaluate its utility for assessment of hepatic fibrogenesis.<h4>Methods</h4>PET with [<sup>18</sup>F]-Alfatide, non-enhanced CT, histopathology, immunofluorescence staining, immunoblotting and gene analysis were performed to evaluate and quantify hepatic integrin αvβ3 levels and liver fibrosis progression in mouse models of fibrosis (carbon tetrachloride [CCl<sub>4</sub>] and bile duct ligation [BDL]). The liver AUC divided by the blood AUC over 30 min was used as an integrin αvβ3-PET index to quantify fibrosis progression. Ex vivo analysis of frozen liver tissue from patients with fibrosis and cirrhosis verified the animal findings.<h4>Results</h4>Fibrotic mouse livers showed enhanced [<sup>18</sup>F]-Alfatide uptake and retention compared to control livers. The radiotracer was demonstrated to bind specifically with integrin αvβ3, which is mainly expressed on aHSCs. Autoradiography and histopathology confirmed the PET imaging results. Further, the mRNA and protein level of integrin αvβ3 and its signaling complex were higher in CCl<sub>4</sub> and BDL models than controls. The results obtained from analyses on human fibrotic liver sections supported the animal findings.<h4>Conclusions</h4>Imaging hepatic integrin αvβ3 with PET and [<sup>18</sup>F]-Alfatide offers a potential non-invasive method for monitoring the progression of liver fibrosis.<h4>Lay summary</h4>Integrin αvβ3 expression on activated hepatic stellate cells (aHSCs) is associated with HSC proliferation during hepatic fibrogenesis. Herein, we show that a radioactive tracer, [<sup>18</sup>F]-Alfatide, binds to integrin αvβ3 with high affinity and specificity. [<sup>18</sup>F]-Alfatide could thus be used as a non-invasive imaging biomarker to track hepatic fibrosis progression.
Project description:<h4>Background</h4>Interleukin-1 (IL-1)? and IL-1 receptor antagonist (IL-1Ra) have been proposed as important mediators during chronic liver diseases. We aimed to determine whether the modulation of IL-1? signaling with IL-1Ra impacts on liver fibrosis.<h4>Methods</h4>We assessed the effects of IL-1? on human hepatic stellate cells (HSC) and in mouse models of liver fibrosis induced by bile duct ligation (BDL) or carbon tetrachloride treatment (CCl-4).<h4>Results</h4>Human HSCs treated with IL-1? had increased IL-1?, IL-1Ra, and MMP-9 expressions in vitro. HSCs treated with IL-1? had reduced ?-smooth muscle actin expression. These effects were all prevented by IL-1Ra treatment. In the BDL model, liver fibrosis and Kuppfer cell numbers were increased in IL-1Ra KO mice compared to wild type mice and wild type mice treated with IL-1Ra. In contrast, after CCl-4 treatment, fibrosis, HSC and Kupffer cell numbers were decreased in IL-1Ra KO mice compared to the other groups. IL-1Ra treatment provided a modest protective effect in the BDL model and was pro-fibrotic in the CCl-4 model.<h4>Conclusions</h4>We demonstrated bivalent effects of IL-1Ra during liver fibrosis in mice. IL-1Ra was detrimental in the CCl-4 model, whereas it was protective in the BDL model. Altogether these data suggest that blocking IL-1-mediated inflammation may be beneficial only in selective liver fibrotic disease.
Project description:Development of liver fibrosis results in drastic changes in the liver microenvironment, which in turn accelerates disease progression. Although the pathological function of various hepatic cells in fibrogenesis is identified, the crosstalk between them remains obscure. The present study demonstrates that hepatic expression of adipocyte fatty acid binding protein (A-FABP) is induced especially in the liver sinusoidal endothelial cells (LSECs) in mice after bile duct ligation (BDL). Genetic ablation and pharmacological inhibition of A-FABP attenuate BDL- or carbon tetrachloride-induced liver fibrosis in mice associating with reduced collagen accumulation, LSEC capillarization, and hepatic stellate cell (HSC) activation. Mechanistically, elevated A-FABP promotes LSEC capillarization by activating Hedgehog signaling, thus impairs the gatekeeper function of LSEC on HSC activation. LSEC-derived A-FABP also acts on HSCs in paracrine manner to potentiate the transactivation of transforming growth factor β1 (TGFβ1) by activating c-Jun N-terminal kinase (JNK)/c-Jun signaling. Elevated TGFβ1 subsequently exaggerates liver fibrosis. These findings uncover a novel pathological mechanism of liver fibrosis in which LSEC-derived A-FABP is a key regulator modulating the onset and progression of the disease. Targeting A-FABP may represent a potential approach against liver fibrosis.
Project description:<h4>Aim</h4>To investigate the inhibitory effect of the natural product Leukamenin F on liver fibrosis and explore its potential underlying mechanisms.<h4>Methods</h4>Carbon tetrachloride (CCl(4))-treated mouse model in vivo and in hepatic stellate cells (HSC) in vitro were used. The effect on CCl(4)-induced liver fibrosis was studied using histochemical and biochemical analysis, while the inhibition on HSC was assessed using cell proliferation/apoptosis assay and collagen I production using real-time PCR. The inhibitory effects of Leukamenin F on Akt/mTOR/p70S6K and TGFbeta/Smad pathways was studied using Western blot and cell image analysis.<h4>Results</h4>Leukamenin F (0.1-1 mg/kg, ip, q.d.x28) significantly reduced alpha-SMA and collagen specific Sirius red staining areas in CCl(4) -treated mouse livers. This compound at 1-2 micromol/L dose-dependently inhibited alpha-SMA expression, cell proliferation and type I procollagen mRNA expression in activated HSC. Furthermore it inhibited the Akt/mTOR/p70S6K pathway and suppressed TGFbeta -induced Smad2/Smad3 phosphorylation and nuclear translocation in HSC.<h4>Conclusion</h4>Our results demonstrated that Leukamenin F could attenuate CCl(4)-induced liver fibrogenesis in mice as an efficient inhibitor against both HSC proliferation and ECM production. This natural product provides a valuable structural hint for the development of anti-liver fibrosis reagents.
Project description:PURPOSE: Adeno-associated virus (AAV) vectors can achieve long-term gene expression and are now feasible for use in human gene therapy. We constructed hepatocyte growth factor (HGF) expressing AAV (AAV5-HGF) and examined its effect in two mouse hepatic fibrosis models. METHODS: A model of hepatic fibrosis was established by carbon tetrachloride (CCl(4)) administration in Balb/c mice. After the establishment of liver fibrosis, AAV5-HGF was injected once into the portal vein. Mice were killed 3, 6, 9, and 12 weeks after injection. Another model was established by bile duct ligation (BDL). Seven weeks after AAV5-HGF injection, mice underwent BDL, and were then killed 2 weeks after BDL. RESULTS: Mice that received AAV5-HGF achieved stable HGF expression both in the serum and liver for at least 12 weeks. In both models, significant improvement of the liver fibrosis was found in all mice receiving AAV5-HGF based on Azan-Mallory staining. Suppression of hepatic stellate cells (HSC) was confirmed by immunohistochemistry. Fibrogenic markers were significantly suppressed and collagenase activity increased in the livers of mice receiving AAV5-HGF. CONCLUSIONS: A single injection of AAV vector containing HGF gene achieved long-term expression of HGF and resulted in resolution of mouse liver fibrosis. HGF gene therapy mediated by AAV is feasible for the treatment of liver fibrosis.
Project description:Chemokines and chemokine receptors contribute to the migration of hepatic stellate cells (HSCs) and Kupffer cells, two key cell types in fibrogenesis. Here, we investigate the role of CCR2, the receptor for monocyte chemoattractant protein (MCP)-1, MCP-2, and MCP-3, in hepatic fibrosis. Hepatic CCR2, MCP-1, MCP-2, and MCP-3 messenger RNA expression was increased after bile duct ligation (BDL). Both Kupffer cells and HSCs, but not hepatocytes, expressed CCR2. BDL- and CCl(4)-induced fibrosis was markedly reduced in CCR2(-/-) mice as assessed through collagen deposition, alpha-smooth muscle actin expression, and hepatic hydroxyproline content. We generated CCR2 chimeric mice by the combination of clodronate, irradiation, and bone marrow (BM) transplantation allowing full reconstitution of Kupffer cells, but not HSCs, with BM cells. Chimeric mice containing wild-type BM displayed increased macrophage recruitment, whereas chimeric mice containing CCR2(-/-) BM showed less macrophage recruitment at 5 days after BDL. Although CCR2 expressed in the BM enhanced macrophage recruitment in early phases of injury, CCR2 expression on resident liver cells including HSCs, but not on the BM, was required for fibrogenic responses in chronic fibrosis models. In vitro experiments demonstrated that HSCs deficient in CCR2(-/-) or its downstream mediator p47phox(-/-) did not display extracellular signal-regulated kinase and AKT phosphorylation, chemotaxis, or reactive oxygen species production in response to MCP-1, MCP-2, and MCP-3.Our results indicate that CCR2 promotes HSC chemotaxis and the development of hepatic fibrosis.
Project description:<h4>Background & aims</h4>Development of liver fibrosis is associated with activation of quiescent hepatic stellate cells (HSCs) into collagen type I-producing myofibroblasts (activated HSCs). Cessation of liver injury often results in fibrosis resolution and inactivation of activated HSCs/myofibroblasts into a quiescent-like state (inactivated HSCs). We aimed to identify molecular features of phenotypes of HSCs from mice and humans.<h4>Methods</h4>We performed studies with Lrat<sup>Cre</sup>, Ets1-floxed, Nf1-floxed, Pparγ-floxed, Gata6-floxed, Rag2<sup>-/-</sup>γc<sup>-/-</sup>, and C57/Bl6 (control) mice. Some mice were given carbon tetrachloride (CCl<sub>4</sub>) to induce liver fibrosis, with or without a peroxisome proliferator-activated receptor-γ (PPARγ) agonist. Livers from mice were analyzed by immunohistochemistry. Quiescent, activated, and inactivated HSCs were isolated from livers of Col1α1<sup>YFP</sup> mice and analyzed by chromatin immunoprecipitation and sequencing. Human HSCs were isolated from livers denied for transplantation. We compared changes in gene expression patterns and epigenetic modifications (histone H3 lysine 4 dimethylation and histone H3 lysine 27 acetylation) in primary mouse and human HSCs. Transcription factors were knocked down with small hairpin RNAs in mouse HSCs.<h4>Results</h4>Motif enrichment identified E26 transcription-specific transcription factors (ETS) 1, ETS2, GATA4, GATA6, interferon regulatory factor (IRF) 1, and IRF2 transcription factors as regulators of the mouse and human HSC lineage. Small hairpin RNA-knockdown of these transcription factors resulted in increased expression of genes that promote fibrogenesis and inflammation, and loss of HSC phenotype. Disruption of Gata6 or Ets1, or Nf1 or Pparγ (which are regulated by ETS1), increased the severity of CCl<sub>4</sub>-induced liver fibrosis in mice compared to control mice. Only mice with disruption of Gata6 or Pparγ had defects in fibrosis resolution after CCl<sub>4</sub> administration was stopped, associated with persistent activation of HSCs. Administration of a PPARγ agonist accelerated regression of liver fibrosis after CCl<sub>4</sub> administration in control mice but not in mice with disruption of Pparγ.<h4>Conclusions</h4>Phenotypes of HSCs from humans and mice are regulated by transcription factors, including ETS1, ETS2, GATA4, GATA6, IRF1, and IRF2. Activated mouse and human HSCs can revert to a quiescent-like, inactivated phenotype. We found GATA6 and PPARγ to be required for inactivation of human HSCs and regression of liver fibrosis in mice.