Hypofibrinogenemia with preserved hemostasis and protection from thrombosis in mice with an Fga truncation mutation.

Genetic variants within the fibrinogen Aα chain encoding the αC-region commonly result in hypodysfibrinogenemia in patients. However, the (patho)physiological consequences and underlying mechanisms of such mutations remain undefined. Here, we generated Fga270 mice carrying a premature termination codon within the Fga gene at residue 271. The Fga270 mutation was compatible with Mendelian inheritance for offspring of heterozygous crosses. Adult Fga270/270 mice were hypofibrinogenemic with ∼10% plasma fibrinogen levels relative to FgaWT/WT mice, linked to 90% reduction in hepatic Fga messenger RNA (mRNA) because of nonsense-mediated decay of the mutant mRNA. Fga270/270 mice had preserved hemostatic potential in vitro and in vivo in models of tail bleeding and laser-induced saphenous vein injury, whereas Fga-/- mice had continuous bleeding. Platelets from FgaWT/WT and Fga270/270 mice displayed comparable initial aggregation following adenosine 5'-diphosphate stimulation, but Fga270/270 platelets quickly disaggregated. Despite ∼10% plasma fibrinogen, the fibrinogen level in Fga270/270 platelets was ∼30% of FgaWT/WT platelets with a compensatory increase in fibronectin. Notably, Fga270/270 mice showed complete protection from thrombosis in the inferior vena cava stasis model. In a model of Staphylococcus aureus peritonitis, Fga270/270 mice supported local, fibrinogen-mediated bacterial clearance and host survival comparable to FgaWT/WT, unlike Fga-/- mice. Decreasing the normal fibrinogen levels to ∼10% with small interfering RNA in mice also provided significant protection from venous thrombosis without compromising hemostatic potential and antimicrobial function. These findings both reveal novel molecular mechanisms underpinning fibrinogen αC-region truncation mutations and highlight the concept that selective fibrinogen reduction may be efficacious for limiting thrombosis while preserving hemostatic and immune protective functions.

Factor XIII cross-links fibrin(ogen) independent of fibrin polymerization in experimental acute liver injury.

Intravascular fibrin clot formation follows a well-ordered series of reactions catalyzed by thrombin cleavage of fibrinogen leading to fibrin polymerization and cross-linking by factor XIIIa (FXIIIa). Extravascular fibrin(ogen) deposits are observed in injured tissues; however, the mechanisms regulating fibrin(ogen) polymerization and cross-linking in this setting are unclear. The objective of this study was to determine the mechanisms of fibrin polymerization and cross-linking in acute liver injury induced by acetaminophen (APAP) overdose. Hepatic fibrin(ogen) deposition and cross-linking were measured following APAP overdose in wild-type mice, mice lacking the catalytic subunit of FXIII (FXIII-/-), and in FibAEK mice, which express mutant fibrinogen insensitive to thrombin-mediated fibrin polymer formation. Hepatic fibrin(ogen) deposition was similar in APAP-challenged wild-type and FXIII-/- mice, yet cross-linking of hepatic fibrin(ogen) was dramatically reduced (>90%) by FXIII deficiency. Surprisingly, hepatic fibrin(ogen) deposition and cross-linking were only modestly reduced in APAP-challenged FibAEK mice, suggesting that in the APAP-injured liver fibrin polymerization is not strictly required for the extravascular deposition of cross-linked fibrin(ogen). We hypothesized that the oxidative environment in the injured liver, containing high levels of reactive mediators (eg, peroxynitrite), modifies fibrin(ogen) such that fibrin polymerization is impaired without impacting FXIII-mediated cross-linking. Notably, fibrin(ogen) modified with 3-nitrotyrosine adducts was identified in the APAP-injured liver. In biochemical assays, peroxynitrite inhibited thrombin-mediated fibrin polymerization in a concentration-dependent manner without affecting fibrin(ogen) cross-linking over time. These studies depict a unique pathology wherein thrombin-catalyzed fibrin polymerization is circumvented to allow tissue deposition and FXIII-dependent fibrin(ogen) cross-linking.

Von Willebrand factor delays liver repair after acetaminophen-induced acute liver injury in mice.

BACKGROUND & AIM: Acetaminophen (APAP)-induced acute liver failure is associated with substantial alterations in the hemostatic system. In mice, platelets accumulate in the liver after APAP overdose and appear to promote liver injury. Interestingly, patients with acute liver injury have highly elevated levels of the platelet-adhesive protein von Willebrand factor (VWF), but a mechanistic connection between VWF and progression of liver injury has not been established. We tested the hypothesis that VWF contributes directly to experimental APAP-induced acute liver injury. METHODS: Wild-type mice and VWF-deficient (Vwf-/-) mice were given a hepatotoxic dose of APAP (300 mg/kg, i.p.) or vehicle (saline). VWF plasma levels were measured by ELISA, and liver necrosis or hepatocyte proliferation was measured by immunohistochemistry. Platelet and VWF deposition were measured by immunofluorescence. RESULTS: In wild-type mice, VWF plasma levels, high molecular weight (HMW) VWF multimers, and VWF activity decreased 24 h after APAP challenge. These changes coupled to robust hepatic VWF and platelet deposition, although VWF deficiency had minimal effect on peak hepatic platelet accumulation or liver injury. VWF plasma levels were elevated 48 h after APAP challenge, but with relative reductions in HMW multimers and VWF activity. Whereas hepatic platelet aggregates persisted in livers of APAP-challenged wild-type mice, platelets were nearly absent in Vwf-/- mice 48 h after APAP challenge. The absence of platelet aggregates was linked to dramatically accelerated repair of the injured liver. Complementing observations in Vwf-/- mice, blocking VWF or the platelet integrin αIIbß3 during development of injury significantly reduced hepatic platelet aggregation and accelerated liver repair in APAP-challenged wild-type mice. CONCLUSION: These studies are the first to suggest a mechanistic link between VWF, hepatic platelet accumulation, and liver repair. Targeting VWF might provide a novel therapeutic approach to improve repair of the APAP-injured liver. LAY SUMMARY: Patients with acute liver injury due to acetaminophen overdose have highly elevated levels of the platelet-adhesive protein von Willebrand factor. It is not known whether von Willebrand factor plays a direct role in the progression of acute liver injury. We discovered that von Willebrand factor delays repair of the acetaminophen-injured liver in mice and that targeting von Willebrand factor, even in mice with established liver injury, accelerates liver repair.

Direct Amplification of Tissue Factor:Factor VIIa Procoagulant Activity by Bile Acids Drives Intrahepatic Coagulation.

OBJECTIVE: Regulation of TF (tissue factor):FVIIa (coagulation factor VIIa) complex procoagulant activity is especially critical in tissues where plasma can contact TF-expressing cells. One example is the liver, where hepatocytes are routinely exposed to plasma because of the fenestrated sinusoidal endothelium. Although liver-associated TF contributes to coagulation, the mechanisms controlling the TF:FVIIa complex activity in this tissue are not known. Approach and Results: Common bile duct ligation in mice triggered rapid hepatocyte TF-dependent intrahepatic coagulation coincident with increased plasma bile acids, which occurred at a time before observable liver damage. Similarly, plasma TAT (thrombin-antithrombin) levels increased in cholestatic patients without concurrent hepatocellular injury. Pathologically relevant concentrations of the bile acid glycochenodeoxycholic acid rapidly increased hepatocyte TF-dependent procoagulant activity in vitro, independent of de novo TF synthesis and necrotic or apoptotic cell death. Glycochenodeoxycholic acid increased hepatocyte TF activity even in the presence of the phosphatidylserine-blocking protein lactadherin. Interestingly, glycochenodeoxycholic acid and taurochenodeoxycholic acid increased the procoagulant activity of the TF:FVIIa complex relipidated in unilamellar phosphatidylcholine vesicles, which was linked to an apparent decrease in the Km for FX (coagulation factor X). Notably, the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, a bile acid structural analog, did not increase relipidated TF:FVIIa activity. Bile acids directly enhanced factor X activation by recombinant soluble TF:FVIIa complex but had no effect on FVIIa alone. CONCLUSIONS: The results indicate that bile acids directly accelerate TF:FVIIa-driven coagulation reactions, suggesting a novel mechanism whereby elevation in a physiological mediator can directly increase TF:FVIIa procoagulant activity.

Plasminogen Activator Inhibitor-1 Reduces Tissue-Type Plasminogen Activator-Dependent Fibrinolysis and Intrahepatic Hemorrhage in Experimental Acetaminophen Overdose.

Acetaminophen (APAP)-induced liver injury in mice is associated with activation of the coagulation cascade and deposition of fibrin in liver. Plasminogen activator inhibitor-1 (PAI-1) is an important physiological inhibitor of tissue-type plasminogen activator (tPA) and plays a critical role in fibrinolysis. PAI-1 expression is increased in both experimental APAP-induced liver injury and patients with acute liver failure. Prior studies have shown that PAI-1 prevents intrahepatic hemorrhage and mortality after APAP challenge, but the downstream mechanisms are not clear. We tested the hypothesis that PAI-1 limits liver-related morbidity after APAP challenge by reducing tPA-dependent fibrinolysis. Compared with APAP-challenged (300 mg/kg) wild-type mice, hepatic deposition of cross-linked fibrin was reduced, with intrahepatic congestion and hemorrhage increased in PAI-1-deficient mice 24 hours after APAP overdose. Administration of recombinant wild-type human PAI-1 reduced intrahepatic hemorrhage 24 hours after APAP challenge in PAI-1-/- mice, whereas a mutant PAI-1 lacking antiprotease function had no effect. Of interest, tPA deficiency alone did not affect APAP-induced liver damage. In contrast, fibrinolysis, intrahepatic congestion and hemorrhage, and mortality driven by PAI-1 deficiency were reduced in APAP-treated tPA-/-/PAI-1-/- double-knockout mice. The results identify PAI-1 as a critical regulator of intrahepatic fibrinolysis in experimental liver injury. Moreover, the results suggest that the balance between PAI-1 and tPA activity is an important determinant of liver pathology after APAP overdose.

Fibrin deposition following bile duct injury limits fibrosis through an αMß2-dependent mechanism.

Coagulation cascade activation and fibrin deposits have been implicated or observed in diverse forms of liver damage. Given that fibrin amplifies pathological inflammation in several diseases through the integrin receptor αMß2, we tested the hypothesis that disruption of the fibrin(ogen)-αMß2 interaction in Fibγ(390-396A) mice would reduce hepatic inflammation and fibrosis in an experimental setting of chemical liver injury. Contrary to our hypothesis, α-naphthylisothiocyanate (ANIT)-induced liver fibrosis increased in Fibγ(390-396A) mice, whereas inflammatory cytokine expression and hepatic necrosis were similar to ANIT-challenged wild-type (WT) mice. Increased fibrosis in Fibγ(390-396A) mice appeared to be independent of coagulation factor 13 (FXIII) transglutaminase, as ANIT challenge in FXIII-deficient mice resulted in a distinct pathological phenotype characterized by increased hepatic necrosis. Rather, bile duct proliferation underpinned the increased fibrosis in ANIT-exposed Fibγ(390-396A) mice. The mechanism of fibrin-mediated fibrosis was linked to interferon (IFN)γ induction of inducible nitric oxide synthase (iNOS), a gene linked to bile duct hyperplasia and liver fibrosis. Expression of iNOS messenger RNA was significantly increased in livers of ANIT-exposed Fibγ(390-396A) mice. Fibrin(ogen)-αMß2 interaction inhibited iNOS induction in macrophages stimulated with IFNγ in vitro and ANIT-challenged IFNγ-deficient mice had reduced iNOS induction, bile duct hyperplasia, and liver fibrosis. Further, ANIT-induced iNOS expression, liver fibrosis, and bile duct hyperplasia were significantly reduced in WT mice administered leukadherin-1, a small molecule that allosterically enhances αMß2-dependent cell adhesion to fibrin. These studies characterize a novel mechanism whereby the fibrin(ogen)-integrin-αMß2 interaction reduces biliary fibrosis and suggests a novel putative therapeutic target for this difficult-to-treat fibrotic disease.

Fibrin(ogen) drives repair after acetaminophen-induced liver injury via leukocyte αMß2 integrin-dependent upregulation of Mmp12.

BACKGROUND & AIMS: Acetaminophen (APAP)-induced liver injury is coupled with activation of the blood coagulation cascade and fibrin(ogen) accumulation within APAP-injured livers of experimental mice. We sought to define the role of fibrin(ogen) deposition in APAP-induced liver injury and repair. METHODS: Wild-type, fibrinogen-deficient mice, mutant mice with fibrin(ogen) incapable of binding leukocyte αMß2 integrin (Fibγ390-396A mice) and matrix metalloproteinase 12 (Mmp12)-deficient mice were fasted, injected with 300mg/kg APAP i.p. and evaluated at a range of time-points. Plasma and liver tissue were analyzed. Rescue of Fibγ390-396A mice was carried out with exogenous Mmp12. To examine the effect of the allosteric leukocyte integrin αMß2 activator leukadherin-1 (LA-1), APAP-treated mice were injected with LA-1. RESULTS: In wild-type mice, APAP overdose increased intrahepatic levels of high molecular weight cross-linked fibrin(ogen). Anticoagulation reduced early APAP hepatotoxicity (6h), but increased hepatic injury at 24h, implying a protective role for coagulation at the onset of repair. Complete fibrin(ogen) deficiency delayed liver repair after APAP overdose, evidenced by a reduction of proliferating hepatocytes (24h) and unresolved hepatocellular necrosis (48 and 72h). Fibγ390-396A mice had decreased hepatocyte proliferation and increased multiple indices of liver injury, suggesting a mechanism related to fibrin(ogen)-leukocyte interaction. Induction of Mmp12, was dramatically reduced in APAP-treated Fibγ390-396A mice. Mice lacking Mmp12 displayed exacerbated APAP-induced liver injury, resembling Fibγ390-396A mice. In contrast, administration of LA-1 enhanced hepatic Mmp12 mRNA and reduced necrosis in APAP-treated mice. Further, administration of recombinant Mmp12 protein to APAP-treated Fibγ390-396A mice restored hepatocyte proliferation. CONCLUSIONS: These studies highlight a novel pathway of liver repair after APAP overdose, mediated by fibrin(ogen)-αMß2 integrin engagement, and demonstrate a protective role of Mmp12 expression after APAP overdose. LAY SUMMARY: Acetaminophen overdose leads to activation of coagulation cascade and deposition of high molecular weight cross-linked fibrin(ogen) species in the liver. Fibrin(ogen) is required for stimulating liver repair after acetaminophen overdose. The mechanism whereby fibrin(ogen) drives liver repair after acetaminophen overdose requires engagement of leukocyte αMß2 integrin and subsequent induction of matrix metalloproteinase 12.

Von Willebrand factor deficiency reduces liver fibrosis in mice.

Liver diseases are associated with complex changes in the hemostatic system and elevated levels of the platelet-adhesive protein Von Willebrand factor (VWF) are reported in patients with acute and chronic liver damage. Although elevated levels of VWF are associated with fibrosis in the general population, the role of VWF in acute and chronic liver injury has not been examined in depth in experimental settings. We tested the hypothesis that VWF deficiency inhibits experimental liver injury and fibrosis. Wild-type (WT) and VWF-deficient mice were challenged with carbon tetrachloride (CCl4) and the impact of VWF deficiency on acute liver injury and chronic liver fibrosis was determined. VWF deficiency did not significantly affect acute CCl4-induced hepatocellular necrosis in mice. Chronic CCl4 challenge, twice weekly for 6weeks, significantly increased hepatic stellate cell activation and collagen deposition in livers of WT mice. Interestingly, hepatic induction of several profibrogenic and stellate cell activation genes was attenuated in VWF-deficient mice. Moreover, birefringent sirius red staining (indicating type I and III collagens) and type I collagen immunofluorescence indicated a reduction in hepatic collagen deposition in CCl4-exposed VWF-deficient mice compared to CCl4-exposed WT mice. The results indicate that VWF deficiency attenuates chronic CCl4-induced liver fibrosis without affecting acute hepatocellular necrosis. The results are the first to demonstrate that VWF deficiency reduces the progression of liver fibrosis, suggesting a mechanistic role of elevated plasma VWF levels in cirrhosis.

Jumonji Domain-containing Protein-3 (JMJD3/Kdm6b) Is Critical for Normal Ovarian Function and Female Fertility.

In females, reproductive success is dependent on the expression of a number of genes regulated at different levels, one of which is through epigenetic modulation. How a specific epigenetic modification regulates gene expression and their downstream effect on ovarian function are important for understanding the female reproductive process. The trimethylation of histone3 at lysine27 (H3K27me3) is associated with gene repression. JMJD3 (or KDM6b), a jumonji domain-containing histone demethylase specifically catalyzes the demethylation of H3K27me3, that positively influences gene expression. This study reports that the expression of JMJD3 specifically in the ovarian granulosa cells (GCs) is critical for maintaining normal female fertility. Conditional deletion of Jmjd3 in the GCs results in a decreased number of total healthy follicles, disrupted estrous cycle, and increased follicular atresia culminating in subfertility and premature ovarian failure. At the molecular level, the depletion of Jmjd3 and RNA-seq analysis reveal that JMJD3 is essential for mitochondrial function. JMJD3-mediated reduction of H3K27me3 induces the expression of Lif (Leukemia inhibitory factor) and Ctnnb1 (ß-catenin), that in turn regulate the expression of key mitochondrial genes critical for the electron transport chain. Moreover, mitochondrial DNA content is also significantly decreased in Jmjd3 null GCs. Additionally, we have uncovered that the expression of Jmjd3 in GCs decreases with age, both in mice and in humans. Thus, in summary, our studies highlight the critical role of JMJD3 in nuclear-mitochondrial genome coordination that is essential for maintaining normal ovarian function and female fertility and underscore a potential role of JMJD3 in female reproductive aging.

Androgen-mediated Perturbation of the Hepatic Circadian System Through Epigenetic Modulation Promotes NAFLD in PCOS Mice.

In women, excess androgen causes polycystic ovary syndrome (PCOS), a common fertility disorder with comorbid metabolic dysfunctions including diabetes, obesity, and nonalcoholic fatty liver disease. Using a PCOS mouse model, this study shows that chronic high androgen levels cause hepatic steatosis while hepatocyte-specific androgen receptor (AR)-knockout rescues this phenotype. Moreover, through RNA-sequencing and metabolomic studies, we have identified key metabolic genes and pathways affected by hyperandrogenism. Our studies reveal that a large number of metabolic genes are directly regulated by androgens through AR binding to androgen response element sequences on the promoter region of these genes. Interestingly, a number of circadian genes are also differentially regulated by androgens. In vivo and in vitro studies using a circadian reporter [Period2::Luciferase (Per2::LUC)] mouse model demonstrate that androgens can directly disrupt the hepatic timing system, which is a key regulator of liver metabolism. Consequently, studies show that androgens decrease H3K27me3, a gene silencing mark on the promoter of core clock genes, by inhibiting the expression of histone methyltransferase, Ezh2, while inducing the expression of the histone demethylase, JMJD3, which is responsible for adding and removing the H3K27me3 mark, respectively. Finally, we report that under hyperandrogenic conditions, some of the same circadian/metabolic genes that are upregulated in the mouse liver are also elevated in nonhuman primate livers. In summary, these studies not only provide an overall understanding of how hyperandrogenism associated with PCOS affects liver gene expression and metabolism but also offer insight into the underlying mechanisms leading to hepatic steatosis in PCOS.

Von Willebrand factor exerts hepatoprotective effects in acute but not chronic cholestatic liver injury in mice.

Acute and chronic liver disease are associated with substantial alterations in the hemostatic system, including elevated levels of the platelet-adhesive protein von Willebrand factor (VWF). Carbon tetrachloride-induced liver fibrosis is reduced in VWF-deficient mice, but it is unclear if VWF plays a pathologic role in all settings of liver fibrosis. Indeed, several studies suggest an anti-fibrotic role for components of the hemostatic system, including platelets, in experimental settings of bile duct fibrosis. However, the role of VWF in this specific pathology has not been examined. We tested the hypothesis that VWF exerts hepatoprotective effects in experimental bile duct injury. Wild-type and VWF-deficient (VWF-/-) mice were challenged with the bile duct toxicant alpha-naphthylisothiocyanate (ANIT) and the impact of VWF deficiency on acute cholestatic liver injury and chronic liver fibrosis was determined. Acute ANIT (60 mg/kg, po)-induced cholestatic liver injury was associated with increased VWF plasma antigen and activity levels. VWF deficiency enhanced ANIT-induced hepatocellular injury, evidenced by increased plasma ALT activity and area of hepatocellular necrosis. Surprisingly, platelet accumulation within necrotic areas was increased in ANIT-challenged VWF-/- mice compared to wild-type mice. Compared to acute ANIT challenge, hepatic platelet accumulation was modest and appeared to be VWF-dependent in mice exposed to ANIT diet (0.05 %) for 6 weeks. However, contrasting the role of VWF after acute ANIT challenge, VWF deficiency did not impact biliary fibrosis induced by chronic ANIT exposure. The results suggest that VWF plays dichotomous roles in experimental acute and chronic ANIT-induced cholestatic liver injury.

Liver fibrosis is driven by protease-activated receptor-1 expressed by hepatic stellate cells in experimental chronic liver injury.

BACKGROUND: Blood coagulation protease activity is proposed to drive hepatic fibrosis through activation of protease-activated receptors (PARs). Whole-body PAR-1 deficiency reduces experimental hepatic fibrosis, and in vitro studies suggest a potential contribution by PAR-1 expressed by hepatic stellate cells. However, owing to a lack of specific tools, the cell-specific role of PAR-1 in experimental hepatic fibrosis has never been formally investigated. Using a novel mouse expressing a conditional PAR-1 allele, we tested the hypothesis that PAR-1 expressed by hepatic stellate cells contributes to hepatic fibrosis. METHODS: PAR-1flox/flox mice were crossed with mice expressing Cre recombinase controlled by the lecithin retinol acyltransferase (LRAT) promoter, which induces recombination in hepatic stellate cells. Male PAR-1flox/flox/LRATCre and PAR-1flox/flox mice were challenged twice weekly with carbon tetrachloride (CCl4, 1 mL/kg i.p.) for 6 weeks to induce liver fibrosis. RESULTS: PAR-1 mRNA levels were reduced (>95%) in hepatic stellate cells isolated from PAR-1flox/flox/LRATCre mice. Hepatic stellate cell activation was evident in CCl4-challenged PAR-1flox/flox mice, indicated by increased α-smooth muscle actin labeling and induction of several profibrogenic genes. CCl4-challenged PAR-1flox/flox mice displayed robust hepatic collagen deposition, indicated by picrosirius red staining and type I collagen immunolabeling. Notably, stellate cell activation and collagen deposition were significantly reduced (>30%) in PAR-1flox/flox/LRATCre mice. Importantly, the reduction in liver fibrosis was not a consequence of reduced acute CCl4 hepatotoxicity in PAR-1flox/flox/LRATCre mice. CONCLUSIONS: The results constitute the first direct experimental evidence that PAR-1 expressed by stellate cells directly promotes their profibrogenic phenotype and hepatic fibrosis in vivo.

Lymphocytes contribute to biliary injury and fibrosis in experimental xenobiotic-induced cholestasis.

The etiology of chronic bile duct injury and fibrosis in patients with autoimmune cholestatic liver diseases is complex, and likely involves immune cells such as lymphocytes. However, most models of biliary fibrosis are not autoimmune in nature. Biliary fibrosis can be induced experimentally by prolonged exposure of mice to the bile duct toxicant alpha-naphthylisothiocyanate (ANIT). We determined whether lymphocytes contributed to ANIT-mediated biliary hyperplasia and fibrosis in mice. Hepatic accumulation of T-lymphocytes and increased serum levels of anti-nuclear-autoantibodies were evident in wild-type mice exposed to ANIT (0.05% ANIT in chow). This occurred alongside bile duct hyperplasia and biliary fibrosis. To assess the role of lymphocytes in ANIT-induced biliary fibrosis, we utilized RAG1-/- mice, which lack T- and B-lymphocytes. ANIT-induced bile duct injury, indicated by increased serum alkaline phosphatase activity, was reduced in ANIT-exposed RAG1-/- mice compared to ANIT-exposed wild-type mice. Despite this reduction in biliary injury, ANIT-induced bile duct hyperplasia was similar in wild-type and RAG1-/- mice. However, hepatic induction of profibrogenic genes including COL1A1, ITGß6 and TGFß2 was markedly attenuated in ANIT-exposed RAG1-/- mice compared to ANIT-exposed wild-type mice. Peribiliary collagen deposition was also reduced in ANIT-exposed RAG1-/- mice. The results indicate that lymphocytes exacerbate bile duct injury and fibrosis in ANIT-exposed mice without impacting bile duct hyperplasia.

Trichloroethylene Exposure Reduces Liver Injury in a Mouse Model of Primary Biliary Cholangitis.

Trichloroethylene (TCE) is a persistent environmental contaminant proposed to contribute to autoimmune disease. Experimental studies in lupus-prone MRL+/+ mice have suggested that TCE exposure can trigger autoimmune hepatitis. The vast majority of studies examining the connection between TCE and autoimmunity utilize this model, and the impact of TCE exposure in other established models of autoimmune liver disease is not known. We tested the hypothesis that TCE exposure exacerbates experimental hepatic autoimmunity in dominant negative transforming growth factor beta receptor type II (dnTGFBRII) mice, which develop serological and histological features resembling human primary biliary cholangitis. Female 8-week-old wild-type and dnTGFBRII mice were exposed to TCE (0.5 mg/ml) or vehicle (1% ethoxylated castor oil) in the drinking water for 12 or 22 weeks. Liver histopathology in 20- and 30-week-old wild-type mice was unremarkable irrespective of treatment. Mild portal inflammation was observed in vehicle-exposed 20-week-old dnTGFBRII mice and was not exacerbated by TCE exposure. Vehicle-exposed 30-week-old dnTGFBRII mice developed anti-mitochondrial antibodies, marked hepatic inflammation with necrosis, and hepatic accumulation of both B and T lymphocytes. To our surprise, TCE exposure dramatically reduced hepatic parenchymal inflammation and injury in 30-week-old dnTGFBRII mice, reflected by changes in hepatic proinflammatory gene expression, serum chemistry, and histopathology. Interestingly, TCE did not affect hepatic B cell accumulation or induction of the anti-inflammatory cytokine IL10. These data indicate that TCE exposure reduces autoimmune liver injury in female dnTGFBRII mice and suggests that the precise effect of environmental chemicals in autoimmunity depends on the experimental model.