Frank E. Uschner

Seven weeks of Western diet in apolipoprotein-E-deficient mice induce metabolic syndrome and non-alcoholic steatohepatitis with liver fibrosis.

Non-alcoholic steatohepatitis (NASH) is characterised by hepatic steatosis, inflammation and fibrosis, which might progress to cirrhosis. Human NASH is associated with metabolic syndrome (MS). Currently, rodent NASH models either lack significant fibrosis or MS. ApoE−/− mice are a MS model used in cardiovascular research. The aim of this work was to establish and characterise a novel mouse NASH model with significant fibrosis and MS. ApoE−/− and wild-type mice (wt) were fed either a western-diet (WD), methionine-choline-deficient-diet (MCD) or normal chow. Liver histology, RT-PCR, hepatic hydroxyproline content, triglycerides and cholesterol levels, and fasting glucose levels assessed hepatic steatosis, inflammation and fibrosis. Further, portal pressure was measured invasively, and kidney pathology was assessed by histology. ApoE−/− mice receiving WD showed abnormal glucose tolerance, hepatomegaly, weight gain and full spectrum of NASH including hepatic steatosis, fibrosis and inflammation, with no sign of renal damage. MCD-animals showed less severe liver fibrosis, but detectable renal pathological changes, besides weight loss and unchanged glucose tolerance. This study describes a murine NASH model with distinct hepatic steatosis, inflammation and fibrosis, without renal pathology. ApoE−/− mice receiving WD represent a novel and fast model with all characteristic features of NASH and MS well suitable for NASH research.

Statins activate the canonical hedgehog-signaling and aggravate non-cirrhotic portal hypertension, but inhibit the non-canonical hedgehog signaling and cirrhotic portal hypertension.

Liver cirrhosis but also portal vein obstruction cause portal hypertension (PHT) and angiogenesis. This study investigated the differences of angiogenesis in cirrhotic and non-cirrhotic PHT with special emphasis on the canonical (Shh/Gli) and non-canonical (Shh/RhoA) hedgehog pathway. Cirrhotic (bile duct ligation/BDL; CCl4 intoxication) and non-cirrhotic (partial portal vein ligation/PPVL) rats received either atorvastatin (15 mg/kg; 7d) or control chow before sacrifice. Invasive hemodynamic measurement and Matrigel implantation assessed angiogenesis in vivo. Angiogenesis in vitro was analysed using migration and tube formation assay. In liver and vessel samples from animals and humans, transcript expression was analyzed using RT-PCR and protein expression using Western blot. Atorvastatin decreased portal pressure, shunt flow and angiogenesis in cirrhosis, whereas atorvastatin increased these parameters in PPVL rats. Non-canonical Hh was upregulated in experimental and human liver cirrhosis and was blunted by atorvastatin. Moreover, atorvastatin blocked the non-canonical Hh-pathway RhoA dependently in activated hepatic steallate cells (HSCs). Interestingly, hepatic and extrahepatic Hh-pathway was enhanced in PPVL rats, which resulted in increased angiogenesis. In summary, statins caused contrary effects in cirrhotic and non-cirrhotic portal hypertension. Atorvastatin inhibited the non-canonical Hh-pathway and angiogenesis in cirrhosis. In portal vein obstruction, statins enhanced the canonical Hh-pathway and aggravated PHT and angiogenesis.

Novel role of nuclear receptor rev‐erbα in hepatic stellate cell activation: Potential therapeutic target for liver injury

Hepatic stellate cell (HSC) transdifferentiation from a quiescent, adipocyte‐like cell to a highly secretory and contractile myofibroblast‐like phenotype contributes to negative pathological consequences, including fibrosis/cirrhosis with portal hypertension (PH). Antiadipogenic mechanisms have been shown to underlie activation of HSCs. We examined the role of heme‐sensing nuclear receptor Rev‐erbα, a transcriptional repressor involved in metabolic and circadian regulation known to promote adipogenesis in preadipocytes, in HSC transdifferentiation. We discovered that Rev‐erbα protein was up‐regulated in activated HSCs and injured livers; however, transcriptional repressor activity was not affected by fibrogenic treatments. Surprisingly, increased protein expression was accompanied with increased cytoplasmic accumulation of Rev‐erbα, which demonstrated distributions similar to myosin, the major cellular motor protein. Cells overexpressing a cytoplasm‐localized Rev‐erbα exhibited enhanced contractility. Ectopically expressed Rev‐erbα responded to both adipogenic ligand and fibrogenic transforming growth factor beta treatment. Rev‐erb ligand SR6452 down‐regulated cytoplasmic expression of Rev‐erbα, decreased expression of fibrogenic markers and the activated phenotype in HSCs, and ameliorated fibrosis and PH in rodent models. Conclusions: Up‐regulation of Rev‐erbα is an intrinsic fibrogenic response characterized by cytoplasmic accumulation of the protein in activated HSCs. Cytoplasmic expression of Rev‐erbα promotes a contractile phenotype. Rev‐erbα acts as a bifunctional regulator promoting either anti‐ or profibrogenic response, depending on milieu. Rev‐erb ligand SR6452 functions by a previously undescribed mechanism, targeting both nuclear activity and cytoplasmic expression of Rev‐erbα. Our studies identify Rev‐erbα as a novel regulator of HSC transdifferentiation and offers exciting new insights on the therapeutic potential of Rev‐erb ligands. (Hepatology 2014;59:2383–2396)

Janus-kinase-2 relates directly to portal hypertension and to complications in rodent and human cirrhosis.

Objective Angiotensin II (AngII) activates via angiotensin-II-type-I receptor (AT1R) Janus-kinase-2 (JAK2)/Arhgef1 pathway and subsequently RHOA/Rho-kinase (ROCK), which induces experimental and probably human liver fibrosis. This study investigated the relationship of JAK2 to experimental and human portal hypertension. Design The mRNA and protein levels of JAK2/ARHGEF1 signalling components were analysed in 49 human liver samples and correlated with clinical parameters of portal hypertension in these patients. Correspondingly, liver fibrosis (bile duct ligation (BDL), carbon tetrachloride (CCl4)) was induced in floxed-Jak2 knock-out mice with SM22-promotor (SM22Cre+-Jak2f/f). Transcription and contraction of primary myofibroblasts from healthy and fibrotic mice and rats were analysed. In two different cirrhosis models (BDL, CCl4) in rats, the acute haemodynamic effect of the JAK2 inhibitor AG490 was assessed using microsphere technique and isolated liver perfusion experiments. Results Hepatic transcription of JAK2/ARHGEF1 pathway components was upregulated in liver cirrhosis dependent on aetiology, severity and complications of human liver cirrhosis (Model for End-stage Liver disease (MELD) score, Child score as well as ascites, high-risk varices, spontaneous bacterial peritonitis). SM22Cre+- Jak2f/f mice lacking Jak2 developed less fibrosis and lower portal pressure (PP) than SM22Cre−-Jak2f/f upon fibrosis induction. Myofibroblasts from SM22Cre+-Jak2f/f mice expressed less collagen and profibrotic markers upon activation. AG490 relaxed activated hepatic stellate cells in vitro. In cirrhotic rats, AG490 decreased hepatic vascular resistance and consequently the PP in vivo and in situ. Conclusions Hepatic JAK2/ARHGEF1/ROCK expression is associated with portal hypertension and decompensation in human cirrhosis. The deletion of Jak2 in myofibroblasts attenuated experimental fibrosis and acute inhibition of JAK2 decreased PP. Thus, JAK2 inhibitors, already in clinical use for other indications, might be a new approach to treat cirrhosis with portal hypertension.

Rationale for the use of statins in liver disease

The evolution of chronic liver injuries from benign and manageable dysfunction to life threatening end-stage liver disease with severe complications renders chronic liver disease a global health burden. Because of the lack of effective medication, transplantation remains the only and final curative option for end-stage liver disease. Since the demand for organ transplants by far exceeds the supply, other treatment options are urgently required to prevent progression and improve end-stage liver disease. Statins are primarily cholesterol-lowering drugs used for primary or secondary prevention of cardiovascular diseases. In addition to the primary effect, statins act beneficially through different pleiotropic mechanisms on inflammation, fibrosis, endothelial function, thrombosis, and coagulation to improve chronic liver diseases. However, concerns remain about the efficacy and safety of statin treatment because of their potential hepatotoxic risks, and as of now, these risks impede broader use of statins in the treatment of chronic liver diseases. The aim of this review is to comprehensively describe the mechanisms by which statins improve prospects for different chronic liver diseases with special focus on the pathophysiological rationale and the clinical experience of statin use in the treatment of liver diseases.

Statins improve NASH via inhibition of RhoA and Ras

Nonalcoholic steatohepatitis (NASH), especially as part of the metabolic syndrome (MS), is an increasing burden in Western countries. Statins are already used in MS and seem to be beneficial in liver diseases. The aim of this study was to investigate the molecular mechanisms underlying pleiotropic effects on small GTPases of statins in NASH. NASH within MS was induced in 12-wk-old apoE-/- mice after 7 wk of Western diet (NASH mice). Small GTPases were inhibited by activated simvastatin (SMV), NSC23766 (NSC), or Clostridium sordellii lethal toxin (LT) by using subcutaneous osmotic minipumps. Hepatic steatosis, inflammation, and fibrosis were assessed by histology, Western blot, and RT-PCR measurements of cholesterol and hydroxyproline content. SMV treatment significantly decreased hepatic inflammation and fibrosis, but had no significant effect on steatosis and hepatic cholesterol content in NASH. SMV blunted fibrosis due to inhibition of both RhoA/Rho kinase and Ras/ERK pathways. Interestingly, inhibition of RAC1 and Ras (by LT) failed to decrease fibrosis to the same extent. Inhibition of RAC1 (by NSC) showed no significant effect at all. Inhibition of RhoA and Ras downstream signaling by statins is responsible for the beneficial hepatic effects in NASH.

Hemodynamic Effects of the Non-Peptidic Angiotensin-(1-7) Agonist AVE0991 in Liver Cirrhosis

Background & Aims Although in cirrhosis with portal hypertension levels of the vasoconstrictor angiotensin II are increased, this is accompanied by increased production of angiotensin (Ang)-(1–7), the endogenous ligand of the Mas receptor (MasR), which blunts hepatic fibrosis and decreases hepatic vascular resistance. Therefore, we investigated the effects of the non-peptidic Ang-(1–7) agonist, AVE0991, in experimental cirrhosis. Methods Cirrhosis was induced by bile duct ligation (BDL) or carbon tetrachloride (CCl4) intoxication. The coloured microsphere technique assessed portal and systemic hemodynamic effects of AVE0991 in vivo. Hepatic expression of eNOS, p-eNOS, iNOS, JAK2, ROCK and p-Moesin were analyzed by western blots. Activities of ACE and ACE2 were investigated fluorometrically. Moreover, fibrosis was assessed in BDL rats receiving AVE0991. Results In vivo, AVE0991 decreased portal pressure (PP) in both rat models of cirrhosis. Importantly, systemic effects were not observed. The hepatic effects of AVE0991 were based on upregulation of vasodilating pathways involving p-eNOS and iNOS, as well as by downregulation of the vasoconstrictive pathways (ROCK, p-Moesin). Short-term treatment with AVE0991 decreased the activity of ACE2, long-term treatment did not affect hepatic fibrosis in BDL rats. Conclusions The non-peptidic agonist of Ang-(1–7), AVE0991, decreases portal pressure without influencing systemic pressure. Thus, although it does not inhibit fibrosis, AVE0991 may represent a promising new therapeutic strategy for lowering portal pressure.

Novel Rat Model of Repetitive Portal Venous Embolization Mimicking Human Non-Cirrhotic Idiopathic Portal Hypertension

Background Non-cirrhotic idiopathic portal hypertension (NCIPH) is characterized by splenomegaly, anemia and portal hypertension, while liver function is preserved. However, no animal models have been established yet. This study assessed a rat model of NCIPH and characterized the hemodynamics, and compared it to human NCIPH. Methods Portal pressure (PP) was measured invasively and coloured microspheres were injected in the ileocecal vein in rats. This procedure was performed weekly for 3 weeks (weekly embolization). Rats without and with single embolization served as controls. After four weeks (one week after last embolization), hemodynamics were investigated, hepatic fibrosis and accumulation of myofibroblasts were analysed. General characteristics, laboratory analyses and liver histology were collected in patients with NCIPH. Results Weekly embolization induced a hyperdynamic circulation, with increased PP. The mesenteric flow and hepatic hydroxyproline content was significantly higher in weekly embolized compared to single embolized rats (mesenteric flow +54.1%, hydroxyproline +41.7%). Mesenteric blood flow and shunt volumes increased, whereas splanchnic vascular resistance was decreased in the weekly embolization group. Fibrotic markers αSMA and Desmin were upregulated in weekly embolized rats. Discussion This study establishes a model using repetitive embolization via portal veins, comparable with human NCIPH and may serve to test new therapies.

Circulating microbiome in blood of different circulatory compartments

We read with interest the recent review by Tilg et al ,1 which summarised the role of microbiota in liver diseases and pointed out that a causal link with systemic inflammation has still not been established. This letter fills in this gap and provides an analysis of the circulating microbiota in portal vein as the link between gut and liver. The access to portal circulation is possible during the implantation of a transjugular intrahepatic portosystemic shunt (TIPS). Therefore, we characterised the circulating microbiome in portal vein (first venous outflow in gut–liver axis), liver outflow, central venous blood and peripheral venous blood from seven patients with decompensated liver cirrhosis receiving TIPS for either variceal bleeding (n=3) or refractory ascites (n=4) (mean Model for End-stage Liver Disease (MELD) 8.4 (range 6–13), Child-Pugh-Score (CHILD) A: n=4, CHILD B: n=3) (figure 1A). We performed 16S ribosomal RNA (rRNA) gene sequencing of buffy coat samples and identified 65 genera belonging to four phyla (predominantly Proteobacteria) in this cohort (online supplementary figure 1 and figure 1B). Blood microbiome phylum compositions identified in our …

The soluble guanylate cyclase stimulator riociguat reduces fibrogenesis and portal pressure in cirrhotic rats

In cirrhotic patients, portal hypertension (PHT) deteriorates survival, yet treatment options are limited. A major contributor to increased intrahepatic vasoconstriction in PHT is dysfunctional nitric-oxide signaling. Soluble guanylate cyclase (sGC) is the receptor of nitric-oxide and can be stimulated by riociguat. Riociguat is approved for pulmonary hypertension but has not been studied in liver cirrhosis. In this study we assessed the effects of riociguat on PHT and liver fibrosis in cholestatic (bile duct ligation, BDL) and toxic (carbon-tetrachloride, CCl4) rat models. In cirrhotic livers sGC expression was upregulated. In BDL rats, riociguat reduced liver fibrosis and decreased portal pressure without affecting systemic hemodynamics. In an early BDL disease stage, riociguat decreased bile duct proliferation, improved sinusoidal vascular dysfunction and inhibited angiogenesis. In advanced BDL riociguat exhibited anti-inflammatory effects. In CCl4 rats the beneficial effects of riociguat treatment were less pronounced and confined to an early disease stage. Similarly, in patients with cholestatic cirrhosis and PHT nitrates (that induce sGC activity) decreased portal pressure more effectively than in patients with non-cholestatic etiology. We also found an improvement of transaminases in patients with pulmonary hypertension receiving riociguat. Our findings support the clinical development of sGC stimulators in patients with cirrhotic PHT.