Zhaolian Bian

Interleukin-17 exacerbates hepatic steatosis and inflammation in non-alcoholic fatty liver disease

Mechanisms associated with the progression of simple steatosis to non‐alcoholic fatty liver disease (NAFLD) remain undefined. Regulatory T cells (Tregs) play a critical role in regulating inflammatory processes in non‐alcoholic steatohepatitis (NASH) and because T helper type 17 (Th17) functionally oppose Treg‐mediated responses, this study focused on characterizing the role of Th17 cells using a NAFLD mouse model. C57BL/6 mice were fed either a normal diet (ND) or high fat (HF) diet for 8 weeks. Mice in the HF group had a significantly higher frequency of liver Th17 cells compared to ND‐fed mice. Neutralization of interleukin (IL)‐17 in HF mice ameliorated lipopolysaccharide (LPS)‐induced liver injury reflected by decreased serum alanine aminotransferase (ALT) levels and reduced inflammatory cell infiltrates in the liver. In vitro, HepG2 cells cultured in the presence of free fatty acids (FFA; oleic acid and palmitic acid) for 24 h and IL‐17 developed steatosis via insulin‐signalling pathway interference. IL‐17 and FFAs synergized to induce IL‐6 production by HepG2 cells and murine primary hepatocytes which, in combination with transforming growth factor (TGF‐β), expanded Th17 cells. It is likely that a similar process occurs in NASH patients, as there were significant levels of IL‐17+ cell infiltrates in NASH patient livers. The hepatic expression of Th17 cell‐related genes [retinoid‐related orphan receptor gamma (ROR)γt, IL‐17, IL‐21 and IL‐23] was also increased significantly in NASH patients compared to healthy controls. Th17 cells and IL‐17 were associated with hepatic steatosis and proinflammatory response in NAFLD and facilitated the transition from simple steatosis to steatohepatitis. Strategies designed to alter the balance between Th17 cells and Tregs should be explored as a means of preventing progression to NASH and advanced liver diseases in NAFLD patients.

THE IMMUNOPATHOLOGY OF LIVER GRANULOMAS IN PRIMARY BILIARY CIRRHOSIS

Liver granulomas and elevated serum IgM are commonly observed in patients with primary biliary cirrhosis (PBC) but their pathogenetic significance remains largely unknown. To address this issue we performed an extensive immunostaining and colocalization study of markers associated with dendritic cells and IgM in a large cohort of tissue samples from PBC and control livers as well as from non-hepatic granulomatous diseases. First, the classical dendritic cell CD11c marker is highly expressed and more sensitive than classical hematoxylin-eosin staining in detecting granulomas associated with PBC and other conditions. Second, PBC cases with CD11c-positive granulomas have significantly higher serum IgM levels and earlier disease stages. Third, granulomas from PBC and other diseases demonstrate markers of dendritic cell immaturity, i.e. CD11b, reduced MHC II, IL-23, CCR7 and CD83 expression, and elevated C1q expression. Lastly, B cells and IgM-positive plasma cells are largely represented around PBC granulomas along with macrophages. In conclusion, our comprehensive immunohistochemical study suggests that dendritic cells are key to the pathogenesis of granulomas, regardless of their origin. More specifically, PBC liver granulomas may result from the interaction between immature dendritic cells and IgM.

CCN1 expression in hepatocytes contributes to macrophage infiltration in nonalcoholic fatty liver disease in mice

Our objective was to investigate the potential roles of CCN1 in the inflammation and macrophage infiltration of nonalcoholic fatty liver disease (NAFLD). The regulation of hepatic CCN1 expression was investigated in vitro with murine primary hepatocytes treated with free fatty acids or lipopolysaccharide (LPS) and in vivo with high-fat (HF) diet-fed mice or ob/ob mice. CCN1 protein and a liver-specific CCN1 expression plasmid were administered to mice fed a normal diet (ND) or HF diet. Myeloid-derived macrophages and RAW264.7 cells were also treated with CCN1 in vitro to determine the chemotactic effects of CCN1 on macrophages. LPS treatment significantly increased hepatic CCN1 expression in HF diet-fed mice and ob/ob mice. LPS and FFAs induced CCN1 expression in primary murine hepatocytes in vitro through the TLR4/MyD88/AP-1 pathway. CCN1 protein and overexpression of CCN1 in the liver induced more severe hepatic inflammation and macrophage infiltrates in HF mice than in ND mice. CCN1 recruited macrophages through activation of the Mek/Erk signaling pathway in myeloid-derived macrophages and RAW264.7 cells in vitro. Endotoxin and FFA-induced CCN1 expression in hepatocytes is involved in the hepatic proinflammatory response and macrophage infiltration in murine NAFLD.

Dynamic expression of miR-126^* and its effects on proliferation and contraction of hepatic stellate cells

In our previous study, miR‐126 was identified as one of the leading miRNAs that is downregulated during activation of hepatic stellate cells (HSCs). However, the roles and related mechanisms of miR‐126 in HSCs are not understood. In this study, we compared expression of miR‐126 during HSC activation both in vitro and in vivo. We also applied RNA interference to analyze the role and mechanism of miR‐126∗ in the activation of HSCs. Restoring HSCs with Lv‐miR‐126∗ resulted in decreased proliferation, accumulation of extracellular matrix components, and cell contraction, while also negatively regulating the vascular endothelial growth factor (VEGF) signal transduction pathways by partially targeted VEGF‐A. Thus, we postulate that miR‐126 may be a biological marker for the activation of HSCs, and useful for reducing intrahepatic vascular resistance and improving the sinusoidal microcirculation in chronic liver diseases.

The cumulative effects of known susceptibility variants to predict primary biliary cirrhosis risk

Multiple genetic variants influence the risk for development of primary biliary cirrhosis (PBC). To explore the cumulative effects of known susceptibility loci on risk, we utilized a weighted genetic risk score (wGRS) to evaluate whether genetic information can predict susceptibility. The wGRS was created using 26 known susceptibility loci and investigated in 1840 UK PBC and 5164 controls. Our data indicate that the wGRS was significantly different between PBC and controls (P=1.61E−142). Moreover, we assessed predictive performance of wGRS on disease status by calculating the area under the receiver operator characteristic curve. The area under curve for the purely genetic model was 0.72 and for gender plus genetic model was 0.82, with confidence limits substantially above random predictions. The risk of PBC using logistic regression was estimated after dividing individuals into quartiles. Individuals in the highest disclosed risk group demonstrated a substantially increased risk for PBC compared with the lowest risk group (odds ratio: 9.3, P=1.91E−084). Finally, we validated our findings in an analysis of an Italian PBC cohort. Our data suggested that the wGRS, utilizing genetic variants, was significantly associated with increased risk for PBC with consistent discriminant ability. Our study is a first step toward risk prediction for PBC.

Autoimmune hepatitis: East meets west.

Autoimmune hepatitis (AIH) is an inflammatory liver disease with diverse clinical spectrum, which predominantly affects females. This review provides detailed comparisons of epidemiology, genetic predispositions, clinical features, risk factors of hepatocellular carcinoma, and mortality in AIH patients between eastern and western countries. AIH prevalence and incidence are lower in Asia‐Pacific area than in Europe and America. European and American patients seem to have more severe disease, characterized with human leukocyte antigen‐DR3 haplotype, younger age, more AIH‐induced “cirrhosis” at diagnosis, higher elevated serum immunoglobulin G levels, and positive rate of antisoluble liver antigen/liver pancreatitis. The overall AIH diagnostic accuracy of revised original criteria and simplified scoring system are similar in European/American populations and Asian. Cirrhosis at presentation and non‐response to immunosuppressive therapy within 1 year are the most important predictors for poor prognosis of AIH patients.

Treatment of cholestatic fibrosis by altering gene expression of Cthrc1: Implications for autoimmune and non-autoimmune liver disease.

Collagen triple helix repeat containing-1 (Cthrc1) is a documented specific inhibitor of TGF-β signaling. Based on this observation, we developed the hypothesis that knocking in/knocking out the Cthrc1 gene in murine models of cholestasis would alter the natural history of cholestatic fibrosis. To study this thesis, we studied two murine models of fibrosis, first, common bile duct ligation (CBDL) and second, feeding of 3, 5-diethoxy-carbonyl-1, 4-dihydrocollidine (DDC). In both models, we administered well-defined adenoviral vectors that expressed either Cthrc1 or, alternatively, a short hairpin RNA (shRNA)-targeting Cthrc1 either before or after establishment of fibrosis. Importantly, when Cthrc1 gene expression was enhanced, we noted a significant improvement of hepatic fibrosis, both microscopically and by analysis of fibrotic gene expression. In contrast, when Cthrc1 gene expression was deleted, there was a significant exacerbation of fibrosis. To identify the mechanism of action of these significant effects produced by knocking in/knocking out Cthrc gene expression, we thence studied the interaction of Cthrc1 gene expression using hepatic stellate cells (HSCs) and human LX-2 cells. Importantly, we demonstrate that Cthrc1 is induced by TGF-β1 via phospho-Smad3 binding to the promoter with subsequent transcription activation. In addition, we demonstrate that Cthrc1 inhibits TGF-β signaling by accelerating degradation of phospho-Smad3 through a proteosomal pathway. Importantly, the anti-fibrotic effects can be recapitulated with a truncated fragment of Cthrc1. In conclusion, our findings uncover a critical negative feedback regulatory loop in which TGF-β1 induces Cthrc1, which can attenuate fibrosis by accelerating degradation of phospho-Smad3.

A Common Variant in CLDN14 is Associated with Primary Biliary Cirrhosis and Bone Mineral Density

Primary biliary cirrhosis (PBC), a chronic autoimmune liver disease, has been associated with increased incidence of osteoporosis. Intriguingly, two PBC susceptibility loci identified through genome-wide association studies are also involved in bone mineral density (BMD). These observations led us to investigate the genetic variants shared between PBC and BMD. We evaluated 72 genome-wide significant BMD SNPs for association with PBC using two European GWAS data sets (n = 8392), with replication of significant findings in a Chinese cohort (685 cases, 1152 controls). Our analysis identified a novel variant in the intron of the CLDN14 gene (rs170183, Pfdr = 0.015) after multiple testing correction. The three associated variants were followed-up in the Chinese cohort; one SNP rs170183 demonstrated consistent evidence of association in diverse ethnic populations (Pcombined = 2.43 × 10−5). Notably, expression quantitative trait loci (eQTL) data revealed that rs170183 was correlated with a decline in CLDN14 expression in both lymphoblastoid cell lines and T cells (Padj = 0.003 and 0.016, respectively). In conclusion, our study identified a novel PBC susceptibility variant that has been shown to be strongly associated with BMD, highlighting the potential of pleiotropy to improve gene discovery.

Quantitation of the Rank-Rankl Axis in Primary Biliary Cholangitis.

There is substantial data that suggests an abnormality of innate immunity in patients with primary biliary cholangitis (PBC) which includes the transcription factor nuclear factor-kB (NF-kB) and well as downstream inflammatory signaling pathways. In addition, ImmunoChip analysis has identified a novel PBC-associated locus near the receptor activator of NF-kB ligand (RANKL) gene. Based on these observations, we investigated the role of the RANKL axis in the liver of patients with PBC compared to controls. We used immunohistochemistry to quantitate liver expression of RANKL, its receptor (RANK), and importantly the decoy receptor osteoprotegerin (OPG), including a total of 122 liver samples (PBC = 37, primary sclerosing cholangitis = 20, autoimmune hepatitis = 26, chronic hepatitis B = 32 and unaffected controls = 7). In addition, we studied RANKL-RANK-OPG co-localization in CD4 and CD8 T cells, B cells, dendritic cells, macrophages, NK, NKT cells, hepatocytes, and cholangiocytes. We report herein that RANK is constitutively expressed by cholangiocytes in both unaffected and diseased liver. However, cholangiocytes from PBC express significantly higher levers of RANK than either the unaffected controls or liver diseased controls. CD4, CD8 and CD19 cells with in the portal areas around bile ducts in PBC express significantly higher levels of RANKL compared to controls. Importantly, the overall hepatic RANKL level and the ratio of hepatic RANKL/OPG correlated with disease severity in PBC. In conclusion, our data indicate a role of RANK-RANKL axis in the innate immune activation in PBC and we hypothesize that the damaged cholangiocytes, which express high levels of RANK, lead to the recruitment of RANKL positive cells and ultimately the classic portal tract infiltrates.

Erratum: The cumulative effects of known susceptibility variants to predict primary biliary cirrhosis risk (Genes and Immunity (2015) 16 (238))

Correction to: Genes and Immunity (2015) 16, 193–198; doi:10.1038/gene.2014.76; published online 8 January 2015. Since the online publication of this paper, the authors have noted that the email address for the author W Liao was incorrectly listed. The correct email address is liaowi@derm.ucsf.edu. The typesetters would like to apologise for any inconvenience caused.