Progression Of Alcoholic Steatohepatitis Research Articles

FABP4 deficiency ameliorates alcoholic steatohepatitis in mice via inhibition of p53 signaling pathway

Fatty acid-binding protein 4 (FABP4) plays an essential role in metabolism and inflammation. However, the role of FABP4 in alcoholic steatohepatitis (ASH) remains unclear. This study aimed to investigate the function and underlying mechanisms of FABP4 in the progression of ASH. We first obtained alcoholic hepatitis (AH) datasets from the National Center for Biotechnology Information–Gene Expression Omnibus database and conducted bioinformatics analysis to identify critical genes in the FABP family. We then established ASH models of the wild-type (WT) and Fabp4-deficient (Fabp4−/−) mice to investigate the role of FABP4 in ASH. Additionally, we performed transcriptional profiling of mouse liver tissue and analyzed the results using integrative bioinformatics. The FABP4-associated signaling pathway was further verified. FABP4 was upregulated in two AH datasets and was thus identified as a critical biomarker for AH. FABP4 expression was higher in the liver tissues of patients with alcoholic liver disease and ASH mice than in the corresponding control samples. Furthermore, the Fabp4−/− ASH mice showed reduced hepatic lipid deposition and inflammation compared with the WT ASH mice. Mechanistically, Fabp4 may be involved in regulating the p53 and sirtuin-1 signaling pathways, subsequently affecting lipid metabolism and macrophage polarization in the liver of ASH mice. Our results demonstrate that Fabp4 is involved in the progression of ASH and that Fabp4 deficiency may ameliorate ASH. Therefore, FABP4 may be a potential therapeutic target for ASH treatment.

Activation of pregnane X receptor sensitizes alcoholic steatohepatitis by transactivating fatty acid binding protein 4

Alcoholic steatohepatitis (ASH) is a liver disease characterized by steatosis, inflammation, and necrosis of the liver tissue as a result of excessive alcohol consumption. Pregnane X receptor (PXR) is a xenobiotic nuclear receptor best known for its function in the transcriptional regulation of drug metabolism and disposition. Clinical reports suggested that the antibiotic rifampicin, a potent human PXR activator, is a contraindication in alcoholics, but the mechanism was unclear. In this study, we showed that the hepatic expression of fatty acid binding protein 4 (FABP4) was uniquely elevated in ASH patients and a mouse model of ASH. Pharmacological inhibiting FABP4 attenuated ASH in mice. Furthermore, treatment of mice with the mouse PXR agonist pregnenolon-16α-carbonitrile (PCN) induced the hepatic and circulating levels of FABP4 and exacerbated ASH in a PXR-dependent manner. Our mechanism study established FABP4 as a transcriptional target of PXR. Treatment with andrographolide, a natural compound and dual inhibitor of PXR and FABP4, alleviated mice from ASH. In summary, our results showed that the PXR–FABP4 gene regulatory axis plays an important role in the progression of ASH, which may have accounted for the contraindication of rifampicin in patients of alcoholic liver disease. Pharmacological inhibition of PXR and/or FABP4 may have its promise in the clinical management of ASH.

Metabolic signature of HepaRG cells exposed to ethanol and tumor necrosis factor alpha to study alcoholic steatohepatitis by LC-MS-based untargeted metabolomics.

Despite the high prevalence of alcoholic liver disease, its identification and characterization remain poor, especially in early stages such as alcoholic fatty liver disease and alcoholic steatohepatitis. This latter implies diagnostic difficulties, few therapeutic options and unclear mechanisms of action. To elucidate the metabolic alterations and pinpoint affected biochemical pathways, alcoholic steatohepatitis was simulated in vitro by exposing HepaRG cells to ethanol (IC10, 368mM) and tumor necrosis factor alpha (TNF-α, 50ng/mL) for 24h. This combined exposure was compared to solely ethanol-exposed as well as -nonexposed cells. Four different metabolomics platforms were used combining liquid chromatography, high-resolution mass spectrometry and drift tube ion mobility to elucidate both intracellular and extracellular metabolic alterations. Some of the key findings include the influence of TNF-α in the upregulation of hepatic triglycerides and the downregulation of hepatic phosphatidylethanolamines and phosphatidylcholines. S-Adenosylmethionine showed to play a central role in the progression of alcoholic steatohepatitis. In addition, fatty acyl esters of hydroxy fatty acid (FAHFA)-containing triglycerides were detected for the first time in human hepatocytes and their alterations showed a potentially important role during the progression of alcoholic steatohepatitis. Ethoxylated phosphorylcholine was identified as a potential new biomarker of ethanol exposure.

Modulation of interleukin-36 based inflammatory feedback loop through the hepatocyte-derived IL-36R-P2X7R axis improves steatosis in alcoholic steatohepatitis.

Interleukin-36 is induced by proinflammatory cytokines and promotes inflammatory responses, creating an IL-36-based inflammation loop. Although hepatocytes, produce IL-36 responses to drug-induced liver injury, little is known about the mechanistic role of IL-36 signalling during the progression of alcoholic steatohepatitis (ASH). Regarding IL-36/IL-36R and P2X7R coregulating the inflammatory response, we elucidated that modulation of IL-36R-P2X7R-TLR axis affected hepatocyte steatosis as well as the IL-36-based inflammatory feedback loop that accompanies the onset of ASH. C57BL/6J mice were subjected to either chronic-plus-binge ethanol feeding or acute gavage with multiple doses of ethanol to establish ASH, followed by pharmacological inhibition or genetic silencing of IL-36R and P2X7R. AML12 cells or mouse primary hepatocytes were stimulated with alcohol, LPS plus ATP or Poly(I:C) plus ATP, followed by silencing of IL-36γ, IL-36R or P2X7R. P2X7R and IL-36R deficiency blocked the inflammatory loop, specifically initiated by IL-36 cytokines, in hepatocytes of mice suffering from ASH. Pharmacological inhibition to P2X7R or IL-36R alleviated lipid accumulation and inflammatory response in ASH. IL-36R was indispensable for P2X7R modulated NLRP3 inflammasome activation in ASH, and IL-36 led to a vicious cycle of P2X7R-driven inflammation in alcohol-treated hepatocytes. TLR ligands promoted IL-36γ production in hepatocytes, based on synergism with P2X7R. Blockade of IL-36 based inflammatory feedback loop, via IL-36R-P2X7R-TLRs-modulated NLRP3 inflammasome activation, circumvented steatosis and inflammation that accompanies the onset of ASH, suggesting that targeting IL-36 can serve as a novel therapeutic approach to combat ASH.

The Role of Epigenetic Changes in the Progression of Alcoholic Steatohepatitis.

Alcoholic steatohepatitis (ASH) is a progression hepatitis with severe fatty liver and its mortality rate for 30-days in patients are over 30%. Additionally, ASH is well known for one-fifth all alcoholic related liver diseases in the world. Excessive chronic alcohol consumption is one of the most common causes of the progression of ASH and is associated with poor prognosis and liver failure. Alcohol abuse dysregulates the lipid homeostasis and causes oxidative stress and inflammation in the liver. Consequently, metabolic pathways stimulating hepatic accumulation of excessive lipid droplets are induced. Recently, many studies have indicated a link between ASH and epigenetic changes, showing differential expression of alcohol-induced epigenetic genes in the liver. However, the specific mechanisms underlying the pathogenesis of ASH remain elusive. Thus, we here summarize the current knowledge about the roles of epigenetics in lipogenesis, inflammation, and apoptosis in the context of ASH pathophysiology. Especially, we highlight the latest findings on the roles of Sirtuins, a conserved family of class-III histone deacetylases, in ASH. Additionally, we discuss the involvement of DNA methylation, histone modifications, and miRNAs in ASH as well as the ongoing efforts for the clinical translation of the findings in ASH-related epigenetic changes.

From the Editor’s desk....: November 2018

From the Editor’s desk....: November 2018

Endocrine Adiponectin-FGF15/19 Axis in Ethanol-Induced Inflammation and Alcoholic Liver Injury.

Alcoholic liver disease (ALD) is the most prevalent form of liver disease, encompassing a spectrum of progressive pathological changes from steatosis to steatohepatitis to fibrosis/cirrhosis and hepatocellular carcinoma. Alcoholic steatosis/steatohepatitis is the initial stage of ALD and a major risk factor for advanced liver injuries. Adiponectin is a hormone secreted from adipocytes. Fibroblast growth factor (FGF) 15 (human homolog, FGF19) is an ileum-derived hormone. Adipocyte-derived adiponectin and gut-derived FGF15/19 regulate each other, share common signaling cascades, and exert similar beneficial functions. Emerging evidence has revealed that dysregulated adiponectin-FGF15/19 axis and impaired hepatic adiponectin-FGF15/19 signaling are associated with alcoholic liver damage in rodents and humans. More importantly, endocrine adiponectin-FGF15/19 signaling confers protection against ethanol-induced liver damage via fine tuning the adipose-intestine-liver crosstalk, leading to limited hepatic inflammatory responses, and ameliorated alcoholic liver injury. This review is focused on the recently discovered endocrine adiponectin-FGF15/19 axis that is emerging as an essential adipose-gut-liver coordinator involved in the development and progression of alcoholic steatohepatitis.

Levels of metacaspase1 and chaperones related to protein quality control in alcoholic and nonalcoholic steatohepatitis

Efficient management of misfolded or aggregated proteins in ASH and NASH is crucial for continued hepatic viability. Cellular protein quality control systems play an important role in the pathogenesis and progression of ASH and NASH. In a recent study, elevated Mca1 expression counteracted aggregation and accumulation of misfolded proteins and extended the life span of the yeast Saccharomyces cerevisiae (Hill et al, 2014). Mca1 may also associate with Ssa1 and Hsp104 in disaggregation and fragmentation of aggregated proteins and their subsequent degradation through the ER-associated degradation (ERAD) pathway. If degradation is not available, protection of the cellular environment from a misfolded protein is accomplished by its sequestration into two distinct inclusion bodies (Kaganovich et al., 2008) called the JUNQ (JUxta Nuclear Quality control compartment) and the IPOD (Insoluble Protein Deposit). Mca1, Hsp104, Hsp40, Ydj1, Ssa1, VCP/p97, and p62 all play important roles in protein quality control systems. This study aims to measure the expression of Mca1 and related chaperones involved in protein quality control in alcoholic steatohepatitis (ASH), and nonalcoholic steatohepatitis (NASH) compared with normal control liver biopsies. Mca1, Hsp104, Hsp40, Ydj1, Ssa1, VCP/p97, and p62 expressions were measured in three to six formalin-fixed paraffin embedded ASH and NASH liver biopsies and control normal liver specimens by immunofluorescence staining and quantified by immunofluorescence intensity. Mca1, Hsp104, Ydj1 and p62 were significantly upregulated compared to control (p<0.05) in ASH specimens. Hsp40 and VCP/p97 were also uptrending in ASH. In NASH, the only significant difference was the increased expression of Hsp104 compared to control (p<0.05). Ssa1 levels were uptrending in both ASH and NASH specimens. The upregulation of Mca1, Hsp104, Ydj1 and p62 in ASH may be elicited as a response to the chronic exposure of the hepatocytes to the toxicity of alcohol. Recruitment of Mca1, Hsp104, Ydj1 and p62 may indicate that autophagy, the ERAD, JUNQ, and IPOD systems are active in ASH. Whereas in NASH, elevated Hsp104 and uptrending Ssa1 levels may indicate that autophagy and IPOD may be the only active protein quality control systems involved.

Anti‐inflammatory strategies in alcoholic steatohepatitis

The hepatotoxic effects of alcohol have been described in detail, but mechanisms underlying the hepatotoxicity have been only partially characterized. Recently, increasing lines of evidence indicate that Kupffer cells play multiple roles in initiation and progression of alcoholic steatohepatitis. After ethanol exposure, Kupffer cells are activated via a mechanism dependent on gut-derived endotoxin, and release active mediators such as proinflammatory cytokines and eicosanoids. These mediators are responsible for the pathophysiology of alcoholic steatohepatitis. This review discusses the current concept of Kupffer cell-mediated steatohepatitis and how it relates to the hypothesis on the mechanism by which alcoholic steatohepetitis is caused, as well as several key issues that have to be addressed in this field: (i) How do Kupffer cells undergo priming and activation during alcoholic steatohepatitis?; (ii) What kind of mediators are involved?; and (iii) How does the concept translate into a strategy for therapeutics of alcoholic steatohepatitis?