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Atorvastatin attenuates diet-induced non-alcoholic steatohepatitis in APOE*3-Leiden mice by reducing hepatic inflammation

ABSTRACT: Abstract: Patients with metabolic syndrome are often prescribed statins to prevent development of 17 cardiovascular disease. Conversely, data on their effects on non-alcoholic steatohepatitis (NASH) 18 are lacking. We evaluated these effects by feeding APOE*3-Leiden mice a Western-type diet (WTD) 19 with or without atorvastatin to induce NASH and hepatic fibrosis. Besides the well-known plasma 20 cholesterol lowering (-30%) and anti-atherogenic effects (severe lesion size -48%), atorvastatin sig-21 nificantly reduced hepatic steatosis (-22%), the number of aggregated inflammatory cells in the liver 22 (-80%) and hepatic fibrosis (-92%) compared to WTD-fed mice. Furthermore, atorvastatin-treated 23 mice showed less immunohistochemically stained area of inflammation markers. Atorvastatin pre-24 vented accumulation of free cholesterol in the form of cholesterol crystals (-78%). Cholesterol crys-25 tals are potent inducers of the NLRP3 inflammasome pathway and atorvastatin prevented its acti-26 vation, which resulted in reduced expression of the pro-inflammatory cytokines interleukin (IL)-1β 27 (-61%) and IL-18 (-26%). Transcriptome analysis confirmed strong reducing effects of atorvastatin 28 on inflammatory mediators, including NLRP3, NFκB and TLR4. The present study demonstrates 29 that atorvastatin reduces hepatic steatosis, inflammation and fibrosis and prevents cholesterol crys-30 tal formation, thereby precluding NLRP3 inflammasome activation. This may render atorvastatin 31 treatment as an attractive approach to reduce NAFLD and prevent progression into NASH in 32 dyslipidemic patients.

ORGANISM(S): Mus musculus

PROVIDER: GSE229188 | GEO | 2023/05/17

REPOSITORIES: GEO

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Project description:Background and Aims: The activation of stimulator of interferon genes (STING) and NOD-like receptors protein 3 (NLRP3) inflammasomes-mediated pyroptosis signaling pathways represent two distinct central mechanisms in liver disease. However, the interconnection between these two pathways and the epigenetic regulation of the STING-NLRP3 axis in hepatocyte pyroptosis during liver fibrosis remain unknown and is the focus of this study. Approach and Results: Liver fibrosis was induced in Sting knockout, Gasdermin D (Gsdmd) knockout mice, and in mice with hepatocyte-specific Nlrp3 deletion. RNA-sequencing, metabolomics, epigenetic compound screening system, and chromatin immunoprecipitation were utilized. STING and NLRP3 inflammasome signaling pathways were activated in cirrhotic livers but were suppressed by Sting knockout. Sting knockout also ameliorated hepatic pyroptosis, inflammation, and fibrosis in the murine cirrhotic model. In vitro, STING induced pyroptosis in primary murine hepatocytes via activating the NLRP3 inflammasome. H3K4-specific histone methyltransferase WD repeat-containing protein 5 (WDR5) and DOT1-like histone H3K79 methyltransferase (DOT1L) were identified to regulate NLRP3 expression in STING-overexpressed AML12 hepatocytes. WDR5/DOT1L-mediated histone methylation enhanced interferon regulatory transcription factor 3 (IRF3) binding to the Nlrp3 promoter and promoted STING-induced Nlrp3 transcription in hepatocytes. The RNA-sequencing and metabolomics analysis in murine livers and primary hepatocytes showed that metabolic reprogramming might participate in NLRP3-mediated hepatocyte pyroptosis and liver fibrosis. Moreover, hepatocyte-specific Nlrp3 deletion and downstream Gsdmd knockout attenuated hepatic pyroptosis, inflammation, and fibrosis in murine cirrhotic models. Conclusions: This study describes a novel epigenetic mechanism by which the STING-WDR5/DOT1L/IRF3-NLRP3 signaling pathway enhances hepatocyte pyroptosis and hepatic inflammation in liver fibrosis.

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Project description:Background & Aims: Overnutrition is one of the major causes of non-alcoholic fatty liver disease (NAFLD) and its advanced form non-alcoholic steatohepatitis (NASH). Besides the quantity of consumed calories, distinct dietary components are increasingly recognized as important contributor to the pathogenesis of NASH. We aimed to develop and characterize a hitherto missing murine model which resembles both the pathology and nutritional situation of NASH-patients in Western societies. Methods: We developed a NASH-inducing diet (ND) enriched with sucrose, cholesterol and a high concentration of fats rich in saturated fatty acids in a composition which mimics Western food. C57Bl6/N mice were fed with the ND or control chow for 12 weeks. Biochemical, real-time polymerase chain reaction, Western Blot and immunohistochemical analyses were performed to characterize systemic and hepatic changes induced by ND-feeding. Immunohistochemistry was used to assess c-Jun levels and activation in 110 human NAFLD and control liver specimens applying tissue micro array technology. Results: ND-fed mice showed significant body weight gain, impaired glucose tolerance, elevated fasting blood glucose levels as well as decreased adiponectin and increased leptin serum levels compared to control mice. In the liver, ND-feeding led to marked steatosis, enhanced cholesterol levels, distinct signs of oxidative stress, hepatocellular damage, inflammation, activation of hepatic stellate cells, and beginning fibrosis. Transcriptome-wide hepatic gene expression analysis comparing ND-fed mice and control mice indicated main alterations in lipid metabolism and inflammatory processes. Search for over-represented transcription factor target sites among the differentially expressed genes identified AP-1 as the most likely factor to cause the transcriptional changes in ND-livers. Combining differentially expressed gene and protein-protein interaction network analysis identified c-Jun (a component of the AP-1 complex) as hub in the largest connected deregulated sub-network in ND-livers. In accordance, ND-livers revealed c-Jun-phosphorylation and nuclear translocation. Moreover, hepatic c-Jun RNA and protein expression was enhanced in ND-fed compared to control mice. Also NAFLD-patients showed enhanced hepatic c-Jun levels, which correlated with inflammation, and notably, with the degree of hepatic steatosis. Conclusions: The new dietary mouse-model shows important pathological changes also found in human NASH and indicates c-jun/AP-1 activation as critical regulator of hepatic alterations. Abundance of c-jun in NAFLD likely facilitates development and progression of NASH, and thus, c-jun appears as attractive prognostic and therapeutic target of NAFLD progression. 14-weeks old male C57BL/6N mice were fed with either regular diet or a newly designed NASH-inducing diet for 12 weeks. Hepatic gene expression levels were measured thereafter.

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Atorvastatin attenuates diet-induced non-alcoholic steatohepatitis in APOE*3-Leiden mice by reducing hepatic inflammation

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