ABSTRACT FINAL ID: 1668
TITLE: Aged mice exhibit a more proinflammatory and fibrogenic NASH phenotype linked to the induction of Shc and NADPH oxidase 2
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Progression of non-alcoholic steatohepatitis (NASH) to fibrosis and cirrhosis is more common in older patients with obesity and/or type II diabetes mellitus. Whether this is due to the natural progression of the disease or to the induction of specific aging-related molecular pathways in this population contributing to faster progression; is unknown. Upregulation of the Shc family of adapter proteins and enhanced production of reactive oxidative species have been recognized in the aging process however the link between these and NASH progression has not been evaluated. We hypothesized that induction of Shc in aged mice on fast food diet is linked to enhanced redox stress and progressive NASH. Methods: Shc expression and activation were studied in young (6w) and aged (27w) mice on fast food diet by RT-qPCR and western blots. A group of mice were treated with LV-sh-Shc targeting all isoforms p46/p52Shc, and p66Shc or control vectors. NADPH oxidase 2 (NOX2) expression, release of redox radicals, inflammation (MCP-1, TNFα, IL-1β), and markers of stellate cell activation (procollagen α1 (I), αSMA, TGFβ) were assessed. In vitro palmitate-induced hepatocyte apoptosis was studied in wt or shcKO hepatocytes. Results: p46 and p52Shc protein expression and activation were more significantly induced in aged compared to young mice on FFD (p<0.05). P66Shc remained at baseline level after fast food diet. Fast food diet induced the expression of MCP-1, TNFα, IL-1β, and fibrogenic makers (procollagen α1 (I) p<0.05, ASMA p<0.05, TGFβ p<0.05) and these were blunted following the treatment with LV-sh-Shc (procollagen α1 (I) p< 0.05, TGFβ p<0.05), compared to control-vector injected mice. NOX2 was induced in the control vector injected mice on FFD but was downregulated in LV-sh-Shc injected mice. The NOX2 subunit p47phox co-localized with Shc. In vitro, we found that palmitate-induced apoptosis was significantly attenuated in Shc KO hepatocytes (p<0.05). Conclusion: Shc-dependent NOX2 activation and redox stress in aged mice contribute to the exacerbated inflammatory and fibrogenic process culminating in a more rapid progression of the disease.