miR-217 regulates ethanol-induced hepatic inflammation by disrupting sirtuin 1 - Lipin-1 signaling

Ethanol-mediated injury, combined with gut-derived lipopolysaccharide (LPS), provokes generation of proinflammatory cytokines in Kupffer cells, causing hepatic inflammation. Among the mediators of these effects, miR-217 aggravates ethanol-induced steatosis in hepatocytes. However, the role of miR-217 in ethanol-induced liver inflammation process is unknown. Here, we examined the role of miR-217 in the responses to ethanol, LPS, or a combination of ethanol and LPS in RAW 264.7 macrophages and in primary Kupffer cells. In macrophages, ethanol substantially exacerbated LPS-mediated induction of miR-217 and production of proinflammatory cytokines compared with LPS or ethanol alone. Consistently, ethanol administration to mice led to increases in miR-217 abundance and increased production of inflammatory cytokines in isolated primary Kupffer cells exposed to the combination of ethanol and LPS. miR-217 promoted combined ethanol and LPS-mediated inhibition of sirtuin 1 expression and activity in macrophages. Moreover, miR-217-mediated sirtuin 1 inhibition was accompanied by increased activities of two vital inflammatory regulators, NF-κB and the nuclear factor of activated T cells c4. Finally, adenovirus-mediated overexpression of miR-217 led to steatosis and inflammation in mice. These findings suggest that miR-217 is a pivotal regulator involved in ethanol-induced hepatic inflammation. Strategies to inhibit hepatic miR-217 could be a viable approach in attenuating alcoholic hepatitis.