Disclosures: The following people have nothing to disclose:

Yasuhiro Miyamoto, Amy S. Mauer, Harmeet Malhi Recent findings that excessive lipid accumulation decreases cellular levels of autophagy, and that autophagy modulates immune responses, suggested that alterations in macrophage autophagy with obesity may regulate innate immunity in NASH. We hypothesized that an obesity-induced impairment of macrophage autophagy promotes NASH development by altering proinflammatory M1 and anti-inflammatory M2 mac-rophage polarization which RG7204 supplier leads to an overactive innate immune response. Methods: Wild-type mice and mice with a LysM-Cre-mediated macrophage knockout of the autophagy gene Atg5 were fed a high fat diet (HFD) alone or together with low-dose lipopolysaccharide (LPS; 0.25 mg/day). Results: Primary bone marrow-derived macrophages (BMDM) and peritoneal Acalabrutinib macrophages from wild-type mice fed 16-20 weeks of HFD had

decreased levels of autophagic flux indicating an impairment of macrophage autophagy in obesity. With 12 weeks of HFD combined with 2 weeks of LPS, macrophage Atg5 knockout mice, but not littermate controls, developed systemic and hepatic inflammation. Contrary to prior reports that autophagy regulates only inflammasome-generated IL-1β, Atg5 null mice had increased serum protein and hepatic mRNA levels for the inflammasome-independent proinflammatory cytokines TNF and IL-6. This effect was liver specific as white adipose tissue cytokine expression was equivalent in control and knockout mice. Hepatic macrophage number was unchanged in knockout mice by F4/80 mRNA levels and CD68 immunofluores-cence. The mechanism by which loss of autophagy promoted inflammation was through effects on macrophage polarization. BMDM and Kupffer cells from HFD-fed, LPS-treated knockout mice stimulated with LPS/IFNβ or IL-4/IL-13 in vitro assumed a more inflammatory phenotype with both increased proinflam-matory M1 and decreased anti-inflammatory M2 polarization as determined by measures of M1/M2 marker genes and proteins. Loss of autophagy altered MCE a number of cellular

signaling pathways that mediate M1/M2 polarization including STAT6, JNK and Akt. The heightened inflammation in HFD-fed, LPS-treated knockout mice triggered liver injury without affecting steatosis. Knockout mice had statistically significant increases in histological grade of liver injury (1.0 vs. 0.2), TUNEL staining (2.1 vs. 0.2 cells/HPF) and caspase 3 and 7 cleavage. Conclusions: Autophagy has critical functions in both M1 and M2 polarization that determine hepatic macrophage pheno-type and down regulate liver inflammation. Obesity impairs macrophage autophagy which promotes proinflammatory mac-rophage activation leading to the progression of simple steato-sis to liver inflammation and hepatocyte injury. Disclosures: Mark J. Czaja – Consulting: Oncozyme Pharma Inc.; Grant/Research Support: Oncozyme Pharma Inc.