ENDOPLASMIC RETICULUM (ER) STRESS MEDIATES ADIPOSE TISSUE INFLAMMATION DURING ALCOHOL INDUCED LIVER INJURY

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Mandrekar P1, Fulham MA1, Lim A1

1Dept. of Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA

 

Alcoholic liver disease (ALD) is linked to inflammatory cell activation and oxidative stress. Endoplasmic reticulum (ER) stress mediated by chaperone glycoprotein 96 (gp96, GRP94, HSP90B1) can regulate macrophage function via toll-like receptors (TLRs) and integrins. The correlation between adipose tissue inflammation and liver injury in human ALD remains unresolved. Chronic alcohol induces ER-gp96 expression in the liver and macrophages. We recently reported that inhibition of HSP90 (inhibits cytoplasmic hsp90AA1 and ER gp96) using a specific inhibitor, 17-DMAG [17-Dimethylamino-ethylamino-17-demethoxygeldanamycin], prevents macrophage activation in the liver. Here we hypothesize that alcohol induces white adipose and liver macrophage activation via gp96-mediated TLR surface expression, contributing to liver injury. To test our hypothesis, we subjected LysMCre+/-Hsp90b1flox/- (gp96KO) mice and wild type (WT) littermates to chronic-binge alcohol feeding. Parameters of liver injury and adipose immune profile were assessed. Alcohol-fed gp96KO mice exhibit significantly lower serum ALT (p<0.05) and triglycerides (p<0.04), compared to WT mice, confirmed by liver histology. Alcohol did not affect adipocyte morphology but reduced cytokines, IL-6, MCP1 and innate immune markers (F4/80, CD68, CD11b, and CCR2) in adipose tissue of gp96KO, suggesting dysfunctional adipose tissue macrophages (ATMs) or decreased infiltration of macrophages in gp96KO mice. Livers from alcohol fed gp96KO mice also exhibit lower levels of TNF╬▒, MCP1 and IL-6. Alcohol metabolizing enzyme, CYP2E1 was induced in adipose tissue, similar to livers, in both WT and gp96KO mice. Inhibition of gp96 activity using a specific inhibitor WS-13 or 17-DMAG or gp96 siRNA in vitro reduced pro-inflammatory cytokine production and TLR4 expression. Our results support our hypothesis that ER chaperone gp96 plays an important role in alcohol mediated activation of adipose tissue and liver macrophages resulting in liver injury. (Supported by the NIH/NIAAA 2AA017986-01A1)

 

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