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Activation of autophagy attenuates EtOH-LPS-induced hepatic steatosis and injury through MD2 associated TLR4 signaling.

ABSTRACT: Autophagy serves as a protective mechanism to degrade damaged organelles and proteins. Acute alcohol exposure is known to activate the hepatic autophagy response, whereas chronic alcohol exposure slows autophagosome formation along with an elevation of gut-derived endotoxin. In the current study, we examined whether lipopolysaccharide (LPS) administration decreased autophagic response in the liver of mice treated by short-term alcohol and whether activation of autophagy by rapamycin attenuates EtOH-LPS-induced liver steatosis and injury. We demonstrated that ten-day alcohol feeding primed the liver to LPS-induced lipid accumulation and liver injury with significantly increased hepatic steatosis and serum AST level as well as hepatic cellular NF-?B activation. LPS increased alcohol-mediated reactive oxygen species (ROS) formation while reducing autophagy activation. These deleterious effects were attenuated by rapamycin administration in mice. The protective effects of rapamycin are associated with decreased cellular MD2/TLR4 expression and interaction in Raw264.7 cells. Taken together, our results demonstrated that enhanced gut-derived LPS decreases the hepatic autophagosome numbers in response to alcohol exposure, and activation of autophagy by rapamycin protects from EtOH-LPS-induced liver injury, probably through reduced macrophage expression and interaction of TLR4/MD2 signaling complex.

SUBMITTER: Kong X

PROVIDER: S-EPMC5571015 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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Activation of autophagy attenuates EtOH-LPS-induced hepatic steatosis and injury through MD2 associated TLR4 signaling.

Kong Xiaoxia X Yang Ying Y Ren Li L Shao Tuo T Li Fengyuan F Zhao Cuiqing C Liu Liming L Zhang Hongyu H McClain Craig J CJ Feng Wenke W

Scientific reports 20170824 1

Autophagy serves as a protective mechanism to degrade damaged organelles and proteins. Acute alcohol exposure is known to activate the hepatic autophagy response, whereas chronic alcohol exposure slows autophagosome formation along with an elevation of gut-derived endotoxin. In the current study, we examined whether lipopolysaccharide (LPS) administration decreased autophagic response in the liver of mice treated by short-term alcohol and whether activation of autophagy by rapamycin attenuates E ...[more]

PMID: 28839246

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Project description:Ethanol-mediated down-regulation of carnitine palmitoyltransferase-1 (CPT-1A) gene expression plays a major role in the development of hepatic steatosis; however, the underlying mechanisms are not completely elucidated. Tributyrin, a butyrate prodrug that can inhibit histone deacetylase (HDAC) activity, attenuates hepatic steatosis and injury. The present study examined the beneficial effect of tributyrin/butyrate in attenuating ethanol-induced pathogenic epigenetic mechanisms affecting CPT-1A promoter-histone modifications and gene expression and hepatic steatosis/injury.MethodsMice were fed a liquid Lieber-DeCarli diet (Research Diet Inc, New Brunswick, NJ) with or without ethanol for 4 weeks. In a subset of mice, tributyrin (2 g/kg) was administered orally by gavage. Primary rat hepatocytes were treated with 50 mmol/L ethanol and/or 2 mmol/L butyrate. Gene expression and epigenetic modifications at the CPT-1A promoter were analyzed by chromatin immunoprecipitation analysis.ResultsIn vivo, ethanol induced hepatic CPT-1A promoter histone H3K9 deacetylation, which is indicative of a repressive chromatin state, and decreased CPT-1A gene expression. Our data identified HDAC1 as the predominant HDAC causing CPT-1A promoter histone H3K9 deacetylation and epigenetic down-regulation of gene expression. Significantly, Specificity Protein 1 (SP1) and Hepatocyte Nuclear Factor 4 Alpha (HNF4α) participated in the recruitment of HDAC1 to the proximal and distal regions of CPT-1A promoter, respectively, and mediated transcriptional repression. Importantly, butyrate, a dietary HDAC inhibitor, attenuated ethanol-induced recruitment of HDAC1 and facilitated p300-HAT binding by enabling SP1/p300 interaction at the proximal region and HNF4α/peroxisomal proliferator-activated receptor-γ coactivator-1α/p300 interactions at the distal region, leading to promoter histone acetylation and enhanced CPT-1A transcription.ConclusionsThis study identifies HDAC1-mediated repressive epigenetic mechanisms that underlie an ethanol-mediated decrease in CPT-1A expression. Importantly, tributyrin/butyrate inhibits HDAC1, rescues CPT-1A expression, and attenuates ethanol-mediated hepatic steatosis and injury, suggesting its potential use in therapeutic strategies for alcoholic liver disease.

Dataset Information

Activation of autophagy attenuates EtOH-LPS-induced hepatic steatosis and injury through MD2 associated TLR4 signaling.

Publications

Activation of autophagy attenuates EtOH-LPS-induced hepatic steatosis and injury through MD2 associated TLR4 signaling.

Similar Datasets

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