TRIF and IRF-3 Binding to the TNF Promoter Results in Macrophage TNF Dysregulation and Steatosis Induced by Chronic Ethanol

Abstract

Chronic ethanol (EtOH) abuse results in the development of steatosis, alcoholic hepatitis, and cirrhosis. Augmented TNF-alpha production by macrophages and Kupffer cells and signaling via the p55 TNF receptor have been shown to be critical for these effects of chronic EtOH; however, the molecular mechanisms leading to augmented TNF-alpha production remain unclear. Using cell culture models and in vivo studies we demonstrate that chronic EtOH results in increased TNF-alpha transcription, which is independent of NF-kappaB. Using reporter assays and chromatin immunoprecipitation we found that this increased transcription is due to increased IRF-3 binding to and transactivation of the TNF promoter. As IRF-3 is downstream from the TLR4 adaptor TIR-domain-containing adapter-inducing IFN-beta (Trif), we demonstrate that macrophages from Trif-/- mice are resistant to this dysregulation of TNF-alpha transcription by EtOH in vitro as well as EtOH-induced steatosis and TNF dysregulation in vivo. These data demonstrate that the Trif/IRF-3 pathway is a target to ameliorate liver dysfunction associated with chronic EtOH.