Induction of Bcl-3 by acute binge alcohol results in Toll-like receptor 4/LPS tolerance

Abstract

Acute alcohol binge results in immunosuppression and impaired production of proinflammatory cytokines, including TNF-α. TNF-α production is induced by LPS, a TLR4 ligand, and is tightly regulated at various levels of the signaling cascade, including the NF-κB transcription factor. Here, we hypothesized that acute alcohol induces TLR4/LPS tolerance via Bcl-3, a nuclear protein and member of the NF-κB family. We found that acute alcohol pretreatment resulted in the same attenuating effect as LPS pretreatment on TLR4-induced TNF-α production in human monocytes and murine RAW 264.7 macrophages. Acute alcohol-induced Bcl-3 expression and IP studies revealed increased association of Bcl-3 with NF-κB p50 homodimers in alcohol-treated macrophages and in mice. ChIP assays revealed increased occupancy of Bcl-3 and p50 at the promoter region of TNF-α in alcohol-pretreated cells. To confirm that the Bcl-3-p50 complex regulates transcription/production of TNF-α during acute alcohol exposure, we inhibited Bcl-3 expression using a targeted siRNA. Bcl-3 knockdown prevented the alcohol-induced inhibition of TNF-α mRNA and protein production. In a mouse model of binge alcohol, an increase in Bcl-3 and a concomitant decrease in TNF-α but no change in IL-10 production were found in mice that received alcohol followed by LPS challenge. In summary, our novel data suggest that acute alcohol treatment in vitro and in vivo induces molecular signatures of TLR4/LPS tolerance through the induction of Bcl-3, a negative regulator of TNF-α transcription via its association with NF-κB p50/p50 dimers.