TLR4 deficiency affects the microbiome and reduces intestinal dysfunctions and inflammation in chronic alcohol- fed mice

Chronic alcohol abuse induces an inflammatory response in the intestinal tract with damage to the integrity of the mucosa, epithelium and dysbiosis in the gut microbiome. However, the role of gut bacteria in ethanol effects and how these microorganisms interact with the immune system are not well understood. Here we hypothesize that ethanol consumption though activating TLR4 is capable of altering the microbiota profile by triggering the intestinal inflammatory response. We analyzed the 16S rRNA sequence of the fecal samples from wild-type (WT) and TLR4-knockout (TLR4-KO) mice with and without ethanol intake for 3 months. The results demonstrated that chronic ethanol consumption reduces microbiota diversity and causes dysbiosis in WT mice. Likewise, ethanol upregulates several inflammatory genes (IL-1Beta, iNOS, TNF-Alpha) and miRNAs (miR-155-5p, miR-146a-5p) and alters structural and permeability genes (INTL1, CDH1, CFTR) in the colon of WT mice. Our results further demonstrated that TLR4-KO mice exhibit a different microbiota that can protect against ethanol-induced activation of the immune system and colon integrity dysfunctions. In summary, our results reveal that TLR4 is a key factor for determining gut microbiota, which can participate in dysbiosis, and the inflammatory response induced by alcohol consumption.