Inhibitory Effects of Ethanol on the NLRP3 Inflammasome

Immunosuppression is a major complication of alcoholism and contributes to increased rates of opportunistic infections and sepsis associated with the addiction. The NLRP3 inflammasome is a central intracellular pattern recognition receptor within the innate immune system, which leads to the cleavage and secretion of the pro-inflammatory cytokines interleukin (IL)-1β and IL-18. Ethanol has been reported to inhibit IL-1β secretion, and here we verify that the alcohol can specifically inhibit activation of the NLRP3 inflammasome resulting in attenuated IL-1β and caspase-1 cleavage and secretion, as well as ASC secretion in response to several agonists. These results were found to be independent of the activation of GABAA receptors or the inhibition of NMDA receptors. Ethanol was only partially able to prevent IL-1β secretion subsequent to NLRC4 activation and was incapable of preventing NLRP1b dependent IL-1β secretion, which are both largely independent of the adapter protein ASC, and ethanol was shown to prevent the formation of ASC specks. Treatment of cells with ethanol resulted in markedly decreased global tyrosine phosphorylation, while administration of the tyrosine phosphatase inhibitor sodium orthovanadate prior to ethanol restored IL-1β secretion. Multiple alcohol containing organic compounds exerted inhibitory effects on the NLRP3 inflammasome parallel to ethanol; however, isoamyl alcohol’s non-alcohol analog, 2-methylbutane, did not. Together, these results show that ethanol antagonizes the NLRP3 inflammasome at an apical event in its activation potentially through the stimulation of protein tyrosine phosphatases. As other short chain alcohols retain this ability, this effect could be dependent on the hydroxyl group of these compounds