Differential effects of short chain fatty acids on endothelial Nlrp3 inflammasome activation and neointima formation: Antioxidant action of butyrate

Short chain fatty acids (SCFAs), a family of gut microbial metabolites, have been reported to promote preservation of endothelial function and thereby exert anti-atherosclerotic action. However, the precise mechanism mediating this protective action of SCFAs remains unknown. The present study investigated the effects of SCFAs (acetate, propionate and butyrate) on the activation of Nod-like receptor pyrin domain 3 (Nlrp3) inflammasome in endothelial cells (ECs) and associated carotid neointima formation. Using a partial ligated carotid artery (PLCA) mouse model fed with the Western diet (WD), we found that butyrate significantly decreased Nlrp3 inflammasome formation and activation in the carotid arterial wall of wild type mice (Asc(+/+)), which was comparable to the effect of gene deletion of the adaptor protein apoptosis-associated speck-like protein gene (Asc(-/-)). Nevertheless, both acetate and propionate markedly enhanced the formation and activation of the Nlrp3 inflammasome as well as carotid neointima formation in the carotid arteries with PLCA in Asc(+/+), but not Asc(-/-) mice. In cultured ECs (EOMA cells), butyrate was found to significantly decrease the formation and activation of Nlrp3 inflammasomes induced by 7-ketocholesterol (7-Ket) or cholesterol crystals (CHC), while acetate did not inhibit Nlrp3 inflammasome activation induced by either 7-Ket or CHC, but itself even activated Nlrp3 inflammsomes. Mechanistically, the inhibitory action of butyrate on the Nlrp3 inflammasome was attributed to a blockade of lipid raft redox signaling platforms to produce O2(•-) upon 7-Ket or CHC stimulations. These results indicate that SCFAs have differential effects on endothelial Nlrp3 inflammasome activation and associated carotid neointima formation.