Trimethylamine‐N‐Oxide Induces Vascular Inflammation by Activating the NLRP3 Inflammasome Through the SIRT3‐SOD2‐mtROS Signaling Pathway

Abstract

Background Trimethylamine‐N‐oxide ( TMAO ) has recently been identified as a novel and independent risk factor for promoting atherosclerosis through inducing vascular inflammation. However, the exact mechanism is currently unclear. Studies have established a central role of nucleotide‐binding oligomerization domain–like receptor family pyrin domain–containing 3 ( NLRP 3) inflammasome in the pathogenesis of vascular inflammation. Here, we examined the potential role of the NLRP 3 inflammasome in TMAO ‐induced vascular inflammation in vitro and in vivo and the underlying mechanisms. Methods and Results Experiments using liquid chromatography‐tandem mass spectrometry, Western blot, and fluorescent probes showed that TMAO ‐induced inflammation in human umbilical vein endothelial cells ( HUVEC s) and aortas from ApoE −/− mice. Moreover, TMAO promoted NLRP 3 and activated caspase‐1 p20 expression and caspase‐1 activity in vitro and in vivo. Notably, a caspase‐1 inhibitor ( YVAD ), an NLRP 3 inhibitor ( MCC 950), as well as NLRP 3 short interfering RNA attenuated TMAO ‐induced activation of the NLRP 3 inflammasome, subsequently leading to suppression of inflammation in HUVEC s. TMAO additionally stimulated reactive oxygen species ( ROS ) generation, in particular, mitochondrial ROS , while inhibiting manganese superoxide dismutase 2 (SOD2) activation and sirtuin 3 ( SIRT 3) expression in HUVEC s and aortas from ApoE −/− mice. TMAO ‐induced endothelial NLRP 3 inflammasome activation was ameliorated by the mitochondrial ROS scavenger Mito‐ TEMPO , or SIRT 3 overexpression in HUVEC s. Conversely, TMAO failed to further inhibit SOD2 and activate the NLRP 3 inflammasome or induce inflammation in SIRT 3 short interfering RNA –treated HUVEC s and aortas from SIRT 3 −/− mice. Conclusions TMAO promoted vascular inflammation by activating the NLRP 3 inflammasome, and the NLRP 3 inflammasome activation in part was mediated through inhibition of the SIRT 3‐ SOD 2–mitochondrial ROS signaling pathway.