Aorta- and liver-generated TMAO enhances trained immunity for increased inflammation via ER stress/mitochondrial ROS/glycolysis pathways

We determined whether gut microbiota-produced trimethylamine (TMA) is oxidized into trimethylamine N-oxide (TMAO) in non-liver tissues, whether TMAO promotes inflammation via trained immunity (TI) and made the following findings: Endoplasmic reticulum (ER) stress genes were co-upregulated with mitoCarta genes in chronic kidney diseases (CKD); TMAO upregulated 190 genes in human aortic endothelial cells (HAECs); TMAO synthesis enzyme flavin-containing monooxygenase 3 (FMO3) was expressed in human and mouse aortas,;4) TMAO trans-differentiated HAECs into innate immune cells; TMAO phosphorylated 12 kinases in cytosol via its receptor PERK and CREB, and integrated with PERK pathways; and PERK inhibitors suppressed TMAO-induced ICAM-1; TMAO upregulated 3 mitochondrial genes and downregulated inflammation inhibitor DARS2, induced mitoROS; and mitoTEMPO inhibited TMAO-induced ICAM-1; and -glucan priming followed by TMAO re-stimulation upregulated TNF-α by inducing metabolic reprogramming; and glycolysis inhibitor suppressed TMAO-induced ICAM-1. Our results have provided novel insights over TMAO roles in inducing EC activation and innate immune trans-differentiation, inducing metabolic reprogramming and TI for enhanced vascular inflammation and new therapeutic targets for treating cardiovascular diseases (CVD), CKD-promoted CVD, inflammations, transplantation, aging, and cancers.