Gut Microbial Metabolite TMAO Induces Endothelial Dysfunction by Activating the HMGB1/TLR‐4 Signalling Pathway

The intestinal microbe derived metabolite trimethylamine N‐oxide (TMAO) is implicated in the pathogenesis of cardiovascular diseases. However, the molecular mechanisms of how TMAO induces atherosclerosis and CVD progression are still unclear. In this regard, high‐mobility group box protein 1 (HMGB1), an inflammatory mediator, has been reported to destroy cell‐cell junctions, resulting in vascular endothelial hyper permeability leading to endothelial dysfunction. The present study tested whether TMAO associated endothelial dysfunction results via HMGB1 activation in in vitro and in vivo models. Biochemical and RT‐PCR analysis showed that TMAO increased the HMGB1 expression in dose dependent manner in endothelial cells compared to control cells. However, prior treatment with glycyrrhizin, an HMGB1 binder abolished the TMAO‐induced HMGB1 production in endothelial cells. Furthermore, western blot and immunofluorescent analysis showed significant decrease in the expression of cell‐cell junction proteins ZO‐1, ZO‐2, Occludin and V‐cadherin in TMAO treated endothelial cells compared to control cells. However, prior treatment with glycyrrhizin attenuated the TMAO‐induced cell‐cell junction proteins disruption. In addition, TMAO induced the HMGB1 expression through TLR‐4 signalling pathway in endothelial cells. In in vivo studies, C57BL/6J wild mice were treated with 3 % choline chloride in drinking water to produce enhanced TMAO levels in plasma. Real time PCR analysis showed that HMGB1, TLR‐4 and inflammatory markers (ICAM & VCAM) were significantly increased in carotid arteries of choline treated mice compared to control mice. In addition, it was also found that collagen I and III expression (fibrotic markers) were significantly increased in carotid arteries of choline treated mice. In conclusion, our results suggested that TMAO modulated endothelial cells phenotype via activating HMGB1 associated TLR‐4 signalling pathway. Support or Funding Information supported by NIH grant, DK104031 This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .