Trimethylamine-N-Oxide Instigates NLRP3 Inflammasome Activation and Endothelial Dysfunction

Abstract

Background/Aim: Plasma trimethylamine-N-oxide (TMAO), a product of intestinal microbial metabolism of dietary phosphatidylcholine has been recently associated with atherosclerosis and increased risk of cardiovascular diseases (CVD) in rodents and humans. However, the molecular mechanisms of how TMAO induces atherosclerosis and CVD progression are still unclear. The present study tested whether TMAO induces NLRP3 inflammasome formation and activation and thereby contributes to endothelial injury initiating atherogenesis. Methods: Inflammasome formation and activation was determined by confocal microscopy, caspase-1 activity was measured by colorimetric assay, IL-1β production was measured using ELISA, cell permeability was determined by microplate reader and ZO-1 expression was determined by western blot analysis and confocal microscopy. In in vivo experiments, TMAO was infused by osmotic pump implantation. Results: TMAO treatment significantly increased the colocalization of NLRP3 with Asc or NLRP3 with caspase-1, caspase-1 activity, IL-1β production, cell permeability in carotid artery endothelial cells (CAECs) compared to control cells. Pretreatment with caspase-1 inhibitor, WEHD or Nlrp3 siRNA abolished the TMAO-induced inflammasome formation, activation and cell permeability in these cells. In addition, we explored the mechanisms by which TMAO activates NLRP3 inflammasomes. TMAO-induced the activation of NLRP3 inflammasomes was associated with both redox regulation and lysosomal dysfunction. In animal experiments, direct infusion of TMAO in mice with partially ligated carotid artery were found to have increased NLRP3 inflammasome formation and IL-1β production in the intima of wild type mice. Conclusion: The formation and activation of NLRP3 inflammasomes by TMAO may be an important initiating mechanism to turn on the endothelial inflammatory response leading to endothelial dysfunction.

The interplay between microbiota‐dependent metabolite trimethylamine N‐oxide, Transforming growth factor β/SMAD signaling and inflammasome activation in chronic kidney disease patients: A new mechanistic perspective

“…6,40,41 It also acts as a sensor to the damaging exogenous and endogenous elements and a switch on inflammatory and noninflammatory responses together. 42 Previous studies have established that ROS generation is the most common pathway in inflammasome assemblage, signing a possible connection between enhanced ROS production and inflammasome activation as Abais et al documented that inhibiting NADPH oxidase-derived ROS prohibited ATP-induced caspase-1 activation as well as IL-1β production. 43 Conversely, treatment with ROS inhibitors has been revealed to suppress silica/asbestosinduced NLRP3 inflammasome activation.…”

MicroRNA-495 Ameliorates Cardiac Microvascular Endothelial Cell Injury and Inflammatory Reaction by Suppressing the NLRP3 Inflammasome Signaling Pathway

“…NLRP3 plays a protective role in age-related macular degeneration via the induction of IL-18 through drusen components [37]. In endothelial cells, the NLRP3 inflammasome exhibits a significant initiating mechanism, and its activation may accelerate the development of endothelial dysfunction or atherogenic pathology by inducing plasma trimethylamine-Noxide (TMAO) [38]. The repression of the NLRP3 inflammasome is a critical factor in I/R or inflammation by correlation with SIRT1, which was proved to be involved in both preventing cells from injury induced by various stress and improving endothelial precursor cell function [39,40].…”

Gut Microbial Metabolism and Nonalcoholic Fatty Liver Disease

“…More recent evidence suggests that elevated serum TMAO levels are also linked to adipose tissue dysfunction and chronic kidney disease . Subsequent mechanistic studies identified the biologic function of TMAO to include endothelial dysfunction and enhancement of platelet hyperreactivity . Oral application of a structural analogue of choline, 3,3‐dimethyl‐1‐butanol, inhibited microbial TMA production, lowered serum TMAO levels, and prevented development of atherosclerotic lesions, despite a proatherosclerosis diet, in an animal model .…”

“…(98) Subsequent mechanistic studies identified the biologic function of TMAO to include endothelial dysfunction and enhancement of platelet hyperreactivity. (99,100) Oral application of a structural analogue of choline, 3,3-dimethyl-1-butanol, inhibited microbial TMA production, lowered serum TMAO levels, and prevented development of atherosclerotic lesions, despite a proatherosclerosis diet, in an animal model. (101) Together, these data support that a microbial-derived metabolite is an important contributor to a variety of interrelated cardiometabolic diseases and that targeting the gut microbial capacity to produce this metabolite offers a potential novel strategy for disease prevention or treatment.…”