Abstract 031: Novel Role of Nlrp3 Inflammasome Activation beyond Canonical Inflammation: Coronary Endothelial Injury and Repair

Abstract

Inflammasomes are intracellular machinery turning on inflammatory response to danger factors. Recent studies reported that activation of inflammasomes also directly produce injurious action on cells or tissues independent of canonical inflammation. The present study hypothesized that activation of endothelial Nlrp3 inflammsome directly induces endothelial dysfunction at early stage of obesity without canonical inflammation yet. It was demonstrated that Nlrp3+/+ mice under 6-week high fat diet (HFD) had increased formation and activation of Nlrp3 inflammasome in coronary arterial endothelium compared to normal diet (ND)-treated mice, as shown by confocal microscopic detection of inflammasome aggregation and active caspase-1 formation. Ultrasound Doppler measurement showed that HFD markedly reduced bradykinin-induced increases in coronary blood flow by 95% in Nlrp3+/+ mice, but only by 45% in Nlrp3-/- mice. Vascular reactivity studies confirmed that HFD impaired endothelium-dependent vasodilation to acetylcholine (10-9-10-5 M) in freshly isolated coronary arteries of Nlrp3+/+ mice (maximum dilation: 53±3% vs. 84±3% of ND), but not in Nlrp3-/- mice (maximum dilation: 81±3% vs. 85±2% of ND). Similarly, visfatin (an injurious adipokine) simulates HFD-induced injurious action on endothelial dysfunction in normal Nlrp3+/+coronary arteries, which was attenuated by Nlrp3 gene deletion. In Nlrp3+/+ mice, HFD markedly increased the number of circulating endothelial progenitor cells (EPCs) in peripheral blood (1.73±0.69% vs. 0.46±0.05% of ND) and adhesion molecule VCAM-1 levels in coronary arterial endothelium. Nlrp3-/- mice fed HFD exibited higher level of circulating EPCs (4.57±1.27% vs. 0.32±0.04% of ND), but similar VCAM-1 expression. Together, these results suggest that endothelial Nlrp3 inflammasome activation in response to obesity or injurious adipokine produces endothelial dysfunction and inhibits EPC mobilization for endothelial repair, which are distinct from its canonical inflammatory responses such as inflammtory cell recruitment and infiltration in the vasculature. It is proposed that Nlrp3 inflammasome activation may trigger endothelial injury resulting in ultimate vascular inflammation and schlerosis.