A6555 Sirtuin 3-induced macrophage autophagy in regulating NLRP3 inflammasome activation

Objectives: Defective autophagy of monocytes or macrophages might result in NLRP3 inflammasome activation and cause vascular metabolic inflammation. Sirtuin 3 (SIRT3), an NAD-dependent deacetylase, is sensitive to the metabolic status and mediates adaptation responses. In this study, we investigated the role of SIRT3-mediated autophagy in regulating NLRP3 inflammasome activation. Methods: 20 patients with a BMI above 25 kg/m2 and 20 healthy controls were enrolled. 8-week male WT and SIRT3 KO mice were injected intraperitoneally with 0.5 g/kg of poloxamer 407 or saline. The expression of autophagy-related proteins and inflammatory mediators were analyzed using western blot. Results: The inhibition of autophagy and the activation of the NLRP3 inflammasome were concomitant with reduced SIRT3 levels both in peripheral blood monocytes from obese humans and in palmitate-treated THP-1 cells. SIRT3 could form a molecular complex with ATG5, while SIRT3 overexpression altered the acetylation of endogenous ATG5. ATG5 acetylation inhibited autophagosome maturation and induced NLRP3 inflammasome activation. In parallel, SIRT3 overexpression in THP-1 cells decreased the palmitate-induced generation of mitochondrial ROS, restored autophagy, and attenuated NLRP3 inflammasome activation. The incubation of HAECs with macrophage-conditioned medium (MCM) induced HAEC expression of VCAM-1, ICAM-1, α-SMA and collagen-1. The effect of MCM could be reversed by the addition of neutralizing anti-IL-1β antibody or the overexpression of SIRT3. En face analyses displayed a marked increase in α-SMC-positive endothelial cells in SIRT3−/− mice with acute hyperlipidaemia. Conclusion: These findings revealed that SIRT3-deficient macrophages displayed impaired autophagy and accelerated NLRP3 inflammasome activation and endothelial dysfunction.