• Jong-Seok Moon, Seonmin Lee, Mi-Ae Park, Ilias I Siempos, Maria Haslip, Patty J Lee, Mijin Yun, Chun K Kim, Judie Howrylak, Stefan W Ryter, Kiichi Nakahira, and Augustine M K Choi.
• J. Clin. Invest. 2015 Feb 1; 125 (2): 665-80.

AbstractCellular lipid metabolism has been linked to immune responses; however, the precise mechanisms by which de novo fatty acid synthesis can regulate inflammatory responses remain unclear. The NLRP3 inflammasome serves as a platform for caspase-1-dependent maturation and secretion of proinflammatory cytokines. Here, we demonstrated that the mitochondrial uncoupling protein-2 (UCP2) regulates NLRP3-mediated caspase-1 activation through the stimulation of lipid synthesis in macrophages. UCP2-deficient mice displayed improved survival in a mouse model of polymicrobial sepsis. Moreover, UCP2 expression was increased in human sepsis. Consistently, UCP2-deficient mice displayed impaired lipid synthesis and decreased production of IL-1β and IL-18 in response to LPS challenge. In macrophages, UCP2 deficiency suppressed NLRP3-mediated caspase-1 activation and NLRP3 expression associated with inhibition of lipid synthesis. In UCP2-deficient macrophages, inhibition of lipid synthesis resulted from the downregulation of fatty acid synthase (FASN), a key regulator of fatty acid synthesis. FASN inhibition by shRNA and treatment with the chemical inhibitors C75 and cerulenin suppressed NLRP3-mediated caspase-1 activation and inhibited NLRP3 and pro-IL-1β gene expression in macrophages. In conclusion, our results suggest that UCP2 regulates the NLRP3 inflammasome by inducing the lipid synthesis pathway in macrophages. These results identify UCP2 as a potential therapeutic target in inflammatory diseases such as sepsis.

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