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HIGH GLUCOSE PROMOTES NLRP3 INFLAMMASOME ACTIVATION VIA CD36/ROS PATHWAY IN RENAL TUBULAR EPITHELIAL CELLS

INTRODUCTION: Tubulointerstitial inflammation plays a key role in the pathogenesis of diabetic nephropathy (DN). IL-1β is the key pro-inflammatory cytokines of tubulointerstitial inflammation. The activation and secretion of IL-1β are regulated by NLRP3 inflammasomes. Reactive oxygen species (ROS) is the main mediator for NLRP3 inflammasome activation. Our previous study reported that CD36, a class B scavenger receptor, mediates ROS production in DN. In this study, we determined whether overexpression of CD36 is involved in activation of the NLRP3 inflammasome and the underlying mechanisms of inflammasome activation by ROS in high glucose (HG)-induced HK-2 cells.

METHODS: The human renal tubular epithelial cell line HK-2 stimulated with high concentrations of glucose was used as a model. The expression of CD36, NLRP3, caspase-1, α–SMA, E-cadherin, TGF-β1 and p-AMPK were quantifed by real-time PCR and western blotting, respectively. Levels of IL-1β in the supernatant were determined using ELISA kits. Intracellular and mitochondrial ROS were detected by flow cytometry techniques. Mitochondrial β-oxidation rate was examined by commercial kits.

RESULTS: The results showed that high glucose (30 mM) was shown to induce increased expression of NLRP3, IL-1β and caspase-1. This was blocked by knockdown of CD36 or antioxidant TEMPO. Meanwhile, we also found that knockdown of CD36 inhibited high glucose-induced generation of mitochondrial ROS, α–SMA, TGF-β1 and increased levels of E-cadherin, p-AMPK, mitochondrial β-oxidation.

CONCLUSIONS: These results suggested that knockdown of CD36 antagonized high glucose-induced NLRP3 inflammasome activation by upregulating mitochondrial fatty acid oxidation and inhibiting ROS production, CD36 as a potential therapy target for diabetic nephropathy.