Podocyte NLRP3 inflammasome activation and glomerular injury by adipokine visfatin: in vitro and in vivo evidence (1134.7)

Abstract

NLRP3 inflammasome formation and activation have recently been reported to be an important early mechanism responsible for glomerular inflammation and injury in obese mice. However, the precise mechanism of obesity‐induced NLRP3 inflammasome activation remains unknown. The present study explored whether adipokine visfatin mediates obesity‐induced podocyte NLRP3 inflammasome activation and consequent glomerular injury in in vitro and in vivo models. Confocal microscopic analysis showed that visfatin treatment increased the colocalization of NLRP3 with Asc or caspase‐1 in podocytes indicating the formation of NLRP3 inflammasomes. This visfatin‐induced inflammasome formation was abolished by pretreatment of podocytes with Asc siRNA. Correspondingly, visfatin treatment significantly increased the caspase‐1 activity and IL‐1β production in podocytes, representing activation of NRLP3 inflammasomes, which was significantly attenuated by Asc siRNA. Further RT‐PCR and confocal microscopic analysis demonstrated that visfatin treatment significantly decreased the podocin expression (podocyte damage), and Asc siRNA transfection attenuated this visfatin‐induced podocin reduction. Similar findings were observed in mouse model in vivo. It was shown that visfatin infusion induced NLRP3 inflammasome formation and activation in glomeruli of Asc+/+ mice, but not in Asc‐/‐ mice. Further functional studies found that visfatin infusion significantly increased the urinary albumin and protein excretion in Asc+/+ mice compared to Asc‐/‐ mice. Fluorescent immunohistochemical examinations using podocin and desmin as podocyte injury markers showed that the inflammasome formation induced by the visfatin were mostly located in podocytes as demonstrated by co‐localization of NLRP3 with podocin or desmin. Based on these results, it is concluded that visfatin induces NLRP3 inflammasome formation and activation in podocytes and thereby results in glomerular injury and sclerosis.Grant Funding Source: supported by NIH grants DK54927 and HL‐75316