Contribution of membrane raft redox signalling to visfatin-induced inflammasome activation and podocyte injury.

Abstract

Recently we have shown that adipokine visfatin-induced NLRP3 inflammasome activation contributes to podocyte injury. However, the molecular mechanisms of how visfatin-induces the Nlrp3 inflammasome activation and podocyte damage is still unknown. The present study tested whether membrane raft (MR) redox signalling pathway plays a central role in visfatin-induced NLRP3 inflammasomes formation and activation in podocytes. Upon visfatin stimulation an aggregation of NADPH oxidase subunits, gp91phox and p47phox was observed in the membrane raft (MR) clusters, forming a MR redox signalling platform in podocytes. The formation of this signalling platform was blocked by prior treatment with MR disruptor MCD or NADPH oxidase inhibitor DPI. In addition, visfatin stimulation significantly increased the colocalization of Nlrp3 with Asc or Nlrp3 with caspase-1, IL-β production, cell permeability in podocytes compared to control cells. Pretreatment with MCD, DPI, WEHD significantly abolished the visfatin-induced colocalization of NLRP3 with Asc or NLRP3 with caspase-1, IL-1β production and cell permeability in podocytes. Furthermore, Immunofluorescence analysis demonstrated that visfatin treatment significantly decreased the podocin and nephrin expression (podocyte damage) and prior treatments with DPI, WEHD, MCD attenuated this visfatin-induced podocin and nephrin reduction. In conclusion, our results suggest that visfatin stimulates membrane raft clustering in the membrane of podocytes to form redox signaling platforms by aggregation and activation of NADPH oxidase subunits enhancing O2·- production and leading to NLRP3 inflammasome activation in podocytes and ultimate podocyte injury.