A novel redox signalling axis mediates nicotine-induced podocyte injury

Abstract

Introduction Nicotine has been shown to induce Nlrp3 (nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3) inflammasome activation, thereby contributing to podocyte injury. However, the molecular mechanisms underlying nicotine-induced Nlrp3 inflammasome activation and subsequent podocyte dysfunction remain largely unknown. The present study investigated whether membrane raft (MR)-associated redox signalling plays a critical role in nicotine-induced Nlrp3 inflammasome activation and podocyte injury. Methods and Results Nicotine treatment induced membrane raft clustering in podocytes in a dose-dependent manner. Upon nicotine stimulation, the NADPH oxidase subunits gp91phox and p47phox were recruited and aggregated within membrane raft clusters, leading to the formation of a membrane raft redox signalling platform. The formation of this signalling platform was significantly inhibited by pretreatment with the membrane raft disruptor methyl-β-cyclodextrin (MCD), the NADPH oxidase inhibitor diphenyleneiodonium (DPI), or the acid sphingomyelinase (Asm) inhibitor amitriptyline. Nicotine also markedly enhanced the colocalization of Nlrp3 with ASC and caspase-1, indicating inflammasome assembly, and significantly increased caspase-1 activity, IL-1β production, desmin expression, podocyte permeability, and apoptosis compared with control cells. These effects were significantly attenuated by pretreatment with MCD, DPI, the caspase-1 inhibitor WEHD, or amitriptyline. Furthermore, immunofluorescence analysis demonstrated that nicotine significantly reduced podocin expression, whereas pretreatment with MCD, DPI, WEHD, or amitriptyline largely preserved podocin expression. Conclusion Our findings demonstrate that membrane raft-associated redox signalling serves as a critical upstream mechanism driving nicotine-induced NLRP3 inflammasome activation and podocyte injury.