Mitigation of nicotine-induced podocyte injury through inhibition of thioredoxin interacting protein

Nicotine has been reported to initiate NLRP3 inflammasome formation and activation in different pathological conditions. The current study assessed whether thioredoxin-interacting protein (TXNIP) mediates nicotine-induced NLRP3 inflammasome activation and consequent podocyte injury. Co-immunoprecipitation analysis demonstrated that nicotine-induced TXNIP/NLRP3 interaction in podocytes relative to control groups. However, pre-treatment with TXNIP inhibitors, verapamil (Vera) or SRI-37330 (SRI) attenuates nicotine-induced TXNIP/NLRP3 interaction. Confocal microscopic analysis showed that nicotine treatment significantly increased the colocalization of Nlrp3 with Asc, Nlrp3 with caspase-1 and Nlrp3 with TXNIP in podocytes compared to control cells. Pretreatment with TXNIP inhibitor Vera or SRI abolished nicotine-induced Nlrp3/Asc, Nlrp3/caspase-1 or Nlrp3/TXNIP colocalization. Correspondingly, nicotine treatment significantly increased the caspase-1 activity and IL-1β production compared to control cells. However, prior treatment with TXNIP inhibiting Vera or SRI significantly attenuated the nicotine-induced caspase-1 activity and IL-1β production. Further immunofluorescence analysis showed that nicotine treatment significantly decreased podocin and nephrin expression compared to control cells. However, pretreatment with TXNIP inhibiting Vera or SRI attenuated the nicotine-induced podocin and nephrin reduction. In addition, confocal, flow cytometry and biochemical analysis showed that nicotine treatment significantly increased desmin expression, apoptosis and cell permeability compared to control cells. However, prior treatment with TXNIP inhibiting Vera or SRI significantly attenuated the nicotine-induced desmin expression, apoptosis and cell permeability. Taken together, our results demonstrate that TXNIP/NLRP3 interaction constitutes a potentially key signalling mechanism driving nicotine-induced NLRP3 inflammasome formation, activation and subsequent podocyte damage.