Activation of NLRP3 inflammasome assembly is associated with smoking status of patients with coronary artery disease

Objective: Cigarette smoke is considered as a sterile inflammatory stimulus which triggers an innate immune response, accountable for vascular events. Previously, we reported smoking-induced NLRP3 inflammasome activation in the pathogenesis of atherosclerosis through caspase-1 activation and secretion of pro-cytokines (interleukin (IL)-1 beta and IL-18) in vitro and in vivo. Therefore, the present study aimed to reconnoitre the association of cigarette smoking and NLRP3 inflammasome activation ex vivo in human subjects with coronary atherosclerosis. Methods and Results: In order to establish and validate the association between smoking status and NLRP3 inflammasome ex vivo, mononuclear cells were isolated from smokers with angiographically-proven coronary artery disease (CAD); non-smokers with CAD; smokers without CAD, and healthy non-smokers (controls) (n = 20 each). The transcriptional and translational expression of NLRP3 inflammasome markers i.e. NLRP3, pro-caspase-1, caspase-1, pro-IL-1 beta, IL-1 beta, pro-IL-18 and IL-18 was significantly increased (2 to 7-fold) in smokers with CAD vs non-smokers with CAD; and smokers without CAD vs non-smoker controls. In addition, the oxidative stress, an upstream mediator of NLRP3 inflammasome was evaluated and found to be significantly augmented in smokers vs non-smokers (with and without CAD respectively). Further, the levels of serum cotnine, oxidative stress markers (8-isoprostane and 8-oxo-2'-deoxyguanosine), caspase-1 and pro-cytokines (IL-1 beta and IL-18) were also higher in smokers vs non-smokers. Moreover, the levels of pro-cytokines were positively correlated with caspase-1 and serum cotinine, corroborating the secretion of cytokines in a caspase-1-dependent manner. Conclusion: Our data may imply NLRP3 inflammasome as a mediator of the pro-atherosclerotic property of cigarette smoking in atherosclerotic patients.