Cigarette smoke modifies neutrophil chemotaxis, neutrophil extracellular trap formation and inflammatory response-related gene expression

Abstract

Background and objective: Cigarette smoking is a major risk factor for periodontitis, and smoking perturbs neutrophil reactive oxygen species production. This study tested the hypothesis that cigarette smoke extract (CSE) and its components/metabolites nicotine, cotinine and thiocyanate (SCN-), may influence neutrophil functions.

Material and methods: Chemotaxis was assessed in neutrophils pre-treated with CSE using real-time video microscopy. Neutrophil extracellular trap (NET) release in response to CSE, nicotine, cotinine, SCN- as well as to phorbol 12-myristate-13-acetate and hypochlorous acid following pre-treatment with CSE, nicotine, cotinine or SCN- was assessed using fluorescence-based assays. The impact of CSE and SCN- treatment on neutrophil respiratory burst- and inflammation-related gene expression (NFKBIE, DNAJB1, CXCL8, NCF1, NCF2, CYBB) was determined by real-time polymerase chain reaction.

Results: Both CSE and SCN- pre-treatment inhibited phorbol 12-myristate-13-acetate-stimulated NET release. Additionally, SCN- inhibited hypochlorous acid-stimulated NET formation, while SCN- alone stimulated NET release. Overall, neutrophils pre-treated with CSE exhibited reduced speed, velocity and directionality relative to untreated neutrophils. Although CSE and SCN- promoted DNAJB1 expression, increased redox-related gene expression was only detected in response to SCN-.

Conclusion: These results suggest that CSE can alter ex vivo neutrophil activation by mechanisms independent of SCN- and nicotine, and SCN- may contribute to the perturbed innate immune responses observed in smokers.

Keywords: cigarette smoke; cotinine; inflammation; neutrophils; nicotine; periodontitis; thiocyanate.