Cytokines present in smokers' serum interact with smoke components to enhance endothelial dysfunction

Abstract

Aims: Cigarette smoking engenders inflammation and endothelial dysfunction, processes implicated in atherothrombotic disease. We hypothesized that an interaction between inflammatory cytokines in smokers' blood and circulating components of cigarette smoke is necessary to induce reactive oxygen species (ROS) and cyclooxygenase-2 (COX-2) in endothelium. We then explored the molecular mechanisms involved in these effects.

Methods and results: Serum from nine healthy active smokers (AS) compared with serum from nine non-smokers (NS) showed higher levels of interleukin-1beta (IL-1β) and tumour necrosis factor-alpha (TNF-α) and a greater ability to induce ROS production, p47phox translocation to the plasma membrane, and COX-2 mRNA and protein expression in endothelial cells (ECs). Similar results were obtained in vivo and in vitro after treatment with aqueous extracts of cigarette smoke plus IL-1β and TNF-α(TS/IL-1β/TNF-α). In ECs increased ROS production and COX-2 mRNA induced by serum from AS correlated positively with their serum levels of IL-1β and TNF-α. Moreover, a positive correlation was observed between ROS generation and COX-2 mRNA. Simultaneous immuno-neutralization of IL-1β and TNF-α prevented endothelial dysfunction induced by serum from AS. Inhibitors of NADPH oxidase and/or p47phox siRNA diminished ROS production and COX-2 expression as well as phosphorylation of p38 mitogen-activated protein kinase (p38MAPK) and Akt mediated either by AS serum or by TS/IL-1β/TNF-α. Finally, direct inhibition of p38MAPK and Akt activity also abolished COX-2 expression mediated by both types of stimuli. Our results suggest a crucial role played by interactions between inflammatory cytokines and tobacco smoke in the induction of endothelial dysfunction.