Cigarette smoke-induced imbalance between PGE2/PGI2 modulates endothelial tissue factor : role of EP1 receptor and SIRT-1

Cigarette smoke exposure increases the incidence of atherothrombotic disease1,2, inducing expression of both cyclooxygenase-2 (COX-2)3, a key enzyme in the inflammatory response, and Tissue Factor (TF)4, initiator of the coagulation cascade. We assessed whether and how the major products of COX-2 activity (PGE2 and PGI2) modulate TF induced by cigarette smoke in endothelial cells (EC). We observed that an aqueous extract of cigarette smoke (TS) in association with inflammatory cytokine IL-1 altered the balance between PGE2/PGI2, increasing PGE2 and reducing PGI2 production, and induced TF (expression and activity) in EC in vitro. Inhibition of PGE synthase (PGES) activity by CAY10526, or by specific PGES siRNA, markedly diminished the amount of TF induced by TS/IL-1. In contrast, treatment with exogenous PGE2 increased TF. EC express three PGE2 receptors: EP1, EP2 and EP4. We showed that EP1 antagonists (AH6809 and SC19220) reduced TF induced by TS/IL-1 whereas an EP1 agonist (17-phenyl-trinor-PGE2,) increased TF. We excluded the involvement of other EP receptors because an EP4 antagonist (GW627368X) and EP2/EP4 agonists (misoprostol, butaprost) did not modify TF. The role of SIRT1, the NAD+-dependent protein deacetylase, in the regulation of TF was analyzed. Sirtinol, a SIRT1 deactivator, increased TF expression; in contrast, resveratrol, a SIRT1 activator, reduced TF induced by both TS/IL-1 and EP1 agonist. Furthermore, carbacyclin, a stable PGI2 receptor (IP) agonist, prevented TF and reduced PGE2 production induced by TS/IL-1 Conversely, both the IP antagonist, CAY10441, and specific PGI2 synthase siRNA increased both TF and PGE2. Finally, we showed that carbacyclin prevented TF expression induced by both PGE2 and Sirtinol. We conclude that cigarette smoke, by modulating the balance between PGE2/PGI2, increases expression and activity of TF by a pathway dependent on EP1/SIRT-1 (Fig. 1). Figure 1: The pathway induced by TS/Il-1β. References [1] J. A. Ambrose et R. S. Barua. The pathophysiology of cigarette smoking and cardiovascular disease: an update. J. Am. Coll. Cardiol., 43, 1731-1737, 2004. [2] P.W. Wilson. Smoking, smoking cessation, and risk of cardiovascular disease. Curr. Treat. Options Cardiovasc. Med., 8, 276-281, 2006. [3] S. S. Barbieri et B. B Weksler. Tobacco smoke cooperates with interleukin-1 to alter β-catenin trafficking in vascular endothelium resulting in increased permeability and induction of ciclooxigenase-2 expression in vitro and in vivo. FASEB J., 21, 1-13, 2007. [4] S. Matetzky, S. Tani, S. Kangavari, P. Dimayuga, J. Yano, H. Xu, K.Y. Chyu, M.C. Fishbein, P.K. Shah, B. Cercek. Smoking increases tissue factor expression in atherosclerotic plaques: implications for plaque thrombogenicity. Circulation, 102, 602-604,2000