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Cigarette smoke (CS) increases the incidence of atherothrombosis, the release of prostaglandin (PG) E2, and the amount of tissue factor (TF). The link between PGE2and TF, and the impact of this interaction on CS-induced thrombosis, is unknown. Plasma from active smokers showed higher concentration of PGE2, TF total antigen, and microparticle-associated TF (MP-TF) activity compared with never smokers. Similar results were obtained in mice and in mouse cardiac endothelial cells (MCECs) after treatment with aqueous CS extracts (CSEs) plus IL-1β [CSE (6.4 puffs/L)/IL-1β (2 µg/L)]. A significant correlation between PGE2 and TF total antigen or MP-TF activity were observed in both human and mouse plasma or tissue. Inhibition of PGE synthase reduced TF in vivo and in vitro and prevented the arterial thrombosis induced by CSE/IL-1β. Only PG E receptor 1 (EP1) receptor antagonists (SC51089:IC50 ~ 1 µM, AH6809:IC50 ~ 7.5 µM) restored the normal TF and sirtuin 1 (SIRT1) levels in MCECs before PGE2 (EC50 ~ 2.5 mM) or CSE/IL-1β exposure. Similarly, SIRT1 activators (CAY10591: IC50 ~ 10 µM, resveratrol: IC50 ~ 5 µM) or prostacyclin analogs (IC50 ~ 5 µM) prevented SIRT1 inhibition and reduced TF induced by CSE/IL-1β or by PGE2. In conclusion, PGE2 increases both TF expression and activity through the regulation of the EP1/SIRT1 pathway. These findings suggest that EP1 may represent a possible target to prevent prothrombotic states. [ABSTRACT FROM AUTHOR]

Tobacco smoke (TS) interacts with interleukin-1β (IL-1β) to modulate generation of reactive oxygen species (ROS) and expression of cyclooxygenase-2. We explored molecular mechanisms by which TS/IL-1β alters expression and activity of microsomal-prostaglandin E synthase-1 (mPGES-1) and of prostacyclin synthase (PGIS) in mouse cardiac endothelial cells. TS (EC50 ~5 puffs/L) interacting with IL-1β (2µg/L) upregulates PGE2 production and mPGES-1 expression, reaching a plateau at 4-6 h, but down-regulates pro- stacyclin (PGI2) release by increasing IL-1β-mediated PGIS tyrosine nitration. Inhibition of NADPH-oxidase, achieved pharmacologically and/or by silencing its catalytic subunit p47phox, or exogenous PGI2 (carbaprostacyclin; IC50 ~5 µM) prevents production of both ROS and PGE2, and negativelymodulatesmPGES-1 expression induced by TS/IL-1β. Moreover, inhibiting PGI2, either using PGIS siRNA and/or CAY10441 (EC50 ~20 nM), a PGI2 receptor antagonist, increases NADPH-oxidase activation, mPGES-1 synthesis, and PGE2 production. Finally, lower PGI2 levels associated with higher PGIS tyrosine nitration, p47phox translocation to the membrane (an index of activation of NADPH-oxidase), and mPGES-1 expression and activity were detected in cardiovascular tissues of ApoE-/- mice exposed to cigarette smoke compared to control mice. In conclusion, cigarette smoke in association with cytokines alters the balance between PGI2/PGE2, reducing PGI2 production and increasing synthesis and activity of mPGES-1 via NADPH-oxidase activation, predisposing to development of pathological conditions. [ABSTRACT FROM AUTHOR]