Cyclooxygenase-2–Derived Prostacyclin Regulates Arterial Thrombus Formation by Suppressing Tissue Factor in a Sirtuin-1–Dependent-Manner

Abstract

Background-Selective inhibitors of cyclooxygenase (COX)-2 increase the risk of myocardial infarction and thrombotic events, but the responsible mechanisms are not fully understood. Methods and Results-We found that ferric chloride-induced arterial thrombus formation was significantly greater in COX-2 knockout compared with wild-type mice. Cross-transfusion experiments excluded the likelihood that COX-2 knockout platelets, despite enhanced aggregation responses to collagen and thrombin, are responsible for increased arterial thrombus formation in COX-2 knockout mice. Importantly, we observed that COX-2 deletion decreased prostacyclin synthase and production and peroxisome proliferator-activated receptor-and sirtuin-1 (SIRT1) expression, with consequent increased upregulation of tissue factor (TF), the primary initiator of blood coagulation. Treatment of wild-type mice with a prostacyclin receptor antagonist or a peroxisome proliferator-activated receptor-␦ antagonist, which predisposes to arterial thrombosis, decreased SIRT1 expression and increased TF activity. Conversely, exogenous prostacyclin or peroxisome proliferator-activated receptor-␦ agonist completely reversed the thrombotic phenotype in COX-2 knockout mice, restoring normal SIRT1 levels and reducing TF activity. Furthermore, inhibition of SIRT1 increased TF expression and activity and promoted generation of occlusive thrombi in wild-type mice, whereas SIRT1 activation was sufficient to decrease abnormal TF activity and prothrombotic status in COX-2 knockout mice. Conclusions-Modulation of SIRT1 and hence TF by prostacyclin/peroxisome proliferator-activated receptor-␦ pathways not only represents a new mechanism in controlling arterial thrombus formation but also might be a useful target for therapeutic intervention in the atherothrombotic complications associated with COX-2 inhibitors. (Circulation. 2012; 126:1373-1384.)Key Words: blood coagulation Ⅲ carotid arteries Ⅲ prostacyclin Ⅲ signal transduction Ⅲ thrombosis P rostanoids are a family of bioactive lipid mediators formed from arachidonic acid by cyclooxygenases (COXs; COX-1 and COX-2). 1 Prostanoids are involved in a variety of physiological activities, including platelet aggregation, vasorelaxation and vasoconstriction, local inflammatory response, and leukocyte-endothelial cell adhesion. 2,3 In this context, prostanoids modulate the pathogenesis of vascular diseases such as arterial thrombosis and atherosclerosis. 4 The role of COX-2 in atherothrombosis is complex. This enzyme generates not only proinflammatory, but also anti-inflammatory prostanoids, such as prostacyclin (PGI 2 ), which, under certain conditions, may counteract platelet-derived thromboxane (TXA 2 ). 5 PGI 2 is a potent vasodilator and an inhibitor of platelet aggregation, leukocyte adhesion, and vascular smooth muscle cell proliferation. 6 These actions of PGI 2 are mediated through specific cell surface receptors known as PGI 2 receptors (IPs). Each IP is a 7-membrane-spanning G-protein-coupled receptor that elicits cAMP p...

Angiotensin 1-7 and Mas decrease thrombosis in Bdkrb2−/− mice by increasing NO and prostacyclin to reduce platelet spreading and glycoprotein VI activation

“…29 Most recently, it has been recognized that prostacyclin regulates arterial thrombus formation by suppressing tissue factor expression in vasculature, leukocytes, and microparticles. 35 Although it is not precisely known if elevated prostacyclin is the major contributor to thrombosis protection in our mice, the thrombosis phenotype of Bdkrb2 2/2 is not influenced by the phenotype of the bone marrow donor. Our data suggest that host factors, derived from vasculature in the Bdkrb2 2/2 mice, are the major determinant for the thrombosis protection observed.…”

Reduced thrombosis in Klkb1−/− mice is mediated by increased Mas receptor, prostacyclin, Sirt1, and KLF4 and decreased tissue factor

“…41 Barberi et al reported that COX-2-deficient mice have decreased Sirt1, enhanced vascular TF expression, and accelerated thrombosis. 31 We observed the opposite in Klkb1 2/2 and Bdkrb2 2/2 mice. Elevated plasma PGI 2 in our mice is associated with increased aortic Sirt1 and KLF4 mRNA and protein that are reduced by nimesulide ( Figure 5C-F).…”

“…Recently COX-2-derived prostacyclin has been recognized to suppress TF expression through the NAD 1 -dependent class III histone deacetylase sirtuin-1 (Sirt1). [29][30][31] The mRNA for both Sirt1 and KLF4 were elevated in Klkb1 2/2 aorta ( Figure 5C). We also found elevated aortic mRNA for Sirt1 and KLF4 in Bdkrb2 2/2 mice 17,18 (supplemental Figure 10).…”

“…31,42 Sirt1, a deacetylase, may indirectly regulate TF expression by inactivating a coactivator for NF-kB. 43 KLF4 may influence TF expression through its ability to influence endothelial nitric oxide and thrombomodulin.…”

EP Receptors and Coxibs

“…In these mice, the production of PGE 2 was restored as compared with COX-2 knockout mice, whereas no differences were found in PGI 2 metabolites (because their production was mainly COX-2-dependent). 9,15 Interestingly, these mice showed an exaggerate hyperplastic neointimal response when compared with both COX-2 knockout and wild-type mice. Taken together, these results suggest that during COX-2 suppression, the beneficial effects of reducing PGE 2 synthesis in VSMCs and macrophages (recruitment is considerably increased after vascular injury) may greatly overlook the detrimental effects of PGI 2 inhibition and may lead to reduction of neointima.…”