Thrombin exposure increased P2Y12 expression in human vascular smooth muscle cells within 6 hours, enhancing 2-methylthio-ADP-induced interleukin 6 expression and mitogenesis.
Thrombin upregulates functionally active P2Y12 receptors in human vascular smooth muscle cells, suggesting a platelet-independent role for P2Y12 in vascular injury and atherosclerosis.
OBJECTIVE: The platelet P2Y12 ADP receptor is a well-known target of thienopyridine-type antiplatelet drugs. This study is the first to describe increased transcriptional expression of a functionally active P2Y12 in response to thrombin in human vascular smooth muscle cells (SMC). METHODS AND RESULTS: On exposure to thrombin, P2Y12 mRNA was transiently increased, whereas total protein and cell surface expression of P2Y12 were markedly increased within 6 hours and remained elevated over 24 hours. This effect was mediated by activation of nuclear factor κB. Preincubation with thrombin significantly enhanced the efficacy of the P2Y receptor agonist 2-methylthio-ADP to induce interleukin 6 expression and SMC mitogenesis. Effects induced by 2-methylthio-ADP were prevented by RNA interference-mediated knockdown of P2Y12 and a selective P2Y12-antagonist R-138727, the active metabolite of prasugrel. In addition, positive P2Y12 immunostaining was shown in SMC of human carotid artery plaques and was found to colocalize with tissue factor, the rate-limiting factor of thrombin formation in vivo. CONCLUSIONS: These data suggest that the P2Y12 receptor not only is central to ADP-induced platelet activation but also may mediate platelet-independent responses, specifically under conditions of enhanced thrombin formation, such as local vessel injury and atherosclerotic plaque rupture.
Rauch et al. (2010) studied Carotid artery lesions. Thrombin exposure was evaluated on P2Y12 mRNA and protein expression, interleukin 6 expression, and SMC mitogenesis. Thrombin exposure increased P2Y12 expression in human vascular smooth muscle cells within 6 hours, enhancing 2-methylthio-ADP-induced interleukin 6 expression and mitogenesis.