Integrin alphaIIbbeta3-dependent Reactive Oxygen Species Production in Platelets

Excessive Reactive Oxygen Species (ROS) is associated with all known cardiovascular risk factors and is believed to play an important role for the onset of cardiovascular diseases. As a family of multisubunit enzymes complexes, NADPH oxidases deliberately generate superoxide and/or hydrogen peroxide. Evidence shows that NADPH oxidase are the key generators of ROS in the blood vessel wall and other tissues during cardiovascular disease progression. Studies from both human and animal platelet has suggested the role of NADPH-dependent ROS in platelet activation and thrombosis. However, the mechanism of how ROS production is regulated during platelet activation, and the effect of NOX-dependent ROS on platelet function remains unclear. This study focuses on illustrating the mechanism of how does integrin αIIbβ3 regulate ROS production and NOX activity in platelets. Integrin outside-in signaling is shown to be important for ROS production and NOX2 activation. Data here demonstrated P47phox phosphorylation and ROS production could be induced by integrin-ligation without need for other stimuli, and it is augmented by outside-in signaling activator, MnCl2, while disrupted by selective outside-in inhibitor, mP6. And the absence of β3 is shown to almost completely abolished p47phox activation, even in CRP-stimulated platelets. In addition, it has demonstrated that NOX1 and NOX2 knockout platelets was defect in stable adhesion, which is not further inhibited by mp6. This could possibly suggest ROS reversely inhibits integrin outside-in signaling. However, platelet spreading is not affected by NOX knockout. Along with previous data showing that NOX1/2 knockout mainly affected platelet granule secretion, and second wave of platelet aggregation, which requires integrin outside-in signaling, we concluded NOX-dependent ROS is important for integrin outside-in signaling and its functional consequences. Altogether, this study, provided insight as how ROS production in activated platelets is regulated, forming a theoretical foundation for new antithrombotic strategy basing on intervening integrin outside-in pathway-regulated NOX activity.