Importance of photo activation of rose bengal for platelet activation in experimental models of photochemically induced thrombosis.

Generation of oxygen free radicals in the lumen of a vessel leads to NO inactivation, modification of lipid components of platelets and endothelial cell membranes, and platelet activation. On this basis, many experimental models of thrombosis have been developed, where the formation of a platelet rich thrombus follows the illumination of a vessel with an appropriately filtered light after intravenous administration of Rose Bengal or another sensitizing dye. However the detailed mechanism of thrombus formation remains poorly known. This work appreciates the contribution of platelet activation directly induced by oxygen free radicals in formation of the platelet rich thrombus, from a study of human platelet aggregation in presence of photo-activated Rose Bengal. The results demonstrate that direct activation of platelets by free radicals generated by Rose Bengal is of low or no importance in formation of the thrombus. Therefore, the main trigger of platelet aggregation and thrombosis in these models is primary endothelial cells injury.