OXIDANT STRESS-INDUCED TRANSENDOTHELIAL MIGRATION OF MONOCYTES IS LINKED TO PHOSPHORYLATION OF PECAM-1

Reactive oxygen species (ROS) are believed to cause vascular injury in the pathophysiology of atherosclerosis, diabetes, and vasoocclusion i n sickle cell disease. Studies have shown that ROS causes increased ad hesion of monocytes and neutrophils to the endothelium. We investigate d the effects of tert-butylhydroperoxide (t-BuOOH), an inducer of oxid ant stress, to determine the cellular signaling pathway leading to the transendothelial migration of polymorphonuclear leukocytes. Our studi es revealed that signaling by t-BuOOH in human umbilical vein endothel ial cells (HUVECs) causes a twofold increase in the transendothelial m igration of monocyte-like HL-60 cells and a fivefold increase in plate let endothelial cell adhesion molecule-1 (PECAM-1) phosphorylation. Th e transmigration induced by t-BuOOH was inhibited by an antibody to PE CAM-1. These events were inhibited by antioxidants and inhibitors of p rotein kinase C, p21(ras) and glutathione synthesis. However, treatmen t of HUVECs with the phosphatase inhibitor calyculin A augmented the t -BuOOH-mediated transendothelial migration of monocytes and PECAM-1 ph osphorylation. Our results suggest that oxidative stress can induce th e transendothelial migration of monocytes as a result of phosphorylati on of PECAM-1, a crucial event in the diapedesis of leukocytes during pathophysiology of vascular diseases.