Protection of Human Endothelial Cells From Oxidative Stress Role of Ras-ERK1/2 Signaling

Background— Reactive oxygen species play a critical role in inducing apoptosis. The small GTPase p21 Ras and the ERK1/2 MAPK have been proposed as key regulators of the signaling cascade triggered by oxidative stress (H2O2). Harvey-Ras (Ha-Ras) and Kirsten-Ras (Ki-Ras) isoforms are so far functionally indistinguishable, because they activate the same downstream effectors, including ERK1/2. Moreover, ERK1/2 signaling has been involved in both protection and induction of apoptosis. Methods and Results— Human umbilical vein endothelial cells (HUVECs) were subjected to H2O2, and apoptosis was detected by fluorescence-activated cell sorting analysis, fluorescence microscopy, and caspase-3 activation. Transfection of Ha-Ras and Ki-Ras genes in HUVECs was performed to evaluate the response to H2O2. We have found that, whereas Ha-Ras decreases tolerance to oxidative stress, Ki-Ras has a potent antiapoptotic activity. Both effects are mediated by ERK1/2. Tolerance to H2O2 is encoded by a unique stretch of lysines ...