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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2008;28:711.)
© 2008 American Heart Association, Inc.

Cell Biology/Signaling

PARP-1 Inhibition Prevents Oxidative and Nitrosative Stress–Induced Endothelial Cell Death via Transactivation of the VEGF Receptor 2

Marlene T. Mathews; Bradford C. Berk

From the Aab Cardiovascular Research Institute, University of Rochester School of Medicine and Dentistry, New York.

Correspondence to Bradford C. Berk, MD, PhD, Aab Cardiovascular Research Institute, University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave, Box 706, Rochester, New York 14642. E-mail Bradford_Berk{at}urmc.rochester.edu

Objective— PARP-1, a DNA base repair enzyme, is activated by DNA breaks induced by oxidative (ROS) and nitrosative (RNS) stress. By consuming NAD⁺, PARP-1 activation can lead to ATP depletion and cell death. Studies suggest that inhibiting PARP-1 activity can attenuate pathologies associated with vascular smooth muscle and endothelial dysfunction. PARP-1 inhibition can also activate the prosurvival serine/threonine kinase, Akt. Vascular endothelial growth factor (VEGF) regulates endothelial cell survival via Akt activation downstream of VEGF receptor 2 (VEGFR2) activation. Here we investigated the hypothesis that PARP-1 inhibition protects human umbilical vein endothelial cells (HUVECs) from ROS- and RNS-induced cell death by limiting NAD⁺ depletion and by activating a prosurvival signaling pathway via VEGFR2 phosphorylation.

Methods and Results— We activated PARP-1 in HUVECs by treatment with hydrogen peroxide (H₂O₂) and peroxynitrite (ONOO^–). Both depleted HUVECs of NAD⁺ and ATP, processes that were limited by the PARP-1 inhibitor, PJ34. ONOO^– and H₂O₂-induced cell death and apoptosis were attenuated in cells treated with PJ34 or PARP-1 siRNA. PARP-1 inhibition increased Akt, BAD, and VEGFR2 phosphorylation in HUVECs and in PJ34-treated rabbit aortas. The VEGFR2-specific tyrosine kinase inhibitor SU1498 decreased PARP-1 inhibition-mediated phosphorylation of VEGFR2 and Akt, and also reversed survival effects of PJ34. Finally, PARP-1 inhibition protected cells from death induced by serum starvation, evidence for a role in cell survival independent of energy protection.

Conclusions— PARP-1 inhibition prevents ROS- and RNS-induced HUVEC death by maintaining cellular energy in the form of NAD⁺ and ATP, and also by activating a survival pathway via VEGFR2, Akt, and BAD phosphorylation.

PARP-1, a DNA repair enzyme activated by oxidative and nitrosative stress, consumes cellular energy and precipitates endothelial cell death. Here we show that PARP-1 inhibition prevents ROS- and RNS-induced HUVEC death not only by maintaining cellular energy, but also through a novel mechanism via VEGFR2, Akt, and Bad phosphorylation.

Key Words: PARP inhibition • endothelial cell survival • VEGF receptor 2 • oxidative stress

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