Upregulation of Proteinase-Activated Receptor-2 and Increased Response to Trypsin in Endothelial Cells after Exposure to Oxidative Stress in Rat Aortas

Background/Aims: The effects of oxidative stress on the vascular responsiveness to the agonists of proteinase-activated receptors (PARs) were investigated. Methods: Serum-free incubation was utilized to impose oxidative stress to isolated rat aortas. Spontaneously hypertensive rats (SHR) were investigated as a model of in vivo oxidative stress. Results: Thrombin, trypsin, PAR(1)-activating peptide (PAR(1)-AP), PAR(2)-AP and PAR(4)-AP induced little or no effect in the aortas of female Wistar-Kyoto rats (WKY). Serum-free incubation induced endothelium-dependent relaxant responses to PAR(2) agonists, but not PAR(1) or PAR(4) agonists, in a manner sensitive to diphenyleneiodonium or ascorbic acid. In male aortas, trypsin and PAR(2)-AP induced a transient endothelium-dependent relaxation without serum-free incubation. The acetylcholine-induced endothelium-dependent relaxation and the sodium nitroprusside-induced endothelium-independent relaxation remained unchanged. Immunoblot analyses revealed the upregulation of PAR(2) in endothelial cells, which was abolished by either diphenyleneiodonium or ascorbic acid. Aortas of female SHR expressed a higher level of PAR(2) than WKY and responded to trypsin without serum-free incubation. Treatment with ascorbic acid attenuated the trypsin-induced relaxation and the PAR(2) expression in SHR. Conclusion: This study provides the first evidence that oxidative stress upregulates PAR(2) in endothelial cells, thereby enhancing the endothelium-dependent relaxant response to PAR(2) agonists in rat aortas. Copyright (C) 2010 S. Karger AG, Basel