Abstract-Cytochrome P450 1B1, expressed in vascular smooth muscle cells, can metabolize arachidonic acid in vitro into several products including 12-and 20-hydroxyeicosatetraenoic acids that stimulate vascular smooth muscle cell growth. This study was conducted to determine whether cytochrome P450 1B1 contributes to angiotensin II-induced rat aortic smooth muscle cell migration, proliferation, and protein synthesis. Angiotensin II stimulated migration of these cells, measured by the wound healing approach, by 1. Metabolism of arachidonic acid to 5-, 12-, 15-, and 20-hydoxyeicosatetraenoic acids in these cells was not altered, but angiotensin II-and arachidonic acid-induced reactive oxygen species production and extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase activity were inhibited by 2,4,3Ј,5Ј-tetramethoxystilbene and cytochrome P450 1B1 small hairpin RNA (shRNA) and by Tempol, which inactivates reactive oxygen species. Tempol did not alter cytochrome P450 1B1 activity. These data suggest that angiotensin II-induced vascular smooth muscle cell migration and growth are mediated by reactive oxygen species generated from arachidonic acid by cytochrome P450 1B1 and activation of extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase. (Hypertension. 2010;55:1461-1467.) Key Words: angiotensin II Ⅲ CYP1B1 Ⅲ vascular smooth muscle cell growth Ⅲ ROS T he renin-angiotensin system is one of the major components of the mechanisms that contribute to the regulation of blood volume and vascular resistance. 1 Angiotensin II (Ang II), the main biologically active agent of this system, also stimulates vascular smooth muscle cell (VSMC) hypertrophy and/or hyperplasia and inflammation and contributes to the development of hypertension, atherosclerosis, heart failure, and restenosis after vascular injury. [1][2][3][4][5][6] The pathophysiological actions of Ang II are mediated by activation of Ն1 serine-threonine and tyrosine kinase, generation of oxygen radicals, 7-9 and/or release of arachidonic acid (AA) by cytosolic phospholipase A 2 (cPLA 2 ) and production of its metabolites, 12-hydroxyeicosatetraenoic acid (12-HETE) and 20-HETE, generated via lipoxygenase and/or cytochrome P450 (CYP) 4A, respectively. 10 -18 Both 12-and 20-HETE promote VSMC migration, hyperplasia, and/or hypertrophy. 11,19 -22 CYP enzymes that metabolize xenobiotics, including polycyclic aromatic hydrocarbons and endobiotics, such as fatty acids and retinoids, are also expressed in extrahepatic tissues, including the cardiovascular system. 23-27 CYP1A1-encoded enzymes are expressed in vascular endothelium and smooth muscle cells, with much higher levels of activity in endothelial cells, whereas CYP1B1 is highly expressed in VSMCs and, to a lesser degree, in endothelial cells, 28,29 but shear stress upregulates mRNA and protein levels of CYP1A1 and CYP1B1 in endothelial cells. 30 Whether CYP1A1 and CYP1B1 contribute to the vascular function is not known. Recombinant CYP1B1 has been shown to me...
