Abstract-Vascular smooth muscle cell (SMC) migration and proliferation contribute to neointimal hyperplasia and restenosis after vascular injury. The epoxyeicosatrienoic acids (EETs), which are products of cytochrome P450 (CYP) epoxygenases, possess vasodilatory, antiinflammatory, and fibrinolytic properties. To determine whether these compounds also possess antimigratory and antiproliferative properties, we stimulated rat aortic SMCs with either 20% serum or platelet-derived growth factor (PDGF-BB, 20 ng/mL). In a concentration-dependent manner, treatment with EETs, particularly 11,12-EET, inhibited SMC migration through a modified transwell filter by 53% to 60%. EETs, however, have no inhibitory effects on PDGF-stimulated SMC proliferation. Adenoviral-mediated overexpression of the CYP isoform, CYP2J2, in SMCs also inhibited serum-and PDGF-induced SMC migration by 32% and 26%, respectively; both effects of which were reversed by the CYP inhibitors SKF525A or clotrimazole, but not by the K Ca channel blocker, charybdotoxin, or the cyclooxygenase inhibitor, diclofenac. The effect of EETs correlated with increases in intracellular cAMP levels. Indeed, forskolin and 8-bromo-cAMP exert similar inhibitory effects on SMC migration as 11,12-EET and the effects of 11,12-EET were blocked by cAMP and protein kinase A (PKA) inhibitors. [1][2][3] The EETs have properties similar to those of endothelium-derived hyperpolarizing factor (EDHF) because they hyperpolarize and relax vascular smooth muscle cells (SMCs) by activating calcium-sensitive potassium (K Ca ) channels. 4,5 Recently, several CYP epoxygenases, including members of the CYP2B, CYP2C, and CYP2J subfamilies, have been identified in vascular endothelial cells. However, their relative importance in endothelial EET biosynthesis has not been determined. 1,6 -8 Treatment of porcine coronary artery endothelial cells in vitro with either ␤-naphthoflavone or nifedipine induces CYP2C expression, increases 11,12-EET biosynthesis, and enhances bradykinin-induced coronary artery relaxation via SMC membrane hyperpolarization. 1,9 Moreover, transfection of endothelial cells with an antisense oligonucleotide to CYP2C8/9 or treatment with the selective CYP2C9 inhibitor, sulfaphenazole, attenuates EDHFmediated vascular responses, thus providing supporting evidence that the EDHF synthase in the porcine vascular bed may be a CYP2C isoform. 1,9 In contrast to their vasodilatory effects, EETs have also been shown to possess important nonvasodilatory actions within the vascular system. For example, EETs which are produced by a member of the CYP2J family, CYP2J2, inhibit cytokine-induced endothelial cell adhesion molecule expression by inhibiting the proinflammatory transcriptional factor, NF-B. 6 Furthermore, in vascular endothelial cells, addition of physiologically relevant concentrations of EETs or overexpression of CYP2J2 increases tissue plasminogen activator (tPA) expression and fibrinolytic activity via a G␣ sdependent, cAMP-mediated mechanism. 10 However, neither the antiin...

(VDRE). 2 VDR belongs to the nuclear receptor superfamily for steroid hormones, retinoic acid, and thyroid hormone (T 4 ). 3 These receptors bind to their responsive elements and alter downstream gene transcription. In addition, 1␣,25-(OH) 2 D 3 has also been shown to produce rapid, nongenomic (ie, VDRE-independent) responses. 4 Indeed, 1␣,25-(OH) 2 D 3 stimulates a wide array of rapid responses including rapid intestinal absorption of calcium (transcaltachia), 5 store-operated calcium influx, 6 activation of protein kinase C, 7 and opening of voltage-gated calcium and chloride channels. 8 Although the precise molecular mechanisms by which these rapid nongenomic responses are regulated remain unclear, a putative membrane receptor for 1␣,25-(OH) 2 D 3 or alternative pathways of the nuclear VDR have been proposed. 9 Analogs of 1␣,25-(OH) 2 D 3 have been used to differentiate the genomic (ie, VDRE-dependent) versus nongenomic responses. These analogs take advantage of the flexible conformation of 1␣,25-(OH) 2 D 3 at the 6,7 carboncarbon single bond (Figure 1). Rapid rotation about this bond allows generation of a continuum of various shapes of 1␣,25-(OH) 2 D 3 ranging from the planar extended 6-s-trans conformation to the steroid-like 6-s-cis conformation 10,11 ; these various shapes are then available to serve as ligands for appropriate receptors. Indeed, the 6-s-cis-locked analog 1␣,25-dihydroxylumisterol is a fully potent agonist of rapid, nongenomic responses of 1␣,25-(OH) 2 D 3 . 5 Thus, it has been proposed that different shapes of the conformationally flexible 1␣,25-(OH) 2 D 3 are agonists for the rapid, nongenomic (6-s-cis) and genomic (twisted 6-s-trans) responses. 12 In addition, analogs that antagonize 1␣,25-(OH) 2 D 3 responses have also been characterized. Indeed, 1␤,25-(OH) 2 D 3 (HL) is a specific antagonist of nongenomic action of 1␣,25-(OH) 2 D 3 , 8,13 whereas (23S)-25-dehydro-1␣-OH-D 3 -26,23-lactone (MK) preferentially inhibits genomic responses. 14 Original