Characterization & Functional Significance Of P450s

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Cytochromes P450 metabolize arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs) which have potent effects on cardiovascular and renal function. Current research involves: (1) characterization of CYP2J subfamily P450s at the biochemical and molecular levels; (2) evaluation of the functional roles of CYP2J products in cardiovascular and renal physiology; and (3) examination of this pathway in selected animal models of human disease (ischemic heart disease, hypertension, atherosclerosis). We have discovered a number of mammalian CYP2Js, although we have focused most of our efforts on human CYP2J2 and mouse CYP2J5. Human CYP2J2 is the major human P450 expressed in heart and vasculature, where it is localized to cardiac myocytes and endothelial cells, and is active in the metabolism of AA to EETs. CYP2J2-derived EETs are vasodilators, inhibit cytokine-induced endothelial cell adhesion molecule expression, induce tissue plasminogen activator gene expression, inhibit vascular smooth muscle cell migration, protect endothelial cells against hypoxia-reoxygenation injury, and upregulate endothelial nitric oxide biosynthesis. CYP2J2 transgenic mice (alpha-myosin heavy chain promoter driven cardiac-specific expression) were developed to study the effects of increased EETs on cardiovascular function in vivo. These mice have normal basal heart anatomy and function, improved post-ischemic left ventricular function, shortened cardiac action potential, altered cardiac electrophysiology, and enhanced beta-adrenergic receptor responsiveness. The human CYP2J2 gene has been cloned, sequenced and characterized. We have identified several functionally relevant CYP2J2 polymorphic variants, one of which is associated with reduced CYP2J2 expression and is present at higher frequency in patients with cardiovascular disease vs. normals in a large German cohort. CYP2J5 is a major murine P450 arachidonic acid epoxygenase expressed in the kidney and localized to proximal tubules. To evaluate the role of this P450 and its eicosanoid products in renal function and blood pressure regulation, we disrupted the Cyp2j5 gene by homologous recombination. CYP2J5 null mice have spontaneous hypertension that persists on both high and low salt diets. The hypertension is much more severe in females, is associated with reduced circulating estradiol levels, and is responsive to estrogen supplementation. CYP2J5 null female mice also have increased proximal tubular transport rates, enhanced vascular responsiveness to angiotensin II and endothelin, and reduced fertility compared to wild type counterparts. This new animal model will lead to a better understanding of the complex interrelationship between renal P450s, sex hormones, renal eicosanoids and blood pressure regulation.