Characterization And Functional Significance Of P450 Arachidonate Epoxygenases

National Institute Of Environmental Health Sciences

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Abstract

Cytochromes P450 metabolize arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs) which have potent effects on cardiovascular and renal function. EETs are metabolized to corresponding diols (DHETs) by microsomal epoxide hydrolase (mEH) and soluble epoxide hydrolase (sEH). Current research involves: (1) characterization of CYP2J and CYP2C subfamily P450s at the biochemical and molecular levels; (2) evaluation of the functional roles of CYP2J products in cardiovascular and renal physiology; (3) evaluation of the functional roles of epoxide hydrolases in cardiovascular physiology; (4) examination of this pathway in selected animal models of human disease (ischemic heart disease, hypertension, atherosclerosis, cancer), and (5) evaluation of the effect of human polymorphisms in genes for CYP2C, CYP2J, sEH and mEH on cardiovascular function and disease. 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 apoptosis, upregulate endothelial nitric oxide biosynthesis, affect cardiac electrophysiology, and protect the heart from ischemic injury. CYP2J2 transgenic mice (alpha-myosin heavy chain promoter driven cardiac-specific expression) were developed to study the effects of increased EETs on cardiac 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. Similarly, sEH null mice which exhibit reduced EET hydrolysis have improved postischemic functional recovery. We discovered that mEH regulates EET levels in vivo and that hearts from mEH/sEH double-null mice have greater recovery of heart function relative to hearts from sEH null mice. We have also developed transgenic mice in which CYP2J2, CYP2C8 or sEH are expressed exclusively in endothelial cells (Tie2 promoter driven) to examine the role of these enzymes and their products on vascular function. Endothelial expression of CYPs or sEH regulate angiogenesis which promotes tumor formation and growth and regulates retinal vascularization. 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 associated with risk of cardiovascular disease in several cohorts. We have also identified functionally relevant polymorphisms in the sEH gene and have shown that they are associated with cardiovascular disease risk in a large multiethnic cohort in the U.S. CYP2J5 is a major murine P450 arachidonic acid epoxygenase expressed in the kidney and localized to proximal tubules. CYP2J5 null mice have spontaneous hypertension that persists on both high and low salt diets. Consistent with these findings, we have shown that there is an association between CYP2J2 polymorphic variants and hypertension in a cohort from Tennessee. Given the anti-inflammatory effects of sEH inhibitors (sEHis), we have examined the role of sEHis in attenuation of SARS-CoV-2-induced eicosanoid and cytokine storm. This project involves research on human coronavirus, novel coronavirus, COVID-19, Severe Acute Respiratory Syndrome coronavirus disease, SARS coronavirus, SARS-coronavirus-2, SARS-cov-2, SARS-cov2, SARS-related coronavirus 2, Severe acute respiratory syndrome coronavirus 2, SARS-Associated Coronavirus, SARS-cov, or SARS-Related Coronavirus.