Enhancement of cardiac L-type Ca2+ currents in transgenic mice with cardiac-specific overexpression of CYP2J2.
ABSTRACT CYP2J2 is abundant in cardiomyocytes and is involved in the metabolism of arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs), which affect multiple cell functions. In this study, we investigated the effect of overexpression of CYP2J2 on cardiac L-type Ca2+ currents (ICa) in adult transgenic mice. Cardiac-specific overexpression of CYP2J2 was achieved using the alpha-myosin heavy chain promoter. ICa was recorded from isolated ventricular cardiomyocytes. Compared with the wild-type cardiomyocytes (n = 60), the density of ICa was significantly increased by 40 +/- 9% in the CYP2J2 transgenic cardiomyocytes (n = 71; P < 0.001). N-Methylsulfonyl-6-(2-proparglyloxyphenyl)hexanamide (MS-PPOH), a specific inhibitor of EET biosynthesis, and clotrimazole, a cytochrome P450 inhibitor, significantly reduced ICa in both wild-type and transgenic cardiomyocytes; however, MS-PPOH inhibited ICa to a greater extent in the CYP2J2 transgenic cells (n = 10) than in the wild-type cells (n = 10; P < 0.01). Addition of 11,12-EET significantly restored ICa in MS-PPOH-treated cells. Intracellular dialysis with either of two inhibitory monoclonal antibodies against CYP2J2 significantly reduced ICa in both wild-type and transgenic mice. Membrane-permeable 8-bromo-cAMP and the beta-adrenergic agonist isoproterenol significantly reversed the monoclonal antibody-induced inhibition of ICa. In addition, the total protein level of the alpha1 subunit of the Cav1.2 L-type Ca2+ channel was not altered in CYP2J2 transgenic hearts, but the phosphorylated portion was markedly increased. In conclusion, overexpression of CYP2J2 increases ICa in CYP2J2 transgenic cardiomyocytes via a mechanism that involves cAMP-protein kinase A-dependent phosphorylation of the L-type Ca2+ channel.
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ABSTRACT: There is limited information on genetic factors associated with sudden cardiac arrest (SCA). To assess the association of common variation in genes in fatty acid pathways with SCA risk. We selected 85 candidate genes and 1155 single nucleotide polymorphisms (SNPs) tagging common variation in each gene. We investigated the SNP associations with SCA in a population-based case-control study. Cases (n=2160) were from a repository of SCA in the greater Seattle area. Controls (n=2615), frequency-matched on age and sex, were from the same area. We used linear logistic regression to examine SNP associations with SCA. We performed p-min permutation tests to account for multiple comparisons within each gene. The SNP associations with corrected p-value < 0.05 were then examined in a meta-analysis of these SNP associations in nine replication studies totaling 2129 SCA cases and 23833 non-cases. Eight SNPs in or near 8 genes were associated with SCA risk in the discovery study, one of which was nominally significant in the replication phase (rs7737692, minor allele frequency 36%, near the LPCAT1 gene). For each copy of the minor allele, rs7737692 was associated with 13% lower SCA risk (-21% to -5%) in the discovery phase and 9% lower risk (95% CI -16% to -1%) in the replication phase. While none of the associations reached significance with Bonferroni correction, a common genetic variant near LPCAT1, a gene involved in the remodeling of phospholipids, was nominally associated with incident SCA risk. Further study is needed to validate this observation.Heart rhythm: the official journal of the Heart Rhythm Society 01/2014; DOI:10.1016/j.hrthm.2014.01.008 · 4.92 Impact Factor
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ABSTRACT: Over the last 20 years, it has become clear that cytochrome P450 (P450) enzymes generate a spectrum of bioactive lipid mediators from endogenous substrates. However, studies focused on the determining biologic activity of the P450 system have focused largely on the metabolites generated by one substrate (i.e., arachidonic acid). However, epoxides and diols derived from other endogenous substrates, such as linoleic acid, eicosapentaenoic acid, and docosahexaenoic acid, may be generated in higher concentrations and may potentially be of more physiologic relevance. Recent studies that used a combination of phenotyping and lipid array analyses revealed that rather than being inactive products, fatty acid diols play important roles in a number of biologic processes including inflammation, angiogenesis, and metabolic regulation. Moreover, inhibitors of the soluble epoxide hydrolase that increase epoxide but decrease diol levels have potential for the treatment of the metabolic syndrome.Pharmacological reviews 10/2014; 66(4):1106-1140. DOI:10.1124/pr.113.007781 · 18.55 Impact Factor
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ABSTRACT: Abstract In addition to their role as xenobiotic metabolizing enzymes, cytochrome P450 (CYP) epoxygenases actively contribute to the metabolism of endogenous substances such as arachidonic acid. Epoxyeicosatrienoic acids (EETs) are epoxide derivative of arachidonic acid. CYP2C8/9 and CYP2J2 are the main epoxygenases expressed in human tissues including endothelial cells which are the chief sources of EET formation in human body. Once formed, EETs are primarily metabolized to their less biologically active metabolites, dihydroxyeicosatrienoic acids, by soluble epoxy hydrolase (sEH) enzyme. EETs possess a wide range of established protective effects on human cardiovascular system of which vasodilatory, angiogenic and anti-inflammatory actions have been more extensively described. On the other hand, inflammation has shown to decrease the expression and activity of CYP enzyme, including epoxygenases. Given the fact that CYP epoxygenase-derive EETs exhibit potent cardiovascular protective effects, including anti-inflammation, and that inflammation suppress CYP activation and EET formation, it would make sense to speculate that under inflammatory conditions there exists an inflammation-epoxygenase-EET-inflammation vicious cycle in which the inflammation-induced downregulation of CYP epoxygenases causes a decrease in the EET production. Insufficient EET synthesis would, in turn, lead to an ineffective EET-mediated anti-inflammatory effect, leading to an augmentation of systemic and regional inflammatory responses and further downregulation of CYP epoxygenase activity/EET production. This cycle, if any, might help to better understanding of pathophysiology of chronic cardiovascular diseases and also could be an emerging target for further pharmacological therapy of disorders in which increased inflammatory responses are known to occur.Drug Metabolism Reviews 09/2013; 46(1). DOI:10.3109/03602532.2013.837916 · 6.29 Impact Factor