Received for publication June 23, 2004.
Revised September 10, 2004.
Accepted for publication September 10, 2004.

Enhancement of 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 (I_Ca) in adult transgenic mice. Cardiac-specific overexpression of CYP2J2 was achieved using the -myosin heavy chain promoter. I_Ca was recorded from isolated ventricular cardiomyocytes. Compared with the wildtype cardiomyocytes (n = 60), the density of I_Ca was significantly increased by 40 ± 9% in the CYP2J2 transgenic cardiomyocytes (n = 71, P < 0.001). N-methylsulphonyl-6-(2-proparglyloxy-phenyl)hexanamide (MS-PPOH), a specific inhibitor of EET biosynthesis, and clotrimazole, a cytochrome P450 inhibitor, significantly reduced I_Ca in both wildtype and transgenic cardiomyocytes; however, MS-PPOH inhibited I_Ca to a greater extent in the CYP2J2 transgenic cells (n = 10) than in the wildtype cells (n = 10, P < 0.01). Addition of 11,12-EET significantly restored I_Ca in MS-PPOH treated cells. Intracellular dialysis with either of two inhibitory monoclonal antibodies against CYP2J2 significantly reduced I_Ca in both wildtype and transgenic mice. Membrane permeable 8-Br-cAMP and the -adrenergic agonist isoproterenol significantly reversed the monoclonal antibody-induced inhibition of I_Ca. In addition, the total protein level of the 1 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 I_Ca in CYP2J2 transgenic cardiomyocytes via a mechanism that involves cAMP-PKA-dependent phosphorylation of the L-type Ca²⁺ channel.

Key words: Ion channel regulation, Calcium (Votage-Gated Channels), Protein Kinase A, Cytochrome P450, Eicosanoids, Overexpression

This article has been cited by other articles:

				M. Z. Wang, J. Q. Wu, A. S. Bridges, D. C. Zeldin, S. Kornbluth, R. R. Tidwell, J. E. Hall, and M. F. Paine Human Enteric Microsomal CYP4F Enzymes O-Demethylate the Antiparasitic Prodrug Pafuramidine Drug Metab. Dispos., November 1, 2007; 35(11): 2067 - 2075. [Abstract] [Full Text] [PDF]

				Q. Ke, Y.-F. Xiao, J. A. Bradbury, J. P. Graves, L. M. DeGraff, J. M. Seubert, and D. C. Zeldin Electrophysiological Properties of Cardiomyocytes Isolated from CYP2J2 Transgenic Mice Mol. Pharmacol., October 1, 2007; 72(4): 1063 - 1073. [Abstract] [Full Text] [PDF]

				T. C. DeLozier, G. E. Kissling, S. J. Coulter, D. Dai, J. F. Foley, J. A. Bradbury, E. Murphy, C. Steenbergen, D. C. Zeldin, and J. A. Goldstein Detection of Human CYP2C8, CYP2C9, and CYP2J2 in Cardiovascular Tissues Drug Metab. Dispos., April 1, 2007; 35(4): 682 - 688. [Abstract] [Full Text] [PDF]

				M. Z. Wang, J. Y. Saulter, E. Usuki, Y.-L. Cheung, M. Hall, A. S. Bridges, G. Loewen, O. T. Parkinson, C. E. Stephens, J. L. Allen, et al. CYP4F Enzymes Are the Major Enzymes in Human Liver Microsomes That Catalyze the O-Demethylation of the Antiparasitic Prodrug DB289 [2,5-Bis(4-amidinophenyl)furan-bis-O-methylamidoxime] Drug Metab. Dispos., December 1, 2006; 34(12): 1985 - 1994. [Abstract] [Full Text] [PDF]

				Y.-F. Xiao, E. M. TenBroek, J. J. Wilhelm, P. A. Iaizzo, and D. C. Sigg Electrophysiological characterization of murine HL-5 atrial cardiomyocytes Am J Physiol Cell Physiol, September 1, 2006; 291(3): C407 - C416. [Abstract] [Full Text] [PDF]

				T. Lu, D. Ye, X. Wang, J. M. Seubert, J. P. Graves, J. A. Bradbury, D. C. Zeldin, and H.-C. Lee Cardiac and vascular KATP channels in rats are activated by endogenous epoxyeicosatrienoic acids through different mechanisms J. Physiol., September 1, 2006; 575(2): 627 - 644. [Abstract] [Full Text] [PDF]

				H. V. Gelboin and K. Krausz Monoclonal antibodies and multifunctional cytochrome p450: drug metabolism as paradigm. J. Clin. Pharmacol., March 1, 2006; 46(3): 353 - 372. [Abstract] [Full Text] [PDF]