Disruption of Ephx2 in cardiomyocytes but not endothelial cells improves functional recovery after ischemia-reperfusion in isolated mouse hearts

Journal of Biological ChemistryJournal of Biological ChemistryVolume 299, Issue 4, April 2023, 103049Journal home page for Journal of Biological ChemistryAuthor links open overlay panel, , , , , , ,

Cytochromes P450 metabolize arachidonic acid to epoxyeicosatrienoic acids (EETs) which have numerous effects. After cardiac ischemia, EET-induced coronary vasodilation increases delivery of oxygen/nutrients to the myocardium, and EET-induced signaling protects cardiomyocytes against postischemic mitochondrial damage. Soluble epoxide hydrolase 2 (EPHX2) diminishes the benefits of EETs through hydrolysis to less active dihydroxyeicosatrienoic acids. EPHX2 inhibition or genetic disruption improves recovery of cardiac function after ischemia. Immunohistochemical staining revealed EPHX2 expression in cardiomyocytes and some endothelial cells but little expression in cardiac smooth muscle cells or fibroblasts. To determine specific roles of EPHX2 in cardiac cell types, we generated mice with cell-specific disruption of Ephx2 in endothelial cells (Ephx2fx/fx/Tek-cre) or cardiomyocytes (Ephx2fx/fx/Myh6-cre) to compare to global Ephx2-deficient mice (global Ephx2−/−) and WT (Ephx2fx/fx) mice in expression, EET hydrolase activity, and heart function studies. Most cardiac EPHX2 expression and activity is in cardiomyocytes with substantially less activity in endothelial cells. Ephx2fx/fx/Tek-cre hearts have similar EPHX2 expression, hydrolase activity, and postischemic cardiac function as control Ephx2fx/fx hearts. However, Ephx2fx/fx/Myh6-cre hearts were similar to global Ephx2−/− hearts with significantly diminished EPHX2 expression, decreased hydrolase activity, and enhanced postischemic cardiac function compared to Ephx2fx/fx hearts. During reperfusion, Ephx2fx/fx/Myh6-cre hearts displayed increased ERK activation compared to Ephx2fx/fx hearts, which could be reversed by EEZE treatment. EPHX2 did not regulate coronary vasodilation in this model. We conclude that EPHX2 is primarily expressed in cardiomyocytes where it regulates EET hydrolysis and postischemic cardiac function, whereas endothelial EPHX2 does not play a significant role in these processes.

Keywords

EPHX2

EETs

epoxide hydrolase

heart

Langendorff

AbbreviationsDHET

dihydroxyeicosatrienoic acid

EET

epoxyeicosatrienoic acid

EEZE

14,15-epoxyeicosa-5(Z)-enoic acid

EpDPE

epoxydocosapentaenoic acid

EpETE

epoxyeicosatetraenoic acid

EPHX1

microsomal epoxide hydrolase

EPHX2

soluble epoxide hydrolase

KATP

ATP-sensitive K+ channels

LVDP

left ventricular developed pressure

mPTP

mitochondrial permeability transition pore

© 2023 THE AUTHORS. Published by Elsevier Inc on behalf of American Society for Biochemistry and Molecular Biology.

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