Role of PI3Kα and sarcolemmal ATP-sensitive potassium channels in epoxyeicosatrienoic acid mediated cardioprotection.

Abstract

AIMS:

Epoxyeicosatrienoic acids (EETs) are cytochrome P450 epoxygenase metabolites of arachidonic acid that have known cardioprotective properties. While the mechanism(s) remains unknown, evidence suggests that phosphoinositide 3-kinase (PI3K) and sarcolemmal ATP-sensitive potassium channels (pmK(ATP)) are important. However the role of specific PI3K isoforms and corresponding intracellular mechanisms remains unknown.

METHODS AND RESULTS:

To study this, mice hearts were perfused in Langendorff mode for 40 min of baseline and subjected to 20 or 30 min of global no-flow ischemia followed by 40 min of reperfusion. C57BL6 mice perfused with 11,12-EET (1 μM) had improved postischemic recovery, whereas co-perfusion with PI3Kα inhibitor, PI-103 (0.1 μM), abolished the EET-mediated effect. In contrast, blocking of PI3Kβ or PI3Kγ isoforms failed to inhibit EET-mediated cardioprotection. In addition to the improved post-ischemic recovery, increased levels of p-Akt, decreased calcineurin activity and decreased translocation of proapoptotic protein BAD to mitochondria were noted in EET-treated hearts. Perfusion of 11,12-EET to Kir6.2 deficient mice (pmK(ATP)) failed to improve postischemic recovery, decrease calcineurin activity and translocation of proapoptotic protein BAD, however increased levels of p-Akt were still observed. Patch-clamp experiments demonstrated that 11,12-EET could not activate pmK(ATP) currents in myocytes pre-treated with PI-103. Mechanistic studies in H9c2 cells demonstrate that 11,12-EET limits anoxia-reoxygenation triggered Ca(2+) accumulation and maintains mitochondrial ΔΨm compared to controls. Both PI-103 and glibenclamide (10 μM, pmK(ATP) inhibitor) abolished EET cytoprotection.

CONCLUSION:

Together our data suggest that EET-mediated cardioprotection involves activation of PI3Kα, upstream of pmK(ATP), which prevents Ca(2+) overload and maintains mitochondrial function.

• Authors: Sri N Batchu, Ketul R Chaudhary, Haitham El-Sikhry, Wei Yang, Peter E Light, Gavin Y Oudit, John M Seubert
• Journal: Journal of molecular and cellular cardiology (J Mol Cell Cardiol) Vol. 53 Issue 1 Pg. 43-52 (Jul 2012) ISSN: 1095-8584 [Electronic] England
• PMID: 22561102 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2012 Elsevier Ltd. All rights reserved.

Chemical References

• Cardiotonic Agents
• Isoenzymes
• KATP Channels
• 11,12-epoxy-5,8,14-eicosatrienoic acid
• Class Ia Phosphatidylinositol 3-Kinase
• 8,11,14-Eicosatrienoic Acid
• Calcium

Topics

• 8,11,14-Eicosatrienoic Acid (analogs & derivatives, pharmacology)
• Animals
• Calcium (metabolism)
• Cardiotonic Agents (pharmacology)
• Cell Line
• Class Ia Phosphatidylinositol 3-Kinase (metabolism)
• Heart (drug effects)
• Hypoxia
• Isoenzymes (metabolism)
• KATP Channels (metabolism)
• Membrane Potential, Mitochondrial (drug effects)
• Mice
• Mice, Inbred C57BL
• Mice, Knockout
• Myocardial Reperfusion Injury (metabolism, physiopathology, prevention & control)
• Myocardium (enzymology, metabolism)
• Sarcolemma (enzymology, metabolism)