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Kinases and phosphatases in ischaemic preconditioning: a re-evaluation
W J Fan1, D van Vuuren, S Genade
1Division of Medical Physiology, Department of Biomedical Sciences, Faculty of Health Sciences, University of Stellenbosch, Tygerberg, Republic of South Africa.
Basic Research in Cardiology
|February 4, 2010
Summary
Inhibition of protein phosphatases PP1 and PP2A before or during ischemia/reperfusion impairs heart recovery, but inhibiting them during reperfusion enhances cardioprotection by prolonging RISK pathway activation.
Area of Science:
- Cardiovascular Biology
- Molecular Cardiology
- Ischemia-Reperfusion Injury
Background:
- Protein kinases are activated during myocardial ischemia and reperfusion, but the role of phosphatases remains unclear.
- Protein phosphatases PP1 and PP2A are key regulators of cellular signaling pathways.
Purpose of the Study:
- To investigate the roles of protein phosphatases PP1 and PP2A in myocardial ischemia/reperfusion injury.
- To determine the effect of inhibiting PP1 and PP2A on ischemic preconditioning-induced cardioprotection.
Main Methods:
- Isolated perfused working rat hearts subjected to global or regional ischemia/reperfusion.
- Hearts were preconditioned using global ischemia protocols.
- Inhibition of PP1 and PP2A using cantharidin or PP2A using okadaic acid at different time points.
- Assessment of mechanical recovery, infarct size, and kinase activation (PKB/Akt, p38 MAPK, ERK p42/p44).
Main Results:
- Inhibition of PP1/PP2A before sustained ischemia significantly reduced mechanical recovery.
- Inhibition during ischemic preconditioning abolished functional recovery and increased infarct size.
- Administration of inhibitors during reperfusion enhanced functional recovery, particularly in preconditioned hearts.
- Time-dependent effects of phosphatase inhibition on kinase activation were observed.
Conclusions:
- Phosphatase inhibition prior to or during ischemia/preconditioning is detrimental to the heart.
- Inhibiting phosphatases during reperfusion can be cardioprotective, potentially by prolonging RISK pathway activation.
- These findings highlight the critical temporal role of phosphatases in regulating myocardial response to ischemia/reperfusion.
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