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Published on: August 6, 2015
Protein kinase C isoform activation and endothelin-1 mediated defects in myocyte contractility after cardioplegic
Rupak Mukherjee1, Kimberly A Apple, Christina E Squires
1Division of Cardiothoracic Surgery Research, 770 MUSC Complex, Suite 625, Medical University of South Carolina, Charleston, SC 29425, USA. mukherr@musc.edu
Insights
Endothelin-1 (ET-1) contributes to heart muscle dysfunction after cardioplegic arrest (CA). Inhibiting classical protein kinase C (PKC) isoforms reversed ET-1
Area of Science:
- Cardiology
- Molecular Biology
- Physiology
Background:
- Endothelin-1 (ET-1) release post-cardioplegic arrest (CA) and reperfusion may impair cardiac contractility.
- ET-1 receptor activation triggers protein kinase C (PKC) isoforms, leading to varied cellular responses.
Purpose of the Study:
- To identify specific PKC isoforms involved in ET-1-induced myocyte contractile dysfunction during CA.
Main Methods:
- Porcine left ventricular myocytes were subjected to normothermia, CA, or ET-1/CA conditions.
- The impact of inhibiting classical (Beta-I, Beta-II, Gamma) and novel (Epsilon, Eta) PKC isoforms on myocyte shortening (PERSHORT) and relaxation (T50) was assessed.
Main Results:
- CA reduced PERSHORT and prolonged T50; ET-1 exacerbated these effects.
- Inhibition of PKC-Beta-II or PKC-Gamma improved PERSHORT in ET-1/CA and CA groups.
- Inhibition of classical PKC isoforms shortened T50 in the ET-1/CA group.
Conclusions:
- Targeting classical PKC isoforms alleviates ET-1's negative effects on cardiac function post-CA.
- These findings support developing strategies to inhibit ET-1 signaling for managing myocyte dysfunction after CA and reperfusion.
Background:
Endothelin-1 (ET-1) is released after hyperkalemic cardioplegic arrest (CA) and reperfusion and may contribute to contractile dysfunction. ET-1 receptor transduction causes activation of protein kinase C (PKC) isoforms, which can cause differential intracellular events. The goal of this study was to determine which PKC isoforms contribute to myocyte contractile dysfunction with ET-1 and CA.
Methods And Results:
Percent shortening (PERSHORT) and the time to 50% relaxation (T50) were measured in porcine (n =22) left ventricular myocytes, randomized (minimum: 30 cells/group) to normothermia: (cell media for 2 hours/37 degrees C), and CA: (2 hours/4 degrees C, 24 mEq K+ solution followed by reperfusion in cell media), ET-1/CA: (100 pM ET-1 during CA). Studies were performed in the presence and absence of PKC inhibitors (500 nM) against the classical (Beta-I, Beta-II, Gamma) and novel (Epsilon, Eta) isoforms (myocytes from a minimum of 3 pigs per inhibitor). CA reduced PERSHORT by approximately 35% from normothermia (P<0.05), which was further reduced with ET-1. PKC-Beta-II or PKC-Gamma inhibition increased PERSHORT from ET-1/CA as well as CA only (P<0.05). CA prolonged T50 by approximately 19% from normothermia (P<0.05) and was further prolonged with ET-1. Inhibition of the classical PKC isoforms reduced T50 from ET-1/CA (P<0.05). Inhibition of novel PKC isoforms did not yield similar effects on either PERSHORT or T50 with ET-1/CA.
Conclusions:
Inhibition of the classical PKC isoforms relieved the negative inotropic and lusitropic effects of ET-1 after CA. These findings provide mechanistic support for developing targeted inhibitory strategies with respect to ET-1 signaling and myocyte contractile dysfunction with cardioplegic arrest and reperfusion.
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