Protein Kinase C Isoform Activation and Endothelin-1 Mediated Defects in Myocyte Contractility After Cardioplegic Arrest and Reperfusion

Abstract

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 ϭ22) left ventricular myocytes, randomized (minimum: 30 cells/group) to normothermia: (cell media for 2 hours/37°C), and CA: (2 hours/4°C, 24 mEq K ϩ 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 Ϸ35% from normothermia (PϽ0.05), 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 (PϽ0.05). CA prolonged T50 by Ϸ19% from normothermia (PϽ0.05) and was further prolonged with ET-1. Inhibition of the classical PKC isoforms reduced T50 from ET-1/CA (PϽ0.05). 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.

Interruption of endothelin signaling modifies membrane type 1 matrix metalloproteinase activity during ischemia and reperfusion

“…In the present study, it is demonstrated that levels of PKC-ε are reduced significantly in the I/R myocardium. These new data along with previous data suggest that differential expression/inhibition of PKC isoforms contributes to myocardial function (26,49).…”

“…For example, in the classical PKC subfamily, total PKC-␤II levels were increased in both remote and I/R myocardium, whereas PKC-␥ was reduced significantly. Past studies have demonstrated that inhibition of PKC-␤II improved contractility in isolated myocytes that have undergone cold cardioplegic arrest and reperfusion with and without the addition of ET (26). Multiple studies have shown the protective effects of PKC-ε activation in the ischemic myocardium (12,48).…”

Focal but reversible diastolic sheet dysfunction reflects regional calcium mishandling in dystrophicmdxmouse hearts

“…Because the calcium relaxation process is not monoexponential, only the latter half of the calcium signal decay could be fitted exponentially to derive the decay constant. Typically, both 50% relaxation decay time (T50) and the decay constant are used to characterize calcium relaxation kinetics (12,29,47,48,57,58,64,72,75,80). Specifically, the Ca 2ϩ relaxation time from the calcium transient peak value to 50% relaxation (T50) was calculated to define the calcium reuptake phase, and Ca 2ϩ decay constant was calculated using an exponential curve fitting program from the 50% calcium peak value to full relaxation.…”

Acute protein kinase C beta inhibition preserves coronary endothelial function after cardioplegic hypoxia/reoxygenation

“…Endothelin-1 alone has been shown to activate PKC and reduce cardiomyocyte contractility during periods of ischemia and reperfusion. 32 Importantly, previous research has shown significant increases in endothelin-1 release in the myocardium and peripheral blood following CP/CPB. 33 , 34 We have demonstrated previously that CP/CPB leads to activation of PKC alpha and beta in human coronary microvessels without the presence of endothelin-1.…”