Protein kinase C-ζ inhibition exerts cardioprotective effects in ischemia-reperfusion injury

Abstract

mia followed by reperfusion (I/R) in the presence of polymorphonuclear leukocytes (PMNs) results in marked cardiac contractile dysfunction. A cell-permeable PKC-peptide inhibitor was used to test the hypothesis that PKC-inhibition could attenuate PMN-induced cardiac contractile dysfunction by suppression of superoxide production from PMNs and increase nitric oxide (NO) release from vascular endothelium. The effects of the PKC-peptide inhibitor were examined in isolated ischemic (20 min) and reperfused (45 min) rat hearts reperfused with PMNs. The PKC-inhibitor (2.5 or 5 M, n ϭ 6) significantly attenuated PMN-induced cardiac dysfunction compared with I/R hearts (n ϭ 6) receiving PMNs alone in left ventricular developed pressure (LVDP) and the maximal rate of LVDP (ϩdP/ dt max) cardiac function indexes (P Ͻ 0.01), and these cardioprotective effects were blocked by the NO synthase inhibitor, N G -nitro-L-arginine methyl ester (50 M). Furthermore, the PKC-inhibitor significantly increased endothelial NO release 47 Ϯ 2% (2.5 M, P Ͻ 0.05) and 54 Ϯ 5% (5 M, P Ͻ 0.01) over basal values from the rat aorta and significantly inhibited superoxide release from phorbol-12-myristate-13-acetate-stimulated rat PMNs by 33 Ϯ 12% (2.5 M) and 40 Ϯ 8% (5 M) (P Ͻ 0.01). The PKC-inhibitor significantly attenuated PMN infiltration into the myocardium by 46 -48 Ϯ 4% (P Ͻ 0.01) at 2.5 and 5 M, respectively. In conclusion, these results suggest that the PKC-peptide inhibitor attenuates PMN-induced post-I/R cardiac contractile dysfunction by increasing endothelial NO release and by inhibiting superoxide release from PMNs thereby attenuating PMN infiltration into I/R myocardium. neutrophils; superoxide radicals; left ventricular developed pressure; endothelial dysfunction THE RESTORATION OF BLOOD FLOW is the primary objective for treatment of cardiac tissue experiencing prolonged ischemia (i.e., Ͼ20 min). However, reperfusion of blood flow induces endothelium and myocyte injury, resulting in cardiac contractile dysfunction (4, 23, 24). The sequential events associated with reperfusion injury are initiated by endothelial dysfunction, which is characterized by a reduction of the basal endothelial cell release of nitric oxide (NO) within the first 2.5-5 min postreperfusion (36). The decrease in endothelium-derived NO is associated with adhesion molecule upregulation on endothelial and polymorphonuclear leukocyte (PMN) cell membranes (26,39). This event promotes PMN-endothelium interaction, which occurs by 10 to 20 min postreperfusion, and subsequent PMN infiltration into the myocardium is observed by 30 min postreperfusion (20,21,35,39). The time course of events are similar in ex vivo and in vivo myocardial ischemia-reperfusion (I/R) models within the first 30 min of reperfusion with respect to endothelial dysfunction and PMN-endothelium interactions (26, 35-37). However, the in vivo model requires a longer reperfusion period (i.e., 270 min) to accumulate PMNs in the reperfused myocardium and induce myocardial injury (i.e., infarct size) (26, 3...

Protein Kinase C βII Peptide Inhibitor Exerts Cardioprotective Effects in Rat Cardiac Ischemia/Reperfusion Injury

“…5) or attenuated superoxide release (Fig. 6), or to a combination of both Yan and Novak, 1999;Phillipson et al, 2005). Oxygenderived free radicals such as superoxide up-regulate endothelial cell adhesion molecules and quench endogenous NO (Patel et al, 1991;Davenpeck et al, 1994).…”

“…The significant restoration of postreperfusion LVDP and ϩdP/dt max is a direct indicator of these cardioprotective effects, which can be attributed to enhanced release of endothelium derived NO, which quenches superoxide, improves vasodilation, and inhibits PMN aggregation Pabla et al, 1996). This is further demonstrated by the absence of these cardioprotective effects in the I/R ϩ PMN ϩ PKC ␤II peptide inhibitor (10 M) ϩ L-NAME group of hearts because the NO release was blocked by the presence of L-NAME (Phillipson et al, 2005). The significant reduction in PMN adherence to the vascular endothelium and infiltration into the postreperfused myocardial tissue also demonstrates these cardioprotective effects Xiao et al, 1998) and suggests that the cardioprotection may be mediated, in part, by a NO mechanism, since L-NAME treatment in heart and aortic tissue resulted in significant increases in postreperfusion PMN vascular adherence and infiltration and decreases in PKC ␤II peptide inhibitor stimulated NO release, respectively.…”

“…Other PKC isoforms have been shown to be either beneficial (e.g., PKC ⑀) or injurious (e.g., PKC ) when activated in cardiac and endothelial function (Hu et al, 2000;Das, 2003;Phillipson et al, 2005). PKC ⑀ activation has been associated with recovery of postreperfusion LVDP (Inagaki et al, 2003), but it requires pretreatment of PKC ⑀ activator before ischemia to elicit cardioprotection in contrast to the PKC ␤II inhibitor given at the beginning of reperfusion.…”

“…PKC ⑀ activation has been associated with recovery of postreperfusion LVDP (Inagaki et al, 2003), but it requires pretreatment of PKC ⑀ activator before ischemia to elicit cardioprotection in contrast to the PKC ␤II inhibitor given at the beginning of reperfusion. PKC has been implicated in superoxide release in PMNs and endothelial cells (Dang et al, 2001;Frey et al, 2002), adhesion molecule up-regulation (Rahman et al, 2000), and restoration of cardiac function in I/R (Peterman et al, 2004;Phillipson et al, 2005). However, the PKC ␤II inhibitor restores early postreperfusion LVDP (i.e., 10 min) sooner and does not exhibit cardiodepressant effects at higher doses compared with compounds that inhibit the PKC isoform (Peterman et al, 2004;Phillipson et al, 2005).…”

“…Therefore, PKC inhibition at the postischemic coronary endothelium will lead to the attenuation of superoxide production as a result of postischemia reperfusion injury and the preservation of NO bioavailability (Young et al, 2001;Peterman et al, 2004;Phillipson et al, 2005).…”