Poly(ADP-ribose) Polymerase Activation and Cell Injury in the Course of Rat Heart Heterotopic Transplantation

Abstract

Free radicals and other reactive species generated during reperfusion of ischemic tissues may cause DNA damage and, consequently, the activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP). An excessive PARP activation may result in a depletion of intracellular NAD + and ATP, hence cell suffering and, ultimately, cell death. The present study is aimed at clarifying the role of PARP in a heart transplantation procedure and the contribution of myocyte necrosis and/or apoptosis to this process.In our experimental model, rat heart subjected to heterotopic transplantation, low temperature global ischemia (2 h) was followed by an in vivo reperfusion (30 or 60 min). Under these conditions clear signs of oxidative stress, such as lipoperoxidation and DNA strand breaks, were evident. In addition to a marked activation, accompanied by a significant NAD + and ATP depletion, PARP protein levels significantly increased after 60 min of reperfusion. Ultrastructural analysis showed nuclear clearings, intracellular oedema and plasma membrane discontinuity. Other relevant observations were the absence of typical signs of apoptosis like caspase-3 activation and PARP cleavage, random DNA fragmentation, rise in serum levels of heart damage markers. Our results suggest that during heart transplantation, the activation of PARP, causing energy depletion, results in myocardial cell injury whose dominant feature, at least in our experimental model, is necrosis rather than apoptosis.

Poly(ADP-ribose) polymerase activation in the reperfused myocardium

“…We described for the first time in a rat heart transplantation model in vivo that different classes of PARP inhibitors effectively prevent PARP activation and myocardial dysfunction after 1 h of cardiac preservation and reperfusion [10] which was recently confirmed by others [52,53] in a nearly identical model. We could also show that the beneficial effects of PARP inhibition are meditated by both the preservation of high-energy phosphate pool and by attenuation of leukocyte -endothelium interaction.…”

“…Immunohistological staining demonstrated a significantly attenuated expression of the adhesion molecules P-selectin and intracellular adhesion molecule-1 after pharmacologic inhibition of PARP. The studies of Fiorillo et al [52,53] clearly indicate that during heart transplantation, the activation of PARP, causing energy depletion, results in myocardial cell injury whose dominant feature, at least in this experimental model, is necrosis rather than apoptosis.…”

Olaparib protects cardiomyocytes against oxidative stress and improves graft contractility during the early phase after heart transplantation in rats

“…The cardiac protective effect of PARP inhibitors was subsequently extended into various models of heart transplantation. Treatment of the recipients with PARP inhibitors resulted in improved myocardial contractility and longer survival time of the transplanted hearts (Fiorillo et al, 2002(Fiorillo et al, , 2003Szabó et al, 2002Szabó et al, , 2005Szabó et al, , 2006Liu et al, 2004;Gao et al, 2007). The mode of action of PARP inhibitors, as cardioprotective agents, appears to involve a combination of mechanisms.…”

Limiting sarcolemmal Na+entry during resuscitation from ventricular fibrillation prevents excess mitochondrial Ca2+accumulation and attenuates myocardial injury

“…The method had previously been shown to have excellent reactivity and specificity for rat cTnI (92.8% homology; Refs. 6,12,45,46).…”