Enhanced ADP-ribosylation and its diminution by lipoamide after ischemia-reperfusion in perfused rat heart

Poly-ADP-ribose polymerase (PARP) is considered to play an important role i n oxidative cell damage. We assumed that ischemia-reperfusion resulting fro m the increasing reactive oxygen species (ROS) can lead to the activation o f endogenous mono- and poly-ADP-ribosylation reactions and that the reducti on of ROS level by Lipoamide, a less known antioxidant, can reverse these u nfavorable processes. Experiments were performed on isolated Langendorff he arts subjected to 60-min ischemia followed by reperfusion. ROS, malondialde hyde, deoxyribonucleic acid (DNA) breaks, and NAD(+) content were assayed i n the hearts, and the ADP-ribosylation of cytoplasmic and nuclear proteins were determined by Western blot assay. Ischemia-reperfusion caused a modera te (30.2 +/- 8%) increase in ROS production determined by the dihydrorhodam inel23 method and significantly increased the malondialdehyde production (f rom <1 to 23 +/- 2.7 nmol/ml), DNA damage (undamaged DNA decreased from 71 +/- 7% to 23.1 +/- 5%), and NAD(+) catabolism. In addition, ischemia-reperf usion activated the mono-ADP-ribosylation of GRP78 and the self-ADP-ribosyl ation of the nuclear PARP. The perfusion of hearts with lipoamide significa ntly decreased the ischemia reperfusion-induced cell membrane damage determ ined by enzyme release (LDH, CK, and GOT), decreased the ROS production, re duced the malondialdehyde production to 5.5 +/- 2.4 nmol/ml, abolished DNA damage, and reduced NAD(+) catabolism. The ischemia-reperfusion-induced act ivation of poly- and mono-ADP-ribosylation reactions were also reverted by lipoamide. In isolated rat heart mitochondria, dihydrolipoamide was found t o be a better antioxidant than dihydrolipoic acid. Ischemia-reperfusion by ROS overproduction and increasing DNA breaks activates PARP leading to acce lerated NAD(+) catabolism, impaired energy metabolism, and cell damage. Lip oamide by reducing ROS levels halts PARP activation and membrane damage and improves the recovery of postischemic myocardium. (C) 1999 Elsevier Scienc e Inc.