Poly-ADP-ribose polymerase (PARP) is considered to play an important role in oxidative cell damage. We assumed that
ischemia-reperfusion resulting from the increasing
reactive oxygen species (ROS) can lead to the activation of endogenous mono- and poly-ADP-ribosylation reactions and that the reduction of ROS level by
lipoamide, a less known
antioxidant, can reverse these unfavorable processes. Experiments were performed on isolated Langendorff hearts subjected to 60-min
ischemia followed by reperfusion. ROS,
malondialdehyde,
deoxyribonucleic acid (DNA) breaks, and NAD+ content were assayed in the hearts, and the ADP-ribosylation of cytoplasmic and
nuclear proteins were determined by Western blot assay.
Ischemia-reperfusion caused a moderate (30.2 +/- 8%) increase in ROS production determined by the
dihydrorhodamine 123 method and significantly increased the
malondialdehyde production (from < 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-reperfusion activated the mono-ADP-ribosylation of
GRP78 and the self-ADP-ribosylation of the nuclear PARP. The perfusion of hearts with
lipoamide significantly decreased the
ischemia-reperfusion-induced cell membrane damage determined by
enzyme release (LDH, CK, and GOT), decreased the ROS production, reduced the
malondialdehyde production to 5.5 +/- 2.4 nmol/ml, abolished DNA damage, and reduced NAD+ catabolism. The
ischemia-reperfusion-induced activation of poly- and mono-ADP-ribosylation reactions were also reverted by
lipoamide. In isolated rat heart mitochondria,
dihydrolipoamide was found to be a better
antioxidant than
dihydrolipoic acid.
Ischemia-reperfusion by ROS overproduction and increasing DNA breaks activates PARP leading to accelerated NAD+ catabolism, impaired energy metabolism, and cell damage.
Lipoamide by reducing ROS levels halts PARP activation and membrane damage and improves the recovery of postischemic myocardium.