Role of iNOS-derived reactive nitrogen species and resultant nitrative stress in leukocytes-induced cardiomyocyte apoptosis after myocardial ischemia/reperfusion.
Polymorphonuclear leukocyte (PMN) accumulation/activation has been implicated as a primary mechanism underlying MI/R injury. Recent studies have demonstrated that PMNs express inducible nitric oxide synthase (iNOS) and produce toxic reactive nitrogen species (RNS). However, the role of iNOS-derived reactive nitrogen species and resultant nitrative stress in PMN-induced cardiomyocyte apoptosis after MI/R remains unclear. Male adult rats were subjected to 30 min of myocardial ischemia followed by 5 h of reperfusion. Animals were randomized to receive one of the following treatments: MI/R+vehicle; MI/R+L-arginine; PMN depletion followed by MI/R+vehicle; PMN depletion followed by MI/R+L-arginine; MI/R+1400 W; MI/R+1400 W+L-arginine and MI/R+ FeTMPyP. Ischemia/reperfusion-induced and L-arginine-enhanced nitrative stress and cardiomyocyte apoptosis were determined. PMN depletion virtually abolished ischemia/reperfusion- induced PMN accumulation, attenuated ischemic/reperfusion-induced and L-arginine-enhanced nitrative stress, and reduced ischemic/reperfusion-induced and L-arginine-enhanced cardiomyocyte apoptosis (P values all <0.01). Pre-treatment with 1400 W, a highly selective iNOS inhibitor, had no effect on PMN accumulation in the ischemic/reperfused tissue. However, this treatment reduced ischemia/reperfusion-induced and L-arginine-enhanced nitrative stress and cardiomyocyte apoptosis to an extent that is comparable as that seen in PMN depletion group. Treatment with FeTMPyP, a peroxynitrite decomposition catalyst, had no effect on either PMN accumulation or total NO production. However, treatment with this ONOO(-) decomposition catalyst also reduced ischemia/reperfusion-induced and L-arginine-enhanced nitrative stress and cardiomyocyte apoptosis (P values all <0.01). These results demonstrated that ischemic/reperfusion stimulated PMN accumulation may result in cardiomyocyte injury by an iNOS-derived nitric oxide initiated and peroxynitrite-mediated mechanism. Therapeutic interventions that block PMN accumulation, inhibit iNOS activity or scavenge peroxynitrite may reduce nitrative stress and attenuate tissue injury.
Wang
Xiao-Liang
XL
Department of Physiology, Shanxi Medical University, 56 South Xinjian Road, Taiyuan, Shanxi, 030001, P.R. China.
Liu
Hui-Rong
HR
Tao
Lin
L
Liang
Feng
F
Yan
Li
L
Zhao
Rong-Rui
RR
Lopez
Bernard L
BL
Christopher
Theodore A
TA
Ma
Xin-Liang
XL
D000818:Animals; D017209:Apoptosis; D001120:Arginine / Q000378:metabolism / Q000633:toxicity*; D053148:Caspase 3 / Q000378:metabolism; D008297:Male; D015425:Myocardial Reperfusion; D015428:Myocardial Reperfusion Injury / Q000503:physiopathology*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D009504:Neutrophils / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D030421:Peroxynitrous Acid / Q000378:metabolism; D011897:Random Allocation; D051381:Rats; D026361:Reactive Nitrogen Species / Q000378:metabolism*
D026361:Reactive Nitrogen Species; D030421:Peroxynitrous Acid; D009569:Nitric Oxide; D001120:Arginine; D052247:Nitric Oxide Synthase Type II; C505410:Casp3 protein, rat; D053148:Caspase 3