The role of NO and superoxide (O2-) in tissue injury during cardiac allograft rejection was investigated by using a rat ex vivo organ perfusion system. Excessive NO production and inducible NO synthase (iNOS) expression were observed in cardiac allografts at 5 days after cardiac transplantation, but not in cardiac isografts, as identified by electron spin resonance spectroscopy and Northern blotting. Cardiac isograffs or allografts obtained on Day 5 after transplantation were perfused with Krebs bicarbonate buffer with or without various antidotes for NO or O2-, including N(ω)-rnonomethyl-L-arginine (L-NMMA; 1 rnM), 2-phenyl-4,4,5,5-tetramethylirnidazoline-1-oxyl 3-oxide (PTIO; 100 μM), 4-amino-6-hydroxypyrazolo[3,4-d]pyrimidine (AHPP; a xanthine oxidase inhibitor; 100 μM), and superoxide dismutase (SOD; 100 units/ml). Treatment of the cardiac allografts with PTIO showed most remarkable improvement of the cardiac injury as revealed by significant reduction in aspartate transaminase, lactate dehydrogenase, and creatine phosphokinase concentrations in the perfusate. Similar but less potent protective effect on the allograft injury was observed by treatment with L-NMMA, AHPP, and SOD. Immunohistochemical analyses for INOS and nitrotyrosine indicated that iNOS is mainly expressed by macrophages infiltrating the allograft tissues, and nitrotyrosine formation was demonstrated not only in macrophages but also in cardiac myocytes of the allografts, providing indirect evidence for the generation of peroxynitrite during allograft rejection. Our results suggest that tissue injury in rat cardiac allografts during acute rejection is mediated by both NO and O2-, possibly through peroxynitrite formation.
|Number of pages||9|
|Journal||Proceedings of the Society for Experimental Biology and Medicine|
|Publication status||Published - 2000 Jan 1|
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)