Protection of myocytes from hypoxia-reoxygenation injury by nitric oxide is mediated by modulation of transforming growth factor-beta1.
BACKGROUND
Reoxygenation injury is a result of several complex events, including release of reactive oxygen species, protein kinase C (PKC) activation, and altered expression of transforming growth factor-beta1 (TGF-beta(1)). Nitric oxide (NO) generally protects tissues from reperfusion injury.


RESULTS
We examined the modulation of TGF-beta1 expression and activity and PKC activation in cultured rat heart myocytes exposed to a brief period of hypoxia-reoxygenation (H-R) by NO donor 3-morpholino-sydnonimine (SIN-1). H-R resulted in an increased expression of total TGF-beta1 (mRNA and protein) but a decrease in the release of active TGF-beta1. Myocyte PKC-alpha protein level was not altered by H-R, but its phosphorylation was augmented. Pretreatment of myocytes with SIN-1 diminished myocyte injury quantified as lactate dehydrogenase release. Simultaneously, release of active TGF-beta1 increased and total TGF-beta1 expression decreased (all P<0.05 versus H-R alone). PKC-alpha phosphorylation increased further in cells treated with SIN-1. The effects of SIN-1 were blocked by the NO scavenger phenyl-tetramethyl-imidazoline-oxyl-oxide as well as by the PKC inhibitor staurosporine. To examine if another NO donor would have a similar effect, cardiomyocytes were treated with nitroglycerin before H-R. With nitroglycerin treatment, similar to SIN-1 treatment, myocyte injury was diminished, TGF-beta1 release increased, and total TGF-beta1 expression decreased.


CONCLUSIONS
These observations suggest modulation of TGF-beta1 expression as a novel mechanism of salutary effect of NO donors. PKC-alpha activation may play an important role in the protective effect of NO against H-R injury.
Mehta
J L
JL
Division of Cardiovascular Medicine, Department of Internal Medicine, Physiology, and Biophysics, University of Arkansas for Medical Sciences and Central Arkansas Veterans Health Care System, Little Rock, Ark 72205-7199, USA. MehtaJL@UAMS.edu
Chen
H J
HJ
Li
D Y
DY
D000818:Animals; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000032:analysis; D019610:Cytoprotection; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D015428:Myocardial Reperfusion Injury / Q000235:genetics / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D009569:Nitric Oxide / Q000502:physiology; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D005996:Nitroglycerin / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D053773:Transforming Growth Factor beta1
D017077:Culture Media, Conditioned; D020030:Nitric Oxide Donors; D012333:RNA, Messenger; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D009569:Nitric Oxide; C002385:linsidomine; D008981:Molsidomine; D011493:Protein Kinase C; D005996:Nitroglycerin