Immunocytochemical evidence for inducible nitric oxide synthase and cyclooxygenase-2 expression with nitrotyrosine formation in human hibernating myocardium.
BACKGROUND
Myocardial hibernation may result from repetitive episodes of transient ischaemia leading to prolonged dysfunction. Inducible nitric oxide synthase (iNOS) expression has been demonstrated in animals following brief, non-lethal ischaemia-reperfusion injury. We therefore, hypothesised that in human hibernating myocardium: 1). iNOS would be present; 2). the reaction of nitric oxide and superoxide would form the strong oxidant peroxynitrite; 3) that this process would be accompanied by the expression of cyclooxygenase-2 (Cox-2) which interacts with NOS and whose products could further affect myocardial function.


RESULTS
In sixteen patients with coronary artery disease (CAD), left ventricular biopsies were obtained from chronically dysfunctional segments subtended by a stenotic artery (> 75 %) and shown to be viable by (18)F-fluorodeoxyglucose positron emission tomography. Comparison was made with myocardial biopsies (n = 8) from normally contracting myocardium in patients undergoing coronary surgery, from unused transplant donors and at post-mortem. Regional wall motion score improved in all patients 6 months post-revascularisation (from 2.7 +/- 0.7 to 1.5 +/- 0.5; p < 0.001), confirming hibernation. Immunocytochemistry localized reactivity to iNOS, Cox-2 and nitrotyrosine (a marker of peroxynitrite formation) to cardiomyocytes from hibernating segments. No difference in reactivity to endothelial NOS was seen between hibernating and control cardiomyocytes.


CONCLUSIONS
Cox-2 and iNOS are co-expressed in hibernating myocardium with nitrotyrosine suggesting nitric oxide production and peroxynitrite formation. We propose that this is secondary to ischaemia-reperfusion and that the products of these enzymes may have consequences for myocardial contractile function and survival.
MRC Clinical Sciences Centre, Imperial College Faculty of Medicine, Hammersmith Hospital, London, United Kingdom.
Christopher S R
CS
Baker
David P
DP
Dutka
Domenico
D
Pagano
Ornella
O
Rimoldi
Michael
M
Pitt
Roger J C
RJ
Hall
Julia M
JM
Polak
Robert S
RS
Bonser
Paolo G
PG
Camici
D000806:Angiotensin-Converting Enzyme Inhibitors / Q000627:therapeutic use; D001706:Biopsy; D003327:Coronary Disease / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D051546:Cyclooxygenase 2; D004232:Diuretics / Q000627:therapeutic use; D004452:Echocardiography; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D007527:Isoenzymes / Q000378:metabolism*; D008565:Membrane Proteins; D008875:Middle Aged; D017682:Myocardial Stunning / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000032:analysis*
D000806:Angiotensin-Converting Enzyme Inhibitors; D004232:Diuretics; D007527:Isoenzymes; D008565:Membrane Proteins; C002744:3-nitrotyrosine; D014443:Tyrosine; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases