(Circulation. 2000;101:430.)
© 2000 American Heart Association, Inc.
Basic Science Reports |
From the Departments of Medicine (X.Y., E.A., R.R.S., P.J.C.), Surgery (R.E.M.) and Pathology (M.J.S.), Columbia University College of Physicians and Surgeons, New York, and G.D. Searle/Montsanto Co (G.D.A., J.F.W., K.M.L., S.G.), St. Louis, Mo.
Correspondence to Paul J. Cannon, MD, Department of Medicine, Division of Cardiology, Columbia University, 630 West 168th Street, New York, NY 10032. E-mail pjc4{at}columbia.edu
BackgroundThe hypothesis that cyclooxygenase-2 (COX-2) is involved in the myocardial inflammatory response during cardiac allograft rejection was investigated using a rat heterotopic abdominal cardiac transplantation model.
Methods and ResultsCOX-2 mRNA and protein in the myocardium of rejecting cardiac allografts were significantly elevated 3 to 5 days after transplantation compared with syngeneic controls (n=3, P<0.05). COX-2 upregulation paralleled in time and extent the upregulation of iNOS mRNA, protein, and enzyme activity in this model. COX-2 immunostaining was prominent in macrophages infiltrating the rejecting allografts and in damaged cardiac myocytes. Prostaglandin (PG) levels in rejecting allografts were also higher than in native hearts. Because NO has been reported to modulate PG synthesis by COX-2, additional transplants were performed using animals treated with a selective COX-2 inhibitor (SC-58125) and a selective inhibitor of the inducible nitric oxide synthase (iNOS) N-aminomethyl-L-lysine. At posttransplant day 5, inhibitor administration resulted in a significant reduction of COX-2 mRNA expression (3764±337 versus 5110±141 arbitrary units, n=3, P<0.05) and iNOS enzymatic activity (1.7±0.4 versus 22.8±14.4 nmol/mg protein, n=3, P<0.01) compared with vehicle-treated allogeneic transplants. Allograft survival in treated animals was increased modestly from 5.4 to 6.4 days (P<0.05). However, apoptosis of cardiac myocytes (TUNNEL method) was only marginally reduced relative to vehicle controls in treated graft recipients. The intensity of allograft rejection was also similar in the treated and untreated allografts.
ConclusionsThe data indicates that COX-2 expression is enhanced in parallel with iNOS in the myocardium during cardiac allograft rejection.
Key Words: prostaglandins nitric oxide rejection
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