P. Massoudy et al., CARDIOPROTECTION BY CYCLOSPORINE-A IN EXPERIMENTAL-ISCHEMIA AND REPERFUSION - EVIDENCE FOR A NITRIC OXIDE-DEPENDENT MECHANISM MEDIATED BY ENDOTHELIN, Journal of Molecular and Cellular Cardiology, 29(2), 1997, pp. 535-544
The acute effect of cyclosporine A (CsA) on myocardial function after
ischemia and reperfusion and the mechanism of action was investigated
in isolated working guinea-pig hearts. Myocardial function was experim
entally infringed by imposing short-term global ischemia and reperfusi
on (15 min each). External heart work (EHW), determined before and aft
er ischemia, served as the criterion for quantitation of recovery. Con
trol hearts were perfused with modified Krebs-Henseleit buffer, other
hearts received buffer supplemented with CsA+/-an endothelin receptor
antagonist or exogenous endothelin+/-an inhibitor of nitric oxide (NO)
synthesis. To assess the importance of endothelial production of medi
ators directly, NO release in coronary effluent (continuously measured
with an amperometric sensor) and release of 6-keto-prostaglandin F-1
alpha (6-keto-PGF(1 alpha)), a stable metabolite of prostacyclin (PGI(
2)), were determined in non-working Langendorff hearts, Oxidative stre
ss during reperfusion was assessed by measuring glutathione release in
coronary venous effluent, Cyclosporine A (0.8 mu) improved post-ische
mic function significantly (59% recovery of EHW v 31% for controls), A
t 0.08 mu M, CsA was without beneficial effect (30% recovery). The end
othelin (ET)(A)- and ETB-receptor antagonist bosentan inhibited the pr
otective action of 0.8 mu M CsA (32% recovery). Exogenous ET-1 (80pM)
improved recovery to 53%, an effect which was blocked by the inhibitor
of NO-synthase, N-G-nitro-L-arginine (NOLAG, 1 mu, 31% recovery). In
the control group, post-ischemic NO release in coronary effluent recov
ered from zero to about 100% of the pre-ischemic value by 10 min, but
then decreased rapidly during the subsequent 15 min of reperfusion. In
hearts treated with 0.8 mu M CsA, NO release stayed at 100% of the pr
e-ischemic value throughout: reperfusion, the difference between contr
ols and CsA-treated hearts being significant after 20 min of reperfusi
on. On the other hand, coronary venous release of 6-keto-PGF(1 alpha)
was not different between the groups. Release of glutathione during ea
rly reperfusion (first 5 min) was significantly lowered (P<0.05) to ab
out 50% in CsA (0.8 mu M)- and ET-1-treated hearts as compared with co
ntrols (8.8 nmol/min). Cyclosporine A acts as a cardioprotective agent
in our model of ischemia and reperfusion, presumably by elevating the
level of endogenous nitric oxide and thereby reducing oxidative stres
s. (C) 1997 Academic Press Limited.