Cyclosporin A but not FK-506 protects against dopamine-induced apoptosis in the stunned heart.
BACKGROUND
Dopamine given at moderate doses for inotropy to postischemic hearts has been shown to augment myocyte apoptosis in association with elevated cytosolic calcium. We hypothesize that dopamine-mediated apoptosis occurs through calcium-induced opening of the mitochondrial permeability transition (mPT) pore. We also hypothesize that cyclosporin A (CSA), a calcineurin inhibitor known to block mPT pore opening, would prevent dopamine-induced apoptosis primarily by inhibiting pore opening (cyclophilin D binding).


METHODS
Isolated perfused rabbit hearts (n = 6/group) were subjected to 30 minutes of 37 degrees C cardioplegic arrest followed by 120 minutes reperfusion (ischemic injury that produces < 3% infarct by triphenyl-tetrazolium chloride [TTC] staining). Four groups were studied: (1) control; (2) dopamine (10 micromol/L) postischemia (dopa); (3) dopamine+CSA (0.2 micromol/L) (CSA+D) group; (4) dopamine+FK-506 (0.2 micromol/L) (FK+D) group. Left ventricular developed pressure and oxygen consumption were measured preischemia and postischemia. Bax, caspase-3 and caspase-9, and poly-ADP-ribose polymerase (PARP) activation were measured by Western blotting. Apoptotic nuclei were quantified by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining.


RESULTS
Dopamine postischemia improved contractile function and heart rate and this was not affected by CSA or FK. However, TUNEL positive nuclei, Bax, caspase-3 and caspase-9 activation, and PARP cleavage were all increased in dopa and FK+D groups, but not in CSA+D.


CONCLUSIONS
Cyclosporin is effective in preventing dopamine-induced apoptosis in the postischemic heart. The mechanism is likely due to inhibition of mPT pore opening since FK-506, a potent calcineurin inhibitor that does not bind to cyclophilin, did not prevent this. Low dose cyclosporin may prove useful to prevent dopamine-induced apoptosis resulting in long-term preservation of cardiac function.
Nathan
Meena
M
Department of Cardiac Surgery, Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
Friehs
Ingeborg
I
Choi
Yeong-Hoon
YH
Cowan
Douglas B
DB
Cao-Danh
Hung
H
McGowan
Francis X
FX
del Nido
Pedro J
PJ
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D016572:Cyclosporine / Q000627:therapeutic use*; D004195:Disease Models, Animal; D004298:Dopamine / Q000494:pharmacology*; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D007511:Ischemia; D017682:Myocardial Stunning / Q000517:prevention & control*; D009206:Myocardium / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects; D011817:Rabbits; D015424:Reperfusion; D016559:Tacrolimus / Q000627:therapeutic use*
D007166:Immunosuppressive Agents; D016572:Cyclosporine; D004298:Dopamine; D016559:Tacrolimus