The voltage-independent B-type Ca2+ channel modulates apoptosis of cardiac myocytes.
In cardiac myocytes, Ca2+ is the second messenger of various physiological processes, including the excitation-contraction coupling phenomenon. Here, we examined how Ca2+ regulates cardiac myocyte apoptosis. Using an adult rat ventricular myocyte culture model, we found that ceramide (Cer) induces an apoptotic process that is highly sensitive to calcium: it is inhibited by the Ca2+buffer BAPTA-AM and is potentiated by the Ca2+ ionophore ionomycin. Cer-treated myocytes maintained their Ca2+ homeostasis and normal activity of their voltage-dependent sarcolemmal Ca2+ entry pathways but showed enhanced activity of B-type Ca2+ channels that were stimulated by Cer in the inside-out patch clamp configuration. Pharmacological modulations of B-type Ca2+ channels modulated Cer-induced apoptosis. Mitochondria were involved in Cer-induced apoptosis, as indicated by the inhibitory effect of cyclosporine A and caspase-9 inhibitor. Both the loss of mitochondrial membrane potential and the caspase-9 activation in Cer-treated myocytes were attenuated by blocking B-type Ca2+ channels. The mitochondrial Ca2+ content was evaluated as changes in [Ca2+]i after a short application of a mitochondrial uncoupler, FCCP, was increased in Cer-treated cells. Together, these results show that Ca2+ modulates Cer-induced cardiac myocyte apoptosis through the coupling of B-type Ca2+ channels with mitochondria.
Hénaff
Morgana
M
INSERM Unité 460, Faculté de Médecine Xavier Bichat, Paris, France.
Antoine
Sylvestre
S
Mercadier
Jean-Jacques
JJ
Coulombe
Alain
A
Hatem
Stephane N
SN
D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000502:physiology*; D002478:Cells, Cultured; D002518:Ceramides / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D006352:Heart Ventricles / Q000166:cytology; D006706:Homeostasis; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D007700:Kinetics; D008928:Mitochondria / Q000502:physiology; D008954:Models, Biological; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D051381:Rats
D015220:Calcium Channels; D002518:Ceramides; D002614:Chelating Agents; D007476:Ionophores; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D015759:Ionomycin; D002118:Calcium