Cyclosporin A targets involved in protection against glutamate excitotoxicity.
The toxicity of glutamate in neuronal cultures has been attributed in part to a mitochondrial dysfunction involving the permeability transition pore. The participation of the permeability transition pore in this process has been pharmacologically demonstrated by the use of cyclosporin A, which inhibits pore opening by interaction with mitochondrial cyclophilin and, thus, prevents cell death and upstream events. Since cyclosporin A also acts on calcineurin, we have investigated which of the targets of cyclosporin A was responsible for the inhibition of glutamate-excitotoxicity in cerebrocortical primary neuronal cultures. Reactive oxygen species production and early (30 min to 2 h) drop in ATP levels are initial events in glutamate excitotoxicity taking place before neuronal death. Cyclosporin A did not inhibit reactive oxygen species production, but reduced the drop in ATP levels and subsequent neuronal death. However, cyclosporin derivatives that do not bind to calcineurin had smaller effect on survival than cyclosporin A, (regardless of whether they were able to bind cyclophilin), indicating that cyclosporin A protects against glutamate toxicity also through calcineurin-related mechanisms. Consistent with this view, ATP loss appears to result from nitric oxide synthase (NOS) activation (including calcineurin-dependent dephosphorylation) and nitric oxide (NO)/peroxinitrite-dependent increase in poly (ADP-ribose) polymerase activity, since it was reduced by inhibitors of these activities. Collectively, these results suggest that cyclosporin A exerts its protective effects through calcineurin-dependent and independent mechanisms.
Ruiz
F
F
Departamento de Biología Molecular, Centro de Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid-C.S.I.C., Campus de Cantoblanco, 28049, Madrid, Spain.
Alvarez
G
G
Ramos
M
M
Hernández
M
M
Bogónez
E
E
Satrústegui
J
J
D000227:Adenine Nucleotides / Q000378:metabolism; D000818:Animals; D016923:Cell Death; D016572:Cyclosporine / Q000494:pharmacology*; D004347:Drug Interactions; D018683:Excitatory Amino Acid Agents / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology*; D066298:In Vitro Techniques; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects*; D009569:Nitric Oxide / Q000502:physiology; D011065:Poly(ADP-ribose) Polymerases / Q000502:physiology; D020011:Protective Agents / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors
D000227:Adenine Nucleotides; D018683:Excitatory Amino Acid Agents; D020011:Protective Agents; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D018698:Glutamic Acid; D016572:Cyclosporine; D011065:Poly(ADP-ribose) Polymerases