Role of calcium in nitric oxide-induced cytotoxicity: EGTA protects mouse oligodendrocytes

Active nitrogen species are overproduced in inflammatory brain lesions in m ultiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE). N O has been shown to mediate the death of oligodendrocytes (OLs), a primary target of damage in MS. To develop strategies to protect OLs, we examined t he mechanisms of cytotoxicity of two NO donors, S-nitroso-N-acetyl-penicill amine (SNAP) and sodium nitroprusside (SNP) on mature mouse OLs. Nitrosoniu m ion (NO+) rather than NO mediates damage with both SNAP and SNP, as shown by significant protection with hemoglobin (HbO(2)), but not with the NO sc avenger PTIO. SNAP and SNP differ in time course and mechanisms of killing OLs. With SNAP, OL death is delayed for at least 6 hr, but with SNP, OL dea th is continuous over 18 hr with no delay. Relative to NO release, SNP is m ore toxic than SNAP, due to synergism of NO with cyanide released by SNP. S NAP elicits a Ca2+ influx in over half of the OLs within min. Further, OL d eath due to NO release from SNAP is Ca2+-dependent, because the Ca2+ chelat or EGTA protects OLs from killing by SNAP, and also from killing by the NON Oates NOC-9 and NOC-18, which spontaneously release NO .. SNP does not elic it a Ca2+ influx, and EGTA is not protective. in comparison to the N20.1 OL cell line (Boullerne et al., [1999] J. Neurochem. 72:1050-1060), mature OL s are (1) more sensitive to SNAP, (2) much more resistant to SNP, (3) sensi tive to cyanide, but not iron, and (4) exhibit a Ca2+ influx and EGTA prote ction in response to NO generated by SNAP. (C) 2001 Wiley-Liss, Inc.