CYSTINE DEPRIVATION INDUCES OLIGODENDROGLIAL DEATH - RESCUE BY FREE-RADICAL SCAVENGERS AND BY A DIFFUSIBLE GLIAL FACTOR

In this study we examined the effect on oligodendroglial survival of e xogenous cystine deprivation, Oligodendroglia isolated from mixed glia l primary cultures derived from brains of 1-day-old rats, and then gro wn for 3 days, were markedly dependent on extracellular cystine for su rvival. The EC(50) values for cystine for a 24-h exposure ranged from 2 to 65 mu M. After 6 h of cystine deprivation, the cellular glutathio ne level decreased to 21 +/- 13% of the control, Free radical scavenge rs (alpha-tocopherol, ascorbate, idebenone, and N-tert-butyl-alpha-phe nylnitrone) were protective against cystine deprivation but had no eff ect on the glutathione level, An iron chelator, desferrioxamine mesyla te, also was protective. These findings suggest that intracellular hyd roxyl radicals are important for this toxicity, In contrast to the obs ervations in 3-day-old cultures, the dependence on exogenous cystine f or cell viability was not observed consistently in oligodendroglia cul tured for 6 days before the onset of cystine deprivation. Several obse rvations suggested that this loss of cystine dependence was due to a d iffusible factor. Sensitivity to the toxicity of cystine deprivation i n day 6 cultures increased as the volume of medium was increased from 0.3 to 2 ml. Furthermore, preincubation of cystine-depleted medium wit h astrocyte cultures eliminated the toxicity of the cystine deprivatio n, HPLC assay of the conditioned cystine-depleted medium showed no sig nificant change in cystine or cysteine concentration, We conclude that oligodendroglia are highly susceptible to cystine deprivation in day 3 cultures and that this susceptibility is due to the accumulation of intracellular free radicals in the setting of glutathione depletion, T he resistance of day 6 oligodendroglial cultures is caused al least in part by a diffusible factor.