Exposure of developing oligodendrocytes to cadmium causes HSP72 induction,free radical generation, reduction in glutathione levels, and cell death

Primary cultures of oligodendrocytes were used to study the toxic effects o f cadmium chloride. Cell viability was evaluated by the mitochondrial dehyd rogenase activity and confirmed by propidium iodide (PI) fluorescence stain ing. The expression of the 72 kDa stress protein, HSP72, was assayed by Wes tern blot analysis. The results showed that Cd2+-induced toxicity was depen dent on the rime and dose of exposure, as well as on the developmental stag e of the cultures. Oligodendrocyte progenitors were more vulnerable to Cd-2 4 toxicity than were mature oligodendrocytes. Mature oligodendrocytes accum ulated relatively higher levels of Cd2+ than did progenitors, as determined by (CdCl2)-Cd-109 uptake; treatment with the metal ion caused a more prono unced reduction in intracellular glutathione levels and significantly highe r free radical accumulation in progenitors. The latter could explain the ob served differences in Cd2+ susceptibility. HSP72 protein expression was inc reased both in progenitors and in mature cells exposed to Cd2+ Pretreatment with N-acetylcysteine, a thiocompound with antioxidant activity and a prec ursor of glutathione, prevented Cd2+-induced (i) reduction in glutathione l evels and (ii) induction of HSP72 and diminished (i) Cd2+ uptake and (ii) C d2+-evoked cell death. In contrast, buthionine sulfoximine, an inhibitor of gamma -glutamyl-cysteine synthetase, depleted glutathione, and potentiated the toxic effect of Cd2+. These results strongly suggest that Cd2+-induced cytotoxicity in oligodendrocytes is mediated by reactive oxygen species an d is modulated by glutathione levels. (C) 2000 Elsevier Science Inc.