Introduction: Cadmium (Cd(2+)) induces limb defects and other malformations in experimental animals. However, the mechanisms of the developmental toxicity of this metal are not fully understood. The ubiquitous intracellular tripeptide glutathione (GSH) protects nonembryonic cells from Cd(2+)-induced cell death and is essential for normal embryonic development. We predicted that pretreatment with GSH would prevent cytotoxicity in cultured mouse embryonic limb bud cells exposed to Cd(2+). Additionally, it was expected that GSH pretreatment would prevent the Cd(2+)-induced activation of the signaling molecule c-Jun N-terminal kinase (JNK), which becomes phosphorylated upon exposure to Cd(2+).
Methods: Primary micromass cultures of limb bud cells obtained from organogenesis-stage mouse embryos were treated with either Cd(2+) or GSH alone, or both Cd(2+) and GSH. Treatment with GSH commenced 4 hr prior to Cd(2+) treatment.
Results: Cell proliferation was inhibited by approximately 50% after exposure to 4 μM Cd(2+) for 5 days. Cd(2+) treatment also resulted in a dose-dependent increase in the intracellular GSH content as measured after 5 days of exposure. Pretreatment with 4 mM GSH for 4 hr prevented the Cd(2+)-induced inhibition of cell proliferation and differentiation and also inhibited a threefold activation of JNK induced by 4 μM Cd(2+) after 24 and 48 hr of exposure.
Conclusion: Exogenous GSH protects cultured embryonic limb bud cells from Cd(2+)-induced inhibition of cell proliferation and differentiation, which is associated with the activation of JNK.
© 2010 Wiley-Liss, Inc.