Reactive oxygen species-dependent c-Jun NH2-terminal kinase/c-Jun signaling cascade mediates neuroblastoma cell death induced by diallyl disulfide

The pharmacological properties of garlic and its derivatives are long known, and their underling mechanisms are being extensively investigated. In this study we have addressed the effects of diallyl disulfide (DADS), an oil-soluble garlic molecule, on cell growth of neuroblastoma cell SH-SY5Y, focusing on the redox events associated with this compound. Treatment of SH-SY5Y cells with DADS resulted in arrest of cell cycle in G(2)/M phase and commitment to apoptosis through the activation of the mitochondrial pathway (Bcl-2 down-regulation, cytochrome c release into the cytosol, and activation of caspase-9 and caspase-3). The earliest oxidative event observed after DADS treatment was the increase of production of reactive oxygen species, which reached the maximum yield on 30 min of DADS treatment. The oxidative burst resulted in protein and lipid damage as demonstrated by protein carbonyl accumulation and lipid peroxidation. We demonstrated that apoptosis induction was highly dependent on the activation of the redox-sensitive c-Jun NH2-terminal kinase (JNK)/c-jun pathway. In particular, we established that DADS treatment induces JNK dissociation from glutathione S-transferase and its activation by phosphorylation. Moreover, treatment with JNK inhibitor I significantly reduced DADS-induced apoptosis and treatment with the spin trap 5,5'-dimethyl-1-pyrroline N-oxide or overexpression of the antioxidant enzyme copper, zinc superoxide dismutase, resulted in the inhibition of DADS-mediated toxicity through attenuation of JNK/c-jun pathway activation. Overall, the results suggest a pivotal role for oxidative stress in DADS-induced apoptosis and, taking into account that tumor cells are deficient in antioxidants, suggest a plausible utilization of this compound as an antiproliferative agent in cancer therapy