Abstract:
Oxidative stress is defined as a disturbance in the prooxidant-antioxidant
balance, leading to potential cell damage. Reactive oxygen species such as superoxide
radicals, hydroxyl radicals and hydrogen peroxide may act also as a second
intermediate in intracellular signaling leading to cell death. The objective of this
research, therefore, was to better understand the cellular mechanisms of neuronal cell
degeneration induced via oxidative stress and the protective roles of melatonin on this
cell death. In the present study, the effects of melatonin on hydrogen peroxide-induced
neuronal cell degeneration in a human dopaminergic neuroblastoma SH-SY5Y
cultured cells were investigated. The results showed that hydrogen peroxide
significantly decreased cell viability as determined by 3-(4,5-dimethylthiazol-2-yl)-
2,5-diphenyl-tetrazolium bromide (MTT) assay, and melatonin was able to reverse the
toxic effects of hydrogen peroxide. Desipramine, a monoamine uptake blocker was
able to abolish the toxic effects of 1-methyl-4-phenylpyridinium iodide (MPP+) but
not hydrogen peroxide on cell viability reduction. An inhibition of caspase enzyme
activity by Ac-DEVD-CHO, a caspase-3 inhibitor significantly increased cell viability
in hydrogen peroxide treated cells. The phosphorylation of transcription factors,
nuclear factor kappa B (NF-κB) was increased in hydrogen peroxide treated cells and
this effect was abolished by melatonin. Translocation of phosphorylated NF-κB to
nuclear site using immunofluorescence was more observed in hydrogen peroxide
treated cells than control-untreated cultured cells and the said effect was abolished by
melatonin. In addition, induction of Bcl-2 and Bax proteins was demonstrated in SHSY5Y
cultured cells treated with hydrogen peroxide, whereas the induction of Bax but
not Bcl-2 was diminished by melatonin.