Acta Pharmacologica Sinica 2005 January; 26 (1): 117-123; doi: 10.1111/j.1745-7254.2005.00004.x

Aim: To explore the effect of melatonin on PC12 cell death induced by 1-methyl-4-phenylpyridinium (MPP⁺).

Methods: MTT assay, lactate dehydrogenase (LDH) efflux assay, and immunohistochemistry methods were used to measure neurotoxicity of PC12 cells treated acutely with MPP⁺ in low glucose and high glucose conditions, and to assess the neuroprotective effect of melatonin on PC12 cell death induced by MPP⁺.

Results: In a low glucose condition, MPP⁺ significantly induced PC12 cell death, which showed time and concentration dependence. In a serum-free low glucose condition, the percentages of viability of cells treated with MPP⁺ for 12, 24, 48, 72, and 96 h were 85.1%, 75.4%, 64.9%, 28.15%, and 9%, respectively. The level of LDH in the culture medium increased and tyrosine hydroxylase positive (TH⁺) cell count decreased. However, in a serum-free high glucose condition, MPP⁺ did not significantly induce PC12 cell death compared with control at various concentrations and time regimens. When the cells were preincubated with melatonin 250 µmol/L for 48, 72, and 96 h in a serum-free low glucose condition, cell survival rate significantly increased to 78.1%, 58.8%, and 31.6%, respectively. Melatonin abolished the LDH leakage of cells treated with MPP⁺ and increased TH⁺ cells count.

Conclusion: MPP⁺ caused concentration-dependent PC12 cell death. The level of glucose was an important factor to MPP⁺ induced dopaminergic PC12 cell death. Low glucose level could potentiate MPP⁺ toxicity, while high glucose level could reduce the toxicity. In addition, melatonin attenuated PC12 cell death induced by MPP⁺.