Melatonin Potentiates the Neuroprotective Properties of Resveratrol Against Beta-Amyloid-Induced Neurodegeneration by Modulating AMP-Activated Protein Kinase Pathways

Background and Purpose Recent studies have demonstrated that resveratrol (RSV) reduces the incidence of age-related macular degeneration, Alzheimer's disease (AD), and stroke, while melatonin (MEL) supplementation reduces the progression of the cognitive impairment in AD patients. The purpose of this investigation was to assess whether the co-administration of MEL and RSV exerts synergistic effects on their neuroprotective properties against beta-amyloid (A beta)-induced neuronal death. Methods The neuroprotective effects of co-treatment with MEL and RSV on A beta 1-42 -induced cell death, was measured by MTT reduction assay. A beta 1-42 caused an increase in intracellular levels of reactive oxygen species (ROS), as assessed by H-2-DCF-DA dye, and a reduction of total glutathione (GSH) levels and mitochondrial membrane potential, as assessed using monochlorobimane and rhodamine 123 fluorescence, respectively. Western blotting was used to investigate the intracellular signaling mechanism involved in these synergic effects. Results We treated a murine HT22 hippocampal cell line with MEL or RSV alone or with both simultaneously. MEL and RSV alone significantly attenuated ROS production, mitochondrial membrane-potential disruption and the neurotoxicity induced by A beta 1-42. They also restored the A beta 1-42-induced depletion of GSH, back to within its normal range and prevented the A beta 1-42-induced activation of glycogen synthase kinase 3 beta (GSK3 beta). However, co-treatment with MEL and RSV did not exert any significant synergistic effects on either the recovery of the A beta 1-42-induced depletion of GSH or on the inhibition of A beta 1-42-induced GSK3 beta activation. A beta 1-42 treatment increased AMP-activated protein kinase (AMPK) activity, which is associated with subsequent neuronal death. We demonstrated that MEL and RSV treatment inhibited the phosphorylation of AMPK. Conclusions Together, our results suggest that co-administration of MEL and RSV acts as an effective treatment for AD by attenuating A beta 1-42-induced oxidative stress and the AMPK-dependent pathway. J Clin Neurol 2010;6:127-137