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Melatonin alters cell death processes in response to age‐related oxidative stress in the brain of senescence‐accelerated mice

Abstract:  We studied the effect of age and melatonin on cell death processes in brain aging. Senescence‐accelerated prone mice 8 (SAMP8) and senescence‐accelerated resistant mice (SAMR1) at 5 and 10 months of age were used as models of the study. Melatonin (10 mg/kg) or its vehicle (ethanol at 0.066%) was administered in the drinking water from 1 to 9 months of age. Neurodegeneration, previously shown in the aged brain of SAMP8 and SAMR1 at 10 months of age, may be due to a drop in age‐related proteolytic activities (cathepsin D, calpains, and caspase‐3). Likewise, lack of apoptotic and macroautophagic processes were found, without apparent modification by melatonin. However, the caspase‐independent cell death, owing to high p53 and apoptosis‐inducing factor (AIF) levels, might be an alternative pathway of cell death in the aged brain. The main effects of melatonin treatment were observed in the aged SAMR1 mice; in this strain we observed a marked increase in antioxidant activity (catalase and superoxide dismutase). Likewise, a key antioxidant role of apoptosis‐related proteins, Bcl‐2 and AIF, was suggested in the aged brain of SAM mice, which was clearly influenced by melatonin. Moreover, the age‐related increase of lysosomal activity of cathepsin B and a lysosomal membrane‐associated protein 2 supports the possibility of the maintenance of lysosomal viability in addition to age‐related impairments of the proteolytic or macroautophagic activities. The effectiveness of melatonin against the oxidative stress‐related impairments and apoptosis during the aging process is, once more, corroborated in this article.