Neuroprotective Effects of (-)-Epigallocatechin-3-gallate on Aging Mice Induced by D-Galactose

The aim of the present study was to investigate the protective effects of (-)-epigallocatechin-3-gallate (EGCG), the main polyphenolic constituent of green tea, in aging mice induced by D-galactose (D-gal). The aging mice model was induced by subcutaneous (s.c.) injection Of D-gal (150 mg/kg) once daily for 6 weeks. EGCG (2 mg/kg or 6 mg/kg) was administered intragastrically (i.g.) once daily for 4 weeks after 2-week D-gal injection. The water maze test was used to evaluate the learning and memory function of mice. The activities of total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px) and the contents of malondialdehyde (MDA) in the hippocampus were measured using different biochemical kits to estimate the changes in the antioxidative ability of mice. TdT-mediated dUTP-biotin nick end labeling (TUNEL) staining method was used to detect neuronal apoptosis, and the activation and expression of proapoptotic protein caspase-3 in the hippocampus were observed and analyzed using immunohistochemical staining and the Western blot method to evaluate apoptosis in the brain. The results indicated that subcutaneous injection of D-gal induced learning and memory impairment in mice, decreased T-SOD and GSH-Px activities, increased MDA contents in the hippocampus, and increased the cell apoptosis index and cleaved caspase-3 protein expression in the hippocampus. Oral administration of EGCG (2 mg/kg or 6 mg/kg) for 4 weeks significantly improved the cognitive deficits in mice and elevated T-SOD and GSH-Px activities, decreased MDA contents in the hippocampus, and reduced the cell apoptosis index and expression of cleaved caspase-3 in the mouse hippocampus. The results suggest that EGCG has potent neuroprotective effects on aging mice induced by D-gal through antioxidative and antiapoptotic mechanisms, indicating that EGCG is worthy of further study in aging.