Protective effects of （-）-epigallocatechin-3-gallate on D-galactose-induced neuronal apoptosis in mice

BACKGROUND： The neuroprotective effects of （-）-epigallocatechin-3-gallate （EGCG）, the main polyphenolic constituent of green tea, have been widely reported. However, the action mechanisms, in particular in D-galactose-induced aging mice, remain poorly understood. OBJECTIVE： The present study investigated the protective effects of EGCG on D-galactose-induced hippocampus neuronal apoptosis in aging mice, as well as the relationship with expression of p751CD, JNK2, and p53 proteins. DESIGN, TIME AND SETTING： A randomized, controlled, molecular biological, animal experiment was performed at the Laboratory of Pharmacology, Pharmaceutical College of China Medical University, China, from September 2006 to July 2008. MATERIALS： D-galactose and EGCG （Sigma, USA）, as well as terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling （TUNEL） In Situ Cell Apoptosis Detection Kit （Promega, USA）, were used in this study. METHODS： A total of 64 mice were equally and randomly divided into D-galactose model, low-dose EGCG, high-dose EGCG, and control groups. Mice in the D-galactose model, low-dose EGCG, and high-dose EGCG groups were subcutaneously injected with 3% D-galactose （150 mg/kg）, daily for 6 weeks, to establish a mouse model of aging. Mice in the control group were treated with saline （5 mL/kg）. At 3 weeks following injection, mice in the low-dose EGCG and high-dose EGCG groups were orally administered EGCG at a dose of 2 mg/kg and 6 mg/kg, respectively, once a day, for 4 consecutive days. Mice in the control and D-galactose model groups received distilled water （5 mL/kg）. MAIN OUTCOME MEASURES： Memory function was evaluated using a step-through passive avoidance test. Neuronal apoptosis in the mouse hippocampus was detected using TUNEL staining. Expression levels of the intracellular domain of the p75 neurotrophin receptor （p75NTR）-p751CD, JNK2, and p53 proteins in the hippocampus were determined using Western blot analysis. RESULTS： The aging mouse model was induced by subcutaneous injection of D-galactose, which resulted in obvious memory impairment, increased apoptotic index, and increased protein expression levels of p751CD, JNK2, and p53 in the hippocampus, compared with control mice （P 〈 0.01）. Oral EGCG administration （2 or 6 mg/kg） for 4 weeks significantly improved levels of memory deficit in the aging mice and reduced apoptotic indices and protein expression levels of p751CD, JNK2, and p53 in the mouse hippocampus （P 〈 0.01）. CONCLUSION： Results from this study demonstrated increased protein expression levels of p751CD, JNK2, and p53, as well as increased hippocampal neuronal apoptosis in a D-galactose-induced mouse model of aging. EGCG provided protective effects against D-galactose-induced neuronal apoptosis in the hippocampus by reducing protein expression levels of p751CD, JNK2, and p53 proteins in the hippocampus of aging mice.

Protective effects of (-)-epigallocatechin-3-gallate on D-galactose-induced neuronal apoptosis in mice

（-）-epigallocatechin-3-gallate D-galactose neuronal apoptosis aging