Protective Effect Of Green Tea Polyphenols Against Oxidative Stress-Induced Injury Of Mammary Epithelial Cells

Second only to water, tea is considered to be the most commonly consumed beverage in the world. It is well known that there are many health benefits associated with the regular consumption of green tea, e.g. prevention and protection in the areas of cardiovascular disorders, obesity, inflammation and against viral and bacterial infections. To investigate the protective effect of different concentration of Green Tea Polyphenols (GTP) on oxidative stress-induced injury of bovine mammary epithelial cells, a model system of H2O2-induced mammary epithelial cells cultured in vitro damage was established. Cell viability was detected by MTT assay. The content of malondialdehyde (MDA), the activities of superoxide dismutase (SOD) and lactate dehydrogenase (LDH) in the cell culture supernatant were determined by a colorimetric method. Apoptotic cells were detected by Hoechst33342/PI staining and Annexin VFITC/PI double labeled flow cytometry. Meanwhile, the caspase-3activity was detected with spectrophotometric method. The results showed that:(1) No statistically significant difference of cells viabilities was found between treated groups with GTP between20to100μg/mL and the control group. Longer treated time of GTP on epithelial cells resulted in increased cells viability. Continuously increasing concentration of GTP resulted to the declination of cell survival rate. Therefore, all subsequent experiments were performed with20to100μg/mL GTP for48h.(2) Compared with that of H2O2group, the GTP-treated groups (20～100μg/mL) displayed higher cell viabilities and SOD activity and lower levels of MDA, LDH. And the treatment of GTP (100μg/mL) showed the most significant effect. It suggested that a certain concentration of GTP may alleviate the injury of mammary epithelial cells induced by oxidative stress.(3) A certain concentration of GTP can increase the caspase-3activity, inhibit the cell apoptosis.It suggested that GTP protects mammary epithelial cells against oxidative stress-induced injury, which is probably related to the attenuation of MDA content, the increase of SOD activity and the inhibition of the caspase-3activity.