Figure 17. Protective effects of EGCG against H2O2 induced oxidative stress on young HDF. Young (PDL20-30) HDF grown in 96 well plates was pre-treated with 25 and 50 μM EGCG for 24 hours and then challenged by 100 and 200 μM H2O2 for hours. Cell viability was determined on the following day (A), and the representative pictures show the cell viability (B); Cell proliferation for continuous days after exposure to 100 μM (C) and 200 μM (D) H2O2 was monitored; intracellular ROS (E) and mitochondrial potential (F) were also evaluated using H2DCF-DA and JC1 staining respectively as mentioned in Section 3.2.5 and 3.2.6 on the following day of H2O2 exposure; RFU, Relative Fluorescence Unit. The data shown are the mean from independent experiments, #p . examined the changes of gene expressions of CAT, SOD1, SOD2 and GPx in both young (PDL20 -30 ) and old (PDL> ;45 ) HDF after 24 hours of treatment with EGCG, since these enzymes are mostly influenced. expressions both in the young and the old HDF. In the young HDF, the gene expressions of CAT, SOD1, SOD2 and GPx increased in response to 25 μM 88 EGCG by 94. 1, 61.9, 44 .6 and 139 .2 % respectively. that in the untreated group, the gene expressions of CAT, SOD2 and GPx in the young HDF were much higher than that in the old HDF. After 24 hours of incubation with EGCG, all the enzymes increased