Epigallocatechin-3-gallate (EGCG), the major polyphenolic constituent of green tea, is a potent antioxidant and free radical scavenger that may have therapeutic applications for the treatment of many disorders. Radiation therapy is widely used for the treatment of various types of cancers; however, radiation-induced skin injury remains a serious concern. EGCG has not yet been reported as protecting skin cells against ionizing radiation. In the present study, we investigated whether EGCG confers cytoprotection against ionizing radiation. We found that, compared with the control, pretreatment with EGCG significantly enhanced the viability of human skin cells that were irradiated with X-rays, and decreased apoptosis induced by X-ray irradiation. Mito-Tracker assay showed that EGCG suppressed the damage to mitochondria induced by ionizing radiation via upregulation of SOD2. Reactive oxygen species (ROS) in HaCaT cells were significantly reduced when pretreated with EGCG before irradiation. Radiation-induced γH2AX foci, which are representative of DNA double-strand breaks, were decreased by pretreatment with EGCG. Furthermore, EGCG induced the expression of the cytoprotective molecule heme oxygenase-1 (HO-1) in a dose-dependent manner via transcriptional activation. HO-1 knockdown or treatment with the HO-1 inhibitor tin protoporphyrin (SnPPIX) reversed the protective role of EGCG, indicating an important role for HO-1. These results suggest that EGCG offers a new strategy for protecting skin against ionizing radiation.

OBJECTIVE:To investigate the effect of proteasome inhibitor MLN2238on human cervical cancer HeLa cell growth inhibition,it's radiosensitivity and its mechanism.METHODS:HeLa cell growth inhibitory effect was detected by CCK-8;colony formation assay was used to detect the radiosensitivity changes;We used the flow cytometry to detect the rate of apoptosis;Mitochondrial fluorescent probe imaging was used to detect the changes in mitochondrial activity;Determination of protein expression in cells were detected by Western Blot method.RESULTS : The results showed that MLN2238significantly inhibited HeLa cells,with the inhibition rate of 3.95% by 0.05μmol/L,14.89% by 0.1μmol/L, 29.37%by 0.5μmol/L,38.95%by 1μmol/L,54.44%by 5μmol/L,70.52%by 10μmol/L,81.76%by 30μmol/L,and its effect was dose-dependent,F=1172.02,P0.001;MLN2238(0.1μmol/L)showed the radiosensitizing effects on HeLa cells,and the sensitizing enhancement ratio(SER)was 1.40.MLN2238interacts with X-ray in HeLa cells.The apoptosis rate of the control group was(2.64±0.07)%,the MLN2238group was(2.76±0.38)%,the 4Gy radiation single group was(9.50±0.14)%,the 8Gy radiation single group was(21.04±0.04)%,the 4Gy combination group was(11.12±0.19)%,the 8Gy combination group was(26.18±0.35)%,the apoptosis rate was increased,the difference was statistically significant(F=20.23,P=0.002 2).0.1μmol/L MLN2238aggravated the menbrane injury while it can increase apoptosis,the combination of X-rays and MLN2238can increase the expression of protein Bcl-2and Bax.CONCLUSION:MLN2238can inhibite HeLa cells growth and has radiosensitizing effect on HeLa cells,which may be mediated through the mitochondrial pathway of apoptosis.

Whether epigallocatechin-3-gallate(EGCG) regulates the expression of PPARα and the effect of PPARα on EGCG sensitivity.Firstly,CCK-8 kit was used to detect cell viability.Western blotting and real-time PCR was used to measure the protein and mRNA level,respectively.PPARα agonist clofibrate and inhibitor GW6471 were used to alter PPARα expression.Luciferase reporter system and chromatin immunoprecipitation(ChIP) were used to investigate the effect of PPARα on HO-1 expression.EGCG inhibits the viability of cancer cell in a dose-dependent manner.When cancer cells were exposed to EGCG,the expression of PPARα was increased at the protein level in a dose-dependent manner.The PPARα agonist clofibrate attenuated heme oxygenase(HO-1) induction and sensitized cancer cells to EGCG-induced cell death.However,the PPARα inhibitor GW6471 increased HO-1 expression.In vivo chromatin immunoprecipitation(ChIP) confirmed that PPARα interacts with the peroxisome proliferator-responsive sequence of the HO-1 promoter.These results indicate that PPARα is a direct negative regulator of HO-1 activation by EGCG and confers cell susceptibility to EGCG.

The radioprotecting effects of EGCG on Human HaCat cells of epidermal keratinocytes irradiated by X rays were investigated.MTT assays were used to evaluate the impact of different concentrations of EGCG on HaCat cells for 24,48 and 72 h to find the optimal concentration.HaCat cells were divided into four groups: control,EGCG treatment,X-ray exposure,and EGCG combined with X-ray.Cell survival rates were analyzed by clonogenic assays.The changes in ROS were measured by the DCFH-DA method,and cell apoptosis was detected with the Annexin V-FITC cell apoptosis kit and the apoptotic fragments were analyzed with DNA fragment analysis.Flow cytometry was employed to analyze cell-cycle progression.An increase of HaCat cell numbers was observed after the HaCat cells were treated with EGCG at 0-50 μmol/L,showing a time-dependent manner,while a high concentration of EGCG inhibiting HaCat cell growth.EGCG(50 μmol/L) increased the cloning efficiency of HaCat cells after radiation.EGCG reduced the apoptosis of HaCat cells by X-ray irradiation,compared with single radiation group,the apoptosis rates of the medicine and radiation group decreased from 9.25% to 7.82%;EGCG reduced the apoptosis fragments of HaCat cells by X-ray irradiation compared with the single radiation group.The G2/M phase arrest population of HaCat cells decreased after X-ray radiation,which was induced by the EGCG pretreatment.EGCG can protect HaCat cells during radiation.Radioprotection of EGCG for the cells from apoptosis is associated with its inhibition of ROS induced by radiation,meanwhile,the decrease of radiation-induced G2/M phase arrest may be involved.

Objective By using conventional chromosome aberration analysis, the radiosensitivity of Hela cells by silencing ATM gene (Hela cell) using siRNA technology was