title: Gliotoxin enhances radiotherapy via inhibition of radiation-induced GADD45a, p38, and NFkappaB activation.
abstract: The purpose of the study was to elucidate the mechanism underlying the enhancement of radiosensitivity to 60Co gamma-irradiation in human hepatoma cell line HepG2 pretreated with gliotoxin. Enhancement of radiotherapy by gliotoxin was investigated in vitro with human hepatoma HepG2 cell line. Apoptosis related proteins were evaluated by Western blotting. Annexin V/PI and reactive oxygen species (ROS) were quantified by Flow Cytometric (FACS) analysis. Gliotoxin (200 ng/ml) combined with radiation (4 Gy) treated cells induced apoptosis. Cells treated with gliotoxin (200 ng/ml) prior to irradiation at 4 Gy induced the expression of bax and nitric oxide (NO). The gliotoxin-irradiated cells also increased caspase-3 activation and ROS. Gadd45a, p38, and nuclear factor kappa B (NFkappaB) activated in irradiated cells was inhibited by Gliotoxin. Specific inhibitors of p38 kinase, SB203580, significantly inhibited NFkappaB activation and increased the cytotoxicity effect in cells exposed to gliotoxin combined with irradiation. However, SB203580 did not suppress the activation of Gadd45a in irradiated cells. Gliotoxin inhibited anti-apoptotic signal pathway involving the activation of Gadd45a-p38-NFkappaB mediated survival pathway that prevent radiation-induced cell death. Therefore, gliotoxin, blocking inflammation pathway and enhancing irradiation-induced apoptosis, is a promising agent to increase the radiotherapy of tumor cells.
authors.affiliation: Radiation Research Center for Bio-Technology, Korea Atomic Energy Research Institute, Jeongeup 580-185, South Korea.
authors.forename: Jung-Mu
authors.initials: JM
authors.lastname: Hur
authors.forename: Hye-Jeong
authors.initials: HJ
authors.lastname: Yun
authors.forename: Soo-Hyung
authors.initials: SH
authors.lastname: Yang
authors.forename: Woo-Yiel
authors.initials: WY
authors.lastname: Lee
authors.forename: Min-Ho
authors.initials: MH
authors.lastname: Joe
authors.forename: Dongho
authors.initials: D
authors.lastname: Kim
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005720:Gamma Rays; D005912:Gliotoxin / Q000494:pharmacology*; D006801:Humans; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D011836:Radiation Tolerance / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D000097642:GADD45 Proteins
chemical_list: D018797:Cell Cycle Proteins; D005912:Gliotoxin; D016328:NF-kappa B; D009569:Nitric Oxide; D009687:Nuclear Proteins; D017382:Reactive Oxygen Species; D048051:p38 Mitogen-Activated Protein Kinases; C439070:GADD45A protein, human; D000097642:GADD45 Proteins