Radiation protection by a new chemical entity, Ex-Rad: efficacy and mechanisms.

Abstract	Ex-Rad is among a series of small molecule kinase inhibitors developed for modifying cell cycle distribution patterns in cancer cells subjected to radiation therapy, and it has been identified as a potential candidate for radiation protection studies. We have investigated its radioprotective efficacy using mouse and in vitro models. Thirty-day survival studies with C3H/HeN male mice revealed 88% survival when 500 mg/kg of Ex-Rad was injected subcutaneously 24 h and 15 min before gamma irradiation with 8.0 Gy. To understand Ex-Rad's mechanism of action, we also studied its radioprotective efficacy in lung fibroblast (HFL-1), skin fibroblast (AG1522) and human umbilical vein endothelial cells (HUVECs). Colony-forming assays indicated that Ex-Rad protected cells from radiation damage after exposure to (60)Co gamma radiation. A study using single-cell gel electrophoresis (SCGE; also known as the alkaline comet assay) showed that Ex-Rad protected cells from radiation-induced DNA damage. Western blot analyses indicated that the radiation protection provided by Ex-Rad resulted in reduced levels of pro-apoptosis proteins such as p53 as well as its downstream regulators p21, Bax, c-Abl and p73, indicating that Ex-Rad could rescue cells from ionizing radiation-induced p53-dependent apoptosis. In conclusion, it appears that Ex-Rad's radioprotective mechanisms involve prevention of p53-dependent and independent radiation-induced apoptosis.
Authors	Sanchita P Ghosh, Michael W Perkins, Kevin Hieber, Shilpa Kulkarni, Tzu-Cheg Kao, E Premkumar Reddy, M V Ramana Reddy, Manoj Maniar, Thomas Seed, K Sree Kumar
Journal	Radiation research (Radiat Res) Vol. 171 Issue 2 Pg. 173-9 (Feb 2009) ISSN: 0033-7587 [Print] United States
PMID	19267542 (Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S.)
Chemical References	(E)-4-carboxystyryl-4-chlorobenzylsulfone, sodium salt Radiation-Protective Agents Sulfonamides
Topics	Animals Blotting, Western Cells, Cultured Comet Assay DNA Damage Dose-Response Relationship, Radiation Down-Regulation Humans Male Mice Mice, Inbred C3H Radiation-Protective Agents (pharmacology) Sulfonamides (pharmacology)

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