Radiation protection by a new chemical entity, Ex-Rad: efficacy and mechanisms.
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.
Ghosh
Sanchita P
SP
Armed Forces Radiobiology Research Institute, USUHS, Bethesda, Maryland 20889-5603, USA. ghosh@afrri.usuhs.mil
Perkins
Michael W
MW
Hieber
Kevin
K
Kulkarni
Shilpa
S
Kao
Tzu-Cheg
TC
Reddy
E Premkumar
EP
Reddy
M V Ramana
MV
Maniar
Manoj
M
Seed
Thomas
T
Kumar
K Sree
KS
D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D020552:Comet Assay; D004249:DNA Damage; D004307:Dose-Response Relationship, Radiation; D015536:Down-Regulation; D006801:Humans; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D013449:Sulfonamides / Q000494:pharmacology*
C520364:(E)-4-carboxystyryl-4-chlorobenzylsulfone, sodium salt; D011837:Radiation-Protective Agents; D013449:Sulfonamides