Reduction of radiation-induced chromosome aberration and apoptosis by dithiothreitol

We have examined in vitro and in vivo radioprotective effects of a well-kno wn thiol-containing compound, dithiothreitol (DTT). The treatment of both 0 .5 and 1 mM of DTT significantly increased clonogenic survival of gamma-ray irradiated Chinese hamster (V79-4) cells. In order to investigate the poss ible radioprotective mechanism of DTT, we measured gamma-ray induced chromo some aberration by micronucleus assay. In the presence of 0.5 mM or 1 mM DT T, the frequencies of micronuclei were greatly reduced in all dose range ex amined (1.5-8 Gy). Slightly higher reduction in micronucleus formation was observed in 1 mM DTT-treated cells than in 0.5 mM DTT-treated cells. in add ition, incubation with both 0.5 and 1 mM of DTT prior to gamma-ray irradiat ion reduced nucleosomal DNA fragmentation at about same extent, this result suggests that treatment of DTT at concentrations of 0.5 and 1 mM reduced r adiation-induced apoptosis. In vivo experiments, we also observed that DTT treatment reduced the incidence of apoptotic cells in mouse small intestine crypts. in irradiated control group 4.4+/-0.5 apoptotic cells per crypt we re observed. In DTT-administered and irradiated mice, only 2.1+/-0.4 apopto tic cells per crypt was observed. In vitro and in vivo data obtained in thi s study showed that DTT reduced radiation-induced damages and it seems that the possible radioprotective mechanisms of action of DTT are prevention of chromosome aberration.