THE AMINOTHIOL WR-1065 PROTECTS T-LYMPHOCYTES FROM IONIZING RADIATION-INDUCED DELETIONS OF THE HPRT GENE

Aminothiols, such as WR-2721 and its active free thiol, WR-1065, reduc e mutations from ionizing radiation in exponentially growing cells, In this study, human noncycling G(o) T lymphocytes were exposed in vitro to gamma-irradiation in the presence or absence of WR-1065. The five treatment groups were: (a) control; (b) treatment with 4 mM WR-1065; ( c) treatment with 3 Gy of gamma-irradiation from a Cs-137 source; and (d) and (e) treatment with WR-1065 30 min prior to or 3 h after 3 Gy o f gamma-irradiation, respectively, A total of 224 cloned HPRT mutants representing 179 independent mutations were analyzed for genetic alter ations using multiplex PCR, Ionizing radiation alone significantly inc reased the percentage of mutations with gross structural alterations c ompared to controls (P = 0.02). Although the frequency of such large s tructural mutations was not different from control cells treated with WR-1065 alone, this aminothiol significantly reduced their frequency a mong irradiated mutants (P = 0.01) when the radioprotector was present during the irradiation, Addition of WR-1065 3 h postirradiation also greatly reduced the percentage of gross structural alterations; howeve r, due to small numbers, this was not statistically significant, This is the first demonstration that the antimutagenicity of WR-1065 in hum an cells specifically protects against these kinds of large-scale DNA alterations induced by ionizing radiation, WR-1065 and similar aminoth iol compounds may afford protection against radiation-induced mutation s through polyamine-like processes, e.g., stabilization of chromatin s tructure, inhibition of cell proliferation, and influences on DNA repa ir systems.