Hydrogen-rich saline attenuates radiation-induced male germ cell loss in mice through reducing hydroxyl radicals

Our recent studies suggest that H₂ (hydrogen) has a potential as a novel radioprotector without known toxic side effects. The present study was designed to examine the underlying radioprotective mechanism of H₂ and its protective role on irradiated germ cells. Produced by the Fenton reaction and radiolysis of H₂O, hydroxyl radicals (^•OH) were identified as the free radical species that were reduced by H₂. We used a H₂ microelectrode to dynamically detect H₂ concentration in vivo, and found H₂ significantly reduced in situ fluorescence intensity of hydroxyphenyl fluorescein; however, as we treated the mice with H₂ after irradiation, the decrease is not significant. We found that pre-treatment of H₂ to IR (ionizing radiation) significantly suppressed the reaction of ^•OH and the cellular macromolecules which caused lipid peroxidation, protein carbonyl and oxidatively damaged DNA. The radioprotective effect of H₂ on male germ cells was supported by ameliorated apoptotic findings examined by morphological changes and TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP nick-end labelling) in testicular tissue, and by preserved viability of stem spermatogonia examined for testicular histological parameters, daily sperm production and sperm quality; we used WR-2721 [S-2-(3-aminopropylamino)ethyl phosphorothioic acid] as a reference compound. Our results represent the first in vivo evidence in support of a radioprotective role of H₂ by neutralizing ^•OH in irradiated tissue with no side effects.