The biological activity of hydrogen peroxide VII. L-Histidine increases incorporation of H(2)O(2) into cells and enhances formation of 8-oxodeoxyguanosine by UV-C plus H(2)O(2) but not by H(2)O(2) alone.
L-Histidine (L-His) enhances the clastogenic effects of hydrogen peroxide (H(2)O(2)). We previously suggested the involvement of active transport in the efficient influx of an L-His--H(2)O(2) adduct into cells (Oya-Ohta et al. [1]). In this study, we detected intracellular H(2)O(2) by monitoring formation of 2',7'-dichlorofluorescein (DCF) from its precursor. More fluoroproduct accumulated dose-dependently in cells treated with a mixture of L-His and H(2)O(2) (mixture) than with H(2)O(2) alone. This observation supports our hypothesis that active transport is involved in the enhanced incorporation of H(2)O(2) into cells. Moreover, both mixture and the L-His--H(2)O(2) adduct were less active in the generation of hydroxyl radicals (*OH) upon addition of FeCl(2) than was H(2)O(2) alone in a cell-free system. This result suggests that the Fenton reaction might occur more effectively around the nucleus in cells. An immunohistochemical assay using 8-oxodG-specific monoclonal antibodies did not reveal whether the accumulation of H(2)O(2) generates 8-oxodeoxyguanosine (8-oxodG). No 8-oxodG was evident in cells treated with mixture or with H(2)O(2) alone, or even in cells treated with H(2)O(2) at high doses up to 20 mM and, in some cases, pre-treated with catalase inhibitors. It appears, therefore, that *OH and, specifically, *OH derived from intracellular Fenton reactions, might not play a role in the formation of 8-oxodG. However, exposure to UV-C of cells treated with H(2)O(2) yielded more 8-oxodG in the presence of L-His than in the absence of L-His. Thus, the previously observed enhancing effects of L-His were also noted during the induction of formation of 8-oxodG by UV-C plus H(2)O(2). The formation of 8-oxodG in response to UV-C alone was very limited and, hence, H(2)O(2) seemed to be an effective source of *OH only in the presence of UV-C. It is suggested that the *OH that induces formation of 8-oxodG is not *OH formed via intracellular Fenton reactions but is *OH formed via the dissociation of H(2)O(2) under UV-C.
Oya-Ohta
Y
Y
Department of Pathology, Kanagawa Prefectural College of Nursing and Medical Technology, Yokahama 241-0815, Japan. eiseidai.1571.kyomu@pref.kanagowa.jp
Ueda
A
A
Ochi
T
T
Harada
M
M
Yamamoto
K
K
D000080242:8-Hydroxy-2'-Deoxyguanosine; D002474:Cell-Free System / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D018736:DNA Adducts / Q000187:drug effects / Q000378:metabolism; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism* / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D006639:Histidine / Q000494:pharmacology*; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism* / Q000494:pharmacology; D017665:Hydroxyl Radical / Q000378:metabolism; D013997:Time Factors; D014466:Ultraviolet Rays
D018736:DNA Adducts; D017665:Hydroxyl Radical; D006639:Histidine; D000080242:8-Hydroxy-2'-Deoxyguanosine; D006861:Hydrogen Peroxide; D003849:Deoxyguanosine