Potassium bromate (KBrO3), a food additive, induces renal-cell tumors in rats. KBrO3 induced 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodG) formation in human leukemia cell line HL-60 as well as in its H2O2-resistant clone, HP100, suggesting no involvement of H2O2. Depletion of GSH by buthionine sulfoximine (BSO) had a little inhibitory effect on KBrO3-induced 8-oxodG formation. However, the amount of 8-oxodG was still significantly higher than that in control, suggesting that intracellular Cys can affect KBrO3 to oxidize DNA, when GSH decreased. KBrO3 caused 8-oxodG in isolated DNA in the presence of GSH (tripeptide; gamma-GluCysGly), gamma-GluCys, CysGly, or Cys. Methional completely inhibited 8-oxodG formation induced by KBrO3 plus GSH, but typical hydroxyl radical scavengers, SOD and catalase, had little or no inhibitory effects. When bromine solution (BrO(-)) was used instead of BrO3(-), similar scavenger effects were observed. Experiments with 32P-labeled DNA fragments obtained from the human p53 tumor suppressor gene and the c-Ha-ras-1 protooncogene suggested that KBrO3 induced 8-oxodG formation at 5'-site guanine of GG and GGG sequences of double-stranded DNA in the presence of GSH and that treatment of formamidopyrimidine-DNA glycosylase led to chain cleavages at the guanine residues. ESR spin-trapping studies showed that 1:2:2:1 quartet DMPO (5,5-dimethyl-1-pyrroline N-oxide) spectrum similar to DMPO/hydroxy radical (*OH) adduct, but the signals were not inhibited by ethanol. Therefore, the signal seemed not to be due to *OH but byproduct due to oxidation of DMPO by the reactive species. The signals were suppressed by the addition of dGMP, but not by other mononucleotides, suggesting the specific reactivity with guanine. On the basis of our results and previous literature, it is speculated that reduction of KBrO3 by SH compounds in renal proximal tubular cells yields bromine oxides and bromine radicals, which are the reactive species that cause guanine oxidation, leading to renal carcinogenesis of KBrO3.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.