sodium-hypochlorite and hypobromous-acid

Although sodium hypochlorite is routinely used as an irrigant, the scope and limitation of another hypohalide sodium hypobromite has not been adequately studied. The objective of this study was to compare the cytotoxic effects of sodium hypobromite and sodium hypochlorite on human osteoblasts by evaluating cell proliferation. One day after plating and every other day after that, cells were treated with a combination of sodium hypochlorite and sodium bromide, resulting into three molar ratios of activated sodium hypobromite. Positive control cells were not treated with hypohalides, while negative controls were separately treated with hypochlorite or bromide alone. Photomicrographic analysis of the cultures was done on days 1 and 6 of treatment. Trypsinized cells were counted to determine cell proliferation. Our results show that sodium bromide is more cytotoxic compared to sodium hypochlorite or activated sodium hypobromite. In activated sodium hypobromite, 4:1 molar ratio was less cytotoxic compared to other molar ratios.

Topics: Analysis of Variance; Bromates; Bromides; Cell Proliferation; Cells, Cultured; Fetus; Humans; Osteoblasts; Root Canal Irrigants; Sodium Compounds; Sodium Hypochlorite; Statistics, Nonparametric

A potential role of DNA damage by leukocyte-derived reactive species in carcinogenesis has been suggested. Leukocyte-derived peroxidases, such as myeloperoxidase and eosinophil peroxidase, use hydrogen peroxide and halides (Cl- and Br-) to generate hypohalous acids (HOCl and HOBr), halogenating intermediates. It has been suggested that these oxidants lead to the formation of halogenated products upon reaction with nucleobases. To verify the consequences of phagocyte-mediated DNA damage at the site of inflammation, we developed a novel monoclonal antibody (mAb2D3) that recognizes the hypohalous acid-modified DNA and found that the antibody most significantly recognized HOCl/HOBr-modified 2'-deoxycytidine residues. The immunoreactivity of HOCl-treated oligonucleotide was attenuated by excess methionine, suggesting that chloramine-like species may be the plausible epitopes of the antibody. On the basis of further characterization combined with mass spectrometric analysis, the epitopes of mAb2D3 were determined to be novel N4,5-dihalogenated 2'-deoxycytidine residues. The formation of the dihalogenated 2'-deoxycytidine in vivo was immunohistochemically demonstrated in the lung and liver nuclei of mice treated with lipopolysaccharides, an experimental inflammatory model. These results strongly suggest that phagocyte-derived oxidants, hypohalous acids, endogenously generate the halogenated DNA bases such as a novel dihalogenated 2'-deoxycytidine in vivo. Halogenation (chlorination and/or bromination) of DNA therefore may constitute one mechanism for oxidative DNA damage at the site of inflammation.

Topics: Animals; Antibodies, Monoclonal; Bromates; Chloramines; Chlorine; Chromatography, High Pressure Liquid; Chromatography, Liquid; Deoxycytidine; DNA; DNA Damage; Dose-Response Relationship, Drug; Enzyme-Linked Immunosorbent Assay; Epitopes; Female; HL-60 Cells; Humans; Hypochlorous Acid; Immunohistochemistry; Inflammation; Leukocytes; Lipopolysaccharides; Liver; Lung; Mass Spectrometry; Mice; Mice, Inbred C57BL; Models, Chemical; Oligonucleotides; Oxidants; Oxygen; Peroxidase; Phagocytosis; Reactive Oxygen Species; Sodium Hypochlorite; Time Factors

Hypohalites (OCl-, OBr-) are formed at inflammation sites as antimicrobial agents. OCl- is also used for the disinfection of water supplies and the association of drinking chlorinated water with cancer risk is pointed out. In this study, OCl- itself induced 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) formation, while OBr- damaged DNA only when glutathione (GSH) was added. OCl- caused oxidative DNA damage more efficiently than OBr-/GSH. In experiment with 32P-labeled DNA fragments, OCl- strongly caused piperidine-labile sites at guanine residues than piperidine-inert 8-oxodG, whereas OBr-/GSH caused no piperidine-labile sites. Endogenous OCl- may play a role in genotoxicity close to the site of inflammation.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Bromates; Carcinogens; Cattle; Cell Line; Deoxyguanosine; Dimethyl Sulfoxide; DNA; DNA Damage; Electron Spin Resonance Spectroscopy; Genes, p53; Genes, ras; Genes, Tumor Suppressor; Glutathione; Humans; Inflammation; Neoplasms; Oxidation-Reduction; Phosphorus Isotopes; Piperidines; Sodium Hypochlorite