sodium-bromide 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

Eosinophils use eosinophil peroxidase, hydrogen peroxide (H(2)O(2)), and bromide ion (Br(-)) to generate hypobromous acid (HOBr), a brominating intermediate. This potent oxidant may play a role in host defenses against invading parasites and eosinophil-mediated tissue damage. In this study, we explore the possibility that HOBr generated by eosinophil peroxidase might oxidize nucleic acids. When we exposed uracil, uridine, or deoxyuridine to reagent HOBr, each reaction mixture yielded a single major oxidation product that comigrated on reversed-phase HPLC with the corresponding authentic brominated pyrimidine. The eosinophil peroxidase-H(2)O(2)-Br(-) system also converted uracil into a single major oxidation product, and the yield was near-quantitative. Mass spectrometry, HPLC, UV--visible spectroscopy, and NMR spectroscopy identified the product as 5-bromouracil. Eosinophil peroxidase required H(2)O(2) and Br(-) to produce 5-bromouracil, implicating HOBr as an intermediate in the reaction. Primary and secondary bromamines also brominated uracil, suggesting that long-lived bromamines also might be physiologically relevant brominating intermediates. Human eosinophils used the eosinophil peroxidase-H(2)O(2)-Br(-) system to oxidize uracil. The product was identified as 5-bromouracil by mass spectrometry, HPLC, and UV--visible spectroscopy. Collectively, these results indicate that HOBr generated by eosinophil peroxidase oxidizes uracil to 5-bromouracil. Thymidine phosphorylase, a pyrimidine salvage enzyme, transforms 5-bromouracil to 5-bromodeoxyridine, a mutagenic analogue of thymidine. These findings raise the possibility that halogenated nucleobases generated by eosinophil peroxidase exert cytotoxic and mutagenic effects at eosinophil-rich sites of inflammation.

Topics: Bromates; Bromides; Bromine; Bromodeoxyuridine; Bromouracil; Catalase; Enzyme Activation; Enzyme Inhibitors; Eosinophil Peroxidase; Eosinophils; Humans; Hydrogen Peroxide; Hydrogen-Ion Concentration; Mutagens; Peroxidases; Pyrimidines; Sodium Compounds; Thymidine Phosphorylase; Uracil