Polaprezinc, a gastroprotective agent: attenuation of monochloramine-evoked gastric DNA fragmentation

We previously reported that NH2Cl induced extensive DNA fragmentation in ga stric cells. Polaprezinc, a zinc-carnosine chelate compound, is reported to be a potent antioxidant in gastric mucosa. The present study was designed to examine whether polaprezine could attenuate the NH2Cl-induced DNA damage . Gastric cell lines, MKN45, were exposed to NH2Cl in Ca2+-containing Hanks ' balanced salt solution. DNA fragmentation was evaluated by photometric en zyme immunoassay for in vitro determination of cytoplasmic mono- and oligon ucleosomes. Polaprezinc, L-carnosine, and zinc sulfate (ZnSO4) were added t o the cell incubation medium to evaluate the inhibitory effect on the forma tion of cytoplasmic mono- and oligonucleosomes. Separately, the bleaching l evel of beta-carotene with the addition of each test solution was evaluated to confirm the inhibitory effect against hypochlorous acid. Polaprezinc or L-carnosine, but not ZnSO4, at a concentration of 0.001 mM, significantly attenuated the increased levels of cytoplasmic mono- and oligonucleosomes e voked by 0.001mM NH2Cl. Polaprezinc and L-carnosine, but not ZnSO4, also in hibited NH2Cl-induced beta-carotene bleaching in the cell-free system. In c onclusion, polaprezinc, especially its subportion L-carnosine, inhibited NH 2Cl-evoked gastric epithelial DNA fragmentation, suggesting a role for this agent in preventing the progression of gastric epithelial injury induced b y NH2Cl.