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JR Reddan, FJ Giblin, MD Sevilla, VA Padgaonkar, DC Dziedzic, VR Leverenz, J Chang, IC Misra, JT Pena; n-Propyl Gallate Protects Lens Epithelial Cells From Oxidative Insult And Acts Catalytically To Destroy The Superoxide Anion . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2369.
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Purpose: n-Propyl gallate (nPG) is a food preservative that is generally regarded as safe by the US FDA. It suppresses oxidation in biological systems. However, the exact manner in which nPG acts in biological systems is uncertain. We investigated whether nPG protected cultured lens epithelial cells from H2O2-induced damage and the mechanism by which nPG acts at the chemical level. Methods: Cultured rabbit lens epithelial cells were treated with H2O2 or with nPG and then H2O2. Morphological, biochemical and growth parameters were determined. The mechanism by which nPG acts at the chemical level was also investigated. Results: H2O2 inhibited growth, caused membrane blebbing, decreased lactate production, increased the level of GSSG, decreased the levels of GSH, ATP, NAD+ and G3PDH activity, stimulated the HMPS and induced single-strand breaks in DNA. nPG prevented the H2O2-induced growth inhibition, membrane blebbing, drop in NAD+ and single-strand breaks in DNA. The action of nPG at the chemical level was explored with EPR, direct spectrophotometric kinetic measurements, and cyclic voltammetry. When nPG at low concentrations (nM to µM) was mixed with a large excess of superoxide anion (O2-•), the superoxide signal was destroyed as indicated by UV visible spectroscopy and EPR. Kinetic analysis indicated that nPG dismutated O2-• in repetitive additions of superoxide with little loss of activity. The rate constant for the overall reaction of nPG with O2-• was ca. 106M-1s-1. nPG had a very low specific binding constant for Fe+2 as determined by cyclic voltammetry. Conclusion: The evidence indicates that nPG dismutates the superoxide ion in a catalytic manner and protects lens cells from oxidative damage.
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