Gliclazide scavenges hydroxyl, superoxide and nitric oxide radicals: an ESR study

The role of reactive oxygen species in diabetes and its complications are well known. Two therapeutic agents commonly used in the treatment of diabetes are the sulfonylureas, gliclazide and glibenclamide. These drugs effectively reduce blood sugar in non-insulin dependent diabetes millitus by augmenting insulin release. Gliclazide is known to be a general free radical scavenger as demonstrated by inhibition of o-dianisidine photo-oxidation. In this study, the effects of gliclazide and glibenclamide on free radicals were examined in vitro, using electron spin resonance (ESR) spectroscopy. Superoxide radical (O2.-) generated from hypoxanthine-xanthine oxidase system, or hydroxyl radical (.OH) generated by the Fenton reaction, were analyzed as spin adducts of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). NO was generated from 1-hydroxy-2-oxo-3-(N-3-methyl-3-aminopropyl)-3-methyl-1-triazene (NOC-7), and analyzed by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl (carboxy-PTI) produced from the reaction between 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO) and NO. Gliclazide scavenged O2.-, .OH and NO in a dose-dependent manner whereas glibenclamide was without effect. These findings suggest that gliclazide is not only effective in reducing blood sugar but also may be beneficial by inhibition of lipid and protein denaturation, which leads to the development of diabetic complications.