Antioxidant and pro-oxidant actions of resveratrol on human serum albumin in the presence of toxic diabetes metabolites: Glyoxal and methyl-glyoxal

Methylglyoxal (MGO) and glyoxal (GO) are attracting considerable attention because of their role in the onset of diabetes symptoms. Therefore, to comprehend the molecular fundamentals of their pathological actions is of the utmost importance. In this study, the molecular interactions between resveratrol (RES) and human serum albumin (HSA) and the ability of the stilbene to counteract the oxidative damage caused by pathological concentrations of MGO and GO to the human plasma protein, was assessed. The oxidation of Cys34 in HSA as well as the formation of specific protein semialdehydes AAS (alpha-aminoadipic), GGS (gamma-glutamic) and the accumulation of Advanced Glycation End-products (AGEs) was investigated. Resveratrol was found to neutralize both alpha-di-carbonyls by forming adducts detected by HESI-Orbitrap-MS. This antioxidant action was manifested in a significant reduction of AGEs. However, RES-alpha-dicarbonyl conjugates oxidized Cys34 and lysine, arginine and/or proline by a nucleophilic attack on SH and epsilon-NH groups in HSA. The formation of specific semialdehydes in HSA after incubation with GO and MGO at pathological concentrations was reported for the first time in this study, and may be used as early and specific biomarkers of the oxidative stress undergone by diabetic patients. The pro oxidative role of the RES-alpha-dicarbonyl conjugates should be further investigated to clarify whether this action leads to positive or harmful clinical consequences. The biological relevance of human protein carbonylation as a redox signaling mechanism and/or as a reflection of oxidative damage and disease should also be studied in future works.