Nitroxides prevent protein glycoxidation in vitro

Abstract

Seven nitroxides of different structures were studied for the ability to prevent glycoxidation of bovine serum albumin incubated with three monosaccharides (glucose, fructose, and ribose). Glycoxidation was estimated by fluorimetric parameters of protein modifications (formation of advanced glycation end products [AGEs], dityrosine, N’-formylkynurenine, and kynurenine) and enzyme-linked immunosorbent assay for AGEs. From among the nitroxides tested, (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), 4-carboxy-TEMPO, and 4-hydroxy-TEMPO offered significant protection against glycoxidation induced by glucose and fructose, while 3-carbamoyl-PROXYL was not protective, enhancing glycoxidation. Lower protection was observed for glycoxidation induced by ribose where only 3-carbamoyl-PROXYL and 4-amino-TEMPO showed some protection. Loss of electron spin resonance signal of the nitroxides was observed during glycoxidation indicating occurrence of free radical reactions in this process. These results suggest for the first time that nitroxides may be promising compounds for preventing glycoxidation.

Keywords::

• glycoxidation
• glucose
• fructose
• ribose
• albumin
• nitroxides

Declaration of interest

The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.

This study was performed within the COST CM1001 Action and was supported by Grant 2011/01/M/NZ3/02065 from the Polish National Science Center.