Aim: 

Redox signalling pathways take part in multiple fundamental cellular functions. These redox pathways are involved in cellular oxidative stress and play an important role in the aging process. The aim of this work was: i) to test the S-(carboxymethyl)cysteine in vivo formation as a new marker of oxidative damage which results of the non-enzymatic reaction of reactive carbonyl compounds with protein thiol groups; and ii) to evaluate the effect of dietary restriction on the formation of this biomarker, taking into account that dietary restriction modulates the aging process.

Methods: 

Detection and quantification of S-(carboxymethyl)cysteine and Ne-(carboxymethyl)lysine in liver mitochondrial proteins of male Wistar rats by gas chromatography-mass spectrometry with selected ion monitoring. Two different diets were applied. One with low calorie restriction, three groups: controls, 8.5% and 25% caloric restriction; the second one a methionine restriction, with three groups: control, 40% and 80% methionine restriction.

Results: 

It is demonstrate the presence of in vivo formation of the carbonyl-thiol adduct S-(carboxymethyl)cysteine in mitochondrial proteins. The basal levels of S-(carboxymethyl)cysteine are in the same range than Ne-(carboxymethyl)lysine. Both the caloric restriction and the methionine restriction modulate the concentration of these two parameters, as well as the total content of protein-thiols.

Conclusions: 

Non-enzymatic and irreversible modification of thiols groups in proteins by carbonyl compounds, which are generated by oxidative reactions, is done in vivo. These modifications can e.g. affect the intracellular signalling pathways. Dietary restriction, which reduces the rate of aging and the oxidative stress, also modulate the rate of modification of thiol groups in intracellular proteins.