γ-Glutamylcysteine inhibits oxidative stress in human endothelial cells

Aimsγ-Glutamylcysteine (GGC) is a dipeptide and substrate for synthesis of the antioxidant glutathione (GSH), whose health promoting properties include reducing risks of oxidative stress-related injuries and diseases. The objective of this study was to investigate the efficacy of GGC on GSH synthesis and oxidative stress in human endothelial cells.Main methodsWe assessed oxidative stress, GSH, GSH synthetase (GSS) expression, and transcription factor DNA binding levels in human umbilical vein endothelial cells (HUVEC).Key findingsWe found significantly higher levels of PPARγ DNA binding and lower levels of GSH, GSS protein, NF-κB p65 DNA binding, thiobarbituric acid reactive substances (TBARS), and 8-epi-PGF2α in a concentration-dependent manner, compared with the control. GSH and GSS protein levels showed a negative correlation with PPARγ DNA binding levels and positive correlation trends with NF-κB p65 DNA binding, TBARS, and 8-epi-PGF2α levels. A putative binding site for NF-κB was found at 4 227 bases upstream from the transcription start site of GSS gene, but none for PPARs. These findings suggest the involvement of NF-κB in regulation of GSS expression. Subsequent GSH synthesis might be affected by the suppression of GSS expression in tested conditions.SignificanceBesides its substrate role in GSH synthesis, GGC may play a role in protection against oxidative stress by serving as an antioxidant and modulating the expression of protein(s) related to antioxidant defense. Thus, we speculate that GGC may serve as a novel intra- and intercellular therapeutic dipeptide for oxidative stress-related injuries and diseases.