Grape seed procyanidins prevent oxidative injury by modulating the expression of antioxidant enzyme systems

In the present paper, we report the effect of a grape seed procyanidin extract (GSPE) on antioxidant enzyme systems (AOEs). Gene expression was tested using the hepatocarcinoma cell line HepG2 by exposing it to several GSPE doses between 0 and 100 mg/L for 24 h. We evaluated mRNA expression and enzyme activity levels using real time RT-PCR and spectrophotometry. The results suggested a transcriptional GSPE regulation of glutathione related enzymes caused by an increase both in mRNA and in enzyme activity levels overall at 15 mg/L. We also assessed the GSPE effect on AOEs in cells submitted to oxidative stress. Under oxidative conditions (1 mM H(2)O(2), 1 h), we found a decrease in GSH content and an increase in MDA, and we suggested a posttranslational regulation of GPx/GR mRNAs and a transcriptional enhancement of GST mRNA. The GSPE pretreatment (15 mg/L, 23 h) before HepG2 submission to H(2)O(2) (1 mM, 1 h) showed an increase of the mRNA of GPx/GR with respect to the H(2)O(2) group, whereas the GSH content was similar to the control group. However, the GPx/GR enzyme activities were not increased. We hypothesize that GSPE probably improves the cellular redox status via glutathione synthesis pathways instead of regulation of the GPx and/or GR activities protecting against oxidative damage.