Synergistic Protective Effect of Curcumin and Resveratrol against Oxidative Stress in Endothelial EAhy926 Cells

Curcumin (C) and resveratrol (R) are two well-known nutraceuticals with strong antioxidant activity that can protect cells from oxidative stress. This study aims to investigate the synergy of CR combinations in protecting human endothelial EAhy926 cells against H(2)O(2)-induced oxidative stress and its related mechanisms. C and R as individual compounds as well as CR combinations at different ratios were screened for their protective effects against H(2)O(2) (2.5 mM) induced cell death assessed by cell viability assays. The synergistic interaction was analysed using the combination index model. The effects of optimal CR combinations on caspase-3 activity, ROS level, SOD activity, NAD cellular production, expression of Nrf2 and HO-1, and Nrf2 translocation were determined. CR combinations produced a synergistic protection against that of H(2)O(2)-induced changes in cell viability, caspase-3 activity, and ROS production. The strongest effect was observed for CR with the ratio of 8 : 2. Further experiments showed that CR 8 : 2 exhibited significantly greater effects in increasing Nrf2 translocation and expressions of Nrf2 and HO-1 proteins, as well as SOD activity and total cellular NAD production, than that of C or R alone. The findings demonstrate that combination of C and R produced a strong synergy in activity against H(2)O(2)-induced oxidative stress in EAhy926 cells. The mechanism of this synergy involves the activation of Nrf2-HO-1 signaling pathway and promotion of antioxidant enzymes. Further studies on CR synergy may help develop a new combination therapy for endothelial dysfunction and other conditions related to oxidative stress.