Selenium and sulforaphane modify the expression of selenoenzymes in the human endothelial cell line EAhy926 and protect cells from oxidative damage

Objective
We examined the ability of sulforaphane and selenium to modify the expression of thioredoxin reductase (TR-1) and the glutathione peroxidases (GPX-1 and GPX-4) in EAhy926 cells. The effectiveness of these agents to protect cells against peroxidative damage was also assessed.

Methods
EAhy926 cells were supplemented with 40 nM of selenite and/or sulforaphane (10 µM) for 72 h and the expression of TR-1, GPX-1, and GPX-4 was assessed. Parallel cultures of selenium- and sulforaphane-treated cells were exposed to tertiary butyl hydroperoxide (t-BuOOH; 0–500 µM) for 20 h, and cell integrity was determined by the percentage of lactate dehydrogenase retained by the cellular layer.

Results
Selenite treatment increased the concentration of TR-1 (1.6 ± 0.17 fold, P < 0.05), GPX-1 activity (8.2 ± 1.08 fold, P < 0.001), and GPX-4 activity (3.1 ± 0.25 fold, P < 0.001). Sulforaphane induced TR-1 expression in selenium-deficient cells (1.83 ± 0.11 fold, P < 0.001) and selenium-supplemented cells (2.90 ± 0.17 fold, P < 0.001) but had no inductive effect on GPX-1 or GPX-4. The combination of selenite and sulforaphane produced an increase in TR-1 expression that was significantly greater (P < 0.001) than that achieved when each agent was added alone. Selenium and sulforaphane acted in a synergistic manner to protect cells from damage caused by t-BuOOH. The susceptibility of cells to damage by t-BuOOH increased in this order: control > sulforaphane > selenite > selenite + sulforaphane (P < 0.0001).

Conclusion
In endothelial cells, sulforaphane increases TR-1 but not GPX-1 and GPX-4 and in doing so confers protection against oxidative damage induced by lipid hydroperoxides. The results highlight the potential important role of TR-1 over the GPXs in protecting endothelial cells from oxidative cell damage. We also suggest that our results indicate a potential beneficial role for sulforaphane in protecting the vascular endothelium from oxidative damage.