Nrf2 transcription factor activation modulates endothelial inflammatory response triggered by TNF-alpha

Oxidants are one of the etiologies of multiple diseases and disorders. Cells are continously exposed to the deleterious consequences of reactive oxigen species generated endogenously and exogenously. However, cells have developed multiple stress adaptive responses, including the system regulated by the transcription factor Nrf2 that modulates a set of cytoprotective genes (such as HO-1, NQO1, γ-GCS). Up today there are few data supporting the atheroprotective and antiinflammatory activity of the Nrf2 pathway in endothelial cells. Since activation of endogenous cellular defense mechanisms can represent an innovative approach to therapeutic intervention in pathological conditions characterized by chronic tissue damage, a better understanding of adaptive response mechanisms at the cellular and molecular levels can lead to novel strategies for the prevention and treatment of many different diseases. Thus, to test the potential atheroprotective and anti-inflammatory role of the Nrf2 pathway we have investigated if some changes in the intracellular redox status, such as those related to endogenous antioxidants depletion, might be able to alter the response to the inflammatory cytokine TNF-α in cultured human endothelial cells through the activation of this pathway. In this study, we revealed that an oxidative intracellular status consequent to an intracellular glutathione depletion induced by HUVECs exposure to buthionine sulfoximine (BSO), an inhibitor of γ-glutamylcysteine synthetase (γ-GCS), a rate-limiting enzyme in glutathione biosynthesis, is able to induce a cellular adaptive response. Interestingly we demonstrated that, in our experimental conditions, activation of Nrf2 pathway is able to reduce endothelial dysfunction by decreasing NFkB nuclear translocation and adhesion molecules gene expression in HUVECs. Furthermore, we confirmed that Nrf2 nuclear translocation activated by GSH depletion is dependent on extracellular signal-regulated kinases 1/2 phosphorylation. In conclusion, we showed that the coordinate induction of endogenous cytoprotective proteins through activation of the Nrf2 pathway might serve as a new therapeutic approach for prevention or treatment of endothelial dysfunction. Corresponding author: Antonio Speciale (specialea@gmail.com)