Redox Activation of DUSP4 by N-Acetyl Cysteine Protects Endothelial Cells from Cd2+-Induced Apoptosis

• Published in: Free radical biology & medicine 2014-06, Vol.74, p.188-199
• Main Authors: Barajas-Espinosa, Alma, Basye, Ariel, Jesse, Erin, Yan, Haixu, Quan, David, Chen, Chun-An
• Format: Article
• Language: English
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2014.06.016

Redox imbalance is a primary cause for endothelial dysfunction (ED). Under oxidant stress, many critical proteins regulating endothelial function undergo oxidative modifications that lead to ED. Cellular levels of GSH, the primary reducing source in cells, can significantly regulate cell function via reversible protein thiol modification. N-Acetyl cysteine (NAC), a precursor for GSH biosynthesis, is beneficial for many vascular diseases; however, the detailed mechanism of these benefits is still not clear. From HPLC analysis, NAC significantly increases both cellular GSH and BH 4 levels. Immunoblotting of eNOS and DUSP4, a dual-specificity phosphatase with a cysteine as its active residue, revealed that both enzymes are up-regulated by NAC. EPR spin-trapping further demonstrated that NAC enhances NO generation from cells. Long-term exposure to Cd 2+ contributes to DUSP4 degradation and the uncontrolled activation of p38 and ERK1/2, leading to apoptosis. Treatment with NAC prevents DUSP4 degradation and protects cells against Cd 2+ -induced apoptosis. Moreover, the increased DUSP4 expression can redox regulate p38 and ERK1/2 pathways from hyper-activation, providing a survival mechanism against the toxicity of Cd 2+ . DUSP4 gene knockdown further supports the hypothesis that DUSP4 is an antioxidant gene, critical in the modulation of eNOS translation, and thus protects against Cd 2+ -induced stress. Depletion of intracellular GSH by BSO makes cells more susceptible to Cd 2+ -induced apoptosis. Pre-treatment with NAC prevents p38 over-activation and thus protects the endothelium from this oxidative stress. Therefore, the identification of DUSP4 activation by NAC provides a novel target for future drug design.