Regulation of Oxidative Stress in Pulmonary Artery Endothelium. Modulation of Extracellular Superoxide Dismutase and NOX4 Expression Using Histone Deacetylase Class I Inhibitors

An imbalance between oxidants and antioxidants is considered a major factor in the development of pulmonary vascular diseases. Oxidative stress seen in pulmonary vascular cells is regulated by increased expression of prooxidant enzymes (e.g., nicotinamide adenine dinucleotide phosphate reduced oxidases) and/or decreased production of antioxidants and antioxidant enzymes (e.g., superoxide dismutases). We and others have shown that expression of antioxidant genes in pulmonary artery cells is regulated by epigenetic mechanisms. In this study, we investigate the regulation of oxidative stress in pulmonary artery cells using inhibitors of histone deacetylases (HDACs). Human pulmonary artery endothelial cells (HPAECs) and human pulmonary artery smooth muscle cells were exposed to an array of HDAC inhibitors followed by analysis of anti- and prooxidant gene expression using quantitative RT-PCR and quantitative RT-PCR array. We found that exposure of HPAECs to scriptaid, N-[4-[(hydroxyamino)carbonyl]phenyl]-α-(1-methylethyl)-benzeneacetamide, and trichostatin A for 24 hours induced expression of extracellular superoxide dismutase (EC-SOD) up to 10-fold, whereas expression of the prooxidant gene NADPH oxidase 4 was decreased by more than 95%. We also found that this differential regulation of anti- and prooxidant gene expression resulted in significant attenuation in the cellular levels of reactive oxygen species. Induction of EC-SOD expression was attenuated by the Janus kinase 2 protein kinase inhibitor AG490 and by silencing Janus kinase 2 expression. Augmentation of EC-SOD expression using scriptaid was associated with increased histone H3 (Lys27) acetylation and H3 (Lys4) trimethylation at the gene promoter. We have determined that oxidative stress in pulmonary endothelial cells is regulated by epigenetic mechanisms and can be modulated using HDAC inhibitors.