Epigenetic remodeling of Nox2 by acetyltransferase Gcn5 drives hyperglycemia-induced endothelial oxidative stress

Introduction: Epigenetic modifications are recently emerging as important modulators of gene expression. The mammalian acetyltransferase gene non-derepressible 5 (GCN5) causes Nox2 upregulation in neutrophils through acetylation of histones. Whether GCN5 modulates oxidative stress in the cardiovascular system remains largely unknown. Hypothesis: The present study investigates GCN5 role in the modulation of diabetes-related endothelial oxidative stress. Methods: Human aortic endothelial cells (HAECs) were exposed to normal (NG, 5 mmol/L) or high glucose concentrations (HG, 25 mmol/L) in the presence or in the absence of GCN5 pharmacological inhibitor CPTH2 or siRNA-mediated knockdown. Superoxide anion (O2-) was measured by ESR spectroscopy. Chromatin immunoprecipitation (ChIP) was performed to investigate epigenetic modifications on Nox2 promoter induced by GCN5. In parallel, 30 patients with type 2 diabetes (T2DM) and 18 age-matched healthy controls were enrolled. All patients underwent flow-mediated vasodilation (FMD) of the brachial artery to assess endothelial function. Urinary levels of 8-isoprostaglandinF2α (8-isoPGF2α) were measured as a marker of oxidative stress. Gene expression of GCN5 and Nox2 was assessed from peripheral blood monocytes (PBM). Data are presented as fold change (FC). Results: HG caused upregulation of NADPH subunit Nox2 (FC vs. NG: 2.5, p<0.05). Interestingly, GCN5 inhibition or siRNA prevented hyperglycemia-induced Nox2 overexpression and subsequent O2- increase. ChIP assay showed that GCN5 binds human Nox2 promoter and mediates lysine 14 acetylation of histone 3, leading to an open chromatin and active transcription. GCN5 expression was increased in PBM of T2DM patients (FC vs. NG: 3.04, p<0.05) and significantly correlated with Nox2 transcript (r=0.32, p<0.05). Consistently, GCN5 upregulation paralleled endothelial dysfunction (r=-0.33, p<0.05) and oxidative stress (r=0.46, p<0.05), as assessed by FMD and 8-isoPGF2α, respectively. Conclusions: Epigenetic changes operated by GCN5 cause endothelial upregulation of Nox2 and subsequent oxidative stress in diabetes. Our findings provide a novel therapeutic opportunity for the prevention of diabetes-related vascular oxidative stress.