HDAC6 inhibition upregulates endothelial SOD3 expression via Sp1 acetylation and attenuates angiotensin II‐induced hypertension

Extracellular superoxide dismutase (SOD3) plays an important role in maintaining vascular redox homeostasis by eliminating superoxides. The angiotensin II (AngII) peptide mediates vasoconstriction in part via reactive oxygen species (ROS) but has pathologic effects when elevated in adults. Histone deacetylase 6 (HDAC6) modulates the acetylation of non‐histone substrates and is associated with hypertensive disorders. Here, we investigated the potential regulation of SOD3 by HDAC6 in human aortic endothelial cells (HAECs) and its implications for AngII‐induced oxidative stress and hypertension. HDAC6 inhibition (via the specific inhibitor tubastatin A (TubA), gene knockdown, or a deacetylase activity‐deficient mutant) significantly increased SOD3 protein and mRNA expression but did not affect SOD1 or SOD2 protein levels. Conversely, AngII downregulated SOD3 levels and increased ROS and superoxide levels; these effects were antagonized by TubA. We confirmed that the transcription factor Sp1 mediates TubA‐induced as well as basal SOD3 expression. Notably, TubA strongly augmented Sp1 acetylation at lysine 703, which activated Sp1 binding to the proximal SOD3 promoter region and, consequently, SOD3 expression. Alternatively, AngII decreased Sp1 acetylation, and TubA‐mediated SOD3 induction was reduced upon overexpression of an acetylation‐resistant Sp1 mutant (K703R) compared to that by the wild‐type protein. Consistent with these findings, aortic SOD3 expression was significantly higher in HDAC6‐deficient mice than in wild‐type mice. Moreover, AngII infusion‐mediated blood pressure elevation was reduced in HDAC6‐deficient mice compared with that in wild‐type mice. Collectively, our results suggest that HDAC6 inhibition leads to SOD3 upregulation by enhancing Sp1 acetylation in HAECs, thereby mitigating AngII‐induced oxidative stress and hypertension.