Tubastatin A suppresses renal fibrosis via regulation of epigenetic histone modification and Smad3-dependent fibrotic genes

Inflammation and fibrosis are implicated in the pathogenesis of hypertensive kidney damage. We previously demonstrated that a nonspecific histone deacetylase (HDAC) inhibitor attenuates cardiac fibrosis in deoxycorticosterone acetate-salt hypertensive rats, which induces HDAC6 protein and enzymatic activity. However, the HDAC inhibitor's effect and mechanism have not yet been demonstrated. We sought to determine whether an HDAC6-selective inhibitor could treat hypertension and kidney damage in angiotensin II-infused mice. Hypertension was induced by infusion of ANG in mice. Tubastatin A, an HDAC6 selective inhibitor, did not regulate blood pressure. Hypertensive stimuli enhanced the expression of HDAC6 in vivo and in vitro. We showed that the inhibition of HDAC6 prevents fibrosis and inflammation as determined by quantitative real-time PCR, western blot, and immunohistochemistry. Small interfering RNA (siRNA) against HDAC6 or Smad3 attenuated hypertensive stimuli-induced fibrosis and inflammation, whereas Smad2 siRNA failed to inhibit fibrosis. Interestingly, the combination of the HDAC6 inhibitor and Smad3 knockdown synergistically blocked transforming growth factor beta (TGF-beta) or ANG-induced fibrosis. We also demonstrated for the first time, to our knowledge, that acetylation of collagen type I can be regulated by HDAC6/p300 acetyltransferase. The chromatin immunoprecipitation assay revealed that the HDAC6 inhibitor suppressed TGF-beta-induced acetylated histone H4 or phospho-Smad2/3 to Smad3 binding elements in the fibrosis-associated gene promoters including collagen type I. These results suggest that HDAC6 may be a valuable therapeutic target for the treatment of hypertension-induced kidney fibrosis and inflammation. (C) 2015 Elsevier Inc. All rights reserved.