Inhibitors of zinc-dependent histone deacetylases (HDACs) profoundly affect cellular function by altering gene expression via changes in nucleosomal histone tail acetylation. Historically, investigators have employed pan-HDAC inhibitors, such as the hydroxamate trichostatin A (TSA), which simultaneously targets members of each of the three zinc-dependent HDAC classes (classes I, II, and IV). More recently, class- and isoform-selective HDAC inhibitors have been developed, providing invaluable chemical biology probes for dissecting the roles of distinct HDACs in the control of various physiologic and pathophysiological processes. For example, the benzamide class I HDAC-selective inhibitor, MGCD0103 [N-(2-aminophenyl)-4-[[(4-pyridin-3-ylpyrimidin-2-yl)amino]methyl] benzamide], was shown to block cardiac fibrosis, a process involving excess extracellular matrix deposition, which often results in heart dysfunction. Here, we compare the mechanisms of action of structurally distinct HDAC inhibitors in isolated primary cardiac fibroblasts, which are the major extracellular matrix–producing cells of the heart. TSA, MGCD0103, and the cyclic peptide class I HDAC inhibitor, apicidin, exhibited a common ability to enhance histone acetylation, and all potently blocked cardiac fibroblast cell cycle progression. In contrast, MGCD0103, but not TSA or apicidin, paradoxically increased expression of a subset of fibrosis-associated genes. Using the cellular thermal shift assay, we provide evidence that the divergent effects of HDAC inhibitors on cardiac fibroblast gene expression relate to differential engagement of HDAC1- and HDAC2-containing complexes. These findings illustrate the importance of employing multiple compounds when pharmacologically assessing HDAC function in a cellular context and during HDAC inhibitor drug development.
- Received September 10, 2016.
- Accepted January 23, 2017.
K.B.S. and M.S.S. contributed equally to this work.
This research was supported by the National Institutes of Health National Heart, Lung and Blood Institute [Grants R01HL116848 and R01HL127240 (to T.A.M.), T32 Training Grants 5T32HL007822-12 (to K.B.S.) and 5T32HL007822 (to M.S.S.), and F32 Fellowship F32HL126354 (to M.S.S.)]; the National Institutes of Health National Institute on Aging [Grant R21AG043822 (to T.A.M.)]; and the American Heart Association [Grant 16SFRN31400013 (to T.A.M.)].
- Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics