Key Event Title
|Level of Biological Organization|
Key Event Components
|enzyme inhibitor activity||histone deacetylase 1||decreased|
Key Event Overview
AOPs Including This Key Event
|AOP Name||Role of event in AOP|
|Histone deacetylase inhibition leading to testicular toxicity||MolecularInitiatingEvent|
|Adult, reproductively mature||Moderate|
Key Event Description
Site of action: The site of action for the molecular initiating event is a cell.
The nucleosome consists of core histones having classes of H2A, H2B, H3 and H4) [Damaskos, 2017]. DNA strand (about 200 bp) wound around the core histones, where histone deacetylase (HDAC) effects on the lysine residue of the histone to hydrolyze the acetyl residue [Damaskos, 2017]. Histone deacetylase inhibitor (HDI) inhibits HDAC and acetylate the histones and release the DNA strand to induce the binding of transcription factors [Taunton, 1996]. HDIs have potentials as anti-cancer pharmaceuticals since HDIs induce the transcriptional restoration of epigenetically silenced tumor suppressor genes by regulating acetylation of histones and non-histone proteins [Lee, 2016] [Minucci, 2006].
It is known that 18 HDAC isoforms are classified into four classes: class I HDACs (isoforms 1, 2, 3, 8), class II isoforms (4, 5, 6, 7, 9, 10) and class III HDACs (the sirtuins) and HDAC11 [Weichert, 2009, Barneda-Zahonero, 2012]. HDACs 1, 2 and 3 are ubiquitously expressed, whereas HDAC8 is predominantly expressed in cells with smooth muscle/myoepithelial differentiation [Weichert, 2009]. HDAC6 is not observed to express in lymphocytes, stromal cells and vascular endothelial cells [Weichert, 2009]. Class III HDACs sirtuins are widely expressed and localized in different cellular compartments [Barneda-Zahonero, 2012]. SirT1 is highly expressed in testis, thymus and multiple types of germ cells [Bell, 2014]. HDAC11 expression is enriched in kidney, brain, testis, heart and skeletal muscle [Barneda-Zahonero, 2012].
How It Is Measured or Detected
The measurement of HDAC inhibition monitors the decrease in histone acetylation. The measurement methods include the immunological detection of histone acetylation with anti-acetylated histone antibodies [Richon, 2004]. The histones are isolated from pellets of cells treated with HDIs, followed by acid-urea-triton gel electrophoresis, western blotting, and immunohistochemistry [Richon, 2004]. Epigenetic modifications including the histone acetylation are measured using chromatin immunoprecipitation-microarray hybridization (ChIP-chip) [ENCODE Project Consortium, 2004, Ren, 2004]. ChIP detects physical interaction between transcription factors or cofactors and the chromosome [Johnson, 2007]. The HDAC activity is measured directly with ultra high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UHPLC-ESI-MS/MS) by calculating the ratio of deacetylated peptide and acetylated peptide [Zwick, 2016].
Domain of Applicability
The inhibition of HDAC by HDIs is well conserved between species from lower organism to mammals.
- HDIs reduced lethality in Drosophila model and the HDAC activity was inhibited with HDIs in rat PC12 cells [Steffan, 2001].
- HDIs inhibited restores the rate of resorption of subretinal blebs in hyper glycemia in brown Norway rat and HDAC activity was inhibited with HDIs in human ARPE19 cells [Desjardins, 2016].
- HDIs were approved as drugs for multiple myeloma and T-cell lymphoma by FDA [Ansari, 2016].
- HDIs inhibited cell growth in human non-small cell lung cancer cell lines [Miyanaga, 2008].
- HDAC acetylation level was increased by HDIs in MRL-lpr/lpr murine model of lupus splenocytes [Mishra, 2003].
- SAHA increased histone acetylation in brain and spleen of mice [Hockly, 2003].
- MAA inhibits HDAC activity in HeLa cells and spleens from C57BL/6 mice [Jansen, 2004].
- It is also reported that MAA inhibits HDAC activity in testis cytosolic and nuclear extract of juvenile rats (27 days old) [Wade, 2008].
- VPA and TSA inhibit HDAC enzymatic activity in mouse embryo and human HeLa cell nuclear extract [Di Renzo, 2007].
- HDAC inhibitors, phenylbutyrate (PB) (2 mM) and TSA (200 nM) acetylate histones H3 and H4 in synovial cells from rats with adjuvant arthritis [Chung, 2003].
Evidence for Perturbation by Stressor
Overview for Molecular Initiating Event
HDIs are classified according to chemical nature and mode of mechanism: the short chain fatty acids (e.g., butyrate, valproate), hydroxamic acids (e.g., suberoylanilide hydroxamic acid or SAHA, Trichostatin A or TSA), cyclic tetrapeptides (e.g., FK-228), benzamides (e.g., N-acetyldinaline and MS-275) and epoxides (depeudecin, trapoxin A) [Richon, 2004, Ropero, 2007, Villar-Garea, 2004]. There is a report showing that TSA and butyrate competitively inhibits HDAC activity [Sekhavat, 2007]. HDIs inhibit preferentially HDACs with some selectiveness [Hu, 2003]. TSA inhibits HDAC1, HDAC3 and HDAC8, whereas MS-27-275 has inhibitory effect for HDAC1 and HDAC3 (IC50 value of ~0.2 mM and ~8 mM, respectively), but no effect for HDAC8 (IC50 value >10 mM) [Hu, 2003]. TSA inhibits HDAC1, 2, 3 of class I HDACs. HDAC 1, 4, 6 are related to tumor size [Damaskos, 2016]. MAA (2 or 5 mM) inhibited HDAC activity in dose-response manner in rat testis cytosolic and nuclear extracts [Wade, 2008].
Damaskos C. et al. (2017) Histone deacetylase inhibitors: an attractive therapeutic strategy against breast cancer. Anticancer Research 37: 35-46.
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Lee SC. et al. (2016) Essential role of insulin-like growth factor 2 in resistance to histone deacetylase inhibitor. Oncogene 35:5515-5526.
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Bell EL et al. (2014) SirT1 is required in the male germ cell for differentiation and fecundity in mice. Development 141:3495-3504
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Johnson DS et al. (2007) Genome-wide mapping of in vivo protein-DNA interactions. Science 316:1497-1502
Zwick V et al. (2016) Cell-based multi-substrate assay coupled to UHPLC-ESI-MS/MS for a quick identification of class-specific HDAC inhibitors. J Enzyme Inhib Med Chem 31: 209-214
Steffan JS et al. (2001) Histone deacetylase inhibitors arrest polyglutamine-dependent neurodegeneration in Drosophila. Nature 413:739-743
Desjardins D et al. (2016) Histone deacetylase inhibition restores retinal pigment epithelium function in hyperglycemia. PLoS ONE 11: e0162596
Ansari J et al. (2016) Epigenetics in non-small cell lung cancer: from basics to therapeutics. Transl Lung Cancer Res 5:155-171
Miyanaga A et al. (2008) Antitumor activity of histone deacetylase inhibitors in non-small cell lung cancer cells: development of a molecular predictive model. Mol Cancer Ther 7:1923-1930
Mishra N et al. (2003) Histone deacetylase inhibitors modulate renal disease in the MRL-lpr/lpr mouse. J Clin Invest 111: 539-552
Hockly E et al. (2003) Suberoylanilide hydroxamic acid, a histone deacetylase inhibitor, ameliorates motor deficits in a mouse model of Huntington’s disease. Proc Nat Acad Sci 100:2041-2046
Jansen MS et al. (2014) Short-chain fatty acids enhance nuclear receptor activity through mitogen-activated protein kinase activation and histone deacetylase inhibition Proc Natl Acad Sci USA 101:7199-7204
Wade MG et al. (2008) Methoxyacetic acid-induced spermatocyte death is associated with histone hyperacetylation in rats. Biol Reprod 78:822-831
Di Renzo F et al. (2007) Boric acid inhibits embryonic histone deacetylases: A suggested mechanism to explain boric acid-related teratogenicity. Toxicol and Appl Pharmacol 220:178-185
Chung YL et al. (2003) A therapeutic strategy uses histone deacetylase inhibitors to modulate the expression of genes involved in the pathogenesis of rheumatoid arthritis. Mol Ther 8:707-717
Ropero S and Esteller M. (2007) The role of histone deacetylases (HDACs) in human cancer. Mol Oncol 1:19-25
Villae-Garea A and Esteller M. (2004) Histone deacetylase inhibitors: understanding a new wave of anticancer agents. Int J Cancer 112:171-178
Sekhavat A et al. (2007) Competitive inhibition of histone deacetylase activity by trichostatin A and butyrate. Biochemistry and Cell Biology 85:751-758
Hu E et al. (2003) Identification of novel isoform-selective inhibitors within class I histone deacetylases. J Pharmacol Exp Ther 307:720-728
Damaskos C et al. (2016) Histone deacetylase inhibitors: a novel therapeutic weapon against medullary thyroid cancer? Anticancer Res 36:5019-5024