Histone Acetylation Dynamics during In Vivo and In Vitro Oocyte Aging in Common Carp Cyprinus carpio

Aging is the most critical factor that influences the quality of post-ovulatory oocytes. Age-related molecular pathways remain poorly understood in fish oocytes. In this study, we examined the effect of oocyte aging on specific histone acetylation in common carp Cyprinus carpio. The capacity to progress to the larval stage in oocytes that were aged for 28 h in vivo and in vitro was evaluated. Global histone modifications and specific histone acetylation (H3K9ac, H3K14ac, H4K5ac, H4K8ac, H4K12ac, and H4K16ac) were investigated during oocyte aging. Furthermore, the activity of histone acetyltransferase (HAT) was assessed in fresh and aged oocytes. Global histone modifications did not exhibit significant alterations during 8 h of oocyte aging. Among the selected modifications, H4K12ac increased significantly at 28 h post-stripping (HPS). Although not significantly different, HAT activity exhibited an upward trend during oocyte aging. Results of our current study indicate that aging of common carp oocytes for 12 h results in complete loss of egg viability rates without any consequence in global and specific histone modifications. However, aging oocytes for 28 h led to increased H4K12ac. Thus, histone acetylation modification as a crucial epigenetic mediator may be associated with age-related defects, particularly in oocytes of a more advanced age.     

Inhibition of Histone Deacetylase by Butyrate Protects Rat Liver from Ischemic Reperfusion Injury

We showed previously that pretreatment of butyrate, which is an endogenous histone deacetylase (HDAC) inhibitor normally fermented from undigested fiber by intestinal microflora, seriously alleviated ischemia reperfusion (I/R)-induced liver injury by inhibiting the nuclear factor κB (NF-κB) pathway. The goal of this study was to investigate the effect of butyrate administrated at the onset of ischemia for HDAC inhibition in hepatic I/R injury. Sprague Dawley rats were subjected to warm ischemia for 60 min followed by 6 and 24 h of reperfusion. Butyrate was administrated at the onset of ischemia. Liver injury was evaluated by serum levels of aminotransferase, inflammatory factors, and histopathology. The levels of acetylated histone H3 and expression of heat shock protein (Hsp) 70 were measured by Western blot. After reperfusion, the levels of acetylated histone H3 significantly decreased. Butyrate treatment markedly prevented the reduction of acetylated histone H3 and upregulated the expression of Hsp70, thereby reducing liver injury. Our study demonstrated that I/R resulted in marked reduction of histone acetylation; butyrate exerted a great hepatoprotective effect through HDAC inhibition and Hsp70 induction.     

Epigenetic Targeting of Histone Deacetylases in Diagnostics and Treatment of Depression

Depression is a highly prevalent, disabling, and often chronic illness that places substantial burdens on patients, families, healthcare systems, and the economy. A substantial minority of patients are unresponsive to current therapies, so there is an urgent need to develop more broadly effective, accessible, and tolerable therapies. Pharmacological regulation of histone acetylation level has been investigated as one potential clinical strategy. Histone acetylation status is considered a potential diagnostic biomarker for depression, while inhibitors of histone deacetylases (HDACs) have garnered interest as novel therapeutics. This review describes recent advances in our knowledge of histone acetylation status in depression and the therapeutic potential of HDAC inhibitors.     

Histone Deacetylase (HDAC) Inhibitors Down-Regulate Endothelial Lineage Commitment of Umbilical Cord Blood Derived Endothelial Progenitor Cells

To test the involvement of histone deacetylases (HDACs) activity in endothelial lineage progression, we investigated the effects of HDAC inhibitors on endothelial progenitors cells (EPCs) derived from umbilical cord blood (UCB). Adherent EPCs, that expressed the endothelial marker proteins (PCAM-1, CD105, CD133, and VEGFR₂) revealed by flow cytometry were treated with three HDAC inhibitors: Butyrate (BuA), Trichostatin A (TSA), and Valproic acid (VPA). RT-PCR assay showed that HDAC inhibitors down-regulated the expression of endothelial genes such as VE-cadherin, CD133, CXCR4 and Tie-2. Furthermore, flow cytometry analysis illustrated that HDAC inhibitors selectively reduce the expression of VEGFR₂, CD117, VE-cadherin, and ICAM-1, whereas the expression of CD34 and CD45 remained unchanged, demonstrating that HDAC is involved in endothelial differentiation of progenitor cells. Real-Time PCR demonstrated that TSA down-regulated telomerase activity probably via suppression of hTERT expression, suggesting that HDAC inhibitor decreased cell proliferation. Cell motility was also decreased after treatment with HDAC inhibitors as shown by wound-healing assay. The balance of acethylation/deacethylation kept in control by the activity of HAT (histone acetyltransferases)/HDAC enzymes play an important role in differentiation of stem cells by regulating proliferation and endothelial lineage commitment.     

Histone Deacetylase Inhibitors as Multitarget Ligands: New Players in Alzheimer's Disease Drug Discovery?

Histone deacetylase inhibitors (HDACIs) are responsible for controlling gene expression by modulating the acetylation status of histone proteins. Furthermore, they modulate the activity of cytoplasmic non-histone proteins. Due to the involvement of HDACs in neurodevelopment, memory formation, and cognitive processes, HDACIs have been suggested as innovative agents for the treatment of neurodegenerative disorders such as Alzheimer's disease (AD). Given their mechanisms of action and the complex nature of AD, HDACIs have been proposed for the design of novel multitarget ligands (MTLs). To this aim, the fragment responsible for HDAC inhibition has been coupled with other structures that are able to provide additional biological actions, such as antioxidant activity or the inhibition of phosphodiesterase 5, transglutaminase 2, and glycogen synthase kinase 3β. Herein we discuss recent efforts to design HDACI-based MTLs as potential disease-modifying entities.     

Natural Products as Zinc‐Dependent Histone Deacetylase Inhibitors

Zinc‐dependent histone deacetylases (HDACs), a family of hydrolases that remove acetyl groups from lysine residues, play an important role in the regulation of multiple processes, from gene expression to protein activity. The dysregulation of HDACs is associated with many diseases including cancer, neurological disorders, cellular metabolism disorders, and inflammation. Molecules that act as HDAC inhibitors (HDACi) exhibit a variety of related bioactivities. In particular, HDACi have been applied clinically for the treatment of cancers. Inhibition through competitive binding of the catalytic domain of these enzymes has been achieved by a diverse array of small‐molecule chemotypes, including a number of natural products. This review provides a systematic introduction of natural HDACi, with an emphasis on their enzyme inhibitory potency, selectivity, and biological activities, highlighting their various binding modes with HDACs.     

Peptide-Based 2-Aminophenylamide Probes for Targeting Endogenous Class I Histone Deacetylase Complexes

Lysine deacetylases or histone deacetylases (HDACs) remove acetylation markers from numerous cellular proteins, thereby regulating their function and activity. Recently established peptide probes containing the HDAC-trapping amino acid α-aminosuberic acid ω-hydroxamate (AsuHd) have been used to investigate the compositions of HDAC complexes in a site-specific manner. Here we report the new HDAC-trapping amino acid 2-amino-8-[(2-aminophenyl)amino]-8-oxooctanoic acid (AsuApa) and the utility of AsuApa-containing probes for HDAC complex profiling on a proteome-wide scale. Unlike AsuHd-containing probes, AsuApa enriched only HDACs 1, 2, and 3 efficiently and was the most potent probe tested for capturing the last of these. These findings indicate that the inherent specificity of reported small-molecule pimelic diphenylamide HDAC inhibitors is preserved in AsuApa and that this HDAC-trapping amino acid represents a potent tool for investigating class I HDAC complexes.     

Design,Synthesis, and Biological Evaluation of New Urushiol Derivatives as Potent Class I Histone Deacetylase Inhibitors

In the present study, a novel series of 11 urushiol-based hydroxamic acid histone deacetylase (HDAC) inhibitors was designed, synthesized, and biologically evaluated. Compounds 1 – 11 exhibited good to excellent inhibitory activities against HDAC1/2/3 (IC₅₀: 42.09–240.17 nM) and HDAC8 (IC₅₀: 16.11–41.15 nM) in vitro, with negligible activity against HDAC6 (>1409.59 nM). Considering HDAC8, docking experiments revealed some important features contributing to inhibitory activity. According to Western blot analysis, select compounds could notably enhance the acetylation of histone H3 and SMC3 but not-tubulin, indicating their privileged structure is appropriate for targeting class I HDACs. Furthermore, antiproliferation assays revealed that six compounds exerted greater in vitro antiproliferative activity against four human cancer cell lines (A2780, HT-29, MDA-MB-231, and HepG2, with IC₅₀ values ranging from 2.31–5.13 μM) than suberoylanilide hydroxamic acid; administration of these compounds induced marked apoptosis in MDA-MB-231 cells, with cell cycle arrest in the G2/M phase. Collectively, specific synthesized compounds could be further optimized and biologically explored as antitumor agents.     

Increased Histone Deacetylase Activity Involved in the Suppressed Invasion of Cancer Cells Survived from ALA-Mediated Photodynamic Treatment

Previously, we have found that cancer cells survived from 5-Aminolevulinic acid-mediated photodynamic therapy (ALA-PDT) have abnormal mitochondrial function and suppressed cellular invasiveness. Here we report that both the mRNA expression level and enzymatic activity of histone deacetylase (HDAC) were elevated in the PDT-derived variants with dysfunctional mitochondria. The activated HDAC deacetylated histone H3 and further resulted in the reduced migration and invasion, which correlated with the reduced expression of the invasion-related genes, matrix metalloproteinase 9 (MMP9), paternally expressed gene 1 (PEG1), and miR-355, the intronic miRNA. Using chromatin immunoprecipitation, we further demonstrate the reduced amount of acetylated histone H3 on the promoter regions of MMP9 and PEG1, supporting the down-regulation of these two genes in PDT-derived variants. These results indicate that HDAC activation induced by mitochondrial dysfunction could modulate the cellular invasiveness and its related gene expression. This argument was further verified in the 51-10 cybrid cells with the 4977 bp mtDNA deletion and A375 ρ⁰ cells with depleted mitochondria. These results indicate that mitochondrial dysfunction might suppress tumor invasion through modulating histone acetylation.     

Synthesis of N‐Hydroxycinnamides Capped with a Naturally Occurring Moiety as Inhibitors of Histone Deacetylase

Histone deacetylase (HDAC) inhibitors are regarded as promising therapeutics for the treatment of cancer. All reported HDAC inhibitors contain three pharmacophoric features: a zinc‐chelating group, a hydrophobic linker, and a hydrophobic cap for surface recognition. In this study we investigated the effectiveness of osthole, a hydrophobic Chinese herbal compound, as the surface recognition cap in hydroxamate‐based compounds as inhibitors of HDAC. Nine novel osthole‐based N‐hydroxycinnamides were synthesized and screened for enzyme inhibition activity. Compounds 9 d , 9 e , 9 g exhibited inhibitory activities (IC₅₀=24.5, 20.0, 19.6 nM ) against nuclear HDACs in HeLa cells comparable to that of suberoylanilide hydroxamic acid (SAHA; IC₅₀=24.5 nM ), a potent inhibitor clinically used for the treatment of cutaneous T‐cell lymphoma (CTCL). While compounds 9 d and 9 e showed SAHA‐like activity towards HDAC1 and HDAC6, compound 9 g was more selective for HDAC1. Compound 9 d exhibited the best cellular effect, which was comparable to that of SAHA, of enhancing acetylation of either α‐tubulin or histone H3. Molecular docking analysis showed that the osthole moiety of compound 9 d may interact with the same hydrophobic surface pocket exploited by SAHA and it may be modified to provide class‐specific selectivity. These results suggest that osthole is an effective hydrophobic cap when incorporated into N‐hydroxycinnamide‐derived HDAC inhibitors.     

Structure-Based Inhibitor Discovery of Class I Histone Deacetylases (HDACs)

Class I histone deacetylases (HDACs) are promising targets for epigenetic therapies for a range of diseases such as cancers, inflammations, infections and neurological diseases. Although six HDAC inhibitors are now licensed for clinical treatments, they are all pan-inhibitors with little or no HDAC isoform selectivity, exhibiting undesirable side effects. A major issue with the currently available HDAC inhibitors is that they have limited specificity and target multiple deacetylases. Except for HDAC8, Class I HDACs (1, 2 and 3) are recruited to large multiprotein complexes to function. Therefore, there are rising needs to develop new, hopefully, therapeutically efficacious HDAC inhibitors with isoform or complex selectivity. Here, upon the introduction of the structures of Class I HDACs and their complexes, we provide an up-to-date overview of the structure-based discovery of Class I HDAC inhibitors, including pan-, isoform-selective and complex-specific inhibitors, aiming to provide an insight into the discovery of additional HDAC inhibitors with greater selectivity, specificity and therapeutic utility.     

Recurrent Herpes Simplex Virus Type 1 (HSV-1) Infection Modulates Neuronal Aging Marks in In Vitro and In Vivo Models

Herpes simplex virus 1 (HSV-1) is a widespread neurotropic virus establishing a life-long latent infection in neurons with periodic reactivations. Recent studies linked HSV-1 to neurodegenerative processes related to age-related disorders such as Alzheimer’s disease. Here, we explored whether recurrent HSV-1 infection might accelerate aging in neurons, focusing on peculiar marks of aged cells, such as the increase in histone H4 lysine (K) 16 acetylation (ac) (H4K16ac); the decrease of H3K56ac, and the modified expression of Sin3/HDAC1 and HIRA proteins. By exploiting both in vitro and in vivo models of recurrent HSV-1 infection, we found a significant increase in H4K16ac, Sin3, and HDAC1 levels, suggesting that the neuronal response to virus latency and reactivation includes the upregulation of these aging markers. On the contrary, we found a significant decrease in H3K56ac that was specifically linked to viral reactivation and apparently not related to aging-related markers. A complex modulation of HIRA expression and localization was found in the brain from HSV-1 infected mice suggesting a specific role of this protein in viral latency and reactivation. Overall, our results pointed out novel molecular mechanisms through which recurrent HSV-1 infection may affect neuronal aging, likely contributing to neurodegeneration.     

The Selective Histone Deacetylase Inhibitor MI192 Enhances the Osteogenic Differentiation Efficacy of Human Dental Pulp Stromal Cells

The use of human dental pulp stromal cells (hDPSCs) has gained increasing attention as an alternative stem cell source for bone tissue engineering. The modification of the cells’ epigenetics has been found to play an important role in regulating differentiation, with the inhibition of histone deacetylases 3 (HDAC3) being linked to increased osteogenic differentiation. This study aimed to induce epigenetic reprogramming using the HDAC2 and 3 selective inhibitor, MI192 to promote hDPSCs osteogenic capacity for bone regeneration. MI192 treatment caused a time–dose-dependent change in hDPSC morphology and reduction in viability. Additionally, MI192 successfully augmented hDPSC epigenetic functionality, which resulted in increased histone acetylation and cell cycle arrest at the G₂/M phase. MI192 pre-treatment exhibited a dose-dependent effect on hDPSCs alkaline phosphatase activity. Quantitative PCR and In-Cell Western further demonstrated that MI192 pre-treatment significantly upregulated hDPSCs osteoblast-related gene and protein expression (alkaline phosphatase, bone morphogenic protein 2, type I collagen and osteocalcin) during osteogenic differentiation. Importantly, MI192 pre-treatment significantly increased hDPSCs extracellular matrix collagen production and mineralisation. As such, for the first time, our findings show that epigenetic reprogramming with the HDAC2 and 3 selective inhibitor MI192 accelerates the osteogenic differentiation of hDPSCs, demonstrating the considerable utility of this MSCs engineering approach for bone augmentation strategies.