Histone Deacetylase Inhibitors: New Hope for Rheumatoid Arthritis?

Dried Blood Spots as Matrix for Evaluation of Valproate Levels and the Immediate and Delayed Metabolomic Changes Induced by Single Valproate Dose Treatment

The immediate and delayed metabolic changes in rats treated with valproate (VPA), a drug used for the treatment of epilepsy, were profiled. An established approach using dried blood spots (DBS) as sample matrices for gas chromatography/mass spectrometry-based metabolomics profiling was modified using double solvents in the extraction of analytes. With the modified method, some of the previously undetectable metabolites were recovered and subtle differences in the metabolic changes upon exposure to a single dose of VPA between males and female rats were identified. In male rats, changes in 2-hydroxybutyric acid, pipecolic acid, tetratriacontane and stearic acid were found between the control and treatment groups at various time points from 2.5 h up to 24 h. In contrast, such differences were not observed in female rats, which could be caused by the vast inter-individual variations in metabolite levels within the female group. Based on the measured DBS drug concentrations, clearance and apparent volume of distribution of VPA were estimated and the values were found to be comparable to those estimated previously from full blood drug concentrations. The current study indicated that DBS is a powerful tool to monitor drug levels and metabolic changes in response to drug treatment.

Therapeutic potential of CKD-506, a novel selective histone deacetylase 6 inhibitor, in a murine model of rheumatoid arthritis

OBJECTIVES

Histone deacetylase (HDAC) 6 promotes inflammation. We investigated the anti-arthritic effects of CKD-506, a novel HDAC6 inhibitor, in vitro and in a murine model of arthritis as a novel treatment option for rheumatoid arthritis (RA).

METHODS

HDAC6 was overexpressed in mouse peritoneal macrophages and RAW 264.7 cells, and the effects of a HDAC6 inhibitor CKD-506 on cytokine production and activity of NF-κB and AP-1 signaling were examined. Peripheral blood mononuclear cells (PBMCs) from RA patients and fibroblast-like synoviocytes (FLS) were activated in the presence of CKD-506. Next, regulatory T cells (Tregs) were induced from RA patients and co-cultured with healthy effector T cells (Teffs) and cell proliferation was analyzed by flow cytometry. Finally, the effects of the inhibitor on the severity of arthritis were assessed in a murine model of adjuvant-induced arthritis (AIA).

RESULTS

Overexpression of HDAC6 induced macrophages to produce TNF-α and IL-6. The inhibitory effect of CKD-506 was mediated via blockade of NF-κB and AP-1 activation. HDAC6 inhibition reduced TNF-α and IL-6 production by activated RA PBMCs. CKD-506 inhibited production of MMP-1, MMP-3, IL-6, and IL-8 by activated FLS. In addition, CKD-506 inhibited proliferation of Teffs directly and indirectly by improving iTreg function. In AIA rats, oral CKD-506 improved clinical arthritis in a dose-dependent manner. A combination of sub-therapeutic CKD-506 and methotrexate exerted a synergistic effect.

CONCLUSION

The novel HDAC6 inhibitor CKD-506 suppresses inflammatory responses by monocytes/macrophages, improves Treg function, and ameliorates arthritis severity in a murine model of RA. Thus, CKD-506 might be a novel and effective treatment option for RA.

Impact of glucocorticoids on systemic sirtuin 1 expression and activity in rats with adjuvant-induced arthritis

The class III histone deacetylase sirtuin 1 (SIRT1) plays a pivotal role in numerous biological and physiological functions, including inflammation. An association between SIRT1 and proinflammatory cytokines might exist. In addition to their important role in inflammation associated with rheumatoid arthritis (RA), proinflammatory cytokines mediate the development of systemic effects. Here, we evaluated systemic SIRT1 expression and enzymatic activity, in peripheral blood mononuclear cells (PBMCs) and in liver isolated from rats with adjuvant-induced arthritis (AIA), treated or not with low or high doses of glucocorticoids (GCs). We also measured the production of tumour necrosis factor alpha (TNF) and interleukin-1 beta (IL-1 beta) in PBMCs and liver. We found that SIRT1 expression and activity increased in PBMCs of AIA rats compared to healthy controls and decreased under GC treatment. Similarly, we observed an increased SIRT1 activity in the liver of AIA rats compared to healthy controls which decreased under high doses of GCs. We also found an increase in IL-1 beta and TNF levels in the liver of AIA rats compared to healthy controls, which decreased under high doses of GC. We did not observe a significant correlation between SIRT1 activity and proinflammatory cytokine production in PBMC or liver. In contrast, a strong positive correlation was found between the liver levels of TNF and IL-1 beta (rho=0.9503, p=7.5x10^-21). Our results indicate that increased inflammation in AIA rats compared to healthy control is accompanied by an increased SIRT1 activity in both PBMCs and liver, which could be decreased under GC treatment.

Novel candidate drugs in anti-tumor necrosis factor refractory Crohn's diseases: in silico study for drug repositioning

Biologicals like anti-tumor necrosis factor (TNF) therapy for Crohn's disease (CD) are safe and effective but there is a significant rate of primary and secondary nonresponse in the patients. In this study, we applied a computational approach to discover novel drug therapies for anti-TNF refractory CD in silico. We use a transcriptome dataset (GSE100833) for the anti-TNF refractory CD patients from NCBI GEO. After co-expression analysis, we specifically investigated the extent of protein-protein interactions among genes in clusters based on a protein-protein interaction database, STRING. Pathway analysis was performed using the clEnrich function based on KEGG gene sets. Co-expressed genes in cluster 1, 2, 3, 4, up or down-regulated genes and all differentially expressed genes are highly connected. Among them, cluster 1, which is highly enriched for chemokine signaling, also showed enrichment for cytokine-cytokine receptor interaction and identifies several drugs including cyclosporin with known efficacy in CD. Vorinostat, histone deacetylase inhibitors, and piperlongumine, which is known to have inhibitory effect on activity of NF-κB, were also identified. Some alkaloids were also selected as potential therapeutic drugs. These finding suggest that they might serve as a novel therapeutic option for anti-TNF refractory CD and support the use of public molecular data and computational approaches to discover novel therapeutic options for CD.

Targeting Histone Deacetylases to Modulate Graft-Versus-Host Disease and Graft-Versus-Leukemia

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the main therapeutic strategy for patients with both malignant and nonmalignant disorders. The therapeutic benefits of allo-HSCT in malignant disorders are primarily derived from the graft-versus-leukemia (GvL) effect, in which T cells in the donor graft recognize and eradicate residual malignant cells. However, the same donor T cells can also recognize normal host tissues as foreign, leading to the development of graft-versus-host disease (GvHD), which is difficult to separate from GvL and is the most frequent and serious complication following allo-HSCT. Inhibition of donor T cell toxicity helps in reducing GvHD but also restricts GvL activity. Therefore, developing a novel therapeutic strategy that selectively suppresses GvHD without affecting GvL is essential. Recent studies have shown that inhibition of histone deacetylases (HDACs) not only inhibits the growth of tumor cells but also regulates the cytotoxic activity of T cells. Here, we compile the known therapeutic potential of HDAC inhibitors in preventing several stages of GvHD pathogenesis. Furthermore, we will also review the current clinical features of HDAC inhibitors in preventing and treating GvHD as well as maintaining GvL.

Anti-rheumatic activity of Phenethyl isothiocyanate via inhibition of histone deacetylase-1

Rheumatoid Arthritis (RA) affects approximately 1% of the total world population. Despite incessant research and development of new therapeutic agents, management of RA is still a troublesome affair. Histone Deacetylase 1 (HDAC1) is an epigenetic regulator which play important role in pathogenesis of RA. In present study, we hypothesized that Phenethyl isothiocyanate (PEITC), a potent inhibitor of HDAC1, may ameliorate RA. Efficacy of PEITC was evaluated in Complete Freund's Adjuvant (CFA) induced arthritis model in rats. CFA (0.1 ml) was injected subplantarly in the left hind paw on day 0 to all the groups except normal control. The administration of test drug PEITC (10, 24 & 50 mg/kg) and standard drug Ibuprofen started simultaneously and was continued for 21 days. Paw edema, total arthritic index, mobility score, stair climbing ability, behavioral parameters, and bone erosion were evaluated. Further, radiographic studies, TNF-alpha as well as HDAC1 levels in synovial tissue homogenate and histological analysis were performed. Prophylactic treatment of PEITC attenuated paw edema, total arthritic index, mobility score, stair climbing ability, behavioral parameters, and bone erosion in dose dependent manner. Furthermore, there was significant decrease in TNF-alpha as well as HDAC1 levels in synovial tissue homogenate. Histological analysis revealed no cartilage damage, bone erosion, hyperplasia at synovial lining as well as infiltration of inflammatory cells in treatment group. Results of this study suggest potent anti-rheumatoid arthritis activity of Phenethyl isothiocyanate in CFA induced RA model in rats.

Sodium Butyrate Ameliorates Intestinal Injury and Improves Survival in a Rat Model of Cecal Ligation and Puncture-Induced Sepsis

Sepsis is a life-threatening condition with a high rate of mortality. Unfortunately, very few therapies can improve outcomes in patients with sepsis. Butyrate, which is the most potent histone deacetylase (HDAC) inhibitor among short-chain fatty acids, exerts anti-inflammatory effects in a variety of inflammatory diseases. Butyrate might thus be valuable in the treatment of sepsis, in which inhibition of overwhelming cytokine release is vitally important. Sepsis was induced in 7- to 8-week-old Sprague-Dawley rats by cecal ligation and puncture (CLP) with a 21-g double-puncture technique. Rats received an intravenous injection of normal saline (vehicle) or sodium butyrate (200 mg/kg) after CLP and were sacrificed 12 h later. Hematoxylin and eosin staining was performed to observe the intestinal mucosal morphology. RT-PCR and ELISA were used to determine the intestinal inflammatory response in vivo. Intestinal permeability was evaluated by measuring fluorescein isothiocyanate dextran (FD-4) absorption in vivo, and tight junction protein expression was examined by western blot. NF-κB p65 activities were assessed by western blot and immunohistochemistry. Sodium butyrate treatment improved the survival rate of CLP rats and alleviated sepsis-induced intestinal mucosal injury. Proinflammatory cytokine expression was lower in butyrate-treated rats than in the vehicle group. FD-4 leakage from the intestinal tract was reduced, and the expression levels of the tight junction proteins claudin-1 and ZO-1 were also restored in rats that received sodium butyrate treatment. These effects were associated with less NF-κB p65 nuclear translocation, whereas the expression of Iκ-Bα was not affected or even increased. Sodium butyrate mitigates the inflammatory response and maintains intestinal barrier function in polymicrobial sepsis partly through inhibition of NF-κB activation and may serve as a novel therapy for sepsis.

DNA Methylation-Governed Gene Expression in Autoimmune Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease hallmarked by progressive and irreversible joint destruction. RA pathogenesis is a T cell-regulated and B cell-mediated process in which activated lymphocyte-produced chemokines and cytokines promote leukocyte infiltration that ultimately leads to destruction of the joints. There is an obvious need to discover new drugs for RA treatment that have different biological targets or modes of action than the currently employed therapeutics. Environmental factors such as cigarette smoke, certain diet components, and oral pathogens can significantly affect gene regulation via epigenetic factors. Epigenetics opened a new field for pharmacology, and DNA methylation and histone modification-implicated factors are feasible targets for RA therapy. Exploring RA pathogenesis involved epigenetic factors and mechanisms is crucial for developing more efficient RA therapies. Here we review epigenetic alterations associated with RA pathogenesis including DNA methylation and interacting factors. Additionally, we will summarize the literature revealing the involved molecular structures and interactions. Finally, potential epigenetic factor-based therapies will be discussed that may help in better management of RA in the future.

miR-138 activates NF-κB signaling and PGRN to promote rheumatoid arthritis via regulating HDAC4

BACKGROUND

Rheumatoid arthritis (RA) is a common immune-related disease worldwide, which is characterized by impaired fibroblast-like synoviocytes (FLS) proliferation and increased release of inflammatory cytokines. Unfortunately, the detailed mechanism by which miR-138-modulated rheumatoid arthritis has not been fully understood.

METHODS

RT-qPCR was used to examined mRNA level of various genes and western blot was utilized to probe protein level of acetylated H3, p-p62 and IκBα. For cytokines detection, we used ELISA method to measure the extracellular level of these cytokines. Bioinformatic tool and dual-luciferase reporter assay were employed to predict and confirm the downstream target of miR-138.

RESULTS

miR-138 was upregulated in serum and synovial tissues of RA patients. Moreover, Increased miR-138 was observed in LPS-treated FLS cells. HDAC4 was shown as the direct target of miR-138 and could be negatively regulated by miR-138. miR-138 and HDAC4 were involved in RA-related inflammatory cytokines release of FLS cells. Next, we revealed NF-κB and PGRN were significantly modulated by HDAC4 and miR-138 in an acetylation-dependent manner. More importantly, IκBα depletion and PGRN overexpression had the ability to rescue miR-138 inhibitor-attenuated inflammatory cytokines release of FLS cells.

CONCLUSION

Here, we reveal miR-138 regulates RA-related inflammatory cytokines in rheumatoid arthritis through HDAC4/PGRN or HDAC4/NF-κB. Our findings uncover a new molecular mechanism implicated in rheumatoid arthritis, which may accelerate development of therapeutical strategy by targeting this mechanism.

Therapeutic potential of selective histone deacetylase 3 inhibition

Histone deacetylases (HDACs) are closely related to the occurrence and development of a variety of diseases, such as tumor, inflammation, diabetes mellitus, cardiovascular and neurodegenerative diseases. Inhibition of HDACs by developing HDAC inhibitors has achieved significant progress in the treatment of diseases caused by epigenetic abnormalities, and especially in the cancer therapy. Isoform selective HDAC inhibitors are emphasized to be disease specific and have less off-target effects and better safety performances. HDAC3 has been illustrated to play specific role in the development of several diseases, and the discovery of HDAC3 selective inhibitors has exhibited potential in the targeted disease treatment. Herein, we summarize the current knowledge about the prospects of selective inhibition of HDAC3 for the drug development.

Histone deacetylases (HDAC) in physiological and pathological bone remodelling

Histone deacetylases (HDACs)² play important roles in the epigenetic regulation of gene expression in cells and are emerging therapeutic targets for treating a wide range of diseases. HDAC inhibitors (HDACi)³ that act on multiple HDAC enzymes have been used clinically to treat a number of solid and hematological malignancies. HDACi are also currently being studied for their efficacy in non-malignant diseases, including pathologic bone loss, but this has necessitated a better understanding of the roles of individual HDAC enzymes, particularly the eleven zinc-containing isozymes. Selective isozyme-specific inhibitors currently being developed against class I HDACs (1, 2, 3 and 8) and class II HDACs (4, 5, 6, 7, 9 and 10) will be valuable tools for elucidating the roles played by individual HDACs in different physiological and pathological settings. Isozyme-specific HDACi promise to have greater efficacy and reduced side effects, as required for treating chronic disease over extended periods of time. This article reviews the current understanding of roles for individual HDAC isozymes and effects of HDACi on bone cells, (osteoblasts, osteoclasts and osteocytes), in relation to bone remodelling in conditions characterised by pathological bone loss, including periodontitis, rheumatoid arthritis and myeloma bone disease.

Largazole Analogues Embodying Radical Changes in the Depsipeptide Ring: Development of a More Selective and Highly Potent Analogue

A number of analogues of the marine-derived histone deacetylase inhibitor largazole incorporating major structural changes in the depsipeptide ring were synthesized. Replacing the thiazole-thiazoline fragment of largazole with a bipyridine group gave analogue 7 with potent cell growth inhibitory activity and an activity profile similar to that of largazole, suggesting that conformational change accompanying switching hybridization from sp³ to sp² at C-7 is well tolerated. Analogue 7 was more class I selective compared to largazole, with at least 464-fold selectivity for class I HDAC proteins over class II HDAC6 compared to a 22-fold selectivity observed with largazole. To our knowledge 7 represents the first example of a potent and highly cytotoxic largazole analogue not containing a thiazoline ring. The elimination of a chiral center derived from the unnatural amino acid R-α-methylcysteine makes the molecule more amenable to chemical synthesis, and coupled with its increased class I selectivity, 7 could serve as a new lead compound for developing selective largazole analogues.

Enhanced in vitro cytotoxicity and anti-tumor activity of vorinostat-loaded pluronic micelles with prolonged release and reduced hepatic and renal toxicities

Vorinostat is the first histone deacetylase inhibitor approved by US FDA for use in cancer therapy. However, its limited aqueous solubility, low permeability, and suboptimal pharmacokinetics hinder its delivery. Thus, in this study, micelles of vorinostat with each of pluronic F68 (PF68) and pluronic F127 (PF127) were developed and optimized based on drug loading and entrapment. The optimized micelles were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), differential scanning calorimetry (DSC), zeta analyzer, and electron transmission microscopy. Their in vitro release, stability, in vitro cytotoxicity against HepG2, Caco-2, and MCF-7 cell lines, and finally, in vivo antitumor activity in mice bearing Ehrlich Ascites Carcinoma (EAC) were assessed. The highest entrapment efficiency was 99.09±2.16% and 94.19±2.37% for micelles of 1:50 drug to polymer ratio with each of PF127 and PF68, respectively. These micelles were nearly spherical with nanoscopic mean diameters of 72.61±10.66nm for PF68 and 91.88±10.70nm for PF127 with narrow size distribution. The micelles provided prolonged release at phosphate buffer saline pH7.4 up to 24h for PF68 and 72h for PF127. Potentiation of in vitro cytotoxicity of vorinostat was more pronounced with PF127 micelles particularly against MCF-7 cells. Compared with free vorinostat, the micelles with PF127 were more effective in inhibiting tumor growth as well as exhibiting significantly (p<0.05) diminished hepatic and renal toxicities. In conclusion, 1:50 vorinostat-PF127 micelles may facilitate i.v. formulations and can be suggested as a promising stable and safe nanoparticulate delivery system with prolonged release and potentiated cytotoxicity.

Epigenetic Modification Prevents Excessive Wound Healing and Scar Formation After Glaucoma Filtration Surgery

PURPOSE

The purpose of this study was to determine the efficacy of suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor (HDACi), in prevention of excessive wound healing and scar formation in a rabbit model of glaucoma filtration surgery (GFS).

METHODS

A rabbit model of GFS was used. Rabbits that underwent GFS received balanced salt solution, or SAHA (50 μM), or mitomycin C (0.02%). Clinical scores of IOP, bleb vascularity, and slit-lamp examination were performed. On postoperative day 14, rabbits were killed and the bleb tissues were collected for evaluation of tissue fibrosis with hematoxylin and eosin, Masson trichrome, α-smooth muscle actin (αSMA), and F-actin staining. Furthermore, SAHA-mediated acetylation of histones in corneal fibroblasts and conjunctiva were determined by Western blot analysis.

RESULTS

Suberoylanilide hydroxamic acid treatment after GFS showed no signs of edema, corneal opacity, endophthalmitis, or cataract formation. Morphometric analysis of SAHA-treated eyes showed higher bleb length (P < 0.001), bleb area (P < 0.05), lower IOP (P < 0.01), and decreased vascularity compared to control. Furthermore, SAHA treatment showed significantly reduced levels of αSMA (P < 0.001), F-actin (P < 0.01), and collagen deposition (P < 0.05) at the sclerotomy site. In addition, SAHA treatment increased the acetylation status of H3 and H4 histones in corneal fibroblasts and conjunctiva.

CONCLUSIONS

This study demonstrates that HDAC inhibition is an attractive pharmacologic target to modulate GFS wound healing, and SAHA, an HDACi, can be a useful adjunct to improve the GFS outcome.

A novel histone deacetylase 6-selective inhibitor suppresses synovial inflammation and joint destruction in a collagen antibody-induced arthritis mouse model

AIM

To investigate the effects of Tubastatin A, a selective histone deacetylase-6 inhibitor, on synovial inflammation and joint destruction in a collagen antibody-induced arthritis (CAIA) mouse model.

METHODS

Collagen antibody-induced arthritis mice were given daily intraperitoneal injections of various concentrations of Tubastatin A (0, 10, 50, 100 mg/kg). The clinical score and paw thickness were measured. Mice were sacrificed on day 15, and the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1 and IL-6 in the serum were analyzed using enyme-linked immunosorbent assay (ELISA). Two pathologists independently measured the synovitis score. Micro-computed tomography (CT) scans of the joints were performed to quantify joint destruction. The expression of IL-6 from human fibroblast-like synoviocytes (FLSs) after incubation with various doses of Tubastatin A (0, 0.75, 1.5, 3 μmol/L) was measured using ELISA.

RESULTS

The clinical arthritis score was significantly attenuated and paw thickness was lower in the group treated with 100 mg/kg Tubastatin A compared with those treated with vehicle alone. The synovitis score was significantly reduced in the 100 mg/kg Tubastatin A-treated group compared with the control group. Micro-CT showed that quantitative measures of joint destruction were significantly attenuated in the 100 mg/kg Tubastatin A-treated group compared with the control. The expression of IL-6 in the sera was lower in the mice treated with Tubastatin A compared with the control. The expression of IL-6 in human FLSs decreased dose-dependently after incubation with Tubastatin A without affecting cell viability.

CONCLUSIONS

Tubastatin A successfully ameliorated synovial inflammation and protected against joint destruction in CAIA mice, at least in part, by modulating IL-6 expression.

Preclinical anti-arthritic study and pharmacokinetic properties of a potent histone deacetylase inhibitor MPT0G009

The pathology of rheumatoid arthritis includes synoviocyte proliferation and inflammatory mediator expression, which may result from dysregulated epigenetic control by histone deacetylase (HDAC). Thus, HDAC inhibitors may be useful for treating inflammatory disease. This was a preclinical study of the HDAC inhibitor, MPT0G009. The IC50 values of MPT0G009 for HDAC1, 2, 3, 6 and 8 enzymatic activities were significantly lower than those for the currently marketed HDAC inhibitor suberoylanilide hydroxamic acid (SAHA; vorinostat). In addition, MPT0G009 markedly inhibited cytokine secretion and macrophage colony-stimulating factor/receptor activator of nuclear factor kappa B ligand-induced osteoclastogenesis by macrophages (50 ng/ml each). These MPT0G009 effects on cytokine secretion and osteoclast formation were reduced by the overexpression of HDAC 1 (class I HDAC) and 6 (class II HDAC) in cells, suggesting that these effects were due to the inhibition of its activity. In an in vivo rat model, oral administration of MPT0G009 (25 mg/kg) significantly inhibited paw swelling and bone destruction. Furthermore, compared with SAHA, MPT0G009 exhibited longer half-life (9.53 h for oral administration) and higher oral bioavailability (13%) in rats. These results established the preclinical anti-arthritic efficacy and pharmacokinetic parameters of MPT0G009, which may provide a new therapeutic approach for treating inflammatory arthritis.

Therapeutic effects of NK-HDAC-1, a novel histone deacetylase inhibitor, on collagen-induced arthritis through the induction of apoptosis of fibroblast-like synoviocytes

The purpose of this study is to investigate the therapeutic effects of a novel histone deacetylase inhibitor (HDACi), NK-HDAC-1, on collagen-induced arthritis (CIA) and pathogenic fibroblast-like synoviocytes (FLSs) from patients with rheumatoid arthritis (RA). The proliferation and apoptosis of FLSs treated with NK-HDAC-1 were evaluated by flow cytometry and fluorescence staining. The effect of NK-HDAC-1 treatment on pro-inflammatory cytokine production was determined by ELISA. CIA was established in DBA/1 mice, and NK-HDAC-1 or vehicle was administered daily after the onset of arthritis. Clinical and histological scores were calculated to assess the therapeutic efficacy of NK-HDAC-1. NK-HDAC-1 significantly inhibited the proliferation of FLSs through cell cycle arrest at the G2/M checkpoint and enhanced apoptosis of FLSs. The activity of caspases was increased during NK-HDAC-1 treatment. IL-6 production by FLSs was also suppressed by NK-HDAC-1. Furthermore, the oral administration of NK-HDAC-1 significantly enhanced synoviocyte apoptosis in vivo and inhibited CIA progression. Compared with subcroylanilide hydroxamic acid which exhibited moderate prophylactic efficacy, NK-HDAC-1 demonstrated therapeutic efficacy in CIA. NK-HDAC-1 is a novel HDACi that may ameliorate inflammatory arthritis by regulating the activation, apoptosis, and inflammatory responses of FLSs. This is the first study to support that NK-HDAC-1 may be a potential therapeutic agent for RA.

Development of vorinostat-loaded solid lipid nanoparticles to enhance pharmacokinetics and efficacy against multidrug-resistant cancer cells

PURPOSE

To investigate whether delivery of a histone deacetylase inhibitor, vorinostat (VOR), by using solid lipid nanoparticles (SLNs) enhanced its bioavailability and effects on multidrug-resistant cancer cells.

METHODS

VOR-loaded SLNs (VOR-SLNs) were prepared by hot homogenization using an emulsification-sonication technique, and the formulation parameters were optimized. The cytotoxicity of the optimized formulation was evaluated in cancer cell lines (MCF-7, A549, and MDA-MB-231), and pharmacokinetic parameters were examined following oral and intravenous (IV) administration to rats.

RESULTS

VOR-SLNs were spherical, with a narrowly distributed average size of ~100 nm, and were physically stable for 3 months. Drug release showed a typical bi-phasic pattern in vitro, and was independent of pH. VOR-SLNs were more cytotoxic than the free drug in both sensitive (MCF-7 and A549) and resistant (MDA-MB-231) cancer cells. Importantly, SLN formulations showed prominent cytotoxicity in MDA-MB-231 cells at low doses, suggesting an ability to effectively counter the P-glycoprotein-related drug efflux pumps. Pharmacokinetic studies clearly demonstrated that VOR-SLNs markedly improved VOR plasma circulation time and decreased its elimination rate constant. The areas under the VOR concentration-time curve produced by oral and IV administration of VOR-SLNs were significantly greater than those produced by free drug administration. These in vivo results clearly highlighted the remarkable potential of SLNs to augment the bioavailability of VOR.

CONCLUSIONS

VOR-SLNs successfully enhanced the oral bioavailability, circulation half-life, and chemotherapeutic potential of VOR.

Histone deacetylase inhibitors increase microRNA-146a expression and enhance negative regulation of interleukin-1β signaling in osteoarthritis fibroblast-like synoviocytes

OBJECTIVE

MiR-146a exerts negative control on inflammatory responses by suppressing cytokine-induced expression of interleukin-1 receptor-associated kinase-1 (IRAK1) and tumor necrosis factor receptor-associated factor 6 (TRAF6) by impairing NF-κB activity and inhibiting the expression of target genes. Recent study suggests that histone deacetylases (HDACs) are involved in the regulation of microRNA (miRNA) expression. Therefore, we determined whether HDAC inhibitors can increase miR-146a expression, thereby inhibiting interleukin-1β (IL-1β)-induced signaling in osteoarthritis fibroblast-like synoviocytes (OA-FLS).

METHOD

MiRNA expression was analyzed using real-time PCR. IL-1β-induced downstream signals and cytokine expression were evaluated using Western blotting and ELISA. Transcription factors regulating promoter activation were identified using chromatin immunoprecipitation assays.

RESULTS

IL-1β treatment of OA-FLS induced a mild (1.7-fold) increase in miR-146a expression that was unable to appropriately downregulate IRAK1 and TRAF6 expression. HDAC inhibitors, SAHA (vorinostat), and LBH589 (panobinostat) significantly (6.1- and 5.4-fold) elevated miR-146a expression by increasing the binding of the transcription factor NF-κB to the miR-146a promoter, and negatively regulated IL-1β-induced IKK/IκB/p65 phosphorylation signaling and IL-6 secretion. The increase in miR-146a expression induced by the HDAC inhibitors was prevented by transfection of miR-146a inhibitor or HDAC1 (class I HDAC), HDAC4 (class IIa HDAC), and HDAC6 (class IIb HDAC) overexpression, suggesting that they were due to inhibition of HDAC activity.

CONCLUSIONS

Our study demonstrated that HDAC inhibitor treatment in OA-FLS significantly increased miR-146a expression and mediated markedly negative regulation to inhibit IL-1β-induced signaling and cytokine secretion. Our results indicate the potential rationale of anti-inflammatory effects for HDAC inhibitors.

The histone deacetylase inhibitors MS-275 and SAHA suppress the p38 mitogen-activated protein kinase signaling pathway and chemotaxis in rheumatoid arthritic synovial fibroblastic E11 cells

MS-275 (entinostat) and SAHA (vorinostat), two histone deacetylase (HDAC) inhibitors currently in oncological trials, have displayed potent anti-rheumatic activities in rodent models of rheumatoid arthritis (RA). To further elucidate their anti-inflammatory mechanisms, the impact of MS-275 and SAHA on the p38 mitogen-activated protein kinase (MAPK) signaling pathway and chemotaxis was assessed in human rheumatoid arthritic synovial fibroblastic E11 cells. MS-275 and SAHA significantly suppressed the expression of p38α MAPK, but induced the expression of MAPK phosphatase-1 (MKP-1), an endogenous suppressor of p38α in E11 cells. At the same time, the association between p38α and MKP-1 was up-regulated and consequently, the activation (phosphorylation) of p38α was inhibited. Moreover, MS-275 and SAHA suppressed granulocyte chemotactic protein-2 (GCP-2), monocyte chemotactic protein-2 (MCP-2) and macrophage migration inhibitory factor (MIF) in E11 cells in a concentration-dependent manner. Subsequently, E11-driven migration of THP-1 and U937 monocytes was inhibited. In summary, suppression of the p38 MAPK signaling pathway and chemotaxis appear to be important anti-rheumatic mechanisms of action of these HDAC inhibitors.

An HDAC inhibitor enhances cancer therapeutic efficiency of RNA polymerase III promoter-driven IDO shRNA

Histone deacetylase (HDAC) inhibitors are used in treating certain human malignancies. Our laboratories demonstrated their capability in enhancing antitumor effect of DNA vaccine driven by an RNA polymerase II (RNA pol II) promoter. However, it is unknown whether HDAC inhibitors enhance the therapeutic short hairpin RNA (shRNA) expressed by an RNA polymerase III (RNA pol III) promoter. We investigated whether HDAC inhibitors augmented antitumor effect of indoleamine 2,3 dioxygenase (IDO) shRNA. HDAC inhibitor OSU-HDAC42 and suberoylanilide hydroxamic acid enhanced RNA pol III-driven U6 and H1 promoter activity in three different cell types in vitro: 293, NIH3T3 and dendritic cell line DC2.4. Subcutaneous injection of OSU-HDAC42 enhanced U6 and H1 promoter activity on abdominal skin of mice in vivo. Combination of IDO shRNA and OSU-HDAC42 increased antitumor effect of IDO shRNA in MBT-2 murine bladder tumor model. IDO shRNA induced tumor-infiltrating CD8⁺ and CD4⁺ T cells, whereas OSU-HDAC42 treatment induced tumor-infiltrating CD4⁺ T cells. Combination of OSU-HDAC42 and IDO shRNA further induced tumor-infiltrating natural killer cells and enhanced interferon-γ in lymphocytes, but suppressed interleukin (IL)-4 expression of lymphocytes. In addition, OSU-HDAC42 treatment did not alter mRNA expression of IL-12 and tumor necrosis factor-α. In conclusion, HDAC inhibitor OSU-HDAC42 may serve as adjuvant of the therapeutic shRNA expressed by an RNA pol III promoter.

Impact of HDAC inhibitors on dendritic cell functions

Histone deacetylase inhibitors are presently used in the routine clinic treatment against cancers. Recent data have established that some of these treatments have potent anti-inflammatory or immunomodulatory effects at noncytotoxic doses that might be of benefit in immuno-inflammatory disorders or post-transplantation. At least some of these effects result from the ability of histone deacetylase inhibitors to modulate the immune system. Dendritic cells are professional antigen presenting cells that play a major role in this immune system. Data summarized in this review brings some novel information on the impact of histone deacetylase inhibitors on dendritic cell functions, which may have broader implications for immunotherapeutic strategies.

Efficacy and safety of suberoylanilide hydroxamic acid (Vorinostat) in the treatment of canine corneal fibrosis

OBJECTIVE

Study aims were to evaluate the safety and efficacy of the Food and Drug Administration-approved drug Vorinostat [suberoylanilide hydroxamic acid (SAHA)] in the treatment of canine corneal fibrosis using an in vitro model.

METHODS

Healthy donor canine corneas were collected and used to generate primary canine corneal fibroblasts (CCFs) by growing cultures in minimal essential medium supplemented with 10% fetal bovine serum. Canine corneal myofibroblasts, used as a model for corneal fibrosis, were produced by growing CCF cultures in serum-free medium containing transforming growth factor β1 (1 ng/mL). Trypan blue exclusion assays were used to determine the optimal SAHA dose for this in vitro model. Four hour after culturing with TGFβ1, CCF cultures were treated with 0.06% SAHA for 5 min (group 1) and for 24 h (group 2), representing single and multiple dose treatment regimes, respectively. Cultures were then further incubated in the presence of TGFβ1 (1 ng/μL) under serum-free conditions until they reached 70% confluence. Trypan blue exclusion, immunocytochemistry, and TUNEL assays were used to evaluate the cytotoxicity of SAHA. Real-time PCR, western blot analysis, and immunocytochemistry were used to determine the efficacy of SAHA to inhibit canine corneal myofibroblast formation.

RESULTS

Topical SAHA application in both treatment groups successfully decreased α-smooth muscle actin expression when compared to the TGFβ1 only treatment group (P < 0.05). Tested SAHA did not affect CCF phenotype or cellular viability and did not cause significant cell death.

CONCLUSIONS

Suberoylanilide hydroxamic acid safely and effectively inhibits TGFβ1-induced CCFs transformation to myofibroblast in vitro.

Histone deacetylase inhibitors as suppressors of bone destruction in inflammatory diseases

OBJECTIVES

Despite progress in developing many new anti-inflammatory treatments in the last decade, there has been little progress in finding treatments for bone loss associated with inflammatory diseases, such as rheumatoid arthritis and periodontitis. For instance, treatment of rheumatic diseases with anti-tumour necrosis factor-alpha agents has been largely successful in reducing inflammation, but there have been varying reports regarding its effectiveness at inhibiting bone loss. In addition, there is often a delay in finding the appropriate anti-inflammatory therapy for individual patients, and some therapies, such as disease modifying drugs, take time to have an effect. In order to protect the bone, adjunct therapies targeting bone resorption are being developed. This review focuses on new treatments based on using histone deacetylase inhibitors (HDACi) to suppress bone loss in these chronic inflammatory diseases.

KEY FINDINGS

A number of selected HDACi have been shown to suppress bone resorption by osteoclasts in vitro and in animal models of chronic inflammatory diseases. Recent reports indicate that these small molecules, which can be administered orally, could protect the bone and might be used in combination with current anti-inflammatory treatments.

SUMMARY

HDACi do have potential to suppress bone destruction in chronic inflammatory diseases including periodontitis and rheumatoid arthritis.

HDACi

Acetylation of histone and non-histone proteins alters gene expression and induces a host of cellular effects. The acetylation process is homeostatically balanced by two groups of cellular enzymes, histone acetyltransferases (HATs) and histone deacetylases (HDACs). HAT activity relaxes the structure of the human chromatin, rendering it transcriptionally active, thereby increasing gene expression. In contrast, HDAC activity leads to gene silencing. The enzymatic balance can be ‘tipped’ by histone deacetylase inhibitors (HDACi), leading to an accumulation of acetylated proteins, which subsequently modify cellular processes including stem cell differentiation, cell cycle, apoptosis, gene expression, and angiogenesis. There is a variety of natural and synthetic HDACi available, and their pleiotropic effects have contributed to diverse clinical applications, not only in cancer but also in non-cancer areas, such as chronic inflammatory disease, bone engineering, and neurodegenerative disease. Indeed, it appears that HDACi-modulated effects may differ between ‘normal’ and transformed cells, particularly with regard to reactive oxygen species accumulation, apoptosis, proliferation, and cell cycle arrest. The potential beneficial effects of HDACi for health, resulting from their ability to regulate global gene expression by epigenetic modification of DNA-associated proteins, also offer potential for application within restorative dentistry, where they may promote dental tissue regeneration following pulpal damage.

Prospects for epigenetic compounds in the treatment of autoimmune disease

There is growing evidence for a role for epigenetic mechanisms in the development of autoimmune diseases. In most cases ofautoimmune disease the precise epigenetic mechanism involved remains to be resolved, however DNA hypomethylation accompanied by hypoacetylation ofhistone H3/H4 is commonly observed. Due to the reversible nature of epigenetic marks their maintenance enzymes such as DNA methyltransferases (DNMTs), histone deacetylases (HDACs) and histone lysine methyltransferases (HKMT) are attractive drug targets. Small molecule inhibitors of histone modification and DNA methylation maintenance are increasingly becoming available and will be useful chemical biological tools to dissect epigenetic mechanisms in these diseases. However, although epigenetic therapies used in cancer treatment are a promising starting point for the exploration of autoimmune disease treatment, there is a requirement for more specific and less toxic agents for these chronic diseases or for use as chemopreventative agents.

Histone deacetylase inhibitors MS-275 and SAHA induced growth arrest and suppressed lipopolysaccharide-stimulated NF-kappaB p65 nuclear accumulation in human rheumatoid arthritis synovial fibroblastic E11 cells

OBJECTIVES

MS-275 and suberoylanilide hydroxamic acid (SAHA) are histone deacetylase (HDAC) inhibitors currently tested in oncology trials. They have also been found to display potent anti-rheumatic activities in rodent models for RA. However, the anti-rheumatic mechanisms of action remain unknown. The study was carried out with the intent of determining the anti-inflammatory and anti-rheumatic mechanisms of the HDAC inhibitors.

METHODS

In this study, the anti-rheumatic mechanisms of MS-275 and SAHA were investigated in several cell culture models.

RESULTS

MS-275 and SAHA inhibited human RA synovial fibroblastic E11 cell proliferation in a non-cytotoxic manner. The anti-proliferative activities were associated with G(0)/G(1) phase arrest and induction of cyclin-dependent kinase inhibitor p21. In addition, MS-275 and SAHA suppressed lipopolysaccharide (LPS)-induced NF-kappaB p65 nuclear accumulation, IL-6, IL-18 and nitric oxide (NO) secretion as well as down-regulated pro-angiogenic VEGF and MMP-2 and MMP-9 production in E11 cells at sub-micromolar levels. At similar concentrations, MS-275 and SAHA suppressed LPS-induced NF-kappaB p65 nuclear accumulation and IL-1beta, IL-6, IL-18 and TNF-alpha secretion in THP-1 monocytic cells. Moreover, NO secretion in RAW264.7 macrophage cells was also inhibited.

CONCLUSIONS

In summary, MS-275 and SAHA exhibited their anti-rheumatic activities by growth arrest in RA synovial fibroblasts, inhibition of pro-inflammatory cytokines and NO, as well as down-regulation in angiogenesis and MMPs. Their anti-rheumatic activities may be mediated through induction of p21 and suppression of NF-kappaB nuclear accumulation.

Histone deacetylase inhibitors: keeping momentum for neuromuscular and cardiovascular diseases treatment

Histone deacetylases (HDACs) are enzymes with a pleiotropic range of intracellular localizations and actions. They are principally involved in the withdrawal of acetyl-groups from a large number of nuclear and cytoplasmic proteins including nuclear core histones as well as cytoskeletal proteins and metabolically relevant enzymes. Initial findings indicated that HDAC inhibitors (DIs) could be successfully applied in a variety of cancer treatment protocols as a consequence of their anti-proliferative and pro-apoptotic properties. Recent observations, however, enlightened the important therapeutic effects of DIs in experimental animal models for arthritis, neurodegenerative and neuromuscular disorders, heart ischemia, cardiac hypertrophy, heart failure and arrhythmias. A small number of clinical trials are now open or planned for the near future to verify the therapeutic properties of DIs in non-cancer-related diseases. This review summarizes some of the most important observations and concepts aroused by the most recent experimental application of DIs to neuromuscular and cardiac diseases.

Protein acetylation in the cardiorenal axis: the promise of histone deacetylase inhibitors

Acetylation of histone and nonhistone proteins provides a key mechanism for controlling signaling and gene expression in heart and kidney. Pharmacological inhibition of protein deacetylation with histone deacetylase (HDAC) inhibitors has shown promise in preclinical models of cardiovascular and renal disease. Efficacy of HDAC inhibitors appears to be governed by pleiotropic salutary actions on a variety of cell types and pathophysiological processes, including myocyte hypertrophy, fibrosis, inflammation and epithelial-to-mesenchymal transition, and occurs at compound concentrations below the threshold required to elicit toxic side effects. We review the roles of acetylation/deacetylation in the heart and kidney and provide rationale for extending HDAC inhibitors into clinical testing for indications involving these organs.

Antifibrotic activity of an inhibitor of histone deacetylases in DOCA-salt hypertensive rats

BACKGROUND AND PURPOSE

Histone deacetylases (HDACs) silence genes by deacetylating lysine residues in histones and other proteins. HDAC inhibitors represent a new class of compounds with anti-inflammatory activity. This study investigated whether treatment with a broad spectrum HDAC inhibitor, suberoylanilide hydroxamic acid (SAHA), would prevent cardiac fibrosis, part of the cardiovascular remodelling in deoxycorticosterone acetate (DOCA)-salt rats.

EXPERIMENTAL APPROACH

Control and DOCA-salt rats were treated with SAHA (25 mg x kg(-1) x day(-1) s.c.) for 32 days. Changes in cardiovascular structure and function were assessed by blood pressure in vivo and in Langendorff perfused hearts, ventricular papillary muscle and in aortic rings in vitro. Left ventricular collagen deposition was assessed by histology.

KEY RESULTS

Administration of SAHA to DOCA-salt rats attenuated the following parameters: the increased concentration of over 20 pro-inflammatory cytokines in plasma, increased inflammatory cell infiltration and interstitial collagen deposition, increased passive diastolic stiffness in perfused hearts, prolongation of action potential duration at 20% and 90% of repolarization in papillary muscle, development of left ventricular hypertrophy, systolic hypertension and changes in vascular dysfunction.

CONCLUSIONS AND IMPLICATIONS

The HDAC inhibitor, SAHA, attenuated the cardiovascular remodelling associated with DOCA-salt hypertensive rats and improved cardiovascular structure and function, especially fibrosis, in the heart and blood vessels, possibly by suppressing inflammation. Control of cardiac histone or non-histone protein acetylation is a potential therapeutic approach to preventing cardiac remodelling, especially cardiac fibrosis.

Histone deacetylase inhibitors suppress inflammatory activation of rheumatoid arthritis patient synovial macrophages and tissue

Macrophages contribute significantly to the pathology of many chronic inflammatory diseases, including rheumatoid arthritis (RA), asthma, and chronic obstructive pulmonary disease. Macrophage activation and survival are tightly regulated by reversible acetylation and deacetylation of histones, transcription factors, and structural proteins. Although histone deacetylase (HDAC) inhibitors (HDACis) demonstrate therapeutic effects in animal models of chronic inflammatory disease, depressed macrophage HDAC activity in patients with asthma, chronic obstructive pulmonary disease, or RA may contribute to inflammation in these diseases, potentially contraindicating the therapeutic administration of HDACis. In this study, we directly examined whether HDACis could influence the activation of macrophages derived from the inflamed joints of patients with RA. We found that inhibition of class I/II HDACs or class III sirtuin HDACs potently blocked the production of IL-6 and TNF-alpha by macrophages from healthy donors and patients with RA. Two HDACis, trichostatin A and nicotinamide, selectively induced macrophage apoptosis associated with specific downregulation of the antiapoptotic protein Bfl-1/A1, and inflammatory stimuli enhanced the sensitivity of macrophages to HDACi-induced apoptosis. Importantly, inflammatory and angiogenic cytokine production in intact RA synovial biopsy explants was also suppressed by HDACis. Our study identifies redundant, but essential, roles for class I/II and sirtuin HDACs in promoting inflammation, angiogenesis, and cell survival in RA.

Proteinases involved in matrix turnover during cartilage and bone breakdown

The joint is a discrete unit that consists of cartilage, bone, tendon and ligaments. These tissues are all composed of an extracellular matrix made of collagens, proteoglycans and specialised glycoproteins that are actively synthesised, precisely assembled and subsequently degraded by the resident connective tissue cells. A balance is maintained between matrix synthesis and degradation in healthy adult tissues. Different classes of proteinases play a part in connective tissue turnover in which active proteinases can cleave matrix protein during resorption, although the proteinase that predominates varies between different tissues and diseases. The metalloproteinases are potent enzymes that, once activated, degrade connective tissue and are inhibited by tissue inhibitors of metalloproteinases (TIMPs); the balance between active matrix metalloproteinases and TIMPs determines, in many tissues, the extent of extracellular matrix degradation. The serine proteinases are involved in the initiation of activation cascades and some, such as elastase, can directly degrade the matrix. Cysteine proteinases are responsible for the breakdown of collagen in bone following the removal of the osteoid layer and the attachment of osteoclasts to the exposed bone surface. Various growth factors increase the synthesis of matrix and proteinase inhibitors, whereas cytokines (alone or in combination) can inhibit matrix synthesis and stimulate proteinase production and matrix destruction.

Conserved responses to trichostatin A in rodent lungs exposed to endotoxin or stretch

Histone deacetylase (HDAC) isoenzymes have been suggested as possible drug targets in pulmonary cancer and in inflammatory lung diseases such as asthma and COPD. Whether HDAC inhibition is pro- or anti-inflammatory is under debate. To further examine this clinically relevant paradigm, we analyzed 8 genes that are upregulated by two pro-inflammatory stimuli, i.e. endotoxin and mechanical stress (overventilation), in isolated rat and mouse lungs, respectively. We studied the effect of the HDAC inhibitor trichostatin A (TSA) under control conditions, in response to endotoxin and overventilation, and on the effects of the steroid dexamethasone. TSA affected gene expression largely independent of the stimulus (endotoxin, overventilation) and the species (rat, mouse) leading to upregulation of some genes (Tnf, Cxcl2) and downregulation of others (Cxcl10, Timp1, Selp, Il6). At the protein level, TSA reduced the stimulated release of TNF, MIP-2alpha and IL-6, indicating that TSA may affect protein translation independent from gene transcription. In general, the anti-inflammatory effects of TSA on gene expression and protein release were additive to that of dexamethasone, suggesting that both drugs employ different mechanisms. We conclude that pro-inflammatory stimuli induce distinct sets of genes that are regulated by HDAC in a diverse, but consistent manner across two rodent species. The present findings together with previous in vivo studies suggest that the effect of HDAC inhibition in the intact lung is in part anti-inflammatory.

Potential pharmacological control of the NF-κB pathway

Nuclear factor (NF)-kappaB governs the expression of numerous genes that are important for various cellular responses. Its activation is induced by a wide variety of stimuli including stress, cigarette smoke, viral and bacterial products, cytokines, free radicals, carcinogens and tumor promoters to name a few. Deregulation of the NF-kappaB pathway has been observed in and attributed to the development of a variety of human ailments including cancers, autoimmune disorders, pulmonary, cardiovascular, neurodegenerative and skin diseases. Efforts to develop modulators of NF-kappaB have yielded several candidates, some of which are currently in Phase I/II of clinical trials. In addition, it is now becoming apparent that several of the approved drugs being currently used also work, in part, owing to their ability to influence the NF-kappaB pathway. In this article, we focus on the druggable components of the NF-kappaB signaling system and on the recent development of novel therapeutics that target NF-kappaB in various diseases.

Targeting histone deacetylase activity in rheumatoid arthritis and asthma as prototypes of inflammatory disease: should we keep our HATs on?

Cellular activation, proliferation and survival in chronic inflammatory diseases is regulated not only by engagement of signal trans-duction pathways that modulate transcription factors required for these processes, but also by epigenetic regulation of transcription factor access to gene promoter regions. Histone acetyl trans-ferases coordinate the recruitment and activation of transcription factors with conformational changes in histones that allow gene promoter exposure. Histone deacetylases (HDACs) counteract histone acetyl transferase activity through the targeting of both histones as well as nonhistone signal transduction proteins important in inflammation. Numerous studies have indicated that depressed HDAC activity in patients with inflammatory airway diseases may contribute to local proinflammatory cytokine production and diminish patient responses to corticosteroid treatment. Recent observations that HDAC activity is depressed in rheumatoid arthritis patient synovial tissue have predicted that strategies restoring HDAC function may be therapeutic in this disease as well. Pharmacological inhibitors of HDAC activity, however, have demonstrated potent therapeutic effects in animal models of arthritis and other chronic inflammatory diseases. In the present review we assess and reconcile these outwardly paradoxical study results to provide a working model for how alterations in HDAC activity may contribute to pathology in rheumatoid arthritis, and highlight key questions to be answered in the preclinical evaluation of compounds modulating these enzymes.