Histone deacetylase inhibitors induce antigen specific anergy in lymphocytes: a comparative study

The impact of histone deacetylase inhibitors on immune cells and implications for cancer therapy

Many cancers possess the ability to suppress the immune response to malignant cells, thus facilitating tumour growth and invasion, and this has fuelled research to reverse these mechanisms and re-activate the immune system with consequent important therapeutic benefit. One such approach is to use histone deacetylase inhibitors (HDACi), a novel class of targeted therapies, which manipulate the immune response to cancer through epigenetic modification. Four HDACi have recently been approved for clinical use in malignancies including multiple myeloma and T-cell lymphoma. Most research in this context has focussed on HDACi and tumour cells, however, little is known about their impact on the cells of the immune system. Additionally, HDACi have been shown to impact the mechanisms by which other anti-cancer therapies exert their effects by, for example, increasing accessibility to exposed DNA through chromatin relaxation, impairing DNA damage repair pathways and increasing immune checkpoint receptor expression. This review details the effects of HDACi on immune cells, highlights the variability in these effects depending on experimental design, and provides an overview of clinical trials investigating the combination of HDACi with chemotherapy, radiotherapy, immunotherapy and multimodal regimens.

An Evaluation of the Fasciola hepatica miRnome Predicts a Targeted Regulation of Mammalian Innate Immune Responses

Understanding mechanisms by which parasitic worms (helminths) control their hosts’ immune responses is critical to the development of effective new disease interventions. Fasciola hepatica, a global scourge of humans and their livestock, suppresses host innate immune responses within hours of infection, ensuring that host protective responses are quickly incapacitated. This allows the parasite to freely migrate from the intestine, through the liver to ultimately reside in the bile duct, where the parasite establishes a chronic infection that is largely tolerated by the host. The recent identification of micro(mi)RNA, small RNAs that regulate gene expression, within the extracellular vesicles secreted by helminths suggest that these non-coding RNAs may have a role in the parasite-host interplay. To date, 77 miRNAs have been identified in F. hepatica comprising primarily of ancient conserved species of miRNAs. We hypothesized that many of these miRNAs are utilized by the parasite to regulate host immune signaling pathways. To test this theory, we first compiled all of the known published F. hepatica miRNAs and critically curated their sequences and annotations. Then with a focus on the miRNAs expressed by the juvenile worms, we predicted gene targets within human innate immune cells. This approach revealed the existence of targets within every immune cell, providing evidence for the universal management of host immunology by this parasite. Notably, there was a high degree of redundancy in the potential for the parasite to regulate the activation of dendritic cells, eosinophils and neutrophils, with multiple miRNAs predicted to act on singular gene targets within these cells. This original exploration of the Fasciola miRnome offers the first molecular insight into mechanisms by which F. hepatica can regulate the host protective immune response.

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.

Combination of specific allergen and probiotics induces specific regulatory B cells and enhances specific immunotherapy effect on allergic rhinitis

The therapeutic efficacy of allergen specific immunotherapy (SIT) on allergic diseases is to be improved. Probiotics can regulate immune response. This study aims to promote the effect of SIT on allergic rhinitis (AR) by co-administration with Clostridium butyricum (Cb). In this study, patients with AR sensitized to mite allergens were enrolled to this study, and treated with SIT or/and Cb. The therapeutic efficacy was evaluated by the total nasal symptom scores (NSS), medication scores, serum specific IgE levels and T helper (Th)2 cytokine levels. The improvement of immune regulation in the AR patients was assessed by immunologic approaches. The results showed that treating AR patients with SIT alone markedly reduced NSS and medication scores; but did not alter the serum specific IgE, Th2 cytokines and skin prick test (SPT) index. The clinical symptoms on AR in SIT group relapsed one month after stopping SIT. Co-administration of Cb significantly enhanced the efficacy of SIT on AR as shown by suppression of NSS, medication scores, serum specific IgE, Th2 cytokines and SPT index; the regulatory B cell frequency was also markedly increased. Such an effect on AR was maintained throughout the observation period even after stopping the treatment. Butyrate blocked the activation of histone deacetylase-1, the downstream activities of epsilon chain promoter activation, and the IgE production in the antigen specific B cells. On the other hand, butyrate induced the IL-10 expression in B cells with a premise of the B cell receptor activation by specific antigens. In conclusion, administration with Cb can markedly enhance the efficacy of SIT on AR.

The Impact of Chemotherapy, Radiation and Epigenetic Modifiers in Cancer Cell Expression of Immune Inhibitory and Stimulatory Molecules and Anti-Tumor Efficacy

Genomic destabilizers, such as radiation and chemotherapy, and epigenetic modifiers are used for the treatment of cancer due to their apoptotic effects on the aberrant cells. However, these therapies may also induce widespread changes within the immune system and cancer cells, which may enable tumors to avoid immune surveillance and escape from host anti-tumor immunity. Genomic destabilizers can induce immunogenic death of tumor cells, but also induce upregulation of immune inhibitory ligands on drug-resistant cells, resulting in tumor progression. While administration of immunomodulatory antibodies that block the interactions between inhibitory receptors on immune cells and their ligands on tumor cells can mediate cancer regression in a subset of treated patients, it is crucial to understand how genomic destabilizers alter the immune system and malignant cells, including which inhibitory molecules, receptors and/or ligands are upregulated in response to genotoxic stress. Knowledge gained in this area will aid in the rational design of trials that combine genomic destabilizers, epigenetic modifiers and immunotherapeutic agents that may be synergized to improve clinical responses and prevent tumor escape from the immune system. Our review article describes the impact genomic destabilizers, such as radiation and chemotherapy, and epigenetic modifiers have on anti-tumor immunity and the tumor microenvironment. Although genomic destabilizers cause DNA damage on cancer cells, these therapies can also have diverse effects on the immune system, promote immunogenic cell death or survival and alter the cancer cell expression of immune inhibitor molecules.

HDAC inhibitors and immunotherapy; a double edged sword?

Epigenetic modifications, like histone acetylation, are essential for regulating gene expression within cells. Cancer cells acquire pathological epigenetic modifications resulting in gene expression patterns that facilitate and sustain tumorigenesis. Epigenetic manipulation therefore is emerging as a novel targeted therapy for cancer. Histone Acetylases (HATs) and Histone Deacetylases (HDACs) regulate histone acetylation and hence gene expression. Histone deacetylase (HDAC) inhibitors are well known to affect cancer cell viability and biology and are already in use for the treatment of cancer patients. Immunotherapy can lead to clinical benefit in selected cancer patients, especially in patients with limited disease after tumor debulking. HDAC inhibitors can potentially synergize with immunotherapy by elimination of tumor cells. The direct effects of HDAC inhibitors on immune cell function, however, remain largely unexplored. Initial data have suggested HDAC inhibitors to be predominantly immunosuppressive, but more recent reports have challenged this view. In this review we will discuss the effects of HDAC inhibitors on tumor cells and different immune cell subsets, synergistic interactions and possible mechanisms. Finally, we will address future challenges and potential application of HDAC inhibitors in immunocombination therapy of cancer.

Treatment of chronic kidney diseases with histone deacetylase inhibitors

Histone deacetylases (HDACs) induce deacetylation of both histone and non-histone proteins and play a critical role in the modulation of physiological and pathological gene expression. Pharmacological inhibition of HDAC has been reported to attenuate progression of renal fibrogenesis in obstructed kidney and reduce cyst formation in polycystic kidney disease. HDAC inhibitors (HDACis) are also able to ameliorate renal lesions in diabetes nephropathy, lupus nephritis, aristolochic acid nephropathy, and transplant nephropathy. The beneficial effects of HDACis are associated with their anti-fibrosis, anti-inflammation, and immunosuppressant effects. In this review, we summarize recent advances on the treatment of various chronic kidney diseases with HDACis in pre-clinical models.

Acute treatment with valproic acid and l-thyroxine ameliorates clinical signs of experimental autoimmune encephalomyelitis and prevents brain pathology in DA rats

Multiple sclerosis (MS) is the most common chronic inflammatory demyelinating disease of the central nervous system (CNS) in young adults. Chronic treatments with histone deacetylase inhibitors (HDACis) have been reported to ameliorate experimental autoimmune encephalomyelitis (EAE), a rodent model of MS, by targeting immune responses. We have recently shown that the HDAC inhibition/knockdown in the presence of thyroid hormone (T3) can also promote oligodendrocyte (OL) differentiation and expression of myelin genes in neural stem cells (NSCs) and oligodendrocyte precursors (OPCs). In this study, we found that treatment with an HDACi, valproic acid (VPA), and T3, alone or in combination, directly affects encephalitogenic CD4+ T cells. VPA, but not T3, compromised their proliferation, while both molecules reduced the frequency of IL-17-producing cells. Transfer of T3, VPA and VPA/T3 treated encephalitogenic CD4+ T cells into naïve rats induced less severe EAE, indicating that the effects of these molecules are persistent and do not require their maintenance after the initial stimuli. Thus, we investigated the effect of acute treatment with VPA and l-thyroxine (T4), a precursor of T3, on myelin oligodendrocyte glycoprotein-induced EAE in Dark Agouti rats, a close mimic of MS. We found that a brief treatment after disease onset led to sustained amelioration of EAE and prevention of inflammatory demyelination in the CNS accompanied with a higher expression of myelin-related genes in the brain. Furthermore, the treatment modulated immune responses, reduced the number of CD4+ T cells and affected the Th1 differentiation program in the brain. Our data indicate that an acute treatment with VPA and T4 after the onset of EAE can produce persistent clinically relevant therapeutic effects by limiting the pathogenic immune reactions while promoting myelin gene expression.

Histone deacetylases as targets for treatment of multiple diseases

HDACs (histone deacetylases) are a group of enzymes that deacetylate histones as well as non-histone proteins. They are known as modulators of gene transcription and are associated with proliferation and differentiation of a variety of cell types and the pathogenesis of some diseases. Recently, HDACs have come to be considered crucial targets in various diseases, including cancer, interstitial fibrosis, autoimmune and inflammatory diseases, and metabolic disorders. Pharmacological inhibitors of HDACs have been used or tested to treat those diseases. In the present review, we will examine the application of HDAC inhibitors in a variety of diseases with the focus on their effects of anti-cancer, fibrosis, anti-inflammatory, immunomodulatory activity and regulating metabolic disorders.

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.

Histone/protein deacetylases and T-cell immune responses

Clinical and experimental studies show that inhibition of histone/protein deacetylases (HDAC) can have important anti-neoplastic effects through cytotoxic and proapoptotic mechanisms. There are also increasing data from nononcologic settings that HDAC inhibitors (HDACi) can exhibit useful anti-inflammatory effects in vitro and in vivo, unrelated to cytotoxicity or apoptosis. These effects can be cell-, tissue-, or context-dependent and can involve modulation of specific inflammatory signaling pathways as well as epigenetic mechanisms. We review recent advances in the understanding of how HDACi alter immune and inflammatory processes, with a particular focus on the effects of HDACi on T-cell biology, including the activation and functions of conventional T cells and the unique T-cell subset, composed of Foxp3(+) T-regulatory cells. Although studies are still needed to tease out details of the various biologic roles of individual HDAC isoforms and their corresponding selective inhibitors, the anti-inflammatory effects of HDACi are already promising and may lead to new therapeutic avenues in transplantation and autoimmune diseases.

Histone deacetylase inhibitors for treating a spectrum of diseases not related to cancer

This issue of Molecular Medicine contains 14 original research reports and state-of-the-art reviews on histone deacetylase inhibitors (HDACi's), which are being studied in models of a broad range of diseases not related to the proapoptotic properties used to treat cancer. The spectrum of these diseases responsive to HDACi's is for the most part due to several antiinflammatory properties, often observed in vitro but importantly also in animal models. One unifying property is a reduction in cytokine production as well as inhibition of cytokine postreceptor signaling. Distinct from their use in cancer, the reduction in inflammation by HDACi's is consistently observed at low concentrations compared with the higher concentrations required for killing tumor cells. This characteristic makes HDACi's attractive candidates for treating chronic diseases, since low doses are well tolerated. For example, low oral doses of the HDACi givinostat have been used in children to reduce arthritis and are well tolerated. In addition to the antiinflammatory properties, HDACi's have shown promise in models of neurodegenerative disorders, and HDACi's also hold promise to drive HIV-1 out of latently infected cells. No one molecular mechanism accounts for the non-cancer-related properties of HDACi's, since there are 18 genes coding for histone deacetylases. Rather, there are mechanisms unique for the pathological process of specific cell types. In this overview, we summarize the preclinical data on HDACi's for therapy in a wide spectrum of diseases unrelated to the treatment of cancer. The data suggest the use of HDACi's in treating autoimmune as well as chronic inflammatory diseases.

Inhibition of histone deacetylases in inflammatory bowel diseases

This review, comprised of our own data and that of others, provides a summary overview of histone deacetylase (HDAC) inhibition on intestinal inflammation as well as inflammation-mediated carcinogenesis. Experimental colitis in mice represents an excellent in vivo model to define the specific cell populations and target tissues modulated by inhibitors of HDAC. Oral administration of either suberyolanilide hydroxamic acid (SAHA) or ITF2357 results in an amelioration in these models, as indicated by a significantly reduced colitis disease score and histological score. This effect was paralleled by suppression of proinflammatory cytokines at the site of inflammation as well as specific changes in the composition of cells within the lamina propria. In addition, tumor number and size was significantly reduced in two models of inflammation-driven tumorigenesis, namely interleukin (IL)-10-deficient mice and the azoxymethane-dextran sulfate sodium (DSS) model, respectively. The mechanisms affected by HDAC inhibition, contributing to this antiinflammatory and antiproliferative potency will be discussed in detail. Furthermore, with regard to the relevance in human inflammatory bowel disease, the doses of ITF2357 considered safe in humans and the corresponding serum concentrations are consistent with the efficacious dosing used in our in vivo as well as in vitro experiments. Thus, the data strongly suggest that HDAC inhibitors could serve as a therapeutic option in inflammatory bowel disease.

HDAC inhibition in rheumatoid arthritis and juvenile idiopathic arthritis

Rheumatoid arthritis (RA) and juvenile idiopathic arthritis (JIA) are heterogeneous autoimmune diseases characterized by chronic joint inflammation. Methotrexate is used as the gold standard to treat rheumatoid arthritis, yet there are many patients in whom the disease cannot be controlled or who experience unacceptable intolerance. Most of the biologics currently used are effective, but mostly if combined with methotrexate. Long-term possible side effects, such as impaired host defense mechanisms against infection and lymphoma, are distinct disadvantages and a major concern of anticytokine therapies. Parenteral administration is a problem, particularly in children. Thus, there is a need to explore new treatment options. Here we review the properties of histone deacetylase inhibitors (HDACi) as they apply to rheumatoid arthritis by looking at effects on cytokine production, T-cell differentiation and the function of macrophages, dendritic cells, osteoblasts, osteoclasts and synovial fibroblasts. We also review the safety and efficacy of givinostat (ITF 2357) in the treatment of systemic onset juvenile idiopathic arthritis (SOJIA) and its influence on the cytokine networks in SOJIA. Givinostat is an orally active HDACi which was given to children with SOJIA. After 12 wk of treatment, there were significant benefits, particularly in reducing the pain and arthritic component of the disease and decreasing the neutrophilia. CD40L, IL-1α and IFNγ in whole blood lysates decreased at wks 2 and 4 compared with baseline levels. The clinical data are consistent with those from animal models of rheumatoid arthritis and suggest that trials with HDACi are promising as a safe oral alternative to anticytokines and methotrexate.

Rationale for HDAC inhibitor therapy in autoimmunity and transplantation

While there are currently more than 70 ongoing clinical trials of inhibitors of so-called classical HDACs (HDACi) as anticancer therapies, given their potency as antiproliferative and angiostatic agents, HDACi also have considerable therapeutic potential as anti-inflammatory and immunosuppressive drugs. The utility of HDACi as anti-inflammatory agents is dependent upon their proving safe and effective in experimental models. Current pan-HDACi compounds are not well suited to this role, given the broad distribution of target HDACs and their complex and multifaceted mechanisms of action. In contrast, the development of isoform-selective HDACi may provide important new tools for therapy in autoimmunity and transplantation. This chapter discusses which HDACs are worthwhile targets in inflammation and progress toward their therapeutic inhibition, including the use of HDAC subclass and isoform-selective HDACi to promote the functions of Foxp3+ T regulatory cells.

Immunomodulatory effects of deacetylase inhibitors: therapeutic targeting of FOXP3+ regulatory T cells

Classical zinc-dependent histone deacetylases (HDACs) catalyse the removal of acetyl groups from histone tails and also from many non-histone proteins, including the transcription factor FOXP3, a key regulator of the development and function of regulatory T cells. Many HDAC inhibitors are in cancer clinical trials, but a subset of HDAC inhibitors has important anti-inflammatory or immunosuppressive effects that might be of therapeutic benefit in immuno-inflammatory disorders or post-transplantation. At least some of these effects result from the ability of HDAC inhibitors to enhance the production and suppressive functions of FOXP3(+) regulatory T cells. Understanding which HDACs contribute to the regulation of the functions of regulatory T cells may further stimulate the development of new class- or subclass-specific HDAC inhibitors with applications beyond oncology.

p21(Cip1) up-regulated during histone deacetylase inhibitor-induced CD4(+) T-cell anergy selectively associates with mitogen-activated protein kinases

Histone deacetylase inhibitor n-butyrate induced proliferative unresponsiveness in antigen-stimulated murine CD4(+) T cells. T cells anergized by n-butyrate demonstrated reduced interleukin-2 (IL-2) secretion and decreased activating protein 1 (AP-1) activity upon restimulation. Mechanistic studies determined that the cyclin-dependent kinase (cdk) inhibitor p21(Cip1) was up-regulated in the anergic CD4(+) T cells. p21(Cip1) is known to inhibit the cell cycle through its interaction with cdk, proliferating cell nuclear antigen (PCNA) or c-Jun N-terminal kinase (JNK). p21(Cip1) did not preferentially associate with PCNA or cdk in anergic T helper type 1 (Th1) cells. Instead, among the three interaction partners, p21(Cip1) was found to interact with phospho-JNK and phospho-c-jun selectively in the anergic CD4(+) T cells. The activity of c-jun and downstream transcription factor AP-1 were suppressed in the anergic Th1 cells. In contrast, p21(Cip1) and the two phospho-proteins were never detected concurrently in the control CD4(+) T cells. The n-butyrate-induced p21(Cip1)-mediated inhibition of JNK and c-jun represents a novel potential mechanism by which proliferative unresponsiveness was maintained in CD4(+) T cells.

Convergent Random Forest predictor: methodology for predicting drug response from genome-scale data applied to anti-TNF response

Biomarker development for prediction of patient response to therapy is one of the goals of molecular profiling of human tissues. Due to the large number of transcripts, relatively limited number of samples, and high variability of data, identification of predictive biomarkers is a challenge for data analysis. Furthermore, many genes may be responsible for drug response differences, but often only a few are sufficient for accurate prediction. Here we present an analysis approach, the Convergent Random Forest (CRF) method, for the identification of highly predictive biomarkers. The aim is to select from genome-wide expression data a small number of non-redundant biomarkers that could be developed into a simple and robust diagnostic tool. Our method combines the Random Forest classifier and gene expression clustering to rank and select a small number of predictive genes. We evaluated the CRF approach by analyzing four different data sets. The first set contains transcript profiles of whole blood from rheumatoid arthritis patients, collected before anti-TNF treatment, and their subsequent response to the therapy. In this set, CRF identified 8 transcripts predicting response to therapy with 89% accuracy. We also applied the CRF to the analysis of three previously published expression data sets. For all sets, we have compared the CRF and recursive support vector machines (RSVM) approaches to feature selection and classification. In all cases the CRF selects much smaller number of features, five to eight genes, while achieving similar or better performance on both training and independent testing sets of data. For both methods performance estimates using cross-validation is similar to performance on independent samples. The method has been implemented in R and is available from the authors upon request: Jadwiga.Bienkowska@biogenidec.com.

Histone deacetylase inhibitor uses p21(Cip1) to maintain anergy in CD4+ T cells

T cell anergy defined as antigen-specific proliferative unresponsiveness was induced in CD4+ T cells exposed to antigen (Ag) in the presence of the histone deacetylase (HDAC) inhibitors n-butyrate, trichostatin A or scriptaid. However, the ability of HDAC inhibitors to induce anergy in Th1 cells was not due to general histone hyperacetylation. Instead, the anergy induced by HDAC inhibitors was associated with upregulation of p21(Cip1), a secondary effect of histone acetylation. Induction of p21(Cip1) in the absence of histone hyperacetylation by exposure to okadaic acid also resulted in T cell anergy. In addition, Ag-specific p21(Cip1)-deficient CD4+ T cells were much less susceptible to anergy induction by n-butyrate. Thus, p21(Cip1) appears to mediate the proliferative unresponsiveness found in CD4+ T cell anergized by exposure to Ag in the presence of HDAC inhibitors.

Effect of the immunosuppressant histone deacetylase inhibitor FR276457 in a canine renal transplant model

The histone deacetylase (HDAC) inhibitor FR276457, a hydroxamic derivative, was identified during chemical library screening and was found to exhibit potent inhibitory effects on the activity of mammalian HDACs. It has been shown that FR276457 exhibited marked immunosuppressive effects in a rat heterotopic cardiac transplant model. To predict clinical efficacy of FR276457, we investigated the inhibitory effect of the proliferation of Jurkat cells in vitro and immunosuppressive effect of orally administered FR276457 on allograft rejection as a monotherapy or in combination with tacrolimus (0.04 mg/kg) injected intramuscularly (i.m.) in a canine renal transplant model. Animal survival, the plasma creatinine level, and histopathology were evaluated. FR276457 inhibited the proliferation of Jurkat cells probably by targeting activity of NF-kappaB. FR276457 prolonged the median survival time (MST) of transplanted grafts from 11.5 days (untreated group) to 29.0 days (FR276457-treated group). FR276457 administered 1 mg/kg twice a day in combination with tacrolimus prevented allograft rejection. In addition, a dose of 1.5 mg/kg twice a day or 5.0 mg/kg once a day prolonged the MST from 18 days (control group) to >73 or >90 days, respectively. Histopathological analysis showed that FR276457 suppressed the score for mononuclear cell infiltration and vasculitis. In conclusion, the HDAC inhibitor FR276457 inhibited the proliferation of T cell line established from human in vitro. And more, FR276457 clinically prolonged allograft survival when administered as a monotherapy, and had additive or synergistic effects when combined with tacrolimus with the canine renal transplant model. These results showed HDAC inhibitor is a promising biological target for treatment in transplant field.

Effect of a new immunosuppressant histon deacetylase (HDAC) inhibitor FR276457 in a rat cardiac transplant model

Histone deacetylase (HDAC) is a known modulator of gene transcription, and the immunosuppressive activity of HDAC inhibitors has been demonstrated in recent several reports. In this study, the HDAC inhibitor FR276457, a hydroxamic derivative, was found to have a similar inhibitory effect on all mammalian HDACs tested, but no isozyme selectivity. Both FR276457 and tacrolimus exerted an immunosuppressive effect on in vitro rat splenocyte proliferation stimulated with Concanavalin A. Next, the effect of FR276457 on allograft rejection when administered either as a monotherapy or in combination with tacrolimus was investigated in a rat heterotopic cardiac transplant model. Orally administered FR276457 prolonged the median survival times (MST) of the transplanted grafts in the vehicle group from 6 d to 17 or 21 d at doses of 20 or 40 mg/kg, respectively. Histopathological analysis showed the structures of the myocardium were not affected, but interstitial cellular infiltration could not be suppressed completely. Tacrolimus (0.032 mg/kg) prolonged allograft MST to 16 d. FR276457, when combined with tacrolimus, prevented allograft rejection at a dose lower than that of the monotherapy. The combination dose prolonged the MST in the groups treated with 10 and 20 mg/kg to >28 d, and cellular infiltration was suppressed completely. In conclusion, this study demonstrated that the oral administration of HDAC inhibitor FR276457 can prevent allograft rejection as a monotherapy, and has additive or synergistic effects when combined with tacrolimus.

A novel histone deacetylase inhibitor reduces abdominal aortic aneurysm formation in angiotensin II-infused apolipoprotein E-deficient mice

BACKGROUND/AIMS

Aberrant expression of components of the matrix metalloproteinase (MMP) enzyme system is implicated in abdominal aortic aneurysm (AAA) formation. We aimed to investigate the influence of a novel histone deacetylase (HDAC) inhibitor (HDACi) metacept-1 (MCT-1), previously documented to reduce MMP expression, on HDAC activity and MMP expression in aortic smooth muscle cells and the in vivo incidence of AAAs.

METHODS

Western blot and gelatin zymography were used to determine HDAC activity and MMP-2 expression and activity in rat (rVSMCs) and human aortic vascular smooth muscle cells (hVSMCs) in vitro. In vivo AAAs were generated using apolipoprotein E-deficient mice infused with angiotensin (Ang) II. Immunohistochemistry detected MMP-2 and -9 expression in AAA tissue samples.

RESULTS

In vitro, MCT-1 inhibited HDAC activity in rVSMCs, and MMP-2 expression and proteolytic activity in hVSMCs. In vivo, Ang II treatment alone exhibited an AAA incidence of 84%. Doxycycline decreased the incidence of AAAs to 50%. Importantly, MCT-1 reduced AAA incidence to approximately 44%. MMP-2 and -9 immunoreactivity was reduced in MCT-1-treated aortic tissue.

CONCLUSION

The novel HDACi MCT-1 inhibits MMP expression and AAA incidence suggesting this compound may warrant further investigation in the context of AAA biology.