HDAC inhibitor therapy in autoimmunity and transplantation

Drug repositioning identifies histone deacetylase inhibitors that promote innate immunity in non-tuberculous mycobacterial infection

Non-tuberculosis infections in immunocompromised patients represent a cause for concern, given the increased risks of infection, and limited treatments available. Herein, we report that molecules for binding to the catalytic site of histone deacetylase (HDAC) inhibit its activity, thus increasing the innate immune response against environmental mycobacteria. The action of HDAC inhibitors (iHDACs) was explored in a model of type II pneumocytes and macrophages infection by Mycobacterium aurum. The results show that the use of 1,3-diphenylurea increases the expression of the TLR-4 in M. aurum infected MDMs, as well as the production of defb4, IL-1β, IL-12, and IL-6. Moreover, we observed that aminoacetanilide upregulates the expression of TLR-4 together with TLR-9, defb4, CAMP, RNase 6, RNase 7, IL-1β, IL-12, and IL-6 in T2P. Results conclude that the tested iHDACs selectively modulate the expression of cytokines and antimicrobial peptides that are associated with reduction of non-tuberculous mycobacteria infection.

Update on Combination Strategies of PARP Inhibitors

The application of PARP inhibitors has revolutionized cancer treatment and has achieved significant advancements, particularly with regard to tumors with defects in genes involved in homologous recombination repair (HRR) processes, such as BRCA1 and BRCA2. Despite the promising outcomes of PARP inhibitors, certain limitations and challenges still exist, including acquired drug resistance, severe side effects, and limited therapeutic benefits for patients without homologous recombination deficiency (HRD). Various combinations involving PARP inhibitors have been developed to overcome these limitations. Among these, combinations with immune checkpoint inhibitors, antiangiogenic agents, and various small-molecule inhibitors are well-studied strategies that show great potential for optimizing the efficacy of PARP inhibitors, overcoming resistance mechanisms, and expanding target populations. However, the efficiency and overlapping toxicity of these combination strategies for cancers vary among studies, thereby limiting their use. In this review, we describe the mechanisms and limitations of PARP inhibitors to better understand the mechanisms of combination treatments. Furthermore, we have summarized recent studies on the combination of PARP inhibitors with a range of medications and discussed their clinical efficacy. The objective of this review is to enhance the comprehensiveness of information pertaining to this topic.

Effects of histone acetyltransferase (HAT) and histone deacetylase (HDAC) inhibitors on proliferative, differentiative, and regenerative functions of Toll-like receptor 2 (TLR-2)-stimulated human dental pulp cells (hDPCs)

OBJECTIVES

This in vitro study aimed to modify TLR-2-mediated effects on the paracrine, proliferative, and differentiation potentials of human dental pulp-derived cells using histone acetyltransferase (HAT) and histone deacetylase (HDAC) inhibitors.

MATERIALS AND METHODS

Cell viability was assessed using the XTT assay. Cells were either treated with 10 μg/ml Pam3CSK4 only, or pre-treated with valproic acid (VPA) (3 mM), trichostatin A (TSA) (3 μM), and MG-149 (3 μM) for a total of 4 h and 24 h. Control groups included unstimulated cells and cells incubated with inhibitors solvents only. Transcript levels for NANOG, OCT3-4, FGF-1 and 2, NGF, VEGF, COL-1A1, TLR-2, hβD-2 and 3, BMP-2, DSPP, and ALP were assessed through qPCR.

RESULTS

After 24 h, TSA pre-treatment significantly upregulated the defensins and maintained the elevated pro-inflammatory cytokines, but significantly reduced healing and differentiation genes. VPA significantly upregulated the pro-inflammatory cytokine levels, while MG-149 significantly downregulated them. Pluripotency genes were not significantly affected by any regimen.

CONCLUSIONS

At the attempted concentrations, TSA upregulated the defensins gene expression levels, and MG-149 exerted a remarkable anti-inflammatory effect; therefore, they could favorably impact the immunological profile of hDPCs.

CLINICAL RELEVANCE

Targeting hDPC nuclear function could be a promising option in the scope of the biological management of inflammatory pulp diseases.

Retuning Mitochondrial Apoptosis/Mitophagy Balance via SIRT3-Energized and Microenvironment-Modulated Hydrogel Microspheres to Impede Osteoarthritis

Full-range therapeutic regimens for osteoarthritis (OA) should consider organs (joints)-tissues (cartilage)-cells (chondrocytes)-organelles cascade, of which the subcellular mitochondria dominate eukaryotic cells' fate, and thus causally influence OA progression. However, the dynamic regulation of mitochondrial rise and demise in impaired chondrocytes and the exact role of mitochondrial metronome sirtuins 3 (SIRT3) is not clarified. Herein, chondrocytes are treated with SIRT3 natural agonist dihydromyricetin (DMY) or chemical antagonist 3-TYP, respectively, to demonstrate the positive action of SIRT3 on preserving cartilage extracellular matrix (ECM). Molecular mechanical investigations disclose that SIRT3-induced chondroprotection depended on the repression of mitochondrial apoptosis (mtApoptosis) and the activation of mitophagy. Inspired by the high-level matrix proteinases and reactive oxygen species (ROS) in the OA environment, by anchoring gelatin methacrylate (GelMA) and benzenediboronic acid (PBA) to hyaluronic acid methacrylate (HAMA) with microfluidic technology, a dual-responsive hydrogel microsphere laden with DMY is tactfully fabricated and named as DMY@HAMA-GelMA-PBA (DMY@HGP). In vivo injection of DMY@HGP ameliorated cartilage abrasion and subchondral bone sclerosis, as well as promoted motor function recovery in post-traumatic OA (PTOA) model via recouping endogenous mtApoptosis and mitophagy balance. Overall, this study unveils a novel mitochondrial dynamic-oriented strategy, holding great promise for the precision treatment of OA.

Regulatory T cells: a new therapeutic link for Sjögren syndrome?

Great advancements have been made in understanding the pathogenesis of SS, but there remain unmet needs for effective and targeted treatments. Glandular and extraglandular dysfunction in SS is associated with autoimmune lymphocytic infiltration that invades the epithelial structures of affected organs. Regulatory T (Treg) cells are a subset of CD4+ T lymphocytes that maintain self-tolerance during physiological conditions. Besides inhibiting excessive inflammation and autoimmune response by targeting various immune cell subsets and tissues, Treg cells have also been shown to promote tissue repair and regeneration in pathogenic milieus. The changes of quantity and function of Treg cells in various autoimmune and chronic inflammatory disorders have been reported, owing to their effects on immune regulation. Here we summarize the recent findings from murine models and clinical data about the dysfunction of Treg cells in SS pathogenesis and discuss the therapeutic strategies of direct or indirect targeting of Treg cells in SS. Understanding the current knowledge of Treg cells in the development of SS will be important to elucidate disease pathogenesis and may guide research for successful therapeutic intervention in this disease.

Advanced Glycation End Products and Activation of Toll-like Receptor-2 and -4 Induced Changes in Aquaporin-3 Expression in Mouse Keratinocytes

Prolonged inflammation and impaired re-epithelization are major contributing factors to chronic non-healing diabetic wounds; diabetes is also characterized by xerosis. Advanced glycation end products (AGEs), and the activation of toll-like receptors (TLRs), can trigger inflammatory responses. Aquaporin-3 (AQP3) plays essential roles in keratinocyte function and skin wound re-epithelialization/re-generation and hydration. Suberanilohydroxamic acid (SAHA), a histone deacetylase inhibitor, mimics the increased acetylation observed in diabetes. We investigated the effects of TLR2/TLR4 activators and AGEs on keratinocyte AQP3 expression in the presence and absence of SAHA. Primary mouse keratinocytes were treated with or without TLR2 agonist Pam3Cys-Ser-(Lys)4 (PAM), TLR4 agonist lipopolysaccharide (LPS), or AGEs, with or without SAHA. We found that (1) PAM and LPS significantly upregulated AQP3 protein basally (without SAHA) and PAM downregulated AQP3 protein with SAHA; and (2) AGEs (100 µg/mL) increased AQP3 protein expression basally and decreased AQP3 levels with SAHA. PAM and AGEs produced similar changes in AQP3 expression, suggesting a common pathway or potential crosstalk between TLR2 and AGEs signaling. Our findings suggest that TLR2 activation and AGEs may be beneficial for wound healing and skin hydration under normal conditions via AQP3 upregulation, but that these pathways are likely deleterious in diabetes chronically through decreased AQP3 expression.

Mechanistic basis and preliminary practice of butyric acid and butyrate sodium to mitigate gut inflammatory diseases: a comprehensive review

A key event featured in the early stage of chronic gut inflammatory diseases is the disordered recruitment and excess accumulation of immune cells in the gut lamina propria. This process is followed by the over-secretion of pro-inflammatory factors and the prolonged overactive inflammatory responses. Growing evidence has suggested that gut inflammatory diseases may be mitigated by butyric acid (BA) or butyrate sodium (NaB). Laboratory studies show that BA and NaB can enhance gut innate immune function through G-protein-mediated signaling pathways while mitigating the overactive inflammatory responses by inhibiting histone deacetylase. The regulatory effects may occur in both epithelial enterocytes and the immune cells in the lamina propria. Prior to further clinical trials, comprehensive literature reviews and rigid examination concerning the underlying mechanism are necessary. To this end, we collected and reviewed 197 published reports regarding the mechanisms, bioactivities, and clinical effects of BA and NaB to modulate gut inflammatory diseases. Our review found insufficient evidence to guarantee the safety of clinical practice of BA and NaB, either by anal enema or oral administration of capsule or tablet. The safety of clinical use of BA and NaB should be further evaluated. Alternatively, dietary patterns rich in "fruits, vegetables and beans" may be an effective and safe approach to prevent gut inflammatory disease, which elevates gut microbiota-dependent production of BA. Our review provides a comprehensive reference to future clinical trials of BA and NaB to treat gut inflammatory diseases.

CKD-506: A novel HDAC6-selective inhibitor that exerts therapeutic effects in a rodent model of multiple sclerosis

Despite advances in therapeutic strategies for multiple sclerosis (MS), the therapy options remain limited with various adverse effects. Here, the therapeutic potential of CKD-506, a novel HDAC6-selective inhibitor, against MS was evaluated in mice with myelin oligodendrocyte glycoprotein35-55 (MOG35-55)-induced experimental autoimmune encephalitis (EAE) under various treatment regimens. CKD-506 exerted prophylactic and therapeutic effects by regulating peripheral immune responses and maintaining blood-brain barrier (BBB) integrity. In MOG35-55-re-stimulated splenocytes, CKD-506 decreased proliferation and downregulated the expression of IFN-γ and IL-17A. CKD-506 downregulated the levels of pro-inflammatory cytokines in the blood of EAE mice. Additionally, CKD-506 decreased the leakage of intravenously administered Evans blue into the spinal cord; CD4+ T cells and CD4-CD11b+CD45+ macrophage/microglia in the spinal cord was also decreased. Moreover, CKD-506 exhibited therapeutic efficacy against MS, even when drug administration was discontinued from day 15 post-EAE induction. Disease exacerbation was not observed when fingolimod was changed to CKD-506 from day 15 post-EAE induction. CKD-506 alleviated depression-like behavior at the pre-symptomatic stage of EAE. In conclusion, CKD-506 exerts therapeutic effects by regulating T cell- and macrophage-mediated peripheral immune responses and strengthening BBB integrity. Our results suggest that CKD-506 is a potential therapeutic agent for MS.

Therapeutic Use of Valproic Acid and All-Trans Retinoic Acid in Acute Myeloid Leukemia-Literature Review and Discussion of Possible Use in Relapse after Allogeneic Stem Cell Transplantation

Even though allogeneic stem cell transplantation is the most intensive treatment for acute myeloid leukemia (AML), chemo-resistant leukemia relapse is still one of the most common causes of death for these patients, as is transplant-related mortality, i.e., graft versus host disease, infections, and organ damage. These relapse patients are not always candidates for additional intensive therapy or re-transplantation, and many of them have decreased quality of life and shortened expected survival. The efficiency of azacitidine for treatment of posttransplant AML relapse has been documented in several clinical trials. Valproic acid is an antiepileptic fatty acid that exerts antileukemic activity through histone deacetylase inhibition. The combination of valproic acid and all-trans retinoic acid (ATRA) is well tolerated even by unfit or elderly AML patients, and low-toxicity chemotherapy (e.g., azacitidine) can be added to this combination. The triple combination of azacitidine, valproic acid, and ATRA may therefore represent a low-intensity and low-toxicity alternative for these patients. In the present review, we review and discuss the general experience with valproic acid/ATRA in AML therapy and we discuss its possible use in low-intensity/toxicity treatment of post-allotransplant AML relapse. Our discussion is further illustrated by four case reports where combined treatments with sequential azacitidine/hydroxyurea, valproic acid, and ATRA were used.

Selective Targeting of Epigenetic Readers and Histone Deacetylases in Autoimmune and Inflammatory Diseases: Recent Advances and Future Perspectives

Histone deacetylases (HDACs) and bromodomain-containing proteins (BCPs) play a key role in chromatin remodeling. Based on their ability to regulate inducible gene expression in the context of inflammation and cancer, HDACs and BCPs have been the focus of drug discovery efforts, and numerous small-molecule inhibitors have been developed. However, dose-limiting toxicities of the first generation of inhibitors, which typically target multiple HDACs or BCPs, have limited translation to the clinic. Over the last decade, an increasing effort has been dedicated to designing class-, isoform-, or domain-specific HDAC or BCP inhibitors, as well as developing strategies for cell-specific targeted drug delivery. Selective inhibition of the epigenetic modulators is helping to elucidate the functions of individual epigenetic proteins and has the potential to yield better and safer therapeutic strategies. In accordance with this idea, several in vitro and in vivo studies have reported the ability of more selective HDAC/BCP inhibitors to recapitulate the beneficial effects of pan-inhibitors with less unwanted adverse events. In this review, we summarize the most recent advances with these strategies, discussing advantages and limitations of these approaches as well as some therapeutic perspectives, focusing on autoimmune and inflammatory diseases.

Hybrid inhibitors of DNA and HDACs remarkably enhance cytotoxicity in leukaemia cells

Chlorambucil is a nitrogen mustard-based DNA alkylating drug, which is widely used as a front-line treatment of chronic lymphocytic leukaemia (CLL). Despite its widespread application and success for the initial treatment of leukaemia, a majority of patients eventually develop acquired resistance to chlorambucil. In this regard, we have designed and synthesised a novel hybrid molecule, chloram-HDi that simultaneously impairs DNA and HDAC enzymes. Chloram-HDi efficiently inhibits the proliferation of HL-60 and U937 leukaemia cells with GI₅₀ values of 1.24 µM and 1.75 µM, whereas chlorambucil exhibits GI₅₀ values of 21.1 µM and 37.7 µM against HL-60 and U937 leukaemia cells, respectively. The mechanism behind its remarkably enhanced cytotoxicity is that chloram-HDi not only causes a significant DNA damage of leukaemia cells but also downregulates DNA repair protein, Rad52, resulting in the escalation of its DNA-damaging effect. Furthermore, chloram-HDi inhibits HDAC enzymes to induce the acetylation of α-tubulin and histone H3.

Garcinol Is an HDAC11 Inhibitor

Garcinol is a natural product from the Garcinia Indica fruit and is well-known as an antioxidant, anti-inflammatory, and anticancer agent. However, the understanding of its mechanism of action is still incomplete. It has been reported to be a histone acetyltransferase (HAT) inhibitor. Here, we surprisingly found that garcinol is a potent histone deacetylase 11 (HDAC11) inhibitor (IC₅₀ ∼ 5 μM in vitro with the HPLC assay and IC₅₀ ∼ 10 μM in the cellular SHMT2 fatty acylation assay), which is comparable to previously reported HDAC11 inhibitors. Additionally, among all the HDACs tested, garcinol specifically inhibits HDAC11 over other HDACs. HDAC11 is the only class IV HDAC, and there are very few inhibitors available for it. Therefore, this study provides a new HDAC11 inhibitor lead from natural products and may help explain the various biological activities of garcinol.

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.

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.

Epigenetics of Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) is a chronic cholestatic liver disease with non-suppurative destruction of the intrahepatic bile ducts. The interplay of genetics and environmental triggers contributes to the onset of the disease and subsequently results in cholestasis and progressive fibrosis. Recently, genome-wide association studies (GWAS) have identified multiple genes influencing the susceptibility to PBC in HLA and non-HLA loci. However, it is estimated that the known risk variants merely account for no more than 20% of the heritability of PBC and causes of the remaining heritability remain uncertain. Increasing evidence suggests that the presence of epigenetic abnormalities may explain the "missing heritability" that cannot be captured by GWAS. Among these epigenetic mechanisms, DNA methylation, histone modification, and noncoding RNAs (i.e. miRNA and lncRNA) are involved in the pathogenesis of PBC. Additionally, telomere dysregulation in biliary epithelial cells (BECs) may play a role in disease onset, whereas a deficiency in sex chromosome and skewed gene expression in the X chromosome may to some extent explain the female dominance in PBC.

HDAC6-specific inhibitor suppresses Th17 cell function via the HIF-1α pathway in acute lung allograft rejection in mice

Background: Previous animal experiments and clinical studies indicated the critical role of Th17 cells in lung transplant rejection. Therefore, the downregulation of Th17 cell function in lung transplant recipients is of great interest. Methods: We established an orthotopic mouse lung transplantation model to investigate the role of histone deacetylase 6-specific inhibitor (HDAC6i), Tubastatin A, in the suppression of Th17 cells and attenuation of pathologic lesions in lung allografts. Moreover, mechanism studies were conducted in vitro. Results: Tubastatin A downregulated Th17 cell function in acute lung allograft rejection, prolonged the survival of lung allografts, and attenuated acute rejection by suppressing Th17 cell accumulation. Consistently, exogenous IL-17A supplementation eliminated the protective effect of Tubastatin A. Also, hypoxia-inducible factor-1α (HIF-1α) was overexpressed in a lung transplantation mouse model. HIF-1α deficiency suppressed Th17 cell function and attenuated lung allograft rejection by downregulating retinoic acid-related orphan receptor γt (ROR γt) expression. We showed that HDAC6i downregulated HIF-1α transcriptional activity under Th17-skewing conditions in vitro and promoted HIF-1α protein degradation in lung allografts. HDAC6i did not affect the suppression of HIF-1α^-/- naïve CD4⁺ T cell differentiation into Th17 cell and attenuation of acute lung allograft rejection in HIF-1α-deficient recipient mice. Conclusion: These findings suggest that Tubastatin A downregulates Th17 cell function and suppresses acute lung allograft rejection, at least partially, via the HIF-1α/ RORγt pathway.

Suberoylanilide hydroxamic acid alleviates orthotopic liver transplantation‑induced hepatic ischemia‑reperfusion injury by regulating the AKT/GSK3β/NF‑κB and AKT/mTOR pathways in rat Kupffer cells

Multiple mechanisms are involved in regulating hepatic ischemia-reperfusion injury (IRI), in which Kupffer cells (KCs), which are liver-resident macrophages, play critical roles by regulating inflammation and the immune response. Suberoylanilide hydroxamic acid (SAHA), a pan-histone deacetylase inhibitor, has anti-inflammatory effects and induces autophagy. To investigate whether SAHA ameliorates IRI and the mechanisms by which SAHA exerts its effects, an orthotopic liver transplantation (OLT) rat model was established after treatment with SAHA. The results showed that SAHA effectively ameliorated OLT-induced IRI by reducing M1 polarization of KCs through inhibition of the AKT/glycogen synthase kinase (GSK)3β/NF-κB signaling pathway. Furthermore, the present study found that SAHA upregulates autophagy 5 protein (ATG5)/LC3B in KCs through the AKT/mTOR signaling pathway and inhibition of autophagy by knockdown of ATG5 in KCs partly impaired the protective effect of SAHA on IR-injured liver. Therefore, the current study demonstrated that SAHA reduces M1 polarization of KCs by inhibiting the AKT/GSK3β/NF-κB pathway and upregulates autophagy in KCs through the AKT/mTOR signaling pathway, which both alleviate OLT-induced IRI. The present study revealed that SAHA may be a novel treatment for the amelioration of OLT-induced IRI.

B cell-intrinsic epigenetic modulation of antibody responses by dietary fiber-derived short-chain fatty acids

Short-chain fatty acids (SCFAs) butyrate and propionate are metabolites from dietary fiber's fermentation by gut microbiota that can affect differentiation or functions of T cells, macrophages and dendritic cells. We show here that at low doses these SCFAs directly impact B cell intrinsic functions to moderately enhance class-switch DNA recombination (CSR), while decreasing at higher doses over a broad physiological range, AID and Blimp1 expression, CSR, somatic hypermutation and plasma cell differentiation. In human and mouse B cells, butyrate and propionate decrease B cell Aicda and Prdm1 by upregulating select miRNAs that target Aicda and Prdm1 mRNA-3′UTRs through inhibition of histone deacetylation (HDAC) of those miRNA host genes. By acting as HDAC inhibitors, not as energy substrates or through GPR-engagement signaling in these B cell-intrinsic processes, these SCFAs impair intestinal and systemic T-dependent and T-independent antibody responses. Their epigenetic impact on B cells extends to inhibition of autoantibody production and autoimmunity in mouse lupus models.

Dietary fiber-derived short-chain fatty acids (SCFA) act as histone deacetylase (HDAC) inhibitors on Tregs and innate immune cells, promoting immune tolerance by altering gene expression. Here the authors show that SCFA HDAC inhibitor activity impacts B cell differentiation, antibody responses and antibody-driven autoimmunity.

Treg cells in health and autoimmune diseases: New insights from single cell analysis

Autoimmune diseases, such as Systemic Lupus Erythematosus (SLE) or Rheumatoid Arthritis (RA) are characterized by the breakdown of immunological tolerance. Defects of regulatory T cells have been described among the various mechanisms, that are important for the development of autoimmune diseases, due to their critical role as regulators of peripheral immune tolerance and homeostasis. Initially T suppressor cells have been described as one population of peripheral T cells. Based on new technological advances a new understanding of the heterogeneity of different Treg cell populations in the lymphoid and non-lymphoid tissue has evolved over the last years. While initially Foxp3 has been defined as the main master regulator of Treg cells, we have learned that Treg cells from various tissue can be identified by a specific transcriptomic and epigenetic signature. Epigenetic mechanisms allow Treg cell stability, but we have also learned that certain Treg subsets are plastic and can under specific circumstances even enhance autoimmunity and inflammatory processes. Quantitative and functional defects of Treg cells have been observed in a variety of autoimmune diseases. Due to our understanding of the nature of this cell population, Treg cells have been a target of new Treg based therapies, such as low-dose IL-2. In addition, ongoing clinical trials aim to test safety and efficacy of transferred, in vitro expanded Treg cells in patients with autoimmune diseases and transplant patients.

Activity-Guided Design of HDAC11-Specific Inhibitors

Mammalian histone deacetylases (HDACs) are a class of enzymes that play important roles in biological pathways. Existing HDAC inhibitors target multiple HDACs without much selectivity. Inhibitors that target one particular HDAC will be useful for investigating the biological functions of HDACs and for developing better therapeutics. Here, we report the development of HDAC11-specific inhibitors using an activity-guided rational design approach. The enzymatic activity and biological function of HDAC11 have been little known, but recent reports suggest that it has efficient defatty-acylation activity and that inhibiting it could be useful for treating a variety of human diseases, including viral infection, multiple sclerosis, and metabolic diseases. Our best inhibitor, SIS17, is active in cells and inhibited the demyristoylation of a known HDAC11 substrate, serine hydroxymethyl transferase 2, without inhibiting other HDACs. The activity-guided design may also be useful for the development of isoform-specific inhibitors for other classes of enzymes.

Achievement of Tolerance Induction to Prevent Acute Graft-vs.-Host Disease

Acute graft-vs.-host disease (GVHD) limits the efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT), a main therapy to treat various hematological disorders. Despite rapid progress in understanding GVHD pathogenesis, broad immunosuppressive agents are most often used to prevent and remain the first line of therapy to treat GVHD. Strategies enhancing immune tolerance in allo-HSCT would permit reductions in immunosuppressant use and their associated undesirable side effects. In this review, we discuss the mechanisms responsible for GVHD and advancement in strategies to achieve immune balance and tolerance thereby avoiding GVHD and its complications.

Alkylating histone deacetylase inhibitors may have therapeutic value in experimental myeloperoxidase-ANCA vasculitis

Current therapies for treating antineutrophil cytoplasm autoantibody (ANCA)-associated vasculitis include cyclophosphamide and corticosteroids. Unfortunately, these agents are associated with severe adverse effects, despite inducing remission in most patients. Histone deacetylase inhibitors are effective in rodent models of inflammation and act synergistically with many pharmacological agents, including alkylating agents like cyclophosphamide. EDO-S101 is an alkylating fusion histone deacetylase inhibitor molecule combining the DNA alkylating effect of Bendamustine with a pan-histone deacetylase inhibitor, Vorinostat. Here we studied the effects of EDO-S101 in two established rodent models of ANCA-associated vasculitis: a passive mouse model of anti-myeloperoxidase IgG-induced glomerulonephritis and an active rat model of myeloperoxidase-ANCA microscopic polyangiitis. Although pretreatment with EDO-S101 reduced circulating leukocytes, it did not prevent the development of passive IgG-induced glomerulonephritis in mice. On the other hand, treatment in rats significantly reduced glomerulonephritis and lung hemorrhage. EDO-S101 also significantly depleted rat B and T cells, and induced DNA damage and apoptosis in proliferating human B cells, suggesting a selective effect on the adaptive immune response. Thus, EDO-S101 may have a role in treatment of ANCA-associated vasculitis, operating primarily through its effects on the adaptive immune response to the autoantigen myeloperoxidase.

Diarylcyclopropane hydroxamic acid inhibitors of histone deacetylase 4 designed by combinatorial approach and QM/MM calculations

Inhibitors of histone deacetylase superfamily (HDAC), which induce cell cycle arrest, trigger cell death and reduce angiogenesis appear as promising anti-cancer drugs targeting the epigenetic regulation of gene expression. Approved HDAC inhibitors were found effective against haematological and solid malignancies, other HDACIs are currently in clinical trials for the treatment of neurological diseases or immune disorders. Among those, diarylcyclopropane hydroxamic acids (DCHA) were found to be potent and selective inhibitors of the class IIa HDACs, specifically HDAC4, a pharmacological target for the treatment of Huntington's disease and muscular atrophy. Crystallographic analysis revealed that one of the aryl groups of the DCHA fills the lower specificity pocket of the HDAC4 catalytic site that is specific for the class IIa HDACs. We have used computer-assisted combinatorial chemistry, hybrid quantum mechanics/molecular mechanics (QM/MM) with implicit solvation and QSAR models to optimize DCHA inhibitors and propose more potent DCHA analogues. The QM/MM approach has been selected since the process of inhibitor binding to the catalytic zinc and polar amino acid residues of the deacetylase active site induces considerable rearrangement of electron density of the inhibitor. Virtual combinatorial library consisting of 12180 DCHA analogues was focused by means of structure-based evaluation to form a small combinatorial subset enriched in potentially interesting inhibitor candidates. Two validated QSAR models making use of computed relative binding affinities of the DCHA inhibitors to the HDAC4 (ΔΔG_com^QM/MM) were utilized to estimate the inhibitory potencies of the new analogues. The predicted half-maximal inhibitory concentrations (IC₅₀^pre) of the designed analogues fall into the low nanomolar concentration range and their predicted ADME properties are also favourable. The best designed DCHA analogues contain indazole, phenylpiperidine, phenyloxazole or hydroxypyridine moieties and stabilize bound inhibitors by hydrogen bonds to the catalytic water molecule and backbone carbonyl groups of the deacetylase active site residues. This makes them more potent and more specific inhibitors towards the HDAC4 isoform than the known diarylcyclopropane hydroxamic acids. The analogues are recommended for synthesis and experimental verification of inhibitory potencies in medicinal chemistry laboratories.

Histone methylation and acetylation in macrophages as a mechanism for regulation of inflammatory responses

Macrophages respond to noxious stimuli and contribute to inflammatory responses by eliminating pathogens or damaged tissue and maintaining homeostasis. Response to activation signals and maintenance of homeostasis require tight regulation of genes involved in macrophage activation and inactivation processes, as well as genes involved in determining their polarization state. Recent evidence has revealed that such regulation occurs through histone modifications that render inflammatory or polarizing gene promoters accessible to transcriptional complexes. Thus, inflammatory and anti-inflammatory genes are regulated by histone acetylation and methylation, determining their activation state. Herein, we review the current knowledge on the role of histone modifying enzymes (acetyltransferases, deacetylases, methyltransferases, and demethylases) in determining the responsiveness and M1 or M2 polarization of macrophages. The contribution of these enzymes in the development of inflammatory diseases is also presented.

Class I histone deacetylase inhibition improves pancreatitis outcome by limiting leukocyte recruitment and acinar-to-ductal metaplasia

BACKGROUND AND PURPOSE

Pancreatitis is a common inflammation of the pancreas with rising incidence in many countries. Despite improvements in diagnostic techniques, the disease is associated with high risk of severe morbidity and mortality and there is an urgent need for new therapeutic interventions. In this study, we evaluated whether histone deacetylases (HDACs), key epigenetic regulators of gene transcription, are involved in the development of the disease.

EXPERIMENTAL APPROACH

We analysed HDAC regulation during cerulein-induced acute, chronic and autoimmune pancreatitis using different transgenic mouse models. The functional relevance of class I HDACs was tested with the selective inhibitor MS-275 in vivo upon pancreatitis induction and in vitro in activated macrophages and primary acinar cell explants.

KEY RESULTS

HDAC expression and activity were up-regulated in a time-dependent manner following induction of pancreatitis, with the highest abundance observed for class I HDACs. Class I HDAC inhibition did not prevent the initial acinar cell damage. However, it effectively reduced the infiltration of inflammatory cells, including macrophages and T cells, in both acute and chronic phases of the disease, and directly disrupted macrophage activation. In addition, MS-275 treatment reduced DNA damage in acinar cells and limited acinar de-differentiation into acinar-to-ductal metaplasia in a cell-autonomous manner by impeding the EGF receptor signalling axis.

CONCLUSIONS AND IMPLICATIONS

These results demonstrate that class I HDACs are critically involved in the development of acute and chronic forms of pancreatitis and suggest that blockade of class I HDAC isoforms is a promising target to improve the outcome of the disease.

Modulation of Donor-Specific Antibody Production After Organ Transplantation by Valproic Acid: A Histone Deacetylase Inhibitor

BACKGROUND

Antibody-mediated rejection, mediated by donor-specific antibodies, is emerging as a leading cause for allograft dysfunction in organ transplantation. Histone deacetylase inhibitors (HDACi) have potential immunosuppressive action, but their effects on antibody-mediated rejection and B cell function in organ transplantation have not been fully explored.

METHODS

The impacts of valproic acid (VPA), an HDACi, on isolated murine B cell proliferation, apoptosis, class switch recombination (CSR), differentiation, and secretion of immunoglobulin were investigated in vitro and in vivo. Molecular mechanisms were also explored by analyzing the expression of the activation-induced cytidinedeaminase, B lymphocyte-induced maturation protein-1 (Blimp-1/Pridm1), X-box-binding protein 1 and interferon-regulatory factor 4. Mouse cardiac transplant model was used to evaluate the regulatory effects of VPA on B cell response in vivo.

RESULTS

Valproic acid significantly inhibited B cell CSR, plasma cell differentiation, thereby reduced antibody generation in a dose-dependent manner without altering B cell proliferation and apoptosis in vitro and in vivo. Activation-induced cytidinedeaminase, Blimp-1/Pridm1 and X-box-binding protein 1 expression were repressed by VPA treatment in a dose-dependent manner, whereas no obvious changes were observed on interferon-regulatory factor 4 expression. Although VPA alone did not prolong the graft medium survival time after murine heart transplantation, the low levels of donor-specific antibody, especially IgG in serum and the less numbers of plasma cells in the spleen were observed in VPA-treated mice.

CONCLUSIONS

Valproic acid inhibited B cell CSR and plasma cell differentiation in vitro and in nitrophenyl-chicken gamma globulin-immunized and heart transplant recipient mice. HDACi might be a therapeutic agent targeting B cell response after organ transplantation.

Empowering Regulatory T Cells in Autoimmunity

Regulatory T cells (Tregs) are capable of dampening immune-mediated inflammation and avert the destructive effects of uncontrolled inflammation. Distinct molecules and pathways, including various transcription factors, phosphatases, and kinases, impact the ability of Tregs to function as negative regulators of the immune response, and are presumably amenable to therapeutic manipulation. Here, we discuss recently identified molecular networks and the therapeutic potential for treating autoimmune diseases.

HDAC Inhibitors as Epigenetic Regulators of the Immune System: Impacts on Cancer Therapy and Inflammatory Diseases

Histone deacetylase (HDAC) inhibitors are powerful epigenetic regulators that have enormous therapeutic potential and have pleiotropic effects at the cellular and systemic levels. To date, HDAC inhibitors are used clinically for a wide variety of disorders ranging from hematopoietic malignancies to psychiatric disorders, are known to have anti-inflammatory properties, and are in clinical trials for several other diseases. In addition to influencing gene expression, HDAC enzymes also function as part of large, multisubunit complexes which have many nonhistone targets, alter signaling at the cellular and systemic levels, and result in divergent and cell-type specific effects. Thus, the effects of HDAC inhibitor treatment are too intricate to completely understand with current knowledge but the ability of HDAC inhibitors to modulate the immune system presents intriguing therapeutic possibilities. This review will explore the complexity of HDAC inhibitor treatment at the cellular and systemic levels and suggest strategies for effective use of HDAC inhibitors in biomedical research, focusing on the ability of HDAC inhibitors to modulate the immune system. The possibility of combining the documented anticancer effects and newly emerging immunomodulatory effects of HDAC inhibitors represents a promising new combinatorial therapeutic approach for HDAC inhibitor treatments.

Exploration of the labeling of [11C]tubastatin A at the hydroxamic acid site with [11C]carbon monoxide

We aimed to label tubastatin A (1) with carbon-11 (t1/2 = 20.4 min) in the hydroxamic acid site to provide a potential radiotracer for imaging histone deacetylase 6 in vivo with positron emission tomography. Initial attempts at a one-pot Pd-mediated insertion of [(11)C]carbon monoxide between the aryl iodide (2) and hydroxylamine gave low radiochemical yields (<5%) of [(11) C]1. Labeling was achieved in useful radiochemical yields (16.1 ± 5.6%, n = 4) through a two-step process based on Pd-mediated insertion of [(11)C]carbon monoxide between the aryl iodide (2) and p-nitrophenol to give the [(11)C]p-nitrophenyl ester ([(11)C]5), followed by ultrasound-assisted hydroxyaminolysis of the activated ester with excess hydroxylamine in a DMSO/THF mixture in the presence of a strong phosphazene base P1-t-Bu. However, success in labeling the hydroxamic acid group of [(11)C]tubastatin A was not transferable to the labeling of three other model hydroxamic acids.

Targeting Treg signaling for the treatment of autoimmune diseases

Regulatory T (Treg) cells are crucial players in the prevention of autoimmunity. Treg lineage commitment and functional stability are influenced by selected extracellular signals from the local environment, shaped by distinctive intracellular signaling network, and secured by their unique epigenetic profile. Recent advances in our understanding of the complex processes of Treg lineage differentiation, maintenance, and function has paved the way for developing strategies to manipulate these important cells for therapeutic benefit in many diseases. In this review, we will summarize recent advances in our understanding of Treg biology as well as Treg-targeted therapies in the context of autoimmune disease.

Targeting downstream transcription factors and epigenetic modifications following Toll-like receptor 7/8 ligation to forestall tissue injury in anti-Ro60 associated heart block

Based on the consistent demonstration of fibrosis of the atrioventricular node surrounded by macrophages and multinucleated giant cells in anti-Ro antibody exposed fetuses dying with heart block, this study focuses on macrophage signaling stimulated by ssRNA associated with the Ro60 protein and the impact of antagonizing innate cell drivers such as TLR7/8. Transcriptome and epigenetic modifications which affect transcription factors, NF-κB and STAT1, were selected to evaluate the phenotype of macrophages in which TLR7/8 was ligated following treatment with either anti-Ro60/Ro60/hY3 RNA immune complexes or transfection with hY3. Based on microarray, TNF and IL6 were among the most highly upregulated genes in both stimulated conditions, each of which was significantly inhibited by preincubation with hydroxychloroquine (HCQ). In contrast, following stimulation of macrophages with either TNF-α or IFN-α, which do not signal through TLR, the resultant gene expression was refractory to HCQ. Ligation of TLR7/8 resulted in increased histone methylation as measured by increased H3K4me2, a requirement for binding of NF-κB at certain promoters, specifically the kB1 region in the TNF promoter (ChIP-qPCR), which was significantly decreased by HCQ. In summary, these results support that the HCQ-sensitive phenotype of hY3 stimulated macrophages reflects the bifurcation of TLR downstream signals involving NF-κB and STAT 1 pathways and for the former dimethylation of H3K4. Accordingly, HCQ may act more as a preventive measure in downregulating the initial production of IFN-α or TNF-α and not affect the resultant autocoid stimulation reflected in TNF-α and IFN-α responsive genes. The beneficial scope of antimalarials in the prevention of organ damage, inclusive of heart block in an anti-Ro offspring or more broadly SLE, may include in part, a mechanism targeting TLR-dependent epigenetic modification.

Mutagenesis Study Reveals the Rim of Catalytic Entry Site of HDAC4 and -5 as the Major Binding Surface of SMRT Corepressor

Histone deacetylases (HDACs) play a pivotal role in eukaryotic gene expression by modulating the levels of acetylation of chromatin and related transcription factors. In contrast to class I HDACs (HDAC1, -2, -3 and -8), the class IIa HDACs (HDAC4, -5, -7 and -9) harbor cryptic deacetylases activity and recruit the SMRT-HDAC3 complex to repress target genes in vivo. In this regard, the specific interaction between the HDAC domain of class IIa HDACs and the C-terminal region of SMRT repression domain 3 (SRD3c) is known to be critical, but the molecular basis of this interaction has not yet been addressed. Here, we used an extensive mutant screening system, named the “partitioned one- plus two-hybrid system”, to isolate SRD3c interaction-defective (SRID) mutants over the entire catalytic domains of HDAC4 (HDAC4c) and -5. The surface presentation of the SRID mutations on the HDAC4c structure revealed that most of the mutations were mapped to the rim surface of the catalytic entry site, strongly suggesting this mutational hot-spot region as the major binding surface of SRD3c. Notably, among the HDAC4c surface residues required for SRD3c binding, some residues (C667, C669, C751, D759, T760 and F871) are present only in class IIa HDACs, providing the molecular basis for the specific interactions between SRD3c and class IIa enzymes. To investigate the functional consequence of SRID mutation, the in vitro HDAC activities of HDAC4 mutants immuno-purified from HEK293 cells were measured. The levels of HDAC activity of the HDAC4c mutants were substantially decreased compared to wild-type. Consistent with this, SRID mutations of HDAC4c prevented the association of HDAC4c with the SMRT-HDAC3 complex in vivo. Our findings may provide structural insight into the binding interface of HDAC4 and -5 with SRD3c, as a novel target to design modulators specific to these enzymes.

Epigenetic pathways in macrophages emerge as novel targets in atherosclerosis

Atherosclerosis is a lipid-driven chronic inflammatory disorder. Monocytes and macrophages are key immune cells in the development of disease and clinical outcome. It is becoming increasingly clear that epigenetic pathways govern many aspects of monocyte and macrophage differentiation and activation. The dynamic regulation of epigenetic patterns provides opportunities to alter disease-associated epigenetic states. Therefore, pharmaceutical companies have embraced the targeting of epigenetic processes as new approaches for interventions. Particularly histone deacetylase (Hdac) inhibitors and DNA-methyltransferase inhibitors have long received attention and several of them have been approved for clinical use in relation to hematological malignancies. The key focus is still on oncology, but Alzheimer's disease, Huntington's disease and inflammatory disorders are coming in focus as well. These developments raise opportunities for the epigenetic targeting in cardiovascular disease (CVD). In this review we discuss the epigenetic regulation of the inflammatory pathways in relation to atherosclerosis with a specific attention to monocyte- and macrophage-related processes. What are the opportunities for future therapy of atherosclerosis by epigenetic interventions?

Manipulation of B-cell responses with histone deacetylase inhibitors

Histone deacetylase inhibitors (HDACi) are approved for treating certain haematological malignancies, however, recent evidence also illustrates they are modulators of the immune system. In experimental models, HDACi are particularly potent against malignancies originating from the B-lymphocyte lineage. Here we examine the ability of this class of compounds to modify both protective and autoimmune antibody responses. In vitro, HDACi affect B-cell proliferation, survival and differentiation in an HDAC-class-dependent manner. Strikingly, treatment of lupus-prone Mrl/lpr mice with the HDACi panobinostat significantly reduces autoreactive plasma-cell numbers, autoantibodies and nephritis, while other immune parameters remain largely unaffected. Immunized control mice treated with panobinostat or the clinically approved HDACi vorinostat have significantly impaired primary antibody responses, but these treatments surprisingly spare circulating memory B cells. These studies indicate that panobinostat is a potential therapy for B-cell-driven autoimmune conditions and HDACi do not induce major long-term detrimental effects on B-cell memory.

[Epigenetics in inflammatory systemic diseases]

In addition to analysis of the genetic code, in recent years more and more studies have concentrated on changes in the epigenetic code. Epigenetic mechanisms determine which genes in a cell are transcribed and thus form the phenotype of a cell. The epigenetic code can be changed by environmental influences, which allows cells to adapt to longstanding changes in the environment. Therefore, it is feasible to assume that epigenetic changes are the molecular basis for long-term effects of the environment on disease development. In particular in tumors and chronic inflammatory diseases epigenetic changes were found to correlate with disease severity and progression. Knowledge about these epigenetic changes might help that epigenetic modifications can be used in the future as biomarkers, prognostic factors and therapeutic targets.

HDAC6 deacetylase activity is critical for lipopolysaccharide-induced activation of macrophages

Activated macrophages play an important role in both innate and adaptive immune responses, and aberrant activation of macrophages often leads to inflammatory and immune disorders. However, the molecular mechanisms of how macrophages are activated are not fully understood. In this study, we identify a novel role for histone deacetylse 6 (HDAC6) in lipopolysaccharide (LPS)-induced macrophage activation. Our data show that suppression of HDAC6 activity significantly restrains LPS-induced activation of macrophages and production of pro-inflammatory cytokines. Further study reveals that the regulation of macrophage activation by HDAC6 is independent of F-actin polymerization and filopodium formation; instead, it is mediated by the effects of HDAC6 on cell adhesion and microtubule acetylation. These data thus suggest that HDAC6 is an important regulator of LPS-induced macrophage activation and might be a potential target for the management of inflammatory disorders.

Histone deacetylases and their inhibitors in cancer, neurological diseases and immune disorders

Epigenetic aberrations, which are recognized as key drivers of several human diseases, are often caused by genetic defects that result in functional deregulation of epigenetic proteins, their altered expression and/or their atypical recruitment to certain gene promoters. Importantly, epigenetic changes are reversible, and epigenetic enzymes and regulatory proteins can be targeted using small molecules. This Review discusses the role of altered expression and/or function of one class of epigenetic regulators--histone deacetylases (HDACs)--and their role in cancer, neurological diseases and immune disorders. We highlight the development of small-molecule HDAC inhibitors and their use in the laboratory, in preclinical models and in the clinic.

Epigenetic therapies - a new direction in clinical medicine

A major biomedical advance from recent years was the finding that gene expression and phenotypic traits may be shaped by potentially reversible and heritable modifications that occur without altering the sequence of the nucleotides, and became known as epigenetic changes. The term 'epigenetics' dates back to the 1940s, when it was first used in context of cellular differentiation decisions that are made during development. Since then, our understanding of epigenetic modifications that govern development and disease expanded considerably. The contribution of epigenetic changes to shaping phenotypes brings at least two major clinically relevant benefits. One of these, stemming from the reversibility of epigenetic changes, involves the possibility to therapeutically revert epigenetic marks to re-establish prior gene expression patterns. The strength and the potential of this strategy are illustrated by the first four epigenetic drugs that were approved in recent years and by the additional candidates that are at various stages in preclinical studies and clinical trials. The second particularity is the finding that epigenetic changes precede the appearance of histopathological modifications. This has the potential to facilitate the emergence of epigenetic biomarkers, some of which already entered the clinical arena, catalysing a major shift in prophylactic and therapeutic strategies, and promising to fill a decades-old gap in preventive medicine.

CD4(+) T cell lineage integrity is controlled by the histone deacetylases HDAC1 and HDAC2

Molecular mechanisms that maintain lineage integrity of helper T cells are largely unknown. Here we show histone deacetylases 1 and 2 (HDAC1 and HDAC2) as crucial regulators of this process. Loss of HDAC1 and HDAC2 during late T cell development led to the appearance of major histocompatibility complex (MHC) class II-selected CD4(+) helper T cells that expressed CD8-lineage genes such as Cd8a and Cd8b1. HDAC1 and HDAC2-deficient T helper type 0 (TH0) and TH1 cells further upregulated CD8-lineage genes and acquired a CD8(+) effector T cell program in a manner dependent on Runx-CBFβ complexes, whereas TH2 cells repressed features of the CD8(+) lineage independently of HDAC1 and HDAC2. These results demonstrate that HDAC1 and HDAC2 maintain integrity of the CD4 lineage by repressing Runx-CBFβ complexes that otherwise induce a CD8(+) effector T cell-like program in CD4(+) T cells.

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.

Regulatory T cells as immunotherapy

Regulatory T cells (Tregs) suppress exuberant immune system activation and promote immunologic tolerance. Because Tregs modulate both innate and adaptive immunity, the biomedical community has developed an intense interest in using Tregs for immunotherapy. Conditions that require clinical tolerance to improve outcomes – autoimmune disease, solid organ transplantation, and hematopoietic stem cell transplantation – may benefit from Treg immunotherapy. Investigators have designed ex vivo strategies to isolate, preserve, expand, and infuse Tregs. Protocols to manipulate Treg populations in vivo have also been considered. Barriers to clinically feasible Treg immunotherapy include Treg stability, off-cell effects, and demonstration of cell preparation purity and potency. Clinical trials involving Treg adoptive transfer to treat graft versus host disease preliminarily demonstrated the safety and efficacy of Treg immunotherapy in humans. Future work will need to confirm the safety of Treg immunotherapy and establish the efficacy of specific Treg subsets for the treatment of immune-mediated disease.

Down-regulation of miR-301a suppresses pro-inflammatory cytokines in Toll-like receptor-triggered macrophages

In many types of tumours, especially pancreatic adenocarcinoma, miR-301a is over-expressed. This over-expression results in negative regulation of the target gene of miR-301a, the nuclear factor-κB (NF-κB) repressing factor (NKRF), increasing the activation of NF-κB and production of NF-κB-responsive pro-inflammatory cytokines such as interleukin-8, interferon-β, nitric oxide synthase 2A and cytochrome oxidase subunit 2 (COX-2). However, in immune cells, mechanisms that regulate miR-301a have not been reported. Similar to tumour cells, Toll-like receptor (TLR) -activated macrophages produce NF-κB-responsive pro-inflammatory cytokines. Therefore, it is of considerable interest to determine whether miR-301a regulates the secretion of cytokines by immune cells. In the present study, we demonstrate that the expression of miR-301a was decreased in TLR-triggered macrophages. Through targeting NKRF, miR-301a affected the activity of NF-κB and the expression of pro-inflammatory genes downstream of NF-κB such as COX-2, prostaglandin E2 and interleukin-6. In addition, when lipopolysaccharide-treated macrophages were simultaneously stimulated with trichostatin A, an inhibitor of histone deacetylases, the expression of miR-301a increased, whereas NKRF and pro-inflammatory cytokine expression decreased. However, further investigation revealed that there was no correlation between the induction of miR-301a and the inhibitory effect of trichostatin A on lipopolysaccharide-induced gene expression in macrophages. In summary, our study indicates a new mechanism by which miR-301a regulates inflammatory cytokine expression in macrophages, which may clarify the regulatory role of microRNAs in immune-mediated inflammatory responses.

Design, synthesis, and biological evaluation of potent and selective class IIa histone deacetylase (HDAC) inhibitors as a potential therapy for Huntington's disease

Inhibition of class IIa histone deacetylase (HDAC) enzymes have been suggested as a therapeutic strategy for a number of diseases, including Huntington's disease. Catalytic-site small molecule inhibitors of the class IIa HDAC4, -5, -7, and -9 were developed. These trisubstituted diarylcyclopropanehydroxamic acids were designed to exploit a lower pocket that is characteristic for the class IIa HDACs, not present in other HDAC classes. Selected inhibitors were cocrystallized with the catalytic domain of human HDAC4. We describe the first HDAC4 catalytic domain crystal structure in a "closed-loop" form, which in our view represents the biologically relevant conformation. We have demonstrated that these molecules can differentiate class IIa HDACs from class I and class IIb subtypes. They exhibited pharmacokinetic properties that should enable the assessment of their therapeutic benefit in both peripheral and CNS disorders. These selective inhibitors provide a means for evaluating potential efficacy in preclinical models in vivo.