Histone deacetylase inhibitors modulate interleukin 6-dependent CD4+ T cell polarization in vitro and in vivo

Mesenchymal stem cells-derived extracellular vesicles ameliorate lupus nephritis by regulating T and B cell responses

BACKGROUND

Human umbilical cord mesenchymal stem cells-derived extracellular vesicles (hUCMSC-EVs) have potent immunomodulatory properties similar to parent cells. This study investigated the therapeutic effects and immunomodulatory mechanisms of hUCMSC-EVs in an experimental lupus nephritis model.

METHODS

The hUCMSC-EVs were isolated by using differential ultracentrifugation. In vivo, the therapeutic effects of hUCMSC-EVs in lupus-prone MRL/lpr mice were investigated, and the mechanisms of treatment were explored according to the abnormal T and B cell responses among both the spleen and kidney.

RESULTS

MRL/lpr mice treated with hUCMSC-EVs reduced proteinuria extent, serum creatinine and renal pathological damage; decreased splenic index and serum anti-dsDNA IgG level; and improved survival rate. hUCMSC-EVs lowered the percentage of T helper (Th)1 cells, double-negative T (DNT) cells, and plasma cells among splenocytes; inhibited the infiltration of Th17 cells but promoted regulatory T (Treg) cells in the kidney, followed by a reduction in pro-inflammatory cytokine levels(IFN-γ, IL-2, IL-6, IL-21, and IL-17 A). In addition, hUCMSC-EVs inhibited the activation of STAT3 and down-regulated IL-17 A protein levels in the kidney.

CONCLUSION

The results of this study demonstrated that hUCMSC-EVs had therapeutic effects on experimental lupus nephritis (LN) by regulating Th1/Th17/Treg imbalance and inhibiting DNT and plasma cells. Additionally, hUCMSC-EVs inhibited Th17 cell differentiation in kidney by regulating the IL-6/STAT3/IL-17 signal pathway, which might be an important mechanism for alleviating renal injury. Taken together, we demonstrated that hUCMSC-EVs regulating T and B cell immune responses might represent a novel mechanism of hUCMSCs in treating LN, thus providing a new strategy for treating LN.

Class IIa HDAC4 and HDAC7 cooperatively regulate gene transcription in Th17 cell differentiation

Class II histone deacetylases (HDACs) are important in regulation of gene transcription during T cell development. However, our understanding of their cell-specific functions is limited. In this study, we reveal that class IIa Hdac4 and Hdac7 (Hdac4/7) are selectively induced in transcription, guiding the lineage-specific differentiation of mouse T-helper 17 (Th17) cells from naive CD4+ T cells. Importantly, Hdac4/7 are functionally dispensable in other Th subtypes. Mechanistically, Hdac4 interacts with the transcription factor (TF) JunB, facilitating the transcriptional activation of Th17 signature genes such as Il17a/f. Conversely, Hdac7 collaborates with the TF Aiolos and Smrt/Ncor1-Hdac3 corepressors to repress transcription of Th17 negative regulators, including Il2, in Th17 cell differentiation. Inhibiting Hdac4/7 through pharmacological or genetic methods effectively mitigates Th17 cell-mediated intestinal inflammation in a colitis mouse model. Our study uncovers molecular mechanisms where HDAC4 and HDAC7 function distinctively yet cooperatively in regulating ordered gene transcription during Th17 cell differentiation. These findings suggest a potential therapeutic strategy of targeting HDAC4/7 for treating Th17-related inflammatory diseases, such as ulcerative colitis.

Propionate functions as a feeding state-dependent regulatory metabolite to counter proinflammatory signaling linked to nutrient load and obesity

Generally, fasting and refeeding confer anti- and proinflammatory effects, respectively. In humans, these caloric-load interventions function, in part, via regulation of CD4+ T cell biology. However, mechanisms orchestrating this regulation remain incomplete. We employed integrative bioinformatics of RNA sequencing and high-performance liquid chromatography-mass spectrometry data to measure serum metabolites and gene expression of peripheral blood mononuclear cells isolated from fasting and refeeding in volunteers to identify nutrient-load metabolite-driven immunoregulation. Propionate, a short chain fatty acid (SCFA), and the SCFA-sensing G protein-coupled receptor 43 (ffar2) were coordinately and inversely regulated by fasting and refeeding. Propionate and free fatty acid receptor agonists decreased interferon-γ and interleukin-17 and significantly blunted histone deacetylase activity in CD4+ T cells. Furthermore, propionate blunted nuclear factor κB activity and diminished interleukin-6 release. In parallel, propionate reduced phosphorylation of canonical T helper 1 (TH1) and TH17 regulators, STAT1 and STAT3, respectively. Conversely, knockdown of free fatty acid receptors significantly attenuated the anti-inflammatory role of propionate. Interestingly, propionate recapitulated the blunting of CD4+ TH cell activation in primary cells from obese individuals, extending the role of this metabolite to a disease associated with low-grade inflammation. Together, these data identify a nutrient-load responsive SCFA-G protein-coupled receptor linked pathway to regulate CD4+ TH cell immune responsiveness.

Histone and Histone Acetylation-Related Alterations of Gene Expression in Uninvolved Psoriatic Skin and Their Effects on Cell Proliferation, Differentiation, and Immune Responses

Psoriasis is a chronic immune-mediated skin disease in which the symptom-free, uninvolved skin carries alterations in gene expression, serving as a basis for lesion formation. Histones and histone acetylation-related processes are key regulators of gene expression, controlling cell proliferation and immune responses. Dysregulation of these processes is likely to play an important role in the pathogenesis of psoriasis. To gain a complete overview of these potential alterations, we performed a meta-analysis of a psoriatic uninvolved skin dataset containing differentially expressed transcripts from nearly 300 individuals and screened for histones and histone acetylation-related molecules. We identified altered expression of the replication-dependent histones HIST2H2AA3 and HIST2H4A and the replication-independent histones H2AFY, H2AFZ, and H3F3A/B. Eight histone chaperones were also identified. Among the histone acetyltransferases, ELP3 and KAT5 and members of the ATAC, NSL, and SAGA acetyltransferase complexes are affected in uninvolved skin. Histone deacetylation-related alterations were found to affect eight HDACs and members of the NCOR/SMRT, NURD, SIN3, and SHIP HDAC complexes. In this article, we discuss how histone and histone acetylation-related expression changes may affect proliferation and differentiation, as well as innate, macrophage-mediated, and T cell-mediated pro- and anti-inflammatory responses, which are known to play a central role in the development of psoriasis.

Structure-activity relationship, bioactivities, molecular mechanisms, and clinical application of nuciferine on inflammation-related diseases

Nuciferine aporphine alkaloid mainly exists in Nelumbo nucifera Gaertn and is a beneficial to human health, such as anti-obesity, lowering blood lipid, prevention of diabetes and cancer, closely associated with inflammation. Importantly, nuciferine may contribute to its bioactivities by exerting intense anti-inflammatory activities in multiple models. However, no review has summarized the anti-inflammatory effect of nuciferine. This review critically summarized the information regarding the structure-activity relationships of dietary nuciferine. Moreover, biological activities and clinical application on inflammation-related diseases, such as obesity, diabetes, liver, cardiovascular diseases, and cancer, as well as their potential mechanisms, involving oxidative stress, metabolic signaling, and gut microbiota has been reviewed. The current work provides a better understanding of the anti-inflammation properties of nuciferine against multiple diseases, thereby improving the utilization and application of nuciferine-containing plants across functional food and medicine.

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.

Taurohyodeoxycholic acid alleviates trinitrobenzene sulfonic acid induced ulcerative colitis via regulating Th1/Th2 and Th17/Treg cells balance

AIMS

Taurohyodeoxycholic acid (THDCA), a natural 6α-hydroxylated bile acid, exhibits intestinal anti-inflammatory effects. This study aimed to explore the efficacy of THDCA on ulcerative colitis and to reveal its mechanisms of action.

MAIN METHODS

Colitis was induced by intrarectal administration of trinitrobenzene sulfonic acid (TNBS) to mice. Mice in the treatment group were gavage THDCA (20, 40, and 80 mg/kg/day) or sulfasalazine (500 mg/kg/day) or azathioprine (10 mg/kg/day). The pathologic markers of colitis were comprehensively assessed. The levels of Th1-/Th2-/Th17-/Treg-related inflammatory cytokines and transcription factors were detected by ELISA, RT-PCR, and Western blotting. The balance of Th1/Th2 and Th17/Treg cells was analyzed by Flow cytometry.

KEY FINDINGS

THDCA significantly alleviated colitis by improving the body weight, colon length, spleen weight, histological characteristics, and MPO activity of colitis mice. THDCA reduced the secretion of Th1-/Th17-related cytokines (IFN-γ, IL-12p70, IL-6, IL-17A, IL-21, IL-22, and TNF-α) and the expressions of transcription factors (T-bet, STAT4, RORγt, and STAT3), but increase the production of Th2-/Treg-related cytokines (IL-4, IL-10, and TGF-β1) and the expressions of transcription factors (GATA3, STAT6, Foxp3, and Smad3) in the colon. Meanwhile, THDCA inhibited the expressions of IFN-γ, IL-17A, T-bet, and RORγt, but improved the expression of IL-4, IL-10, GATA3, and Foxp3 in the spleen. Furthermore, THDCA restored the proportion of Th1, Th2, Th17, and Treg cells, and balanced the Th1/Th2 and Th17/Treg immune response of colitis mice.

SIGNIFICANCE

THDCA can alleviate TNBS-induced colitis via regulating Th1/Th2 and Th17/Treg balance, which may represent a promising treatment for patients with colitis.

Histone deacetylase 1 and 3 inhibitors alleviate colon inflammation by inhibiting Th17 cell differentiation

Background

The etiology of inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), is not completely clear, but its pathogenesis is closely related to T helper 17 (Th17) cells. Several histone deacetylase (HDAC) inhibitors have been shown to exert potent anti‐inflammatory effects and modulate Th17 cell polarization. Owing to the large variety and broad expression of HDACs, finding specific therapeutic targets for IBD is of clinical importance.

Methods

The proportions of Th17 cells and interleukin (IL)‐17A produced between patients with UC and healthy volunteers were compared. The differentiation of human peripheral blood mononuclear cells (PBMCs) into Th17 cells was induced in vitro. Differentiated Th17 cells were treated with RGFP109 (RG), a selective inhibitor of HDAC1 and 3, to observe its effects on these cells. Subsequently, colitis was induced in mice and treated with RG. The proportion of Th17 cells, the severity of colitis in mice, and colon histopathology and immunohistochemistry were evaluated respectively.

Results

The proportion of Th17 cells and IL‐17A production was significantly increased in patients with UC than in healthy individuals. RG inhibited the differentiation of human PBMCs into Th17 cells and reduced IL‐17A secretion in vitro. RG‐treated colitis mice had a lower Th17 ratio, mild colon inflammation, and decreased expression of HDAC1 and 3 in the colon.

Conclusions

HDAC1 and 3 inhibitors can modulate the differentiation of inflammatory Th17 cells, downregulate IL‐17A levels, and exert anti‐inflammatory effects in experimental colitis mice, indicating that HDAC1 and 3 may be potential therapeutic targets for patients with IBD.

Nuciferine Regulates Immune Function and Gut Microbiota in DSS-Induced Ulcerative Colitis

Nuciferine, a major aporphine alkaloid obtained from the leaves of Nelumbo nucifera, exhibits anti-cancer and anti-inflammatory properties; however, its protective effects against inflammatory bowel diseases (IBD) has never been explored. In this study, an ulcerative colitis (UC) model was established in BALb/c mice by the continuous administration of 5% dextran sulfate sodium (DSS) in drinking water for 1 week. From day 8 to day 14, the DSS-treated mice were divided into a high-dose and a low-dose nuciferine treatment group and were intraperitoneally injected with the corresponding dose of the drug. Body weight loss, disease activity index (DAI), and colon length were measured. Histological changes were observed using hematoxylin and eosin staining. T lymphocyte proliferation was assessed by MTT assay. The ratio of CD3+, CD4+, CD8+, Th1, Th2, Th17, and Treg cells were estimated by flow cytometry. Finally, 16S rRNA sequencing was performed to compare the composition and relative abundance of the gut microbiota among the different treatment groups. The results showed that nuciferine treatment led to a significant improvement in symptoms, such as histological injury and colon shortening in mice with DSS-induced UC. Nuciferine treatment improved the Th1/Th2 and Treg/Th17 balance in the DSS-induced IBD model, as well as the composition of the intestinal microflora. At the phylum level, compared with the control group, the abundance of Firmicutes and Actinobacteriota was decreased in the model group, whereas that of Bacteroidetes increased. Meanwhile, at the genus level, compared with the control group, the numbers of the genera Lachnospiraceae_Clostridium, Bilophila and Halomonas reduced in the model group, while those of Bacteroides, Parabacteroides, and Paraprevotella increased. Notably, nuciferine administration reversed this DSS-induced gut dysbiosis. These results indicated that nuciferine modulates gut microbiota homeostasis and immune function in mice with DSS-induced UC.

HDAC inhibition as neuroprotection in COVID-19 infection

The SARS-CoV-2 virus is responsible of COVID-19 affecting millions of humans around the world. COVID-19 shows diverse clinical symptoms (fever, cough, fatigue, diarrhea, body aches, headaches, anosmia and hyposmia). Approximately 30% of the patients with COVID-19 showed neurological symptoms, these going from mild to severe manifestations including headache, dizziness, impaired consciousness, encephalopathy, anosmia, hypogeusia, hyposmia, psychology and psychiatry among others. The neurotropism of SARS-CoV-2 virus explains its neuroinvasion provoking neurological damage as acute demyelination, neuroinflammation etc. At molecular level, the COVID-19 patients had higher levels of cytokines and chemokines known as cytokines storms which disrupt the blood brain barrier allowing the entrance of monocytes and lymphocytes causing neuroinflammation, neurodegeneration and demyelination. In addition, ischemic, hemorrhagic strokes, seizures and encephalopathy have been observed due to the proinflammatory cytokines. In this sense, to avoid or decrease neurological damage due to SARS-CoV-2 infection, an early neuroprotective management should be adopted. Several approaches can be used; one of them includes the use of HDAC inhibitors (HDACi) due to their neuroprotective effects. Also, the HDACi down regulates the pro-inflammatory cytokines (IL-6 and TNF- decreasing the neurotoxicity. HDACi can also avoid and prevent the entrance of the virus into the Central nervous System (CNS) as well as decrease the virus replication by downregulating the virus receptors. Here we review the mechanisms that could explain how the SARS-CoV-2 virus could reach the CNS, induce the neurological damage and symptoms, as well as the possibility to use HDACi as neuroprotective therapy.

Histone Deacetylase Isoforms Differentially Modulate Inflammatory and Autoantibody Responses in a Mouse Model of Myasthenia Gravis

Myasthenia gravis (MG) is an autoimmune disease characterized by chronic muscle fatigue and weakness caused by autoantibodies and complement-mediated damage at neuromuscular junctions. Histone deacetylases (HDACs) are crucial epigenetic regulators of proinflammatory gene expression; however, it is unclear whether HDACs modulate chronic inflammation or autoantibody production associated with MG pathogenesis. We examined expression profiles and serum levels of key inflammatory cytokines (IL-6 and IL-21) and acetylcholine receptor (AChR)-specific autoantibodies following pharmacological inhibition of key HDAC isoforms in a mouse model of MG. We found that HDAC inhibition significantly reduced the production of IL-6, but not IL-21, in AChR-stimulated PBMCs and splenocytes (n = 5 per group). Trichostatin (pan-HDAC inhibitor) treatment of MG-PBMCs (n = 2) also exhibited reduced production of induced IL-6. Although HDAC1 inhibition lowered IL-6 levels the most, HDAC2 inhibition depleted intracellular IL-6 and markedly reduced serum anti-AChR IgG2b in EAMG mice. The transcriptomic profiling and pathway mapping also revealed that autoimmunity-linked, major cell signaling pathways were differentially altered by HDAC1/2 inhibition. HDAC inhibition-mediated reduction in IL-6 and autoantibody levels also correlated with milder disease and preservation of muscle AChR in the treated mice. Overall, our findings revealed isoform-specific functional variance of HDACs in reducing inflammation and identified HDAC-regulated many genes underlying specific inflammatory and autoantibody pathways in EAMG. Thus, the study provides a rationale for further research to evaluate the HDACs or their gene targets as a potential adjunct treatment for MG.

T Helper Cell Lineage-Defining Transcription Factors: Potent Targets for Specific GVHD Therapy?

Allogenic hematopoietic stem cell transplantation (allo-HSCT) represents a potent and potentially curative treatment for many hematopoietic malignancies and hematologic disorders in adults and children. The donor-derived immunity, elicited by the stem cell transplant, can prevent disease relapse but is also responsible for the induction of graft-versus-host disease (GVHD). The pathophysiology of acute GVHD is not completely understood yet. In general, acute GVHD is driven by the inflammatory and cytotoxic effect of alloreactive donor T cells. Since several experimental approaches indicate that CD4 T cells play an important role in initiation and progression of acute GVHD, the contribution of the different CD4 T helper (Th) cell subtypes in the pathomechanism and regulation of the disease is a central point of current research. Th lineages derive from naïve CD4 T cell progenitors and lineage commitment is initiated by the surrounding cytokine milieu and subsequent changes in the transcription factor (TF) profile. Each T cell subtype has its own effector characteristics, immunologic function, and lineage specific cytokine profile, leading to the association with different immune responses and diseases. Acute GVHD is thought to be mainly driven by the Th1/Th17 axis, whereas Treg cells are attributed to attenuate GVHD effects. As the differentiation of each Th subset highly depends on the specific composition of activating and repressing TFs, these present a potent target to alter the Th cell landscape towards a GVHD-ameliorating direction, e.g. by inhibiting Th1 and Th17 differentiation. The finding, that targeting of Th1 and Th17 differentiation appears more effective for GVHD-prevention than a strategy to inhibit Th1 and Th17 cytokines supports this concept. In this review, we shed light on the current advances of potent TF inhibitors to alter Th cell differentiation and consecutively attenuate GVHD. We will focus especially on preclinical studies and outcomes of TF inhibition in murine GVHD models. Finally, we will point out the possible impact of a Th cell subset-specific immune modulation in context of GVHD.

Challenges of pectic polysaccharides as a prebiotic from the perspective of fermentation characteristics and anti-colitis activity

Several studies are described that contribute to the systematic exploration of new aspects of digestion, fermentation, and biological activities of pectic polysaccharides (PPS) leading to a better understanding of prebiotics. Inflammatory bowel disease (IBD) is thought to be associated with the dysbacteriosis induced by different environmental agents in genetically susceptible persons. PPS are considered as an indispensable gut-microbiota-accessible carbohydrate that play a dominant role in maintaining gut microbiota balance and show a better effect in ameliorating IBD than some traditional prebiotics. The aim of this review is to summarize the fermentation characteristics of PPS, highlight its role in improving IBD, and propose a view that PPS may be a new and effective prebiotic.

Juglone regulates gut microbiota and Th17/Treg balance in DSS-induced ulcerative colitis

Juglone, mainly isolates from the green walnut husks of Juglans mandshurica, exhibits anti-cancer and anti-inflammaroty activities. But its protection on ulcerative colitis (UC) has never been explored. In this study, we first evaluated whether juglone ameliorated UC, and investigated its effects on gut microbiota and Th17/Treg balance in DSS-induced UC mice model. The model was established by administrating 2.7% DSS for seven days. Juglone was given daily by gavage for ten days, once a day. The disease activity index (DAI) decrease and pathological characteristics improvement demonstrated that the UC in mice was alleviated by juglone. Juglone treatment significantly inhibited the protein levels of IL-6, TNF-α and IL-1β, improved the protein expression of IL-10. In addition, juglone altered microbial diversity and gut microbiota composition, including the enhancement of the ratio of Firmicutes to Bacteroidota and the abundance of Actinobacteriota, and decrease of the abundance of Verrucomicrobiota. Juglone treatment also inhibited the protein expressions of IL-6, STAT3 and RORγt, meanwhile improved the protein level of FOXP3. Furthermore, juglone inhibited Th17 development and increased Treg generation, beneficial to Th17/Treg balance. Together, we herein provided the first evidence to support that juglone, especially the high dose, possibly protected mice against UC by modulating gut microbiota and restoring Th17/Treg homeostasis.

SAHA attenuates rotenone-induced toxicity in primary microglia and HT-22 cells

Rotenone is an industrial and environmental toxicant that has been strongly associated with neurodegeneration. It is clear that rotenone induces inflammatory and oxidative stress; however, information on the role of histone acetylation in neurotoxicity is limited. Epigenetic alterations, neuroinflammation, and oxidative stress play a role in the progression of neurodegeneration and can be caused by exposure to environmental chemicals, such as rotenone. Histone modifications, such as methylation and acetylation, play an important role in mediating epigenetic changes. Therefore, we here investigated the effects of histone acetylation on rotenone-induced inflammation and oxidative stress in both primary mouse microglia and hippocampal HT-22 cells using the pan-histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA). Our results showed that SAHA suppressed the inflammatory response by decreasing nuclear factor kappa B and inducible nitric oxide synthase expression. Additionally, SAHA inhibited the rotenone-induced elevation of interleukin 6 and tumor necrosis factor α levels in both cell lines. Furthermore, SAHA improved the rotenone-induced antioxidant status by mitigating the decrease in cellular glutathione levels. Additionally, SAHA prevented the rotenone-induced increase in the HDAC activity in microglial and hippocampal HT-22 cells. Together, our results showed that SAHA reduced rotenone-induced inflammatory and oxidative stress, suggesting a role for histone deacetylation in environmental-related neurotoxicity.

Targeting epigenetics as atherosclerosis treatment: an updated view

PURPOSE OF REVIEW

This review discusses the current developments on epigenetic inhibition as treatment for atherosclerosis.

RECENT FINDINGS

The first phase III clinical trial targeting epigenetics in cardiovascular disease (CVD), BETonMACE, using the bromodomain inhibitor apabetalone (RVX-208) showed no significant effect on major adverse cardiovascular events (MACE) in patients with type II diabetes, low HDL-c and a recent acute coronary artery event compared with its placebo arm.

SUMMARY

Preclinical and clinical studies suggest that targeting epigenetics in atherosclerosis is a promising novel therapeutic strategy against CVD. Interfering with histone acetylation by targeting histone deacetylates (HDACs) and bromodomain and extraterminal domain (BET) proteins demonstrated encouraging results in modulating disease progression in model systems. Although the first phase III clinical trial targeting BET in CVD showed no effect on MACE, we suggest that there is sufficient potential for future clinical usage based on the outcomes in specific subgroups and the fact that the study was slightly underpowered. Lastly, we propose that there is future window for targeting repressive histone modifications in atherosclerosis.

Histone deacetylases as targets in autoimmune and autoinflammatory diseases

Reversible lysine acetylation of histones is a key epigenetic regulatory process controlling gene expression. Reversible histone acetylation is mediated by two opposing enzyme families: histone acetyltransferases (HATs) and histone deacetylases (HDACs). Moreover, many non-histone targets of HATs and HDACs are known, suggesting a crucial role for lysine acetylation as a posttranslational modification on the cellular proteome and protein function far beyond chromatin-mediated gene regulation. The HDAC family consists of 18 members and pan-HDAC inhibitors (HDACi) are clinically used for the treatment of certain types of cancer. HDACi or individual HDAC member-deficient (cell lineage-specific) mice have also been tested in a large number of preclinical mouse models for several autoimmune and autoinflammatory diseases and in most cases HDACi treatment results in an attenuation of clinical disease severity. A reduction of disease severity has also been observed in mice lacking certain HDAC members. This indicates a high therapeutic potential of isoform-selective HDACi for immune-mediated diseases. Isoform-selective HDACi and thus targeted inactivation of HDAC isoforms might also overcome the adverse effects of current clinically approved pan-HDACi. This review provides a brief overview about the fundamental function of HDACs as epigenetic regulators, highlights the roles of HDACs beyond chromatin-mediated control of gene expression and summarizes the studies showing the impact of HDAC inhibitors and genetic deficiencies of HDAC members for the outcome of autoimmune and autoinflammatory diseases with a focus on rheumatoid arthritis, inflammatory bowel disease and experimental autoimmune encephalomyelitis (EAE) as an animal model of multiple sclerosis.

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

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

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.

Faecalibacterium prausnitzii produces butyrate to decrease c-Myc-related metabolism and Th17 differentiation by inhibiting histone deacetylase 3

Decreased levels of Faecalibacterium prausnitzii (F. prausnitzii), whose supernatant plays an anti-inflammatory effect, are frequently found in inflammatory bowel disease (IBD) patients. However, the anti-inflammatory products in F. prausnitzii supernatant and the mechanism have not been fully investigated. Here we found that F. prausnitzii and F. prausnitzii-derived butyrate were decreased in the intestines of IBD patients. Supplementation with F. prausnitzii supernatant and butyrate could ameliorate colitis in an animal model. Butyrate, but not other substances produced by F. prausnitzii, exerted an anti-inflammatory effect by inhibiting the differentiation of T helper 17 (Th17) cells. The mechanism underlying the anti-inflammatory effects of the butyrate produced by F. prausnitzii involved the enhancement of the acetylation-promoted degradation of c-Myc through histone deacetylase 3 (HDAC3) inhibition. In conclusion, F. prausnitzii produced butyrate to decrease Th17 differentiation and attenuate colitis through inhibiting HDAC3 and c-Myc-related metabolism in T cells. The use of F. prausnitzii may be an effective new approach to decrease the level of Th17 cells in the treatment of inflammatory diseases.

Overcoming resistance to anabolic SARM therapy in experimental cancer cachexia with an HDAC inhibitor

No approved therapy exists for cancer-associated cachexia. The colon-26 mouse model of cancer cachexia mimics recent late-stage clinical failures of anabolic anti-cachexia therapy and was unresponsive to anabolic doses of diverse androgens, including the selective androgen receptor modulator (SARM) GTx-024. The histone deacetylase inhibitor (HDACi) AR-42 exhibited anti-cachectic activity in this model. We explored combined SARM/AR-42 therapy as an improved anti-cachectic treatment paradigm. A reduced dose of AR-42 provided limited anti-cachectic benefits, but, in combination with GTx-024, significantly improved body weight, hindlimb muscle mass, and grip strength versus controls. AR-42 suppressed the IL-6/GP130/STAT3 signaling axis in muscle without impacting circulating cytokines. GTx-024-mediated β-catenin target gene regulation was apparent in cachectic mice only when combined with AR-42. Our data suggest cachectic signaling in this model involves catabolic signaling insensitive to anabolic GTx-024 therapy and a blockade of GTx-024-mediated anabolic signaling. AR-42 mitigates catabolic gene activation and restores anabolic responsiveness to GTx-024. Combining GTx-024, a clinically established anabolic therapy, with AR-42, a clinically evaluated HDACi, represents a promising approach to improve anabolic response in cachectic patients.

Piperlongumine regulates epigenetic modulation and alleviates psoriasis-like skin inflammation via inhibition of hyperproliferation and inflammation

Psoriasis is an autoimmune skin disease, where chronic immune responses due to exaggerated cytokine signaling, abnormal differentiation, and evasion of keratinocytes apoptosis plays a crucial role in mediating abnormal keratinocytes hyperproliferation. From the therapeutic perspective, the molecules with strong anti-proliferative and anti-inflammatory properties could have tremendous relevance. In this study, we demonstrated that piperlongumine (PPL) treatment effectively abrogated the hyperproliferation and differentiation of keratinocytes by inducing ROS-mediated late apoptosis with loss of mitochondrial membrane potential. Besides, the arrest of cell cycle was found at Sub-G1 phase as a result of DNA fragmentation. Molecularly, inhibition of STAT3 and Akt signaling was observed with a decrease in proliferative markers such as PCNA, ki67, and Cyclin D1 along with anti-apoptotic Bcl-2 protein expression. Keratin 17 is a critical regulator of keratinocyte differentiation, and it was found to be downregulated with PPL significantly. Furthermore, prominent anti-inflammatory effects were observed by inhibition of lipopolysaccharide (LPS)/Imiquimod (IMQ)-induced p65 NF-κB signaling cascade and strongly inhibited the production of cytokine storm involved in psoriasis-like skin inflammation, thus led to the restoration of normal epidermal architecture with reduction of epidermal hyperplasia and splenomegaly. In addition, PPL epigenetically inhibited histone-modifying enzymes, which include histone deacetylases (HDACs) of class I (HDAC1-4) and class II (HDAC6) evaluated by immunoblotting and HDAC enzyme assay kit. In addition, our results show that PPL effectively inhibits the nuclear translocation of p65 and a histone modulator HDAC3, thus sequestered in the cytoplasm of macrophages. Furthermore, PPL effectively enhanced the protein-protein interactions of HDAC3 and p65 with IκBα, which was disrupted by LPS stimulation and were evaluated by Co-IP and molecular modeling. Collectively, our findings indicate that piperlongumine may serve as an anti-proliferative and anti-inflammatory agent and could serve as a potential therapeutic option in treating psoriasis.

The Epigenetics of Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a life-threatening autoimmune disease that is characterized by dysregulated dendritic cells, T and B cells, and abundant autoantibodies. The pathogenesis of lupus remains unclear. However, increasing evidence has shown that environment factors, genetic susceptibilities, and epigenetic regulation contribute to abnormalities in the immune system. In the past decades, several risk gene loci have been identified, such as MHC and C1q. However, genetics cannot explain the high discordance of lupus incidence in homozygous twins. Environmental factor-induced epigenetic modifications on immune cells may provide some insight. Epigenetics refers to inheritable changes in a chromosome without altering DNA sequence. The primary mechanisms of epigenetics include DNA methylation, histone modifications, and non-coding RNA regulations. Increasing evidence has shown the importance of dysregulated epigenetic modifications in immune cells in pathogenesis of lupus, and has identified epigenetic changes as potential biomarkers and therapeutic targets. Environmental factors, such as drugs, diet, and pollution, may also be the triggers of epigenetic changes. Therefore, this chapter will summarize the up-to-date progress on epigenetics regulation in lupus, in order to broaden our understanding of lupus and discuss the potential roles of epigenetic regulations for clinical applications.

Histone Deacetylase Inhibitors in Tumor Immunotherapy

BACKGROUND

With an increasing understanding of the antitumor immune response, considerable progress has been made in the field of tumor immunotherapy in the last decade. Inhibition of histone deacetylases represents a new strategy in tumor therapy and histone deacetylase inhibitors have been recently developed and validated as potential antitumor drugs. In addition to the direct antitumor effects, histone deacetylase inhibitors have been found to have the ability to improve tumor recognition by immune cells that may contribute to their antitumor activity. These immunomodolutory effects are desirable, and their in-depth comprehension will facilitate the design of novel regimens with improved clinical efficacy.

OBJECTIVE

Our goal here is to review recent developments in the application of histone deacetylase inhibitors as immune modulators in cancer treatment.

METHODS

Systemic compilation of the relevant literature in this field.

RESULTS & CONCLUSION

In this review, we summarize recent advances in the understanding of how histone deacetylase inhibitors alter immune process and discuss their effects on various cytokines. We also discuss the challenges to optimize the use of these inhibitors as immune modulators in cancer treatment. Information gained from this review will be valuable to this field and may be helpful for designing tumor immunotherapy trials involving histone deacetylase inhibitors.

Glycan utilisation system in Bacteroides and Bifidobacteria and their roles in gut stability and health

Gut residential hundred trillion microbial cells are indispensable for maintaining gut homeostasis and impact on host physiology, development and immune systems. Many of them have displayed excellence in utilising dietary- and host-derived complex glycans and are producing useful postbiotics including short-chain fatty acids to primarily fuel different organs of the host. Therefore, employing individual microbiota is nowadays becoming a propitious target in biomedical for improving gut dysbiosis conditions of the host. Among other gut microbial communities, Bacteroides and Bifidobacteria are coevolved to utilise diverse ranges of diet- and host-derived glycans through harmonising distinct glycan utilisation systems. These gut symbionts frequently share digested oligosaccharides, carbohydrate-active enzymes and fermentable intermediate molecules for sustaining gut microbial symbiosis and improving fitness of own or other communities. Genomics approaches have provided unprecedented insights into these functions, but their precise mechanisms of action have poorly known. Sympathetic glycan-utilising strategy of each gut commensal will provide overview of mechanistic dynamic nature of the gut environment and will then assist in applying aptly personalised nutritional therapy. Thus, the review critically summarises cutting edge understanding of major plant- and host-derived glycan-utilising systems of Bacteroides and Bifidobacteria. Their evolutionary adaptation to gut environment and roles of postbiotics in human health are also highlighted.

Immunoepigenetics Combination Therapies: An Overview of the Role of HDACs in Cancer Immunotherapy

Long-standing efforts to identify the multifaceted roles of histone deacetylase inhibitors (HDACis) have positioned these agents as promising drug candidates in combatting cancer, autoimmune, neurodegenerative, and infectious diseases. The same has also encouraged the evaluation of multiple HDACi candidates in preclinical studies in cancer and other diseases as well as the FDA-approval towards clinical use for specific agents. In this review, we have discussed how the efficacy of immunotherapy can be leveraged by combining it with HDACis. We have also included a brief overview of the classification of HDACis as well as their various roles in physiological and pathophysiological scenarios to target key cellular processes promoting the initiation, establishment, and progression of cancer. Given the critical role of the tumor microenvironment (TME) towards the outcome of anticancer therapies, we have also discussed the effect of HDACis on different components of the TME. We then have gradually progressed into examples of specific pan-HDACis, class I HDACi, and selective HDACis that either have been incorporated into clinical trials or show promising preclinical effects for future consideration. Finally, we have included examples of ongoing trials for each of the above categories of HDACis as standalone agents or in combination with immunotherapeutic approaches.

Non-coding DNA in IBD: from sequence variation in DNA regulatory elements to novel therapeutic potential

Genome-wide association studies have identified over 200 loci associated with IBD. We and others have recently shown that, in addition to variants in protein-coding genes, the majority of the associated loci are related to DNA regulatory elements (DREs). These findings add a dimension to the already complex genetic background of IBD. In this review we summarise the existing evidence on the role of DREs in IBD. We discuss how epigenetic research can be used in candidate gene approaches that take non-coding variants into account and can help to pinpoint the essential pathways and cell types in the pathogenesis of IBD. Despite the increased level of genetic complexity, these findings can contribute to novel therapeutic options that target transcription factor binding and enhancer activity. Finally, we summarise the future directions and challenges of this emerging field.

HDAC inhibitors promote intestinal epithelial regeneration via autocrine TGFβ1 signalling in inflammation

Intact epithelial barrier function is pivotal for maintaining intestinal homeostasis. Current therapeutic developments aim at restoring the epithelial barrier in inflammatory bowel disease. Histone deacetylase (HDAC) inhibitors are known to modulate immune responses and to ameliorate experimental colitis. However, their direct impact on epithelial barrier function and intestinal wound healing is unknown. In human and murine colonic epithelial cell lines, the presence of the HDAC inhibitors Givinostat and Vorinostat not only improved transepithelial electrical resistance under inflammatory conditions but also attenuated the passage of macromolecules across the epithelial monolayer. Givinostat treatment mediated an accelerated wound closure in scratch assays. In vivo, Givinostat treatment resulted in improved barrier recovery and epithelial wound healing in dextran sodium sulphate-stressed mice. Mechanistically, these regenerative effects could be linked to an increased secretion of transforming growth factor beta1 and interleukin 8, paralleled by differential expression of the tight junction proteins claudin-1, claudin-2 and occludin. Our data reveal a novel tissue regenerative property of the pan-HDAC inhibitors Givinostat and Vorinostat in intestinal inflammation, which may have beneficial implications by repurposing HDAC inhibitors for therapeutic strategies for inflammatory bowel disease.

HDAC Inhibitors: Therapeutic Potential in Fibrosis-Associated Human Diseases

Fibrosis is characterized by excessive deposition of the extracellular matrix and develops because of fibroblast differentiation during the process of inflammation. Various cytokines stimulate resident fibroblasts, which differentiate into myofibroblasts. Myofibroblasts actively synthesize an excessive amount of extracellular matrix, which indicates pathologic fibrosis. Although initial fibrosis is a physiologic response, the accumulated fibrous material causes failure of normal organ function. Cardiac fibrosis interferes with proper diastole, whereas pulmonary fibrosis results in chronic hypoxia; liver cirrhosis induces portal hypertension, and overgrowth of fibroblasts in the conjunctiva is a major cause of glaucoma surgical failure. Recently, several reports have clearly demonstrated the functional relevance of certain types of histone deacetylases (HDACs) in various kinds of fibrosis and the successful alleviation of the condition in animal models using HDAC inhibitors. In this review, we discuss the therapeutic potential of HDAC inhibitors in fibrosis-associated human diseases using results obtained from animal models.

Regulation of Chemokines and Cytokines by Histone Deacetylases and an Update on Histone Decetylase Inhibitors in Human Diseases

Histone acetyltransferases (HATs) and histone deacetylases (HDACs) counteract with each other to regulate gene expression by altering chromatin structure. Aberrant HDAC activity was reported in many human diseases including wide range of cancers, viral infections, cardiovascular complications, auto-immune diseases and kidney diseases. HDAC inhibitors are small molecules designed to block the malignant activity of HDACs. Chemokines and cytokines control inflammation, immunological and other key biological processes and are shown to be involved in various malignancies. Various HDACs and HDAC inhibitors were reported to regulate chemokines and cytokines. Even though HDAC inhibitors have remarkable anti-tumor activity in hematological cancers, they are not effective in treating many diseases and many patients relapse after treatment. However, the role of HDACs and cytokines in regulating these diseases still remain unclear. Therefore, understanding exact mechanisms and effector functions of HDACs are urgently needed to selectively inhibit them and to establish better a platform to combat various malignancies. In this review, we address regulation of chemokines and cytokines by HDACs and HDAC inhibitors and update on HDAC inhibitors in human diseases.

Rhubarb Peony Decoction ameliorates ulcerative colitis in mice by regulating gut microbiota to restoring Th17/Treg balance

ETHNOPHARMACOLOGY RELEVANCE

Rhubarb Peony Decoction (RPD) is a formula of traditional Chinese medicine chronicled in Jin Gui Yao Lve, commonly used to treat ulcerative colitis (UC). However, the underlying mechanism of RPD treating UC remains elusive. In our study, we investigated the therapeutic efficacy of RPD and potential mechanism involved in inhibiting dextran sulfate sodium (DSS)-induced ulcerative colitis in mice.

METHODS

The colitis was induced by DSS in mice for 5 days and estimated body weight loss, disease activity index (DAI) and colon length. Histological changes were observed by H&E staining. The number and abundance of gut mircrobiota were measured with 16 S rDNA sequencing. GC-MS was used to detect the concentration of short chain fatty acids (SCFAs) in cecum. Flow cytometry analyzed the proportion of Th17 and Treg cells in mesenteric lymph nodes (MLNs). IL-17A and Foxp3 in colon were determined by immunohistochemical analyses. The level of cytokine was determined by Multi-Analyte Flow Assay Kit.

RESULTS

Administration of RPD significantly alleviated the pathological changes of UC mice, involving rescued the inflammation-related reduction of colon length, ameliorated body weight loss and damaged tissue. In addition, RPD altered the gut microbiota, involving restored α diversity, increased significantly the abundance of Firmicutes and Actinobacteria, decreased the Proteobacteria and Bacteroidetes. Furthermore, the number of Butyricicoccus pullicaecorum, a butyrate-producing bacterium, were augmented obviously by RPD. Besides, RPD restored the content of SCFA in intestinal tract. Additionally, the proportion of Th17 cells and Treg cells in mesenteric lymph nodes, likewise, the expression of IL-17A and Foxp3 in colon were regulated by RPD, contributing to the restoration of Th17/Treg balance. Moreover, RPD significantly decreased the level of IL-6, TNF-α, IFNγ, IL-10, IL-17A, IL-21, IL-22 in colon, simultaneously increased Treg-related cytokine TGF-β at dose-dependently.

CONCLUSIONS

These results demonstrated that RPD had effect on ulcerative colitis, which was related to regulating gut microbiota, especially Butyricicoccus pullicaecorum, and SCFAs to restore the gut Th17/Treg homeostasis.

Faecalibacterium prausnitzii Produces Butyrate to Maintain Th17/Treg Balance and to Ameliorate Colorectal Colitis by Inhibiting Histone Deacetylase 1

BACKGROUND

Inflammatory bowel disease (IBD)-associated dysbiosis is characterized by a loss of Faecalibacterium prausnitzii, whose supernatant exerts an anti-inflammatory effect. However, the anti-inflammatory substances in F. prausnitzii supernatant and the mechanism in ameliorating colitis in IBD have not yet been fully investigated.

METHODS

Experimental colitis models were induced and evaluated by clinical examination and histopathology. Levels of cytokines and ratio of T cells were detected by enzyme-linked immunosorbent assay and flow cytometry analysis, respectively. F. prausnitzii supernatant was separated by macroporous resins. After extraction, the substances in supernatant were identified by gas chromatography-mass spectrometer. T-cell differentiation assay was conducted in vitro. Changes in signaling pathways were examined by immunoblot, immunohistochemistry, and immunofluorescent staining.

RESULTS

We found that the supernatant of F. prausnitzii could regulate T helper 17 cell (Th17)/regulatory T cell (Treg) differentiation. Then, we identified butyrate produced by F. prausnitzii that played the anti-inflammatory effects by inhibiting interleukin (IL)-6/signal transducer and the activator of transcription 3 (STAT3)/IL-17 pathway and promoting forkhead box protein P3 (Foxp3). Finally, we demonstrated that the target of butyrate was histone deacetylase 1 (HDAC1).

CONCLUSIONS

It is butyrate, instead of other substances produced by F. prausnitzii, that maintains Th17/Treg balance and exerts significant anti-inflammatory effects in colorectal colitis rodents, by inhibiting HDAC1 to promote Foxp3 and block the IL-6/STAT3/IL-17 downstream pathway. F. prausnitzii could be an option for further investigation for IBD treatment. Targeting the butyrate-HDAC1-T-cell axis offers an effective novel approach in the treatment of inflammatory disease.

Oleate but not stearate induces the regulatory phenotype of myeloid suppressor cells

Tumor infiltrating myeloid cells play contradictory roles in the tumor development. Dendritic cells and classical activated macrophages support anti-tumor immune activity via antigen presentation and induction of pro-inflammatory immune responses. Myeloid suppressor cells (MSCs), for instance myeloid derived suppressor cells (MDSCs) or tumor associated macrophages play a critical role in tumor growth. Here, treatment with sodium oleate, an unsaturated fatty acid, induced a regulatory phenotype in the myeloid suppressor cell line MSC-2 and resulted in an increased suppression of activated T cells, paralleled by increased intracellular lipid droplets formation. Furthermore, sodium oleate potentiated nitric oxide (NO) production in MSC-2, thereby increasing their suppressive capacity. In primary polarized bone marrow cells, sodium oleate (C18:1) and linoleate (C18:2), but not stearate (C18:0) were identified as potent FFA to induce a regulatory phenotype. This effect was abrogated in MSC-2 as well as primary cells by specific inhibition of droplets formation while the inhibition of de novo FFA synthesis proved ineffective, suggesting a critical role for exogenous FFA in the functional induction of MSCs. Taken together our data introduce a new unsaturated fatty acid-dependent pathway shaping the functional phenotype of MSCs, facilitating the tumor escape from the immune system.

蛋白修饰与炎症性肠病

近年来炎症性肠病(inflammatory bowel disease, IBD)的发病率明显呈持续上升趋势, 越来越多的证据表明, 肠道内蛋白质的异常表达或蛋白修饰的异常与IBD的发病有关. 蛋白修饰是指蛋白质通过翻译后修饰改变自身的空间构象、活性、稳定性及与其他分子相互作用等方面的性能, 从而参与调节机体多样化的生命过程. 虽然蛋白修饰不会改变DNA的序列, 但可以影响相关基因的表达. 研究显示, 蛋白修饰可能通过患者的饮食、环境及肠道微生物等多方面影响基因表型从而参与IBD的发病过程. 本文就蛋白修饰在IBD发病过程中所起的作用做一综述.

Targeting transcription factor lysine acetylation in inflammatory airway diseases

Asthma and chronic obstructive pulmonary disease are inflammatory airway diseases for which alternative therapeutic strategies are urgently needed. Interestingly, HDAC inhibitors show anti-inflammatory effects in mouse models for these diseases. Here we explore underlying mechanisms that may explain these effects. In previous studies, effects of HDAC inhibitors on histone acetylation are often correlated with their effects on gene expression. However, effects of HDAC inhibitors on transcription factors and their acetylation status may be particularly important in explaining these effects. These effects are also cell type-specific. Recent developments (including chemoproteomics and acetylomics) allow for a more detailed understanding of the selectivity of HDAC inhibitors, which will drive their further development into applications in inflammatory airway diseases.

Epi-drugs in combination with immunotherapy: a new avenue to improve anticancer efficacy

Immune checkpoint factors, such as programmed cell death protein-1/2 (PD-1, PD-2) or cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) receptors, are targets for monoclonal antibodies (MAbs) developed for cancer immunotherapy. Indeed, modulating immune inhibitory pathways has been considered an important breakthrough in cancer treatment. Although immune checkpoint blockade therapy used to treat malignant diseases has provided promising results, both solid and haematological malignancies develop mechanisms that enable themselves to evade the host immune system. To overcome some major limitations and ensure safety in patients, recent strategies have shown that combining epigenetic modulators, such as inhibitors of histone deacetylases (HDACi) or DNA methyltransferases (DNMTi), with immunotherapeutics can be useful. Preclinical data generated using mouse models strongly support the feasibility and effectiveness of the proposed approaches. Indeed, co-treatment with pan- or class I-selective HDACi or DNMTi improved beneficial outcomes in both in vitro and in vivo studies. Based on the evidence of a pivotal role for HDACi and DNMTi in modulating various components belonging to the immune system, recent clinical trials have shown that both HDACi and DNMTi strongly augmented response to anti-PD-1 immunotherapy in different tumour types. This review describes the current strategies to increase immunotherapy responses, the effects of HDACi and DNMTi on immune modulation, and the advantages of combinatorial therapy over single-drug treatment.

A Systems Pharmacology Approach to Determine Active Compounds and Action Mechanisms of Xipayi KuiJie'an enema for Treatment of Ulcerative colitis

Xipayi Kui Jie’an (KJA), a type of traditional Uygur medicine (TUM), has shown promising therapeutic effects in Ulcerative colitis (UC). Owing to the complexity of TUM, the pharmacological mechanism of KJA remains vague. Therefore, the identification of complex molecular mechanisms is a major challenge and a new method is urgently needed to address this problem. In this study, we established a feasible pharmacological model based on systems pharmacology to identify potential compounds and targets. We also applied compound-target and target-diseases network analysis to evaluate the action mechanisms. According to the predicted results, 12 active compounds were selected and these compounds were also identified by HPLC-ESI-MS/MS analysis. The main components were tannins, this result is consistent with the prediction. The active compounds interacted with 22 targets. Two targets including PTGS2 and PPARG were demonstrated to be the main targets associated with UC. Systematic analysis of the constructed networks revealed that these targets were mainly involved in NF-κB signaling pathway. Furthermore, KJA could also regulate the CD4 + CD25 + Foxp3 + Treg cells. In conclusion, this systems pharmacology-based approach not only explained that KJA could alleviate the UC by regulating its candidate targets, but also gave new insights into the potential novel therapeutic strategies for UC.

The histone deacetylase inhibitor, sodium butyrate, exhibits neuroprotective effects for ischemic stroke in middle-aged female rats

Background

Sodium butyrate (NaB) is a histone deacetylase (HDAC) inhibitor exhibiting anti-inflammatory and neuroprotective effects in a rat ischemic model of stroke as well as a myocardial ischemia model. Although clinical evidence shows that older women are at higher risk for stroke occurrence and greater stroke severity, no studies have evaluated the effectiveness of NaB either in females or in older animals.

Methods

To determine the effects of NaB on stroke in older females, acyclic middle-aged Sprague-Dawley female rats (9–11 months old, constant diestrus) were subject to middle cerebral artery occlusion (MCAo) by intracerebral injection of recombinant endothelin-1. Rats were treated with NaB (300 mg/kg, i.p.) at 6 and 30 h following ET-1 injection. Animals were sacrificed at the early (2 days) or late (5 days) acute phase after MCAo. Serum and tissue lysates were collected for biochemical analyses.

Results

NaB treatment reduced infarct volume and ameliorated sensory motor impairment in middle-aged female rats, when measured at 2 and 5 days post MCAo. At the early acute phase (2 days post stroke), NaB treatment decreased brain lipid peroxides, and reduced serum levels of GFAP, a surrogate marker of blood-brain barrier (BBB) permeability. NaB also reduced expression of the inflammatory cytokine IL-1beta in circulation and IL-18 in the ischemic hemisphere. At the late acute phase (5 days post stroke), NaB treatment further suppressed MCAo-induced increase of IL-1beta, IL-17A, and IL-18 in brain lysates (cortex and striatum) from the ischemic hemisphere, and decreased ischemia-induced upregulation of IL-1beta and IL-18 in circulation, indicating a potent anti-inflammatory effect of the HDAC inhibitor. Moreover, NaB treatment also increased expression of IGF-1, a known neuroprotectant, in peripheral tissue including serum, liver, and spleen at the late acute phase.

Conclusions

These data provide the first evidence that delayed (>6 h) NaB treatment post-stroke is neuroprotective in older female rats. Additionally, these data also show that in addition to its well-known anti-inflammatory actions, NaB may exert a biphasic effect after stroke, operating initially to reduce BBB permeability and oxidative stress in the brain, and later, elevating IGF-1 expression in peripheral tissues.

Macrophage polarization in response to epigenetic modifiers during infection and inflammation

Macrophages are a heterogeneous population of phagocytic cells present in all tissues. Recently, several drugs that target the epigenetic machinery have emerged as attractive molecules for treating infection and inflammation by modulating macrophages. Treatment of lipopolysaccharide (LPS)-challenged macrophages with epigenetic modifiers leads to phenotype switching. This could provide stimulatory/destructive (M1) or suppressive/protective (M2) therapeutic strategies, which are crucial in the cytokine milieu in which the macrophages reside. In this review, we provide an overview of macrophage functional diversity during various diseases, including infection, as well as the current status in the development and clinical utility of epigenetic modifiers.

Histone deacetylase inhibitors as immunomodulators in cancer therapeutics

HDAC inhibitors (HDACIs) are anticancer agents being developed in preclinical and clinical settings due to their capacity to modulate gene expression involved in cell growth, differentiation and apoptosis, through modification of both chromatin histone and nonhistone proteins. Most HDACIs in clinical development have cytotoxic or cytostatic properties and their direct inhibitory effects on tumor cells are well documented. Numerous studies have revealed that HDACIs have potent immunomodulatory activity in tumor-bearing animals and cancer patients, providing guidance to apply these agents in cancer immunotherapies. Here, we summarize recent reports addressing the effects of HDACIs on tumor cell immunogenicity, and on different components of the host immune system. In addition, we discuss the complexity of the immunomodulatory activity of these agents, which depends on the class specificity of the HDACIs, different experimental settings and the target immune cell populations.

Exploiting IL-17-producing CD4+ and CD8+ T cells to improve cancer immunotherapy in the clinic

Cancer immunotherapy is one the most effective approaches for treating patients with tumors, as it bolsters the generation and persistence of memory T cells. In preclinical work, it has been reported that adoptively transferred CD4+ and CD8+ lymphocytes that secrete IL-17A (i.e., Th17 and Tc17 cells) regress tumors to a greater extent than IFN-γ(+)Th1 or Tc1 cells in vivo. Herein, we review the mechanisms underlying how infused Th17 and Tc17 cells regress established malignancies in clinically relevant mouse models of cancer. We also discuss how unique signaling cues--such as co-stimulatory molecules (ICOS and 41BB), cytokines (IL-12 and IL-23) or pharmaceutical reagents (Akt inhibitors, etc.)--can be exploited to bolster the therapeutic potential of IL-17(+) lymphocytes with an emphasis on using this knowledge to improve next-generation clinical trials for patients with cancer.

Reciprocal regulation of RORγt acetylation and function by p300 and HDAC1

T helper 17 (Th17) cells not only play critical roles in protecting against bacterial and fungal infections but are also involved in the pathogenesis of autoimmune diseases. The retinoic acid-related orphan receptor (RORγt) is a key transcription factor involved in Th17 cell differentiation through direct transcriptional activation of interleukin 17(A) (IL-17). How RORγt itself is regulated remains unclear. Here, we report that p300, which has histone acetyltransferase (HAT) activity, interacts with and acetylates RORγt at its K81 residue. Knockdown of p300 downregulates RORγt protein and RORγt-mediated gene expression in Th17 cells. In addition, p300 can promote RORγt-mediated transcriptional activation. Interestingly, the histone deacetylase (HDAC) HDAC1 can also interact with RORγt and reduce its acetylation level. In summary, our data reveal previously unappreciated posttranslational regulation of RORγt, uncovering the underlying mechanism by which the histone acetyltransferase p300 and the histone deacetylase HDAC1 reciprocally regulate the RORγt-mediated transcriptional activation of IL-17.

Norisoboldine ameliorates DSS-induced ulcerative colitis in mice through induction of regulatory T cells in colons

Norisoboldine (NOR), the main active constituent of Radix Linderae, was previously demonstrated to ameliorate collagen-induced arthritis in rats through regulating the imbalance of T cells in intestines, which implied its therapeutic potential in inflammatory bowel disease. Here, we investigated the effect of NOR on ulcerative colitis (UC) induced by dextran sulfate sodium (DSS) in mice. Results showed that NOR (20, 40mg/kg) markedly reduced the symptoms of colitis, the levels of IL-1β and TNF-α, and the activation of ERK, p38 MAPK and NF-κB-p65. NOR only slightly decreased the levels of IFN-γ and IL-17A in mouse colons, but it dramatically increased the level of IL-10 at both protein and mRNA grades. Consistently, NOR increased the number of CD4(+)CD25(+)Foxp3(+) Treg cells more obviously than it decreased that of CD4(+)IL-17(+) Th17 cells in mesenteric lymph nodes (MLNs) and colonic lamina proprias (LPs) of colitis mice, and promoted the expression of Foxp3 mRNA in colon tissues. It could facilitate the in vitro differentiation of Treg cells from naive T cells and promote the phosphorylations of Smad2/3 in colon tissues of colitis mice. On the other hand, NOR did not affect the expressions of homing receptors CCR9 and α4β7 in SPs, and homing ligands CCL25 and Madcam-1 in MLNs and colonic LPs, suggesting that the increase of Treg cells in colons by NOR was not due to gut homing. In conclusion, NOR can ameliorate DSS-induced UC in mice, and the mechanisms involve reduction of pro-inflammatory cytokines and selective induction of Treg cells in colons.