Suppression of histone deacetylase 11 promotes expression of IL-10 in Kupffer cells and induces tolerance following orthotopic liver transplantation in rats

miR-27a-5p inhibits acute rejection of liver transplantation in rats by inducing M2 polarization of Kupffer cells through the PI3K/Akt pathway

Liver transplantation (LT), a major therapy for end-stage liver disease, is often associated with acute rejection (AR). MicroRNAs (miRNAs) have been implicated in AR-related gene regulation. In this experiment, the mechanism of miR-27a-5p in AR of LT was studied. Allotransplantation model (LEW-BN) and syngeneic transplantation model (LEW-LEW) of rat orthotopic liver transplantation (OLT) were established. miR-27a-5p was overexpressed in recipient rats 28 days before LT to detect its effects on LT pathology, liver function, and survival time. Kupffer cells (KCs) were isolated and treated with lipopolysaccharide (LPS) and miR-27a-5p overexpression. miR-27a-5p overexpression reduced lymphocyte numbers around portal areas and central veins after LT and mitigated degeneration of epithelial cells of the bile duct. Expression levels of IL-10 and TGF-β1 were increased while IL-12 was decreased. Liver function damage was alleviated and the survival time of rats with LT was prolonged. miR-27a-5p induced M2 polarization of rats with AR after LT and LPS-treated KCs in vitro and promoted activation of the PI3K/Akt pathway in KCs. Inhibition of the PI3K/Akt pathway averted induction of miR-27a-5p on M2 polarization of KCs. Taken together, miR-27a-5p inhibited AR after LT in rats by inducing M2 polarization of KCs through the PI3K/Akt pathway.

HDAC11, an emerging therapeutic target for metabolic disorders

Histone deacetylase 11 (HDAC11) is the only member of the class IV HDAC, and the latest member identified. It is highly expressed in brain, heart, kidney and some other organs, and located in mitochondria, cytoplasm and nuclei, depending on the tissue and cell types. Although studies in HDAC11 total knockout mice suggest its dispensable features for tissue development and life, it participates in diverse pathophysiological processes, such as DNA replication, tumor growth, immune regulation, oxidant stress injury and neurological function of cocaine. Recent studies have shown that HDAC11 is also critically involved in the pathogenesis of some metabolic diseases, including obesity, diabetes and complications of diabetes. In this review, we summarize the recent progress on the role and mechanism of HDAC11 in the regulation of metabolic disorders, with the focus on its regulation on adipogenesis, lipid metabolism, metabolic inflammation, glucose tolerance, immune responses and energy consumption. We also discuss the property and selectivity of HDAC11 inhibitors and their applications in a variety of in vitro and in vivo models of metabolic disorders. Given that pharmacological and genetic inhibition of HDAC11 exerts a beneficial effect on various metabolic disorders, HDAC11 may be a potential therapeutic target to treat chronic metabolic diseases.

The role of HDAC11 in obesity-related metabolic disorders: A critical review

At present, metabolic diseases, such as obesity and diabetes, have become the world's top health threats. These diseases are closely related to the abnormal development and function of adipocytes and metabolic inflammation associated with obesity. Histone deacetylase 11 (HDAC11), with a relatively unique structure and function in the HDAC family, plays a vital role in regulating cell growth, migration, and cell death. Currently, research on new key regulatory functions of HDAC11 in metabolic homeostasis is receiving more and more attention, and HDAC11 has also become a potential therapeutic target in the treatment of obesity and obesity-related diseases. Here, we summarized the latest literature on the role of HDAC11 in regulating the progress of obesity-related metabolic disorders.

Epigenetic alterations and advancement of treatment in peripheral T-cell lymphoma

Peripheral T-cell lymphoma (PTCL) is a rare and heterogeneous group of clinically aggressive diseases associated with poor prognosis. Except for ALK + anaplastic large-cell lymphoma (ALCL), most peripheral T-cell lymphomas are highly malignant and have an aggressive disease course and poor clinical outcomes, with a poor remission rate and frequent relapse after first-line treatment. Aberrant epigenetic alterations play an important role in the pathogenesis and development of specific types of peripheral T-cell lymphoma, including the regulation of the expression of genes and signal transduction. The most common epigenetic alterations are DNA methylation and histone modification. Histone modification alters the level of gene expression by regulating the acetylation status of lysine residues on the promoter surrounding histones, often leading to the silencing of tumour suppressor genes or the overexpression of proto-oncogenes in lymphoma. DNA methylation refers to CpG islands, generally leading to tumour suppressor gene transcriptional silencing. Genetic studies have also shown that some recurrent mutations in genes involved in the epigenetic machinery, including TET2, IDH2-R172, DNMT3A, RHOA, CD28, IDH2, TET2, MLL2, KMT2A, KDM6A, CREBBP, and EP300, have been observed in cases of PTCL. The aberrant expression of miRNAs has also gradually become a diagnostic biomarker. These provide a reasonable molecular mechanism for epigenetic modifying drugs in the treatment of PTCL. As epigenetic drugs implicated in lymphoma have been continually reported in recent years, many new ideas for the diagnosis, treatment, and prognosis of PTCL originate from epigenetics in recent years. Novel epigenetic-targeted drugs have shown good tolerance and therapeutic effects in the treatment of peripheral T-cell lymphoma as monotherapy or combination therapy. NCCN Clinical Practice Guidelines also recommended epigenetic drugs for PTCL subtypes as second-line therapy. Epigenetic mechanisms provide new directions and therapeutic strategies for the research and treatment of peripheral T-cell lymphoma. Therefore, this paper mainly reviews the epigenetic changes in the pathogenesis of peripheral T-cell lymphoma and the advancement of epigenetic-targeted drugs in the treatment of peripheral T-cell lymphoma (PTCL).

HDAC11: a rising star in epigenetics

Epigenetic mechanisms, such as acetylation, methylation, and succinylation, play pivotal roles in the regulation of multiple normal biological processes, including neuron regulation, hematopoiesis, bone cell maturation, and metabolism. In addition, epigenetic mechanisms are closely associated with the pathological processes of various diseases, such as metabolic diseases, autoimmune diseases and cancers. Epigenetic changes may precede genetic mutation, so research on epigenetic changes and regulation may be important for the early detection and diagnosis of disease. Histone deacetylase11 (HDAC11) is the newest member of the histone deacetylase (HDAC) family and the only class IV histone deacetylase. HDAC11 has different expression levels and biological functions in different systems of the human body and is among the top 1 to 4% of genes overexpressed in cancers, such as breast cancer, hepatocellular carcinoma and renal pelvis urothelial carcinoma. This article analyzes the role and mechanism of HDAC11 in disease, especially in tumorigenesis, in an attempt to provide new ideas for clinical and basic research.

Recent Progress in Histone Deacetylase Inhibitors as Anticancer Agents

Histone Deacetylase (HDAC) inhibitors are a relatively new class of anti-cancer agents that play important roles in epigenetic or non-epigenetic regulation, inducing death, apoptosis, and cell cycle arrest in cancer cells. Recently, their use has been clinically validated in cancer patients resulting in the approval by the FDA of four HDAC inhibitors, vorinostat, romidepsin, belinostat and panobinostat, used for the treatment of cutaneous/peripheral T-cell lymphoma and multiple myeloma. Many more HDAC inhibitors are at different stages of clinical development for the treatment of hematological malignancies as well as solid tumors. Also, clinical trials of several HDAC inhibitors for use as anti-cancer drugs (alone or in combination with other anti-cancer therapeutics) are ongoing. In the intensifying efforts to discover new, hopefully, more therapeutically efficacious HDAC inhibitors, molecular modelingbased rational drug design has played an important role. In this review, we summarize four major structural classes of HDAC inhibitors (hydroxamic acid derivatives, aminobenzamide, cyclic peptide and short-chain fatty acids) that are in clinical trials and different computer modeling tools available for their structural modifications as a guide to discover additional HDAC inhibitors with greater therapeutic utility.

Roles of Histone Deacetylases and Inhibitors in Anticancer Therapy

Histones are the main structural proteins of eukaryotic chromatin. Histone acetylation/ deacetylation are the epigenetic mechanisms of the regulation of gene expression and are catalyzed by histone acetyltransferases (HAT) and histone deacetylases (HDAC). These epigenetic alterations of DNA structure influence the action of transcription factors which can induce or repress gene transcription. The HATs catalyze acetylation and the events related to gene transcription and are also responsible for transporting newly synthesized histones from the cytoplasm to the nucleus. The activity of HDACs is mainly involved in silencing gene expression and according to their specialized functions are divided into classes I, II, III and IV. The disturbance of the expression and mutations of HDAC genes causes the aberrant transcription of key genes regulating important cancer pathways such as cell proliferation, cell-cycle regulation and apoptosis. In view of their role in cancer pathways, HDACs are considered promising therapeutic targets and the development of HDAC inhibitors is a hot topic in the search for new anticancer drugs. The present review will focus on HDACs I, II and IV, the best known inhibitors and potential alternative inhibitors derived from natural and synthetic products which can be used to influence HDAC activity and the development of new cancer therapies.

Zinc Dependent Histone Deacetylase Inhibitors in Cancer Therapeutics: Recent Update

BACKGROUND

Histone deacetylases (HDAC) are an important class of enzymes that play a pivotal role in epigenetic regulation of gene expression that modifies the terminal of core histones leading to remodelling of chromatin topology and thereby controlling gene expression. HDAC inhibitors (HDACi) counter this action and can result in hyperacetylation of histones, thereby inducing an array of cellular consequences such as activation of apoptotic pathways, generation of reactive oxygen species (ROS), cell cycle arrest and autophagy. Hence, there is a growing interest in the potential clinical use of HDAC inhibitors as a new class of targeted cancer therapeutics. Methodology and Result: Several research articles spanning between 2016 and 2017 were reviewed in this article and presently offer critical insights into the important strategies such as structure-based rational drug design, multi-parameter lead optimization methodologies, relevant SAR studies and biology of various class of HDAC inhibitors, such as hydroxamic acids, benzamides, cyclic peptides, aliphatic acids, summarising the clinical trials and results of various combination drug therapy till date.

CONCLUSION

This review will provide a platform to the synthetic chemists and biologists to cater the needs of both molecular targeted therapy and combination drug therapy to design and synthesize safe and selective HDAC inhibitors in cancer therapeutics.

Cigarette smoke extract modulates Pseudomonas aeruginosa bacterial load via USP25/HDAC11 axis in lung epithelial cells

Cigarette smoking increases susceptibility for microbial infection in respiratory system. However, the underlying molecular mechanism(s) is not fully elucidated. Here we report that cigarette smoking extract (CSE) increases bacterial load in lung epithelial cells via downregulation of the ubiquitin-specific protease 25 (USP25)/histone deacetylase 11 (HDAC11) axis. CSE treatment decreases HDAC11 at protein level in lung epithelial cells without significant changes of its transcription. Concomitantly, CSE treatment accelerates a ubiquitin-specific protease USP25 ubiquitination and degradation. Coimmunoprecipitation studies showed that USP25 associated with HDAC11. USP25 catalyzes deubiquitination of HDAC11, which regulates HDAC11 protein stability. CSE-mediated degradation of USP25 thereafter reduces HDAC11 at the protein level. Interestingly, CSE-downregulated USP25/HDAC11 axis increases the bacterial load of Pseudomonas aeruginosa in lung epithelial cells. These findings suggest that CSE-downregulated USP25 and HDAC11 may contribute to high susceptibility of bacterial infection in the cigarette smoking population.

Histone deacetylases (HDACs) as therapeutic target for depressive disorders

Major depressive disorder (MDD) represents approximately 40% of the disability caused by mental illnesses globally. The poorly understood pathophysiology and limited efficiency of pharmacological treatment (based primarily on the principles of the monoaminergic hypothesis) make depression a serious medical, public and socio-economical problem. An increasing number of studies suggest that epigenetic modifications (alterations in gene expression that are not due to changes in DNA sequence) in certain brain regions and neural circuits represent a key mechanism through which environmental factors interact with individual's genetic constitution to affect risk of mental disorders. Accordingly, chromatin-based epigenetic regulation seems to be a promising direction for the development of new, more effective antidepressant drugs. Recently, several inhibitors of histone deacetylases (HDAC) have been extensively studied in the context of antidepressant action. So far, none of them has been used to treat depression in humans due to the low selectivity for specific HDAC isoforms, and consequently, a risk of serious adverse events. In this review, we focus on the HDAC inhibitors (HDACi) with the greatest antidepressant efficacy and their activity in the preclinical studies. Moreover, we discuss their potential therapeutic usefulness in depression and the main limitations.

Vorinostat suppresses hypoxia signaling by modulating nuclear translocation of hypoxia inducible factor 1 alpha

Histone deacetylase inhibitors (HDACis) are a potent class of tumor-suppressive agents traditionally believed to exert their effects through loosening tightly-wound chromatin resulting in de-inhibition of various tumor suppressive genes. Recent literature however has shown altered intratumoral hypoxia signaling with HDACi administration not attributable to changes in chromatin structure. We sought to determine the precise mechanism of HDACi-mediated hypoxia signaling attenuation using vorinostat (SAHA), an FDA-approved class I/IIb/IV HDACi. Through an in-vitro and in-vivo approach utilizing cell lines for hepatocellular carcinoma (HCC), osteosarcoma (OS), and glioblastoma (GBM), we demonstrate that SAHA potently inhibits HIF-a nuclear translocation via direct acetylation of its associated chaperone, heat shock protein 90 (Hsp90). In the presence of SAHA we found elevated levels of acetyl-Hsp90, decreased interaction between acetyl-Hsp90 and HIF-a, decreased nuclear/cytoplasmic HIF-α expression, absent HIF-α association with its nuclear karyopharyin Importin, and markedly decreased HIF-a transcriptional activity. These changes were associated with downregulation of downstream hypoxia molecules such as endothelin 1, erythropoietin, glucose transporter 1, and vascular endothelial growth factor. Findings were replicated in an in-vivo Hep3B HRE-Luc expressing xenograft, and were associated with significant decreases in xenograft tumor size. Altogether, this study highlights a novel mechanism of action of an important class of chemotherapeutic.

The role of Kupffer cells in hepatic diseases

Kupffer cells (KCs) constitute 80-90% of the tissue macrophages present in the body. Essential to innate and adaptive immunity, KCs are responsible for the swift containment and clearance of exogenous particulates and immunoreactive materials which are perceived as foreign and harmful to the body. Similar to other macrophages, KCs also sense endogenous molecular signals that may result from perturbed homeostasis of the host. KCs have been implicated in host defense and the pathogenesis of various hepatic diseases, including endotoxin tolerance, liver transplantation, nonalcoholic fatty liver disease, and alcoholic liver disease. In this review, we summarized some novel findings associated with the role of KCs in hepatic diseases, such as the origin and mechanisms KCs polarization, molecular basis for caspase-1 activation called "non-canonical inflammasome pathway" involving the cleavage of Gsdmd by caspase-11, the important role of microRNA in liver transplantation, and so on. A better understanding of KCs biological characteristics and immunologic function in liver homeostasis and pathology may pave the way to investigate new diagnostic and therapeutic approaches for hepatic diseases.

Epigenetic Modulation of Stem Cells in Neurodevelopment: The Role of Methylation and Acetylation

The coordinated development of the nervous system requires fidelity in the expression of specific genes determining the different neural cell phenotypes. Stem cell fate decisions during neurodevelopment are strictly correlated with their epigenetic status. The epigenetic regulatory processes, such as DNA methylation and histone modifications discussed in this review article, may impact both neural stem cell (NSC) self-renewal and differentiation and thus play an important role in neurodevelopment. At the same time, stem cell decisions regarding fate commitment and differentiation are highly dependent on the temporospatial expression of specific genes contingent on the developmental stage of the nervous system. An interplay between the above, as well as basic cell processes, such as transcription regulation, DNA replication, cell cycle regulation and DNA repair therefore determine the accuracy and function of neuronal connections. This may significantly impact embryonic health and development as well as cognitive processes such as neuroplasticity and memory formation later in the adult.

Mesenchymal stromal cell-dependent reprogramming of Kupffer cells is mediated by TNF-α and PGE2 and is crucial for liver transplant tolerance

The role of mesenchymal stromal cells (MSCs) in the modulation of liver transplant tolerance has attracted significant interest. However, the interaction between MSCs and Kupffer cells (KCs) has received little attention, and the effect of this interaction on liver transplant tolerance remains unclear. KCs were cultured in the presence and absence of MSCs. After 24 h, cells were treated with lipopolysaccharide (LPS), after which the production of cytokines and the expression of surface antigens were measured for cell function identification. Moreover, the effects of the KCs and the prostaglandin E2 (PGE2) levels produced by the MSCs were determined using an experimental rat liver transplantation model. Blood and liver samples were collected at three time points after transplantation for further analysis. After LPS treatment, when compared with the KC single cultures, the expression of pro-inflammatory cytokines (IL-1β, IL-6, MHC-II, CD40, CD80, and CD86) in the coculture system was down-regulated, whereas the expression of anti-inflammatory cytokines (TGF-β, IL-4, PGE2, and IL-10) was markedly increased. These data indicate that MSCs can reprogram the phenotype of KCs. However, KCs treated with miR/TNF-α (tumor necrosis factor) plasmid prior to coculture to inhibit the production of TNF-α resulted in an inhibition of the reprogramming effect of MSCs. Moreover, overexpression of PGE2 in MSCs increased the effect of MSCs on KC reprogramming. After rat liver transplantation, allograft recipients that received MSCs showed better allograft tolerance when compared with rats in which KC function was inhibited. Furthermore, rats treated with MSCs overexpressing PGE2 demonstrated the best liver tolerance of all of the groups tested. MSCs reprogram the phenotype of KCs through TNF-α and PGE2, and this process is crucial for the immunomodulatory function of MSCs in liver transplantation.

Role of Kupffer cells in hepatitis B/C viral hepatitis

Kupffer cells (KCs) are the largest group of tissue macrophages. KCs in the hepatic sinusoid contact with pathogens from circulation earliest. The quantity of KCs increases significantly in patients with viral hepatitis, suggesting that KCs play an important role in viral hepatitis related immunity. KCs can not only engulf virus particles, but also present antigens, secrete cytokines, and participate in a variety of inflammatory responses, immune tolerance and liver injury. In hepatitis B virus (HBV)/hepatitis C virus (HCV) infections, the diversity of KCs-related cytokines, the complexity of interactions of receptor signaling pathways as well as the duality of cytotoxic effect, indicate that KCs play a dual role in the immune response; the activation of KCs regulates the balance of inflammatory and anti-inflammatory mechanisms in viral hepatitis.

Kupffer cells and liver transplantation

Nowadays, liver transplantation is globally considered the most effective treatment for end-stage liver diseases. Ischemia-reperfusion (I/R) injury and immune rejection response (IRR) are the two major imperfections which severely affect the recipients' prognosis and survival rate without satisfactory clinical management strategies. Therefore, exploring effective methods to improve I/R injury and IRR have important clinical significance under circumstances of shortage of donor livers. Kupffer cells (KCs) are the largest population of antigen representing cells (APCs) which settle in the liver. As the first defensive line of the live, KCs exhibit various biological effects. However, the exact mechanisms responsible for the role of KCs in I/R injury and IRR remain elusive. We hereby review the current finding about the role of KCs in I/R injury and IRR.

Histone deacetylase inhibitors in clinical studies as templates for new anticancer agents

Histone dacetylases (HDACs) are a group of enzymes that remove acetyl groups from histones and regulate expression of tumor suppressor genes. They are implicated in many human diseases, especially cancer, making them a promising therapeutic target for treatment of the latter by developing a wide variety of inhibitors. HDAC inhibitors interfere with HDAC activity and regulate biological events, such as cell cycle, differentiation and apoptosis in cancer cells. As a result, HDAC inhibitor-based therapies have gained much attention for cancer treatment. To date, the FDA has approved three HDAC inhibitors for cutaneous/peripheral T-cell lymphoma and many more HDAC inhibitors are in different stages of clinical development for the treatment of hematological malignancies as well as solid tumors. In the intensifying efforts to discover new, hopefully more therapeutically efficacious HDAC inhibitors, molecular modeling-based rational drug design has played an important role in identifying potential inhibitors that vary in molecular structures and properties. In this review, we summarize four major structural classes of HDAC inhibitors that are in clinical trials and different computer modeling tools available for their structural modifications as a guide to discover additional HDAC inhibitors with greater therapeutic utility.

Histone deacetylases and atherosclerosis

Atherosclerosis is the most common pathological process that leads to cardiovascular diseases, a disease of large- and medium-sized arteries that is characterized by a formation of atherosclerotic plaques consisting of necrotic cores, calcified regions, accumulated modified lipids, smooth muscle cells (SMCs), endothelial cells, leukocytes, and foam cells. Recently, the question about how to suppress the occurrence of atherosclerosis and alleviate the progress of cardiovascular disease becomes the hot topic. Accumulating evidence suggests that histone deacetylases(HDACs) play crucial roles in arteriosclerosis. This review summarizes the effect of HDACs and HDAC inhibitors(HDACi) on the progress of atherosclerosis.

Towards selective inhibition of histone deacetylase isoforms: what has been achieved, where we are and what will be next

Histone deacetylases (HDACs) are widely studied targets for the treatment of cancer and other diseases. Up to now, over twenty HDAC inhibitors have entered clinical studies and two of them have already reached the market, namely the hydroxamic acid derivative SAHA (vorinostat, Zolinza) and the cyclic depsipeptide FK228 (romidepsin, Istodax) that have been approved for the treatment of cutaneous T-cell lymphoma (CTCL). A common aspect of the first HDAC inhibitors is the absence of any particular selectivity towards specific isozymes. Some of molecules resulted to be “pan”-HDAC inhibitors, while others are class I selective. In the meantime, the knowledge of HDAC biology has continuously progressed. Key advances in the structural biology of various isozymes, reliable molecular homology models as well as suitable biological assays have provided new tools for drug discovery activities. This Minireview aims at surveying these recent developments as well as the design, synthesis and biological characterization of isoform-selective derivatives.

Gadolinium chloride suppresses acute rejection and induces tolerance following rat liver transplantation by inhibiting Kupffer-cell activation

The aim of the present study was to investigate the mechanism by which gadolinium chloride (GdCl₃) inhibits Kupffer cell (KC) activation and its ability to suppress acute rejection and induce tolerance following liver transplantation in rats. Rats were randomly divided into control, liver transplantation with GdCl₃ pretreatment and liver transplantation with normal saline pretreatment groups. The survival rate, liver function, hepatic pathological histology, cytokine levels in the liver and bile, activity of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) in KCs, and expression levels of membranous molecules on the KCs were observed. It was identified that the one-month survival rate in the GdCl₃ group was significantly higher compared with that in the saline group (P<0.05). The liver function in the GdCl₃ group gradually recovered following transplantation surgery; however, it progressively deteriorated in the saline group. There were minor changes of hepatic pathological histology in the GdCl₃ group, whereas changes typical of acute rejection occurred in the saline group. In the GdCl₃ group, the levels of interferon γ and interleukin (IL)-2 were significantly lower whereas the levels of IL-10 were significantly higher compared with those in the control and saline groups (all P<0.01). The IL-4 levels in the GdCl₃ and control groups were similar. The activity of NF-κB in the saline group was significantly higher compared with those in the control and GdCl₃ groups (P<0.01). The expression levels of major histocompatibility complex-II, cluster of differentiation (CD)80 and CD86 on the KC membranes in the GdCl₃ group was significantly lower compared with those in the control group (P<0.05); however, these membranous proteins were highly expressed in the saline group. These data indicate that GdCl₃ efficiently inhibits the immunological activity of KCs, suppresses acute rejection and induces tolerance following liver allograft transplantation in rats.

DAP12 deficiency in liver allografts results in enhanced donor DC migration, augmented effector T cell responses and abrogation of transplant tolerance

Liver interstitial dendritic cells (DC) have been implicated in immune regulation and tolerance induction. We found that the transmembrane immuno-adaptor DNAX-activating protein of 12 kDa (DAP12) negatively regulated conventional liver myeloid (m) DC maturation and their in vivo migratory and T cell allostimulatory ability. Livers were transplanted from C57BL/6(H2(b) ) (B6) WT or DAP12(-/-) mice into WT C3H (H2(k) ) recipients. Donor mDC (H2-K(b+) CD11c(+) ) were quantified in spleens by flow cytometry. Anti-donor T cell reactivity was evaluated by ex vivo carboxyfluorescein diacetate succinimidyl ester-mixed leukocyte reaction and delayed-type hypersensitivity responses, while T effector and regulatory T cells were determined by flow analysis. A threefold to fourfold increase in donor-derived DC was detected in spleens of DAP12(-/-) liver recipients compared with those given WT grafts. Moreover, pro-inflammatory cytokine gene expression in the graft, interferon gamma (IFNγ) production by graft-infiltrating CD8(+) T cells and systemic levels of IFNγ were all elevated significantly in DAP12(-/-) liver recipients. DAP12(-/-) grafts also exhibited reduced incidences of CD4(+) Foxp3(+) cells and enhanced CD8(+) T cell IFNγ secretion in response to donor antigen challenge. Unlike WT grafts, DAP12(-/-) livers failed to induce tolerance and were rejected acutely. Thus, DAP12 expression in liver grafts regulates donor mDC migration to host lymphoid tissue, alloreactive T cell responses and transplant tolerance.

Knockdown of microRNA-155 in Kupffer cells results in immunosuppressive effects and prolongs survival of mouse liver allografts

BACKGROUND

Our previous studies have shown that Kupffer cells (KCs) play a crucial role in postoperative pathologic changes. Recent reports have demonstrated that microRNA-155 (miR-155) is associated with inflammation and upregulation of proinflammatory mediators in the peripheral blood and allografts of transplant patients. However, the precise mechanism for this remains unknown.

METHODS

KCs isolated from BALB/c mice were transfected with miR-155 mimic or inhibitor. Levels of suppressor of cytokine signaling 1/Janus kinase/signal transducer and activator of transcription (SOCS1/JAK/STAT) proteins and surface molecules (MHC-II, CD40, and CD86) were then measured. T-cell proliferation and apoptosis were evaluated in mixed lymphocyte reactions. Orthotopic liver transplantation was performed in mice after miR-155 short hairpin RNA lentivirus treatment, and postoperative survival, liver function and histology, and mRNA and protein expression were analyzed.

RESULTS

miR-155 knockdown in KCs decreased MHC-II, CD40, and CD86 expression, suppressed antigen-presenting function, and affected SOCS1/JAK/STAT inflammatory pathways. In addition, KCs transfected with miR-155 inhibitor and cocultured with T lymphocytes showed reduced T-cell responses but a greater number of apoptotic T cells. Finally, miR-155 suppression in graft liver prolonged liver allograft survival and improved liver function. The changes were closely associated with the levels of T helper 1 and 2 (Th1/Th2) cytokines and T-cell apoptosis, but a direct mechanistic link in vivo was not established.

CONCLUSION

These data suggest miR-155 regulates the balance of Th1/Th2 cytokines and the maturation and function of KCs in mice. miR-155 repression in KCs positively regulates KC function toward immunosuppression and prolongs liver allograft survival.

Myeloid-derived suppressor cells: the dark knight or the joker in viral infections?

Myeloid derived suppressor cells (MDSCs) are immature cells of myeloid origin, frequently found in tumor microenvironments and in the blood of cancer patients. In recent years, MDSCs have also been found in non-cancer settings, including a number of viral infections. The evasion of host immunity employed by viruses to establish viral persistence strikingly parallels mechanisms of tumor escape, prompting investigations into the generation and function of MDSCs in chronic viral infections. Importantly, analogous to the tumor microenvironment, MDSCs effectively suppress antiviral host immunity by limiting the function of several immune cells including T cells, natural killer cells, and antigen-presenting cells. In this article, we review studies on the mechanisms of MDSC generation, accumulation, and survival in an effort to understand their emergent importance in viral infections. We include a growing list of viral infections in which MDSCs have been reported. Finally, we discuss how MDSCs might play a role in establishing chronic viral infections and identify potential therapeutics that target MDSCs.

Proliferative status regulates HDAC11 mRNA abundance in nontransformed fibroblasts

Histone deacetylases (HDACs) are important determinants of gene transcription and other biological processes. HDAC11 is one of the least characterized HDACs and is the only member of the class IV HDAC family. Our studies examined the events that control the expression of the HDAC11 transcript. We show that platelet-derived growth factor (PDGF) rapidly reduces the abundance of HDAC11 mRNA when added to density-arrested Balb/c-3T3 cells, which are nontransformed fibroblasts. Reduction required mRNA and protein synthesis, but not AKT or ERK activity, and resulted from accelerated turnover of the HDAC11 transcript. Reduction was transient in cells receiving PDGF alone but sustained in cells receiving both PDGF and platelet-poor plasma, which together promote G₀/G₁ traverse and S phase entry. Plasma alone did not appreciably reduce HDAC11 mRNA abundance, nor did epidermal growth factor, insulin-like growth factor, or insulin. HDAC11 mRNA accumulated in Balb/c-3T3 cells exiting the cell cycle due to density-dependent growth inhibition or serum deprivation. Of note, HDAC11 mRNA did not accumulate in a spontaneously transformed Balb/c-3T3 clonal variant (clone 2) that does not density arrest. The HDAC11 promoter was active in Balb/c-3T3 but not clone 2 cells; inactivity in clone 2 cells did not result from methylation of CpG islands. Overexpression of HDAC11 inhibited the cell cycle progression of both transformed and nontransformed fibroblasts. Our studies identify the HDAC11 transcript as a PDGF target and show that HDAC11 mRNA abundance correlates inversely with proliferative status.

HDAC inhibitor-based therapies: can we interpret the code?

Abnormal epigenetic control is a common early event in tumour progression, and aberrant acetylation in particular has been implicated in tumourigenesis. One of the most promising approaches towards drugs that modulate epigenetic processes has been seen in the development of inhibitors of histone deacetylases (HDACs). HDACs regulate the acetylation of histones in nucleosomes, which mediates changes in chromatin conformation, leading to regulation of gene expression. HDACs also regulate the acetylation status of a variety of other non-histone substrates, including key tumour suppressor proteins and oncogenes. Histone deacetylase inhibitors (HDIs) are potent anti-proliferative agents which modulate acetylation by targeting histone deacetylases. Interest is increasing in HDI-based therapies and so far, two HDIs, vorinostat (SAHA) and romidepsin (FK228), have been approved for treating cutaneous T-cell lymphoma (CTCL). Others are undergoing clinical trials. Treatment with HDIs prompts tumour cells to undergo apoptosis, and cell-based studies have shown a number of other outcomes to result from HDI treatment, including cell-cycle arrest, cell differentiation, anti-angiogenesis and autophagy. However, our understanding of the key pathways through which HDAC inhibitors affect tumour cell growth remains incomplete, which has hampered progress in identifying malignancies other than CTCL which are likely to respond to HDI treatment.

Regulation of immune responses by histone deacetylase inhibitors

Both genetic and epigenetic factors are important regulators of the immune system. There is an increasing body of evidence attesting to epigenetic modifications that influence the development of distinct innate and adaptive immune response cells. Chromatin remodelling via acetylation, methylation, phosphorylation, and ubiquitination of histone proteins as well as DNA, methylation is epigenetic mechanisms by which immune gene expression can be controlled. In this paper, we will discuss the role of epigenetics in the regulation of host immunity, with particular emphasis on histone deacetylase inhibitors. In particular, the role of HDAC inhibitors as a new class of immunomodulatory therapeutics will also be reviewed.

Role of interleukin-10 in breast cancer

Cytokines are low molecular weight regulatory proteins or glycoprotein that modulates the intensity and duration of immune response by stimulating or inhibiting the activation, proliferation, and/or differentiation of target cells. Different cytokines are known to have diverse role in breast cancer initiation and progression. Interleukin-10 (IL-10), a pleiotropic anti-inflammatory cytokine, induces immunosuppression and assists in escape from tumor immune surveillance. Like several other cytokines, IL-10 also can exert dual proliferative and inhibitory effect on breast tumor cells indicating a complex role of IL-10 in breast cancer initiation and progression. In this review, we tried to put together a comprehensive current view on significance of IL-10 in promotion, inhibition, and importance as prognosticator in breast cancer based on in vitro, in vivo, and clinical evidences. For literature collection, we conducted PubMed search with keywords "IL-10" and "breast cancer".