Histone deacetylases as regulators of inflammation and immunity

Histone deacetylase 5 deacetylates the phosphatase PP2A for positively regulating NF-κB signaling

Histone deacetylase 5 (HDAC5) has been reported to have a strong regulatory function in the proinflammatory response, but the mechanism is still unknown. Here, we identified HDAC5 as a positive regulator of NF-κB signaling in vivo. HDAC5-deficient mice exhibited enhanced survival in response to LPS challenge. Using LPS, TNFα, different kinds of viruses, hydrogen peroxide, or ultraviolet stimulation, we demonstrate that HDAC5-mediated regulation of NF-κB occurs in manners both dependent on and independent of IKK, an upstream kinase in the NF-κB signaling pathway. Deficiency in HDAC5 impaired the phosphorylation of IKKβ, subsequent phosphorylation of the NF-κB inhibitor protein IκBα and NF-κB subunit p65. We also show that the phosphatase PP2A repressed transcriptional activation of NF-κB by decreasing phosphorylation of IKKβ, p65, and IκBα. In vitro deacetylation experiments and site-directed mutagenesis experiments indicated that HDAC5 directly deacetylated PP2Ac at Lys136, which resulted in the deactivation of PP2A. Our data add mechanistic insight into the cross talk between epigenetic and posttranslational modifications regulating NF-κB signaling and protein phosphatase activation that mediate survival in response to inflammatory challenges.

Lower HDAC6 mRNA expression and promoter hypomethylation are associated with RA susceptibility

BACKGROUND/PURPOSE

Recent studies showed that Histone deacetylases 6 (HDAC6) inhibitors could improve arthritis in rheumatoid arthritis (RA) rodent models, whereas lower HDAC6 expression was observed in RA patients' synovial fibroblasts, raising the concerns to use HDAC6 inhibitors to treat RA patients. In the present study, we investigated the involvement of HDAC6 mRNA expression and promoter methylation in RA.

METHODS

The DNA and RNAs were extracted from the peripheral blood mononuclear cells (PBMCs) from 138 RA patients and 102 healthy controls. The pyrosequencing technique was used for promoter methylation analysis. The quantitative real-time polymerase chain reaction was used to determine the HDAC6 mRNA expression. The patients' clinical characteristics and disease biomarkers were recorded when blood sampling.

RESULTS

The HDAC6 mRNA expression was lower in the RA patients than controls (p = 0.001). The RA patients had significant hypomethylation of the HDAC6 promoter (p < 0.001). The HDAC6 promoter was hypo-methylated in the -229, -225, -144, and -142 CpG sites in RA patients (p < 0.05). Unexpectedly, promoter methylation and mRNA expression of the HDAC6 gene were positively associated (p < 0.001). The HDAC6 mRNA expression and promoter methylation status were associated with the risk of RA (p = 0.006 and 0.002, respectively). The inflammatory cytokines, TNF-α and IL-6, were significantly increased after HDAC6 knockdown in PMA-stimulated THP1 cells and SW982 cells (p < 0.05).

CONCLUSION

The HDAC6 mRNA expression and promoter methylation were lower in RA patients. Both HDAC6 mRNA expression level and promoter hypomethylation were associated the susceptibility of RA. HDAC6 inhibitors seem not proper for RA patients' treatment.

Resistance Against Leishmania major Infection Depends on Microbiota-Guided Macrophage Activation

Innate immune cells present a dual role during leishmaniasis: they constitute the first line of host defense but are also the main host cells for the parasite. Response against the infection that results in the control of parasite growth and lesion healing depends on activation of macrophages into a classical activated phenotype. We report an essential role for the microbiota in driving macrophage and monocyte-derived macrophage activation towards a resistance phenotype against Leishmania major infection in mice. Both germ-free and dysbiotic mice showed a higher number of myeloid innate cells in lesions and increased number of infected cells, mainly dermal resident and inflammatory macrophages. Despite developing a Th1 immune response characterized by the same levels of IFN-γ production as the conventional mice, germ-free mice presented reduced numbers of iNOS+ macrophages at the peak of infection. Absence or disturbance of host microbiota impaired the capacity of bone marrow-derived macrophage to be activated for Leishmania killing in vitro, even when stimulated by Th1 cytokines. These cells presented reduced expression of inos mRNA, and diminished production of microbicidal molecules, such as ROS, while presenting a permissive activation status, characterized by increased expression of arginase I and il-10 mRNA and higher arginase activity. Colonization of germ-free mice with complete microbiota from conventional mice rescued their ability to control the infection. This study demonstrates the essential role of host microbiota on innate immune response against L. major infection, driving host macrophages to a resistance phenotype.

The importance of endothelial protection: the emerging role of defibrotide in reversing endothelial injury and its sequelae

Hepatic veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS), a potentially life-threatening complication of hematopoietic cell transplantation (HCT), results from prolonged sinusoidal endothelial cell activation and profound endothelial cell damage, with sequelae. Defibrotide, the only drug approved in the United States and Europe for treating VOD/SOS post-HCT, has European Commission orphan drug designation for preventing graft-versus-host disease (GvHD), associated with endothelial dysfunction. This endothelial cell protector and stabilizing agent restores thrombo-fibrinolytic balance and preserves endothelial homeostasis through antithrombotic, fibrinolytic, anti-inflammatory, anti-oxidative, and anti-adhesive activity. Defibrotide also preserves endothelial cell structure by inhibiting heparanase activity. Evidence suggests that downregulating p38 mitogen-activated protein kinase (MAPK) and histone deacetylases (HDACs) is key to defibrotide’s endothelial protective effects; phosphatidylinositol 3-kinase/Akt (PI3K/AKT) potentially links defibrotide interaction with the endothelial cell membrane and downstream effects. Despite defibrotide’s being most extensively studied in VOD/SOS, emerging preclinical and clinical data support defibrotide for treating or preventing other conditions driven by endothelial cell activation, dysfunction, and/or damage, such as GvHD, transplant-associated thrombotic microangiopathy, or chimeric antigen receptor T-cell (CAR-T) therapy-associated neurotoxicity, underpinned by cytokine release syndrome and endotheliitis. Further preclinical and clinical studies will explore defibrotide’s potential utility in a broader range of disorders resulting from endothelial cell activation and dysfunction.

Porcine Epidemic Diarrhea Virus Inhibits HDAC1 Expression To Facilitate Its Replication via Binding of Its Nucleocapsid Protein to Host Transcription Factor Sp1

Porcine epidemic diarrhea virus (PEDV) is an enteric coronavirus causing acute intestinal infection in pigs, with high mortality often seen in neonatal pigs. The newborns rely on innate immune responses against invading pathogens because of lacking adaptive immunity. However, how PEDV disables the innate immunity of newborns toward severe infection remains unknown. We found that PEDV infection led to reduced expression of histone deacetylases (HDACs), especially HDAC1, in porcine IPEC-J2 cells. HDACs are considered important regulators of innate immunity. We hypothesized that PEDV interacts with certain host factors to regulate HDAC1 expression in favor of its replication. We show that HDAC1 acted as a negative regulator of PEDV replication in IPEC-J2 cells, as shown by chemical inhibition, gene knockout, and overexpression. A GC-box (GCCCCACCCCC) within the HDAC1 promoter region was identified for Sp1 binding in IPEC-J2 cells. Treatment of the cells with Sp1 inhibitor mithramycin A inhibited HDAC1 expression, indicating direct regulation of HDAC1 expression by Sp1. Of the viral proteins that were overexpressed in IPEC-J2 cells, the N protein was found to be present in the nuclei and more inhibitory to HDAC1 transcription. The putative nuclear localization sequence ²⁶¹PKKNKSR²⁶⁷ contributed to its nuclear localization. The N protein interacted with Sp1 and interfered with its binding to the promoter region, thereby inhibiting its transcriptional activity for HDAC1 expression. Our findings reveal a novel mechanism of PEDV evasion of the host responses, offering implications for studying the infection processes of other coronaviruses. IMPORTANCE The enteric coronavirus porcine epidemic diarrhea virus (PEDV) causes fatal acute intestinal infection in neonatal pigs that rely on innate immune responses. Histone deacetylases (HDACs) play important roles in innate immune regulation. Our study found PEDV suppresses HDAC1 expression via the interaction of its N protein and porcine Sp1, which identified a novel mechanism of PEDV evasion of the host responses to benefit its replication. This study suggests that other coronaviruses, including SARS-CoV and SARS-CoV-2, also make use of their N proteins to intercept the host immune responses in favor of their infection.

Extensive Changes in Transcription Dynamics Reflected on Alternative Splicing Events in Systemic Lupus Erythematosus Patients

In addition to increasing the complexity of the transcriptional output, alternative RNA splicing can lead to the reduction of mRNA translation or the production of non-functional or malfunctional proteins, thus representing a vital component of the gene regulation process. Herein, we set out to detect and characterize alternative splicing events that occur in whole-blood samples of patients with Systemic Lupus Erythematosus (SLE) as compared to healthy counterparts. Through the implementation of a computational pipeline on published RNA-sequencing data, we identified extensive changes in the transcription dynamics affecting a large number of genes. We found a predominance of intron retention events, with the majority introducing premature stop codons, suggestive of gene repression, in both inactive and active SLE patient samples. Alternative splicing affected a distinct set of genes from the ones detected as differentially expressed in the same comparisons, while alternatively spliced genes tended to reside in genome areas associated with increased gene co-expression. Functional analysis of genes affected by alternative splicing pointed towards particular functions related to metabolism and histone acetylation as of potential interest. Together, our findings underline the importance of incorporating alternative splicing analyses in the context of molecular characterization of complex diseases such as SLE.

IFN-γ Drives Human Monocyte Differentiation into Highly Proinflammatory Macrophages That Resemble a Phenotype Relevant to Psoriasis

As key cells of the immune system, macrophages coordinate the activation and regulation of the immune response. Macrophages present a complex phenotype that can vary from homeostatic, proinflammatory, and profibrotic to anti-inflammatory phenotypes. The factors that drive the differentiation from monocyte to macrophage largely define the resultant phenotype, as has been shown by the differences found in M-CSF- and GM-CSF-derived macrophages. We explored alternative inflammatory mediators that could be used for in vitro differentiation of human monocytes into macrophages. IFN-γ is a potent inflammatory mediator produced by lymphocytes in disease and infections. We used IFN-γ to differentiate human monocytes into macrophages and characterized the cells at a functional and proteomic level. IFN-γ alone was sufficient to generate macrophages (IFN-γ Mϕ) that were phagocytic and responsive to polarization. We demonstrate that IFN-γ Mϕ are potent activators of T lymphocytes that produce IL-17 and IFN-γ. We identified potential markers (GBP-1, IP-10, IL-12p70, and IL-23) of IFN-γ Mϕ and demonstrate that these markers are enriched in the skin of patients with inflamed psoriasis. Collectively, we show that IFN-γ can drive human monocyte to macrophage differentiation, leading to bona fide macrophages with inflammatory characteristics.

Epigenetic Regulation of Cancer Immune Cells

The epigenetic regulation of immune response involves reversible and heritable changes that do not alter the DNA sequence. Though there have been extensive studies accomplished relating to epigenetic changes in cancer cells, recent focus has been shifted on epigenetic-mediated changes in the immune cells including T cells, Macrophages, Natural Killer cells and anti-tumor immune responses. This review compiles the most relevant and recent literature related to the role of epigenetic mechanisms including DNA methylation and histone modifications in immune cells of wide range of cancers. We also include recent research with respect to role of the most relevant transcription factors that epigenetically control the anti-tumor immune response. Finally, a statement of future direction that promises to look forward for strategies to improve immunotherapy in cancer.

Histone deacetylase 9 deficiency exaggerates uterine M2 macrophage polarization

The maternal‐foetal interface is an immune‐privileged site where the semi‐allogeneic embryo is protected from attacks by the maternal immune system. Uterine macrophages are key players in establishing and maintaining pregnancy, and the dysregulation of the M1‐M2 subpopulation balance causes abortion. We separated two distinct mouse uterine macrophage subpopulations during early pregnancy, CD45⁺F4/80⁺CD206⁻ M1‐like (M1) and CD45⁺F4/80⁺CD206⁺ M2‐like (M2) cells. The M1 preponderance was significantly exaggerated at 6 hours after lipopolysaccharide (LPS) treatment, and adoptive transfer of M2 macrophages partially rescued LPS‐induced abortion. RNA sequencing analysis of mouse uterine M2 versus M1 revealed 1837 differentially expressed genes (DEGs), among which 629 was up‐regulated and 1208 was down‐regulated. Histone deacetylase 9 (Hdac9) was one of the DEGs and validated to be significantly up‐regulated in uterine M2 as compared with M1. Remarkably, this differential expression profile between M1 and M2 was also evident in primary splenic macrophages and in vitro polarized murine peritoneal, bone marrow–derived and RAW 264.7 macrophages. In Hdac9/HDAC9 knockout RAW 264.7 and human THP‐1–derived macrophages, the expression of M1 differentiation markers was unchanged or decreased whereas M2 markers were increased compared with the wild‐type cells, and these effects were unrelated to compromised proliferation. Furthermore, Hdac9/HDAC9 ablation significantly enhanced the phagocytosis of fluorescent microspheres in M2 Raw 264.7 cells yet decreased the capacity of THP‐1‐derived M1 macrophages. The above results demonstrate that Hdac9/HDAC9 deficiency exaggerates M2 macrophage polarization in mouse and human macrophages, which may provide clues for our understanding of the epigenetic regulation on macrophage M1/M2 polarization in maternal‐foetal tolerance.

Restoring the Immunity in the Tumor Microenvironment: Insights into Immunogenic Cell Death in Onco-Therapies

Immunogenic cell death (ICD) elicited by cancer therapy reshapes the tumor immune microenvironment. A long-term adaptative immune response can be initiated by modulating cell death by therapeutic approaches. Here, the major hallmarks of ICD, endoplasmic reticulum (ER) stress, and damage-associated molecular patterns (DAMPs) are correlated with ICD inducers used in clinical practice to enhance antitumoral activity by suppressing tumor immune evasion. Approaches to monitoring the ICD triggered by antitumoral therapeutics in the tumor microenvironment (TME) and novel perspective in this immune system strategy are also reviewed to give an overview of the relevance of ICD in cancer treatment.

Treatment with Histone Deacetylase Inhibitor Attenuates Peripheral Inflammation-Induced Cognitive Dysfunction and Microglial Activation: The Effect of SAHA as a Peripheral HDAC Inhibitor

It has been demonstrated that peripheral inflammation induces cognitive dysfunction. Several histone deacetylase (HDAC) inhibitors ameliorate cognitive dysfunction in animal models of not only peripheral inflammation but also Alzheimer's disease. However, it is not clear which HDAC expressed in the central nervous system or peripheral tissues is involved in the therapeutic effect of HDAC inhibition on cognitive dysfunction. Hence, the present study investigated the effect of peripheral HDAC inhibition on peripheral inflammation-induced cognitive dysfunction. Suberoylanilide hydroxamic acid (SAHA), a pan-HDAC inhibitor that is mainly distributed in peripheral tissues after intraperitoneal administration, was found to prevent peripheral inflammation-induced cognitive dysfunction. Moreover, pretreatment with SAHA dramatically increased mRNA expression of interleukin-10, an anti-inflammatory cytokine, in peripheral and central tissues and attenuated peripheral inflammation-induced microglial activation in the CA3 region of the hippocampus. Minocycline, a macrophage/microglia inhibitor, also ameliorated cognitive dysfunction. Furthermore, as a result of treatment with liposomal clodronate, depletion of peripheral macrophages partially ameliorated the peripheral inflammation-evoked cognitive dysfunction. Taken together, these findings demonstrate that inhibition of peripheral HDAC plays a critical role in preventing cognitive dysfunction induced by peripheral inflammation via the regulation of anti-inflammatory cytokine production and the inhibition of microglial functions in the hippocampus. Thus, these findings could provide support for inhibition of peripheral HDAC as a novel therapeutic strategy for inflammation-induced cognitive dysfunction.

HDAC3 increases HMGB3 expression to facilitate the immune escape of breast cancer cells via down-regulating microRNA-130a-3p

OBJECTIVE

Histone deacetylase 3 (HDAC3) has been reported to repress the expression of various genes by eliminating acetyl group from histone. The objective of this study was to discuss the effect of HDAC3/microRNA-130a-3p (miR-130a-3p)/high-mobility group box 3 (HMGB3) on immune escape of breast cancer.

METHODS

HDAC3, miR-130a-3p and HMGB3 expression in breast cancer tissues and cells were tested, and the correlation between HDAC3, miR-130a-3p and HMGB3 was analyzed. CD8, CD69 and programmed cell death protein 1 (PD-1) expression was detected. MDA-MB-231 cells were treated with relative plasmid of HDAC3 or miR-130a-3p to test cell viability, migration, epithelial-mesenchymal transition (EMT) and apoptosis in MDA-MB-231 cells. The cytotoxicity of CD8+/CD69+/PD-1+T cells in MDA-MB-231 cells was tested, and CD8+/CD69+/PD-1+T cell proliferation and apoptosis before and after co-culture with MDA-MB-231 cells were detected.

RESULTS

HDAC3 and HMGB3 expression were raised and miR-130a-3p expression was diminished in breast cancer tissues and cells. HDAC3 was negatively correlated with miR-130a-3p while miR-130a-3p was negatively correlated with HMGB3. Down-regulating HDAC3 or up-regulating miR-130a-3p restrained cell viability, migration, EMT and anti-CD8+/CD69+/PD-1+T cytotoxicity and facilitated apoptosis of breast cancer cells. HDAC3 regulated HMGB3 by mediating miR-130a-3p expression. Down-regulating miR-130a-3p reversed the role of HDAC3 reduction on breast cancer cells. HDAC3 regulated CD8+/CD69+/PD-1+T cell proliferation and apoptosis by mediating miR-130a-3p.

CONCLUSION

This study provides evidence that HDAC3 increases HMGB3 expression to promote the immune escape of breast cancer cells via down-regulating miR-130a-3p.

The Emerging Role of HDACs: Pathology and Therapeutic Targets in Diabetes Mellitus

Diabetes mellitus (DM) is one of the principal manifestations of metabolic syndrome and its prevalence with modern lifestyle is increasing incessantly. Chronic hyperglycemia can induce several vascular complications that were referred to be the major cause of morbidity and mortality in DM. Although several therapeutic targets have been identified and accessed clinically, the imminent risk of DM and its prevalence are still ascending. Substantial pieces of evidence revealed that histone deacetylase (HDAC) isoforms can regulate various molecular activities in DM via epigenetic and post-translational regulation of several transcription factors. To date, 18 HDAC isoforms have been identified in mammals that were categorized into four different classes. Classes I, II, and IV are regarded as classical HDACs, which operate through a Zn-based mechanism. In contrast, class III HDACs or Sirtuins depend on nicotinamide adenine dinucleotide (NAD+) for their molecular activity. Functionally, most of the HDAC isoforms can regulate β cell fate, insulin release, insulin expression and signaling, and glucose metabolism. Moreover, the roles of HDAC members have been implicated in the regulation of oxidative stress, inflammation, apoptosis, fibrosis, and other pathological events, which substantially contribute to diabetes-related vascular dysfunctions. Therefore, HDACs could serve as the potential therapeutic target in DM towards developing novel intervention strategies. This review sheds light on the emerging role of HDACs/isoforms in diabetic pathophysiology and emphasized the scope of their targeting in DM for constituting novel interventional strategies for metabolic disorders/complications.

Genome-Wide Association Studies of Somatic Cell Count in the Assaf Breed

Simple Summary

Mastitis causes economic loss due to discarded milk and reduced milk production and quality, increased medical care costs and somatic cell count (SCC) penalties. The use of genetic markers associated with the variability of this trait through marker-assisted selection (MAS) could help traditional methods. Our objectives were to identify new single nucleotide polymorphisms (SNPs) and genes associated with mastitis resistance in Assaf sheep by using the Illumina Ovine Infinium® HD SNP BeadChip (680K). Firstly, corrected phenotype estimates for somatic cell score (SCS) were calculated using 6173 records from 1894 multiparous Assaf ewes, and were used to select 192 extreme animals (low SCS group: n = 96; and high SCS group: n = 96) for the genome-wide association study (GWAS). Four SNPs (rs419096188, rs415580501, rs410336647, and rs424642424), three of them totally linked, were found to be significant at the chromosome level (FDR 10%) in two different regions of OAR19 close to genes related to the immune system response. Validation studies of two SNPs (rs419096188 and rs424642424) by Kompetitive Allele-Specific PCR (KASP) genotyping in the total population (n = 1894) confirmed previous GWAS association results for the SCS trait. Finally, the SNP rs419096188 was also associated with lactose content trait.

Abstract

A genome-wide association study (GWAS) was performed to identify new single nucleotide polymorphisms (SNPs) and genes associated with mastitis resistance in Assaf sheep by using the Illumina Ovine Infinium^® HD SNP BeadChip (680K). In total, 6173 records from 1894 multiparous Assaf ewes with at least three test day records and aged between 2 and 7 years old were used to estimate a corrected phenotype for somatic cell score (SCS). Then, 192 ewes were selected from the top (n = 96) and bottom (n = 96) tails of the corrected SCS phenotype distribution to be used in a GWAS. Although no significant SNPs were found at the genome level, four SNPs (rs419096188, rs415580501, rs410336647, and rs424642424) were significant at the chromosome level (FDR 10%) in two different regions of OAR19. The SNP rs419096188 was located in intron 1 of the NUP210 and close to the HDAC11 genes (61 kb apart), while the other three SNPs were totally linked and located 171 kb apart from the ARPP21 gene. These three genes were related to the immune system response. These results were validated in two SNPs (rs419096188 and rs424642424) in the total population (n = 1894) by Kompetitive Allele-Specific PCR (KASP) genotyping. Furthermore, rs419096188 was also associated with lactose content.

Nasal Epithelial Barrier Integrity and Tight Junctions Disruption in Allergic Rhinitis: Overview and Pathogenic Insights

Allergic rhinitis (AR) is a common disorder affecting up to 40% of the population worldwide and it usually persists throughout life. Nasal epithelial barrier constitutes the first line of defense against invasion of harmful pathogens or aeroallergens. Cell junctions comprising of tight junctions (TJs), adherens junctions, desmosomes and hemidesmosomes form the nasal epithelial barrier. Impairment of TJ molecules plays causative roles in the pathogenesis of AR. In this review, we describe and discuss the components of TJs and their disruption leading to development of AR, as well as regulation of TJs expression by epigenetic changes, neuro-immune interaction, epithelial-derived cytokines (thymic stromal lymphopoietin, IL-25 and IL-33), T helper 2 (Th2) cytokines (IL-4, IL-5, IL-6 and IL-13) and innate lymphoid cells. These growing evidence support the development of novel therapeutic approaches to restore nasal epithelial TJs expression in AR patients.

The regulation of protein acetylation influences the redox homeostasis to protect the heart

The cellular damage caused by redox imbalance is involved in the pathogenesis of many cardiovascular diseases. Besides, redox imbalance is related to the alteration of protein acetylation processes, causing not only chromatin remodeling but also disturbances in so many processes where protein acetylation is involved, such as metabolism and signal transduction. The modulation of acetylases and deacetylases enzymes aids in maintaining the redox homeostasis, avoiding the deleterious cellular effects associated with the dysregulation of protein acetylation. Of note, regulation of protein acetylation has shown protective effects to ameliorate cardiovascular diseases. For instance, HDAC inhibition has been related to inducing cardiac protective effects and it is an interesting approach to the management of cardiovascular diseases. On the other hand, the upregulation of SIRT protein activity has also been implicated in the relief of cardiovascular diseases. This review focuses on the major protein acetylation modulators described, involving pharmacological and bioactive compounds targeting deacetylase and acetylase enzymes contributing to heart protection through redox homeostasis.

From Anti-infective Agents to Cancer Therapy: a Drug Repositioning Study Revealed a New Use for Nitrofuran Derivatives

BACKGROUND

The progression of ovarian cancer seems to be related to HDAC1, HDAC3 and HDAC6 activity. A possible strategy for improving therapies for treating ovarian carcinoma, minimizing the preclinical screenings, is the repurposing of already approved pharmaceutical products as inhibitors of these enzymes.

OBJECTIVE

This work was aimed to implement a computational strategy for identifying new HDAC inhibitors for ovarian carcinoma treatment among approved drugs.

METHOD

The CHEMBL database was used to construct training, test and decoys sets for performing and validating HDAC1, HDAC3 and HDAC6 3D-QSAR models obtained by using FLAP program. Docking and MD simulations were used in combination with the generated models to identify novel potential HDAC inhibitors. Cell viability assays and Western blot analyses were performed on normal and cancer cells for a direct evaluation of the anti-proliferative activity and an in vitro estimation of HDAC inhibition of the compounds selected through in silico screening.

RESULT

The best quantitative prediction was obtained for the HDAC6 3D-QSAR model. The screening of approved drugs highlighted a new potential use as HDAC inhibitors for some compounds, in particular nitrofuran derivatives, usually known for their antibacterial activity, and frequently used as antimicrobial adjuvant therapy in cancer treatment. Experimental evaluation of these derivatives highlighted a significant antiproliferative activity against cancer cell lines overexpressing HDAC6, and an increase in acetylated alpha-tubulin levels.

CONCLUSION

Experimental results support the hypothesis of a potential direct interaction of nitrofuran derivatives with HDACs. In addition to the possible repurposing of already approved drugs, this work suggests the nitro group as a new zinc binding group, able to interact with the catalytic zinc ion of HDACs.

Inflammasome, the Constitutive Heterochromatin Machinery, and Replication of an Oncogenic Herpesvirus

The success of long-term host–virus partnerships is predicated on the ability of the host to limit the destructive potential of the virus and the virus’s skill in manipulating its host to persist undetected yet replicate efficiently when needed. By mastering such skills, herpesviruses persist silently in their hosts, though perturbations in this host–virus equilibrium can result in disease. The heterochromatin machinery that tightly regulates endogenous retroviral elements and pericentromeric repeats also silences invading genomes of alpha-, beta-, and gammaherpesviruses. That said, how these viruses disrupt this constitutive heterochromatin machinery to replicate and spread, particularly in response to disparate lytic triggers, is unclear. Here, we review how the cancer-causing gammaherpesvirus Epstein–Barr virus (EBV) uses the inflammasome as a security system to alert itself of threats to its cellular home as well as to flip the virus-encoded lytic switch, allowing it to replicate and escape in response to a variety of lytic triggers. EBV provides the first example of an infectious agent able to actively exploit the inflammasome to spark its replication. Revealing an unexpected link between the inflammasome and the epigenome, this further brings insights into how the heterochromatin machinery uses differential strategies to maintain the integrity of the cellular genome whilst guarding against invading pathogens. These recent insights into EBV biology and host–viral epigenetic regulation ultimately point to the NLRP3 inflammasome as an attractive target to thwart herpesvirus reactivation.

P300/CBP-associated factor (PCAF) attenuated M1 macrophage inflammatory responses possibly through KLF2 and KLF4

Macrophages exhibit distinct phenotypes in response to environmental signals. The polarization of M1 macrophages plays an essential role in the inflammatory response. However, the specific molecular mechanisms regulating the inflammatory response during M1 macrophage polarization remain to be further understood. Here, we found that the histone acetyltransferase P300/CBP-associated factor (PCAF) was a potential negative regulator of the M1 macrophage inflammatory response. During M1 macrophage polarization, the inflammatory response gradually reduced, but PCAF expression increased. Furthermore, the overexpression of PCAF significantly inhibited the expression of the M1 macrophage-related pro-inflammatory genes TNF-α, IL-6 and CXCL10, while PCAF deficiency enhanced the expression of these genes. Furthermore, we found that PCAF overexpression suppressed the NF-κB signaling pathway and promoted the expression of the Krüppel-like factors (KLF) KLF2 and KLF4 through regulating their transcriptional levels. In addition, KLF2 and KLF4 deficiency reversed the PCAF-induced inhibition of the expression of pro-inflammatory genes in M1 macrophages. Collectively, the present results demonstrate a potential negative regulatory mechanism of the inflammatory response during M1 macrophage polarization and propose a novel mechanism of inflammation resolution for maintaining homeostasis.

HDAC inhibition reduces white matter injury after intracerebral hemorrhage

Inhibition of histone deacetylases (HDACs) has been shown to reduce inflammation and white matter damage after various forms of brain injury via modulation of microglia/macrophage polarization. Previously we showed that the HDAC inhibitor scriptaid could attenuate white matter injury (WMI) after ICH. To access whether modulation of microglia/macrophage polarization might underlie this protection, we investigated the modulatory role of HDAC2 in microglia/macrophage polarization in response to WMI induced by intracerebral hemorrhage (ICH) and in primary microglia and oligodendrocyte co-cultures. HDAC2 activity was inhibited via conditional knockout of the Hdac2 gene in microglia or via administration of scriptaid. Conditional knockout of the Hdac2 gene in microglia and HDAC inhibition with scriptaid both improved neurological functional recovery and reduced WMI after ICH. Additionally, HDAC inhibition shifted microglia/macrophage polarization toward the M2 phenotype and reduced proinflammatory cytokine secretion after ICH in vivo. In vitro, a transwell co-culture model of microglia and oligodendrocytes also demonstrated that the HDAC inhibitor protected oligodendrocytes by modulating microglia polarization and mitigating neuroinflammation. Moreover, we found that scriptaid decreased the expression of pJAK2 and pSTAT1 in cultured microglia when stimulated with hemoglobin. Thus, HDAC inhibition ameliorated ICH-mediated neuroinflammation and WMI by modulating microglia/macrophage polarization.

Regulation of Monocyte Adhesion and Type I Interferon Signaling by CD52 in Patients With Systemic Sclerosis

OBJECTIVE

Systemic sclerosis (SSc) is characterized by dysregulation of type I interferon (IFN) signaling. CD52 is known for its immunosuppressive functions in T cells. This study was undertaken to investigate the role of CD52 in monocyte adhesion and type I IFN signaling in patients with SSc.

METHODS

Transcriptome profiles of circulating CD14+ monocytes from patients with limited cutaneous SSc (lcSSc), patients with diffuse cutaneous SSc (dcSSs), and healthy controls were analyzed by RNA sequencing. Levels of CD52, CD11b/integrin αΜ, and CD18/integrin β2 in whole blood were assessed by flow cytometry. CD52 expression was analyzed in relation to disease phenotype (early, lcSSc, dcSSc) and autoantibody profiles. The impact of overexpression, knockdown, and antibody blocking of CD52 was analyzed by gene and protein expression assays and functional assays.

RESULTS

Pathway enrichment analysis indicated an increase in adhesion- and type I IFN-related genes in monocytes from SSc patients. These cells displayed up-regulated expression of CD11b/CD18, reduced expression of CD52, and enhanced adhesion to intercellular adhesion molecule 1 and endothelial cells. Changes in CD52 expression were consistent with the SSc subtypes, as well as with immunosuppressive treatments, autoantibody profiles, and monocyte adhesion properties in patients with SSc. Overexpression of CD52 led to decreased levels of CD18 and monocyte adhesion, while knockdown of CD52 increased monocyte adhesion. Experiments with the humanized anti-CD52 monoclonal antibody alemtuzumab in blood samples from healthy controls increased monocyte adhesion and CD11b/CD18 expression, and enhanced type I IFN responses. Monocytic CD52 expression was up-regulated by interleukin-4 (IL-4)/IL-13 via the STAT6 pathway, and was down-regulated by lipopolysaccharide and IFNs α, β, and γ in a JAK1 and histone deacetylase IIa (HDAC IIa)-dependent manner.

CONCLUSION

Down-regulation of the antiadhesion CD52 antigen in CD14+ monocytes represents a novel mechanism in the pathogenesis of SSc. Targeting of the IFN-HDAC-CD52 axis in monocytes might represent a new therapeutic option for patients with early SSc.

Antibiotics Modulate Intestinal Regeneration

Simple Summary

The impact of the microbial community on host’s biological functions has uncovered the potential outcomes of antibiotics on host physiology, introducing the caveats of the antibiotic usage. Within animals, the digestive function is closely related to the microorganisms that inhabit this organ. The proper maintenance of the digestive system requires constant regeneration. These processes vary from self-renewal of some cells or tissues in some species to the complete regeneration of the organ in others. Whether antibiotics influence digestive organ regeneration remains unknown. We employ the sea cucumber, Holothuria glaberrima, for its capacity to regenerate the whole intestine after ejection from its internal cavity. We explored the antibiotics’ effects on several intestinal regeneration processes. In parallel, we studied the effect of antibiotics on the animals’ survival, toxicity, and gut bacteria growth. Our results show that tested antibiotics perturbed key cellular processes that occur during intestinal regeneration. Moreover, this happens at doses that inhibited bacteria growth but did not alter holothurian’s metabolic activity. We propose that antibiotics can perturb the cellular events of intestinal regeneration via their impact on the microbiota. These results highlight H. glaberrima as a promising model to study the importance of the microbiota during organ regeneration.

Abstract

The increased antibiotics usage in biomedical and agricultural settings has been well documented. Antibiotics have now been shown to exert effects outside their purposive use, including effects on physiological and developmental processes. We explored the effect of various antibiotics on intestinal regeneration in the sea cucumber Holothuria glaberrima. For this, holothurians were eviscerated and left to regenerate for 10 days in seawater with different penicillin/streptomycin-based cocktails (100 µg/mL PS) including: 100 µg/mL kanamycin (KPS), 5 µg/mL vancomycin (VPS), and 4 µg/mL (E4PS) or 20 µg/mL (E20PS) erythromycin. Immunohistological and histochemical analyses were performed to analyze regenerative processes, including rudiment size, extracellular matrix (ECM) remodeling, cell proliferation, and muscle dedifferentiation. A reduction in muscle dedifferentiation was observed in all antibiotic-treated animals. ECM remodeling was decreased by VPS, E4PS, and E20PS treatments. In addition, organisms subjected to E20PS displayed a significant reduction in the size of their regenerating rudiments while VPS exposure altered cell proliferation. MTT assays were used to discard the possibility that the antibiotics directly affect holothurian metabolic activity while bacterial cultures were used to test antibiotic effects on holothurian enteric microbiota. Our results demonstrate a negative effect on intestinal regeneration and strongly suggest that these effects are due to alterations in the microbial community.

Class IIa Histone Deacetylases Drive Toll-like Receptor-Inducible Glycolysis and Macrophage Inflammatory Responses via Pyruvate Kinase M2

Histone deacetylases (HDACs) drive innate immune cell-mediated inflammation. Here we identify class IIa HDACs as key molecular links between Toll-like receptor (TLR)-inducible aerobic glycolysis and macrophage inflammatory responses. A proteomic screen identified the glycolytic enzyme pyruvate kinase M isoform 2 (Pkm2) as a partner of proinflammatory Hdac7 in murine macrophages. Myeloid-specific Hdac7 overexpression in transgenic mice amplifies lipopolysaccharide (LPS)-inducible lactate and promotes a glycolysis-associated inflammatory signature. Conversely, pharmacological or genetic targeting of Hdac7 and other class IIa HDACs attenuates LPS-inducible glycolysis and accompanying inflammatory responses in macrophages. We show that an Hdac7-Pkm2 complex acts as an immunometabolism signaling hub, whereby Pkm2 deacetylation at lysine 433 licenses its proinflammatory functions. Disrupting this complex suppresses inflammatory responses in vitro and in vivo. Class IIa HDACs are thus pivotal intermediates connecting TLR-inducible glycolysis to inflammation via Pkm2.

Role of PI3K in the Progression and Regression of Atherosclerosis

Phosphatidylinositol 3 kinase (PI3K) is a key molecule in the initiation of signal transduction pathways after the binding of extracellular signals to cell surface receptors. An intracellular kinase, PI3K activates multiple intracellular signaling pathways that affect cell growth, proliferation, migration, secretion, differentiation, transcription and translation. Dysregulation of PI3K activity, and as aberrant PI3K signaling, lead to a broad range of human diseases, such as cancer, immune disorders, diabetes, and cardiovascular diseases. A growing number of studies have shown that PI3K and its signaling pathways play key roles in the pathophysiological process of atherosclerosis. Furthermore, drugs targeting PI3K and its related signaling pathways are promising treatments for atherosclerosis. Therefore, we have reviewed how PI3K, an important regulatory factor, mediates the development of atherosclerosis and how targeting PI3K can be used to prevent and treat atherosclerosis.

New Insights Into the Cancer-Microbiome-Immune Axis: Decrypting a Decade of Discoveries

The past decade has witnessed groundbreaking advances in the field of microbiome research. An area where immense implications of the microbiome have been demonstrated is tumor biology. The microbiome affects tumor initiation and progression through direct effects on the tumor cells and indirectly through manipulation of the immune system. It can also determine response to cancer therapies and predict disease progression and survival. Modulation of the microbiome can be harnessed to potentiate the efficacy of immunotherapies and decrease their toxicity. In this review, we comprehensively dissect recent evidence regarding the interaction of the microbiome and anti-tumor immune machinery and outline the critical questions which need to be addressed as we further explore this dynamic colloquy.

Sepsis, immunosuppression and the role of epigenetic mechanisms

Introduction: Sepsis has pro- and anti-inflammatory processes caused by infectious agents. Sepsis survivors have impaired immune response due to immunosuppression. Gene expression during the inflammatory process is guided by transcriptional access to chromatin, with post-translational changes made in histones that determine whether the loci of the inflammatory gene are active, balanced, or suppressed. For this, a review literature was performed in PubMed included 'sepsis' and 'epigenetic' and 'immunosuppression' terms until May 2020.Areas covered: This review article explores the relationship between epigenetic mechanisms and the pathophysiology of sepsis. Epigenetic changes, vulnerable gene expression, and immunosuppression are related to inflammatory insults that can modify the dynamics of the central nervous system. Therefore, it is important to investigate the timing of these changes and their dynamics during the disease progression.Expert opinion: Epigenetic changes are associated with the main stages of sepsis, from the pathogen-host interaction to inflammation and immunosuppression. These changes are key regulators of gene expression during physiological and pathological conditions. Thus, epigenetic markers have significant prognostic and diagnostic potential in sepsis, and epigenetic changes can be explored in combination with therapeutic strategies in experimental models of the disease.

SIRT3-mediated deacetylation of NLRC4 promotes inflammasome activation

Salmonella typhimurium (S. typhimurium) infection of macrophage induces NLRC4 inflammasome-mediated production of the pro-inflammatory cytokines IL-1β. Post-translational modifications on NLRC4 are critical for its activation. Sirtuin3 (SIRT3) is the most thoroughly studied mitochondrial nicotinamide adenine dinucleotide (NAD+) -dependent deacetylase. We wondered whether SIRT3 mediated-deacetylation could take part in NLRC4 inflammasome activation. Methods: We initially tested IL-1β production and pyroptosis after cytosolic transfection of flagellin or S. typhimurium infection in wild type and SIRT3-deficient primary peritoneal macrophages via immunoblotting and ELISA assay. These results were confirmed in SIRT3-deficient immortalized bone marrow derived macrophages (iBMDMs) which were generated by CRISPR-Cas9 technology. In addition, in vivo experiments were conducted to confirm the role of SIRT3 in S. typhimurium-induced cytokines production. Then NLRC4 assembly was analyzed by immune-fluorescence assay and ASC oligomerization assay. Immunoblotting, ELISA and flow cytometry were performed to clarify the role of SIRT3 in NLRP3 and AIM2 inflammasomes activation. To further investigate the mechanism of SIRT3 in NLRC4 activation, co-immunoprecipitation (Co-IP), we did immunoblot, cellular fractionation and in-vitro deacetylation assay. Finally, to clarify the acetylation sites of NLRC4, we performed liquid chromatography-mass spectrometry (LC-MS) and immunoblotting analysis. Results: SIRT3 deficiency led to significantly impaired NLRC4 inflammasome activation and pyroptosis both in vitro and in vivo. Furthermore, SIRT3 promotes NLRC4 inflammasome assembly by inducing more ASC speck formation and ASC oligomerization. However, SIRT3 is dispensable for NLRP3 and AIM2 inflammasome activation. Moreover, SIRT3 interacts with and deacetylates NLRC4 to promote its activation. Finally, we proved that deacetylation of NLRC4 at Lys71 or Lys272 could promote its activation. Conclusions: Our study reveals that SIRT3 mediated-deacetylation of NLRC4 is pivotal for NLRC4 activation and the acetylation switch of NLRC4 may aid the clearance of S. typhimurium infection.

NFAT2-HDAC1 signaling contributes to the malignant phenotype of glioblastoma

BACKGROUND

Deregulation of the nuclear factor of activated T cell (NFAT) pathway has been reported in several human cancers. Particularly, NFAT2 is involved in the malignant transformation of tumor cells and is identified as an oncogene. However, the role of NFAT2 in glioblastoma (GBM) is largely unknown.

METHODS

The expression and prognostic value of NFAT2 were examined in the databases of the Repository of Molecular Brain Neoplasia Data and The Cancer Genome Atlas (TCGA) and clinical samples. The functional effects of silencing or overexpression of NFAT2 were evaluated in glioma stem cell (GSC) viability, invasion, and self-renewal in vitro and in tumorigenicity in vivo. The downstream target of NFAT2 was investigated.

RESULTS

High NFAT2 expression was significantly associated with mesenchymal (MES) subtype and recurrent GBM and predicted poor survival. NFAT2 silencing inhibited the invasion and clonogenicity of MES GSC-enriched spheres in vitro and in vivo. NFAT2 overexpression promoted tumor growth and MES differentiation of GSCs. A TCGA database search showed that histone deacetylase 1 (HDAC1) expression was significantly correlated with that of NFAT2. NFAT2 regulates the transcriptional activity of HDAC1. Rescue of HDAC1 in NFAT2-knockdown GSCs partially restored tumor growth and MES phenotype. Loss of NFAT2 and HDAC1 expression resulted in hyperacetylation of nuclear factor-kappaB (NF-κB), which inhibits NF-κB-dependent transcriptional activity.

CONCLUSION

Our findings suggest that the NFAT2-HDAC1 pathway might play an important role in the maintenance of the malignant phenotype and promote MES transition in GSCs, which provide potential molecular targets for the treatment of GBMs.

Histone deacetylase 9 inhibition upregulates microRNA-92a to repress the progression of intracranial aneurysm via silencing Bcl-2-like protein 11

OBJECTIVE

Histone deacetylases (HDACs) have been revealed to be involved in cerebrovascular diseases, while the role of HDAC9 in intracranial aneurysm (IA) remains seldom studied. We aim to explore the role of the HDAC9/microRNA-92a (miR-92a)/Bcl-2-like protein 11 (BCL2L11) axis in IA progression.

METHODS

Expression of HDAC9, miR-92a and BCL2L11 in IA tissues was assessed. IA rat models were established by ligation of left renal artery and common carotid artery, and the rats were respectively injected with relative plasmid vectors and/or oligonucleotides. The blood pressure was measured to estimate the IA degree, and the pathological changes were observed. The expression of matrix metalloproteinase (MMP)-2, MMP-9 and vascular endothelial growth factor (VEGF) was detected, and the levels of inflammatory factors were evaluated. Expression of apoptosis-related proteins, HDAC9, miR-92a and BCL2L11 was assessed.

RESULTS

HDAC9 and BCL2L11 were upregulated while miR-92a was downregulated in IA clinical samples and rat models. HDAC9 inhibition or miR-92a elevation improved pathological changes and repressed apoptosis and expression of MMP-2, MMP-9, VEGF and inflammatory factors in vascular tissues from IA rats. Oppositely, HDAC9 overexpression or miR-92a reduction had contrary effects. miR-92a downregulation reversed the effect of silenced HDAC9 on IA rats.

CONCLUSION

HDAC9 inhibition upregulates miR-92a to repress the progression of IA via silencing BCL2L11.

Epigenetic Remodeling in Innate Immunity and Inflammation

The innate immune response is a rapid response to pathogens or danger signals. It is precisely activated not only to efficiently eliminate pathogens but also to avoid excessive inflammation and tissue damage. cis-Regulatory element-associated chromatin architecture shaped by epigenetic factors, which we define as the epiregulome, endows innate immune cells with specialized phenotypes and unique functions by establishing cell-specific gene expression patterns, and it also contributes to resolution of the inflammatory response. In this review, we focus on two aspects: (a) how niche signals during lineage commitment or following infection and pathogenic stress program epiregulomes by regulating gene expression levels, enzymatic activities, or gene-specific targeting of chromatin modifiers and (b) how the programed epiregulomes in turn mediate regulation of gene-specific expression, which contributes to controlling the development of innate cells, or the response to infection and inflammation, in a timely manner. We also discuss the effects of innate immunometabolic rewiring on epiregulomes and speculate on several future challenges to be encountered during the exploration of the master regulators of epiregulomes in innate immunity and inflammation.

Increased transcription of TSPO, HDAC2, and HDAC6 in the amygdala of males with alcohol use disorder

INTRODUCTION

Repeated exposure to high doses of alcohol triggers neuroinflammatory processes that contribute to craving and mood dysfunction in alcohol use disorder (AUD). The upregulation of the translocator protein (TSPO) is considered a biomarker of neuroinflammation, and TSPO ligands have been used as neuroimaging biomarkers of neuroinflammation. Epigenetic mechanisms are also implicated in neuroinflammatory responses to alcohol, and elevated expression of HDAC2 and HDAC6 has been reported in the brain of animals exposed to chronic alcohol.

METHODS

The present study examined the transcriptional regulation of TSPO, HDAC2, and HDAC6 in human postmortem brain tissue from males previously diagnosed with AUD (n = 11) compared to age-matched nondependent males (n = 13) in four brain regions relevant to AUD: prefrontal cortex (PFC), nucleus accumbens (NAc), hippocampus (HPP), and amygdala (AMY).

RESULTS

Translocator protein mRNA levels in AMY and PFC and HDAC2 and HDAC6 mRNA levels in AMY were upregulated in AUD compared to controls. In AMY, TSPO mRNA levels were positively associated with HDAC2 and HDAC6 mRNA levels, suggesting a possible regulation of TSPO by HDAC2 and HDAC6 in this brain region. In contrast, there were no group differences for TSPO, HDAC2, and HDAC6 in NAc and HPP.

CONCLUSION

Our study is the first to find upregulated TSPO mRNA levels in AMY and PFC in postmortem brains from AUD consistent with neuroinflammation, and in the amygdala, they implicate epigenetic regulation of TSPO by HDAC2 and HDAC6.

Fluoxetine regulates eEF2 activity (phosphorylation) via HDAC1 inhibitory mechanism in an LPS-induced mouse model of depression

BACKGROUND

Selective serotonin reuptaker inhibitors, including fluoxetine, are widely studied and prescribed antidepressants, while their exact molecular and cellular mechanism are yet to be defined. We investigated the involvement of HDAC1 and eEF2 in the antidepressant mechanisms of fluoxetine using a lipopolysaccharide (LPS)-induced depression-like behavior model.

METHODS

For in vivo analysis, mice were treated with LPS (2 mg/kg BW), fluoxetine (20 mg/kg BW), HDAC1 activator (Exifone: 54 mg/kg BW) and NH125 (1 mg/kg BW). Depressive-like behaviors were confirmed via behavior tests including OFT, FST, SPT, and TST. Cytokines were measured by ELISA while Iba-1 and GFAP expression were determined by immunofluorescence. Further, the desired gene expression was measured by immunoblotting. For in vitro analysis, BV2 cell lines were cultured; treated with LPS, exifone, and fluoxetine; collected; and analyzed.

RESULTS

Mice treated with LPS displayed depression-like behaviors, pronounced neuroinflammation, increased HDAC1 expression, and reduced eEF2 activity, as accompanied by altered synaptogenic factors including BDNF, SNAP25, and PSD95. Fluoxetine treatment exhibited antidepressant effects and ameliorated the molecular changes induced by LPS. Exifone, a selective HDAC1 activator, reversed the antidepressant and anti-inflammatory effects of fluoxetine both in vivo and in vitro, supporting a causing role of HDAC1 in neuroinflammation allied depression. Further molecular mechanisms underlying HDAC1 were explored with NH125, an eEF2K inhibitor, whose treatment reduced immobility time, altered pro-inflammatory cytokines, and NLRP3 expression. Moreover, NH125 treatment enhanced eEF2 and GSK3β activities, BDNF, SNAP25, and PSD95 expression, but had no effects on HDAC1.

CONCLUSIONS

Our results showed that the antidepressant effects of fluoxetine may involve HDAC1-eEF2 related neuroinflammation and synaptogenesis.

Microbiota-immune system interactions and enteric virus infection

Enteric viruses are important human pathogens that pose a significant global health problem. These viruses infect the gastrointestinal tract, which contains a community of microbes called the 'microbiota'. We and others have shown that intestinal microbiota are crucial for the replication, pathogenesis, and transmission of a variety of enteric viruses. However, the mechanisms underlying microbiota enhancement of enteric virus infection remain unclear. Interestingly, the host immune system is dependent on both the abundance and composition of the intestinal microbiota. Here we review several aspects of how microbiota influence the immune system and how this could potentially impact enteric virus infection.

A Review of Progress in Histone Deacetylase 6 Inhibitors Research: Structural Specificity and Functional Diversity

Histone deacetylases (HDACs) are essential for maintaining homeostasis by catalyzing histone deacetylation. Aberrant expression of HDACs is associated with various human diseases. Although HDAC inhibitors are used as effective chemotherapeutic agents in clinical practice, their applications remain limited due to associated side effects induced by weak isoform selectivity. HDAC6 displays unique structure and cellular localization as well as diverse substrates and exhibits a wider range of biological functions than other isoforms. HDAC6 inhibitors have been effectively used to treat cancers, neurodegenerative diseases, and autoimmune disorders without exerting significant toxic effects. Progress has been made in defining the crystal structures of HDAC6 catalytic domains which has influenced the structure-based drug design of HDAC6 inhibitors. This review summarizes recent literature on HDAC6 inhibitors with particular reference to structural specificity and functional diversity. It may provide up-to-date guidance for the development of HDAC6 inhibitors and perspectives for optimization of therapeutic applications.

ATF4-mediated histone deacetylase HDAC1 promotes the progression of acute pancreatitis

Acute pancreatitis (AP), an acute inflammatory process, can be difficult to diagnose. Activating transcription factor 4 (ATF4) has been reported to participate in the pathogenesis of AP. Additionally, histone deacetylases (HDACs) are shown to be closely related to the development of a variety of diseases, including inflammation disease. In our study, we tried to highlight the role of ATF4 in AP through regulation of HDAC1. Firstly, we validated the effect of ATF4 on pancreatic acinar cell proliferation, apoptosis, and inflammation through in vitro experiments on cellular models of caerulein-induced AP. Next, we examined the correlation between ATF4 and HDAC1, and between HDAC1 with neutral endopeptidase (NEP) and kruppel-like factor 4 (KLF4). Finally, the regulatory role of ATF4 in AP was further assessed by determination of pathological conditions, biochemical indicators and inflammation through in vivo experiments on caerulein-induced AP mouse models. After AP induction, highly expressed ATF4 was observed, and silencing ATF4 could promote pancreatic acinar cell proliferation and inhibit apoptosis. ATF4 could bind to the HDAC1 promoter and upregulate its expression in AP. Moreover, HDAC1 could increase KLF4 expression by inhibiting NEP expression. Functionally, silencing ATF4 could suppress AP through regulation of NEP-mediated KLF4 via downregulation of HDAC1. Above all, our study uncovered the promotive role of ATF4 in AP through upregulation of HDAC1.

Molecular Mechanisms of Vascular Damage During Lung Injury

A variety of pulmonary and systemic insults promote an inflammatory response causing increased vascular permeability, leading to the development of acute lung injury (ALI), a condition necessitating hospitalization and intensive care, or the more severe acute respiratory distress syndrome (ARDS), a disease with a high mortality rate. Further, COVID-19 pandemic-associated ARDS is now a major cause of mortality worldwide. The pathogenesis of ALI is explained by injury to both the vascular endothelium and the alveolar epithelium. The disruption of the lung endothelial and epithelial barriers occurs in response to both systemic and local production of pro-inflammatory cytokines. Studies that evaluate the association of genetic polymorphisms with disease risk did not yield many potential therapeutic targets to treat and revert lung injury. This failure is probably due in part to the phenotypic complexity of ALI/ARDS, and genetic predisposition may be obscured by the multiple environmental and behavioral risk factors. In the last decade, new research has uncovered novel epigenetic mechanisms that control ALI/ARDS pathogenesis, including histone modifications and DNA methylation. Enzyme inhibitors such as DNMTi and HDACi may offer new alternative strategies to prevent or reverse the vascular damage that occurs during lung injury. This review will focus on the latest findings on the molecular mechanisms of vascular damage in ALI/ARDS, the genetic factors that might contribute to the susceptibility for developing this disease, and the epigenetic changes observed in humans, as well as in experimental models of ALI/ADRS.

Histone Deacetylases in the Pathogenesis of Diabetic Cardiomyopathy

The global burden of diabetes mellitus and its complications are currently increasing. Diabetic cardiomyopathy (DCM) is the main cause of diabetes mellitus associated morbidity and mortality; therefore, a comprehensive understanding of DCM development is required for more effective treatment. A disorder of epigenetic posttranscriptional modification of histones in chromatin has been reported to be associated with the pathology of DCM. Recent studies have implicated that histone deacetylases could regulate cardiovascular and metabolic diseases in cellular processes including cardiac fibrosis, hypertrophy, oxidative stress and inflammation. Therefore in this review, we summarized the roles of histone deacetylases in the pathogenesis of DCM, aiming to provide insights into exploring potential preventative and therapeutic strategies of DCM.

HDAC Inhibition Increases HLA Class I Expression in Uveal Melanoma

Simple Summary

Chemotherapy and immunotherapy are both used to treat malignancies. The immunotherapy of cancer often involves T cells, which recognise the antigens presented in HLA molecules. Uveal melanoma (UM) is an intraocular malignancy, which often gives rise to metastases. We determined whether high-risk tumours expressed the target of two drugs, histone deacetylase (HDAC) inhibitor Quisinostat and Tazemetostat, an inhibitor of Enhancer of zeste homologue 2 (EZH2). We observed that especially high-risk UM tumours (monosomy 3, gain of 8q, loss of BAP1) expressed several HDACs, and showed a high HLA Class I expression. We further tested whether these drugs influenced HLA Class I expression on three UM cell lines. The drug Quisinostat led to an upregulation of HLA protein and mRNA levels in three UM cell lines, while Tazemetostat had little effect. We concluded that the use of drugs that influence epigenetic regulators may impact immunotherapy approaches.

Abstract

The treatment of uveal melanoma (UM) metastases or adjuvant treatment may imply immunological approaches or chemotherapy. It is to date unknown how epigenetic modifiers affect the expression of immunologically relevant targets, such as the HLA Class I antigens, in UM. We investigated the expression of HDACs and the histone methyl transferase EZH2 in a set of 64 UMs, using an Illumina HT12V4 array, and determined whether a histone deacetylase (HDAC) inhibitor and EZH2 inhibitor modified the expression of HLA Class I on three UM cell lines. Several HDACs (HDAC1, HDAC3, HDAC4, and HDAC8) showed an increased expression in high-risk UM, and were correlated with an increased HLA expression. HDAC11 had the opposite expression pattern. While in vitro tests showed that Tazemetostat did not influence cell growth, Quisinostat decreased cell survival. In the three tested cell lines, Quisinostat increased HLA Class I expression at the protein and mRNA level, while Tazemetostat did not have an effect on the cell surface HLA Class I levels. Combination therapy mostly followed the Quisinostat results. Our findings indicate that epigenetic drugs (in this case an HDAC inhibitor) may influence the expression of immunologically relevant cell surface molecules in UM, demonstrating that these drugs potentially influence immunotherapy.

Inhibition of HDAC Enzymes Contributes to Differential Expression of Pro-Inflammatory Proteins in the TLR-4 Signaling Cascade

Class I and II histone deacetylases (HDAC) are considered important regulators of immunity and inflammation. Modulation of HDAC expression and activity is associated with altered inflammatory responses but reports are controversial and the specific impact of single HDACs is not clear. We examined class I and II HDACs in TLR-4 signaling pathways in murine macrophages with a focus on IκB kinase epsilon (IKKε) which has not been investigated in this context before. Therefore, we applied the pan-HDAC inhibitors (HDACi) trichostatin A (TSA) and suberoylanilide hydroxamic acid (SAHA) as well as HDAC-specific siRNA. Administration of HDACi reduced HDAC activity and decreased expression of IKKε although its acetylation was increased. Other pro-inflammatory genes (IL-1β, iNOS, TNFα) also decreased while COX-2 expression increased. HDAC 2, 3 and 4, respectively, might be involved in IKKε and iNOS downregulation with potential participation of NF-κB transcription factor inhibition. Suppression of HDAC 1–3, activation of NF-κB and RNA stabilization mechanisms might contribute to increased COX-2 expression. In conclusion, our results indicate that TSA and SAHA exert a number of histone- and HDAC-independent functions. Furthermore, the data show that different HDAC enzymes fulfill different functions in macrophages and might lead to both pro- and anti-inflammatory effects which have to be considered in therapeutic approaches.

Therapeutic mechanisms of traditional Chinese medicine to improve metabolic diseases via the gut microbiota

Metabolic diseases such as obesity, type 2 diabetes mellitus, and hyperlipidemia are associated with the dysfunction of gut microbiota. Traditional Chinese medicines (TCMs) have shown considerable effects in the treatment of metabolic disorders by regulating the gut microbiota. However, the underlying mechanisms are unclear. Studies have shown that TCMs significantly affect glucose and lipid metabolism by modulating the gut microbiota, particularly mucin-degrading bacteria, bacteria with anti-inflammatory properties, lipopolysaccharide- and short-chain fatty acid (SCFA)-producing bacteria, and bacteria with bile-salt hydrolase activity. In this review, we explored potential mechanisms by which TCM improved metabolic disorders via regulating gut microbiota composition and functional structure. In particular, we focused on the protection of the intestinal barrier function, modulation of metabolic endotoxemia and inflammatory responses, regulation of the effects of SCFAs, modulation of the gut-brain axis, and regulation of bile acid metabolism and tryptophan metabolism as therapeutic mechanisms of TCMs in metabolic diseases.

The roles and functions of Paneth cells in Crohn's disease: A critical review

Paneth cells (PCs) are located at the base of small intestinal crypts and secrete the α‐defensins, human α‐defensin 5 (HD‐5) and human α‐defensin 6 (HD‐6) in response to bacterial, cholinergic and other stimuli. The α‐defensins are broad‐spectrum microbicides that play critical roles in controlling gut microbiota and maintaining intestinal homeostasis. Inflammatory bowel disease, including ulcerative colitis and Crohn's disease (CD), is a complicated autoimmune disorder. The pathogenesis of CD involves genetic factors, environmental factors and microflora. Surprisingly, with regard to genetic factors, many susceptible genes and pathogenic pathways of CD, including nucleotide‐binding oligomerization domain 2 (NOD2), autophagy‐related 16‐like 1 (ATG16L1), immunity‐related guanosine triphosphatase family M (IRGM), wingless‐related integration site (Wnt), leucine‐rich repeat kinase 2 (LRRK2), histone deacetylases (HDACs), caspase‐8 (Casp8) and X‐box‐binding protein‐1 (XBP1), are relevant to PCs. As the underlying mechanisms are being unravelled, PCs are identified as the central element of CD pathogenesis, integrating factors among microbiota, intestinal epithelial barrier dysfunction and the immune system. In the present review, we demonstrate how these genes and pathways regulate CD pathogenesis via their action on PCs and what treatment modalities can be applied to deal with these PC‐mediated pathogenic processes.

Cannabinoid Receptor Subtype 2 (CB2R) in a Multitarget Approach: Perspective of an Innovative Strategy in Cancer and Neurodegeneration

The cannabinoid receptor subtype 2 (CB2R) represents an interesting and new therapeutic target for its involvement in the first steps of neurodegeneration as well as in cancer onset and progression. Several studies, focused on different types of tumors, report a promising anticancer activity induced by CB2R agonists due to their ability to reduce inflammation and cell proliferation. Moreover, in neuroinflammation, the stimulation of CB2R, overexpressed in microglial cells, exerts beneficial effects in neurodegenerative disorders. With the aim to overcome current treatment limitations, new drugs can be developed by specifically modulating, together with CB2R, other targets involved in such multifactorial disorders. Building on successful case studies of already developed multitarget strategies involving CB2R, in this Perspective we aim at prompting the scientific community to consider new promising target associations involving HDACs (histone deacetylases) and σ receptors by employing modern approaches based on molecular hybridization, computational polypharmacology, and machine learning algorithms.

Inhibition of alcohol-induced inflammation and oxidative stress by astaxanthin is mediated by its opposite actions in the regulation of sirtuin 1 and histone deacetylase 4 in macrophages

We previously demonstrated that astaxanthin (ASTX), a xanthophyll carotenoid, repressed ethanol-induced inflammation and oxidative stress in macrophages. We explored the role of sirtuin 1 (SIRT1) and histone deacetylase 4 (HDAC4) in the inhibitory effect of ASTX on inflammation and oxidative stress in macrophages exposed to ethanol. Ethanol decreased mRNA and protein of SIRT1 while increasing those of HDAC4, which was attenuated by ASTX in RAW 264.7 macrophages and mouse bone marrow-derived macrophages (BMDMs). Inhibition of SIRT1 expression or activity augmented ethanol-induced Hdac4 expression, but SIRT1 activation elicited the opposite effect. Consistently, Hdac4 knockdown increased Sirt1 expression with decreases in ethanol-induced inflammatory gene expression, but its overexpression resulted in the opposite effects. Furthermore, BMDMs from mice with macrophage specific-deletion of Hdac4 (Hdac4^MKO) showed significant decreases in ethanol-induced inflammatory genes and ROS accumulation but an increase in Sirt1 expression. Macrophage specific deletion of Hdac4 or ASTX abolished the changes in genes for mitochondrial biogenesis and glycolysis by ethanol. Ethanol increased mitochondrial respiration, ATP production, and proton leak, but decreased maximal respiration and spare respiratory capacity, all of which were abolished by ASTX in RAW 264.7 macrophages. The ethanol-induced alterations in mitochondrial respiration were abrogated in Hdac4^MKO BMDMs. In conclusion, the anti-inflammatory and antioxidant properties of ASTX in ethanol-treated macrophages may be mediated, at least partly, by its opposite effect on SIRT1 and HDAC4 to empower SIRT1 to counteract ethanol-induced activation of HDAC4.

Zonula occludens and nasal epithelial barrier integrity in allergic rhinitis

Allergic rhinitis (AR) is a common disease affecting 400 million of the population worldwide. Nasal epithelial cells form a barrier against the invasion of environmental pathogens. These nasal epithelial cells are connected together by tight junction (TJ) proteins including zonula occludens-1 (ZO-1), ZO-2 and ZO-3. Impairment of ZO proteins are observed in AR patients whereby dysfunction of ZOs allows allergens to pass the nasal passage into the subepithelium causing AR development. In this review, we discuss ZO proteins and their impairment leading to AR, regulation of their expression by Th1 cytokines (i.e., IL-2, TNF-α and IFN-γ), Th2 cytokines (i.e., IL-4 and IL-13) and histone deacetylases (i.e., HDAC1 and HDAC2). These findings are pivotal for future development of targeted therapies by restoring ZO protein expression and improving nasal epithelial barrier integrity in AR patients.

Acetylation-Dependent Deubiquitinase OTUD3 Controls MAVS Activation in Innate Antiviral Immunity

Accurate regulation of innate immunity is necessary for the host to efficiently respond to invading pathogens and avoid excessive harmful immune pathology. Here we identified OTUD3 as an acetylation-dependent deubiquitinase that restricts innate antiviral immune signaling. OTUD3 deficiency in mice results in enhanced innate immunity, a diminished viral load, and morbidity. OTUD3 directly hydrolyzes lysine 63 (Lys63)-linked polyubiquitination of MAVS and thus shuts off innate antiviral immune response. Notably, the catalytic activity of OTUD3 relies on acetylation of its Lys129 residue. In response to virus infection, the acetylated Lys129 is removed by SIRT1, which promptly inactivates OTUD3 and thus allows timely induction of innate antiviral immunity. Importantly, acetyl-OTUD3 levels are inversely correlated with IFN-β expression in influenza patients. These findings establish OTUD3 as a repressor of MAVS and uncover a previously unknown regulatory mechanism by which the catalytic activity of OTUD3 is tightly controlled to ensure timely activation of antiviral defense.

Convergent epigenetic regulation of glial plasticity in myelin repair and brain tumorigenesis: A focus on histone modifying enzymes

Brain regeneration and tumorigenesis are complex processes involving in changes in chromatin structure to regulate cellular states at the molecular and genomic level. The modulation of chromatin structure dynamics is critical for maintaining progenitor cell plasticity, growth and differentiation. Oligodendrocyte precursor cells (OPC) can be differentiated into mature oligodendrocytes, which produce myelin sheathes to permit saltatory nerve conduction. OPCs and their primitive progenitors such as pri-OPC or pre-OPC are highly adaptive and plastic during injury repair or brain tumor formation. Recent studies indicate that chromatin modifications and epigenetic homeostasis through histone modifying enzymes shape genomic regulatory landscape conducive to OPC fate specification, lineage differentiation, maintenance of myelin sheaths, as well as brain tumorigenesis. Thus, histone modifications can be convergent mechanisms in regulating OPC plasticity and malignant transformation. In this review, we will focus on the impact of histone modifying enzymes in modulating OPC plasticity during normal development, myelin regeneration and tumorigenesis.

Carbon black nanoparticles induce HDAC6-mediated inflammatory responses in 16HBE cells

Long-term inhalation of carbon black nanoparticles (CBNPs) leads to pulmonary inflammatory diseases. Histone deacetylase 6 (HDAC6) has been identified as an important regulator in the development of inflammatory disorders. However, the direct involvement of HDAC6 in CBNPs-induced pulmonary inflammatory responses remains unclear. To explore whether HDAC6 participates in CBNPs-induced pulmonary inflammation, human bronchial epithelial cell line (16HBE cells) was transfected with HDAC6 small interference RNA (siRNA) and then exposed to CBNPs at concentrations of 0, 25, and 50 µg/ml for 24 h. Intracellular HDAC6 and intraflagellar transport protein 88 (IFT88) mRNA and protein were determined by real-time polymerase chain reaction and Western blot, respectively. The secretions of inflammatory cytokines including interleukin (IL)-8, tumor necrosis factor (TNF)-α, IL-6, and IL-1β were measured by enzyme-linked immunosorbent assay. CBNPs induced a significant increase in the expressions of IL-8 and IL-6, accompanied by a high level of intracellular HDAC6 mRNA when compared with a blank control group (p < 0.05). However, there were no significant changes in the levels of TNF-α secretion, intracellular HDAC6 and IFT88 protein induced by CBNPs (p > 0.05). The HDAC6 mRNA expression was significantly suppressed in HDAC6 siRNA-transfected cells (p < 0.05). The secretions of IL-8, TNF-α, and IL-6 were significantly less in HDAC6 siRNA-transfected cells than that in normal 16HBE cells with exposure to 25 or 50 µg/ml of CBNPs, but intracellular IFT88 mRNA expression was markedly increased in HDAC6 siRNA-transfected cells when compared with normal 16HBE cells exposed to 50 µg/ml of CBNPs (all p < 0.05). Downregulation of the HDAC6 gene inhibits CBNPs-induced inflammatory responses in bronchial epithelial cells, partially through regulating IFT88 expression. It is suggested that CBNPs may trigger inflammatory responses in bronchial epithelial cells by an HDAC6/IFT88-dependent pathway.

Sequential changes in histone modifications shape transcriptional responses underlying microglia polarization by glioma

Microglia, resident myeloid cells of the central nervous system (CNS), act as immune sentinels that contribute to maintenance of physiological homeostasis and respond to any perturbation in CNS. Microglia could be polarized by various stimuli to perform dedicated functions and instigate inflammatory or pro-regenerative responses. Microglia and peripheral macrophages accumulate in glioblastomas (GBMs), malignant brain tumors, but instead of initiating antitumor responses, these cells are polarized to the pro-invasive and immunosuppressive phenotype which persists for a long time and contributes to a "cold" immune microenvironment of GBMs. Molecular mechanisms underlying this long-lasting "microglia memory" are unknown. We hypothesized that this state may rely on epigenetic silencing of inflammation-related genes. In this study, we show that cultured microglia pre-exposed to glioma-conditioned medium (GCM) acquire a "transcriptional memory" and display reduced expression of inflammatory genes after re-stimulation with lipopolysaccharide. Unstimulated microglia have unmethylated DNA and active histone marks at selected gene promoters indicating chromatin accessibility. Adding GCM increases expression and enzymatic activity of histone deacetylases (Hdac), leading to erasure of histone acetylation at tested genes. Later inflammatory genes acquire repressive histone marks (H3K27 trimethylation), which correlates with silencing of their expression. GCM induced genes acquire active histone marks. Hdac inhibitors block GCM-induced changes of histone modifications and restore microglia ability to initiate effective inflammatory responses. Altogether, we show a scenario of distinct histone modifications underlying polarization of microglia by glioma. We demonstrate contribution of epigenetic mechanisms to glioma-induced "transcriptional memory" in microglia resulting in the tumor-supportive phenotype.

The application of histone deacetylases inhibitors in glioblastoma

The epigenetic abnormality is generally accepted as the key to cancer initiation. Epigenetics that ensure the somatic inheritance of differentiated state is defined as a crucial factor influencing malignant phenotype without altering genotype. Histone modification is one such alteration playing an essential role in tumor formation, progression, and resistance to treatment. Notably, changes in histone acetylation have been strongly linked to gene expression, cell cycle, and carcinogenesis. The balance of two types of enzyme, histone acetyltransferases (HATs) and histone deacetylases (HDACs), determines the stage of histone acetylation and then the architecture of chromatin. Changes in chromatin structure result in transcriptional dysregulation of genes that are involved in cell-cycle progression, differentiation, apoptosis, and so on. Recently, HDAC inhibitors (HDACis) are identified as novel agents to keep this balance, leading to numerous researches on it for more effective strategies against cancers, including glioblastoma (GBM). This review elaborated influences on gene expression and tumorigenesis by acetylation and the antitumor mechanism of HDACis. Besdes, we outlined the preclinical and clinical advancement of HDACis in GBM as monotherapies and combination therapies.