HDAC1-3 inhibitor MS-275 enhances IL10 expression in RAW264.7 macrophages and reduces cigarette smoke-induced airway inflammation in mice

The role of histone deacetylases in inflammatory respiratory diseases: an update

INTRODUCTION

Histone deacetylases (HDACs) catalyze the removal of acetyl groups from lysine residues of histones and other proteins, generally leading to a closed chromosomal configuration and transcriptional repression. Different HDACs have distinct substrate specificities and functions in different biological processes. Accumulating evidence indicates that HDACs play a key role in the pathogenesis of multiple respiratory diseases.

AREAS COVERED

After an extensive search of the PubMed database, Web of Science and ClinicalTrials.gov, covering the period from 1992 to 2024, this review summarizes recent advances in understanding the role of HDACs in inflammatory respiratory diseases, including allergic rhinitis (AR), chronic rhinosinusitis (CRS), asthma and chronic obstructive pulmonary disease (COPD). We also examine recent progress on the efficacy and potential use of histone deacetylase inhibitors (HDACi) for the treatment of these diseases.

EXPERT OPINION

Available data indicate that HDACs play an important role in the development of common inflammatory respiratory diseases, and HDACi have shown promise as treatments for these diseases. However, the exact roles and underlying mechanisms of specific HDACs in disease pathogenesis require further study. Additional work is necessary to develop novel potent HDACi with high isoform selectivity.

Involvement of GPR43 Receptor in Effect of Lacticaseibacillus rhamnosus on Murine Steroid Resistant Chronic Obstructive Pulmonary Disease: Relevance to Pro-Inflammatory Mediators and Oxidative Stress in Human Macrophages

BACKGROUND

Cytokine storm and oxidative stress are present in chronic obstructive pulmonary disease (COPD). Individuals with COPD present high levels of NF-κB-associated cytokines and pro-oxidant agents as well as low levels of Nrf2-associated antioxidants. This condition creates a steroid-resistant inflammatory microenvironment. Lacticaseibacillus rhamnosus (Lr) is a known anti-cytokine in lung diseases; however, the effect of Lr on lung inflammation and oxidative stress in steroid-resistant COPD mice remains unknown.

OBJECTIVE

Thus, we investigated the Lr effect on lung inflammation and oxidative stress in mice and macrophages exposed to cigarette smoke extract (CSE) and unresponsive to steroids.

METHODS

Mice and macrophages received dexamethasone or GLPG-094 (a GPR43 inhibitor), and only the macrophages received butyrate (but), all treatments being given before CSE. Lung inflammation was evaluated from the leukocyte population, airway remodeling, cytokines, and NF-κB. Oxidative stress disturbance was measured from ROS, 8-isoprostane, NADPH oxidase, TBARS, SOD, catalase, HO-1, and Nrf2.

RESULTS

Lr attenuated cellularity, mucus, collagen, cytokines, ROS, 8-isoprostane, NADPH oxidase, and TBARS. Otherwise, SOD, catalase, HO-1, and Nrf2 were upregulated in Lr-treated COPD mice. Anti-cytokine and antioxidant effects of butyrate also occurred in CSE-exposed macrophages. GLPG-094 rendered Lr and butyrate less effective.

CONCLUSIONS

Lr attenuates lung inflammation and oxidative stress in COPD mice, suggesting the presence of a GPR43 receptor-dependent mechanism also found in macrophages.

Effects of lysine deacetylase inhibitor treatment on LPS responses of alveolar-like macrophages

Macrophages are key immune cells that can adapt their metabolic phenotype in response to different stimuli. Lysine deacetylases are important enzymes regulating inflammatory gene expression and lysine deacetylase inhibitors have been shown to exert anti-inflammatory effects in models of chronic obstructive pulmonary disease. We hypothesized that these anti-inflammatory effects may be associated with metabolic changes in macrophages. To validate this hypothesis, we used an unbiased and a targeted proteomic approach to investigate metabolic enzymes, as well as liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry, to quantify metabolites in combination with the measurement of functional parameters in primary murine alveolar-like macrophages after lipopolysaccharide-induced activation in the presence or absence of lysine deacetylase inhibition. We found that lysine deacetylase inhibition resulted in reduced production of inflammatory mediators such as tumor necrosis factor α and interleukin 1β. However, only minor changes in macrophage metabolism were observed, as only one of the lysine deacetylase inhibitors slightly increased mitochondrial respiration while no changes in metabolite levels were seen. However, lysine deacetylase inhibition specifically enhanced expression of proteins involved in ubiquitination, which may be a driver of the anti-inflammatory effects of lysine deacetylase inhibitors. Our data illustrate that a multiomics approach provides novel insights into how macrophages interact with cues from their environment. More detailed studies investigating ubiquitination as a potential driver of lysine deacetylase inhibition will help developing novel anti-inflammatory drugs for difficult-to-treat diseases such as chronic obstructive pulmonary disease.

Identification of histone deacetylase inhibitors as neutrophil recruitment modulators in zebrafish using a chemical library screen

Tissue injury-induced neutrophil recruitment is a prerequisite for the initiation and amplification of inflammatory responses. Although multiple proteases and enzymes involved in post-translational modification (PTM) of proteins regulate leukocyte recruitment, an unbiased functional screen of enzymes regulating inflammatory leukocyte recruitment has yet to be undertaken. Here, using a zebrafish tail fin amputation (TFA) model to screen a chemical library consisting of 295 compounds that target proteases and PTM enzymes, we identified multiple histone deacetylase (HDAC) inhibitors that modulate inflammatory neutrophil recruitment. AR-42, a pan-HDAC inhibitor, was shown to inhibit neutrophil recruitment in three different zebrafish sterile tissue injury models: a TFA model, a copper-induced neuromast damage and mechanical otic vesicle injury (MOVI) model, and a sterile murine peritonitis model. RNA sequencing analysis of AR-42-treated fish embryos revealed downregulation of neutrophil-associated cytokines/chemokines, and exogenous supplementation with recombinant human IL-1β and CXCL8 partially restored the defective neutrophil recruitment in AR-42-treated MOVI model fish embryos. We thus demonstrate that AR-42 non-cell-autonomously modulates neutrophil recruitment by suppressing transcriptional expression of cytokines/chemokines, thereby identifying AR-42 as a promising anti-inflammatory drug for treating sterile tissue injury-associated diseases.

The Selective CB2 Agonist COR167 Reduced Symptoms in a Mice Model of Trauma-Induced Peripheral Neuropathy through HDAC-1 Inhibition

Neuropathic pain is a chronic disabling condition with a 7-10% of prevalence in the general population that is largely undertreated. Available analgesic therapies are poorly effective and are often accompanied by numerous side effects. Growing evidence indicates cannabinoids are a valuable treatment opportunity for neuropathic pain. The endocannabinoid system is an important regulator of pain perception through the CB1 receptors, but CB1 agonists, while largely effective, are not always satisfactory pain-relieving agents in clinics because of their serious adverse effects. Recently, several CB2 agonists have shown analgesic, anti-hyperalgesic, and anti-allodynic activity in the absence of CB1-induced psychostimulant effects, offering promise in neuropathic pain management. The aim of this study was to evaluate the anti-neuropathic activity of a novel selective CB2 agonist, COR167, in a preclinical model of peripheral neuropathy, the spared nerve injury (SNI). Oral COR167, in a dose-dependent manner, attenuated mechanical allodynia and thermal hyperalgesia after acute and repeated administration, showing the absence of tolerance induction. At anti-neuropathic doses, COR167 did not show any alteration in the locomotor behavior. SNI mice showed increased microglial levels of HDAC1 protein in the ipsilateral side of the spinal cord, along with NF-kB activation. COR167 treatment prevented the HDAC1 overexpression and the NF-kB activation and increased the levels of the anti-inflammatory cytokine IL-10 through a CB2-mediated mechanism. Oral administration of COR167 shows promising therapeutic potential in the management of neuropathic pain conditions.

Epigenetic regulation of macrophage polarization in wound healing

The immune microenvironment plays a critical role in regulating skin wound healing. Macrophages, the main component of infiltrating inflammatory cells, play a pivotal role in shaping the immune microenvironment in the process of skin wound healing. Macrophages comprise the classic proinflammatory M1 subtype and anti-inflammatory M2 population. In the early inflammatory phase of skin wound closure, M1-like macrophages initiate and amplify the local inflammatory response to disinfect the injured tissue. In the late tissue-repairing phase, M2 macrophages are predominant in wound tissue and limit local inflammation to promote tissue repair. The biological function of macrophages is tightly linked with epigenomic organization. Transcription factors are essential for macrophage polarization. Epigenetic modification of transcription factors determines the heterogeneity of macrophages. In contrast, transcription factors also regulate the expression of epigenetic enzymes. Both transcription factors and epigenetic enzymes form a complex network that regulates the plasticity of macrophages. Here, we describe the latest knowledge concerning the potential epigenetic mechanisms that precisely regulate the biological function of macrophages and their effects on skin wound healing.

The emerging role of histone deacetylase 1 in allergic diseases

Histone deacetylase 1 (HDAC1) is a unique member of the classes I HDACs and helps to regulate acute and chronic adaptation to environmental stimuli such as allergen, stress. Allergic diseases are complex diseases resulting from the effect of multiple genetic and interacting foreign substances. Epigenetics play an important role in both pathological and immunomodulatory conditions of allergic diseases. To be consistent with this role, recent evidence strongly suggests that histone deacetylase 1 (HDAC1) plays a critical role in allergic response. HDAC1 expression is stimulated by allergen and attributes to increase T helper 2 (Th2) cytokine levels, decrease Th1/Th17 cells and anti-inflammatory cytokine Interleukin-10 (IL-10), and TWIK-related potassium channel-1 (Trek-1) expression. This review focuses on the contribution of HDAC1 and the regulatory role in characterizing allergic endotypes with common molecular pathways and understanding allergic multimorbidity relationships, as well as addressing their potential as therapeutic targets for these conditions.

Identification and Validation of CDKN1A and HDAC1 as Senescence-Related Hub Genes in Chronic Obstructive Pulmonary Disease

Purpose

Cellular senescence participates in the occurrence and development of chronic obstructive pulmonary disease (COPD). This study aimed to identify senescence-related hub genes and explore effective diagnostic markers and therapeutic targets for COPD.

Methods

The microarray data from the GSE38974 dataset was downloaded from the Gene Expression Omnibus (GEO) database. The overlapping genes between genes from the GSE38974 dataset and CellAge database were considered differentially expressed senescence-related genes (DESRGs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed using R software. Protein-protein interaction (PPI), miRNA-mRNA network, and competitive endogenous RNA (ceRNA) network were constructed and visualized by Cytoscape software. GSE100281 and GSE103174 datasets were employed to validate the expression and diagnostic value of hub genes. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to measure the mRNA levels of hub genes in peripheral blood mononuclear cells (PBMCs) from COPD and control samples.

Results

A total of 23 DESRGs were identified between COPD samples and healthy controls. Enrichment analysis revealed that DESRGs were mainly related to apoptosis and senescence. Moreover, four hub genes and two key clusters were acquired by Cytohubba and MCODE plugin, respectively. CDKN1A and HDAC1 were verified as final hub genes based on GSE100281 and GSE103174 datasets validation. The mRNA expression level of CDKN1A was negatively related to forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC), and HDAC1 expression had the opposite correlation. Finally, an HDAC1-based ceRNA network, including 6 miRNAs and 11 lncRNAs, was constructed.

Conclusion

We identified two senescence-related hub genes, CDKN1A and HDAC1, which may be effective biomarkers for COPD diagnosis and treatment. An HDAC1-related ceRNA network was constructed to clarify the role of senescence in COPD pathogenesis.

MiR-192-5p/RB1/NF-κBp65 signaling axis promotes IL-10 secretion during gastric cancer EMT to induce Treg cell differentiation in the tumour microenvironment

BACKGROUND

Regulatory T (Treg) cells are important components of the tumour microenvironment (TME) that play roles in gastric cancer (GC) metastasis. Although tumour cells that undergo epithelial-mesenchymal transition (EMT) regulate Treg cell function, their regulatory mechanism in GC remains unclear.

METHODS

The miR-192-5p was identified by examining three Gene Expression Omnibus GC miRNA expression datasets. RNA immunoprecipitation (RIP) and dual-luciferase reporter assays were conducted to identify interactions between miR-192-5p and RB1. The role of miR-192-5p/RB1 in GC progression was evaluated based on EdU incorporation, wound healing and Transwell assays. An in vitro co-culture assay was performed to measure the effect of miR-192-5p/RB1 on Treg cell differentiation. In vivo experiments were conducted to explore the role of miR-192-5p in GC progression and Treg cell differentiation.

RESULTS

MiR-192-5p was overexpressed in tumour and was associated with poor prognosis in GC. MiR-192-5p bound to the RB1 3'-untranslated region, resulting in GC EMT, proliferation, migration and invasion. MiR-192-5p/RB1 mediated interleukin-10 (IL-10) secretion by regulating nuclear factor-kappaBp65 (NF-κBp65), affecting Treg cell differentiation. NF-κBp65, in turn, promoted miR-192-5p expression and formed a positive feedback loop. Furthermore, in vivo experiments confirmed that miR-192-5p/RB1 promotes GC growth and Treg cell differentiation.

CONCLUSION

Collectively, our studies indicate that miR-192-5p/RB1 promotes EMT of tumour cells, and the miR-192-5p/RB1/NF-κBp65 signaling axis induces Treg cell differentiation by regulating IL-10 secretion in GC. Our results suggest that targeting miR-192-5p/RB1/NF-κBp65 /IL-10 may pave the way for the development of new immune treatments for GC.

Oleic acid-related anti-inflammatory effects in force-stressed PdL fibroblasts are mediated by H3 lysine acetylation associated with altered IL10 expression

The initiation of a spatially and temporally limited inflammation is essential for tissue and bone remodelling by the periodontal ligament (PdL) located between teeth and alveolar bone. Nutritional components may cause alterations in the inflammatory response of PdL fibroblasts to mechanical stress such as those occurring during orthodontic tooth movement (OTM). Recently, we reported an attenuated pro-inflammatory response of human PdL fibroblasts (HPdLFs) to compressive forces when stimulated with oleic acid (OA), a monounsaturated fatty acid particularly prominent in the Mediterranean diet. Fatty acids could serve as alternative source of acetyl-CoA, thereby affecting epigenetic histone marks, such as histone 3 lysine acetylation (H3Kac) in a lipid metabolism-dependent manner. In this study, we aimed to investigate the extent to which OA exerts its anti-inflammatory effect in compressed HPdLFs via changes in H3Kac. Six-hour compressed HPdLFs showed increased H3Kac when cultured with OA. Inhibition of histone deacetylases resulted in a comparable IL10-increase as observed in compressed OA-cultures. In contrast, inhibition of histone acetyltransferases, particularly p300/CBP, in compressed HPdLFs exposed to OA normalized the inflammatory response to control levels. OA-dependent increased association of H3Kac to IL10 promoter regions in compressed HPdLFs further strengthened the assumption that OA exhibits its anti-inflammatory properties via modulation of this epigenetic mark. In conclusion, our study strongly suggests that nutritional components can directly affect PdL cells via changes in their epigenetic code. Since epigenetic inhibitors are already widely used clinically, they may hold promise for novel approaches for personalized orthodontic treatment that incorporates nutritional and metabolism-related changes.

Attenuation of Cigarette-Smoke-Induced Oxidative Stress, Senescence, and Inflammation by Berberine-Loaded Liquid Crystalline Nanoparticles: In Vitro Study in 16HBE and RAW264.7 Cells

Cigarette smoke is considered a primary risk factor for chronic obstructive pulmonary disease. Numerous toxicants present in cigarette smoke are known to induce oxidative stress and airway inflammation that further exacerbate disease progression. Generally, the broncho-epithelial cells and alveolar macrophages exposed to cigarette smoke release massive amounts of oxidative stress and inflammation mediators. Chronic exposure of cigarette smoke leads to premature senescence of airway epithelial cells. This impairs cellular function and ultimately leads to the progression of chronic lung diseases. Therefore, an ideal therapeutic candidate should prevent disease progression by controlling oxidative stress, inflammation, and senescence during the initial stage of damage. In our study, we explored if berberine (an alkaloid)-loaded liquid crystalline nanoparticles (berberine-LCNs)-based treatment to human broncho-epithelial cells and macrophage inhibits oxidative stress, inflammation, and senescence induced by cigarette-smoke extract. The developed berberine-LCNs were found to have favourable physiochemical parameters, such as high entrapment efficiency and sustained in vitro release. The cellular-assay observations revealed that berberine-LCNs showed potent antioxidant activity by suppressing the generation of reactive oxygen species in both broncho-epithelial cells (16HBE) and macrophages (RAW264.7), and modulating the genes involved in inflammation and oxidative stress. Similarly, in 16HBE cells, berberine-LCNs inhibited the cigarette smoke-induced senescence as revealed by X-gal staining, gene expression of CDKN1A (p21), and immunofluorescent staining of p21. Further in-depth mechanistic investigations into antioxidative, anti-inflammatory, and antisenescence research will diversify the current findings of berberine as a promising therapeutic approach for inflammatory lung diseases caused by cigarette smoking.

Systemic study of selected histone deacetylase inhibitors in cardiac complications associated with cancer cachexia

Cancer cachexia is mainly characterized by wasting of skeletal muscles and fat and body weight loss, along with severe complications of major organs like liver, heart, brain and bone. There can be diminishing performance of these major organs as cancer cachexia progresses, one such drastic effect on the cardiac system. In the present study, differential effect of histone deacetylase inhibitors (HDACi) on cardiac complications associated with cancer cachexia is studied. Two models were used to induce cancer cachexia: B16F1 induced metastatic cancer cachexia and Lewis lung carcinoma cell - induced cancer cachexia. Potential of Class I HDACi entinostat, Class II HDACi MC1568, and nonspecific HDACi sodium butyrate on cardiac complications were evaluated using the cardiac hypertrophy markers, hemodynamic markers, and cardiac markers along with histopathological evaluation of heart sections by Periodic acid-Schiff staining, Masson's trichrome staining, Picro-sirius red staining, and haematoxylin and eosin staining. Immunohistochemistry evaluation by vimentin and caspase 3 protein expression was evaluated. Entinostat showed promising results by attenuating the cardiac complications, and MC1568 treatment further exacerbated the cardiac complications, while non-conclusive effect were recorded after treatment with sodium butyrate. This study will be helpful in evaluating other HDACi for potential in cardiac complications associated with cancer cachexia.

Environmental Impact on the Epigenetic Mechanisms Underlying Parkinson’s Disease Pathogenesis: A Narrative Review

Parkinson’s disease (PD) is the second most common neurodegenerative disorder with an unclear etiology and no disease-modifying treatment to date. PD is considered a multifactorial disease, since both genetic and environmental factors contribute to its pathogenesis, although the molecular mechanisms linking these two key disease modifiers remain obscure. In this context, epigenetic mechanisms that alter gene expression without affecting the DNA sequence through DNA methylation, histone post-transcriptional modifications, and non-coding RNAs may represent the key mediators of the genetic–environmental interactions underlying PD pathogenesis. Environmental exposures may cause chemical alterations in several cellular functions, including gene expression. Emerging evidence has highlighted that smoking, coffee consumption, pesticide exposure, and heavy metals (manganese, arsenic, lead, etc.) may potentially affect the risk of PD development at least partially via epigenetic modifications. Herein, we discuss recent accumulating pre-clinical and clinical evidence of the impact of lifestyle and environmental factors on the epigenetic mechanisms underlying PD development, aiming to shed more light on the pathogenesis and stimulate future research.

Epigenetic Mechanisms in Parenchymal Lung Diseases: Bystanders or Therapeutic Targets?

Epigenetic responses due to environmental changes alter chromatin structure, which in turn modifies the phenotype, gene expression profile, and activity of each cell type that has a role in the pathophysiology of a disease. Pulmonary diseases are one of the major causes of death in the world, including lung cancer, idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD), pulmonary hypertension (PH), lung tuberculosis, pulmonary embolism, and asthma. Several lines of evidence indicate that epigenetic modifications may be one of the main factors to explain the increasing incidence and prevalence of lung diseases including IPF and COPD. Interestingly, isolated fibroblasts and smooth muscle cells from patients with pulmonary diseases such as IPF and PH that were cultured ex vivo maintained the disease phenotype. The cells often show a hyper-proliferative, apoptosis-resistant phenotype with increased expression of extracellular matrix (ECM) and activated focal adhesions suggesting the presence of an epigenetically imprinted phenotype. Moreover, many abnormalities observed in molecular processes in IPF patients are shown to be epigenetically regulated, such as innate immunity, cellular senescence, and apoptotic cell death. DNA methylation, histone modification, and microRNA regulation constitute the most common epigenetic modification mechanisms.

Histone Deacetylase 3: A Potential Therapeutic Target for Atherosclerosis

Atherosclerosis, the pathological basis of most cardiovascular disease, is characterized by plaque formation in the intima. Secondary lesions include intraplaque hemorrhage, plaque rupture, and local thrombosis. Vascular endothelial function impairment and smooth muscle cell migration lead to vascular dysfunction, which is conducive to the formation of macrophage-derived foam cells and aggravates inflammatory response and lipid accumulation that cause atherosclerosis. Histone deacetylase (HDAC) is an epigenetic modifying enzyme closely related to chromatin structure and gene transcriptional regulation. Emerging studies have demonstrated that the Class I member HDAC3 of the HDAC super family has cell-specific functions in atherosclerosis, including 1) maintenance of endothelial integrity and functions, 2) regulation of vascular smooth muscle cell proliferation and migration, 3) modulation of macrophage phenotype, and 4) influence on foam cell formation. Although several studies have shown that HDAC3 may be a promising therapeutic target, only a few HDAC3-selective inhibitors have been thoroughly researched and reported. Here, we specifically summarize the impact of HDAC3 and its inhibitors on vascular function, inflammation, lipid accumulation, and plaque stability in the development of atherosclerosis with the hopes of opening up new opportunities for the treatment of cardiovascular diseases.

Meta-Inflammation and Metabolic Reprogramming of Macrophages in Diabetes and Obesity: The Importance of Metabolites

Diabetes mellitus type II and obesity are two important causes of death in modern society. They are characterized by low-grade chronic inflammation and metabolic dysfunction (meta-inflammation), which is observed in all tissues involved in energy homeostasis. A substantial body of evidence has established an important role for macrophages in these tissues during the development of diabetes mellitus type II and obesity. Macrophages can activate into specialized subsets by cues from their microenvironment to handle a variety of tasks. Many different subsets have been described and in diabetes/obesity literature two main classifications are widely used that are also defined by differential metabolic reprogramming taking place to fuel their main functions. Classically activated, pro-inflammatory macrophages (often referred to as M1) favor glycolysis, produce lactate instead of metabolizing pyruvate to acetyl-CoA, and have a tricarboxylic acid cycle that is interrupted at two points. Alternatively activated macrophages (often referred to as M2) mainly use beta-oxidation of fatty acids and oxidative phosphorylation to create energy-rich molecules such as ATP and are involved in tissue repair and downregulation of inflammation. Since diabetes type II and obesity are characterized by metabolic alterations at the organism level, these alterations may also induce changes in macrophage metabolism resulting in unique macrophage activation patterns in diabetes and obesity. This review describes the interactions between metabolic reprogramming of macrophages and conditions of metabolic dysfunction like diabetes and obesity. We also focus on different possibilities of measuring a range of metabolites intra-and extracellularly in a precise and comprehensive manner to better identify the subsets of polarized macrophages that are unique to diabetes and obesity. Advantages and disadvantages of the currently most widely used metabolite analysis approaches are highlighted. We further describe how their combined use may serve to provide a comprehensive overview of the metabolic changes that take place intracellularly during macrophage activation in conditions like diabetes and obesity.

Entinostat, a histone deacetylase inhibitor, increases the population of IL-10+ regulatory B cells to suppress contact hypersensitivity

IL-10⁺ regulatory B (Breg) cells play a vital role in regulating the immune responses in experimental autoimmune encephalomyelitis, colitis, and contact hypersensitivity (CHS). Several sti-mulants such as lipopolysaccharide (LPS), CD40 ligand, and IL-21 spur the activation and maturation of IL-10⁺ Breg cells, while the epigenetic mechanism for the IL-10 expression remains largely unknown. It is well accepted that the histone acetylation/deacetylation is an important mechanism that regulates the expression of IL-10. We found that entinostat, an HDAC inhibitor, stimulated the induction of IL-10⁺ Breg cells by LPS in vitro and the formation of IL-10⁺ Breg cells to suppress CHS in vivo. We further demonstrated that entinostat inhibited HDAC1 from binding to the proximal region of the IL-10 expression promoter in splenic B cells, followed by an increase in the binding of NF-κB p65, eventually enhancing the expression of IL-10 in Breg cells.

Preclinical and clinical progress for HDAC as a putative target for epigenetic remodeling and functionality of immune cells

Genetic changes are difficult to reverse; thus, epigenetic aberrations, including changes in DNA methylation, histone modifications, and noncoding RNAs, with potential reversibility, have attracted attention as pharmaceutical targets. The current paradigm is that histone deacetylases (HDACs) regulate gene expression via deacetylation of histone and nonhistone proteins or by forming corepressor complexes with transcription factors. The emergence of epigenetic tools related to HDACs can be used as diagnostic and therapeutic markers. HDAC inhibitors that block specific or a series of HDACs have proven to be a powerful therapeutic treatment for immune-related diseases. Here, we summarize the various roles of HDACs and HDAC inhibitors in the development and function of innate and adaptive immune cells and their implications for various diseases and therapies.

Cigarette smoke promotes oral leukoplakia via regulating glutamine metabolism and M2 polarization of macrophage

Oral immunosuppression caused by smoking creates a microenvironment to promote the occurrence and development of oral mucosa precancerous lesions. This study aimed to investigate the role of metabolism and macrophage polarization in cigarette-promoting oral leukoplakia. The effects of cigarette smoke extract (CSE) on macrophage polarization and metabolism were studied in vivo and in vitro. The polarity of macrophages was detected by flow cytometric analysis and qPCR. Liquid chromatography-mass spectrometry (LC-MS) was used to perform a metabolomic analysis of Raw cells stimulated with CSE. Immunofluorescence and flow cytometry were used to detect the polarity of macrophages in the condition of glutamine abundance and deficiency. Cell Counting Kit-8 (CCK-8), wound-healing assay, and Annexin V-FITC (fluorescein isothiocyanate)/PI (propidium iodide) double-staining flow cytometry were applied to detect the growth and transferability and apoptosis of Leuk-1 cells in the supernatant of Raw cells which were stimulated with CSE, glutamine abundance and deficiency. Hyperkeratosis and dysplasia of the epithelium were evident in smoking mice. M2 macrophages increased under CSE stimulation in vivo and in vitro. In total, 162 types of metabolites were detected in the CSE group. The metabolites of nicotine, glutamate, arachidic acid, and arginine changed significantly. The significant enrichment pathways were also selected, including nicotine addiction, glutamine and glutamate metabolism, and arginine biosynthesis. The results also showed that the supernatant of Raw cells stimulated by CSE could induce excessive proliferation of Leuk-1 and inhibit apoptosis. Glutamine abundance can facilitate this process. Cigarette smoke promotes oral leukoplakia via regulating glutamine metabolism and macrophage M2 polarization.

Baicalin ameliorates cigarette smoke-induced airway inflammation in rats by modulating HDAC2/NF-κB/PAI-1 signalling

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory disease distinguished by airway remodelling and progressive inflammation. PAI-1 is an important regulator of fibrosis. Recent studies have shown that PAI-1 seems to be involved in COPD progression. Elevated levels of PAI-1 have been found in the lungs of patients with acute inflammation. PAI-1 has been shown to regulate the levels of proinflammatory cytokines in the lungs, such as tumour necrosis factor (TNF)-α and interleukin (IL)-6, indicating that PAI-1 may play a fundamental role during inflammation. In the present study, we investigated the anti-inflammatory role of baicalin, the main active component of Scutellaria baicalensis, against cigarette smoke (extract) (CS/CSE)-induced airway inflammation in vivo and in vitro. For the in vivo study, SD rats were exposed to CS for 1 h/day, 6 days/week, for 24 weeks and treated with baicalin (40, 80 and 160 mg/kg) or budesonide (0.2 mg/kg). For this study, HBE cells were pretreated with baicalin (10, 20, 40 μM) or dexamethasone (10^-7 M) and then exposed to CSE. We found that baicalin treatment could ameliorate CS-induced airway inflammatory infiltration in rats and decrease PAI-1 expression. The ELISA results showed that baicalin significantly inhibited the levels of TNF-α and IL-1β in CS/CSE-exposed rats and cells. Mechanistic studies showed that baicalin enhanced histone deacetylase 2 (HDAC2) protein expression and inhibited the expression of NF-κB and its downstream target PAI-1, and these effects were reversed by the HDAC2 inhibitor CAY-10683. In conclusion, baicalin ameliorated CS-induced airway inflammation in rats, and these effects were partially attributed to the modulation of HDAC2/NF-κB/PAI-1 signalling.

Epigenetics Involvement in Oxaliplatin-Induced Potassium Channel Transcriptional Downregulation and Hypersensitivity

Peripheral neuropathy is the most frequent dose-limiting adverse effect of oxaliplatin. Acute pain symptoms that are induced or exacerbated by cold occur in almost all patients immediately following the first infusions. Evidence has shown that oxaliplatin causes ion channel expression modulations in dorsal root ganglia neurons, which are thought to contribute to peripheral hypersensitivity. Most dysregulated genes encode ion channels involved in cold and mechanical perception, noteworthy members of a sub-group of potassium channels of the K2P family, TREK and TRAAK. Downregulation of these K2P channels has been identified as an important tuner of acute oxaliplatin-induced hypersensitivity. We investigated the molecular mechanisms underlying this peripheral dysregulation in a murine model of neuropathic pain triggered by a single oxaliplatin administration. We found that oxaliplatin-mediated TREK-TRAAK downregulation, as well as downregulation of other K+ channels of the K2P and Kv families, involves a transcription factor known as the neuron-restrictive silencer factor (NRSF) and its epigenetic co-repressors histone deacetylases (HDACs). NRSF knockdown was able to prevent most of these K+ channel mRNA downregulation in mice dorsal root ganglion neurons as well as oxaliplatin-induced acute cold and mechanical hypersensitivity. Interestingly, pharmacological inhibition of class I HDAC reproduces the antinociceptive effects of NRSF knockdown and leads to an increased K+ channel expression in oxaliplatin-treated mice.

Efficient Synthesis and Bioevaluation of Novel Dual Tubulin/Histone Deacetylase 3 Inhibitors as Potential Anticancer Agents

Novel dual HDAC3/tubulin inhibitors were designed and efficiently synthesized by combining the pharmacophores of SMART (tubulin inhibitor) and MS-275 (HDAC inhibitor), among which compound 15c was found to be the most potent and balanced HDAC3/tubulin dual inhibitor with high HDAC3 activity (IC50 = 30 nM) and selectivity (SI > 1000) as well as excellent antiproliferative potency against various cancer cell lines, including an HDAC-resistant gastric cancer cell line (YCC3/7) with IC50 values in the range of 30-144 nM. Compound 15c inhibited B16-F10 cancer cell migration and colony formation. In addition, 15c demonstrated significant in vivo antitumor efficacy in a B16-F10 melanoma tumor model with a better TGI (70.00%, 10 mg/kg) than that of the combination of MS-275 and SMART. Finally, 15c presented a safe cardiotoxicity profile and did not cause nephro-/hepatotoxicity. Collectively, this work shows that compound 15c represents a novel tubulin/HDAC3 dual-targeting agent deserving further investigation as a potential anticancer agent.

Juglanin protects against high fat diet-induced renal injury by suppressing inflammation and dyslipidemia via regulating NF-κB/HDAC3 signaling

Obesity is an important factor implicated in chronic kidney disease (CKD). Juglanin (Jug) is a natural compound extracted from the crude Polygonumaviculare, showing anti-inflammatory and anti-diabetic effects. However, whether Jug has protective effects against obesity-induced renal injury, little has been investigated. Herein, we attempted to explore the potential of Jug in mediating obesity-induced kidney disease in high fat diet (HFD)-challenged mice. Our results suggested that chronic HFD feeding markedly increased the body weights of mice compared to the ones fed with normal chow diet (NCD), along with significant glucose intolerance and insulin resistance. However, these metabolic disorders induced by HFD were effectively alleviated by Jug treatments in a dose-dependent manner. Moreover, HFD-challenged mice showed apparent histopathological changes in renal tissues with significant collagen accumulation, which were attenuated by Jug supplementation. In addition, Jug treatment decreased the expression levels of kidney injury molecule-1 (KIM-1), while increased nephrin and podocin expression levels in kidney of HFD-challenged mice, improving the renal dysfunction. Furthermore, HFD led to lipid deposition in kidney samples of mice by enhancing abnormal lipid metabolism. In addition, HFD promoted the releases of circulating pro-inflammatory cytokines, and enhanced the renal inflammation by activating nuclear factor-kappa B/histone deacetylase 3 (NF-κB/HDAC3) signaling. HFD-induced dyslipidemia and inflammation were considerably abrogated by Jug administration in mice. The protective effects of Jug against renal injury were confirmed in palmitate (PA)-stimulated HK2 cells in vitro mainly through suppressing the nuclear translocation of NF-κB and HDAC3, repressing inflammation and lipid accumulation eventually. Hence, Jug could ameliorate HFD-induced kidney injury mainly through blocking the NF-κB/HDAC3 nuclear translocation.

HDAC inhibitor, MS-275, increases vascular permeability by suppressing Robo4 expression in endothelial cells

Roundabout guidance receptor 4 (Robo4) is an endothelial-specific membrane protein that suppresses pathological angiogenesis and vascular hyperpermeability by stabilizing endothelial cells. Robo4 suppresses severe systemic inflammation induced by pathogens and endotoxins and inhibits tumor growth and metastasis, therefore serving as a potential therapeutic target. Although the regulation of Robo4 expression through transcription factors and epigenetic mechanisms has been studied, the role of histone deacetylases (HDACs) has not been explored. In the present study, we investigated the involvement of HDACs in the regulation of Robo4 expression. An HDAC inhibitor, MS-275, which inhibits HDAC1, HDAC2, and HDAC3, was found to suppress Robo4 expression in endothelial cells. Small interfering RNA (siRNA)-mediated knockdown of HDAC3, but not of HDAC1 and 2, also decreased its expression level. MS-275 downregulated the expression of the transcription factor complex GABP, in addition to suppressing Robo4 promoter activity. GABP expression was also downregulated by the siRNA against HDAC3. MS-275 decreased the transendothelial electrical resistance of a monolayer of mouse endothelial cells and increased the rate of leakage of Evans blue dye in the mouse lungs. In addition, MS-275 accelerated cell migration through the endothelial cell monolayer and augmented cell extravasation in the mouse lungs. Taken together, we demonstrated that MS-275 suppresses Robo4 expression by inhibiting HDAC3 in endothelial cells and enhances endothelial and vascular permeability. Thus, we demonstrated a novel mechanism regulating Robo4 expression and vascular permeability, which is anticipated to contribute to future therapies for infectious and inflammatory diseases.

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

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

A Class I Histone Deacetylase Inhibitor Attenuates Insulin Resistance and Inflammation in Palmitate-Treated C2C12 Myotubes and Muscle of HF/HFr Diet Mice

Histone deacetylase (HDAC) inhibitors, which regulate gene expression by inhibiting the deacetylation of histones and nonhistone proteins, have been shown to exert a wide array of biological effects; these include anti-cancer, anti-obesity, and anti-diabetes effects, as well as cardiovascular-protective activity. However, the effects of class I HDAC inhibition on lipotoxicity in C2C12 myotubes and skeletal muscle tissue remain poorly understood. In this study, we investigated the molecular mechanism underlying the protective effect of class I HDAC inhibition under lipotoxic conditions, i.e., in palmitate (PA)-treated C2C12 myotubes and skeletal muscle tissue in high fat (HF)/high fructose (HFr) diet mice. PA treatment of C2C12 myotubes increased HDAC3 protein expression and impaired mitochondrial oxidation, resulting in increased mitochondrial ROS generation and an accumulation of intracellular triglycerides (TG). Prolonged exposure led to increased inflammatory cytokine expression and insulin resistance. In contrast, MS-275, a class I HDAC inhibitor, dramatically attenuated lipotoxicity, preventing PA-induced insulin resistance and inflammatory cytokine expression. Similar beneficial effects were also seen following HDAC3 knockdown. In addition, MS-275 increased the mRNA expression of peroxisome proliferator activator receptor γ-coactivator 1α (PGC1α) and mitochondrial transcription factor A (TFAM), which serve as transcriptional coactivators in the context of mitochondrial metabolism and biogenesis, and restored expression of peroxisome proliferator-activated receptor alpha (PPARα), medium-chain acyl-coenzyme A dehydrogenase (MCAD), enoyl-CoA hydratase, and 3-hydroxyacyl CoA dehydrogenase (EHHADH). In vivo, treatment of HF/HFr-fed mice with MS-275 ameliorated hyperglycemia, insulin resistance, stress signals, and TNF-α expression in skeletal muscle. Taken together, these results suggest that HDAC3 inhibition rather than HDAC1/2 inhibition by MS-275 protects against lipotoxicity in C2C12 myotubes and skeletal muscle, and may be effective for the treatment of obesity and insulin resistance.

A conserved acetylation switch enables pharmacological control of tubby-like protein stability

Tubby-like proteins (TULPs) are characterized by a conserved C-terminal domain that binds phosphoinositides. Collectively, mammalian TULP1-4 proteins play essential roles in intracellular transport, cell differentiation, signaling, and motility. Yet, little is known about how the function of these proteins is regulated in cells. Here, we present the protein–protein interaction network of TULP3, a protein that is responsible for the trafficking of G-protein-coupled receptors to cilia and whose aberrant expression is associated with severe developmental disorders and polycystic kidney disease. We identify several protein interaction nodes linked to TULP3 that include enzymes involved in acetylation and ubiquitination. We show that acetylation of two key lysine residues on TULP3 by p300 increases TULP3 protein abundance and that deacetylation of these sites by HDAC1 decreases protein levels. Furthermore, we show that one of these sites is ubiquitinated in the absence of acetylation and that acetylation inversely correlates with ubiquitination of TULP3. This mechanism is evidently conserved across species and is active in zebrafish during development. Finally, we identify this same regulatory module in TULP1, TULP2, and TULP4 and demonstrate that the stability of these proteins is similarly modulated by an acetylation switch. This study unveils a signaling pathway that links nuclear enzymes to ciliary membrane receptors via TULP3, describes a dynamic mechanism for the regulation of all tubby-like proteins, and explores how to exploit it pharmacologically using drugs.

Inhibition of Histone Deacetylation by MS-275 Alleviates Colitis by Activating the Vitamin D Receptor

BACKGROUND

Ulcerative colitis [UC] is a common chronic inflammatory bowel disease without curative treatment.

METHODS

We conducted gene set enrichment analysis to explore potential therapeutic agents for UC. Human colon tissue samples were collected to test H3 acetylation in UC. Both in vivo and in vitro colitis models were constructed to verify the role and mechanism of H3 acetylation modification in UC. Intestine-specific vitamin D receptor [VDR]-/- mice and VD [vitamin D]-deficient diet-fed mice were used to explore downstream molecular mechanisms accordingly.

RESULTS

According to the Connectivity Map database, MS-275 [class I histone deacetylase inhibitor] was the top-ranked agent, indicating the potential importance of histone acetylation in the pathogenesis of UC. We then found that histone H3 acetylation was significantly lower in the colon epithelium of UC patients and negatively associated with disease severity. MS-275 treatment inhibited histone H3 deacetylation, subsequently attenuating nuclear factor kappa B [NF-κB]-induced inflammation, reducing cellular apoptosis, maintaining epithelial barrier function, and thereby reducing colitis activity in a mouse model of colitis. We also identified VDR as be a downstream effector of MS-275. The curative effect of MS-275 on colitis was abolished in VDR-/- mice and in VD-deficient diet-fed mice and VDR directly targeted p65. In UC patients, histone H3 acetylation, VDR and zonulin-1 expression showed similar downregulation patterns and were negatively associated with disease severity.

CONCLUSIONS

We demonstrate that MS-275 inhibits histone deacetylation and alleviates colitis by ameliorating inflammation, reducing apoptosis, and maintaining intestinal epithelial barrier via VDR, providing new strategies for UC treatment.

Induced protein degradation of histone deacetylases 3 (HDAC3) by proteolysis targeting chimera (PROTAC)

Histone deacetylases (HDACs) play important roles in inflammatory diseases like asthma and chronic obstructive pulmonary disease (COPD). Unravelling of and interfering with the functions of specific isoenzymes contributing to inflammation provides opportunities for drug development. Here we synthesize proteolysis targeting chimeras (PROTACs) for degradation of class I HDACs in which o-aminoanilide-based class I HDAC inhibitors are tethered to the cereblon ligand pomalidomide. One of these PROTACs, denoted HD-TAC7, showed promising degradation effects for HDAC3 with a DC₅₀ value of 0.32 μM. In contrast to biochemical evidence using siRNA, HD-TAC7 showed a minimal effect on gene expression in LPS/IFNγ-stimulated RAW 264.7 macrophages. The lack of effect can be attributed to downregulation of the NF-κB subunit p65, which is a known side effect of pomalidomide treatment. Altogether, we describe a novel PROTAC that enables selective downregulation of HDAC3 levels, however we note that concomitant downregulation of the NF-κB subunit p65 can confound the biological outcome.

CRISPR-mediated ablation of overexpressed EGFR in combination with sunitinib significantly suppresses renal cell carcinoma proliferation

Receptor tyrosine kinases, such as VEGFR, PDGFR and EGFR, play important roles in renal cancer. In this study, we investigated EGFR knockout as a therapeutic approach in renal cell carcinoma (RCC). We showed that a renal cell carcinoma cell line (RC21) has higher expression of EGFR as compared to other frequently used cell lines such as HEK293, A549, Hela and DLD1. Ablation of EGFR by CRISPR/Cas9 significantly restrained tumor cell growth and activated the MAPK (pERK1/2) pathway. The VEGFR and PDGFR inhibitor, sunitinib, attenuated the expression of MAPK (pERK1/2) and pAKT induced by EGFR loss and further inhibited EGFR-/- cell proliferation. We showed that loss of EGFR eventually leads to resistance to SAHA and cisplatin. Furthermore, EGFR loss induced G2/M phase arrest and resulted in an increased resistance to TNF-related apoptosis-inducing ligand (TRAIL) in renal cell carcinoma. Thus, ablation of overexpressed EGFR by CRISPR/Cas9 alone or in combination with sunitinib may be a new treatment option for renal cell carcinoma.

Spirulina maxima extract prevents activation of the NLRP3 inflammasome by inhibiting ERK signaling

The blue-green alga Spirulina maxima is a microscopic filamentous cyanobacterium. Spirulina was recently reported to elicit beneficial effects such as reducing cholesterol and inducing weight loss; however, its effects on inflammation are unknown. To determine the effect of S. maxima extract (SME) on innate immunity, we investigated the NLRP3 inflammasome activation, which is a multiprotein scaffolding complex that plays important roles in innate immune responses to many pathogenic infections in macrophages. SME suppressed lipopolysaccharide (LPS)-induced upregulation of the pro-inflammatory cytokines tumor necrosis factor-α, interleukin (IL)-12, IL-1β, and IL-18 in RAW264.7 cells. In addition, SME attenuated LPS-induced NLRP3 inflammasome activation, and thus pro-IL-1β could not be cleaved to IL-1β by activated caspase-1, which is activated by the NLRP3 inflammasome in RAW264.7 cells. Moreover, SME inhibited LPS-induced phosphorylation of extracellular signal-regulated kinase (ERK) in RAW264.7 cells, and attenuated the generation of ERK1 induced-reactive oxygen species (ROS), resulting in decreased expression of NF-κB. These findings suggest that SME suppresses the effects of the NLRP3 inflammasome via regulation of extracellular signal-regulated kinase (ERK). In summary, we demonstrated that SME prevents activation of the NLRP3 inflammasome by inhibiting ERK signaling.

Functional Inhibition of Host Histone Deacetylases (HDACs) Enhances in vitro and in vivo Anti-mycobacterial Activity in Human Macrophages and in Zebrafish

The rapid and persistent increase of drug-resistant Mycobacterium tuberculosis (Mtb) infections poses increasing global problems in combatting tuberculosis (TB), prompting for the development of alternative strategies including host-directed therapy (HDT). Since Mtb is an intracellular pathogen with a remarkable ability to manipulate host intracellular signaling pathways to escape from host defense, pharmacological reprogramming of the immune system represents a novel, potentially powerful therapeutic strategy that should be effective also against drug-resistant Mtb. Here, we found that host-pathogen interactions in Mtb-infected primary human macrophages affected host epigenetic features by modifying histone deacetylase (HDAC) transcriptomic levels. In addition, broad spectrum inhibition of HDACs enhanced the antimicrobial response of both pro-inflammatory macrophages (Mϕ1) and anti-inflammatory macrophages (Mϕ2), while selective inhibition of class IIa HDACs mainly decreased bacterial outgrowth in Mϕ2. Moreover, chemical inhibition of HDAC activity during differentiation polarized macrophages into a more bactericidal phenotype with a concomitant decrease in the secretion levels of inflammatory cytokines. Importantly, in vivo chemical inhibition of HDAC activity in Mycobacterium marinum-infected zebrafish embryos, a well-characterized animal model for tuberculosis, significantly reduced mycobacterial burden, validating our in vitro findings in primary human macrophages. Collectively, these data identify HDACs as druggable host targets for HDT against intracellular Mtb.

The key role of macrophage depolarization in the treatment of COPD with ergosterol both in vitro and in vivo

Macrophages are the most abundant immune cells in the lung, which play an important role in COPD. The anti-inflammatory and anti-oxidation of ergosterol are well documented. However, the effect of ergosterol on macrophage polarization has not been studied. The objective of this work was to investigate the effect of ergosterol on macrophage polarization in CSE-induced RAW264.7 cells and Sprague-Dawley (SD) rats COPD model. Our results demonstrate that CSE-induced macrophages tend to the M1 polarization via increasing ROS, IL-6 and TNF-α, as well as increasing MMP-9 to destroy the lung construction in both RAW264.7 cells and SD rats. However, treatment of RAW264.7 cells and SD rats with ergosterol inhibited CSE-induced inflammatory by decreasing ROS, IL-6 and TNF-α, and increasing IL-10 and TGF-β, shuffling the dynamic polarization of macrophages from M1 to M2 both in vitro and in vivo. Ergosterol also decreased the expression of M1 marker CD40, while increased that of M2 marker CD163. Moreover, ergosterol improved the lung characters in rats by decreasing MMP-9. Furthermore, ergosterol elevated HDAC3 activation and suppressed P300/CBP and PCAF activation as well as acetyl NF-κB/p65 and IKKβ, demonstrating that HDAC3 deacetylation was involved in the effect of ergosterol on macrophage polarization. These results also provide a proof in immunoregulation of ergosterol for therapeutic effects of cultured C. sinensis on COPD patients.

Mass spectrometric analysis of PTM dynamics using stable isotope labeled metabolic precursors in cell culture

Biological organisms represent highly dynamic systems, which are continually exposed to environmental factors and always strive to restore steady-state homeostasis. Posttranslational modifications are key regulators with which biological systems respond to external stimuli. To understand how homeostasis is restored, it is important to study the kinetics of posttranslational modifications. In this review we discuss proteomic approaches using stable isotope labeled metabolic precursors to study dynamics of posttranslational modifications in cell culture.

Epigenetic and transcriptional mechanisms for the regulation of IL-10

IL-10 is a critical immunoregulatory cytokine expressed in virtually all immune cell types. Maintaining a delicate balance between effective immune response and tolerance requires meticulous and dynamic control of IL-10 expression both epigenetically and transcriptionally. In this Review, we describe the epigenetic mechanisms controlling IL-10 expression, including chromatin remodeling, 3D chromatin loops, histone modification and DNA methylation. We discuss the role of transcription factors in directing chromatin modifications, with a special highlight on the emerging concept of pioneer transcription factors in setting up the chromatin landscape in T helper cells for IL-10 induction. Besides summarizing the recent progress on transcriptional regulation in specialized IL-10 producers such as type 1 regulatory T cells, regulatory B cells and regulatory innate lymphoid cells, we also discuss common transcriptional mechanisms for IL-10 regulation that are shared with other IL-10 producing cells.

Targeting HDAC Complexes in Asthma and COPD

Around three million patients die due to airway inflammatory diseases each year. The most notable of these diseases are asthma and chronic obstructive pulmonary disease (COPD). Therefore, new therapies are urgently needed. Promising targets are histone deacetylases (HDACs), since they regulate posttranslational protein acetylation. Over a thousand proteins are reversibly acetylated, and acetylation critically influences aberrant intracellular signaling pathways in asthma and COPD. The diverse set of selective and non-selective HDAC inhibitors used in pre-clinical models of airway inflammation show promising results, but several challenges still need to be overcome. One such challenge is the design of HDAC inhibitors with unique selectivity profiles, such as selectivity towards specific HDAC complexes. Novel strategies to disrupt HDAC complexes should be developed to validate HDACs further as targets for new anti-inflammatory pulmonary treatments.

Hollow Metal-Organic-Framework Micro/Nanostructures and their Derivatives: Emerging Multifunctional Materials

Hollow metal-organic framework (MOF) micro/nanostructures and their derivatives are attracting a great amount of research interest in recent years because their hierarchical porous structures not only provide abundant, easily accessed metal sites but also endow 3D channels for rapid mass transport. As a result, they demonstrate significant advantages in many applications including catalysis, gas sensors, batteries, supercapacitors, and so on. Nevertheless, studies on hollow MOFs and their derivatives are still at the beginning of this field, and the relationship between their structures and application performances is not yet reviewed comprehensively. Herein, the synthetic strategies and practical applications of hollow micro/nanostructured MOFs and their derivatives are summarized, and their corresponding prospects are also discussed.

Histone Deacetylase Inhibitor MS-275 Alleviates Postoperative Cognitive Dysfunction in Rats by Inhibiting Hippocampal Neuroinflammation

Neuroinflammation in the hippocampus plays essential roles in postoperative cognitive dysfunction (POCD). Histone deacetylases (HDACs) have recently been identified as key regulators of neuroinflammation. MS-275, an inhibitor of HDAC, has been reported to have neuroprotective effects. Therefore, the present study aimed to test the hypothesis that pretreatment with MS-275 prevents POCD by inhibiting neuroinflammation in rats. In this study, anesthesia/surgery impaired cognition, demonstrated by an increase escape latency and reduction in the number of platform crossings in Morris water maze (MWM) trials, through activating microglia neuroinflammation and decreasing PSD-95 expression. However, pretreatment with MS-275 attenuated postoperative cognitive impairment severity. Furthermore, pretreatment with MS-275 decreased activated microglia levels and increased PSD95 protein expression in the hippocampus. Pretreatment with MS-275 reduced NF-κB-p65 protein expression and nuclear accumulation as well as the neuroinflammatory response (production of proinflammatory cytokines including TNF-α and IL-1β) in the hippocampus. Additionally, MS-275 reduced HDAC2 expression and HDAC activity in the hippocampus, which were enhanced in vehicle-treated rats. These results suggest that MS-275 alleviates postoperative cognitive dysfunction by reducing neuroinflammation in the hippocampus of rats via HDAC inhibition.

Therapeutic Epigenetic Reprogramming of Trained Immunity in Myeloid Cells

Infiltrating and tissue-resident myeloid cells are essential regulators of innate and adaptive immunity. During inflammation, and in response to microbial products, these cells can adapt to microenvironmental conditions and acquire specialized functions, including phagocytosis and the production of proinflammatory cytokines. Such myeloid plasticity is driven, in part, by epigenetic dynamics that can sustain stable phenotypes after activation, and which may lead to maladaptive cell polarization states associated with inflammation and autoimmunity. Here, we review recent reports describing epigenetic mechanisms linked to such polarization states and innate immune memory (tolerance and training) in monocyte and macrophage lineages. We discuss how these mechanisms might be targeted to develop putative immunomodulatory tools that might be used to treat a variety of immune-mediated diseases.

Inhibitory selectivity among class I HDACs has a major impact on inflammatory gene expression in macrophages

Histone deacetylases (HDACs) play an important role in cancer, degenerative diseases and inflammation. The currently applied HDAC inhibitors in the clinic lack selectivity among HDAC isoforms, which limits their application for novel indications such as inflammatory diseases. Recent, literature indicates that HDAC 3 plays an important role among class I HDACs in gene expression in inflammation. In this perspective, the development and understanding of inhibitory selectivity among HDACs 1, 2 and 3 and their respective influence on gene expression need to be characterized to facilitate drug discovery. Towards this aim, we synthesized nine structural analogues of the class I HDAC inhibitor Entinostat and investigated their selectivity profile among HDACs 1, 2 and 3. We found that we can explain the observed structure activity relationships by small structural and conformational differences between HDAC 1 and HDAC 3 in the 'lid' interacting region. Cell-based studies indicated, however, that application of inhibitors with improved HDAC 3 selectivity did not provide an anti-inflammatory response in contrast to expectations from biochemical evidence in literature. Altogether, in this study, we identified structure activity relationships among class I HDACs and we connected isoform selectivity among class I HDACs with pro- and anti-inflammatory gene transcription in macrophages.

Inflammation-mediated deacetylation of the ribonuclease 1 promoter via histone deacetylase 2 in endothelial cells

Ribonuclease 1 (RNase1) is a circulating extracellular endonuclease that regulates the vascular homeostasis of extracellular RNA and acts as a vessel- and tissue-protective enzyme. Upon long-term inflammation, high amounts of proinflammatory cytokines affect endothelial cell (EC) function by down-regulation of RNase1. Here, we investigated the transcriptional regulation of RNase1 upon inflammation in HUVECs. TNF-α or IL-1β stimulation reduced the expression of RNase1 relative to the acetylation state of histone 3 at lysine 27 and histone 4 of the RNASE1 promoter. Inhibition of histone deacetylase (HDAC) 1, 2, and 3 by the specific class I HDAC inhibitor MS275 abolished the TNF-α- or IL-1β-mediated effect on the mRNA and chromatin levels of RNase1. Moreover, chromatin immunoprecipitation kinetics revealed that HDAC2 accumulates at the RNASE1 promoter upon TNF-α stimulation, indicating an essential role for HDAC2 in regulating RNase1 expression. Thus, proinflammatory stimulation induced recruitment of HDAC2 to attenuate histone acetylation at the RNASE1 promoter site. Consequently, treatment with HDAC inhibitors may provide a new therapeutic strategy to stabilize vascular homeostasis in the context of inflammation by preventing RNase1 down-regulation in ECs.-Bedenbender, K., Scheller, N., Fischer, S., Leiting, S., Preissner, K. T., Schmeck, B. T., Vollmeister, E. Inflammation-mediated deacetylation of the ribonuclease 1 promoter via histone deacetylase 2 in endothelial cells.

Epigenetic impacts of maternal tobacco and e-vapour exposure on the offspring lung

In utero exposure to tobacco products, whether maternal or environmental, have harmful effects on first neonatal and later adult respiratory outcomes. These effects have been shown to persist across subsequent generations, regardless of the offsprings' smoking habits. Established epigenetic modifications induced by in utero exposure are postulated as the mechanism underlying the inherited poor respiratory outcomes. As e-cigarette use is on the rise, their potential to induce similar functional respiratory deficits underpinned by an alteration in the foetal epigenome needs to be explored. This review will focus on the functional and epigenetic impact of in utero exposure to maternal cigarette smoke, maternal environmental tobacco smoke, environmental tobacco smoke and e-cigarette vapour on foetal respiratory outcomes.

Nimbolide protects against endotoxin-induced acute respiratory distress syndrome by inhibiting TNF-α mediated NF-κB and HDAC-3 nuclear translocation

Acute respiratory distress syndrome (ARDS) is characterized by an excessive acute inflammatory response in lung parenchyma, which ultimately leads to refractory hypoxemia. One of the earliest abnormalities seen in lung injury is the elevated levels of inflammatory cytokines, among them, the soluble tumor necrosis factor (TNF-α) has a key role, which exerts cytotoxicity in epithelial and endothelial cells thus exacerbates edema. The bacterial lipopolysaccharide (LPS) was used both in vitro (RAW 264.7, THP-1, MLE-12, A549, and BEAS-2B) and in vivo (C57BL/6 mice), as it activates a plethora of overlapping inflammatory signaling pathways involved in ARDS. Nimbolide is a chemical constituent of Azadirachta indica, which contains multiple biological properties, while its role in ARDS is elusive. Herein, we have investigated the protective effects of nimbolide in abrogating the complications associated with ARDS. We showed that nimbolide markedly suppressed the nitrosative-oxidative stress, inflammatory cytokines, and chemokines expression by suppressing iNOS, myeloperoxidase, and nitrotyrosine expression. Moreover, nimbolide mitigated the migration of neutrophils and mast cells whilst normalizing the LPS-induced hypothermia. Also, nimbolide modulated the expression of epigenetic regulators with multiple HDAC inhibitory activity by suppressing the nuclear translocation of NF-κB and HDAC-3. We extended our studies using molecular docking studies, which demonstrated a strong interaction between nimbolide and TNF-α. Additionally, we showed that treatment with nimbolide increased GSH, Nrf-2, SOD-1, and HO-1 protein expression; concomitantly abrogated the LPS-triggered TNF-α, p38 MAPK, mTOR, and GSK-3β protein expression. Collectively, these results indicate that TNF-α-regulated NF-κB and HDAC-3 crosstalk was ameliorated by nimbolide with promising anti-nitrosative, antioxidant, and anti-inflammatory properties in LPS-induced ARDS.

Preventive Effect of Garlic Oil and Its Organosulfur Component Diallyl-Disulfide on Cigarette Smoke-Induced Airway Inflammation in Mice

Garlic (Allium sativum) has traditionally been used as a medicinal food and exhibits various beneficial activities, such as antitumor, antimicrobial, hypolipidemic, antiarthritic, and hypoglycemic activities. The aim of this study was to explore the preventive effect of garlic oil (GO) and its organosulfur component diallyl disulfide (DADS) on cigarette smoke (CS)-induced airway inflammation. Mice were exposed to CS daily for 1 h (equivalent to eight cigarettes per day) for two weeks, and intranasally instilled with lipopolysaccharide (LPS) on day 12 after the initiation of CS exposure. GO and DADS were administered to mice by oral gavage, both at rates of 20 and 40 mg/kg, for 1 h before CS exposure for two weeks. In the bronchoalveolar lavage fluid, GO and DADS inhibited the elevation in the counts of inflammatory cells, particularly neutrophils, which were induced in the CS and LPS (CS + LPS) group. This was accompanied by the lowered production (relative to the CS + LPS group) of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α. Histologically, GO and DADS inhibited the CS- and LPS-induced infiltration of inflammatory cells into lung tissues. Additionally, GO and DADS inhibited the phosphorylation of extracellular signal-regulated kinase and the expression of matrix metalloproteinase-9 in the lung tissues. Taken together, these findings indicate that GO and DADS could be a potential preventive agent in CS-induced airway inflammation.

Mechanisms of NF-κB p65 and strategies for therapeutic manipulation

The transcription factor NF-κB is a critical regulator of immune and inflammatory responses. In mammals, the NF-κB/Rel family comprises five members: p50, p52, p65 (Rel-A), c-Rel, and Rel-B proteins, which form homo- or heterodimers and remain as an inactive complex with the inhibitory molecules called IκB proteins in resting cells. Two distinct NF-κB signaling pathways have been described: 1) the canonical pathway primarily activated by pathogens and inflammatory mediators, and 2) the noncanonical pathway mostly activated by developmental cues. The most abundant form of NF-κB activated by pathologic stimuli via the canonical pathway is the p65:p50 heterodimer. Disproportionate increase in activated p65 and subsequent transactivation of effector molecules is integral to the pathogenesis of many chronic diseases such as the rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis, and even neurodegenerative pathologies. Hence, the NF-κB p65 signaling pathway has been a pivotal point for intense drug discovery and development. This review begins with an overview of p65-mediated signaling followed by discussion of strategies that directly target NF-κB p65 in the context of chronic inflammation.

Histone Deacetylases Enhance Ca2+-Activated K⁺ Channel KCa3.1 Expression in Murine Inflammatory CD4⁺ T Cells

The up-regulated expression of the Ca²⁺-activated K⁺ channel K_Ca3.1 in inflammatory CD4⁺ T cells has been implicated in the pathogenesis of inflammatory bowel disease (IBD) through the enhanced production of inflammatory cytokines, such as interferon-γ (IFN-γ). However, the underlying mechanisms have not yet been elucidated. The objective of the present study is to clarify the involvement of histone deacetylases (HDACs) in the up-regulation of K_Ca3.1 in the CD4⁺ T cells of IBD model mice. The expression levels of K_Ca3.1 and its regulators, such as function-modifying molecules and transcription factors, were quantitated using a real-time polymerase chain reaction (PCR) assay, Western blotting, and depolarization responses, which were induced by the selective K_Ca3.1 blocker TRAM-34 (1 μM) and were measured using a voltage-sensitive fluorescent dye imaging system. The treatment with 1 μM vorinostat, a pan-HDAC inhibitor, for 24 h repressed the transcriptional expression of K_Ca3.1 in the splenic CD4⁺ T cells of IBD model mice. Accordingly, TRAM-34-induced depolarization responses were significantly reduced. HDAC2 and HDAC3 were significantly up-regulated in the CD4⁺ T cells of IBD model mice. The down-regulated expression of K_Ca3.1 was observed following treatments with the selective inhibitors of HDAC2 and HDAC3. The K_Ca3.1 K⁺ channel regulates inflammatory cytokine production in CD4⁺ T cells, mediating epigenetic modifications by HDAC2 and HDAC3.