Manipulating macrophage polarization and function using classical HDAC inhibitors: Implications for autoimmunity and inflammation

Histone deacetylases facilitate Th17-cell differentiation and pathogenicity in autoimmune uveitis via CDK6/ID2 axis

INTRODUCTION

Autoimmune uveitis (AU) is a prevalent ocular autoimmune disease leading to significant visual impairment. However, underlying pathogenesis of AU required to develop more efficient therapy remain unclear.

METHODS

We isolated peripheral blood mononuclear cells (PBMCs) from AU patients and performed single-cell RNA sequencing (scRNA-seq). Besides, experimental autoimmune uveitis (EAU) model was established and treated with histone deacetylase inhibitor (HDACi) Belinostat or vehicle. We extracted immune cells from Blank, EAU, and HDACi-treated EAU mice and used scRNA-seq, flow cytometry, siRNA, specific inhibitors, and adoptive transfer experiments to explore the role of HDACs and its downstream potential molecular mechanisms in the immune response of EAU and AU.

RESULTS

We found highly expressed histone deacetylases (HDACs) family in AU patients and identified it as a key factor related to CD4+ effector T cell differentiation in the pathogenesis of AU. Our further studies showed that targeted inhibition of HDACs effectively alleviated EAU, restored its Th17/Treg balance, and reduced inflammatory gene expression, especially in CD4+ T cells. Post-HDACs inhibition, Treg proportions increased with enhanced immunomodulatory effects. Importantly, HDACs exhibited a positive promoting role on Th17 cells. Based on scRNA-seq screening and application of knock-down siRNAs and specific inhibitors in vitro and vivo, we identified CDK6 as a key downstream molecule regulated by HDAC1/3/6 through acetyl-histone H3/p53/p21 axis, which is involved in Th17 pathogenicity and EAU development. Additionally, HDACs-regulated CDK6 formed a positive loop with ID2, inducing PIM1 upregulation, promoting Th17 cell differentiation and pathogenicity, and correlates with AU progression.

CONCLUSION

Based on the screening of clinical samples and downstream molecular functional validation experiments, we revealed a driving role for HDACs and the HDACs-regulated CDK6/ID2 axis in Th17 cell differentiation and pathogenicity in AU, proposing a promising therapeutic strategy.

Macrophage polarization and its impact on idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a lung disease that worsens over time, causing fibrosis in the lungs and ultimately resulting in respiratory failure and a high risk of death. Macrophages play a crucial role in the immune system, showing flexibility by transforming into either pro-inflammatory (M1) or anti-inflammatory (M2) macrophages when exposed to different stimuli, ultimately impacting the development of IPF. Recent research has indicated that the polarization of macrophages is crucial in the onset and progression of IPF. M1 macrophages secrete inflammatory cytokines and agents causing early lung damage and fibrosis, while M2 macrophages support tissue healing and fibrosis by releasing anti-inflammatory cytokines. Developing novel treatments for IPF relies on a thorough comprehension of the processes involved in macrophage polarization in IPF. The review outlines the regulation of macrophage polarization and its impact on the development of IPF, with the goal of investigating the possible therapeutic benefits of macrophage polarization in the advancement of IPF.

Targeting Macrophage Polarization in Infectious Diseases: M1/M2 Functional Profiles, Immune Signaling and Microbial Virulence Factors

INTRODUCTION

An event of increasing interest during host-pathogen interactions is the polarization of patrolling/naive monocytes (MOs) into macrophage subsets (MФs). Therapeutic strategies aimed at modulating this event are under investigation.

METHODS

This review focuses on the mechanisms of induction/development and profile of MФs polarized toward classically proinflammatory (M1) or alternatively anti-inflammatory (M2) phenotypes in response to bacteria, fungi, parasites, and viruses.

RESULTS AND DISCUSSION

It highlights nuclear, cytoplasmic, and cell surface receptors (pattern recognition receptors/PPRs), microenvironmental mediators, and immune signaling. MФs polarize into phenotypes: M1 MФs, activated by IFN-γ, pathogen-associated molecular patterns (PAMPs, e.g. lipopolysaccharide) and membrane-bound PPRs ligands (TLRs/CLRs ligands); or M2 MФs, induced by interleukins (ILs-4, -10 and -13), antigen-antibody complexes, and helminth PAMPs. Polarization toward M1 and M2 profiles evolve in a pathogen-specific manner, with or without canonicity, and can vary widely. Ultimately, this can result in varying degrees of host protection or more severe disease outcome. On the one hand, the host is driving effective MФs polarization (M1 or M2); but on the other hand, microorganisms may skew the polarization through virulence factors to increase pathogenicity. Cellular/genomic reprogramming also ensures plasticity of M1/M2 phenotypes. Because modulation of polarization can occur at multiple points, new insights and emerging perspectives may have clinical implications during the inflammation-to-resolution transition; translated into practical applications as for therapeutic/vaccine design target to boost microbicidal response (M1, e.g. triggering oxidative burst) with specifics PAMPs/IFN-γ or promote tissue repair (M2, increasing arginase activity) via immunotherapy.

Anti-inflammatory effects of Mentha pulegium L. extract on human peripheral blood mononuclear cells are mediated by TLR-4 and NF-κB suppression

There is great interest in evaluating the anti-inflammatory properties of new herbal products. Thus, the effects of Mentha pulegium L. extract on gene and protein expressions of pro-inflammatory mediators and transcription factors were determined. The hydro-ethanolic extract of Mentha pulegium L. was obtained and optimal non-cytotoxic concentrations of the extract were determined by MTT assay. Then, three different concentrations of Mentha pulegium L. (10, 30, and 90 μg/mL) were used to pre-treat the lipopolysaccharide (LPS)-stimulated and non-stimulated peripheral blood mononuclear cells (PBMCs) of 10 healthy individuals. Finally, the tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, Toll-like receptor-4 (TLR-4), nuclear factor-kappa B (NF-κB) p65, activator protein-1 (AP-1), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) gene expressions and TNF-α, IL-1β, IL-6, TLR-4, prostaglandin E2 (PGE2), and COX-2 protein levels were measured. MTT results showed that there is no significant difference in cell viability among 10, 20, 40, and 80 μg/mL concentrations of Mentha pulegium L. extract at 24, 48, and 72 h (P > 0.05). The IC50 values were 236.1, 147.0, and 118.0 μg/mL after 24, 48, and 72 h respectively. TNF-α, IL-1β, IL-6, TLR-4, iNOS, and NF-κB p65 mRNA levels in the pre-treated LPS-stimulated PBMCs were concentration-dependently reduced (P < 0.01 for TNF-α, TLR-4, and NF-κB p65; P < 0.05 for IL-1β, IL-6, and iNOS). Also, the protein levels of pro-inflammatory mediators decreased and these differences were significant for TNF-α, IL-1β, and TLR-4 (P < 0.001, P < 0.01, and P < 0.001, respectively). Mentha pulegium L. extract decreased the expression and biosynthesis of pro-inflammatory mediators. These effects are mainly mediated by TLR-4 and NF-κB suppression. Thus, Mentha pulegium L. could be useful in treating or ameliorating chronic inflammatory diseases.

Sargentodoxa cuneata and Patrinia villosa extract inhibits LPS-induced inflammation by shifting macrophages polarization through FAK/PI3K/Akt pathway regulation and glucose metabolism reprogramming

ETHNOPHARMACOLOGICAL RELEVANCE

Sargentodoxa cuneata and Patrinia villosa (S&P) are two natural herbal medicine widely used for treatment of various inflammatory diseases in Traditional Chinese Medicine, whereas the mode of action needs to be further investigated.

AIM OF THE STUDY

This study aimed to explore the anti-inflammatory effects and unravel the involved mechanism of S&P extract.

MATERIALS AND METHODS

The components of S&P extract were first detected using the liquid chromatography-tandem mass spectrometry (LC-MS/MS). The effects of S&P extract on the viability and migration ability of macrophages were detected using CCK8, LDH, adhesion and transwell assays. Cytokine release and macrophage phenotype transition were measured using a cytometric bead array and flow cytometry. The potential mechanism was uncovered using an integrative approach combining RNA sequencing and LC-MS/MS-based metabolic analysis. The expression of related proteins was further validated using western blotting.

RESULTS

S&P extract inhibited the proliferation and migration of LPS-induced macrophages, changed the morphology of macrophages, and inhibited the production of NO and the expression of iNOS. Furthermore, the extract inhibited tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) production and the expression of the M1 phenotype markers CD11c and CD16/32, whereas it promoted interleukin-10 (IL-10) production and the expression of the M2 phenotype markers CD206 and arginase 1 (Arg1). RNA sequencing analysis demonstrated that the upregulated genes by S&P extract treatment were involved in M2 macrophages: Il10, Ccl17, Ccl22, Cd68. The downregulated genes were involved in M1 macrophages and glycolysis processes: Stat1, Il18, Cd80, Cd86, Nos2, Il6, Pik3ap1, Raf1, Pdhb, etc. Metabolomics results showed that the S&P extract strongly ameliorated lipopolysaccharide (LPS)-induced metabolic disturbances. KEGG analysis indicated that most of these metabolites were involved in glucose metabolism, which is involved in the tumor necrosis factor (TNF), phosphatidylinositol 3 kinase/protein kinase B (PI3K/Akt), Glycolysis, and mitogen-activated protein kinase (MAPK) pathways. In vitro experiments further confirmed that the extract significantly inhibited the phosphorylation of focal adhesion kinase (FAK), PI3K and Akt, and the expression of glucose metabolism-related proteins. Adding a FAK inhibitor (defactinib) further inhibited the expression of M1/M2 phenotypic markers and the phosphorylation of FAK, PI3K, and Akt.

CONCLUSIONS

S&P extract can induce M2 polarization and shift macrophages from M1 to M2 tissue repair in LPS-induced inflammation by regulating glucose metabolism and the FAK/PI3K/Akt pathway.

The roles of HDAC with IMPDH and mTOR with JAK as future targets in the treatment of rheumatoid arthritis with combination therapy

Various studies have shown that cytokines are important regulators in rheumatoid arthritis (RA). In synovial inflammation alteration of the enzyme HDAC, IMPDH enzyme, mTOR pathway, and JAK pathway increase cytokine level. These increased cytokine levels are responsible for the inflammation in RA. Inflammation is a physiological and normal reaction of the immune system against dangerous stimuli such as injury and infection. The cytokine-based approach improves the treatment of RA. To reach this goal, various researchers and scientists are working more aggressively by using a combination approach. The present review of combination therapy provides essential evidence about the possible synergistic effect of combinatorial agents. We have focused on the effects of HDAC inhibitor with IMPDH inhibitor and mTOR inhibitor with JAK inhibitor in combination for the treatment of RA. Combining various targeted strategies can be helpful for the treatment of RA.

From nature to therapy: Luteolin's potential as an immune system modulator in inflammatory disorders

Inflammation is an essential immune response that helps fight infections and heal tissues. However, chronic inflammation has been linked to several diseases, including cancer, autoimmune disorders, cardiovascular diseases, and neurological disorders. This has increased interest in finding natural substances that can modulate the immune system inflammatory signaling pathways to prevent or treat these diseases. Luteolin is a flavonoid found in many fruits, vegetables, and herbs. It has been shown to have anti-inflammatory effects by altering signaling pathways in immune cells. This review article discusses the current research on luteolin's role as a natural immune system modulator of inflammatory signaling mechanisms, such as its effects on nuclear factor-kappa B, mitogen-activated protein kinases, Janus kinase/signal transducer and activator of transcription, and inflammasome signaling processes. The safety profile of luteolin and its potential therapeutic uses in conditions linked to inflammation are also discussed. Overall, the data point to Luteolin's intriguing potential as a natural regulator of immune system inflammatory signaling processes. More research is needed to fully understand its mechanisms of action and possible therapeutic applications.

Histone Deacetylase 3-Directed PROTACs Have Anti-inflammatory Potential by Blocking Polarization of M0-like into M1-like Macrophages

Macrophage polarization plays a crucial role in inflammatory processes. The histone deacetylase 3 (HDAC3) has a deacetylase-independent function that can activate pro-inflammatory gene expression in lipopolysaccharide-stimulated M1-like macrophages and cannot be blocked by traditional small-molecule HDAC3 inhibitors. Here we employed the proteolysis targeting chimera (PROTAC) technology to target the deacetylase-independent function of HDAC3. We developed a potent and selective HDAC3-directed PROTAC, P7, which induces nearly complete HDAC3 degradation at low micromolar concentrations in both THP-1 cells and human primary macrophages. P7 increases the anti-inflammatory cytokine secretion in THP-1-derived M1-like macrophages. Importantly, P7 decreases the secretion of pro-inflammatory cytokines in M1-like macrophages derived from human primary macrophages. This can be explained by the observed inhibition of macrophage polarization from M0-like into M1-like macrophage. In conclusion, we demonstrate that the HDAC3-directed PROTAC P7 has anti-inflammatory activity and blocks macrophage polarization, demonstrating that this molecular mechanism can be targeted with small molecule therapeutics.

Therapeutic Effect of HDAC5 Binding and Cell Penetrating Peptide for the Treatment of Inflammatory Bowel Disease

BACKGROUND

Inflammatory bowel disease (IBD) is an incurable disease that negatively influences the quality of life of patients. Current and emerging therapies target proinflammatory cytokines and/or receptors to downregulate proinflammatory responses, but insufficient remission requires other therapeutic agents. Herein, we report that the synthetic anti-inflammatory peptide 15 (SAP15) is capable of cell penetration and anti-inflammatory activity in human macrophages.

METHODS

SAP15 was labeled with fluorescence and administered to human leukemia monocytic cells (THP-1) cells for cell penetration analysis. Using biolayer interferometry analysis, the binding affinity of SAP15 with histone deacetylase 5 (HDAC5) was measured. SAP15-treated THP-1 cells were analyzed by protein phosphorylation assay, flow cytometry, and enzyme-linked immunosorbent assay (ELISA). In addition, in vivo analysis of the therapeutic effect on IBD was observed in a dextran sulfate sodium (DSS)-induced model. Samples from SAP15-treated mice were analyzed at both the macroscopic and microscopic levels using ELISA, myeloperoxidase (MPO) assays, and histological evaluations.

RESULTS

SAP15 was internalized within the cytosol and nucleus of THP-1 cells and bound to the HDAC5 protein. SAP15-treated macrophages were assessed for protein phosphorylation and showed inhibited phosphorylation of HDAC5 and other immune-related proteins, which led to increased M2-like macrophage markers and decreased M1-like macrophage markers and tumor necrosis factor-α and interleukin-6 cytokine levels. The SAP15 treatment on IBD model showed significant recovery of colon length. Further histological analysis of colon demonstrated the therapeutic effect of SAP15 on mucosal layer. Moreover, proinflammatory cytokine levels and MPO activity from the plasma show that SAP15 is effective in reduced proinflammatory responses.

CONCLUSION

These findings suggest that SAP15 is a novel peptide with a novel cell-penetrating peptide with anti-inflammatory property that can be used as a therapeutic agent for IBD and other inflammatory diseases.

Anti-inflammatory mechanism of the optimized active ingredients of Sargentodoxa cuneata and Patrinia villosa

Pelvic inflammatory disease (PID) is a common gynecological infection. The combined use of Sargentodoxa cuneata (da xue teng) and Patrinia villosa (bai jiang cao) has been shown to inhibit PID progression. The active components of S. cuneata (emodin, Emo) and P. villosa (acacetin, Aca; oleanolic acid, OA; sinoacutine, Sin) have been identified but the mode of action of this combination of compounds against PID has not been clarified. Therefore, this study aims to investigate the mechanism of these active components against PID through network pharmacological, molecular docking and experimental validation. The results showed the optimal combination of components was 40 µM Emo + 40 µM OA, 40 µM Emo + 40 µM Aca, and 40 µM Emo + 150 µM Sin by cell proliferation and NO release. The potential key targets of this combination in the treatment of PID include SRC, GRB2, PIK3R1, PIK3CA, PTPN11, and SOS1, which act on signaling pathways such as EGFR, PI3K/Akt, TNF, and IL-17. Emo, Aca, OA, and their optimal combination inhibited the expression of IL-6, TNF-α, MCP-1, IL-12p70, IFN-γ, and the M1 phenotype markers CD11c and CD16/32, and promoted the expression of the M2 phenotype markers CD206 and arginase 1 (Arg1). Western blotting confirmed that Emo, Aca, OA, and their optimal combination significantly inhibited the expression of glucose metabolism-related proteins PKM2, PD, HK I, and HK II. This study proved the advantage of combination use of active components from S. cuneata and P. villosa, and clarified that they exert the anti-inflammatory effect by regulation of M1/M2 phenotype transition and regulation of glucose metabolism. The results provide a theoretical basis for the clinical treatment of PID.

An Overview of Drug Delivery Nanosystems for Sepsis-Related Liver Injury Treatment

Sepsis, which is a systemic inflammatory response syndrome caused by infection, has high morbidity and mortality. Sepsis-related liver injury is one of the manifestations of sepsis-induced multiple organ syndrome. To date, an increasing number of studies have shown that the hepatic inflammatory response, oxidative stress, microcirculation coagulation dysfunction, and bacterial translocation play extremely vital roles in the occurrence and development of sepsis-related liver injury. In the clinic, sepsis-related liver injury is mainly treated by routine empirical methods on the basis of the primary disease. However, these therapies have some shortcomings, such as serious side effects, short duration of drug effects and lack of specificity. The emergence of drug delivery nanosystems can significantly improve drug bioavailability and reduce toxic side effects. In this paper, we reviewed drug delivery nanosystems designed for the treatment of sepsis-related liver injury according to their mechanisms (hepatic inflammation response, oxidative stress, coagulation dysfunction in the microcirculation, and bacterial translocation). Although much promising progress has been achieved, translation into clinical practice is still difficult. To this end, we also discussed the key issues currently facing this field, including immune system rejection and single treatment modalities. Finally, with the rigorous optimization of nanotechnology and the deepening of research, drug delivery nanosystems have great potential for the treatment of sepsis-related liver injury.

Central and peripheral regulations mediated by short-chain fatty acids on energy homeostasis

The human gut microbiota influences obesity, insulin resistance, and the subsequent development of type 2 diabetes (T2D). The gut microbiota digests and ferments nutrients resulting in the production of short-chain fatty acids (SCFAs), which generate various beneficial metabolic effects on energy and glucose homeostasis. However, their roles in the central nervous system (CNS)-mediated outputs on the metabolism have only been minimally studied. Here, we explore what is known and future directions that may be worth exploring in this emerging area. Specifically, we searched studies or data in English by using PubMed, Google Scholar, and the Human Metabolome Database. Studies were filtered by time from 1978 to March 2022. As a result, 195 studies, 53 reviews, 1 website, and 1 book were included. One hundred and sixty-five of 195 studies describe the production and metabolism of SCFAs or the effects of SCFAs on energy homeostasis, glucose balance, and mental diseases through the gut-brain axis or directly by a central pathway. Thirty of 195 studies show that inappropriate metabolism and excessive of SCFAs are metabolically detrimental. Most studies suggest that SCFAs exert beneficial metabolic effects by acting as the energy substrate in the TCA cycle, regulating the hormones related to satiety regulation and insulin secretion, and modulating immune cells and microglia. These functions have been linked with AMPK signaling, GPCRs-dependent pathways, and inhibition of histone deacetylases (HDACs). However, the studies focusing on the central effects of SCFAs are still limited. The mechanisms by which central SCFAs regulate appetite, energy expenditure, and blood glucose during different physiological conditions warrant further investigation.

Noncoding RNA-mediated macrophage and cancer cell crosstalk in hepatocellular carcinoma

The tumor microenvironment (TME) is a well-recognized system that plays an essential role in tumor initiation, development, and progression. Intense intercellular communication between tumor cells and other cells (especially macrophages) occurs in the TME and is mediated by cell-to-cell contact and/or soluble messengers. Emerging evidence indicates that noncoding RNAs (ncRNAs) are critical regulators of the relationship between cells within the TME. In this review, we provide an update on the regulation of ncRNAs (primarily micro RNAs [miRNAs], long ncRNAs [lncRNAs], and circular RNAs [circRNAs]) in the crosstalk between macrophages and tumor cells in hepatocellular carcinoma (HCC). These ncRNAs are derived from macrophages or tumor cells and act as oncogenes or tumor suppressors, contributing to tumor progression not only by regulating the physiological and pathological processes of tumor cells but also by controlling macrophage infiltration, activation, polarization, and function. Herein, we also explore the options available for clinical therapeutic strategies targeting crosstalk-related ncRNAs to treat HCC. A better understanding of the relationship between macrophages and tumor cells mediated by ncRNAs will uncover new diagnostic biomarkers and pharmacological targets in cancer.

Corticosteroid resistance in asthma: Cellular and molecular mechanisms

Inhaled glucocorticoids (GCs) are drugs widely used as treatment for asthma patients. They prevent the recruitment and activation of lung immune and inflammatory cells and, moreover, have profound effects on airway structural cells to reverse the effects of disease on airway inflammation. GCs bind to a specific receptor, the glucocorticoid receptor (GR), which is a member of the nuclear receptor superfamily and modulates pro- and anti-inflammatory gene transcription through a number of distinct and complementary mechanisms. Targets genes include many pro-inflammatory mediators such as chemokines, cytokines, growth factors and their receptors. Inhaled GCs are very effective for most asthma patients with little, if any, systemic side effects depending upon the dose. However, some patients show poor asthma control even after the administration of high doses of topical or even systemic GCs. Several mechanisms relating to inflammation have been considered to be responsible for the onset of the relative GC resistance observed in these patients. In these patients, the side-effect profile of GCs prevent continued use of high doses and new drugs are needed. Targeting the defective pathways associated with GC function in these patients may also reactivate GC responsiveness.

Berberine as a natural modulator of inflammatory signaling pathways in the immune system: Focus on NF-κB, JAK/STAT, and MAPK signaling pathways

Three main inflammatory signaling pathways include nuclear factor-κB (NF-κB), Janus kinases/Signal transducer and activator of transcriptions (JAKs/STATs), and mitogen-activated protein kinases (MAPKs) play crucial roles in inducing, promoting, and regulating inflammatory responses in the immune system. Importantly, the breakdown of mechanisms that tightly regulate inflammatory signaling pathways can be the underlying cause of uncontrolled inflammatory responses and be associated with the generation and development of several inflammatory diseases. Hence, therapeutic strategies targeting inflammatory signaling pathways and their downstream components may promise to treat inflammatory diseases. Studies over the past two decades have provided important information on the polytrophic pharmacological and biochemical properties of berberine (BBR) as a naturally occurring compound, such as antioxidant, antitumor, antimicrobial, and antiinflammatory activates. Interestingly, the modulatory effects of BBR on inflammatory signaling cascades, which lead to the inhibition of inflammation, have been widely investigated in several in vitro and in vivo studies. For the first time, herein, this comprehensive review attempts to put together these studies and provide important insight into the modulatory effects of BBR on NF-κB, JAKs/STATs, and MAPKs signaling pathways in vitro in various types of immune cells and in vivo in several experimental inflammatory diseases. As the second achievement of this review, we also explore the therapeutic efficacy and antiinflammatory effects of BBR regarding its modulatory action.

Entinostat Improves Motor Function and Neuronal Damage Via Downregulating NLRP3 Inflammasome Activation After Spinal Cord Injury

Background: Spinal cord injury (SCI), a major public health problem, has no effective treatment. A large number of studies have confirmed that histone deacetylases (HDACs) are involved in the physiologic processes that occur following SCI. We tried to uncover the potential neuroprotective role of entinostat (a class I HDAC inhibitor) in SCI.

Methods: We conducted a study on a preclinical mouse model of SCI and OGD-induced neuronal damage to present the role of entinostat by the analysis of motor function, histopathologic damage, local NLRP3 inflammasome activation, and neuronal damage.

Results: The results showed that entinostat suppressed HDAC activation (including HDAC1 and HDAC3 expression), improved the grip strength and BMS score, spinal edema, cell death, and local NLRP3 inflammasome activation in the spinal cord following SCI. Furthermore, entinostat significantly increased OGD-inhibited neuronal activity and decreased PI-positive cells, HDAC activation, caspase-1 activation, IL-1β and IL-18 levels, and NLRP3 expression.

Conclusion: In summary, we first documented that entinostat improved the motor function, histopathologic damage, and local inflammatory response and NLRP3 inflammasome activation in the spinal cord following SCI and also presented the neuroprotective role of OGD-induced neuronal damage via the NLRP3 inflammasome. Thus, our study has the potential to reveal the interaction between the HDAC and NLRP3 inflammasome in the pathologic process as well as SCI and further promote the clinical indications of HDACi entinostat and clinical treatment for the inflammatory response after SCI.

Acetylation in Tumor Immune Evasion Regulation

Acetylation is considered as one of the most common types of epigenetic modifications, and aberrant histone acetylation modifications are associated with the pathological process of cancer through the regulation of oncogenes and tumor suppressors. Recent studies have shown that immune system function and tumor immunity can also be affected by acetylation modifications. A comprehensive understanding of the role of acetylation function in cancer is essential, which may help to develop new therapies to improve the prognosis of cancer patients. In this review, we mainly discussed the functions of acetylase and deacetylase in tumor, immune system and tumor immunity, and listed the information of drugs targeting these enzymes in tumor immunotherapy.

Dietary Patterns and Associated Microbiome Changes that Promote Oncogenesis

The recent increases in cancer incidences have been linked to lifestyle changes that result in obesity and metabolic syndrome. It is now evident that these trends are associated with the profound changes that occur in the intestinal microbiome, producing altered microbial population signatures that interact, directly or indirectly, with potentially pro-carcinogenic molecular pathways of transcription, proliferation, and inflammation. The effects of the entire gut microbial population on overall health are complex, but individual bacteria are known to play important and definable roles. Recent detailed examinations of a large number of subjects show a tight correlation between habitual diets, fecal microbiome signatures, and markers of metabolic health. Diets that score higher in healthfulness or diversity such as plant-based diets, have altered ratios of specific bacteria, including an increase in short-chain fatty acid producers, which in turn have been linked to improved metabolic markers and lowered cancer risk. Contrarily, numerous studies have implicated less healthy, lower-scoring diets such as the Western diet with reduced intestinal epithelial defenses and promotion of specific bacteria that affect carcinogenic pathways. In this review, we will describe how different dietary patterns affect microbial populations in the gut and illustrate the subsequent impact of bacterial products and metabolites on molecular pathways of cancer development, both locally in the gut and systemically in distant organs.

Global characterization of macrophage polarization mechanisms and identification of M2-type polarization inhibitors

Macrophages undergoing M1- versus M2-type polarization differ significantly in their cell metabolism and cellular functions. Here, global quantitative time-course proteomics and phosphoproteomics paired with transcriptomics provide a comprehensive characterization of temporal changes in cell metabolism, cellular functions, and signaling pathways that occur during the induction phase of M1- versus M2-type polarization. Significant differences in, especially, metabolic pathways are observed, including changes in glucose metabolism, glycosaminoglycan metabolism, and retinoic acid signaling. Kinase-enrichment analysis shows activation patterns of specific kinases that are distinct in M1- versus M2-type polarization. M2-type polarization inhibitor drug screens identify drugs that selectively block M2- but not M1-type polarization, including mitogen-activated protein kinase kinase (MEK) and histone deacetylase (HDAC) inhibitors. These datasets provide a comprehensive resource to identify specific signaling and metabolic pathways that are critical for macrophage polarization. In a proof-of-principle approach, we use these datasets to show that MEK signaling is required for M2-type polarization by promoting peroxisome proliferator-activated receptor-γ (PPARγ)-induced retinoic acid signaling.

Classical HDACs in the regulation of neuroinflammation

Neuroinflammation is a key factor of the pathology of various neurological diseases (brain injury, depression, neurodegenerative diseases). It is a complex and orderly process that relies on various types of glial cells and peripheral immune cells. Inhibition of neuroinflammation can reduce the severity of neurological diseases. The initiation, progression, and termination of inflammation require gene activation, epigenetic modification, transcriptional translation, and post-translational regulation, all of which are tightly regulated by different enzymes. Epigenetics refers to the regulation of epigenetic gene expression by epigenetic changes (DNA methylation, histone modification, and non-coding RNAs such as miRNA) that are not dependent on changes in gene sequence and are heritable. Histone deacetylases (HDACs) are a group of important enzymes that regulate epigenetics. They can remove the acetyl group on the lysine ϵ-amino group of the target protein, thereby affecting gene transcription or altering protein activity. HDACs are involved in the regulation of immunity and inflammation. HDAC inhibitor (HDACi) has also become a new hotspot in the research of anti-inflammatory drugs. Therefore, the aim of the current review is to discuss and summarize the role and mechanism of different HDACs in neuroinflammation and the corresponding role of HDACi in neurological diseases, and to providing new ideas for future research on neuroinflammation-related diseases and drug development.

Downregulation of HDAC8 expression decreases CD163 levels and promotes the apoptosis of macrophages by activating the ERK signaling pathway in recurrent spontaneous miscarriage

Recurrent spontaneous miscarriage (RSM) is a systemic disorder that has been defined as two or more pregnancies lost before the 20th week of gestation. Although the impaired function of macrophages at the maternal-fetal interface has been reported to be associated with RSM, the underlying mechanisms have not been fully elucidated. Here, we revealed that HDAC8 plays a critical role in RSM. Our results show that the mRNA and protein expression of HDAC8 was decreased in decidual macrophages from RSM patients. Moreover, the knockdown of HDAC8 resulted in a significant decrease in CD163 expression and an increase in apoptosis in dTHP-1 macrophages. Mechanistically, the ERK signaling pathway was activated in HDAC8-knockdown macrophages. When HDAC8-knockdown cells were pretreated with the ERK inhibitor U0126, expression levels of CD163, activated caspases 3, 7 and 9, and the apoptosis rate, were rescued. Taken together, our current results suggest that HDAC8 plays an important role in macrophage activation and apoptosis and may contribute to maintaining normal pregnancy by increasing the expression of M2 marker genes and inhibiting the apoptosis of macrophages at the maternal-fetal interface.

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.

Dexamethasone and Fumaric Acid Ester Conjugate Synergistically Inhibits Inflammation and NF-κB in Macrophages

Macrophage-mediated inflammation drives autoimmune and chronic inflammatory diseases. Treatment with anti-inflammatory agents can be an effective strategy to reduce this inflammation; however, high concentrations of these agents can have immune-dampening and other serious side effects. Synergistic combination of anti-inflammatory agents can mitigate dosing by requiring less drug. Multiple anti-inflammatory agents were evaluated in combination for synergistic inhibition of macrophage inflammation. The most potent synergy was observed between dexamethasone (DXM) and fumaric acid esters (e.g., monomethyl fumarate (MMF)). Furthermore, this combination was found to synergistically inhibit inflammatory nuclear factor κB (NF-κB) transcription factor activity. The optimal ratio for synergy was determined to be 1:1, and DXM and MMF were conjugated by esterification at this molar ratio. The DXM-MMF conjugate displayed improved inhibition of inflammation over the unconjugated combination in both murine and human macrophages. In the treatment of human donor monocyte-derived macrophages, the combination of DXM and MMF significantly inhibited inflammatory gene expression downstream of NF-κB and overall performed better than either agent alone. Further, the DXM-MMF conjugate significantly inhibited expression of NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome-associated genes. The potent anti-inflammatory activity of the DXM-MMF conjugate in human macrophages indicates that it may have benefits in the treatment of autoimmune and inflammatory diseases.

Curcumin: A Dietary Phytochemical for Targeting the Phenotype and Function of Dendritic Cells

Dendritic cells (DCs) are the most powerful antigen-presenting cells which link the innate and adaptive immune responses. Depending on the context, DCs initiate the immune responses or contribute to immune tolerance. Any disturbance in their phenotypes and functions may initiate inflammatory or autoimmune diseases. Hence, dysregulated DCs are the most attractive pharmacological target for the development of new therapies aiming at reducing their immunogenicity and at enhancing their tolerogenicity. Curcumin is the polyphenolic phytochemical component of the spice turmeric with a wide range of pharmacological activities. It acts in several ways as a modulator of DCs and converts them into tolerogenic DCs. Tolerogenic DCs possess anti-inflammatory and immunomodulatory activities that regulate the immune responses in health and disease. Curcumin by blocking maturation markers, cytokines and chemokines expression, and disrupting the antigen-presenting machinery of DCs render them non- or hypo-responsive to immunostimulants. It also reduces the expression of co-stimulatory and adhesion molecules on DCs and prevents them from both migration and antigen presentation but enhances their endocytosis capacity. Hence, curcumin causes DCs-inducing regulatory T cells and dampens CD4+ T helper 1 (Th1), Th2, and Th17 polarization. Inhibition of transcription factors such as NF-κB, AP-1, MAPKs (p38, JNK, ERK) and other intracellular signaling molecules such as JAK/STAT/SOCS provide a plausible explanation for most of these observations. In this review, we summarize the potential effects of curcumin on the phenotypes and functions of DCs as the key players in orchestration, stimulation, and modulation of the immune responses.

Effects of Tranilast on Inflammasome and Macrophage Phenotype in a Mouse Model of Myocardial Infarction

Acute myocardial infarction (AMI) has been a devastating actuality and accounts for half of cardiovascular emergency department visits. Nucleotide oligomerization domain, leucine-rich repeat, and pyrin domain-containing protein 3 (NLRP3) inflammasome participates in the mediation of myocardial inflammation during AMI. Therefore, this study aimed to reveal the therapeutic function of tranilast, an agent targeting NLRP3, for AMI. AMI mouse model was first established by transient myocardial ischemia. Western blot and quantitative reverse transcription polymerase chain reaction assay were performed to estimate the expression levels of related genes. Flow cytometry was used to analyze the macrophage types, and the therapeutic effects of tranilast were estimated by echocardiographic analysis and Masson's trichrome stain. We demonstrated that AMI induced the activation of NLRP3 inflammasome in the heart tissues of mice with AMI. Tranilast decreased the expression of interleukin-1β and cleaved caspase-1 in bone marrow-derived macrophages and thus re-educated M1-macrophages toward the M2-phenotype both in vitro and in vivo. Tranilast inhibited the activation in the heart tissues of AMI mice and thus improved cardiac functional recovery in the AMI mouse model. In conclusion, we revealed that tranilast ameliorated myocardial infarction by inhibiting NLRP3 inflammasome and re-educating macrophage phenotype in this study.

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.

Histone deacetylases as targets in autoimmune and autoinflammatory diseases

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

Epigenetic inhibitors eliminate senescent melanoma BRAFV600E cells that survive long‑term BRAF inhibition

It is estimated that ~50% of patients with melanoma harbour B‑Raf (BRAF)V600 driver mutations, with the most common of these being BRAFV600E, which leads to the activation of mitogen‑activated protein kinase proliferative and survival pathways. BRAF inhibitors are used extensively to treat BRAF‑mutated metastatic melanoma; however, acquired resistance occurs in the majority of patients. The effects of long‑term treatment with PLX4032 (BRAFV600 inhibitor) were studied in vitro on sensitive V600E BRAF‑mutated melanoma cell lines. After several weeks of treatment with PLX4032, the majority of the melanoma cells died; however, a proportion of cells remained viable and quiescent, presenting senescent cancer stem cell‑like characteristics. This surviving population was termed SUR cells, as discontinuing treatment allowed the population to regrow while retaining equal drug sensitivity to that of parental cells. RNA sequencing analysis revealed that SUR cells exhibit changes in the expression of 1,415 genes (P<0.05) compared with parental cells. Changes in the expression levels of a number of epigenetic regulators were also observed. These changes and the reversible nature of the senescence state were consistent with epigenetic regulation; thus, it was investigated as to whether the senescent state could be reversed by epigenetic inhibitors. It was found that both parental and SUR cells were sensitive to different histone deacetylase (HDAC) inhibitors, such as SAHA and MGCD0103, and to the cyclin‑dependent kinase (CDK)9 inhibitor, CDKI‑73, which induced apoptosis and reduced proliferation both in the parental and SUR populations. The results suggested that the combination of PLX4032 with HDAC and CDK9 inhibitors may achieve complete elimination of SUR cells that persist after BRAF inhibitor treatment, and reduce the development of resistance to BRAF inhibitors.

Time-dependent effects of histone deacetylase inhibition in sepsis-associated acute kidney injury

BACKGROUND

Sepsis, a dysregulated host response to infection with results in organ dysfunction, has been a major challenge to the development of effective therapeutics. Sepsis-associated acute kidney injury (S-AKI) results in a 3-5-fold increase in the risk of hospital mortality compared to sepsis alone. The development of therapies to reverse S-AKI could therefore significantly affect sepsis outcomes. However, the translation of therapies from preclinical studies into humans requires model systems that recapitulate clinical scenarios and the development of renal fibrosis indicative of the transition from acute to chronic kidney disease.

RESULTS

Here we characterized a murine model of S-AKI induced by abdominal sepsis developing into a chronic phenotype. We applied a small molecule histone deacetylase-8 inhibitor, UPHD186, and found that early treatment, beginning at 48 h post-sepsis, worsened renal outcome accompanied by decreasing mononuclear cell infiltration in the kidney, skewing cells into a pro-inflammatory phenotype, and increased pro-fibrotic gene expression, while delayed treatment, beginning at 96 h post-sepsis, after the acute inflammation in the kidney had subsided, resulted in improved survival and kidney histology presumably through promoting proliferation and inhibiting fibrosis.

CONCLUSIONS

These findings not only present a clinically relevant S-AKI model, but also introduce a timing dimension into S-AKI therapeutic interventions that delayed treatment with UPHD186 may enhance renal histologic repair. Our results provide novel insights into successful repair of kidney injury and sepsis therapy.

Asaronic Acid Attenuates Macrophage Activation toward M1 Phenotype through Inhibition of NF-κB Pathway and JAK-STAT Signaling in Glucose-Loaded Murine Macrophages

Macrophage polarization has been implicated in the pathogenesis of obesity and type 2 diabetes, which are recognized as chronic proinflammatory diseases. This study investigated that high level of glucose, similar to lipopolysaccharide (LPS), activated macrophages toward M1 phenotypes and 1-20 μM asaronic acid (AA) counteracted diabetic macrophage activation. AA reduced the LPS-promoted secretion of proinflammatory interleukin (IL)-6 and monocyte chemoattractant protein-1. The LPS markedly elevated the macrophage induction of the M1 markers of Toll-like receptor 4 (TLR4), CD36, and CD68, which was attenuated by AA. Also, the LPS significantly enhanced the nuclear factor (NF)-κB transactivation, signal transducers, and activators of transcription 1 (STAT1)/STAT3 activation and suppressor of cytokine signaling 3 (SOCS3) induction in macrophages. However, AA highly suppressed the aforementioned effects of LPS. Glucose-stimulated macrophages expressed advanced glycation end products (AGEs) and receptor for AGE (RAGE). Administration of 20 μM AA to macrophages partly but significantly attenuated such effects (1.65 ± 0.12 vs 0.95 ± 0.25 times glucose control for AGE; 2.33 ± 0.31 vs 1.40 ± 0.22 times glucose control for RAGE). Furthermore, glucose enhanced the macrophage induction of TLR4 and inducible nitric oxide synthase and IL-6 production, while it demoted the production of anti-inflammatory arginase-1 and IL-10. In contrast, AA reversed the induction of these markers in glucose-loaded macrophages. AA dose-dependently and significantly encumbered NF-κB transactivation, Janus kinase 2 (JAK2) and STAT1/STAT3 activation, and SOCS3 induction upregulated in glucose-supplemented macrophages. These results demonstrated for the first time that AA may limit diabetic macrophage activation toward the M1 phenotype through the inhibition of TLR4-/IL-6-mediated NF-κB/JAK2-STAT signaling entailing AGE-RAGE interaction.

Pharmacological strategies to regain steroid sensitivity in severe asthma and COPD

Corticosteroid is the most widely used anti-inflammatory agent for asthma and chronic obstructive pulmonary disease (COPD). However, most of the severe asthmatics and COPD patients show poor response to the anti-inflammatory benefits of corticosteroids. Corticosteroid resistance is a major therapeutic challenge to the treatment of severe asthma and COPD. Cellular and molecular mechanisms underlying steroid insensitivity in severe asthma and COPD are still not fully understood. This review aims to recapitulate recent discoveries of potential contributing mechanisms of steroid resistance, and to appraise new therapeutic strategies shown to restore steroid sensitivity in experimental models of severe asthma and COPD, and in human clinical trials. It has been revealed that pro-inflammatory cytokines such as IFN-γ, TNF-α, TGF-β, IL-17A, IL-27, IL-33 and thymic stromal lymphopoietin (TSLP) may contribute to steroid resistance in severe asthma and COPD. These cytokines together with allergens, pathogens, and cigarette smoke can modulate multiple signaling pathways including PI3Kδ/Akt/mTOR, JAK1/2-STAT1/5, p38MAPK/JNK, Nrf2/HDAC2/c-Jun, heightened glucocorticoid receptor (GR)β/GRα ratio, and casein kinase 1 (CK1δ/ε)/cofilin 1, to induce steroid insensitivity. More recently, microRNAs such as miR-9, miR-21, and miR-126 have been implicated for corticosteroid insensitivity in asthma and COPD. Therapeutic strategies such as cytokine-specific biologics, signaling molecule-specific small molecule inhibitors, and microRNA-specific antagomir oligonucleotides are potentially promising approaches to reverse corticosteroid resistance. A panel of clinically effective drugs have shown promise in restoring steroid resistance in experimental models, and it is highly probable that some of these molecules can be successfully repositioned for the clinical use in COPD and severe asthma.

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

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

Dose-dependent modulation effects of bioactive glass particles on macrophages and diabetic wound healing

Many pathophysiologic conditions can interrupt the normal wound healing process and lead to chronic wounds due to the arrest of macrophages in their inflammatory phenotype.