The histone deacetylase Hdac7 supports LPS-inducible glycolysis and Il-1β production in murine macrophages via distinct mechanisms

Reprogramming macrophage metabolism following myocardial infarction: A neglected piece of a therapeutic opportunity

Given the global prevalence of myocardial infarction (MI) as the leading cause of mortality, there is an urgent need to devise novel strategies that target reducing infarct size, accelerating cardiac tissue repair, and preventing detrimental left ventricular (LV) remodeling. Macrophages, as a predominant type of innate immune cells, undergo metabolic reprogramming following MI, resulting in alterations in function and phenotype that significantly impact the progression of MI size and LV remodeling. This article aimed to delineate the characteristics of macrophage metabolites during reprogramming in MI and elucidate their targets and functions in cardioprotection. Furthermore, we summarize the currently proposed regulatory mechanisms of macrophage metabolic reprogramming and identify the regulators derived from endogenous products and natural small molecules. Finally, we discussed the challenges of macrophage metabolic reprogramming in the treatment of MI, with the goal of inspiring further fundamental and clinical research into reprogramming macrophage metabolism and validating its potential therapeutic targets for MI.

A novel inhibitor of class IIa histone deacetylases attenuates collagen-induced arthritis

BACKGROUND AND PURPOSE

Most inhibitors of histone deacetylases (HDACs) are not selective and are cytotoxic. Some have anti-inflammatory activity in disease models, but cytotoxicity prevents long-term uses in non-fatal diseases. Inhibitors selective for class IIa HDACs are much less cytotoxic and may have applications in management of chronic inflammatory diseases.

EXPERIMENTAL APPROACH

LL87 is a novel HDAC inhibitor examined here for HDAC enzyme selectivity. It was also investigated in macrophages for cytotoxicity and for inhibition of lipopolysaccharide (LPS)-stimulated cytokine secretion. In a rat model of collagen-induced arthritis, LL87 was investigated for effects on joint inflammation in Dark Agouti rats. Histological, immunohistochemical, micro-computed tomography and molecular analyses characterise developing arthritis and anti-inflammatory efficacy.

KEY RESULTS

LL87 was significantly more inhibitory against class IIa than class I or IIb HDAC enzymes. In macrophages, LL87 was not cytotoxic and reduced both LPS-induced secretion of pro-inflammatory cytokines, and IL6-induced class IIa HDAC activity. In rats, LL87 attenuated paw swelling and clinical signs of arthritis, reducing collagen loss and histological damage in ankle joints. LL87 decreased immune cell infiltration, especially pro-inflammatory macrophages and osteoclasts, into synovial joints and significantly reduced expression of pro-inflammatory cytokines and tissue-degrading proteases.

CONCLUSION AND IMPLICATIONS

A novel inhibitor of class IIa HDACs has been shown to have an anti-inflammatory and anti-arthritic profile distinct from current therapies. It is efficacious in reducing macrophage infiltration and joint inflammation in a chronic model of rat arthritis.

Histone deacetylase 7 activates 6-phosphogluconate dehydrogenase via an enzyme-independent mechanism that involves the N-terminal protein-protein interaction domain

Histone deacetylase 7 (HDAC7) is a member of the class IIa family of classical HDACs with important roles in cell development, differentiation, and activation, including in macrophages and other innate immune cells. HDAC7 and other class IIa HDACs act as transcriptional repressors in the nucleus but, in some cell types, they can also act in the cytoplasm to modify non-nuclear proteins and/or scaffold signalling complexes. In macrophages, HDAC7 is a cytoplasmic protein with both pro- and anti-inflammatory functions, with the latter activity involving activation of the pentose phosphate pathway (PPP) enzyme 6-phosphogluconate dehydrogenase (6PGD) and the generation of anti-inflammatory metabolite ribulose-5-phosphate. Here, we used ectopic expression systems and biochemical approaches to investigate the mechanism by which HDAC7 promotes 6PGD enzyme activity. We reveal that HDAC7 enzyme activity is not required for its activation of 6PGD and that the N-terminal protein-protein interaction domain of HDAC7 is sufficient to initiate this response. Mechanistically, the N-terminus of HDAC7 increases the affinity of 6PGD for NADP+, promotes the generation of a shorter form of 6PGD, and enhances the formation of higher order protein complexes, implicating its scaffolding function in engagement of the PPP. This contrasts with the pro-inflammatory function of HDAC7 in macrophages, in which it promotes deacetylation of the glycolytic enzyme pyruvate kinase M2 for inflammatory cytokine production.

PROTAC-Mediated HDAC7 Protein Degradation Unveils Its Deacetylase-Independent Proinflammatory Function in Macrophages

Class IIa histone deacetylases (Class IIa HDACs) play critical roles in regulating essential cellular metabolism and inflammatory pathways. However, dissecting the specific roles of each class IIa HDAC isoform is hindered by the pan-inhibitory effect of current inhibitors and a lack of tools to probe their functions beyond epigenetic regulation. In this study, a novel PROTAC-based compound B4 is developed, which selectively targets and degrades HDAC7, resulting in the effective attenuation of a specific set of proinflammatory cytokines in both lipopolysaccharide (LPS)-stimulated macrophages and a mouse model. By employing B4 as a molecular probe, evidence is found for a previously explored role of HDAC7 that surpasses its deacetylase function, suggesting broader implications in inflammatory processes. Mechanistic investigations reveal the critical involvement of HDAC7 in the Toll-like receptor 4 (TLR4) signaling pathway by directly interacting with the TNF receptor-associated factor 6 and TGFβ-activated kinase 1 (TRAF6-TAK1) complex, thereby initiating the activation of the downstream mitogen-activated protein kinase/nuclear factor-κB (MAPK/NF-κB) signaling cascade and subsequent gene transcription. This study expands the insight into HDAC7's role within intricate inflammatory networks and highlights its therapeutic potential as a novel target for anti-inflammatory treatments.

Multi-metabolomics and intestine microbiome analysis: YZC extract ameliorates septic-ALI by modulating intestine microbiota to reduce TMAO/NLRP3 signaling

BACKGROUND

Sepsis causes inflammation in response to infection, often leading to acute lung injury (ALI). Yazhicao (Commelina communis L., YZC) is widely distributed in the global tropics and has good anti-respiratory inflammatory activity; however, the protection of YZC against septic-ALI has not been established.

PURPOSE

The role of YZC in septic-ALI will be investigated in this study.

METHODS AND RESULTS

In this study, YZC was shown to inhibit excessive inflammation and alleviate septic-ALI. Network pharmacology predicts that Quercetin, Acacetin and Diosmetin have the potential to serve as the pharmacological substance basis of YZC in alleviating septic-ALI. The metabolomics results indicated that YZC could improve the metabolic disorders caused by septic-ALI, which were mostly concerned with energy metabolism and amino acid metabolism, with Trimethylamine (TMA)/Trimethylamine N-oxide (TMAO) being potential small molecule metabolic markers for the clinical diagnosis and treatment of septic-ALI. YZC inhibits the initiation and progression of septic-ALI by controlling the TMA/TMAO metabolites. Our results also suggest that YZC protects the intestinal barrier from damage. Furthermore, our research indicated that YZC reduces TMAO synthesis by inhibiting TMA production through remodeling the intestine microbiota. We investigated the mechanism of YZC-mediated protection against septic-ALI and showed that YZC reduced the expression of proteins associated with NLRP3 inflammatory vesicles in the lung by inhibiting the expression of NF-κB.

CONCLUSION

These results show that YZC inhibits the NF-κB/NLRP3 signaling pathway by regulating metabolic and intestinal flora disorders in septic-ALI mice to reduce TMAO synthesis. This study presents a theoretical groundwork for the advancement of novel medications and clinical use of YZC to enhance septic-ALI and furnishes a theoretical rationale for regulating intestinal microbiota as a therapeutic instrument to treat sepsis and septic-ALI.

Unconventional posttranslational modification in innate immunity

Pattern recognition receptors (PRRs) play a crucial role in innate immunity, and a complex network tightly controls their signaling cascades to maintain immune homeostasis. Within the modification network, posttranslational modifications (PTMs) are at the core of signaling cascades. Conventional PTMs, which include phosphorylation and ubiquitination, have been extensively studied. The regulatory role of unconventional PTMs, involving unanchored ubiquitination, ISGylation, SUMOylation, NEDDylation, methylation, acetylation, palmitoylation, glycosylation, and myristylation, in the modulation of innate immune signaling pathways has been increasingly investigated. This comprehensive review delves into the emerging field of unconventional PTMs and highlights their pivotal role in innate immunity.

HDAC7: a promising target in cancer

Histones have a vital function as components of nucleosomes, which serve as the fundamental building blocks of chromatin. Histone deacetylases (HDACs), which target histones, suppress gene transcription by compacting chromatin. This implies that HDACs have a strong connection to the suppression of gene transcription. Histone deacetylase 7 (HDAC7), a member of the histone deacetylase family, may participate in multiple cellular pathophysiological processes and activate relevant signaling pathways to facilitate the progression of different tumors by exerting deacetylation. In recent years, HDAC7 has been increasingly studied in the pathogenesis of tumors. Studies that are pertinent have indicated that it has a significant impact on the growth and metastasis of tumors, the formation of the vascular microenvironment, and the emergence of resistance to drugs. Therefore, HDAC7 could potentially function as a potent predictor for tumor prognosis and a promising target for mitigating drug resistance in tumors. This review primarily concentrates on elucidating the structure and function of HDAC7, its involvement in the development of various tumors, and its interplay with relevant signaling pathways. Meanwhile, we briefly discuss the research direction and prospect of HDAC7.

The Role of Histone Deacetylases in NLRP3 Inflammasomesmediated Epilepsy

Epilepsy is one of the most common brain disorders that not only causes death worldwide, but also affects the daily lives of patients. Previous studies have revealed that inflammation plays an important role in the pathophysiology of epilepsy. Activation of inflammasomes can promote neuroinflammation by boosting the maturation of caspase-1 and the secretion of various inflammatory effectors, including chemokines, interleukins, and tumor necrosis factors. With the in-depth research on the mechanism of inflammasomes in the development of epilepsy, it has been discovered that NLRP3 inflammasomes may induce epilepsy by mediating neuronal inflammatory injury, neuronal loss and blood-brain barrier dysfunction. Therefore, blocking the activation of the NLRP3 inflammasomes may be a new epilepsy treatment strategy. However, the drugs that specifically block NLRP3 inflammasomes assembly has not been approved for clinical use. In this review, the mechanism of how HDACs, an inflammatory regulator, regulates the activation of NLRP3 inflammasome is summarized. It helps to explore the mechanism of the HDAC inhibitors inhibiting brain inflammatory damage so as to provide a potential therapeutic strategy for controlling the development of epilepsy.

The Intertwining Roads between Psychological Distress and Gut Microbiota in Inflammatory Bowel Disease

Inflammatory bowel disease represents one of the most life-altering gastrointestinal pathologies, with its multifactorial nature and unclear physiopathology. The most relevant clinical forms, ulcerative colitis and Crohn's disease, clinically manifest with mild to severe flares and remission periods that alter the patient's social, familial and professional integration. The chronic inflammatory activity of the intestinal wall determines severe modifications of the local environment, such as dysbiosis, enteric endocrine, nervous and immune system disruptions and intestinal wall permeability changes. These features are part of the gastrointestinal ecosystem that modulates the bottom-to-top signaling to the central nervous system, leading to a neurobiologic imbalance and clinical affective and/or behavioral symptoms. The gut-brain link is a bidirectional pathway and psychological distress can also affect the central nervous system, which will alter the top-to-bottom regulation, leading to possible functional digestive symptoms and local inflammatory responses. In the middle of this neuro-gastrointestinal system, the microbiome is a key player, as its activities offer basic functional support for both relays. The present article presents current scientific information that links the pathophysiology and clinical aspects of inflammatory bowel disease and psychiatric symptomatology through the complex mechanism of the gut-brain axis and the modulatory effects of the gut microbiota.

Histone deacetylase 7: a signalling hub controlling development, inflammation, metabolism and disease

Histone deacetylases (HDACs) catalyse removal of acetyl groups from lysine residues on both histone and non-histone proteins to control numerous cellular processes. Of the 11 zinc-dependent classical HDACs, HDAC4, 5, 7 and 9 are class IIa HDAC enzymes that regulate cellular and developmental processes through both enzymatic and non-enzymatic mechanisms. Over the last two decades, HDAC7 has been associated with key roles in numerous physiological and pathological processes. Molecular, cellular, in vivo and disease association studies have revealed that HDAC7 acts through multiple mechanisms to control biological processes in immune cells, osteoclasts, muscle, the endothelium and epithelium. This HDAC protein regulates gene expression, cell proliferation, cell differentiation and cell survival and consequently controls development, angiogenesis, immune functions, inflammation and metabolism. This review focuses on the cell biology of HDAC7, including the regulation of its cellular localisation and molecular mechanisms of action, as well as its associative and causal links with cancer and inflammatory, metabolic and fibrotic diseases. We also review the development status of small molecule inhibitors targeting HDAC7 and their potential for intervention in different disease contexts.

MicroRNAs Promote the Progression of Sepsis-Induced Cardiomyopathy and Neurovascular Dysfunction Through Upregulation of NF-kappaB Signaling Pathway-Associated HDAC7/ACTN4

Introduction

The objective of this study was to determine the NF-kappaB pathway, hub genes, and transcription factors (TFs) in monocytes implicated in the progression of neurovascular-related sepsis-induced cardiomyopathy (SIC) as well as potential miRNAs with regulatory functions.

Methods

: Sepsis-induced cardiomyopathy—and heart failure (HF)-related differentially expressed genes (DEGs) between SIC and HF groups were identified separately by differential analysis. In addition, DEGs and differentially expressed miRNAs (DEmiRNAs) in monocytes between sepsis and the HC group were identified. Then, common DEGs in SIC, HF, and monocyte groups were identified by intersection analysis. Based on the functional pathways enriched by these DEGs, genes related to the NF-kB-inducing kinase (NIK)/NF-kappaB signaling pathway were selected for further intersection analysis to obtain hub genes. These common DEGs, together with sepsis-related DEmiRNAs, were used to construct a molecular interplay network and to identify core TFs in the network.

Results

: A total of 153 upregulated genes and 25 downregulated genes were obtained from SIC-, HF-, and monocyte-related DEGs. Functional pathway analysis revealed that the upregulated genes were enriched in NF-κB signaling pathway. A total of eight genes associated with NF-κB signaling pathway were then further identified from the 178 DEGs. In combination with sepsis-related DEmiRNAs, HDAC7/ACTN4 was identified as a key transcriptional regulatory pair in the progression of SIC and in monocyte regulation. hsa-miR-23a-3p, hsa-miR-3175, and hsa-miR-23b-3p can regulate the progression of SIC through the regulation of HDAC7/ACTN4. Finally, gene set enrichment analysis (GSEA) suggested that HDAC7/ACTN4 may be associated with apoptosis in addition to the inflammatory response.

Conclusion

: hsa-miR-23a-3p, hsa-miR-3175, and hsa-miR-23b-3p are involved in SIC progression by regulating NF-κB signaling signaling pathway-related HDAC7/ACTN4 in monocytes and cardiac tissue cells. These mechanisms may contribute to sepsis-induced neurovascular damage.