Validation of the epigenetic reader bromodomain-containing protein 4 (BRD4) as a therapeutic target for treatment of airway remodeling

BRD4: an effective target for organ fibrosis

Fibrosis is an excessive wound-healing response induced by repeated or chronic external stimuli to tissues, significantly impacting quality of life and primarily contributing to organ failure. Organ fibrosis is reported to cause 45% of all-cause mortality worldwide. Despite extensive efforts to develop new antifibrotic drugs, drug discovery has not kept pace with the clinical demand. Currently, only pirfenidone and nintedanib are approved by the FDA to treat pulmonary fibrotic illness, whereas there are currently no available antifibrotic drugs for hepatic, cardiac or renal fibrosis. The development of fibrosis is closely related to epigenetic alterations. The field of epigenetics primarily studies biological processes, including chromatin modifications, epigenetic readers, DNA transcription and RNA translation. The bromodomain and extra-terminal structural domain (BET) family, a class of epigenetic readers, specifically recognizes acetylated histone lysine residues and promotes the formation of transcriptional complexes. Bromodomain-containing protein 4 (BRD4) is one of the most well-researched proteins in the BET family. BRD4 is implicated in the expression of genes related to inflammation and pro-fibrosis during fibrosis. Inhibition of BRD4 has shown promising anti-fibrotic effects in preclinical studies; however, no BRD4 inhibitor has been approved for clinical use. This review introduces the structure and function of BET proteins, the research progress on BRD4 in organ fibrosis, and the inhibitors of BRD4 utilized in fibrosis. We emphasize the feasibility of targeting BRD4 as an anti-fibrotic strategy and discuss the therapeutic potential and challenges associated with BRD4 inhibitors in treating fibrotic diseases.

BRD4 as a potential target for human papillomaviruses associated cancer

Around 99% of cervical cancer and 5%-10% of human cancer are associated with human papillomaviruses (HPV). Notably, the life-cycle of HPV begins by low-level infection of the basal cells of the stratified epithelium, where the viral genomes are replicated and passed on to the daughter proliferating basal cells. The production of new viral particles remains restricted to eventually differentiated cells. HPVs support their persistent infectious cycle by hijacking pivotal pathways and cellular processes. Bromodomain-containing protein 4 (BRD4) is one of the essential cellular factors involved in multiple stages of viral transcription and replication. In this review, we demonstrate the role of BRD4 in the multiple stages of HPV infectious cycle. Also, we provide an overview of the intense research about the cellular functions of BRD4, the mechanism of action of bromodomain and extra terminal inhibitors, and how it could lead to the development of antiviral/anticancer therapies.

Sanguinarine targets BRD4 to suppress cell proliferation and migration in clear cell renal cell carcinoma

Sanguinarine is an alkaloid with diverse biological activities, nevertheless, whether it can target epigenetic modifiers remains unknown. In this study, sanguinarine was characterized as a strong BRD4 inhibitor with IC50  = 361.3 nM against BRD4 (BD1) and IC50  = 302.7 nM against BRD4 (BD2) that can inactivate BRD4 reversibly. Additional cellular assays suggested that sanguinarine can bind BRD4 in human clear cell renal cell carcinoma (ccRCC) cell line 786-O and inhibit cell growth with IC50 (24 h) = 0.6752 μM and IC50 (48 h) = 0.5959 μM in a BRD4 dependent manner partially. Meanwhile, sanguinarine can inhibit the migration of 786-O cells in vitro and in vivo, and reverse epithelial-mesenchymal transition. Moreover, it can inhibit 786-O cells proliferation in vivo in a BRD4 dependent manner partially. In sum, our study identified BRD4 as a new target of sanguinarine, and sanguinarine may serve as a potential therapeutic agent against ccRCC.

BRD4 as a Therapeutic Target in Pulmonary Diseases

Bromodomain and extra-terminal domain (BET) proteins are epigenetic modulators that regulate gene transcription through interacting with acetylated lysine residues of histone proteins. BET proteins have multiple roles in regulating key cellular functions such as cell proliferation, differentiation, inflammation, oxidative and redox balance, and immune responses. As a result, BET proteins have been found to be actively involved in a broad range of human lung diseases including acute lung inflammation, asthma, pulmonary arterial hypertension, pulmonary fibrosis, and chronic obstructive pulmonary disease (COPD). Due to the identification of specific small molecular inhibitors of BET proteins, targeting BET in these lung diseases has become an area of increasing interest. Emerging evidence has demonstrated the beneficial effects of BET inhibitors in preclinical models of various human lung diseases. This is, in general, largely related to the ability of BET proteins to bind to promoters of genes that are critical for inflammation, differentiation, and beyond. By modulating these critical genes, BET proteins are integrated into the pathogenesis of disease progression. The intrinsic histone acetyltransferase activity of bromodomain-containing protein 4 (BRD4) is of particular interest, seems to act independently of its bromodomain binding activity, and has implication in some contexts. In this review, we provide a brief overview of the research on BET proteins with a focus on BRD4 in several major human lung diseases, the underlying molecular mechanisms, as well as findings of targeting BET proteins using pharmaceutical inhibitors in different lung diseases preclinically.

Drug Discovery Targeting Nuclear Receptor Binding SET Domain Protein 2 (NSD2)

Nuclear receptor binding SET domain proteins (NSDs) catalyze the mono- or dimethylation of histone 3 lysine 36 (H3K36me1 and H3K36me2), using S-adenosyl-l-methionine (SAM) as a methyl donor. As a key member of the NSD family of proteins, NSD2 plays an important role in the pathogenesis and progression of various diseases such as cancers, inflammations, and infectious diseases, serving as a promising drug target. Developing potent and specific NSD2 inhibitors may provide potential novel therapeutics. Several NSD2 inhibitors and degraders have been discovered while remaining in the early stage of drug development. Excitingly, KTX-1001, a selective NSD2 inhibitor, has entered clinical trials. In this Perspective, the structures and functions of NSD2, its roles in various human diseases, and the recent advances in drug discovery strategies targeting NSD2 have been summarized. The challenges, opportunities, and future directions for developing NSD2 inhibitors and degraders are also discussed.

Novel formats of antibody conjugates: recent advances in payload diversity, conjugation, and linker chemistry

INTRODUCTION

In the field of bioconjugates, the focus on antibody - drug conjugates (ADCs) with novel payloads beyond the traditional categories of potent cytotoxic agents is increasing. These innovative ADCs exhibit various molecular formats, ranging from small-molecule payloads, such as immune agonists and proteolytic agents, to macromolecular payloads, such as oligonucleotides and proteins.

AREAS COVERED

This review offers an in-depth exploration of unconventional strategies for designing conjugates with novel mechanisms of action and notable examples of approaches that show promising prospects. Representative examples of novel format payloads and their classification, attributes, and appropriate conjugation techniques are discussed in detail.

EXPERT OPINION

The existing basic technologies used to manufacture ADCs can be directly applied to synthesize novel formatted conjugates. However, a wide variety of new payloads require the creation of customized technologies adapted to the unique characteristics of these payloads. Consequently, fundamental technologies, such as conjugation methods aimed at achieving high drug - antibody ratios and developing stable crosslinkers, are likely to become increasingly important research areas in the future.

BRD4 is involved in viral exacerbation of chronic obstructive pulmonary disease

BACKGROUND

Our previous studies have suggested that bromodomain protein 4 (BRD4) is increased in the lung of stable chronic obstructive pulmonary disease (COPD) patients, which has been shown to be involved in inflammatory responses. We investigated its role in the viral exacerbation of COPD.

METHODS

BRD4, interleukin (IL)-6 and IL-8 were measured in the blood and sputum of stable COPD patients and patients with viral exacerbation. Mice were exposed to cigarette smoke (CS) and/or infected with influenza virus as an in vivo model. BRD4, IL-6 and keratinocyte-derived chemokine (KC) were measured in the lung. BEAS-2B cells were treated with CS extract and/or influenza virus as an in vitro model. BRD4, IL-6 and IL-8 were measured in the cells and/or culture supernatant.

RESULTS

BRD4 was increased in COPD patients with viral exacerbation compared with those in stable condition and its expression was correlated with IL-6 and IL-8 expression. Inflammatory cells, IL-6, KC and BRD4 were synergistically induced in the lung of mice by viral infection and CS exposure, and the former three were decreased by JQ1 (BRD4 inhibitor) treatment. IL-6, IL-8 and BRD4 were significantly induced by CS extract and influenza virus in bronchial epithelial cells, and this upregulation was suppressed by knockdown of BRD4 expression.

CONCLUSIONS

Our findings indicate that CS and viruses may synergistically induce IL-6 and IL-8 expression through their synergistic induction of BRD4 expression, which might contribute to the enhanced inflammatory response in the viral exacerbation of COPD.

Bromodomain-containing protein 4 (BRD4): a key player in inflammatory bowel disease and potential to inspire epigenetic therapeutics

INTRODUCTION

Inflammatory bowel diseases (IBDs) are debilitating chronic inflammatory disorders with increasing prevalence worldwide. Epigenetic regulator bromodomain-containing protein 4 (BRD4) is critical in controlling gene expression of IBD-associated inflammatory cytokine networks. BRD4 as a promising therapeutic target is also tightly associated with many other diseases, such as airway inflammation and fibrosis, cancers, infectious diseases and central nervous system disorders.

AREAS COVERED

This review briefly summarized the critical role of BRD4 in the pathogenesis of IBDs and the current clinical landscape of developing bromodomain and extra terminal domain (BET) inhibitors. The challenges and opportunities as well as future directions of targeting BRD4 inhibition for potential IBD medications were also discussed.

EXPERT OPINION

Targeting BRD4 with potent and specific inhibitors may offer novel effective therapeutics for IBD patients, particularly those who are refractory to anti-TNFα therapy and IBD-related profibrotic. Developing highly specific BRD4 inhibitors for IBD medications may help erase the drawbacks of most current pan-BET/BRD4 inhibitors, such as off-target effects, poor oral bioavailability, and low gut mucosal absorbance. Novel strategies such as combinatorial therapy, BRD4-based dual inhibitors and proteolysis targeting chimeras (PROTACs) may also have great potential to mitigate side effects and overcome drug resistance during IBD treatment.

Inhibition of BET Family Proteins Suppresses African Swine Fever Virus Infection

African swine fever (ASF), an acute, severe, highly contagious disease caused by African swine fever virus (ASFV) infection in domestic pigs and boars, has a mortality rate of up to 100%. Because effective vaccines and treatments for ASF are lacking, effective control of the spread of ASF remains a great challenge for the pig industry. Host epigenetic regulation is essential for the viral gene transcription. Bromodomain and extraterminal (BET) family proteins, including BRD2, BRD3, BRD4, and BRDT, are epigenetic "readers" critical for gene transcription regulation. Among these proteins, BRD4 recognizes acetylated histones via its two bromodomains (BD1 and BD2) and recruits transcription factors, thereby playing a pivotal role in transcriptional regulation and chromatin remodeling during viral infection. However, how BET/BRD4 regulates ASFV replication and gene transcription is unknown. Here, we randomly selected 12 representative BET family inhibitors and compared their effects on ASFV infection in pig primary alveolar macrophages (PAMs). These were found to inhibit viral infection by interfering viral replication. The four most effective inhibitors (ARV-825, ZL0580, I-BET-762, and PLX51107) were selected for further antiviral activity analysis. These BET/BRD4 inhibitors dose dependently decreased the ASFV titer, viral RNA transcription, and protein production in PAMs. Collectively, we report novel function of BET/BRD4 inhibitors in inducing suppression of ASFV infection, providing insights into the role of BET/BRD4 in the epigenetic regulation of ASFV and potential new strategies for ASF prevention and control. IMPORTANCE Due to the continuing spread of the ASFV in the world and the lack of commercial vaccines, the development of improved control strategies, including antiviral drugs, is urgently needed. BRD4 is an important epigenetic factor and has been commonly used for drug development for tumor treatment. Furthermore, the latest research showed that BET/BRD4 inhibition could suppress replication of virus. In this study, we first showed the inhibitory effect of agents targeting BET/BRD4 on ASFV infection with no significant host cytotoxicity. Then, we found four BET/BRD4 inhibitors that can inhibit ASFV replication, RNA transcription, and protein synthesis. Our findings support the hypothesis that BET/BRD4 can be considered as attractive host targets in antiviral drug discovery against ASFV.

Selective Inhibition of Bromodomain-Containing Protein 4 Reduces Myofibroblast Transdifferentiation and Pulmonary Fibrosis

Idiopathic pulmonary fibrosis is a lethal disease driven by myofibroblast expansion. Currently no therapies exist that target the epigenetic mechanisms controlling myofibroblast transdifferentiation, which is responsible for unregulated extracellular matrix (ECM) production. We have recently shown that bromodomain-containing protein 4 (BRD4), an epigenetic regulator that forms a scaffold for nuclear activators and transcription factors, is essential for TGFβ-induced myofibroblast transdifferentiation. However, its role in the development and progression of pulmonary fibrosis in vivo has not been established. Here, we evaluate the hypothesis that BRD4 bromodomain interactions mediate myofibroblast expansion and fibrosing disease in vivo. C57BL/6J mice challenged with intratracheal bleomycin were systemically treated with a selective allosteric inhibitor of the BRD4 bromodomain 1 (BD1), ZL0591 (10 mg/kg), during the established fibrotic phase (14 days post-bleomycin) in a rigorous therapeutic paradigm. Eleven days after initiation of ZL0591 treatment (25 days post-bleomycin), we detected a significant improvement in blood O2 saturation compared to bleomycin/vehicle control. Twenty-eight days post-bleomycin, we observed a reduction in the volumetric Hounsfield Unit (HU) density by micro computed tomography (µCT) in the ZL0591-treated group, as well as a reduction in collagen deposition (hydroxyproline content) and severity of injury (Ashcroft scoring). Myofibroblast transdifferentiation was measured by smooth muscle α-actin (αSMA) staining, indicating a loss of this cell population in the ZL0591-treated group, and corresponded to reduced transcript levels of myofibroblast-associated extracellular matrix genes, tenascin-C and collagen 1α1. We conclude that BRD4 BD1 interactions are critical for myofibroblast transdifferentiation and fibrotic progression in a mouse model of pulmonary fibrosis.

Discovery, X-ray Crystallography, and Anti-inflammatory Activity of Bromodomain-containing Protein 4 (BRD4) BD1 Inhibitors Targeting a Distinct New Binding Site

Bromodomain-containing protein 4 (BRD4) is an emerging epigenetic drug target for intractable inflammatory disorders. The lack of highly selective inhibitors among BRD4 family members has stalled the collective understanding of this critical system and the progress toward clinical development of effective therapeutics. Here we report the discovery of a potent BRD4 bromodomain 1 (BD1)-selective inhibitor ZL0590 (52) targeting a unique, previously unreported binding site, while exhibiting significant anti-inflammatory activities in vitro and in vivo. The X-ray crystal structural analysis of ZL0590 in complex with human BRD4 BD1 and the associated mutagenesis study illustrate a first-in-class nonacetylated lysine (KAc) binding site located at the helix αB and αC interface that contains important BRD4 residues (e.g., Glu151) not commonly shared among other family members and is spatially distinct from the classic KAc recognition pocket. This new finding facilitates further elucidation of the complex biology underpinning bromodomain specificity among BRD4 and its protein-protein interaction partners.

Discovery of 1-(5-(1H-benzo[d]imidazole-2-yl)-2,4-dimethyl-1H-pyrrol-3-yl)ethan-1-one derivatives as novel and potent bromodomain and extra-terminal (BET) inhibitors with anticancer efficacy

As epigenetic readers, bromodomain and extra-terminal domain (BET) family proteins bind to acetylated-lysine residues in histones and recruit protein complexes to promote transcription initiation and elongation. Inhibition of BET bromodomains by small molecule inhibitors has emerged as a promising therapeutic strategy for cancer. Herein, we describe our efforts toward the discovery of a novel series of 1-(5-(1H-benzo[d]imidazole-2-yl)-2,4-dimethyl-1H-pyrrol-3-yl)ethan-1-one derivatives as BET inhibitors. Intensive structural modifications led to the identification of compound 35f as the most active inhibitor of BET BRD4 with selectivity against BET family proteins. Further biological studies revealed that compound 35f can arrest the cell cycle in G₀/G₁ phase and induce apoptosis via decreasing the expression of c-Myc and other proteins related to cell cycle and apoptosis. More importantly, compound 35f showed favorable pharmacokinetic properties and antitumor efficacy in MV4-11 mouse xenograft model with acceptable tolerability. These results indicated that BET inhibitors could be potentially used to treat hematologic malignancies and some solid tumors.

The binding mechanism of NHWD-870 to bromodomain-containing protein 4 based on molecular dynamics simulations and free energy calculation

Bromodomain and extra-terminal (BET) proteins (BRD2, BRD3, BRD4, and BRDT) are epigenetic readers with tandem bromodomains.

Target-Based Small Molecule Drug Discovery Towards Novel Therapeutics for Inflammatory Bowel Diseases

Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), is a class of severe and chronic diseases of the gastrointestinal (GI) tract with recurrent symptoms and significant morbidity. Long-term persistence of chronic inflammation in IBD is a major contributing factor to neoplastic transformation and the development of colitis-associated colorectal cancer. Conversely, persistence of transmural inflammation in CD is associated with formation of fibrosing strictures, resulting in substantial morbidity. The recent introduction of biological response modifiers as IBD therapies, such as antibodies neutralizing tumor necrosis factor (TNF)-α, have replaced nonselective anti-inflammatory corticosteroids in disease management. However, a large proportion (~40%) of patients with the treatment of anti-TNF-α antibodies are discontinued or withdrawn from therapy because of (1) primary nonresponse, (2) secondary loss of response, (3) opportunistic infection, or (4) onset of cancer. Therefore, the development of novel and effective therapeutics targeting specific signaling pathways in the pathogenesis of IBD is urgently needed. In this comprehensive review, we summarize the recent advances in drug discovery of new small molecules in preclinical or clinical development for treating IBD that target biologically relevant pathways in mucosal inflammation. These include intracellular enzymes (Janus kinases, receptor interacting protein, phosphodiesterase 4, IκB kinase), integrins, G protein-coupled receptors (S1P, CCR9, CXCR4, CB2) and inflammasome mediators (NLRP3), etc. We will also discuss emerging evidence of a distinct mechanism of action, bromodomain-containing protein 4, an epigenetic regulator of pathways involved in the activation, communication, and trafficking of immune cells. We highlight their chemotypes, mode of actions, structure-activity relationships, characterizations, and their in vitro/in vivo activities and therapeutic potential. The perspectives on the relevant challenges, new opportunities, and future directions in this field are also discussed.

Research-Based Product Innovation to Address Critical Unmet Needs of Patients with Inflammatory Bowel Diseases

Despite progress in recent decades, patients with inflammatory bowel diseases face many critical unmet needs, demonstrating the limitations of available treatment options. Addressing these unmet needs will require interventions targeting multiple aspects of inflammatory bowel disease pathology, including disease drivers that are not targeted by available therapies. The vast majority of late-stage investigational therapies also focus primarily on a narrow range of fundamental mechanisms. Thus, there is a pressing need to advance to clinical stage differentiated investigational therapies directly targeting a broader range of key mechanistic drivers of inflammatory bowel diseases. In addition, innovations are critically needed to enable treatments to be tailored to the specific underlying abnormal biological pathways of patients; interventions with improved safety profiles; biomarkers to develop prognostic, predictive, and monitoring tests; novel devices for nonpharmacological approaches such as minimally invasive monitoring; and digital health technologies. To address these needs, the Crohn's & Colitis Foundation launched IBD Ventures, a venture philanthropy-funding mechanism, and IBD Innovate®, an innovative, product-focused scientific conference. This special IBD Innovate® supplement is a collection of articles reflecting the diverse and exciting research and development that is currently ongoing in the inflammatory bowel disease field to deliver innovative and differentiated products addressing critical unmet needs of patients. Here, we highlight the pipeline of new product opportunities currently advancing at the preclinical and early clinical development stages. We categorize and describe novel and differentiated potential product opportunities based on their potential to address the following critical unmet patient needs: (1) biomarkers for prognosis of disease course and prediction/monitoring of treatment response; (2) restoration of eubiosis; (3) restoration of barrier function and mucosal healing; (4) more effective and safer anti-inflammatories; (5) neuromodulatory and behavioral therapies; (6) management of disease complications; and (7) targeted drug delivery.

Bromodomain Containing Protein 4 (BRD4) Regulates Expression of its Interacting Coactivators in the Innate Response to Respiratory Syncytial Virus

Bromodomain-containing protein 4 plays a central role in coordinating the complex epigenetic component of the innate immune response. Previous studies implicated BRD4 as a component of a chromatin-modifying complex that is dynamically recruited to a network of protective cytokines by binding activated transcription factors, polymerases, and histones to trigger their rapid expression via transcriptional elongation. Our previous study extended our understanding of the airway epithelial BRD4 interactome by identifying over 100 functionally important coactivators and transcription factors, whose association is induced by respiratory syncytial virus (RSV) infection. RSV is an etiological agent of recurrent respiratory tract infections associated with exacerbations of chronic obstructive pulmonary disease. Using a highly selective small-molecule BRD4 inhibitor (ZL0454) developed by us, we extend these findings to identify the gene regulatory network dependent on BRD4 bromodomain (BD) interactions. Human small airway epithelial cells were infected in the absence or presence of ZL0454, and gene expression profiling was performed. A highly reproducible dataset was obtained which indicated that BRD4 mediates both activation and repression of RSV-inducible gene regulatory networks controlling cytokine expression, interferon (IFN) production, and extracellular matrix remodeling. Index genes of functionally significant clusters were validated independently. We discover that BRD4 regulates the expression of its own gene during the innate immune response. Interestingly, BRD4 activates the expression of NFκB/RelA, a coactivator that binds to BRD4 in a BD-dependent manner. We extend this finding to show that BRD4 also regulates other components of its functional interactome, including the Mediator (Med) coactivator complex and the SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin (SMARC) subunits. To provide further insight into mechanisms for BRD4 in RSV expression, we mapped 7,845 RSV-inducible Tn5 transposase peaks onto the BRD4-dependent gene bodies. These were located in promoters and introns of cytostructural and extracellular matrix (ECM) formation genes. These data indicate that BRD4 mediates the dynamic response of airway epithelial cells to RNA infection by modulating the expression of its coactivators, controlling the expression of host defense mechanisms and remodeling genes through changes in promoter accessibility.

Dual-target inhibitors of bromodomain and extra-terminal proteins in cancer: A review from medicinal chemistry perspectives

Bromodomain-containing protein 4 (BRD4), as the most studied member of the bromodomain and extra-terminal (BET) family, is a chromatin reader protein interpreting epigenetic codes through binding to acetylated histones and non-histone proteins, thereby regulating diverse cellular processes including cell cycle, cell differentiation, and cell proliferation. As a promising drug target, BRD4 function is closely related to cancer, inflammation, cardiovascular disease, and liver fibrosis. Currently, clinical resistance to BET inhibitors has limited their applications but synergistic antitumor effects have been observed when used in combination with other tumor inhibitors targeting additional cellular components such as PLK1, HDAC, CDK, and PARP1. Therefore, designing dual-target inhibitors of BET bromodomains is a rational strategy in cancer treatment to increase potency and reduce drug resistance. This review summarizes the protein structures and biological functions of BRD4 and discusses recent advances of dual BET inhibitors from a medicinal chemistry perspective. We also discuss the current design and discovery strategies for dual BET inhibitors, providing insight into potential discovery of additional dual-target BET inhibitors.

The Underappreciated Role of Epithelial Mesenchymal Transition in Chronic Obstructive Pulmonary Disease and Its Strong Link to Lung Cancer

The World Health Organisation reported COPD to be the third leading cause of death globally in 2019, and in 2020, the most common cause of cancer death was lung cancer; when these linked conditions are added together they come near the top of the leading causes of mortality. The cell-biological program termed epithelial-to-mesenchymal transition (EMT) plays an important role in organ development, fibrosis and cancer progression. Over the past decade there has emerged a substantial literature that also links EMT specifically to the pathophysiology of chronic obstructive pulmonary disease (COPD) as primarily an airway fibrosis disease; COPD is a recognised strong independent risk factor for the development of lung cancer, over and above the risks associated with smoking. In this review, our primary focus is to highlight these linkages and alert both the COPD and lung cancer fields to these complex interactions. We emphasise the need for inter-disciplinary attention and research focused on the likely crucial roles of EMT (and potential for its inhibition) with recognition of its strategic place mechanistically in both COPD and lung cancer. As part of this we discuss the future potential directions for novel therapeutic opportunities, including evidence-based strategic repurposing of currently used familiar/approved medications.

Fully integrating pathophysiological insights in COPD: an updated working disease model to broaden therapeutic vision

Our starting point is that relatively new findings into the pathogenesis and pathophysiology of airway disease in smokers that lead to chronic obstructive pulmonary disease (COPD) need to be reassessed as a whole and integrated into "mainstream" thinking along with traditional concepts which have stood the test of time. Such a refining of the accepted disease paradigm is urgently needed as thinking on therapeutic targets is currently under active reconsideration. We feel that generalised airway wall "inflammation" is unduly over-emphasised, and highlight the patchy and variable nature of the pathology (with the core being airway remodelling). In addition, we present evidence for airway wall disease in smokers/COPD as including a hypocellular, hypovascular, destructive, fibrotic pathology, with a likely spectrum of epithelial-mesenchymal transition states as significant drivers of this remodelling. Furthermore, we present data from a number of research modalities and integrate this with the aetiology of lung cancer, the role of chronic airway luminal colonisation/infection by a specific group of "respiratory" bacteria in smokers (which results in luminal inflammation) and the central role for oxidative stress on the epithelium. We suggest translation of these insights into more focus on asymptomatic smokers and early COPD, with the potential for fresh preventive and therapeutic approaches.

Discovery of benzo[f]pyrido[4,3-b][1,4]oxazepin-10-one derivatives as orally available bromodomain and extra-terminal domain (BET) inhibitors with efficacy in an in vivo psoriatic animal model

Bromodomain and extra-terminal domain (BET) protein plays an important role in epigenetic regulation, and the regulation of disruption contributes to the pathogenesis of cancer and inflammatory disease. With the goal of discovering novel BET inhibitors, especially BRD4 inhibitors, we designed and synthesized several compounds starting from our previously reported pyrido-benzodiazepinone derivative 4 to enhance BRD4 inhibitory activity while avoiding hERG inhibition. Molecular docking studies and structure-activity relationship studies led to the identification of 9-fluorobenzo[f]pyrido[4,3-b][1,4]oxazepin-10-one derivative 43, which exhibited potent BRD4 inhibitory activity with excellent potency in imiquimod-induced psoriasis model mice.

Epigenetics and expression of key genes associated with cardiac fibrosis: NLRP3, MMP2, MMP9, CCN2/CTGF and AGT

Aims:

Excessive inflammatory signaling and pathological remodeling of the extracellular matrix drive cardiac fibrosis and require changes in gene expression.

Materials and methods:

Using bioinformatics, both tissue-specific expression profiles and epigenomic profiles of some genes critical for cardiac fibrosis were examined, namely, NLRP3, MMP2, MMP9, CCN2/CTGF, AGT (encodes angiotensin II precursors) and hsa-mir-223 (post-transcriptionally regulates NLRP3).

Results:

In monocytes, neutrophils, fibroblasts, venous cells, liver and brain, enhancers or super-enhancers were found that correlate with high expression of these genes. One enhancer extended into a silent gene neighbor. These enhancers harbored tissue-specific foci of DNA hypomethylation, open chromatin and transcription factor binding.

Conclusions:

This study identified previously undescribed enhancers containing hypomethylated transcription factor binding subregions that are predicted to regulate expression of these cardiac fibrosis-inducing genes.

Binding selectivity of inhibitors toward the first over the second bromodomain of BRD4: theoretical insights from free energy calculations and multiple short molecular dynamics simulations

Bromodomain-containing protein 4 (BRD4) plays an important role in mediating gene transcription involved in cancers and non-cancer diseases such as acute heart failure and inflammatory diseases. In this work, multiple short molecular dynamics (MSMD) simulations are integrated with a molecular mechanics generalized Born surface area (MM-GBSA) approach to decipher binding selectivity of three inhibitors 8NS, 82Y, and 837 toward two domains BD1 and BD2 of BRD4. The results demonstrate that the enthalpy effects play critical roles in selectivity identification of inhibitors toward BD1 and BD2, determining that 8NS has better selectivity toward BD2 than BD1, while 82Y and 837 more favorably bind to BD1 than BD2. A residue-based free-energy decomposition method was used to calculate an inhibitor-residue interaction spectrum and unveil contributions of separate residues to binding selectivity. The results identify six common residues, containing (P82, P375), (V87, V380), (L92, L385), (L94, L387), (N140, N433), and (I146, V439) individually belonging to (BD1, BD2) of BRD4, and yield a considerable binding difference of inhibitors to BD1 and BD2, suggesting that these residues play key roles in binding selectivity of inhibitors toward BD1 and BD2 of BRD4. Therefore, these results provide useful dynamics information and a structure affinity relationship for the development of highly selective inhibitors targeting BD1 and BD2 of BRD4.

Nanoapproaches to Modifying Epigenetics of Epithelial Mesenchymal Transition for Treatment of Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a chronically progressive interstitial lung that affects over 3 M people worldwide and rising in incidence. With a median survival of 2-3 years, IPF is consequently associated with high morbidity, mortality, and healthcare burden. Although two antifibrotic therapies, pirfenidone and nintedanib, are approved for human use, these agents reduce the rate of decline of pulmonary function but are not curative and do not reverse established fibrosis. In this review, we discuss the prevailing epithelial injury hypothesis, wherein pathogenic airway epithelial cell-state changes known as Epithelial Mesenchymal Transition (EMT) promotes the expansion of myofibroblast populations. Myofibroblasts are principal components of extracellular matrix production that result in airspace loss and mortality. We review the epigenetic transition driving EMT, a process produced by changes in histone acetylation regulating mesenchymal gene expression programs. This mechanistic work has focused on the central role of bromodomain-containing protein 4 in mediating EMT and myofibroblast transition and initial preclinical work has provided evidence of efficacy. As nanomedicine presents a promising approach to enhancing the efficacy of such anti-IPF agents, we then focus on the state of nanomedicine formulations for inhalable delivery in the treatment of pulmonary diseases, including liposomes, polymeric nanoparticles (NPs), inorganic NPs, and exosomes. These nanoscale agents potentially provide unique properties to existing pulmonary therapeutics, including controlled release, reduced systemic toxicity, and combination delivery. NP-based approaches for pulmonary delivery thus offer substantial promise to modify epigenetic regulators of EMT and advance treatments for IPF.

Suppression of bromodomain-containing protein 4 protects trophoblast cells from oxidative stress injury by enhancing Nrf2 activation

Oxidative stress is considered a key hallmark of preeclampsia, which causes the dysregulation of trophoblast cells, and it contributes to the pathogenesis of preeclampsia. Emerging evidence has suggested bromodomain-containing protein 4 (BRD4) as a key regulator of oxidative stress in multiple cell types. However, whether BRD4 participates in regulating oxidative stress in trophoblast cells remains undetermined. The current study was designed to explore the potential function of BRD4 in the regulation of oxidative stress in trophoblast cells. Our data revealed that BRD4 expression was elevated in trophoblast cells stimulated with hydrogen peroxide. Exposure to hydrogen peroxide caused marked decreases in the levels of proliferation and invasion but promoted apoptosis and the production of ROS in trophoblast cells. Knockdown of BRD4, or treatment with a BRD4 inhibitor, markedly increased the levels of cell proliferation and invasion and decreased apoptosis and ROS production following the hydrogen peroxide challenge. Further data indicated that suppression of BRD4 markedly decreased the expression levels of Keap1, but increased the nuclear expression of Nrf2 and enhanced Nrf2-mediated transcriptional activity. BRD4 inhibition-mediated protective effects were markedly reversed by Keap1 overexpression or Nrf2 inhibition. Overall, these results demonstrated that BRD4 inhibition attenuated hydrogen peroxide-induced oxidative stress injury in trophoblast cells by enhancing Nrf2 activation via the downregulation of Keap1. Our study highlights the potential importance of the BRD4/Keap1/Nrf2 axis in the modulation of the oxidative stress response in trophoblast cells. Targeted inhibition of BRD4 may offer new opportunities for the development of innovative therapeutic approaches to treat preeclampsia.

Status and prospects: personalized treatment and biomarker for airway remodeling in asthma

Airway remodeling, as a major characteristic of bronchial asthma, is critical to the progression of this disease, whereas it is of less importance in clinical management. Complying with the current stepwise treatment standard for asthma, the choice of intervention on the clinical status is primarily determined by the patient’s treatment response to airway inflammation. However, a considerable number of asthmatic patients, especially severe asthmatic subjects, remain uncontrolled though they have undergone fortified anti-inflammation treatment. In the past few years, a growing number of biologics specific to asthma phenotypes have emerged, bringing new hope for patients with refractory asthma and severe asthma. While at the same time, the effect of airway remodeling on asthma treatment has become progressively prominent. In the era of personalized treatment, it has become one of the development directions for asthma treatment to find reliable airway remodeling biomarkers to assist in asthma phenotypes classification, and to further combine multiple phenotypes to accurately treat patients. In the present study, the research status of airway remodeling in asthma is reviewed to show the basis for classifying and treating such disease. Besides, several selected airway remodeling biomarkers and possibility to use them in individual treatment are discussed as well. This study considers that continuously optimized mechanisms and emerging biomarkers for airway remodeling in the future may further support individual therapy for asthma patients.

Inhibition of Brd4 by JQ1 Promotes Functional Recovery From Spinal Cord Injury by Activating Autophagy

Spinal cord injury (SCI) is a destructive neurological disorder that is characterized by impaired sensory and motor function. Inhibition of bromodomain protein 4 (Brd4) has been shown to promote the maintenance of cell homeostasis by activating autophagy. However, the role of Brd4 inhibition in SCI and the underlying mechanisms are poorly understood. Thus, the goal of the present study was to evaluate the effects of sustained Brd4 inhibition using the bromodomain and extraterminal domain (BET) inhibitor JQ1 on the regulation of apoptosis, oxidative stress and autophagy in a mouse model of SCI. First, we observed that Brd4 expression at the lesion sites of mouse spinal cords increased after SCI. Treatment with JQ1 significantly decreased the expression of Brd4 and improved functional recovery for up to 28 day after SCI. In addition, JQ1-mediated inhibition of Brd4 reduced oxidative stress and inhibited the expression of apoptotic proteins to promote neural survival. Our results also revealed that JQ1 treatment activated autophagy and restored autophagic flux, while the positive effects of JQ1 were abrogated by autophagy inhibitor 3-MA intervention, indicating that autophagy plays a crucial role in therapeutic effects Brd4 induced by inhibition of the functional recovery SCI. In the mechanistic analysis, we observed that modulation of the AMPK-mTOR-ULK1 pathway is involved in the activation of autophagy mediated by Brd4 inhibition. Taken together, the results of our investigation provides compelling evidence that Brd4 inhibition by JQ1 promotes functional recovery after SCI and that Brd4 may serve as a potential target for SCI treatment.

A Bromodomain-Containing Protein 4 (BRD4) Inhibitor Suppresses Angiogenesis by Regulating AP-1 Expression

Angiogenesis dysregulation contributes to inflammation, infections, immune disorders, and carcinogenesis. Bromodomain-containing protein 4 (BRD4) is an epigenetic reader that recognizes histone proteins and acts as a transcriptional regulator to trigger tumor growth and the inflammatory response. The pan-bromodomain and extra-terminal domain (BET) inhibitor, (+)-JQ1 (1), was reported to inhibit angiogenesis. However, owing to the non-selectivity action of (+)-JQ1 towards all BET family members, the role of BRD4 and that of its bromodomains (BD1 and BD2) in angiogenesis remains elusive. Herein, we identified a potent BRD4 inhibitor, ZL0513 (7), which exhibited significant anti-angiogenic effects in chick embryo chorioallantoic membrane (CAM) and yolk sac membrane (YSM) models. This inhibitor also directly suppressed the viability and tube formation of human umbilical vascular endothelial cells (HUVECs). Moreover, ZL0513 (7) was found to inhibit the phosphorylation of c-jun and c-fos, important members of activating protein-1 (AP-1) transcription factor complexes that enhance angiogenesis. The findings on this novel BRD4 inhibitor indicate that, in addition to being a powerful pharmacological tool for further elucidating the roles and functions of BRD4 and its BD domains in angiogenesis, it may serve as a potential therapeutic strategy for targeting the vasculature in various angiogenesis-dysregulated human diseases.

Discovery of Orally Bioavailable Chromone Derivatives as Potent and Selective BRD4 Inhibitors: Scaffold Hopping, Optimization, and Pharmacological Evaluation

Bromodomain-containing protein 4 (BRD4) represents a promising drug target for anti-inflammatory therapeutics. Herein, we report the design, synthesis, and pharmacological evaluation of novel chromone derivatives via scaffold hopping to discover a new class of orally bioavailable BRD4-selective inhibitors. Two potent BRD4 bromodomain 1 (BD1)-selective inhibitors 44 (ZL0513) and 45 (ZL0516) have been discovered with high binding affinity (IC₅₀ values of 67-84 nM) and good selectivity over other BRD family proteins and distant BD-containing proteins. Both compounds significantly inhibited the expression of Toll-like receptor-induced inflammatory genes in vitro and airway inflammation in murine models. The cocrystal structure of 45 in complex with human BRD4 BD1 at a high resolution of 2.0 Å has been solved, offering a solid structural basis for its binding validation and further structure-based optimization. These BRD4 BD1 inhibitors demonstrated impressive in vivo efficacy and overall promising pharmacokinetic properties, indicating their therapeutic potential for the treatment of inflammatory diseases.