Chronic inflammation of pancreatic islets is a key driver of β-cell damage that can lead to autoreactivity and the eventual onset of autoimmune diabetes (T1D). In the islet, elevated levels of ...proinflammatory cytokines induce the transcription of the inducible nitric oxide synthase (iNOS) gene,
, ultimately resulting in increased nitric oxide (NO). Excessive or prolonged exposure to NO causes β-cell dysfunction and failure associated with defects in mitochondrial respiration. Recent studies showed that inhibition of the bromodomain and extraterminal domain (BET) family of proteins, a druggable class of epigenetic reader proteins, prevents the onset and progression of T1D in the non-obese diabetic mouse model. We hypothesized that BET proteins co-activate transcription of cytokine-induced inflammatory gene targets in β-cells and that selective, chemotherapeutic inhibition of BET bromodomains could reduce such transcription. Here, we investigated the ability of BET bromodomain small molecule inhibitors to reduce the β-cell response to the proinflammatory cytokine interleukin 1 beta (IL-1β). BET bromodomain inhibition attenuated IL-1β-induced transcription of the inflammatory mediator
and consequent iNOS protein and NO production. Reduced
transcription is consistent with inhibition of NF-κB facilitated by disrupting the interaction of a single BET family member, BRD4, with the NF-κB subunit, p65. Using recently reported selective inhibitors of the first and second BET bromodomains, inhibition of only the first bromodomain was necessary to reduce the interaction of BRD4 with p65 in β-cells. Moreover, inhibition of the first bromodomain was sufficient to mitigate IL-1β-driven decreases in mitochondrial oxygen consumption rates and β-cell viability. By identifying a role for the interaction between BRD4 and p65 in controlling the response of β-cells to proinflammatory cytokines, we provide mechanistic information on how BET bromodomain inhibition can decrease inflammation. These studies also support the potential therapeutic application of more selective BET bromodomain inhibitors in attenuating β-cell inflammation.
Studies investigating the causes of autism spectrum disorder (ASD) point to genetic, as well as epigenetic, mechanisms of the disease. Identification of epigenetic processes that contribute to ASD ...development and progression is of major importance and may lead to the development of novel therapeutic strategies. Here, we identify the bromodomain and extraterminal domain-containing proteins (BETs) as epigenetic regulators of genes involved in ASD-like behaviors in mice. We found that the pharmacological suppression of BET proteins in the brain of young mice, by the novel, highly specific, brain-permeable inhibitor I-BET858 leads to selective suppression of neuronal gene expression followed by the development of an autism-like syndrome. Many of the I-BET858-affected genes have been linked to ASD in humans, thus suggesting the key role of the BET-controlled gene network in the disorder. Our studies suggest that environmental factors controlling BET proteins or their target genes may contribute to the epigenetic mechanism of ASD.
Display omitted
•Bromodomains are an exciting and important target class for drug discovery.•Multiple small molecule BET bromodomain inhibitors undergoing clinical trials with encouraging emerging ...data.•High quality chemical probes are an important tool for the target validation of non-BET bromodomains.•Increasing number of non-BET bromodomain chemical probes showing interesting pharmacology.
Bromodomains have emerged as an exciting target class for drug discovery over the past decade. Research has primarily focused on the bromodomain and extra terminal (BET) family of bromodomains, which has led to the development of multiple small molecule inhibitors and an increasing number of clinical assets. The excitement centred on the clinical potential of BET inhibition has stimulated intense interest in the broader family and the growing number of non-BET bromodomain chemical probes has facilitated phenotypic investigations, implicating these targets in a variety of disease pathways including cancer, inflammation, embryonic development and neurological disorders.
Disruption of the interaction of bromo and extraterminal (BET) proteins with acetylated histones using small molecule inhibitors suppresses Myc‐driven cancers and TLR‐induced inflammation in mouse ...models. The predominant mechanism of BET inhibitor action is to suppress BET‐mediated recruitment of positive transcription elongation factor b and, thus, transcription elongation. We investigated the effects of BET inhibitor I‐BET151 on transcriptional responses to TLR4 and TNF in primary human monocytes and also on responses to cytokines IFN‐β, IFN‐γ, IL‐4, and IL‐10, which activate the JAK‐STAT signaling pathway and are important for monocyte polarization and inflammatory diseases. I‐BET151 suppressed TLR4‐ and TNF‐induced IFN responses by diminishing both autocrine IFN‐β expression and transcriptional responses to IFN‐β. I‐BET151 inhibited cytokine‐induced transcription of STAT targets in a gene‐specific manner without affecting STAT activation or recruitment. This inhibition was independent of Myc or other upstream activators. IFN‐stimulated gene transcription is regulated primarily at the level of transcription initiation. Accordingly, we found that I‐BET151 suppressed the recruitment of transcriptional machinery to the CXCL10 promoter and an upstream enhancer. Our findings suggest that BET inhibition reduces inflammation partially through suppressing cytokine activity and expands the understanding of the inhibitory and potentially selective immunosuppressive effects of inhibiting BET proteins.
Targeted therapies against disruptor of telomeric silencing 1-like (DOT1L) and bromodomain-containing protein 4 (BRD4) are currently being evaluated in clinical trials. However, the mechanisms by ...which BRD4 and DOT1L regulate leukemogenic transcription programs remain unclear. Using quantitative proteomics, chemoproteomics and biochemical fractionation, we found that native BRD4 and DOT1L exist in separate protein complexes. Genetic disruption or small-molecule inhibition of BRD4 and DOT1L showed marked synergistic activity against MLL leukemia cell lines, primary human leukemia cells and mouse leukemia models. Mechanistically, we found a previously unrecognized functional collaboration between DOT1L and BRD4 that is especially important at highly transcribed genes in proximity to superenhancers. DOT1L, via dimethylated histone H3 K79, facilitates histone H4 acetylation, which in turn regulates the binding of BRD4 to chromatin. These data provide new insights into the regulation of transcription and specify a molecular framework for therapeutic intervention in this disease with poor prognosis.
Latency reversal strategies for HIV cure using inhibitor of apoptosis protein (IAP) antagonists (IAPi) induce unprecedented levels of latent reservoir expression without immunotoxicity during ...suppressive antiretroviral therapy (ART). However, full targeting of the reservoir may require combinatorial approaches. A Jurkat latency model screen for IAPi combination partners demonstrated synergistic latency reversal with bromodomain (BD) and extraterminal domain protein inhibitors (BETi). Mechanistic investigations using CRISPR-CAS9 and single-cell RNA-Seq informed comprehensive ex vivo evaluations of IAPi plus pan-BET, bD-selective BET, or selective BET isoform targeting in CD4+ T cells from ART-suppressed donors. IAPi+BETi treatment resulted in striking induction of cell-associated HIV gag RNA, but lesser induction of fully elongated and tat-rev RNA compared with T cell activation-positive controls. IAPi+BETi resulted in HIV protein induction in bulk cultures of CD4+ T cells using an ultrasensitive p24 assay, but did not result in enhanced viral outgrowth frequency using a standard quantitative viral outgrowth assay. This study defines HIV transcriptional elongation and splicing as important barriers to latent HIV protein expression following latency reversal, delineates the roles of BET proteins and their BDs in HIV latency, and provides a rationale for exploration of IAPi+BETi in animal models of HIV latency.
MicroRNAs have essential functional roles in brain development and neuronal specification but their roles in neurodegenerative diseases such as Alzheimer's disease (AD) is unknown. Using a sensitive ...qRT-PCR platform we identified regional and stage-specific deregulation of miRNA expression in AD patient brains. We used experimental validation in addition to literature to reveal how the deregulated brain microRNAs are biomarkers for known and novel pathways in AD pathogenesis related to amyloid processing, neurogenesis, insulin resistance, and innate immunity. We additionally recovered miRNAs from cerebrospinal fluid and discovered AD-specific miRNA changes consistent with their role as potential biomarkers of disease.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Pulmonary hypertension is a co-morbidity, which strongly participates in morbi-mortality in patients with chronic obstructive pulmonary disease (COPD). Recent findings showed that ...bromodomain-containing proteins, in charge of reading histone acetylation, could be involved in pulmonary arterial hypertension. Our aim was to study the effect of I-BET151, an inhibitor of bromodomain and extra-terminal domain (BET), on the right ventricle hypertrophy and pulmonary hypertension, induced by a combination of chronic hypoxia and pulmonary inflammation, as the two main stimuli encountered in COPD. Adult Wistar male rats, exposed to chronic hypoxia plus pulmonary inflammation (CHPI), showed a significant right ventricle hypertrophy (+57%,
< 0.001), an increase in systolic pressure (+46%,
< 0.001) and in contraction speed (+36%,
< 0.001), when compared to control animals. I-BET151 treated animals (CHPI-iB) showed restored hemodynamic parameters to levels similar to control animals, despite chronic hypoxia plus exposure to pulmonary inflammation. They displayed lower right ventricle hypertrophy and hematocrit compared to the CHPI group (respectively -16%,
< 0.001; and -9%,
< 0.05). Our descriptive study shows a valuable effect of the inhibition of bromodomain and extra-terminal domain proteins on hemodynamic parameters, despite the presence of chronic hypoxia and pulmonary inflammation. This suggests that such inhibition could be of potential interest for COPD patients with pulmonary hypertension. Further studies are needed to unravel the underlying mechanisms involved and the net benefits of inhibiting adaptations to chronic hypoxia.
Epigenetic changes are widespread in melanoma and contribute to the pathogenic biology of this disease. In the present study, we show that I-BET151, which belongs to a new class of drugs that target ...the BET family of epigenetic “reader” proteins, inhibits melanoma growth in vivo and induced variable degrees of apoptosis in a panel of melanoma cells. Apoptosis was caspase dependent and associated with G1 cell cycle arrest. All melanoma cells tested had increased levels of the BH3 proapoptotic protein BIM, which appeared to be regulated by the BRD2 BET protein and to some extent by BRD3. In contrast, knockdown experiments indicated that inhibition of BRD4 was associated with decreased levels of BIM. Apoptosis was dependent on BIM in some but not all cell lines, indicating that other factors were determinants of apoptosis, such as downregulation of antiapoptotic proteins revealed in gene expression arrays. G1 cell cycle arrest appeared to be mediated by p21 and resulted from inhibition of the BRD4 protein. The activity of BET protein inhibitors appears independent of the BRAF and NRAS mutational status of melanoma, and further studies to assess their therapeutic role in melanoma are warranted.
Second-generation bromodomain and extra terminal (BET) inhibitors, which selectively target one of the two bromodomains in the BET proteins, have begun to emerge in the literature. These inhibitors ...aim to help determine the roles and functions of each domain and assess whether they can demonstrate an improved safety profile in clinical settings compared to pan-BET inhibitors. Herein, we describe the discovery of a novel BET BD2-selective chemotype using a structure-based drug design from a hit identified by DNA-encoded library technologies, showing a structural differentiation from key previously reported greater than 100-fold BD2-selective chemotypes GSK620, GSK046, and ABBV-744. Following a structure-based hypothesis for the selectivity and optimization of the physicochemical properties of the series, we identified 60 (GSK040), an in vitro ready and in vivo capable BET BD2-inhibitor of unprecedented selectivity (5000-fold) against BET BD1, excellent selectivity against other bromodomains, and good physicochemical properties. This novel chemical probe can be added to the toolbox used in the advancement of epigenetics research.
PDF
