Histone deacetylase 3 (HDAC 3) as emerging drug target in NF-kappa B-mediated inflammation

Activation of inflammatory gene expression is regulated, among other factors, by post-translational modifications of histone proteins. The most investigated type of histone modifications is lysine acetylations. Histone deacetylases (HDACs) remove acetylations from lysines, thereby influencing (inflammatory) gene expression. Intriguingly, apart from histones, HDACs also target non-histone proteins. The nuclear factor kappa B (NF-kappa B) pathway is an important regulator in the expression of numerous inflammatory genes, and acetylation plays a crucial role in regulating its responses. Several studies have shed more light on the role of HDAC 1-3 in inflammation with a particular pro-inflammatory role for HDAC 3. Nevertheless, the HDAC-NF-kappa B interactions in inflammatory signalling have not been fully understood. An important challenge in targeting the regulatory role of HDACs in the NF-kappa B pathway is the development of highly potent small molecules that selectively target HDAC iso-enzymes. This review focuses on the role of HDAC 3 in (NF-kappa B-mediated) inflammation and NF-kappa B lysine acetylation. In addition, we address the application of frequently used small molecule HDAC inhibitors as an approach to attenuate inflammatory responses, and their potential as novel therapeutics. Finally, recent progress and future directions in medicinal chemistry efforts aimed at HDAC 3-selective inhibitors are discussed.</p

HDAC 3-selective inhibitor RGFP966 demonstrates anti-inflammatory properties in RAW 264.7 macrophages and mouse precision-cut lung slices by attenuating NF-κB p65 transcriptional activity

AbstractThe increasing number of patients suffering from chronic obstructive pulmonary disease (COPD) represents a major and increasing health problem. Therefore, novel therapeutic approaches are needed. Class I HDACs 1, 2 and 3 play key roles in the regulation of inflammatory gene expression with a particular pro-inflammatory role for HDAC 3. HDAC 3 has been reported to be an important player in inflammation by deacetylating NF-κB p65, which has been implicated in the pathology of COPD. Here, we applied the pharmacological HDAC 3-selective inhibitor RGFP966, which attenuated pro-inflammatory gene expression in models for inflammatory lung diseases. Consistent with this, a robust decrease of the transcriptional activity of NF-κB p65 was observed. HDAC 3 inhibition affected neither the acetylation status of NF-κB p65 nor histone H3 or histone H4. This indicates that HDAC 3 inhibition does not inhibit NF-κB p65 transcriptional activity by affecting its deacetylation but rather by inhibiting enzymatic activity of HDAC 3. Taken together, our findings indicate that pharmacological HDAC 3-selective inhibition by inhibitors such as RGFP966 may provide a novel and effective approach toward development of therapeutics for inflammatory lung diseases

A Sensitive Assay for Virus Discovery in Respiratory Clinical Samples

In 5–40% of respiratory infections in children, the diagnostics remain negative, suggesting that the patients might be infected with a yet unknown pathogen. Virus discovery cDNA-AFLP (VIDISCA) is a virus discovery method based on recognition of restriction enzyme cleavage sites, ligation of adaptors and subsequent amplification by PCR. However, direct discovery of unknown pathogens in nasopharyngeal swabs is difficult due to the high concentration of ribosomal RNA (rRNA) that acts as competitor. In the current study we optimized VIDISCA by adjusting the reverse transcription enzymes and decreasing rRNA amplification in the reverse transcription, using hexamer oligonucleotides that do not anneal to rRNA. Residual cDNA synthesis on rRNA templates was further reduced with oligonucleotides that anneal to rRNA but can not be extended due to 3′-dideoxy-C6-modification. With these modifications >90% reduction of rRNA amplification was established. Further improvement of the VIDISCA sensitivity was obtained by high throughput sequencing (VIDISCA-454). Eighteen nasopharyngeal swabs were analysed, all containing known respiratory viruses. We could identify the proper virus in the majority of samples tested (11/18). The median load in the VIDISCA-454 positive samples was 7.2 E5 viral genome copies/ml (ranging from 1.4 E3–7.7 E6). Our results show that optimization of VIDISCA and subsequent high-throughput-sequencing enhances sensitivity drastically and provides the opportunity to perform virus discovery directly in patient material

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

Chronic obstructive pulmonary disease (COPD) constitutes a major health burden. Studying underlying molecular mechanisms could lead to new therapeutic targets. Macrophages are orchestrators of COPD, by releasing pro-inflammatory cytokines. This process relies on transcription factors such as NF-κB, among others. NF-κB is regulated by lysine acetylation; a post-translational modification installed by histone acetyltransferases and removed by histone deacetylases (HDACs). We hypothesized that small molecule HDAC inhibitors (HDACi) targeting class I HDACs members that can regulate NF-κB could attenuate inflammatory responses in COPD via modulation of the NF-κB signaling output. MS-275 is an isoform-selective inhibitor of HDAC1-3. In precision-cut lung slices and RAW264.7 macrophages, MS-275 upregulated the expression of both pro- and anti-inflammatory genes, implying mixed effects. Interestingly, anti-inflammatory IL10 expression was upregulated in these model systems. In the macrophages, this was associated with increased NF-κB activity, acetylation, nuclear translocation, and binding to the IL10 promoter. Importantly, in an in vivo model of cigarette smoke-exposed C57Bl/6 mice, MS-275 robustly attenuated inflammatory expression of KC and neutrophil influx in the lungs. This study highlights for the first time the potential of isoform-selective HDACi for the treatment of inflammatory lung diseases like COPD

Small molecule inhibitors of histone deacetylases and acetyltransferases as potential therapeutics in oncology

Uncontrolled cell proliferation and resistance to apoptosis in cancer are, among others, regulated by post-translational modifications of histone proteins. The most investigated type of histone modification is lysine acetylation. Histone acetyltransferases (HATs), acetylate histone lysine residues, and histone deacetylases (HDACs) remove acetyl residues from lysines, thereby influencing gene expression. Whereas HAT inhibitors are relatively undeveloped, four HDAC inhibitors (HDACi) reached the clinic for treatment of hematological cancers. HDACi induce apoptosis via inhibition of histone deacetylation and concomitant transcription of aberrantly silenced genes. Nevertheless, other mechanisms have also been described. Intriguingly, HDACs also target nonhistone proteins such as the nuclear factor κB (NF-κB) pathway, which is an important regulator of gene transcription for which a role in cancer has been implicated. Despite the studies that shed more light on the role of HDAC isoenzymes in the NF-κB pathway the challenge remains to develop isoenzymeselective HDACi to target this pathway

Progress in hydrometallurgical technologies to recover critical raw materials and precious metals from low-concentrated streams

Critical and precious metals are essential in many modern applications. While their natural sources are depleting, one must adapt to guarantee a reliable supply by developing new and optimizing existing techniques to recover the elements from unexplored material flows. The aquatic phase is of great meaning to this issue, as migration from solid to liquid streams is ubiquitous during industrial manipulation of the raw materials. The resulting (waste) waters are characterized by low concentrations and varying chemical composition. Hence, hydrometallurgical technologies should cope with such specific system conditions and physico-chemical properties of critical and precious metals when elaborating a recovery strategy. This review provides an overview of the present status and outlook on technologies used to recover critical metals from solution, including cementation, precipitation, reduction, ion exchange, solvent extraction, electrochemical methods and adsorption onto novel, sustainable materials. Special attention is given to adsorption technology, which is considered as one of the most promising metal recovery options owing to its facile implementation, low cost, high availability and high removal efficiencies even at low target metal concentrations. Key directions are suggested to tackle existing challenges in the field of resource recovery and improve the sustainability of future material cycling

Progress in hydrometallurgical technologies to recover critical raw materials and precious metals from low-concentrated streams

Critical and precious metals are essential in many modern applications. While their natural sources are depleting, one must adapt to guarantee a reliable supply by developing new and optimizing existing techniques to recover the elements from unexplored material flows. The aquatic phase is of great meaning to this issue, as migration from solid to liquid streams is ubiquitous during industrial manipulation of the raw materials. The resulting (waste) waters are characterized by low concentrations and varying chemical composition. Hence, hydrometallurgical technologies should cope with such specific system conditions and physico-chemical properties of critical and precious metals when elaborating a recovery strategy. This review provides an overview of the present status and outlook on technologies used to recover critical metals from solution, including cementation, precipitation, reduction, ion exchange, solvent extraction, electrochemical methods and adsorption onto novel, sustainable materials. Special attention is given to adsorption technology, which is considered as one of the most promising metal recovery options owing to its facile implementation, low cost, high availability and high removal efficiencies even at low target metal concentrations. Key directions are suggested to tackle existing challenges in the field of resource recovery and improve the sustainability of future material cycling

Chemical epigenetics to assess the role of HDAC1-3 inhibition in macrophage pro-inflammatory gene expression

Histone deacetylases (HDACs) have been used as pharmacological targets for the treatment of various diseases. Some non-selective HDAC inhibitors (HDACi) have been clinically-used as therapeutic agents for treatment of hematological cancers but their cytotoxic side effects are an important downside. The discovery of more selective inhibitors has certified the involvement of individual HDACs in pathological processes but the elucidation of the role of specific family members in inflammatory responses still remains a challenge. Here, we report the development of closely related, structural analogues of the clinically-used HDACi Entinostat via a chemical epigenetic approach. Three compounds were designed and synthesized in which the cap moiety of Entinostat was replaced by an azobenzene group that is either para, meta or ortho substituted. The compounds were then evaluated for selectivity towards HDACs 1-3 and their effect on pro-inflammatory gene expression in macrophages. One analogue, compound 4, lacked selectivity and demonstrated inhibition of NF-kappa B reporter gene activity and pro-inflammatory gene expression in RAW264.7 macrophages, thus indicating that there is a delicate balance between the selectivity of HDACi over specific family members and their pro-or anti-inflammatory effects