Novel tight-binding inhibitory factor-kappaB kinase (IKK-2) inhibitors demonstrate target-specific anti-inflammatory activities in cellular assays and following oral and local delivery in an in vivo model of airway inflammation

Advances in Immunosuppressive Agents Based on Signal Pathway

Immune abnormality involves in various diseases, such as infection, allergic diseases, autoimmune diseases, as well as transplantation. Several signal pathways have been demonstrated to play a central role in the immune response, including JAK/STAT, NF-κB, PI3K/AKT-mTOR, MAPK, and Keap1/Nrf2/ARE pathway, in which multiple targets have been used to develop immunosuppressive agents. In recent years, varieties of immunosuppressive agents have been approved for clinical use, such as the JAK inhibitor tofacitinib and the mTOR inhibitor everolimus, which have shown good therapeutic effects. Additionally, many immunosuppressive agents are still in clinical trials or preclinical studies. In this review, we classified the immunosuppressive agents according to the immunopharmacological mechanisms, and summarized the phase of immunosuppressive agents.

Control of APOBEC3B induction and cccDNA decay by NF-κB and miR-138-5p

Background & Aims

Immune-mediated induction of cytidine deaminase APOBEC3B (A3B) expression leads to HBV covalently closed circular DNA (cccDNA) decay. Here, we aimed to decipher the signalling pathway(s) and regulatory mechanism(s) involved in A3B induction and related HBV control.

Methods

Differentiated HepaRG cells (dHepaRG) knocked-down for NF-κB signalling components, transfected with siRNA or micro RNAs (miRNA), and primary human hepatocytes ± HBV or HBVΔX or HBV-RFP, were treated with lymphotoxin beta receptor (LTβR)-agonist (BS1). The biological outcomes were analysed by reverse transcriptase-qPCR, immunoblotting, luciferase activity, chromatin immune precipitation, electrophoretic mobility-shift assay, targeted-bisulfite-, miRNA-, RNA-, genome-sequencing, and mass-spectrometry.

Results

We found that canonical and non-canonical NF-κB signalling pathways are mandatory for A3B induction and anti-HBV effects. The degree of immune-mediated A3B production is independent of A3B promoter demethylation but is controlled post-transcriptionally by the miRNA 138-5p expression (hsa-miR-138-5p), promoting A3B mRNA decay. Hsa-miR-138-5p over-expression reduced A3B levels and its antiviral effects. Of note, established infection inhibited BS1-induced A3B expression through epigenetic modulation of A3B promoter. Twelve days of treatment with a LTβR-specific agonist BS1 is sufficient to reduce the cccDNA pool by 80% without inducing significant damages to a subset of cancer-related host genes. Interestingly, the A3B-mediated effect on HBV is independent of the transcriptional activity of cccDNA as well as on rcDNA synthesis.

Conclusions

Altogether, A3B represents the only described enzyme to target both transcriptionally active and inactive cccDNA. Thus, inhibiting hsa-miR-138-5p expression should be considered in the combinatorial design of new therapies against HBV, especially in the context of immune-mediated A3B induction.

Lay summary

Immune-mediated induction of cytidine deaminase APOBEC3B is transcriptionally regulated by NF-κB signalling and post-transcriptionally downregulated by hsa-miR-138-5p expression, leading to cccDNA decay. Timely controlled APOBEC3B-mediated cccDNA decay occurs independently of cccDNA transcriptional activity and without damage to a subset of cancer-related genes. Thus, APOBEC3B-mediated cccDNA decay could offer an efficient therapeutic alternative to target hepatitis B virus chronic infection.

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Impairment of NF-κB signalling prevents APOBEC3B induction and cccDNA decay.

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APOBEC3B is post-transcriptionally regulated by the hsa-miR-138-5p.

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Over-expression of the hsa-miR-138-5p inhibits APOBEC3B expression and cccDNA decay.

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A3B timely induces cccDNA decay without damage to cancer-related genes.

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APOBEC3B-mediated cccDNA decay is independent of cccDNA transcriptional activity.

Lactate Suppresses Macrophage Pro-Inflammatory Response to LPS Stimulation by Inhibition of YAP and NF-κB Activation via GPR81-Mediated Signaling

Recent evidence from cancer research indicates that lactate exerts a suppressive effect on innate immune responses in cancer. This study investigated the mechanisms by which lactate suppresses macrophage pro-inflammatory responses. Macrophages [Raw 264.7 and bone marrow derived macrophages (BMDMs)] were treated with LPS in the presence or absence of lactate. Pro-inflammatory cytokines, NF-κB and YAP activation and nuclear translocation were examined. Our results show that lactate significantly attenuates LPS stimulated macrophage TNF-α and IL-6 production. Lactate also suppresses LPS stimulated macrophage NF-κB and YAP activation and nuclear translocation in macrophages. Interestingly, YAP activation and nuclear translocation are required for LPS stimulated macrophage NF-κB activation and TNFα production. Importantly, lactate suppressed YAP activation and nuclear translocation is mediated by GPR81 dependent AMKP and LATS activation which phosphorylates YAP, resulting in YAP inactivation. Finally, we demonstrated that LPS stimulation induces an interaction between YAP and NF-κB subunit p65, while lactate decreases the interaction of YAP and NF-κB, thus suppressing LPS induced pro-inflammatory cytokine production. Our study demonstrates that lactate exerts a previously unknown role in the suppression of macrophage pro-inflammatory cytokine production via GPR81 mediated YAP inactivation, resulting in disruption of YAP and NF-κB interaction and nuclear translocation in macrophages.

In vitro benchmarking of NF-κB inhibitors

Dysregulated activity of the transcription factors of the nuclear factor κb (NF-κB) family has been implicated in numerous cancer types, inflammatory diseases, autoimmune disease, and other disorders. As such, selective NF-κB pathway inhibition is an attractive target to researchers for preclinical and clinical drug development. A plethora of commercially and clinically available inhibitors claim to be NF-κB specific; however, such claims of specificity are rarely quantitative or benchmarked, making the biomedical literature difficult to contextualize. This imprecision is worsened because some NF-κB reporter systems have low signal-to-noise ratios. Herein, we use a robust, defined, commercially available reporter system to benchmark NF-κB agonists and antagonists for the field. We also functionally characterize a RELA fusion-positive ependymoma cell culture with validated NF-κB inhibitor compounds.

Inhaled Janus Kinase (JAK) inhibitors for the treatment of asthma

Multiple asthma-relevant cytokines including IL-4, IL-5, IL-13, and TSLP depend upon JAKs for signaling. JAK inhibition may, therefore, offer a novel intervention strategy for patients with disease refractory to current standards of care. Multiple systemically delivered JAK inhibitors have been approved for human use or are under clinical evaluation in autoimmune diseases such as rheumatoid arthritis. However, the on-target side effect profiles of these agents are likely not tolerable for many asthmatic patients. Limiting JAK inhibition to the lung is expected to improve therapeutic index relative to systemic inhibition. Thus, inhaled JAK inhibitors with lung-restricted exposure are of high interest as potential treatments for asthma.

A Symphytum officinale Root Extract Exerts Anti-inflammatory Properties by Affecting Two Distinct Steps of NF-κB Signaling

Symphytum officinale, commonly known as comfrey, constitutes a traditional medicinal plant with a long-standing therapeutic history, and preparations thereof have been widely used for the treatment of painful muscle and joint complaints, wound and bone healing, and inflammation. Today, its topical use is based on its analgesic and anti-inflammatory effects, which have been substantiated by modern clinical trials. However, the molecular basis of its action remained elusive. Here, we show that a hydroalcoholic extract of comfrey root impairs the development of a pro-inflammatory scenario in primary human endothelial cells in a dose-dependent manner. The extract, and especially its mucilage-depleted fraction, impair the interleukin-1 (IL-1) induced expression of pro-inflammatory markers including E-selectin, VCAM1, ICAM1, and COX-2. Both preparations inhibit the activation of NF-κB, a transcription factor of central importance for the expression of these and other pro-inflammatory genes. Furthermore, our biochemical studies provide evidence that comfrey inhibits NF-κB signaling at two stages: it dampens not only the activation of IKK1/2 and the subsequent IκBα degradation, but also interferes with NF-κB p65 nucleo-cytoplasmatic shuttling and transactivation. These results provide a first mechanistic insight into the mode of action of a century-old popular herbal medicine.

Targeting IKKβ in Cancer: Challenges and Opportunities for the Therapeutic Utilisation of IKKβ Inhibitors

Deregulated NF-κB signalling is implicated in the pathogenesis of numerous human inflammatory disorders and malignancies. Consequently, the NF-κB pathway has attracted attention as an attractive therapeutic target for drug discovery. As the primary, druggable mediator of canonical NF-κB signalling the IKKβ protein kinase has been the historical focus of drug development pipelines. Thousands of compounds with activity against IKKβ have been characterised, with many demonstrating promising efficacy in pre-clinical models of cancer and inflammatory disease. However, severe on-target toxicities and other safety concerns associated with systemic IKKβ inhibition have thus far prevented the clinical approval of any IKKβ inhibitors. This review will discuss the potential reasons for the lack of clinical success of IKKβ inhibitors to date, the challenges associated with their therapeutic use, realistic opportunities for their future utilisation, and the alternative strategies to inhibit NF-κB signalling that may overcome some of the limitations associated with IKKβ inhibition.

Targeting IκappaB kinases for cancer therapy

The inhibitory kappa B kinases (IKKs) and IKK related kinases are crucial regulators of the pro-inflammatory transcription factor, nuclear factor kappa B (NF-κB). The dysregulation in the activities of these kinases has been reported in several cancer types. These kinases are known to regulate survival, proliferation, invasion, angiogenesis, and metastasis of cancer cells. Thus, IKK and IKK related kinases have emerged as an attractive target for the development of cancer therapeutics. Several IKK inhibitors have been developed, few of which have advanced to the clinic. These inhibitors target IKK either directly or indirectly by modulating the activities of other signaling molecules. Some inhibitors suppress IKK activity by disrupting the protein-protein interaction in the IKK complex. The inhibition of IKK has also been shown to enhance the efficacy of conventional chemotherapeutic agents. Because IKK and NF-κB are the key components of innate immunity, suppressing IKK is associated with the risk of immune suppression. Furthermore, IKK inhibitors may hit other signaling molecules and thus may produce off-target effects. Recent studies suggest that multiple cytoplasmic and nuclear proteins distinct from NF-κB and inhibitory κB are also substrates of IKK. In this review, we discuss the utility of IKK inhibitors for cancer therapy. The limitations associated with the intervention of IKK are also discussed.

Kinases as Novel Therapeutic Targets in Asthma and Chronic Obstructive Pulmonary Disease

Multiple kinases play a critical role in orchestrating the chronic inflammation and structural changes in the respiratory tract of patients with asthma and chronic obstructive pulmonary disease (COPD). Kinases activate signaling pathways that lead to contraction of airway smooth muscle and release of inflammatory mediators (such as cytokines, chemokines, growth factors) as well as cell migration, activation, and proliferation. For this reason there has been great interest in the development of kinase inhibitors as anti-inflammatory therapies, particular where corticosteroids are less effective, as in severe asthma and COPD. However, it has proven difficult to develop selective kinase inhibitors that are both effective and safe after oral administration and this has led to a search for inhaled kinase inhibitors, which would reduce systemic exposure. Although many kinases have been implicated in inflammation and remodeling of airway disease, very few classes of drug have reached the stage of clinical studies in these diseases. The most promising drugs are p38 MAP kinases, isoenzyme-selective PI3-kinases, Janus-activated kinases, and Syk-kinases, and inhaled formulations of these drugs are now in development. There has also been interest in developing inhibitors that block more than one kinase, because these drugs may be more effective and with less risk of losing efficacy with time. No kinase inhibitors are yet on the market for the treatment of airway diseases, but as kinase inhibitors are improved from other therapeutic areas there is hope that these drugs may eventually prove useful in treating refractory asthma and COPD.

A sirtuin activator and an anti-inflammatory molecule-multifaceted roles of adjudin and its potential applications for aging-related diseases

Adjudin was originally developed as an improved analog of lonidamine to serve as a non-hormonal reversible male contraceptive that could cause exfoliation of the immature sperms from the seminiferous epithelium. Recently, the functionality spectrum of adjudin expands beyond as an anti-spermatogenic agent, namely, it could function as an anti-cancer drug potentially useful for combination chemotherapy, and as an anti-inflammatory molecule that could protect against ischemic stroke injury. Most strikingly, adjudin acts through activation of mitochondrion-located Sirt3 to safeguard hair cells of the cochlea from ototoxicant such as gentamycin. Recent studies also indicate that adjudin could attenuate oxidative stress and cellular senescence. These findings suggest wider applications of this small molecule, particularly in aging-related diseases.

NF-kappaB Signaling in Chronic Inflammatory Airway Disease

Asthma and chronic obstructive pulmonary disease (COPD) are obstructive airway disorders which differ in their underlying causes and phenotypes but overlap in patterns of pharmacological treatments. In both asthma and COPD, oxidative stress contributes to airway inflammation by inducing inflammatory gene expression. The redox-sensitive transcription factor, nuclear factor (NF)-kappaB (NF-κB), is an important participant in a broad spectrum of inflammatory networks that regulate cytokine activity in airway pathology. The anti-inflammatory actions of glucocorticoids (GCs), a mainstay treatment for asthma, involve inhibition of NF-κB induced gene transcription. Ligand bound GC receptors (GRs) bind NF-κB to suppress the transcription of NF-κB responsive genes (i.e., transrepression). However, in severe asthma and COPD, the transrepression of NF-κB by GCs is negated as a consequence of post-translational changes to GR and histones involved in chromatin remodeling. Therapeutics which target NF-κB activation, including inhibitors of IκB kinases (IKKs) are potential treatments for asthma and COPD. Furthermore, reversing GR/histone acetylation shows promise as a strategy to treat steroid refractory airway disease by augmenting NF-κB transrepression. This review examines NF-κB signaling in airway inflammation and its potential as target for treatment of asthma and COPD.

Inhaled LPS challenges in smokers: a study of pulmonary and systemic effects

AIMS

Lipopolysaccharide (LPS) is a TLR4 agonist which activates NFκB dependent cytokine production. We investigated LPS inhalation in healthy smokers as a model of COPD bacterial exacerbations. We studied safety, reproducibility, the translocation of the NFκB subunit p65 in sputum cells and changes in systemic biomarkers of inflammation.

METHODS

Twelve smokers inhaled 5 and 30 µg LPS and safety was monitored over 24 h. IL-6, CRP, CCl-18, SP-D, CC-16 and β-defensin 2 were measured in serum samples collected at baseline, 4, 8 and 24 h. Sputum was induced at baseline, 6 and 24 h for cell counts and p65 expression. Repeated challenges were performed after a 2 week interval in 10 smokers.

RESULTS

LPS inhalation was well tolerated. Significant increases occurred in sputum neutrophil counts with both doses, with a maximum increase of 21.5% at 6 h after 30 µg which was reproducible, r(i ) (intraclass correlation coefficient) = 0.88. LPS increased sputum cell nuclear p65 translocation and phospho-p65 expression. All of the serum biomarkers increased following challenge but with different temporal patterns.

DISCUSSION

Inhaled LPS challenge in smokers causes pulmonary and systemic inflammation that involves NFκB activation. This appears to be a suitable model for studying bacterial exacerbations of COPD.

The AGC kinase inhibitor H89 attenuates airway inflammation in mouse models of asthma

BACKGROUND

H89 is a potent inhibitor of Protein Kinase A (PKA) and Mitogen- and Stress-Activated protein Kinase 1 (MSK1) with some inhibitory activity on other members of the AGC kinase family. H89 has been extensively used in vitro but its anti-inflammatory potential in vivo has not been reported to date. To assess the anti-inflammatory properties of H89 in mouse models of asthma.

METHODOLOGY/PRINCIPAL FINDINGS

Mice were sensitized intraperitoneally (i.p.) to ovalbumin (OVA) with or without alum, and challenged intranasally with OVA. H89 (10 mg/kg) or vehicle was given i.p. two hours before each OVA challenge. Airway hyperresponsiveness (AHR) was assessed by whole-body barometric plethysmography. Inflammation was assessed by the total and differential cell counts and IL-4 and IL-5 levels in bronchoalveolar lavage (BAL) fluid. Lung inflammation, mucus production and mast cell numbers were analyzed after histochemistry. We show that treatment with H89 reduces AHR, lung inflammation, mast cell numbers and mucus production. H89 also inhibits IL-4 and IL-5 production and infiltration of eosinophils, neutrophils and lymphocytes in BAL fluid.

CONCLUSIONS/SIGNIFICANCE

Taken together, our findings implicate that blockade of AGC kinases may have therapeutic potential for the treatment of allergic airway inflammation.

Adjudin attenuates lipopolysaccharide (LPS)- and ischemia-induced microglial activation

Neuroinflammation caused by microglial activation plays a key role in ischemia, neurodegeneration and many other CNS diseases. In this study, we found that Adjudin, a potential non-hormonal male contraceptive, exhibits additional function to reduce the production of proinflammatory mediators. Adjudin significantly inhibited LPS-induced IL-6 release and IL-6, IL-1β, TNF-α expression in BV2 microglial cells. Furthermore, Adjudin exhibited anti-inflammatory properties by suppression of NF-κB p65 nuclear translocation and DNA binding activity as well as ERK MAPK phosphorylation. To determine the in vivo effect of Adjudin, we used a permanent middle cerebral artery occlusion (pMCAO) mouse model and found that Adjudin could reduce ischemia-induced CD11b expression, a marker of microglial activation. Furthermore, Adjudin treatment attenuated brain edema and neurological deficits after ischemia but did not reduce infarct volume. Thus, our data suggest that Adjudin may be useful for mitigating neuroinflammation.

p38 MAPK inhibitors, IKK2 inhibitors, and TNFα inhibitors in COPD

COPD represents a major respiratory disorder, causing significant morbidity and mortality throughout the world. While therapies exist for COPD, they are not always effective, and many patients experience exacerbations and morbidity despite current therapies. Study of the molecular mechanisms involved in the underlying physiological manifestations of COPD has yielded multiple new targets for therapeutic intervention. In this review, we discuss signaling pathways involved in COPD pathogenesis and review clinical studies of p38 MAPK inhibitors, TNFα inhibitors, and IKK2 inhibitors as potential COPD therapies.

Bindarit: an anti-inflammatory small molecule that modulates the NFκB pathway

The activation of nuclear factor (NF)κB pathway and its transducing signaling cascade has been associated with the pathogenesis of many inflammatory diseases. The central role that IκBα and p65 phosphorylation play in regulating NFκB signalling in response to inflammatory stimuli made these proteins attractive targets for therapeutic strategies. Although several chemical classes of NFκB inhibitors have been identified, it is only for a few of those that a safety assessment based on a comprehensive understanding of their pharmacologic mechanism of action has been reported. Here, we describe the specific anti-inflammatory effect of bindarit, an indazolic derivative that has been proven to have anti-inflammatory activity in a variety of models of inflammatory diseases (including lupus nephritis, arthritis and pancreatitis). The therapeutic effects of bindarit have been associated with its ability to selectively interfere with monocyte recruitment and the "early inflammatory response," although its specific molecular mechanisms have remained ill-defined. For this purpose, we investigated the effect of bindarit on the LPS-induced production of inflammatory cytokines (MCP-1 and MCPs, IL-12β/p40, IL-6 and IL-8/KC) in both a mouse leukaemic monocyte-macrophage cell line and bone marrow derived macrophages (BMDM). Bindarit inhibits the LPS-induced MCP-1 and IL-12β/p40 expression without affecting other analyzed cytokines. The effect of bindarit is mediated by the downregulation of the classical NFκB pathway, involving a reduction of IκBα and p65 phosphorylation, a reduced activation of NFκB dimers and a subsequently reduced nuclear translocation and DNA binding. Bindarit showed a specific inhibitory effect on the p65 and p65/p50 induced MCP-1 promoter activation, with no effect on other tested activated promoters. We conclude that bindarit acts on a specific subpopulation of NFκB isoforms and selects its targets wihtin the whole NFκB inflammatory pathway. These findings pave the way for future applications of bindarit as modulator of the inflammatory response.

Effect of inhibition of the ubiquitin-proteasome-system and IκB kinase on airway inflammation and hyperresponsiveness in a murine model of asthma

The current treatment of asthma is far from optimal and there is a need for novel therapeutic approaches. NFkB has recently been highlighted as an important pro-inflammatory transcriptional factor and its blockade is believed to represent a new therapeutic approach for asthma. The purpose of this study is to investigate the effects of blocking the actions of NFkB, through inhibition of the ubiquitin-proteasome system (UPS) or IkB kinase (IKK), in a murine model of asthma. Treatment with the UPS inhibitor, MG-132 (0.03 and 0.1 mg/kg), did not significantly affect the ovalbumin-induced increase in total and differential cell numbers, histological changes such as perivascular and peribronchial inflammatory cell infiltration, perivascular and peribronchial fibrosis or the increased Penh to methacholine. In contrast, treatment of mice with the IKK inhibitor, BAY 11-7085, (3 and 10 mg/kg) dose-dependently inhibited the ovalbumin-induced increase in airway leukocyte influx and decreased the percentage of airway lymphocytes, neutrophils and eosinophils. Also, BAY 11-7085-treated (10 mg/kg) mice showed a significant decrease in the histologically assessed inflammatory indices as well as a significant reduction in the ovalbumin-induced increase in Penh to inhaled methacholine. Furthermore, BAY 11-7085 significantly inhibited the ovalbumin-induced increase in the level of phosphorylation of IkBalpha and extracellular regulated kinases (ERK) 1/2, whilst MG-132 significantly increased the phosphorylation of (ERK) 1/2. These findings confirm the critical role that NFkB plays in airway inflammation, highlight the importance of IKK in regulating the pro-inflammatory activity of NFkB and also suggest that UPS may not be a useful drug target for asthma treatment.

Identification of human IKK-2 inhibitors of natural origin (part I): modeling of the IKK-2 kinase domain, virtual screening and activity assays

BACKGROUND

Their large scaffold diversity and properties, such as structural complexity and drug similarity, form the basis of claims that natural products are ideal starting points for drug design and development. Consequently, there has been great interest in determining whether such molecules show biological activity toward protein targets of pharmacological relevance. One target of particular interest is hIKK-2, a serine-threonine protein kinase belonging to the IKK complex that is the primary component responsible for activating NF-κB in response to various inflammatory stimuli. Indeed, this has led to the development of synthetic ATP-competitive inhibitors for hIKK-2. Therefore, the main goals of this study were (a) to use virtual screening to identify potential hIKK-2 inhibitors of natural origin that compete with ATP and (b) to evaluate the reliability of our virtual-screening protocol by experimentally testing the in vitro activity of selected natural-product hits.

METHODOLOGY/PRINCIPAL FINDINGS

We thus predicted that 1,061 out of the 89,425 natural products present in the studied database would inhibit hIKK-2 with good ADMET properties. Notably, when these 1,061 molecules were merged with the 98 synthetic hIKK-2 inhibitors used in this study and the resulting set was classified into ten clusters according to chemical similarity, there were three clusters that contained only natural products. Five molecules from these three clusters (for which no anti-inflammatory activity has been previously described) were then selected for in vitro activity testing, in which three out of the five molecules were shown to inhibit hIKK-2.

CONCLUSIONS/SIGNIFICANCE

We demonstrated that our virtual-screening protocol was successful in identifying lead compounds for developing new inhibitors for hIKK-2, a target of great interest in medicinal chemistry. Additionally, all the tools developed during the current study (i.e., the homology model for the hIKK-2 kinase domain and the pharmacophore) will be made available to interested readers upon request.

Discovery of a novel IKK-β inhibitor by ligand-based virtual screening techniques

Various inflammatory stimuli that activate the nuclear factor kappa B (NF-κB) signaling pathway converge on a serine/threonine kinase that displays a key role in the activation of NF-κB: the I kappa B kinase β (IKK-β). Therefore, IKK-β is considered an interesting target for combating inflammation and cancer. In our study, we developed a ligand-based pharmacophore model for IKK-β inhibitors. This model was employed to virtually screen commercial databases, giving a focused hit list of candidates. Subsequently, we scored by molecular shape to rank and further prioritized virtual hits by three-dimensional shape-based alignment. One out of ten acquired and biologically tested compounds showed inhibitory activity in the low micromolar range on IKK-β enzymatic activity in vitro and on NF-κB transactivation in intact cells. Compound 8 (2-(1-adamantyl)ethyl 4-[(2,5-dihydroxyphenyl)methylamino]benzoate) represents a novel chemical class of IKK-β inhibitors and shows that the presented model is a valid approach for identification and development of new IKK-β ligands.

Aminopyridinecarboxamide-based inhaled IKK-2 inhibitors for asthma and COPD: Structure-activity relationship

Installation of sites for metabolism in the lead compound PHA-767408 was the key focus of the IKK-2 inhaled program. This paper reports our efforts to identify a novel series of aminopyridinecarboxamide-based IKK-2 inhibitors, which display low nanomolar potency against IKK-2 with long duration of action (DOA), and metabolically labile to phase I and/or phase II metabolizing enzymes with potential capability for multiple routes of clearance. Several compounds have demonstrated their potential usefulness in the treatment of asthma and chronic obstructive pulmonary disease (COPD).

Targeting kinases for the treatment of inflammatory diseases

IMPORTANCE OF THE FIELD

Inflammatory diseases are one of the major health issues and have become a major focus in the pharmaceutical and biotech industries. To date, drugs prescribed for treatment of these diseases target enzymes that are not specific to the immune system resulting in adverse effects. The main challenge of this research field is, therefore, identifying targets that act specifically on the diseased tissue.

AREAS COVERED IN THIS REVIEW

This review summarizes drug discovery efforts on kinases that have been identified as key players mediating inflammation and autoimmune disorders. In particular, we discuss recent developments on well-established targets such as mammalian target of rapamycin, JAK3, spleen tyrosine kinase, p38α and lymphocyte specific kinase but provide also a perspective on emerging targets.

WHAT THE READER WILL GAIN

The reader will obtain an overview of drug discovery efforts on kinases in inflammation, recent clinical and preclinical data and developed inhibitor scaffolds. In addition, the reader will be updated on issues in target validation of current drug targets and the potential of selected novel kinase targets in this important disease area.

TAKE HOME MESSAGE

Cellular signaling networks that regulate inflammatory response are still poorly understood making rational selection of targets challenging. Recent data suggest that kinase targets that are specific to the immune system and mediate signals immediately downstream of surface receptors are most efficacious in the clinic.

Novel insights into the cellular mechanisms of the anti-inflammatory effects of NF-kappaB essential modulator binding domain peptides

The classical nuclear factor κB (NF-κB) signaling pathway is under the control of the IκB kinase (IKK) complex, which consists of IKK-1, IKK-2, and NF-κB essential modulator (NEMO). This complex is responsible for the regulation of cell proliferation, survival, and differentiation. Dysregulation of this pathway is associated with several human diseases, and as such, its inhibition offers an exciting opportunity for therapeutic intervention. NEMO binding domain (NBD) peptides inhibit the binding of recombinant NEMO to IKK-2 in vitro. However, direct evidence of disruption of this binding by NBD peptides in biological systems has not been provided. Using a cell system, we expanded on previous observations to show that NBD peptides inhibit inflammation-induced but not basal cytokine production. We report that these peptides cause the release of IKK-2 from an IKK complex and disrupt NEMO-IKK-2 interactions in cells. We demonstrate that by interfering with NEMO-IKK-2 interactions, NBD peptides inhibit IKK-2 phosphorylation, without affecting signaling intermediates upstream of the IKK complex of the NF-κB pathway. Furthermore, in a cell-free system of IKK complex activation by TRAF6 (TNF receptor-associated factor 6), we show that these peptides inhibit the ability of this complex to phosphorylate downstream substrates, such as p65 and inhibitor of κBα (IκBα). Thus, consistent with the notion that NEMO regulates IKK-2 catalytic activity by serving as a scaffold, appropriately positioning IKK-2 for activation by upstream kinase(s), our findings provide novel insights into the molecular mechanisms by which NBD peptides exert their anti-inflammatory effects in cells.

Anti-inflammatory effect of a selective IkappaB kinase-beta inhibitor in rat lung in response to LPS and cigarette smoke

RATIONALE

IkappaB kinase (IKK) activates NF-kappaB which plays a pivotal role in pro-inflammatory response in the lung. NF-kappaB has been shown to be activated in alveolar macrophages and peripheral lungs of smokers and patients with chronic obstructive pulmonary disease. We investigated the anti-inflammatory effect of a highly selective and novel IKKbeta/IKK2 inhibitor, PHA-408 [8-(5-chloro-2-(4-methylpiperazin-1-yl)isonicotinamido)-1-(4-fluorophenyl)-4,5-dihydro-1H-benzo[gamma]indazole-3-carboxamide], in lungs of rat in vivo.

METHODS

Adult Sprague-Dawley rats were administered orally with PHA-408 (15 and 45 mg/kg) daily for 3 days and exposed to LPS aerosol (once on day 3, 2 h post-last PHA-408 administration) or cigarette smoke (CS; 2h after PHA-408 administration for 3 days). Animals were sacrificed at 1, 4 and 24 h after the last exposure, and lung inflammatory response and NF-kappaB activation were measured.

RESULTS

Oral administration of IKKbeta/IKK2 inhibitor PHA-408 significantly inhibited LPS- and CS-mediated neutrophil influx in bronchoalveolar lavage (BAL) fluid of rats. The levels of pro-inflammatory mediators in BAL fluid (CINC-1) and lungs (IL-6, TNF-alpha, IL-1beta and GM-CSF) were also reduced by PHA-408 administration in response to LPS or CS exposures. The reduced pro-inflammatory response in PHA-408-administered rats was associated with decreased nuclear translocation and DNA binding activity of NF-kappaB in response to LPS or CS.

CONCLUSION

These results suggest that IKKbeta/IKK2 inhibitor PHA-408 is a powerful anti-inflammatory agent against LPS- and CS-mediated lung inflammation.