Effect of imatinib on airway smooth muscle thickening in a murine model of chronic asthma

Lignosus rhinocerotis extract ameliorates airway inflammation and remodelling via attenuation of TGF-β1 and Activin A in a prolonged induced allergic asthma model

Allergic asthma is associated with chronic airway inflammation and progressive airway remodelling. The sclerotium of Lignosus rhinocerotis (Cooke) Ryvarden (Tiger Milk mushroom) is used traditionally to treat various illnesses, including asthma in Southeast Asia. This study was carried out to evaluate the effect of L. rhinocerotis extract (LRE) on airway inflammation and remodelling in a chronic model of asthma. The present study investigated the therapeutic effects of LRE on airway inflammation and remodelling in prolonged allergen challenged model in allergic asthma. Female Balb/C mice were sensitised using ovalbumin (OVA) on day 0 and 7, followed by OVA-challenged (3 times/week) for 2, 6 and 10 weeks. LRE (125, 250, 500 mg/kg) were administered by oral gavage one hour after every challenge. One group of mice were left untreated after the final challenge for two weeks. LRE suppressed inflammatory cells and Th2 cytokines (IL-4, IL-5 and IL-13) in BALF and reduced IgE level in the serum. LRE also attenuated eosinophils infiltration and goblet cell hyperplasia in the lung tissues; as well as ameliorated airway remodelling by reducing smooth muscle thickness and reducing the expressions of TGF-β1 and Activin A positive cell in the lung tissues. LRE attenuated airway inflammation and remodelling in the prolonged allergen challenge of allergic asthma model. These findings suggest the therapeutic potential of LRE as an alternative for the management of allergic asthma.

Effects of human adipose tissue- and bone marrow-derived mesenchymal stem cells on airway inflammation and remodeling in a murine model of chronic asthma

It is challenging to overcome difficult-to-treat asthma, and cell-based therapies are attracting increasing interest. We assessed the effects of mesenchymal stem cell (MSC) treatments using a murine model of chronic ovalbumin (OVA)-challenged asthma. We developed a murine model of chronic allergic asthma using OVA sensitization and challenge. Human adipose-derived MSCs (hADSCs) or human bone marrow-derived MSCs (hBMSCs) were administered. We measured the levels of resistin-like molecule-β (RELM-β). We also measured RELM-β in asthma patients and normal controls. OVA-challenged mice exhibited increased airway hyper-responsiveness, inflammation, and remodeling. hBMSC treatment remarkably decreased airway hyper-responsiveness but hADSC treatment did not. Both MSCs alleviated airway inflammation, but hBMSCs tended to have a more significant effect. hBMSC treatment reduced Th2-cytokine levels but hADSC treatment did not. Both treatments reduced airway remodeling. The RELM-β level decreased in the OVA-challenged control group, but increased in both treatment groups. We found that the serum level of RELM-β was lower in asthma patients than controls. MSC treatments alleviated the airway inflammation, hyper-responsiveness, and remodeling associated with chronic asthma. hBMSCs were more effective than hADSCs. The RELM-β levels increased in both treatment groups; the RELM-β level may serve as a biomarker of MSC treatment efficacy.

Efficacy and Safety of Masitinib in Corticosteroid-Dependent Severe Asthma: A Randomized Placebo-Controlled Trial

Background

Masitinib is an oral tyrosine kinase inhibitor that selectively targets mast cell activity and platelet-derived growth factor receptor (PDGFR) signaling, both of which are implicated in various mechanisms of asthma pathogenesis.

Objective

Assessment of masitinib as an add-on to standard maintenance therapy as compared with placebo in the treatment of oral corticosteroid-dependent severe asthma.

Methods

We conducted a randomized (2:1), placebo-controlled study of masitinib (6 mg/kg/d) in adults with severe asthma uncontrolled by high dose inhaled corticosteroids and long-acting beta-adrenoreceptor agonists plus oral corticosteroids (OCS) (≥7.5 mg/d). No minimum baseline blood eosinophil count was specified. Following a protocol amendment, the primary endpoint was reduction of annualized severe asthma exacerbation rate adjusted for the overall time on treatment (SAER). Subgroup analysis according to yearly cumulative OCS intake was also performed, a higher OCS dose indicating more severe asthma that is harder to control.

Results

Following an average exposure of approximately 13 months, masitinib (n = 240) reduced the SAER by 35% relative to placebo (n = 115) (rate ratio (RR) 0.65 (95% CI [0.47–0.90]; P = 0.010)). For patients with eosinophil ≥150 cell/µL, masitinib (n = 181) reduced SAER by 38% relative to placebo (n = 87); RR 0.62 (95% CI [0.42–0.91]; P = 0.016). Benefit of masitinib was shown to increase in the most severely affected patients (OCS intake of >1000 mg/year), with a significant (P < 0.01) reduction in SAER of 50%–70%. Safety was consistent with the known masitinib profile.

Conclusion

Orally administered masitinib reduces the risk of asthma exacerbations in severe asthma patients, with an acceptable safety profile. Masitinib may potentially provide a new treatment option for oral corticosteroid-dependent severe asthma.

Effect of miR-506-3p on Proliferation and Apoptosis of Airway Smooth Muscle Cells in Asthmatic Mice by Regulating CCL2 Gene Expression and Mediating TLR4/NF-κB Signaling Pathway Activation

We aimed to investigate the effect of miR-506-3p on the proliferation and apoptosis of airway smooth muscle cells (ASMCS) in asthmatic mice by regulating the activation of TLR4/NF-κB signaling pathway through targeted regulation of C-C Motif Chemokine Ligand 2 (CCL2) expression. Twenty-four BALB/c mice of specific pathogen-free grade were selected to establish asthmatic mouse model, which were randomly divided into normal control group and asthma model group (n = 12 for each group). HE and IHC staining, bioinformatics and dual luciferase reporter assay, RT-PCR MTT, flow cytometry and Western blot were used in this research. HE staining showed airway epithelium thickening, submucosal inflammatory cell infiltration and airway smooth muscle thickening, and the positive expression rate of CCL2 was significantly increased in asthma model group (all P < 0.05). CCL2 was the target gene of miR-506-3p. Moreover, the expression of miR-506-3p in asthma model group was significantly decreased, the mRNA and protein expression levels of CCL2, TLR4, NF-κB (p65) and Bcl-2 were significantly increased, while those of Bax were decreased (all P < 0.05). In miR-506-3p mimic group or siRNA-CCL2 group, the expression of CCL2, TLR4, NF-κB (p65) and Bcl-2 decreased obviously, while that of Bax increased, cell proliferation decreased, G1 phase prolonged, G2 & S phases shortened, and apoptosis rate increased significantly (all P < 0.05), whereas the opposite trends were found in miR-506-3p inhibitor group (all P < 0.05). However, there was no statistical difference in the above-mentioned indexes in miR-506-3p inhibitor + siRNA-CCL2 group (all P > 0.05). Overexpression of miR-506-3p can inhibit ASMCS proliferation and promote apoptosis via inhibiting CCL2 expression and suppressing the activation of TLR4/NF-κB signaling pathway. Inhibited expression of miR-506-3p can reverse the positive role of CCL2 gene silencing. Our study is the first to prove the beneficial role of miR-506-3p-CCL2-TLR4/NF-κB regulatory axis in the development of asthma.

MicroRNA-21 Inhibition Suppresses Alveolar M2 Macrophages in an Ovalbumin-Induced Allergic Asthma Mice Model

Purpose

MicroRNA-21 (miR-21) influences the Th2 immune pathway by suppressing the expressions of interleukin (IL)-12 and interferon (IFN)-γ. The effects of miR-21 suppression on alveolar macrophage polarization and airway inflammation are not known.

Methods

BALB/c and miR-21 knockout (KO) mice were sensitized and challenged with ovalbumin (OVA). The anti-miR-21 antagomir was administered to BALB/c mice by intranasal inhalation from the day of OVA sensitization. Changes in cell counts, cytokine levels in bronchoalveolar lavage fluid (BALF), and airway hyperresponsiveness (AHR) were examined. Total, M1, and M2 macrophages were examined in the lung tissues by immunohistochemistry (IHC). M2 macrophages from the OVA mice lung were inhaled into the anti-miR-21 antagomir-treated asthmatic mice. Moreover, the polarization of M0 to M2 macrophages upon IL-4 stimulation was analyzed after anti-miR-21 antagomir transfection.

Results

The miR-21 KO mice showed decreases in AHR, total cell and eosinophil counts in BALF, and in the levels of IL-4, IL-5, IL-10, and IL-13. Expression of IL-12 and IFN-γ were increased in the miR-21 KO mice. Peribronchial inflammation and goblet cell dysplasia were significantly decreased in the lung tissues of miR-21 KO OVA mice compared to the wild type OVA mice. IHC for M1, M2, and total macrophage in the lung tissues showed that miR-21 inhalation suppressed alveolar M2 macrophages in KO mice. M2 macrophage inhalation restored AHR and eosinophilic airway inflammation in the miR-21 antagomir-treated mice. Moreover, anti-miR-21 antagomir transfection decreased the expression of M2 markers and increased the expression of M1 markers in M0 macrophages after IL-4 stimulation.

Conclusions

The results suggest that miR-21 antagonism could suppress alveolar M2 macrophage polarization, decreasing not only the Th2 eosinophilic airway inflammation but also AHR and airway remodeling process.

Phosphorylation of GMFγ by c-Abl Coordinates Lamellipodial and Focal Adhesion Dynamics to Regulate Airway Smooth Muscle Cell Migration

Airway smooth muscle cells require coordinated protrusion and focal adhesion dynamics to migrate properly. However, the signaling cascades that connect these two processes remain incompletely understood. Glia maturation factor (GMF)-γ has been implicated in inducing actin debranching and inhibiting nucleation. In this study, we discovered that GMFγ phosphorylation at Y104 regulates human airway smooth muscle cell migration. Using high-resolution microscopy coupled with three-dimensional object-based quantitative image analysis software, Imaris 9.2.0, phosphomimetic mutant, Y104D-GMFγ, was enriched at nascent adhesions along the leading edge where it recruited activated neural Wiskott-Aldrich syndrome protein (N-WASP; pY256) to promote actin-branch formation, which enhanced lamellipodial dynamics and limited the growth of focal adhesions. Unexpectedly, we found that nonphosphorylated mutant, Y104F-GMFγ, was enriched in growing adhesions where it promoted a linear branch organization and focal adhesion clustering, and recruited zyxin to increase maturation, thus inhibiting lamellipodial dynamics and cell migration. The localization of GMFγ between the leading edge and focal adhesions was dependent upon myosin activity. Furthermore, c-Abl tyrosine kinase regulated the GMFγ phosphorylation-dependent processes. Together, these results unveil the importance of GMFγ phosphorylation in coordinating lamellipodial and focal adhesion dynamics to regulate cell migration.

Role of Platelet-Derived Growth Factor (PDGF) in Asthma as an Immunoregulatory Factor Mediating Airway Remodeling and Possible Pharmacological Target

Asthma is a chronic and heterogenic disease of the respiratory system, one of the most common lung diseases worldwide. The underlying pathologies, which are chronic inflammatory process and airway remodeling (AR), are mediated by numerous cells and cytokines. Particularly interesting in this field is the platelet-derived growth factor (PDGF), one of the members of the human growth factor family. In this article, the authors analyze the available data on the role of PDGF in asthma in experimental models and in human research. PDGF is expressed in airway by various cells contributing to asthma pathogenesis—mast cells, eosinophils, and airway epithelial cells. Research confirms the thesis that this factor is also secreted by these cells in the course of asthma. The main effects of PDGF on bronchi are the proliferation of airway smooth muscle (ASM) cells, migration of ASM cells into the epithelium and enhanced collagen synthesis by lung fibroblasts. The importance of AR in asthma is well recognized and new therapies should also aim to manage it, possibly targeting PDGFRs. Further studies on new and already existing drugs, mediating the PDGF signaling and related to asthma are necessary. Several promising drugs from the tyrosine kinase inhibitors group, including nilotinib, imatinib masitinib, and sunitinib, are currently being clinically tested and other molecules are likely to emerge in this field.

Mast Cell-Mediated Orchestration of the Immune Responses in Human Allergic Asthma: Current Insights

Improving the lung function after experimental allergen challenge by blocking of mast cell (MC) mediators and the capability of MC mediators (including histamine, prostaglandin (PG) D2, and leukotriene (LT) C4) in induction of mucosal edema, bronchoconstriction, and mucus secretion provide evidence that MCs play a key role in pathophysiology of asthma. In asthma, the number of MCs increases in the airways and infiltration of MCs in a variety of anatomical sites including the epithelium, the submucosal glands, and the smooth muscle bundles occurs. MC localization within the ASM is accompanied with the hypertrophy and hyperplasia of the layer, and smooth muscle dysfunction that is mainly observed in forms of bronchial hyperresponsiveness, and variable airflow obstruction. Owing to the expression of a wide range of surface receptors and releasing various cytoplasmic mediators, MCs orchestrate the pathologic events of the disease. MC-released preformed mediators including chymase, tryptase, and histamine and de novo synthesized mediators such as PGD2, LTC4, and LTE4 in addition of cytokines mainly TGFβ1, TSLP, IL-33, IL-4, and IL-13 participate in pathogenesis of asthma. The release of MC mediators and MC/airway cell interactions during remodeling phase of asthma results in persistent cellular and structural changes in the airway wall mainly epithelial cell shedding, goblet cell hyperplasia, hypertrophy of ASM bundles, fibrosis in subepithelial region, abnormal deposition of extracellular matrix (ECM), increased tissue vascularity, and basement membrane thickening. We will review the current knowledge regarding the participation of MCs in each stage of asthma pathophysiology including the releasing mediators and their mechanism of action, expression of receptors by which they respond to stimuli, and finally the pharmaceutical products designed based on the strategy of blocking MC activation and mediator release.

Effect of nintedanib on airway inflammation in a mouse model of acute asthma

Objective: New treatments are needed for cases of asthma that are refractory to traditional therapies. In this study, we examined the effect of oral nintedanib, an intracellular inhibitor of tyrosine kinases, on airway hyper-responsiveness (AHR) and airway smooth muscle cells, using a mouse model of experimental asthma. Methods: Asthma was experimentally induced in mice via subcutaneous injection of ovalbumin (OVA). A group of saline-injected mice served as a control group. The OVA mice were then divided into four treatment groups according to the dose of nintedanib. AHR was examined via exposure to vaporized methacholine. Airway inflammation was assessed via bronchoalveolar lavage fluid (BALF) cell counts and Th2 cytokine concentrations. Results: Baseline levels of AHR and airway inflammation were higher in OVA mice than in the control group. Treatment with nintedanib lowered AHR, BALF cell counts and BALF cytokine levels in a dose-dependent fashion. The effect of nintedanib was comparable to that of dexamethasone. In particular, treatment with nintedanib lowered the expression of transforming growth factor-β1 and inhibited the expression and phosphorylation of platelet-derived growth factor receptor-β, vascular endothelial growth factor receptor 1 (VEGFR1), VEGFR2, fibroblast growth factor receptor 2 (FGFR2), FGFR3, and extracellular signal-regulated kinase. Conclusions: Nintedanib lowered AHR and the expression of factors associated with airway inflammation and remodeling in a mouse model of experimental asthma. Our results suggest that nintedanib may be useful in the treatment of asthma.

Specific protein 1, c-Abl and ERK1/2 form a regulatory loop

The tyrosine kinase c-Abl participates in the regulation of various cellular functions including cell proliferation, adhesion, migration, smooth muscle contraction and cancer progression. However, knowledge regarding transcriptional regulation of c-Abl is surprisingly limited. Sp1 is a founding member of the Sp1 transcription factor family that has been implicated in housekeeping gene expression, tumor cell proliferation and differentiation. Here, we show that knockdown and rescue of Sp1 affected growth factor-mediated c-Abl expression in cells. c-Abl promoter activity was also affected by Sp1 knockdown. This is the first evidence to suggest that Sp1 is an important transcription factor to regulate c-Abl expression. In addition, Sp1 phosphorylation at Thr-453 and Thr-739 has been proposed to regulate its activity in Drosophila cells. We unexpectedly found that growth factors did not induce Sp1 phosphorylation at these two residues. In contrast, growth factor stimulation upregulated Sp1 expression. Intriguingly, inhibition of ERK1 and ERK2 (ERK1/2, also known as MAPK3 and MAPK1, respectively) reduced expression of Sp1 and c-Abl. Furthermore, c-Abl knockdown diminished ERK1/2 phosphorylation and Sp1 expression. Taken together, these studies suggest that Sp1 can modulate c-Abl expression at transcription level. Conversely, c-Abl affects ERK1/2 activation and Sp1 expression in cells.

A Novel Role of a Chemotherapeutic Agent in a Rat Model of Endotoxemia: Modulation of the STAT-3 Signaling Pathway

Sepsis caused by lipopolysaccharide (LPS) is a life-threatening disease accompanied by multiple organ failure. This study investigated the curative effects of imatinib (IMA) against hepatic, renal, and pulmonary responses caused by a single administration of LPS (10 mg/kg, i.p.) in rats. Treatment with IMA (15 mg/kg, i.p.) 30 min after LPS antagonized the LPS-induced boost of liver enzymes (ALT, AST), kidney functions (BUN, sCr) as well as the elevated pulmonary vascular permeability and edema. IMA declined tissue contents of NF-κB, STAT-3, P38-MAPK, TNF-α, IL-1β, and iNOS. It also amplified the anti-inflammatory cytokine IL-10 as well as the Bcl-2/Bax ratio, a cardinal indicator of the anti-apoptotic effect. Meanwhile, the rats exhibited marked reduction of the broncho-alveolar lavage fluid (BALF) contents of TNF-α, IL-1β, IFN-γ, and neutrophil count; however, they revealed prominent augmentation of the BALF content IL-10. In conclusion, these findings suggest that IMA is endowed with anti-inflammatory, anti-oxidant, and anti-apoptotic properties and hence may provide a novel agent for the management of sepsis.

Drug repurposing to treat asthma and allergic disorders: Progress and prospects

Allergy and atopic asthma have continued to become more prevalent in modern society despite the advent of new treatments, representing a major global health problem. Common medications such as antihistamines and steroids can have undesirable long-term side-effects and lack efficacy in some resistant patients. Biologic medications are increasingly given to treatment-resistant patients, but they can represent high costs, complex dosing and management, and are not widely available around the world. The field needs new, cheap, and convenient treatment options in order to bring better symptom relief to patients. Beyond continued research and development of new drugs, a focus on drug repurposing could alleviate this problem by repositioning effective and safe small-molecule drugs from other fields of medicine and applying them toward the treatment for asthma and allergy. Herein, preclinical models, case reports, and clinical trials of drug repurposing efficacy in allergic disease are reviewed. Novel drugs are also proposed for repositioning based on their mechanism of action to treat asthma and allergy. Overall, drug repurposing could become increasingly important as a way of advancing allergy and atopic asthma therapy, filling a need in treatment of patients today.

Effect of roflumilast on airway remodelling in a murine model of chronic asthma

BACKGROUND

Airway remodelling is associated with irreversible, or partially reversible, airflow obstruction and ultimately unresponsiveness to asthma therapies such as corticosteroids. Roflumilast is a selective phosphodiesterase-4 inhibitor that has an anti-inflammatory effect in chronic obstructive pulmonary disease (COPD).

OBJECTIVE

The objective of this study was to study the effect of roflumilast on airway inflammation and remodelling in a murine model of chronic asthma.

METHODS

BALB/c mice sensitized to ovalbumin (OVA) were chronically exposed to intranasal OVA administration twice a week for additional 3 months. Roflumilast was administered orally during the intranasal OVA challenge. A lung fibroblast cell line was used in the proliferation assay.

RESULTS

Compared with control mice, mice chronically exposed to OVA developed eosinophilic airway inflammation, airway hyper-responsiveness (AHR), and exhibited features of airway remodelling. Administration of roflumilast significantly inhibited airway inflammation and AHR. Roflumilast also significantly decreased goblet cell hyperplasia and pulmonary fibrosis, which are parameters of airway remodelling. The levels of interleukin (IL)-4, IL-5, and IL-13 in the bronchoalveolar lavage (BAL) fluids were significantly lower in the roflumilast group. In vitro, roflumilast significantly inhibited stem cell factor (SCF)-induced cell proliferation of fibroblasts. The SCF concentration and mRNA expression in a murine model also significantly decreased with roflumilast treatment.

CONCLUSIONS

These results suggest that the administration of roflumilast regulates airway inflammation, AHR, and airway remodelling in a model of chronic asthma. The beneficial effects from roflumilast may be related to the SCF/c-kit pathway.

Effect of nintedanib on airway inflammation and remodeling in a murine chronic asthma model

INTRODUCTION

Nintedanib is a multi-tyrosine kinase receptor inhibitor recently approved for treatment of idiopathic pulmonary fibrosis. Although angiogenesis is a key process involved in airway structural changes in patients with bronchial asthma, the effect of nintedanib targeting the angiokinase pathway on airway inflammation and remodeling has not been evaluated.

METHODS

We used a 3-month ovalbumin (OVA) challenge mouse model of airway remodeling. Nintedanib was orally administrated during the challenge period, and the effects were examined based on the percentage of airway inflammatory cells, airway hyper-reactivity (AHR), peribronchial goblet cell hyperplasia, total lung collagen and smooth muscle area. The expression of growth factor receptors was analyzed in mice lung tissues.

RESULTS

The OVA challenged group showed a significant increase in airway eosinophilic inflammation, elevated Th2 cytokines, AHR, and airway remodeling compared to those in the control group. The airway remodeling process, as evaluated by goblet cell hyperplasia, total lung collagen level, and airway smooth muscle area, was suppressed by nintedanib compared to that by OVA. Nintedanib effectively suppressed the phosphorylation of vascular endothelial growth factor/ platelet derived growth factor subunit2/fibroblast growth factor3 receptors in the mice lung.

CONCLUSIONS

Nintedanib effectively ameliorated airway inflammation and remodeling in an OVA-induced chronic asthma model. These results suggest that nintedanib could be a new treatment agent targeting airway remodeling in patients with severe asthma.

The roles and regulation of the actin cytoskeleton, intermediate filaments and microtubules in smooth muscle cell migration

Smooth muscle cell migration has been implicated in the development of respiratory and cardiovascular systems; and airway/vascular remodeling. Cell migration is a polarized cellular process involving a protrusive cell front and a retracting trailing rear. There are three cytoskeletal systems in mammalian cells: the actin cytoskeleton, the intermediate filament network, and microtubules; all of which regulate all or part of the migrated process. The dynamic actin cytoskeleton spatially and temporally regulates protrusion, adhesions, contraction, and retraction from the cell front to the rear. c-Abl tyrosine kinase plays a critical role in regulating actin dynamics and migration of airway smooth muscle cells and nonmuscle cells. Recent studies suggest that intermediate filaments undergo reorganization during migration, which coordinates focal adhesion dynamics, cell contraction, and nucleus rigidity. In particular, vimentin intermediate filaments undergo phosphorylation and reorientation in smooth muscle cells, which may regulate cell contraction and focal adhesion assembly/disassembly. Motile cells are characterized by a front-rear polarization of the microtubule framework, which regulates all essential processes leading to cell migration through its role in cell mechanics, intracellular trafficking, and signaling. This review recapitulates our current knowledge how the three cytoskeletal systems spatially and temporally modulate the migratory properties of cells. We also summarize the potential role of migration-associated biomolecules in lung and vascular diseases.

New and developing non-adrenoreceptor small molecule drugs for the treatment of asthma

INTRODUCTION

Inhaled corticosteroids (ICS) alone or in combination with an inhaled long-acting beta₂-agonist (LABA) are the preferred long-term treatment for adults and adolescents with symptomatic asthma. Additional drugs include leukotriene-receptor antagonists, slow-release theophylline and the long-acting muscarinic antagonist (LAMA) tiotropium (approved in 2015). There is a need for more effective therapies, as many patients continue to have poorly controlled asthma. Areas covered: New and developing long-acting non-adrenoreceptor synthetic drugs for the treatment of symptomatic chronic asthma despite treatment with an ICS alone or combined with a LABA. Data was reviewed from studies published up until November 2016. Expert opinion: Tiotropium improves lung function and has a modest effect in reducing exacerbations when added to ICS alone or ICS and LABA. The LAMAs umeclidinium and glycopyrronium are under development in fixed dose combination with ICS and LABA. Novel small molecule drugs, such as CRTH2 receptor antagonists, PDE₄ inhibitors, protein kinase inhibitors and nonsteroidal glucocorticoid receptor agonists and 'off-label' use of licensed drugs, such as macrolides and statins are under investigation for asthma, although their effectiveness in clinical practice is not established. To better achieve the goal of developing effective novel small molecule drugs for asthma will require greater understanding of mechanisms of disease and the different phenotypes and endotypes of asthma.

Inhibitory Effects of Resveratrol on Airway Remodeling by Transforming Growth Factor-β/Smad Signaling Pathway in Chronic Asthma Model

Purpose

Asthma is a chronic airway disease characterized by airway remodeling, leading to a progressive decline in lung function. Therapeutic agents that attenuate airway remodeling can complement the limited effects of traditional glucocorticoids. In this study, we investigated the effect of resveratrol on allergic airway inflammation and remodeling in a murine model of chronic bronchial asthma.

Methods

Peribronchial smooth muscle thickening that developed in mice challenged with a 3-month repeated exposure to ovalbumin (OVA) was used to study airway remodeling. Oral resveratrol was administered daily during the OVA challenge. The expression of TGF-β1/Smad signaling proteins and downstream mesenchymal markers in the presence or absence of resveratrol was examined in bronchial epithelial cells.

Results

OVA sensitization and chronic challenge increased airway hyperresponsiveness, inflammation, goblet cell hyperplasia, α-smooth muscle actin (SMA), and collagen deposition. Resveratrol effectively suppressed OVA-induced airway inflammation and remodeling. The expression of TGF-β1/phosphorylated Smad2/3 was increased in the lung tissues of OVA-challenged mice but effectively inhibited by resveratrol. In bronchial epithelial cells, the TGF-β1-induced expression of the mesenchymal markers snail, slug, vimentin, and α-SMA was suppressed by resveratrol treatment.

Conclusions

Resveratrol effectively ameliorated both airway inflammation and airway structural changes in a mouse model of bronchial asthma. These effects were mediated by decreased TGF-β1 expression, in turn suppressing TGF-β1/Smad signaling and the epithelial-mesenchymal transition process. Our results demonstrate the potential benefits of resveratrol for the treatment of airway remodeling associated with bronchial asthma.

Different anti-remodeling effect of nilotinib and fluticasone in a chronic asthma model

BACKGROUND/AIMS

Inhaled corticosteroids are the most effective treatment currently available for asthma, but their beneficial effect against airway remodeling is limited. The tyrosine kinase inhibitor nilotinib has inhibitory activity against c-kit and the platelet-derived growth factor receptor. We compared the effects of fluticasone and nilotinib on airway remodeling in a chronic asthma model. We also examined whether co-treatment with nilotinib and fluticasone had any synergistic effect in preventing airway remodeling.

METHODS

We developed a mouse model of airway remodeling, including smooth muscle thickening, in which ovalbumin (OVA)-sensitized female BALB/c-mice were repeatedly exposed to intranasal OVA administration twice per week for 3 months. Mice were treated with fluticasone and/or nilotinib intranasally during the OVA challenge.

RESULTS

Mice chronically exposed to OVA developed eosinophilic airway inflammation and showed features of airway remodeling, including thickening of the peribronchial smooth muscle layer. Both fluticasone and nilotinib attenuated airway smooth muscle thickening. However, only nilotinib suppressed fibrotic changes, demonstrating inhibition of collagen deposition. Fluticasone reduced pro-inflammatory cells, such as eosinophils, and several cytokines, such as interleukin 4 (IL-4), IL-5, and IL-13, induced by repeated OVA challenges. On the other hand, nilotinib reduced transforming growth factor β1 levels in bronchoalveolar lavage fluid and inhibited fibroblast proliferation significantly.

CONCLUSIONS

These results suggest that fluticasone and nilotinib suppressed airway remodeling in this chronic asthma model through anti-inflammatory and anti-fibrotic pathways, respectively.

Molecular Background of miRNA Role in Asthma and COPD: An Updated Insight

Inflammatory airway diseases are a significant health problems requiring new approaches to the existing therapies and addressing fundamental issues. Difficulties in developing effective therapeutic strategies might be caused by lack of understanding of their exact molecular mechanism. MicroRNAs (miRNAs) are a class of regulators that already revolutionized the view of gene expression regulation. A cumulating number of investigations show a pivotal role of miRNAs in the pathogenesis of asthma, chronic obstructive pulmonary disease (COPD), or airway remodeling through the regulation of many pathways involved in their pathogenesis. Expression changes of several miRNAs have also been found to play a role in the development and/or improvement in asthma or COPD. Still, relatively little is known about the role of miRNAs in inflammatory disorders. The microRNA profiles may differ depending on the cell type or antigen-presenting cell. Based on the newest literature, this review discusses the current knowledge concerning miRNA contribution and influence on lung inflammation and chosen inflammatory airway diseases: asthma and COPD.

Novel approaches to the management of noneosinophilic asthma

Noneosinophilic airway inflammation occurs in approximately 50% of patients with asthma. It is subdivided into neutrophilic or paucigranulocytic inflammation, although the proportion of each subtype is uncertain because of variable cut-off points used to define neutrophilia. This article reviews the evidence for noneosinophilic inflammation being a target for therapy in asthma and assesses clinical trials of licensed drugs, novel small molecules and biologics agents in noneosinophilic inflammation. Current symptoms, rate of exacerbations and decline in lung function are generally less in noneosinophilic asthma than eosinophilic asthma. Noneosinophilic inflammation is associated with corticosteroid insensitivity. Neutrophil activation in the airways and systemic inflammation is reported in neutrophilic asthma. Neutrophilia in asthma may be due to corticosteroids, associated chronic pulmonary infection, altered airway microbiome or delayed neutrophil apoptosis. The cause of poorly controlled noneosinophilic asthma may differ between patients and involve several mechanism including neutrophilic inflammation, T helper 2 (Th2)-low or other subtypes of airway inflammation or corticosteroid insensitivity as well as noninflammatory pathways such as airway hyperreactivity and remodelling. Smoking cessation in asthmatic smokers and removal from exposure to some occupational agents reduces neutrophilic inflammation. Preliminary studies of 'off-label' use of licensed drugs suggest that macrolides show efficacy in nonsmokers with noneosinophilic severe asthma and statins, low-dose theophylline and peroxisome proliferator-activated receptor gamma (PPARγ) agonists may benefit asthmatic smokers with noneosinophilic inflammation. Novel small molecules targeting neutrophilic inflammation, such as chemokine (CXC) receptor 2 (CXCR2) antagonists reduce neutrophils, but do not improve clinical outcomes in studies to date. Inhaled phosphodiesterase (PDE)4 inhibitors, dual PDE3 and PDE4 inhibitors, p38MAPK (mitogen-activated protein kinase) inhibitors, tyrosine kinase inhibitors and PI (phosphoinositide) 3kinase inhibitors are under development and these compounds may be of benefit in noneosinophilic inflammation. The results of clinical trials of biological agents targeting mediators associated with noneosinophilic inflammation, such as interleukin (IL)-17 and tumor necrosis factor (TNF)-α are disappointing. Greater understanding of the mechanisms of noneosinophilic inflammation in asthma should lead to improved therapies.

Pharmacological Therapy of Bronchial Asthma: The Role of Biologicals

Bronchial asthma is a heterogeneous, complex, chronic inflammatory and obstructive pulmonary disease driven by various pathways to present with different phenotypes. A small proportion of asthmatics (5-10%) suffer from severe asthma with symptoms that cannot be controlled by guideline therapy with high doses of inhaled steroids plus a second controller, such as long-acting β2 agonists (LABA) or leukotriene receptor antagonists, or even systemic steroids. The discovery and characterization of the pathways that drive different asthma phenotypes have opened up new therapeutic avenues for asthma treatment. The approval of the humanized anti-IgE antibody omalizumab for the treatment of severe allergic asthma has paved the way for other cytokine-targeting therapies, particularly those targeting interleukin (IL)-4, IL-5, IL-9, IL-13, IL-17, and IL-23 and the epithelium-derived cytokines IL-25, IL-33, and thymic stromal lymphopoietin. Knowledge of the molecular basis of asthma phenotypes has helped, and continues to help, the development of novel biologicals that target a diverse array of phenotype-specific molecular targets in patients suffering from severe asthma. This review summarizes potential therapeutic approaches that are likely to show clinical efficacy in the near future, focusing on biologicals as promising novel therapies for severe asthma.

Addressing corticosteroid insensitivity in adults with asthma

Corticosteroids are the most effective treatment for asthma, but the therapeutic response varies markedly between individuals, with up to one third of patients showing evidence of insensitivity to corticosteroids. This article summarizes information on genetic, environmental and asthma-related factors as well as demographic and pharmacokinetic variables associated with corticosteroid insensitivity in asthma. Molecular mechanisms proposed to explain corticosteroid insensitivity are reviewed including alterations in glucocorticoid receptor subtype, binding and nuclear translocation, increased proinflammatory transcription factors and defective histone acetylation. Current therapies and future interventions that may restore corticosteroid sensitivity in asthma are discussed, including small molecule drugs and biological agents. In the future, biomarkers may be used in the clinic to predict corticosteroid sensitivity in patients with poorly controlled asthma.

Effect of intranasal rosiglitazone on airway inflammation and remodeling in a murine model of chronic asthma

BACKGROUND/AIMS

Asthma is characterized by airway hyperresponsiveness, inflammation, and remodeling. Peroxisome proliferator-activated receptors have been reported to regulate inflammatory responses in many cells. In this study, we examined the effects of intranasal rosiglitazone on airway remodeling in a chronic asthma model.

METHODS

We developed a mouse model of airway remodeling, including smooth muscle thickening, in which ovalbumin (OVA)-sensitized mice were repeatedly exposed to intranasal OVA administration twice per week for 3 months. Mice were treated intranasally with rosiglitazone with or without an antagonist during OVA challenge. We determined airway inflammation and the degree of airway remodeling by smooth muscle actin area and collagen deposition.

RESULTS

Mice chronically exposed to OVA developed sustained eosinophilic airway inflammation, compared with control mice. Additionally, the mice developed features of airway remodeling, including thickening of the peribronchial smooth muscle layer. Administration of rosiglitazone intranasally inhibited the eosinophilic inflammation significantly, and, importantly, airway smooth muscle remodeling in mice chronically exposed to OVA. Expression of Toll-like receptor (TLR)-4 and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) was increased in the OVA group and decreased in the rosiglitazone group. Co-treatment with GW9660 (a rosiglitazone antagonist) and rosiglitazone increased the expression of TLR-4 and NF-κB.

CONCLUSIONS

These results suggest that intranasal administration of rosiglitazone can prevent not only air way inf lammation but also air way remodeling associated with chronic allergen challenge. This beneficial effect is mediated by inhibition of TLR-4 and NF-κB pathways.

The tyrosine kinase inhibitor imatinib prevents lung injury and death after intravenous LPS in mice

Severe sepsis and septic shock are frequent causes of the acute respiratory distress syndrome, and important sources of human mortality. Lipopolysaccharide (LPS), a component of Gram-negative bacterial cell walls, plays a major role in the pathogenesis of severe sepsis and septic shock. LPS exposure induces the production of harmful reactive oxygen species, and the resultant oxidant injury has been implicated in the pathogenesis of both severe sepsis and ARDS. We previously showed that the tyrosine kinase inhibitor imatinib increases lung endothelial antioxidant enzymes and protects against pulmonary endothelial antioxidant injury. In the present study, we tested the hypothesis that imatinib would protect against lung injury and systemic inflammation caused by intravenous LPS in an intact mouse model of endotoxemia mimicking early sepsis. We found that intravenous LPS induced a significant increase in the activity of lung xanthine oxidoreductase (XOR), an enzyme which is a major source of reactive oxygen species and implicated in the pathogenesis of acute lung injury. Imatinib had no effect of LPS-induced XOR activity. However, pretreatment of mice with imatinib increased lung catalase activity and decreased intravenous LPS-induced lung oxidant injury as measured by γ-H2AX, a marker of oxidant-induced DNA damage, lung apoptosis, and pulmonary edema. Imatinib also attenuated systemic cytokine expression after intravenous LPS exposure. Finally, imatinib completely prevented mortality in an in vivo, intravenous LPS mouse model of endotoxemia and lung injury. These results support the testing of imatinib as a novel pharmacologic agent in the treatment of Gram-negative sepsis and sepsis-induced ARDS.

Effect of P2X4R on airway inflammation and airway remodeling in allergic airway challenge in mice

P2X4 receptor (P2X4R) is the most widely expressed subtype of the P2XRs in the purinergic receptor family. Adenosine triphosphate (ATP), a ligand for this receptor, has been implicated in the pathogenesis of asthma. ATP-P2X4R signaling is involved in pulmonary vascular remodeling, and in the proliferation and differentiation of airway and alveolar epithelial cell lines. However, the role of P2X4R in asthma remains to be elucidated. This aim of the present study was to investigate the effects of P2X4R in a murine experimental asthma model. The asthmatic model was established by the inhalation of ovalbumin (OVA) in BALB/c mice. The mice were treated with P2X4R-specific agonists and antagonists to investigate the role of this receptor in vivo. Pathological changes in the bronchi and lung tissues were examined using hematoxylin and eosin staining, Masson's trichrome staining and Alcian blue staining. The inflammatory cells in the bronchoalveolar lavage fluid were counted, and the expression levels of P2X4R, α-smooth muscle actin (α-SMA) and proliferating cell nuclear antigen (PCNA) were detected using western blotting. In the OVA-challenged mice, inflammation, infiltration, collagen deposition, mucus production, and the expression levels of P2X4R and PCNA were all increased; however, the expression of α-SMA was decreased, compared with the mice in the control group. Whereas treatment with the P2X4R agonist, ATP, enhanced the allergic reaction, treatment with the P2X4R antagonist, 5-BDBD, attenuated the allergic reaction. The results suggested that ATP-P2X4R signaling may not only contribute to airway inflammation, but it may also contribute to airway remodeling in allergic asthma in mice.

MicroRNA-203 negatively regulates c-Abl, ERK1/2 phosphorylation, and proliferation in smooth muscle cells

The nonreceptor tyrosine kinase c-Abl has a role in regulating smooth muscle cell proliferation, which contributes to the development of airway remodeling in chronic asthma. MicroRNAs (miRs) are small noncoding RNA molecules that regulate gene expression by binding to complementary sequences in the 3′ untranslated regions (3′ UTR) of target mRNAs. Previous analysis suggests that miR-203 is able to bind to the 3′ UTR of human c-Abl mRNA. In this report, treatment with miR-203 attenuated the expression of c-Abl mRNA and protein in human airway smooth muscle (HASM) cells. Furthermore, transfection with an miR-203 inhibitor enhanced the expression of c-Abl at mRNA and protein levels in HASM cells. Treatment with platelet-derived growth factor (PDGF) induced the proliferation and ERK1/2 phosphorylation in HASM cells. Exposure to miR-203 attenuated the PDGF-stimulated proliferation and ERK1/2 phosphorylation in HASM cells. The expression of c-Abl at protein and mRNA levels was higher in asthmatic HASM cells, whereas the level of miR-203 was reduced in asthmatic HASM cells as compared to control HASM cells. Taken together, our present results suggest that miR-203 is a negative regulator of c-Abl expression in smooth muscle cells. miR-203 regulates smooth muscle cell proliferation by controlling c-Abl expression, which in turn modulates the activation of ERK1/2.

Parabromophenacyl bromide inhibits subepithelial fibrosis by reducing TGF-β1 in a chronic mouse model of allergic asthma

BACKGROUND

Our previous study showed that parabromophenacyl bromide (PBPB) inhibits the features of allergic airway inflammation and airway hyperresponsiveness (AHR). However, its effect on airway remodeling, e.g. subepithelial fibrosis in a chronic allergic asthma model, was not investigated. We examined this issue in this study.

METHODS

PBPB was administered to mice with an induced chronic asthmatic condition. AHR was estimated at the end of the experiment, followed by euthanasia. Lung sections were stained with hematoxylin and eosin, periodic acid-Schiff and Masson's trichrome to determine airway inflammation, goblet cell metaplasia and subepithelial fibrosis, respectively. Transforming growth factor-β1 (TGF-β1) was estimated in lung homogenates. To determine the effect of PBPB on smooth-muscle hyperplasia, immunohistochemistry against α-smooth-muscle actin was performed on the lung sections.

RESULTS

Chronic ovalbumin challenges in a mouse model of allergic asthma caused significant subepithelial fibrosis and elevated TGF-β1, along with significant AHR. PBPB attenuated subepithelial fibrosis with a reduction of lung TGF-β1, airway inflammation and AHR without affecting goblet cell metaplasia. It also attenuated smooth-muscle hyperplasia with a reduction in the expression of α-smooth-muscle actin in the lungs.

CONCLUSION

Our findings indicate that PBPB attenuates some crucial features of airway remodeling such as subepithelial fibrosis and smooth-muscle hyperplasia. These data suggest that PBPB could therefore be a therapeutic drug for chronic asthma.

Asthma therapy and its effect on airway remodelling

Asthma remains a major health problem with significant morbidity, mortality and economic costs. In asthma, airway remodelling, which refers to all the microscopic structural changes seen in the airway tissue, has been recognised for many decades and remains one of the defining characteristics of the disease; however, it is still poorly understood. The detrimental pathophysiological consequences of some features of remodelling, like increased airway smooth muscle mass and subepithelial fibrosis, are well documented. However, whether targeting these by therapy would be beneficial is unknown. Although the prevailing thinking is that remodelling is an abnormal response to persistent airway inflammation, recent evidence, especially from studies of remodelling in asthmatic children, suggests that the two processes occur in parallel. The effects of asthma therapy on airway remodelling have not been studied extensively due to the challenges of obtaining airway tissue in the context of clinical trials. Corticosteroids remain the cornerstone of asthma therapy, and their effects on remodelling have been better studied than other drugs. Bronchial thermoplasty is the only asthma therapy to primarily target remodelling, although how it results in the apparent clinical benefits seen is not exactly clear. In this article we discuss the mechanisms of airway remodelling in asthma and review the effects of conventional and novel asthma therapies on the process.

Pericytes in chronic lung disease

Pericytes are mesenchymal cells embedded within the abluminal surface of the endothelium of microvessels such as capillaries, pre-capillary arterioles, post-capillary and collecting venules, where they maintain microvascular homeostasis and participate in angiogenesis. In addition to their roles in supporting the vasculature and facilitating leukocyte extravasation, pericytes have been recently investigated as a subpopulation of mesenchymal stem cells (MSCs) due to their capacity to differentiate into numerous cell types including the classic MSC triad, i.e. osteocytes, chondrocytes and adipocytes. Other studies in models of fibrotic inflammatory disease of the lung have demonstrated a vital role of pericytes in myofibroblast activation, collagen deposition and microvascular remodelling, which are hallmark features of chronic lung diseases such as asthma, chronic obstructive pulmonary disorder, pulmonary fibrosis and pulmonary hypertension. Further studies into the mechanisms of the pericyte-to-myofibroblast transition and migration to fibrotic foci will hopefully clarify the role of these cells in chronic lung disease and confirm the importance of pericytes in human fibrotic pulmonary disease.

Effect of nilotinib on airway remodeling in a murine model of chronic asthma

ABSTRACT Objective: The tyrosine kinase inhibitor nilotinib has potent inhibitory activity against the stem cell growth factor receptor c-Kit and platelet-derived growth factor receptor (PDGFR). The present study aimed to determine whether nilotinib suppresses airway remodeling and whether its effect is associated with the c-Kit and PDGFR pathways. We also aimed to compare the effect of nilotinib and imatinib on remodeling.

METHODS

We developed a mouse model of airway remodeling, which includes smooth muscle thickening, in which ovalbumin (OVA)-sensitized mice were repeatedly exposed to intranasal OVA administration twice a week for 3 months. Mice were treated with nilotinib or imatinib during the OVA challenge.

RESULTS

Compared with control mice, the mice chronically exposed to OVA developed sustained eosinophilic airway inflammation, airway hyperresponsiveness (AHR), and exhibited features of airway remodeling, including thickening of the peribronchial smooth muscle layer. Administration of nilotinib significantly inhibited eosinophilic inflammation, AHR, and remodeling in mice chronically exposed to OVA. Nilotinib showed a trend of more potent effect than imatinib on attenuating remodeling in hydroxyproline assay and smooth muscle staining. Nilotinib treatment significantly reduced the expression of phosphorylated (p)-c-Kit, p-PDGFRβ, and p-extracellular signal-regulated kinase 1/2. The expression levels of the genes encoding c-Kit and PDGFRβ were also reduced by nilotinib treatment. Treatment with nilotinib did not affect significantly the level of OVA-specific IgE and IgG1 in serum. In vitro, nilotinib significantly inhibited cell proliferation of fibroblast.

CONCLUSIONS

These results suggest that nilotinib administration can prevent airway inflammation, AHR, and airway remodeling associated with chronic allergen challenge.

Mechanisms of airway remodeling

Airway remodeling comprises the structural changes of airway walls, induced by repeated injury and repair processes. It is characterized by the changes of tissue, cellular, and molecular composition, affecting airway smooth muscle, epithelium, blood vessels, and extracellular matrix. It occurs in patients with chronic inflammatory airway diseases such as asthma, COPD, bronchiectasis, and cystic fibrosis. Airway remodeling is arguably one of the most intractable problems in these diseases, leading to irreversible loss of lung function. Current therapeutics can ameliorate inflammation, but there is no available therapy proven to prevent or reverse airway remodeling, although reversibility of airway remodeling is suggested by studies in animal models of disease. Airway remodeling is often considered the result of longstanding airway inflammation, but it may be present to an equivalent degree in the airways of children with asthma, raising the necessity for early and specific therapeutic interventions. In this review, we consider the factors that may contribute to airway remodeling and discuss the current and potential therapeutic interventions.

The effect of Shenmai injection on the proliferation of Rat airway smooth muscle cells in asthma and underlying mechanism

BACKGROUND

Over-proliferation of airway smooth muscle cell (ASMC) is one of the important contributors to airway remodeling in asthma. The aim of this study was to investigate the effect of Shenmai injection (SMI) on the proliferation of the rat ASMC in asthma.

METHODS

Rats were randomly divided into three groups: the control group, the asthma group, and the SMI treatment group. Reverse transcription-polymerase chain reaction (RT-PCR) and immunocytochemistry staining were used to detect the mRNA and protein expression of transient receptor potential vanilloid 1 (TRPV1) and proliferating cell nuclear antigen (PCNA) in rat ASMC respectively. Intracellular Ca²⁺ concentration ( [Ca²⁺](i)) in rat ASMC were measured with Fluo-3/AM by confocal microscopy. The proliferation was detected by MTT assay.

RESULTS

Compared with the control group, the asthma group showed an increased expression of TRPV1 and [Ca²⁺](i) in rat ASMC. The expression of PCNA and absorbance of MTT assay in asthma rat ASMC was also significantly increased. SMI could significantly decrease the expression of TRPV1 channel and [Ca²⁺](i) in the asthmatic rat ASMC. Furthermore, the expression of PCNA and absorbance of MTT assay in asthmatic rat ASMC was significantly reduced after SMI treatment.

CONCLUSIONS

SMI may prevent asthma-induced ASMC over-proliferation probably by inhibiting the expression of TRPV1 channel, which regulates the intracellular calcium concentration.

Effect of tyrosine kinase inhibitors, imatinib and nilotinib, in murine lipopolysaccharide-induced acute lung injury during neutropenia recovery

Introduction

Neutrophil recovery has been implicated in deterioration of oxygenation and exacerbation of preexisting acute lung injury (ALI). The aim of this study was to investigate whether imatinib or nilotinib was effective on lipopolysaccharide (LPS)-induced ALI during neutropenia recovery in mice.

Methods

Mice were rendered neutropenic with cyclophosphamide prior to the intratracheal instillation of LPS. Imatinib or nilotinib was administrated by oral gavage during neutropenia recovery. In order to study the effects of drugs, mice were killed on day 5 and blood, bronchoalveolar lavage (BAL) fluid and lung tissue samples were obtained. The lung wet/dry weight ratio and protein levels in the BAL fluid or lung tissue were determined.

Results

Treatment with imatinib or nilotinib significantly attenuated the LPS-induced pulmonary edema, and this result was supported by the histopathological examination. The concentrations of tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and myeloperoxidase in BAL fluid were significantly inhibited by imatinib or nilotinib in mice of ALI during neutropenia recovery. The mRNA expressions of platelet-derived growth factor receptor-β and c-KIT in imatinib or nilotinib group were significantly lower than LPS group.

Conclusions

Our data indicated that imatinib or nilotinib effectively attenuated LPS-induced ALI during neutropenia recovery. These results provide evidence for the therapeutic potential of imatinib and nilotinib in ALI during neutropenia recovery.

Abl family kinases regulate FcγR-mediated phagocytosis in murine macrophages

Phagocytosis of Ab-coated pathogens is mediated through FcγRs, which activate intracellular signaling pathways to drive actin cytoskeletal rearrangements. Abl and Arg define a family of nonreceptor tyrosine kinases that regulate actin-dependent processes in a variety of cell types, including those important in the adaptive immune response. Using pharmacological inhibition as well as dominant negative and knockout approaches, we demonstrate a role for the Abl family kinases in phagocytosis by macrophages and define a mechanism whereby Abl kinases regulate this process. Bone marrow-derived macrophages from mice lacking Abl and Arg kinases exhibit inefficient phagocytosis of sheep erythrocytes and zymosan particles. Treatment with the Abl kinase inhibitors imatinib and GNF-2 or overexpression of kinase-inactive forms of the Abl family kinases also impairs particle internalization in murine macrophages, indicating Abl kinase activity is required for efficient phagocytosis. Further, Arg kinase is present at the phagocytic cup, and Abl family kinases are activated by FcγR engagement. The regulation of phagocytosis by Abl family kinases is mediated in part by the spleen tyrosine kinase (Syk). Loss of Abl and Arg expression or treatment with Abl inhibitors reduced Syk phosphorylation in response to FcγR ligation. The link between Abl family kinases and Syk may be direct, as purified Arg kinase phosphorylates Syk in vitro. Further, overexpression of membrane-targeted Syk in cells treated with Abl kinase inhibitors partially rescues the impairment in phagocytosis. Together, these findings reveal that Abl family kinases control the efficiency of phagocytosis in part through the regulation of Syk function.

Emerging airway smooth muscle targets to treat asthma

Asthma is characterized in part by variable airflow obstruction and non-specific hyperresponsiveness to a variety of bronchoconstrictors, both of which are mediated by the airway smooth muscle (ASM). The ASM is also involved in the airway inflammation and airway wall remodeling observed in asthma. For all these reasons, the ASM provides an important target for the treatment of asthma. Several classes of drugs were developed decades ago which targeted the ASM - including β-agonists, anti-cholinergics, anti-histamines and anti-leukotrienes - but no substantially new class of drug has appeared recently. In this review, we summarize the on-going work of several laboratories aimed at producing novel targets and/or tools for the treatment of asthma. These range from receptors and ion channels on the ASM plasmalemma, to intracellular effectors (particularly those related to cyclic nucleotide signaling, calcium-homeostasis and phosphorylation cascades), to anti-IgE therapy and outright destruction of the ASM itself.

Targeting c-kit in the therapy of mast cell disorders: current update

Classically, mast cells have been widely associated with allergic reactions and parasite infections, but recent studies have elucidated the important role of these cells in innate and acquired immunity, wound healing, fibrosis, and chronic inflammatory diseases. Mast cells release an impressive array of proinflammatory and immunoregulatory mediators after activation induced by either immunoglobulin-E (IgE)-dependent or IgE-independent mechanisms. Proliferation, differentiation, survival and activation of mast cells are regulated by stem cell factor (SCF), the ligand for the c-kit tyrosine kinase receptor which is expressed on the mast cell surface. Inappropriate c-kit activation causes accumulation of mast cells in tissues resulting in mastocytosis. A number of activating mutations in c-kit have recently been identified and these mutations results in aberrant mast cell growth. Thus, c-kit inhibitors may have potential application in multiple conditions associated with mast cell disorders including systemic mastocytosis, anaphylaxis, and asthma. The present perspective aims to summarize recent findings in mast cell biology and the role of c-kit tyrosine kinase inhibitors in the treatment of different mast cell associated disorders.

What effect does asthma treatment have on airway remodeling? Current perspectives

Airway remodeling, or structural changes of the airway wall arising from injury and repair, plays an important role in the pathophysiology of asthma. Remodeling is characterized as structural changes involving the composition, content, and organization of many of the cellular and molecular constituents of the bronchial wall. These structural changes can include epithelial injury, subepithelial thickening/fibrosis, airway smooth muscle hyperplasia, goblet cell hypertrophy and hyperplasia, and angiogenesis. Historically, these changes are considered a consequence of long-standing airway inflammation. Recent infant and child studies, however, suggest that remodeling occurs in parallel with inflammation in asthmatic subjects. Despite advancements in the recognition of key cellular and molecular mechanisms involved in remodeling, there remains a paucity of information about which treatments or interactions are most likely to regulate these processes. Furthermore, it is unclear as to when is the best time to initiate treatments to modify remodeling, which components to target, and how best to monitor interventions on remodeling. Indeed, inhaled corticosteroids, which are generally considered to have limited influence on remodeling, have been shown to be beneficial in studies in which the dose and duration of treatment were increased and prolonged, respectively. Moreover, several studies have identified the need to identify novel asthma indices and phenotypes that correlate with remodeling and, as a consequence, might specifically respond to new therapies, such as anti-IgE, anti-IL-5, and anti-TNF-α mAbs. Our review will evaluate the development of remodeling in asthmatic subjects and the effects of treatment on these processes.