Target For Asthma Therapy Research Articles

STIM1 is a core trigger of airway smooth muscle remodeling and hyperresponsiveness in asthma

Airway remodeling and airway hyperresponsiveness are central drivers of asthma severity. Airway remodeling is a structural change involving the dedifferentiation of airway smooth muscle (ASM) cells from a quiescent to a proliferative and secretory phenotype. Here, we show up-regulation of the endoplasmic reticulum Ca2+ sensor stromal-interacting molecule 1 (STIM1) in ASM of asthmatic mice. STIM1 is required for metabolic and transcriptional reprogramming that supports airway remodeling, including ASM proliferation, migration, secretion of cytokines and extracellular matrix, enhanced mitochondrial mass, and increased oxidative phosphorylation and glycolytic flux. Mechanistically, STIM1-mediated Ca2+ influx is critical for the activation of nuclear factor of activated T cells 4 and subsequent interleukin-6 secretion and transcription of pro-remodeling transcription factors, growth factors, surface receptors, and asthma-associated proteins. STIM1 drives airway hyperresponsiveness in asthmatic mice through enhanced frequency and amplitude of ASM cytosolic Ca2+ oscillations. Our data advocates for ASM STIM1 as a target for asthma therapy.

The STE20 kinase TAOK3 controls the development of house dust mite–induced asthma in mice

The most common endotype of asthma is type 2-high asthma, which is sometimes driven by adaptive allergen-specific TH2 lymphocytes that react to allergens presented by dendritic cells (DCs), or sometimes by an innate immune response dominated by type 2 innate lymphocytes (ILC2s). Understanding the underlying pathophysiology of asthma is essential to improve patient-tailored therapy. The STE20 kinase thousand-and-one kinase 3 (TAOK3) controls key features in the biology of DCs and lymphocytes, but to our knowledge, its potential usefulness as a target for asthma therapy has not yet been addressed. We examined if and how loss of Taok3 affects the development of house dust mite (HDM)-driven allergic asthma in an invivo mouse model. Wild-type Taok3+/+ and gene-deficient Taok3-/- mice were sensitized and challenged with HDM, and bronchoalveolar lavage fluid composition, mediastinal lymph node cytokine production, lung histology, and bronchial hyperreactivity measured. Conditional Taok3fl/fl mice were crossed to tissue- and cell-specific specific deletor Cre mice to understand how Taok3 acted on asthma susceptibility. Kinase-dead (KD) Taok3KD mice were generated to probe for the druggability of this pathway. Activation of HDM-specific T cells was measured in adoptively transferred HDM-specific T-cell receptor-transgenic CD4+ T cells. ILC2 biology was assessed by invivo and invitro IL-33 stimulation assays in Taok3-/- and Taok3+/+, Taok3KD, and Red5-Cre Taok3fl/fl mice. Taok3-/- mice failed to mount salient features of asthma, including airway eosinophilia, TH2 cytokine production, IgE secretion, airway goblet cell metaplasia, and bronchial hyperreactivity compared to controls. This was due to intrinsic loss of Taok3 in hematopoietic and not epithelial cells. Loss of Taok3 resulted in hampered HDM-induced lung DC migration to the draining lymph nodes and defective priming of HDM-specific TH2 cells. Strikingly, HDM and IL-33-induced ILC2 proliferation and function were also severely affected in Taok3-deficient and Taok3KD mice. Absence of Taok3 or loss of its kinase activity protects from HDM-driven allergic asthma as a result of defects in both adaptive DC-mediated TH2 activation and innate ILC2 function. This identifies Taok3 as an interesting drug target, justifying further testing as a new treatment for type 2-high asthma.

Synthesis and Regulation of Th2 Cell And Il–4 As Target for Asthma Therapy

Salah satu karakteristik dari penyakit asma adalah terjadinya reaksi hipersensitivitas di saluran respirasi manusia. Hal ini disebabkan oleh reaksi peradangan pada otot polos pada bronkus. Pengobatan asma yang paling bayak diketahui adalah bronkodilator dengan prinsip kerjanya menurunkan respons otot polos bronkus terhadap sitokin – sitokin pro-inflamasi. Namun, penggunaan obat bronkodilator ini menyebabkan efek samping yang tidak diharapkan. Di sisi lain, pengobatan asma yang langsung menargetkan penyebab reaksi hipersensitivitas seperti faktor pro-inflamasi IL-4 jarang dibahas. Oleh karena itu, tinjauan literatur ini akan membahas potensi obat baru yang menargetkan regulasi IL-4 dan Th2. Kumpulan data diambil dengan cara mencari beberapa studi dan tinjauan yang sudah dilakukan sebelumnya. Dalam tinjauan literatur ini, ditemukan bahwa terdapat potensi obat asma yang menargetkan langsung ke IL-4, Th2, dan faktor transkripsi.

Long non-coding RNA TCF7 contributes to the growth and migration of airway smooth muscle cells in asthma through targeting TIMMDC1/Akt axis

BackgroundLong noncoding RNAs (lncRNAs) have been revealed to participate in cellular biological processes in multiple diseases, including asthma. Nevertheless, the role of lncRNA TCF7 (lncTCF7) in airway smooth muscle cells (ASMCs) is still covered. MethodsThe expression of lncTCF7 and TIMMDC1 in ASMCs from 12 asthma patients and 12 healthy controls were detected using qRT-PCR. Then MTT assay, EdU assay and transwell assay were conducted respectively to assess the impact of lncTCF7 on ASMCs viability, proliferation and migration. Besides, western blotting was performed to determine the protein levels of TIMMDC1 and AKT/p-AKT. ResultsWe discovered that lncTCF7 and TIMMDC1 were upregulated in asthma groups and lncTCF7 improved ASMCs viability/proliferation and migration. In addition, lncTCF7 regulated TIMMDC1 expression indeed and PDGF-BB treated ASMCs exhibited elevated levels of lncTCF7 and TIMMDC1. Moreover, lncTCF7 suppression diminished both the mRNA and protein levels of TIMMDC1 and markedly reduced p-AKT level which could be enhanced under TIMMDC1 overexpression. Finally, both TIMMDC1 overexpression and AKT activator could restored the inhibitory impacts of lncTCF7 silence on PDGF-BB treated ASMCs. ConclusionOur study uncovered that lncTCF7 facilitated human ASMCs growth and migration via targeting TIMMDC1 thus activating AKT signaling, providing a novel possible target for asthma therapy.

Ghrelin Ameliorates Asthma by Inhibiting Endoplasmic Reticulum Stress

BackgroundThis study aimed to confirm the ameliorative effect of ghrelin on asthma and investigate its mechanism. Materials and MethodsThe murine model of asthma was induced by ovalbumin (OVA) treatment and assessed by histological pathology and airway responsiveness to methacholine. The total and differential leukocytes were counted. Tumor necrosis factor α, interferon γ, interleukin-5 and interleukin-13 levels in bronchoalveolar lavage fluid were quantified by commercial kits. The protein levels in pulmonary tissues were measured by Western blot analysis. ResultsGhrelin ameliorated the histological pathology and airway hyperresponsiveness in the OVA-induced asthmatic mouse model. Consistently, OVA-increased total and differential leukocytes and levels of tumor necrosis factor α, interferon γ, interleukin-5 and interleukin-13 in bronchoalveolar lavage fluid were significantly attenuated by ghrelin. Ghrelin prevented the increased protein levels of the endoplasmic reticulum stress markers glucose regulated protein 78 and CCAAT/enhancer binding protein homologous protein and reversed the reduced levels of p-Akt in asthmatic mice. ConclusionsGhrelin might prevent endoplasmic reticulum stress activation by stimulating the Akt signaling pathway, which attenuated inflammation and ameliorated asthma in mice. Ghrelin might be a new target for asthma therapy.

Effects of icariin on asthma mouse model are associated with regulation of prostaglandin D2 level

BackgroundWe aimed to observe the effect of icariin on an asthma mouse model and explore the potential underlying mechanisms. MethodsThe asthma mouse model was established by ovalbumin (OVA) sensitisation and respiratory syncytial virus (RSV) infection and then treated with icariin. Airway resistance was assessed by whole body plethysmograph. In addition, pathological slides were stained with haematoxylin–eosin, and the peribronchial inflammation was observed microscopically. The concentration of prostaglandin D2 (PGD2) in serum and bronchoalveolar lavage fluid (BALF) was detected by enzyme-linked immuno sorbent assay (ELISA). The relative level of prostaglandin D2 receptor 2 (CRTH2) mRNA was assessed by real-time quantitative PCR. ResultsCompared with the icariin-untreated group, there was a significant reduction of Penh in the treated group. Total leucocyte amount and all sorts of leukocytes were lower in the treated group than in the untreated group. HE staining results revealed that a large number of inflammatory cells infiltrated into the peribronchial tissues of untreated group, and the degree of airway inflammation decreased significantly in the treated group. PGD2 in serum and BALF, as well as CRTH2 mRNA level in lung tissues were lower in the treated group than in the untreated group. ConclusionIcariin is a promising therapeutic strategy for asthma, and PGD2 might be a new target for asthma therapy in OVA-induced and RSV-infected asthma model.

Interleukin-17A directly acts on bronchial smooth muscle cells and augments the contractility.

Although interleukin-17 (IL-17) contributes to the induction of airway hyperresponsiveness in asthma, its effect on bronchial smooth muscle (BSM) remains largely unknown. Evidence support an involvement of RhoA/Rho-kinase in BSM contraction, and the pathway has now been proposed as a novel target for asthma therapy. To clarify the role of IL-17 on the development of BSM hyperresponsiveness, effects of IL-17A on BSM contractility and RhoA expression were investigated. Male BALB/c mice and cultured human BSM cells (hBSMCs) were used. In the murine model of allergic asthma, BSM hyperresponsiveness with an IL-17A up-regulation in bronchoalveolar lavage fluids were observed. RT-PCR analyses revealed the expression of receptors for IL-17A in mouse BSMs and hBSMCs. In the hBSMCs, incubation with IL-17A caused an up-regulation of RhoA protein. Western blot analyses also revealed phosphorylations of JNKs/ERKs and a down-regulation of IκB-α in the IL-17A-treated hBSMCs, indicating that IL-17A could act on BSM cells directly. However, IL-17A did not activate STAT6, which is also known as a signaling molecule that causes an up-regulation of RhoA when activated by IL-13. On the other hand, IL-17A caused a down-regulation of miR-133a-3p, a microRNA that negatively regulates RhoA translation. In the naive mice, in vivo IL-17A treatment to the airways by intranasal instillation induced a BSM hyperresponsiveness with RhoA protein up-regulation. These findings indicate that IL-17 directly acts on BSM cells and up-regulates RhoA protein probably via a down-regulation of miR-133a-3p, resulting in an induction of the BSM hyperresponsiveness.

IL-27 and type 2 immunity in asthmatic patients: Association with severity, CXCL9, and signal transducer and activator of transcription signaling

Severe asthma (SA) can involve both innate and type 2 cytokine-associated adaptive immunity. Although IL-27 has been reported to potentiate TH1 responses (including the chemokine CXCL9) and suppress TH2 responses, its function in asthmatic patients is unknown. We sought to evaluate IL-27 expression in human asthma alone and in combination with type 2 immunity to determine the relationship to disease severity and CXCL9 expression. We also sought to model these interactions in vitro in human bronchial epithelial cells. Bronchoalveolar lavage cells from 87 participants were evaluated for IL-27 mRNA and protein alone and in association with epithelial CCL26 (a marker of type 2 activation) in relation to asthma severity and CXCL9 mRNA. Human bronchial epithelial cells cultured at the air-liquid interface and stimulated with IL-27 (1-100 ng/mL) with or without IL-13 (1 ng/mL) were evaluated for CXCL9 expression by using quantitative real-time PCR and ELISA. Phosphorylated and total signal transducer and activator of transcription (STAT) 1/3 were detected by means of Western blotting. Small interfering RNA knockdown of STAT1 or STAT3 was performed. Bronchoalveolar lavage cell IL-27 mRNA and protein levels were increased in asthmatic patients. Patients with evidence for type 2 pathway activation had higher IL-27 expression (P = .02). Combined IL-27 and CCL26 expression associated with more SA and higher CXCL9 expression (P = .004 and P = .007 respectively), whereas IL-27 alone was associated with milder disease. In vitro IL-13 augmented IL-27-induced CXCL9 expression, which appeared to be due to augmented STAT1 activation and reduced STAT3 activation. IL-27, in combination with a type 2/CCL26 signature, identifies a more SA phenotype, perhaps through combined effects of IL-27 and IL-13 on STAT signaling. Understanding these interactions could lead to new targets for asthma therapy.

Mechanisms of pathogenesis in allergic asthma: role of interleukin-23.

Asthma is a chronic airway inflammatory disease characterized by intense leukocyte and eosinophilic infiltration accompanied by mucus hypersecretion and tissue hyperresponsiveness. Recent evidence suggests that T-helper (Th)2 cells and their cytokine products orchestrate the pathology of asthma. In addition, Th17 cells are implicated in the pathogenesis of antigen-induced airway inflammation. The Th17 related cytokine interleukin (IL)-23 plays important roles in many immunological diseases, such as experimental autoimmune encephalomyelitis, rheumatoid arthritis, psoriasis and inflammatory bowel disease. Several reports describe the role of IL-23 in the pathogenesis of allergic asthma in both human and mice. IL-23 leads to neutrophil infiltration in the airway of asthmatic mice, which is characteristic of severe asthma resulting from Th17 development and subsequently IL-17 secretion. IL-23 can also promote eosinophil infiltration in the airway, which is a hallmark of allergic asthma. These studies suggest that IL-23 could be a promoting factor in the development of allergic asthma and likewise would be a target for asthma therapy. In support of this view, trials of anti-IL-23 therapy have been attempted in human and mouse asthma models with encouraging outcomes. This review presents the role of IL-23 in asthma according to recent clinical trials and animal model studies. The proposed mechanisms of IL-23-induced airway inflammation and the agents currently being tested that target IL-23 related pathways are discussed.

ADAM metallopeptidase domain 33 (ADAM33): a promising target for asthma.

Over the last few years, a significant progress has been made in understanding the role of a disintegrin and metalloproteinase 33 (ADAM33) in asthma. The previous observations for the association with asthma have been replicated in over 33 different population samples worldwide. We and others have performed association analysis and meta-analysis and provided further evidence that several polymorphisms in the ADAM33 are risk factors for asthma, especially in the Asian population. Further, several studies have suggested that alterations in epigenetic marks alter the patterns of DNA methylation of ADAM33 and result in potentially adverse biological effects. Finally, while the biological activities of ADAM33 are as yet unknown, ADAM33 may play a possible role in airway remodeling because of its high expression in epithelium, myo/fibroblasts, and airway smooth muscle cells (ASMCs) and its role in promoting angiogenesis and stimulating cell proliferation and differentiation. Thus, ADAM33 represents a promising target for asthma. However, further investigations are clearly needed to discover functional ADAM33 gene polymorphisms and the role of genetic/epigenetic factors in conferring genetic susceptibility to environmental exposure induced asthma as well as biological function in asthma. This, in turn, will unlock the possibility of ADAM33 as a target for asthma therapy.

How Sweet It Is: Intestinal Sweet Taste Receptors in Type 2 Diabetes

In humans, there are a number of taste receptors on the tongue. These include G protein–coupled receptors (GPRs) for sweet, bitter, and umami (savory) tastes and ion channel–based receptors for salt and sour. In recent years, there has been increasing interest in the distribution and function of these receptors elsewhere in the body (1). This has led to interesting and occasionally surprising findings, some with potential therapeutic implications (e.g., activation of bitter taste receptors in the airway’s smooth muscle causes bronchodilation, suggesting a novel target for asthma therapy) (2). Of particular interest in the area of diabetes and obesity is the role of sweet taste receptors (STRs) in the intestine (3,4). The upper gastrointestinal tract is well-endowed with taste and fat receptors, with sweet taste being detected, as elsewhere, by a heterodimer of the taste 1 receptor (T1R) family, T1R2/T1R3. These receptors have been localized to intestinal brush and enteroendocrine cells, and are coupled with α-gustducin as the α-subunit of the G protein (Fig. 1). They recognize sugars, d-amino acids, sweet proteins, and artificial sweeteners. Of importance to a possible role in the incretin response, these receptors are colocalized with glucagon-like peptide 1 (GLP-1) and L cells containing peptide YY (PYY) and K cells containing glucose-dependent insulinotropic polypeptide (GIP) (3). Incidentally, fatty acid responsive GPRs are also coupled to GLP-1 release, but are found predominantly …

Increased Nicotinamide Adenine Dinucleotide Phosphate Oxidase 4 Expression Mediates Intrinsic Airway Smooth Muscle Hypercontractility in Asthma

Asthma is characterized by disordered airway physiology as a consequence of increased airway smooth muscle contractility. The underlying cause of this hypercontractility is poorly understood. We sought to investigate whether the burden of oxidative stress in airway smooth muscle in asthma is heightened and mediated by an intrinsic abnormality promoting hypercontractility. We examined the oxidative stress burden of airway smooth muscle in bronchial biopsies and primary cells from subjects with asthma and healthy controls. We determined the expression of targets implicated in the control of oxidative stress in airway smooth muscle and their role in contractility. We found that the oxidative stress burden in the airway smooth muscle in individuals with asthma is heightened and related to the degree of airflow obstruction and airway hyperresponsiveness. This was independent of the asthmatic environment as in vitro primary airway smooth muscle from individuals with asthma compared with healthy controls demonstrated increased oxidative stress-induced DNA damage together with an increased production of reactive oxygen species. Genome-wide microarray of primary airway smooth muscle identified increased messenger RNA expression in asthma of NADPH oxidase (NOX) subtype 4. This NOX4 overexpression in asthma was supported by quantitative polymerase chain reaction, confirmed at the protein level. Airway smooth muscle from individuals with asthma exhibited increased agonist-induced contraction. This was abrogated by NOX4 small interfering RNA knockdown and the pharmacological inhibitors diphenyleneiodonium and apocynin. Our findings support a critical role for NOX4 overexpression in asthma in the promotion of oxidative stress and consequent airway smooth muscle hypercontractility. This implicates NOX4 as a potential novel target for asthma therapy.

A potential new target for asthma therapy: A Disintegrin and Metalloprotease 10 (ADAM10) involvement in murine experimental asthma

Elevated levels of CD23, a natural regulator of IgE production, have been shown to decrease the signs of lung inflammation in mice. The aim of this study was to study the involvement of ADAM10, the primary CD23 sheddase, in experimental asthma. ADAM10 was blocked either by using mice with a B-cell-specific deletion of the protease or pharmacologically by intranasal administration of selective ADAM10 inhibitors. Airway hypersensitivity (AHR) and bronchoaveolar lavage fluid (BALF) eosinophilia and select BALF cytokine/chemokine levels were then determined. Using an IgE and mast cell-dependent mouse model, B-cell-specific ADAM10(-/-) mice (C57B/6 background) exhibited decreased eosinophilia and AHR when compared with littermate (LM) controls. Treatment of C57B/6 mice with selective inhibitors of ADAM10 resulted in an even further decrease in BALF eosinophilia, as compared with the ADAM10(-/-) animals. Even in the Th2 selective strain, Balb/c, BALF eosinophilia was reduced from 60% to 23% respectively. In contrast, when an IgE/mast cell-independent model of lung inflammation was used, the B-cell ADAM10(-/-) animals and ADAM10 inhibitor treated animals had lung inflammation levels that were similar to the controls. These results thus show that ADAM10 is important in the progression of IgE-dependent lung inflammation. The use of the inhibitor further suggested that ADAM10 was important for maintaining Th2 levels in the lung. These results thus suggest that decreasing ADAM10 activity could be beneficial in controlling asthma and possibly other IgE-dependent diseases.

Kv7 Channels in Airway Smooth Muscle Cells as Targets for Asthma Therapy

Asthma is commonly associated with airway hyperresponsiveness (AHR) involving hypercontraction of airway smooth muscle cells (ASMCs). The mechanisms underlying this process are, however, not well understood. Here we test the hypothesis that bronchoconstrictor agonists suppress Kv7 potassium currents leading to ASMC contraction. We detected Kv7.1–7.5 mRNAs in guinea pig lung by RT‐PCR and Kv7.3–7.5 proteins by immunostaining of isolated ASMCs. Function of Kv7 channels was demonstrated in freshly isolated guinea pig ASMCs: currents measured by perforated patch whole cell voltage clamp displayed electrophysiological characteristics (slow voltage‐dependent non‐inactivating Kv currents with a very negative activation threshold (~−60mV) and a V0.5 ~ −31 mV) and pharmacological characteristics (enhancement by selective activators, suppression by selective blockers) of Kv7 currents. Bronchoconstrictor agonists methacholine (100 nM) and histamine (30 μM), significantly suppressed Kv7 currents and this effect was reversed by Kv7 channel activators. Our results provide the first evidence that Kv7 channels are present in ASMCs, that their activity is suppressed by bronchoconstrictor agonists, and that this effect can be reversed by Kv7 channel activators. Our findings reveal novel mechanisms for ASMC hypercontraction and identify a potential new therapeutic strategy for the treatment of AHR in asthma.

Inhibition of geranylgeranyltransferase inhibits bronchial smooth muscle hyperresponsiveness in mice

Recent studies revealed an involvement of RhoA/Rho-kinase in the contraction of bronchial smooth muscle (BSM), and this pathway has now been proposed as a new target for asthma therapy. A posttranslational geranylgeranylation of RhoA is required for its activation. Thus selective inhibition of geranylgeranyltransferase may be a novel strategy for treatment of the BSM hyperresponsiveness in asthmatics. To test this hypothesis, we investigated the effect of a geranylgeranyltransferase inhibitor, GGTI-2133, on antigen-induced BSM hyperresponsiveness by using mice with experimental asthma. Mice were sensitized and repeatedly challenged with ovalbumin antigen. Animals also were treated with GGTI-2133 (5 mg/kg ip) once a day before and during the antigen inhalation period. Repeated antigen inhalation caused a BSM hyperresponsiveness to acetylcholine with the increased expressions of RhoA and the anti-farnesyl-positive 21-kDa proteins, probably geranylgeranylated RhoA. The in vivo GGTI-2133 treatments significantly inhibited BSM hyperresponsiveness induced by antigen exposure. In another series of experiments, BSM tissues isolated from the repeatedly antigen-challenged mice were cultured for 48 h in the absence or presence of GGTI-2133. Under these conditions, the putative geranylgeranylated RhoA was decreased in a GGTI-2133 concentration-dependent manner. The in vitro incubation with GGTI-2133 also inhibited BSM hyperresponsiveness induced by antigen exposure. These findings suggest that GGTI-2133 inhibits antigen-induced BSM hyperresponsiveness, probably by reducing downstream signal transduction of RhoA. Selective geranylgeranyltransferase inhibitors may be beneficial for the treatment of airway hyperresponsiveness, one of the characteristic features of allergic bronchial asthma.

Down-Regulation of miR-133a Contributes to Up-Regulation of RhoA in Bronchial Smooth Muscle Cells

Augmented bronchial smooth muscle (BSM) contraction is one of the causes of bronchial hyperresponsiveness. The protein RhoA and its downstream pathways have now been proposed as a new target for asthma therapy. MicroRNAs (miRNAs) play important roles in normal and diseased cell functions, and a contribution of miR-133 to RhoA expression has been suggested in cardiomyocytes. To make clear the mechanism(s) of up-regulation of RhoA observed in the BSMs of experimental asthma, the role of miR-133a in RhoA expression was tested. Total proteins and RNAs (containing miRNAs) were extracted from cultured human BSM cells (hBSMCs) that were treated with antagomirs and/or IL-13, and bronchial tissues of BALB/c mice that were sensitized and repeatedly challenged with ovalbumin. RhoA protein and miR-133a were detected by immunoblotting and quantified real-time reverse transcriptase-polymerase chain reaction, respectively. In hBSMCs, an up-regulation of RhoA was observed when the function of endogenous miR-133a was inhibited by its antagomir. Treatment of hBSMCs with IL-13 caused an up-regulation of RhoA and a down-regulation of miR-133a. In bronchial tissues of the repeatedly ovalbumin-challenged mice, a significant increase in RhoA was observed. Interestingly, the level of miR-133a was significantly decreased in BSMs of the challenged mice. These findings suggest that RhoA expression is negatively regulated by miR-133a in BSMs. IL-13 might, at least in part, contribute to the reduction of miR-133a.

The K+ channels K(Ca)3.1 and K(v)1.3 as novel targets for asthma therapy.

Asthma affects 10% of the UK population and is an important cause of morbidity and mortality at all ages. Current treatments are either ineffective or carry unacceptable side effects for a number of patients; in consequence, development of new approaches to therapy are important. Ion channels are emerging as attractive therapeutic targets in a variety of non-excitable cells. Ion channels conducting K(+) modulate the activity of several structural and inflammatory cells which play important roles in the pathophysiology of asthma. Two channels of particular interest are the voltage-gated K(+) channel K(v)1.3 and the intermediate conductance Ca(2+)-activated K(+) channel K(Ca)3.1 (also known as IK(Ca)1 or SK4). K(v)1.3 is expressed in IFNgamma-producing T cells while K(Ca)3.1 is expressed in T cells, mast cells, macrophages, airway smooth muscle cells, fibroblasts and epithelial cells. Both channels play important roles in cell activation, migration, and proliferation through the regulation of membrane potential and calcium signalling. We hypothesize that K(Ca)3.1- and/or K(v)1.3-dependent cell processes are one of the common denominators in asthma pathophysiology. If true, these channels might serve as novel targets for the treatment of asthma. Emerging evidence lends support to this hypothesis. Further validation through the study of the role that these channels play in normal and asthmatic airway cell (patho)physiology and in vivo models will provide further justification for the assessment of small molecule blockers of K(v)1.3 and K(Ca)3.1 in the treatment of asthma.

Triad of polar residues implicated in pH specificity of acidic mammalian chitinase

Acidic mammalian chitinase (AMCase) is a mammalian chitinase that has been implicated in allergic asthma. One of only two active mammalian chinases, AMCase, is distinguished from other chitinases by several unique features. Here, we present the novel structure of the AMCase catalytic domain, both in the apo form and in complex with the inhibitor methylallosamidin, determined to high resolution by X-ray crystallography. These results provide a structural basis for understanding some of the unique characteristics of this enzyme, including the low pH optimum and the preference for the beta-anomer of the substrate. A triad of polar residues in the second-shell is found to modulate the highly conserved chitinase active site. As a novel target for asthma therapy, structural details of AMCase activity will help guide the future design of specific and potent AMCase inhibitors.

Interleukin-13 Augments Bronchial Smooth Muscle Contractility with an Up-Regulation of RhoA Protein

Interleukin-13 (IL-13) is one of the central mediators for development of airway hyperresponsiveness in asthma. However, its effect on bronchial smooth muscle (BSM) is not well known. Recent studies revealed an involvement of RhoA/Rho-kinase in BSM contraction, and this pathway has now been proposed as a new target for asthma therapy. To elucidate the role of IL-13 on the induction of BSM hyperresponsiveness, effects of IL-13 on contractility and RhoA expression in BSMs were investigated. Male BALB/c mice were sensitized and repeatedly challenged with ovalbumin antigen. In the repeatedly antigen-challenged mice, marked airway inflammation and BSM hyperresponsiveness with an up-regulation of IL-13 in bronchoalveolar lavage fluids were observed. In cultured human BSM cells, IL-13 caused an up-regulation of RhoA. The IL-13-induced up-regulation of RhoA was inhibited by leflunomide, an inhibitor of signal transducer and activator of transcription 6 (STAT6). In isolated BSM tissues of naive mice, the contractility was significantly enhanced by organ culture in the presence of IL-13. Moreover, in vivo treatment of airways with IL-13 by intranasal instillation caused a BSM hyperresponsiveness with an up-regulation of RhoA in naive mice. These findings suggest that IL-13/STAT6 signaling is critical for development of antigen-induced BSM hyperresponsiveness and that agents that specifically inhibit this pathway in BSM may provide a novel strategy for the treatment of asthma.

How should airway smooth muscle be punished for causing asthma?

asthma is a complex disease that has varied manifestations, is often difficult to treat, and indeed is even a challenge to define. Nevertheless, there are some features of asthma that are characteristic. Key among these is airways hyperresponsiveness (AHR), defined as an abnormally large mechanical