A disintegrin and metalloproteinase 33 protein in patients with asthma: Relevance to airflow limitation

ADAM33's Role in Asthma Pathogenesis: An Overview

Asthma is a complex chronic respiratory disease characterized by airway hyperresponsiveness, inflammation, and obstruction. Many genes have been identified as associated with asthma but none with such substantial significance as the ADAM33 gene due to its role in airway remodeling and bronchial hyperresponsiveness. This review summarizes the current knowledge on the genetic and functional aspects of ADAM33 in asthma pathogenesis. We highlight its genetic variants associated with asthma susceptibility and severity, as well as the functional effects of ADAM33 on airway remodeling, smooth muscle cell proliferation, and its interplay with environmental factors. Additionally, we discuss the potential clinical implications of ADAM33 as a therapeutic target for asthma management.

Review of the British Thoracic Society Winter Meeting 23 November 2022 23-25 November 2022

The British Thoracic Society Winter Meeting at the QEII Centre in London provided the first opportunity for the respiratory community to meet and disseminate research findings face to face since the start of the COVID-19 pandemic. World-leading researchers from the UK and abroad presented their latest findings across a range of respiratory diseases. This article aims to represent the range of the conference and as such is written from the perspective of a basic scientist, a physiotherapist and two doctors. The authors reviewed showcase sessions plus a selection of symposia based on their personal highlights. Content ranged from exciting new developments in basic science to new and unpublished results from clinical trials, delivered by leading scientists from their fields including former deputy chief medical officer Professor Sir Jonathan Van-Tam and former WHO chief scientist Dr Soumya Swaminathan.

Early Origins of Chronic Obstructive Pulmonary Disease: Prenatal and Early Life Risk Factors

The main risk factor for chronic obstructive pulmonary disease (COPD) is active smoking. However, a considerable amount of people with COPD never smoked, and increasing evidence suggests that adult lung disease can have its origins in prenatal and early life. This article reviews some of the factors that can potentially affect lung development and lung function trajectories throughout the lifespan from genetics and prematurity to respiratory tract infections and childhood asthma. Maternal smoking and air pollution exposure were also analyzed among the environmental factors. The adoption of preventive strategies to avoid these risk factors since the prenatal period may be crucial to prevent, delay the onset or modify the progression of COPD lung disease throughout life.

Association between ADAM33 Single-Nucleotide Polymorphisms and Treatment Response to Inhaled Corticosteroids and a Long-Acting Beta-Agonist in Asthma

ADAM33 has been linked to airway structural changes in patients with asthma, leading to airway hyperresponsiveness, narrowing, and ultimately poor treatment responsiveness. This study aimed to evaluate the genetic association of ADAM33 SNPs with asthma, disease severity, and treatment responsiveness to ICS+LABA in the South Indian population. In this case-control study (486 controls and 503 cases), we performed genotyping using MassArray for six SNPs of ADAM33, namely rs2280091, rs2787094, rs3918396, rs67044, rs2853209, and rs3918392. We studied the association with asthma and treatment responsiveness to ICS+LABA, using genotype, allele frequency distribution, and haplotype analysis. A significant clinical finding of the study was that certain patients in the disease severity group (moderate and mild) showed poor or no improvement after a three-month follow-up of regular ICS+LABA therapy. Of the studied ADAM33 SNPs, rs2853209 showed an association with asthma. The further analysis of asthma patients according to disease severity suggested an association between moderate disease and the minor allele "T" for rs2853209. The homozygous minor allele of SNP rs2787094 was found to be associated with poorer lung function and the least lung-function improvement after three months of ICS+LABA therapy. The haplotype analysis of six SNPs showed a significant association between the rs2853209 and rs3918396 blocks and asthma. ADAM33 gene polymorphism has clinical relevance in terms of disease association and response to treatment. SNP rs2853209 seemed most relevant to asthma, and SNP rs2787094 could be a genetic marker for predicting response to ICS+LABA therapy in the study population.

Role for the metalloproteinase ADAM28 in the control of airway inflammation, remodelling and responsiveness in asthma

Background

Asthma is characterized by morphological modifications of the airways (inflammation and remodelling) and bronchial hyperresponsiveness. Mechanisms linking these two key features of asthma are still poorly understood. ADAM28 (a disintegrin and metalloproteinase 28) might play a role in asthma pathophysiology. ADAM28 exists as membrane-bound and soluble forms and is mainly expressed by lymphocytes and epithelial cells.

Methods

ADAM28^-/- mice and ADAM28^+/+ counterparts were sensitized and exposed to ovalbumin (OVA). Airway responsiveness was measured using the flexiVent^® system. After sacrifice, bronchoalveolar lavage (BAL) was performed and lungs were collected for analysis of airway inflammation and remodelling.

Results

The expression of the soluble form of ADAM28 was lower in the lungs of OVA-exposed mice (as compared to PBS-exposed mice) and progressively increased in correlation with the duration of allergen exposure. In lungs of ADAM28^-/- mice exposed to allergens, the proportion of Th2 cells among CD 4 + cells and the number of B cells were decreased. Bronchial responsiveness was lower in ADAM28^-/- mice exposed to allergens and similar to the responsiveness of sham-challenged mice. Similarly, features of airway remodelling (collagen deposition, smooth muscle hyperplasia, mucous hyperplasia) were significantly less developed in OVA-exposed ADAM28^-/- animals in sharp contrasts to ADAM28^+/+. In addition, we report the first evidence of ADAM28 RNA expression by lung fibroblasts and we unveil a decreased capacity of lung fibroblasts extracted from OVA-exposed ADAM28^-/- mice to proliferate as compared to those extracted from OVA-exposed ADAM28^+/+ suggesting a direct contribution of this enzyme to the modulation of airway remodelling.

Conclusion

These results suggest that ADAM28 might be a key contributor to the pathophysiology of asthma.

ADAM33 Silencing Inhibits Vascular Smooth Muscle Cell Migration and Regulates Cytokine Secretion in Airway Vascular Remodeling via the PI3K/AKT/mTOR Pathway

Introduction. Vascular smooth muscle cells (VSMCs) are highly involved in airway vascular remodeling in asthma. Objectives. This study aimed to investigate the mechanisms underlying the effects of a disintegrin and metalloproteinase-33 (ADAM33) gene on the migration capacity and inflammatory cytokine secretion of VSMCs. Methods. Human aortic smooth muscle cells (HASMCs) were transfected with lentiviral vectors carrying short hairpin RNA (shRNA) targeting ADAM33 or negative control vectors. The migration capacity of HASMCs was evaluated by a transwell assay. The levels of secreted inflammatory cytokines were measured using enzyme-linked immunosorbent assay (ELISA) kits. Reverse transcription-quantitative polymerase chain reaction and Western blot assays were performed to detect mRNA and protein expression levels. Results. Silencing of ADAM33 significantly inhibited the migration of HASMCs. The expression of tumor necrosis factor alpha (TNF-α) in the supernatant of HASMCs was decreased, while that of interferon gamma (IFN-γ) was increased after the transfection of shRNA targeting ADAM33. Insufficient ADAM33 expression also suppressed the expression levels of phosphatidylinositol 3-kinase (PI3K), phospho-protein kinase B (AKT), phospho-mammalian target of rapamycin (mTOR), Rho-associated protein kinases, phospho-forkhead box protein O1 (FOXO1), and cyclin D1, but it did not affect the levels of AKT, mTOR, or Rho. Conclusion. Silencing of the ADAM33 gene inhibited HASMC migration and regulated inflammatory cytokine secretion via targeting the PI3K/AKT/mTOR pathway and its downstream signaling. These data contribute to a better understanding of the regulatory mechanisms of airway vascular remodeling in asthma.

Gene polymorphisms in asthma: a narrative review

Background and Objective

Asthma is a heterogeneous disease caused by interactions between genetic and environmental factors. Genome-wide association studies (GWAS) have revealed that genetic variation plays a crucial role in the occurrence and development of asthma. The objective is to systematically review the existing literature on the association between gene polymorphisms and asthma to better understand the relationship between genetic factors and the occurrence and development of asthma.

Methods

We used keywords "asthma" and "gene polymorphism" with their combinations to search for relevant literature published from 2000 to 2021 in the PubMed database and the foreign medical literature retrieval service (FMRS). All articles included in the review are English. Then, we summarized the information pertaining to the genetic factors related to asthma susceptibility.

Key Content and Findings

This study summarized the information on 10 gene variants related to the risk of asthma published over the past 20 years, which will assist in further understanding the role of genetic variants in the risk of asthma.

Conclusion

Dozens of candidate genes have been identified that were associated with asthma risk. Asthmatics existed specific gene variation performed different response to therapy. Personalized therapy based on genotypic profiling would be an important direction in the future. However, it remains a great challenge for us to explore the relationship between gene polymorphisms and pathophysiological mechanism of asthma.

Silencing a disintegrin and metalloproteinase‑33 attenuates the proliferation of vascular smooth muscle cells via PI3K/AKT pathway: Implications in the pathogenesis of airway vascular remodeling

Accumulating evidence suggests that pulmonary expression of a disintegrin and metalloproteinase-33 (ADAM33) serves a key role in the pathogenesis of airway remodeling-related diseases, including asthma. Airway vascular proliferation has been recognized as a key feature of airway remodeling. Our previous study showed that ADAM33 is constitutively expressed in airway vascular smooth muscle cells in patients with asthma, suggesting a potential role of ADAM33 in regulating airway vascular remodeling. Using in vitro human aortic smooth muscle cells (HASMCs) and lentiviral vector carrying short hairpin RNA for ADAM33, the present study aimed to evaluate the influence of ADAM33 silencing on the proliferation and apoptosis of HASMCs and the underlying molecular pathways. Cellular proliferation was observed using the Cell Counting Kit-8 method. Cellular apoptosis was evaluated with Annexin V-PE/7-AAD staining and flow cytometry. Reverse transcription-quantitative PCR and western blotting were used to evaluate the changes in mRNA and protein levels of involved signaling molecules. It was found that silencing of ADAM33 expression in HASMCs significantly inhibited proliferation, but induced the apoptosis of HASMCs. These changes were accompanied by inhibition of the PI3K/AKT/ERK pathway and Bcl-2, but an increase in Bax expression. These results suggested that constitutive expression of ADAM33 may be important to maintain a proliferative phenotype in HASMCs. The influences of ADAM33 on proliferation and apoptosis of HASMCs may involve regulation of PI3K/AKT/ERK and Bax/Bcl-2 pathways. These findings suggested an important role of ADAM33 in airway vascular remodeling and potential therapeutic significance of ADAM33 inhibition in airway remodeling-related diseases.

The evolution of ADAM gene family in eukaryotes

The ADAM (A Disintegrin And Metalloprotease) gene family encodes proteins with adhesion and proteolytic functions. ADAM proteins are associated with diseases like cancers. Twenty ADAM genes have been identified in humans. However, little is known about the evolution of the family. We analyzed the repertoire of ADAM genes in a vast number of eukaryotic genomes to clarify the main gene copy number expansions. For the first time, we provide compelling evidence that early-branching green algae (Mamiellophyceae) have ADAM genes, suggesting that they originated in the last common ancestor of eukaryotes, before the split of plants, fungi and animals. The ADAM family expanded in early metazoans, with the most significative gene expansion happening during the first steps of vertebrate evolution. We concluded that most of mammal ADAM diversity can be explained by gene duplications in early bone fish. Our data suggest that ADAM genes were lost early in green plant evolution.

The etiologic origins for chronic obstructive pulmonary disease

COPD, characterized by long-term poorly irreversible airway limitation and persistent respiratory symptoms, has resulted in enormous challenges to human health worldwide, with increasing rates of prevalence, death, and disability. Although its origin was thought to be in the interactions of genetic with environmental factors, the effects of environmental factors on the disease during different life stages remain little known. Without clear mechanisms and radical cure for it, early screening and prevention of COPD seem to be important. In this review, we will discuss the etiologic origins for poor lung function and COPD caused by specific adverse effects during corresponding life stages, as well as try to find new insights and potential prevention strategies for this disease.

Association between ADAM33 polymorphisms and asthma risk: a systematic review and meta-analysis

Background

Asthma is a common complex chronic, inflammatory polygenic disease with heterogeneous manifestations, affecting individuals of all age groups and posing an immense burden on healthcare resources. A number of studies have identified the association between a disintegrin and metalloprotease 33 (ADAM33) polymorphisms and asthma risk, however, the results still remain inconclusive. The objective of the present study was to identify the effect of ADAM33 variants in asthma susceptibility.

Methods

Eligible case-control studies published between January 2000 and June 2018 was searched and retrieved from online electronic databases. The odds ratio (OR) with its 95% confidence interval (CI) was employed to calculate the effect.

Results

A total of 63 case-control studies were finally screened out, including 13,280 asthma patients and 13,340 controls. Eleven SNPs of ADAM33 gene were identified. Our results detected a significant association between ADAM33 T2, Q1, F + 1 and AA genotype of T + 1 polymorphisms and asthma risk in total population. Subgroup analysis by ethnicities showed that the alleles and genotypes of T2, Q1 and F + 1 polymorphisms were associated with asthma susceptibility among Asian populations, while V4 polymorphism was associated with asthma among Caucasian populations. Subgroup analysis by ages showed that T2, F + 1 and ST + 4 polymorphisms were associated with childhood asthma, while Q1 and V4 polymorphisms were associated with asthma risk in adults. Subgroup analysis by asthma severity showed that only the G allele of ADAM33 T1 polymorphism was associated with the severity of asthma when compared with the controls. In addition, T2, Q1 and F + 1 polymorphisms of ADAM33 were significantly associated with increased the asthma risk in Chinese asthma patients.

Conclusions

Our results found that T2, Q1 and F + 1 polymorphisms of ADAM33 gene might contribute to asthma risk. Future well-designed case-control studies with large population and more ethnicities are still needed to estimate the association.

Artesunate attenuates airway resistance in vivo and relaxes airway smooth muscle cells in vitro via bitter taste receptor-dependent calcium signalling

NEW FINDINGS

What is the central question of this study? The aim of this study was to evaluate artesunate for its use as a bronchodilator in asthma treatment. What is the main finding and its importance? We found that artesunate reduces airway resistance in both normal and ovalbumin-treated Balb/c mice in vivo. Artesunate reduces traction force while inducing Ca²⁺ influx into cultured airway smooth muscle cells in vitro, most probably via the bitter taste receptor. These findings provide important evidence at both animal and cellular levels that artesunate might potentially be used as a bronchodilator for treating obstructive airway diseases, such as asthma.

ABSTRACT

Following the surprising discovery that bitter taste receptors (TAS2Rs) expressed in the lung and can be stimulated to relax airway smooth muscle cells (ASMCs), there is great interest in searching for a bitter taste receptor agonist as a new bronchodilator for asthma therapy. Among the great many other natural bitter substances, artesunate is of special interest to be evaluated for this purpose because of its pharmacological value as a derivative from the well-known anti-malarial, artemisinin. Therefore, in this study we treated either normal or ovalbumin (OVA)-induced asthmatic Balb/c mice in vivo with artesunate (30, 60 or 120 μg) via aerosol inhalation. Subsequently, we measured the airway resistance of the mice in the presence or absence of artesunate. In addition, we treated either mouse or human ASMCs cultured in vitro with artesunate (0.25-2.0 mM) and then measured the traction force and [Ca²⁺ ]_i flux of the cells in the presence or absence of artesunate. The results demonstrate that artesunate attenuated airway resistance in a dose-dependent manner in both the normal and the OVA-treated mice, but more potently in the latter. The in vivo efficacy of artesunate at 120 μg was comparable to that of the conventional bronchodilator, salbutamol, at 3 μg in terms of the reduction in airway resistance. Artesunate also reduced traction force and induced an increase in [Ca²⁺ ]_i in the cultured ASMCs, which was mediated, at least in part, by TAS2R signalling in the human ASMCs. These results together suggest that artesunate might potentially be a cheap and safe bronchodilator to complement the current therapy of asthma.

Lung Development and Aging

The onset of chronic obstructive pulmonary disease (COPD) can arise either from failure to attain the normal spirometric plateau or from an accelerated decline in lung function. Despite reports from numerous big cohorts, no single adult life factor, including smoking, accounts for this accelerated decline. By contrast, five childhood risk factors (maternal and paternal asthma, maternal smoking, childhood asthma and respiratory infections) are strongly associated with an accelerated rate of lung function decline and COPD. Among adverse effects on lung development are transgenerational (grandmaternal smoking), antenatal (exposure to tobacco and pollution), and early childhood (exposure to tobacco and pollution including pesticides) factors. Antenatal adverse events can operate by causing structural changes in the developing lung, causing low birth weight and prematurity and altered immunological responses. Also important are mode of delivery, early microbiological exposures, and multiple early atopic sensitizations. Early bronchial hyperresponsiveness, before any evidence of airway inflammation, is associated with adverse respiratory outcomes. Overlapping cohort studies established that spirometry tracks from the preschool years to late middle age, and those with COPD in the sixth decade already had the worst spirometry at age 10 years. Alveolar development is now believed to continue throughout somatic growth and is adversely impacted by early tobacco smoke exposure. Genetic factors are also important, with genes important in lung development and early wheezing also being implicated in COPD. The inescapable conclusion is that the roots of COPD are in early life, and COPD is a disease of childhood adverse factors interacting with genetic factors.

TGF-β1 stimulates epithelial-mesenchymal transition mediated by ADAM33

The present study aimed to determine the effects of transforming growth factor (TGF)-β1 on disintegrin and metalloproteinase domain-containing protein 33 (ADAM33) expression in airway epithelial cells in order to investigate the association between ADAM33 expression and TGF-β1-induced epithelial to mesenchymal transition (EMT), and to further explore the mechanisms underlying the role of ADAM33 in airway remodeling in asthma. The human bronchial epithelial cell line HBE was transfected with small interfering RNA targeting ADAM33 (siADAM33) and treated with different concentrations of TGF-β1 (10, 20 or 30 ng/ml), while untransfected cells were used as controls. At 72 h after treatment, cellular morphology and immunohistochemical staining were observed under a microscope. The protein and mRNA expression levels of ADAM33 and the EMT markers E-cadherin and vimentin were detected by western blot analysis and reverse-transcription quantitative polymerase chain reaction, respectively. In addition, a correlation analysis of ADAM33 expression and E-cadherin/vimentin expression was performed. A wound healing migration assay and a cell invasion assay were also performed. The results of the cellular morphology, migration and invasion studies suggested that TGF-β1 treatment induced typical EMT changes in HBE cells. In addition, treatment with various concentrations of TGF-β1 significantly increased the protein and mRNA expression levels of ADAM33 and vimentin compared with those in untreated cells. TGF-β1 treatment also decreased the protein and mRNA expression levels of E-cadherin in a dose-dependent manner. By contrast, transfection with siADAM33 promoted the protein expression of E-cadherin and decreased the protein expression of vimentin. Furthermore, ADAM33 and E-cadherin expression levels exhibited a significant negative correlation, whereas ADAM33 and vimentin were positively correlated. In conclusion, the results suggested that TGF-β1 enhances ADAM33 expression in airway epithelial cells, and that ADAM33 induces the EMT of airway epithelial cells, thus participating in airway remodeling in asthma.

Locked Nucleic Acid Gapmers and Conjugates Potently Silence ADAM33, an Asthma-Associated Metalloprotease with Nuclear-Localized mRNA

Two mechanisms dominate the clinical pipeline for oligonucleotide-based gene silencing, namely, the antisense approach that recruits RNase H to cleave target RNA and the RNAi approach that recruits the RISC complex to cleave target RNA. Multiple chemical designs can be used to elicit each pathway. We compare the silencing of the asthma susceptibility gene ADAM33 in MRC-5 lung fibroblasts using four classes of gene silencing agents, two that use each mechanism: traditional duplex small interfering RNAs (siRNAs), single-stranded small interfering RNAs (ss-siRNAs), locked nucleic acid (LNA) gapmer antisense oligonucleotides (ASOs), and novel hexadecyloxypropyl conjugates of the ASOs. Of these designs, the gapmer ASOs emerged as lead compounds for silencing ADAM33 expression: several gapmer ASOs showed subnanomolar potency when transfected with cationic lipid and low micromolar potency with no toxicity when delivered gymnotically. The preferential susceptibility of ADAM33 mRNA to silencing by RNase H may be related to the high degree of nuclear retention observed for this mRNA. Dynamic light scattering data showed that the hexadecyloxypropyl ASO conjugates self-assemble into clusters. These conjugates showed reduced potency relative to unconjugated ASOs unless the lipophilic tail was conjugated to the ASO using a biocleavable linkage. Finally, based on the lead ASOs from (human) MRC-5 cells, we developed a series of homologous ASOs targeting mouse Adam33 with excellent activity. Our work confirms that ASO-based gene silencing of ADAM33 is a useful tool for asthma research and therapy.

IL4Rα and ADAM33 as genetic markers in asthma exacerbations and type-2 inflammatory endotype

BACKGROUND

Genetic markers of susceptibility to asthma exacerbations in adults remain unclear.

OBJECTIVE

To identify genetic markers of asthma exacerbations, particularly in patients with type-2 inflammatory endotype.

METHODS

In this observational study of patients enrolled in the Kinki Hokuriku Airway disease Conference multicenter study, frequency of exacerbations requiring systemic corticosteroids during 2 years after enrolment and associated risk factors was determined. For genetic marker analysis, interleukin-4 receptor α (IL4RA) rs8832 and a disintegrin and metalloprotease 33 (ADAM33) S_2 (rs528557), T_1 (rs2280091), T_2 (rs2280090), and V_4 (rs2787094) variants were included. Elevated serum periostin levels at enrolment (≥95 ng/mL, defined as type-2 inflammatory endotype) were considered in the analysis.

RESULTS

Among 217 patients who were successfully followed up for 2 years after enrolment, 60 patients showed at least one asthma exacerbation during the 2 years. Airflow limitation (%FEV₁ <80%) and recent exacerbations but not genetic variants were identified as risk markers of exacerbations. A total of 27 patients showed type-2 inflammatory endotype (serum periostin ≥95 ng/mL at enrolment) and subsequent exacerbations; risk factors in these patients were airflow limitation (odds ratio, 6.51; 95% confidence interval (CI): 2.37-18.6; P=.0003), GG genotype of IL4RA rs8832 (odds ratio, 4.01; 95% CI: 1.47-11.0; P=.007), and A allele of ADAM33 T_2 (odds ratio, 2.81; 95% CI: 1.05-7.67; P=.04) by multivariate analysis. In addition, GG genotype of IL4RA rs8832 was associated with type-2 endotype, whereas A allele of ADAM33 T_2 was associated with mixed type of eosinophilic/type-2 and neutrophilic inflammations.

CONCLUSIONS AND CLINICAL RELEVANCE

IL4RA and ADAM33 variants may be risk markers of asthma exacerbations in type-2 inflammatory endotype. Precise endotyping may facilitate the identification of genetic risk markers of asthma exacerbations.

Down regulation of ADAM33 as a Predictive Biomarker of Aggressive Breast Cancer

Breast cancer is a heterogeneous disease with differences in its clinical, molecular and biological features. Traditionally, immunohistochemical markers together with clinicopathologic parameters are used to classify breast cancer and to predict disease outcome. Triple-negative breast cancer (TNBC) is a particular type of breast cancer that is defined by a lack of expression of hormonal receptors and the HER2 gene. Most cases of TNBC also have a basal-like phenotype (BLBC) with expression of cytokeratin 5/6 and/or EGFR. A basal marker alone is insufficient for a better understanding of the tumor biology of TNBC. In that regard, the ADAM33 gene is silenced by DNA hypermethylation in breast cancer, which suggests that ADAM33 might be useful as a molecular marker. In the present study, we have produced monoclonal antibodies against the ADAM33 protein and have investigated the role of ADAM33 protein in breast cancer. We used 212 breast tumor samples and lower levels of ADAM33 were correlated with TNBC and basal-like markers. A lower level of ADAM33 was also correlated with shorter overall survival and metastasis-free survival and was considered an independent prognostic factor suggesting that ADAM33 is a novel molecular biomarker of TNBC and BLBC that might be useful as a prognostic factor.

T1 polymorphism in a disintegrin and metalloproteinase 33 (ADAM33) gene may contribute to the risk of childhood asthma in Asians

OBJECTIVE

Polymorphisms in ADAM33 gene have been implicated in susceptibility to the risk of childhood asthma. However, the results remain controversial. We performed meta-analyses to clarify the relationship between them.

METHODS

Relevant articles were searched in PubMed, Embase, Wanfang, and China National Knowledge Infrastructure. The Odds ratio (OR) with 95% confidence interval (CI) was used to assess the strength of the associations.

RESULTS

Fourteen studies with five ADAM33 polymorphisms (F + 1, T1, T2, S2, and V4) were identified, involving 2687 cases and 2996 controls. ADAM33 F + 1, T2, and T1 polymorphisms showed significant associations with asthma risks in the overall and Caucasian children, Asian children, and Caucasian and Chinese children, respectively; however, these significant results were unstable in sensitivity analysis. T1 revealed significant and stable associations with asthma risks among Asian children in the dominant (OR = 2.00, 95% CI = 1.40-2.87, P = 0.0002) and codominant (OR = 3.06, 95% CI = 1.71-5.50, P = 0.0002) models; in cumulative meta-analyses, these significant results were robust. Concerning S2 or V4 polymorphism, no significant associations were observed.

CONCLUSION

These findings demonstrate that ADAM33 T1 polymorphism might be a potential susceptible predictor of asthma for Asian children. Further functional studies between this polymorphism and asthma risks are warranted.

Effect of active vitamin D3 on VEGF-induced ADAM33 expression and proliferation in human airway smooth muscle cells: implications for asthma treatment

BACKGROUND

Asthma is a chronic respiratory disease characterized by reversible airway obstruction with persistent airway inflammation and airway remodeling, which is associated with increased airway smooth muscle (ASM) mass. Vascular endothelial growth factor (VEGF) has been implicated in inflammatory and airway blood vessel remodeling in asthma. Recent evidence indicates that a deficiency of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) may influence asthma pathogenesis. A disintegrin and metalloproteinase (ADAM)33 has been identified as playing a role in the pathophysiology of asthma. ADAM33, which is expressed in ASM cells, is suggested to play a role in the function of these cells. Recent studies show that 1,25-(OH)2D3 exerts direct inhibitory effects on passively sensitized human ASM cells in vitro, including inhibition of ADAM33 expression and cell proliferation; however, the mechanism has not been fully understood.

METHODS

In order to elucidate the precise mechanism underlying the effect of 1,25(OH)2D3 on VEGF-induced ADAM33 expression and ASM cell proliferation, we tested the effects of 1,25(OH)2D3 on cell cycle progression and evaluated the levels of phospho-VEGF receptor 2 (VEGFR2), phospho-extracellular signal-regulated kinase 1/2 (ERK1/2), and phospho-Akt in VEGF-stimulated ASM cells.

RESULTS

We found that 1,25(OH)2D3 inhibited VEGF-induced ADAM33 expression and ASM cell proliferation, as well as cell cycle arrest. Additionally, VEGF-induced ADAM33 expression and ASM cell proliferation was suppressed via inhibition of ERK1/2 activity, but not that of Akt. Furthermore, 1,25(OH)2D3 treatment inhibited VEGF-induced activation of VEGFR2 as well as that of ERK and Akt in a concentration-dependent manner. 1,25(OH)2D3 also inhibited transforming growth factor (TGF)-β-induced VEGF secretion by ASM cells.

CONCLUSIONS

Collectively, our findings suggest that 1,25(OH)2D3 inhibits VEGF-induced ASM cell proliferation by suppressing VEGFR2 and ERK1/2 activation and downregulating ADAM33. Further studies of these mechanisms are needed to facilitate the development of treatments for smooth muscle hyperplasia-associated diseases of the airway such as asthma.

Overexpression of soluble ADAM33 promotes a hypercontractile phenotype of the airway smooth muscle cell in rat

A disintegrin and metalloproteinase 33 (ADAM33) has been identified as a susceptibility gene for asthma, but details of the causality are not fully understood. We hypothesize that soluble ADAM33 (sADAM33) overexpression can alter the mechanical behaviors of airway smooth muscle cells (ASMCs) via regulation of the cell's contractile phenotype, and thus contributes to airway hyperresponsiveness (AHR) in asthma. To test this hypothesis, we either overexpressed or knocked down the sADAM33 in rat ASMCs by transfecting the cells with sADAM33 coding sequence or a small interfering RNA (siRNA) that specifically targets the ADAM33 disintegrin domain, and subsequently assessed the cells for stiffness, contractility and traction force, together with the expression level of contractile and proliferative phenotype markers. We also investigated whether these changes were dependent on Rho/ROCK pathway by culturing the ASMCs either in the absence or presence of ROCK inhibitor (H1152). The results showed that the ASMCs with sADAM33 overexpression were stiffer and more contractile, generated greater traction force, exhibited increased expression levels of contractile phenotype markers and markedly enhanced Rho activation. Furthermore these changes were largely attenuated when the cells were cultured in the presence of H-1152. However, the knock-down of ADAM33 seemed insufficient to influence majority of the mechanical behaviors of the ASMCs. Taken together, we demonstrated that sADAM33 overexpression altered the mechanical behaviors of ASMCs in vitro, which was most likely by promoting a hypercontractile phenotype transition of ASMCs through Rho/ROCK pathway. This revelation may establish the previously missing link between ADAM33 expression and AHR, and also provide useful insight for targeting sADAM33 in asthma prevention and therapy.

Upregulation of a disintegrin and metalloproteinase-33 by VEGF in human airway smooth muscle cells: Implications for asthma

Asthma is a chronic respiratory disease characterized by reversible airway obstruction with persistent airway inflammation and airway remodeling. Features of airway remodeling include increased airway smooth muscle (ASM) mass. A disintegrin and metalloproteinase (ADAM)-33 has been identified as playing a role in the pathophysiology of asthma. ADAM-33 is expressed in ASM cells and is suggested to play a role in the function of these cells. However, the regulation of ADAM-33 is not fully understood. Vascular endothelial growth factor (VEGF) has been implicated in inflammatory and airway blood vessel remodeling in asthmatics. Although VEGF was initially thought of as an endothelial-specific growth factor, recent reports have found that VEGF can promote proliferation of other cell types, including ASM cells. To investigate the precise mechanism of VEGF's effect on ASM cell proliferation, we tested the expression of ADAM-33, phospho-extracellularsignal-regulated kinase 1/2 (ERK1/2), and phospho-Akt in VEGF-stimulated ASM cells. We found that VEGF up-regulates ADAM-33 mRNA and protein levels in a dose- and time-dependent manner as well as phosphorylation of ERK1/2 and Akt. We also found that VEGF-induced ASM cell proliferation is inhibited by both ADAM-33 knockdown and a selective VEGF receptor 2 (VEGFR2) inhibitor (SU1498). Furthermore, VEGF-induced ADAM-33 expression and ASM cell proliferation were suppressed by inhibiting ERK1/2 activity, but not by inhibiting Akt activity. Collectively, our findings suggest that VEGF enhances ADAM-33 expression and ASM cell proliferation by activating the VEGFR2/ERK1/2 signaling pathway, which might be involved in the pathogenesis of airway remodeling. Further elucidation of the mechanisms underlying these observations might help develop therapeutic strategies for airway diseases associated with smooth muscle hyperplasia such as asthma.

Abnormal corticosteroid signalling in airway smooth muscle: mechanisms and perspectives for the treatment of severe asthma

Growing in vivo evidence supports the concept that airway smooth muscle produces various immunomodulatory factors that could contribute to asthma pathogenesis via the regulation of airway inflammation, airway narrowing and remodelling. Targeting ASM using bronchial thermoplasty has provided undeniable clinical benefits for patients with uncontrolled severe asthma who are refractory to glucocorticoid therapy. The present review will explain why the failure of glucocorticoids to adequately manage patients with severe asthma could derive from their inability to affect the immunomodulatory potential of ASM. We will support the view that ASM sensitivity to glucocorticoid therapy can be blunted in severe asthma and will describe some of the factors and mechanisms that could be responsible for glucocorticoid insensitivity.

Soluble ADAM33 initiates airway remodeling to promote susceptibility for allergic asthma in early life

Asthma is a chronic inflammatory airways disease that usually begins in early life and involves gene-environment interactions. Although most asthma exhibits allergic inflammation, many allergic individuals do not have asthma. Here, we report how the asthma gene a disintegrin and metalloprotease 33 (ADAM33) acts as local tissue susceptibility gene that promotes allergic asthma. We show that enzymatically active soluble ADAM33 (sADAM33) is increased in asthmatic airways and plays a role in airway remodeling, independent of inflammation. Furthermore, remodeling and inflammation are both suppressed in Adam33-null mice after allergen challenge. When induced in utero or added ex vivo, sADAM33 causes structural remodeling of the airways, which enhances postnatal airway eosinophilia and bronchial hyperresponsiveness following subthreshold challenge with an aeroallergen. This substantial gene-environment interaction helps to explain the end-organ expression of allergic asthma in genetically susceptible individuals. Finally, we show that sADAM33-induced airway remodeling is reversible, highlighting the therapeutic potential of targeting ADAM33 in asthma.

Loss of ADAM33 suppresses airway remodeling and allergic inflammation in mice, suggesting the therapeutic potential of targeting ADAM33 in asthma.

Expression of a disintegrin and metalloproteinase-33 protein in vocal fold polyps

BACKGROUND

This study aimed to evaluate the association of a disintegrin and metalloproteinase-33 protein ('ADAM-33') expression in vocal polyp formation and to determine its correlation with clinical characteristics.

METHODS

Medical charts and histological sections of 32 patients diagnosed with vocal polyps who underwent surgery were analysed. Controls were histopathologically normal vocal fold tissues obtained from 36 patients who underwent surgery for laryngeal squamous cell carcinoma. Immunohistochemical staining was performed to detect ADAM-33 expression in epithelial cells, stroma and vessels.

RESULTS

All epithelial, stromal and vascular staining scores were significantly greater in polyp tissue than in controls (p < 0.001). Stromal ADAM-33 staining scores were higher in vocal polyp patients with a symptom duration of less than six months (p < 0.05). Vocal overuse or the presence of reflux symptoms, sinonasal symptoms or allergy did not affect ADAM-33 immunostaining scores (p = 0.05).

CONCLUSION

In this study, ADAM-33 immunostaining was significantly increased in vocal polyps. Therefore, over-expression of this protein may be associated with vocal polyp pathogenesis.

Effect of the plant derivative Compound A on the production of corticosteroid-resistant chemokines in airway smooth muscle cells

Preclinical models of human conditions including asthma showed the therapeutic potential of Compound A (CpdA), a dissociated glucocorticoid (GC) receptor (GRα) ligand. Whether CpdA inhibits GC resistance, a central feature of severe asthma, has not been addressed. We investigated whether CpdA modulates cytokine-induced GC resistance in human airway smooth muscle (ASM) cells. Healthy and asthmatic ASM cells were treated with TNF-α/IFN-γ for 24 hours in the presence or absence of CpdA. ELISA and quantitative PCR assays were used to assess the effect of CpdA on chemokine expression. Activation of GRα by CpdA was assessed by quantitative PCR, immunostaining, and receptor antagonism using RU486. An effect of CpdA on the transcription factor interferon regulatory factor 1 (IRF-1) was investigated using immunoblot, immunostaining, and small interfering RNA (siRNA) knockdown. CpdA inhibited production of fluticasone-resistant chemokines CCL5, CX3CL1, and CXCL10 at protein and mRNA levels in both asthmatic and healthy cells. CpdA failed to induce expression of GC-induced Leucine Zipper while transiently inducing mitogen-activated protein kinase phosphatase 1 (MKP-1) at both mRNA and protein levels. CpdA inhibitory action was not associated with GRα nuclear translocation, nor was it prevented by RU486 antagonism. Activation of IRF-1 by TNF-α/IFN-γ was inhibited by CpdA. IRF-1 siRNA knockdown reduced cytokine-induced CCL5 and CX3CL1 production. siRNA MKP-1 prevented the inhibitory effect of CpdA on cytokine-induced CXCL10 production. For the first time, we show that CpdA inhibits the production of GC-resistant chemokines via GRα-independent mechanisms involving the inhibition of IRF-1 and up-regulation of MKP-1. Thus, targeting CpdA-sensitive pathways in ASM cells represents an alternative therapeutic approach to treat GC resistance in asthma.

Immunohistochemical study on ADAM33 in sinonasal inverted papillomas and squamous cell carcinomas of the larynx

INTRODUCTION

ADAM33 protein is a member of the family of transmembrane glycoproteins composed of multidomains. Members of the ADAM family have different activities, such as proteolysis and adhesion, making them good candidates to mediate the extracellular matrix remodeling and changes in cellular adhesion that characterize certain pathologies and cancer development.

MATERIAL AND METHODS

The immunohistochemical method was used to examine the immunoexpression of ADAM33 in 39 formalin-fixed, paraffin-embedded tissue specimens of sinonasal inverted papillomas (IP), 44 laryngeal squamous cell carcinomas (GI grade = 11, GII grade = 33) and 14 disease-free tissue specimens as a control.

RESULTS

The immunoexpression of ADAM33 was localized in the epithelial cells, mesenchymal cells of the vessels and infrequently in the stromal cells. The majority of the ADAM33 was localized intracellularly, although membrane immunoexpression was also noted. All epithelial and vascular staining scores were found to be significantly increased in GI and GII grades of laryngeal cancer compared with controls (p < 0.001) and IP (p < 0.001). No statistically significant differences were found in immunoexpression of ADAM33 between GI and GII tumors. The immunoexpression of ADAM33 was significantly higher in IP patients than in controls (p < 0.02).

CONCLUSIONS

Our findings suggest that ADAM33 could potentially contribute to tumorigenesis of the laryngeal and sinonasal region.

ADAM33 and ADAM12 genetic polymorphisms and their expression in Egyptian children with asthma

BACKGROUND

The ADAM family is involved in some pathologic processes, such as inflammation and asthma.

OBJECTIVES

To assess the association between ADAM33 and ADAM12 single-nucleotide polymorphisms (SNPs) with asthma risk and severity and to investigate the effect of ADAM33 and ADAM12 polymorphisms on expression of these proteases in sputum.

METHODS

Two SNPs of the ADAM33 gene, F+1 (rs511898) G/A and ST+4 (rs44707) A/C, and 2 SNPs of the ADAM12 gene, rs3740199 and rs1871054, were analyzed in 400 asthma cases and 200 controls aged 3 to 14 years using the polymerase chain reaction-restriction fragment length polymorphism method. Messenger RNA expression profile of ADAM33 and ADAM12 proteases in sputum from studied groups was determined by reverse transcription polymerase chain reaction.

RESULTS

ADAM33 F+1 homozygous mutant genotype (AA) and ST+4 heterozygous and homozygous mutant genotype (AC and CC) and mutant alleles of both polymorphisms were significantly associated with asthma risk and severity in moderate and severe subgroups. Patients with the ADAM12 (rs3740199) CC genotype were at increased risk for moderate and severe asthma. Messenger RNA levels of ADAM12 were significantly increased in asthmatic children compared with controls, whereas we were not able to detect the expression of ADAM33 in the sputum of the groups studied. The ADAM12 expression was significantly higher in homozygous CC (variant type) compared with homozygous GG (wild type) of both ADAM12 rs3740199 and rs1871054 in the asthmatic group.

CONCLUSION

Our analysis suggests a likely role for ADAM33 and ADAM12 in the development of asthma in Egyptian children. Furthermore, ADAM12 polymorphisms may affect ADAM12 expression in asthma.

Oxidative stress and nasal polyposis: does it affect the severity of the disease?

BACKGROUND

Nasal polyposis (NP) is a chronic inflammatory disease and the waste products of this inflammation are reactive oxygen species composed of free radicals. Changes in oxidative status have already been revealed in NP. The aim of this study was to investigate the effect of oxidative status to the severity of the disease and the quality of life.

METHODS

The study group included 24 patients with NP and 20 controls. The Turkish version of the Rhinosinusitis Disability Index, visual analog scale (VAS), polyp stage, computed tomography (CT) score, and the eosinophilic cationic protein (ECP) levels in nasal lavage (NAL) fluid were used to assess the severity of the disease. Malondialdehyde, nitric oxide (NO), and the total antioxidant status (TAS) levels in NAL fluids were measured representing the oxidative stress.

RESULTS

NO values were correlated with nasal congestion (p = 0.031). TAS values were correlated with nasal obstruction (p = 0.039). ECP values showed correlation with all the nasal obstruction (p = 0.003), congestion (p = 0.009), rhinorrhea (p = 0.009), and VAS scores (p = 0.039).

CONCLUSION

In NP, ECP levels detected in NAL fluid were significantly high and were correlated with the severity of the disease. Moreover, the severity of oxidative stress, in the forms of TAS and NO, is significantly correlated with the severity of the nasal obstruction and congestion, respectively.

Differential gene expression profiles of peripheral blood mononuclear cells in childhood asthma

OBJECTIVE

Asthma is a common childhood disease with strong genetic components. This study compared whole-genome expression differences between asthmatic young children and healthy controls to identify gene signatures of childhood asthma.

METHODS

Total RNA extracted from peripheral blood mononuclear cells (PBMC) was subjected to microarray analysis. QRT-PCR was performed to verify the microarray results. Classification and functional characterization of differential genes were illustrated by hierarchical clustering and gene ontology analysis. Multiple logistic regression (MLR) analysis, receiver operating characteristic (ROC) curve analysis, and discriminate power were used to scan asthma-specific diagnostic markers.

RESULTS

For fold-change>2 and p < 0.05, there were 758 named differential genes. The results of QRT-PCR confirmed successfully the array data. Hierarchical clustering divided 29 highly possible genes into seven categories and the genes in the same cluster were likely to possess similar expression patterns or functions. Gene ontology analysis presented that differential genes primarily enriched in immune response, response to stress or stimulus, and regulation of apoptosis in biological process. MLR and ROC curve analysis revealed that the combination of ADAM33, Smad7, and LIGHT possessed excellent discriminating power.

CONCLUSIONS

The combination of ADAM33, Smad7, and LIGHT would be a reliable and useful childhood asthma model for prediction and diagnosis.

Urban particulate matter induces pro-remodeling factors by airway epithelial cells from healthy and asthmatic children

CONTEXT

Chronic exposure to ambient particulate matter pollution during childhood is associated with decreased lung function growth and increased prevalence of reported respiratory symptoms. The role of airway epithelium-derived factors has not been well determined.

OBJECTIVE

To determine if urban particulate matter (UPM) stimulates production of vascular endothelial growth factor (VEGF) and transforming growth factor-β2 (TGF-β2), and gene expression of mucin 5AC (MUC5AC) and interleukin-(IL)-8 by primary airway epithelial cells (AECs) obtained from carefully phenotyped healthy and atopic asthmatic school-aged children.

METHODS

Primary AECs from 9 healthy and 14 asthmatic children were differentiated in air--liquid interface (ALI) culture. The apical surface was exposed to UPM suspension or phosphate buffered saline (PBS) vehicle control for 96 h. VEGF and TGF-β2 concentrations in cell media at baseline, 48 and 96 h were measured via ELISA. MUC5AC and IL-8 expression by AECs at 96 h was measured via quantitative polymerase chain reaction.

RESULTS

Baseline concentrations of VEGF, but not TGF-β2, were significantly higher in asthmatic versus healthy cultures. UPM stimulated production of VEGF, but not TGF-β2, at 48 and 96 h; the magnitude of change was comparable across groups. At 96 h there was greater MUC5AC and IL-8 expression by UPM exposed compared to PBS exposed AECs.

CONCLUSIONS

Induction of the pro-remodeling cytokine VEGF may be a potential mechanism by which UPM influences lung function growth in children irrespective of asthma status. Respiratory morbidity associated with UPM exposure in children may be related to increased expression of MUC5AC and IL-8.

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.

ADAM33 protein expression and the mechanics of airway smooth muscle cells are highly correlated in ovalbumin-sensitized rats

A disintegrin and metalloproteinase 33 (ADAM33) has been identified as an asthma susceptibility gene; however, the role of ADAM33 in the pathogenesis and progression of asthma remains to be elucidated. As ADAM33 is predominantly expressed in airway smooth muscle cells (ASMCs), it is feasible to investigate whether ADAM33 protein expression is correlated with ASMC mechanics that are ultimately responsible for airway hyperresponsiveness in asthma. To determine this, Sprague Dawley rats were sensitized with ovalbumin (OVA) for up to 12 weeks to simulate asthma symptoms. Subsequently, ASMCs were isolated from the rats and cultured in vitro. The protein expression of ADAM33 and cytoskeletal proteins (including F‑actin and vinculin), cell stiffness and contractility, as well as traction force were measured. The results demonstrated that compared with the non‑sensitized rats, the protein expression of ADAM33 in ASMCs from the OVA‑sensitized rats increased in a time‑dependent manner, reaching a maximum level at 4 weeks of sensitization and gradually subsiding as OVA sensitization continued (P<0.001). The cell stiffness, traction force and expression of vinculin and F‑actin changed similarly, resulting in a positive correlation with ADAM33 protein expression (Pearson's correlation coefficient, 0.864, 0.716, 0.774 and 0.662, respectively; P=0.1‑0.3). The in vivo results of OVA‑induced ADAM33 protein expression and its association with the mechanics of ASMCs suggested that ADAM33 is a mediator of ASMC dysfunction in asthma, and may provide a rationale for the therapeutic targeting of ADAM33 in the treatment of asthma.

Functional KCa3.1 channels regulate steroid insensitivity in bronchial smooth muscle cells

Identifying the factors responsible for relative glucocorticosteroid (GC) resistance present in patients with severe asthma and finding tools to reverse it are of paramount importance. In asthma we see in vivo evidence of GC-resistant pathways in airway smooth muscle (ASM) bundles that can be modeled in vitro by exposing cultured ASM cells to TNF-α/IFN-γ. This action drives GC insensitivity via protein phosphatase 5-dependent impairment of GC receptor phosphorylation. In this study, we investigated whether KCa3.1 ion channels modulate the activity of GC-resistant pathways using our ASM model of GC insensitivity. Immunohistochemical staining of endobronchial biopsies revealed that KCa3.1 channels are localized to the plasma membrane and nucleus of ASM in both healthy controls and asthmatic patients, irrespective of disease severity. Western blot assays and immunofluorescence staining confirmed the nuclear localization of KCa3.1 channels in ASM cells. The functional importance of KCa3.1 channels in the regulation of GC-resistant chemokines induced by TNF-α/IFN-γ was assessed using complementary inhibitory strategies, including KCa3.1 blockers (TRAM-34 and ICA-17043) or KCa3.1-specific small hairpin RNA delivered by adenoviruses. KCa3.1 channel blockade led to a significant reduction of fluticasone-resistant CX3CL1, CCL5, and CCL11 gene and protein expression. KCa3.1 channel blockade also restored fluticasone-induced GC receptor-α phosphorylation at Ser(211) and transactivation properties via the suppression of cytokine-induced protein phosphatase 5 expression. The effect of KCa3.1 blockade was evident in ASM cells from both healthy controls and asthmatic subjects. In summary, KCa3.1 channels contribute to the regulation of GC-resistant inflammatory pathways in ASM cells: blocking KCa3.1 channels may enhance corticosteroid activity in severe asthma.

Unraveling the genetic basis of aspirin hypersensitivity in asthma beyond arachidonate pathways

Although aspirin-exacerbated respiratory disease (AERD) has attracted a great deal of attention because of its association with severe asthma, it remains widely under-diagnosed in the asthmatic population. Oral aspirin challenge is the best method of diagnosing AERD, but this is a time-consuming procedure with serious complications in some cases. Thus, development of non-invasive methods for easy diagnosis is necessary to prevent unexpected complications of aspirin use in susceptible patients. For the past decade, many studies have attempted to elucidate the genetic variants responsible for risk of AERD. Several approaches have been applied in these genetic studies. To date, a limited number of biologically plausible candidate genes in the arachidonate and immune and inflammatory pathways have been studied. Recently, a genome-wide association study was performed. In this review, the results of these studies are summarized, and their limitations discussed. In addition to the genetic variants, changes in methylation patterns on CpG sites have recently been identified in a target tissue of aspirin hypersensitivity. Finally, perspectives on application of new genomic technologies are introduced; these will aid our understanding of the genetic pathogenesis of aspirin hypersensitivity in asthma.

Asthma severity, polymorphisms in 20p13 and their interaction with tobacco smoke exposure

BACKGROUND

We investigated the association between genetic variation in chromosomal region 20p13-p12 (ADAM33 and flanking genes ATRN, GFRA4, SIGLEC1 and HSPA12B) and asthma. Amongst asthmatics, we then investigated the association between genetic variants and asthma severity. We evaluated the effect of environmental tobacco smoke (ETS) exposure in the context of genetic variants.

METHODS

In a case-control study, we recruited 423 asthmatic children and 414 non-asthmatic controls (age 5-18 yr). Amongst asthmatics, we measured lung function and extracted data on hospitalisation for asthma exacerbation from medical records. Early-life ETS exposure was assessed by questionnaire. We included 85 single-nucleotide polymorphisms (SNPs) in the analysis.

RESULTS

Seventeen SNPs were significantly associated with asthma; one (rs41534847 in ADAM33) remained significant after correction for multiple testing. Thirty-six SNPs were significantly associated with lung function, of which 15 (six ARTN, three ADAM33, five SIGLEC1 and one HSPA12B) remained significant after correction. We observed a significant interaction between 23 SNPs and early-life ETS exposure in relation to lung function measures. For example, for rs512625 in ADAM33, there was significant interaction with ETS exposure in relation to hospitalisations (p(int)  = 0.02) and lung function (p(int)  = 0.03); G-allele homozygotes had a 9.15-fold [95% CI 2.28-36.89] higher risk of being hospitalized and had significantly poorer lung function if exposed to ETS, with no effect of ETS exposure amongst A-allele carriers.

CONCLUSION

We demonstrated several novel significant interactions between polymorphisms in 20p13-p12 and early-life ETS exposure with asthma presence and, amongst asthmatics, a significant association with the severity of their disease.

Pathophysiology of asthma: lessons from genetic research with particular focus on severe asthma

There is good evidence that both inherited and environmental factors influence the risk of developing asthma. Only recently, large well-designed studies have been undertaken with the power to identify the genetic causes for asthma, and methods developed in parallel with the Human Genome Project, such as gene expression and epigenetic studies, have made large-scale analyses of functional genetics possible. In this review, we discuss the recent findings from genetic and genomic research studies of asthma, particularly severe asthma, and highlight specific genes for which there are multiple lines of evidence for involvement in asthma pathogenesis. Bio-ontologic enrichment analyses of the most recently identified asthma-related genes point to attributes such as 'molecular and signal transducer activity' and 'immune system processes', which indicates the importance of immunoregulation and inflammatory response in the pathogenesis of asthma. Finally, we discuss how genetic and environmental factors jointly influence asthma susceptibility and summarize how the results may increase understanding of the pathophysiology of asthma-related diseases.

How to diagnose and phenotype asthma

Asthma has been described as a chronic disease of the airways characterized by variable airflow obstruction, airway hyperresponsiveness, and airway inflammation. This review discusses the diagnosis and phenotyping of asthma, with a special emphasis on phenotyping based on the nature of cellular inflammation and radiological imaging and how this could be used to direct the treatment of asthma and, in the future, to apply specifically directed therapies to specific phenotypes.

Cytokines alter glucocorticoid receptor phosphorylation in airway cells: role of phosphatases

Corticosteroid insensitivity (CSI) represents a profound challenge in managing patients with asthma. We recently demonstrated that short exposure of airway smooth muscle cells (ASMCs) to proasthmatic cytokines drastically reduced their responsiveness to glucocorticoids (GCs), an effect that was partially mediated via interferon regulatory factor-1, suggesting the involvement of additional mechanisms (Am J Respir Cell Mol Biol 2008;38:463-472). Although GC receptor (GR) can be phosphorylated at multiple serines in the N-terminal region, the major phosphorylation sites critical for GR transcriptional activity are serines 211 (Ser211) and 226 (Ser226). We tested the novel hypothesis that cytokine-induced CSI in ASMCs is due to an impaired GR phosphorylation. Cells were treated with TNF-α (10 ng/ml) and IFN-γ (500 UI/ml) for 6 hours and/or fluticasone (100 nm) added 2 hours before. GR was constitutively phosphorylated at Ser226 but not at Ser211 residues. Cytokines dramatically suppressed fluticasone-induced phosphorylation of GR on Ser211 but not on Ser226 residues while increasing the expression of Ser/Thr protein phosphatase (PP)5 but not that of PP1 or PP2A. Transfection studies using a reporter construct containing GC responsive elements showed that the specific small interfering RNA-induced mRNA knockdown of PP5, but not that of PP1 or PP2A, partially prevented the cytokine suppressive effects on GR-meditated transactivation activity. Similarly, cytokines failed to inhibit GC-induced GR-Ser211 phosphorylation when expression of PP5 was suppressed. We propose that the novel mechanism that proasthmatic cytokine-induced CSI in ASMCs is due, in part, to PP5-mediated impairment of GR-Ser211 phosphorylation.

Regulation of a disintegrin and metalloprotease-33 expression by transforming growth factor-β

The asthma susceptibility gene, a disintegrin and metalloprotease-33 (ADAM33), is selectively expressed in mesenchymal cells, and the activity of soluble ADAM33 has been linked to angiogenesis and airway remodeling. Transforming growth factor (TGF)-β is a profibrogenic growth factor, the expression of which is increased in asthma, and recent studies show that it enhances shedding of soluble ADAM33. In this study, we hypothesized that TGF-β also affects ADAM33 expression in bronchial fibroblasts in asthma. Primary fibroblasts were grown from bronchial biopsies from donors with and those without asthma, and treated with TGF-β(2) to induce myofibroblast differentiation. ADAM33 expression was assessed using quantitative RT-PCR and Western blotting. To examine the mechanisms whereby TGF-β(2) affected ADAM33 expression, quantitative methylation-sensitive PCR, chromatin immunoprecipitation, and nuclear accessibility assays were conducted on the ADAM33 promoter. We found that TGF-β(2) caused a time- and concentration-dependent reduction in ADAM33 mRNA expression in normal and asthmatic fibroblasts, affecting levels of splice variants similarly. TGF-β(2) also induced ADAM33 protein turnover and appearance of a cell-associated C-terminal fragment. TGF-β(2) down-regulated ADAM33 mRNA expression by causing chromatin condensation around the ADAM33 promoter with deacetylation of histone H3, demethylation of H3 on lysine-4, and hypermethylation of H3 on lysine-9. However, the methylation status of the ADAM33 promoter did not change. Together, these data suggest that TGF-β(2) suppresses expression of ADAM33 mRNA in normal or asthmatic fibroblasts. This occurs by altering chromatin structure, rather than by gene silencing through DNA methylation as in epithelial cells. This may provide a mechanism for fine regulation of levels of ADAM33 expression in fibroblasts, and may self-limit TGF-β(2)-induced ectodomain shedding of ADAM33.

A disintegrin and metalloprotease (ADAM) 33 protein in patients with pulmonary sarcoidosis

BACKGROUND AND OBJECTIVE

A disintegrin and metalloproteinase (ADAM) 33 is a susceptibility gene associated with inflammatory lung and skin diseases. It is selectively expressed in mesenchymal cells, and its metalloprotease activity has been linked to angiogenesis and tissue remodelling. A soluble form of ADAM33 (sADAM33) has been identified in the bronchoalveolar lavage fluid (BALF) of asthmatic patients, and its levels inversely correlate with lung function. Because of its association with inflammatory lung diseases, it was hypothesized that sADAM33 is elevated in BALF of patients with pulmonary sarcoidosis.

METHODS

After removal of Ig using Protein A/G and enrichment using Concanavalin A beads, sADAM33 was identified in BALF by Western blotting. A fluorescence resonance energy transfer peptide cleavage assay was used to assess ADAM33-like activity in BALF.

RESULTS

sADAM33 protein in BALF was detected as a 25 kDa fragment, and levels were significantly increased in samples from sarcoid patients when compared to healthy controls (P < 0.05). Levels of sADAM33 were inversely correlated with lung function (FVC%) (P < 0.05) and DL(CO) % predicted (P < 0.01). No difference in sADAM33 enzymatic activity was observed between healthy and sarcoid BALF samples.

CONCLUSIONS

Release of sADAM33 is increased in sarcoid and may be associated with abnormal lung function. sADAM33 may be a biomarker of lung tissue inflammation and remodelling in sarcoid.

Airway epithelial cells from asthmatic children differentially express proremodeling factors

BACKGROUND

The airway epithelium can express factors that drive subepithelial airway remodeling. TGF-β2, vascular epithelial growth factor (VEGF), a disintegrin and metalloprotease 33 (ADAM33), and periostin are hypothesized to be involved in subepithelial remodeling and are overexpressed in adult asthmatic airways. Epidemiologic data suggest that lung function deficits in asthmatic patients are acquired in childhood.

OBJECTIVES

We sought to determine whether airway epithelial cells (AECs) from asthmatic children differentially express TGF-β2, VEGF, ADAM33, or periostin compared with cells from atopic nonasthmatic and healthy children intrinsically or in response to IL-4/IL-13 stimulation.

METHODS

Bronchial and nasal epithelial cells were obtained from brushings from well-characterized asthmatic (n = 16), atopic nonasthmatic (n = 9), and healthy (n = 15) children after achievement of anesthesia for elective procedures. After differentiation at an air-liquid interface (ALI) for 3 weeks, conditioned media were sampled and RNA was extracted from unstimulated and IL-4/IL-13-stimulated cultures. TGF-β2 and VEGF levels were measured with ELISA. ADAM33 and periostin expression was assessed by using real-time PCR.

RESULTS

TGF-β2 and VEGF production was significantly greater in bronchial and nasal ALI cultures from asthmatic children than in cultures from atopic nonasthmatic and healthy children. TGF-β2 levels increased significantly in asthmatic cultures after IL-4/IL-13 stimulation. Within-subject correlation between nasal and bronchial ALI production of TGF-β2 (r = 0.64, P = .001) and VEGF (r = 0.73, P < .001) was good. Periostin expression was 3.7-fold higher in bronchial cells (P < .001) and 3.9-fold higher in nasal cells (P < .004) from asthmatic children than in cells from atopic nonasthmatic or healthy children. ADAM33 was not differentially expressed by AECs from asthmatic patients compared with that from cells from atopic nonasthmatic or healthy children.

CONCLUSION

AECs from asthmatic children differentially express TGF-β2, VEGF, and periostin compared with cells from atopic nonasthmatic and healthy children. Nasal epithelial cells might be a suitable surrogate for bronchial cells that could facilitate investigation of the airway epithelium in future longitudinal pediatric studies.

Increased expression of a disintegrin and metalloprotease 8 in allergic rhinitis

BACKGROUND

A disintegrin and metalloproteases (ADAMs) constitute a family of cell surface proteins containing disintegrin and metalloprotease domain, which associate features of adhesion molecules and proteases. ADAM8 is a member of the ADAM family and has recently been implicated to have a role in allergic lung inflammation. Therefore, our aims were to determine the expression of ADAM8 mRNA and protein and to localize ADAM8 protein in the nasal mucosa of patients with allergic rhinitis and control subjects.

METHODS

Inferior turbinate mucosa samples were obtained from 20 patients with allergic rhinitis and 20 matched healthy normal controls. ADAM8 mRNA was extracted from the inferior turbinate mucosa, and then reverse transcription-polymerase chain reaction was performed. Western blot testing was used to analyze differences in the level of ADAM8 protein expression between patients with allergic rhinitis and normal controls, and the ADAM8 protein was localized with immunohistochemical staining.

RESULTS

The level of expression of ADAM8 mRNA and protein in the nasal mucosa was significantly increased in patients with allergic rhinitis compared with normal controls. ADAM8 protein was expressed in the epithelium, infiltrating inflammatory cells, and submucosal glands.

CONCLUSION

ADAM8 is expressed in human nasal mucosa and is increased in patients with allergic rhinitis. These results suggest a possible contribution for ADAM8 in chronic inflammation of the nasal mucosa in patients with allergic rhinitis.

ADAM33 gene polymorphisms associate with asthma susceptibility and severity in East China han population

OBJECTIVE

Multiple genetic and environmental factors impact the pathogenesis of asthma. ADAM33 (a disintegrin and metalloproteinase domain 33) represents a novel susceptibility gene for asthma in several diverse populations. The aim of this study was to determine whether single nucleotide polymorphisms (SNPs) of the ADAM33 gene associate with asthma susceptibility and severity in the Chinese Han population.

METHODS

A total of 224 subjects were enrolled, including 74 normal controls and 150 asthmatic patients. The asthmatic enrollees were further categorized into high- or low-severity groups according to the percentage of forced expiratory volume in 1 second of predicted value, symptoms, nighttime awakening, requirement for short-acting β2-agonist, and interference with normal activities. Six SNPs (F + 1, ST + 4, S1, S2, T1, and T2) in ADAM33 were genotyped using the polymerase chain restriction fragment length polymorphism method.

RESULTS

Three SNPs (F + 1, T1, and T2) of ADAM33 were found to have significant associations with asthma in the study population (p = .0058-.0067). The allele frequencies of two SNPs (F + 1, T1) in both the low- and high-severity groups were significantly different from the allele frequency in the control group. The allelic frequency of the T2 SNP was significantly different from that of the control group only in the high-severity group (p = .0081). Haplotype analysis demonstrated that the frequency of 7575G, 12433T, and 12462C (GTC haplotype) is higher in healthy controls than amongst asthma patients (78.4% vs. 61.8%, p = .0004).

CONCLUSIONS

Polymorphisms of the ADAM33 gene associate with asthma susceptibility in the east China Han population, and the genetic association is stronger in high-severity asthmatics.

Application of proteomics in asthma research

Bronchial asthma is caused by allergic airway inflammation, resulting in reversible airway obstruction, characterized by airway hyper-responsiveness, bronchoconstriction, increased mucus secretion and an increase in lung vessel permeability. The pathophysiological changes in asthma have been attributed to the altered expression of biologically plausible proteins associated with transcriptional pathways, inflammatory mediators, chemokines, cytokines, apoptosis and cell proliferation. Such multifactorial diseases characteristically involve an interplay of many genetic variations of molecular and biochemical pathways and their interactions with environmental factors. The complex nature of the asthma phenotype, together with genetic heterogeneity and environmental influences, has made it difficult to uncover the aspects that underlie this common disease. Recently, genomic and proteomic technologies have been developed to identify associations between genes, proteins and disease. This approach, called 'omics biology', aims to recognize early onset of disease, institute preventive treatment and identify new molecular targets for novel drugs in multifactorial diseases. This article reviews examples of how proteomic technology can be used to find asthma marker proteins (from the cell model to clinical samples). Identification of protein changes in different stages of asthma could provide further insights into the complex molecular mechanisms involved in this disease. These studies provide new insights for finding novel pathological mediators and biomarkers of asthma.

Predicting the long-term course of asthma in wheezing infants is still a challenge

Background. In recurrent wheezing infants, it is important to identify those likely to remain asthmatic in order to propose appropriate long-term management. Objective. To establish predictive factors for persistent asthma at adolescence in a population of recurrent wheezing infants. Methods. Retrospective study of 227 infants. Inclusion criteria were age under 36 months, a history of at least three wheezing episodes assessed via a doctor-led ISAAC questionnaire and a standardized allergy testing programme. At 13 years, active asthma was assessed by questionnaire. Results. Risk factors for asthma persisting into adolescence were allergic sensitization to multiple airborne allergens (OR 4.6, CI-95% (1.9–11.2) P = 0.001), initial atopic dermatitis (OR 3.4, CI-95% (1.9–6.3) P < 0.001), severe recurrent wheezing (OR 2.3, CI-95% (1.3–4.2) P = 0.007), and hypereosinophilia ≥470/mm³ (OR 2.2, CI-95% (1.07–4.7) P = 0.033). Conclusion. While it is still difficult to predict the long-term course of asthma, atopy remains the major risk factor for persistent asthma.