ADAM33 expression in asthmatic airways and human embryonic lungs

Evaluation of the association between clinical parameters and ADAM33 and ORMDL3 asthma gene single-nucleotide polymorphisms with the severity of COVID-19

BACKGROUND

Coronavirus Disease of 2019 (COVID-19) is a contagious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Patients had varying clinical symptoms and disease severity (mild, moderate, severe, and critical). Several risk factors, including genetic polymorphisms, have been reported to be associated with disease risk and severity. This study aimed to investigate the association of two polymorphisms in the orosomucoid1-like 3 (ORMDL3) and a disintegrin and metalloprotease 33 (ADAM33) asthma-related genes with the severity of COVID-19.

MATERIAL AND METHODS

The study included 116 COVID-19 patients with a positive polymerase chain reaction (PCR) test for the SARS-CoV-2 Delta variant. 58 patients with moderate symptoms, 28 patients with severe symptoms, and 30 outpatients with mild symptoms. Genotyping of rs7216389 in the ORMDL3 and rs2280091 in ADAM33 genes was performed by polymerase chain reaction-restriction fragment length polymorphism. Furthermore, records of patients were studied for hematological profiles and biochemical markers.

RESULTS

No significant association was found between rs7216389 and rs2280091 and the severity of COVID-19 between different groups of COVID-19 patients. The serum levels of RBC and neutrophil-to-lymphocyte ratio were significantly increased; the erythrocyte sedimentation rate (ESR), and Aspartate transaminase (SGOT) were significantly decreased during treatment in intensive care unit (ICU) patients. The serum levels of red blood cells, Platelets, Urea, Alkaline phosphatase, ESR, Alanine transaminase (SGPT), and SGOT were significantly increased during treatment in hospitalized patients. The serum levels of inflammatory factors, including C-reactive protein (CRP), D-dimer, and Ferritin at the time of admission, were significantly higher in patients admitted to the ICU patients compared to the other group of patients.

CONCLUSION

The two polymorphisms studied in this research are not suitable markers for predicting the severity of COVID-19. However, there are significant differences in the amounts of some blood factors in different groups of COVID-19 patients (P < 0.05) and these factors can be used as a marker for the disease severity prediction.

Role of ADAM33 short isoform as a tumor suppressor in the pathogenesis of thyroid cancer via oncogenic function disruption of full-length ADAM33

Thyroid cancer is the most prevalent endocrine malignancy globally; however, its underlying pathogenesis remains unclarified. Reportedly, alternative splicing is involved in processes such as embryonic stem and precursor cell differentiation, cell lineage reprogramming, and epithelial-mesenchymal transitions. ADAM33-n, an alternative splicing isoform of ADAM33, encodes a small protein containing 138 amino acids of the N-terminal of full-length ADAM33, which constructs a chaperone-like domain that was previously reported to bind and block the proteolysis activity of ADAM33. In this study, we reported for the first time that ADAM33-n was downregulated in thyroid cancer. The results of cell counting kit-8 and colony formation assays showed that ectopic ADAM33-n in papillary thyroid cancer cell lines restricted cell proliferation and colony formation. Moreover, we demonstrated that ectopic ADAM33-n reversed the oncogenic function of full-length ADAM33 in cell growth and colony formation in the MDA-T32 and BCPAP cells. These findings indicate the tumor suppressor ability of ADAM33-n. Altogether, our study findings present a potential explanatory model of how the downregulation of the oncogenic gene ADAM33 promotes the pathogenesis of thyroid cancer.

Towards an artificial human lung: modelling organ-like complexity to aid mechanistic understanding

Respiratory diseases account for over 5 million deaths yearly and are a huge burden to healthcare systems worldwide. Murine models have been of paramount importance to decode human lung biology in vivo, but their genetic, anatomical, physiological and immunological differences with humans significantly hamper successful translation of research into clinical practice. Thus, to clearly understand human lung physiology, development, homeostasis and mechanistic dysregulation that may lead to disease, it is essential to develop models that accurately recreate the extraordinary complexity of the human pulmonary architecture and biology. Recent advances in micro-engineering technology and tissue engineering have allowed the development of more sophisticated models intending to bridge the gap between the native lung and its replicates in vitro Alongside advanced culture techniques, remarkable technological growth in downstream analyses has significantly increased the predictive power of human biology-based in vitro models by allowing capture and quantification of complex signals. Refined integrated multi-omics readouts could lead to an acceleration of the translational pipeline from in vitro experimental settings to drug development and clinical testing in the future. This review highlights the range and complexity of state-of-the-art lung models for different areas of the respiratory system, from nasal to large airways, small airways and alveoli, with consideration of various aspects of disease states and their potential applications, including pre-clinical drug testing. We explore how development of optimised physiologically relevant in vitro human lung models could accelerate the identification of novel therapeutics with increased potential to translate successfully from the bench to the patient's bedside.

Airway Remodeling in Asthma

Asthma is an inflammatory disease of the airways that may result from exposure to allergens or other environmental irritants, resulting in bronchoconstriction, wheezing, and shortness of breath. The structural changes of the airways associated with asthma, broadly referred to as airway remodeling, is a pathological feature of chronic asthma that contributes to the clinical manifestations of the disease. Airway remodeling in asthma constitutes cellular and extracellular matrix changes in the large and small airways, epithelial cell apoptosis, airway smooth muscle cell proliferation, and fibroblast activation. These pathological changes in the airway are orchestrated by crosstalk of different cell types within the airway wall and submucosa. Environmental exposures to dust, chemicals, and cigarette smoke can initiate the cascade of pro-inflammatory responses that trigger airway remodeling through paracrine signaling and mechanostimulatory cues that drive airway remodeling. In this review, we explore three integrated and dynamic processes in airway remodeling: (1) initiation by epithelial cells; (2) amplification by immune cells; and (3) mesenchymal effector functions. Furthermore, we explore the role of inflammaging in the dysregulated and persistent inflammatory response that perpetuates airway remodeling in elderly asthmatics.

Molecular mechanisms of action of naringenin in chronic airway diseases

Chronic airway inflammatory diseases are characterized by persistent proinflammatory responses in the respiratory tract. Although, several treatment strategies are currently available, lifelong therapy is necessary for most of these diseases. In recent years, phytophenols, namely, flavonoids, derived from fruits and vegetables have been gaining tremendous interest and have been extensively studied due to their low toxicological profile. Naringenin is a bioflavonoid abundantly found in citrus fruits. This substance has shown notable therapeutic potential in various diseases due to its promising diverse biological activities. In this review, we have attempted to review the published studies from the available literature, discussing the molecular level mechanisms of naringenin in different experimental models of airway inflammatory diseases including asthma, chronic obstructive pulmonary disease (COPD), lung cancer, pulmonary fibrosis and cystic fibrosis. Current evidences have proposed that the anti-inflammatory properties of naringenin play a major role in ameliorating inflammatory disease states. In addition, naringenin also possesses several other biological properties. Despite the proposed mechanisms suggesting remarkable therapeutic benefits, the clinical use of naringenin is, however, hampered by its low solubility and bioavailability. Furthermore, this review also discusses on the studies that utilise nanocarriers as a drug delivery system to address the issue of poor solubility.

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.

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.

Review of Methods to Study Gene Expression Regulation Applied to Asthma

Gene expression regulation is the cellular process that controls, increasing or decreasing, the expression of gene products (RNA or protein). A complex set of interactions between genes, RNA molecules, protein, and other components determined when and where specific genes are activated and the amount of protein or RNA produced. Here, we focus on several methods to study gene regulation applied to asthma and allergic research such as: Western Blot to identify and quantify proteins, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) to study protein interactions with nucleic acids, and RNA interference (RNAi) by which gene expression could be silenced.

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.

Association between ADAM metallopeptidase domain 33 gene polymorphism and risk of childhood asthma: a meta-analysis

This study aimed to investigate the association between ADAM metallopeptidase domain 33 (ADAM33) gene polymorphisms and the risk of childhood asthma. The relevant studies about the relationship between ADAM33 gene polymorphisms and childhood asthma were searched from electronic databases and the deadline of retrieval was May 2016. The single nucleotide polymorphisms (SNPs) of ADAM33 (rs511898, rs2280092, rs3918396, rs528557, rs2853209, rs44707, rs2280091 and rs2280089) were analyzed based on several models including the allele, codominant, recessive and dominant models. The results showed that the ADAM33 rs2280091 polymorphism in all four genetic models was associated with an increased risk of childhood asthma. Positive associations were also found between the polymorphisms rs2280090, rs2787094, rs44707 and rs528557 and childhood asthma in some genetic models. This meta-analysis suggested that ADAM33 polymorphisms rs2280091, rs2280090, rs2787094, rs44707 and rs528557 were significantly associated with a high risk of childhood asthma.

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.

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.

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.

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.

Does allergy begin in utero?

It has been recognized for centuries that allergic disease runs in families, implying a role for genetic factors in determining individual susceptibility. More recently, a range of evidence shows that many of these genetic factors, together with in utero environmental exposures, lead to the development of allergic disease through altered immune and organ development. Environmental exposures during pregnancy including diet, nutrient intake and toxin exposures can alter the epigenome and interact with inherited genetic and epigenetic risk factors to directly and indirectly influence organ development and immune programming. Understanding of these factors will be essential in identifying at-risk individuals and possible development of therapeutic interventions for the primary prevention of allergic disease. In this review, we summarize the evidence that suggests allergic disease begins in utero, together with possible mechanisms for the effect of environmental exposures during pregnancy on allergic disease risk, including epigenetics.

An ADAM33 polymorphism associates with progression of preschool wheeze into childhood asthma: a prospective case-control study with replication in a birth cohort study

BACKGROUND

The influence of asthma candidate genes on the development from wheeze to asthma in young children still needs to be defined.

OBJECTIVE

To link genetic variants in asthma candidate genes to progression of wheeze to persistent wheeze into childhood asthma.

MATERIALS AND METHODS

In a prospective study, children with recurrent wheeze from the ADEM (Asthma DEtection and Monitoring) study were followed until the age of six. At that age a classification (transient wheeze or asthma) was based on symptoms, lung function and medication use. In 198 children the relationship between this classification and 30 polymorphisms in 16 asthma candidate genes was assessed by logistic regression. In case of an association based on a p<0.10, replication analysis was performed in an independent birth cohort study (KOALA study, n = 248 included for the present analysis).

RESULTS

In the ADEM study, the minor alleles of ADAM33 rs511898 and rs528557 and the ORMDL3/GSDMB rs7216389 polymorphisms were negatively associated, whereas the minor alleles of IL4 rs2243250 and rs2070874 polymorphisms were positively associated with childhood asthma. When replicated in the KOALA study, ADAM33 rs528557 showed a negative association of the CG/GG-genotype with progression of recurrent wheeze into childhood asthma (0.50 (0.26-0.97) p = 0.04) and no association with preschool wheeze.

CONCLUSION

Polymorphisms in ADAM33, ORMDL3/GSDMB and IL4 were associated with childhood asthma in a group of children with recurrent wheeze. The replication of the negative association of the CG/GG-genotype of rs528557 ADAM33 with childhood asthma in an independent birth cohort study confirms that a compromised ADAM33 gene may be implicated in the progression of wheeze into childhood asthma.

ADAM33 gene polymorphisms and mortality. A prospective cohort study

The ADAM33 gene is associated with the pathophysiology of Chronic Obstructive Pulmonary Disease (COPD) and atherosclerosis. In this study we investigated all-cause, COPD and cardiovascular mortality, in relation to single nucleotide polymorphisms (SNPs) in ADAM33 (Q_1, S_1, S_2, T_1 and T_2) that were genotyped in 1,390 subjects from the Vlagtwedde/Vlaardingen cohort. Participants were examined at entry in 1989/1990 and followed up till evaluation of the vital status on December 31(st), 2008. Using Cox proportional hazards regression we estimated the risk of the SNPs in relation to mortality, adjusting for gender, age, FEV1, height, place of residence and packyears of smoking. Additionally, we performed stratified analyses according to gender and smoking habits. After 18 years, 284 (20.4%) subjects had died (107 due to cardiovascular disease and 20 due to COPD). Individuals homozygous for the minor allele of SNP T_2 had an increased risk of all-cause and cardiovascular mortality compared to wild types: hazard ratio 3.6 (95% confidence interval 2.0 to 6.7) and 3.4 (1.2 to 9.5) respectively. Individuals homozygous for the minor allele of S_1, S_2, T_2 or Q_1 had a significantly increased risk of COPD mortality. In stratified analyses the risk of all-cause mortality associated with SNP T_2 did not change: females 3.5 (1.5 to 8.3), males 3.1 (1.2 to 7.6), never smokers 3.8 (0.9 to 16.3), ever smokers 3.6 (1.8 to 7.2). This study shows for the first time that ADAM33 is a pleiotropic gene that is associated with all-cause, COPD and cardiovascular mortality, independent of potential confounders.

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.

Fetal origins of asthma

There is convincing evidence that asthma has its origins in early life. We review the epidemiological and biological evidence for fetal exposures that may have a causal role in asthma development. However, those factors that provoke asthma exacerbations are not necessarily the same as those associated with disease induction. Epidemiological studies have identified many potential exposures linked to asthma but these do not confirm causality and have not been replicated by experiment. Asthma is a heterogeneous disease and there are developmental influences on at least two pathways, airway structure and airway inflammation. The fetus is not immunologically naive and intrauterine exposures can act directly to invoke immunological sensitisation leading postnatally to airway inflammation. Other potential mechanisms include indirect effects on airway and lung growth through fetal nutrition and epigenetic modifications of DNA expression by environmental exposures. Identifying the causal factors will provide the targets for interventions to prevent disease.

Soluble IgE receptors--elements of the IgE network

Soluble isoforms of three human IgE Fc receptors, namely FcεRI, FcεRII, and galectin-3, can be found in serum. These soluble IgE receptors are a diverse family of proteins unified by the characteristic of interacting with IgE in the extracellular matrix. A truncated form of the alpha-chain of FcεRI, the high affinity IgE receptor, has recently been described as a soluble isoform (sFcεRI). Multiple soluble isoforms of CD23 (sCD23), the low affinity IgE receptor also known as FcεRII, are generated via different mechanisms of extracellular and intracellular proteolysis. The second low affinity IgE receptor, galectin-3, only exists as a secretory protein. We here discuss the physiological roles of these three soluble IgE receptors as elements of the human IgE network. Additionally, we review the potential and current use of sFcεRI, sCD23, and galectin-3 as biomarkers in human disease.

Genetics and asthma disease susceptibility in the US Latino population

The US Latino population is heterogeneous with diversity in environmental exposures and socioeconomic status. Moreover, the US Hispanic population derives from numerous countries previously under Spanish rule, and many Hispanics have complex proportions of European, Native American, and African ancestry. Disparities in asthma severity and control are due to complex interactions between environmental exposures, socioeconomic factors, and genetic variations. In addition, diseases within the Latino community may also differ by country of origin. Although US Census data show low asthma rates in the Hispanic population as a whole, there is a lot of variability in the prevalence and morbidity of asthma, with a prevalence of 5.0% in Mexican Americans versus 17.0% in Puerto Ricans. The diversity and population admixture make the study of the genetics of asthma complex in Latino populations. However, an understanding of the genetics of asthma in all populations, including the Latino population, can enhance risk identification, help us to target pharmacological therapy, and guide environmental regulations, all of which can promote a reduction in health disparities. The inclusion of markers of ancestral diversity and the incorporation of techniques to adjust for stratification now make these studies feasible in complex populations, including the Latino population. To date, studies using linkage analyses, genome-wide associations, or candidate gene analyses have identified an association of asthma or asthma-related phenotypes with candidate genes, including interleukin 13, beta-2 adrenergic receptor, a disintegrin and metalloproteinase 33, orosomucoid 1-like 3, and thymic stromal lymphopoietin. As reviewed here, although these genes have been identified in diverse populations, limited studies have been performed in Latino populations, and they have had variable replication. There is a need for the development of registries with well-phenotyped pediatric and adult Latino populations and subgroups for inclusion in the rapidly expanding field of genetic studies, and these studies need to be used to reduce health disparities.

What's new in asthma pathophysiology and immunopathology?

Research on asthma pathophysiology over the past decade has expanded the complex repertoire involved in the pathophysiology of asthma to include inflammatory, immune and structural cells, as well as a wide range of mediators. Studies have identified a role for connective and other mesenchymal tissues involved in airway remodeling. Recent findings have implicated the innate immune response in asthma and have revealed interesting patterns of interaction between the innate and adaptive immune response and the associated complex chronic inflammatory reaction. New immune cell populations have also been added to this repertoire, including Tregs, natural killer T cells and Th17 cells. The role of the eosinophil, a prominent pathological feature in most asthma phenotypes, has also been expanding to include roles such as tissue modifiers and immune regulators via a number of fascinating and hitherto unexplored mechanistic pathways. In addition, new and significant roles have been proposed for airway smooth muscle cells, fibroblasts, epithelial and endothelial cells. Tissue remodeling is now considered an integral element of asthma pathophysiology. Finally, an intricate network of mediators, released from both immune and inflammatory cells, including thymus stromal lymphopoietin and matrix metalloproteinases, have added to the complex milieu of asthma immunity and inflammation. These findings have implications for therapy and the search for novel strategies towards better disease management. Sadly, and perhaps due to the complex nature of asthma, advances in therapeutic discoveries and developments have been limited. Thus, understanding the precise roles played by the numerous dramatis personae in this odyssey, both individually and collectively within the context of asthma pathophysiology, continues to pose new challenges. It is clear that the next stage in this saga is to embark on studies that transcend reductionist approaches to involve system analysis of the complex and multiple variables involved in asthma, including the need to narrow down the phenotypes of this condition based on careful analysis of the organs (lung and airways), cells, mediators and other factors involved in bronchial asthma.

The relationship between infant lung function and the risk of wheeze in the preschool years

RATIONALE

There is evidence that perinatal lung development predicts childhood wheeze. However, very few studies have examined whether preschool wheeze is associated with lower premorbid lung function in early infancy, and as yet there is no information relating atopic and non-atopic preschool wheeze to early lung development.

OBJECTIVE

To examine the association between premorbid infant lung function and preschool wheeze, and to explore associations with atopic and non-atopic wheeze phenotypes.

METHODS

Infant lung function was measured in 147 healthy term infants aged 5-14 weeks. Rapid thoracoabdominal compression was performed during tidal breathing and at raised volume to measure maximal expiratory flow at functional residual capacity (V' max FRC) and forced expiratory volume in 0.4 sec (FEV(0.4)). Atopic status was determined by skin prick testing at 3 years and wheeze ascertained from parental questionnaires (1 and 3 years).

MEASUREMENTS AND MAIN RESULTS

Lower early infancy V' max FRC was associated with wheeze in both the first and third years of life (P=0.002 and 0.006, respectively). Lower early infancy FEV(0.4) was associated with wheeze in the first year (P=0.03). Compared to non-atopic children who did not wheeze, non-atopic children who wheezed in their third year of life had lower FEV(0.4) (P=0.02), while FEV(0.4) values of atopic children who wheezed were not significantly different (P=0.4).

CONCLUSIONS

Lower premorbid infant lung function was present in infants who subsequently wheezed during the first and third years of life. Lower FEV(0.4) in early infancy was associated with non-atopic wheeze but not atopic wheeze at 3 years of age.

A possible association of EMID2 polymorphisms with aspirin hypersensitivity in asthma

Aspirin-intolerant asthma (AIA) is an asthma phenotype characterized by the development of bronchoconstriction following ingestion of aspirin. Despite the well-defined pathological trigger, the underlying mechanisms of AIA are still unclear. With the biophysical characteristics of the human EMI domain-containing protein 2 (EMID2) gene in relation to the extracellular matrix deposition and epithelial-mesenchymal transition as pivotal characteristics of airway remodeling in asthma, we hypothesized that genetic polymorphisms of EMID2 might affect the development of AIA. In this study, the allelic associations of 49 single-nucleotide polymorphisms (SNPs) of the human EMID2 gene were evaluated from 163 AIA patients and 429 aspirin-tolerant asthma (ATA) subjects as controls in a Korean population. Logistic analysis showed that five SNPs (P = 0.01-0.04, but P (corr) > 0.05) and EMID2_BL2_ht2 haplotype (unique to the minor alleles of rs4727494 and rs13233066; P = 0.02; P (corr) = 0.02) were significantly associated with AIA. More interestingly, regression analysis of the decline of forced expiratory volume in one second (FEV(1)) by aspirin provocation revealed that 10 SNPs (P = 0.003-0.04) and four relevant haplotypes (P = 0.002-0.02) were significantly associated with the fall rate of FEV(1) by aspirin provocation, indicating that genetic polymorphisms of EMID2 could cause meaningful deficits in the upper and lower airways among AIA patients. These findings provide evidence that EMID2 may be a susceptible genetic factor for aspirin hypersensitivity among asthmatics in Korean population.

Expression of a disintegrin and metalloproteinase 33 protein in nasal polyposis: an immunohistochemical study

BACKGROUND

A disintegrin and metalloproteinase (ADAM)-33 is a member of matrix metalloproteinases. This protein takes a role in angiogenesis and airway remodeling in asthma. Because histopathological findings of airway remodeling in asthma and nasal polyposis (NP) are similar, the aim of this study was to evaluate the ADAM-33 expression in NP.

METHODS

Immunohistochemical staining of specimens of 47 patients with NP and 8 patients with concha bullosa was performed to detect the expression of ADAM-33. Paraffin blocks were used to identify the expression of ADAM-33 polyclonal antibodies. Immunostaining of epithelial cells, stroma, mesenchymal cells of vessels, and inflammatory cells were analyzed by using light microscopy.

RESULTS

Immunopositivity scores in epithelial cells in NP (median, 2; range, 1-3) were significantly higher than those of controls (median, 1.5; range, 1-2; p < 0.001). ADAM-33 staining was increased in the mesenchymal cells of vessels of nasal polyps (median, 2; range, 1-3) compared with control tissues (median, 1.5; range, 1-2; p = 0.006). Although the staining scores of fibroblasts in nasal polyp specimens were also high (median, 3; range 1-3), there was no statistical significance when compared with controls (median 2; range, 1-3; p = 0.228). ADAM-33 immunostaining was not related with the presence of allergies, asthma, and aspirin intolerance (p > 0.05). Moreover, no relationship was found between increased expression of ADAM-33 and the stages of polyp or computerized tomography scores (p > 0.05).

CONCLUSION

This study suggests that the increased expression of ADAM-33 protein may have a role in the pathogenesis of NP.

Using genetics to predict the natural history of asthma?

Clinical practice reminds us that there is considerable variability in the course of asthma over time. Treatment of patients with asthma would be considerably improved if one could accurately predict the likely course of disease over the life course. Recently, with the advent of the era of genome-wide association studies, there has been a monumental shift in our understanding of the genetic factors that underlie inherited susceptibility to asthma. Genes have been identified that modulate many aspects of the natural history of asthma, such as susceptibility to atopy, altered lung development, and susceptibility to more severe disease. Heritability studies have even suggested a role for genetic factors in remission of asthma. However, although the discovery of novel genetic factors underlying disease susceptibility has undoubtedly improved our understanding of disease pathogenesis, whether these advances have improved the ability to predict the natural history in individual patients is questionable, and the application of genetic testing to clinical practice remains some way off.

The role of the epithelium in airway remodeling in asthma

The bronchial epithelium is the barrier to the external environment and plays a vital role in protection of the internal milieu of the lung. It functions within the epithelial-mesenchymal trophic unit to control the local microenvironment and help maintain tissue homeostasis. However, in asthma, chronic perturbation of these homeostatic mechanisms leads to alterations in the structure of the airways, termed remodeling. Damage to the epithelium is now recognized to play a key role in driving airway remodeling. We have postulated that epithelial susceptibility to environmental stress and injury together with impaired repair responses results in generation of signals that act on the underlying mesenchyme to propagate and amplify inflammatory and remodeling responses in the submucosa. Many types of challenges to the epithelium, including pathogens, allergens, environmental pollutants, cigarette smoke, and even mechanical forces, can elicit production of mediators by the epithelium, which can be translated into remodeling responses by the mesenchyme. Several important mediators of remodeling have been identified, most notably transforming growth factor-beta, which is released from damaged/repairing epithelium or in response to inflammatory mediators, such as IL-13. The cross talk between the epithelium and the underlying mesenchyme to drive remodeling responses is considered in the context of subepithelial fibrosis and potential pathogenetic mechanisms linked to the asthma susceptibility gene, a disintegrin and metalloprotease (ADAM)33.

Role of ADAM and ADAMTS metalloproteinases in airway diseases

Lungs are exposed to the outside environment and therefore to toxic and infectious agents or allergens. This may lead to permanent activation of innate immune response elements. A Disintegrin And Metalloproteinases (ADAMs) and ADAMs with Thrombospondin motifs (ADAMTS) are proteinases closely related to Matrix Metalloproteinases (MMPs). These multifaceted molecules bear metalloproteinase and disintegrin domains endowing them with features of both proteinases and adhesion molecules. Proteinases of the ADAM family are associated to various physiological and pathological processes and display a wide spectrum of biological effects encompassing cell fusion, cell adhesion, "shedding process", cleavage of various substrates from the extracellular matrix, growth factors or cytokines... This review will focus on the putative roles of ADAM/ADAMTS proteinases in airway diseases such as asthma and COPD.

A role for Wnt signaling genes in the pathogenesis of impaired lung function in asthma

RATIONALE

Animal models demonstrate that aberrant gene expression in utero can result in abnormal pulmonary phenotypes.

OBJECTIVES

We sought to identify genes that are differentially expressed during in utero airway development and test the hypothesis that variants in these genes influence lung function in patients with asthma.

METHODS

Stage 1 (Gene Expression): Differential gene expression analysis across the pseudoglandular (n = 27) and canalicular (n = 9) stages of human lung development was performed using regularized t tests with multiple comparison adjustments. Stage 2 (Genetic Association): Genetic association analyses of lung function (FEV(1), FVC, and FEV(1)/FVC) for variants in five differentially expressed genes were conducted in 403 parent-child trios from the Childhood Asthma Management Program (CAMP). Associations were replicated in 583 parent-child trios from the Genetics of Asthma in Costa Rica study.

MEASUREMENTS AND MAIN RESULTS

Of the 1,776 differentially expressed genes between the pseudoglandular (gestational age: 7-16 wk) and the canalicular (gestational age: 17-26 wk) stages, we selected 5 genes in the Wnt pathway for association testing. Thirteen single nucleotide polymorphisms in three genes demonstrated association with lung function in CAMP (P < 0.05), and associations for two of these genes were replicated in the Costa Ricans: Wnt1-inducible signaling pathway protein 1 with FEV(1) (combined P = 0.0005) and FVC (combined P = 0.0004), and Wnt inhibitory factor 1 with FVC (combined P = 0.003) and FEV(1)/FVC (combined P = 0.003).

CONCLUSIONS

Wnt signaling genes are associated with impaired lung function in two childhood asthma cohorts. Furthermore, gene expression profiling of human fetal lung development can be used to identify genes implicated in the pathogenesis of lung function impairment in individuals with asthma.

Induction of a disintegrin and metalloprotease 33 during embryonic lung development and the influence of IL-13 or maternal allergy

BACKGROUND

Asthma pathogenesis involves gene and environmental interactions. A disintegrin and metalloprotease 33 (ADAM33)/Adam33 is a susceptibility gene for asthma and bronchial hyperresponsiveness in human beings and mice. ADAM33 is almost exclusively expressed in mesenchymal cells, including mesenchymal progenitors in developing lungs.

OBJECTIVE

Because maternal allergy is a risk factor for asthma, we hypothesized that an allergic environment affects ADAM33/Adam33 expression during human and mouse lung development.

METHODS

Human embryonic/fetal lung (HEL) tissues were collected from first-trimester terminations of pregnancy. These were processed immediately or used for explant culture +/- IL-13. MF1 mice or ovalbumin-sensitized A/J mice (Bronchial hyperresponsivness (Bhr)1/Adam33 locus-positive) were time-mated and challenged with ovalbumin (A/J mice only) during pregnancy. Lungs were harvested at different times during gestation and post partum. ADAM33/Adam33 expression was analyzed by using reverse transcriptase quantitative polymerase chain reaction and Western blotting.

RESULTS

ADAM33 mRNA was detectable in HELs in the pseudoglandular stage of development and showed a significant increase from 7 to 9 weeks postconception. IL-13 significantly suppressed ADAM33 mRNA in HEL explants. In developing murine lungs, Adam33 mRNA and protein expression increased significantly in the early pseudoglandular stage and showed another large increase post partum. In A/J mice, maternal allergy significantly suppressed Adam33 mRNA in lungs of newborn pups, whereas processed Adam33 protein increased and several smaller isoforms were detected.

CONCLUSION

Adam33/Adam33 shows 2 significant increments in expression during lung morphogenesis, suggesting important developmental regulation. The ability of maternal allergy or exogenous IL-13 to suppress Adam33/ADAM33 mRNA but enhance Adam33 processing suggests a gene-environment interaction that may be relevant for asthma pathogenesis.

The effects of Th2 cytokines on the expression of ADAM33 in allergen-induced chronic airway inflammation

A disintegrin and metalloprotease domain 33 (ADAM33) has been identified as an asthma susceptibility gene, which is associated with small-airway remodeling. However, the role of ADAM33 in the development of allergic airway inflammation is unclear. The present study used an established murine model of allergen-induced chronic airway inflammation, which was sensitized and then challenged by nebulized 2.5% ovalbumin (OVA) for 8 weeks (30 min/day, three times a week). The expression of ADAM33 mRNA detected by real time RT-PCR was significantly enhanced in the lung tissue of mice with OVA challenge, as compared with the group challenged with saline. This OVA-challenged model showed significant Th2-biased airway inflammation as well as airway remodeling with features of sub-epithelial fibrosis and mucus hyper-secretion. Furthermore, in vitro studies showed that IL-4 and IL-13 could significantly up-regulate the expression of ADAM33 mRNA in human fibroblasts in a concentration- and time-dependent manner as compared to normal controls. These results support the note that Th2 cytokines can up-regulate the expression of ADAM33 mRNA and ADAM33 may play an important role in the development of airway remodeling in allergen-induced chronic airway inflammation.

ADAM8: a new therapeutic target for asthma

BACKGROUND

A proteinase with a disintegrin and a metalloproteinase domain-8 (ADAM8) has been linked to asthma.

OBJECTIVE

To explore whether ADAM8 is a therapeutic target for asthma.

METHODS

We reviewed literature on ADAM8's function and expression and activities in lungs of humans and mice with allergic airway inflammation (AAI). We used these data to generate hypotheses about the contributions of ADAM8 to asthma pathogenesis.

CONCLUSIONS

ADAM8 levels are increased in airway epithelium and airway inflammatory cells in mice with AAI and human asthma patients. Data from murine models of AAI indicate that ADAM8 dampens airway inflammation. It is not clear whether ADAM8 contributes directly to structural remodeling in asthmatic airways. Additional studies are required to validate ADAM8 as a therapeutic target for asthma.

Smoke exposure interacts with ADAM33 polymorphisms in the development of lung function and hyperresponsiveness

INTRODUCTION

ADAM33 is the first identified asthma gene by positional cloning, especially asthma combined with bronchial hyperresponsiveness (BHR). Moreover, ADAM33 is associated with early-life lung function and decline of forced expiratory volume in 1 s (FEV(1)) in the general population. In utero and postnatal cigarette smoke exposure (CSE) are associated with reduced lung function, and development of BHR and asthma. We hypothesized that this may occur via interaction with ADAM33.

AIM

To replicate the role of ADAM33 in childhood lung function and development of BHR and asthma. Furthermore, we investigated gene-environment interaction of ADAM33 with in utero and postnatal CSE in the Dutch PIAMA cohort.

METHODS

Six ADAM33 single-nucleotide polymorphisms (SNPs) were genotyped. Rint was measured at age 4 and 8 years, FEV(1) and BHR at age 8 years; asthma was based on questionnaire data at age 8.

RESULTS

In the total cohort, the rs511898 A, rs528557 C, and rs2280090 A alleles increased the risk to develop asthma (+BHR). There existed interaction between in utero but not postnatal CSE and the rs528557 and rs3918396 SNPs with respect to development of BHR, the rs3918396 SNP with Rint at age 8 and the rs528557 SNP with FEV(1)% predicted.

CONCLUSIONS

We confirm associations between ADAM33 and the development of asthma (+BHR). This is the first study suggesting that interaction of in utero CSE with ADAM33 results in reduced lung function and the development of BHR, which needs further confirmation.

ADAM33 gene silencing by promoter hypermethylation as a molecular marker in breast invasive lobular carcinoma

Background

ADAM33 protein is a member of the family of transmembrane glycoproteins composed of multidomains. ADAM family members have different activities, such as proteolysis and adhesion, making them good candidates to mediate the extracellular matrix remodelling and changes in cellular adhesion that characterise certain pathologies and cancer development. It was reported that one family member, ADAM23, is down-regulated by promoter hypermethylation. This seems to correlate with tumour progression and metastasis in breast cancer. In this study, we explored the involvement of ADAM33, another ADAM family member, in breast cancer.

Methods

First, we analysed ADAM33 expression in breast tumour cell lines by RT-PCR and western blotting. We also used 5-aza-2'-deoxycytidine (5azadCR) treatment and DNA bisulphite sequencing to study the promoter methylation of ADAM33 in breast tumour cell lines. We evaluated ADAM33 methylation in primary tumour samples by methylation specific PCR (MSP). Finally, ADAM33 promoter hypermethylation was correlated with clinicopathological data using the chi-square test and Fisher's exact test.

Results

The expression analysis of ADAM33 in breast tumour cell lines by RT-PCR revealed gene silencing in 65% of tumour cell lines. The corresponding lack of ADAM33 protein was confirmed by western blotting. We also used 5-aza-2'-deoxycytidine (5-aza-dCR) demethylation and bisulphite sequencing methodologies to confirm that gene silencing is due to ADAM33 promoter hypermethylation. Using MSP, we detected ADAM33 promoter hypermethylation in 40% of primary breast tumour samples. The correlation between methylation pattern and patient's clinicopathological data was not significantly associated with histological grade; tumour stage (TNM); tumour size; ER, PR or ERBB2 status; lymph node status; metastasis or recurrence. Methylation frequency in invasive lobular carcinoma (ILC) was 76.2% compared with 25.5% in invasive ductal carcinoma (IDC), and this difference was statistically significant (p = 0.0002).

Conclusion

ADAM33 gene silencing may be related to the discohesive histological appearance of ILCs. We suggest that ADAM33 promoter methylation may be a useful molecular marker for differentiating ILC and IDC.

Expression of ADAMs ("a disintegrin and metalloprotease") in the human lung

In view of the associations of "a disintegrin and metalloprotease" (ADAM) with respiratory diseases, we assessed the expression of various ADAMs in human lung tissue. Lung tissue was obtained from nine individuals who underwent surgery for lung cancer or underwent lung transplantation for emphysema. Also, 16HBE 14o- (human bronchial epithelial) and A549 (alveolar type II epithelium-like) cell lines were used. Immunohistochemistry was performed with antibodies recognizing different ADAM domains. The ADAMs were typically distributed over the bronchial epithelium. ADAM8 and ADAM10 were expressed diffusely in all layers of the epithelium. ADAM9, ADAM17, and ADAM19 were predominantly expressed in the apical part of the epithelium, and ADAM33 was predominantly and strongly expressed in basal epithelial cells. In smooth muscle, ADAM19 and ADAM17 were strongly expressed, as was ADAM33, though this expression was weaker. ADAM33 was strongly expressed in vascular endothelium. All ADAMs were generally expressed in inflammatory cells. The typical distribution of ADAMs in the lung, especially in the epithelium, is interesting and suggests a localized function. As most ADAMs are involved in release of (pro-) inflammatory mediators and growth factors, they may play an important role in the first line of defense and in initiation of repair events in the airways.

Interpatient variability in rates of asthma progression: can genetics provide an answer?

Asthma is a heterogeneous disorder with a variable natural history. In children 3 patterns of the natural history of asthma have been described: early onset but transient, persistent, and later onset, with only the former leading to persistent asthma later in childhood. In adults a range of different asthma phenotypes differing in their environmental, inflammatory, and prognostic characteristics have also been described. These extend beyond allergic (extrinsic) and nonallergic (intrinsic) asthma to include persistent airflow obstruction and accelerated decrease in lung function over time. Asthma progression can be defined as the change in an individual's phenotype along a continuum ranging from nonasthmatic to asthmatic and subsequent development of severe chronic disease. It is clear that for prevention of asthma progression in patients, there is a need for both better understanding of the pathophysiology of asthma and identification of predictors of progression. Interpatient genetic variability has been shown to affect multiple facets of asthma progression, including increased susceptibility to atopy and subsequent asthma, progression to severe disease, and modification of the response to treatment. Thus genetic testing might provide a means for predicting the likely progression of an individual along the continuum, allowing targeting of preventative treatment. However, the prospect of the use of genetic information in clinical practice raises important social and ethical issues that will need to be addressed before genetic testing can be used to inform the preventative treatment of patients to prevent the development of progression of asthma in individuals.

Epigenetic mechanisms silence a disintegrin and metalloprotease 33 expression in bronchial epithelial cells

BACKGROUND

A disintegrin and metalloprotease 33 (ADAM33) polymorphism is strongly associated with asthma and bronchial hyperresponsiveness. Although considered to be a mesenchymal cell-specific gene, recent reports have suggested epithelial expression of ADAM33 in patients with severe asthma.

OBJECTIVES

Because dysregulated expression of ADAM33 can contribute to disease pathogenesis, we characterized the mechanism or mechanisms that control its transcription and investigated ADAM33 expression in bronchial biopsy specimens and brushings from healthy and asthmatic subjects.

METHODS

The ADAM33 promoter and CpG island methylation were analyzed by using bioinformatics, luciferase reporters, and bisulfite sequencing of genomic DNA. Epithelial-mesenchymal transition was induced by using TGF-beta1. ADAM33 mRNA was scrutinized in bronchial biopsy specimens and brushings by using reverse transcriptase-quantitative polymerase chain reaction, melt-curve analysis, and direct sequencing.

RESULTS

The predicted ADAM33 promoter (-550 to +87) had promoter transcriptional activity. Bisulfite sequencing showed that the predicted promoter CpG island (-362 to +80) was hypermethylated in epithelial cells but hypomethylated in ADAM33-expressing fibroblasts. Treatment of epithelial cells with 5-aza-deoxycytidine caused demethylation of the CpG island and induced ADAM33 expression. In contrast, phenotypic transformation of epithelial cells through a TGF-beta-induced epithelial-mesenchymal transition was insufficient to induce ADAM33 expression. ADAM33 mRNA was confirmed in bronchial biopsy specimens, but no validated signal was detected in bronchial brushings from healthy or asthmatic subjects.

CONCLUSION

The ADAM33 gene contains a regulatory CpG island within its promoter, the methylation status of which tightly controls its expression in a cell type-specific manner. ADAM33 repression is a stable feature of airway epithelial cells, irrespective of disease.

The soluble form of a disintegrin and metalloprotease 33 promotes angiogenesis: implications for airway remodeling in asthma

BACKGROUND

A disintegrin and metalloprotease (ADAM)-33 is a susceptibility gene for asthma and chronic obstructive pulmonary disease whose function remains unknown.

OBJECTIVE

Because asthmatic bronchoalveolar lavage fluid contains high levels of soluble ADAM33 (sADAM33), which includes the catalytic domain, we postulated that its release from cell membranes might play functional roles in airway remodeling by promoting angiogenesis.

METHODS

The proangiogenic activity of the highly purified catalytic domain of ADAM33 or a catalytically inactive mutant was studied in vitro (Matrigel assay), ex vivo (human embryonic/fetal lung explants) and in vivo (chorioallantoic membrane assay). The regulation of sADAM33 release from cells overexpressing full-length ADAM33 and its biological activity were characterized.

RESULTS

We show that the purified catalytic domain of ADAM33, but not its inactive mutant, causes rapid induction of endothelial cell differentiation in vitro, and neovascularization ex vivo and in vivo. We also show that TGF-beta(2) enhances sADAM33 release from cells overexpressing full-length ADAM33 and that this truncated form is biologically active.

CONCLUSION

The discovery that sADAM33 promotes angiogenesis defines it as a tissue remodeling gene with potential to affect airflow obstruction and lung function independently of inflammation. As TGF-beta(2) enhances sADAM33 release, environmental factors that cause epithelial damage may synergize with ADAM33 in asthma pathogenesis, resulting in a disease-related gain of function. This highlights the potential for interplay between genetic and environmental factors in this complex disease.

How early do airway inflammation and remodeling occur?

Eosinophilic airway inflammation and structural airway changes are present in school age asthmatics. When these changes occur, and their relationship, are controversial. Some structural airway changes, up-regulation of collagens 1 and 111, and increased distance between alveolar tethering points, may be antenatal, and independent of inflammation. We have established that there is no eosinophilic inflammation or reticular basement membrane thickening in wheezing infants median age one year; but by age three years, both are present. This accords with cohort studies, showing that children who become persistent wheezers have a drop in lung function in the pre-school years. Thereafter, lung function tracks into middle age, so the preschool years represent window during which an intervention might have long term benefit. Supportive are measurements in blood and bronchoalveolar lavage fluid, implicating the neutrophil as the key inflammatory cell in early wheeze. Models of the pathophysiology of asthma include (1) that eosinophilic inflammation is the primary event, and leads to remodelling as a secondary event, which itself results in progressive airflow obstruction (the least likely model); (2) eosinophilic inflammation is the primary event, but remodelling is protective, preventing worsening AHR. It should be noted that these first two are not mutually exclusive; rbm thickening may be protective, but other components of remodeling, for example increased ASM, may have adverse effects; (3) eosinophilic inflammation and airway remodelling are parallel processes, driven by some underlying 'asthma factor'; and (4) the primary abnormality is not airway inflammation, but some form of disordered airway repair.

Biophysical basis for airway hyperresponsiveness

Airway hyperresponsiveness is the excessive narrowing of the airway lumen caused by stimuli that would cause little or no narrowing in the normal individual. It is one of the cardinal features of asthma, but its mechanisms remain unexplained. In asthma, the key end-effector of acute airway narrowing is contraction of the airway smooth muscle cell that is driven by myosin motors exerting their mechanical effects within an integrated cytoskeletal scaffolding. In just the past few years, however, our understanding of the rules that govern muscle biophysics has dramatically changed, as has their classical relationship to airway mechanics. It has become well established, for example, that muscle length is equilibrated dynamically rather than statically, and that in a dynamic setting nonclassical features of muscle biophysics come to the forefront, including unanticipated interactions between the muscle and its time-varying load, as well as the ability of the muscle cell to adapt (remodel) its internal microstructure rapidly in response to its ever-changing mechanical environment. Here, we consider some of these emerging concepts and, in particular, focus on structural remodeling of the airway smooth muscle cell as it relates to excessive airway narrowing in asthma.