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Delineation of a Gene Network Underlying the Pulmonary Response to Oxidative Stress in Asthma
Abstract and Figures
Cigarette smoke exposure induces a respiratory epithelial response that is mediated in part by oxidative stress. The contribution of oxidative stress to cigarette smoke-induced responses in asthmatic respiratory epithelium is not well understood. We sought to increase this understanding by employing data integration and systems biology approaches to publicly available microarray data deposited over the last several years. In this study, we analyzed 14 publicly available asthma- or tobacco-relevant data series and found 4 (2 mice and 2 human) that fulfilled adequate signal/noise thresholds using unsupervised clustering and F test statistics. Using significance filters and a 4-way Venn diagram approach, we identified 26 overlapping genes in the epithelial transcriptional stress response to cigarette smoke and asthma. This test set corresponded to a 26-member gene/protein network containing 18 members that were highly regulated in a fifth data series of direct lung oxidative stress. Of those network members, 2 stood out (ie, tissue inhibitor of metalloproteinase 1 and thrombospondin 1) owing to central location within the network and marked up-regulation sustained at later times in response to oxidative stress. These analyses identified key relationships and primary hypothetical targets for future studies of cigarette smoke-induced oxidative stress in asthma.
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... S100 Calcium Binding Protein A9 (S100A9) was the only gene that contributed to all gene sets, and has been associated with asthma in mice [38]. All genes associated with 4 or more gene sets have also been associated with asthma in humans or mice and include S100A9, thrombospondin 1 (THBS1), TLR4, IL8, complement component 5a receptor 1 (C5AR1), MMP9, NLR Family, Pyrin Domain Containing 12 (NLRP12) and triggering receptor expressed on myeloid cells 1 (TREM1) [20,[38][39][40][41][42][43][44][45][46][47][48]. Other genes associated with 3 or fewer gene sets have also been associated with asthma such as Plasminogen Activator, Urokinase Receptor (PLAUR) and Serpin Family E Member 2 (SERPINE2), and several additional genes were first identified here. ...
... Central in a network linked to pulmonary response to oxidative stress in asthma [39] Cell-to-cell and cell-to-matrix interactions ...
Background
Severe equine asthma is a naturally occurring lung inflammatory disease of mature animals characterized by neutrophilic inflammation, bronchoconstriction, mucus hypersecretion and airway remodeling. Exacerbations are triggered by inhalation of dust and microbial components. Affected animals eventually are unable of aerobic performance. In this study transcriptomic differences between asthmatic and non-asthmatic animals in the response of the bronchial epithelium to an inhaled challenge were determined.
Results
Paired endobronchial biopsies were obtained pre- and post-challenge from asthmatic and non-asthmatic animals. The transcriptome, determined by RNA-seq and analyzed with edgeR, contained 111 genes differentially expressed (DE) after challenge between horses with and without asthma, and 81 of these were upregulated. Genes involved in neutrophil migration and activation were in central location in interaction networks, and related gene ontology terms were significantly overrepresented. Relative abundance of specific gene products as determined by immunohistochemistry was correlated with differential gene expression. Gene sets involved in neutrophil chemotaxis, immune and inflammatory response, secretion, blood coagulation and apoptosis were overrepresented among up-regulated genes, while the rhythmic process gene set was overrepresented among down-regulated genes. MMP1, IL8, TLR4 and MMP9 appeared to be the most important proteins in connecting the STRING protein network of DE genes.
Conclusions
Several differentially expressed genes and networks in horses with asthma also contribute to human asthma, highlighting similarities between severe human adult and equine asthma. Neutrophil activation by the bronchial epithelium is suggested as the trigger of the inflammatory cascade in equine asthma, followed by epithelial injury and impaired repair and differentiation. Circadian rhythm dysregulation and the sonic Hedgehog pathway were identified as potential novel contributory factors in equine asthma.
Electronic supplementary material
The online version of this article (10.1186/s12864-017-4107-6) contains supplementary material, which is available to authorized users.
... Other lung-focused stress networks have been generated using systems biology data (specifically gene expression profiling), however they differ in their construction methods, content, applications, and explanatory power. For example, Freishtat et al. report a 26-member lung stress network comprised of genes regulated by asthma-relevant challenges or tobacco smoke in multiple gene expression data sets [16]. A second example network used information-theoretic network inference algorithms to identify NRF2 targets and regulatory relationships using a large number of mouse lung microarray data sets [15]. ...
... One of the central challenges faced by contemporary investigators is how to comprehensively assess the biological impact of complex processes such as the cellular stress response at a molecular level, in order to understand their influence on disease susceptibility and progression. Computational approaches are increasingly being applied to analyze complex biological systems like the cellular stress response, including investigations into the role of key transcription factors such as NRF2 (mediating the antioxidative stress response), or identifying potential mechanisms for how stress can lead to diseases such as asthma [15,16]. Large scale, systems biology measurements (e.g., transcriptomics, proteomics, and metabolomics) can be applied to molecular regulatory network models in an effort to understand the underlying cellular response to biological insults. ...
Humans and other organisms are equipped with a set of responses that can prevent damage from exposure to a multitude of endogenous and environmental stressors. If these stress responses are overwhelmed, this can result in pathogenesis of diseases, which is reflected by an increased development of, e.g., pulmonary and cardiac diseases in humans exposed to chronic levels of environmental stress, including inhaled cigarette smoke (CS). Systems biology data sets (e.g., transcriptomics, phosphoproteomics, metabolomics) could enable comprehensive investigation of the biological impact of these stressors. However, detailed mechanistic networks are needed to determine which specific pathways are activated in response to different stressors and to drive the qualitative and eventually quantitative assessment of these data. A current limiting step in this process is the availability of detailed mechanistic networks that can be used as an analytical substrate.
We have built a detailed network model that captures the biology underlying the physiological cellular response to endogenous and exogenous stressors in non-diseased mammalian pulmonary and cardiovascular cells. The contents of the network model reflect several diverse areas of signaling, including oxidative stress, hypoxia, shear stress, endoplasmic reticulum stress, and xenobiotic stress, that are elicited in response to common pulmonary and cardiovascular stressors. We then tested the ability of the network model to identify the mechanisms that are activated in response to CS, a broad inducer of cellular stress. Using transcriptomic data from the lungs of mice exposed to CS, the network model identified a robust increase in the oxidative stress response, largely mediated by the anti-oxidant NRF2 pathways, consistent with previous reports on the impact of CS exposure in the mammalian lung.
The results presented here describe the construction of a cellular stress network model and its application towards the analysis of environmental stress using transcriptomic data. The proof-of-principle analysis described here, coupled with the future development of additional network models covering distinct areas of biology, will help to further clarify the integrated biological responses elicited by complex environmental stressors such as CS, in pulmonary and cardiovascular cells.
... High levels of this protein were detected in the serum of refractory asthma patients in relation to non-refractory asthma [44], but it has not yet been associated with asthma phenotypes. The THBS1 gene has been implicated in the response to stress in asthma [45,46] and in the cellular immunity activity in allergic asthma [47], corroborating with the high levels in eosinophilic asthma demonstrated in our study. ...
Asthma drug responses may differ due to inflammatory mechanisms triggered by the immune cells in the pulmonary microenvironment. Thus, asthma phenotyping based on the local inflammatory profile may aid in treatment definition and the identification of new therapeutic targets. Here, we investigated protein profiles of induced sputum and serum from asthma patients classified into eosinophilic, neutrophilic, mixed granulocytic, and paucigranulocytic asthma, according to inflammatory phenotypes. Proteomic analyses were performed using an ultra-performance liquid chromatography (ultra-HPLC) system coupled to the Q Exactive Hybrid Quadrupole Orbitrap Mass Spectrometer. Fifty-two (52) proteins showed significant differences in induced sputum among the groups, while only 12 were altered in patients’ sera. Five proteins in the induced sputum were able to discriminate all phenotypic groups, while four proteins in the serum could differentiate all except the neutrophilic from the paucigranulocytic inflammatory pattern. This is the first report on comparative proteomics of inflammatory asthma phenotypes in both sputum and serum samples. We have identified a potential five-biomarker panel that may be able to discriminate all four inflammatory phenotypes in sputum. These findings not only provide insights into potential therapeutic targets but also emphasize the potential for personalized treatment approaches in asthma management.
... Expression of matrix metalloproteases (MMPs) is increased in asthmatic airways and these enzymes play a central role in the pathology of asthma 59,60 . MMP1 was upregulated in myofibroblasts, suggesting a potential source of the increased enzyme in the airway. ...
Asthma is the most common chronic lung disease in children and young adults worldwide. Airway remodelling (including increased fibroblasts and myofibroblasts in airway walls due to chronic inflammation) differentiates asthmatic from non-asthmatic airways. The increase in airway fibroblasts and myofibroblasts occurs via epithelial to mesenchymal transition (EMT) where epithelial cells lose their tight junctions and are transdifferentiated to mesenchymal cells, with further increases in myofibroblasts occurring via fibroblast-myofibroblast transition (FMT). Transforming growth factor (TGF)-β is the central EMT- and FMT-inducing cytokine. In this study, we have used next generation sequencing to delineate the changes in the transcriptome induced by TGF-β treatment of WI-38 airway fibroblasts in both the short term and after differentiation into myofibroblasts, to gain an understanding of the contribution of TGF-β induced transdifferentiation to the asthmatic phenotype. The data obtained from RNAseq analysis was confirmed by quantitative PCR (qPCR) and protein expression investigated by western blotting. As expected, we found that genes coding for intermediates in the TGF-β signalling pathways (SMADs) were differentially expressed after TGF-β treatment, SMAD2 being upregulated and SMAD3 being downregulated as expected. Further, genes involved in cytoskeletal pathways (FN1, LAMA, ITGB1) were upregulated in myofibroblasts compared to fibroblasts. Importantly, genes that were previously shown to be changed in asthmatic lungs (ADAMTS1, DSP, TIMPs, MMPs) were similarly differentially expressed in myofibroblasts, strongly suggesting that TGF-β mediated differentiation of fibroblasts to myofibroblasts may underlie important changes in the asthmatic airway. We also identified new intermediates of signalling pathways (PKB, PTEN) that are changed in myofibroblasts compared to fibroblasts. We have found a significant number of genes that are altered after TGF-β induced transdifferentiation of WI-38 fibroblasts into myofibroblasts, many of which were expected or predicted. We also identified novel genes and pathways that were affected after TGF-β treatment, suggesting additional pathways are activated during the transition between fibroblasts and myofibroblasts and may contribute to the asthma phenotype.
... The THBS1 gene has been implicated in a network underlying the pulmonary response to oxidative stress in asthma. 63 Aspirin leads to a reduction in THBS1 levels. 64 These data suggest that FSIP1 affects aspirin hypersensitivity in asthma associated with the nearby THBS1 gene. ...
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.
... TSP1 is consistently expressed in the quiescent lung of rodents and humans (10,67), where TSP1 protein is mostly detectable in epithelium, basement membranes, and the intercellular matrix, whereas RNA expression is more diffuse (35,68). TSP1 expression is typically induced in many other cells during chronic lung disease (14,67), including in smooth muscle cells and fibroblasts in pulmonary hypertension (PH) (6). Basal TSP1 expression in lung, although not high, is similar in level to that of proteins such as plasminogen-activator inhibitor 1 (59). ...
Most patients with familial pulmonary arterial hypertension (FPAH) carry mutations in the bone morphogenic protein receptor 2 gene (BMPR2). Yet carriers have only a 20% risk of disease, suggesting that other factors influence penetrance. Thrombospondin-1 (TSP1) regulates activation of TGF-β and inhibits endothelial and smooth muscle cell proliferation, pathways coincidentally altered in pulmonary arterial hypertension (PAH). To determine whether a subset of FPAH patients also have mutations in the TSP1 gene (THBS1) we resequenced the type I repeats of THBS1 encoding the TGF-β regulation and cell growth inhibition domains in 60 FPAH probands, 70 nonfamilial PAH subjects, and in large control groups. We identified THBS1 mutations in three families: a novel missense mutation in two (Asp362Asn), and an intronic mutation in a third (IVS8+255 G/A). Neither mutation was detected in population controls. Mutant 362Asn TSP1 had less than half of the ability of wild-type TSP1 to activate TGF-β. Mutant 362Asn TSP1 also lost the ability to inhibit growth of pulmonary arterial smooth muscle cells and was over threefold less effective at inhibiting endothelial cell growth. The IVS8+255 G/A mutation decreased and/or eliminated local binding of the transcription factors SP1 and MAZ but did not affect RNA splicing. These novel mutations implicate THBS1 as a modifier gene in FPAH. These THBS1 mutations have implications in the genetic evaluation of FPAH patients. However, since FPAH is rare, these data are most relevant as evidence for the importance of TSP1 in pulmonary vascular homeostasis. Further examination of THBS1 in the pathogenesis of PAH is warranted.
... Cytokine (i.e., TGF-b1, IL-10, IL-13, and IL-1b) secretion in our experiments in response to epithelial injury is important given accumulating evidence for airway epithelium-induced inflammatory cell recruitment (21,22) and the proliferation of fibroblasts (23-25) and smooth muscle (12). In particular, basolateral secretion of TGF-b1, which was increased in asthmatic epithelia in our experiments, is one of the key mediators of fibroblast and smooth muscle proliferation (26) and is a central component of our previously published airway epithelial stress response gene/ protein network (27). Furthermore, IL-1b activates many inflammatory genes in asthma (28), and IL-13 is a critical mediator of the classical Th2 asthmatic inflammation (29,30). ...
Asthma is an inflammatory condition for which anti-inflammatory glucocorticoids are the standard of care. However, similar efficacy has not been shown for agents targeting inflammatory cells and pathways. This suggests a noninflammatory cell contributor (e.g., epithelium) to asthmatic inflammation. Herein, we sought to define the intrinsic and glucocorticoid-affected properties of asthmatic airway epithelium compared with normal epithelium. Human primary differentiated normal and asthmatic airway epithelia were cultured in glucocorticoid-free medium beginning at -48 hours. They were pulsed with dexamethasone (20 nM) or vehicle for 2 hours at -26, -2, +22, and +46 hours. Cultures were mechanically scrape-wounded at 0 hours and exposed continuously to bromodeoxyuridine (BrdU). Cytokine secretions were analyzed using cytometric bead assays. Wound regeneration/mitosis was analyzed by microscopy and flow cytometry. Quiescent normal (n = 3) and asthmatic (n = 6) epithelia showed similar minimal inflammatory cytokine secretion and mitotic indices. After wounding, asthmatic epithelia secreted more basolateral TGF-β1, IL-10, IL-13, and IL-1β (P < 0.05) and regenerated less efficiently than normal epithelia (+48 h wound area reduction = [mean ± SEM] 50.2 ± 7.5% versus 78.6 ± 7.7%; P = 0.02). Asthmatic epithelia showed 40% fewer BrdU(+) cells at +48 hours (0.32 ± 0.05% versus 0.56 ± 0.07% of total cells; P = 0.03), and those cells were more dyssynchronously distributed along the cell cycle (52 ± 10, 25 ± 4, 23 ± 7% for G1/G0, S, and G2/M, respectively) than normal epithelia (71 ± 1, 12 ± 2, and 17 ± 2% for G1/G0, S, and G2/M, respectively). Dexamethasone pulses improved asthmatic epithelial inflammation and regeneration/mitosis. In summary, we show that inflammatory/fibrogenic cytokine secretions are correlated with dyssynchronous mitosis upon injury. Intermittent glucocorticoids simultaneously decreased epithelial cytokine secretions and resynchronized mitosis. These data, generated in an airway model lacking inflammatory cells, support the concept that epithelium contributes to asthmatic inflammation.
Systems biology provides opportunities to fully understand the genes and pathways in disease pathogenesis. We used literature knowledge and unbiased multiple data meta-analysis paradigms to analyze microarray datasets across different mouse strains and acute allergic asthma models. Our combined gene-driven and pathway-driven strategies generated a stringent signature list totaling 933 genes with 41% (440) asthma-annotated genes and 59% (493) ignorome genes, not previously associated with asthma. Within the list, we identified inflammation, circadian rhythm, lung-specific insult response, stem cell proliferation domains, hubs, peripheral genes, and super-connectors that link the biological domains (Il6, Il1ß, Cd4, Cd44, Stat1, Traf6, Rela, Cadm1, Nr3c1, Prkcd, Vwf, Erbb2). In conclusion, this novel bioinformatics approach will be a powerful strategy for clinical and across species data analysis that allows for the validation of experimental models and might lead to the discovery of novel mechanistic insights in asthma.
Chronic respiratory diseases are complex multifactorial disorders whose pathogenesis depends on the interplay between host and environmental factors. To fully understand them and to identify novel treatments, a holistic approach that integrates multiple types and levels of clinical and biological data is necessary. Towards this end, the application of systems biology-based strategies, in particular, network analysis, offers great potential. These systems-based approaches rely heavily upon computational methods that can be challenging for the non-specialist. Accordingly, this Pulmonary Perspective: (1) outlines the basic concepts of networks in biology and the fundamentals of network analysis; and, (2) discusses recent applications of network analysis to understand respiratory diseases. The intent of this Perspective is to provide readers with increased understanding of the strengths and weaknesses of network analysis methods - as well as their utility in addressing research questions involving chronic respiratory diseases.
Transcriptomics (gene expression profiling) refers to the quantitative and qualitative characterization of the collection of ribose nucleic acid (RNA) elements expressed in a biological system and represents one of the first truly genome-wide hypothesis-free investigative approaches in molecular biology. The advent of synthetic oligonucleotide microarray technologies has enabled large-scale application of gene expression profiling in the study of human disease, particularly malignant and hematological processes. Due to favorable characteristics of these processes, including their involvement of one cellular compartment (and often a specific, monoclonal cell type), the severity of the underlying cellular perturbation under study (malignant vs. benign cells), and the accessibility to large numbers of available banked samples obtained during clinically indicated medical procedures, the study of transcriptomics in oncology has been quite fruitful, with notable translation of these techniques to novel clinical applications with diagnostic, prognostic, and therapeutic implications. Furthermore, the discovery of large populations of noncoding RNA elements, including microRNA and long-intergenic noncoding RNA (LINCC-RNA) has expanded the scope of transciptomic profiling beyond the protein-coding messenger RNAs (mRNA).
In this chapter, we provide a brief survey of prior applications of this approach to the study of asthma, followed by an overview of the primary technical and analytical considerations that should be addressed when conducting such studies. For more detailed review of study protocols and specific analytical platforms, readers are referred to several recent publications (Matson 2009; Yakovlev et al. 2013; Dehmer et al. 2012; Rodriguez-Ezpelete et al. 2012).
This study aimed to locate respiratory-related neurons in NA/NRA complex within the ventrolateral medulla (VLM), characterise them, and study their responses to the stimulation of midbrain periaque-ductal gray matter (PAG) and vagal afferents.
Stereotactic mapping of the medullary NA/NRA complex using stainless steel microelectrodes was undertaken in Nembutal-anaesthetised (80 mg/kg), spontaneously-breathing rats (n = 60, 300-400 g). Individual cells and cell populations showing respiratory-related firing patterns were recorded along the VLM, 2.5 mm rostral -2.1 mm caudal to the obex, 1.4-2.2 mm lateral to midline and 1.5-3.00 mm below dorsal medullary surface. The cells were classified according to their temporal relationship with the diaphragm electromyogram (dEMG). Early inspiratory cells (eIcells) were found to start firing up to 20 ms before dEMG activity and to cease activity through mid-inspiration, exhibiting a decrementing discharge pattern. Late inspiratory (lateI) cells commenced their activity midway through inspiration and stopped firing prior to the cessation of dEMG. These cells exhibited an incrementing discharge pattern. Cells firing in phase with the dEMG have been classified as I-all cells and exhibit a steady impulse pattern throughout inspiration. Neurons active during the expiratory phase have been categorised as early expiratory cells (earlyE), late expiratory cells (lateE) and E-all neurons according to their discharge pattern in relation to dEMG.
Cells in the dorso-lateral PAG were activated with microinjections of excitatory amino acid D,L-homocysteic acid (DLH0.2 M, 10-60 nl) and VLM respiratory neuronal and muscle responses were studied. PAG stimulation induced dose-dependent changes to respiratory output. Inspiratory and expiratory durations were shortened, respiratory frequency and dEMG activity increased along with increases in heart rate and blood pressure. Concurrently PAG stimulation led to increased activation of eI cells, I-all cells and E-all cells found in the NA/NRA complex. Abdominal muscle activity was not evident during quiet breathing though expiratory neuronal activity was seen. However, activation of PAG elicited synchronous aEMG bursts along with an increase in E-all cell activity.
Unilateral vagal nerve stimulation, in order to simulate activation of the pulmonary stretch receptors, was undertaken. I-all cell and dEMG activity were inhibited upon stimulation of the vagus. However, I-all neuronal firing as well as the diaphragm activity resurfaced whilst vagal stimulation was prolonged. Expiratory cells are yet to be tested for responses to vagal stimulation.
Our previous studies [1] demonstrated a physiological link between the PAG and NTS in the rat. The current investigation shows that chemical activation of PAG influences the discharge patterns of the VLM respiratory neurons within the NA/NRA complex suggesting a possible physiological link between the two centres. These results indicate that both NTS and NA/NRA respiratory neurons participate in the mediation of PAG induced respiratory changes. Roles for NA/NRA neurons in the brainstem control of respiration in the rat and the interactions between the neural centres in the midbrain are discussed.
The activity of TGF-β1 is regulated primarily extracellularly where the secreted latent form must be modified to expose the active molecule. Here we show that thrombospondin-1 is responsible for a significant proportion of the activation of TGF-β1 in vivo. Histological abnormalities in young TGF-β1 null and thrombospondin-1 null mice were strikingly similar in nine organ systems. Lung and pancreas pathologies similar to those observed in TGF-β1 null animals could be induced in wild-type pups by systemic treatment with a peptide that blocked the activation of TGF-β1 by thrombospondin-1. Although these organs produced little active TGF-β1 in thrombospondin null mice, when pups were treated with a peptide derived from thrombospondin-1 that could activate TGF-β1, active cytokine was detected in situ, and the lung and pancreatic abnormalities reverted toward wild type.
Based on previous studies on Panjin wetlands along the coast of the Bohai Sea, this paper adopts RS, GIS and GPS techniques
and establishes the information system for Panjin wetlands. The system involves many functions, such as identification and
classification of wetlands, calculation of the area of wetlands and storage of the information of the wetland management.
Moreover, our study indicates that remote sensing technique is a useful tool for great macrography, speediness and accuracy
to carry out the extraction, analysis, management and handling of information together with geography information system,
which has prospective applications in similar kinds of research.
Background:
The ratio of matrix metalloproteinase-9 (MMP-9) and its inhibitor, tissue inhibitor of metalloproteinase-1 (TIMP-1) may be a marker of the balance between airway tissue destruction and repair. TIMP-1 may potentially contribute to the pathogenesis of increased submucosal extracellular matrix deposition in asthma.
Objective:
Our purpose was to assess the variation in sputum MMP-9 and TIMP-1 during acute asthma.
Methods:
We evaluated the MMP-9 and TIMP-1 balance in sputa of 16 asthmatic patients admitted with spontaneous exacerbation, conducting measurement before (day 1) and after methylprednisolone infusion therapy (days 2, 3, 5, and 7), and on remission days.
Results:
Peak expiratory flow and eosinophilic cationic protein levels were significantly (P <.05) improved within 7 days in all patients. Sputum MMP-9 levels on day 2 tended to be lower than on day 1, but not significantly. Zymography revealed that the main enzyme was identified immunologically as MMP-9, and gelatinase activity on day 1 had a tendency to decrease for the following 7 days. The TIMP-1 levels gradually increased until day 5, were significantly (P <.05) high on day 5, and decreased on day 7. The MMP-9/TIMP-1 molar ratios were significantly (P <.05) decreased on days 2, 3, 5, and 7 compared with day 1. Sputum levels of MMP-9 and TIMP-1 and the MMP-9/TIMP-1 molar ratios on day 1 were significantly higher (P <.02) than those on remission days.
Conclusions:
An imbalance between MMP-9 and TIMP-1 was present in acute asthma, with an excess of MMP-9 resulting in a high ratio of MMP-9/TIMP-1 before treatment, and over time with glucocorticosteroid the TIMP-1 levels rose, dropping the ratio of MMP-9/TIMP-1. It was suggested that overproduction of MMP-9 and TIMP-1 after asthma exacerbation might contribute significantly to airway tissue remodeling and that TIMP-1 production in acute asthma might not be suppressed by glucocorticosteroid.
Allergic asthma results from inappropriate T(H)2-mediated inflammation. Both IL-4 and IL-13 contribute to asthma pathogenesis, but IL-4 predominantly drives T(H)2 induction, whereas IL-13 is necessary and sufficient for allergen-induced airway hyperresponsiveness and goblet cell hyperplasia. Although these 2 cytokines share signaling components, the molecular mechanisms by which they mediate different phases of the allergic asthmatic response remain elusive.
We sought to clarify the role or roles of IL-4 and IL-13 in asthma-pathogenesis.
We used DNA Affymetrix microarrays to profile pulmonary gene expression in BALB/c mice inoculated intratracheally with ragweed pollen, house dust mite, IL-4, IL-13, or both cytokines. IL-13 dependence was confirmed by comparing pulmonary gene expression in house dust mite-inoculated wild-type and IL-13 knockout mice.
A signature gene expression profile consisting of 23 genes was commonly induced by means of inoculation with house dust mite, ragweed pollen, or IL-4 plus IL-13. Although rIL-4 and rIL-13 treatment induced an overlapping set of genes, IL-4 uniquely induced 21 genes, half of which were interferon response genes and half of which were genes important in immunoregulation. IL-13 uniquely induced 8 genes, most of which encode proteins produced by epithelial cells.
IL-4 and IL-13 together account for most allergen-induced pulmonary genes. Selective IL-4 induction of IFN-gamma response genes and other genes that might negatively regulate allergic inflammation could partially explain the greater importance of IL-13 in the effector phase of allergic airway disease.
Matrix metalloproteinases (MMPs) modulate development, inflammation, and repair in lungs. Tissue inhibitors of MMPs (TIMPs) interact with MMPs, controlling the intensity and nature of the response to injury. Absence of MMP-9, -2, and -8 activities is associated with altered lung inflammation during allergic sensitization. To test the hypothesis that the absence of TIMP-1 enhances allergic lung inflammation, airway hyperreactivity (AHR), and lung remodeling in asthma, we studied TIMP-1 null (TIMP-1 KO) mice and their WT controls using an ovalbumin (OVA) asthma model. TIMP-1 KO mice, compared to WT controls, developed an asthma phenotype characterized by AHR, pronounced cellular lung infiltrates, greater reduction in lung compliance, enhanced Th2 cytokine mRNA and protein expression, and altered collagen lung content associated with enhanced MMP-9 activity. Our findings support the hypothesis that TIMP-1 plays a protective role by preventing AHR and modulating inflammation, remodeling, and cytokine expression in an animal model of asthma.
The association of exposure to environmental tobacco smoke (ETS) at home with asthma and several measures of wheeze was examined among 11,534 children aged 8 to 11 yr in 24 communities in the United States and Canada in 1988 through 1990. Information on the child's respiratory symptoms in the past year and history of exposure to ETS was provided by the child's mother on a questionnaire. After adjusting for potential confounders, children currently exposed to ETS were at greater risk of wheezing with colds (odds ratio [OR] = 1.7; 95% confidence interval [95% CI], 1.4 to 1.9), going to a hospital emergency room for wheeze (OR = 1.6; 95% CI, 1.2 to 2.2), and having persistent wheeze (OR = 1.4; 95% CI, 1.1 to 1.8). The relative odds of these symptoms increased with exposure level, and there was no evidence of a difference in the association with smoking by mother, father, or other adults. In contrast to wheeze symptoms, active doctor-diagnosed asthma and asthma medication use were not significantly associated with ETS exposure at home, possibly reflecting underdiagnosis of asthma, reporting bias, or smoking cessation by parents whose child is labeled asthmatic. We conclude that exposure to ETS is associated with wheezing symptoms, medical therapy for wheezing, and wheezing-related emergency department visits in U.S. and Canadian children.
An imbalance between oxidants and antioxidants has been considered in the pathogenesis of smoking-induced lung diseases, such as chronic obstructive pulmonary disease (COPD), particularly emphysema. Recent evidence indicates that increased neutrophil sequestration and activation occurs in the pulmonary microvasculature in smokers and in patients with COPD, with the potential to release reactive oxygen species (ROS). ROS generated by airspace phagocytes or inhaled directly from the environment also increase the oxidant burden and may contribute to the epithelial damage. Although much research has focused on the protease/antiprotease theory of the pathogenesis of emphysema, less attention has been paid to the role of ROS in this condition. The injurious effects of the increased oxidant burden in smokers and in patients with COPD are opposed by the lung antioxidant defences. Hence, determining the mechanisms regulating the antioxidant responses is critical to our understanding of the role of oxidants in the pathogenesis of smoking-induced lung disease and to devising future strategies for antioxidant therapy. In this article we have reviewed the evidence for the presence of an oxidant/antioxidant imbalance in smoking-induced lung disease and its relevance to therapy in these conditions.
Evidence suggests that thrombospondin-1 (TSP-1), a 450-kDa glycoprotein in platelets and extracellular matrix, is involved in angiogenesis. However, the mechanisms by which TSP-1 regulates angiogenesis are unknown, and the exact role of TSP-1 in angiogenesis has been controversial: both stimulatory and inhibitory effects of TSP-1 have been reported. In this study, we evaluated the effect of TSP-1 on the capacity of bovine aortic endothelial (BAE) cells to both invade and form microvessel-like tubes in collagen gels. BAE cell tube formation was enhanced by exogenous TSP-1 at relatively low concentrations (1-10 microg/ml) but inhibited at higher concentrations of TSP-1 (>15 microg/ml). In addition, we correlated this biphasic effect on tube formation with the capacity of TSP-1 to stimulate the activity of a matrix metalloproteinase-9 (MMP-9) in BAE cell collagen gel cultures. The TSP-1-mediated stimulation of MMP-9 activity was specific and dose- and time-dependent. Furthermore, TSP-1-stimulated BAE cell invasion and tube formation were reversed by antibodies against both TSP-1 and MMP-9, suggesting that TSP-1 modulates endothelial cell invasion and morphogenesis in vitro by a mechanism involving the regulation of MMP-9 activity. These findings support the conclusion that TSP-1 is a multifunctional modulator of angiogenesis and are consistent with the dynamic presence of TSP-1 in remodeling tissues in which matrix degradation is required.