PlexinD1 Deficiency in Lung Interstitial Macrophages Exacerbates House Dust Mite-Induced Allergic Asthma.

Interstitial macrophages (IMs) are key regulators of allergic inflammation. We previously showed that the absence of semaphorin 3E (Sema3E) exacerbates asthma features in both acute and chronic asthma models. However, it has not been studied whether Sema3E, via its receptor plexinD1, regulates IM function in allergic asthma. Therefore, we investigated the role of plexinD1 deficiency on IMs in allergic asthma. We found that the absence of plexinD1 in IMs increased airway hyperresponsiveness, airway leukocyte numbers, allergen-specific IgE, goblet cell hyperplasia, and Th2/Th17 cytokine response in the house dust mite (HDM)-induced allergic asthma model. Muc5ac, Muc5b, and α-SMA genes were increased in mice with Plxnd1-deficient IMs compared with wild-type mice. Furthermore, plexinD1-deficient bone marrow-derived macrophages displayed reduced IL-10 mRNA expression, at both the baseline and following HDM challenge, compared with their wild-type counterpart mice. Our data suggest that Sema3E/plexinD1 signaling in IMs is a critical pathway that modulates airway inflammation, airway resistance, and tissue remodeling in the HDM murine model of allergic asthma. Reduced IL-10 expression by plexinD1-deficient macrophages may account for these enhanced allergic asthma features.

Store-operated calcium entry-associated regulatory factor regulates airway inflammation and airway remodeling in asthma mice models.

Store-operated calcium entry (SOCE) is involved in the pathogenesis of airway inflammation and remodeling in asthma. Store-operated calcium entry-associated regulatory factor (SARAF) can downregulate SOCE. We sought to investigate the role of SARAF in the regulation of airway inflammation and remodeling in asthma mice models, as well as in the functional regulation of human airway smooth muscle cells (hASMCs). Balb/c mice were sensitized and challenged with ovalbumin to establish the asthma mice models. Mice were transfected with lentivirus, which expressed the SARAF gene + GFP (green fluorescence protein) or the negative control gene + GFP. Airway resistance was measured with the animal pulmonary function system. Airway inflammation and remodeling were evaluated via histological staining. In vitro cultured hASMCs were transfected with scrambled small interfering RNA (siRNA) or SARAF-specific siRNA, respectively. The proliferation, migration rate, hypertrophy, and SOCE activity of hASMCs were examined with Cell Counting Kit-8, wound healing test, bright field imaging, and Ca2+ fluorescence imaging, respectively. SARAF expression was measured by quantitative real-time PCR. Asthma mice models showed decreased SARAF mRNA expression in the lungs. SARAF overexpression attenuated airway inflammation, resistance, and also remodeling. Downregulation of SARAF expression with siRNA promoted the proliferation, migration, hypertrophy, and SOCE activity in hASMCs. SARAF plays a protective role against airway inflammation and remodeling in asthma mice models by blunting SOCE; SARAF may also be a functional regulating factor of hASMCs.

Role of biomarkers and effect of FIP-fve in acute and chronic animal asthma models.

BACKGROUND: Asthma is a consequence of complex gene-environment interactions. Exploring the heterogeneity of asthma in different stages is contributing to our understanding of its pathogenesis and the development of new therapeutic strategies, especially in severe cases. OBJECTIVE: This study aimed to further understand the relationship between manifestations of acute and chronic asthma and various endotypes, and explore the severity of lung inflammation, cell types, cytokine/chemokine differences, and the effects of FIP-fve. MATERIALS AND METHODS: Acute and chronic OVA-sensitization mouse asthma models, based on our previously published method, were used and FIP-fve was used to evaluate the effect on these two models. BALF cytokines/chemokines were detected according to the manufacturer's protocol. RESULTS: Seventeen cytokine/chemokine secretions were higher in the chronic stage than in the acute stage. Whether in acute stage or chronic stage, the FIP-fve treatment groups had reduced airway hyperresponsiveness, infiltration of airway inflammatory cells, secretion of cytokines, chemokines by Th2 cells, and TNF-α, IL-8, IL-17, CXCL-1, CXCL-10, CCL-17, and CCL-22, and it was also found that the Treg cell cytokine IL-10 had increased significantly. PCA (Principal Component Analysis) was also used to compare statistics and laboratory data to find the important biomarkers in different stages and after treatment with FIP-fve. CONCLUSIONS: There are many different immune responses in the different stages of the asthma process. Drug treatment at the appropriate times might help reduce the worsening of asthma.

Effect of IL­7 on Th17 cell responses in a mouse model of neutrophilic asthma.

Neutrophilic asthma (NA) is characterized by neutrophil­mediated inflammation and the presence of Th17 cells. However, the mechanisms underlying Th17 cell responses in NA remain unknown. The aim of the present study was to examine the effects of interleukin (IL)­7 on Th17 cell responses in NA. A NA mouse model was sensitized by airway delivery of ovalbumin (OVA) and lipopolysaccharide and challenged with 1% OVA aerosol from day 21 for 3 consecutive days. Airway resistance was then measured to assess airway hyper­responsiveness (AHR). Cells from bronchoalveolar lavage fluid (BALF) underwent Diff­Quick and hematoxylin and eosin staining for classification. The levels of IL­17 in the BALF were determined by ELISA. The effects of IL­7 administration and STAT5 inhibition on Th17 cells were also characterized in vitro using splenic CD4+ T cells. Ki­67, Bcl­2 and activated caspase­3 expression in differentiated Th17 cells were analyzed by flow cytometry. The mouse model of NA was characterized by increased AHR, elevated levels of IL­17, high neutrophil counts in BALF, accumulated inflammatory cells in the lung and Th17 cell responses. IL­7 promoted the expression of Ki­67 and Bcl­2 while reducing caspase­3 expression. STAT5 inhibitor treatment decreased the levels of Ki­67 and Bcl­2, and resulted in increased expression of caspase­3. These results suggested that the IL­7/JAK/STAT5 signaling pathway may be involved in Th17 cell responses in NA.

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

Objective: New treatments are needed for cases of asthma that are refractory to traditional therapies. In this study, we examined the effect of oral nintedanib, an intracellular inhibitor of tyrosine kinases, on airway hyper-responsiveness (AHR) and airway smooth muscle cells, using a mouse model of experimental asthma. Methods: Asthma was experimentally induced in mice via subcutaneous injection of ovalbumin (OVA). A group of saline-injected mice served as a control group. The OVA mice were then divided into four treatment groups according to the dose of nintedanib. AHR was examined via exposure to vaporized methacholine. Airway inflammation was assessed via bronchoalveolar lavage fluid (BALF) cell counts and Th2 cytokine concentrations. Results: Baseline levels of AHR and airway inflammation were higher in OVA mice than in the control group. Treatment with nintedanib lowered AHR, BALF cell counts and BALF cytokine levels in a dose-dependent fashion. The effect of nintedanib was comparable to that of dexamethasone. In particular, treatment with nintedanib lowered the expression of transforming growth factor-ß1 and inhibited the expression and phosphorylation of platelet-derived growth factor receptor-ß, vascular endothelial growth factor receptor 1 (VEGFR1), VEGFR2, fibroblast growth factor receptor 2 (FGFR2), FGFR3, and extracellular signal-regulated kinase. Conclusions: Nintedanib lowered AHR and the expression of factors associated with airway inflammation and remodeling in a mouse model of experimental asthma. Our results suggest that nintedanib may be useful in the treatment of asthma.

Inflammatory profile in optimally treated patients with adult versus early-onset asthma.

Introduction: The age of asthma onset is often implicated in clinical manifestation, diagnosis, and management of the disease. Aim: To define demographic, clinical and functional features and inflammatory characteristics in induced sputum in patients with adult-onset asthma. Methods: Optimally treated patients from asthma clinics of two tertiary hospitals were included in the study. Patients underwent assessment of demographic characteristics, severity and treatment regimes, pulmonary function tests, and skin prick tests, as well as measurement of blood eosinophils and sputum induction for the assessment of sputum inflammatory cells, IL-8 and IL-13 levels in the supernatant. Results: Of the 333 patients recruited, 234 (70.2%) had adult-onset asthma. Adult-onset asthmatics were older, had a higher BMI, a shorter disease duration, and were less often atopic, compared to patients with early onset asthma. Higher proportions of patients with severe asthma presented increased levels of FeNO and blood eosinophils, both in the early and the adult-onset patient groups. Finally, obese patients with early onset asthma were characterized by less atopy compared to non-obese patients in the same group. Conclusion: Adult-onset asthma was characterized by less sputum eosinophilia, a nonatopic profile and a higher BMI compared to early-onset asthma. The presence of blood eosinophilia and increased FeNO in patients with severe asthma was comparable in the two groups.

Modulation of Bronchomotor Tone Pathways in Airway Smooth Muscle Function and Bronchomotor Tone in Asthma.

Airway smooth muscle is the primary cell mediating bronchomotor tone. The milieu created in the asthmatic lung modulates airway smooth muscle contractility and relaxation. Experimental findings suggest intrinsic abnormalities in airway smooth muscle derived from patients with asthma in comparison with airway smooth muscle from those without asthma. These changes to excitation-contraction pathways may underlie airway hyperresponsiveness and increased airway resistance associated with asthma.

Time-dependent distinct roles of Toll-like receptor 4 in a house dust mite-induced asthma mouse model.

House dust mites (HDMs) are a common source of allergens that trigger both allergen-specific and innate immune responses in humans. Here, we examined the effect of allergen concentration and the involvement of Toll-like receptor 4 (TLR4) in the process of sensitization to house dust mite allergens in an HDM extract-induced asthma mouse model.　Intranasal administration of HDM extract induced an immunoglobulin E response and eosinophilic inflammation in a dose-dependent manner from 2.5 to 30 µg/dose. In TLR4-knockout mice, the infiltration of eosinophils and neutrophils into the lung was decreased compared with that in wild-type mice in the early phase of inflammation (total of three doses). However, in the late phase of inflammation (total of seven doses), eosinophil infiltration was significantly greater in TLR4-knockout mice than in wild-type mice. This suggests that the roles of TLR4 signaling are different between the early phase and the later phase of HDM allergen-induced inflammation. Thus, innate immune response through TLR4 regulated the response to HDM allergens, and the regulation was altered during the phase of inflammation.

Effects of leukotriene D4 and histamine nasal challenge on airway responsiveness and inflammation in persistent allergic rhinitis patients.

BACKGROUND: Both histamine and leukotrienes are implicated in the pathogenesis of allergic rhinitis (AR), although the pattern and severity of the nasal response to these two potent inflammatory mediators may differ, which has not been adequately studied in patients with persistent AR. OBJECTIVE: We sought to compare the differential effects of nasal challenge with leukotriene D4 (LTD4 ) and histamine on the airway response and inflammation in patients with AR. METHODS: An open-label, crossover study was performed in 25 persistent AR patients (AR group) and 16 healthy subjects (control group). Participants randomly underwent histamine and LTD4 nasal provocation within a two-week interval. Nasal symptoms according to a visual analogue scale (VAS), fractional exhaled nitric oxide (FENO), nasal lavage, induced sputum, and spirometry were evaluated before and after nasal challenge. RESULTS: Nasal airway resistance (NAR) increased significantly after both LTD4 and histamine nasal challenge in AR patients (P < .05). The potency of LTD4 was 142-fold higher than that of histamine in increasing NAR (P < .001). The nasal symptom score induced by histamine challenge was significantly higher than that triggered by LTD4 (3.42 ± 0.83 vs. 1.16 ± 0.94, P < .05) in the AR group. LTD4 and histamine nasal challenge led to a significant increase in neutrophils in the nasal lavage and induced sputum (P < .05) in AR patients. There were no significant differences in the changes of eosinophils before and after LTD4 and histamine nasal challenges in nasal lavage and induced sputum. No significant changes in NAR, the induced symptom score, or inflammatory cells in the nasal lavage and sputum were found in the control group. CONCLUSIONS: LTD4 and histamine nasal challenge caused different patterns and severities of nasal symptoms, which correlated with symptoms (TSS) that affect patient's daily life. LTD4 was far more potent than histamine at increasing the NAR, while histamine nasal challenge induced more sneezing and nasal discharge. These results may guide the prescription of anti-histamine or anti-leukotriene agents for treating different AR phenotypes.

The effects of chrysophanol on ovalbumin (OVA)-induced chronic lung toxicology by inhibiting Th17 response.

Chrysophanol (CH), extracted from plants of Rheum genus, possesses various pharmacological effects including anti-inflammatory activity. The purpose of the present study was to evaluate the protective effects and the underlying mechanisms of CH on ovalbumin (OVA)-induced asthma in mice. Fifty mice were randomly assigned to five experimental groups: control group, model group, dexamethasone (2 mg/kg) group and CH (5 and 10 mg/kg) groups. The number of eosinophil cells and the production of interleukin-6 (IL-6), IL-1ß, IL-17 A and tumor necrosis factor-α in bronchoalveolar lavage fluid (BALF) were measured. In addition, pulmonary histopathology, airway resistance (Raw), T-helper17 (Th17) cells frequency and RORγt expression were evaluated. Our study demonstrated that CH effectively decreased eosinophil count and inflammatory cytokines production in BALF. In addition, treatment with CH significantly inhibited the Raw, Th17 percentage and RORγt expression in OVA-induced animals compared with those in model group. Histological studies also demonstrated that CH significantly suppressed OVA-induced eosinophilia in lung tissue compared with model group. Our findings supported that CH can prevent allergic asthma in the mouse model.

Pharmacological investigation on the anti-oxidant and anti-inflammatory activity of N-acetylcysteine in an ex vivo model of COPD exacerbation.

BACKGROUND: Oxidative stress is recognized to be one of predisposing factor in the pathogenesis of COPD. The oxidant/antioxidant imbalance is significantly pronounced in patients with COPD exacerbation. N-acetylcysteine (NAC) seems to be able to reduce COPD exacerbations by modulating the oxidative stress in addition to its well-known mucolytic activity, but there are discordant findings on the actual anti-oxidant activity of NAC. METHODS: The anti-oxidant effect of NAC and its impact on the inflammatory response have been pharmacologically characterized on a human ex vivo model of COPD exacerbation induced by lipopolysaccharide (LPS). RESULTS: NAC prevented the desensitization induced by LPS incubation on the contractile tone in linear concentration-response manner. Concentrations of NAC ≥1 µM reduced the pro-oxidant response (peroxidase activity, hydrogen peroxide, malondialdehyde, nitric oxide), and improved the anti-oxidant response (total anti-oxidant capacity, glutathione, superoxide dismutase) induced by LPS. Lower concentrations of NAC (<1 µM) did not modulate the bronchial oxidative imbalance. Concentrations of NAC ≥300 µM inhibited the inflammatory response (release of IL-1ß, IL-8, and TNF-α) of human airways induced by the overnight stimulation with LPS, whereas lower concentrations of NAC (≥1 µM) were sufficient to reduce the release of IL-6 elicited by LPS. Both the anti-oxidant effect and the anti-inflammatory effect of NAC were inversely correlated with the release of NKA. CONCLUSIONS: The findings of this study suggest that NAC may have a role in modulating the detrimental effect induced by LPS in course of COPD exacerbation. It may elicit both anti-oxidant and anti-inflammatory effects when administered at high concentrations.

Identification of genes differentially regulated by vitamin D deficiency that alter lung pathophysiology and inflammation in allergic airways disease.

Vitamin D deficiency is associated with asthma risk. Vitamin D deficiency may enhance the inflammatory response, and we have previously shown that airway remodeling and airway hyperresponsiveness is increased in vitamin D-deficient mice. In this study, we hypothesize that vitamin D deficiency would exacerbate house dust mite (HDM)-induced inflammation and alterations in lung structure and function. A BALB/c mouse model of vitamin D deficiency was established by dietary manipulation. Responsiveness to methacholine, airway smooth muscle (ASM) mass, mucus cell metaplasia, lung and airway inflammation, and cytokines in bronchoalveolar lavage (BAL) fluid were assessed. Gene expression patterns in mouse lung samples were profiled by RNA-Seq. HDM exposure increased inflammation and inflammatory cytokines in BAL, baseline airway resistance, tissue elastance, and ASM mass. Vitamin D deficiency enhanced the HDM-induced influx of lymphocytes into BAL, ameliorated the HDM-induced increase in ASM mass, and protected against the HDM-induced increase in baseline airway resistance. RNA-Seq identified nine genes that were differentially regulated by vitamin D deficiency in the lungs of HDM-treated mice. Immunohistochemical staining confirmed that protein expression of midline 1 (MID1) and adrenomedullin was differentially regulated such that they promoted inflammation, while hypoxia-inducible lipid droplet-associated, which is associated with ASM remodeling, was downregulated. Protein expression studies in human bronchial epithelial cells also showed that addition of vitamin D decreased MID1 expression. Differential regulation of these genes by vitamin D deficiency could determine lung inflammation and pathophysiology and suggest that the effect of vitamin D deficiency on HDM-induced allergic airways disease is complex.

Following up infant bronchiolitis patients provided new evidence for and against the united airway disease hypothesis.

AIM: The united airway disease (UAD) hypothesis suggests that allergic rhinitis and asthma develop together. We evaluated the evidence for and against the UAD hypothesis at five to seven years of age after hospitalisation for bronchiolitis at less than six months. METHODS: This study used prospective follow-up data for 102 children hospitalised for bronchiolitis under the age of six months. We included the presence of previous and current asthma, prolonged rhinitis and skin prick tests (SPT) to common inhaled allergens and lung function by impulse oscillometry (IOS) at five to seven years of age. Bronchial hyper-reactivity (BHR) was assessed using the exercise challenge test and bronchodilation test. RESULTS: Current asthma, but not previous transient asthma, was associated with prolonged rhinitis and a positive SPT. BHR, which reflected reactive airways, but not lung function, was associated with respiratory allergy, namely the combination of current asthma, prolonged rhinitis and a positive SPT. CONCLUSION: This post-bronchiolitis follow-up study suggested an association between respiratory allergy and reactive airways at five to seven years of age, which supported the UAD hypothesis. However, previous transient asthma and a reduction in lung function reduction did not support the hypothesis.

The Guinea Pig Sensitized by House Dust Mite: A Model of Experimental Cough Studies.

The guinea pig sensitized by ovalbumin is the most widely used model to study cough experimentally, as the neurophysiology of the vagus nerve in the guinea pig is closest to humans. Nonetheless, the choice of the antigen remains questionable, which influences the translation of results into clinical medicine. The present study seeks to develop an alternative model of cough study using house dust mite sensitization (HDM). Thirty guinea pigs were divided into the HDM group, ovalbumin (OVA) group, and control group based on their cough response to 0.4 M citric acid. In the HDM group animals were sensitized by 0.25 %HDM aerosol, which they inhaled for 5 min over 5 days, followed by inhalation of 0.5 %HDM in the same protocol. Sensitization was confirmed by a skin test. Symptoms of allergic rhinitis were induced by intranasal application of 15 µl 0.5 %HDM and cough challenges with citric acid were performed. Airway resistance was measured in vivo by Pennock's method. We found that both HDM and OVA-sensitized groups showed a significantly enhanced nasal reactivity and cough response compared with controls. The airway resistance data did not show significant differences. We conclude that the HDM cough model replicates functional aspects of the OVA model, which may make it an alternative to the latter. However, the superiority of the HDM model for experimental cough studies remains to be further explored.

Pretreatment With Inactivated Bacillus Calmette-Guerin Increases CD4+CD25+ Regulatory T Cell Function and Decreases Functional and Structural Effects of Asthma Induction in a Rat Asthma Model.

Bacillus Calmette-Guerin (BCG) has been shown to have therapeutic effects on asthma through CD4+CD25+ regulatory T cells (Tregs). We sought to assess pretreatment with inactivated BCG on CD4+CD25+ Tregs and its functional and structural effects in rat asthma model. The rat asthma model was established using ovalbumin (OVA) sensitization and challenge. Ten rats were pretreated with BCG prior to OVA and received continued BCG injections during OVA challenge (BCG+OVA group), 10 rats were treated with OVA alone (OVA group), and 10 rats were treated with saline (control group). After 9 weeks, histamine dihydrochloride effect on airway resistance was measured. Number of CD4+CD25+ Tregs was measured by flow cytometry, expression of Foxp3 and CTLA-4 mRNA was measured, and serum TGF-ß levels were determined. Differential cell count in bronchoalveolar lavage fluid (BALF) was determined, and lung tissue was processed and stained with hematoxylin and eosin, Masson's trichrome, and alcine blue and periodic acid Schiff's reaction to evaluate inflammatory cell infiltration, collagen deposition, and presence of goblet cells, respectively. BCG treatment led to an increase in CD4+CD25+ Tregs, as well as an increase in Foxp3 and CTLA-4 expression and serum TGF-ß levels. In addition, we observed a decrease in histamine dihydrochloride-induced airway resistance, a decrease in inflammatory leukocytes in BALF, and a decrease in airway remodeling indicators in BCG+OVA-treated rats compared with OVA-treated rats. Intradermally injected inactivated BCG has the potential to improve airway inflammation, airway resistance, and airway remodeling through a mechanism that may involve CD4+CD25+ Tregs.

The effects of in utero vitamin D deficiency on airway smooth muscle mass and lung function.

We have previously demonstrated increased airway smooth muscle (ASM) mass and airway hyperresponsiveness in whole-life vitamin D-deficient female mice. In this study, we aimed to uncover the molecular mechanisms contributing to altered lung structure and function. RNA was extracted from lung tissue of whole-life vitamin D-deficient and -replete female mice, and gene expression patterns were profiled by RNA sequencing. The data showed that genes involved in embryonic organ development, pattern formation, branching morphogenesis, Wingless/Int signaling, and inflammation were differentially expressed in vitamin D-deficient mice. Network analysis suggested that differentially expressed genes were connected by the hubs matrix metallopeptidase 9; NF-κ light polypeptide gene enhancer in B cells inhibitor, α; epidermal growth factor receptor; and E1A binding protein p300. Given our findings that developmental pathways may be altered, we investigated if the timing of vitamin D exposure (in utero vs. postnatal) had an impact on lung health outcomes. Gene expression was measured in in utero or postnatal vitamin D-deficient mice, as well as whole-life vitamin D-deficient and -replete mice at 8 weeks of age. Baseline lung function, airway hyperresponsiveness, and airway inflammation were measured and lungs fixed for lung structure assessment using stereological methods and quantification of ASM mass. In utero vitamin D deficiency was sufficient to increase ASM mass and baseline airway resistance and alter lung structure. There were increased neutrophils but decreased lymphocytes in bronchoalveolar lavage. Expression of inflammatory molecules S100A9 and S100A8 was mainly increased in postnatal vitamin D-deficient mice. These observations suggest that in utero vitamin D deficiency can alter lung structure and function and increase inflammation, contributing to symptoms in chronic diseases, such as asthma.

Syk mediates airway contractility independent of leukocyte function.

BACKGROUND: Syk, an immune regulatory tyrosine kinase, plays a role in inflammatory disease processes. We recently reported a role for epithelial expression of Syk in the airways hyper-responsiveness in response to air pollution in a mouse model of asthma. The aim of this study was to further investigate the role of Syk in airway contractility in response to methacholine (MCh) and particulate matter (PM) air pollutants, in the absence of underlying inflammation. METHODS: We used Syk(flox/flox) //rosa26CreER(T) (2) conditional Syk knockout mice to evaluate respiratory mechanics and MCh responsiveness following PM exposure in vivo using the ventilator-based flexiVent system. RESULTS: While total and differential cell counts in bronchoalveolar lavage fluid were similar between the Syk(flox/flox) and Syk(del/del) mice, central airways respiratory resistance (RN ) to MCh was significantly augmented following PM exposure between Syk-intact (Syk(flox/flox) ) and Syk-deficient (Syk(del/del) ) mice (RN (max) : 2.06 ± 0.29 vs. 1.29 ± 0.10, respectively; p < 0.05, n = 8-10/group). We employed live videomicroscopy to investigate changes in airway luminal diameter using ex vivo lung slices, which were devoid of circulating leukocytes. MCh reduced the airway luminal area of Syk(flox/flox) mice to 81.1 ± 1.4% of baseline, which was virtually abrogated in Syk(del/del) mice (luminal area = 93.2 ± 0.5%, n = 5/group, p < 0.05). In response to PM exposure, Syk(flox/flox) airways contracted to 73.8 ± 2.7% of baseline luminal diameter, whereas Syk(del/del) airways exhibited minimal contractility to PM and MCh (90.0 ± 1.3% of baseline, n = 5/group, p < 0.05). CONCLUSIONS: These observations suggest that Syk mediates airway contractility in the normal and allergic airways, independent of its role and function in leukocytes, and supports a paracrine role for airway epithelial Syk in modulating airway smooth muscle activity.

Current clinical diagnostic tests for asthma.

Asthma involves variable airflow obstruction in both large and small airways. The physiological consequences of obstruction include increased airway resistance and decreased expiratory flow rates, which lead to air trapping and dynamic hyperinflation. This chapter reviews current methods for pulmonary function testing to detect these physiological changes for both diagnosis and monitoring.