Jennifer L. Trevor

IL-33 and M2a Alveolar Macrophages Promote Lung Defense against the Atypical Fungal Pathogen Pneumocystis murina

We have recently reported that mice deficient in the myeloid Src-family tyrosine kinases Hck, Fgr, and Lyn (Src triple knockout [TKO]) had augmented innate lung clearance of Pneumocystis murina that correlated with a higher ability of alveolar macrophages (AMs) from these mice to kill P. murina. In this article, we show that despite possessing enhanced killing, AMs from naive Src TKO mice did not demonstrate enhanced inflammatory responses to P. murina. We subsequently discovered that both AMs and lungs from P. murina-infected Src TKO mice expressed significantly greater levels of the M2a markers RELM-α and Arg1, and the M2a-associated chemokines CCL17 and CCL22 than did wild-type mice. IL-4 and IL-13, the primary cytokines that promote M2a polarization, were not differentially produced in the lungs between wild-type and Src TKO mice. P. murina infection in Src TKO mice resulted in enhanced lung production of the novel IL-1 family cytokine IL-33. Immunohistochemical analysis of IL-33 in lung tissue revealed localization predominantly in the nucleus of alveolar epithelial cells. We further demonstrate that experimental polarization of naive AMs to M2a resulted in more efficient killing of P. murina compared with untreated AMs, which was further enhanced by the addition of IL-33. Administration of IL-33 to C57BL/6 mice increased lung RELM-α and CCL17 levels, and enhanced clearance of P. murina, despite having no effect on the cellular composition of the lungs. Collectively, these results indicate that M2a AMs are potent effector cells against P. murina. Furthermore, enhancing M2a polarization may be an adjunctive therapy for the treatment of Pneumocystis.

Refractory asthma: mechanisms, targets, and therapy

Asthma is a common medical condition affecting 300 million people worldwide. Airway inflammation, smooth muscle bronchoconstriction leading to airflow obstruction, and mucous hypersecretion are clinical hallmarks of asthma. The NHLBI Expert Panel Report 3 recommends inhaled corticosteroids (ICS) for patients with moderate to severe persistent asthma. Inhaled corticosteroids (ICS) target gene transcription through their interactions with the glucocorticoid (GC) receptor (GR) at the glucocorticoid response element (GRE). The GC/GR complex enhances anti-inflammatory but inhibits pro-inflammatory mediator production. Classically, asthma has been described as a Th2-associated eosinophil-predominant disease, but recently alternative models have been described including a Th17-mediated neutrophil-predominant phenotype resulting in patients with more severe disease who may be less responsive to steroids. Additional mechanisms of steroid resistance include increased activity of GR phosphorylating kinases which modify the interactions of GR with transcription factors to inhibit the ability of GR to bind with GRE, leading to an increase in pro-inflammatory gene transcription. Oxidative stress also affects the balance between pro-inflammatory and anti-inflammatory gene transcription through the modification of transcription factors and cofactors (such as PI3K) leading to the inhibition of histone deacetylase 2. Continued investigations into the mechanisms behind glucocorticoid resistance will lead to novel treatments that improve control of severe refractory asthma.

Efficacy of mepolizumab add-on therapy on health-related quality of life and markers of asthma control in severe eosinophilic asthma (MUSCA): a randomised, double-blind, placebo-controlled, parallel-group, multicentre, phase 3b trial

BACKGROUND Mepolizumab, an anti-interleukin-5 monoclonal antibody approved as add-on therapy to standard of care for patients with severe eosinophilic asthma, has been shown in previous studies to reduce exacerbations and dependency on oral corticosteroids compared with placebo. We aimed to further assess mepolizumab in patients with severe eosinophilic asthma by examining its effect on health-related quality of life (HRQOL). METHODS We did a randomised, double-blind, placebo-controlled, parallel-group, multicentre, phase 3b trial (MUSCA) in 146 hospitals or research centres in 19 countries worldwide. Eligible participants were patients aged 12 years or older with severe eosinophilic asthma and a history of at least two exacerbations requiring treatment in the previous 12 months before screening despite regular use of high-dose inhaled corticosteroids plus other controller medicines. Exclusion criteria included current smokers or former smokers with a history of at least ten pack-years. We randomly assigned participants (1:1) by country to receive a subcutaneous injection of either mepolizumab 100 mg or placebo, plus standard of care, every 4 weeks for 24 weeks (the final dose was given at week 20). We did the randomisation using an interactive voice response system and a centralised, computer-generated, permuted-block design of block size six. The two treatments were identical in appearance and administered in a masked manner; patients, investigators, other site staff and the entire study team including those assessing outcomes data were also masked to group assignment. The primary endpoint was the mean change from baseline in the St Georges Respiratory Questionnaire (SGRQ) total score at week 24 in the modified intention-to-treat (modified ITT) population (analysed according to their randomly assigned treatment). Safety was assessed in all patients who received at least one dose of trial medication (analysed according to the actual treatment received). This trial is registered with ClinicalTrials.gov, number NCT02281318. FINDINGS We recruited patients between Dec 11, 2014, and Nov 20, 2015, and the study was undertaken between Dec 11, 2014, and June 10, 2016. The modified ITT population comprised 274 patients assigned to mepolizumab 100 mg and 277 assigned to placebo. Mepolizumab versus placebo showed significant improvements at week 24 from baseline in SGRQ total score (least squares mean [SE] change from baseline -15·6 (1·0) vs -7·9 (1·0), a treatment difference of -7·7 (95% CI -10·5 to -4·9; p<0·0001). No deaths occurred during the study. 192 (70%) of 273 patients who received mepolizumab and 207 (74%) of 278 who received placebo reported at least one on-treatment adverse event, the most common of which were headache (in 45 [16%] given mepolizumab vs 59 [21%] given placebo) and nasopharyngitis (in 31 [11%] given mepolizumab vs 46 [17%] given placebo). 15 (5%) and 22 (8%) patients had an on-treatment serious adverse event in the mepolizumab and placebo groups, respectively; the most common was asthma in both groups (in three [1%] given mepolizumab vs nine [3%] given placebo). INTERPRETATION Mepolizumab was associated with significant improvements in HRQOL in patients with severe eosinophilic asthma, and had a safety profile similar to that of placebo. These results add to and support the use of mepolizumab as a favourable add-on treatment option to standard of care in patients with severe eosinophilic asthma. FUNDING GlaxoSmithKline.

KIT Inhibition by Imatinib in Patients with Severe Refractory Asthma

BACKGROUND Mast cells are present in the airways of patients who have severe asthma despite glucocorticoid treatment; these cells are associated with disease characteristics including poor quality of life and inadequate asthma control. Stem cell factor and its receptor, KIT, are central to mast‐cell homeostasis. We conducted a proof‐of‐principle trial to evaluate the effect of imatinib, a KIT inhibitor, on airway hyperresponsiveness, a physiological marker of severe asthma, as well as on airway mast‐cell numbers and activation in patients with severe asthma. METHODS We conducted a randomized, double‐blind, placebo‐controlled, 24‐week trial of imatinib in patients with poorly controlled severe asthma who had airway hyperresponsiveness despite receiving maximal medical therapy. The primary end point was the change in airway hyperresponsiveness, measured as the concentration of methacholine required to decrease the forced expiratory volume in 1 second by 20% (PC20). Patients also underwent bronchoscopy. RESULTS Among the 62 patients who underwent randomization, imatinib treatment reduced airway hyperresponsiveness to a greater extent than did placebo. At 6 months, the methacholine PC20 increased by a mean (±SD) of 1.73±0.60 doubling doses in the imatinib group, as compared with 1.07±0.60 doubling doses in the placebo group (P=0.048). Imatinib also reduced levels of serum tryptase, a marker of mast‐cell activation, to a greater extent than did placebo (decrease of 2.02±2.32 vs. 0.56±1.39 ng per milliliter, P=0.02). Airway mast‐cell counts declined in both groups. Muscle cramps and hypophosphatemia were more common in the imatinib group than in the placebo group. CONCLUSIONS In patients with severe asthma, imatinib decreased airway hyperresponsiveness, mast‐cell counts, and tryptase release. These results suggest that KIT‐dependent processes and mast cells contribute to the pathobiologic basis of severe asthma. (Funded by the National Institutes of Health and others; ClinicalTrials.gov number, NCT01097694.)

STAT4-Dependent and -Independent Th2 Responses Correlate with Protective Immunity against Lung Infection with Pneumocystis murina

Although it is clear that the loss of CD4+ T cells is a predisposing factor for the development of Pneumocystis pneumonia, specific Th mechanisms mediating protection are not well understood. Th1, Th2, and Th17 responses have each been implicated in protective responses during infection. As STAT4 may promote Th1 and Th17 development, yet antagonize Th2 development, we investigated its role in Pneumocystis murina host defense. STAT4 was required for Th1 and, unexpectedly, Th2 responses in the lungs of C57BL/6 (BL/6) and BALB/c mice 14 d postchallenge, but only BALB/c Stat4−/− mice demonstrated susceptibility to P. murina lung infection. BL/6 Stat4−/−, but not BALB/c Stat4−/−, mice maintained an enhanced alternatively activated (M2) macrophage signature in the lungs, which we have previously reported to be associated with enhanced P. murina clearance. In addition, anti-P. murina class-switched Abs were increased in BL/6 Stat4−/− mice, but not BALB/c Stat4−/− mice. Supporting our experimental observations, plasma from HIV-infected individuals colonized with Pneumocystis jirovecii contained significantly lower levels of the Th2 cytokines IL-4, IL-5, and IL-13 compared with HIV-infected individuals who were not colonized. Collectively, our data suggest that robust local and systemic Th2-mediated responses are critical for immunity to Pneumocystis.

The effect of biomass fuel exposure on the prevalence of asthma in adults in India – review of current evidence

Abstract Introduction: The combustion of biomass fuels is a major source of respiratory disease among individuals in the developing world. Over two million people world-wide rely on biomass fuels to supply their household energy needs with an estimated 1.6 million deaths annually being attributable to biomass smoke exposure. As a developing country, India relies heavily on the use of solid fuels as a source of energy. These materials supply 75% of the country’s domestic energy need and are attributed as the cause of over 600 000 deaths annually. Diseases such as chronic bronchitis and acute lower respiratory tract infections are strongly correlated to biomass smoke exposure. While not as strongly correlated, accumulating evidence suggests that asthma prevalence may be related to solid fuel smoke. Methods: This review examines the current literature linking biomass smoke exposure to the reporting of asthma symptoms. A PubMed search was performed using key terms biomass, asthma, India and respiratory disease. Preference was given to recent articles that surveyed the adult population within India. Results: The reviewed articles showed an increased odds ratio for reporting a diagnosis of asthma or symptoms consistent with asthma following biomass smoke exposure. While the literature supports a strong association between household air pollution and the development of chronic bronchitis and acute lower respiratory tract infections in India, this review establishes a more firm relationship between reported asthma symptoms and biomass smoke exposure. Conclusion: The exposure to biomass fuel smoke results in respiratory diseases in developing countries. Among these diseases, asthma appears to be a preventable pulmonary pathology that is associated with household air pollution. Measures to reduce exposure may decrease the burden of disease which could help advance social and economic progress in these nations. Further research and out-reach efforts are needed to reduce the total burden of lung diseases, including asthma, across the developing world. This reduction could save millions of dollars annually and lower morbidity and mortality in the affected populations.

Benefits of completing pulmonary rehabilitation in patients with asthma

Abstract Background: Asthma affects 30 million Americans and results in reduced productivity and quality of life. Pulmonary rehabilitation (PR) is known to improve physical conditioning and exercise performance in chronic lung diseases such as COPD, however, few studies have examined its benefits in patients with asthma. We aimed to determine the benefits of PR in this population as well as the predictors of completion of therapy. Methods: We performed a retrospective review of data from patients with a diagnosis of asthma who participated in PR at our institution from 1996 to 2013. Nine hundred and nineteen patients participated in the program of whom 75 were referred with a primary diagnosis of asthma. Patients underwent physiologic testing and their symptoms and quality of life were assessed using validated questionnaires. For patients who completed PR (n = 37), data obtained at the initial and exit visit was compared. Characteristics of completers were compared to non-completers to determine predictors of successful completion. Results: Individuals with asthma completing PR had improvement from baseline to exit visit in Six Minute Walk Distance (326 vs. 390 feet; p < 0.0001), decreased body mass index (33 vs. 32 kg/m2; p < 0.046), decreased Beck Depression Inventory scores (15 vs. 9; p < 0.0009), and increased Short Form-36 scores (345 vs. 445; p = 0.0005). In a multivariate logistic regression analysis, lower depression scores predicted completion (OR 1.08, 95% CI 1.02–1.15, p = 0.02). Conclusion: Patients with asthma who completed PR had improvement in physical function and emotional well-being. Depression is a risk factor for non-completion of PR. Further research is needed to determine which patients will benefit most from therapy.

Severe Asthma in Primary Care: Identification and Management

Most patients with asthma are managed by primary care providers. Severe asthma is associated with substantial morbidity and health care resource use, and long-term sequelae of severe asthma include airway remodeling and a greater risk of developing chronic obstructive pulmonary disease. These consequences highlight the importance of early identification and improved management of patients with severe asthma. Although treatment guidelines can be confusing and it can be difficult to keep abreast of updates, routine assessments of lung function, frequency and severity of exacerbations, symptom control, and medication adherence in the primary care setting provide the necessary information for identifying severe asthma and determining appropriate management strategies. An increased understanding of asthma pathophysiology and its relationship to disease activity has identified therapeutic targets and associated biomarkers. Biologic therapies directed at these targets offer individualized targeted treatment of severe asthma. We review evidence-based guidelines for identification and management of severe asthma, clarify the relationship of asthma control and asthma severity, and provide an overview of new biologic therapies offering additional treatment options for patients with severe asthma.

Unique Lipid Signatures of Extracellular Vesicles from the Airways of Asthmatics

Asthma is a chronic inflammatory disease process involving the conductive airways of the human lung. The dysregulated inflammatory response in this disease process may involve multiple cell-cell interactions mediated by signaling molecules, including lipid mediators. Extracellular vesicles (EVs) are lipid membrane particles that are now recognized as critical mediators of cell-cell communication. Here, we compared the lipid composition and presence of specific lipid mediators in airway EVs purified from the bronchoalveolar lavage (BAL) fluid of healthy controls and asthmatic subjects with and without second-hand smoke (SHS) exposure. Airway exosome concentrations were increased in asthmatics, and correlated with blood eosinophilia and serum IgE levels. Frequencies of HLA-DR+ and CD54+ exosomes were also significantly higher in asthmatics. Lipidomics analysis revealed that phosphatidylglycerol, ceramide-phosphates, and ceramides were significantly reduced in exosomes from asthmatics compared to the non-exposed control groups. Sphingomyelin 34:1 was more abundant in exosomes of SHS-exposed asthmatics compared to healthy controls. Our results suggest that chronic airway inflammation may be driven by alterations in the composition of lipid mediators within airway EVs of human subjects with asthma.

An extracellular matrix fragment drives epithelial remodeling and airway hyperresponsiveness

The matrikine PGP is a mediator of pathological epithelial remodeling in asthma. Extracellular matrix extends its influence in asthma The interplay between immune cells and smooth muscle cells in asthma pathogenesis and response to treatment is under increasing scrutiny. Patel et al. focused on how leukotrienes can modulate immune inflammation and airway hypersensitivity. Mice lacking leukotriene A4 hydrolase had exaggerated epithelial remodeling but dampened immune responses in a house dust mite model of asthma. This was due to release of Pro-Gly-Pro (PGP), a component of the extracellular matrix, which was also elevated in the sputum from severe asthmatics in two clinical cohorts. Their results showcase how the extracellular matrix is a dynamic player in disease and reveal a mediator to be targeted in asthma therapy. It is anticipated that bioactive fragments of the extracellular matrix (matrikines) can influence the development and progression of chronic diseases. The enzyme leukotriene A4 hydrolase (LTA4H) mediates opposing proinflammatory and anti-inflammatory activities, through the generation of leukotriene B4 (LTB4) and degradation of proneutrophilic matrikine Pro-Gly-Pro (PGP), respectively. We show that abrogation of LTB4 signaling ameliorated inflammation and airway hyperresponsiveness (AHR) in a murine asthma model, yet global loss of LTA4H exacerbated AHR, despite the absence of LTB4. This exacerbated AHR was attributable to a neutrophil-independent capacity of PGP to promote pathological airway epithelial remodeling. Thus, we demonstrate a disconnect between airway inflammation and AHR and the ability of a matrikine to promote an epithelial remodeling phenotype that negatively affects lung function. Subsequently, we show that substantial quantities of PGP are detectable in the sputum of moderate-severe asthmatics in two distinct cohorts of patients. These studies have implications for our understanding of remodeling phenotypes in asthma and may rationalize the failure of LTA4H inhibitors in the clinic.