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 George's 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.

Integrated analyses of gene expression and genetic association studies in a founder population

Genome-wide association studies (GWASs) have become a standard tool for dissecting genetic contributions to disease risk. However, these studies typically require extraordinarily large sample sizes to be adequately powered. Strategies that incorporate functional information alongside genetic associations have proved successful in increasing GWAS power. Following this paradigm, we present the results of 20 different genetic association studies for quantitative traits related to complex diseases, conducted in the Hutterites of South Dakota. To boost the power of these association studies, we collected RNA-sequencing data from lymphoblastoid cell lines for 431 Hutterite individuals. We then used Sherlock, a tool that integrates GWAS and expression quantitative trait locus (eQTL) data, to identify weak GWAS signals that are also supported by eQTL data. Using this approach, we found novel associations with quantitative phenotypes related to cardiovascular disease, including carotid intima-media thickness, left atrial volume index, monocyte count and serum YKL-40 levels.

Noninvasive analysis of the sputum transcriptome discriminates clinical phenotypes of asthma

RATIONALE

The airway transcriptome includes genes that contribute to the pathophysiologic heterogeneity seen in individuals with asthma.

OBJECTIVES

We analyzed sputum gene expression for transcriptomic endotypes of asthma (TEA), gene signatures that discriminate phenotypes of disease.

METHODS

Gene expression in the sputum and blood of patients with asthma was measured using Affymetrix microarrays. Unsupervised clustering analysis based on pathways from the Kyoto Encyclopedia of Genes and Genomes was used to identify TEA clusters. Logistic regression analysis of matched blood samples defined an expression profile in the circulation to determine the TEA cluster assignment in a cohort of children with asthma to replicate clinical phenotypes.

MEASUREMENTS AND MAIN RESULTS

Three TEA clusters were identified. TEA cluster 1 had the most subjects with a history of intubation (P = 0.05), a lower prebronchodilator FEV1 (P = 0.006), a higher bronchodilator response (P = 0.03), and higher exhaled nitric oxide levels (P = 0.04) compared with the other TEA clusters. TEA cluster 2, the smallest cluster, had the most subjects that were hospitalized for asthma (P = 0.04). TEA cluster 3, the largest cluster, had normal lung function, low exhaled nitric oxide levels, and lower inhaled steroid requirements. Evaluation of TEA clusters in children confirmed that TEA clusters 1 and 2 are associated with a history of intubation (P = 5.58 × 10(-6)) and hospitalization (P = 0.01), respectively.

CONCLUSIONS

There are common patterns of gene expression in the sputum and blood of children and adults that are associated with near-fatal, severe, and milder asthma.

Genetic variation in chitinase 3-like 1 (CHI3L1) contributes to asthma severity and airway expression of YKL-40

BACKGROUND

Single nucleotide polymorphisms (SNPs) in the chitinase 3-like 1 (CHI3L1) promoter, the gene encoding YKL-40, are associated with circulating YKL-40 levels and asthma prevalence. However, the effects of gene polymorphisms on asthma severity and airway expression of YKL-40 have not been examined.

OBJECTIVE

We sought to determine the effect of genetic variation in CHI3L1 on asthma severity and YKL-40 expression in subjects from the Yale Center for Asthma and Airways Disease and the Severe Asthma Research Program.

METHODS

SNPs spanning the CHI3L1 gene were genotyped in 259 Yale Center for Asthma and Airways Disease and 919 Severe Asthma Research Program subjects. Association and haplotype analyses were conducted to identify effects on airflow obstruction, YKL-40 levels, and asthma severity.

RESULTS

Fifteen SNPs in CHI3L1 were associated with FEV1, serum YKL-40 levels, or both. rs12141494 (intron 6) was the only SNP in subjects of European ancestry in both cohorts that was associated with serum YKL-40 levels and postbronchodilator FEV1. Conditional analysis demonstrated that the effect on lung function was independent of the promoter SNP rs4950928, and haplotype analysis demonstrated that G alleles at rs12141494 and rs4950928 are associated with lower YKL-40 expression and higher FEV1 percent predicted values. In asthmatic subjects the risk allele A at rs12141494 was associated with severe asthma and higher YKL-40 expression in the airway (P ≤ .05).

CONCLUSION

In contrast to the promoter SNP rs4950928, the intronic SNP rs12141494 in CHI3L1 is associated with asthma severity, lung function, and YKL-40 expression in the blood and airway. These data suggest that SNP rs12141494 modulates YKL-40 expression in the airway and contributes to airway remodeling and asthma severity.

Chitinase 3-like-1 regulates both visceral fat accumulation and asthma-like Th2 inflammation

RATIONALE

Obesity, especially truncal obesity, is a risk factor for asthma incidence, prevalence, and severity. Chitinase 3-like-1 (Chi3l1) is an evolutionarily conserved moiety that plays a critical role in antipathogen and Th2 responses. However, the mechanisms that underlie the association between asthma and obesity and the role(s) of Chi3l1 in fat accumulation have not been defined.

OBJECTIVES

To determine whether Chi3l1 is regulated by a high-fat diet (HFD) and simultaneously plays an important role(s) in the pathogenesis of asthma and obesity.

METHODS

We evaluated the regulation of Chi3l1 by an HFD and Th2 inflammation. We also used genetically modified mice to define the roles of Chi3l1 in white adipose tissue (WAT) accumulation and Th2 inflammation and blockers of sirtuin 1 (Sirt1) to define its roles in these responses. Finally, the human relevance of these findings was assessed with a case-control study involving obese and lean control subjects and those with asthma.

MEASUREMENTS AND MAIN RESULTS

These studies demonstrate that an HFD and aeroallergen challenge augment the expression of WAT and pulmonary Chi3l1. Chi3l1 also played a critical role in WAT accumulation and lung Th2 inflammation. In addition, Chi3l1 inhibited Sirt1 expression, and the deficient visceral fat and Th2 responses in Chi3l1 null mice were reversed by Sirt1 inhibition. Finally, serum and sputum Chi3l1 were positively associated with truncal adiposity, and serum Chi3l1 was associated with persistent asthma and low lung function in obese subjects with asthma.

CONCLUSIONS

Chi3l1 is induced by an HFD and Th2 inflammation, and simultaneously contributes to the genesis of obesity and asthma.

IL-6 receptor α defines effector memory CD8+ T cells producing Th2 cytokines and expanding in asthma

RATIONALE

Cytokine receptors can be markers defining different T-cell subsets and considered as therapeutic targets. The association of IL-6 and IL-6 receptor α (IL-6Rα) with asthma was reported, suggesting their involvement in asthma.

OBJECTIVES

To determine whether and how IL-6Rα defines a distinct effector memory (EM) CD8+ T-cell population in health and disease.

METHODS

EM CD8+ T cells expressing IL-6Rα (IL-6Rα(high)) were identified in human peripheral blood and analyzed for function, gene, and transcription factor expression. The relationship of these cells with asthma was determined using blood and sputum.

MEASUREMENTS AND MAIN RESULTS

A unique population of IL-6Rα(high) EM CD8+ T cells was found in peripheral blood. These cells that potently proliferated, survived, and produced high levels of the Th2-type cytokines IL-5 and IL-13 had increased levels of GATA3 and decreased levels of T-bet and Blimp-1 in comparison with other EM CD8+ T cells. In fact, GATA3 was required for IL-6Rα expression. Patients with asthma had an increased frequency of IL-6Rα(high) EM CD8+ T cells in peripheral blood compared with healthy control subjects. Also, IL-6Rα(high) EM CD8+ T cells exclusively produced IL-5 and IL-13 in response to asthma-associated respiratory syncytial virus and bacterial superantigens.

CONCLUSIONS

Human IL-6Rα(high) EM CD8+ T cells is a unique cell subset that may serve as a reservoir for effector CD8+ T cells, particularly the ones producing Th2-type cytokines, and expand in asthma.

Role of growth arrest-specific gene 6 in the development of fungal allergic airway disease in mice

Growth arrest-specific gene (Gas)6 is a secreted vitamin K-dependent protein with pleiotropic effects via activation of receptor tyrosine kinase Tyro3, Axl, and Mertk receptors, but little is known about its role in allergic airway disease. We investigated the role of Gas6 in the development of fungal allergic airway disease in mice. The immune response was evaluated in Gas6-deficient (Gas6-/-) and wild-type (WT) mice and in recombinant Gas6-treated WT mice during Aspergillus fumigatus-induced allergic airway disease. Gas6 plasma levels were significantly elevated in adult clinical asthma of all severities compared with subjects without asthma. In a murine model of fungal allergic airway disease, increased protein expression of Axl and Mertk were observed in the lung. Airway hyperresponsiveness (AHR), whole lung Th2 cytokine levels, goblet cell metaplasia, and peribronchial fibrosis were ameliorated in Gas6-/- mice compared with WT mice with fungal allergic airway disease. Intranasal Gas6 administration into WT mice had a divergent effect on airway inflammation and AHR. Specifically, a total dose of 2 μg of exogenous Gas6 (i.e., low dose) significantly increased whole lung Th2 cytokine levels and subsequent AHR, whereas a total dose of 7 μg of exogenous Gas6 (i.e., high dose) significantly suppressed Th1 and Th2 cytokines and AHR compared with appropriate control groups. Mechanistically, Gas6 promoted Th2 activation via its highest affinity receptor Axl expressed by myeloid DCs. Intranasal administration of Gas6 consistently exacerbated airway remodeling compared with control WT groups. These results demonstrate that Gas6 enhances several features of fungal allergic airway disease.

Hospital readmission after pulmonary lobectomy is not affected by surgical approach

BACKGROUND

The aim of this study is to identify the predictors of hospital readmission or early unplanned return to clinic within 30 days of discharge after pulmonary lobectomy.

METHODS

The medical records of patients undergoing lobectomy by the thoracic surgery service between January 2009 and July 2012 were reviewed. All lobectomies were included irrespective of the etiology of disease. Multivariate logistic regression methods were used to identify predictors of readmission and or early unplanned return to clinic.

RESULTS

Two hundred thirteen patients underwent a pulmonary lobectomy during the study period (median age, 67 years). Pathologic diagnosis was malignant in 94% of the patients and benign in 6%. Minimally invasive approaches were used in 69% of the patients, whereas open thoracotomy was used in 31%. Median hospital length of stay was 4 days, and postoperative mortality occurred in 1 patient (0.5%). The Charlson comorbidity index was 1 ± 1. Predicted postoperative forced expiratory volume in 1 second and diffusing capacity of the lung for carbon monoxide were 68% ± 18% and 64% ± 17%, respectively. Postoperative complications occurred in 31% of patients; 13% required readmission to the hospital within 30 days of discharge or early unplanned return to clinic. Predictors of readmission or early unplanned return to clinic were unplanned transfer to the intensive care unit (odds ratio, 10.4; 95% confidence interval, 1.1 to 103.5; p = 0.04) and Charlson comorbidity index greater than 0 (odds ratio, 1.5; 95% confidence interval, 1.04 to 2.03; p = 0.03). Readmission or early unplanned return to clinic was independent of surgical approach (p = 0.32).

CONCLUSIONS

Patients who require a postoperative transfer to the intensive care unit or with higher Charlson comorbidity index are at higher risk for hospital readmission after pulmonary lobectomy. Readmission was not affected by the surgical approach. Whether a different strategy to follow-up for these high-risk patients can prevent readmission remains to be determined.

Improvement in asthma control and inflammation in children undergoing adenotonsillectomy

BACKGROUND

Observational studies suggest that asthma control improves after adenotonsillectomy, but longitudinal studies that correlate the effect of the procedure on the levels of biomarkers associated with airway inflammation are limited.

METHODS

We conducted a longitudinal, observational study on pediatric patients, both with and without asthma, undergoing adenotonsillectomy. Asthma control test (ACT) scores and chitinase activity in the circulation were measured at time of surgery and at 6-mo follow-up.

RESULTS

Sixty-six children with asthma and 64 control subjects were enrolled. Mean ACT scores improved by three points (P < 0.001) after 6 mo. 85% of children with poorly controlled asthma demonstrated an increase in ACT score of at least three points or a decrease in emergency department/urgent care visits, oral corticosteroid courses, or rescue short acting bronchodilator usage. Chitinase activity decreased significantly in asthmatics who improved (P < 0.01). Higher chitinase activity levels at baseline were associated with improved asthma control following surgery (P < 0.01).

CONCLUSION

In children with high preoperative circulating chitinase activity levels, asthma control and healthcare utilization were significantly improved after adenotonsillecotmy. Chitinase activity decreased after surgery in children with improved control. This suggests that adenotonsillectomy modulates chitinase activity, affecting airway inflammation and improving airway disease.

Segmental allergen challenge enhances chitinase activity and levels of CCL18 in mild atopic asthma

BACKGROUND

Allergic airway inflammation contributes to the airway remodelling that has been linked to increased obstruction and morbidity in asthma. However, the mechanisms by which allergens contribute to airway remodelling in humans are not fully established. CCL18, chitotriosidase (CHIT1) and YKL-40 are readily detectable in the lungs and contribute to remodelling in other fibrotic diseases, but their involvement in allergic asthma is unclear.

OBJECTIVE

We hypothesized that CCL18, YKL-40 and CHIT1 bioactivity are enhanced in allergic asthma subjects after segmental allergen challenge and are related to increased pro-fibrotic and Th2-associated mediators in the lungs.

METHODS

Levels of CCL18 and YKL-40 protein and chitotriosidase (CHIT1) bioactivity in bronchoalveolar lavage (BAL) fluid, as well as CCL18, YKL-40 and CHIT1 mRNA levels in BAL cells were evaluated in patients with asthma at baseline and 48 h after segmental allergen challenge. We also examined the correlation between CCL18 and YKL-40 levels and CHIT1 activity with the levels of other pro-fibrotic factors and chemokines previously shown to be up-regulated after allergen challenge.

RESULTS

Chitotriosidase activity and YKL-40 and CCL18 levels were elevated after segmental allergen challenge and these levels correlated with those of other pro-fibrotic factors, T cell chemokines, and inflammatory cells after allergen challenge. CCL18 and YKL-40 mRNA levels also increased in BAL cells after allergen challenge.

CONCLUSIONS AND CLINICAL RELEVANCE

Our results suggest that CCL18 and YKL-40 levels and CHIT1 activity are enhanced in allergic airway inflammation and thus may contribute to airway remodelling in asthma.

Chitinase-like protein Brp-39/YKL-40 modulates the renal response to ischemic injury and predicts delayed allograft function

Kidney hypoperfusion during episodes of systemic hypotension or after surgical procurement for transplantation can lead to tubular cell death via necrosis and apoptosis, which trigger a series of responses that promote repair. The factors that contribute to the repair phase after kidney injury are not well understood. Using a urine proteomic screen in mice, we identified the macrophage-secreted chitinase-like protein Brp-39, the murine protein product of the chitinase 3-like 1 gene, as a critical component of this reparative response that serves to limit tubular cell apoptotic death via activation of Akt, improving animal survival after kidney ischemia/reperfusion. Examination of graded times of renal ischemia revealed a direct correlation between the degree of kidney injury and both Chi3l1/Brp-39 expression in the kidney and its levels in the urine. In samples collected from patients undergoing deceased-donor kidney transplantation, we found higher levels of the orthologous human protein, YKL-40, in urine and blood from allografts subjected to sufficient peri-transplant ischemia to cause delayed graft function than from allografts with slow or immediate graft function. Urinary levels of YKL-40 obtained within hours of transplant predicted the need for subsequent dialysis in these patients. In summary, these data suggest that Brp-39/YKL-40 is a sensor of the degree of injury, a critical mediator of the reparative response, and a possible biomarker to identify patients at greatest risk of sustained renal failure after transplantation.

Pathways activated during human asthma exacerbation as revealed by gene expression patterns in blood

BACKGROUND

Asthma exacerbations remain a major unmet clinical need. The difficulty in obtaining airway tissue and bronchoalveolar lavage samples during exacerbations has greatly hampered study of naturally occurring exacerbations. This study was conducted to determine if mRNA profiling of peripheral blood mononuclear cells (PBMCs) could provide information on the systemic molecular pathways involved during asthma exacerbations.

METHODOLOGY/PRINCIPAL FINDINGS

Over the course of one year, gene expression levels during stable asthma, exacerbation, and two weeks after an exacerbation were compared using oligonucleotide arrays. For each of 118 subjects who experienced at least one asthma exacerbation, the gene expression patterns in a sample of peripheral blood mononuclear cells collected during an exacerbation episode were compared to patterns observed in multiple samples from the same subject collected during quiescent asthma. Analysis of covariance identified genes whose levels of expression changed during exacerbations and returned to quiescent levels by two weeks. Heterogeneity among visits in expression profiles was examined using K-means clustering. Three distinct exacerbation-associated gene expression signatures were identified. One signature indicated that, even among patients without symptoms of respiratory infection, genes of innate immunity were activated. Antigen-independent T cell activation mediated by IL15 was also indicated by this signature. A second signature revealed strong evidence of lymphocyte activation through antigen receptors and subsequent downstream events of adaptive immunity. The number of genes identified in the third signature was too few to draw conclusions on the mechanisms driving those exacerbations.

CONCLUSIONS/SIGNIFICANCE

This study has shown that analysis of PBMCs reveals systemic changes accompanying asthma exacerbation and has laid the foundation for future comparative studies using PBMCs.

Targeting ST2L potentiates CpG-mediated therapeutic effects in a chronic fungal asthma model

IL-33 and its soluble receptor and cell-associated receptor (ST2L) are all increased in clinical and experimental asthma. The present study addressed the hypothesis that ST2L impairs the therapeutic effects of CpG in a fungal model of asthma. C57BL/6 mice were sensitized to Aspergillus fumigatus and challenged via i.t. instillation with live A. fumigatus conidia. Mice were treated with IgG alone, anti-ST2L monoclonal antibody (mAb) alone, CpG alone, IgG plus CpG, or anti-ST2L mAb plus CpG every other day from day 14 to day 28 and investigated on day 28 after conidia. Lung ST2L and toll-like receptor 9 protein expression levels concomitantly increased in a time-dependent manner during fungal asthma. Therapeutic blockade of ST2L with an mAb attenuated key pathological features of this model. At subtherapeutic doses, neither anti-ST2L mAb nor CpG alone affected fungal asthma severity. However, airway hyperresponsiveness, mucus cell metaplasia, peribronchial fibrosis, and fungus retention were markedly reduced in asthmatic mice treated with the combination of both. Whole lung CXCL9 levels were significantly elevated in the combination group but not in the controls. Furthermore, in asthmatic mice treated with the combination therapy, dendritic cells generated significantly greater IL-12p70 with CpG in vitro compared with control dendritic cells. The combination of anti-ST2L mAb with CpG significantly attenuated experimental asthma, suggesting that targeting ST2L might enhance the therapeutic efficacy of CpG during allergic inflammation.

CHIT1 mutations: genetic risk factor for severe asthma with fungal sensitization?

Fungi can exacerbate symptoms in patients with asthma. To our knowledge, genetic risk factors for fungal-associated asthma have not been described. We present here the cases of 6 children who carried the diagnosis of severe asthma with fungal sensitization, 3 of whom were treated with and responded clinically to itraconazole therapy. All 6 patients were heterozygous for a 24-base pair duplication in the CHIT1 gene, which has been associated with decreased levels of circulating chitotriosidase and susceptibility to fungal infection.

Role of breast regression protein-39 in the pathogenesis of cigarette smoke-induced inflammation and emphysema

The exaggerated expression of chitinase-like protein YKL-40, the human homologue of breast regression protein-39 (BRP-39), was reported in a number of diseases, including chronic obstructive pulmonary disease (COPD). However, the in vivo roles of YKL-40 in normal physiology or in the pathogenesis of specific diseases such as COPD remain poorly understood. We hypothesized that BRP-39/YKL-40 plays an important role in the pathogenesis of cigarette smoke (CS)-induced emphysema. To test this hypothesis, 10-week-old wild-type and BRP-39 null mutant mice (BRP-39(-/-)) were exposed to room air (RA) and CS for up to 10 months. The expression of BRP-39 was significantly induced in macrophages, airway epithelial cells, and alveolar Type II cells in the lungs of CS-exposed mice compared with RA-exposed mice, at least in part via an IL-18 signaling-dependent pathway. The null mutation of BRP-39 significantly reduced CS-induced bronchoalveolar lavage and tissue inflammation. However, CS-induced epithelial cell apoptosis and alveolar destruction were further enhanced in the absence of BRP-39. Consistent with these findings in mice, the tissue expression of YKL-40 was significantly increased in the lungs of current smokers compared with the lungs of ex-smokers or nonsmokers. In addition, serum concentrations of YKL-40 were significantly higher in smokers with COPD than in nonsmokers or smokers without COPD. These studies demonstrate a novel regulatory role of BRP-39/YKL-40 in CS-induced inflammation and emphysematous destruction. These studies also underscore that maintaining physiologic concentrations of YKL-40 in the lung is therapeutically important in preventing excessive inflammatory responses or emphysematous alveolar destruction.

Effect of variation in CHI3L1 on serum YKL-40 level, risk of asthma, and lung function

BACKGROUND

The chitinase-like protein YKL-40 is involved in inflammation and tissue remodeling. We recently showed that serum YKL-40 levels were elevated in patients with asthma and were correlated with severity, thickening of the subepithelial basement membrane, and pulmonary function. We hypothesized that single-nucleotide polymorphisms (SNPs) that affect YKL-40 levels also influence asthma status and lung function.

METHODS

We carried out a genomewide association study of serum YKL-40 levels in a founder population of European descent, the Hutterites, and then tested for an association between an implicated SNP and asthma and lung function. One associated variant was genotyped in a birth cohort at high risk for asthma, in which YKL-40 levels were measured from birth through 5 years of age, and in two populations of unrelated case patients of European descent with asthma and controls.

RESULTS

A promoter SNP (-131C-->G) in CHI3L1, the chitinase 3-like 1 gene encoding YKL-40, was associated with elevated serum YKL-40 levels (P=1.1 x 10(-13)), asthma (P=0.047), bronchial hyperresponsiveness (P=0.002), and measures of pulmonary function (P=0.046 to 0.002) in the Hutterites. The same SNP could be used to predict the presence of asthma in the two case-control populations (combined P=1.2 x 10(-5)) and serum YKL-40 levels at birth (in cord-blood specimens) through 5 years of age in the birth cohort (P=8.9 x 10(-3) to 2.5 x 10(-4)).

CONCLUSIONS

CHI3L1 is a susceptibility gene for asthma, bronchial hyperresponsiveness, and reduced lung function, and elevated circulating YKL-40 levels are a biomarker for asthma and decline in lung function.

A chitinase-like protein in the lung and circulation of patients with severe asthma

BACKGROUND

The evolutionarily conserved 18-glycosyl-hydrolase family contains true chitinases and chitinase-like proteins that lack enzymatic activity. Acidic mammalian chitinase has recently been associated with animal models of asthma. The related chitinase-like protein, YKL-40 (also called human cartilage glycoprotein 39 [HCgp-39] and chitinase 3-like 1), can be readily measured in the serum. However, its relationship to asthma has not been evaluated.

METHODS

We quantified serum YKL-40 levels in three cohorts of patients with asthma--one recruited from the patient population at Yale University, one from the University of Paris, and one from the University of Wisconsin--as well as in controls from the surrounding communities. In the Paris cohort, immunohistochemical analysis and morphometric quantitation were used to evaluate the locus of expression of YKL-40 in the lung. The clinical characteristics of the patients with high serum or lung YKL-40 levels were also evaluated.

RESULTS

Serum YKL-40 levels were significantly elevated in patients with asthma as compared with controls. In the Paris cohort, lung YKL-40 levels were elevated and were correlated with circulating YKL-40 levels (r=0.55, P<0.001) and with airway remodeling (measured as the thickness of the subepithelial basement membrane) (r=0.51, P=0.003). In all three cohorts, serum YKL-40 levels correlated positively with the severity of asthma and inversely with the forced expiratory volume in 1 second. Patients with elevated levels of YKL-40 had significantly more frequent rescue-inhaler use, greater oral corticosteroid use, and a greater rate of hospitalization than patients with lower levels.

CONCLUSIONS

YKL-40 is found in increased quantities in the serum and lungs in a subgroup of patients with asthma, in whom expression of chitinase in both compartments correlates with the severity of asthma. The recovery of YKL-40 from these patients indicates either a causative or a sentinel role for this molecule in asthma.

Massive cavitary pulmonary rheumatoid nodules in a patient with HIV

The case of a 52-yr-old female with rheumatoid arthritis and HIV who developed massive, progressive, cavitary pulmonary nodules is described. Multiple diagnostic bronchoscopies and lung biopsies failed to demonstrate the presence of any microorganisms. Pathological analysis showed palisading histiocytes with necrobiosis consistent with rheumatoid nodules. The effect of co-existing HIV infection on the course and prognosis of rheumatoid arthritis is discussed, and it is concluded that the complex relationship between these two disease processes warrants further investigation.

Hyperoxia causes angiopoietin 2-mediated acute lung injury and necrotic cell death

The angiogenic growth factor angiopoietin 2 (Ang2) destabilizes blood vessels, enhances vascular leak and induces vascular regression and endothelial cell apoptosis. We considered that Ang2 might be important in hyperoxic acute lung injury (ALI). Here we have characterized the responses in lungs induced by hyperoxia in wild-type and Ang2-/- mice or those given either recombinant Ang2 or short interfering RNA (siRNA) targeted to Ang2. During hyperoxia Ang2 expression is induced in lung epithelial cells, while hyperoxia-induced oxidant injury, cell death, inflammation, permeability alterations and mortality are ameliorated in Ang2-/- and siRNA-treated mice. Hyperoxia induces and activates the extrinsic and mitochondrial cell death pathways and activates initiator and effector caspases through Ang2-dependent pathways in vivo. Ang2 increases inflammation and cell death during hyperoxia in vivo and stimulates epithelial necrosis in hyperoxia in vitro. Ang2 in plasma and alveolar edema fluid is increased in adults with ALI and pulmonary edema. Tracheal Ang2 is also increased in neonates that develop bronchopulmonary dysplasia. Ang2 is thus a mediator of epithelial necrosis with an important role in hyperoxic ALI and pulmonary edema.

Asthma: mechanisms of disease persistence and progression

When asthma is diagnosed, eosinophilic inflammation and airway remodeling are established in the bronchial airways and can no longer be separated as cause and effect because both processes contribute to persistence and progression of disease, despite anti-inflammatory therapy. Th2 cells are continually active in the airways, even when disease is quiescent. IL-13 is the key effector cytokine in asthma and stimulates airway fibrosis through the action of matrix metalloproteinases on TGF-beta and promotes epithelial damage, mucus production, and eosinophilia. The production of IL-13 and other Th2 cytokines by non-T cells augments the inflammatory response. Inflammation is amplified by local responses of the epithelium, smooth muscle, and fibroblasts through the production of chemokines, cytokines, and proteases. Injured cells produce adenosine that enhances IL-13 production. We review human and animal data detailing the cellular and molecular interactions in established allergic asthma that promote persistent disease, amplify inflammation, and, in turn, cause disease progression.

Reactive oxygen species and extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase mediate hyperoxia-induced cell death in lung epithelium

Therapy with high oxygen concentrations (hyperoxia) is often necessary to treat patients with respiratory failure. However, hyperoxia may exacerbate the development of acute lung injury, perhaps by increasing lung epithelial cell death. Therefore, interrupting lung epithelial cell death is an important protective and therapeutic strategy. In the present study, hyperoxia (95% O(2)) results in murine lung epithelium cell death by DNA-laddering, terminal deoxynucleotidyltransferase dUTP nick end labeling, and Annexin V-fluorescein isothiocyanate flow cytometry assay. We show that hyperoxia increases superoxide production, as assessed by nicotinamide adenine dinucleotide phosphate reduced (NADPH) oxidase activity and flow cytometric assay, and increases phospho-extracellular signal-regulated kinase (ERK)1/2 by Western blot analysis. These processes are inhibited by a reactive oxygen species inhibitor, diphenylene iodonium (DPI), and by an inhibitor of the mitogen-activated protein (MAP) or ERK kinase (MEK)/ERK1/2 pathway, PD98059. ERK1/2 activation in hyperoxia is also inhibited by DPI. Hyperoxia-induced cell death is associated with cytochrome c release, subsequent caspase 9 and 3 activation, and poly (ADP-ribosyl) polymerase cleavage, which can all be suppressed by DPI and PD98059. However, the broad caspase inhibitor z-VAD-FMK protects cells from death without affecting superoxide generation and ERK1/2 activation. Taken together, our data suggest that hyperoxia, by virtue of activating NADPH oxidase, generates reactive oxygen species (ROS), which mediates cell death of lung epithelium via ERK1/2 MAPK activation, and functions upstream of caspase activation in lung epithelial cells.