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

Recently Updated Role of Chitinase 3-like 1 on Various Cell Types as a Major Influencer of Chronic Inflammation

Chitinase 3-like 1 (also known as CHI3L1 or YKL-40) is a mammalian chitinase that has no enzymatic activity, but has the ability to bind to chitin, the polymer of N-acetylglucosamine (GlcNAc). Chitin is a component of fungi, crustaceans, arthropods including insects and mites, and parasites, but it is completely absent from mammals, including humans and mice. In general, chitin-containing organisms produce mammalian chitinases, such as CHI3L1, to protect the body from exogenous pathogens as well as hostile environments, and it was thought that it had a similar effect in mammals. However, recent studies have revealed that CHI3L1 plays a pathophysiological role by inducing anti-apoptotic activity in epithelial cells and macrophages. Under chronic inflammatory conditions such as inflammatory bowel disease and chronic obstructive pulmonary disease, many groups already confirmed that the expression of CHI3L1 is significantly induced on the apical side of epithelial cells, and activates many downstream pathways involved in inflammation and carcinogenesis. In this review article, we summarize the expression of CHI3L1 under chronic inflammatory conditions in various disorders and discuss the potential roles of CHI3L1 in those disorders on various cell types.

Airway remodelling in asthma and the epithelium: on the edge of a new era

Asthma is a chronic, heterogeneous disease of the airways, often characterised by structural changes known collectively as airway remodelling. In response to environmental insults, including pathogens, allergens and pollutants, the epithelium can initiate remodelling via an inflammatory cascade involving a variety of mediators that have downstream effects on both structural and immune cells. These mediators include the epithelial cytokines thymic stromal lymphopoietin, interleukin (IL)-33 and IL-25, which facilitate airway remodelling through cross-talk between epithelial cells and fibroblasts, and between mast cells and airway smooth muscle cells, as well as through signalling with immune cells such as macrophages. The epithelium can also initiate airway remodelling independently of inflammation in response to the mechanical stress present during bronchoconstriction. Furthermore, genetic and epigenetic alterations to epithelial components are believed to influence remodelling. Here, we review recent advances in our understanding of the roles of the epithelium and epithelial cytokines in driving airway remodelling, facilitated by developments in genetic sequencing and imaging techniques. We also explore how new and existing therapeutics that target the epithelium and epithelial cytokines could modify airway remodelling.

Impact of obesity on airway remodeling in asthma: pathophysiological insights and clinical implications

The prevalence of obesity among asthma patients has surged in recent years, posing a significant risk factor for uncontrolled asthma. Beyond its impact on asthma severity and patients' quality of life, obesity is associated with reduced lung function, increased asthma exacerbations, hospitalizations, heightened airway hyperresponsiveness, and elevated asthma-related mortality. Obesity may lead to metabolic dysfunction and immune dysregulation, fostering chronic inflammation characterized by increased pro-inflammatory mediators and adipocytokines, elevated reactive oxygen species, and reduced antioxidant activity. This chronic inflammation holds the potential to induce airway remodeling in individuals with asthma and obesity. Airway remodeling encompasses structural and pathological changes, involving alterations in the airway's epithelial and subepithelial layers, hyperplasia and hypertrophy of airway smooth muscle, and changes in airway vascularity. In individuals with asthma and obesity, airway remodeling may underlie heightened airway hyperresponsiveness and increased asthma severity, ultimately contributing to the development of persistent airflow limitation, declining lung function, and a potential increase in asthma-related mortality. Despite efforts to address the impact of obesity on asthma outcomes, the intricate mechanisms linking obesity to asthma pathophysiology, particularly concerning airway remodeling, remain incompletely understood. This comprehensive review discusses current research investigating the influence of obesity on airway remodeling, to enhance our understanding of obesity's role in the context of asthma airway remodeling.

Significance of chitinase-3-like protein 1 in the pathogenesis of inflammatory diseases and cancer

Chitinase-3-like protein 1 (CHI3L1) is a secreted glycoprotein that mediates inflammation, macrophage polarization, apoptosis, and carcinogenesis. The expression of CHI3L1 is strongly upregulated by various inflammatory and immunological diseases, including several cancers, Alzheimer's disease, and atherosclerosis. Several studies have shown that CHI3L1 can be considered as a marker of disease diagnosis, prognosis, disease activity, and severity. In addition, the proinflammatory action of CHI3L1 may be mediated via responses to various proinflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, interleukin-6, and interferon-γ. Therefore, CHI3L1 may contribute to a vast array of inflammatory diseases. However, its pathophysiological and pharmacological roles in the development of inflammatory diseases remain unclear. In this article, we review recent findings regarding the roles of CHI3L1 in the development of inflammatory diseases and suggest therapeutic approaches that target CHI3L1.

ACE2 in chronic disease and COVID-19: gene regulation and post-translational modification

Angiotensin-converting enzyme 2 (ACE2), a counter regulator of the renin-angiotensin system, provides protection against several chronic diseases. Besides chronic diseases, ACE2 is the host receptor for SARS-CoV or SARS-CoV-2 virus, mediating the first step of virus infection. ACE2 levels are regulated by transcriptional, post-transcriptional, and post-translational regulation or modification. ACE2 transcription is enhanced by transcription factors including Ikaros, HNFs, GATA6, STAT3 or SIRT1, whereas ACE2 transcription is reduced by the transcription factor Brg1-FoxM1 complex or ERRα. ACE2 levels are also regulated by histone modification or miRNA-induced destabilization. The protein kinase AMPK, CK1α, or MAP4K3 phosphorylates ACE2 protein and induces ACE2 protein levels by decreasing its ubiquitination. The ubiquitination of ACE2 is induced by the E3 ubiquitin ligase MDM2 or UBR4 and decreased by the deubiquitinase UCHL1 or USP50. ACE2 protein levels are also increased by the E3 ligase PIAS4-mediated SUMOylation or the methyltransferase PRMT5-mediated ACE2 methylation, whereas ACE2 protein levels are decreased by AP2-mediated lysosomal degradation. ACE2 is downregulated in several human chronic diseases like diabetes, hypertension, or lung injury. In contrast, SARS-CoV-2 upregulates ACE2 levels, enhancing host cell susceptibility to virus infection. Moreover, soluble ACE2 protein and exosomal ACE2 protein facilitate SARS-CoV-2 infection into host cells. In this review, we summarize the gene regulation and post-translational modification of ACE2 in chronic disease and COVID-19. Understanding the regulation and modification of ACE2 may help to develop prevention or treatment strategies for ACE2-mediated diseases.

Chitinase-3-like 1 regulates TH2 cells, TFH cells and IgE responses to helminth infection

Introduction

Data from patient cohorts and mouse models of atopic dermatitis, food allergy and asthma strongly support a role for chitinase-3-like-1 protein (CHI3L1) in allergic disease.

Methods

To address whether Chi3l1 also contributes to TH2 responses following nematode infection, we infected Chi3l1 -/- mice with Heligmosomoides polygyrus (Hp) and analyzed T cell responses.

Results

As anticipated, we observed impaired TH2 responses in Hp-infected Chi3l1 -/- mice. However, we also found that T cell intrinsic expression of Chi3l1 was required for ICOS upregulation following activation of naïve CD4 T cells and was necessary for the development of the IL-4+ TFH subset, which supports germinal center B cell reactions and IgE responses. We also observed roles for Chi3l1 in TFH, germinal center B cell, and IgE responses to alum-adjuvanted vaccination. While Chi3l1 was critical for IgE humoral responses it was not required for vaccine or infection-induced IgG1 responses.

Discussion

These results suggest that Chi3l1 modulates IgE responses, which are known to be highly dependent on IL-4-producing TFH cells.

Chitinases and chitinase-like proteins in asthma

Despite the lack of endogenous chitin synthesis, mammalian genomes encode two enzymatically active true chitinases (chitotriosidase and acidic mammalian chitinase) and a variable number of chitinase-like proteins (CLPs) that have no enzyme activity but bind chitin. Chitinases and CLPs are prominent components of type-2 immune response-mediated respiratory diseases. However, despite extensive research into their role in allergic airway disease, there is still no agreement on whether they are mere biomarkers of disease or actual disease drivers. Functions ascribed to chitinases and CLPs include, but are not limited to host defense against chitin-containing pathogens, directly promoting inflammation, and modulating tissue remodeling and fibrosis. Here, we discuss in detail the chitin-dependent and -independent roles of chitinases and CLPs in the context of allergic airway disease, and recent advances and emerging concepts in the field that might identify opportunities for new therapies.

Chitinase 3-like-1 is a therapeutic target that mediates the effects of aging in COVID-19

COVID-19 is caused by SARS-CoV-2 (SC2) and is more prevalent and severe in elderly and patients with comorbid diseases (CM). Because chitinase 3-like-1 (CHI3L1) is induced during aging and CM, the relationships between CHI3L1 and SC2 were investigated. Here, we demonstrate that CHI3L1 is a potent stimulator of the SC2 receptor angiotensin converting enzyme 2 (ACE2) and viral spike protein priming proteases (SPP), that ACE2 and SPP are induced during aging, and that anti-CHI3L1, kasugamycin, and inhibitors of phosphorylation abrogate these ACE2- and SPP-inductive events. Human studies also demonstrate that the levels of circulating CHI3L1 are increased in the elderly and patients with CM, where they correlate with COVID-19 severity. These studies demonstrate that CHI3L1 is a potent stimulator of ACE2 and SPP, that this induction is a major mechanism contributing to the effects of aging during SC2 infection, and that CHI3L1 co-opts the CHI3L1 axis to augment SC2 infection. CHI3L1 plays a critical role in the pathogenesis of and is an attractive therapeutic target in COVID-19.

Association between YKL-40 and asthma: a systematic meta-analysis

PURPOSE

Many studies have shown that chitinase-3-like protein 1 (CHI3L1), also known as YKL-40, is associated with asthma. The purpose of this meta-analysis was to evaluate the role of serum YKL-40 in the diagnosis and differential diagnosis of asthma, severity grading, and determination of disease state.

METHODS

The PubMed, Ovid, and Cochrane databases were searched. A total of 17 articles involving 5696 subjects were included in this meta-analysis.

RESULTS

The results showed that the level of YKL-40 was significantly higher in asthmatic patients than in the normal group regardless of age and residential location, and increased with severity and acute exacerbation (p < 0.05). YKL-40 levels were significantly different between chronic obstructive pulmonary disease (COPD) and asthma, and also between asthma-COPD overlap syndrome (ACO) and asthma (p < 0.05).

CONCLUSION

YKL-40 may act as a potential serological marker for the diagnosis of asthma, assessment of severity, indicator of the disease state, and differential diagnosis of COPD, ACO, and asthma.

Repetitive aeroallergen challenges elucidate maladaptive epithelial and inflammatory traits that underpin allergic airway diseases

BACKGROUND

Signifying the 2-compartments/1-disease paradigm, allergic rhinoconjunctivitis (ARC) and asthma (AA) are prevalent, comorbid conditions triggered by environmental factors (eg, house dust mites [HDMs]). However, despite the ubiquity of triggers, progression to severe ARC/AA is infrequent, suggesting either resilience or adaptation.

OBJECTIVE

We sought to determine whether ARC/AA severity relates to maladaptive responses to disease triggers.

METHODS

Adults with HDM-associated ARC were challenged repetitively with HDMs in an aeroallergen challenge chamber. Mechanistic traits associated with disease severity were identified.

RESULTS

HDM challenges evoked maladaptive (persistently higher ARC symptoms), adaptive (progressive symptom reduction), and resilient (resistance to symptom induction) phenotypes. Symptom severity in the natural environment was an imprecise correlate of the phenotypes. Nasal airway traits, defined by low inflammation-effectual epithelial integrity, moderate inflammation-effectual epithelial integrity, and higher inflammation-ineffectual epithelial integrity, were hallmarks of the resilient, adaptive, and maladaptive evoked phenotypes, respectively. Highlighting a crosstalk mechanism, peripheral blood inflammatory tone calibrated these traits: ineffectual epithelial integrity associated with CD8⁺ T cells, whereas airway inflammation associated with both CD8⁺ T cells and eosinophils. Hallmark peripheral blood maladaptive traits were increased natural killer and CD8⁺ T cells, lower CD4⁺ mucosal-associated invariant T cells, and deficiencies along the TLR-IRF-IFN antiviral pathway. Maladaptive traits tracking HDM-associated ARC also contributed to AA risk and severity models.

CONCLUSIONS

Repetitive challenges with HDMs revealed that maladaptation to disease triggers may underpin ARC/AA disease severity. A combinatorial therapeutic approach may involve reversal of loss-of-beneficial-function traits (ineffectual epithelial integrity, TLR-IRF-IFN deficiencies), mitigation of gain-of-adverse-function traits (inflammation), and blocking of a detrimental crosstalk between the peripheral blood and airway compartments.

A genetic variation in CHI3L1 is associated with bronchial asthma

BACKGROUND

This study was aimed to investigate the associations among Chitinase 3-like 1 (CHI3L1) polymorphisms, asthma and plasma YKL-40 levels in Chinese population.

MATERIAL AND METHODS

Four CHI3L1 single nucleotide polymorphisms (SNPs) were genotyped. The YKL-40 level in plasma and eosinophil percentage in peripheral blood were quantified.

RESULTS

A SNP (rs4950928) in the CHI3L1 promoter was associated with elevated plasma YKL-40 levels (p = .02), asthma (p = .042) and lung function (p = .029 to .002) in this Chinese population. Plasma YKL-40 levels were significantly elevated in patients with asthma compared to those in control subjects (p < .05). Plasma YKL-40 levels were significantly correlated with forced expiratory volume per cent (FEV1%) measurements (p < .05). Although plasma YKL-40 levels were decreased after treatment, the correlation with FEV1% still existed.

CONCLUSIONS

CHI3L1 locus is a risk factor for asthma in Chinese population.

Chitinase 3-like-1 is a Therapeutic Target That Mediates the Effects of Aging in COVID-19

COVID-19 is caused by the SARS-CoV-2 (SC2) virus and is more prevalent and severe in the elderly and patients with comorbid diseases (CM). Because chitinase 3-like-1 (CHI3L1) is induced during aging and CM, the relationships between CHI3L1 and SC2 were investigated. Here we demonstrate that CHI3L1 is a potent stimulator of the SC2 receptor ACE2 and viral spike protein priming proteases (SPP), that ACE2 and SPP are induced during aging and that anti-CHI3L1, kasugamycin and inhibitors of phosphorylation, abrogate these ACE2- and SPP- inductive events. Human studies also demonstrated that the levels of circulating CHI3L1 are increased in the elderly and patients with CM where they correlate with COVID-19 severity. These studies demonstrate that CHI3L1 is a potent stimulator of ACE2 and SPP; that this induction is a major mechanism contributing to the effects of aging during SC2 infection and that CHI3L1 coopts the CHI3L1 axis to augment SC2 infection. CHI3L1 plays a critical role in the pathogenesis of and is an attractive therapeutic target in COVID-19.

Natural polymorphism of Ym1 regulates pneumonitis through alternative activation of macrophages

We have positionally cloned the Ym1 gene, with a duplication and a promoter polymorphism, as a major regulator of inflammation. Mice with the RIIIS/J haplotype, with the absence of Ym1 expression, showed reduced susceptibility to mannan-enhanced collagen antibody-induced arthritis and to chronic arthritis induced by intranasal exposure of mannan. Depletion of lung macrophages alleviated arthritis, whereas intranasal supplement of Ym1 protein to Ym1-deficient mice reversed the disease, suggesting a key role of Ym1 for inflammatory activity by lung macrophages. Ym1-deficient mice with pneumonitis had less eosinophil infiltration, reduced production of type II cytokines and IgG1, and skewing of macrophages toward alternative activation due to enhanced STAT6 activation. Proteomics analysis connected Ym1 polymorphism with changed lipid metabolism. Induced PPAR-γ and lipid metabolism in Ym1-deficient macrophages contributed to cellular polarization. In conclusion, the natural polymorphism of Ym1 regulates alternative activation of macrophages associated with pulmonary inflammation.

Status and prospects: personalized treatment and biomarker for airway remodeling in asthma

Airway remodeling, as a major characteristic of bronchial asthma, is critical to the progression of this disease, whereas it is of less importance in clinical management. Complying with the current stepwise treatment standard for asthma, the choice of intervention on the clinical status is primarily determined by the patient’s treatment response to airway inflammation. However, a considerable number of asthmatic patients, especially severe asthmatic subjects, remain uncontrolled though they have undergone fortified anti-inflammation treatment. In the past few years, a growing number of biologics specific to asthma phenotypes have emerged, bringing new hope for patients with refractory asthma and severe asthma. While at the same time, the effect of airway remodeling on asthma treatment has become progressively prominent. In the era of personalized treatment, it has become one of the development directions for asthma treatment to find reliable airway remodeling biomarkers to assist in asthma phenotypes classification, and to further combine multiple phenotypes to accurately treat patients. In the present study, the research status of airway remodeling in asthma is reviewed to show the basis for classifying and treating such disease. Besides, several selected airway remodeling biomarkers and possibility to use them in individual treatment are discussed as well. This study considers that continuously optimized mechanisms and emerging biomarkers for airway remodeling in the future may further support individual therapy for asthma patients.

Chitinase-3 like-protein-1 function and its role in diseases

Non-enzymatic chitinase-3 like-protein-1 (CHI3L1) belongs to glycoside hydrolase family 18. It binds to chitin, heparin, and hyaluronic acid, and is regulated by extracellular matrix changes, cytokines, growth factors, drugs, and stress. CHI3L1 is synthesized and secreted by a multitude of cells including macrophages, neutrophils, synoviocytes, chondrocytes, fibroblast-like cells, smooth muscle cells, and tumor cells. It plays a major role in tissue injury, inflammation, tissue repair, and remodeling responses. CHI3L1 has been strongly associated with diseases including asthma, arthritis, sepsis, diabetes, liver fibrosis, and coronary artery disease. Moreover, following its initial identification in the culture supernatant of the MG63 osteosarcoma cell line, CHI3L1 has been shown to be overexpressed in a wealth of both human cancers and animal tumor models. To date, interleukin-13 receptor subunit alpha-2, transmembrane protein 219, galectin-3, chemo-attractant receptor-homologous 2, and CD44 have been identified as CHI3L1 receptors. CHI3L1 signaling plays a critical role in cancer cell growth, proliferation, invasion, metastasis, angiogenesis, activation of tumor-associated macrophages, and Th2 polarization of CD4⁺ T cells. Interestingly, CHI3L1-based targeted therapy has been increasingly applied to the treatment of tumors including glioma and colon cancer as well as rheumatoid arthritis. This review summarizes the potential roles and mechanisms of CHI3L1 in oncogenesis and disease pathogenesis, then posits investigational strategies for targeted therapies.

Profiling cellular heterogeneity in asthma with single cell multiparameter CyTOF

Asthma is a chronic inflammatory disease of the airways that afflicts over 30 million individuals in the United States and over 300 million individuals worldwide. The inflammatory response in the airways is often characterized by the analysis of sputum, which contains multiple types of cells including neutrophils, macrophages, lymphocytes, and rare bronchial epithelial cells. Subtyping patients using microscopy of the sputum has identified both neutrophilic and eosinophilic infiltrates in airway inflammation. However, with the extensive heterogeneity among these cell types, a higher resolution understanding of the inflammatory cell types present in the sputum is needed to dissect the heterogeneity of disease. Improved recognition of the distinct phenotypes and sources of inflammation in asthmatic granulocytes may identify relevant pathways for clinical management or investigation of novel therapeutic mediators. Here, we employed mass cytometry or cytometry by time-of-flight to quantify frequency and define functional status of sputum derived airway cells in asthmatic patients and healthy controls. This in-depth single cell analysis method identified multiple distinct subtypes of airway immune cells, especially in neutrophils. Significance was discovered by statistical analysis as well as a data-driven unbiased clustering approach. Our multidimensional assessment method identifies differences in cellular function and supports identification of cellular status that may contribute to diverse clinical responses. This technical advance is relevant for studies of pathogenesis and may provide meaningful insights to advance our knowledge of asthmatic inflammation.

BAL Cell Gene Expression in Severe Asthma Reveals Mechanisms of Severe Disease and Influences of Medications

Rationale: Gene expression of BAL cells, which samples the cellular milieu within the lower respiratory tract, has not been well studied in severe asthma.Objectives: To identify new biomolecular mechanisms underlying severe asthma by an unbiased, detailed interrogation of global gene expression.Methods: BAL cell expression was profiled in 154 asthma and control subjects. Of these participants, 100 had accompanying airway epithelial cell gene expression. BAL cell expression profiles were related to participant (age, sex, race, and medication) and sample traits (cell proportions), and then severity-related gene expression determined by correlating transcripts and coexpression networks to lung function, emergency department visits or hospitalizations in the last year, medication use, and quality-of-life scores.Measurements and Main Results: Age, sex, race, cell proportions, and medications strongly influenced BAL cell gene expression, but leading severity-related genes could be determined by carefully identifying and accounting for these influences. A BAL cell expression network enriched for cAMP signaling components most differentiated subjects with severe asthma from other subjects. Subsequently, an in vitro cellular model showed this phenomenon was likely caused by a robust upregulation in cAMP-related expression in nonsevere and β-agonist-naive subjects given a β-agonist before cell collection. Interestingly, ELISAs performed on BAL lysates showed protein levels may partly disagree with expression changes.Conclusions: Gene expression in BAL cells is influenced by factors seldomly considered. Notably, β-agonist exposure likely had a strong and immediate impact on cellular gene expression, which may not translate to important disease mechanisms or necessarily match protein levels. Leading severity-related genes were discovered in an unbiased, system-wide analysis, revealing new targets that map to asthma susceptibility loci.

Measured and genetically predicted plasma YKL-40 levels and melanoma mortality

PURPOSE

High plasma levels of YKL-40 might be associated with mortality in patients with melanoma, and it is unknown if YKL-40 is causally related to mortality.

EXPERIMENTAL DESIGN

We studied two cohorts: 2618 patients with melanoma from hospital clinics and 1413 general population patients with melanoma, totalling 4031 patients followed up for mortality end-points for up to 20 years. All were genotyped for CHI3L1 rs4950928, highly predictive of lifelong plasma YKL-40, and plasma YKL-40 levels were measured in 2165 patients. We tested the hypotheses that measured and genetically predicted high plasma YKL-40 are associated with increased mortality in patients with melanoma.

RESULTS

For the hospital melanoma cohort, age- and sex-adjusted hazard ratios for death in individuals with measured plasma YKL-40 in the 96-100th percentile versus 1-95th percentile and per 10-percentile increase were 1.52 (95% confidence interval, 1.07-2.16) and 1.07 (1.02-1.11), respectively, most pronounced for patients with localised melanomas. Each C-allele of the CHI3L1 rs4950928 genotype was associated with plasma YKL-40 level increases of 32% in the hospital melanoma cohort (p = 6 × 10^-48) and 43% in the general population melanoma cohort (p = 7 × 10^-13). Multifactorially adjusted ratios for these increases in the combined cohorts were 1.04 (1.00-1.09) observationally for measured plasma YKL-40 and 0.98 (0.86-1.12) for the genetically predicted plasma YKL-40.

CONCLUSION

Measured, but not genetically predicted, increasing plasma YKL-40 was associated with increased mortality in patients with melanoma. Plasma YKL-40 is a marker but less likely to be a cause of increased mortality in patients with melanoma.

Overexpression of chitotriosidase and YKL-40 in peripheral blood and sputum of healthy smokers and patients with chronic obstructive pulmonary disease

Background

Despite the absence of endogenous chitin in humans, chitinases are present in the serum of healthy subjects and their levels are increased in a variety of chronic inflammatory conditions. It has been shown that chitotriosidase and structurally related chitinase-like protein-YKL-40 contribute to the pathogenesis of COPD. However, details regarding the relation of their systemic and local airways levels remain unknown.

Objectives

To examine peripheral blood and sputum chitotriosidase and YKL-40 expression in smokers and patients with COPD.

Methods

Forty patients with COPD, 20 healthy smokers and 10 healthy never-smokers were studied. Serum and induced sputum chitotriosidase protein and activity levels, YKL-40 concentrations, and their gene expression in sputum cells and peripheral blood mononuclear cells (PBMC) were evaluated.

Results

Both chitotriosidase protein levels and activity were higher in sputum obtained from COPD subjects compared to healthy never-smokers (P<0.05 and P<0.01, respectively). A similar pattern was observed for PBMC chitotriosidase mRNA expression (P<0.001). YKL-40 serum concentrations were elevated in healthy smokers and COPD subjects compared to healthy never-smokers (P<0.001 and P<0.01, respectively). In sputum, YKL-40 levels were increased in COPD compared to healthy never-smokers (P<0.01). PBMC YKL-40 mRNA expression was increased in COPD and healthy smokers compared to healthy never-smokers (P<0.0001). No associations were found between chitotriosidase or YKL-40 peripheral blood levels and sputum levels.

Conclusions

Our results demonstrate that chitotriosidase and YKL-40 are overexpressed in peripheral blood and airways in both healthy smokers and COPD subjects which may indicate smoking-related activation of macrophages, neutrophils, and epithelial cells.

Local Expression of Mucosal YKL-40; Correlation of YKL-40 with Clinical Manifestations and Immunopathogenesis of Moderate/Severe Persistent Allergic Rhinitis Patients

YKL-40 is an important protein that plays a critical role in chronic inflammation in hypersensitivity disease. In this study, the expression of YKL-40 was investigated among patients with moderate/severe persistent allergic rhinitis (M/S PAR), patients with mild (M) PAR and healthy individuals. Moreover, the association between YKL-40 and immunopathogenesis of M/S PAR was meticulously surveyed. For this purpose, surgical samples were tested by real-time polymerase chain reaction to evaluate YKL-40 mRNA expression. The presence and location of YKL-40 protein in the tissue samples were determined by immunohistochemistry. Additionally, we measured the number of eosinophils per field in the tissue samples, blood eosinophils, total serum IgE, specific serum IgE, total nasal syndrome score (TNSS) and YKL-40 serum levels. The data indicated that production of YKL-40 in patients with M/S PAR increased significantly when compared with the control group. Furthermore, local production of YKL-40 correlated with specific IgE, nasal eosinophil count and TNSS. The results of the present study indicate that YKL-40, for its correlation with allergic clinical manifestations and symptom severity in M/S PAR patients, should be considered as a trigger factor in AR.

Functional study of the association of CHI3L1 polymorphisms with asthma susceptibility in the Southwest Chinese Han population

Background: Chitinase 3-like 1 (CHI3L1) is involved in the Th2 cell mediated pathway, tissue remodeling and fibrosis. Correlations of CHI3L1 gene polymorphisms with asthma in previous studies have been inconsistent. The present study was designed to investigate the association between CHI3L1 polymorphisms and asthma in the southwest Chinese Han population. Methods: Two single nucleotide polymorphisms (SNPs), rs4950928 and rs10399931, were genotyped in 410 asthma patients and 418 healthy controls from Southwest China. Dual-luciferase reporter gene analysis was performed to detect allele-dependent promoter activity of CHI3L1 variants in HEK293 cells. Real-time quantitative PCR was applied to detect the relative mRNA expression associated with different genotypes of CHI3L1 rs10399931. A meta-analysis was performed using data collected from previously published reports and the present study. Results: No significant association was found between rs4950928 and asthma. The rs10399931 CT/TT genotype increased the risk of asthma under the dominant model (P = 0.031, OR = 1.428, 95% CI, 1.033-1.974), while the CT genotype showed the same tendency under the heterozygous model (P = 0.003, OR = 1.680, 95% CI, 1.186-2.380). No statistically significant difference was found between alleles T and C of rs10399931in the dual-luciferase reporter gene analysis (P = 0.201). The rs10399931 CT/TT genotypes reduced the relative mRNA expression detected by real-time quantitative PCR (P = 0.002). There was no significant association between the CHI3L1 rs4950928 polymorphism and the risk of asthma in the meta-analysis. Conclusion: In the southwest Chinese Han population, the CHI3L1 rs10399931 CT/TT genotypes may increase the risk of asthma. rs10399931 may be a functional variant of CHI3L1 due to its effect on mRNA expression.

Biomarkers and asthma management: analysis and potential applications

PURPOSE OF REVIEW

Asthma features a high degree of heterogeneity in both pathophysiology and therapeutic response, resulting in many asthma patients being treated inadequately. Biomarkers indicative of underlying pathological processes could be used to identify disease subtypes, determine prognosis and to predict or monitor treatment response. However, the newly identified as well as more established biomarkers have different applications and limitations.

RECENT FINDINGS

Conventional markers for type 2-high asthma, such as blood eosinophils, fraction of exhaled nitric oxide, serum IgE and periostin, feature limited sensitivity and specificity despite their significant correlations. More distinctive models have been developed by combining biomarkers and/or using omics techniques. Recently, a model with a positive predictive value of 100% for identification of type 2-high asthma based on a combination of minimally invasive biomarkers was developed.

SUMMARY

Individualisation of asthma treatment regimens on the basis of biomarkers is necessary to improve asthma control. However, the suboptimal properties of currently available conventional biomarkers limit its clinical utility. Newly identified biomarkers and models based on combinations and/or omics analysis must be validated and standardised before they can be routinely applied in clinical practice. The development of robust biomarkers will allow development of more efficacious precision medicine-based treatment approaches for asthma.

Genes and Pathways Regulating Decline in Lung Function and Airway Remodeling in Asthma

Asthma is a common disorder of the airways characterized by airway inflammation and by decline in lung function and airway remodeling in a subset of asthmatics. Airway remodeling is characterized by structural changes which include airway smooth muscle hypertrophy/hyperplasia, subepithelial fibrosis due to thickening of the reticular basement membrane, mucus metaplasia of the epithelium, and angiogenesis. Epidemiologic studies suggest that both genetic and environmental factors may contribute to decline in lung function and airway remodeling in a subset of asthmatics. Environmental factors include respiratory viral infection-triggered asthma exacerbations, and tobacco smoke. There is also evidence that several asthma candidate genes may contribute to decline in lung function, including ADAM33, PLAUR, VEGF, IL13, CHI3L1, TSLP, GSDMB, TGFB1, POSTN, ESR1 and ARG2. In addition, mediators or cytokines, including cysteinyl leukotrienes, matrix metallopeptidase-9, interleukin-33 and eosinophil expression of transforming growth factor-β, may contribute to airway remodeling in asthma. Although increased airway smooth muscle is associated with reduced lung function (i.e. forced expiratory volume in 1 second) in asthma, there have been few long-term studies to determine how individual pathologic features of airway remodeling contribute to decline in lung function in asthma. Clinical studies with inhibitors of individual gene products, cytokines or mediators are needed in asthmatic patients to identify their individual role in decline in lung function and/or airway remodeling.

Genetic Mechanisms of Asthma and the Implications for Drug Repositioning

Asthma is a chronic disease that is caused by airway inflammation. The main features of asthma are airway hyperresponsiveness (AHR) and reversible airway obstruction. The disease is mainly managed using drug therapy. The current asthma drug treatments are divided into two categories, namely, anti-inflammatory drugs and bronchodilators. However, disease control in asthma patients is not very efficient because the pathogenesis of asthma is complicated, inducing factors that are varied, such as the differences between individual patients. In this paper, we delineate the genetic mechanisms of asthma, and present asthma-susceptible genes and genetic pharmacology in an attempt to find a diagnosis, early prevention, and treatment methods for asthma. Finally, we reposition some clinical drugs for asthma therapy, based on asthma genetics.

Role of genetic variations of chitinase 3-like 1 in bronchial asthmatic patients

Background

Single nucleotide polymorphisms (SNPs) in chitinase 3-like 1 (CHI3L1) are associated with bronchial severity and pulmonary function. CHI3L1 proteins are involved in both innate and adaptive immune responses; however, to date, the correlation of these SNPs and their age of onset of bronchial asthma has not been demonstrated.

Methods

To address the role of these genetic variations, 390 patients with well-controlled bronchial asthma and living in Japan were recruited, genotyped, and had a pulmonary function test performed on them in this study. To analyze the concentration levels of CHI3L1 protein, bronchial lavage fluids were examined.

Results

Forced expiratory volume in one second, %predicted (%FEV1), was significantly decreased in homozygotes of rs1214194 compared to heterozygotes and wild type. The age of onset of adult bronchial asthma was significantly younger in GG homozygotes of rs4950928 and AA homozygotes of rs1214194 than in the other two genotypes. The concentration of CHI3L1 protein in bronchial lavage fluid increased in both homozygotes of rs4950928 and rs1214194.

Conclusions

Our study demonstrated that the homozygotes of rs4950928 and rs1214194 of CHI3L1 might predict an early onset of bronchial asthma and have the propensity to promote airway remodeling.

Trial registration JMA-IIA00045 remodeling-ICS

Association between risk of asthma and gene polymorphisms in CHI3L1 and CHIA: a systematic meta-analysis

Background

Previous studies have indicated that chitinase 3-like 1 (CHI3L1) gene rs4950928 polymorphism and acidic mammalian chitinase (AMCase or CHIA) gene rs10494132 polymorphism are associated with the risk of asthma. However, the results are inconsistent because of small sample size and varied ethnicity and age in studies. Therefore, a systematic meta-analysis was important to clarify the effect of CHI3L1 rs4950928 polymorphism and CHIA rs10494132 variant on asthma risk.

Methods

An electronic literature search was conducted to identify all the eligible studies. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated and sensitivity analysis as well as publication bias were assessed to investigate the associations. All statistical analyses were performed using STATA 12.0.

Results

Eight published articles with 10 case-control studies were included, 5 studies were of CHI3L1 rs4950928 polymorphism and another 5 studies involved CHIA rs10494132 polymorphism. Overall, no significant association was found between CHI3L1 polymorphism and asthma susceptibility. After stratified according to ethnicity, CHI3L1 rs4950928 variant was associated with decreased asthma risk in Caucasians (GG + GC vs. CC: OR = 0.621, 95% CI = 0.484–0.797, P = 0.000; GC vs. CC: OR = 0.612, 95% CI = 0.470–0.796, P = 0.000; G vs. C: OR = 0.696, 95% CI = 0.567–0.856, P = 0.001). When stratified population by age, there was no association in children under all genetic models. As for CHIA rs10494132 polymorphism, no evidence of association between CHIA rs10494132 polymorphism and asthma risk was identified. Furthermore, subgroup analysis by ethnicity revealed a positive correlation between CHIA rs10494132 polymorphism and asthma risk among Asians (TT vs. TC + CC: OR = 1.476, 95% CI = 1.071–2.032, P = 0.017; T vs. C: OR = 1.326, 95% CI = 1.024–1.717, P = 0.032). Additionally, in the subgroup analysis conducted according to age, CHIA rs10494132 variant was also found to be associated with the increased risk of asthma in children (TT vs. TC + CC: OR = 1.472, 95% CI = 1.067–2.030, P = 0.019; T vs. C: OR = 1.320, 95% CI = 1.016–1.713, P = 0.037).

Conclusions

The G allele of CHI3L1 rs4950928 might be a protective factor against the development of asthma. However, the rs10494132 polymorphism of CHIA might be a risk factor for asthma.

Characterisation of asthma subgroups associated with circulating YKL-40 levels

The chitinase-like protein YKL-40 mediates airway inflammation and serum levels are associated with asthma severity. However, asthma phenotypes associated with YKL-40 levels have not been precisely defined.We conducted an unsupervised cluster analysis of asthma patients treated at the Yale Center for Asthma and Airways Disease (n=156) to identify subgroups according to YKL-40 level. The resulting YKL-40 clusters were cross-validated in cohorts from the Severe Asthma Research Programme (n=167) and the New York University/Bellevue Asthma Repository (n=341). A sputum transcriptome analysis revealed molecular pathways associated with YKL-40 subgroups.Four YKL-40 clusters (C1-C4) were identified. C3 and C4 had high serum YKL-40 levels compared with C1 and C2. C3 was associated with earlier onset and longer duration of disease, severe airflow obstruction, and near-fatal asthma exacerbations. C4 had the highest serum YKL-40 levels, adult onset and less airflow obstruction, but frequent exacerbations. An airway transcriptome analysis in C3 and C4 showed activation of non-type 2 inflammatory pathways.Elevated serum YKL-40 levels were associated with two distinct clinical asthma phenotypes: one with irreversible airway obstruction and another with severe exacerbations. The YKL-40 clusters are potentially useful for identification of individuals with severe or exacerbation-prone asthma.

CHI3L1 is correlated with childhood asthma

OBJECTIVE

The aim of this study was to assess the association between CHI3L1 gene two single nucleotide polymorphisms (SNPs) (rs12141494 and rs4950928) and susceptibility to pediatric asthma in a Chinese Han population.

METHODS

The case-control study was carried out on 115 children with asthma and 108 healthy controls. Genotypes of rs12141494 and rs4950928 within CHI3L1 gene were determined with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) approach. Chi-square test was employed to analyze the differences of genotype and allele frequencies of the two polymorphisms between case and control groups. Odds ratios (ORs) and 95% confidence intervals (CIs) were applied to explain relative susceptibility of pediatric asthma.

RESULTS

The frequencies of genotypes and alleles of rs4950928 in CHI3L1 gene showed a significant difference between asthmatic children and healthy controls (P<0.05). However, no significant differences were found in CHI3L1 SNP rs12141494 between two groups (P>0.05).

CONCLUSION

Our results suggested that rs4950928 in CHI3L1 gene was associated with pediatric asthma risk in a Chinese Han population, while rs12141494 was not.

Transcriptomic analysis comparing mouse strains with extreme total lung capacities identifies novel candidate genes for pulmonary function

BACKGROUND

Failure to attain peak lung function by early adulthood is a risk factor for chronic lung diseases. Previously, we reported that C3H/HeJ mice have about twice total lung capacity (TLC) compared to JF1/MsJ mice. We identified seven lung function quantitative trait loci (QTL: Lfnq1-Lfnq7) in backcross/intercross mice derived from these inbred strains. We further demonstrated, superoxide dismutase 3, extracellular (Sod3), Kit oncogene (Kit) and secreted phosphoprotein 1 (Spp1) located on these Lfnqs as lung function determinants. Emanating from the concept of early origin of lung disease, we sought to identify novel candidate genes for pulmonary function by investigating lung transcriptome in C3H/HeJ and JF1/MsJ mice at the completion of embryonic development, bulk alveolar formation and maturity.

METHODS

Design-based stereological analysis was performed to study lung structure in C3H/HeJ and JF1/MsJ mice. Microarray was used for lung transcriptomic analysis [embryonic day 18, postnatal days 28, 70]. Quantitative real time polymerase chain reaction (qRT-PCR), western blot and immunohistochemical analysis were used to confirm selected differences.

RESULTS

Stereological analysis revealed decreased alveolar number density, elastin to collagen ratio and increased mean alveolar volume in C3H/HeJ mice compared to JF1/MsJ. Gene ontology term "extracellular region" was enriched among the decreased JF1/MsJ transcripts. Candidate genes identified using the expression-QTL strategy include: ATP-binding cassette, sub-family G (WHITE), member 1 (Abcg1), formyl peptide receptor 1 (Fpr1), gamma-aminobutyric acid (GABA) B receptor, 1 (Gabbr1); histocompatibility 2 genes: class II antigen E beta (H2-Eb1), D region locus 1 (H2-D1), and Q region locus 4 (H2-Q4); leucine rich repeat containing 6 (testis) (Lrrc6), radial spoke head 1 homolog (Rsph1), and surfactant associated 2 (Sfta2). Noteworthy genes selected as candidates for their consistent expression include: Wnt inhibitor factor 1 (Wif1), follistatin (Fst), chitinase-like 1 (Chil1), and Chil3.

CONCLUSIONS

Comparison of late embryonic, adolescent and adult lung transcript profiles between mouse strains with extreme TLCs lead to the identification of candidate genes for pulmonary function that has not been reported earlier. Further mechanistic investigations are warranted to elucidate their mode of action in determining lung function.

Genetic and epigenetic regulation of YKL-40 in childhood

BACKGROUND

Circulating levels of the chitinase-like protein YKL-40 are influenced by genetic variation in its encoding gene (chitinase 3-like 1 [CHI3L1]) and are increased in patients with several diseases, including asthma. Epigenetic regulation of circulating YKL-40 early in life is unknown.

OBJECTIVE

We sought to determine (1) whether methylation levels at CHI3L1 CpG sites mediate the association of CHI3L1 single nucleotide polymorphisms (SNPs) with YKL-40 levels in the blood and (2) whether these biomarkers (CHI3L1 SNPs, methylation profiles, and YKL-40 levels) are associated with asthma in early childhood.

METHODS

We used data from up to 2405 participants from the Spanish Infancia y Medio Ambiente; the Swedish Barn/Children, Allergy, Milieu, Stockholm, Epidemiological survey; and the Dutch Prevention and Incidence of Asthma and Mite Allergy birth cohorts. Associations between 68 CHI3L1 SNPs, methylation levels at 14 CHI3L1 CpG sites in whole-blood DNA, and circulating YKL-40 levels at 4 years of age were tested by using correlation analysis, multivariable regression, and mediation analysis. Each of these biomarkers was also tested for association with asthma at 4 years of age by using multivariable logistic regression.

RESULTS

YKL-40 levels were significantly associated with 7 SNPs and with methylation at 5 CpG sites. Consistent associations between these 7 SNPs (particularly rs10399931 and rs4950928) and 5 CpG sites were observed. Alleles linked to lower YKL-40 levels were associated with higher methylation levels. Participants with high YKL-40 levels (defined as the highest YKL-40 tertile) had increased odds for asthma compared with subjects with low YKL-40 levels (meta-analyzed adjusted odds ratio, 1.90 [95% CI, 1.08-3.36]). In contrast, neither SNPs nor methylation levels at CpG sites in CHI3L1 were associated with asthma.

CONCLUSIONS

The effects of CHI3L1 genetic variation on circulating YKL-40 levels are partly mediated by methylation profiles. In our study YKL-40 levels, but not CHI3L1 SNPs or methylation levels, were associated with childhood asthma.

A longitudinal assessment of circulating YKL-40 levels in preschool children with wheeze

BACKGROUND

The chitinase-like protein YKL-40 (CHI3L1) is elevated in the circulation of adults and schoolchildren with chronic severe asthma. It is unknown whether YKL-40 is altered in younger, preschool children with wheeze, acute or chronic. We therefore examined YKL-40 in preschool children during an acute episode of wheeze and during remission, in comparison with healthy controls.

METHODS

Blood was obtained from 128 children (aged 6-44 months) at the emergency department during an acute episode of wheeze, and at two follow-up visits (approximately 3 months and 1 year later), as well as from 100 age-matched healthy controls on one occasion. Plasma YKL-40 levels were examined in relation to CHI3L1 rs4950928 genotype and clinical characteristics including Asthma Predictive Index, medication use, time spent with respiratory symptoms, atopic status, and blood leukocytes.

RESULTS

Children with wheeze had higher median YKL-40 levels at the acute visit (14.7 (11.5-22.6) ng/ml, p < 0.001) and 3-month follow-up (15.9 (11.5-20.2), p < 0.001) compared to the 1-year follow-up (11.9 (9.5-17.3)). YKL-40 levels in healthy controls (13.6 (11.0-17.0)) tended to be lower than those during acute wheeze (p = 0.07) and 3-month follow-up (p = 0.04), but were no different at the 1-year follow-up. CHI3L1 rs4950928 affected YKL-40 in all subjects, with highest levels present in those with the CC genotype (p < 0.001). Genotype frequency was similar in the two subject groups. YKL-40 levels showed a positive correlation with blood neutrophil counts but no consistent relationships with clinical characteristics of relevance to continuous wheeze.

CONCLUSION

YKL-40 levels were elevated during acute wheeze in preschool children, a finding which may be related to current neutrophilic inflammation, but YKL-40 was not associated with characteristics of persistent wheeze in this young cohort.

High serum YKL-40 level positively correlates with coronary artery disease

AIM

We investigated the predictive value of chitinase-like protein YKL-40 in coronary artery disease (CAD).

PATIENTS

Serum YKL-40 levels in 116 CAD patients and 82 healthy controls were analyzed. Severity of CAD was evaluated using Gensini scores. Spearman's correlation was used to evaluate the correlation between Gensini scores and YKL-40 levels. The predictive value of YKL-40 was determined by receivers operating characteristic curve analysis.

RESULTS

Serum YKL-40 levels were significantly elevated in CAD group as compared with control group. A positive correlation was found between the serum YKL-40 level and Gensini score. The optimum cut-off value of YKL-40 concentration was 127.7 ng/ml for distinguishing CAD patients from healthy controls with a 75.9% sensitivity and 57.3% specificity.

CONCLUSION

A positive correlation exists between YKL-40 levels and CAD, and YKL-40 might be a useful adjunct in the diagnosis of CAD.

The nature and nurture of cell heterogeneity: accounting for macrophage gene-environment interactions with single-cell RNA-Seq

BACKGROUND

Single-cell RNA-Seq can be a valuable and unbiased tool to dissect cellular heterogeneity, despite the transcriptome's limitations in describing higher functional phenotypes and protein events. Perhaps the most important shortfall with transcriptomic 'snapshots' of cell populations is that they risk being descriptive, only cataloging heterogeneity at one point in time, and without microenvironmental context. Studying the genetic ('nature') and environmental ('nurture') modifiers of heterogeneity, and how cell population dynamics unfold over time in response to these modifiers is key when studying highly plastic cells such as macrophages.

RESULTS

We introduce the programmable Polaris™ microfluidic lab-on-chip for single-cell sequencing, which performs live-cell imaging while controlling for the culture microenvironment of each cell. Using gene-edited macrophages we demonstrate how previously unappreciated knockout effects of SAMHD1, such as an altered oxidative stress response, have a large paracrine signaling component. Furthermore, we demonstrate single-cell pathway enrichments for cell cycle arrest and APOBEC3G degradation, both associated with the oxidative stress response and altered proteostasis. Interestingly, SAMHD1 and APOBEC3G are both HIV-1 inhibitors ('restriction factors'), with no known co-regulation.

CONCLUSION

As single-cell methods continue to mature, so will the ability to move beyond simple 'snapshots' of cell populations towards studying the determinants of population dynamics. By combining single-cell culture, live-cell imaging, and single-cell sequencing, we have demonstrated the ability to study cell phenotypes and microenvironmental influences. It's these microenvironmental components - ignored by standard single-cell workflows - that likely determine how macrophages, for example, react to inflammation and form treatment resistant HIV reservoirs.

Personalized management of asthma exacerbations: lessons from genetic studies

INTRODUCTION

The genetics of severe asthma and asthma exacerbations are distinct from milder forms of asthma. Gene-environmental interactions contribute to the complexity and heterogeneity of severe asthma and asthma exacerbations, and pharmacogenomic studies have also identified genes that affect susceptibility to asthma exacerbations.

AREAS COVERED

Studies on the genetics, gene-environment interactions, and pharmacogenomics of asthma exacerbations are reviewed. Multiple individual genetic variants have been identified to be associated with asthma exacerbations but each genetic polymorphism explains only a fraction of the disease and by itself is not able to translate into clinical practice. Research is shifting from candidate gene studies and genome wide association studies towards more integrative approaches to translate genetic findings into clinical diagnostic and therapeutic tools.

EXPERT COMMENTARY

Integrative approaches combining polygenic or genomic data with multi-omics technologies have the potential to discover new biologic mechanisms and biomarkers for severe asthma and asthma exacerbations. Greater understanding of genomics and underlying biologic pathways will also lead to improved prevention and treatment, lowering costs, morbidity, and mortality. The utilization of genomic testing and personalized medicine may revolutionize asthma management, in particular for patients with severe, refractory asthma.

Chitinase 3-like-1 is produced by human Th17 cells and correlates with the level of inflammation in juvenile idiopathic arthritis patients

BACKGROUND

CHI3L1 is a chitinase-like protein without enzymatic activity, produced by activated macrophages, chondrocytes, neutrophils. Recent studies on arthritis, asthma, and inflammatory bowel diseases suggest that chitinases are important in inflammatory processes and tissue remodeling, but their production by human T cells, has never been reported.

METHODS

A microarray analysis of gene expression profile was performed on Th17 and classic Th1 cell clones and CHI3L1 was found among the up-regulated genes on Th17 cells. Different types of helper T cell clones (TCCs) were then evaluated by Real Time PCR (RT-PCR) for CHI3L1 mRNA expression; protein expression was investigated in cell lysates by western blotting and in cultures supernatants by ELISA. ELISA was also used to measure CHI3L1 in the serum and in the synovial fluid (SF) of juvenile idiopathic arthritis (JIA) patients.

RESULTS

At mRNA level CHI3L1 was highly expressed by Th17, Th17/Th1, non classic Th1 and even in Th17/Th2 cell clones, whereas it was virtually absent in CD161- classic Th1 and Th2 TCCs. CHI3L1 was also detected in cell culture supernatants of Th17 and Th17-derived cells but not of classic Th1. Moreover CHI3L1 was higher in the SF than in serum of JIA patients, and it positively correlated with the frequency of Th17 and non-classic Th1 cells in SF. CHI3L1 in SF also positively correlated with the C reactive protein (CRP) serum levels, and with the levels of some proinflammatory cytokines, such as IL-6 and p40, which is the common subunit of IL12 and IL23.

CONCLUSIONS

Here we describe for the first time CHI3L1 production by T cells owing the Th17 family. Moreover the positive correlation found between the frequency of Th17 and Th17-derived cell subsets and CHI3L1 levels in SF of JIA patients, in agreement with the suggested role of these cells in inflammatory process, candidates CHI3L1 as a possible biological target in JIA treatment.

Severe Asthma in Children: Lessons Learned and Future Directions

Severe asthma in children is a complicated and heterogeneous disorder that is extremely challenging to treat. Although most children with asthma derive clinical benefit from daily administration of low-to-medium-dose inhaled corticosteroid (ICS) therapy, a small subset of children with "severe" or "refractory" asthma require high doses of ICS and even systemic corticosteroids to maintain symptom control. These children with severe asthma are at increased risk for adverse outcomes including medication-related side effects and recurrent and life-threatening exacerbations that significantly impair quality of life. This review highlights findings on severe asthma in school-age children (age 6-17 years) from the National Heart, Lung and Blood Institute's Severe Asthma Research Program (SARP) over a 10-year period, between 2001 and 2011. Although SARP has advanced knowledge of the unique clinical, biological, and molecular attributes of severe asthma in children, considerable gaps remain for which additional studies are needed.

Increased YKL-40 and Chitotriosidase in Asthma and Chronic Obstructive Pulmonary Disease

RATIONALE

Serum chitinases may be novel biomarkers of airway inflammation and remodeling, but less is known about factors regulating their levels.

OBJECTIVES

To examine serum chitotriosidase activity and YKL-40 levels in patients with asthma and chronic obstructive pulmonary disease (COPD) and evaluate clinically relevant factors that may affect chitinase levels, including genetic variability, corticosteroid treatment, disease exacerbations, and allergen exposure.

METHODS

Serum chitotriosidase (CHIT1) activity and YKL-40 (CHI3L1) levels, as well as the CHIT1 rs3831317 and CHI3L1 rs4950928 genotypes, were examined in subsets of patients with mild to moderate asthma (n = 76), severe asthma (n = 93), and COPD (n = 64) taking part in the European multicenter BIOAIR (Longitudinal Assessment of Clinical Course and Biomarkers in Severe Chronic Airway Disease) study. Blood was obtained at baseline, before and after a 2-week oral steroid intervention, up to six times during a 1-year period, and during exacerbations. Baseline chitinase levels were also measured in 72 healthy control subjects. The effect of allergen inhalation on blood and sputum YKL-40 levels was measured in two separate groups of patients with mild atopic asthma; one group underwent repeated low-dose allergen challenge (n = 15), and the other underwent high-dose allergen challenge (n = 16).

MEASUREMENTS AND MAIN RESULTS

Serum chitotriosidase and YKL-40 were significantly elevated in patients with asthma and those with COPD compared with healthy control subjects. Genotype and age strongly affected both YKL-40 and chitotriosidase activity, but associations with disease remained following adjustment for these factors. Correlations were observed with lung function but not with other biomarkers, including exhaled nitric oxide, blood eosinophils, periostin, and IgE. Generally, acute exacerbations, allergen-induced airway obstruction, and corticosteroid treatment did not affect circulating chitinase levels.

CONCLUSIONS

YKL-40 and chitotriosidase are increased in asthma and more so in COPD. The data in the present study support these substances as being relatively steroid-insensitive, non-T-helper cell type 2-type biomarkers distinctly related to chronic inflammatory disease processes.

CHI3L1 polymorphisms, cord blood YKL-40 levels and later asthma development

BACKGROUND

Single nucleotide polymorphisms (SNPs) in chitinase 3-like 1 (CHI3L1), the gene encoding YKL-40, and increased serum YKL-40 levels are associated with severe forms of asthma. It has never been addressed whether SNPs in CHI3L1 and cord blood YKL-40 levels could already serve as potential biomarkers for milder forms of asthma. We assessed in an unselected population whether SNPs in CHI3L1 and cord blood YKL-40 levels at birth are associated with respiratory symptoms, lung function changes, asthma, and atopy.

METHODS

In a prospective birth cohort of healthy term-born neonates (n = 260), we studied CHI3L1 polymorphisms, and measured cord blood YKL-40 levels by ELISA in (n = 170) infants. Lung function was performed at 5 weeks and 6 years. Respiratory health during the first year of life was assessed weekly by telephone interviews. Diagnosis of asthma and allergic sensitisation was assessed at 6 years (n = 142).

RESULTS

The SNP rs10399805 was significantly associated with asthma at 6 years. The odds ratio for asthma was 4.5 (95 % CI 1.59-12.94) per T-allele. This finding was unchanged when adjusting for cord blood YKL-40 levels. There was no significant association for cord blood YKL-40 levels and asthma. SNPs in CHI3L1 and cord blood YKL-40 were not associated with lung function measurements at 5 weeks and 6 years, respiratory symptoms in the first year, and allergic sensitisation at 6 years.

CONCLUSION

Genetic variation in CHI3L1 might be related to the development of milder forms of asthma. Larger studies are warranted to establish the role of YKL-40 in that pathway.

Multidimensional endotyping in patients with severe asthma reveals inflammatory heterogeneity in matrix metalloproteinases and chitinase 3-like protein 1

Background

Disease heterogeneity in patients with severe asthma and its relationship to inflammatory mechanisms remain poorly understood.

Objective

We aimed to identify and replicate clinicopathologic endotypes based on analysis of blood and sputum parameters in asthmatic patients.

Methods

One hundred ninety-four asthmatic patients and 21 control subjects recruited from 2 separate centers underwent detailed clinical assessment, sputum induction, and phlebotomy. One hundred three clinical, physiologic, and inflammatory parameters were analyzed by using topological data analysis and Bayesian network analysis.

Results

Severe asthma was associated with anxiety and depression, obesity, sinonasal symptoms, decreased quality of life, and inflammatory changes, including increased sputum chitinase 3–like protein 1 (YKL-40) and matrix metalloproteinase (MMP) 1, 3, 8, and 12 levels. Topological data analysis identified 6 clinicopathobiologic clusters replicated in both geographic cohorts: young, mild paucigranulocytic; older, sinonasal disease; obese, high MMP levels; steroid resistant T_H2 mediated, eosinophilic; mixed granulocytic with severe obstruction; and neutrophilic, low periostin levels, severe obstruction. Sputum IL-5 levels were increased in patients with severe particularly eosinophilic forms, whereas IL-13 was suppressed and IL-17 levels did not differ between clusters. Bayesian network analysis separated clinical features from intricately connected inflammatory pathways. YKL-40 levels strongly correlated with neutrophilic asthma and levels of myeloperoxidase, IL-8, IL-6, and IL-6 soluble receptor. MMP1, MMP3, MMP8, and MMP12 levels were associated with severe asthma and were correlated positively with sputum IL-5 levels but negatively with IL-13 levels.

Conclusion

In 2 distinct cohorts we have identified and replicated 6 clinicopathobiologic clusters based on blood and induced sputum measures. Our data underline a disconnect between clinical features and underlying inflammation, suggest IL-5 production is relatively steroid insensitive, and highlight the expression of YKL-40 in patients with neutrophilic inflammation and the expression of MMPs in patients with severe asthma.