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

Immune pathways for translating viral infection into chronic airway disease

To better understand the immune basis for chronic inflammatory lung disease, we analyzed a mouse model of lung disease that develops after respiratory viral infection. The disease that develops in this model is similar to asthma and chronic obstructive pulmonary disease (COPD) in humans and is manifested after the inciting virus has been cleared to trace levels. The model thereby mimics the relationship of paramyxoviral infection to the development of childhood asthma in humans. When the acute lung disease appears in this model (at 3 weeks after viral inoculation), it depends on an immune axis that is initiated by expression and activation of the high-affinity IgE receptor (FcvarepsilonRI) on conventional lung dendritic cells (cDCs) to recruit interleukin (IL)-13-producing CD4(+) T cells to the lower airways. However, when the chronic lung disease develops fully (at 7 weeks after inoculation), it is driven instead by an innate immune axis that relies on invariant natural killer T (iNKT) cells that are programmed to activate macrophages to produce IL-13. The interaction between iNKT cells and macrophages depends on contact between the semi-invariant Valpha14Jalpha18-TCR on lung iNKT cells and the oligomorphic MHC-like protein CD1d on macrophages as well as NKT cell production of IL-13 that binds to the IL-13 receptor (IL-13R) on the macrophage. This innate immune axis is also activated in the lungs of humans with severe asthma or COPD based on detection of increased numbers of iNKT cells and alternatively activated IL-13-producing macrophages in the lung. Together, the findings identify an adaptive immune response that mediates acute disease and an innate immune response that drives chronic inflammatory lung disease in experimental and clinical settings.

Toward understanding of carbohydrate binding and substrate specificity of a glycosyl hydrolase 18 family (GH-18) chitinase from Trichoderma harzianum

Surface plasmon resonance (SPR) has been used to assay the roles of amino acid residues in the substrate binding cleft of Trichoderma harzianum chitinase Chit42, which belongs to the glycoside hydrolase family 18 (GH-18). Nine different Chit42 variants having amino acid mutations along the binding site cleft at subsites -4 to +2 were created and characterized with regard to their affinity toward chitinous and non-chitinous oligosaccharides. The catalytically inactive Chit42 mutant E172Q was used as the template for making the additional mutations. The E172Q mutant bound chitinoligosaccharides (tetra-, penta- and hexamer) with an increasing affinity from 12 to 0.2 microM whereas no binding of chitinbiose, -triose or 3'-sialyl-N-acetyllactosamine (Neu5Acalpha-3Galbeta-4GlcNAc) could be measured, indicative of significantly lower affinity for these shorter oligosaccharides. The strongest binding affinity was displayed toward allosamidin, a transition state analog (K(d) = 3 nM), and this was shown to be dependent on the E172 residue, the acid/base catalyst of Chit42. Hydrogen bonding by the glutamic acid E317 between subsites -2 and -3 and particularly the stacking interactions by tryptophanes at subsites -3 and +2 provided to be important, as mutations to these amino acids had a substantial negative effect to the overall binding affinity. Moreover, the substrate binding specificity of Chit42 could be altered toward binding of GlcNbeta-4(GlcNAc)(4) by providing a counter charge through substitution of residue T133 at subsite -3 against aspartic acid. In addition, the introduction of glutamine and particularly an asparagine residue at position 133 seemed to broaden the substrate preference of Chit42 toward Galbeta-4(GlcNAc)(4).

Association of polymorphisms of the CHI3L1 gene with asthma and atopy: a populations-based study of 6514 Danish adults

Background

YKL-40 is a chitinase-like glycoprotein encoded by the chitinase 3-like 1 gene, CHI3L1, localized at chromosome 1q32.1. Increased levels of serum YKL-40 have been reported to be a biomarker for asthma and a reduced lung function. Interestingly, the C-allele of the -131 C→G (rs4950928) polymorphism of CHI3L1 has been shown to associate with bronchial hyperresponsiveness and reduced lung function suggesting that variations in CHI3L1 may influence risk of asthma. The objective of the present study was to investigate the association of common variation in the CHI3L1 locus with asthma, atopy and lung function in a large population-based sample of adults.

Methods/Principal Findings

Eleven single nucleotide polymorphisms (SNPs) of CHI3L1 including rs4950928 were genotyped in 6514 individuals. Asthma was defined as self-reported history of physician-diagnosed asthma. Total IgE and specific IgE to inhalant allergens were measured on serum samples. Lung function was measured by spirometry. Homozygosity of the rs4950928 G allele as compared to homozygosity of the C allele was associated with self-reported physician diagnosed asthma (OR 1.5 (95% CI, 1.00–2.26)) and with prevalence of atopic asthma (OR 1.93 (95% CI, 1.21–3.07)) after adjustment for age, sex, smoking status, socio-economic class and BMI. Carriers of rs883125 G allele had a significantly lower prevalence of atopy (OR 0.82 (CI, 0.72; 0.94)) as compared to homozygosity of the C allele. None of the SNPs examined were significantly associated with FEV1. However, two SNPs (rs10399931and rs4950930) appeared to be significantly associated with FEV₁/FVC-ratio. Subgroup analyses of never-smokers did not consistently influence the associations in an either positively og negatively way.

Conclusions

In contrast to previous studies, the rs4950928 G allele, and not the C allele, was found to be associated with asthma. A few other SNPs of the CHI3L1 was found to be significantly associated with atopy and FEV1/FVC ratio, respectively. Thus, more studies seem warranted to establish the role of CHI3L1 gene in asthma and atopy.

Ym1/2 promotes Th2 cytokine expression by inhibiting 12/15(S)-lipoxygenase: identification of a novel pathway for regulating allergic inflammation

The Ym1/2 lectin is expressed abundantly in the allergic mouse lung in an IL-13-dependent manner. However, the role of Ym1/2 in the development of allergic airways disease is largely unknown. In this investigation, we show that treatment of mice with anti-Ym1/2 Ab during induction of allergic airways disease attenuated mediastinal lymph node production of IL-5 and IL-13. Ym1/2 was found to be expressed by dendritic cells (DCs) in an IL-13-dependent manner and supplementation of DC/CD4(+) T cell cocultures with Ym1/2 enhanced the ability of IL-13(-/-) DCs to stimulate the secretion of IL-5 and IL-13. Affinity chromatography identified 12/15(S)-lipoxygenase (12/15-LOX) as a Ym1/2-interacting protein and functional studies suggested that Ym1/2 promoted the ability of DCs to stimulate cytokine production by inhibiting 12/15-LOX-mediated catalysis of 12-hydroxyeicosatetraenoic acid (12(S)-HETE). Treatment of DC/CD4(+) T cell cultures with the 12/15-LOX inhibitor baicalein enhanced, whereas 12(S)-HETE inhibited the production of Th2 cytokines. Notably, delivery of 12(S)-HETE to the airways of mice significantly attenuated the development of allergic airways inflammation and the production of IL-5 and IL-13. In summary, our results suggest that production of Ym1/2 in response to IL-13 promotes Th2 cytokine production and allergic airways inflammation by inhibiting the production of 12(S)-HETE by 12/15-LOX.

Modulation of human dermal microvascular endothelial cells by Sarcoptes scabiei in combination with proinflammatory cytokines, histamine, and lipid-derived biologic mediators

The ectoparasitic mite, Sarcoptes scabiei, produces molecules that depress initiation of host inflammatory and immune responses. Some of these down-regulate expression of adhesion molecules or secretion of chemokines or cytokines on and by cultured dermal endothelial cells (HMVEC-D). This study was undertaken to determine if the response of HMVEC-D to scabies is altered in the presence of various proinflammatory cytokines (tumor necrosis factor alpha and interleukins 1alpha, 1beta and 6), histamine, and lipid-derived mediators (prostaglandins D2 and E2, leukotriene B4, platelet activation factor) that likely occur in scabietic lesions in vivo. Scabies extract down-regulated the TNFalpha-induced expression of VCAM-1 by HMVEC-D and this down-regulation still occurred in the presence of the other proinflammatory cytokines, histamine or the lipid-derived mediators. Scabies inhibited the IL-1alpha and IL-1beta-induced secretion of IL-6, while a combination of scabies and histamine or LTB4 reduced the TNFalpha-induced secretion of IL-6. Scabies extract inhibited secretion of IL-8. Histamine, PGD2, PGE2, LTB4, PAF, and IL-6 alone had no effect on this inhibition, but the scabies-induced inhibition of IL-8 secretion was reduced in a dose-dependent fashion in the presence of IL-1alpha and IL-1beta.

Failure to confirm genetic association of the CHI3L1 gene with schizophrenia in Japanese and Chinese populations

Recently, three common polymorphisms in the promoter region of the Chitinase 3-Like 1 (CHI3L1) gene, rs6691378, rs10399805 and rs4950928, have been identified as schizophrenia predisposing single nucleotide polymorphisms (SNPs) in the Han Chinese population. The at-risk haplotype comprising these SNPs was also related to decreased expression of CHI3L1 in peripheral blood cells. In contrast, two independent postmortem brain studies have reported elevated expression of the transcript in the hippocampus and prefrontal cortex, from schizophrenic patients. The gene encodes a secreted glycoprotein (HC-gp39 or YKL40), which is deemed to be involved in the inflammatory process. These pieces of evidence signify the potential importance of CHI3L1 in the pathogenesis of schizophrenia. In this study, we aimed to replicate the prior genetic association findings using two sample sets, one set of Chinese samples (293 pedigrees consisting of 1,163 subjects) that are ethnically identical to those used in the original report and a second set from the relatively close Japanese population (570 schizophrenic patients and 570 matched controls). We analyzed the same five SNPs as in the original study, including the three promoter SNPs. None of these SNPs showed association signals with schizophrenia (P values >0.108) in our sample sets. These results suggest that the genetic contribution of CHI3L1 to schizophrenia is variable, even though it is mechanistically involved in the disease process.

Role of breast regression protein 39 (BRP-39)/chitinase 3-like-1 in Th2 and IL-13-induced tissue responses and apoptosis

Mouse breast regression protein 39 (BRP-39; Chi3l1) and its human homologue YKL-40 are chitinase-like proteins that lack chitinase activity. Although YKL-40 is expressed in exaggerated quantities and correlates with disease activity in asthma and many other disorders, the biological properties of BRP-39/YKL-40 have only been rudimentarily defined. We describe the generation and characterization of BRP-39(-/-) mice, YKL-40 transgenic mice, and mice that lack BRP-39 and produce YKL-40 only in their pulmonary epithelium. Studies of these mice demonstrated that BRP-39(-/-) animals have markedly diminished antigen-induced Th2 responses and that epithelial YKL-40 rescues the Th2 responses in these animals. The ability of interleukin13 to induce tissue inflammation and fibrosis was also markedly diminished in the absence of BRP-39. Mechanistic investigations demonstrated that BRP-39 and YKL-40 play an essential role in antigen sensitization and immunoglobulin E induction, stimulate dendritic cell accumulation and activation, and induce alternative macrophage activation. These proteins also inhibit inflammatory cell apoptosis/cell death while inhibiting Fas expression, activating protein kinase B/AKT, and inducing Faim 3. These studies establish novel regulatory roles for BRP-39/YKL-40 in the initiation and effector phases of Th2 inflammation and remodeling and suggest that these proteins are therapeutic targets in Th2- and macrophage-mediated disorders.

Plasma YKL-40, a new biomarker for atrial fibrillation?

AIMS

The aim of this study was to determine changes in a new potential biomarker plasma YKL-40 in patients with atrial fibrillation (AF) before and after electrical cardioversion (CV).

METHODS AND RESULTS

Plasma concentrations of YKL-40 were measured in 56 patients (mean age 65 years, range 34-84) with persistent AF (lasting mean 128 days, range 14-960), in 19 age-matched patients with permanent AF, and in 19 healthy subjects. The patients with persistent AF underwent CV. Plasma YKL-40 was measured prior to CV, and at follow-up after 24 h, 30 and 180 days. Patients with persistent AF had lower plasma YKL-40 than patients with permanent AF [70 microg/L (42-105)] vs. [138 microg/L (48-225)] (P = 0.003), and higher levels than healthy subjects [41 microg/L (29-52)] (P = 0.001). Patients (n = 22) who were still in sinus rhythm (SR) at follow-up 30 days after CV had unchanged plasma YKL-40 compared with baseline levels. The baseline levels of YKL-40 were correlated to the levels of IL-6, but not to high sensitivity C-reactive protein.

CONCLUSION

Patients with AF have significantly elevated levels of YKL-40. YKL-40 was not a significant predictor of successful CV to SR. Plasma levels of YKL-40 did not fall after restoration of SR.

Expression of survivin in lung eosinophils is associated with pathology in a mouse model of allergic asthma

Humans vary markedly in their propensity to develop asthma, despite often being exposed to similar environmental stimuli. Similarly, mouse strains vary in susceptibility to airways pathology in experimental asthma. Sensitization and aerosol challenge with ovalbumin (OVA) induces eosinophil accumulation, mucus production and airways obstruction in BALB/c and C57BL/6 mice. In contrast, CBA/Ca mice show relatively little pathology. Allergen-induced production of IL-4, IL-5, IL-10 and IFN-gamma was detected in all three strains, with BALB/c mice generating the highest levels of IL-4, IL-5 and IL-10. Microarray analysis was used to identify genes differentially regulated in lung tissue after OVA challenge. Differentially regulated genes in the lungs of the asthma-susceptible C57BL/6 and BALB/c strains numbered 242 and 145, respectively, whereas only 42 genes were differentially expressed in the resistant CBA/Ca strain. In C57BL/6 mice, transcripts were enriched for adhesion molecules and this was associated with high levels of eosinophil recruitment. Differentially regulated genes in the lungs of only the asthma-susceptible strains numbered 64 and several of these have not previously been associated with asthma. Many of the genes differentially regulated in the susceptible strains were enzymes involved in inflammation. Using network analysis, mRNA for the anti-apoptotic protein survivin was found to be up-regulated in the lungs following allergen challenge. Survivin mRNA and protein were also expressed at high levels in eosinophils recovered by bronchoalveolar lavage from BALB/c and C57BL/6 mice. We propose that rapid apoptosis of lung eosinophils due to low expression of survivin contributes to the limitation of pathology in CBA/Ca mice.

Acidic mammalian chitinase regulates epithelial cell apoptosis via a chitinolytic-independent mechanism

Acidic mammalian chitinase (AMCase) is produced during and plays an important role in the pathogenesis of Th2-mediated diseases and antiparasite responses. However, the effector responses of AMCase in these settings have not been adequately defined and the relationship(s) between its chitinolytic and other biologic properties have not been investigated. In these studies, we demonstrate that AMCase protects airway epithelial cells from Fas ligand- and growth factor withdrawal-induced apoptosis. This cytoprotection was associated with Akt phosphorylation and abrogated when the PI3K/Akt pathway was inhibited. Comparable cytoprotection was also seen in experiments comparing wild-type AMCase and mutant AMCase that lacked chitinolytic activity. Importantly, the apoptosis-inhibiting effect of enzymatically active and inactive AMCase was abrogated by treatment with allosamidin. These studies demonstrate that secreted AMCase feeds back in an autocrine and/or paracrine manner to protect pulmonary epithelial cells from growth factor withdrawal- and Fas ligand-induced apoptosis. They also demonstrate that the cytoprotection is mediated via a PI3K/Akt-dependent and allosamidin-sensitive pathway that is independent of the chitinolytic activity of this chitinase.

Animal models of airway inflammation and airway smooth muscle remodelling in asthma

Asthma is a complex disease that involves chronic inflammation and subsequent decline in airway function. The widespread use of animal models has greatly contributed to our understanding of the cellular and molecular pathways underlying human allergic asthma. Animal models of allergic asthma include smaller animal models which offer 'ease of use' and availability of reagents, and larger animal models that may be used to address aspects of allergic airways disease not possible in humans or smaller animal models. This review examines the application and suitability of various animal models for studying mechanisms of airway inflammation and tissue remodelling in allergic asthma, with a specific focus on airway smooth muscle.

Chitinases and chitinase-like proteins: potential therapeutic targets for the treatment of T-helper type 2 allergies

Mammalian chitinase and chitinase-like proteins (CLPs) are a family of mediators increasingly associated with infection, T cell-mediated inflammation, wound healing, allergy and asthma. Although our current knowledge of the function of mammalian chitinases and CLPs is very limited, important information can be deduced from research carried out in lower organisms, and in different immunopathological conditions. Enzymatically active mammalian chitinase proteins may have evolved to degrade the copious amounts of chitin mammals are exposed to on a daily basis, and to form an innate barrier to chitin-containing organisms. CLPs are homologous to chitinases but lack the ability to degrade chitin. It is most striking that both chitinases and CLPs are up-regulated in T-helper type 2 (Th2)-driven conditions, and the first evidence is now emerging that these proteins may accentuate Th2 reactivity, and possibly contribute to the repair process that follows inflammation. Following studies demonstrating that chitinase inhibition leads to an attenuated allergic response, several strategies are being used to develop enzyme inhibitors for therapeutic use in human diseases. In this review, we will summarize recent insights into the effects of chitinases and CLPs in the context of Th2-dominated pathology with particular focus on allergy and asthma, discussing whether chitinase enzyme inhibitors may be of therapeutic value.

The impact of surfactant protein-A on ozone-induced changes in the mouse bronchoalveolar lavage proteome

Background

Ozone is a major component of air pollution. Exposure to this powerful oxidizing agent can cause or exacerbate many lung conditions, especially those involving innate immunity. Surfactant protein-A (SP-A) plays many roles in innate immunity by participating directly in host defense as it exerts opsonin function, or indirectly via its ability to regulate alveolar macrophages and other innate immune cells. The mechanism(s) responsible for ozone-induced pathophysiology, while likely related to oxidative stress, are not well understood.

Methods

We employed 2-dimensional difference gel electrophoresis (2D-DIGE), a discovery proteomics approach, coupled with MALDI-ToF/ToF to compare the bronchoalveolar lavage (BAL) proteomes in wild type (WT) and SP-A knockout (KO) mice and to assess the impact of ozone or filtered air on the expression of BAL proteins. Using the PANTHER database and the published literature most identified proteins were placed into three functional groups.

Results

We identified 66 proteins and focused our analysis on these proteins. Many of them fell into three categories: defense and immunity; redox regulation; and protein metabolism, modification and chaperones. In response to the oxidative stress of acute ozone exposure (2 ppm; 3 hours) there were many significant changes in levels of expression of proteins in these groups. Most of the proteins in the redox group were decreased, the proteins involved in protein metabolism increased, and roughly equal numbers of increases and decreases were seen in the defense and immunity group. Responses between WT and KO mice were similar in many respects. However, the percent change was consistently greater in the KO mice and there were more changes that achieved statistical significance in the KO mice, with levels of expression in filtered air-exposed KO mice being closer to ozone-exposed WT mice than to filtered air-exposed WT mice.

Conclusion

We postulate that SP-A plays a role in reactive oxidant scavenging in WT mice and that its absence in the KO mice in the presence or absence of ozone exposure results in more pronounced, and presumably chronic, oxidative stress.

Asthma-related environmental fungus, Alternaria, activates dendritic cells and produces potent Th2 adjuvant activity

Asthma is thought to result from dysregulated Th2-like airway inflammatory responses to the environment. Although the etiology of asthma is not fully understood in humans, clinical and epidemiological evidence suggest a potential link between exposure to environmental fungi, such as Alternaria, and development and/or exacerbation of asthma. The goal of this project was to investigate the mechanisms of airway Th2 responses by using Alternaria as a clinically relevant model for environmental exposure. Airway exposure of naive animals to an experimental Ag, OVA, or a common allergen, short ragweed pollen, induced no or minimal immune responses to these Ags. In contrast, mice developed strong Th2-like immune responses when they were exposed to these Ags in the presence of Alternaria extract. Extracts of other fungi, such as Aspergillus and Candida, showed similar Th2 adjuvant effects, albeit not as potently. Alternaria stimulated bone marrow-derived dendritic cells (DCs) to express MHC class II and costimulatory molecules, including OX40 ligand, in vitro. Importantly, Alternaria inhibited IL-12 production by activated DCs, and DCs exposed to Alternaria enhanced Th2 polarization of CD4(+) T cells. Furthermore, adoptive airway transfer of DCs, which had been pulsed with OVA in the presence of Alternaria, showed that the recipient mice had enhanced IgE Ab production and Th2-like airway responses to OVA. Thus, the asthma-related environmental fungus Alternaria produces potent Th2-like adjuvant effects in the airways. Such immunogenic properties of certain environmental fungi may explain their strong relationships with human asthma and allergic diseases.

Chitin, chitinases and chitinase-like proteins in allergic inflammation and tissue remodeling

Chitin, the second most abundant polysaccharide in nature after cellulose, consist exoskeleton of lower organisms such as fungi, crustaceans and insects except mammals. Recently, several studies evaluated immunologic effects of chitin in vivo and in vitro and revealed new aspects of chitin regulation of innate and adaptive immune responses. It has been shown that exogenous chitin activates macrophages and other innate immune cells and also modulates adaptive type 2 allergic inflammation. These studies further demonstrate that chitin stimulate macrophages by interacting with different cell surface receptors such as macrophage mannose receptor, toll-like receptor 2 (TLR-2), C-type lectin receptor Dectin-1, and leukotriene B4 receptor (BLT1). On the other hand, a number of chitinase or chitinase-like proteins (C/CLP) are ubiquitously expressed in the airways and intestinal tracts from insects to mammals. In general, these chitinase family proteins confer protective functions to the host against exogenous chitin-containing pathogens. However, substantial body of recent studies also set light on new roles of C/CLP in the development and progression of allergic inflammation and tissue remodeling. In this review, recent findings on the role of chitin and C/CLP in allergic inflammation and tissue remodeling will be highlighted and controversial and unsolved issues in this field of studies will be discussed.

Low grade inflammation as measured by levels of YKL-40: association with an increased overall and cardiovascular mortality rate in an elderly population

BACKGROUND

Low grade inflammation is of pathogenic importance in the development of cardiovascular disease (CVD) and type 2 diabetes. The inflammation marker YKL-40 correlates with insulin resistance and is highly expressed in atherosclerotic plaques. We aimed to investigate whether YKL-40 could predict overall and cardiovascular (CV) mortality in a 50+ years population without known CVD.

METHODS

A representative population sample of 639 individuals aged 50-89 years was recruited from general practices. Examination at baseline included echocardiography and blood and urine samples for CV risk factors and markers including lipids, high sensitive C-reactive protein (hsCRP), N-terminal fragment of pro-brain natriuretic peptide (NT-proBNP) and urinary albumin/creatinine-ratio (UACR). Median follow-up period was 5.0 (0.17-5.28) years.

RESULTS

In subjects without diabetes and CVD at baseline, increasing YKL-40 levels independently predicted overall and CV mortality rate with hazard ratios of 1.58 (95% confidence interval (CI), 1.12-2.23, p=0.009) and 1.57 (95% CI, 1.00-2.46, p=0.049) after adjustment for age, sex, smoking, total cholesterol, hsCRP, NT-proBNP and UACR. In combined Kaplan-Meier analyses, baseline values of both YKL-40 and UACR above median significantly predicted increased cumulative overall and CV mortality rates in subjects without diabetes or CVD at baseline (30.6% vs. <or=8%, respectively 10.6%<or=3%, p<0.0001).

CONCLUSIONS

YKL-40 seems to be an independent predictor of overall and CV mortality in an elderly part of the general population without diabetes and CVD. YKL-40 and UACR are both independent predictors, that seem to predict overall and CV mortality in a synergistic way.

A novel antiinflammatory role for andrographolide in asthma via inhibition of the nuclear factor-kappaB pathway

RATIONALE

Persistent activation of nuclear factor (NF)-kappaB has been associated with the development of asthma. Andrographolide, the principal active component of the medicinal plant Andrographis paniculata, has been shown to inhibit NF-kappaB activity.

OBJECTIVES

We hypothesized that andrographolide may attenuate allergic asthma via inhibition of the NF-kappaB signaling pathway.

METHODS

BALB/c mice sensitized and challenged with ovalbumin (OVA) developed airway inflammation. Bronchoalveolar lavage fluid was assessed for total and differential cell counts, and cytokine and chemokine levels. Serum IgE levels were also determined. Lung tissues were examined for cell infiltration and mucus hypersecretion, and the expression of inflammatory biomarkers. Airway hyperresponsiveness was monitored by direct airway resistance analysis.

MEASUREMENTS AND MAIN RESULTS

Andrographolide dose-dependently inhibited OVA-induced increases in total cell count, eosinophil count, and IL-4, IL-5, and IL-13 levels recovered in bronchoalveolar lavage fluid, and reduced serum level of OVA-specific IgE. It attenuated OVA-induced lung tissue eosinophilia and airway mucus production, mRNA expression of E-selectin, chitinases, Muc5ac, and inducible nitric oxide synthase in lung tissues, and airway hyperresponsiveness to methacholine. In normal human bronchial epithelial cells, andrographolide blocked tumor necrosis factor-alpha-induced phosphorylation of inhibitory kappaB kinase-beta, and downstream inhibitory kappaB alpha degradation, p65 subunit of NF-kappaB phosphorylation, and p65 nuclear translocation and DNA-binding activity. Similarly, andrographolide blocked p65 nuclear translocation and DNA-binding activity in the nuclear extracts from lung tissues of OVA-challenged mice.

CONCLUSIONS

Our findings implicate a potential therapeutic value of andrographolide in the treatment of asthma and it may act by inhibiting the NF-kappaB pathway at the level of inhibitory kappaB kinase-beta activation.

Elevated Plasma YKL-40 Predicts Increased Risk of Gastrointestinal Cancer and Decreased Survival After Any Cancer Diagnosis in the General Population

Purpose

Elevated plasma YKL-40 is a biomarker of poor prognosis in cancer patients. We tested the hypotheses that elevated plasma YKL-40 predicts risk of cancer as well as survival after a cancer diagnosis in the general population.

Patients and Methods

A prospective cohort study of 8,899 subjects (20 to 95 years) from the Danish general population, the Copenhagen City Heart Study, observed for 11 years for cancer incidence and 14 years for death: 1,432 participants had a first incident cancer, 968 of these died. Hazard ratios (HRs) for cancer events and death after events according to plasma YKL-40 in sex and 10 years age percentile categories: 0% to 33%, 34% to 66%, 67% to 90%, 91% to 95%, and 96% to 100%.

Results

The cumulative incidence of gastrointestinal cancer increased with increasing YKL-40 (trend P < .0001). Multifactorially adjusted HRs for gastrointestinal cancer were 1.0 (95% CI, 0.7 to 1.5) for YKL-40 in category 34% to 66%, 1.5 for 67% to 90% (95% CI, 1.0 to 2.3), 2.4 for 91% to 95%, (95% CI, 1.3 to 4.6), and 3.4 for 96% to 100% (95% CI, 1.9 to 6.1) versus YKL-40 category 0% to 33% (P < .0001). Participants with any cancer event and YKL-40 category 91% to 100% had a median survival time after the diagnosis of 1 year versus 4 years in participants with YKL-40 category 0% to 33% (P < .0001). Corresponding values for gastrointestinal cancer were 6 months versus 1 year (P = .007). Multifactorially adjusted HRs for early death were 1.8 (95% CI, 1.3 to 2.5; P < .0001) after any cancer and 2.4 (95% CI, 1.3 to 4.3; P = .005) after gastrointestinal cancer in participants with YKL-40 category 91% to 100% versus 0% to 33%.

Conclusion

In the general population, elevated plasma YKL-40 predicts increased risk of gastrointestinal cancer and decreased survival after any cancer diagnosis.

A functional variation in CHI3L1 is associated with severity of liver fibrosis and YKL-40 serum levels in chronic hepatitis C infection

BACKGROUND/AIMS

YKL-40 is a chitinase-like protein involved in matrix remodelling and a non-invasive fibrosis marker. We assessed whether a functional promoter polymorphism in CHI3L1, encoding YKL-40, is associated with HCV-induced liver fibrosis and influences YKL-40 serum concentrations.

METHODS

The CHI3L1 -131G-->C promoter polymorphism was genotyped in two cohorts of HCV infected patients (n=440) by 5'-endonuclease assays. Histological fibrosis scores and YKL-40 serum levels (ELISA) were associated with CHI3L1 -131G-->C by quantitative and qualitative genetic analyses and corrected by multivariate analysis.

RESULTS

CHI3L1 -131G-->C genotype was strongly associated with the stage of liver fibrosis in the screening (n=265, P=0.001) and validation cohort (n=175, P=0.009). Homozygous carriers of the G allele were protected from severe fibrosis (F3/F4). This association was confirmed after correction for age and gender. Functionally, the G allele was associated with reduced serum levels of YKL-40 in HCV infected patients (P=0.002).

CONCLUSIONS

The CHI3L1 promoter polymorphism -131G-->C determines YKL-40 serum levels and is associated with the severity of HCV-induced liver fibrosis. These results suggest a functional role of YKL-40 in liver fibrogenesis and should be taken into account when using YKL-40 as a non-invasive fibrosis marker.

The cytokine network in asthma and chronic obstructive pulmonary disease

Asthma and chronic obstructive pulmonary disease (COPD) are very common inflammatory diseases of the airways. They both cause airway narrowing and are increasing in incidence throughout the world, imposing enormous burdens on health care. Cytokines play a key role in orchestrating the chronic inflammation and structural changes of the respiratory tract in both asthma and COPD and have become important targets for the development of new therapeutic strategies in these diseases.

YKL-40 is elevated in patients with chronic obstructive pulmonary disease and activates alveolar macrophages

YKL-40 is a chitin-binding protein that is elevated in patients with various inflammatory conditions associated with ongoing remodeling. We investigated whether the levels of YKL-40 were up-regulated in the circulation and the airways of patients with chronic obstructive pulmonary disease (COPD), and whether it promoted the production of inflammatory mediators from macrophages. Serum, bronchoalveolar lavage (BAL), bronchial biopsies, lung tissue specimens, and alveolar macrophages from never-smokers (n = 15), smokers without COPD (n = 20), and smokers with COPD (n = 30) were assessed for YKL-40 levels and immunolocalization. In addition, YKL-40-induced mediator release from alveolar macrophages was examined. We found that smokers with COPD had elevated levels of YKL-40 in serum (p </= 0.027) and BAL (p </= 0.007), more YKL-40-positive cells in bronchial biopsies (p </= 0.03), and a greater proportion of alveolar macrophages expressing YKL-40 than smokers without COPD or never-smokers. YKL-40 levels in serum and BAL were associated with airflow obstruction (pre-beta(2) agonist forced expiratory volume in 1 s, r(s) = -0.3892, p = 0.0072 and r(s) = -0.5491, p < 0.0001, respectively) and impaired diffusion lung capacity (transfer factor of the lung for carbon monoxide, r(s) = -0.4667, p = 0.002 and r(s) = -0.3854, p = 0.0045, respectively). TNF-alpha stimulated YKL-40 synthesis in alveolar macrophages from smokers with COPD, and exposure of these cells to YKL-40 promoted the release of IL-8, MCP-1, MIP-1alpha, and metalloproteinase-9. We conclude that YKL-40 is up-regulated in COPD, in which it may contribute to tissue inflammation and remodeling by sustaining the synthesis of proinflammatory and fibrogenic chemokines and of metalloproteinases by alveolar macrophages.

Genetic variation in the promoter region of chitinase 3-like 1 is associated with atopy

RATIONALE

Atopy or atopic syndrome is an allergic hypersensitivity subject to hereditary influences. Aberrant expression of chitinase 3-like 1 (CHI3L1), also known as YKL-40 or HC gp-39, is involved in the pathogenesis of inflammatory and allergic diseases.

OBJECTIVES

The genetic contribution of CHI3L1 gene to atopic susceptibility was investigated using an integrated population genetic and molecular analysis.

METHODS

Genetic variations in CHI3L1 were identified and genotyped in 295 unrelated patients with atopy and 180 control subjects. Serum YKL-40 and IgE levels were analyzed according to genotype. The effects of a promoter polymorphism (g.-247C/T) on promoter activity were examined in reporter and protein binding assays.

MEASUREMENTS AND MAIN RESULTS

In the case-control association analysis, the g.-247C/T polymorphism at the promoter region (rs10399805; P = 0.0062) and the IVS7+82C/T polymorphism at intron 7 (rs2275353; P = 0.0056) of CHI3L1 showed a significant association with atopy. Subjects with the g.-247T risk allele had significantly higher serum YKL-40 (P < 0.0001) and IgE (P = 0.012) levels. An in vitro promoter assay using THP-1 human monocyte cells revealed that the C to T conversion at g.-247 induced a more than twofold increase of reporter gene expression. Moreover, the g.-247T allele showed an increased affinity for CCAAT enhancer-binding protein, a well known transcriptional activator, by electrophoretic mobility shift assay. Accordingly, subjects with the g.-247TT genotype showed a 2.5-fold increase in CHI3L1 mRNA expression in peripheral blood cells compared with those with the g.-247CC genotype.

CONCLUSIONS

These results strongly suggest that the g.-247C/T polymorphism in the CHI3L1 promoter region is associated with the risk of atopy.

Genes in asthma: new genes and new ways

PURPOSE OF REVIEW

Asthma is a disease of unknown aetiology characterized by intermittent inflammation of the small airways of the lung. Asthma is familial due to an interaction between strong genetic and environmental factors. This article aims to review the current understanding of the genetic factors underlying asthma, looking historically as well as highlighting the latest developments in the field.

RECENT FINDINGS

Findings from recent candidate gene studies and microsatellite genome screens have continued to highlight the importance of the epithelial barrier and its defence mechanisms in asthma. Completion of the human genome sequence and the advent of genome-wide association studies have resulted in the identification of two novel asthma susceptibility genes, ORMDL3 and CHI3L1, in the past year.

SUMMARY

With the advances in genetics and genomics substantial steps have been taken in the last decade in understanding the genetic factors underlying asthma. Studies have highlighted the importance of the role of the epithelium with many of the genes so far identified being expressed in this key barrier. With the application of genome-wide expression, microRNA studies, metagenomics, proteomics and metabolomics the next decade will undoubtedly result in a further substantial increment in our understanding of the mechanisms underlying asthma.

Chitin regulation of immune responses: an old molecule with new roles

Chitin, the second most abundant polysaccharide in nature, is commonly found in lower organisms such as fungi, crustaceans, and insects, but not in mammals. Although the non-specific anti-viral and anti-tumor activities of chitin/chitin derivatives were described two decades ago, the immunological effects of chitin have been only recently been addressed. Recent studies demonstrated that chitin has complex and size-dependent effects on innate and adaptive immune responses including the ability to recruit and activate innate immune cells and induce cytokine and chemokine production via a variety of cell surface receptors including macrophage mannose receptor, toll-like receptor 2 (TLR-2), and Dectin-1. They also demonstrated adjuvant effects of chitin in allergen-induced type 1 or type 2 inflammation and provided insights into the important roles of chitinases and chitinase-like proteins (C/CLP) in pulmonary inflammation. The status of the field and areas of controversy are highlighted.

Chitotriosidase is the primary active chitinase in the human lung and is modulated by genotype and smoking habit

BACKGROUND

Chitinolytic enzymes play important roles in the pathophysiology of allergic airway responses in mouse models of asthma. Acidic mammalian chitinase (AMCase) and chitotriosidase (CHIT1) have chitinolytic activity, but relatively little is known about their expression in human asthma.

OBJECTIVE

We sought to determine the expression and activity of AMCase and CHIT1 in healthy subjects, subjects with asthma, and habitual smokers, taking account of the null 24-bp duplication in the CHIT1 gene.

METHODS

We measured chitinase activity in bronchoalveolar lavage (BAL) fluid at multiple pHs by using a synthetic chitin substrate. We also determined AMCase and CHIT1 gene expression in epithelial brushings and BAL fluid macrophages by means of real time RT-PCR. Paired DNA samples were genotyped for the CHIT1 duplication.

RESULTS

In all subgroups the pH profile of chitinase activity in BAL fluid matched that of CHIT1, but not AMCase, and chitinase activity was absent in subjects genetically deficient in active CHIT1. Although AMCase protein was detectable in lavage fluid, AMCase transcripts in macrophages were consistent with an isoform lacking enzymatic activity. Median chitinase activity in BAL fluid tended to be lower than normal in asthmatic subjects but was increased 7-fold in habitual smokers, where CHIT1 gene expression in macrophages was increased.

CONCLUSIONS

Chitinase activity in the lung is the result of CHIT1 activity. Although AMCase protein is detectable in the lung, our data indicate that it is inactive. Chitinase activity is not increased in subjects with asthma and in fact tends to be decreased. The high levels of chitinase activity in habitual smokers result from upregulation of CHIT1 gene expression, especially in macrophages.

Innate antifungal immunity of human eosinophils mediated by a beta 2 integrin, CD11b

Eosinophils produce and release various proinflammatory mediators and also show immunomodulatory and tissue remodeling functions; thus, eosinophils may be involved in the pathophysiology of asthma and other eosinophilic disorders as well as host defense. Several major questions still remain. For example, how do human eosinophils become activated in diseased tissues or at the site of an immune response? What types of host immunity might potentially involve eosinophils? Herein, we found that human eosinophils react vigorously to a common environmental fungus, Alternaria alternata, which is implicated in the development and/or exacerbation of human asthma. Eosinophils release their cytotoxic granule proteins, such as eosinophil-derived neurotoxin and major basic protein, into the extracellular milieu and onto the surface of fungal organisms and kill the fungus in a contact-dependent manner. Eosinophils use their versatile beta(2) integrin molecule, CD11b, to adhere to a major cell wall component, beta-glucan, but eosinophils do not express other common fungal receptors, such as dectin-1 and lactosylceramide. The I-domain of CD11b is distinctively involved in the eosinophils' interaction with beta-glucan. Eosinophils do not react with another fungal cell wall component, chitin. Because human eosinophils respond to and kill certain fungal organisms, our findings identify a previously unrecognized innate immune function for eosinophils. This immune response by eosinophils may benefit the host, but, in turn, it may also play a role in the development and/or exacerbation of eosinophil-related allergic human diseases, such as asthma.

Acidic mammalian chitinase is secreted via an ADAM17/epidermal growth factor receptor-dependent pathway and stimulates chemokine production by pulmonary epithelial cells

Acidic mammalian chitinase (AMCase) is expressed in an exaggerated fashion in epithelial cells at sites of pulmonary T helper cell type 2 inflammation and plays important roles in the pathogenesis of anti-parasite and asthma-like responses. However, the mechanisms that control epithelial cell AMCase secretion and its effector responses have not been adequately defined. To address these issues, we used in vivo and in vitro experimental systems to define the pathways of epithelial AMCase secretion and its epithelial regulatory effects. Here we demonstrate that, in murine T helper cell type 2 modeling systems, AMCase colocalizes with the epidermal growth factor receptor (EGFR) and ADAM17 (a membrane disintegrin and metallopeptidase 17) in lung epithelial cells. In vitro cotransfection experiments in A549 cells demonstrated that AMCase and EGFR physically interact with each other. Cotransfection of AMCase and EGFR also increased, whereas EGFR inhibition decreased AMCase secretion. Interestingly, AMCase secretion was not significantly altered by treatment with EGF but was significantly decreased when the upstream EGFR transactivator ADAM17 was inhibited. AMCase secretion was also decreased when the EGFR-downstream Ras was blocked. Transfected and recombinant AMCase induced epithelial cell production of CCL2, CCL17, and CXCL8. These studies demonstrate that lung epithelial cells secrete AMCase via an EGFR-dependent pathway that is activated by ADAM17 and mediates its effects via Ras. They also demonstrate that the AMCase that is secreted feeds back in an autocrine and/or paracrine fashion to stimulate pulmonary epithelial cell chemokine production.

Endotyping asthma: new insights into key pathogenic mechanisms in a complex, heterogeneous disease

Clinical asthma is very widely assumed to be the net result of excessive inflammation driven by aberrant T-helper-2 (Th2) immunity that leads to inflamed, remodelled airways and then functional derangement that, in turn, causes symptoms. This notion of disease is actually poorly supported by data, and there are substantial discrepancies and very poor correlation between inflammation, damage, functional impairment, and degree of symptoms. Furthermore, this problem is compounded by the poor understanding of the heterogeneity of clinical disease. Failure to recognise and discover the underlying mechanisms of these major variants or endotypes of asthma is, arguably, the major intellectual limitation to progress at present. Fortunately, both clinical research and animal models are very well suited to dissecting the cellular and molecular basis of disease endotypes. This approach is already suggesting entirely novel pathways to disease-eg, alternative macrophage specification, steroid refractory innate immunity, the interleukin-17-regulatory T-cell axis, epidermal growth factor receptor co-amplification, and Th2-mimicking but non-T-cell, interleukins 18 and 33 dependent processes that can offer unexpected therapeutic opportunities for specific patient endotypes.

Expanding roles for leukotrienes in airway inflammation

Leukotrienes (LTs) are lipid mediators derived from the 5-lipoxygenase pathway of arachidonic acid metabolism. Cysteinyl (cys) LTs C(4), D(4), and E(4) are long known to contribute to airway contractile responses via ligation of the cysLT1 receptor, and cysLT1 antagonists are beneficial in some patients with asthma. Research advances over the past several years suggest that cysLT1 also mediates the ability of cysLTs to modulate inflammation, immune responses, and airway remodeling. Although less is known about an additional receptor, cysLT2, emerging evidence indicates that it likely also contributes to cysLT actions promoting inflammation, vascular permeability, and perhaps fibrosis. LTB(4), best known as a neutrophil chemoattractant, is now recognized to exert other important effects contributing to inflammatory and immune responses. These recent data highlight a growing appreciation for LTs as pleiotropic effectors, which are integral components in the network of molecules that mediate the expression of asthma.

Selective repression of YKL-40 by NF-kappaB in glioma cell lines involves recruitment of histone deacetylase-1 and -2

Here we show that in contrast to other cancer types, tumor necrosis factor (TNF)-alpha suppresses YKL-40 expression in glioma cell lines in a nuclear factor kappaB (NF-kappaB) dependent manner. Even though TNF-alpha causes recruitment of p65 and p50 subunits of NF-kappaB to the YKL-40 promoter in all cell types, recruitment of histone deacetylases (HDAC)-1 and -2, and a consequent deacetylation of histone H3 at the YKL-40 promoter occurs only in glioma cells. Importantly, using chromatin immunoprecipitation assays in frozen glioblastoma multiforme tissues, we show that YKL-40 levels decrease consistent with HDAC1 recruitment despite high levels of nuclear p-p65. This study presents a paradigm for NF-kappaB regulation of one of its targets in a strict cell type specific manner.

Human innate immune responses to hexamethylene diisocyanate (HDI) and HDI-albumin conjugates

BACKGROUND

Isocyanates, a leading cause of occupational asthma, are known to induce adaptive immune responses; however, innate immune responses, which generally precede and regulate adaptive immunity, remain largely uncharacterized.

OBJECTIVE

The aim of the study was to identify and characterize the cellular, molecular and systemic innate immune responses induced by hexamethylene diisocyanate (HDI).

METHODS

Human peripheral blood mononuclear cells (PBMCs) were stimulated in vitro with HDI-albumin conjugates or control antigen, and changes in phenotype, gene and protein expression were characterized by flow cytometry, microarray, Western blot and ELISA. Cell uptake of isocyanate was visualized microscopically using HDI-albumin conjugates prepared with fluorescently labelled albumin. In vivo, human HDI exposure was performed via a specific inhalation challenge, and subsequent changes in PBMCs and serum proteins were measured by flow cytometry and ELISA. Genotypes were determined by PCR.

RESULTS

Human monocytes take up HDI-albumin conjugates and undergo marked changes in morphology and gene/protein expression in vitro. The most significant (P-values 0.007-0.05) changes in microarray gene expression were noted in lysosomal genes, especially peptidases and proton pumps involved in antigen processing. Chemokines that regulate monocyte/macrophage trafficking (MIF, MCP-1) and pattern-recognition receptors that bind chitin (chitinases) and oxidized low-density lipoprotein (CD68) were also increased following isocyanate-albumin exposure. In vivo, HDI-exposed subjects exhibited a drastic increase in the percentage of PBMCs with the same HDI-albumin responsive phenotype characterized in vitro (HLA-DR(+)/CD11c(+) with altered light scatter properties). An exposure-dependent decrease (46+/-11%; P<0.015) in serum concentrations of chitinase 3-like-1 was also observed in individuals who lack the major (type 1) human chitinase (due to genetic polymorphism), but not in individuals possessing at least one functional chitinase-1 allele.

CONCLUSIONS

Previously unrecognized innate immune responses to HDI and HDI-albumin conjugates could influence the clinical spectrum of exposure reactions.

T(H)2 adjuvants: implications for food allergy

A persistent question for immunologists studying allergic disease has been to define the characteristics of a molecule that make it allergenic. There has been substantial progress elucidating mechanisms of innate priming of T(H)2 immunity in the past several years. These accumulating data demonstrate that T(H)2 immunity is actively induced by an array of molecules, many of which were first discovered in the context of antihelminthic immune responses. Similar intrinsic or associated activities are now known to account for the T(H)2 immunogenicity of some allergens, and may prove to play a role for many more. In this review, we discuss what has been discovered regarding molecules that induce innate immune activation and the pathways that promote T(H)2-polarized immune responses generally, and specifically what role these mechanisms may play in food allergy from models of food allergy and the study of T(H)2 gastrointestinal adjuvants.

Pulmonary cryptococcosis induces chitinase in the rat

Background

We previously demonstrated that chronic pulmonary infection with Cryptococcus neoformans results in enhanced allergic inflammation and airway hyperreactivity in a rat model. Because the cell wall of C. neoformans consists of chitin, and since acidic mammalian chitinase (AMCase) has recently been implicated as a novel mediator of asthma, we sought to determine whether such infection induces chitinase activity and expression of AMCase in the rat.

Methods

We utilized a previously-established model of chronic C. neoformans pulmonary infection in the rat to analyze the activity, expression and localization of AMCase.

Results

Our studies indicate that intratracheal inoculation of C. neoformans induces chitinase activity within the lung and bronchoalveolar lavage fluid of infected rats. Chitinase activity is also elicited by pulmonary infection with other fungi (e.g. C. albicans), but not by the inoculation of dead organisms. Enhanced chitinase activity reflects increased AMCase expression by airway epithelial cells and alveolar macrophages. Systemic cryptococcosis is not associated with increased pulmonary chitinase activity or AMCase expression.

Conclusion

Our findings indicate a possible link between respiratory fungal infections, including C. neoformans, and asthma through the induction of AMCase.

Distinct roles for IL-13 and IL-4 via IL-13 receptor alpha1 and the type II IL-4 receptor in asthma pathogenesis

IL-13 and IL-4 are central T helper 2 (Th2) cytokines in the immune system and potent activators of inflammatory responses and fibrosis during Th2 inflammation. Recent studies using Il13ra1(-/-) mice have demonstrated a critical role for IL-13 receptor (IL-13R) alpha1 in allergen-induced airway responses. However, these observations require further attention especially because IL-4 can induce similar lung pathology to IL-13, independent of IL-13, and is still present in the allergic lung. Thus, we hypothesized that IL-13Ralpha1 regulates IL-4-induced responses in the lung. To dissect the role of IL-13Ralpha1 and the type I and II IL-4Rs in experimental asthma, we examined lung pathology induced by allergen, IL-4, and IL-13 challenge in Il13ra1(-/-) mice. We report that IL-13Ralpha1 is essential for baseline IgE production, but Th2 and IgE responses to T cell-dependent antigens are IL-13Ralpha1-independent. Furthermore, we demonstrate that increased airway resistance, mucus, TGF-beta, and eotaxin(s) production, but not cellular infiltration, are critically dependent on IL-13Ralpha1. Surprisingly, our results identify a CCR3- and IL-13Ralpha1-independent pathway for lung eosinophilia. Global expression profiling of lungs from mice stimulated with allergen or IL-4 demonstrated that marker genes of alternatively activated macrophages are differentially regulated by the type I and type II IL-4R. Taken together, our data provide a comprehensive mechanistic analysis of the critical role by which IL-13Ralpha1 mediates allergic lung pathology and highlight unforeseen roles for the type II IL-4R.

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.

Effect of chitinase inhibitors on endotoxin-induced uveitis (EIU) in rabbits

The acidic mammalian chitinase (AMCase) is significantly increased in tears of human allergic conjunctivitis. The aim of the study was to investigate the effects of chitinase inhibitors, allosamidin and caffeine versus dexamethasone, in rabbit endotoxin-induced uveitis (EIU). EIU was induced in rabbits by a single intravitreal injection of 100ng/10microl lipopolysaccharide (LPS). Drugs at four different concentrations (0.1, 0.01, 0.001 and 0.0001mM) were topically applied to the rabbit eye five times in 24h. Tears were collected at 0, 6 and 24h after LPS to measure the AMCase activity. The effect of treatment was also evaluated at the same time by slit lamp examination. Tear AMCase activity increased 6 and 24h after LPS injection. The AMCase activity was significantly inhibited in all treated groups with all doses of allosamidin and caffeine except with the lowest concentration. A higher AMCase inhibition at 24h was found with allosamidin and caffeine compared to dexamethasone. Moreover, topical administration of allosamidin, caffeine and dexamethasone produced a remarkable reduction of inflammatory signs, in the order: dexamethasone>caffeine>allosamidin. AMCase inhibitors showed in this rabbit model of uveitis a notable control of inflammatory response with a significant reduction of AMCase activity in tears with caffeine and allosamidin. These results support the key role of AMCase in the pathogenesis of human ocular inflammatory diseases and the therapeutic effect of AMCase inhibitors on experimental uveitis.