Intelectin is required for IL-13-induced monocyte chemotactic protein-1 and -3 expression in lung epithelial cells and promotes allergic airway inflammation

Exploring the Role of Lactoferrin in Managing Allergic Airway Diseases among Children: Unrevealing a Potential Breakthrough

The prevalence of allergic diseases has dramatically increased among children in recent decades. These conditions significantly impact the quality of life of allergic children and their families. Lactoferrin, a multifunctional glycoprotein found in various biological fluids, is emerging as a promising immunomodulatory agent that can potentially alleviate allergic diseases in children. Lactoferrin's multifaceted properties make it a compelling candidate for managing these conditions. Firstly, lactoferrin exhibits potent anti-inflammatory and antioxidant activities, which can mitigate the chronic inflammation characteristic of allergic diseases. Secondly, its iron-binding capabilities may help regulate the iron balance in allergic children, potentially influencing the severity of their symptoms. Lactoferrin also demonstrates antimicrobial properties, making it beneficial in preventing secondary infections often associated with respiratory allergies. Furthermore, its ability to modulate the immune response and regulate inflammatory pathways suggests its potential as an immune-balancing agent. This review of the current literature emphasises the need for further research to elucidate the precise roles of lactoferrin in allergic diseases. Harnessing the immunomodulatory potential of lactoferrin could provide a novel add-on approach to managing allergic diseases in children, offering hope for improved outcomes and an enhanced quality of life for paediatric patients and their families. As lactoferrin continues to capture the attention of researchers, its properties and diverse applications make it an intriguing subject of study with a rich history and a promising future.

A common polymorphism in the Intelectin-1 gene influences mucus plugging in severe asthma

By incompletely understood mechanisms, type 2 (T2) inflammation present in the airways of severe asthmatics drives the formation of pathologic mucus which leads to airway mucus plugging. Here we investigate the molecular role and clinical significance of intelectin-1 (ITLN-1) in the development of pathologic airway mucus in asthma. Through analyses of human airway epithelial cells we find that ITLN1 gene expression is highly induced by interleukin-13 (IL-13) in a subset of metaplastic MUC5AC+ mucus secretory cells, and that ITLN-1 protein is a secreted component of IL-13-induced mucus. Additionally, we find ITLN-1 protein binds the C-terminus of the MUC5AC mucin and that its deletion in airway epithelial cells partially reverses IL-13-induced mucostasis. Through analysis of nasal airway epithelial brushings, we find that ITLN1 is highly expressed in T2-high asthmatics, when compared to T2-low children. Furthermore, we demonstrate that both ITLN-1 gene expression and protein levels are significantly reduced by a common genetic variant that is associated with protection from the formation of mucus plugs in T2-high asthma. This work identifies an important biomarker and targetable pathways for the treatment of mucus obstruction in asthma.

The Role of Peptides in Asthma-Obesity Phenotype

The co-occurrence of asthma and obesity is becoming an increasingly common health problem. It became clear that both diseases are closely related, since overweight/obesity are associated with an increased risk of asthma development, and more than half of the subjects with severe or difficult-to-treat asthma are obese. Currently, there are no specific guidelines for the treatment of this group of patients. The mechanisms involved in the asthma-obesity phenotype include low-grade chronic inflammation and changes in pulmonary physiology. However, genetic predispositions, gender differences, comorbid conditions, and gut microbiota also seem to be important. Regulatory peptides affect many processes related to the functioning of the respiratory tract and adipose tissue. Adipokines such as leptin, adiponectin, resistin, and the less studied omentin, chemerin, and visfatin, as well as the gastrointestinal hormones ghrelin, cholecystokinin, glucagon-like peptide-1, and neuropeptides, including substance P or neuropeptide Y, can play a significant role in asthma with obesity. The aim of this article is to provide a concise review of the contribution of particular peptides in inflammatory reactions, obesity, asthma, and a combination of both diseases, as well as emphasize their potential role in the effective treatment of the asthma-obesity phenotype in the future.

Omentin expression in the ovarian follicles of Large White and Meishan sows during the oestrous cycle and in vitro effect of gonadotropins and steroids on its level: Role of ERK1/2 and PI3K signaling pathways

Omentin (ITLN1) is a novel adipokine mainly expressed in the white adipose tissue. It plays a crucial role in the metabolic homeostasis and insulin sensitivity. Our last study documented that ITLN1 levels in the adipose tissue and plasma are lower in fat Meishan (MS) compared to normal weight Large White (LW) pigs. The aim of this study was to investigate transcript and protein concentrations of ITLN1 as well as its immunolocalisation in the ovarian follicles and examine the molecular mechanism involved in the regulation of its expression in response to gonadotropins (FSH, LH) and steroids (P4, T, E2). Ovarian follicles were collected from LW and MS sows on days 2-3, 10-12, and 14-16 of the oestrous. We found the elevated ITLN1 expression in the ovarian follicles and the increase of concentrations in follicular fluid (FF) of LW pigs vs MS pigs; in both breeds of pigs, the levels of ITLN1 increased with the oestrous progression. We noted ITLN1 signals in oocyte, granulosa and theca cells. Gonadotropins and steroids increased ITLN1 levels in the ovarian follicle cells of LW pigs, while in MS pigs, we observed only the stimulatory effect of LH and T. Both extracellular signal-regulated kinase (ERK1/2) and phosphatidylinositol 3'-kinase (PI3K) were involved in the regulation of ITLN1. Our study demonstrated the levels and regulation of ITLN1 in the porcine ovarian follicles through ERK1/2 and PI3K signaling pathways.

Plasma level of omentin-1, its expression, and its regulation by gonadotropin-releasing hormone and gonadotropins in porcine anterior pituitary cells

Omentin-1 (OMNT1) is an adipokine involved in the regulation of energy metabolism, insulin sensitivity, and reproduction. The present study was the first to investigate the plasma levels and expression of OMNT1 in the anterior pituitary (AP) gland on days 2-3, 10-12, 14-16, and 17-19 of the estrous cycle of normal-weight Large White (LW) and fat Meishan (MS) pigs. Next, we determined the effect of GnRH, LH, and FSH on the OMNT1 levels in cultured AP cells. The gene and protein expression of OMNT1 in AP fluctuated during the estrous cycle, with a higher expression in MS than in LW (except on days 10-12). However, plasma levels of OMNT1 were higher in LW than in MS. OMNT1 was localized in somatotrophs, lactotrophs, thyrotrophs, and gonadotrophs. In LW pituitary cells, GnRH and gonadotropins stimulated OMNT1 protein expression (except FSH on days 14-16) and had no effect on OMNT1 levels in the culture medium. In MS pituitary cells, we observed that GnRH and LH increased while FSH decreased OMNT1 protein expression. These findings showed OMNT1 expression and regulation in the porcine AP and suggested that OMNT1 could be a new player modifying the pituitary functions.

A 'tad' of hope in the fight against airway disease

Xenopus tadpoles have emerged as a powerful in vivo model system to study mucociliary epithelia such as those found in the human airways. The tadpole skin has mucin-secreting cells, motile multi-ciliated cells, ionocytes (control local ionic homeostasis) and basal stem cells. This cellular architecture is very similar to the large airways of the human lungs and represents an easily accessible and experimentally tractable model system to explore the molecular details of mucociliary epithelia. Each of the cell types in the tadpole skin has a human equivalent and a conserved network of genes and signalling pathways for their differentiation has been discovered. Great insight into the function of each of the cell types has been achieved using the Xenopus model and this has enhanced our understanding of airway disease. This simple model has already had a profound impact on the field but, as molecular technologies (e.g. gene editing and live imaging) continue to develop apace, its use for understanding individual cell types and their interactions will likely increase. For example, its small size and genetic tractability make it an ideal model for live imaging of a mucociliary surface especially during environmental challenges such as infection. Further potential exists for the mimicking of human genetic mutations that directly cause airway disease and for the pre-screening of drugs against novel therapeutic targets.

Early Events Triggering the Initiation of a Type 2 Immune Response

Type 2 immune responses are typically associated with protection against helminth infections and also with harmful inflammation in response to allergens. Recent advances have revealed that type 2 immunity also contributes to sterile inflammation, cancer, and microbial infections. However, the early events that initiate type 2 immune responses remain poorly defined. New insights reveal major contributions from danger-associated molecular patterns (DAMPs) in the initiation of type 2 immune responses. In this review, we examine the molecules released by the host and pathogens and the role they play in mediating the initiation of mammalian innate type 2 immune responses under a variety of conditions.

A comparative review of intelectins

Intelectin (ITLN) is a new type of glycan-binding lectin. It has been demonstrated to agglutinate bacteria probably due to its carbohydrate-binding capacity, suggesting its role in an innate immune response. It is involved not only in many physiological processes but also in some human diseases such as asthma, heart disease, inflammatory bowel disease, chronic obstructive pulmonary disease and cancer. Up to now, intelectin orthologs have been identified in placozoans, urochordatas, cephalochordates and several vertebrates, such as cyclostomata, fish, amphibians and mammals. Although the sequences of intelectins in different species are conserved, their expression patterns, quaternary structures and functions differ considerably among and within species. We summarize the evolution of the intelectin gene family, the tissue distribution, structure and functions of intelectins. We conclude that intelectin plays a role in innate immune response and there are still potential functions of intelectin awaiting discovery.

Different effects of titanium dioxide nanoparticles instillation in young and adult mice on DNA methylation related with lung inflammation and fibrosis

Wide use of titanium dioxide nanoparticles (TiO₂ NPs) as white pigments induces unintentionally release in environment which increases concerns about their adverse health effects on respiratory system. So it is crucial to get a deep understanding of the disease process and molecular mechanism. Epigenetic mechanisms, such as DNA methylation, have been found to play a role in the development of lung diseases by affecting expression of key genes. In addition, there could be potential different toxic effects of TiO₂ NPs between young and adult. Thus, the comparative toxicity of TiO₂ NPs in 5-week (young) and 10-week (adult) old NIH mice is investigated in this study following nasal inhalation of TiO₂ NPs at dose of 20 mg/kg (body weight)/day for 30 days. Global DNA methylation and hydroxymethylation in lung were measured. Promoter methylation of inflammatory genes (IFN-γ and TNF-α) and tissue fibrosis gene (Thy-1) were determined. Additional, RNA-sequencing runs were performed on the pulmonic libraries. We found the induced pulmonary inflammation and fibrosis were more severe in young mice. Decreased global methylation and hydroxymethylation were only found in the young group. The altered methylation in promoter of TNF-α and Thy-1 were found to play a role in the inflammatory response and fibration. RNA-sequencing showed that in pathways in cancer expression of 197 genes was up-regulated in the young mice more that in the adult mice. All these results suggested that the young ages are more sensitive to TiO₂ NP exposure and the potential of abnormal DNA methylation might be used as biomarkers of both exposure and disease development.

Sonic hedgehog (Shh) and CC chemokine ligand 2 signaling pathways in asthma

Asthma is a chronic inflammatory disease of the airways in which many cells are involved, including mast cells, eosinophils, T lymphocytes, and so on. During the process, many chemokines and mediators are released to engage in recruiting and activating eosinophils and other inflammatory cells. Also, some signaling pathways are involved in the pathobiology of asthma. Sonic hedgehog (Shh) is one of the members of hedgehog gene families. Shh signaling plays a critical role in the embryonic development, including the lung. Previous findings from our team reveal that Shh is involved in the asthma pathogenesis. Recombinant Shh could induce the CC chemokine ligand 2 (CCL2) overexpressing and Smo inhibitor GDC-O449 could inhibit CCL2 expression in airway epithelial cells, monocytes, or macrophages. Hence, we reviewed the effects of Shh and CCL2 signaling pathways, and the interaction between signaling pathways in asthma.

Elevated Levels of Intelectin-1, a Pathogen-binding Lectin, in the BAL Fluid of Patients with Chronic Eosinophilic Pneumonia and Hypersensitivity Pneumonitis

Objective Human intelectin-1 (hITLN-1) binds to galactofuranosyl residues, which are present in the microbial cell wall, but which are absent in mammalian tissues, and has been suggested to play an immunological role against microorganisms. However, the involvement of hITLN-1 in the pathogenesis of diffuse pulmonary diseases remains unknown. The aim of this study was to compare the hITLN-1 concentrations in the bronchoalveolar lavage (BAL) fluid of patients with diffuse pulmonary diseases. Methods The cell components and concentrations of hITLN-1 were analyzed in the BAL fluid of 8 patients with idiopathic chronic eosinophilic pneumonia (ICEP), 3 patients with drug-induced eosinophilic pneumonia, 4 patients with hypersensitivity pneumonitis (HP), 11 patients with sarcoidosis, 9 patients with cryptogenic organizing pneumonia, and 5 patients with idiopathic fibrosing interstitial pneumonia (fibrosing nonspecific interstitial pneumonia or usual interstitial pneumonia). Results The hITLN-1 concentrations in the BAL fluid of patients with ICEP and HP were higher than in those with other diseases. In the ICEP group, no significant difference was observed in the hITLN-1 concentrations of patients with or without a history of bronchial asthma. Conclusion The results of the present study suggest that hITLN-1 may be involved in the pathogenesis of ICEP and HP, and that an increase in the hITLN-1 concentration in the BAL fluid may represent a new biomarker for these diseases.

The D5 region of the intelectin domain is a new type of carbohydrate recognition domain in the intelectin gene family

Intelectin is a recently characterized soluble galactofuranose-binding lectin that exists in species ranging from amphioxus to human. Interestingly, intelectin does not contain a canonical carbohydrate-recognition domain (CRD). Therefore, we designed serial deletions of intelectin in the Chinese amphioxus (Branchiostoma belcheri tsingtauense, AmphiITLN71469) in order to identify functional regions required for carbohydrate binding. Our results revealed that Domain 5 (aa 203-302) was able to bind lipopolysaccarides (LPS) or peptidoglycan (PGN) and agglutinate bacteria as efficiently as the full-length protein. Three dimensional (3D) atomic models of Domain 5 were generated by ab initio based program QUARK and by Iterative Threading Assembly Refinement (I-TASSER) programs, in which four amino acids mediating calcium-binding (G54-G55-G56-E91) were identified by hemagglutination assay. Furthermore, a striking functional conservation of Domain 5 was detected in zebrafish intelectin 1. Taken together, our findings identified for the first time a new CRD domain in intelectin, thereby providing new knowledge leading to a better understanding of pathogen-host interactions.

Saccharide binding by intelectins

This communication probes ligand binding by human Intelectin-1 with several saccharides. Human Intelectin-1 was previously reported to bind to microbial glycans via ribofuranoside or galactofuranoside residues, whereas subsequently, a crystal structure of ligand bound hITLN1 indicated that hITLN1 does not bind to ribofuranoside but distinguishes between microbial and human glycans through a glycan motif - a terminal, acyclic 1,2-diol, which is present on galactofuranose and other microbial saccharides. Here, we demonstrate that besides glycerol and glycerol derivatives (which have an acyclic 1,2-diol), and 2-deoxy-d-galactose, d-ribose and 2-deoxy-d-ribose, which have been previously reported as human Intelectin-1 ligands, 2-C-hydroxymethyl-d-ribose, d-talose, d-idose, d-altrose and sorbitol also elute human Intelectin-1 from Sepharose CL-6B. Interestingly, Sepharose, 2-deoxy-d-galactose (in its pyranose form), 2-C-hydroxymethyl-d-ribose, d-ribose and 2-deoxy d-ribose lack a terminal, acyclic 1,2-diol. We discuss the implications of these observations and rationalize the discrepancies in the apparent affinity of saccharide ligands for hITLN1 with different assay formats. We also report the distinct saccharide binding profiles of the hITLN1 homologues, HaloITLN and XL35ITLN, and demonstrate that hITLN1 binding to a saccharide ligand may modulate binding to its protein ligand, lactoferrin and vice versa.

Omentin-A Novel Adipokine in Respiratory Diseases

Adipokines, secreted by the adipose tissue, are extensively involved in the regulation and maintenance of various physiological and pathological processes, including insulin sensitivity, energy expenditure, glucose and lipid metabolism, inflammatory activity, neuroendocrine activity, immunity, cancer, homeostasis, angiogenesis, cardiovascular function, breeding and bone metabolism, and all functions of the endocrine-reproductive system axis. Omentin is a recently identified adipokine, which has become a research hotspot due to its pleiotropic effects on various diseases. However, the specific receptor for omentin has not been identified so far. In this study, we report that omentin levels fluctuate in various diseases. In addition, we have focused on the pleiotropic roles of omentin in pulmonary diseases, as it may act as a biomarker for malignant pleural mesothelioma (MPM) and is related to disease severity. Omentin may play significant roles in other pulmonary diseases, such as asthma, obstructive sleep apnea syndrome (OSAS), pulmonary arterial hypertension (PAH), acute respiratory distress syndrome (ARDS), and chronic obstructive pulmonary disease (COPD). This review summarizes the advances in current knowledge and future trends, which may provide a concise and general view on omentin and its effects on pulmonary biology.

Intelectin contributes to allergen-induced IL-25, IL-33, and TSLP expression and type 2 response in asthma and atopic dermatitis

The epithelial and epidermal innate cytokines IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) have pivotal roles in the initiation of allergic inflammation in asthma and atopic dermatitis (AD). However, the mechanism by which the expression of these innate cytokines is regulated remains unclear. Intelectin (ITLN) is expressed in airway epithelial cells and promotes allergic airway inflammation. We hypothesized that ITLN is required for allergen-induced IL-25, IL-33, and TSLP expression. In two asthma models, Itln knockdown reduced allergen-induced increases in Il-25, Il-33, and Tslp and development of type 2 response, eosinophilic inflammation, mucus overproduction, and airway hyperresponsiveness. Itln knockdown also inhibited house dust mite (HDM)-induced early upregulation of Il-25, Il-33, and Tslp in a model solely inducing airway sensitization. Using human airway epithelial cells, we demonstrated that HDM-induced increases in ITLN led to phosphorylation of epidermal growth factor receptor and extracellular-signal regulated kinase, which were required for induction of IL-25, IL-33, and TSLP expression. In two AD models, Itln knockdown suppressed expression of Il-33, Tslp, and Th2 cytokines and eosinophilic inflammation. In humans, ITLN1 expression was significantly increased in asthmatic airways and in lesional skin of AD. We conclude that ITLN contributes to allergen-induced Il-25, Il-33, and Tslp expression in asthma and AD.

Relationship of circulating chemerin and omentin levels with Th17 and Th9 cell immune responses in patients with asthma

OBJECTIVE

Adipokines are correlated with immune responses in asthma, but data on the roles of chemerin and omentin in asthma are limited. This study explored the relationship of chemerin and omentin levels with Th17 and Th9 cells in asthma.

METHODS

Seventy-six asthmatics were divided into intermittent-to-mild persistent (n  =  28), moderate persistent (n  =  26) and severe persistent (n  =  22) and were enrolled in the study. Additionally, 20 healthy subjects were enrolled as controls. Clinical characteristics of the subjects, the Asthma Control Test, lung function, fractional exhaled nitric oxide score, and plasma chemerin and omentin levels were evaluated, and the percentages of Th17 and Th9 cells were determined by flow cytometry.

RESULTS

The percentages of Th17 and Th9 cells were higher in the moderate-to-severe persistent asthmatics than in the intermittent-to-mild persistent asthmatics or healthy controls (p < 0.05). The severe persistent asthma group had a higher chemerin level but lower omentin levels than the control group (p < 0.05). Chemerin levels were positively correlated with Th17 and Th9 cell percentages, while omentin levels were negatively correlated with Th17 and Th9 cell percentages (p < 0.01).

CONCLUSIONS

The regulatory functions of adipokines on immune responses may be associated with pathogenesis and processes of asthma.

Expression of intelectin-1 in bronchial epithelial cells of asthma is correlated with T-helper 2 (Type-2) related parameters and its function

Background

Intelectin-1 (ITLN-1) is secreted by intestinal goblet cells and detectable in blood. Its expression is increased in IL-13-overexpressing mouse airways. However, its expression and function in human airways is poorly understood.

Methods

Distal and proximal bronchial epithelial cells (BECs) were isolated from bronchoscopic brushings of disease control (D-CON), COPD, inhaled corticosteroid-treated asthma (ST-Asthma) and inhaled corticosteroid-naïve asthma (SN-Asthma) patients. ITLN-1 mRNA expression in freshly isolated BECs, primary cultured BECs with or without IL-13 and inhibition effects of mometasone furoate (MF) were investigated by quantitative real-time PCR (qPCR). Correlations between ITLN-1 mRNA and Type-2 related parameters (e.g. FeNO, IgE, iNOS, CCL26, periostin and DPP4 mRNA) were analyzed. ITLN-1 protein distribution in asthmatic airway tissue was assessed by immunohistochemistry. Bronchial alveolar lavage (BAL) and serum ITLN-1 protein were measured by ELISA. The effect of recombinant human (rh) ITLN-1 on stimulated production of CXCL10 and phospho(p)-STAT1 expression examined in lung fibroblasts.

Results

ITLN-1 mRNA was expressed in freshly isolated BECs and was correlated with Type-2 related parameters. ITLN-1 protein was increased in goblet cells in SN-Asthmatics and increased in SN-Asthmatic BAL fluid. There were no any differences in serum ITLN-1 concentration between ST and SN-Asthma. IL-13 enhanced ITLN-1 expression and inhibited by MF from BECs in vitro, while rhITLN-1 inhibited CXCL10 production and p-STAT1 expression in HFL-1 cells.

Conclusion

ITLN-1 is induced by IL-13 and expressed mainly in goblet cells in untreated asthma where its levels correlate with known Type-2 related parameters. Further, ITLN-1 inhibits Type-1 chemokine expression.

Electronic supplementary material

The online version of this article (doi:10.1186/s13223-017-0207-8) contains supplementary material, which is available to authorized users.

Adipose Tissue-Derived Omentin-1 Function and Regulation

Omentin-1, also known as intelectin-1, is a recently identified novel adipocytokine of 313 amino acids, which is expressed in visceral (omental and epicardial) fat as well as mesothelial cells, vascular cells, airway goblet cells, small intestine, colon, ovary, and plasma. The level of omentin-1 expression in (pre)adipocytes is decreased by glucose/insulin and stimulated by fibroblast growth factor-21 and dexamethasone. Several lines of experimental evidence have shown that omentin-1 plays crucial roles in the maintenance of body metabolism and insulin sensitivity, and has anti-inflammatory, anti-atherosclerotic, and cardiovascular protective effects via AMP-activated protein kinase/Akt/nuclear factor-κB/mitogen-activated protein kinase (ERK, JNK, and p38) signaling. Clinical studies have indicated the usage of circulating omentin-1 as a biomarker of obesity, metabolic disorders including insulin resistance, diabetes, and metabolic syndrome, and atherosclerotic cardiovascular diseases. It is also possible to use circulating omentin-1 as a biomarker of bone metabolism, inflammatory diseases, cancers, sleep apnea syndrome, preeclampsia, and polycystic ovary syndrome. Decreased omentin-1 levels are generally associated with these diseases. However, omentin-1 increases to counteract the acute phase after onset of these diseases. These findings indicate that omentin-1 may be a negative risk factor for these diseases, and also act as an acute-phase reactant by its anti-inflammatory and atheroprotective effects. Therapeutic strategies to restore omentin-1 levels may be valuable for the prevention or treatment of these diseases. Weight loss, olive oil-rich diet, aerobic training, and treatment with atorvastatin and antidiabetic drugs (metformin, pioglitazone, and exenatide) are effective means of increasing circulating omentin-1 levels. This review provides insights into the potential use of omentin-1 as a biomarker and therapeutic target for these diseases. © 2017 American Physiological Society. Compr Physiol 7:765-781, 2017.

Intratracheal myriocin enhances allergen-induced Th2 inflammation and airway hyper-responsiveness

Introduction

Ceramide is the central substrate of sphingolipid metabolism and plays a key role in cellular signal transduction pathways, regulating apoptosis, differentiation, and chemotaxis. Alterations in airway ceramide levels are observed in multiple pulmonary diseases and recent human genetic association studies have linked dysregulation of sphingolipid regulatory genes with asthma pathogenesis.

Methods

Utilizing myriocin, a potent inhibitor of sphingolipid synthesis, we evaluated the immune regulatory role of de novo ceramide generation in vitro and in vivo. Intratracheal myriocin was administered alone or during house dust mite sensitization (HDM) of BALB/C mice and airway hyper‐responsiveness (AHR) was evaluated by invasive plethysmography followed by bronchial lavage (BAL) cytology and cytokine quantification.

Results

Myriocin inhibits and HDM exposure activates de novo ceramide synthesis in bone marrow‐derived dendritic cells. Mice receiving intratracheal myriocin developed a mild airway neutrophilic infiltrate without inducing a significant increase in AHR. CXCL1 was elevated in the BAL fluid of myriocin‐treated mice while the neutrophilic chemotactic factors anaphylatoxin C5a, leukotriene B4, and IL‐17 were unaffected. HDM treatment combined with myriocin led to a dramatic enhancement of AHR (63% increase over HDM alone, p < 0.001) and increased granulocyte pulmonary infiltrates versus HDM or myriocin alone. Elevated Th2 T cell counts and Th2 cytokines/chemokines (IL5, IL13, CCL17) were observed in mice treated with combined HDM/myriocin compared to HDM alone. Myriocin‐treated pulmonary CD11c+ cells stimulated with HDM secreted significantly more CXCL1 than cells stimulated with HDM alone while HDM stimulated airway epithelial cells showed no change in CXCL1 secretion following myriocin treatment.

Conclusions

Intratracheal myriocin, likely acting via ceramide synthesis inhibition, enhances allergen‐induced airway inflammation, granulocyte and Th2 lymphocyte recruitment, and allergen‐induced AHR. Sphingolipid pathways may represent novel targets for possible future anti‐inflammatory asthma medications.

Identification and characterization of a novel intelectin in the digestive tract of Xenopus laevis

The intelectin (Intl) family is a group of secretory lectins in chordates that serve multiple functions, including innate immunity, through Ca(2+)-dependent recognition of carbohydrate chains. Although six Intl family lectins have so far been reported in Xenopus laevis, none have been identified in the intestine. Using a monoclonal antibody to the Xenopus embryonic epidermal lectin (XEEL or Intl-1), I identified cross-reactive proteins in the intestines. The proteins were purified by affinity chromatography on a galactose-Sepharose column and found to be oligomers consisting of N-glycosylated 39 kDa and 40.5 kDa subunit peptides. N-terminal amino acid sequencing of these peptides, followed by cDNA cloning, identified two novel Intls (designated Intl-3 and Intl-4) that showed 59-79% amino acid identities with known Xenopus Intl family proteins. From the amino acid sequence, immunoreactivity, and properties of the recombinant protein, Intl-3 was considered the intestinal lectin identified by the anti-XEEL antibody. The purified Intl-3 protein could potentially bind to Escherichia coli and its lipopolysaccharides (LPS), and to Staphylococcus aureus and its peptidoglycans, depending on Ca(2+). In addition, the Intl-3 protein agglutinated E. coli cells in the presence of Ca(2+). Intraperitoneal injection of LPS increased the intestinal and rectal contents of Intl-3 and XCL-1 (or 35K serum lectin) proteins within three days; however, unlike XCL-1, Intl-3 was detectable in neither the sera nor the other tissues regardless of LPS stimulation. Immunohistochemical analyses revealed accumulation of the Intl-3 protein in mucus secretory granules of intestinal goblet cells. The results of this study suggest that Xenopus Intl-3 is involved in the innate immune protection of the digestive tract against bacterial infections.

Secreted phosphoprotein 1 is a determinant of lung function development in mice

Secreted phosphoprotein 1 (Spp1) is located within quantitative trait loci associated with lung function that was previously identified by contrasting C3H/HeJ and JF1/Msf mouse strains that have extremely divergent lung function. JF1/Msf mice with diminished lung function had reduced lung SPP1 transcript and protein during the peak stage of alveologenesis (postnatal day [P]14-P28) as compared with C3H/HeJ mice. In addition to a previously identified genetic variant that altered runt-related transcription factor 2 (RUNX2) binding in the Spp1 promoter, we identified another promoter variant in a putative RUNX2 binding site that increased the DNA protein binding. SPP1 induced dose-dependent mouse lung epithelial-15 cell proliferation. Spp1((-/-)) mice have decreased specific total lung capacity/body weight, higher specific compliance, and increased mean airspace chord length (Lm) compared with Spp1((+/+)) mice. Microarray analysis revealed enriched gene ontogeny categories, with numerous genes associated with lung development and/or respiratory disease. Insulin-like growth factor 1, Hedgehog-interacting protein, wingless-related mouse mammary tumor virus integration site 5A, and NOTCH1 transcripts decreased in the lung of P14 Spp1((-/-)) mice as determined by quantitative RT-PCR analysis. SPP1 promotes pneumocyte growth, and mice lacking SPP1 have smaller, more compliant lungs with enlarged airspace (i.e., increased Lm). Microarray analysis suggests a dysregulation of key lung developmental transcripts in gene-targeted Spp1((-/-)) mice, particularly during the peak phase of alveologenesis. In addition to its known roles in lung disease, this study supports SPP1 as a determinant of lung development in mice.

Asthma research in China: a five-year review

Asthma is one of the most common chronic diseases worldwide with increasing morbidity. China has the largest asthmatic population and is one of the countries with the highest asthma mortality. Fortunately, asthma research in China, both clinical and scientific, has developed markedly over the past few years. This has resulted in significant increases in our understanding of Chinese asthma prevalence, risk factors, control status, pathogenesis, and new prevention or treatment strategies. In this review, the major achievements of asthma research in China from 2008 to 2012 are summarized.

Oleanolic acid controls allergic and inflammatory responses in experimental allergic conjunctivitis

Pollen is the most common aeroallergen to cause seasonal conjunctivitis. The result of allergen exposure is a strong Th2-mediated response along with conjunctival mast cell degranulation and eosinophilic infiltration. Oleanolic acid (OA) is natural a triterpene that displays strong anti-inflammatory and immunomodulatory properties being an active anti-allergic molecule on hypersensitivity reaction models. However, its effect on inflammatory ocular disorders including conjunctivitis, has not yet been addressed. Hence, using a Ragweed pollen (RWP)-specific allergic conjunctivitis (EAC) mouse model we study here whether OA could modify responses associated to allergic processes. We found that OA treatment restricted mast cell degranulation and infiltration of eosinophils in conjunctival tissue and decreased allergen-specific Igs levels in EAC mice. Th2-type cytokines, secreted phospholipase A2 type-IIA (sPLA2-IIA), and chemokines levels were also significantly diminished in the conjunctiva and serum of OA-treated EAC mice. Moreover, OA treatment also suppressed RWP-specific T-cell proliferation. In vitro studies, on relevant cells of the allergic process, revealed that OA reduced the proliferative and migratory response, as well as the synthesis of proinflammatory mediators on EoL-1 eosinophils and RBL-2H3 mast cells exposed to allergic and/or crucial inflammatory stimuli such as RWP, sPLA2-IIA or eotaxin. Taken together, these findings demonstrate the beneficial activity of OA in ocular allergic processes and may provide a new intervention strategy and potential therapy for allergic diseases.

TWEAK/Fn14 pathway promotes a T helper 2-type chronic colitis with fibrosis in mice

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK), a TNF superfamily member, induces damage of the epithelial cells (ECs) and production of inflammatory mediaters through its receptor Fn14 in a model of acute colitis. In our current study of chronic colitis induced by repeated rectal injection of a hapten, we found that inflammation, fibrosis, and T helper 2 (Th2)-type immunity were significantly reduced in Fn14 gene knockout (KO) mice when compared with wild-type (WT) control mice. Expression of thymic stromal lymphopoietin (TSLP) was lower in Fn14 KO colon ECs than in WT ECs. TWEAK potentiates the induction of TSLP by interleukin-13 (IL-13) in colon explants from WT but not in Fn14 KO tissue. TSLP receptor KO mice exhibit milder chronic colitis, similar to that in Fn14 KO mice. TWEAK and IL-13 synergistically promote fibroblast proliferation. Thus we propose an IL-13-TWEAK/Fn14-TSLP axis as a key mechanism underlying chronic colitis with fibrosis.

Inhibitory effect of dexamethasone on expression of cysteine-rich 61 protein in airway epithelial cells of allergic mouse models

In order to study whether cysteine-rich 61 protein (cyr61) is involved in the pathogenesis of asthma and its relation to airway inflammation, the effect of dexamethasone (Dxm) on the expression of cyr61 in the lung tissues of asthmatic mice was investigated. Forty BALB/c mice were divided into asthma group (n=15), control group (n=10) and Dxm group (n=15). The asthma group was sensitized and challenged by ovalbumin (OVA). The mice in Dxm group were intraperitoneally administered with Dxm after OVA challenge. The expression of cyr61 in the lung tissues was detected by using immunohistochemistry, and that of eotaxin protein in the bronchoalveolar lavage fluid (BALF) by using enzyme-linked immunosorbent assay (ELISA). The number of inflammatory cells in BALF was also analyzed. The results showed that the cyr61 expression was highest in asthma group (P<0.05), followed by Dxm group (P<0.05) and control group. The cyr61 had a positive correlation with the total nucleated cells (r=0.867, P<0.05), especially eosinophils (r=0.856, P<0.05), and eotaxin level (r=0.983, P<0.05) in the BALF. Our findings suggested that cyr61 is expressed in airway epithelial cells and has a positive correlation with eotaxin and number of airway infiltrating eosinophils.

Acute helminth infection enhances early macrophage mediated control of mycobacterial infection

Co-infection with mycobacteria and helminths is widespread in developing countries, but how this alters host immunological control of each pathogen is not comprehensively understood. In this study, we demonstrate that acute Nippostrongylus brasiliensis (Nb) murine infection reduce early pulmonary mycobacterial colonization. This Nb-associated reduction in pulmonary Mycobacterium tuberculosis colony-forming units was associated with early and increased activation of pulmonary CD4 T cells and increased T helper type 1 (Th1) and Th2 cytokine secretion. An accelerated and transient augmentation of neutrophils and alveolar macrophages (AMs) was also observed in co-infected animals. AMs displayed markers of both classical and alternative activation. Intranasal transfer of pulmonary macrophages obtained from donor mice 5 days after Nb infection significantly reduced pulmonary Mycobacterium bovis Bacille Calmette-Guérin clearance in recipient mice. These data demonstrate that early stage Nb infection elicits a macrophage response, which is protective during the early stages of subsequent mycobacterial infection.

Impact of adiponectin overexpression on allergic airways responses in mice

Obesity is an important risk factor for asthma. Obese individuals have decreased circulating adiponectin, an adipose-derived hormone with anti-inflammatory properties. We hypothesized that transgenic overexpression of adiponectin would attenuate allergic airways inflammation and mucous hyperplasia in mice. To test this hypothesis, we used mice overexpressing adiponectin (Adipo Tg). Adipo Tg mice had marked increases in both serum adiponectin and bronchoalveolar lavage (BAL) fluid adiponectin. Both acute and chronic ovalbumin (OVA) sensitization and challenge protocols were used. In both protocols, OVA-induced increases in total BAL cells were attenuated in Adipo Tg versus WT mice. In the acute protocol, OVA-induced increases in several IL-13 dependent genes were attenuated in Adipo Tg versus WT mice, even though IL-13 per se was not affected. With chronic exposure, though OVA-induced increases in goblet cells numbers per millimeter of basement membrane were greater in Adipo Tg versus WT mice, mRNA abundance of mucous genes in lungs was not different. Also, adiponectin overexpression did not induce M2 polarization in alveolar macrophages. Our results indicate that adiponectin protects against allergen-induced inflammatory cell recruitment to the airspaces, but not development of goblet cell hyperplasia.

Bacterial lipopolysaccharides stimulate production of XCL1, a calcium-dependent lipopolysaccharide-binding serum lectin, in Xenopus laevis

Xenopus laevis serum lectin XCL1 is a newly identified molecule of the XCGL (or X-lectin) family, a unique group of Ca(2+)-dependent lectins that have a fibrinogen-like domain. The XCL1 protein was purified from lipopolysaccharide (LPS)-stimulated frog sera by sequential affinity chromatography on heparin-acrylic beads and galactose-Sepharose. XCL1 comprises multiple oligomeric proteins consisting of 37-kDa subunit polypeptides, as revealed by sodium dodecyl sulfate-polyacrylamide electrophoresis (SDS-PAGE) and Western blot analyses using the monoclonal antibody (mAb) produced against the recombinant XCL1 polypeptide. In the presence of Ca(2+), the protein bound to Escherichia coli, Staphylococcus aureus, LPS and galactose and the bound XCL1 was competitively eluted using ribose and xylose, and the elution was as efficient as that using EDTA, whereas elution using hexoses, GalNAc or GlcNAc was less effective. In reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analyses, XCL1 expression was ubiquitously detected in frog tissues, with relatively high levels in hematopoietic tissues including the spleen, liver and kidney. Intraperitoneal injection of E. coli, S. aureus or 100-300μg S-type LPS from various bacteria induced several-fold increases in serum XCL1 concentrations on day 3, and the elevated levels retained up to day 12. It also caused a remarkable increase of the splenic XCL1 expression on day 3, followed by a rapid decline to nearly nonstimulated control levels by day 7. The R-type LPS with shortened polysaccharide chains was less effective in inducing the serum XCL1 response, indicating that the sugar chains of LPS were important, if not essential, for the stimulation of XCL1 production. These results suggest that XCL1 is a pathogen recognition molecule involved in antimicrobial innate immunity in Xenopus.

Characterization and comparative analyses of two amphioxus intelectins involved in the innate immune response

Intelectin is a new type of soluble galactofuranose-binding lectin involved in innate immunity. Here we report another intelectin homolog, AmphiITLN239631, obtained from amphioxus, the transitional form between vertebrates and invertebrates. AmphiITLN239631 encoded 396 amino acids with a highly conserved fibrinogen-related domain (FReD), An intelectin domain and a putative Collagen domain. AmphiITLN239631 was ubiquitously expressed in all tissues we tested and transcripts in skin increased after challenge of both Escherichia coli and Staphylococcus aureus, although in different levels. Recombinant AmphiITLN239631 expressed in E. coli system could agglutinate both Gram-positive and Gram-negative bacteria in a calcium independent manner. Furthermore, recombinant protein was able to bind to lipopolysaccharide (LPS) and peptidoglycan (PGN), the major components of Gram-positive and Gram-negative bacteria cell walls, respectively. We also compared AmphiITLN239631 with previously identified AmphiITLN71469 and found that their tissue specificities, expression patterns upon bacteria challenge, and polysaccharide-binding affinities etc vary considerably. Our results could provide insight into the evolution and function of the intelectin family.

Interleukin-13 inhibits cytokines synthesis by blocking nuclear factor-κB and c-Jun N-terminal kinase in human mesangial cells

Objective

Monocytes/macrophages, proinflammatory cytokines and chemokines are important in the pathogenesis of glomerulonephritis. Interleukin (IL) -13 has been shown to exert potent anti-inflammatory properties. This study was designed to investigate the effect of IL-13 on the expression of proinflammatory cytokines, chemokines and profibrogenic cytokines and the involved molecular mechanism in cultured human mesangial cells (HMCs).

Methods

The expressions of proinflammatory cytokines, chemokines and profibrogenic cytokines were determined by ribonuclease protection assay (RPA). Activity of nuclear factor-kappa B (NF-κB) and activator protein-1 (AP-1) was examined by electrophoretic mobility shift assay (EMSA). NF-κB subunit p65 nuclear transportation and c-Jun N-terminal kinase (JNK) activity were assayed by immunoblot.

Results

Recombinant IL-13 inhibited tumor necrosis factor-α (TNF-α), IL-1α, IL-1β, monocyte chemoattractant protein-1 (MCP-1), IL-8, and transforming growth factor-β1 (TGF-β1) mRNA expressions in a dose-dependent manner. Lipopolysacchorides (LPS) dramatically increased NF-κB DNA binding activity of HMCs, which was inhibited by IL-13 in a dose-dependent manner. LPS-activated NF-κB contained p50 and p65 dimers, but not c-Rel subunit. IL-13 blocked LPS-induced NF-κB subunit p65. LPS stimulated JNK/AP-1 activation, which was inhibited by IL-13 in a dose-dependent manner.

Conclusion

IL-13 inhibits proinflammatory cytokines, chemokines, and profibrogenic cytokines synthesis by blocking NF-κB and JNK/AP-1 activation. These observations point to the importance of IL-13 in the modulation of inflammatory processes in the renal glomerulus.

Increased expression of intelectin-1 in nasal polyps

BACKGROUND

Intelectin-1 is a new type of Ca(2+)-dependant soluble lectin in humans that has affinity for galactofuranose in carbohydrate chains of bacterial cell walls, indicating that intelectin-1 may play a role in immune defense against bacteria. The purpose of the current study was to determine the expression of intelectin-1 mRNA and protein and to localize intelectin-1 protein in nasal polyps and tissues from control subjects.

METHODS

Normal sphenoid sinus mucosa was obtained from 10 patients undergoing surgery for pituitary tumor. Nasal polyp samples were obtained from 10 patients undergoing endoscopic sinus surgery for chronic polypoid rhinosinusitis. Real-time polymerase chain reaction (PCR) was performed for intelectin-1 mRNA. Immunofluorescent staining was done for localization of intelectin-1 and quantitatively analyzed using computer-based image analysis. Western blot analysis was performed.

RESULTS

Real-time PCR and Western blot analysis showed that intelectin-1 expression in nasal polyps was increased compared with normal sinus mucosa. Using immunofluorescent staining, intelectin-1 was strongly stained in epithelium and submucosa of nasal polyps, and faint staining was found in normal sinus mucosa.

CONCLUSIONS

Intelectin-1 is expressed in human sinus mucosa and is increased in patients with nasal polyps. These results suggest a possible contribution for intelectin-1 in the pathophysiology of nasal polyps.

Shuanghuanglian injection downregulates nuclear factor-kappa B expression in mice with viral encephalitis

A mouse model of viral encephalitis was induced by intracranial injection of a Coxsackie virus B3 suspension. Quantitative real-time reverse transcription-PCR and western blot assay were applied to detect mRNA and protein expression of intelectin-2 and nuclear factor-kappa B in the viral encephalitis and control groups. Nuclear factor-kappa B and intelectin-2 mRNA and protein expression were significantly increased in mice with viral encephalitis. After intraperitoneal injection of Shuanghuanglian at a dose of 1.5 mg/kg for 5 successive days, intelectin-2 and nuclear factor-kappa B protein and mRNA expression were significantly decreased. To elucidate the relationship between intelectin-2 and nuclear factor-kappa B, mice with viral encephalitis were administered an intracerebral injection of 107 pfu recombinant lentivirus expressing intelectin shRNA. Both protein and mRNA levels of intelectin and nuclear factor-kappa B in brain tissue of mice were significantly decreased. Experimental findings suggest that Shuanghuanglian injection may downregulate nuclear factor-kappa B production via suppression of intelectin production, thus inhibiting inflammation associated with viral encephalitis.

Identification of an amphioxus intelectin homolog that preferably agglutinates gram-positive over gram-negative bacteria likely due to different binding capacity to LPS and PGN

Intelectin is a recently described galactofuranose-binding lectin that plays a role in innate immunity in vertebrates. Little is known about intelectin in invertebrates, including amphioxus, the transitional form between vertebrates and invertebrates. We cloned an amphioxus intelectin homolog, AmphiITLN-like, coding 302 amino acids with a conserved fibrinogen-related domain (FReD) in the N-terminus and an Intelectin domain in the C-terminus. In situ hybridization in adult amphioxus showed that AmphiITLN-like transcripts were highly expressed in the digestive tract and the skin. Quantitative real-time PCR revealed that AmphiITLN-like is significantly up-regulated in response to Staphylococcus aureus challenge, but only modestly to Escherichia coli. In addition, recombinant AmphiITLN-like expressed in E. coli agglutinates Gram-negative and Gram-positive bacteria to different degrees in a calcium dependent manner. Recombinant AmphiITLN-like could bind lipopolysaccharide (LPS) and peptidoglycan (PGN), the major cell wall components of Gram-negative and Gram-positive bacteria, respectively, with a higher affinity to PGN. Our work identified and characterized for the first time an amphioxus intelectin homolog, and provided insight into the evolution and function of the intelectin family.

The p110δ subunit of PI3K regulates bone marrow-derived eosinophil trafficking and airway eosinophilia in allergen-challenged mice

Trafficking and recruitment of eosinophils during allergic airway inflammation is mediated by the phosphatidylinositol 3-kinase (PI3K) family of signaling molecules. The role played by the p110δ subunit of PI3K (PI3K p110δ) in regulating eosinophil trafficking and recruitment was investigated using a selective pharmacological inhibitor (IC87114). Treatment with the PI3K p110δ inhibitor significantly reduced murine bone marrow-derived eosinophil (BM-Eos) adhesion to VCAM-1 as well as ICAM-1 and inhibited activation-induced changes in cell morphology associated with reduced Mac-1 expression and aberrant cell surface localization/distribution of Mac-1 and α4. Infused BM-Eos demonstrated significantly decreased rolling and adhesion in inflamed cremaster muscle microvessels of mice treated with IC87114 compared with vehicle-treated mice. Furthermore, inhibition of PI3K p110δ significantly attenuated eotaxin-1-induced BM-Eos migration and prevented eotaxin-1-induced changes in the cytoskeleton and cell morphology. Knockdown of PI3K p110δ with siRNA in BM-Eos resulted in reduced rolling, adhesion, and migration, as well as inhibition of activation-induced changes in cell morphology, validating its role in regulating trafficking and migration. Finally, in a mouse model of cockroach antigen-induced allergic airway inflammation, oral administration of the PI3K p110δ inhibitor significantly inhibited airway eosinophil recruitment, resulting in attenuation of airway hyperresponsiveness in response to methacholine, reduced mucus secretion, and expression of proinflammatory molecules (found in inflammatory zone-1 and intelectin-1). Overall, these findings indicate the important role played by PI3K p110δ in mediating BM-Eos trafficking and migration by regulating adhesion molecule expression and localization/distribution as well as promoting changes in cell morphology that favor recruitment during inflammation.

N-Glycans differentially regulate eosinophil and neutrophil recruitment during allergic airway inflammation

Allergic airway inflammation, including asthma, is usually characterized by the predominant recruitment of eosinophils. However, neutrophilia is also prominent during severe exacerbations. Cell surface-expressed glycans play a role in leukocyte trafficking and recruitment during inflammation. Here, the involvement of UDP-N-acetylglucosamine:α-6-D-mannoside β1,6-N-acetylglucosaminyltransferase V (MGAT5)-modified N-glycans in eosinophil and neutrophil recruitment during allergic airway inflammation was investigated. Allergen-challenged Mgat5-deficient (Mgat5(-/-)) mice exhibited significantly attenuated airway eosinophilia and inflammation (decreased Th2 cytokines, mucus production) compared with WT counterparts, attributable to decreased rolling, adhesion, and survival of Mgat5(-/-) eosinophils. Interestingly, allergen-challenged Mgat5(-/-) mice developed airway neutrophilia and increased airway reactivity with persistent elevated levels of proinflammatory cytokines (IL-17A, TNFα, IFNγ)). This increased neutrophil recruitment was also observed in LPS- and thioglycollate (TG)-induced inflammation in Mgat5(-/-) mice. Furthermore, there was significantly increased recruitment of infused Mgat5(-/-) neutrophils compared with WT neutrophils in the peritoneal cavity of TG-exposed WT mice. Mgat5(-/-) neutrophils demonstrated enhanced adhesion to P-selectin as well as increased migration toward keratinocyte-derived chemokine compared with WT neutrophils in vitro along with increased calcium mobilization upon activation and expression of elevated levels of CXCR2, which may contribute to the increased neutrophil recruitment. These data indicate an important role for MGAT5-modified N-glycans in differential regulation of eosinophil and neutrophil recruitment during allergic airway inflammation.

Strain-specific copy number variation in the intelectin locus on the 129 mouse chromosome 1

BACKGROUND

C57BL/6J mice possess a single intelectin (Itln) gene on chromosome 1. The function of intelectins is not well understood, but roles have been postulated in insulin sensitivity, bacterial recognition, intestinal lactoferrin uptake and response to parasites and allergens. In contrast to C57BL/6J mice, there is evidence for expansion of the Itln locus in other strains and at least one additional mouse Itln gene product has been described. The aim of this study was to sequence and characterise the Itln locus in the 129S7 strain, to determine the nature of the chromosomal expansion and to inform possible future gene deletion strategies.

RESULTS

Six 129S7 BAC clones were sequenced and assembled to generate 600 kbp of chromosomal sequence, including the entire Itln locus of approximately 500 kbp. The locus contained six distinct Itln genes, two CD244 genes and several Itln- and CD244-related pseudogenes. It was approximately 433 kbp larger than the corresponding C57BL/6J locus. The expansion of the Itln locus appears to have occurred through multiple duplications of a segment consisting of a full-length Itln gene, a CD244 (pseudo)gene and an Itln pseudogene fragment. Strong evidence for tissue-specific distribution of Itln variants was found, indicating that Itln duplication contributes more than a simple gene dosage effect.

CONCLUSIONS

We have characterised the Itln locus in 129S7 mice to reveal six Itln genes with distinct sequence and expression characteristics. Since C57BL/6J mice possess only a single Itln gene, this is likely to contribute to functional differences between C57BL/6J and other mouse strains.

New concepts of IL-10-induced lung fibrosis: fibrocyte recruitment and M2 activation in a CCL2/CCR2 axis

IL-10 is most commonly recognized as an anti-inflammatory cytokine possessing immunosuppressive effects necessary for regulated resolution of proinflammation. However, its role in the development of fibrosis during inflammatory resolution has not been clear. Few prior studies have linked IL-10 with the inhibition of fibrosis principally on the basis of regulating inflammation thought to be driving fibroproliferation. In contrast, in a model of long-term overexpression of IL-10, we observed marked induction of lung fibrosis in mice. The total cell number retrieved by bronchoalveolar lavage (BAL) increased 10-fold in the IL-10 overexpression (IL-10 OE) mice, with significant infiltration of T and B lymphocytes and collagen-producing cells. The presence of increased fibrocytes, isolated from collagenase-digested lungs, was identified by flow cytometry using dual staining of CD45 and collagen 1. Quantitative PCR analysis on an array of chemokine/chemokine receptor genes showed that receptor CCR2 and its ligand, CCL2, were highly upregulated in IL-10 OE mice, suggesting that IL-10-induced fibrocyte recruitment was CCL2/CCR2 specific. Given the prior association of alternatively activated (M(2)) macrophages with development of fibrosis in other disease states, we also examined the effect of IL-10 OE on the M(2) macrophage axis. We observed significantly increased numbers of M(2) macrophages in both BAL and whole lung tissue from the IL-10 OE mice. Administration of rabbit anti-CCL2 antiserum to IL-10 OE mice for three consecutive weeks significantly decreased fibrosis as evidenced by lung hydroxyproline content, compared with mice that received preimmune rabbit serum. These results indicate that overexpression of IL-10 induces fibrosis, in part, by fibrocyte recruitment and M(2) macrophage activation, and likely in a CCL2/CCR2 axis.