Identification of a novel eosinophil chemotactic cytokine (ECF-L) as a chitinase family protein

Serum YKL-40 as a marker of disease activity and stricture formation in patients with Crohn's disease

BACKGROUND AND AIM

YKL-40 is secreted by macrophages and neutrophils and is a growth factor for vascular endothelial cells and fibroblasts. Elevated serum levels of YKL-40 have been reported in patients with various inflammatory conditions and ongoing fibrosis. The aim of this study was to investigate the relationship between serum concentrations of YKL-40 and disease activity, acute phase reactants, and the presence of strictures in patients with Crohn's disease (CD).

METHODS

We studied the serum concentrations of YKL-40 in 41 patients with CD, in which 12 had an endoscopically- or radiologically-proven stricture formation. Forty-six age- and sex-matched healthy volunteers served as controls and a multivariate regression analysis was performed to find out the independent predictors of intestinal strictures and clinical activity.

RESULTS

The serum YKL-40 concentrations in the patients were significantly higher than that in the healthy controls (105.69 +/- 88.08 ng/mL [range 20.23-333.57]vs 44.92 +/- 24.89 ng/mL [range 18.31-113.43], P = 0.000) and patients with a stricture formation had significantly higher YKL-40 levels than those without strictures (167.50 +/- 119.30 ng/mL [range 23.62-333.57]vs 80.12 +/- 56.38 ng/mL [range 20.23-259.19], P = 0.003). Significant correlations were noted between YKL-40 levels and clinical activity (r = 0.681; P = 0.000) and the presence of intestinal strictures (r = 0.457; P = 0.003). The multivariate regression analysis found the serum YKL-40 levels to be an independent predictor of intestinal strictures (P = 0.001) and clinical activity (P = 0.001).

CONCLUSION

Patients with CD, particularly those with a stricture formation, have significantly higher levels of YKL-40. YKL-40 seems to be a useful marker of disease activity as well as stricture formation in patients with CD.

Gaucher disease: New developments in treatment and etiology

Gaucher disease (GD) is an autosomal recessive disease which if undiagnosed or diagnosed late results in devastating complications. Because of the heterozygous nature of GD, there is a wide spectrum of clinical presentation. Clinicians should be aware of this rare but potentially treatable disease in patients who present with unexplained organomegaly, anemia, massive splenomegaly, ascites and even cirrhosis of unknown origin. The treatment options for adult type GD include enzyme replacement treatment (ERT) and substrate reduction treatment (SRT) depending on the status of the patient. Future treatment options are gene therapy and “smart molecules” which provide specific cure and additional treatment options. In this review, we present the key issues about GD and new developments that gastroenterologists should be aware of.

Chitinase levels in the tears of subjects with ocular allergies

PURPOSE

Chitin is abundant in the structural coatings of fungi, insects, and parasitic nematodes. The host defense against chitin-containing pathogens includes production of chitinases. An acidic mammalian chitinase (AMCase) is produced in human epithelial cells of lower airways through a TH2-specific, interleukin-13-dependent pathway and appears to be associated with allergic asthma. The role of AMCase in allergic ocular pathologies has never been studied previously.

METHODS

Six patients with vernal keratoconjunctivitis (VKC), 7 patients with season allergic conjunctivitis (SAC), and 8 healthy controls (4 children and 4 adults) were enrolled in this study. AMCase activity was measured in tears, RNA was extracted from epithelial cells of the conjunctiva, and AMCase mRNA expression was evaluated by real-time polymerase chain reaction.

RESULTS

AMCase activity was increased in patients affected by VKC (33.7 +/- 10.8 nmol/mL/h) and SAC (7.3 +/- 4.1 nmol/mL/h) compared with healthy controls (1.6 +/- 0.2 nmol/mL/h), and AMCase activity was higher in subjects with VKC (P = 0.0001). Receiver operating characteristic analysis showed that the sensitivity and specificity were 100%, addressing the use of AMCase assay in the biochemical diagnosis of VKC and SAC. AMCase mRNA was detected in epithelial cells of the conjunctiva, and the expression was significantly higher in VKC and SAC.

CONCLUSIONS

AMCase may be an important mediator in the pathogenesis of TH2 inflammation eye diseases, suggesting a potential diagnostic and therapeutic target in these pathologies.

Role of arginine metabolism in immunity and immunopathology

A heterogeneous set of cells that are commonly grouped as "myeloid cells", interacts in a complex landscape of physiological and pathological situations. In this review we attempt to trace a profile of the "myeloid connection" through different normal and pathological states, by analyzing common metabolic pathways of the amino acid l-arginine. Myeloid cells exert various, often divergent, actions on the immune response through mechanisms that exploit mediators of this peculiar metabolic pathway, ranging from l-arginine itself to its downstream metabolites, like nitric oxide and polyamines. Various pathological situations, including neoplastic and autoimmune diseases, as well as injury repair and infections are discussed here, showing how l-arginine metabolism is able to play a dual role, both as an active protector and a possible threat to the organism.

Alternatively activated macrophages in helminth infections

Helminthic parasites can trigger highly polarized immune responses typically associated with increased numbers of CD4(+) Th2 cells, eosinophils, mast cells, and basophils. These cell populations are thought to coordinate an effective response ultimately leading to parasite expulsion, but they also play a role in the regulation of associated pathologic inflammation. Recent studies suggest that macrophages, conventionally associated with IFN-gamma-dominant Th1-type responses to many bacteria and viruses, also play an essential role in the Th2-type inflammatory response. These macrophages are referred to as alternatively activated macrophages (AAMPhis) as they express a characteristic pattern of cell surface and secreted molecules distinct from that of classically activated macrophages (CAMPhis) associated with microbe infections. In this review, we will discuss recent findings regarding the role of AAMPhis in the development of disease and host protection following helminth infection.

Cysteinyl leukotriene receptor antagonist MK-571 alters bronchoalveolar lavage fluid proteome in a mouse asthma model

Cysteinyl leukotriene receptor type 1 (leukotriene CysLT(1) receptor) antagonist is one of the most effective anti-inflammatory agents for asthma. The spectrum of protein targets that can be regulated by leukotriene CysLT(1) receptor antagonist in asthma is not fully understood. The present study tried to identify novel protein targets of a selective leukotriene CysLT(1) receptor antagonist MK-571 in allergic airway inflammation by analyzing the proteome of mouse bronchoalveolar lavage fluid. BALB/c mice sensitized and challenged with ovalbumin showed increased pulmonary inflammatory cell infiltration, airway mucus production and serum ovalbumin-specific IgE level. MK-571 inhibited all these allergic airway inflammation endpoints. Lavage fluid proteins were resolved by two-dimensional gel electrophoresis and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The level of fourteen bronchoalveolar lavage fluid protein spots was markedly altered by MK-571. A family of chitinases (Ym1, Ym2 and acidic mammalian chitinase), lungkine, surfactant protein-D and gamma-actin have been found for the first time to be down-regulated by leukotriene CysLT(1) receptor antagonist in mouse allergic airways. Some of the down-regulatory effects were confirmed with reverse transcription-polymerase chain reaction analyses. Taken together, we have identified novel protein targets that can be regulated by leukotriene CysLT(1) receptor antagonist in mouse allergic airway inflammation, and our findings reveal additional pharmacological actions of leukotriene CysLT(1) receptor antagonist in the treatment of asthma.

Characterization of chitinase-like proteins (Cg-Clp1 and Cg-Clp2) involved in immune defence of the mollusc Crassostrea gigas

Chitinase-like proteins have been identified in insects and mammals as nonenzymatic members of the glycoside hydrolase family 18. Recently, the first molluscan chitinase-like protein, named Crassostrea gigas (Cg)-Clp1, was shown to control the proliferation and synthesis of extracellular matrix components of mammalian chondrocytes. However, the precise physiological roles of Cg-Clp1 in oysters remain unknown. Here, we report the cloning and the characterization of a new chitinase-like protein (Cg-Clp2) from the oyster Crassostrea gigas. Gene expression profiles monitored by quantitative RT-PCR in adult tissues and through development support its involvement in tissue growth and remodelling. Both Cg-Clp1- and Cg-Clp2-encoding genes were transcriptionally stimulated in haemocytes in response to bacterial lipopolysaccharide challenge, strongly suggesting that these two close paralogous genes play a role in oyster immunity.

The biology of the Gaucher cell: the cradle of human chitinases

Gaucher disease (GD) is the most common lysosomal storage disorder and is caused by inherited deficiencies of glucocerebrosidase, the enzyme responsible for the lysosomal breakdown of the lipid glucosylceramide. GD is characterized by the accumulation of pathological, lipid laden macrophages, so-called Gaucher cells. Following the development of enzyme replacement therapy for GD, the search for suitable surrogate disease markers resulted in the identification of a thousand-fold increased chitinase activity in plasma from symptomatic Gaucher patients and that decreases upon successful therapeutic intervention. Biochemical investigations identified a single enzyme, named chitotriosidase, to be responsible for this activity. Chitotriosidase was found to be an excellent marker for lipid laden macrophages in Gaucher patients and is now widely used to assist clinical management of patients. In the wake of the identification of chitotriosidase, the presence of other members of the chitinase family in mammals was discovered. Amongst these is AMCase, an enzyme recently implicated in the pathogenesis of asthma. Chitinases are omnipresent throughout nature and are also produced by vertebrates in which they play important roles in defence against chitin-containing pathogens and in food processing.

Eosinophil chemotactic factor-L (ECF-L) enhances osteoclast formation by increasing in osteoclast precursors expression of LFA-1 and ICAM-1

ECF-L is a novel autocrine stimulator of osteoclast (OCL) formation that enhances the effects of 1,25-(OH)2D3 and RANK ligand (RANKL) and is increased in inflammatory conditions such as rheumatoid arthritis. ECF-L acts at the later stages of OCL formation and does not increase RANKL expression. Thus, its mechanism of action is unclear. Therefore, RAW 264.7 cells and M-CSF-dependent murine bone marrow macrophage (MDBM) cells were treated with RANKL and/or with recombinant ECF-L expressed as a Fc fusion protein (ECF-L-Fc) to determine their effects on NF-kappaB, AP-1 and JNK activity, and on the expression of the adhesion molecules that have been implicated in OCL formation. These parameters were measured by semiquantitative and PCR and Western blot analysis. In addition, the role of ICAM-1 was further assessed by treating normal mouse marrow cultures with ECF-L-Fc and 10(-10) M 1,25-(OH)2D3 in the presence or absence of a blocking ICAM-1 antibody or treating marrow cultures from ICAM-1 knockout mice with ECF-L and 1,25-(OH)2D3. ECF-L-Fc by itself only modestly increased NF-kappaB binding and JNK activity in RAW 264.7 cells, which was further enhanced by RANKL. In contrast, ECF-L-Fc increased LFA-1alpha and ICAM-1 mRNA levels 1.8-fold in mouse marrow cultures, and anti-ICAM-1 almost completely inhibited OCL formation induced by 10(-10) M 1,25-(OH)2D3 and ECF-L. Furthermore, ECF-L did not increase OCL formation in marrow cultures from ICAM-1 knockout mice. Taken together, these results demonstrate that ECF-L enhances RANKL and 1,25-(OH)2D3-induced OCL formation by increasing adhesive interactions between OCL precursors through increased expression of ICAM-1 and LFA-1.

Is YKL-40 a new therapeutic target in cancer?

YKL-40 is produced by cancer cells and tumour-associated macrophages. YKL-40 may play a role in cancer cell proliferation, differentiation, survival, invasiveness, metastasis, in angiogenesis and the inflammation and remodelling of the extracellular matrix surrounding the tumour. Serum YKL-40 is a biomarker of prognosis, confirmed in 13 different types of cancer including > 2500 patients. Highest serum YKL-40 is found in patients with metastatic cancer with the shortest recurrence-free interval and shortest overall survival. Serum YKL-40 provides independent information compared with clinical characteristics and biomarkers, such as HER2, carcinoembryonic antigen, CA-125, prostate-specific antigen and lactate dehydrogenase. The authors hypothesise that inhibition of YKL-40 by monoclonal antibodies either directly or towards its receptor may be as efficient a cancer therapeutic as the monoclonal antibodies against HER2, HER1, vascular endothelial growth factor and CD20. Drugs inhibiting YKL-40 should be explored as new cancer therapeutics.

Stabilin-1, a homeostatic scavenger receptor with multiple functions

The multifunctional scavenger receptor stabilin-1 (STAB1, FEEL-1, CLEVER-1, KIAA0246) was originally identified as the MS-1 antigen, expressed by sinusoidal endothelial cells in human spleen. Extensive histological studies revealed that stabilin-1 is also expressed by tissue macrophages and sinusoidal endothelial cells in the healthy organism; its expression on both macrophages and different subtypes of endothelial cells is induced during chronic inflammation and tumorigenesis. In vitro induction of stabilin-1 in macrophages requires the presence of glucocorticoids. Stabilin-1 is involved in two intracellular trafficking pathways: receptor mediated endocytosis and recycling; and shuttling between the endosomal compartment and trans-Golgi network (TGN). The latter intracellular pathway of stabilin-1 trafficking is mediated by GGAs, clathrin adaptors that interact with the DDSLL motif in the cytoplasmic tail of stabilin-1. When expressed by alternatively activated macrophages, stabilin-1 mediates the uptake and targeting for degradation of acLDL and SPARC, a regulator of tissue remodeling. Likewise, stabilin-1 in macrophages is involved in intracellular sorting and lysosomal delivery of the novel stabilin- 1-interacting chitinase-like protein (SI-CLP). Indirect evidence suggests that stabilin-1 is involved in adhesion and transmigration in various cell types (including tumor cells, leukocytes, and lymphocytes); however, its rapid recycling and scant level of surface expression argue against its universal role in cell adhesion. In summary, stabilin-1 is a homeostatic receptor which links signals from the extracellular environment to intracellular vesicular processes, creating a potential impact on the macrophage secretion profile.

Expression of chitinase-like proteins in the skin of chronic proliferative dermatitis (cpdm/cpdm) mice

Mammalian chitinase-like proteins belong to a family of proteins structurally related to chitinases but devoid of enzymatic activity. They have a postulated role in remodeling of extracellular matrix and defense mechanisms against chitin-containing pathogens. The expression of these proteins is increased in parasitic infections and allergic airway disease, but their expression in dermatitis has not been examined. The mRNA expression of two chitinase 3-like (Chi3L) proteins, Chi3L3 (Ym1) and Chi3L4 (Ym2), was determined in the skin of normal mice, chronic proliferative dermatitis (cpdm/cpdm) mutant mice and mice with experimentally induced contact hypersensitivity reaction. The localization of Chi3L3 and Chi3L4 proteins in cells was determined by fluorescence microscopy of double-labeled frozen sections of skin, and confirmed in vitro by stimulation of macrophages and mast cells with cytokines. Quantitative RT-PCR demonstrated a 976-fold increase of Chi3l4 mRNA expression and a 24-fold increase of Chi3l3 mRNA expression in the skin of cpdm/cpdm mice. Their expression was also increased in the ears of mice with 2,4-dinitrofluorobenzene-induced contact hypersensitivity, but the increase was greater for Chi3l3 mRNA (51-fold) than Chi3l4 mRNA (32-fold). Western blot analysis with an antibody against Chi3L3 and Chi3L4 confirmed the increased amount of these proteins in the skin of cpdm/cpdm mice. Two-color immunofluorescence identified macrophages, dendritic cells and mast cells as cellular sources of Chi3L3 and Chi3L4 proteins. Eosinophils and neutrophils did not contain detectable concentrations of these proteins. Treatment of macrophages and mast cells in vitro with interleukin-4 induced expression of Chi3l3 and Chi3l4 mRNA.

Characterisation of Host Defence Proteins in Milk Using a Proteomic Approach

Besides providing nutrition to the newborn, milk also protects the neonate and the mammary gland against infection. As well as the six major proteins, bovine milk contains minor proteins, not all of which have been characterized. In this study, we have subjected bovine skim milk, whey, and milk fat globule membrane (MFGM) fractions to both direct liquid chromatography-tandem mass spectrometry (LC-MS/MS), and two-dimensional electrophoresis (2-DE) followed by matrix assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry (MS) of individual protein spots to better characterize the repertoire of minor milk proteins, particularly those involved with host defense. Milk from peak lactation as well as during the period of colostrum formation and during mastitis were analyzed to gain a more complete sampling of the milk proteome. In total, 2903 peptides were detected by LC-MS and 2770 protein spots by 2-DE. From these, 95 distinct gene products were identified, comprising 53 identified through direct LC-MS/MS and 57 through 2-DE-MS. The latter were derived from a total of 363 spots analyzed with 181 being successfully identified. At least 15 proteins were identified that are involved in host defense. These results demonstrate that the proteome of milk is more complex than has previously been reported and a significant fraction of minor milk proteins are involved in protection against infection.

Dexamethasone alters bronchoalveolar lavage fluid proteome in a mouse asthma model

BACKGROUND

Glucocorticoid is the most effective anti-inflammatory agent for asthma. The spectrum of protein targets that can be regulated by glucocorticoid in asthma is not fully understood. The present study tried to identify novel protein targets of dexamethasone in allergic airway inflammation by analyzing the proteome of mouse bronchoalveolar lavage (BAL) fluid.

METHODS

BALB/c mice sensitized and challenged with ovalbumin (OVA) showed increased pulmonary inflammatory cell infiltration, airway mucus production and serum OVA-specific IgE level. Dexamethasone inhibited all these allergic airway inflammation endpoints. BAL fluid proteins were resolved by two-dimensional gel electrophoresis and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

RESULTS

The levels of 26 BAL fluid proteins were found to be markedly altered by dexamethasone. A family of chitinases (Ym1, Ym2 and acidic mammalian chitinase, AMCase), lungkine, gob-5, surfactant protein D and polymeric immunoglobulin receptor have been found for the first time to be downregulated by dexamethasone in allergic airways. The downregulatory effects were confirmed by immunoblotting and RT-PCR analyses. Dexamethasone was also shown to significantly inhibit lavage fluid chitinase bioactivity. In addition, dexamethasone promoted airway expression of vitamin D-binding protein, heptoglobin and alpha(1)-antitrypsin.

CONCLUSIONS

Among all these newly identified protein targets of dexamethasone, AMCase and gob-5 have been shown to be pro-inflammatory in asthma. Downregulation of AMCase and gob-5 may be considered as two novel anti-inflammatory actions of glucocorticoid in asthma.

Serum YKL-40, a new prognostic biomarker in cancer patients?

YKL-40, a member of the "mammalian chitinase-like proteins," is expressed and secreted by several types of solid tumors. The exact function of YKL-40 in cancer diseases is unknown and is an important objective of future studies. YKL-40 exhibits growth factor activity for cells involved in tissue remodeling processes. YKL-40 may have a role in cancer cell proliferation, survival, and invasiveness, in the inflammatory process around the tumor, angiogenesis, and remodeling of the extracellular matrix. YKL-40 is neither organ- nor tumor-specific. However, the present retrospective clinical studies of patients with eight different types of primary or advanced solid tumors suggest that serum concentration of YKL-40 may be a new biomarker in cancer patients used as a "prognosticator." Elevated serum YKL-40 is found in a subgroup of patients with different types of solid tumors, including several types of adenocarcinomas, small cell lung carcinoma, glioblastoma, and melanoma. The highest serum YKL-40 is detected in patients with advanced cancer and with the poorest prognosis. In many cases, serum YKL-40 provides independent information of survival. Serum YKL-40 cannot be used as a single screening test for cancer. The use of serum YKL-40 has not received Food and Drug Administration approval for use as a biomarker for cancer or any other disease. Large multicenter retrospective and prospective studies of patients with different types of cancer are required to determine: (a) if serum YKL-40 is a useful prognostic cancer biomarker, (b) if serum YKL-40 can be of value in monitoring patients with cancer in order to provide information about metastases before these are detected by routine methods, and (c) if serum YKL-40 can be useful for screening of cancer together with a panel of other cancer biomarkers and imaging techniques.

F4/80+Alternatively Activated Macrophages Control CD4+T Cell Hyporesponsiveness at Sites Peripheral to Filarial Infection

Both T cells and APC have been strongly implicated in the immune suppression observed during filarial nematode infections, but their relative roles are poorly understood, particularly in regard to timing and locality of action. Using Litomosoides sigmodontis infection of susceptible BALB/c mice, we have studied the progression of filarial immunosuppression leading to patent infection with blood microfilaremia. Patent infection is associated with decreased immune responsiveness in the draining thoracic lymph nodes (tLN) and intrinsically hyporesponsive CD4+ T cells at the infection site. We now show that we are able to separate, both in time and space, different suppressive mechanisms and cell populations that contribute to filarial hyporesponsiveness. L. sigmodontis infection recruited a F4/80+ population of alternatively activated macrophages that potently inhibited Ag-specific CD4+ T cell proliferative responses even in the presence of competent naive APC. T cell responsiveness was partially restored by neutralizing TGF-beta, but not by blocking IL-10 or CTLA-4 signaling. During prepatent infection, the macrophage population was restricted to the infection site. However, once infection became patent with systemic release of microfilariae, the suppressive macrophage activity extended peripherally into the tLN. In contrast, the hyporesponsive CD4+ T cell phenotype remained localized at the infection site, and the tLN CD4+ T cell population recovered full Ag responsiveness in the absence of suppressive macrophages. Filarial immunosuppression, therefore, evolves over time at sites increasingly distal to infection, and the mechanisms of filarial down-regulation are dependent on proximity to the infection site.

Characterization of CD4+ T cell responses in mice infected with Schistosoma japonicum

To better understand the interaction between Schistosoma japonicum and its murine host, we characterized the immune response of CD4+ T cells generated during an experimental S. japonicum infection based on different key aspects, from gene expression to cell behavior. Mouse oligonucleotide microarrays were used to compare gene expression profiles of CD4+ T cells from spleens of mice at 0, 3, 6 and 13 weeks post-infection. Flow cytometry analysis was used to determine type 1 and type 2 cytokine-secreting CD4+ T cells, to test apoptosis of CD4+ T cells and to count CD4+CD25+ T cells, a kind of regulatory subpopulation of CD4+ T cells. The percentage of interleukin-4-producing CD4+ T cells was found to be much higher than that of gamma-interferon-producing cells, especially after stimulation with S. japonicum egg antigen, which was consistent with type 1 and type 2 cytokine gene expression in the genechip. Microarray data also showed that S. japonicum induced the increased expression of Th2 response-related genes, whereas some transcripts related to the Th1 responsive pathway were depressed. Flow cytometry analysis showed a marked increase in the apoptotic CD4+ T cells from 6 weeks post-infection and in the ratio of CD4+CD25+ to CD4+ T cells in infected mice after 13 weeks. We therefore concluded that experimental infection of mice with S. japonicum resulted in a Th2-skewed immune response, which was to a great extent monitored by the immune regulatory network, including cytokine cross-modulation, cell apoptosis and the subpopulation of regulatory cells.

Eosinophil Chemotactic Factor-L (ECF-L) Enhances Osteoclast Formation by Increasing ICAM-1 Expression

Eosinophil chemotactic factor-L (ECF-L) is a novel stimulator of osteoclast (OCL) formation that acts at the differentiation/fusion stage of OCL formation, and is a cofactor for RANK ligand (RANKL). We examined the effects of ECF-L on the intracellular signaling pathways utilized by RANKL, and on the expression of ICAM-1/LFA-1 to determine its mechanism of action. RAW 264.7 and bone marrow cells were treated with RANKL and/or ECF-L Fc protein to determine their effect on NF-kappaB and AP-1 activity. ECF-L by itself only modestly increased NF-kappaB binding and JNK activity in RAW 264.7 cells, which were further enhanced by RANKL. In contrast, ECF-L Fc increased LFA-1alpha and ICAM-1 mRNA levels 1.8-fold in mouse marrow cultures, and anti-ICAM-1 almost completely inhibited OCL formation induced by 10(-10) M 1,25-(OH)2D3, and ECF-L Fc. Furthermore, ECF-L Fc did not enhance OCL formation by ICAM-1 knockout (KO) cells. Increased expression of ICAM-1 by ECF-L appears to be critical for its effects on OCL formation.

Exploiting worm and allergy models to understand Th2 cytokine biology

PURPOSE OF REVIEW

Helminthic parasites and many allergens trigger highly polarized Th2-type immune responses. In most helminth infections, the Th2 response often leads to parasite expulsion or sequestration. During murine Schistosoma mansoni infection, however, the parasites persist and the chronic Th2 response induces severe pathological changes in the gut and liver. Thus, the study of schistosome infections in mice has become a popular model to study the pathogenesis of Th2 cytokine-mediated disease. This review will discuss recent findings from the schistosomiasis model that may be relevant to the understanding of allergic inflammation, asthma and Th2 cytokine biology in general.

RECENT FINDINGS

Evidence is accumulating that the Th2 pathway is not a 'default pathway' but one that is actively instructed by mechanisms that are only beginning to be understood. Other areas of intensive investigation include studies on alternatively activated macrophages, the role of dendritic cells in Th2 response development, the inhibitory function of IL-10, regulatory T-cells and decoy receptors on chronic Th2-mediated inflammation, and the role of chitinases in mediating Th2 disease. Finally, the development of novel eosinophil-deficient mice has also accelerated our understanding of the contribution of this important cell type to Th2 immunity.

SUMMARY

Many findings from the schistosomiasis model have been subsequently demonstrated in models of allergic disease, illustrating the utility of this model to dissect basic mechanisms of Th2-mediated inflammation. Further study of helminth-induced Th2 responses may expedite the discovery of new therapeutics for a wide range of Th2-associated diseases.

New weapons in the war on worms: identification of putative mechanisms of immune-mediated expulsion of gastrointestinal nematodes

Parasitic nematode infections of humans and livestock continue to impose a significant public health and economic burden worldwide. Murine models of intestinal nematode infection have proved to be relevant and tractable systems to define the cellular and molecular basis of how the host immune system regulates resistance and susceptibility to infection. While susceptibility to chronic infection is propagated by T helper cell type 1 cytokine responses (characterised by production of IL-12, IL-18 and interferon-gamma), immunity to intestinal-dwelling adult nematode worms is critically dependent on a type 2 cytokine response (controlled by CD4+T helper type 2 cells that secrete the cytokines IL-4, IL-5, IL-9 and IL-13). However, the immune effector mechanisms elicited by type 2 cytokines in the gut microenvironment that precipitate worm expulsion have remained elusive. This review focuses on new studies that implicate host intestinal epithelial cells as one of the dominant immune effector cells against this group of pathogens. Specifically, three recently identified type 2 cytokine-dependent pathways that could offer insights into the mechanisms of expulsion of parasitic nematodes will be discussed: (i) the intelectins, a new family of galactose-binding lectins implicated in innate immunity, (ii) the resistin-like molecules, a family of small cysteine-rich proteins expressed by multiple cell types, and (iii) cytokine regulation of intestinal epithelial cell turnover. Identifying how the mammalian immune response fights gastrointestinal nematode infections is providing new insights into host protective immunity. Harnessing these discoveries, coupled with identifying what the targets of these responses are within parasitic nematodes, offers promise in the design of a new generation of anti-parasitic drugs and vaccines.

Role of eosinophil chemotactic factor by T lymphocytes on airway hyperresponsiveness in a murine model of allergic asthma

Airway hyperresponsiveness (AHR) is an important feature of bronchial asthma. Although the incidence of AHR has genetic and environmental components, the mechanism of AHR in asthma remains unclear. The identification of genes that are preferentially expressed in a murine model of AHR could help elucidate the molecular mechanisms of this pulmonary pathology. Suppressive subtractive hybridization analysis revealed that eosinophil chemotactic factor by T lymphocytes (ECF-L), a mouse chitinase family protein, was selectively expressed in the lungs of mice with AHR. Induction of ECF-L expression was observed soon after allergen exposure but before the onset of airway inflammation. Cell-specific ECF-L expression was examined by in situ hybridization using digoxigenin-labeled antisense RNA probes and immunofluorescence staining. The assay revealed that the ECF-L-expressing cells in the lungs of the AHR-model mice are alveolar macrophages. Intratracheal administration of an adenoviral vector that expressed antisense ECF-L RNA (Ad-ECF-L-AS) suppressed AHR and eosinophil infiltration. These results indicate that ECF-L may play a critical role in allergic inflammation and bronchial asthma.

Novel stabilin-1 interacting chitinase-like protein (SI-CLP) is up-regulated in alternatively activated macrophages and secreted via lysosomal pathway

Mammalian Glyco_18-domain-containing proteins include catalytically active chitinases and chitinase-like proteins with cytokine activity involved in host defense and Th2-type inflammatory reactions. Here, we describe a novel human Glyco_18-domain-containing protein, SI-CLP, as an interacting partner of the endocytic/sorting receptor stabilin-1. Similarly to the chitinase-like cytokines YKL-39, YKL-40, and YM1/2, SI-CLP lacks a chitin-binding domain and catalytic amino acids. Using a novel mAb 1C11, we demonstrated that SI-CLP is sorted into late endosomes and secretory lysosomes in human alternatively activated macrophages. The direct interaction of SI-CLP with stabilin-1, their colocalization in the trans-Golgi network, and the reduced sorting of SI-CLP into lysosomes in macrophages treated with stabilin-1 siRNA suggest that stabilin-1 is involved in intracellular sorting of SI-CLP. Expression of SI-CLP in macrophages was strongly up-regulated by the Th2 cytokine IL-4 and by dexamethasone. This effect was suppressed by IFNgamma but not affected by IL-10. In contrast, expression of YKL-40 was induced by IFNgamma and suppressed by dexamethasone. Macrophages treated with IL-4 secreted SI-CLP, while costimulation with dexamethasone blocked secretion and resulted in intracellular accumulation of SI-CLP. The 1C11 mAb detected SI-CLP in human bronchoalveolar lavage and peripheral-blood leukocytes (PBLs), and can be used to analyze the role of SI-CLP in human disorders.

Increased lungkine and chitinase levels in allergic airway inflammation: a proteomics approach

Asthma is a chronic inflammatory disease characterized by pulmonary eosinophilia and airway hyperresponsiveness. Mechanisms underlying the pathogenesis of asthma are still not fully understood. The present study investigated alterations in global protein expression in bronchoalveolar lavage fluid in allergic airway inflammation using a proteomics approach. BALB/c mice sensitized and challenged with ovalbumin developed airway eosinophilia, mucus hypersecretion, elevation of immunoglobulin E, and airway hyperresponsiveness. Lavage fluid proteins from normal and asthmatic mice were resolved by two-dimensional gel electrophoresis, and identified by peptide mass fingerprinting matrix-assisted laser desorption/ionization-time of flight mass spectrometry. A total of 28 protein spots were significantly altered. Several of these proteins were undetectable or at very low levels in normal mice but were significantly increased in airway inflammation. These include lungkine, a recently described chemokine, a family of chitinases including Ym1, Ym2, and acidic mammalian chitinase, gob-5, a protein that mediates mucus secretion, and surfactant protein-D, a C-type lectin capable of modulating inflammatory responses. Overall, proteomics is a powerful tool in unraveling protein expression changes in allergic airway inflammation. The proteins identified in this study may be associated with the pathogenesis of allergic airway inflammation and may also be found useful as surrogate biomarkers for asthma.

Arginase activity differs with allergen in the effector phase of ovalbumin- versus trimellitic anhydride-induced asthma

Both trimellitic anhydride (TMA), a small molecular weight chemical, and ovalbumin (OVA), a reference protein allergen, cause asthma with eosinophilia. To test the hypothesis that different allergens elicit symptoms of asthma via different effector pathways, gene expression was compared in lungs of Balb/c mice sensitized with either TMA or OVA, followed by intratracheal challenge with TMA conjugated to mouse serum albumin (TMA-MSA) or OVA, respectively. Sensitized animals challenged with mouse serum albumin (MSA) alone were controls. Seventy-two hours after challenge, lung eosinophil peroxidase indicated that both allergens caused the same significant change in eosinophilia. Total RNA was isolated from lung lobes of 6-8 animals in each of four treatment groups and hybridized to Affymetrix U74Av2 GeneChips. False discovery rates (q-values) were calculated from an overall F test to identify candidate genes with differences in expression for the four groups. Using a q-value cutoff of 0.1, 853 probe sets had significantly different expression across the four treatment groups. Of these 853 probe sets, 376 genes had an Experimental/Control ratio of greater than 1.2 or less than 1/1.2 for either OVA- or TMA-treated animals, and 249 of the 376 genes were uniquely up- or down-regulated for OVA or TMA (i.e., differentially expressed with the allergen). qRT-PCR analysis of selected transcripts confirmed the gene expression analysis. Increases in both arginase transcript and enzyme activity were significantly greater in OVA-induced asthma compared to TMA-induced asthma. These data suggest that pathways of arginine metabolism and the importance of nitric oxide may differ in OVA- and TMA-induced asthma.

Schistosoma mekongi: a prominent neutrophil chemotactic activity of egg antigen with reference to that of Schistosoma japonicum

Schistosoma mekongi causes granulomatous lesions around eggs deposited in the liver with neutrophil-rich inflammatory reactions in the early stage of the egg laying. To define the aspects of the typical pathogenesis of S. mekongi infection, we determined the difference between soluble egg antigen (SEA) from S. mekongi and S. japonicum with a focus on chemotactic factors for neutrophils or eosinophils. Mean volume and protein amount of S. mekongi eggs was 71 and 58% of those of Schistosoma japonicum eggs, respectively. Neutrophil chemotactic activity of S. mekongi SEA was about two times higher than that of S. japonicum. In contrast, eosinophil chemotactic activity of S. mekongi SEA was about half of that of S. japonicum SEA. Molecular analysis revealed that S. mekongi SEA contains higher molecular-weight components with a lower level of glycosylation, and this is likely to be related to the intense neutrophil chemotactic activity in comparison with S. japonicum SEA. The prominent chemotactic reactivity for neutrophils is likely to be involved in the typical pathogenesis of mekongi schistosomiasis.

Expression of the full-length form of gp2 of equine herpesvirus 1 (EHV-1) completely restores respiratory virulence to the attenuated EHV-1 strain KyA in CBA mice

Wild-type equine herpesvirus 1 (EHV-1) strains express a large (250-kDa) glycoprotein, gp2, that is encoded by EUs4 (gene 71) located within the unique short region of the genome. DNA sequence analysis revealed that EUs4 of the pathogenic EHV-1 strain RacL11 is an open reading frame of 2,376 bp that encodes a protein of 791 amino acids. The attenuated EHV-1 vaccine strain KyA harbors an in-frame deletion of 1,242 bp from bp 222 to 1461 and expresses a truncated gp2 of 383 amino acids. To determine the relative contribution of gp2 to EHV-1 pathogenesis, we compared the course of respiratory infection of CBA mice infected with either wild-type RacL11, attenuated KyA, or a recombinant KyA that expresses the full-length gp2 protein (KyARgp2F). Mice infected with KyA lost a negligible amount of body weight (0.18% total weight loss) on day 1 postinfection and regained weight thereafter, whereas mice infected with KyARgp2F or RacL11 steadily lost weight beginning on day 1 and experienced a 20 and 18% loss in body weight, respectively, by day 3. Immunohistochemical and flow cytometric analyses revealed higher numbers of T and B lymphocytes and an extensive consolidation consisting of large numbers of Mac-1-positive cells in the lungs of animals infected with KyARgp2F compared to animals infected with KyA. RNase protection analyses revealed increased expression of numerous cytokines and chemokines, including interleukin-1beta (IL-1beta), IL-6, tumor necrosis factor alpha, macrophage inflammatory protein 1alpha (MIP-1alpha), MIP-1beta, MIP-2, interferon gamma-inducible protein, monocyte chemotactic protein 1, and T-cell activation gene 3 at 12 h postinfection with KyARgp2F. Three independent DNA array experiments confirmed these results and showed a 2- to 13-fold increase in the expression of 31 inflammatory genes at 8 and 12 h postinfection with KyARgp2F compared to infection with KyA. Taken together, the results indicate that expression of full-length gp2 is sufficient to restore full respiratory virulence to the attenuated KyA strain and raise caution concerning the inclusion of full-length gp2 in the development of EHV-1 vaccines.

Circulating YKL-40 levels during human endotoxaemia

YKL-40 is secreted by macrophages and neutrophils and patients with bacterial infections have elevated circulating YKL-40. The aim was to evaluate changes in plasma YKL-40 (determined by enzyme-linked immunosorbent assay (ELISA) at 0, 2, 4, 8, 24 and 32 h) in eight healthy volunteers after injection with Esherichia coli endotoxin or saline. Plasma YKL-40 increased after endotoxin injection from 31 microg/l (range 19-39 microg/l) to a maximum of 159 microg/l (61-552 microg/l, P < 0.01) at 24 h. The finding that plasma YKL-40 increased after endotoxin injection compared with saline (P < 0.001) suggests that YKL-40 has a functional role in infections.

The crystal structure of Ym1 at 1.31 A resolution

Upon nematode infection, murine peritoneal macrophages synthesize and secrete large amounts of the Ym1 protein, which is a unique functional marker for alternatively activated macrophages in T(H)2-mediated inflammatory responses. Ym1 shares significant structural similarity to the family 18 chitinases. Previously, Ym1 has been studied with respect to its carbohydrate-binding ability and glycosyl hydrolysis activity and this has led to various inconclusive interpretations. Our present co-crystallization and soaking experiments with various glucosamine or N-acetylglucosamine oligomers yield only the uncomplexed Ym1. The refined Ym1 structure at 1.31A resolution clearly displays a water cluster forming an extensive hydrogen bond network with the "active-site" residues. This water cluster contributes notable electron density to lower resolution maps and this might have misled and given rise to a previous proposal for a monoglucosamine-binding site for Ym1. A structural comparison of family 18 glycosidase (-like) proteins reveals a lack of several conserved residues in Ym1, and illustrates the versatility of the divergent active sites. Therefore, Ym1 may lack N-acetylglucosamine-binding affinity, and this suggests that a new direction should be taken to unravel the function of Ym1.

Helminth parasites--masters of regulation

Immune regulation by parasites is a global concept that includes suppression, diversion, and conversion of the host immune response to the benefit of the pathogen. While many microparasites escape immune attack by antigenic variation or sequestration in specialized niches, helminths appear to thrive in exposed extracellular locations, such as the lymphatics, bloodstream, or gastrointestinal tract. We review here the multiple layers of immunoregulation that have now been discovered in helminth infection and discuss both the cellular and the molecular interactions involved. Key events among the host cell population are dominance of the T-helper 2 cell (Th2) phenotype and the selective loss of effector activity, against a background of regulatory T cells, alternatively activated macrophages, and Th2-inducing dendritic cells. Increasingly, there is evidence of important effects on other innate cell types, particularly mast cells and eosinophils. The sum effect of these changes to host reactivity is to create an anti-inflammatory environment, which is most favorable to parasite survival. We hypothesize therefore that parasites have evolved specific molecular strategies to induce this conducive landscape, and we review the foremost candidate immunomodulators released by helminths, including cytokine homologs, protease inhibitors, and an intriguing set of novel products implicated in immune suppression.

Chitinase and Fizz family members are a generalized feature of nematode infection with selective upregulation of Ym1 and Fizz1 by antigen-presenting cells

Ym1 and Fizz1 are secreted proteins that have been identified in a variety of Th2-mediated inflammatory settings. We originally found Ym1 and Fizz1 as highly expressed macrophage genes in a Brugia malayi infection model. Here, we show that their expression is a generalized feature of nematode infection and that they are induced at the site of infection with both the tissue nematode Litomosoides sigmodontis and the gastrointestinal nematode Nippostrongylus brasiliensis. At the sites of infection with N. brasiliensis, we also observed induction of other chitinase and Fizz family members (ChaFFs): acidic mammalian chitinase (AMCase) and Fizz2. The high expression of both Ym1 and AMCase in the lungs of infected mice suggests that abundant chitinase production is an important feature of Th2 immune responses in the lung. In addition to expression of ChaFFs in the tissues, Ym1 and Fizz1 expression was observed in the lymph nodes. Expression both in vitro and in vivo was restricted to antigen-presenting cells, with the highest expression in B cells and macrophages. ChaFFs may therefore be important effector or wound-repair molecules at the site of nematode infection, with potential regulatory roles for Ym1 and Fizz1 in the draining lymph nodes.

Acidic mammalian chitinase--a potential target for asthma therapy

Recently, inhibition of acidic mammalian chitinase in a murine asthmatic model was reported to have a profound anti-inflammatory effect, leading to the suggestion that this enzyme might be a novel therapeutic target for T helper 2-driven diseases such as asthma. The mechanism of action of such an enzyme in asthma pathology is unclear but the enzyme appears to mediate interleukin 13-dependent responses in a STAT6-independent manner. This observation has led to the proposal that chitinase family members are important mediators in allergic diseases including asthma.

The chitinase 3-like protein human cartilage glycoprotein 39 inhibits cellular responses to the inflammatory cytokines interleukin-1 and tumour necrosis factor-alpha

Expression of the chitinase 3-like protein HC-gp39 (human cartilage glycoprotein 39) is associated with conditions of increased matrix turnover and tissue remodelling. High levels of this protein have been found in sera and synovial fluids of patients with inflammatory and degenerative arthritis. In order to assess the role of HC-gp39 in matrix degradation induced by inflammatory cytokines, we have examined its effect on the responses of connective tissue cells to TNF-alpha (tumour necrosis factor-alpha) and IL-1 (interleukin-1) with respect to activation of signalling pathways and production of MMPs (matrix metalloproteases) and chemokines. Stimulation of human skin fibroblasts or articular chondrocytes with IL-1 or TNF-alpha in the presence of HC-gp39 resulted in a marked reduction of both p38 mitogen-activated protein kinase and stress-activated protein kinase/Jun N-terminal kinase phosphorylation, whereas nuclear translocation of nuclear factor kappaB proceeded unimpeded. HC-gp39 suppressed the cytokine-induced secretion of MMP1, MMP3 and MMP13, as well as secretion of the chemokine IL-8. The suppressive effects of HC-gp39 were dependent on phosphoinositide 3-kinase activity, and treatment of cells with HC-gp39 resulted in AKT-mediated serine/threonine phosphorylation of apoptosis signal-regulating kinase 1. This process could therefore be responsible for the down-regulation of cytokine signalling by HC-gp39. These results suggest a physiological role for HC-gp39 in limiting the catabolic effects of inflammatory cytokines.

Identification and molecular characterization of two immune-responsive chitinase-like proteins from Anopheles gambiae

Two haemolymph proteins that are processed rapidly and specifically in response to exposure to bacteria have been identified from Anopheles gambiae. Both proteins, Anopheles gambiae bacteria-responsive 1 (AgBR1) and AgBR2, are similar to chitinases but belong to a family of proteins that have lost chitinolytic activity. AgBR1 and AgBR2 are converted to smaller forms in vivo or in vitro on exposure to bacteria, and AgBR2 also can be processed on exposure to peptidoglycan alone. AgBR1 and AgBR2 do not bind to bacteria or chitin beads. The AgBR1 and AgBR2 genes are expressed in all developmental stages. In adults, AgBR1 expression is restricted to the fat body, whereas AgBR2 is expressed in many tissues.

Highly up-regulated CXCR3 expression on eosinophils in mice infected with Schistosoma japonicum

CXCR3, predominately expressed on memory/activated T cells, is a receptor for both interferon-gamma inducible protein-10/CXC ligand 10 (CXCL10) and monokine induced by interferon-gamma/CXCL9. We reported here that CXCR3 was highly up-regulated on infiltrating eosinophils in Schistosoma japonicum egg-induced granuloma in the mouse liver. It was also highly and functionally up-regulated on peritoneal exudate eosinophils in mice infected with S. japonicum. The phenomena were demonstrated at protein and mRNA levels using immunohisto- and immunocytochemistry evaluation of biopsy, flow cytometry and real-time quantitative reverse transcriptase-polymerase chain reaction technique, and verified by Northern blotting and chemotaxis assay in vitro. We also found that CCR3 expression on the infiltrating and peritoneal exudate cells was significantly decreased, CXCR4 expression was unchanged during the 42-day period of infection. We screened mRNA expression levels of the all known chemokine receptors in purified peritoneal exudate eosinophils and liver granuloma dominated by eosinophils. CXCR3 was highly and functionally up-regulated on peritoneal exudate eosinophils in mice infected with S. japonicum, meanwhile CCR3 was significantly and functionally down-regulated in these cells. The findings could lead to a better understanding of the chemokine receptor expression pattern of eosinophils at inflamed tissue sites caused by parasites. These could be also crucial for establishing a therapeutic strategy for eosinophilic inflammation via intervention in chemokine actions.

Identification of a ubiquitin family protein as a novel neutrophil chemotactic factor

Neutrophil chemotaxis is a process that is essential for the recruitment of neutrophils to an inflamed site. In the present study, we found a remarkable increase in neutrophil chemotactic activity in the lysate of red blood cells (RBC) of mice infected with murine malaria, Plasmodium yoelii. A neutrophil chemotactic factor with an apparent molecular weight of 17 kDa (IP17) was isolated from RBC by a combination of anion-exchange chromatography on DE52 and cation-exchange chromatography on Mono S. A comprehensive GenBank database search of N-terminal amino acid sequences and MALDI-TOF mass analysis of IP17 revealed that IP17 is identical to a murine homologue of ISG15/UCRP, a member of the ubiquitin family of proteins that are inducible by interferon-beta. Recombinant mouse ISG15 showed neutrophil chemotactic activity comparable to that of natural IP17. IP17 showed specific chemotactic activity forward neutrophils and activated neutrophils to induce the release of eosinophil chemotactic factors. These results suggest that the ubiquitin family protein ISG15/UCRP has novel functions in neutrophil-mediated immune mechanisms.

Structure and ligand-induced conformational change of the 39-kDa glycoprotein from human articular chondrocytes

The 39-kDa human cartilage glycoprotein (HCGP39), a member of a novel family of chitinase-like lectins (Chilectins), is overexpressed in articular chondrocytes and certain cancers. Proposed functions of this protein include a role in connective tissue remodeling and defense against pathogens. Similar to other Chi-lectins, HCGP39 promotes the growth of connective tissue cells. The ability of HCGP39 to activate cytoplasmic signaling pathways suggests the presence of a ligand for this protein at the cell surface. There is currently no information regarding the identity of any physiological or pathological ligands of the Chi-lectins or the nature of the protein-ligand interaction. Here, we show that HCGP39 is able to bind chitooligosaccharides with micromolar affinity. Crystal structures of the native protein and a complex with GlcNAc8 show that the ligand is bound in identical fashion to family 18 chitinases. However, unlike the chitinases, binding of the oligosaccharide ligand to HCGP39 induces a large conformational change. Thus, HCGP39 could be a lectin that binds chitin-like oligosaccharide ligands and possibly plays a role in innate responses to chitinous pathogens, such as fungi and nematodes.

Eosinophil chemotactic factor-L (ECF-L): a novel osteoclast stimulating factor

Screening a cDNA library enriched for genes expressed in OCLs identified ECF-L. ECF-L enhanced OCL formation without increasing RANKL levels. Anti-ECF-L inhibited RANKL-induced OCL formation. These results support a potent role of ECF-L in osteoclastogenesis.

INTRODUCTION

To investigate the molecular mechanisms that control osteoclastogenesis, we developed an immortalized osteoclast (OCL) precursor cell line that forms mature OCLs in the absence of stromal cells and used it to form pure populations of OCLs.

MATERIALS AND METHODS

Polymerase chain reaction (PCR) selective cDNA subtraction was used to identify genes that are highly expressed in mature OCLs compared with OCL precursors employing OCL and OCL precursors derived from this cell line.

RESULTS

Eosinophil chemotactic factor-L (ECF-L), a previously described chemotactic factor for eosinophils, was one of the genes identified. Conditioned media from 293 cells transfected with mECF-L cDNA, or purified ECF-L Fc protein, increased OCL formation in a dose-dependent manner in mouse bone marrow cultures treated with 10(-10) M 1,25(OH)2D3. OCLs derived from marrow cultures treated with ECF-L conditioned media formed increased pit numbers and resorption area per dentin slice compared with OCLs induced by 1,25(OH)2D3 (p < 0.01). Addition of an antisense S-oligonucleotide to mECF-L inhibited OCL formation in murine bone marrow cultures treated only with 10(-9) M 1,25(OH)2D3 compared with the sense S-oligonucleotide control. Time course studies demonstrated that ECF-L acted at the later stages of OCL formation, and chemotactic assays showed that mECF-L increased migration of OCL precursors. mECF-L mRNA was detectable in mononuclear and multinucleated cells by in situ hybridization. Interestingly, a neutralizing antibody to ECF-L blocked RANKL or 10(-9) M 1,25(OH)2D3-induced OCL formation in mouse bone marrow cultures, although ECF-L did not induce RANKL expression.

CONCLUSIONS

These data show ECF-L is a previously unknown factor that is a potent mediator of OCL formation, which acts at the later stages of OCL formation and enhances the effects of RANKL.

Transcriptional profiling during the early differentiation of granulocyte and monocyte progenitors controlled by conditional versions of the E2a-Pbx1 oncoprotein

The E2a-Pbx1 oncoprotein of human pre-B cell leukemia prevents differentiation and maintains continued cell division in cultured myeloid progenitors. Previously, estrogen-dependent forms of E2a-Pbx1 were generated that immortalized neutrophil (ECoM-G cells) or monocyte (ECoM-M cells) progenitors and that permitted their terminal differentiation upon estrogen withdrawal. Here, representational difference analysis (RDA) and Affymetrix array analysis are used to identify changes in gene expression that accompany the early differentiation of these cells. The promoters of these genes, whose expression changes upon E2a-Pbx1 inactivation, integrate the biochemical mechanism through which E2a-Pbx1 arrests differentiation and maintains cell division. Inactivation of E2a-Pbx1 caused the 10- to 80-fold up regulation of a small subset of myeloid differentiation genes (MRP8, Cnlp, NB1, Bactenecin, YM1, Stefin 1, Lipocortin, Lactoferrin, gp91 phox and Ly6-G) and a 10-fold down regulation of the TLE1 corepressor gene, as well as of a group of genes expressed in dividing cells (c-Myc, Nucleophosmin, Spermidine synthase, NOP56, Hnrpa1). Transcription of 97% of cellular genes, including 300 other transcription factor genes (21 Hox genes) and other myeloid genes, varied less than 3-fold, with most varying less than 50%. Therefore, E2a-Pbx1 prevents transcription and maintains the cell cycle by a specific rather than a global transcriptional mechanism. Monocyte progenitors were distinguished by persistent expression of IRF8 and of a category of other genes characterized as "interferon-stimulated" (ISG15, ISG20, Ifit1, Ifi202a, Ifi203, IfiS204, Ifi204-related, IRF7 and Ly6-E.1), as well as by the upregulation of the Lrg21 bZip transcription factor gene during late differentiation. The synchronous expression of stage-specific and cell cycle genes regulated by E2a-Pbx1 in these cell lines comprises a model system in which analysis of their promoters can be used as a starting point to backtrack to the transcriptional mechanisms of oncogenesis by E2a-Pbx1.

Identification and molecular characterization of a chitinase from the hard tick Haemaphysalis longicornis

A cDNA encoding tick chitinase was cloned from a cDNA library of mRNA from Haemaphysalis longicornis eggs and designated as CHT1 cDNA. The CHT1 cDNA contains an open reading frame of 2790 bp that codes for 930 amino acid residues with a coding capacity of 104 kDa. The deduced amino acid sequence shows a 31% amino acid homology to Aedes aegypti chitinase and a multidomain structure containing one chitin binding peritrophin A domain and two glycosyl hydrolase family 18 chitin binding domains. The endogenous chitinase of H. longicornis was identified by a two-dimensional immunoblot analysis with mouse anti-rCHT1 serum and shown to have a molecular mass of 108 kDa with a pI of 5.0. A recombinant baculovirus AcMNPV.CHT1-expressed rCHT1 is glycosylated and able to degrade chitin. Chitin degradation was ablated by allosamidin in a dose-dependent manner. The optimal temperature and pH for activity of the purified chitinase were 45 degrees C and pH 5-7. The CHT1 cDNA has an ELR motif for chemokine-mediated angiogenesis and appears to be a chitinase of the chemokine family. Localization analysis using mouse anti-rCHT1 serum revealed that native chitinase is highly expressed in the epidermis and midgut of the tick. AcMNPV.CHT1 topically applied to H. longicornis ticks exhibited replication. This is the first report of insect baculovirus infection of ticks. The importance of AcMNPV.CHT1 as a novel bio-acaricide for tick control is discussed.

Eosinophilic crystals as a distinctive morphologic feature of a hyaline droplet nephropathy in a mouse model of acute myelogenous leukaemia

Eosinophilic crystals have been described in the upper and lower respiratory tract, gall bladder, intrahepatic bile ducts and glandular stomach of different laboratory mice strains. They have been recently identified as chitinase-like (Ym1/Ym2) proteins. Here we describe the occurrence of eosinophilic crystals in the renal tubules of mice with experimentally induced acute myelogenous leukaemia. Fourteen FVB/N and 29 129Sv mice of both sexes, 8-10 weeks of age, were employed to establish a model of human acute myelogenous leukaemia. Nine mice that developed a widespread acute myelogenous leukaemia revealed the presence of eosinophilic crystals in renal tubules. The presence of eosinophilic crystals in the kidneys was constantly associated with a hyaline droplet nephropathy. Immunohistochemistry showed that the crystals and the hyaline droplets were composed of chitinase-like (Ym1/Ym2) proteins. Furthermore, immunoreactivity for Ym1/Ym2 proteins was also detected in the crystalline material stored in the cytoplasm of large macrophage-like cells or in extracellular localization within the leukaemic infiltrates. On the basis of our results we hypothesize that the detection of the Ym1/Ym2 proteins in the urine of mice might represent a feasible indicator of the burden and progression of the leukaemic condition in our murine model.

Macrophages in chronic type 2 inflammation have a novel phenotype characterized by the abundant expression of Ym1 and Fizz1 that can be partly replicated in vitro

Using a murine model of nematode infection, we have discovered macrophages that display a novel phenotype that may be characteristic of macrophages in chronic type 2 inflammation. These nematode-elicited macrophages (NeMphi) are characterized by two unique features: the ability to actively suppress proliferation of a broad range of cell types and the high level expression of two novel macrophage genes, Ym1 and Fizz1. NeMphi also show some similarities with in vitro-derived 'alternatively activated macrophages' such as the downregulation of inflammatory cytokines. We therefore investigated how much of the phenotype discovered in vivo could be replicated by activation with Th2 cytokines in vitro. Fizz1 and Ym1 were upregulated by IL-4 and IL-13 in vitro but at a considerably lower level than in NeMphi. In vitro treatment with IL-4 could also partly replicate the ability of NeMphi to block cellular proliferation. As well as the quantitative differences in gene expression and suppressive phenotype, we also observed phenotypic differences in the cell morphology between macrophages activated in vivo and in vitro. Although this study illustrated that macrophages activated in chronic inflammation have distinct features that cannot be readily reproduced in vitro it also demonstrated that some features of the complex NeMphi phenotype can be replicated by treatment of cultured macrophages with Th2 cytokines. In future, we hope to use in vitro analysis to help define the pathways that lead to this distinctive in vivo macrophage phenotype.

TH2 cytokines and allergic challenge induce Ym1 expression in macrophages by a STAT6-dependent mechanism

The diverse functions of macrophages as participants in innate and acquired immune responses are regulated by the specific milieu of environmental factors, cytokines, and other signaling molecules that are encountered at sites of inflammation. Microarray analysis of the transcriptional response of mouse peritoneal macrophages to the T(H)2 cytokine interleukin-4 (IL-4) identified Ym1 and arginase as the most highly up-regulated genes, exhibiting more than 68- and 88-fold induction, respectively. Molecular characterization of the Ym1 promoter in transfected epithelial and macrophage cell lines revealed the presence of multiple signal transducers and activators of transcription 6 (STAT6) response elements that function in a combinatorial manner to mediate transcriptional responses to IL-4. The participation of STAT6 as an obligate component of protein complexes binding to these sites was established by analysis of nuclear extracts derived from STAT6-deficient macrophages. Macrophage expression of Ym1 was highly induced in vivo by an IL-4- and STAT6-dependent mechanism during the evolution of allergic peritonitis, supporting the biological relevance of the IL-4-dependent pathway characterized ex vivo in peritoneal macrophages. These studies establish Ym1 as a highly inducible STAT6-dependent transcript in T(H)2-biased inflammation and define Cis-active elements in the Ym1 promoter that are required for this transcriptional response.

IL-4 dependent alternatively-activated macrophages have a distinctive in vivo gene expression phenotype

BACKGROUND

"Alternatively-activated" macrophages are found in Th2-mediated inflammatory settings such as nematode infection and allergic pulmonary inflammation. Due in part to a lack of markers, these cells have not been well characterized in vivo and their function remains unknown.

RESULTS

We have used murine macrophages elicited by nematode infection (NeM(phi)) as a source of in vivo derived alternatively activated macrophages. Using three distinct yet complementary molecular approaches we have established a gene expression profile of alternatively activated macrophages and identified macrophage genes that are regulated in vivo by IL-4. First, genes abundantly expressed were identified by an expressed sequence tag strategy. Second, an array of 1176 known mouse genes was screened for differential expression between NeM(phi) from wild type or IL-4 deficient mice. Third, a subtractive library was screened to identify novel IL-4 dependent macrophage genes. Differential expression was confirmed by real time RT-PCR analysis.

CONCLUSIONS

Our data demonstrate that alternatively activated macrophages generated in vivo have a gene expression profile distinct from any macrophage population described to date. Several of the genes we identified, including those most abundantly expressed, have not previously been associated with macrophages and thus this study provides unique new information regarding the phenotype of macrophages found in Th2-mediated, chronic inflammatory settings. Our data also provide additional in vivo evidence for parallels between the inflammatory processes involved in nematode infection and allergy.

The chitinase 3-like protein human cartilage glycoprotein 39 (HC-gp39) stimulates proliferation of human connective-tissue cells and activates both extracellular signal-regulated kinase- and protein kinase B-mediated signalling pathways

Human cartilage glycoprotein 39 (HC-gp39) is a glycoprotein secreted by articular chondrocytes, synoviocytes and macrophages. Increased levels of HC-gp39 have been demonstrated in synovial fluids of patients with rheumatoid or osteoarthritis. The increased secretion of HC-gp39 under physiological and pathological conditions with elevated connective-tissue turnover suggests its involvement in the homoeostasis of these tissues. We report here that HC-gp39 promotes the growth of human synovial cells as well as skin and fetal lung fibroblasts. A dose-dependent growth stimulation was observed when each of the fibroblastic cell lines was exposed to HC-gp39 in a concentration range from 0.1 to 2 nM, which is similar to the effective dose of the well-characterized mitogen, insulin-like growth factor-1. At suboptimal concentrations, the two growth factors work in a synergistic fashion. The use of selective inhibitors of the mitogen-activated protein kinase and the protein kinase B (AKT) signalling pathways indicates that both are involved in mediating the mitogenic response to HC-gp39. Phosphorylation of both extracellular signal-regulated kinases 1/2 and AKT occurred in a dose- and time-dependent fashion upon addition of HC-gp39. Activation of these signalling pathways could also be demonstrated in human chondrocytes. Thus HC-gp39 initiates a signalling cascade in connective-tissue cells which leads to increased cell proliferation, suggesting that this protein could play a major role in the pathological conditions leading to tissue fibrosis.

YKL-40 is elevated in cerebrospinal fluid from patients with purulent meningitis

YKL-40, a member of the family 18 glycosyl hydrolases, is secreted by activated neutrophils and macrophages. It is a growth factor for connective tissue cells and a potent migration factor for endothelial cells and may function in inflammation and tissue remodeling. YKL-40 was determined in 134 cerebrospinal fluid (CSF) samples taken on admission from patients suspected of having meningitis (48 with purulent meningitis, 49 with lymphocytic meningitis, 5 with encephalitis, and 32 without evidence of meningitis). YKL-40 levels in CSF were significantly higher in patients with purulent meningitis (median, 663 microg/liter [range, 20 to 8,960]) and encephalitis (5,430 microg/liter [620 to 11,600]) than in patients with lymphocytic meningitis (137 microg/liter [41 to 1,865]) or patients without meningitis (167 microg/liter [24 to 630]) (Kruskal-Wallis and Dunn multiple comparison tests, P < 0.001). CSF YKL-40 levels were also determined for 26 patients with purulent meningitis having a repuncture, and patients who died (n = 5) had significantly higher YKL-40 levels than patients who survived (n = 21) (2,100 microg/liter [1,160 to 7,050] versus 885 microg/liter [192 to 15,400], respectively; Mann-Whitney test, P = 0.018). YKL-40 was most likely locally produced, since patients with infections of the central nervous system had CSF YKL-40 levels that were at least 10-fold higher than the corresponding levels in serum (2,033 microg/liter [470 to 11,600] versus 80 microg/liter [19 to 195]). The CSF neopterin level was the biochemical parameter in CSF and blood that correlated best with CSF YKL-40 levels, indicating that YKL-40 may be produced by activated macrophages within the central nervous system. In conclusion, high levels of YKL-40 in CSF are found in patients with purulent meningitis.

Crystal structure of imaginal disc growth factor-2. A member of a new family of growth-promoting glycoproteins from Drosophila melanogaster

Imaginal disc growth factor-2 (IDGF-2) is a member of a recently described family of Drosophila melanogaster-soluble polypeptide growth factors that promote cell proliferation in imaginal discs. Although their precise mode of action has not been established, IDGFs cooperate with insulin in stimulating the growth of imaginal disc cells. We report the crystal structure of IDGF-2 at 1.3-A resolution. The structure shows the classical (betaalpha)(8) barrel-fold of family 18 glycosyl hydrolases, with an insertion of an alpha + beta domain similar to that of Serratia marcescens chitinases A and B. However, amino acid substitutions in the consensus catalytic sequence of chitinases give IDGF-2 a less negatively charged environment in its putative ligand-binding site and preclude the nucleophilic attack mechanism of chitin hydrolysis. Particularly important is the replacement of Glu by Gln at position 132, which has been shown to abolish enzymatic activity in chitinases. Nevertheless, a modest conservation of residues that participate in oligosaccharide recognition suggests that IDGF-2 could bind carbohydrates, assuming several conformational changes to open the partially occluded binding site. Thus, IDGFs may have evolved from chitinases to acquire new functions as growth factors, interacting with cell surface glycoproteins implicated in growth-promoting processes, such as the Drosophila insulin receptor.

Ym1 is a neutrophil granule protein that crystallizes in p47phox-deficient mice

Crystals were discovered within the aged lung and at sites of chronic inflammation in a mouse model of chronic granulomatous disease. Following re-crystallization at neutral pH, the crystals were identified as the chitinase-like protein Ym1, expressed in organs of the lymphoreticular system, the lung, and distal stomach. Ym1 was shown to be a neutrophil granule protein and to have weak beta-N-acetylglucosaminidase activity, indicating that it might contribute to the digestion of glycosaminoglycans. Crystal formation is likely to be a function of excess neutrophil turnover at sites of inflammation in the chronic granulomatous disease mouse. Failure to remove subcutaneous Ym1 crystals injected into knockout mice indicates that a failure of digestion may also contribute to crystallization.