Synthesis, sorting, and processing into distinct isoforms of human macrophage chitotriosidase

Inhibition of NF-κB with an Analog of Withaferin-A Restores TDP-43 Homeostasis and Proteome Profiles in a Model of Sporadic ALS

The current knowledge on pathogenic mechanisms in amyotrophic lateral sclerosis (ALS) has widely been derived from studies with cell and animal models bearing ALS-linked genetic mutations. However, it remains unclear to what extent these disease models are of relevance to sporadic ALS. Few years ago, we reported that the cerebrospinal fluid (CSF) from sporadic ALS patients contains toxic factors for disease transmission in mice via chronic intracerebroventricular (i.c.v.) infusion. Thus a 14-day i.c.v. infusion of pooled CSF samples from ALS cases in mice provoked motor impairment as well as ALS-like pathological features. This offers a unique paradigm to test therapeutics in the context of sporadic ALS disease. Here, we tested a new Withaferin-A analog (IMS-088) inhibitor of NF-κB that was found recently to mitigate disease phenotypes in mouse models of familial disease expressing TDP-43 mutant. Our results show that oral intake of IMS-088 ameliorated motor performance of mice infused with ALS-CSF and it alleviated pathological changes including TDP-43 proteinopathy, neurofilament disorganization, and neuroinflammation. Moreover, CSF infusion experiments were carried out with transgenic mice having neuronal expression of tagged ribosomal protein (hNfL-RFP mice), which allowed immunoprecipitation of neuronal ribosomes for analysis by mass spectrometry of the translational peptide signatures. The results indicate that treatment with IMS-088 prevented many proteomic alterations associated with exposure to ALS-CSF involving pathways related to cytoskeletal changes, inflammation, metabolic dysfunction, mitochondria, UPS, and autophagy dysfunction. The effective disease-modifying effects of this drug in a mouse model based on i.c.v. infusion of ALS-CSF suggest that the NF-κB signaling pathway represents a compelling therapeutic target for sporadic ALS.

Metabolism-driven glycosylation represents therapeutic opportunities in interstitial lung diseases

Metabolic changes are coupled with alteration in protein glycosylation. In this review, we will focus on macrophages that are pivotal in the pathogenesis of pulmonary fibrosis and sarcoidosis and thanks to their adaptable metabolism are an attractive therapeutic target. Examples presented in this review demonstrate that protein glycosylation regulates metabolism-driven immune responses in macrophages, with implications for fibrotic processes and granuloma formation. Targeting proteins that regulate glycosylation, such as fucosyltransferases, neuraminidase 1 and chitinase 1 could effectively block immunometabolic changes driving inflammation and fibrosis, providing novel avenues for therapeutic interventions.

A novel humanized Chi3l1 blocking antibody attenuates acetaminophen-induced liver injury in mice

Acetaminophen (APAP) overdose is a leading cause of acute liver injury in the USA. The chitinase 3-like-1 (Chi3l1) protein contributes to APAP-induced liver injury (AILI) by promoting hepatic platelet recruitment. Here, we report the development of a Chi3l1-targeting antibody as a potential therapy for AILI. By immunizing a rabbit successively with the human and mouse Chi3l1 proteins, we isolated cross-reactive monoclonal antibodies (mAbs) from single memory B cells. One of the human and mouse Chi3l1 cross-reactive mAbs was humanized and characterized in both in vitro and in vivo biophysical and biological assays. X-ray crystallographic analysis of the lead antibody C59 in complex with the human Chi3l1 protein revealed that the kappa light contributes to majority of the antibody-antigen interaction; and that C59 binds to the 4α-5β loop and 4α-helix of Chi3l1, which is a functional epitope and hotspot for the development of Chi3l1 blocking antibodies. We humanized the C59 antibody by complementarity-determining region grafting and kappa chain framework region reverse mutations. The humanized C59 antibody exhibited similar efficacy as the parental rabbit antibody C59 in attenuating AILI in vivo. Our findings validate Chi3l1 as a potential drug target for AILI and provide proof of concept of developing Chi3l1 blocking antibody as a therapy for the treatment of AILI.

Chitotriosidase as a biomarker for gangliosidoses

Elevated serum chitotriosidase (CHITO) is an indication of macrophage activation, and its capacity have been explored as a marker of inflammation in a number of disease states. For over a decade, CHITO plasma levels have been used by clinicians as a biomarker of inflammation in the lysosomal disease, Gaucher disease, including monitoring response to therapies in patients with Gaucher disease type I. Although it is becoming increasingly recognized that inflammation is a prominent component of many lysosomal diseases, the relation of CHITO levels to disease burden has not been well-characterized in the large majority of lysosomal diseases. Moreover, the role of CHITO in lysosomal diseases that affect the central nervous system (CNS) has not been systematically studied. In this study, one hundred and thirty-four specimens of CSF and serum were collected from 34 patients with lysosomal diseases affecting the CNS. This study included patients with GM1-gangliosidosis, GM2-gangliosidosis, mucopolysaccharidoses (MPS), multiple sulfatase deficiency and Gaucher disease. CHITO levels in the CSF were significantly higher in patients with more rapidly progressing severe neurological impairment: GM1-gangliosidosis vs MPS (p < 0.0001); GM2-gangliosidosis vs MPS (p < 0.0001). CHITO levels were higher in patients with the more severe phenotypes compared to milder phenotypes in GM1-gangliosidosis and GM2-gangliosidosis (serum CHITO in GM1-gangliosidosis infantile vs juvenile p = 0.025; CSF CHITO in Tay-Sachs infantile vs Tay-Sachs late-onset p < 0.0001). Moreover, higher CHITO levels in the CSF were significantly associated with lower cognitive test scores in patients with GM1-gangliosidosis, GM2-gangliosidosis, and MPS (p = 1.12*10^-5, R² = 0.72). Patients with infantile GM1-gangliosidosis showed increasing CSF CHITO over time, suggesting that CSF CHITO reflects disease progression and a possible surrogate endpoint for future clinical trials with infantile GM1-gangliosidosis. In summary, these results support the use of CSF CHITO to diagnose between different disease phenotypes and as a valuable tool for monitoring disease progression in patients. These results necessitate the inclusion of CHITO as an exploratory biomarker for clinical trials.

Expression of Chitotriosidase in Macrophages Modulates Atherosclerotic Plaque Formation in Hyperlipidemic Mice

Objective

To determine whether overexpression of the chitin degrading enzyme, chitotriosidase (CHIT1), modulates macrophage function and ameliorates atherosclerosis.

Approach and Results

Using a mouse model that conditionally overexpresses CHIT1 in macrophages (CHIT1-Tg) crossbred with the Ldlr ^-/- mouse provided us with a means to investigate the effects of CHIT1 overexpression in the context of atherosclerosis. In vitro, CHIT1 overexpression by murine macrophages enhanced protein expression of IL-4, IL-8, and G-CSF by BMDM upon stimulation with a combination of lipopolysaccharide (LPS) and interferon-γ (IFN-γ). Phosphorylation of ERK1/2 and Akt was also down regulated when exposed to the same inflammatory stimuli. Hyperlipidemic, Ldlr ^-/--CHIT1-Tg (CHIT1-OE) mice were fed a high-fat diet for 12 weeks in order to study CHIT1 overexpression in atherosclerosis. Although plaque size and lesion area were not affected by CHIT1 overexpression in vivo, the content of hyaluronic acid (HA) and collagen within atherosclerotic plaques of CHIT1-OE mice was significantly greater. Localization of both ECM components was markedly different between groups.

Conclusions

These data demonstrate that CHIT1 alters cytokine expression and signaling pathways of classically activated macrophages. In vivo, CHIT1 modifies ECM distribution and content in atherosclerotic plaques, both of which are important therapeutic targets.

LC-MS/MS analysis of plasma glucosylsphingosine as a biomarker for diagnosis and follow-up monitoring in Gaucher disease in the Spanish population

Background

Gaucher disease (GD), caused by a deficiency in acid β-glucosidase, leads to the accumulation of glucosylsphingosine (GluSph), which has been used as a powerful biomarker for the diagnosis and follow-up of GD. Our aim was to perform the first retrospective study of GluSph in Spanish patients, analyzing its relationship with classical biomarkers and other parameters of disease and its utility regarding treatment monitoring.

Methods

Classical biomarkers were evaluated retrospectively by standard methods in a total of 145 subjects, including 47 GD patients, carriers, healthy controls and patients suffering from other lysosomal lipidoses. GluSph was also measured using a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method developed as part of the present study.

Results

The optimized method presented intra- and inter-assay variations of 3.1 and 11.5%, respectively, overall recovery higher than 96% and linearity up to plasma concentrations of 1000 ng/mL with 100% specificity and sensitivity. Only GD patients displayed GluSph levels above 5.4 ng/mL at diagnosis and this was significantly correlated with the classical biomarkers chitotriosidase (r = 0.560) and the chemokine CCL18/PARC (CCL18/PARC) (ρ = 0.515), as well as with the Spanish magnetic resonance imaging index (S-MRI, r = 0.364), whereas chitotriosidase correlated with liver volume (r = 0.372) and CCL18/PARC increased in patients with bone manifestations (p = 0.005). GluSph levels decreased with treatment in naïve patients.

Conclusions

Plasma GluSph is the most disease-specific biomarker for GD with demonstrated diagnostic value and responsiveness to therapy. GluSph in the present series of patients failed to demonstrate better correlations with clinical characteristics at onset than classical biomarkers.

YKL-39 as a Potential New Target for Anti-Angiogenic Therapy in Cancer

YKL-39 belongs to the evolutionarily conserved family of Glyco_18-containing proteins composed of chitinases and chitinase-like proteins. Chitinase-like proteins (CLPs) are secreted lectins that lack hydrolytic activity due to the amino acid substitutions in their catalytic domain and combine the functions of cytokines and growth factors. One of the major cellular sources that produce CLPs in various pathologies, including cancer, are macrophages. Monocytes recruited to the tumor site and programmed by tumor cells differentiate into tumor-associated macrophages (TAMs), which are the primary source of pro-angiogenic factors. Tumor angiogenesis is a crucial process for supplying rapidly growing tumors with essential nutrients and oxygen. We recently determined that YKL-39 is produced by tumor-associated macrophages in breast cancer. YKL-39 acts as a strong chemotactic factor for monocytes and stimulates angiogenesis. Chemotherapy is a common strategy to reduce tumor size and aggressiveness before surgical intervention, but chemoresistance, resulting in the relapse of tumors, is a common clinical problem that is critical for survival in cancer patients. Accumulating evidence indicates that TAMs are essential regulators of chemoresistance. We have recently found that elevated levels of YKL-39 expression are indicative of the efficiency of the metastatic process in patients who undergo neoadjuvant chemotherapy. We suggest YKL-39 as a new target for anti-angiogenic therapy that can be combined with neoadjuvant chemotherapy to reduce chemoresistance and inhibit metastasis in breast cancer patients.

Differences in the chitinolytic activity of mammalian chitinases on soluble and insoluble substrates

Chitin is an abundant polysaccharide used by many organisms for structural rigidity and water repulsion. As such, the insoluble crystalline structure of chitin poses significant challenges for enzymatic degradation. Acidic mammalian chitinase, a processive glycosyl hydrolase, is the primary enzyme involved in the degradation of environmental chitin in mammalian lungs. Mutations to acidic mammalian chitinase have been associated with asthma, and genetic deletion in mice increases morbidity and mortality with age. We initially set out to reverse this phenotype by engineering hyperactive acidic mammalian chitinase variants. Using a screening approach with commercial fluorogenic substrates, we identified mutations with consistent increases in activity. To determine whether the activity increases observed were consistent with more biologically relevant chitin substrates, we developed new assays to quantify chitinase activity with insoluble chitin, and identified a one-pot fluorogenic assay that is sufficiently sensitive to quantify changes to activity due to the addition or removal of a carbohydrate-binding domain. We show that the activity increases from our directed evolution screen were lost when insoluble substrates were used. In contrast, naturally occurring gain-of-function mutations gave similar results with oligomeric and insoluble substrates. We also show that activity differences between acidic mammalian chitinase and chitotriosidase are reduced with insoluble substrate, suggesting that previously reported activity differences with oligomeric substrates may have been driven by differential substrate specificity. These results highlight the need for assays against physiological substrates when engineering metabolic enzymes, and provide a new one-pot assay that may prove to be broadly applicable to engineering glycosyl hydrolases.

NMR and Fluorescence Spectroscopies Reveal the Preorganized Binding Site in Family 14 Carbohydrate-Binding Module from Human Chitotriosidase

Carbohydrate-binding modules (CBM) play important roles in targeting and increasing the concentration of carbohydrate active enzymes on their substrates. Using NMR to get the solution structure of CBM14, we can gain insight into secondary structure elements and intramolecular interactions with our assigned nuclear overhauser effect peaks. This reveals that two conserved aromatic residues (Phe437 and Phe456) make up the hydrophobic core of the CBM. These residues are also responsible for connecting the two β-sheets together, by being part of β2 and β4, respectively, and together with disulfide bridges, they create CBM14's characteristic "hevein-like" fold. Most CBMs rely on aromatic residues for substrate binding; however, CBM14 contains just a single tryptophan (Trp465) that together with Asn466 enables substrate binding. Interestingly, an alanine mutation of a single residue (Leu454) located behind Trp465 renders the CBM incapable of binding. Fluorescence spectroscopy performed on this mutant reveals a significant blue shift, as well as a minor blue shift for its neighbor Val455. The reduction in steric hindrance causes the tryptophan to be buried into the hydrophobic core of the structure and therefore suggests a preorganized binding site for this CBM. Our results show that both Trp465 and Asn466 are affected when CBM14 interacts with both (GlcNAc)3 and β-chitin, that the binding interactions are weak, and that CBM14 displays a slightly higher affinity toward β-chitin.

Roles of chitinase 3-like 1 in the development of cancer, neurodegenerative diseases, and inflammatory diseases

Chitinase 3-like 1 (CHI3L1) is a secreted glycoprotein that mediates inflammation, macrophage polarization, apoptosis, and carcinogenesis. The expression of CHI3L1 is strongly increased by various inflammatory and immunological conditions, including rheumatoid arthritis, multiple sclerosis, Alzheimer's disease, and several cancers. However, its physiological and pathophysiological roles in the development of cancer and neurodegenerative and inflammatory diseases remain unclear. Several studies have reported that CHI3L1 promotes cancer proliferation, inflammatory cytokine production, and microglial activation, and that multiple receptors, such as advanced glycation end product, syndecan-1/αVβ3, and IL-13Rα2, are involved. In addition, the pro-inflammatory action of CHI3L1 may be mediated via the protein kinase B and phosphoinositide-3 signaling pathways and responses to various pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, interleukin-6, and interferon-γ. Therefore, CHI3L1 could contribute to a vast array of inflammatory diseases. In this article, we review recent findings regarding the roles of CHI3L1 and suggest therapeutic approaches targeting CHI3L1 in the development of cancers, neurodegenerative diseases, and inflammatory diseases.

Human Chitinases: Structure, Function, and Inhibitor Discovery

Chitinases are glycosyl hydrolases that hydrolyze the β-(1-4)-linkage of N-acetyl-D-glucosamine units present in chitin polymers. Chitinases are widely distributed enzymes and are present in a wide range of organisms including insects, plants, bacteria, fungi, and mammals. These enzymes play key roles in immunity, nutrition, pathogenicity, and arthropod molting. Humans express two chitinases, chitotriosidase 1 (CHIT1) and acid mammalian chitinase (AMCase) along with several chitinase-like proteins (CLPs). Human chitinases are reported to play a protective role against chitin-containing pathogens through their capability to degrade chitin present in the cell wall of pathogens. Now, human chitinases are gaining attention as the key players in innate immune response. Although the exact mechanism of their role in immune response is not known, studies in recent years begin to relate chitin recognition and degradation with the activation of signaling pathways involved in inflammation. The roles of both CHIT1 and AMCase in the development of various diseases have been revealed and several classes of inhibitors have been developed. However, a clear understanding could not be established due to complexities in the design of the right experiment for studying the role of human chitinase in various diseases. In this chapter, we will first outline the structural features of CHIT1 and AMcase. We will then review the progress in understanding the role of human chitinases in the development of various diseases. Finally, we will summarize the inhibitor discovery efforts targeting both CHIT1 and AMCase.

Chitin: A "Hidden Figure" in the Fungal Cell Wall

Chitin and chitosan are two related polysaccharides that provide important structural stability to fungal cell walls. Often embedded deeply within the cell wall structure, these molecules anchor other components at the cell surface. Chitin-directed organization of the cell wall layers allows the fungal cell to effectively monitor and interact with the external environment. For fungal pathogens, this interaction includes maintaining cellular strategies to avoid excessive detection by the host innate immune system. In turn, mammalian and plant hosts have developed their own strategies to process fungal chitin, resulting in chitin fragments of varying molecular size. The size-dependent differences in the immune activation behaviors of variably sized chitin molecules help to explain how chitin and related chitooligomers can both inhibit and activate host immunity. Moreover, chitin and chitosan have recently been exploited for many biomedical applications, including targeted drug delivery and vaccine development.

Glycoprotein Non-Metastatic Protein B: An Emerging Biomarker for Lysosomal Dysfunction in Macrophages

Several diseases are caused by inherited defects in lysosomes, the so-called lysosomal storage disorders (LSDs). In some of these LSDs, tissue macrophages transform into prominent storage cells, as is the case in Gaucher disease. Here, macrophages become the characteristic Gaucher cells filled with lysosomes laden with glucosylceramide, because of their impaired enzymatic degradation. Biomarkers of Gaucher cells were actively searched, particularly after the development of costly therapies based on enzyme supplementation and substrate reduction. Proteins selectively expressed by storage macrophages and secreted into the circulation were identified, among which glycoprotein non-metastatic protein B (GPNMB). This review focusses on the emerging potential of GPNMB as a biomarker of stressed macrophages in LSDs as well as in acquired pathologies accompanied by an excessive lysosomal substrate load in macrophages.

Chitotriosidase enhances TGFβ-Smad signaling and uptake of β-amyloid in N9 microglia

TGFβ-Smad signaling is involved in the modulation of β-amyloid (Aβ) clearance in microglia. This signaling is impaired in the brain of Alzheimer's disease (AD). Chitotriosidase (CHIT1) is elevated in the cerebrospinal fluid and peripheral blood of AD patients, and has been reported to augment TGFβ signaling in fibroblast and T cells. In this study, we investigated the role of CHIT1 in TGFβ-Smad signaling and Aβ phagocytosis in N9 microglia. We found that CHIT1 significantly enhanced TGFβ1-induced expression of TβRI (TGFβ receptor I) and activation of Smad signaling. CHIT1 did not affect Aβ uptake in microglia by itself, but did enhance TGFβ1-induced phagocytosis of Aβ, which was blocked by pretreatment with SB431542 (TβRI inhibitor). These results indicate that CHIT1 may play a protective role in Aβ clearance by enhancing TGFβ signaling in microglia.

Immunomodulation of Host Chitinase 3-Like 1 During a Mammary Pathogenic Escherichia coli Infection

Chitin is a N-acetyl-d-glucosamine biopolymer that can be recognized by chitin-binding proteins. Although mammals lack chitin synthase, they induce proteins responsible for detecting chitin in response to bacterial infections. Our aim was to investigate whether chitinase 3-like 1 (CHI3L1) has a potential role in the innate immunity of the Escherichia coli (E. coli) infected mammary gland. CHI3L1 protein was found to be secreted in whey of naturally coliform-affected quarters compared to whey samples isolated from healthy udders. In addition, gene expression of CHI3L1 was confirmed in udder tissue of cows experimentally infected with a mammary pathogenic E. coli (MPEC) strain. Despite the known anatomical differences, the bovine udders’ innate immune response was mimicked by applying an experimental mouse model using MPEC or non-MPEC isolates. The effect of CHI3L1 expression in the murine mammary gland in response to coliform bacteria was investigated through the use of CHI3L1^−/− mice as well as through treatment with either a pan-caspase inhibitor or chitin particles in wild-type mice. The local induction of CHI3L1 postinfection with different E. coli strains was demonstrated to be independent of both bacterial growth and mammary interleukin (IL)-8 levels. Indeed, CHI3L1 emerged as a regulator impacting on the transcytosis of Ly6G-positive cells from the interstitial space into the alveolar lumen of the mammary tissue. Furthermore, CHI3L1 was found to be upstream regulated by caspase activity and had a major downstream effect on the local pro-inflammatory cytokine profile, including IL-1beta, IL-6, and RANTES/CCL5. In conclusion, CHI3L1 was demonstrated to play a key role in the cytokine and caspase signaling during E. coli triggered inflammation of the mammary gland.

Chitin, chitinases, and chitin lectins: Emerging roles in human pathophysiology

Chitin is a simple β-linked repeating sugar polymer prominent in the building block structures of a wide variety of organisms, from the yeast cell wall to the exoskeleton and shells of arthropods and other forms of invertebrate life. It had previously been assumed that vertebrates did not contain chitins. However, chitin and chitinases are now documented to occur in vertebrate tissues. Chitin, chitinases and particularly chitinase-like proteins are involved in important human pathologies, though the mechanisms by which these function is unknown. These chitinase-like proteins bind to chitin and function as chitin lectins in that they bind to chitin but have lost the ability to degrade it. Emphasis is placed on one of the chitinase-like proteins, CHI3L1, that has acquired wide clinical importance. The purpose of this review is to place an array of bewildering observations associated with various human disorders into a framework, particularly the pathologies of the human gastro-intestinal tract. A reasonably cohesive story may eventually emerge.

Human Chitotriosidase Does Not Catabolize Hyaluronan

Humans express an enzyme that degrades chitin, called chitotriosidase, despite the fact that we do not produce chitin. One possible explanation for this is that chitinase also degrades hyaluronan, a polysaccharide that is abundant in human tissues and shares structural attributes in common with chitinase. The objective of this study was to determine whether human chitotriosidase is capable of hydrolyzing hyaluronan. Hyaluronan of various sizes under a range of pH conditions displayed no degradation when incubated with various chitinases over a period of 5 days, while commercial hyaluronidase readily digested the hyaluronan. Under the same conditions, recombinant chitinase but not our negative control chitinase, was able to digest chitosan. We conclude that human chitinase does not digest hyaluronan. Because chitin is a prominent component of certain fungi and insects, it seems likely that human chitinase evolved for roles in host defense rather than serving to catabolize the endogenous polymer hyaluronan.

Human Chitinases and Chitinase-Like Proteins as Indicators for Inflammation and Cancer

Human Glyco_18 domain-containing proteins constitute a family of chitinases and chitinase-like proteins. Chitotriosidase and AMCase are true enzymes which hydrolyse chitin and have a C-terminal chitin-binding domain. YKL-40, YKL-39, SI-CLP and murine YM1/2 proteins possess solely Glyco_18 domain and do not have the hydrolytic activity. The major sources of Glyco_18 containing proteins are macrophages, neutrophils, epithelial cells, chondrocytes, synovial cells, and cancer cells. Both macrophages and neutrophils use the regulated secretory mechanism for the release of Glyco_18 containing proteins. Glyco_18 containing proteins are established biomarkers for human diseases. Chitotriosidase is overproduced by lipid-laden macrophages and is a major marker for the inherited lysosomal storage Gaucher disease. AMCase and murine lectin YM1 are upregulated in Th2-environment, and enzymatic activity of AMCase contributes to asthma pathogenesis. YKL proteins act as soluble mediators for the cell proliferation and migration, and are also involved in rheumatoid arthritis, inflammatory bowel disease, hepatic fibrosis and cirrhosis. Chitotriosidase and YKL-40 reflect the macrophage activation in atherosclerotic plaques. Serum level of YKL-40 is a diagnostic and prognostic marker for numerous types of solid tumors. YKL-39 is a marker for the activation of chondrocytes and the progression of the osteoarthritis in human. Recently identified SI-CLP is upregulated by Th2 cytokine IL-4 as well as by glucocorticoids. This unique feature of SI-CLP makes it an attractive candidate for the examination of individual sensitivity of patients to glucocorticoid treatment and prediction of side effects of glucocorticoid therapy. Human chitinases and chitinase-like proteins are found in tissues and circulation, and can be detected by non-invasive technologies.

Human Chitotriosidase Is an Endo-Processive Enzyme

Human chitotriosidase (HCHT) is involved in immune response to chitin-containing pathogens in humans. The enzyme is able to degrade chitooligosaccharides as well as crystalline chitin. The catalytic domain of HCHT is connected to the carbohydrate binding module (CBM) through a flexible hinge region. In humans, two active isoforms of HCHT are found-the full length enzyme and its truncated version lacking CBM and the hinge region. The active site architecture of HCHT is reminiscent to that of the reducing-end exo-acting processive chitinase ChiA from bacterium Serratia marcescens (SmChiA). However, the presence of flexible hinge region and occurrence of two active isoforms are reminiscent to that of non-processive endo-chitinase from S. marcescens, SmChiC. Although the studies on soluble chitin derivatives suggest the endo-character of HCHT, the mode of action of the enzyme on crystalline chitin is not known. Here, we made a thorough characterization of HCHT in terms of the mode of action, processivity, binding, and rate constants for the catalysis and dissociation using α-chitin as substrate. HCHT efficiently released the end-label from reducing-end labelled chitin and had also high probability (95%) of endo-mode initiation of processive run. These results qualify HCHT as an endo-processive enzyme. Processivity and the rate constant of dissociation of HCHT were found to be in-between those, characteristic to processive exo-enzymes, like SmChiA and randomly acting non-processive endo-enzymes, like SmChiC. Apart from increasing the affinity for chitin, CBM had no major effect on kinetic properties of HCHT.

Inhibition of Mammalian Glycoprotein YKL-40: IDENTIFICATION OF THE PHYSIOLOGICAL LIGAND

YKL-40 is a mammalian glycoprotein associated with progression, severity, and prognosis of chronic inflammatory diseases and a multitude of cancers. Despite this well documented association, identification of the lectin's physiological ligand and, accordingly, biological function has proven experimentally difficult. YKL-40 has been shown to bind chito-oligosaccharides; however, the production of chitin by the human body has not yet been documented. Possible alternative ligands include proteoglycans, polysaccharides, and fibers like collagen, all of which makeup the extracellular matrix. It is likely that YKL-40 is interacting with these alternative polysaccharides or proteins within the body, extending its function to cell biological roles such as mediating cellular receptors and cell adhesion and migration. Here, we consider the feasibility of polysaccharides, including cello-oligosaccharides, hyaluronan, heparan sulfate, heparin, and chondroitin sulfate, and collagen-like peptides as physiological ligands for YKL-40. We use molecular dynamics simulations to resolve the molecular level recognition mechanisms and calculate the free energy of binding the hypothesized ligands to YKL-40, addressing thermodynamic preference relative to chito-oligosaccharides. Our results suggest that chitohexaose and hyaluronan preferentially bind to YKL-40 over collagen, and hyaluronan is likely the preferred physiological ligand, because the negatively charged hyaluronan shows enhanced affinity for YKL-40 over neutral chitohexaose. Collagen binds in two locations at the YKL-40 surface, potentially related to a role in fibrillar formation. Finally, heparin non-specifically binds at the YKL-40 surface, as predicted from structural studies. Overall, YKL-40 likely binds many natural ligands in vivo, but its concurrence with physical maladies may be related to associated increases in hyaluronan.

Decreased Chitotriosidase Activity and Levels in Familial Mediterranean Fever

Different studies have demonstrated changes in chitotriosidase (ChT) activity and concentrations in multiple diseases. However, changes in ChT activity and concentrations have not been concurrently evaluated in patients with Familial Mediterranean Fever (FMF). In this study, we analyzed the changes in serum ChT activity and concentrations in patients with FMF. The study included a total of 80 patients with FMF and 80 healthy controls. ChT enzyme activity and concentrations were measured and then compared between the groups. ChT activity was measured by using fluorometric ELISA and ChT concentrations were measured by using colorimetric ELISA methods. The median ChT activity was 10.00 (6.00-15.00) nmol/mL/hr in the patients and 14.00 (6.25-20.75) nmol/mL/hr in the controls. There was a statistically significant difference in the ChT activity between the controls and patients (P = 0.027). The median ChT concentrations were 65.40 (46.20-84.92) pg/mL and 125.00 (75.72-143.95) pg/mL in the patients and controls, respectively (P < 0.001), which were expressed as median percentiles (25th-75th). Additionally, we found no correlation between C-reactive protein and ChT activity (P = 0.978, r = 0.003) and concentrations (P = 0.446, r = -0.87). Serum ChT enzyme activity and concentrations may not be considered as a biomarker in FMF patients taking colchicine. New studies are needed to evaluate the changes of enzyme activity and concentration in colchicine-negative patients.

Functional Properties of Mouse Chitotriosidase Expressed in the Periplasmic Space of Escherichia coli

Chitotriosidase (Chit1) is an enzyme associated with various diseases, including Gaucher disease, chronic obstructive pulmonary disease, Alzheimer disease and cystic fibrosis. In this study, we first expressed mouse mature Chit1 fused with V5 and (His)₆ tags at the C-terminus (Chit1-V5-His) in the cytoplasm of Escherichia coli and found that most of the expressed protein was insoluble. In contrast, Chit1 tagged with Protein A at the N-terminus and V5-His at the C-terminus, was expressed in the periplasmic space of E. coli as a soluble protein and successfully purified. We evaluated the chitinolytic properties of the recombinant enzyme using 4-nitrophenyl N,N’-diacetyl-β-D-chitobioside [4NP-chitobioside, 4NP-(GlcNAc)₂] and found that its activity was comparable to CHO cells-expressed Chit1-V5-His. Optimal conditions for the E. coli-produced Chit1 were pH ~5.0 at 50°C. Chit1 was stable after 1 h incubation at pH 5.0~11.0 on ice and its chitinolytic activity was lost at pH 2.0, although the affinity to chitin remained unchanged. Chit1 efficiently cleaved crystalline and colloidal chitin substrates as well as oligomers of N-acetyl-D-glucosamine (GlcNAc) releasing primarily (GlcNAc)₂ fragments at pH 5.0. On the other hand, (GlcNAc)₃ was relatively resistant to digestion by Chit1. The degradation of 4NP-(GlcNAc)₂ and (GlcNAc)₃ was less evident at pH 7.0~8.0, while (GlcNAc)₂ production from colloidal chitin and (GlcNAc)₆ at these pH conditions remained strong at the neutral conditions. Our results indicate that Chit1 degrades chitin substrates under physiological conditions and suggest its important pathophysiological roles in vivo.

Treatment with rhDNase in patients with cystic fibrosis alters in-vitro CHIT-1 activity of isolated leucocytes

Recent data suggest a possible relationship between cystic fibrosis (CF) pharmacotherapy, Aspergillus fumigatus colonization (AC) and/or allergic bronchopulmonary aspergillosis (ABPA). The aim of this study was to determine if anti-fungal defence mechanisms are influenced by CF pharmacotherapy, i.e. if (1) neutrophils form CF and non-CF donors differ in their ability to produce chitotriosidase (CHIT-1); (2) if incubation of isolated neutrophils with azithromycin, salbutamol, prednisolone or rhDNase might influence the CHIT-1 activity; and (3) if NETosis and neutrophil killing efficiency is influenced by rhDNase. Neutrophils were isolated from the blood of CF patients (n = 19; mean age 26·8 years or healthy, non-CF donors (n = 20; 38·7 years) and stimulated with phorbol-12-myristate-13-acetate (PMA), azithromycin, salbutamol, prednisolone or rhDNase. CHIT-1 enzyme activity was measured with a fluorescent substrate. NETosis was induced by PMA and neutrophil killing efficiency was assessed by a hyphae recovery assay. Neutrophil CHIT-1 activity was comparable in the presence or absence of PMA stimulation in both CF and non-CF donors. PMA stimulation and preincubation with rhDNase increased CHIT-1 activity in culture supernatants from non-CF and CF donors. However, this increase was significant in non-CF donors but not in CF patients (P < 0·05). RhDNase reduced the number of NETs in PMA-stimulated neutrophils and decreased the killing efficiency of leucocytes in our in-vitro model. Azithromycin, salbutamol or prednisolone had no effect on CHIT-1 activity. Stimulation of isolated leucocytes with PMA and treatment with rhDNase interfered with anti-fungal defence mechanisms. However, the impact of our findings for treatment in CF patients needs to be proved in a clinical cohort.

X-Ray Crystal Structure of the Full Length Human Chitotriosidase (CHIT1) Reveals Features of Its Chitin Binding Domain

Chitinases are enzymes that catalyze the hydrolysis of chitin. Human chitotriosidase (CHIT1) is one of the two active human chitinases, involved in the innate immune response and highly expressed in a variety of diseases. CHIT1 is composed of a catalytic domain linked by a hinge to its chitin binding domain (ChBD). This latter domain belongs to the carbohydrate-binding module family 14 (CBM14 family) and facilitates binding to chitin. So far, the available crystal structures of the human chitinase CHIT1 and the Acidic Mammalian Chitinase (AMCase) comprise only their catalytic domain. Here, we report a crystallization strategy combining cross-seeding and micro-seeding cycles which allowed us to obtain the first crystal structure of the full length CHIT1 (CHIT1-FL) at 1.95 Å resolution. The CHIT1 chitin binding domain (ChBD_CHIT1) structure shows a distorted β-sandwich 3D fold, typical of CBM14 family members. Accordingly, ChBD_CHIT1 presents six conserved cysteine residues forming three disulfide bridges and several exposed aromatic residues that probably are involved in chitin binding, including the highly conserved Trp465 in a surface- exposed conformation. Furthermore, ChBD_CHIT1 presents a positively charged surface which may be involved in electrostatic interactions. Our data highlight the strong structural conservation of CBM14 family members and uncover the structural similarity between the human ChBD_CHIT1, tachycitin and house mite dust allergens. Overall, our new CHIT1-FL structure, determined with an adapted crystallization approach, is one of the few complete bi-modular chitinase structures available and reveals the structural features of a human CBM14 domain.

Molecular Analysis of Atypical Family 18 Chitinase from Fujian Oyster Crassostrea angulata and Its Physiological Role in the Digestive System

Chitinolytic enzymes have an important physiological significance in immune and digestive systems in plants and animals, but chitinase has not been identified as having a role in the digestive system in molluscan. In our study, a novel chitinase homologue, named Ca-Chit, has been cloned and characterized as the oyster Crassostrea angulate. The 3998bp full-length cDNA of Ca-Chit consisted of 23bp 5-UTR, 3288 ORF and 688bp 3-UTR. The deduced amino acids sequence shares homologue with the chitinase of family 18. The molecular weight of the protein was predicted to be 119.389 kDa, with a pI of 6.74. The Ca-Chit protein was a modular enzyme composed of a glycosyl hydrolase family 18 domain, threonine-rich region profile and a putative membrane anchor domain. Gene expression profiles monitored by quantitative RT-PCR in different adult tissues showed that the mRNA of Ca-Chit expressed markedly higher visceral mass than any other tissues. The results of the whole mount in-situ hybridization displayed that Ca-Chit starts to express the visceral mass of D-veliger larvae and then the digestive gland forms a crystalline structure during larval development. Furthermore, the adult oysters challenged by starvation indicated that the Ca-Chit expression would be regulated by feed. All the observations made suggest that Ca-Chit plays an important role in the digestive system of the oyster, Crassostrea angulate.

Dup-24 bp in the CHIT1 Gene in Six Mexican Amerindian Populations

Chitotriosidase (CHIT, EC 3.2.1.14) is an enzyme secreted by activated macrophages with the ability to hydrolyze the chitin of pathogens. The high activity of this enzyme has been used as a secondary biomarker of response to treatment in patients with Gaucher disease (OMIM 230800). Within the world's population, approximately 6% is homozygous and 35% is heterozygous for the most common polymorphism in the CHIT1 gene, a 24-bp duplication (dup-24 bp), with homozygosity of this duplication causing inactivation of the enzyme but without major consequences for health. To determine the frequency of the dup-24 bp CHIT1 gene in indigenous populations from Mexico, 692 samples were analyzed: Purepecha (49), Tarahumara (97), Huichol (97), Mayan (139), Tenek (97), and Nahua (213). We found that the groups were in Hardy-Weinberg equilibrium. The dup-24 bp allele frequency was found to be (in order of highest to lowest) 37% (Mayan), 34% (Huichol and Nahua), 33% (Purepecha), 31% (Tenek), and 29% (Tarahumara).

The chemistry of negotiation: rhythmic, glycan-driven acidification in a symbiotic conversation

Glycans have emerged as critical determinants of immune maturation, microbial nutrition, and host health in diverse symbioses. In this study, we asked how cyclic delivery of a single host-derived glycan contributes to the dynamic stability of the mutualism between the squid Euprymna scolopes and its specific, bioluminescent symbiont, Vibrio fischeri. V. fischeri colonizes the crypts of a host organ that is used for behavioral light production. E. scolopes synthesizes the polymeric glycan chitin in macrophage-like immune cells called hemocytes. We show here that, just before dusk, hemocytes migrate from the vasculature into the symbiotic crypts, where they lyse and release particulate chitin, a behavior that is established only in the mature symbiosis. Diel transcriptional rhythms in both partners further indicate that the chitin is provided and metabolized only at night. A V. fischeri mutant defective in chitin catabolism was able to maintain a normal symbiont population level, but only until the symbiotic organ reached maturity (∼ 4 wk after colonization); this result provided a direct link between chitin utilization and symbiont persistence. Finally, catabolism of chitin by the symbionts was also specifically required for a periodic acidification of the adult crypts each night. This acidification, which increases the level of oxygen available to the symbionts, enhances their capacity to produce bioluminescence at night. We propose that other animal hosts may similarly regulate the activities of epithelium-associated microbial communities through the strategic provision of specific nutrients, whose catabolism modulates conditions like pH or anoxia in their symbionts' habitat.

Characterization of a novel antimicrobial peptide with chitin-biding domain from Mytilus coruscus

Using reverse phase high performance liquid chromatography (RP-HPLC), a novel antimicrobial peptide with 55 amino acid residues was isolated from the hemolymph of Mytilus coruscus. This new antimicrobial peptide displays predominant antimicrobial activity against fungi and Gram-positive bacteria. The molecular mass and the N-terminal sequence of this peptide were analyzed by Mass Spectrometry and Edman degradation, respectively. This antimicrobial peptide, with molecular mass of 6621.55 Da, is characterized by a chitin-biding domain and by 6 Cysteine residues engaged in three intra-molecular disulfide bridges. The full-length of cDNA sequence of this new peptide was obtained by rapid amplification of cDNA ends (RACE) and the encoded precursor was turn out to be a chitotriosidase-like protein. Therefore, we named the precursor with mytichitin-1 and the new antimicrobial peptide (designated as mytichitin-CB) is the carboxyl-terminal part of mytichitin-1. The mRNA transcripts of mytichitin-1 are mainly detected in gonad and the expression level of mytichitin-1 in gonad was up-regulated and reached the highest level at 12 h after bacterial challenge, which was 9-fold increase compared to that of the control group. These results indicated that mytichitin-1 was involved in the host immune response against bacterial infection and might contribute to the clearance of invading bacteria.

Functional characterization of chitinase-3 reveals involvement of chitinases in early embryo immunity in zebrafish

The function and mechanism of chitinases in early embryonic development remain largely unknown. We show here that recombinant chitinase-3 (rChi3) is able to hydrolyze the artificial chitin substrate, 4-methylumbelliferyl-β-D-N,N',N″-triacetylchitotrioside, and to bind to and inhibit the growth of the fungus Candida albicans, implicating that Chi3 plays a dual function in innate immunity and chitin-bearing food digestion in zebrafish. This is further corroborated by the expression profile of Chi3 in the liver and gut, which are both immune- and digestion-relevant organs. Compared with rChi3, rChi3-CD lacking CBD still retains partial capacity to bind to C. albicans, but its enzymatic and antifungal activities are significantly reduced. By contrast, rChi3-E140N with the putative catalytic residue E140 mutated shows little affinity to chitin, and its enzymatic and antifungal activities are nearly completely lost. These suggest that both enzymatic and antifungal activities of Chi3 are dependent on the presence of CBD and E140. We also clearly demonstrate that in zebrafish, both the embryo extract and the developing embryo display antifungal activity against C. albicans, and all the findings point to chitinase-3 (Chi3) being a newly-identified factor involved in the antifungal activity. Taken together, a dual function in both innate immunity and food digestion in embryo is proposed for zebrafish Chi3. It also provides a new angle to understand the immune role of chitinases in early embryonic development of animals.

Determination of chitinases family during osteoclastogenesis

Mammalian chitinases consisting of CHIA, CHIT1, CHI3L1, CHI3L2 and CHID1 exert important biological roles in the monocyte lineage and chronic inflammatory diseases. Pathological bone resorption is a cause of significant morbidity in diseases affecting the skeleton such as rheumatoid arthritis, osteoporosis, periodontitis and cancer metastasis. The biologic role of chitinases in bone resorption is poorly understood. In this study, we evaluated the expression of the chitinases family during osteoclast differentiation. The expression of CHIA, CHI3L2 and CHID1 resulted unchanged during osteoclast differentiation, whereas CHIT1 and CHI3L1 increased significantly. We also observed that CHIT1 and CHI3L1 are involved in osteoclast function. Indeed, silencing CHIT1 and CHI3L1 with siRNA resulted in a significant decrease in bone resorption activity. In addition, transfection with CHIT1 or CHI3L1 siRNA and co-transfection with both decreased the levels of the pro-differentiative marker MMP9. Overall, these discoveries reveal a novel and crucial role for both CHIT1 and CHI3L1 in promoting bone resorption and identifying new potential candidate markers for therapeutic targeting.

Gaucher disease: a diagnostic challenge for internists

Gaucher disease (GD), the most common inherited lysosomal storage disorder, is a multiorgan disease due to an autosomal recessive defect of the gene encoding glucocerebrosidase enzyme, responsible for the accumulation of glucosylceramide (glucocerebroside) into reticuloendothelial cells, particularly in the liver, spleen and bone marrow. GD is a clinically heterogeneous disorder and it is conventionally classified in type 1 (non-neuronopathic disease), types 2 and 3 (acute and chronic neuronopathic disease, respectively). Features of clinical presentation and organ involvement as well as age, at presentation are highly variable among affected patients. Splenomegaly and/or thrombocytopenia are the most common presenting features either as incidental findings during routine blood count or physical examination. Other possible clinical manifestations can be hepatomegaly with abnormal liver function tests, bone pain often associated with skeletal complications (pathological fractures, avascular necrosis, osteopenia), pulmonary hypertension and, in neuronopathic forms, neurological manifestations (dysfunction of eye motility, mild mental retardation, behavioural difficulties, choreoathetosis and cramp attacks). For all these reasons GD diagnosis is often a real challenge for internists. In the presence of clinical suspicion of GD, the diagnosis has to be confirmed measuring the betaglucocerebrosidase activity in the peripheral leukocytes and by molecular analysis. Each patient needs an accurate initial multisystemic assessment, staging the damage of all the possible organs involved, and the burden of the disease, followed by regular followup. The correct and early diagnosis permits to treat patients properly, avoiding the complications of the disease.

Human chitotriosidase CHIT1 cross reacts with mammalian-like substrates

Humans do not synthesize chitin, yet they produce a number of active and inactive chitinases. One of the active enzymes is chitotriosidase whose serum levels are elevated in a number of diseases such as Gaucher's disease and upon fungal infection. Since the biological role of chitotriosidase in disease pathogenesis is not understood we screened a panel of mammalian GlcNAc-containing glycoconjugates as alternate substrates. LacNAc and LacdiNAc-terminating substrates are hydrolyzed, the latter with a turnover comparable to that of pNP-chitotriose. Glycolipids or glycoproteins with LacNAc and LacdiNAc represent potential chitinase substrates and the subsequent alteration of glycosylation pattern could be a factor in disease pathogenesis.

Evidence supporting a role for mammalian chitinases in efficacy of caspofungin against experimental aspergillosis in immunocompromised rats

Objectives

Caspofungin, currently used as salvage therapy for invasive pulmonary aspergillosis (IPA), strangely only causes morphological changes in fungal growth in vitro but does not inhibit the growth. In vivo it has good efficacy. Therefore the question arises how this in vivo activity is reached. Caspofungin is known to increase the amount of chitin in the fungal cell wall. Mammals produce two chitinases, chitotriosidase and AMCase, which can hydrolyse chitin. We hypothesized that the mammalian chitinases play a role in the in vivo efficacy of caspofungin.

Methods

In order to determine the role of chitotriosidase and AMCase in IPA, both chitinases were measured in rats which did or did not receive caspofungin treatment. In order to understand the role of each chitinase in the breakdown of the caspofungin-exposed cells, we also exposed caspofungin treated fungi to recombinant enzymes in vitro.

Results

IPA in immunocompromised rats caused a dramatic increase in chitinase activity. This increase in chitinase activity was still noted when rats were treated with caspofungin. In vitro, it was demonstrated that the action of both chitinases were needed to lyse the fungal cell wall upon caspofungin exposure.

Conclusion

Caspofungin seemed to alter the cell wall in such a way that the two chitinases, when combined, could lyse the fungal cell wall and assisted in clearing the fungal pathogen. We also found that both chitinases combined had a direct effect on the fungus in vitro.

Chitotriosidase variants in patients with Gaucher disease. Implications for diagnosis and therapeutic monitoring

OBJECTIVES

Human plasma chitotriosidase (ChT) activity, a biomarker for evaluating and monitoring Gaucher disease (GD), varies in the general population owing to variants in the CHIT1 gene. Our aim is to determine the frequency of the c.1049_1072dup24 (dup24) and p.G102S polymorphisms, their influence on plasma ChT activity, and its change with enzyme replacement therapy (ERT).

DESIGN AND METHODS

The study included 269 type1 GD patients. Genomic DNA was genotyped using PCR, restriction isotyping and agarose gel electrophoresis. ChT activity was measured with the 4-methylumbelliferyl-β-D-N,N',N″triacetylchitotrioside substrate at non-saturating concentrations at diagnosis, before beginning therapy and after one year on ERT.

RESULTS

Allele frequencies for dup24 and p.G102S were 0.22 and 0.27, respectively. Four percent of patients were homozygous and 37% heterozygous for dup24, and 9% homozygous and 37% heterozygous for p.G102S. The presence of dup24 and p.G102S polymorphisms in the CHIT1 gene significantly reduced plasma ChT activity in naïve patients. By contrast, the percentage of ChT activity decrease after one year of ERT was independent of the presence of these genetic variants.

CONCLUSIONS

This study indicates that genotyping for c.1049_1072dup24 and p.G102S polymorphisms will improve the interpretation of plasma chitotriosidase activity at diagnosis but, this is not mandatory for monitoring of enzyme replacement therapy.

Can chitotriosidase be a surrogate marker for invasive fungal disease?

BACKGROUND

Chitotriosidase (CHT) enzyme has been known to be secreted from the activated macrophages. We infer with these data that CHT activity is an indicator for the defence.

METHODS

In this study, we evaluated CHT levels in both neutropenic and non neutropenic patients. CHT enzyme activity was measured and compared to each other groups.

RESULTS

Chitotriosidase levels were found to be significantly higher in neutropenic patients with candidemia.

CONCLUSION

In the comparison between neutropenic and non neutropenic patients, there was a significant difference for CHT levels. The use of this enzyme as a surrogate marker for candidemias were evaluated in neutropenic and non neutropenic patients.

Serum chitotriosidase, a putative marker of chronically activated macrophages, increases with normal aging

BACKGROUND

Chitotriosidase (ChT) is secreted by chronically activated macrophages in Gaucher's disease. We hypothesize that circulating levels of ChT are altered with normal aging, reflecting age-related chronic macrophage activation. Potential sources that might contribute to altered levels were assessed by measuring systemic levels of ChT are α-naphthyl acetate esterase, a macrophage lysosomal enzyme; granulocyte-macrophage colony-stimulating factor (GM-CSF), which stimulates neutrophilic granule release of ChT; interleukin-6 (IL-6); and neopterin, a macrophage activation marker.

METHODS

Serum was obtained from 315 healthy participants whose age ranged from 18 to 92 years. Anthropometric measures included percent body fat and body mass index. ChT and α-naphthyl acetate esterase levels were measured by enzyme activity assays. GM-CSF, IL-6, and neopterin concentrations were measured by commercial enzyme-linked immunosorbent assays. Serum marker values were statistically analyzed using nonparametric tests.

RESULTS

Six percent of the participants had undetectable ChT levels. A positive association with age was observed for ChT and IL-6, whereas a negative correlation with age was seen for α-naphthyl acetate esterase and GM-CSF. ChT values were not associated with α-naphthyl acetate esterase or GM-CSF levels. ChT was independently associated with IL-6 and neopterin levels, but statistical significance was attenuated when controlled for age.

CONCLUSIONS

The data are consistent with increased serum ChT activity not arising from altered macrophage lysosomal enzyme trafficking or GM-CSF-stimulated release of neutrophil granule stores. The association of ChT with age remains significant after controlling for neopterin and IL-6 changes with age, suggesting that ChT levels reflect a macrophage state distinct from acute macrophage activation or inflammatory state.

Molecular characterization and expression analysis of chitinase from the Pacific oyster Crassostrea gigas

Chitinases are necessary enzymes supporting functions as a host defense factor against chitin-coated pathogens. They also function as a digestive enzyme for the hydrolysis of dietary chitin. We conducted characterization and assessed the tissue expression of the encoding gene of a chitinase (EC 3.2.1.14), Cg-Chit1, and the production of recombinant protein of Cg-Chit1, from the Pacific oyster, Crassostrea gigas. Chitinase activity in mantle extracts was detected to a marked degree in samples collected in July and August. Mantle chitinase worked well at pH 5.5, 7.0, and 8.5 tested in this study. RT-PCR showed that Cg-Chit1 expression is highly tissue-specific in the hemocytes and mantle. We then determined the distribution of Cg-Chit1 mRNA in C. gigas hemocytes and mantle histologically using in situ hybridization. Of the two subgroups of oyster hemocytes, granulocytes (main phagocytes) and hyalinocytes, only the former were found to express Cg-Chit1. In the mantle, chitinase-2 was expressed at the inner lobe of the mantle edge. Recombinant Cg-Chit1 clearly showed chitinase activity in a wide range of neutral/basic pH. These findings suggest that Cg-Chit1 functions as a host defense factor to hydrolyze chitin-coated organisms after phagocytosis by granulocytes and to exclude foreign substances from the mantle cavity.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS AND CLINICAL RELEVANCE

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

Significant association of elevated concentration of plasma YKL-40 with disease severity in patients with pelvic inflammatory disease

INTRODUCTION

To date, no study reports the implication of YKL-40 in pelvic inflammatory disease (PID). Therefore, we investigate the levels of plasma YKL-40 in patients with PID and further associate its expression with the severity of disease.

METHODS

We designed a hospital-based case-control study with approximate 1:1 ratio and consecutively recruited 64 patients with PID and 70 control women. We collected blood samples from 64 women with PID before and after they received treatment and 70 control women to detect levels of plasma YKL-40 and C-reactive protein (CRP) as well as white blood cell and neutrophil counts.

RESULTS

The results revealed that levels of plasma YKL-40 were significantly elevated in patients with PID as compared to those in controls (38.36 vs. 21.69 ng/ml, P = 0.001) but the significant difference was restricted to women aged 30 years or old after age stratification (56.75 vs. 23.61 ng/ml, P ≤ 0.001). It declined significantly after they received treatment (median: 38.36 vs. 27.54 ng/ml; P ≤ 0.001). Although both plasma YKL-40 and CRP were elevated in patients with tubo-ovarian abscess, PID patients with surgery exhibited higher YKL-40 concentration than those without surgery (median: 82.05 vs. 30.19 ng/ml, P = 0.005) and only plasma YKL-40 was significantly associated with the length of the hospital stay (P ≤ 0.001, R = 0.604).

CONCLUSION

We conclude that once individuals are diagnosed to have PID, YKL-40 may act as a biomarker to predict the severity and clinical outcome of the disease.

The mechanism of the anticancer function of M1 macrophages and their use in the clinic

M1-type macrophages are capable of inducing lysis in various types of cancer cells, but the mechanism of action is unclear. It has been noted that an "unknown protein" produced together with protease by activated macrophages is responsible for this action. Activated M1 macrophages have been recently reported to produce family 18 chitinases, all of which have been named chitotriosidase. Our experiments have demonstrated that family 18 chitinases work together with proteases and can damage various cancer cells both in vitro and in vivo. Thus, in this article, we suggest that the 50-kDa chitotriosidase is the reported "unknown protein". In addition, we discuss how to properly stimulate activated M1 macrophages to produce 50-kDa chitotriosidases and proteases for destroying cancer cells. Because family 19 chitinase has recently been reported to kill cancer cells, we also discuss the possibility of directly using human family 18 chitotriosidase and the humanized plant family 19 chitinase for cancer treatment.

Efficacy of serum chitotriosidase activity in early treatment of patients with active tuberculosis and a negative sputum smear

Background

The results of sputum culture for Mycobacterium tuberculosis must be awaited in most cases, which delays the start of treatment in patients with sputum smear-negative pulmonary tuberculosis. We investigated whether plasma chitotriosidase activity is a strong marker for early diagnosis of tuberculosis in patients for whom a bacillus smear is negative and tuberculosis culture is positive.

Methods

Clinical, radiological, and laboratory features were evaluated in 75 patients, 17 of whom were diagnosed as having active tuberculosis by negative acid-fast bacillus smear and positive culture, 38 as having sequel tuberculosis which was radiologically and microbiologically negative, and 20 who served as healthy controls. Serum chitotriosidase activity levels were measured in both cases and controls.

Results

The mean age of the cases with active pulmonary tuberculosis, cases with sequel lesions, and controls was 23 ± 2.4 years, 22 ± 1.7 years, and 24 ± 2.1 years, respectively. Serum chitotriosidase levels were 68.05 ± 72.61 nmol/hour/mL in smear-negative, culture-positive pulmonary tuberculosis cases (Group A) and 29.73 ± 20.55 nmol/hour/mL in smear-negative, culture-negative sequel pulmonary tuberculosis cases (Group B). Serum chitotriosidase levels from patients in Group A were significantly higher than in Group B and Group C. There was no statistically significant difference in serum chitotriosidase levels between cases with sequel pulmonary tuberculosis (Group B, smear-negative, culture-negative) and healthy controls (Group C).

Conclusion

In patients with active tuberculosis and a negative sputum smear for acid-fast bacillus, plasma chitotriosidase activity seems to be a strong marker for diagnosis of active disease which can be used while awaiting culture results.