Chitinase 3-like-1 Inhibits Innate Antitumor and Tissue Remodeling Immune Responses by Regulating CD47-SIRPα- and CD24-Siglec10-Mediated Phagocytosis.

Innate immune responses such as phagocytosis are critically linked to the generation of adaptive immune responses against the neoantigens in cancer and the efferocytosis that is essential for homeostasis in diseases characterized by lung injury, inflammation, and remodeling as in chronic obstructive pulmonary disease (COPD). Chitinase 3-like-1 (CHI3L1) is induced in many cancers where it inhibits adaptive immune responses by stimulating immune checkpoint molecules (ICPs) and portends a poor prognosis. CHI3L1 is also induced in COPD where it regulates epithelial cell death. In this study, we demonstrate that pulmonary melanoma metastasis inhibits macrophage phagocytosis by stimulating the CD47-SIRPα and CD24-Siglec10 phagocytosis checkpoint pathways while inhibiting macrophage "eat me" signals from calreticulin and HMGB1. We also demonstrate that these effects on macrophage phagocytosis are associated with CHI3L1 stimulation of the SHP-1 and SHP-2 phosphatases and inhibition of the accumulation and phosphorylation of cytoskeleton-regulating nonmuscle myosin IIa. This inhibition of innate immune responses such as phagocytosis provides a mechanistic explanation for the ability of CHI3L1 to stimulate ICPs and inhibit adaptive immune responses in cancer and diseases such as COPD. The ability of CHI3L1 to simultaneously inhibit innate immune responses, stimulate ICPs, inhibit T cell costimulation, and regulate a number of other oncogenic and inflammation pathways suggests that CHI3L1-targeted therapeutics are promising interventions in cancer, COPD, and other disorders.

Targeting protumor factor chitinase-3-like-1 secreted by Rab37 vesicles for cancer immunotherapy.

Background: Chitinase 3-like-1 (CHI3L1) is a secretion glycoprotein associated with the immunosuppressive tumor microenvironment (TME). The secretory mode of CHI3L1 makes it a promising target for cancer treatment. We have previously reported that Rab37 small GTPase mediates secretion of IL-6 in macrophages to promote cancer progression, whereas the roles of Rab37 in the intracellular trafficking and exocytosis of CHI3L1 are unclear. Methods: We examined the concentration of CHI3L1 in the culture medium of splenocytes and bone marrow derived macrophages (BMDMs) from wild-type or Rab37 knockout mice, and macrophage or T cell lines expressing wild type, active GTP-bound or inactive GDP-bound Rab37. Vesicle isolation, total internal reflection fluorescence microscopy, and real-time confocal microscopy were conducted. We developed polyclonal neutralizing-CHI3L1 antibodies (nCHI3L1 Abs) to validate the therapeutic efficacy in orthotopic lung, pancreas and colon cancer allograft models. Multiplex fluorescence immunohistochemistry was performed to detect the protein level of Rab37 and CHI3L1, and localization of the tumor-infiltrating immune cells in allografts from mice or tumor specimens from cancer patients. Results: We demonstrate a novel secretion mode of CHI3L1 mediated by the small GTPase Rab37 in T cells and macrophages. Rab37 mediated CHI3L1 intracellular vesicle trafficking and exocytosis in a GTP-dependent manner, which is abolished in the splenocytes and BMDMs from Rab37 knockout mice and attenuated in macrophage or T cell lines expressing the inactive Rab37. The secreted CHI3L1 activated AKT, ß-catenin and NF-κB signal pathways in cancer cells and macrophages to foster a protumor TME characterized by activating M2 macrophages and increasing the population of regulatory T cells. Our developed nCHI3L1 Abs showed the dual properties of reducing tumor growth/metastases and eliciting an immunostimulatory TME in syngeneic orthotopic lung, pancreas and colon tumor models. Clinically, high plasma level or intratumoral expression of CHI3L1 correlated with poor survival in 161 lung cancer, 155 pancreatic cancer and 180 colon cancer patients. Conclusions: These results provide the first evidence that Rab37 mediates CHI3L1 secretion in immune cells and highlight nCHI3L1 Abs that can simultaneously target both cancer cells and tumor microenvironment.

CHI3L1 regulates PD-L1 and anti-CHI3L1-PD-1 antibody elicits synergistic antitumor responses.

Evasion of the immune response is a hallmark of cancer, and programmed cell death 1 (PD-1) and PD-1 ligand 1 (PD-L1) are major mediators of this immunosuppression. Chitinase 3-like 1 (CHI3L1) is induced in many cancers, where it portends a poor prognosis and contributes to tumor metastasis and spread. However, the mechanism(s) that CHI3L1 uses in metastasis have not been defined. Here we demonstrate that CHI3L1 regulates the expression of PD-L1, PD-L2, PD-1, LAG3, and TIM3 and plays a critical role in melanoma progression and lymphatic spread. CHI3L1 also contributed to IFN-γ-stimulated macrophage PD-L1 expression, and RIG-like helicase innate immunity suppressed CHI3L1, PD-L1, and melanoma progression. Individual antibodies against CHI3L1 or PD-1 had discrete antitumor effects and additive antitumor responses in metastasis models and T cell-tumor cell cocultures when administered simultaneously. Synergistic cytotoxic tumor cell death was seen in T cell-tumor cell cocultures, and significantly enhanced antitumor responses were seen in in vivo tumor models treated with bispecific antibodies that simultaneously target CHI3L1 and PD-1. CHI3L1 contributes to tumor progression by stimulating the PD-1/PD-L1 axis and other checkpoint molecules. The simultaneous targeting of CHI3L1 and the PD-1/PD-L1 axis with individual and, more powerfully, with bispecific antibodies represents a promising therapy for pulmonary metastasis and progression.

Changes in Cerebrospinal Fluid Balance of TNF and TNF Receptors in Naïve Multiple Sclerosis Patients: Early Involvement in Compartmentalised Intrathecal Inflammation.

An imbalance of TNF signalling in the inflammatory milieu generated by meningeal immune cell infiltrates in the subarachnoid space in multiple sclerosis (MS), and its animal model may lead to increased cortical pathology. In order to explore whether this feature may be present from the early stages of MS and may be associated with the clinical outcome, the protein levels of TNF, sTNF-R1 and sTNF-R2 were assayed in CSF collected from 122 treatment-naïve MS patients and 36 subjects with other neurological conditions at diagnosis. Potential correlations with other CSF cytokines/chemokines and with clinical and imaging parameters at diagnosis (T0) and after 2 years of follow-up (T24) were evaluated. Significantly increased levels of TNF (fold change: 7.739; p < 0.001), sTNF-R1 (fold change: 1.693; p < 0.001) and sTNF-R2 (fold change: 2.189; p < 0.001) were detected in CSF of MS patients compared to the control group at T0. Increased TNF levels in CSF were significantly (p < 0.01) associated with increased EDSS change (r = 0.43), relapses (r = 0.48) and the appearance of white matter lesions (r = 0.49). CSF levels of TNFR1 were associated with cortical lesion volume (r = 0.41) at T0, as well as with new cortical lesions (r = 0.56), whilst no correlation could be found between TNFR2 levels in CSF and clinical or MRI features. Combined correlation and pathway analysis (ingenuity) of the CSF protein pattern associated with TNF expression (encompassing elevated levels of BAFF, IFN-γ, IL-1ß, IL-10, IL-8, IL-16, CCL21, haptoglobin and fibrinogen) showed a particular relationship to the interaction between innate and adaptive immune response. The CSF sTNF-R1-associated pattern (encompassing high levels of CXCL13, TWEAK, LIGHT, IL-35, osteopontin, pentraxin-3, sCD163 and chitinase-3-L1) was mainly related to altered T cell and B cell signalling. Finally, the CSF TNFR2-associated pattern (encompassing high CSF levels of IFN-ß, IFN-λ2, sIL-6Rα) was linked to Th cell differentiation and regulatory cytokine signalling. In conclusion, dysregulation of TNF and TNF-R1/2 pathways associates with specific clinical/MRI profiles and can be identified at a very early stage in MS patients, at the time of diagnosis, contributing to the prediction of the disease outcome.

M2a Macrophage-Secreted CHI3L1 Promotes Extracellular Matrix Metabolic Imbalances via Activation of IL-13Rα2/MAPK Pathway in Rat Intervertebral Disc Degeneration.

The accumulation of macrophages in degenerated discs is a common phenomenon. However, the roles and mechanisms of M2a macrophages in intervertebral disc degeneration (IDD) have not been illuminated. This study investigated the expression of the M2a macrophage marker (CD206) in human and rat intervertebral disc tissues by immunohistochemistry. To explore the roles of M2a macrophages in IDD, nucleus pulposus (NP) cells were co-cultured with M2a macrophages in vitro. To clarify whether the CHI3L1 protein mediates the effect of M2a macrophages on NP cells, siRNA was used to knock down CHI3L1 transcription. To elucidate the underlying mechanisms, NP cells were incubated with recombinant CHI3L1 proteins, then subjected to western blotting analysis of the IL-13Rα2 receptor and MAPK pathway. CD206-positive cells were detected in degenerated human and rat intervertebral disc tissues. Notably, M2a macrophages promoted the expression of catabolism genes (MMP-3 and MMP-9) and suppressed the expression of anabolism genes (aggrecan and collagen II) in NP cells. These effects were abrogated by CHI3L1 knockdown in M2a macrophages. Exposure to recombinant CHI3L1 promoted an extracellular matrix metabolic imbalance in NP cells via the IL-13Rα2 receptor, along with activation of the ERK and JNK MAPK signaling pathways. This study elucidated the roles of M2a macrophages in IDD and identified potential mechanisms for these effects.

Inflammatory Biomarkers in AD: Implications for Diagnosis.

Alzheimer's disease is the most common form of dementia. Due to the lack of effective interventions, early and accurate diagnosis for new interventions are emphasized. However, significant neuronal loss and neuropathological lesions can damage the brain substantially before diagnosis. With our growing knowledge of the role of neuroinflammation in the pathogenesis of Alzheimer's disease, inflammatory biomarkers are attracting increasing interest in the context of diagnosis. This review is focused on the use of inflammatory biomarkers detected through neuroimaging, cerebrospinal fluid, and peripheral blood for diagnosing Alzheimer's disease, and also suggests clinical implications. This review includes the following biomarkers: neuroimaging, various ligands binding to the translocator protein (TSPO); cerebrospinal fluid, soluble triggering receptor expressed on myeloid cells (sTREM2), human cartilage glycoprotein-39 (YKL-40), and monocyte chemoattractant protein 1 (MCP-1), and various biomarkers in peripheral blood. Although accumulating evidence has suggested the potential role of these inflammatory biomarkers in diagnosing AD, there are limitations to their use. However, combining these biomarkers with conventional diagnostic clues such as genotype and amyloid pathology may improve the stratification and selection of patients for targeted early interventions.

Selection and Characterization of YKL-40-Targeting Monoclonal Antibodies from Human Synthetic Fab Phage Display Libraries.

YKL-40, also known as chitinase-3-like 1 (CHI3L1), is a glycoprotein that is expressed and secreted by various cell types, including cancers and macrophages. Due to its implications for and upregulation in a variety of diseases, including inflammatory conditions, fibrotic disorders, and tumor growth, YKL-40 has been considered as a significant therapeutic biomarker. Here, we used a phage display to develop novel monoclonal antibodies (mAbs) targeting human YKL-40 (hYKL-40). Human synthetic antibody phage display libraries were panned against a recombinant hYKL-40 protein, yielding seven unique Fabs (Antigen-binding fragment), of which two Fabs (H1 and H2) were non-aggregating and thermally stable (75.5 °C and 76.5 °C, respectively) and had high apparent affinities (KD = 2.3 nM and 4.0 nM, respectively). Reformatting the Fabs into IgGs (Immunoglobulin Gs) increased their apparent affinities (notably, for H1 and H2, KD = 0.5 nM and 0.3 nM, respectively), presumably due to the effects of avidity, with little change to their non-aggregation property. The six anti-hYKL-40 IgGs were analyzed using a trans-well migration assay in vitro, revealing that three clones (H1, H2, and H4) were notably effective in reducing cell migration from both A549 and H460 lung cancer cell lines. The three clones were further analyzed in an in vivo animal test that assessed their anti-cancer activities, demonstrating that the tumor area and the number of tumor nodules were significantly reduced in the lung tissues treated with H1 (IgG). Given its high affinity and desirable properties, we expect that the H1 anti-hYKL-40 mAb will be a suitable candidate for developing anti-cancer therapeutics.

Serum YKL40: A novel potential link between inflammation and dyslipidemia in acne vulgaris.

BACKGROUND: Acne vulgaris (AV) is an inflammatory skin disorder that may be associated with metabolic disorders. The relation between lipid profile in acne is not widely investigated. Chitinase-3-like protein 1 (YKL-40) has been found to be implicated in different inflammatory conditions. AIMS: We aimed at investigating the role YKL-40 in acne pathogenesis and associated dyslipidemia in acne patients. PATIENTS/METHODS: This study included 50 acne vulgaris patients and 30 matched control subjects. Serum YKL-40 in addition to lipid profile were assessed in all studied subjects. RESULTS: Serum YKL-40 level was significantly elevated in acne patients than healthy controls (P < .001). We also found a significant positive correlations between serum YKL-40, serum TGs, TC, and LDL-C (P value: .022, .001, .017 respectively) while, a significant negative correlation between serum YKL-40 and HDL-c (P value: .036) was detected. CONCLUSION: Our study results suggest that YKL-40 might have a role in AV pathogenesis. In addition, it could provide a new potential link between inflammation and dyslipidemia observed in acne patients.

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

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

Chitinase 3-like 1 drives allergic skin inflammation via Th2 immunity and M2 macrophage activation.

BACKGROUND: Atopic dermatitis (AD) is a chronic inflammatory skin disorder characterized by defective skin barrier and Th2 immune responses. Chitinase 3-like 1 (CHI3L1), also known as breast regression protein 39 (BRP-39) in mice and human homologue YKL-40, plays important roles in Th2 inflammation and allergen sensitization. CHI3L1 has been implicated in a variety of diseases including asthma characterized by inflammation, apoptosis and tissue remodelling, but its role in AD remains elusive. OBJECTIVE: The aim of this study was to investigate the role of CHI3L1 in the development and progression of AD. RESULTS: We investigated YKL-40 levels in the serum and skin of AD patients by ELISA and immunofluorescence, respectively. Using a murine model of AD induced by ovalbumin (OVA), we investigated Th2 immune responses, M2 macrophage activation and skin barrier gene expression using wild-type (WT) and BRP-39 null mutant (BRP-39-/- ) mice. YKL-40 level was significantly increased in serum of AD patients. In addition, both mRNA and protein expression levels of BRP-39 were higher in OVA-sensitized WT mice than in control mice. OVA-sensitized BRP-39-/- mice showed decreased epidermal thickness, lower total serum IgE, Th2 cytokine levels and CD4+ effector T cell populations than OVA-sensitized WT mice. Induction of BRP-39 was dominant in dermal macrophages. BRP-39 deficiency was found to be involved in M2 macrophage activation. Consistently, the YKL-40 level in the skin of AD patients was higher than in normal subjects and it was expressed in dermal macrophages. BRP-39 deficiency attenuated dysregulation of skin barrier and tight junction genes. CONCLUSIONS AND CLINICAL RELEVANCE: These findings demonstrate that CHI3L1 mediates the development of AD induced by OVA, affecting Th2 inflammation, M2 macrophage activation and skin barrier function.

Identification of Chitinase-3-Like Protein 1 as a Novel Neutrophil Antigenic Target in Crohn's Disease.

BACKGROUND AND AIMS: There is an increasing incidence of inflammatory bowel disease [IBD]. Autoimmune responses are involved in the pathophysiology of IBD, but their underlying pathways and target antigens have not yet been fully elucidated. METHODS: Autoantigenic targets in IBD were identified after separation of whole cell proteins isolated from neutrophils using two-dimensional electrophoresis and matrix assisted laser desorption ionization - time of flight mass spectrometry-based protein identification of the spots that displayed Western blotting signals with anti-neutrophil cytoplasmic antibody-positive sera. The prevalence of IgG, IgA and secretory IgA [sIgA] to chitinase 3-like protein 1 [CHI3L1] was analysed by enzyme-linked immunosorbent assays using recombinant CHI3L1 in 110 patients with Crohn's disease [CD], 95 with ulcerative colitis [UC], 126 with coeliac disease [CeD] and 86 healthy controls [HCs]. RESULTS: The 18-glycosylhydrolase family member CHI3L1 was identified as a neutrophil autoantigenic target. CD patients displayed significantly higher levels of IgG to CHI3L1 than patients with UC and CeD (p < 0.0001, respectively). IgA and sIgA to CHI3L1 was significantly higher in CD than in UC, CeD and HCs [p < 0.0001, respectively]. IgA and sIgA to CHI3L1 demonstrated the highest prevalence in CD [25.5%, 28/110; and 41.8%%, 46/110] compared to HCs [2.3%, 2/86; and 4.7%%, 4/86; p = 0.0015 and p < 0.0001] and are associated with a more complicated progression of CD. CONCLUSION: CHI3L1 is a novel neutrophil autoantigenic target in CD. IgA and sIgA to CHI3L1 may serve as novel markers for CD and may facilitate the serological diagnosis of IBD.

Different neuroinflammatory profile in amyotrophic lateral sclerosis and frontotemporal dementia is linked to the clinical phase.

OBJECTIVE: To investigate the role of neuroinflammation in asymptomatic and symptomatic amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) mutation carriers. METHODS: The neuroinflammatory markers chitotriosidase 1 (CHIT1), YKL-40 and glial fibrillary acidic protein (GFAP) were measured in cerebrospinal fluid (CSF) and blood samples from asymptomatic and symptomatic ALS/FTD mutation carriers, sporadic cases and controls by ELISA. RESULTS: CSF levels of CHIT1, YKL-40 and GFAP were unaffected in asymptomatic mutation carriers (n=16). CHIT1 and YKL-40 were increased in gALS (p<0.001, n=65) whereas GFAP was not affected. Patients with ALS carrying a CHIT1 polymorphism had lower CHIT1 concentrations in CSF (-80%) whereas this polymorphism had no influence on disease severity. In gFTD (n=23), increased YKL-40 and GFAP were observed (p<0.05), whereas CHIT1 was nearly not affected. The same profile as in gALS and gFTD was observed in sALS (n=64/70) and sFTD (n=20/26). CSF and blood concentrations correlated moderately (CHIT1, r=0.51) to weak (YKL-40, r=0.30, GFAP, r=0.39). Blood concentrations of these three markers were not significantly altered in any of the groups except CHIT1 in gALS of the Ulm cohort (p<0.05). CONCLUSION: Our data indicate that neuroinflammation is linked to the symptomatic phase of ALS/FTD and shows a similar pattern in sporadic and genetic cases. ALS and FTD are characterised by a different neuroinflammatory profile, which might be one driver of the diverse presentations of the ALS/FTD syndrome.

The loss of tolerance to CHI3L1 - A putative role in inflammatory bowel disease?

The incidence of inflammatory bowel disease (IBD) is steadily increasing. IBD is characterized by chronic inflammation of the gastrointestinal tract and is divided into the two main entities Crohn's disease (CD) and ulcerative colitis (UC). Genetic predispositions, environmental factors and a dysregulated immune response are known to be involved at the beginning of IBD. However, their etiopathogenesis is not yet fully understood. Over the last ten years, there has been increasing evidence of the involvement of the member of the 18-glycosylhydrolase family chitinase-3-like protein 1 (CHI3L1) in IBD. CHI3L1 is associated with various diseases such as cancer and chronic inflammatory diseases including rheumatoid arthritis or IBD as well as neurological diseases where it can act as a chemoattractant, mitogen or growth factor. This review will focus on the role of autoimmunity to CHI3L1 in IBD in the context of its expression in inflamed colonic epithelia and interaction with intestinal microbiota. Further, it will provide insights into the interaction of CHI3L1 with different mechanisms of the innate and adaptive immune response in IBD.

ΔNp63-driven recruitment of myeloid-derived suppressor cells promotes metastasis in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is particularly aggressive, with enhanced incidence of tumor relapse, resistance to chemotherapy, and metastases. As the mechanistic basis for this aggressive phenotype is unclear, treatment options are limited. Here, we showed an increased population of myeloid-derived immunosuppressor cells (MDSCs) in TNBC patients compared with non-TNBC patients. We found that high levels of the transcription factor ΔNp63 correlate with an increased number of MDSCs in basal TNBC patients, and that ΔNp63 promotes tumor growth, progression, and metastasis in human and mouse TNBC cells. Furthermore, we showed that MDSC recruitment to the primary tumor and metastatic sites occurs via direct ΔNp63-dependent activation of the chemokines CXCL2 and CCL22. CXCR2/CCR4 inhibitors reduced MDSC recruitment, angiogenesis, and metastasis, highlighting a novel treatment option for this subset of TNBC patients. Finally, we found that MDSCs secrete prometastatic factors such as MMP9 and chitinase 3-like 1 to promote TNBC cancer stem cell function, thereby identifying a nonimmunologic role for MDSCs in promoting TNBC progression. These findings identify a unique crosstalk between ΔNp63+ TNBC cells and MDSCs that promotes tumor progression and metastasis, which could be exploited in future combined immunotherapy/chemotherapy strategies for TNBC patients.

Shrimp Antiviral mja-miR-35 Targets CHI3L1 in Human M2 Macrophages and Suppresses Breast Cancer Metastasis.

Virus infection can change host's metabolism, while tumorigenesis results from metabolic disorder. MicroRNAs (miRNAs), crucial regulatory factors overlaying transcriptional control mechanisms, can guide metabolic homeostasis. In terms of metabolic disorder, antiviral miRNAs may have anti-tumor activity. However, this issue has not been extensively investigated. In the present study, the results revealed that shrimp mja-miR-35, which showed antiviral activity in shrimp against white spot syndrome virus (WSSV) infection, could suppress the metastasis of breast cancer by targeting human CHI3L1 gene of M2 macrophages in a cross-phylum manner. Furthermore, the feed expressing shrimp mja-miR-35 had antiviral capacity in shrimp and anti-tumor activity in humans, leading to the simultaneous control of virus infection and tumor progression. Therefore, our findings indicated that the antiviral miRNAs derived from shrimp stress responses against virus infection might be an important source of human anti-tumor drugs and miRNAs could bridge the control of aquaculture diseases and the prevention of human tumors.

Regulation of chitinase-3-like-1 in T cell elicits Th1 and cytotoxic responses to inhibit lung metastasis.

Chitinase-3-like-1 (Chi3l1) is known to play a significant role in the pathogenesis of Type 2 inflammation and cancer. However, the function of Chi3l1 in T cell and its clinical implications are largely unknown. Here we show that Chi3l1 expression was increased in activated T cells, especially in Th2 cells. In addition, Chi3l1-deficient T cells are hyper-responsive to TcR stimulation and are prone to differentiating into Th1 cells. Chi3l1-deficient Th1 cells show increased expression of anti-tumor immunity genes and decreased Th1 negative regulators. Deletion of Chi3l1 in T cells in mice show reduced melanoma lung metastasis with increased IFNγ and TNFα-producing T cells in the lung. Furthermore, silencing of Chi3l1 expression in the lung using peptide-siRNA complex (dNP2-siChi3l1) efficiently inhibit lung metastasis with enhanced Th1 and CTL responses. Collectively, this study demonstrates Chi3l1 is a regulator of Th1 and CTL which could be a therapeutic target to enhance anti-tumor immunity.

YKL-40 and cytokines - a New Diagnostic Constellation in Rheumatoid Arthritis?

BACKGROUND: Rheumatoid arthritis (RA) causes chronic inflammation and alteration of articular tissue and joints. The pathogenesis of the disease remains unclear although it is known that proinflammatory cytokines play a major role in its induction. YKL-40 is a chitinase-like glycoprotein produced by activated macrophages, neutrophils, arthritic chondrocytes and cancer cells. It has been shown that YKL-40 is implicated in tissue remodeling, angiogenesis and inflammation. AIM: to investigate serum and synovial YKL-40 levels in relation to IL-1ß, TNF-α, and IL-6 in RA patients. MATERIALS AND METHODS: Serum and synovial concentrations of YKL-40, TNF-α, IL- 6, and IL-1ß were determined by ELISA in 39 patients (mean age 53.18 ± 16.54 yrs) with active RA. RESULTS: Serum YKL-40 levels were increased in all patients. The highest levels were found in synovial fluid (P<0.01). Our study showed a strong association between serum and synovial levels of YKL-40 and serum TNF-α and IL-1 ß (P<0.05). CONCLUSION: This is the first study finding a significant correlation between serum TNF-α and IL-1ß and YKL-40 in active RA. We suggest that these molecules together might play a dominant role in the pathogenesis and disease activity and could possibly serve as a new diagnostic constellation in rheumatoid arthritis.