Increase in hepatic NKT cells in leukocyte cell-derived chemotaxin 2-deficient mice contributes to severe concanavalin A-induced hepatitis

Updates on the role of leukocyte cell-derived chemotaxin-2 in inflammation regulation and immunomodulation

Leukocyte cell-derived chemotaxin-2 (LECT2), originally identified as a novel neutrophil chemokine, is a multifunctional secreted factor primarily produced in hepatocytes. However, many studies have shown that LECT2 is a pleiotropic protein that not only exerts chemotaxis properties as a cytokine but also plays an important role in inflammatory regulation and immune regulation. Pathogens such as bacteria and the role of the host immune system are key factors in the inflammatory response. In antibacterial, LECT2 can directly destroy bacterial structure or affect the normal metabolism of bacteria to inactivate bacteria and can also achieve this effect by activating immune cells and regulating cytokines. In immunomodulation, LECT2 has neutrophil chemotactic activity and regulates the quantities of Natural killer T (NKT) cells, regulatory T cells, monocytes/macrophages, granulocytes, and/or the expression of associated cytokines, thereby influencing their effect in immune reaction. Inflammation and immune regulation are closely related to a variety of diseases, such as bacterial infection, liver cirrhosis, dermatitis, coronary atherosclerotic heart disease, and so on. This review summarizes the basic and clinical studies of LECT2 in antibacterial effects and its effects on immune cells to explore the mechanism of LECT in inflammatory regulation and immune regulation in physiological and pathological conditions better.

LECT2 Deletion Exacerbates Liver Steatosis and Macrophage Infiltration in a Male Mouse Model of LPS-mediated NASH

Leukocyte cell-derived chemotaxin 2 (LECT2) is a protein initially isolated as a neutrophil chemotactic factor. We previously found that LECT2 is an obesity-associated hepatokine that senses liver fat and induces skeletal muscle insulin resistance. In addition, hepatocyte-derived LECT2 activates macrophage proinflammatory activity by reinforcing the lipopolysaccharide (LPS)-induced c-Jun N-terminal kinase signaling. Based on these findings, we examined the effect of LECT2 deletion on nonalcoholic fatty liver disease/nonalcoholic steatohepatitis (NAFLD/NASH) caused by bacterial translocation. We created the bacterial translocation-mediated NAFLD/NASH model using LECT2 knockout mice (LECT2 KO) with 28 times a low-dose LPS injection under high-fat diet feeding conditions. LECT2 deletion exacerbated steatosis and significantly reduced p38 phosphorylation in the liver. In addition, LECT2 deletion increased macrophage infiltration with decreased M1/M2 ratios. LECT2 might contribute to protecting against lipid accumulation and macrophage activation in the liver under pathological conditions, which might be accomplished via p38 phosphorylation. This study provides novel aspects of LECT2 in the bacterial translocation-mediated NAFLD/NASH model.

Loss of LECT2 promotes ovarian cancer progression by inducing cancer invasiveness and facilitating an immunosuppressive environment

Leukocyte cell-derived chemotaxin 2 (LECT2) is a multifunctional cytokine that can bind to several receptors and mediate distinct molecular pathways in various cell settings. Changing levels of LECT2 have been implicated in multiple human disease states, including cancers. Here, we have demonstrated reduced serum levels of LECT2 in patients with epithelial ovarian cancer (EOC) and down-regulated circulating Lect2 as the disease progresses in a syngeneic mouse ID8 EOC model. Using the murine EOC model, we discovered that loss of Lect2 promotes EOC progression by modulating both tumor cells and the tumor microenvironment. Lect2 inhibited EOC cells' invasive phenotype and suppressed EOC's transcoelomic metastasis by targeting c-Met signaling. In addition, Lect2 downregulation induced the accumulation and activation of myeloid-derived suppressor cells (MDSCs). This fostered an immunosuppressive microenvironment in EOC by inhibiting T-cell activation and skewing macrophages toward an M2 phenotype. The therapeutic efficacy of programmed cell death-1 (PD-1)/PD-L1 pathway blockade for the ID8 model was significantly hindered. Overall, our data highlight multiple functions of Lect2 during EOC progression and reveal a rationale for synergistic immunotherapeutic strategies by targeting Lect2.

Interorgan communication with the liver: novel mechanisms and therapeutic targets

The liver is a multifunctional organ that plays crucial roles in numerous physiological processes, such as production of bile and proteins for blood plasma, regulation of blood levels of amino acids, processing of hemoglobin, clearance of metabolic waste, maintenance of glucose, etc. Therefore, the liver is essential for the homeostasis of organisms. With the development of research on the liver, there is growing concern about its effect on immune cells of innate and adaptive immunity. For example, the liver regulates the proliferation, differentiation, and effector functions of immune cells through various secreted proteins (also known as "hepatokines"). As a result, the liver is identified as an important regulator of the immune system. Furthermore, many diseases resulting from immune disorders are thought to be related to the dysfunction of the liver, including systemic lupus erythematosus, multiple sclerosis, and heart failure. Thus, the liver plays a role in remote immune regulation and is intricately linked with systemic immunity. This review provides a comprehensive overview of the liver remote regulation of the body's innate and adaptive immunity regarding to main areas: immune-related molecules secreted by the liver and the liver-resident cells. Additionally, we assessed the influence of the liver on various facets of systemic immune-related diseases, offering insights into the clinical application of target therapies for liver immune regulation, as well as future developmental trends.

Leukocyte cell-derived chemotaxin 2 correlates with pediatric non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD), newly renamed metabolic dysfunction-associated liver disease (MASLD), is a leading cause of liver disease in children and adults. There is a paucity of data surrounding potential biomarkers and therapeutic targets, especially in pediatric NAFLD. Leukocyte cell-derived chemotaxin 2 (LECT2) is a chemokine associated with both liver disease and skeletal muscle insulin resistance. Our aim was to determine associations between LECT2 and common clinical findings of NAFLD in pediatric patients. Enzyme-linked immunosorbent assay (ELISA) was used to measure serum LECT2 concentrations in children (aged 2-17 years) with and without NAFLD. LECT2 concentrations were then correlated to clinical parameters in NAFLD. Mean LECT2 was significantly elevated in children with NAFLD versus healthy controls (n = 63 vs. 42, 5.83 ± 1.98 vs. 4.02 ± 2.02 ng/mL, p < 0.005). Additionally, LECT2 had strong correlations with body mass index (BMI) (Pearson r = 0.301, p = 0.002). A LECT2 concentration of 3.76 mg/mL predicts NAFLD with a sensitivity of 90.5% and specificity of 54.8%. Principal component analysis and logistic regression models further confirmed associations between LECT2 and NAFLD status. This study demonstrates increased serum LECT2 concentrations in pediatric NAFLD, which correlates with BMI and shows strong predictive value within these patients. Our data indicate that LECT2 is a potential diagnostic biomarker of disease and should be further investigated in pediatric as well as adult NAFLD.

Serum Leukocyte Cell-Derived Chemotaxin 2 (LECT2) Level Is Associated with Osteoporosis

OBJECTIVE

The aim of this study was to examine serum leukocyte cell-derived chemotaxin 2 (LECT2) levels in osteoporosis subjects to confirm its association with osteoporosis.

METHODS

A total of 204 adult subjects were recruited. Bone mineral densities (BMD) were assessed and blood samples were collected for measurements of biomedical parameters and the bone turnover markers. Serum LECT2 levels were measured by enzyme-linked immunosorbent assay. The relationships between serum LECT2 levels and other parameters were analyzed using the Spearman correlation coefficient.

RESULTS

Serum LECT2 levels were significantly increased in osteoporosis subjects over controls. We found a significantly negative correlation of serum LECT2 with BMD, 25-hydroxy-vitamin D, and creatinine and a significantly positive correlation with C-terminal telopeptide of type 1 collagen and total cholesterol.

CONCLUSION

Serum LECT2 levels were significantly upregulated in osteoporosis subjects and correlated with the severity of bone loss. Serum LECT2 could be a potential biomarker to assess the risk of bone loss.

Leukocyte cell-derived chemotaxin 2 regulates epithelial-mesenchymal transition and cancer stemness in hepatocellular carcinoma

Leukocyte cell-derived chemotaxin 2 (LECT2) acts as a tumor suppressor in hepatocellular carcinoma (HCC). However, the antineoplastic mechanism of LECT2, especially its influence on hepatic cancer stem cells (CSCs), remains largely unknown. In The Cancer Genome Atlas cohort, LECT2 mRNA expression was shown to be associated with stage, grade, recurrence, and overall survival in human HCC patients, and LECT2 expression was downregulated in hepatoma tissues compared with the adjacent nontumoral liver. Here, we show by immunofluorescence and immunoblot analyses that LECT2 was expressed at lower levels in tumors and in poorly differentiated HCC cell lines. Using functional assays, we also found LECT2 was capable of suppressing oncogenic behaviors such as cell proliferation, anchorage-independent growth, migration, invasiveness, and epithelial-mesenchymal transition in hepatoma cells. Moreover, we show exogenous LECT2 treatment inhibited CSC functions such as tumor sphere formation and drug efflux. Simultaneously, hepatic CSC marker expression was also downregulated, including expression of CD133 and CD44. This was supported by infection with adenovirus encoding LECT2 (Ad-LECT2) in HCC cells. Furthermore, in animal experiments, Ad-LECT2 gene therapy showed potent efficacy in treating HCC. We demonstrate LECT2 overexpression significantly promoted cell apoptosis and reduced neovascularization/CSC expansion in rat hepatoma tissues. Mechanistically, we showed using immunoblot and immunofluorescence analyses that LECT2 inhibited β-catenin signaling via the suppression of the hepatocyte growth factor/c-MET axis to diminish CSC properties in HCC cells. In summary, we reveal novel functions of LECT2 in the suppression of hepatic CSCs, suggesting a potential alternative strategy for HCC therapy.

LECT2: A pleiotropic and promising hepatokine, from bench to bedside

LECT2 (leucocyte cell-derived chemotaxin 2) is a 16-kDa protein mainly produced by hepatocytes. It was first isolated in PHA-activated human T-cell leukaemia SKW-3 cells and originally identified as a novel neutrophil chemotactic factor. However, many lines of studies suggested that LECT2 was a pleiotropic protein, it not only functioned as a cytokine to exhibit chemotactic property, but also played multifunctional roles in some physiological conditions and pathological abnormalities, involving liver regeneration, neuronal development, HSC(haematopoietic stem cells) homeostasis, liver injury, liver fibrosis, hepatocellular carcinoma, metabolic disorders, inflammatory arthritides, systemic sepsis and systemic amyloidosis. Among the above studies, it was discovered that LECT2 could be a promising molecular biomarker and therapeutic target. This review summarizes LECT2-related receptors and pathways, basic and clinical researches, primarily in mice and human, for a better comprehension and management of these diseases in the future.

Leukocyte cell-derived chemotaxin 2 is an antiviral regulator acting through the proto-oncogene MET

Retinoic acid-inducible gene (RIG)-I is an essential innate immune sensor that recognises pathogen RNAs and induces interferon (IFN) production. However, little is known about how host proteins regulate RIG-I activation. Here, we show that leukocyte cell-derived chemotaxin 2 (LECT2), a hepatokine and ligand of the MET receptor tyrosine kinase is an antiviral regulator that promotes the RIG-I-mediated innate immune response. Upon binding to MET, LECT2 induces the recruitment of the phosphatase PTP4A1 to MET and facilitates the dissociation and dephosphorylation of phosphorylated SHP2 from MET, thereby protecting RIG-I from SHP2/c-Cbl-mediated degradation. In vivo, LECT2 overexpression enhances RIG-I-dependent IFN production and inhibits lymphocytic choriomeningitis virus (LCMV) replication in the liver, whereas these changes are reversed in LECT2 knockout mice. Forced suppression of MET abolishes IFN production and antiviral activity in vitro and in vivo. Interestingly, hepatocyte growth factor (HGF), an original MET ligand, inhibits LECT2-mediated anti-viral signalling; conversely, LECT2-MET signalling competes with HGF-MET signalling. Our findings reveal previously unrecognized crosstalk between MET-mediated proliferation and innate immunity and suggest that targeting LECT2 may have therapeutic value in infectious diseases and cancer.

The innate antiviral immune response is an important defense against infection. Here, the authors show that leukocyte cell-derived chemotaxin 2 (LECT2) promotes RIG-I-mediated innate immune responses by preventing its degradation, and inhibits lymphocytic choriomeningitis virus replication in the liver.

LECT2 Is a Novel Antibacterial Protein in Vertebrates

In vertebrates, leukocyte-derived chemotaxin-2 (LECT2) is an important immunoregulator with conserved chemotactic and phagocytosis-stimulating activities to leukocytes during bacterial infection. However, whether LECT2 possesses direct antibacterial activity remains unknown. In this article, we show that, unlike tetrapods with a single LECT2 gene, two LECT2 genes exist in teleost fish, named LECT2-a and LECT2-b Using grass carp as a research model, we found that the expression pattern of grass carp LECT2-a (gcLECT2-a) is more similar to that of LECT2 in tetrapods, while gcLECT2-b has evolved to be highly expressed in mucosal immune organs, including the intestine and skin. Interestingly, we found that gcLECT2-b, with conserved chemotactic and phagocytosis-stimulating activities, can also kill Gram-negative and Gram-positive bacteria directly in a membrane-dependent and a non-membrane-dependent manner, respectively. Moreover, gcLECT2-b could prevent the adherence of bacteria to epithelial cells through agglutination by targeting peptidoglycan and lipoteichoic acid. Further study revealed that gcLECT2-b can protect grass carp from Aeromonas hydrophila infection in vivo, because it significantly reduces intestinal necrosis and tissue bacterial load. More importantly, we found that LECT2 from representative tetrapods, except human, also possesses direct antibacterial activities, indicating that the direct antibacterial property of LECT2 is generally conserved in vertebrates. Taken together, to our knowledge, our study discovered a novel function of LECT2 in the antibacterial immunity of vertebrates, especially teleost fish, greatly enhancing our knowledge of this important molecule.

Identifying Biomarkers to Predict the Prognosis of Biliary Atresia by Weighted Gene Co-Expression Network Analysis

The prognosis of children with biliary atresia (BA) after Kasai operation remains difficult to predict, and liver fibrosis is closely related to the prognosis of children with BA. We aimed to find biomarkers for native liver survival (NLS) prediction by weighted gene co-expression network analysis (WGCNA). The biological processes and signal pathways that biomarkers involved in were further analyzed by bioinformatics. Quantitative Real-time PCR, Western blot and immunohistochemistry was performed to detect biomarkers expression. The relationship of biomarkers with clinicopathological characteristics of BA was also investigated. LECT2 was overexpressed or knockdown in LX-2 cells, and the expression of fibrogenic genes such as a-SMA and COL1A1 was quantified. We found that LECT2 mRNA expression was higher in BA liver tissues compared with normal liver tissues. Bioinformatics showed that LECT2 mainly played a fibrosis-promoting role in the development in BA by regulating bile acid metabolism and promoting inflammatory response. LECT2 immunohistochemistry scores of BA children were higher than control group (p = 0.001). Survival analysis revealed that LECT2 high expression is an unfavorable prognostic factor for native liver survival in BA patients. Additionally, the high LECT2 expression was an independent prognostic factor affecting native liver survival (HR 3.702, 95%CI:2.085–6.575, p = 0.001). LECT2 modulates TGF-β mediated a-SMA and COL1A1 expression in LX-2 cells. siRNA-LECT2 inhibits the expression of a-SMA and COL1A1 in LX-2 cells. Overexpression of LECT2 resulted in an increase in a-SMA and COL1A1 expression. Knockdown of LECT2 inhibits the proliferation and increase apoptosis in activated LX-2 cells. LECT2 may act as a new prognostic biomarker for native liver survival in BA patients.

LECT2 as a hepatokine links liver steatosis to inflammation via activating tissue macrophages in NASH

It remains unclear how hepatic steatosis links to inflammation. Leukocyte cell-derived chemotaxin 2 (LECT2) is a hepatokine that senses fat in the liver and is upregulated prior to weight gain. The aim of this study was to investigate the significance of LECT2 in the development of nonalcoholic steatohepatitis (NASH). In human liver biopsy samples, elevated LECT2 mRNA levels were positively correlated with body mass index (BMI) and increased in patients who have steatosis and inflammation in the liver. LECT2 mRNA levels were also positively correlated with the mRNA levels of the inflammatory genes CCR2 and TLR4. In C57BL/6J mice fed with a high-fat diet, mRNA levels of the inflammatory cytokines Tnfa and Nos2 were significantly lower in Lect2 KO mice. In flow cytometry analyses, the number of M1-like macrophages and M1/M2 ratio were significantly lower in Lect2 KO mice than in WT mice. In KUP5, mouse kupffer cell line, LECT2 selectively enhanced the LPS-induced phosphorylation of JNK, but not that of ERK and p38. Consistently, LECT2 enhanced the LPS-induced phosphorylation of MKK4 and TAB2, upstream activators of JNK. Hepatic expression of LECT2 is upregulated in association with the inflammatory signature in human liver tissues. The elevation of LECT2 shifts liver residual macrophage to the M1-like phenotype, and contributes to the development of liver inflammation. These findings shed light on the hepatokine LECT2 as a potential therapeutic target that can dissociate liver steatosis from inflammation.

Natural Killer T Cells in Various Mouse Models of Hepatitis

Natural killer T (NKT) cells are a key component of innate immunity. Importantly, a growing body of evidence indicates that NKT cells play an integral role in various acute and chronic liver injuries. NKT cells participate in the progression of an injury through the secretion of cytokines, which promote neutrophil infiltration and enhance Fas ligand (FasL) and granzyme-mediated NKT cytotoxic activity. Therefore, examining the role of NKT cells in hepatic disease is critical for a comprehensive understanding of disease pathogenesis and may provide insight into novel approaches for treatment. For more than a century, mouse models that imitate the physiopathological conditions of human disease have served as a critical tool in biological and medical basic research, including studies of liver disease. Here, we review the role of NKT cells in various mouse models of hepatitis.

Expression of signal-transducing adaptor protein-1 attenuates experimental autoimmune hepatitis via down-regulating activation and homeostasis of invariant natural killer T cells

Objective

Signal-transducing adaptor protein (STAP) family members function as adaptor molecules and are involved in several events during immune responses. Notably however, the biological functions of STAP-1 in other cells are not known. We aimed to investigate the functions of STAP-1 in invariant natural killer T (iNKT) cells and iNKT cell-dependent hepatitis.

Methods

We employed concanavalin A (Con A)-induced hepatitis and α-galactosylceramide (α-GalCer)-induced hepatitis mouse models, both are models of iNKT cell-dependent autoimmune hepatitis, and STAP-1 overexpressing 2E10 cells to investigate the role of STAP-1 in iNKT cell activation in vivo an in vitro, respectively.

Results

After Con A- or α-GalCer-injection, hepatocyte necrotic areas and plasma alanine aminotransferase elevation were more severe in STAP-1 knockout (S1KO) mice and milder in lymphocyte-specific STAP-1 transgenic (S1Tg) mice, as compared to wild-type (WT) mice. Two events that may be related to Con A-induced and/or α-GalCer-induced hepatitis were influenced by STAP-1 manipulation. One is that iNKT cell populations in the livers and spleens were increased in S1KO mice and were decreased in S1Tg mice. The other is that Con A-induced interleukin-4 and interferon-γ production was attenuated by STAP-1 overexpression. These effects of STAP-1 were confirmed using 2E10 cells overexpressing STAP-1 that showed impairment of interleukin-4 and interferon-γ production as well as phosphorylation of Akt and mitogen-activated protein kinases in response to Con A stimulation.

Conclusions

These results conclude that STAP-1 regulates iNKT cell maintenance/activation, and is involved in the pathogenesis of autoimmune hepatitis.

Plasma half-life and tissue distribution of leukocyte cell-derived chemotaxin 2 in mice

Leukocyte cell-derived chemotaxin 2 (LECT2) is a hepatokine that causes skeletal muscle insulin resistance. The circulating levels of LECT2 are a possible biomarker that can predict weight cycling because they reflect liver fat and precede the onset of weight loss or gain. Herein, to clarify the dynamics of this rapid change in serum LECT2 levels, we investigated the in vivo kinetics of LECT2, including its plasma half-life and tissue distribution, by injecting ¹²⁵I-labelled LECT2 into ICR mice and radioactivity tracing. The injected LECT2 was eliminated from the bloodstream within 10 min (approximate half-life, 5 min). In the kidneys, the radioactivity accumulated within 10 min after injection and declined thereafter. Conversely, the radioactivity in urine increased after 30 min of injection, indicating that LECT2 is mainly excreted by the kidneys into the urine. Finally, LECT2 accumulated in the skeletal muscle and liver until 30 min and 2 min after injection, respectively. LECT2 accumulation was not observed in the adipose tissue. These findings are in agreement with LECT2 action on the skeletal muscle. The present study indicates that LECT2 is a rapid-turnover protein, which renders the circulating level of LECT2 a useful rapid-response biomarker to predict body weight alterations.

Renal leukocyte chemotactic factor 2 (ALECT2)-associated amyloidosis in Chinese patients

Background: Leukocyte chemotactic factor 2 (ALECT2) amyloidosis is one of the recently described types of amyloidosis. In this study, we reported the first large case series of renal ALECT2 amyloidosis in Chinese patients.Methods: We studied the prevalence, clinical characteristics, renal pathology, outcome and genetic features among seven patients diagnosed with renal ALECT2 amyloidosis at Peking University First Hospital of China from 2000 to 2018.Results: Seven patients were diagnosed with ALECT2 amyloidosis, representing 1.9% of the renal biopsy-proven amyloidosis cases. The mean age at diagnosis was 68 years without gender preference. The patients mainly manifested with varying impaired kidney function with a mean estimated glomerular filtration rate of 42.7 mL/min/1.73 m² (range 8.0-80.5) and proteinuria at 3.9 g/24 h (range 0.4-11.3). There were four ALECT2 amyloidosis patients with concurrent membranous nephropathy (MN), who presented a higher proteinuria (6.4 ± 4.0 g/24 h vs. 2.0 ± 1.8 g/24 h) and higher frequency of nephrotic syndrome (50% vs. 0) than patients with isolated ALECT2 amyloidosis. Renal biopsy showed strongly congophilic amyloid deposits distributed mainly in the renal cortical interstitium, as well as the glomerular mesangium, the inner layer of glomerular basement membrane (GBM), and vascular walls. Two patients with concurrent ALECT2 amyloidosis and MN showed mild amyloid deposits, which have not been identified as ALECT2 amyloidosis by IHC and LMD/MS methods. All patients were corroborated by immunoelectron microscopy to exhibit the specific location of LECT2 in the amyloid fibrils. Genetic analysis revealed no mutations but homozygosity for the G allele encoding valine at position 40 in the mature protein in all patients. Except for one patient who died 8 years later after he was diagnosed with ALECT2 amyloidosis, the others presented with relatively stable renal function during the mean follow-up period of 12.5 months.Conclusions: ALECT2 amyloidosis was the third most common type of renal amyloidosis in Chinese patients from a single centre. The majority of ALECT2 amyloidosis patients were of Han ethnicity, with a high rate of concurrent MN. The recognition and accurate diagnosis of renal ALECT2 amyloidosis should be considered in Chinese patients.

Transcriptional regulation of chicken leukocyte cell-derived chemotaxin 2 in response to toll-like receptor 3 stimulation

Objective

Leukocyte cell-derived chemotaxin 2 (LECT2) is associated with several physiological processes including inflammation, tumorigenesis, and natural killer T cell generation. Chicken LECT2 (chLECT2) gene was originally identified as one of the differentially expressed genes in chicken kidney tissue, where the chickens were fed with different calcium doses. In this study, the molecular characteristics and gene expression of chLECT2 were analyzed under the stimulation of toll-like receptor 3 (TLR3) ligand to understand the involvement of chLECT2 expression in chicken metabolic disorders.

Methods

Amino acid sequence of LECT2 proteins from various species including fowl, fish, and mammal were retrieved from the Ensembl database and subjected to Insilco analyses. In addition, the time- and dose-dependent expression of chLECT2 was examined in DF-1 cells which were stimulated with polyinosinic:polycytidylic acid (poly [I:C]), a TLR3 ligand. Further, to explore the transcription factors required for the transcription of chLECT2, DF-1 cells were treated with poly (I:C) in the presence or absence of the nuclear factor κB (NFκB) and activated protein 1 (AP-1) inhibitors.

Results

The amino acid sequence prediction of chLECT2 protein revealed that along with duck LECT2 (duLECT2), it has unique signal peptide different from other vertebrate orthologs, and only chLECT2 and duLECT2 have an additional 157 and 161 amino acids on their carboxyl terminus, respectively. Phylogenetic analysis suggested that chLECT2 is evolved from a common ancestor along with the actinopterygii hence, more closely related than to the mammals. Our quantitative polymerase chain reaction results showed that, the expression of chLECT2 was up-regulated significantly in DF-1 cells under the stimulation of poly (I:C) (p<0.05). However, in the presence of NFκB or AP-1 inhibitors, the expression of chLECT2 is suppressed suggesting that both NFκB and AP-1 transcription factors are required for the induction of chLECT2 expression.

Conclusion

The present results suggest that chLECT2 gene might be a target gene of TLR3 signaling. For the future, the expression pattern or molecular mechanism of chLECT2 under stimulation of other innate immune receptors shall be studied. The protein function of chLECT2 will be more clearly understood if further investigation about the mechanism of LECT2 in TLR pathways is conducted.

Lect2 Controls Inflammatory Monocytes to Constrain the Growth and Progression of Hepatocellular Carcinoma

Leukocyte cell-derived chemotaxin-2 (LECT2) was originally identified as a hepatocyte-secreted chemokine-like factor and a positive target of β-catenin signaling. Here, we dissected out the mechanisms by which LECT2 modulates hepatocellular carcinoma (HCC) development using both HCC mouse models and human HCC samples. We have demonstrated that LECT2 exhibits dual abilities as it has profound repercussions on the tumor phenotype itself and the immune microenvironment. Its absence confers Ctnnb-1-mutated tumor hepatocytes a stronger ability to undergo epithelial to mesenchymal transition and fosters the accumulation of pejorative inflammatory monocytes harboring immunosuppressive properties and strong tumor-promoting potential. Consistent with our HCC mouse model, a low level of LECT2 in human HCC is strongly associated with high tumor grade and the presence of inflammatory infiltrates, emphasizing the clinical value of LECT2 in human liver tumorigenesis. Conclusion: Our findings have demonstrated that LECT2 is a key player in liver tumorigenesis because its absence reshapes the tumor microenvironment and the tumor phenotype, revealing LECT2 as a promising immunotherapeutic option for HCC.

Lect2 deficiency is characterised by altered cytokine levels and promotion of intestinal tumourigenesis

Leukocyte cell-derived chemotaxin 2 (Lect2) is a chemokine-like chemotactic factor that has been identified as a downstream target of the Wnt signalling pathway. Whilst the primary function of Lect2 is thought to be in modulating the inflammatory process, it has recently been implicated as a potential inhibitor of the Wnt pathway. Deregulation of the Wnt pathway, often due to loss of the negative regulator APC, is found in ~80% of colorectal cancer (CRC). Here we have used the ApcMin/+Lect2-/- mouse model to characterise the role of Lect2 in Wnt-driven intestinal tumourigenesis. Histopathological, immunohistochemical, PCR and flow cytometry analysis were employed to identify the role of Lect2 in the intestine. The ApcMin/+Lect2-/- mice had a reduced mean survival and a significantly increased number of adenomas in the small intestine with increased severity. Analysis of Lect2 loss indicated it had no effect on the Wnt pathway in the intestine but significant differences were observed in circulating inflammatory markers, CD4+ T cells, and T cell lineage-specification factors. In summary, in the murine intestine loss of Lect2 promotes the initiation and progression of Wnt-driven colorectal cancer. This protection is performed independently of the Wnt signalling pathway and is associated with an altered inflammatory environment during Wnt-driven tumorigenesis.

Pathophysiological significance of hepatokine overproduction in type 2 diabetes

Currently, many studies draw attention to novel secretory factors, such as adipokines or myokines, derived from the tissues that were not originally recognized as endocrine organs. The liver may contribute to the onset of various kinds of pathologies of type 2 diabetes by way of the production of secretory proteins "hepatokines." Using the comprehensive gene expression analyses in human livers, we have rediscovered selenoprotein P and LECT2 as hepatokines involved in the onset of dysregulated glucose metabolism. Overproduction of selenoprotein P, previously reported as a transport protein of selenium, induces insulin resistance and hyperglycemia in type 2 diabetic condition. Selenoprotein P also contributes to vascular complications of type 2 diabetes directly by inducing VEGF resistance in vascular endothelial cells. Notably, selenoprotein P impairs health-promoting effects of exercise by inhibiting ROS/AMPK/PGC-1α pathway in the skeletal muscle through its receptor LRP1. Overproduction of LECT2, previously reported as a neutrophil chemotactic protein, links obesity to insulin resistance in the skeletal muscle. Further studies would develop novel diagnostic or therapeutic procedures targeting hepatokines to combat over-nutrition-related diseases such as type 2 diabetes.

LECT2 promotes inflammation and insulin resistance in adipocytes via P38 pathways

Leukocyte cell-derived chemotaxin 2 (LECT2) is a recently identified novel hepatokine that causes insulin resistance in skeletal muscle by activating c-Jun N-terminal kinase (JNK), thereby driving atherosclerotic inflammation. However, the role of LECT2 in inflammation and insulin resistance in adipocytes has not been investigated. In this study, we report that LECT2 treatment of differentiated 3T3-L1 cells stimulates P38 phosphorylation in a dose-dependent manner. LECT2 also enhanced inflammation markers such as IκB phosphorylation, nuclear factor kappa beta (NF-κB) phosphorylation and IL-6 expression. Moreover, LECT2 treatment impaired insulin signaling in differentiated 3T3-L1 cells, as evidenced by the decreased levels of insulin receptor substrate (IRS-1) and Akt phosphorylation and reduced insulin-stimulated glucose uptake. Furthermore, LECT2 augmented lipid accumulation during 3T3-L1 cell differentiation by activating SREBP1c-mediated signaling. All these effects were significantly abrogated by siRNA-mediated silencing of P38, CD209 expression or a JNK inhibitor. Our findings suggest that LECT2 stimulates inflammation and insulin resistance in adipocytes via activation of a CD209/P38-dependent pathway. Thus, these results suggest effective therapeutic targets for treating inflammation-mediated insulin resistance.

Circulating LECT2 levels in newly diagnosed type 2 diabetes mellitus and their association with metabolic parameters: An observational study

Leukocyte cell-derived chemotaxin 2 (LECT2) is a hepatokine expressed in hepatocytes and appears to be involved in energy metabolism. The aim of this study was to determine plasma LECT2 levels in newly diagnosed type 2 diabetic patients and to correlate the results with various metabolic parameters.A total of 93 newly diagnosed type 2 diabetic patients and 80 age- and sex-matched nondiabetes mellitus ones were enrolled in the study. Plasma LECT2 levels were measured by enzyme-linked immunosorbent assay.Circulating LECT2 levels were approximately 1.3 times higher in newly diagnosed type 2 diabetic patients than in controls (mean 30.30 vs 23.23 ng/mL, P < .001). Correlation analysis showed that LECT2 was negatively associated with high-density lipoprotein-cholesterol (HDL-C) levels in type 2 diabetic patients and obese subjects (P < .05). In multiple stepwise regression analysis, HDL-C, HOMA-IR, BMI, FINS, and TG were significantly independent determinants for LECT2 (P < .05).Our study showed that circulating LECT2 concentrations are significantly higher in newly diagnosed type 2 diabetic patients and further elevated in obese type 2 diabetic patients. LECT2 concentrations are significantly negatively associated with HDL-cholesterol levels in newly diagnosed type 2 diabetic patients and obese subjects.

Effect of a LECT2 on the immune response of peritoneal lecukocytes against Vibrio anguillarum in roughskin sculpin

Leukocyte cell-derived chemotaxin 2 (LECT2) is a multi-functional protein that is mainly synthesized by the liver. However, its role in roughskin scalping is less known. Here, we cloned a leukocyte cell-derived chemotaxin 2 (TfLECT2) genes in the liver of roughskin scalping, Trachidermus fasciatus, and studied its possible role involved in the immune response against Vibrio anguillarum (V. anguillarum) of peritoneal lecukocytes under in vivo conditions. The cDNA sequence of TfLECT2 is 566 bp in size. Its deduced amino acid (aa) sequence comprises 151 residues, of which the first 16 residues form a putative signal peptide and 101 residues compose a typical peptidase M23 domain in the C-terminal region. The domain structure is conserved in all LECT2 proteins, which suggests a close phylogenetic relationship between TfLECT2 and LECT2 in other fish species. Real-time quantitative PCR analysis revealed that TfLECT2 gene expression was dramatically increased in liver after V. anguillarum stimulation. Subsequently, TfLECT2 was prokaryotic expressed and purified to prepare anti-TfLECT2 antibody. After V. anguillarum challenge, leukocytes recruitment and LECT2 levels in peritoneal exudates were increased, and positively correlated with each other. Moreover, recombinant TfLECT2 administration significantly improved immune responses after infection, principally in stimulating the recruitment, phagocytosis and respiratory burst of leukocytes at the site of infection; however, anti-TfLECT2 treatment neutralized these abilities. Therefore, TfLECT2 may trigger the early immune events of peritoneal leukocytes and it will be useful to induce innate immune response of fish.

Alleviation of lipopolysaccharide/d-galactosamine-induced liver injury in leukocyte cell-derived chemotaxin 2 deficient mice

Leukocyte cell-derived chemotaxin 2 (LECT2) is a secreted pleiotropic protein that is mainly produced by the liver. We have previously shown that LECT2 plays an important role in the pathogenesis of inflammatory liver diseases. Lipopolysaccharide/d-galactosamine (LPS/d-GalN)-induced acute liver injury is a known animal model of fulminant hepatic failure. Here we found that this hepatic injury was alleviated in LECT2-deficient mice. The levels of TNF-α and IFN-γ, which mediate this hepatitis, had significantly decreased in these mice, with the decrease in IFN-γ production notably greater than that in TNF-α. We therefore analyzed IFN-γ-producing cells in liver mononuclear cells. Flow cytometric analysis showed significantly reduced IFN-γ production in hepatic NK and NKT cells in LECT2-deficient mice compared with in wild-type mice. We also demonstrated a decrease in IFN-γ production in LECT2-deficient mice after systemic administration of recombinant IL-12, which is known to induce IFN-γ in NK and NKT cells. These results indicate that a decrease of IFN-γ production in NK and NKT cells was involved in the alleviation of LPS/d-GalN-induced liver injury in LECT2-deficient mice.

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LECT2-deficient mice are less sensitive to LPS/d-GalN-induced hepatitis.

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The IFN-γ level in hepatic NK and NKT cells is lower in LECT2-deficient mice.

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IL-12-induced IFN-γ production is diminished in LECT2-deficient mice.

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The pathological role of LECT2 in hepatitis could depend on the initiation of immune response cells.

Comparative transcriptomics of genetically divergent lines of chickens in response to Marek's disease virus challenge at cytolytic phase

Marek's disease (MD), caused by Marek's disease virus (MDV), remains an economically significant threat to the poultry industry worldwide. Genetic resistance to MD is a promising alternative strategy to augment current control measures (vaccination and management). However, only a few functional genes reportedly conferring MD resistance have been identified. Here, we performed a comparative transcriptomics analysis of two highly inbred yet genetically divergent lines of chickens (line 63 and 72) that are resistant and susceptible to MD, respectively, in response to a very virulent plus strain of MDV (vv+MDV) challenge at cytolytic phase. A total of 203 DEGs in response to MDV challenge were identified in the two lines. Of these, 96 DEGs were in common for both lines, in addition to 36 and 71 DEGs that were specific for line 63 and 72, respectively. Functional enrichment analysis results showed the DEGs were significantly enriched in GO terms and pathways associated with immune response. Especially, the four DEGs, FGA, ALB, FN1, and F13A1 that reportedly facilitate virus invasion or immunosuppression, were found to be significantly up-regulated in the susceptible line 72 but down-regulated in the resistant line 63 birds. These results provide new resources for future studies to further elucidate the genetic mechanism conferring MD resistance.

Association of leukocyte cell-derived chemotaxin 2 (LECT2) with NAFLD, metabolic syndrome, and atherosclerosis

Objective

Previous studies have shown that leukocyte cell-derived chemotaxin 2 (LECT2), a recently discovered hepatokine, is associated with the inflammatory response and insulin resistance. We examined circulating plasma LECT2 levels in the subjects with non-alcoholic fatty liver disease (NAFLD) or metabolic syndrome.

Methods

We analyzed plasma LECT2 levels from the subjects of age- and sex-matched 320 adults with or without NAFLD who completed a health check-up at the Health Promotion Center of Korea University Guro Hospital.

Results

Individuals with NAFLD showed significantly higher LECT2 levels (31.2 [20.9, 41.5] vs. 24.5[16.3, 32.7] ng/ml, P <0.001) as well as components of MetS compared to those without NAFLD. Furthermore, circulating LECT2 concentrations were greater in subjects with MetS (32.6 [17.8, 45.0] vs. 27.0 [18.7, 33.7] ng/ml, P = 0.016) and were associated with anthropometric measures of obesity, lipid profiles, high sensitivity C-reactive protein (hsCRP) and liver aminotransferase levels. However, there was no significant relationship between LECT2 levels and indicators of subclinical atherosclerosis, such as carotid intima-media thickness (CIMT) and brachial ankle pulse wave velocity (baPWV). Multivariate analysis demonstrated a progressively increasing trend of odds ratios for NAFLD according to quartiles of LECT2 levels after adjusting for risk factors, although the relationship was attenuated after further adjustment for waist circumference and lipid levels.

Conclusion

Circulating LECT2 concentrations were increased in individuals with NAFLD and those with MetS, but not in those with atherosclerosis. The relationship between LECT2 and both NAFLD and MetS might be mediated by its association with abdominal obesity and lipid metabolism.

Trial registration

Clinicaltrials.gov NCT01594710

Metabolic Adaptation in Obesity and Type II Diabetes: Myokines, Adipokines and Hepatokines

Obesity and type II diabetes are characterized by insulin resistance in peripheral tissues. A high caloric intake combined with a sedentary lifestyle is the leading cause of these conditions. Whole-body insulin resistance and its improvement are the result of the combined actions of each insulin-sensitive organ. Among the fundamental molecular mechanisms by which each organ is able to communicate and engage in cross-talk are cytokines or peptides which stem from secretory organs. Recently, it was reported that several cytokines or peptides are secreted from muscle (myokines), adipose tissue (adipokines) and liver (hepatokines) in response to certain nutrition and/or physical activity conditions. Cytokines exert autocrine, paracrine or endocrine effects for the maintenance of energy homeostasis. The present review is focused on the relationship and cross-talk amongst muscle, adipose tissue and the liver as secretory organs in metabolic diseases.

Reduced serum level of leukocyte cell-derived chemotaxin 2 is associated with the presence of diabetic retinopathy

BACKGROUND

Vascular endothelial growth factor (VEGF) signaling is an important pathway in the development of diabetic retinopathy (DR). A recent report showed that leukocyte cell-derived chemotaxin 2 (LECT2) suppresses the VEGF signaling in endothelial cells. However, the clinical relevance of LECT2 in DR is unknown. This study aimed to investigate serum LECT2 levels and the presence of DR.

METHODS

The study included 230 people with type 2 diabetes mellitus (DM), 95 with DR and 135 without DR. Serum LECT2 levels were measured using an enzyme-linked immunosorbent assay. Data were evaluated using Spearman's rank correlation, univariate and multivariate logistic regression.

RESULTS

Serum LECT2 levels were significantly lower in participants with DM having DR than in those not having DR (35.6±14.9ng/ml vs. 44.5±17.6ng/ml, P<0.001). Spearman's rank correlation analysis revealed a significant association between serum LECT2 levels and the presence of DR (P<0.001). Multiple regression analysis revealed that serum LECT2 levels were independently related to DR (P<0.001).

CONCLUSIONS

These findings indicated that serum LECT2 level is negatively associated with the presence of DR and suggest that low circulating LECT2 level is a risk factor for DR.

Inhibition of VEGF165/VEGFR2-dependent signaling by LECT2 suppresses hepatocellular carcinoma angiogenesis

Hepatocellular carcinoma (HCC) relies on angiogenesis for growth and metastasis. Leukocyte cell-derived chemotaxin 2 (LECT2) is a cytokine and preferentially expressed in the liver. Previous studies have found that LECT2 targets to both immune and tumor cells to suppress HCC development and vascular invasion. Although LECT2 did not affect HCC cells growth in vitro, it still suppressed HCC xenografts growth in immune-deficient mice, suggesting other cells such as stroma cells may also be targeted by LECT2. Here, we sought to determine the role of LECT2 in tumor angiogenesis in HCC patients. We found that LECT2 expression inhibited tumor growth via angiogenesis in the HCC xenograft model. Specifically, we demonstrated that recombinant human LECT2 protein selectively suppressed vascular endothelial growth factor (VEGF)₁₆₅-induced endothelial cell proliferation, migration, and tube formation in vitro and in vivo. Mechanistically, LECT2 reduced VEGF receptor 2 tyrosine phosphorylation and its downstream extracellular signal-regulated kinase and AKT phosphorylation. Furthermore, LECT2 gene expression correlated negatively with angiogenesis in HCC patients. Taken together, our findings demonstrate that LECT2 inhibits VEGF₁₆₅-induced HCC angiogenesis through directly binding to VEGFR2 and has broad applications in treating VEGF-mediated solid tumors.

Crystal Structure of Human Leukocyte Cell-derived Chemotaxin 2 (LECT2) Reveals a Mechanistic Basis of Functional Evolution in a Mammalian Protein with an M23 Metalloendopeptidase Fold

Human leukocyte cell-derived chemotaxin 2 (LECT2), which is predominantly expressed in the liver, is a multifunctional protein. LECT2 is becoming a potential therapeutic target for several diseases of worldwide concern such as rheumatoid arthritis, hepatocellular carcinoma, and obesity. Here, we present the crystal structure of LECT2, the first mammalian protein whose structure contains an M23 metalloendopeptidase fold. The LECT2 structure adopts a conserved Zn(II) coordination configuration but lacks a proposed catalytic histidine residue, and its potential substrate-binding groove is blocked in the vicinity of the Zn(II)-binding site by an additional intrachain loop at the N terminus. Consistent with these structural features, LECT2 was found to be catalytically inactive as a metalloendopeptidase against various types of peptide sequences, including pentaglycine. In addition, a surface plasmon resonance analysis demonstrated that LECT2 bound to the c-Met receptor with micromolar affinity. These results indicate that LECT2 likely plays its critical roles by acting as a ligand for the corresponding protein receptors rather than as an enzymatically active peptidase. The intrachain loop together with the pseudo-active site groove in LECT2 structure may be specific for interactions between LECT2 and receptors. Our study reveals a mechanistic basis for the functional evolution of a mammalian protein with an M23 metalloendopeptidase fold and potentially broadens the implications for the biological importance of noncatalytic peptidases in the M23 family.

A transmembrane C-type lectin receptor mediates LECT2 effects on head kidney-derived monocytes/macrophages in a teleost, Plecoglossus altivelis

Leukocyte cell-derived chemotaxin 2 (LECT2) is a multifunctional cytokine involved in many diseases in which immune dysfunction is present. Ayu LECT2 (PaLECT2), which interacts with a C-type lectin receptor (PaCLR), was shown to activate ayu head kidney-derived monocytes/macrophages (MO/MΦ) to improve the outcomes of fish upon bacterial infections. However, it is not known if PaCLR mediates PaLECT2 effects on ayu MO/MΦ. In this study, we determined the role of PaCLR in signal transduction of PaLECT2 on ayu MO/MΦ. We expressed the PaCLR ectodomain in Escherichia coli and produced a refolded recombinant protein (rPaCLR) that was then used to produce the anti-PaCLR IgG (anti-PaCLR) for neutralization. Addition of the refolded PaLECT2 mature peptide (rPaLECT2m) to ayu MO/MΦ cultures, increased cytokine expression, induced chemotaxis, and enhanced phagocytosis and bactericidal activity of these cells were observed. When we added anti-PaCLR to block the ectodomain of PaCLR, these effects were significantly inhibited. Based on our previous works and the data presented here, we conclude that PaCLR mediates the immunomodulatory effects of PaLECT2 on ayu MO/MΦ, thus defining a mechanism by which LECT2 protects fish against pathogens.

Implication of hepatokines in metabolic disorders and cardiovascular diseases

The liver is a central regulator of systemic energy homeostasis and has a pivotal role in glucose and lipid metabolism. Impaired gluconeogenesis and dyslipidemia are often observed in patients with nonalcoholic fatty liver disease (NAFLD). The liver is now recognized to be an endocrine organ that secretes hepatokines, which are proteins that regulate systemic metabolism and energy homeostasis. Hepatokines are known to contribute to the pathogenesis of metabolic syndrome, NAFLD, type 2 diabetes (T2DM), and cardiovascular diseases (CVDs). In this review, we focus on the roles of two major hepatokines, fetuin-A and fibroblast growth factor 21 (FGF21), as well as recently-redefined hepatokines, such as selenoprotein P, angiopoietin-like protein 4 (ANGPTL4), and leukocyte cell-derived chemotaxin 2 (LECT2). We also assess the biology and molecular mechanisms of hepatokines in the context of their potential as therapeutic targets for metabolic disorders and cardiovascular diseases.

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The roles of hepatokines such as fetuin-A, FGF21, selenoprotein P, ANGPTL4, and LECT2

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The molecular mechanisms of hepatokines in metabolic disorders and CVD

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Hepatokines as therapeutic strategies for metabolic disorders and CVD

LECT2 induces atherosclerotic inflammatory reaction via CD209 receptor-mediated JNK phosphorylation in human endothelial cells

OBJECTIVE

Leukocyte cell-derived chemotaxin 2 (LECT2) is a recently discovered novel hepatokine, leading to skeletal muscle insulin resistance by activating c-Jun N-terminal kinase (JNK). However, its role in atherosclerotic inflammatory reactions has not been examined. Therefore, we investigated the function of LECT2 on the expression of vascular adhesion molecules and inflammatory cytokines in human endothelial cells.

METHODS

Human umbilical vein endothelial cells (HUVECs) and THP-1 cells were treated with various doses of LECT2 and the functions and signaling pathways were analyzed through Western blot and quantitative real-time PCR (qPCR).

RESULTS

The level of phosphorylated c-Jun N-terminal kinases (JNK) was significantly increased by LECT2 treatment in HUVECs and THP-1 cells, an effect that was not seen in cells treated with CD209 siRNA, a known LECT2 receptor. LECT2 treatment efficiently increased the expression of intercellular adhesion molecule-1 (ICAM-1) and pro-inflammatory cytokines tumor necrosis factor α (TNFα), monocyte chemo-attractant protein-1 (MCP-1), and interleukin-1β (IL-1β) in HUVECs and THP-1 cells. However, all these reactions were significantly reduced in response to treatment with JNK inhibitor. Furthermore, LECT2 treatment significantly exacerbated the adhesion of monocytic cells to human endothelial cells, which was also efficiently attenuated by JNK inhibitor.

CONCLUSIONS

LECT2 significantly induced adhesion molecules and pro-inflammatory cytokines in HUVECs via CD209-mediated JNK phosphorylation, suggesting that liver-derived novel hepatokine, LECT2, might directly mediate in the atherosclerotic inflammatory reactions in human endothelial cells.

Leukocyte Cell-Derived Chemotaxin 2-Associated Amyloidosis: A Recently Recognized Disease with Distinct Clinicopathologic Characteristics

Amyloidosis derived from leukocyte cell-derived chemotaxin 2 is a recently recognized form of amyloidosis, and it has already been established as a frequent form of systemic amyloidosis in the United States, with predominant involvement of kidney and liver. The disease has a strong ethnic bias, affecting mainly Hispanics (particularly Mexicans). Additional ethnic groups prone to develop amyloidosis derived from leukocyte cell-derived chemotaxin 2 include Punjabis, First Nations people in British Columbia, and Native Americans. Most patients are elderly who present with chronic renal insufficiency and bland urinary sediment. Proteinuria is variable, being absent altogether in about one third of patients. Liver involvement is frequently an incidental finding. Amyloidosis derived from leukocyte cell-derived chemotaxin 2 deposits shows a characteristic distribution: in the kidney, there is consistent involvement of cortical interstitium, whereas in the liver, there is a preferential involvement of periportal and pericentral vein regions. Concurrent renal disease is frequent, with diabetic nephropathy and IgA nephropathy being the most common. Patient survival is excellent, likely because of the rarity of cardiac involvement, whereas renal survival is guarded, with a median renal survival of 62 months in those without concurrent renal disease. There is currently no efficacious therapy for amyloidosis derived from leukocyte cell-derived chemotaxin 2 amyloidosis. Renal transplantation seems to be a reasonable treatment for patients with advanced renal failure, although the disease may recur in the allograft. The pathogenesis of amyloidosis derived from leukocyte cell-derived chemotaxin 2 amyloidosis has not yet been elucidated. It could be a result of leukocyte cell-derived chemotaxin 2 overexpression by hepatocytes either constitutively (controlled by yet-uncharacterized genetic defects) or secondary to hepatocellular damage. It is critical not to misdiagnose amyloidosis derived from leukocyte cell-derived chemotaxin 2 amyloidosis as Ig light chain-derived amyloidosis to avoid harmful chemotherapy.

Hydrogel nanoparticle harvesting of plasma or urine for detecting low abundance proteins

Novel biomarker discovery plays a crucial role in providing more sensitive and specific disease detection. Unfortunately many low-abundance biomarkers that exist in biological fluids cannot be easily detected with mass spectrometry or immunoassays because they are present in very low concentration, are labile, and are often masked by high-abundance proteins such as albumin or immunoglobulin. Bait containing poly(N-isopropylacrylamide) (NIPAm) based nanoparticles are able to overcome these physiological barriers. In one step they are able to capture, concentrate and preserve biomarkers from body fluids. Low-molecular weight analytes enter the core of the nanoparticle and are captured by different organic chemical dyes, which act as high affinity protein baits. The nanoparticles are able to concentrate the proteins of interest by several orders of magnitude. This concentration factor is sufficient to increase the protein level such that the proteins are within the detection limit of current mass spectrometers, western blotting, and immunoassays. Nanoparticles can be incubated with a plethora of biological fluids and they are able to greatly enrich the concentration of low-molecular weight proteins and peptides while excluding albumin and other high-molecular weight proteins. Our data show that a 10,000 fold amplification in the concentration of a particular analyte can be achieved, enabling mass spectrometry and immunoassays to detect previously undetectable biomarkers.

LECT2 functions as a hepatokine that links obesity to skeletal muscle insulin resistance

Recent articles have reported an association between fatty liver disease and systemic insulin resistance in humans, but the causal relationship remains unclear. The liver may contribute to muscle insulin resistance by releasing secretory proteins called hepatokines. Here we demonstrate that leukocyte cell-derived chemotaxin 2 (LECT2), an energy-sensing hepatokine, is a link between obesity and skeletal muscle insulin resistance. Circulating LECT2 positively correlated with the severity of both obesity and insulin resistance in humans. LECT2 expression was negatively regulated by starvation-sensing kinase adenosine monophosphate-activated protein kinase in H4IIEC hepatocytes. Genetic deletion of LECT2 in mice increased insulin sensitivity in the skeletal muscle. Treatment with recombinant LECT2 protein impaired insulin signaling via phosphorylation of Jun NH2-terminal kinase in C2C12 myocytes. These results demonstrate the involvement of LECT2 in glucose metabolism and suggest that LECT2 may be a therapeutic target for obesity-associated insulin resistance.

Characterization of the LECT2 gene and its associations with resistance to the big belly disease in Asian seabass

Leukocyte cell-derived chemotaxin-2 (LECT2) is an important protein of the innate immune system for the defense against bacterial infection. We cloned and characterized the LECT2 gene from Asian seabass (Lates calcarifer). Its complete cDNA consisted of an open reading frame of 459 bp encoding a protein of 152 amino acids. The genomic DNA sequence of this gene consists of four exons and three introns. Quantitative real-time PCR revealed that the LECT2 gene was expressed predominantly in liver while its expression was moderate in spleen and heart, and weak in other tissues. The LECT2 transcript was up-regulated in the kidney, spleen and liver in response to a challenge with a pathogenic bacterium Vibrio harveyi. In addition, we identified three single nucleotide polymorphisms (SNPs) in the LECT2 gene, and found significant associations between these polymorphisms and resistance to the big belly disease. These results suggest that the LECT2 gene play an important role in resistance to bacterial pathogens in fish. The SNP markers in the gene associated with the resistance to bacterial pathogens may facilitate selecting Asian seabass resistant to bacterial diseases.

Extracellular adenosine controls NKT-cell-dependent hepatitis induction

Extracellular adenosine regulates inflammatory responses via the A2A adenosine receptor (A2AR). A2AR deficiency results in much exaggerated acute hepatitis, indicating nonredundancy of adenosine-A2AR pathway in inhibiting immune activation. To identify a critical target of immunoregulatory effect of extracellular adenosine, we focused on NKT cells, which play an indispensable role in hepatitis. An A2AR agonist abolished NKT-cell-dependent induction of acute hepatitis by concanavalin A (Con A) or α-galactosylceramide in mice, corresponding to downregulation of activation markers and cytokines in NKT cells and of NK-cell co-activation. These results show that A2AR signaling can downregulate NKT-cell activation and suppress NKT-cell-triggered inflammatory responses. Next, we hypothesized that NKT cells might be under physiological control of the adenosine-A2AR pathway. Indeed, both Con A and α-galactosylceramide induced more severe hepatitis in A2AR-deficient mice than in WT controls. Transfer of A2AR-deficient NKT cells into A2AR-expressing recipients resulted in exaggeration of Con A-induced liver damage, suggesting that NKT-cell activation is controlled by endogenous adenosine via A2AR, and this physiological regulatory mechanism of NKT cells is critical in the control of tissue-damaging inflammation. The current study suggests the possibility to manipulate NKT-cell activity in inflammatory disorders through intervention to the adenosine-A2AR pathway.

Crystallization and preliminary X-ray analysis of human leukocyte cell-derived chemotaxin 2 (LECT2)

Human leukocyte cell-derived chemotaxin 2 (LECT2) is a chemotactic factor for neutrophils that plays multifunctional roles in liver regeneration, regulation of neuritic development and proliferation of chondrocytes and osteoblasts. In addition, the C-terminal region of LECT2 belongs to the zinc metalloendopeptidase M23 (PF01551) family. Purified LECT2 was crystallized using the sitting-drop vapour-diffusion method at 293 K. Crystals of selenomethionine-substituted LECT2 that diffracted X-rays to 1.94 Å resolution were obtained using a reservoir solution consisting of 0.2 M ammonium sulfate, 0.1 M HEPES pH 7.5, 25%(w/v) PEG 8000. The crystal belonged to space group P2₁2₁2₁, with unit-cell parameters a=59.4, b=63.5, c=64.0 Å. The calculated Matthews coefficient (VM=2.10 Å3 Da(-1), solvent content 40%) indicates that the crystal consists of two molecules per asymmetric unit.

LECT2 protects mice against bacterial sepsis by activating macrophages via the CD209a receptor

Leukocyte cell–derived chemotaxin 2 enhances phagocytosis and bacterial killing of macrophages to improve the outcome of bacterial-induced sepsis.

Leukocyte cell–derived chemotaxin 2 (LECT2) is a multifunctional cytokine and reduced plasma levels were found in patients with sepsis. However, precise functions and mechanisms of LECT2 remain unclear. The aim of the present study was to determine the role of LECT2 in modulating immune responses using mouse sepsis models. We found that LECT2 treatment improved outcome in mice with bacterial sepsis. Macrophages (MΦ), but not polymorphonuclear neutrophils, mediated the beneficial effect of LECT2 on bacterial sepsis. LECT2 treatment could alter gene expression and enhance phagocytosis and bacterial killing of MΦ in vitro. CD209a was identified to specifically interact with LECT2 and mediate LECT2-induced MΦ activation. CD209a-expressing MΦ was further confirmed to mediate the effect of LECT2 on sepsis in vivo. Our data demonstrate that LECT2 improves protective immunity in bacterial sepsis, possibly as a result of enhanced MΦ functions via the CD209a receptor. The modulation of MΦ functions by LECT2 may serve as a novel potential treatment for sepsis.

Genomic organization, promoter characterization and expression analysis of the leukocyte cell-derived chemotaxin-2 gene in Epinephelus akaraa

Leucocyte cell-derived chemotaxin 2 (LECT2) was first identified as a chemotactic factor and has been subsequently proven to be a multifunctional protein that mediates the regulation of liver regeneration, carcinogenesis and Natural killer T (NKT) cell homeostasis in mammals. In fish, it has been recently found to be critical for the inflammatory response to stimuli. However, the in vivo function of LECT2 in fish remains obscure. Base on the full-length cDNA of the Epinephelus akaraa LECT2 (EaLECT2) gene we previously isolated, we sought to analyze its genomic structure and context. The genomic DNA of the EaLECT2 gene spans 2866bp from the transcription start site to the termination codon. As in most LECT2 genes in other vertebrates, the EaLECT2 genomic DNA contains four exons and three introns. An analysis of the promoter region revealed the presence of a TATA box and several putative transcription factor-binding sites. And transcriptional activity analysis suggested that most basal DNA regulatory elements required for EaLECT2 transcriptional activity might be contained within the 581bp region upstream of the transcription start codon. A real-time PCR analysis showed that the EaLECT2 expression levels were slightly increased in the head kidney, liver, gill and brain by bacterial challenge with Vibrio harveyi. Furthermore, the transcriptional level of the EaLECT2 gene in the liver was significantly up-regulated within 1h and reached its peak level at 12h post-stimulation. Higher levels of LECT2 expression were also observed in head kidney in challenged individuals.The expression pattern demonstrates the role of EaLECT2 in the immune response and its functions under other conditions. Additionally, we found that the recombinant EaLECT2 could be expressed as a soluble protein using a prokaryotic expression system with the expression vector pET32a(+) and the soluble protein was further proved to be the recombinant EaLECT2 with the rat antiserum against EaLECT2 we obtained. This work provides a unique basis for substantial work in future projects.

CD4+ T-cell dysfunctions through the impaired lipid rafts ameliorate concanavalin A-induced hepatitis in sphingomyelin synthase 1-knockout mice

Membrane microdomains consisting of sphingomyelin (SM) and cholesterol appear to be important for signal transduction in T-cell activation. The present study was designed to elucidate the role of membrane SM in vivo and in vitro using sphingomyelin synthase 1 (SMS1) knock out (SMS1(-/-)) mice and Concanavalin A (ConA)-induced hepatitis. After establishing SMS1(-/-) mice, we investigated CD4+ T-cell functions including proliferation, cytokine production and signal transduction in vivo. We also examined severity of hepatitis, cytokine production in serum and liver after ConA injection at a dose of 20 mg kg(-1). CD4+ T cells from SMS1(-/-) mice showed severe deficiency of membrane SM and several profound defects compared with wild-type controls as follows: (i) cellular proliferation and production of IL-2 and IFN-γ by co-cross-linking of CD3 and CD4; (ii) tyrosine phosphorylation of LAT and its association with ZAP-70; (iii) clustering and co-localization of TCR with lipid rafts. Consistent with these impaired CD4+ T-cell functions in vitro, SMS1(-/-) mice showed decreased serum levels of IL-6 and IFN-γ by ConA injection, which renders SMS1(-/-) mice less sensitive to ConA-induced hepatitis. These results indicated that the deficiency of membrane SM caused the CD4+ T-cell dysfunction through impaired lipid raft function contributed to protection of ConA-induced liver injury, suggesting that the membrane SM is critical for full T-cell activation both in vitro and in vivo.

The inhibitory effect of environmental ammonia on Danio rerio LPS induced acute phase response

Ammonia is a toxic by-product of amino acid catabolism and a common environmental pollutant that has been associated with increased disease susceptibility in fish although the mechanism is not well understood. We addressed the hypothesis that elevated environmental ammonia acts by impairing the acute phase response (APR). Specifically, we determined the impact of sub-lethal acute (24 h) and chronic (14 d) ammonia exposure on acute phase protein gene expression in zebrafish (Danio rerio) in response to a challenge with bacterial lipopolysaccharide (LPS: i.p. 10 μg/g after 24h). A panel of LPS-responsive genes (SAA, HAMP, LECT2, Hp and IL1β) were identified and evaluated by real-time quantitative PCR. Ammonia was found to impair induction of SAA, HAMP and LECT2 by 50-90%. Both short (15 min, 1h and 24h) and long-term (14 days) exposure to high environmental ammonia concentrations significantly elevated whole-body cortisol levels compared with control fish. Our results reveal for the first time that exposure to high environmental levels of ammonia suppresses the innate immune response in fish. We hypothesize that high environmental ammonia-mediated elevation of cortisol levels in zebrafish may be playing a key role in this immunosuppression, while the mechanisms involved remains to be elucidated.

Oncogenic β-catenin triggers an inflammatory response that determines the aggressiveness of hepatocellular carcinoma in mice

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide. Its pathogenesis is frequently linked to liver inflammation. Gain-of-function mutations in the gene encoding β-catenin are frequent genetic modifications found in human HCCs. Thus, we investigated whether inflammation was a component of β-catenin-induced tumorigenesis using genetically modified mouse models that recapitulated the stages of initiation and progression of this tumoral process. Oncogenic β-catenin signaling was found to induce an inflammatory program in hepatocytes that involved direct transcriptional control by β-catenin and activation of the NF-κB pathway. This led to a specific inflammatory response, the intensity of which determined the degree of tumor aggressiveness. The chemokine-like chemotactic factor leukocyte cell-derived chemotaxin 2 (LECT2) and invariant NKT (iNKT) cells were identified as key interconnected effectors of liver β-catenin-induced inflammation. In genetic deletion models lacking the gene encoding LECT2 or iNKT cells, hepatic β-catenin signaling triggered the formation of highly malignant HCCs with lung metastasis. Thus, our results identify inflammation as a key player in β-catenin-induced liver tumorigenesis. We provide strong evidence that, by activating pro- and antiinflammatory mediators, β-catenin signaling produces an inflammatory microenvironment that has an impact on tumoral development. Our data are consistent with the fact that most β-catenin-activated HCCs are of better prognosis.