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

An update on Ym1 and its immunoregulatory role in diseases

Ym1 is a rodent-specific chitinase-like protein (CLP) lacking catalytic activity, whose cellular origins are mainly macrophages, neutrophils and other cells. Although the detailed function of Ym1 remains poorly understood, Ym1 has been generally recognized as a fundamental feature of alternative activation of macrophages in mice and hence one of the prevalent detecting targets in macrophage phenotype distinguishment. Studies have pointed out that Ym1 may have regulatory effects, which are multifaceted and even contradictory, far more than just a mere marker. Allergic lung inflammation, parasite infection, autoimmune diseases, and central nervous system diseases have been found associations with Ym1 to varying degrees. Thus, insights into Ym1’s role in diseases would help us understand the pathogenesis of different diseases and clarify the genuine roles of CLPs in mammals. This review summarizes the information on Ym1 from the gene to its expression and regulation and focuses on the association between Ym1 and diseases.

Use of FVB Myc-CaP cells as an immune competent, androgen receptor positive, mouse model of prostate cancer bone metastasis

Prostate cancer (PCa) metastasis research has been hamstrung by lack of animal models that closely resemble the disease present in most patients - that metastasize to bone, are dependent on the androgen receptor (AR), and grow in an immune competent host. Here, we adapt the Myc-CaP cell line for use as a PCa androgen dependent, immune competent bone metastases model and characterize the metastases. After injection into the left cardiac ventricle of syngeneic FVB/NJ mice, these cells formed bone metastases in the majority of animals; easily visible on H&E sections and confirmed by immunohistochemistry for Ar and epithelial cell adhesion molecule. Mediastinal tumors were also observed. We also labeled Myc-CaP cells with tdTomato, and confirmed the presence of cancer cells in bone by flow cytometry. To adapt the model to a bone predominant metastasis pattern and further examine the bone phenotype, we labeled the cells with luciferase, injected in the tibia and observed tumor formation only in tibia with a mixed osteolytic/osteoblastic phenotype. The presence of Myc-CaP tumors significantly increased tibia bone volume as compared to sham injected controls. The osteoclast marker, TRAcP-5b was not significantly changed in plasma from tibial tumor bearing animals vs. sham animals. However, conditioned media from Myc-CaP cells stimulated osteoclast formation in vitro from FVB/NJ mouse bone marrow. Overall, Myc-CaP cells injected in the left ventricle or tibia of syngeneic mice recapitulate key aspects of human metastatic PCa.

Metastatic Breast Cancer, Organotropism and Therapeutics: A Review

The final stage of breast cancer involves spreading breast cancer cells to the vital organs like the brain, liver lungs and bones in the process called metastasis. Once the target organ is overtaken by the metastatic breast cancer cells, its usual function is compromised causing organ dysfunction and death. Despite the significant research on breast cancer metastasis, it's still the main culprit of breast cancer-related deaths. Exploring the complex molecular pathways associated with the initiation and progression of breast cancer metastasis could lead to the discovery of more effective ways of treating the devastating phenomenon. The present review article highlights the recent advances to understand the complexity associated with breast cancer metastases, organotropism and therapeutic advances.

Soluble antigen derived from IV larva of Angiostrongylus cantonensis promotes chitinase-like protein 3 (Chil3) expression induced by interleukin-13

Angiostrongyliasis caused by Angiostrongylus cantonensis (A. cantonensis) is an emerging food-borne parasitic disease, which refers basically to eosinophilic meningitis. Chitinase-like protein 3 (Chil3), a member of chitinase-like protein family which has chemotactic activity for eosinophils, is reported to be highly upregulated in brain of mouse infected with A. cantonensis. The mechanisms of high expression of Chil3 and the association between A. cantonensis and Chil3 are rarely reported. In order to understand the mechanism of high expression of Chil3 in A. cantonensis-infected mouse, we measured the level of Chil3 in RAW 264.7 and BV2 cell lines stimulated with soluble antigen of A. cantonensis by qPCR and ELISA. To explore the role of Chil3 in inflammation caused by A. cantonensis, we extracted and cultured brain mononuclear cells (BMNCs) and detected the eosinophil chemotactic activity of Chil3 using transwell assay and flow cytometer. Furthermore, we treated the infected mice by injection with rmChil3 and then counted the number of larvae in brains of infected mice and treated mice to examine the association between the worm and Chil3. Our results showed the soluble antigen from A. cantonensis could promote the Chil3 expression in macrophage and microglial cell lines induced by interleukin-13. In conclusion, we supposed that high expression of Chil3 enhanced by soluble antigens from A. cantonensis might be the reason of serious eosinophil infiltration in mouse brain after A. cantonensis infection.

Myeloid skewing in murine autoimmune arthritis occurs in hematopoietic stem and primitive progenitor cells

Skewing toward myeloid cell production is often observed in chronic inflammation and autoimmune diseases. Herein, we determined whether persistent myeloid activation and proinflammatory output occurring in pathologic conditions is at the level of hematopoietic stem and primitive progenitor cells (HSPPCs). By using a mouse arthritis model, we found that even though HSPPCs in arthritis still retained the capacity to differentiate into different lineages, they acquired enhanced in vitro and in vivo propensity in a disease-dependent manner to generate myeloid cells, the key perpetrators of tissue damage in arthritis. This myeloid skewing was cell intrinsic, as arthritic HSPPCs up-regulate myeloid-specific transcripts including S100a8. Exogenous S100a8 promoted myeloid cell output from wild-type HSPPCs, suggesting mechanistic involvement of this gene in the myeloid priming that occurs in arthritic HSPPCs. Therefore, our results indicate that in arthritic mice, HSPPCs adopt a pathologic state that favors disease persistence.

Osteoclasts are important for bone angiogenesis

Increased osteoclastogenesis and angiogenesis occur in physiologic and pathologic conditions. However, it is unclear if or how these processes are linked. To test the hypothesis that osteoclasts stimulate angiogenesis, we modulated osteoclast formation in fetal mouse metatarsal explants or in adult mice and determined the effect on angiogenesis. Suppression of osteoclast formation with osteoprotegerin dose-dependently inhibited angiogenesis and osteoclastogenesis in metatarsal explants. Conversely, treatment with parathyroid hormone related protein (PTHrP) increased explant angiogenesis, which was completely blocked by osteoprotegerin. Further, treatment of mice with receptor activator of nuclear factor-kappaB ligand (RANKL) or PTHrP in vivo increased calvarial vessel density and osteoclast number. We next determined whether matrix metalloproteinase-9 (MMP-9), an angiogenic factor predominantly produced by osteoclasts in bone, was important for osteoclast-stimulated angiogenesis. The pro-angiogenic effects of PTHrP or RANKL were absent in metatarsal explants or calvaria in vivo, respectively, from Mmp9(-/-) mice, demonstrating the importance of MMP-9 for osteoclast-stimulated angiogenesis. Lack of MMP-9 decreased osteoclast numbers and abrogated angiogenesis in response to PTHrP or RANKL in explants and in vivo but did not decrease osteoclast differentiation in vitro. Thus, MMP-9 modulates osteoclast-stimulated angiogenesis primarily by affecting osteoclasts, most probably by previously reported migratory effects on osteoclasts. These results clearly demonstrate that osteoclasts stimulate angiogenesis in vivo through MMP-9.

Transcriptome analysis of the salivary glands of the female tick Amblyomma americanum (Acari: Ixodidae)

Ticks infest a wide range of hosts while bypassing their immune, inflammatory and haemostatic responses during their extended feeding, which may last for more than two weeks. Here, we present a transcriptome analysis of 3868 expressed sequence tags (ESTs) from three cDNA libraries generated from the salivary glands of adult female Ambyomma americanum ticks at different stages of feeding. We applied a normalization step for one library, significantly decreasing the abundance of mitochondrial sequences amongst the 2292 sequences from the normalized library. Our ESTs include homologues that may modulate haemostatic, immune and inflammatory responses of the hosts. Other ESTs probably represent important components of the highly efficient secretory pathways for salivary proteins and concomitantly transmitted pathogens.

Blood and sputum eosinophil levels in asthma and their relationship to sinus computed tomographic findings

OBJECTIVE

To investigate the relationship among blood and sputum eosinophil levels, sinus mucosal thickening, and osteitis in patients with asthma.

PATIENTS AND METHODS

We conducted an observational study of 201 patients with asthma who underwent sinus computed tomographic (CT) imaging and induced sputum analysis at Mayo Clinic's site in Rochester, MN, from November 1, 2000, through December 31, 2005. Sinus CT scans were reviewed by an investigator blinded to patients' identity and chart information (J.B.H.) to assess for mucosal thickening. Each scan was assigned a CT score based on the Lund-Mackay staging scale. Approximately 20% of the scans were reviewed at random by a radiologist (N.G.C.) to ensure quality control. Bone changes consistent with osteitis were ascertained from radiology reports. Lung function was measured, and sputum was analyzed by conventional methods.

RESULTS

Sinus CT scans revealed abnormalities in 136 (68%) of the 201 study patients. Severe mucosal thickening (CT score, > or = 12) was found in 60 patients (30%) and osteitis in 18 patients (9%). There was a positive correlation between CT scores and eosinophil levels in both peripheral blood (rho=0.45; 95% confidence interval, 0.33-0.56; P<.001) and induced sputum (rho=0.46; 95% confidence interval, 0.34-0.57; P<.001). Further, elevated blood and sputum eosinophil levels were associated with the presence of osteitis on CT scan and previous sinus surgery.

CONCLUSION

Blood and sputum eosinophil levels in patients with asthma are directly correlated with sinus mucosal thickening and are associated with osteitis, lending further support to the hypothesis that asthma and chronic rhinosinusitis are mediated by similar inflammatory processes.

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

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

Stabilin-1, a homeostatic scavenger receptor with multiple functions

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

Cloning and Characterization of the Annexin II Receptor on Human Marrow Stromal Cells

Annexin II is a heterotetramer, consisting of two 11-kDa (p11) and two 36-kDa (p36) subunits, that is produced by osteoclasts and stimulates osteoclast formation. However, its receptor is unknown. We showed that annexin II binds to normal primary human marrow stromal cells and the Paget's marrow-derived PSV10 stromal cell line to induce osteoclast formation. 125I-Labeled annexin II binding assays with PSV10 cells demonstrated that there was a single class of annexin II receptors with a Kd of 5.79 nm and Bmax of 2.13 x 10(5) receptors/cell. Annexin III or annexin V did not bind this receptor. Using 125I-labeled annexin II binding to screen NIH3T3 transfected with a human marrow cDNA expression library, we identified a putative annexin II receptor clone, which encoded a novel 26-kDa type I membrane receptor protein when expressed in HEK 293 cells. HEK 293 cells transformed with the cloned annexin II receptor cDNA showed a similar binding affinity to annexin II as that observed in PSV10 cells. Chemical cross-linking experiments with biotinylated annexin II and intact PSV10 cells identified a 55-kDa band on Western blot analysis that reacted with both an anti-p11 antibody and streptavidin but not anti-p36 antibody. A rabbit polyclonal antibody raised against the putative recombinant annexin II receptor also recognized the same 26-kDa protein band detected in PSV10 cells. Importantly, the annexin II receptor antibody dose-dependently blocked the stimulatory effects of annexin II on human osteoclast formation, demonstrating that the receptor mediates the effects of annexin II on osteoclast formation.

Alpha9beta1: a novel osteoclast integrin that regulates osteoclast formation and function

We identified a previously unknown integrin, alpha(9)beta(1), on OCLs and their precursors. Antibody to alpha(9) inhibited OCL formation in human marrow cultures, and OCLs from alpha(9) knockout mice had a defect in actin ring reorganization and an impaired bone resorption capacity.

INTRODUCTION

Integrins play important roles in osteoclast (OCL) formation and function. Mature OCLs mainly express alpha(v)beta(3) integrin, a heterodimer adhesion receptor that has been implicated in osteoclastic bone resorption. We identified ADAM8, a disintegrin and metalloproteinase, as a novel stimulator of OCL differentiation and showed that the disintegrin domain of ADAM8 mediated its effects on OCL formation. Because the disintegrin domain of ADAM8 does not bind Arg-Gly-Asp (RGD) sequences, we determined which integrin bound ADAM8 and characterized its role in OCL formation and activity.

MATERIALS AND METHODS

Chinese hamster ovary cells (CHO) expressing different integrin subunits were tested for their capacity to bind the disintegrin domain of ADAM8. Mouse or human bone marrow cells and purified OCL precursors were tested for alpha(9)beta(1) integrin expression by Western blot, immunocytochemistry, and real-time RT-PCR. A monoclonal antibody to human alpha(9) was used to block alpha(9)beta(1) on OCL precursors stimulated by 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)] or RANKL. Vertebrae of 7-day-old alpha(9)(-/-) mice and wildtype (WT) littermates were compared using bone histomorphometry and 3D microCT analysis.

RESULTS

Alpha(9) integrin was expressed by mouse and human bone marrow-derived OCLs and their precursors. Importantly, the anti-alpha(9) antibody inhibited human OCL formation stimulated by 1alpha,25(OH)(2)D(3) or RANKL dose-dependently. Furthermore, analysis of OCLs formed in marrow cultures from alpha(9)(-/-) mice showed that the OCLs formed were more contracted and formed significantly less bone resorption pits on dentin slices. Histologic analysis of alpha(9)(-/-) vertebrae showed thickened trabecular regions and retained cartilage within vertebral bodies of alpha(9)(-/-) mice. 3D microCT analysis of alpha(9)(-/-) vertebrae also showed a significant increase in trabecular bone volume/total tissue volume and a tendency for decreased trabecular separation compared with WT mice.

CONCLUSIONS

These results support a previously unknown role for alpha(9)beta(1) integrin in OCL formation and function.

Regulation of osteoclast differentiation

The osteoclast (OCL) is derived from the cells in monocyte-macrophage lineage. The earliest identifiable OCL precursor is the granulocyte-macrophage colony-forming unit (CFU-GM), which gives rise to granulocytes, monocytes, and OCL. CFU-GM-derived cells then differentiate to committed OCL precursors, which are post-mitotic cells, and fuse to form multinucleated OCL. A variety of factors both positively and negatively regulate OCL formation and activity. These include growth factors, such as macrophage colony-simulating factor, which simulates the proliferation and prevents apoptosis of early OCL precursors, and RANK ligand (RANKL), which is the primary mediator of OCL formation. Most factors that induce OCL differentiation, such as PTHrP, IL-11, and prostaglandins, do so by inducing expression of RANKL on the surface of immature osteoblasts. Osteoprotegerin is a decoy receptor that blocks RANKL activity. In addition, OCL produce autocrine-paracrine factors that regulate OCL formation, such as IL-6, which is produced at high levels by OCL in Paget's disease and increases OCL formation. We screened human and murine OCL cDNA libraries to identify autocrine-paracrine factors that regulate OCL activity. We identified annexin-II, MIP-1alpha, ADAM8, eosinophil chemotactic factor, and OCL inhibitor factors 1 and 2 as factors involved in OCL formation. Most recently, we have identified the receptor for ADAM8, alpha9beta1 integrin, which appears to be critical for normal OCL activity. OCL differentiation is controlled by exogenous hormones and cytokines as well as autocrine-paracrine factors that positively or negatively regulate OCL proliferation and differentiation.

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

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

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

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