Junctional adhesion molecule C mediates leukocyte adhesion to rheumatoid arthritis synovium

The Lnc-ENST00000602558/IGF1 axis as a predictor of response to treatment with tripterygium glycosides in rheumatoid arthritis patients

AIMS

Growing clinical evidence suggests that not all patients with rheumatoid arthritis (RA) benefit to the same extent by treatment with tripterygium glycoside (TG), which highlights the need to identify RA-related genes that can be used to predict drug responses. In addition, single genes as markers of RA are not sufficiently accurate for use as predictors. Therefore, there is a need to identify paired expression genes that can serve as biomarkers for predicting the therapeutic effects of TG tablets in RA.

METHODS

A total of 17 pairs of co-expressed genes were identified as candidates for predicting an RA patient's response to TG therapy, and genes involved in the Lnc-ENST00000602558/GF1 axis were selected for that purpose. A partial-least-squares (PLS)-based model was constructed based on the expression levels of Lnc-ENST00000602558/IGF1 in peripheral blood. The model showed high efficiency for predicting an RA patient's response to TG tablets.

RESULTS

Our data confirmed that genes co-expressed in the Lnc-ENST00000602558/IGF1 axis mediate the efficacy of TG in RA treatment, reduce tumor necrosis factor-α induced IGF1 expression, and decrease the inflammatory response of MH7a cells.

CONCLUSION

We found that genes expressed in the Lnc-ENST00000602558/IGF1 axis may be useful for identifying RA patients who will not respond to TG treatment. Our findings provide a rationale for the individualized treatment of RA in clinical settings.

The Roles of Junctional Adhesion Molecules (JAMs) in Cell Migration

The review briefly summarizes the role of the family of adhesion molecules, JAMs (junctional adhesion molecules), in various cell migration, covering germ cells, epithelial cells, endothelial cells, several leukocytes, and different cancer cells. These functions affect multiple diseases, including reproductive diseases, inflammation-related diseases, cardiovascular diseases, and cancers. JAMs bind to both similar and dissimilar proteins and take both similar and dissimilar effects on different cells. Concluding relevant results provides a reference to further research.

An Atypical Presentation of Rheumatoid Arthritis as an Asymmetrical Arthropathy

We report a rare entity of distinctly asymmetrical rheumatoid arthritis (RA) in a 71-year-old Chinese lady with a history of cervical radiculopathy secondary to trauma sustained during childhood. The joints on the side of the paresis were spared from severe clinical and radiological manifestations of RA. We review the plausible mechanisms that could explain the link between neurological impairment and rheumatoid joint involvement.

The impact of sex on susceptibility to systemic lupus erythematosus and rheumatoid arthritis; a bioinformatics point of view

The unknown etiology of systemic autoimmune diseases, such as Systemic Lupus Erythematosus (SLE) and Rheumatoid Arthritis (RA), with a remarkable predominance of female, have prompted many researchers for unveiling the precise molecular mechanisms involved in this gender bias. In fact, depending on hormones and transcribed genes from sex chromosomes, at least, the initial mechanisms involved in pathogenesis might differ largely. With the aim of elucidating the above mechanisms, we have tried to specify the differentially expressed genes (DEGs) extracted from microarray libraries from both female and male SLE and RA patients. Subsequently, the androgen and estrogen receptor elements (ARE and ERE) among differentially expressed transcription factors (TFs) and the DEGs located on X or Y chromosomes have been determined. Moreover, the pathways regarding the common DEGs in both sexes are enriched. Our data revealed several ARE and ERE-containing genes (LCN2, LTF, RPL31, RPL9, RPS17, RPS24, RPS27L, S100A8, ABCA1, HIST1H2BD, ISG15, MAFB, GNLY, EVL, and HDC) to be associated with the related autoimmune disease and sex. Also, two DEGs (KDM5D and RPS4Y1) in SLE patients were determined to be on Y chromosome with one had been proved to be associated with autoantigens in SLE. Altogether, our data showed a number of plausible pathways in both autoimmune conditions together with the relevance of several sex-related genes in the mentioned diseases pathogenesis.

A novel gene-expression-signature-based model for prediction of response to Tripterysium glycosides tablet for rheumatoid arthritis patients

Background

Approximately 30% of rheumatoid arthritis (RA) patients treated with Tripterysium glycosides (TG) tablets fail to achieve clinical improvement, implying the essentiality of predictive biomarkers and tools. Herein, we aimed to identify possible biomarkers predictive of therapeutic effects of TG tablets in RA.

Methods

Gene expression profile in peripheral blood mononuclear cells obtained from a discovery cohort treated with TG tablets was detected by Affymetrix EG1.0 arrays. Then, a list of candidate gene biomarkers of response to TG tablets were identified by integrating differential expression data analysis and gene signal transduction network analysis. After that, a partial-least-squares (PLS) model based on the expression levels of the candidate gene biomarkers in RA patients was constructed and evaluated using a validation cohort.

Results

Six candidate gene biomarkers (MX1, OASL, SPINK1, CRK, GRAPL and RNF2) were identified to be predictors of TG therapy. Following the construction of a PLS-based model using their expression levels in peripheral blood, both the 5-fold cross-validation and independent dataset validations showed the high predictive efficiency of this model, and demonstrated a distinguished improvement of the PLS-model based on six candidate gene biomarkers’ expression in combination over the commonly used clinical and inflammatory parameters, as well as the gene biomarkers alone, in predicting RA patients’ response to TG tablets.

Conclusions

This hypothesis-generating study identified MX1, OASL, SPINK1, CRK, GRAPL and RNF2 as novel targets for RA therapeutic intervention, and the PLS model based on the expression levels of these candidate biomarkers may have a potential prognostic value in RA patients treated with TG tablets.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1549-9) contains supplementary material, which is available to authorized users.

Structural cartilage damage attracts circulating rheumatoid arthritis synovial fibroblasts into affected joints

BACKGROUND

Rheumatoid arthritis synovial fibroblasts (RASFs) are known to travel via the bloodstream from sites of cartilage destruction to new locations where they reinitiate the destructive processes at distant articular cartilage surfaces. In this study, we examined the role of interleukin (IL)-1-induced cartilage changes and their chemotactic effect on RASF transmigratory capacity.

METHODS

To investigate synovial fibroblast (SF) transmigration through endothelial layers, we used a modified Boyden chamber with an endothelioma cell layer (bEnd.5) as a barrier and IL-1-treated murine cartilage explants as a chemotactic stimulus for SFs from human tumor necrosis factor-transgenic (hTNFtg) mice. We injected recombinant IL-1 or collagenase into knee joints of wild-type mice, followed by tail vein injection of fluorescence-labeled hTNFtg SFs. The distribution and intensity of transmigrating hTNFtg SFs were measured by fluorescence reflectance imaging with X-ray coregistration. Toluidine blue staining was performed to evaluate the amount of cartilage destruction.

RESULTS

Histomorphometric analyses and in vivo imaging revealed a high degree of cartilage proteoglycan loss after intra-articular IL-1 and collagenase injection, accompanied by an enhanced in vivo extravasation of hTNFtg SFs into the respective knee joints, suggesting that structural cartilage damage contributes significantly to the attraction of hTNFtg SFs into these joints. In vitro results showed that degraded cartilage was directly responsible for the enhanced transmigratory capacity because stimulation with IL-1-treated cartilage, but not with IL-1 or cartilage alone, was required to increase hTNFtg SF migration.

CONCLUSIONS

The present data indicate that structural cartilage damage facilitates the migration of arthritic SF into affected joints. The prevention of early inflammatory cartilage damage may therefore help prevent the progression of rheumatoid arthritis and its spread to previously unaffected joints.

Endothelial Cell Junctional Adhesion Molecules: Role and Regulation of Expression in Inflammation

Endothelial cells line the lumen of all blood vessels and play a critical role in maintaining the barrier function of the vasculature. Sealing of the vessel wall between adjacent endothelial cells is facilitated by interactions involving junctionally expressed transmembrane proteins, including tight junctional molecules, such as members of the junctional adhesion molecule family, components of adherence junctions, such as VE-Cadherin, and other molecules, such as platelet endothelial cell adhesion molecule. Of importance, a growing body of evidence indicates that the expression of these molecules is regulated in a spatiotemporal manner during inflammation: responses that have significant implications for the barrier function of blood vessels against blood-borne macromolecules and transmigrating leukocytes. This review summarizes key aspects of our current understanding of the dynamics and mechanisms that regulate the expression of endothelial cells junctional molecules during inflammation and discusses the associated functional implications of such events in acute and chronic scenarios.

Divergent JAM-C Expression Accelerates Monocyte-Derived Cell Exit from Atherosclerotic Plaques

Atherosclerosis, caused in part by monocytes in plaques, continues to be a disease that afflicts the modern world. Whilst significant steps have been made in treating this chronic inflammatory disease, questions remain on how to prevent monocyte and macrophage accumulation in atherosclerotic plaques. Junctional Adhesion Molecule C (JAM-C) expressed by vascular endothelium directs monocyte transendothelial migration in a unidirectional manner leading to increased inflammation. Here we show that interfering with JAM-C allows reverse-transendothelial migration of monocyte-derived cells, opening the way back out of the inflamed environment. To study the role of JAM-C in plaque regression we used a mouse model of atherosclerosis, and tested the impact of vascular JAM-C expression levels on monocyte reverse transendothelial migration using human cells. Studies in-vitro under inflammatory conditions revealed that overexpression or gene silencing of JAM-C in human endothelium exposed to flow resulted in higher rates of monocyte reverse-transendothelial migration, similar to antibody blockade. We then transplanted atherosclerotic, plaque-containing aortic arches from hyperlipidemic ApoE^-/- mice into wild-type normolipidemic recipient mice. JAM-C blockade in the recipients induced greater emigration of monocyte-derived cells and further diminished the size of atherosclerotic plaques. Our findings have shown that JAM-C forms a one-way vascular barrier for leukocyte transendothelial migration only when present at homeostatic copy numbers. We have also shown that blocking JAM-C can reduce the number of atherogenic monocytes/macrophages in plaques by emigration, providing a novel therapeutic strategy for chronic inflammatory pathologies.

Paired Ig-Like Type 2 Receptor-Derived Agonist Ligands Ameliorate Inflammatory Reactions by Downregulating β1 Integrin Activity

The paired immunoglobulin-like type 2 receptor (PILR) family consists of two functionally opposite members, inhibitory PILRα and activating PILRβ receptors. PILRs are widely expressed in various immune cells and interact with their ligands, especially CD99 expressed on activated T cells, to participate in immune responses. Here we investigated whether PILR-derived agonists inhibit β1 integrin activity as ligands for CD99. PILR-derived peptides as well as PILR-Fc fusion proteins prevented cell adhesion to fibronectin through the regulation of β1 integrin activity. Especially, PILRpep3, a representative 3-mer peptide covering the conserved motifs of the PILR extracellular domain, prevented the clustering and activation of β1 integrin by dephosphorylating FAK and vinculin, which are major components of focal adhesion. In addition, PILRpep3 inhibited transendothelial migration of monocytes as well as endothelial cell tube formation. Furthermore, upon intraperitoneal injection of PILRpep3 into mice with collagen-induced arthritis, the inflammatory response of rheumatoid arthritis was strongly suppressed. Taken together, these results suggest that PILR-derived agonist ligands may prevent the inflammatory reactions of rheumatoid arthritis by activating CD99.

The pathogenic role of angiogenesis in rheumatoid arthritis

Angiogenesis is the formation of new capillaries from pre-existing vasculature, which plays a critical role in the pathogenesis of several inflammatory autoimmune diseases such as rheumatoid arthritis (RA), spondyloarthropathies, psoriasis, systemic lupus erythematosus, systemic sclerosis, and atherosclerosis. In RA, excessive migration of circulating leukocytes into the inflamed joint necessitates formation of new blood vessels to provide nutrients and oxygen to the hypertrophic joint. The dominance of the pro-angiogenic factors over the endogenous angiostatic mediators triggers angiogenesis. In this review article, we highlight the underlying mechanisms by which cells present in the RA synovial tissue are modulated to secrete pro-angiogenic factors. We focus on the significance of pro-angiogenic factors such as growth factors, hypoxia-inducible factors, cytokines, chemokines, matrix metalloproteinases, and adhesion molecules on RA pathogenesis. As pro-angiogenic factors are primarily produced from RA synovial tissue macrophages and fibroblasts, we emphasize the key role of RA synovial tissue lining layer in maintaining synovitis through neovascularization. Lastly, we summarize the specific approaches utilized to target angiogenesis. We conclude that the formation of new blood vessels plays an indispensable role in RA progression. However, since the function of several pro-angiogenic mediators is cross regulated, discovering novel approaches to target multiple cascades or selecting an upstream cascade that impairs the activity of a number of pro-angiogenic factors may provide a promising strategy for RA therapy.

Fucosyltransferase 1 mediates angiogenesis in rheumatoid arthritis

OBJECTIVE

To determine the role of α(1,2)-linked fucosylation of proteins by fucosyltransferase 1 (FUT1) in rheumatoid arthritis (RA) angiogenesis.

METHODS

Analysis of α(1,2)-linked fucosylated proteins in synovial tissue (ST) samples was performed by immunohistologic staining. Expression of α(1,2)-linked fucosylated angiogenic chemokine in synovial fluid (SF) was determined by immunoprecipitation and lectin blotting. To determine the angiogenic role of α(1,2)-linked fucosylated proteins in RA, we performed human dermal microvascular endothelial cell (HMVEC) chemotaxis and Matrigel assays using sham-depleted and α(1,2)-linked fucosylated protein-depleted RA SF samples. To examine the production of proangiogenic chemokines by FUT1 in HMVECs, cells were transfected with FUT1 sense or antisense oligonucleotides, and enzyme-linked immunosorbent assay was performed. We then studied mouse lung endothelial cell (EC) chemotaxis using wild-type and FUT1 gene-deficient mouse lung ECs.

RESULTS

RA ST endothelial cells showed high expression of α(1,2)-linked fucosylated proteins compared to normal ST. The expression of α(1,2)-linked fucosylated monocyte chemoattractant protein 1 (MCP-1)/CCL2 was significantly elevated in RA SF compared with osteoarthritis SF. Depletion of α(1,2)-linked fucosylated proteins in RA SF induced less HMVEC migration and tube formation than occurred in sham-depleted RA SF. We found that blocking FUT1 expression in ECs resulted in decreased MCP-1/CCL2 and RANTES/CCL5 production. Finally, we showed that FUT1 regulates EC migration in response to vascular endothelial cell growth factor.

CONCLUSION

Our findings indicate that α(1,2)-linked fucosylation by FUT1 may be an important new target for angiogenic diseases such as RA.

Fucosyltransferase 1 mediates angiogenesis, cell adhesion and rheumatoid arthritis synovial tissue fibroblast proliferation

INTRODUCTION

We previously reported that sialyl Lewis(y), synthesized by fucosyltransferases, is involved in angiogenesis. Fucosyltransferase 1 (fut1) is an α(1,2)-fucosyltransferase responsible for synthesis of the H blood group and Lewis(y) antigens. However, the angiogenic involvement of fut 1 in the pathogenesis of rheumatoid arthritis synovial tissue (RA ST) has not been clearly defined.

METHODS

Assay of α(1,2)-linked fucosylated proteins in RA was performed by enzyme-linked lectin assay. Fut1 expression was determined in RA ST samples by immunohistological staining. We performed angiogenic Matrigel assays using a co-culture system of human dermal microvascular endothelial cells (HMVECs) and fut1 small interfering RNA (siRNA) transfected RA synovial fibroblasts. To determine if fut1 played a role in leukocyte retention and cell proliferation in the RA synovium, myeloid THP-1 cell adhesion assays and fut1 siRNA transfected RA synovial fibroblast proliferation assays were performed.

RESULTS

Total α(1,2)-linked fucosylated proteins in RA ST were significantly higher compared to normal (NL) ST. Fut1 expression on RA ST lining cells positively correlated with ST inflammation. HMVECs from a co-culture system with fut1 siRNA transfected RA synovial fibroblasts exhibited decreased endothelial cell tube formation compared to control siRNA transfected RA synovial fibroblasts. Fut1 siRNA also inhibited myeloid THP-1 adhesion to RA synovial fibroblasts and RA synovial fibroblast proliferation.

CONCLUSIONS

These data show that α(1,2)-linked fucosylated proteins are upregulated in RA ST compared to NL ST. We also show that fut1 in RA synovial fibroblasts is important in angiogenesis, leukocyte-synovial fibroblast adhesion, and synovial fibroblast proliferation, all key processes in the pathogenesis of RA.

Differential expression of junctional adhesion molecules in different stages of systemic sclerosis

OBJECTIVE

Systemic sclerosis (SSc) is characterized by early perivascular inflammation, microvascular endothelial cell (MVEC) activation/damage, and defective angiogenesis. Junctional adhesion molecules (JAMs) regulate leukocyte recruitment to sites of inflammation and ischemia-reperfusion injury, vascular permeability, and angiogenesis. This study was undertaken to investigate the possible role of JAMs in SSc pathogenesis.

METHODS

JAM-A and JAM-C expression levels in skin biopsy samples from 25 SSc patients and 15 healthy subjects were investigated by immunohistochemistry and Western blotting. Subcellular localization of JAMs in cultured healthy dermal MVECs and SSc MVECs was assessed by confocal microscopy. Serum levels of soluble JAM-A (sJAM-A) and sJAM-C in 64 SSc patients and 32 healthy subjects were examined by enzyme-linked immunosorbent assay.

RESULTS

In control skin, constitutive JAM-A expression was observed in MVECs and fibroblasts. In early-stage SSc skin, JAM-A expression was strongly increased in MVECs, fibroblasts, and perivascular inflammatory cells. In late-stage SSc, JAM-A expression was decreased compared with controls. JAM-C was weakly expressed in control and late-stage SSc skin, while it was strongly expressed in MVECs, fibroblasts, and inflammatory cells in early-stage SSc. Surface expression of JAM-A was higher in early-stage SSc MVECs and increased in healthy MVECs stimulated with early-stage SSc sera. JAM-C was cytoplasmic in resting healthy MVECs, while it was recruited to the cell surface upon challenge with early-stage SSc sera. Early-stage SSc MVECs exhibited constitutive surface JAM-C expression. In SSc, increased levels of sJAM-A and sJAM-C correlated with early disease and measures of vascular damage.

CONCLUSION

Our findings indicate that JAMs may participate in MVEC activation, inflammatory processes, and impaired angiogenesis in different stages of SSc.

ADAM-10 is overexpressed in rheumatoid arthritis synovial tissue and mediates angiogenesis

OBJECTIVE

To examine the expression of ADAM-10 in rheumatoid arthritis (RA) synovial tissue (ST) and the role it plays in angiogenesis.

METHODS

ADAM-10 expression was determined using immunohistology, Western blotting, and quantitative polymerase chain reaction. In order to examine the role of ADAM-10 in angiogenesis, we performed in vitro Matrigel tube formation and chemotaxis assays using human microvascular endothelial cells (HMVECs) transfected with control or ADAM-10 small interfering RNA (siRNA). To determine whether ADAM-10 plays a role in angiogenesis in the context of RA, we performed Matrigel assays using a coculture system of HMVECs and RA synovial fibroblasts.

RESULTS

Endothelial cells and lining cells within RA ST expressed high levels of ADAM-10 compared with cells within osteoarthritis ST and normal ST. ADAM-10 expression was significantly elevated at the protein and messenger RNA levels in HMVECs and RA synovial fibroblasts stimulated with proinflammatory mediators compared with unstimulated cells. ADAM-10 siRNA-treated HMVECs had decreased endothelial cell tube formation and migration compared with control siRNA-treated HMVECs. In addition, ADAM-10 siRNA-treated HMVECs from the RA synovial fibroblast coculture system had decreased endothelial cell tube formation compared with control siRNA-treated HMVECs.

CONCLUSION

These data show that ADAM-10 is overexpressed in RA and suggest that ADAM-10 may play a role in RA angiogenesis. ADAM-10 may be a potential therapeutic target in inflammatory angiogenic diseases such as RA.

Blockade but not overexpression of the junctional adhesion molecule C influences virus-induced type 1 diabetes in mice

Type 1 diabetes (T1D) results from the autoimmune destruction of insulin-producing beta-cells in the pancreas. Recruitment of inflammatory cells is prerequisite to beta-cell-injury. The junctional adhesion molecule (JAM) family proteins JAM-B and JAM–C are involved in polarized leukocyte transendothelial migration and are expressed by vascular endothelial cells of peripheral tissue and high endothelial venules in lympoid organs. Blocking of JAM-C efficiently attenuated cerulean-induced pancreatitis, rheumatoid arthritis or inflammation induced by ischemia and reperfusion in mice. In order to investigate the influence of JAM-C on trafficking and transmigration of antigen-specific, autoaggressive T-cells, we used transgenic mice that express a protein of the lymphocytic choriomeningitis virus (LCMV) as a target autoantigen in the β-cells of the islets of Langerhans under the rat insulin promoter (RIP). Such RIP-LCMV mice turn diabetic after infection with LCMV. We found that upon LCMV-infection JAM-C protein was upregulated around the islets in RIP-LCMV mice. JAM-C expression correlated with islet infiltration and functional beta-cell impairment. Blockade with a neutralizing anti-JAM-C antibody reduced the T1D incidence. However, JAM-C overexpression on endothelial cells did not accelerate diabetes in the RIP-LCMV model. In summary, our data suggest that JAM-C might be involved in the final steps of trafficking and transmigration of antigen-specific autoaggressive T-cells to the islets of Langerhans.

Suppression of endothelial cell activity by inhibition of TNFα

Introduction

TNFα is a proinflammatory cytokine that plays a central role in the pathogenesis of rheumatoid arthritis (RA). We investigated the effects of certolizumab pegol, a TNFα blocker, on endothelial cell function and angiogenesis.

Methods

Human dermal microvascular endothelial cells (HMVECs) were stimulated with TNFα with or without certolizumab pegol. TNFα-induced adhesion molecule expression and angiogenic chemokine secretion were measured by cell surface ELISA and angiogenic chemokine ELISA, respectively. We also examined the effect of certolizumab pegol on TNFα-induced myeloid human promyelocytic leukemia (HL-60) cell adhesion to HMVECs, as well as blood vessels in RA synovial tissue using the Stamper-Woodruff assay. Lastly, we performed HMVEC chemotaxis, and tube formation.

Results

Certolizumab pegol significantly blocked TNFα-induced HMVEC cell surface angiogenic E-selectin, vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 expression and angiogenic chemokine secretion (P < 0.05). We found that certolizumab pegol significantly inhibited TNFα-induced HL-60 cell adhesion to HMVECs (P < 0.05), and blocked HL-60 cell adhesion to RA synovial tissue vasculature (P < 0.05). TNFα also enhanced HMVEC chemotaxis compared with the negative control group (P < 0.05) and this chemotactic response was significantly reduced by certolizumab pegol (P < 0.05). Certolizumab pegol inhibited TNFα-induced HMVEC tube formation on Matrigel (P < 0.05).

Conclusion

Our data support the hypothesis that certolizumab pegol inhibits TNFα-dependent leukocyte adhesion and angiogenesis, probably via inhibition of angiogenic adhesion molecule expression and angiogenic chemokine secretion.

Cytokines profiling by multiplex analysis in experimental arthritis: which pathophysiological relevance for articular versus systemic mediators?

INTRODUCTION

We have taken advantage of the large screening capacity of a multiplex immunoassay to better define the respective contribution of articular versus systemic cytokines in experimental arthritis.

METHODS

We performed a follow up (from 7 hours to 14 days) multiplex analysis of 24 cytokines in synovial fluid and sera of rats developing Antigen-Induced Arthritis (AIA) and confronted their protein level changes with molecular, biochemical, histological and clinical events occurring in the course of the disease.

RESULTS

The time-scheduled findings in arthritic joints correlated with time-dependent changes of cytokine amounts in joint effusions but not with their blood levels. From seven hours after sensitization, high levels of chemokines (MCP-1, MIP1α, GRO/KC, RANTES, eotaxin) were found in synovial fluid of arthritic knees whereas perivascular infiltration occurred in the synovium; local release of inflammatory cytokines (IFNγ, IL-1β, IL-6) preceded the spreading of inflammation and resulted in progressive degradation of cartilage and bone. Finally a local overexpression of several cytokines/adipocytokines poorly described in arthritis (IL-13, IL-18, leptin) was observed.

CONCLUSIONS

Distinct panels of cytokines were found in arthritic fluid during AIA, and the expected effect of mediators correlated well with changes occurring in joint tissues. Moreover, multiplex analysis could be helpful to identify new pathogenic mediators and to elucidate the mechanisms supporting the efficacy of putative targeted therapies.

Pathobiology of junctional adhesion molecules

Junctional adhesion molecules are transmembrane proteins that belong to the immunoglobulin superfamily. In addition to their localization in close proximity to the tight junctions in endothelial and epithelial cells, junctional adhesion molecules are also expressed in circulating cells that do not form junctions, such as leukocytes and platelets. As a consequence, these proteins are associated not only with the permeability-regulating barrier function of the tight junctions, but also with other biologic processes, such as inflammatory reactions, responses to vascular injury, and tumor angiogenesis. Furthermore, because of their transmembrane topology, junctional adhesion molecules are poised both for receiving inputs from the cell interior (their expression, localization, and function being regulated in response to inflammatory cytokines and growth factors) and for translating extracellular adhesive events into functional responses. This review focuses on the different roles of junctional adhesion molecules in normal and pathologic conditions, with emphasis on inflammatory reactions and vascular responses to injury.

CD248 and its cytoplasmic domain: a therapeutic target for arthritis

OBJECTIVE

CD248 is a transmembrane glycoprotein expressed on the surface of activated perivascular and fibroblast-like cells. This study was undertaken to explore the function of CD248 and its cytoplasmic domain in arthritis.

METHODS

Synovial tissue biopsy samples from healthy controls, from patients with psoriatic arthritis (PsA), and from patients with rheumatoid arthritis (RA) were stained for CD248. Transgenic mice that were CD248-deficient (CD248-knockout [CD248(KO/KO) ]) or mice with CD248 lacking the cytoplasmic domain (CD248(CyD/CyD) ) were generated. Collagen antibody-induced arthritis (CAIA) was induced in these mice and in corresponding wild-type (WT) mice as controls. Clinical signs and histologic features of arthritis were evaluated. Cytokine levels were determined by enzyme-linked immunosorbent assay, and the number of infiltrating inflammatory cells was quantified by immunohistochemistry. In vitro studies were performed with fibroblasts from CD248-transgenic mouse embryos to explain the observed effects on inflammation.

RESULTS

Immunostaining of synovium from patients with PsA and patients with RA and that from mice after the induction of CAIA revealed strong CD248 expression in perivascular and fibroblast-like stromal cells. CD248(KO/KO) and CD248(CyD/CyD) mice had less severe arthritis, with lower plasma levels of proinflammatory cytokines, as compared with WT controls. Moreover, the joints of these mice had less synovial hyperplasia, reduced accumulation of inflammatory cells, and less articular cartilage and bone damage. Tumor necrosis factor α-induced monocyte adhesion to CD248(CyD/CyD) fibroblasts was impaired. CD248(CyD/CyD) fibroblasts exhibited reduced expression of hypoxia-inducible factor 1α, placental growth factor, vascular endothelial growth factor, and matrix metalloproteinase 9 activity in response to transforming growth factor β.

CONCLUSION

CD248 contributes to synovial hyperplasia and leukocyte accumulation in inflammatory arthritis, the effects of which are mediated partly via its cytoplasmic domain. CD248 is therefore a potential new target in the treatment of arthritis.

Dysregulated expression of MIG/CXCL9, IP-10/CXCL10 and CXCL16 and their receptors in systemic sclerosis

Introduction

Systemic sclerosis (SSc) is characterized by fibrosis and microvascular abnormalities including dysregulated angiogenesis. Chemokines, in addition to their chemoattractant properties, have the ability to modulate angiogenesis. Chemokines lacking the enzyme-linked receptor (ELR) motif, such as monokine induced by interferon-γ (IFN-γ) (MIG/CXCL9) and IFN-inducible protein 10 (IP-10/CXCL10), inhibit angiogenesis by binding CXCR3. In addition, CXCL16 promotes angiogenesis by binding its unique receptor CXCR6. In this study, we determined the expression of these chemokines and receptors in SSc skin and serum.

Methods

Immunohistology and enzyme-linked immunosorbent assays (ELISAs) were used to determine chemokine and chemokine receptor expression in the skin and serum, respectively, of SSc and normal patients. Endothelial cells (ECs) were isolated from SSc skin biopsies and chemokine and chemokine receptor expression was determined by quantitative PCR and immunofluorescence staining.

Results

Antiangiogenic IP-10/CXCL10 and MIG/CXCL9 were elevated in SSc serum and highly expressed in SSc skin. However, CXCR3, the receptor for these chemokines, was decreased on ECs in SSc vs. normal skin. CXCL16 was elevated in SSc serum and increased in SSc patients with early disease, pulmonary arterial hypertension, and those that died during the 36 months of the study. In addition, its receptor CXCR6 was overexpressed on ECs in SSc skin. At the mRNA and protein levels, CXCR3 was decreased while CXCR6 was increased on SSc ECs vs. human microvascular endothelial cells (HMVECs).

Conclusions

These results show that while the expression of MIG/CXCL9 and IP-10/CXCL10 are elevated in SSc serum, the expression of CXCR3 is downregulated on SSc dermal ECs. In contrast, CXCL16 and CXCR6 are elevated in SSc serum and on SSc dermal ECs, respectively. In all, these findings suggest angiogenic chemokine receptor expression is likely regulated in an effort to promote angiogenesis in SSc skin.

Downstream gene activation of the receptor ALX by the agonist annexin A1

BACKGROUND

Our understanding of pro-resolution factors in determining the outcome of inflammation has recently gained ground, yet not many studies have investigated whether specific genes or patterns of genes, are modified by these mediators. Here, we have focussed on the glucocorticoid modulated pro-resolution factor annexin A1 (AnxA1), studying if its interaction with the ALX receptor would affect downstream genomic targets.

METHODOLOGY/PRINCIPAL FINDINGS

Using microarray technology in ALX transfected HEK293 cells, we discovered an over-lapping, yet distinct gene activation profile for AnxA1 compared to its N-terminal mimetic peptide Ac2-26, which may be suggestive of unique downstream inflammatory outcomes for each substance. When the up-regulated genes were explored, consistently induced was the sphingosine phosphate phosphatase-2 gene (SGPP2), involved in regulation of the sphingosine 1 phosphate chemotactic system. Up-regulation of this gene, as well as JAG1 (and down-regulation of JAM3), was confirmed using real time PCR both with transfected HEK293 cells and human peripheral blood leukocytes. Furthermore, lymph nodes taken from AnxA1(null) mice displayed lower SGPP2 gene activity. Finally, connectivity map analysis for AnxA1 and peptide Ac2-26 indicated striking similarities with known anti-inflammatory therapeutics, glucocorticoids and aspirin-like compounds, as well as with histone deacetylase inhibitors.

CONCLUSION/SIGNIFICANCE

We believe these new data raise the profile of AnxA1 from being solely a short-term anti-inflammatory factor, to being a 'trigger' of the endogenous pro-resolution arsenal.

Junctional adhesion molecule-C is a soluble mediator of angiogenesis

Junctional adhesion molecule-C (JAM-C) is an adhesion molecule expressed by endothelial cells (ECs) that plays a role in tight junction formation, leukocyte adhesion, and transendothelial migration. In the current study, we investigated whether JAM-C is found in soluble form and whether soluble JAM-C (sJAM-C) mediates angiogenesis. We found that JAM-C is present in soluble form in normal serum and elevated in rheumatoid arthritis (RA) serum. The concentration of sJAM-C is also elevated locally in RA synovial fluid compared with RA serum or osteoarthritis synovial fluid. sJAM-C was also present in the culture supernatant of human microvascular ECs (HMVECs) and immortalized human dermal microvascular ECs, and its concentration was increased following cytokine stimulation. In addition, sJAM-C cleavage from the cell surface was mediated in part by a disintegrin and metalloproteinases 10 and 17. In functional assays, sJAM-C was both chemotactic and chemokinetic for HMVECs and induced HMVEC tube formation on Matrigel in vitro. Neutralizing anti-JAM-C Abs inhibited RA synovial fluid-induced HMVEC chemotaxis and sJAM-C-induced HMVEC tube formation on Matrigel. sJAM-C also induced angiogenesis in vivo in the Matrigel plug and sponge granuloma models. Moreover, sJAM-C-mediated HMVEC chemotaxis was dependent on Src, p38, and PI3K. Our results show that JAM-C exists in soluble form and suggest that modulation of sJAM-C may provide a novel route for controlling pathological angiogenesis.

Junctional adhesion molecule-A is abnormally expressed in diffuse cutaneous systemic sclerosis skin and mediates myeloid cell adhesion

OBJECTIVE

To investigate the role of junctional adhesion molecule-A (JAM-A) in the pathogenesis of systemic sclerosis (SSc).

METHODS

Biopsy specimens from proximal and distal arm skin and serum were obtained from patients with SSc and normal volunteers. To determine the expression of JAM-A on SSc dermal fibroblasts and in SSc skin, cell surface ELISAs and immunohistology were performed. An ELISA was designed to determine the amount of soluble JAM-A (sJAM-A) in serum. Myeloid U937 cell-SSc dermal fibroblast and skin adhesion assays were performed to determine the role of JAM-A in myeloid cell adhesion.

RESULTS

The stratum granulosum and dermal endothelial cells (ECs) from distal arm SSc skin exhibited significantly decreased expression of JAM-A in comparison with normal volunteers. However, sJAM-A was increased in the serum of patients with SSc compared with normal volunteers. Conversely, JAM-A was increased on the surface of SSc compared with normal dermal fibroblasts. JAM-A accounted for a significant portion of U937 binding to SSc dermal fibroblasts. In addition, JAM-A contributed to U937 adhesion to both distal and proximal SSc skin.

CONCLUSIONS

JAM-A expression is dysregulated in SSc skin. Decreased expression of JAM-A on SSc ECs may result in a reduced response to proangiogenic basic fibroblast growth factor. Increased JAM-A expression on SSc fibroblasts may serve to retain myeloid cells, which in turn secrete angiogenic factors.

Angiogenesis in rheumatoid arthritis

Angiogenesis is the formation of new capillaries from pre-existing vessels. A number of soluble and cell-bound factors may stimulate neovascularization. The perpetuation of angiogenesis involving numerous soluble and cell surface-bound mediators has been associated with rheumatoid arthritis (RA). These angiogenic mediators, among others, include growth factors, primarily vascular endothelial growth factor (VEGF) and hypoxia-inducible factors (HIFs), as well as pro-inflammatory cytokines, various chemokines, matrix components, cell adhesion molecules, proteases and others. Among the several potential angiogenesis inhibitors, targeting of VEGF, HIF-1, angiogenic chemokines, tumor necrosis factor-alpha and the alpha(V)beta(3) integrin may attenuate the action of angiogenic mediators and thus synovial angiogenesis. In addition, some naturally produced or synthetic compounds including angiostatin, endostatin, paclitaxel, fumagillin analogues, 2-methoxyestradiol and thalidomide may be included in the management of RA.