Expression of ADAM15 in rheumatoid synovium: up-regulation by vascular endothelial growth factor and possible implications for angiogenesis

ADAM15 expression is increased in lung CD8+ T cells, macrophages, and bronchial epithelial cells in patients with COPD and is inversely related to airflow obstruction

BACKGROUND

A disintegrin and metalloproteinase domain-15 (ADAM15) is expressed by activated leukocytes, and fibroblasts in vitro. Whether ADAM15 expression is increased in the lungs of COPD patients is not known.

METHODS

ADAM15 gene expression and/or protein levels were measured in whole lung and bronchoalveolar lavage (BAL) macrophage samples obtained from COPD patients, smokers, and non-smokers. Soluble ADAM15 protein levels were measured in BAL fluid (BALF) and plasma samples from COPD patients and controls. Cells expressing ADAM15 in the lungs were identified using immunostaining. Staining for ADAM15 in different cells in the lungs was related to forced expiratory volume in 1 s (FEV1), ratio of FEV1 to forced vital capacity (FEV1/FVC), and pack-years of smoking history.

RESULTS

ADAM15 gene expression and/or protein levels were increased in alveolar macrophages and whole lung samples from COPD patients versus smokers and non-smokers. Soluble ADAM15 protein levels were similar in BALF and plasma samples from COPD patients and controls. ADAM15 immunostaining was increased in macrophages, CD8+ T cells, epithelial cells, and airway α-smooth muscle (α-SMA)-positive cells in the lungs of COPD patients. ADAM15 immunostaining in macrophages, CD8+ T cells and bronchial (but not alveolar) epithelial cells was related inversely to FEV1 and FEV1/FVC, but not to pack-years of smoking history. ADAM15 staining levels in airway α-SMA-positive cells was directly related to FEV1/FVC. Over-expressing ADAM15 in THP-1 cells reduced their release of matrix metalloproteinases and CCL2.

CONCLUSIONS

These results link increased ADAM15 expression especially in lung leukocytes and bronchial epithelial cells to the pathogenesis of COPD.

The metalloproteinase ADAM15 is upregulated by shear stress and promotes survival of endothelial cells

Reduced shear stress resulting from disturbed blood flow can impair endothelial integrity and drive the development of vascular inflammatory lesions. Metalloproteinases of the ADAM family have been implicated in the regulation of cell survival and inflammatory responses. Here we investigate the mechanism and function of ADAM15 upregulation in primary flow cultured endothelial cells. Transcriptomic analysis indicated that within the ADAM family ADAM15 mRNA is most prominently upregulated (4-fold) when endothelial cells are exposed to physiologic shear stress. This induction was confirmed in venous, arterial and microvascular endothelial cells and is associated with increased presence of ADAM15 protein in the cell lysates (5.6-fold) and on the surface (3.1-fold). The ADAM15 promoter contains several consensus sites for the transcription factor KLF2 which is also upregulated by shear stress. Induction of endothelial KLF2 by simvastatin treatment is associated with ADAM15 upregulation (1.8-fold) which is suppressed by counteracting simvastatin with geranylgeranyl pyrophosphate. KLF2 overexpression promotes ADAM15 expression (2.1-fold) under static conditions whereas KLF2 siRNA knockdown prevents ADAM15 induction by shear stress. Functionally, ADAM15 promotes survival of endothelial cells challenged by growth factor depletion or TNF stimulation as shown by ADAM15 shRNA knockdown (1.6-fold). Exposure to shear stress increases endothelial survival while additional knockdown of ADAM15 reduces survival (6.7-fold) under flow conditions. Thus, physiologic shear stress resulting from laminar flow promotes KLF2 induced ADAM15 expression which contributes to endothelial survival. The absence of ADAM15 at low shear stress or static conditions may therefore lead to increased endothelial damage and promote vascular inflammation.

Integrating predicted transcriptome from multiple tissues improves association detection

Integration of genome-wide association studies (GWAS) and expression quantitative trait loci (eQTL) studies is needed to improve our understanding of the biological mechanisms underlying GWAS hits, and our ability to identify therapeutic targets. Gene-level association methods such as PrediXcan can prioritize candidate targets. However, limited eQTL sample sizes and absence of relevant developmental and disease context restrict our ability to detect associations. Here we propose an efficient statistical method (MultiXcan) that leverages the substantial sharing of eQTLs across tissues and contexts to improve our ability to identify potential target genes. MultiXcan integrates evidence across multiple panels using multivariate regression, which naturally takes into account the correlation structure. We apply our method to simulated and real traits from the UK Biobank and show that, in realistic settings, we can detect a larger set of significantly associated genes than using each panel separately. To improve applicability, we developed a summary result-based extension called S-MultiXcan, which we show yields highly concordant results with the individual level version when LD is well matched. Our multivariate model-based approach allowed us to use the individual level results as a gold standard to calibrate and develop a robust implementation of the summary-based extension. Results from our analysis as well as software and necessary resources to apply our method are publicly available.

We develop a new method, MultiXcan, to test the mediating role of gene expression variation on complex traits, integrating information available across multiple tissue studies. We show this approach has higher power than traditional single-tissue methods. We extend this method to use only summary-statistics from public GWAS. We apply these methods to 222 complex traits available in the UK Biobank cohort, and 109 complex traits from public GWAS and discuss the findings.

A Disintegrin and Metalloprotease 15 is Expressed on Rheumatoid Arthritis Synovial Tissue Endothelial Cells and may Mediate Angiogenesis

A disintegrin and metalloprotease 15 (ADAM15) is involved in several malignancies. In this study, we investigated the role of ADAM15 in rheumatoid arthritis (RA) angiogenesis. Soluble ADAM15 (s-ADAM15) in serum from RA and normal (NL) subjects was measured using ELISA. To determine membrane-anchored ADAM15 (ADAM15) expression in RA synovial tissues, immunohistochemistry was performed. To examine the role of ADAM15 in angiogenesis, we performed in vitro Matrigel assays and monocyte adhesion assays using human umbilical vein endothelial cells (HUVECs) transfected with ADAM15 siRNA. Finally, to investigate whether angiogenic mediators were affected by ADAM15, cytokines in ADAM15 siRNA-transfected HUVEC-conditioned medium were measured. ADAM15 was significantly higher in RA serum than in NL serum. ADAM15 was also expressed on RAST endothelial cells. ADAM15 siRNA-treated HUVECs had decreased EC tube formation in response to RA synovial fluids compared with non-treated HUVECs. The adhesion index of ADAM15 siRNA-transfected HUVECs was significantly lower than the adhesion index of control siRNA-transfected HUVECs. ENA-78/CXCL5 and ICAM-1 were decreased in tumor necrosis factor (TNF)-α-stimulated ADAM15 siRNA-transfected HUVEC-conditioned medium compared with TNF-α-stimulated control siRNA-transfected HUVEC-conditioned medium. These data show that ADAM15 plays a role in RA angiogenesis, suggesting that ADAM15 might be a potential target in inflammatory diseases such as RA.

Fine Tuning Cell Migration by a Disintegrin and Metalloproteinases

Cell migration is an instrumental process involved in organ development, tissue homeostasis, and various physiological processes and also in numerous pathologies. Both basic cell migration and migration towards chemotactic stimulus consist of changes in cell polarity and cytoskeletal rearrangement, cell detachment from, invasion through, and reattachment to their neighboring cells, and numerous interactions with the extracellular matrix. The different steps of immune cell, tissue cell, or cancer cell migration are tightly coordinated in time and place by growth factors, cytokines/chemokines, adhesion molecules, and receptors for these ligands. This review describes how a disintegrin and metalloproteinases interfere with several steps of cell migration, either by proteolytic cleavage of such molecules or by functions independent of proteolytic activity.

Localization, Shedding, Regulation and Function of Aminopeptidase N/CD13 on Fibroblast like Synoviocytes

Aminopeptidase N/CD13 is highly expressed by fibroblast like synoviocytes (FLS) and may play a role in rheumatoid arthritis (RA). CD13 was previously detected in human synovial fluid where it was significantly increased in RA compared to osteoarthritis. In this study we found that CD13 in biological fluids (plasma, synovial fluid, FLS culture supernatant) is present as both a soluble molecule and on extracellular vesicles, including exosomes, as assessed by differential ultracentrifugation and density gradient separation. Having determined CD13 could be released as a soluble molecule from FLS, we examined potential mechanisms by which CD13 might be shed from the FLS membrane. The use of protease inhibitors revealed that CD13 is cleaved from the FLS surface by metalloproteinases. siRNA treatment of FLS revealed one of those proteases to be MMP14. We determined that pro-inflammatory cytokines (TNFα, IFNγ, IL-17) upregulated CD13 mRNA in FLS, which may contribute to the increased CD13 in RA synovium and synovial fluid. Inhibition of CD13 function by either inhibitors of enzymatic activity or anti-CD13 antibodies resulted in decreased growth and diminished migration of FLS. This suggests that CD13 may be involved in the pathogenic hyperplasia of RA FLS. This data expands potential roles for CD13 in the pathogenesis of RA.

A disintegrin and metallproteinase 15 knockout decreases migration of fibroblast-like synoviocytes and inflammation in rheumatoid arthritis

The aim of the present study was to determine whether the expression of A disintegrin and metallproteinase 15 (ADAM15) affected the inflammatory conditions and cell migration in human fibroblast‑like synoviocytes (FLSs) in a rat model of rheumatoid arthritis (RA). The expression of ADAM15 in FLSs stimulated with lipopolysaccharide (LPS) was confirmed by reverse transcription‑quantitative polymerase chain reaction and western blot analysis. The effects of small interfering RNA targeting ADAM15 (siADAM5) on pro‑inflammatory cytokines and chemokines were assessed using an enzyme‑linked immunosorbent assay. The effects of siADAM15 on cell invasion and migration in FLS were also assessed in vitro. The therapeutic effects and side effects of ADAM15 in a rat model of collagen‑induced arthritis (CIA) were examined in vivo. The present results revealed that ADAM15 expression was significantly elevated at the mRNA and protein level in FLSs stimulated with LPS and that silencing ADAM15 suppressed the expression of pro‑inflammatory cytokines and chemokines, preventing FLS cell migration and invasion via inhibiting vascular endothelial growth factor‑A, matrix metalloproteinase (MMP)1 and MMP‑3 expression. In addition, treatment of CIA rats using siADAM15 significantly reduced the arthritis score and extent of joint damage in the rats. These findings indicated that silencing ADAM15 had anti‑inflammatory effects in FLSs and efficiently inhibited the development of CIA. Therefore, ADAM15 may be a potential target molecule for RA therapies.

MicroRNA-147b regulates vascular endothelial barrier function by targeting ADAM15 expression

A disintegrin and metalloproteinase15 (ADAM15) has been shown to be upregulated and mediate endothelial hyperpermeability during inflammation and sepsis. This molecule contains multiple functional domains with the ability to modulate diverse cellular processes including cell adhesion, extracellular matrix degradation, and ectodomain shedding of transmembrane proteins. These characteristics make ADAM15 an attractive therapeutic target in various diseases. The lack of pharmacological inhibitors specific to ADAM15 prompted our efforts to identify biological or molecular tools to alter its expression for further studying its function and therapeutic implications. The goal of this study was to determine if ADAM15-targeting microRNAs altered ADAM15-induced endothelial barrier dysfunction during septic challenge by bacterial lipopolysaccharide (LPS). An in silico analysis followed by luciferase reporter assay in human vascular endothelial cells identified miR-147b with the ability to target the 3′ UTR of ADAM15. Transfection with a miR-147b mimic led to decreased total, as well as cell surface expression of ADAM15 in endothelial cells, while miR-147b antagomir produced an opposite effect. Functionally, LPS-induced endothelial barrier dysfunction, evidenced by a reduction in transendothelial electric resistance and increase in albumin flux across endothelial monolayers, was attenuated in cells treated with miR-147b mimics. In contrast, miR-147b antagomir exerted a permeability-increasing effect in vascular endothelial cells similar to that caused by LPS. Taken together, these data suggest the potential role of miR147b in regulating endothelial barrier function by targeting ADAM15 expression.

Characterization of oxygen-induced retinopathy in mice carrying an inactivating point mutation in the catalytic site of ADAM15

PURPOSE

Retinal neovascularization is found in diseases such as macular degeneration, diabetic retinopathy, or retinopathy of prematurity and is usually caused by alterations in oxygen supply. We have previously described that mice lacking the membrane-anchored metalloproteinase ADAM15 (a Disintegrin and Metalloprotease 15) have decreased pathological neovascularization of the retina in the oxygen-induced retinopathy (OIR) model. The main purpose of the present study was to determine the contribution of the catalytic activity of ADAM15 to OIR.

METHODS

To address this question, we generated knock-in mice carrying an inactivating Glutamate to Alanine (E>A) point mutation in the catalytic site of ADAM15 (Adam15E>A mice) and subjected these animals to the OIR model and a heterotopic tumor model. Moreover, we used cell-based assays to determine whether ADAM15 can process cell surface receptors involved in angiogenesis.

RESULTS

We found that pathological neovascularization in the OIR model in Adam15E>A mice was comparable to that observed in wild type mice, but tumor implantation by heterotopically injected melanoma cells was reduced. In cell-based assays, overexpressed ADAM15 could process the FGFR2iiib, but was unable to process several receptors with roles in angiogenesis.

CONCLUSIONS

Collectively, these results suggest that the catalytic activity of ADAM15 is not crucial for its function in promoting pathological neovascularization in the mouse OIR model, most likely because of the very limited substrate repertoire of ADAM15. Instead, other noncatalytic functions of ADAM15 must be important for its role in the OIR model.

The potential role of angiogenic factors in rheumatoid arthritis

Angiogenesis is an important phenomenon in the pathogenesis of some diseases, such as numerous types of tumors and autoimmunity, and also a number of soluble and cell-bound factors may stimulate neovascularization in inflammatory reaction processes. Here, by highlighting the significance of angiogenesis reaction in rheumatoid arthritis (RA), we will mainly focus on the role of various growth factors, cytokines, enzymes, cells, hypoxic conditions and transcription factors in the angiogenic process and we will then explain some therapeutic strategies based on blockage of angiogenesis and modification of the vascular pathology in RA.

ADAM15 adds to apoptosis resistance of synovial fibroblasts by modulating focal adhesion kinase signaling

OBJECTIVE

To study the contribution of ADAM15, a disintegrin metalloproteinase that is up-regulated in the rheumatoid arthritis (RA) synovial membrane, to the characteristic resistance of RA synovial fibroblasts (RASFs) to apoptosis induction by genotoxic stress or stimulation with proapoptotic FasL, which is present at high concentrations in RA synovial fluid.

METHODS

Caspase 3/7 activity and the total apoptosis rate in RASFs upon exposure to the DNA-damaging agent camptothecin or FasL were determined using enzyme assays and annexin V staining. Phosphorylated signaling proteins were analyzed by immunoblotting. RNA interference was used to silence ADAM15 expression. NF-κB activity was determined by enzyme-linked immunosorbent assay.

RESULTS

RASFs displayed significantly higher caspase 3/7 activity upon camptothecin and FasL exposure when ADAM15 had been down-regulated by specific small interfering RNAs. Upon FasL stimulation, RASFs phosphorylated focal adhesion kinase (FAK) and c-Src (Src), and activated phosphatidylinositol 3-kinase as well as the transcription factor NF-κB. This ADAM15-dependent, FasL-induced activation of antiapoptotic kinases and NF-κB was demonstrated by a marked reduction of apoptosis upon knockdown of ADAM15 protein expression. Inhibitors specifically interfering with FAK and Src signaling, such as FAK inhibitor 14 and dasatinib, potently induce apoptosis in RASFs, with significant enhancement by the silencing of ADAM15.

CONCLUSION

ADAM15 contributes to apoptosis resistance in RASFs by activating the Src/FAK pathway upon FasL exposure, rendering the FAK/Src signaling pathway an interesting target for potential therapeutic intervention in RA.

Src plays a key role in ADAM28 expression in v-src-transformed epithelial cells and human carcinoma cells

ADAM28, a disintegrin and metalloproteinase 28, is overexpressed by carcinoma cells with direct correlations with carcinoma cell proliferation and progression in human lung and breast carcinomas. However, the molecular mechanisms of ADAM28 gene expression in carcinoma cells remain elusive. Herein, we investigated the expression of ADAM28 in Madin-Darby canine kidney epithelial cells transformed by oncogenes, including v-src, LMP1, ErbB2, Ha-Ras, and c-Fos, and found that v-src transformants selectively induce ADAM28. Implantation of the v-src transformants showed a progressively growing tumor, which was significantly suppressed by local injections of anti-ADAM28 antibody. ADAM28 expression in v-src transformants was partially inhibited by treatment with inhibitors to Src kinase, mitogen-activated protein kinase kinase (MEK), phosphatidylinositol 3-kinase (PI3K), or mammalian target of rapamycin, and abrogated by v-Src kinase inhibitor, radicicol, or a mixture of MEK and PI3K inhibitors. Human carcinoma cell lines of the lung, breast, ovary, kidney, and colon showed ADAM28 expression, which was correlated with phosphorylation of c-Src and suppressed by the inhibitors in a similar way to v-src transformants. IHC of the human tumor tissues demonstrated co-expression of ADAM28 and phosphorylated Src in neoplastic cells of the breast, lung, and colon carcinomas and some adenomas of the colon, but not in nonneoplastic colon mucosa. Our data provide, to the best of our knowledge, the first evidence that Src is an inducer of ADAM28 gene expression through the MEK/extracellular signal-regulated kinase and PI3K/mammalian target of rapamycin pathways.

Recombinant disintegrin domain of ADAM15 inhibits the proliferation and migration of Bel-7402 cells

ADAM15 (A Disintegrin And Metalloproteinase 15), a transmembrane protein containing seven domains, interacts with some integrins via its disintegrin domain and overexpresses in many solid tumors. In this study, the effect of the recombinant human disintegrin domain (rhddADAM15) on the proliferation and migration of Bel-7402 cells was evaluated in vitro and in vivo in zebrafish xenografts. rhddADAM15 (4 μM) severely inhibited the proliferation and migration of Bel-7402 cells, inducing a partial G2/S arrest and morphological nucleus changes of apoptosis. Moreover, the activity of caspases 8, 9 and 3 in Bel-7402 cells was increased. In addition, the zebrafish was used as a model for apoptosis-induction and tumor-xenograft. rhddADAM15 (1 pM) inhibited the growth and metastasis of Bel-7402 cell xenografts in zebrafish and a lower concentration (0.1 pM) induced severe apoptosis in the somatic cells of zebrafish. In conclusion, our data identified rhddADAM15 as a potent inhibitor of tumor growth and metastasis, making it a promising tool for use in anticancer treatment.

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.

The role of ADAM-mediated shedding in vascular biology

Within the vasculature the disintegrins and metalloproteinases (ADAMs) 8, 9, 10, 12, 15, 17, 19, 28 and 33 are expressed on endothelial cells, smooth muscle cells and on leukocytes. As surface-expressed proteases they mediate cleavage of vascular surface molecules at an extracellular site close to the membrane. This process is termed shedding and leads to the release of a soluble substrate ectodomain thereby critically modulating the biological function of the substrate. In the vasculature several surface molecules undergo ADAM-mediated shedding including tumour necrosis factor (TNF) α, interleukin (IL) 6 receptor α, L-selectin, vascular endothelial (VE)-cadherin, the transmembrane CX3C-chemokine ligand (CX3CL) 1, Notch, transforming growth factor (TGF) and heparin-binding epidermal growth factor (HB-EGF). These substrates play distinct roles in vascular biology by promoting inflammation, permeability changes, leukocyte recruitment, resolution of inflammation, regeneration and/or neovascularisation. Especially ADAM17 and ADAM10 are capable of cleaving many substrates with diverse function within the vasculature, whereas other ADAMs have a more restricted substrate range. Therefore, targeting ADAM17 or ADAM10 by pharmacologic inhibition or gene knockout not only attenuates the inflammatory response in animal models but also affects tissue regeneration and neovascularisation. Recent discoveries indicate that other ADAMs (e.g. ADAM8 and 9) also play important roles in vascular biology but appear to have more selective effects on vascular responses (e.g. on neovascularisation only). Although, targeting of ADAM17 and ADAM10 in inflammatory diseases is still a promising approach, temporal and spatial as well as substrate-specific inhibition approaches are required to minimise undesired side effects on vascular cells.

Matrix metalloproteinases, a disintegrin and metalloproteinases, and a disintegrin and metalloproteinases with thrombospondin motifs in non-neoplastic diseases

Cellular functions within tissues are strictly regulated by the tissue microenvironment which comprises extracellular matrix and extracellular matrix-deposited factors such as growth factors, cytokines and chemokines. These molecules are metabolized by matrix metalloproteinases (MMP), a disintegrin and metalloproteinases (ADAM) and ADAM with thrombospondin motifs (ADAMTS), which are members of the metzincin superfamily. They function in various pathological conditions of both neoplastic and non-neoplastic diseases by digesting different substrates under the control of tissue inhibitors of metalloproteinases (TIMP) and reversion-inducing, cysteine-rich protein with Kazal motifs (RECK). In neoplastic diseases MMP play a central role in cancer cell invasion and metastases, and ADAM are also important to cancer cell proliferation and progression through the metabolism of growth factors and their receptors. Numerous papers have described the involvement of these metalloproteinases in non-neoplastic diseases in nearly every organ. In contrast to the numerous review articles on their roles in cancer cell proliferation and progression, there are very few articles discussing non-neoplastic diseases. This review therefore will focus on the properties of MMP, ADAM and ADAMTS and their implications for non-neoplastic diseases of the cardiovascular system, respiratory system, central nervous system, digestive system, renal system, wound healing and infection, and joints and muscular system.

Suppression of Autoimmune Arthritis by Small Molecule Inhibitors of the JAK/STAT Pathway

A skewed ratio of pro-inflammatory to anti-inflammatory cytokines, elevated growth factor synthesis and T- and B-lymphocyte activation are 3 hallmarks of rheumatoid arthritis (RA) pathology. Interleukin-6 (IL-6), IL-7, IL-17, IL-12/IL-23 and growth factors, granulocyte macrophage-colony stimulating factor, IL-3, and erythropoietin activate the Janus Kinase/Signal Transducers and Activators of Transcription (JAK/STAT) pathway. Evidence showed that STAT protein phosphorylation (p-STAT) by activated JAKs is permissive for p-STAT to act as transcription factors by binding to STAT-responsive gene promoter sequences. This event is critical for perpetuating RA, in part, by up-regulating pro-inflammatory cytokine gene transcription. Activation of JAK/STAT by cytokines and growth factors can induce ‘cross-talk’ with other signaling pathways by which Stress-Activated Protein/Mitogen-Activated Protein Kinase (SAP/MAPK) and Phosphatidylinositide-3-Kinase (PI3K)-mediated signaling are also activated. JAK-specific small molecule inhibitors (SMIs) were developed to test whether JAK/STAT pathway blockade would regulate autoimmune-mediated inflammation. JAK-specific SMI blockade inhibited p-STAT induced by pro-inflammatory cytokines in vitro. Systemically administered JAK-specific SMI blockade also ameliorated biomarkers of inflammation in well-validated arthritis animal models. A few JAK-specific SMIs have made their way into RA clinical trials. In fact, the JAK3-specific SMI, CP-690,500 is the first JAK/STAT SMI to be assessed for clinical efficacy in a Phase III RA trial.

Gene hunting of the Genetic Analysis Workshop 16 rheumatoid arthritis data using rough set theory

We propose to use the rough set theory to identify genes affecting rheumatoid arthritis risk from the data collected by the North American Rheumatoid Arthritis Consortium. For each gene, we employ generalized dynamic reducts in the rough set theory to select a subset of single-nucleotide polymorphisms (SNPs) to represent the genetic information from this gene. We then group the study subjects into different clusters based on their genotype similarity at the selected markers. Statistical association between disease status and cluster membership is then studied to identify genes associated with rheumatoid arthritis. Based on our proposed approach, we are able to identify a number of statistically significant genes associated with rheumatoid arthritis. Aside from genes on chromosome 6, our identified genes include known disease-associated genes such as PTPN22 and TRAF1. In addition, our list contains other biologically plausible genes, such as ADAM15 and AGPAT2. Our findings suggest that ADAM15 and AGPAT2 may contribute to a genetic predisposition through abnormal angiogenesis and adipose tissue.

MMP-13 plays a role in keratinocyte migration, angiogenesis, and contraction in mouse skin wound healing

Matrix metalloproteinases (MMPs) have been implicated in wound healing. To analyze the roles of MMP-9 and MMP-13 in wound healing, we generated full-thickness cutaneous wounds in MMP-9 knockout (KO), MMP-13 KO, MMP-9/13 double KO, and wild-type mice. Macroscopic wound closure was delayed in all of the KO mice, as compared with wild-type mice. The rate of re-epithelialization was significantly delayed in MMP-9 KO and MMP-13 KO mice and remarkably delayed in MMP-9/13 double KO mice, as compared with wild-type mice. Both MMP-9 and MMP-13 were expressed by the leading edges of epidermal cells in wild-type mice, and the migration of keratinocytes was suppressed by treatment with an MMP inhibitor or transfection of small interfering RNAs for MMP-9 or MMP-13, as compared with controls. The vascular density in wound granulation was significantly lower in both MMP-13 KO and MMP-9/13 double KO mice than in wild-type mice. Degradation of connective tissue growth factor in wound tissue was transiently prevented in MMP-13 KO mice. Morphometric analyses demonstrated a reduction in both wound contraction and myofibroblast formation in both MMP-13 KO and MMP-9/13 double KO mice. Proliferation and transforming growth factor-beta1-induced myofibroblast differentiation of dermal fibroblasts from MMP-13 KO mice were decreased, as compared with wild-type dermal fibroblasts. These data suggest that MMP-13 plays a role in keratinocyte migration, angiogenesis, and contraction in wound healing, while MMP-9 functions in keratinocyte migration.

Enhancement of recombinant human ADAM15 disintegrin domain expression level by releasing the rare codons and amino acids restriction

This study was aimed at increasing the production of the recombinant human ADAM15 disintegrin domain (RADD) in Escherichia coli by releasing the rare codons and restricting amino acid residues. Three different strategies for increasing RADD production were examined: to select the suitable host strain, to optimize the rare codons, and to delete the amino acids residues. The total fusion protein glutathione-S-transferase (GST)-RADD concentration of 298 mg/l and 326 mg/l were achieved by selecting E. coli Rosetta (DE3) as the host strain and by changing GGA to GGC at the GST-RADD cassette, respectively. The RADD concentration was increased by 35.7% by eliminating the "Pro-Glu-Phe" residues at the GST-RADD junction. By combinational utilizing the preferred codon introduction and amino acid sequence optimization in E. coli Rosetta (DE3), the highest RADD concentration of 68 mg/l was achieved. The proposed strategy may provide an alternative approach for other enhanced recombinant protein production by E. coli.

Molecular network of cartilage homeostasis and osteoarthritis

This review article presents the current understanding of the molecular basis of articular cartilaginous homeostasis, and outlines potential areas to focus on within the developing field of therapeutics for cartilage disorders. Articular cartilage, an integral component of joints in extremities and the vertebral column, is essential for locomotion. Disturbance of joint development or cartilage homeostasis causes congenital osteocartilaginous dysplasia or osteoarthritic diseases, respectively. Symptomatic treatments and surgical replacement of joints are effective but can also be problematic in terms of quality of life over time. Recently, new insights into the molecular biological basis of chondrocyte differentiation and cartilage homeostasis have been reported. While joint formation is regulated by several growth factors such as Wnts (wingless-related MMTV integration site) and Gdfs (growth and differentiation factors), the pathology of osteoarthritis is now interpreted as the disruption of balance between anabolic and catabolic signals. Current findings in molecular biology on joint development are reviewed concisely to aid in the understanding of the molecular network that governs articular cartilage development and homeostasis.

Critical role of ADAM15 in tumor progression: targeting multiple factors for metastasis promotion

Evaluation of: Najy AJ, Day KC, Day ML: ADAM15 supports prostate cancer metastasis by modulating tumor cell–endothelial cell interaction. Cancer Res. 68, 1092–1099 (2008). Products of a disintegrin and metalloproteinase (ADAM) gene family are multifunctional proteins and have activities of metalloproteinase, integrin-binding, cell adhesion and intracellular signaling. ADAMs play important roles in many biological processes, such as neurogenesis, myogenesis, fertilization and growth factor shedding. Several ADAM genes are also implicated in various types of cancers; however, the exact function of ADAMs in tumorigenesis and tumor progression has not been well understood. In this report, Najy and colleagues have shown that ADAM15 plays a critical role in tumor growth and metastasis in human prostate cancer. Their results indicate that ADAM15 promotes the binding to extracellular matrix proteins, expression of metastatic-associated cell surface proteins, cleavage of N-cadherin and activation of matrix metalloproteinase 9. These events were followed by stimulation of transendothelial migration and bone metastasis. Therefore, ADAM15 signaling may serve as a potential therapeutic target for prostate cancer.

An Adam15 amplification loop promotes vascular endothelial growth factor-induced ocular neovascularization

Proteins with a disintegrin and a metalloproteinase domain (ADAMs) are a family of membrane-bound proteinases that bind integrins through their disintegrin domain. In this study, we have found modest expression of ADAM15 in pericytes in normal retina and strong up-regulation of ADAM15 in retinal vascular endothelial cells in ischemic retina. Increased expression of vascular endothelial growth factor (VEGF) in the retina in the absence of ischemia also increased ADAM15 levels, and knockdown of Vegf mRNA in ischemic retina reduced Adam15 mRNA. Mice deficient in ADAM15 showed a significant reduction in ischemia-induced retinal neovascularization, choroidal neovascularization at rupture sites in Bruch's membrane, and VEGF-induced subretinal neovascularization. ADAM15-deficient mice also showed reduced levels of VEGF(164), VEGF receptor 1, and VEGF receptor 2 in ischemic retina. These data suggest that ADAM15 and VEGF participate in an amplification loop; VEGF increases expression of ADAM15, which in turn increases expression of VEGF and its receptors. Perturbation of the loop by elimination of ADAM15 suppresses ocular neovascularization in 3 different model systems, and thus ADAM15 provides a new therapeutic target for diseases complicated by neovascularization.

The potential role of vascular endothelial growth factor (VEGF) in cartilage: how the angiogenic factor could be involved in the pathogenesis of osteoarthritis?

Although adult human cartilage is physiologically avascular tissue, angiogenesis can be observed during the process of endochondral bone development. Inflammation in articular joints can also lead to neovascularization in cartilage. In such conditions, the expression of angiogenic factors, such as vascular endothelial growth factor (VEGF), has been shown to play a key role, controlling not only angiogenesis but also chondrocyte metabolism. Here we review recent research findings concerning the potential role of VEGF in cartilage, focusing in particular on its possible involvement in the pathogenesis of osteoarthritis.

ADAM15 gene structure and differential alternative exon use in human tissues

Background

ADAM15 is a metalloprotease-disintegrin implicated in ectodomain shedding and cell adhesion. Aberrant ADAM15 expression has been associated with human cancer and other disorders. We have previously shown that the alternative splicing of ADAM15 transcripts is mis-regulated in cancer cells. To gain a better understanding of ADAM15 regulation, its genomic organization and regulatory elements as well as the alternative exon use in human tissues were characterized.

Results

Human ADAM15, flanked by the FLJ32785/DCST1 and ephrin-A4 genes, spans 11.4 kb from the translation initiation codon to the polyadenylation signal, being the shortest multiple-exon ADAM gene. The gene contains 23 exons varying from 63 to 316 bp and 22 introns from 79 to 1283 bp. The gene appeared to have several transcription start sites and their location suggested the promoter location within a CpG island proximal to the translation start. Reporter expression experiments confirmed the location of functional GC-rich, TATAless and CAATless promoter, with the most critical transcription-supporting elements located -266 to -23 bp relative to the translation start. Normal human tissues showed different complex patterns of at least 13 different ADAM15 splice variants arising from the alternative use of the cytosolic-encoding exons 19, 20a/b, and 21a/b. The deduced ADAM15 protein isoforms have different combinations of cytosolic regulatory protein interaction motifs.

Conclusion

Characterization of human ADAM15 gene and identification of elements involved in the regulation of transcription and alternative splicing provide important clues for elucidation of physiological and pathological roles of ADAM15. The present results also show that the alternative exon use is a physiological post-transcriptional mechanism regulating ADAM15 expression in human tissues.

ADAM-15: a metalloprotease that mediates inflammation

Cell-cell and cell-matrix interactions are of utmost importance in the pathogenesis of inflammatory diseases. For example, cell-cell and cell-matrix interactions are crucial for leukocyte homing and recruitment to inflammatory sites. The discovery of the disintegrin and metalloprotease (ADAM) proteins, which have both adhesive and proteolytic activities, raised the question of their involvement in inflammatory processes. More interestingly, the presence of the RGD integrin-binding sequence in the disintegrin domain of ADAM-15 (MDC-15; metargidin) highlighted ADAM-15 as a protein particularly involved in cell-cell interactions. These findings therefore prompted authors to investigate the roles of ADAM-15 in inflammatory diseases. Because of the early description of ADAM-15 expression in endothelial cells, work first focused on the roles of ADAM-15 in vascular diseases, and ADAM-15 was found to be associated with atherosclerosis. Other studies also pointed at ADAM-15 as a mediator of rheumatoid arthritis and intestinal inflammation as well as inherent angiogenesis. The roles of ADAM-15 in these diseases appear to involve mechanisms as different as cell-cell interactions, cell-extracellular matrix (ECM) interactions, and shedding activity. Here we review and discuss these recent discoveries pointing to ADAM-15 as a mediator of mechanisms underlying inflammation and as a possible therapeutic target for prevention of inflammatory diseases.

Growth hormone, VEGF and FGF: involvement in rheumatoid arthritis

Adult rheumatoid arthritis (RA), a systemic autoimmune disorder of unknown etiology, is characterized by dysfunctional cellular and humoral immunity, enhanced migration and attachment of peripheral macrophages and pro-inflammatory leukocytes to the synovium and articular cartilage of diarthrodial joints. The progressive destruction of cartilage and bone in RA is a result of elevated pro-inflammatory cytokine gene expression, synovial neovascularization, proteinase-mediated dissolution of articular cartilage matrix and osteoclast-mediated subchondral bone resorption. Juvenile chronic arthritis (JCA) is disease with manifestations similar to adult RA that occurs in childhood. JCA usually causes precocious joint destruction and often also presents with evidence of growth plate anomalies and reduced stature. Three proteins play an integral role in both adult RA and JCA. These are somatotropin (also called pituitary growth hormone (GH)), vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). GH is responsible for regulating long bone growth and skeletal maturation through its capacity to stimulate insulin-like growth factor-I (IGF-1) synthesis by hepatocytes. Mechanisms responsible for growth plate disturbances and short stature in children with JCA include deficient GH production, GH-insensitivity resulting from defects in the GH receptor, suppressed IGF-1 synthesis or neutralization of IGF-1 action by IGF-1 binding proteins (IGFBPs). In addition, GH has also been implicated in perpetuating inflammation and pain in adult RA. VEGF has been shown to be the critical angiogenesis factor responsible for vascular proliferation and blood vessel invasion of the synovial lining membrane in RA. Acidic FGF (FGF-1) and basic FGF (FGF-2) have also been implicated in aberrant synoviocyte proliferation (i.e. synovial hyperplasia) and apoptosis resistance in adult RA.