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Biomedical subjects

H Stanton

Publications and source records attributed to H Stanton.

At least 19 recordsLinked to original sources
PubMed2003

Neoepitopes as biomarkers of cartilage catabolism.

Progressive degradation of articular cartilage is a central feature of arthritis and a major determinant of long term joint dysfunction. There are no treatments able to halt the progression of cartilage destruction presently available, and monitoring the benefit of potential therapies is hampered by our inability to measure the "health" of articular cartilage. Serial radiographic assessment of joint space narrowing, the current gold standard, requires measurements over a prolonged time (1-5 years) and is prone to technical difficulties. Other strategies for evaluating cartilage degradation are needed to enable both short and long term monitoring of disease progression and response to therapy. One avenue that holds promise is the use of biomarkers that accurately reflect the degradative state of the articular cartilage. Antibodies that recognise terminal amino acid sequences generated by proteolysis at specific sites in the core protein of both aggrecan and type II collagen (neoepitope antibodies) have become available in recent years. These antibodies have been invaluable for identifying the proteinases responsible for cartilage breakdown both in vitro and in vivo. The presence of neoepitope sequences generated by specific metalloenzyme cleavage of aggrecan and type II collagen correlates well with the progression of cartilage degeneration, both in vitro and in mouse models of arthritis. Preliminary results with quantitative assays of type II collagen neoepitopes suggest that they may be useful markers of joint disease in humans. Long term studies correlating neoepitope concentration with clinical and radiographic disease are now required to validate the utility of neoepitopes as surrogate markers of cartilage degeneration and joint disease.

Animals↗
PubMed2000

Generation and novel distribution of matrix metalloproteinase-derived aggrecan fragments in porcine cartilage explants.

We have studied aggrecan catabolism mediated by matrix metalloproteinases (MMPs) in a porcine cartilage culture system. Using antibodies specific for DIPEN(341) and (342)FFGVG neoepitopes, we have detected MMP-derived fragments in conditioned medium and cultured cartilage, by radioimmunoassay, Western blotting, and immunolocalization. Radioimmunoassay revealed that the amount (pmol of epitope/mg of total glycosaminoglycan) of (342)FFGVG epitope released from cartilage remained constant over a 5-day culture period and was not increased by IL-1alpha or retinoate. However, the proportion (pmol of epitope/mg of released glycosaminoglycan) of (342)FFGVG epitope released was decreased upon stimulation, consistent with the involvement of a non-MMP proteinase, such as aggrecanase. The data suggest that in vitro MMPs may be involved in the base-line catabolism of aggrecan. Immunolocalization experiments showed that DIPEN(341) and ITEGE(373) epitopes were increased by treatment with IL-1alpha and retinoate. Confocal microscopy revealed that ITEGE(373) epitope was largely intracellular but with matrix staining in the superficial zone, whereas DIPEN(341) epitope was cell-associated and widely distributed in the matrix. Surprisingly, the majority of (342)FFGVG epitope, determined by radioimmunoassay and Western blotting, was retained in the tissue despite the absence of a G1 domain anchor. Interleukin-1alpha stimulation caused a marked increase in tissue DIPEN(341) and (342)FFGVG epitope, and the (342)FFGVG fragments retained in the tissue were larger than those released into the medium. Active porcine aggrecanase was unable to cleave (342)FFGVG fragments at the downward arrowGlu(373) downward arrowAla(374) bond but cleaved intact aggrecan at this site, suggesting that (342)FFGVG fragments are not substrates for aggrecanase. The apparent retention of large (342)FFGVG fragments within cartilage, and their resistance to N-terminal cleavage by aggrecanase suggests that (342)FF6V6 fragments may have a role in cartilage homeostasis.

Aggrecans↗
PubMed2000

Localisation of matrix metalloproteinases and TIMP-2 in resorbing mouse bone.

There is strong evidence that matrix metalloproteinases (MMPs) play a crucial role during osteogenesis and bone remodelling. Their synthesis by osteoblasts has been demonstrated during osteoid degradation prior to resorption of mineralised matrix by osteoclasts and their activities are regulated by tissue inhibitors of metalloproteinases (TIMPs). For this study we developed and utilised specific polyclonal antibodies to assess the presence of collagenase (MMP13), stromelysin 1 (MMP3), gelatinase A (MMP2), gelatinase B (MMP9) and TIMP-2 in both freshly isolated neonatal mouse calvariae and tissues cultured with and without bone-resorbing agents. Monensin was added towards the end of the culture period in order to promote intracellular accumulation of proteins and facilitate antigen detection. In addition, bone sections were stained for the osteoclast marker, tartrate-resistant acid phosphatase (TRAP). In uncultured tissues the bone surfaces had isolated foci of collagenase staining, and cartilage matrix stained for gelatinase B (MMP9) and TIMP-2. Calvariae cultured for as little as 3 h with monensin revealed intracellular staining for MMPs and TIMP-2 in mesenchymal tissues, as well as in cells lining the bone plates. The addition of cytokines to stimulate bone resorption resulted in pronounced TRAP activity along bone surfaces, indicating active resorption. There was a marked upregulation of enzyme synthesis, with matrix staining for collagenase and gelatinase B observed in regions of eroded bone. Increased staining for TIMP-2 was also observed in association with increased synthesis of MMPs. The new antibodies to murine MMPs should prove valuable in future studies of matrix degradation.

Acid Phosphatase↗
PubMed1999

Evaluation of some newer matrix metalloproteinases.

Recombinant protein expression techniques have been utilized to facilitate the biochemical and cell biological characterization of human matrix metalloproteinases (MMPs). The importance of the membrane type 1 MMP (MMP 14) in the regulation of pericellular proteolysis, either directly or through the activation of MMP-2, MMP-9, and MMP-13 has been identified. Studies on an in vitro chondrocyte-like cell and an in vivo cartilage repair model indicated that such MT1 MMP-regulated activation cascades are physiologically feasible. MMP19 shows a limited sequence identity with other MMPs and may represent a novel subclass. However, analysis of the recombinant protein identified a number of biochemical properties typical of the MMP family.

Animals↗
PubMed1999

Mechanisms for pro matrix metalloproteinase activation.

The activation of pro matrix metalloproteinases (MMPs) by sequential proteolysis of the propeptide blocking the active site cleft is regarded as one of the key levels of regulation of these proteinases. Potential physiological mechanisms including cell-associated plasmin generation by urokinase-like plasminogen activator, or the action of cell surface MT1-MMPs appear to be involved in the initiation of cascades of pro MMP activation. Gelatinase A, collagenase 3 and gelatinase B may be activated by MT-MMP based mechanisms, as evidenced by both biochemical and cell based studies. Hence the regulation of MT-MMPs themselves becomes critical to the determination of MMP activity. This includes activation, assembly at the cell surfaces as TIMP-2 complexes and subsequent inactivation by proteolysis or TIMP inhibition.

Animals↗
PubMed1998

Induction of matrix metalloproteinase activation cascades based on membrane-type 1 matrix metalloproteinase: associated activation of gelatinase A, gelatinase B and collagenase 3.

SW1353 chondrosarcoma cells cultured in the presence of interleukin-1, concanavalin A or PMA secreted procollagenase 3 (matrix metalloproteinase-13). The enzyme was detected in the culture medium by Western blotting using a specific polyclonal antibody raised against recombinant human procollagenase 3. Oncostatin M enhanced the interleukin-1-induced production of procollagenase 3, whereas interleukin-4 decreased procollagenase 3 synthesis. The enzyme was latent except when the cells had been treated with concanavalin A, when a processed form of 48 kDa, which corresponds to the active form, was found in the culture medium and collagenolytic activity was detected by degradation of 14C-labelled type I collagen. The concanavalin A-induced activation of procollagenase 3 coincided with the processing of progelatinase A (matrix metalloproteinase-2) by the cells, as measured by gelatin zymography. In addition, progelatinase B (matrix metalloproteinase-9) was activated when gelatinase A and collagenase 3 were in their active forms. Concanavalin A treatment of SW1353 cells increased the amount of membrane-type-1 matrix metalloproteinase protein in the cell membranes, suggesting that this membrane-bound enzyme participates in an activation cascade involving collagenase 3 and the gelatinases. This cascade was effectively inhibited by tissue inhibitors of metalloproteinases-2 and -3. Tissue inhibitor of metalloproteinases-1, which is a much weaker inhibitor of membrane-type 1 matrix metalloproteinase than tissue inhibitors of metalloproteinases-2 and -3 [Will, Atkinson, Butler, Smith and Murphy (1996) J. Biol. Chem. 271, 17119-17123], was a weaker inhibitor of the activation cascade.

Blotting, Western↗
PubMed1998

MT1-MMP on the cell surface causes focal degradation of gelatin films.

The membrane-type matrix metalloproteinases (MT-MMPs) are a subclass of the matrix metalloproteinase (MMP) family which uniquely possess a C-terminal transmembrane domain and are initiators of an activation cascade for progelatinase A (MMP-2). Recent studies have shown that they can also efficiently directly degrade a number of matrix macromolecules. We now show that cells expressing MT1-MMP on their cell surfaces cause subjacent proteolysis of a gelatin film and that this proteolysis is inhibited by TIMP-2 but not by TIMP-1. These data indicate that expression of MT1-MMP on the cell surface may lead to both progelatinase A activation and extracellular matrix degradation.

Animals↗
PubMed1998

The activation of ProMMP-2 (gelatinase A) by HT1080 fibrosarcoma cells is promoted by culture on a fibronectin substrate and is concomitant with an increase in processing of MT1-MMP (MMP-14) to a 45 kDa form.

We have assessed the effect of fibronectin and laminin-1 on the expression of molecules involved in the activation pathway of MMP-2, a key proteinase in tissue remodelling. HT1080 fibrosarcoma cells cultured on fibronectin were shown to activate endogenous MMP-2, to a level comparable with that elicited by treatment with phorbol ester. In contrast, the MMP-2 expressed by HT1080 cells cultured on laminin-1 was mainly in the pro- (inactive form). Culture of the cells on peptide fragments of fibronectin derived from the central cell binding domain also promoted MMP-2 activation, indicating that signals via fibronectin binding to integrin receptors may be involved. HT1080 cells cultured on immobilised antibodies to the alpha5 and beta1 integrin subunits secreted levels of active MMP-2 similar to those observed for full length fibronectin, whereas cells cultured on an antibody to the alpha6 integrin subunit secreted mainly proMMP-2. The data demonstrate that the activation of MMP-2 by HT1080 cells is regulated by the nature of the extracellular matrix, and that signals via the alpha5beta1 integrin receptor may be involved in the fibronectin induced up-regulation of MMP-2 activation. We then assessed the effect of fibronectin on the components of the putative MT1-MMP/TIMP-2 'receptor' complex implicated in MMP-2 activation. Levels of TIMP-2 protein expressed by HT1080 cells did not vary detectably between cells cultured on fibronectin or laminin-1. However, the expression of MT1-MMP protein was up-regulated when the cells were cultured on fibronectin, which could be attributed to an increase in levels of a truncated 45 kDa form. Parallel studies using gelatin zymography demonstrated that the up-regulation of the production of the 45 kDa band was concomitant with MMP-2 activation. Inhibitor studies revealed that the truncation of MT1-MMP to a 45 kDa form is MMP mediated, although not inhibited by TIMP-1. In vitro, the 45 kDa form could be generated by cleavage of membrane-bound native MT1-MMP with several recombinant MMPs, including both active MT1-MMP and MMP-2. The implication that either MMP-2 or MT1-MMP can process MT1-MMP to 45 kDa, raises the possibility that truncation of MT1-MMP represents a self-regulatory end-point in the activation pathway of MMP-2.

Cell Adhesion↗
PubMed1996

The recognition sites of the integrins alpha1beta1 and alpha2beta1 within collagen IV are protected against gelatinase A attack in the native protein.

The susceptibility of three different solubilized forms of type IV collagen to gelatinase A cleavage and the concomitant effects on cell and integrin binding have been assessed. Dithiothreitol-solubilized Engelbreth-Holm Swarm (EHS) type IV collagen with disrupted intramolecular disulfide bonds in the CB3[IV] region was cleaved N-terminally to the CB3[IV] region into the two characteristic 100-300-nm fragments at 30 degrees C and was totally degraded at 37 degrees C. This was reflected in the partial or total loss of the alpha1beta1 and alpha2beta1 integrin binding sites within this region. The ability of gelatinase A to cleave EHS type IV collagen preparations with intact interchain disulfide bonds in CB3[IV] only occurred at higher temperatures. Furthermore, no effect on binding of cells or isolated integrins to the gelatinase-treated collagen could be detected after treatment at 37 degrees C. Dimeric collagen IV of human placenta with intact disulfide bonds in the CB3[IV] region was not degraded at all by gelatinase A at 37 degrees C.

Amino Acid Sequence↗
PubMed1996

Cellular mechanisms for human procollagenase-3 (MMP-13) activation. Evidence that MT1-MMP (MMP-14) and gelatinase a (MMP-2) are able to generate active enzyme.

Gelatinase A and membrane-type metalloproteinase (MT1-MMP) were able to process human procollagenase-3 (Mr 60,000) to the fully active enzyme (Tyr85 N terminus; Mr 48,000). MT1-MMP activated procollagenase-3 via a Mr 56,000 intermediate (Ile36 N terminus) to 48,000 which was the result of the cleavage of the Glu84-Tyr85 peptide bond. We have established that the activation rate of procollagenase-3 by MT1-MMP was enhanced in the presence of progelatinase A, thereby demonstrating a unique new activation cascade consisting of three members of the matrix metalloproteinase family. In addition, procollagenase-3 can be activated by plasmin, which cleaved the Lys38-Glu39 and Arg76-Cys77 peptide bonds in the propeptide domain. Autoproteolysis then resulted in the release of the rest of the propeptide domain generating Tyr85 N-terminal active collagenase-3. However, plasmin cleaved the C-terminal domain of collagenase-3 which results in the loss of its collagenolytic activity. Concanavalin A-stimulated fibroblasts expressing MT1-MMP and fibroblast-derived plasma membranes were able to process human procollagenase-3 via a Mr 56,000 intermediate form to the final Mr 48,000 active enzyme which, by analogy with progelatinase A activation, may represent a model system for in vivo activation. Inhibition experiments using tissue inhibitor of metalloproteinases, plasminogen activator inhibitor-2, or aprotinin demonstrated that activation in the cellular model system was due to MT1-MMP/gelatinase A and excluded the participation of serine proteinases such as plasmin during procollagenase-3 activation. We have established that progelatinase A can considerably potentiate the activation rate of procollagenase-3 by crude plasma membrane preparations from concanavalin A-stimulated fibroblasts, thus confirming our results using purified progelatinase A and MT1-MMP. This new activation cascade may be significant in human breast cancer pathology, where all three enzymes have been implicated as playing important roles.

Amino Acid Sequence↗
PubMed1994

Cytokine interactions promoting DNA synthesis in human synovial fibroblasts.

OBJECTIVE: To evaluate in vitro cytokine combinations that may contribute to the pronounced hyperplasia often found in the joints of patients with rheumatoid arthritis. METHODS: DNA synthesis, in the presence of various combinations of cytokines, was measured in vitro using low serum cultures of passaged synovial fibroblasts derived from nonrheumatoid tissue. RESULTS: Coculture of synovial fibroblasts with platelet derived growth factor (PDGF) and fibroblast growth factor (FGF), at their respective optimal concentrations for DNA synthesis, led to a further increase. In combination with the described synovial fibroblast mitogen, interleukin 1 (IL-1), which can also generate a growth inhibitory cyclooxygenase product, the proliferative responses to PDGF, FGF, transforming growth factor alpha, and epidermal growth factor were enhanced; in some, but not in all of these fibroblast cultures containing IL-1, the achievement of maximal DNA synthesis required that the cyclooxygenase inhibitor, indomethacin, be included. Similar results were obtained when PDGF and FGF were cultured with tumor necrosis factor alpha (TNF alpha), and when IL-1 and TNF alpha were combined. The neuropeptide, substance P (10(-11)-10(-7)M), was inactive by itself and in the presence of IL-1. CONCLUSION: While cytokines individually may be activators of various signalling pathways in the synovial fibroblasts, it is when they are combined that they show their full potential as growth promoters, with possible ramifications for inflammatory joint disease.

DNA↗
PubMed1993

Macrophage colony-stimulating factor and granulocyte-macrophage colony-stimulating factor stimulate the synthesis of plasminogen-activator inhibitors by human monocytes.

Macrophage colony-stimulating factor (M-CSF or CSF-1) and granulocyte-macrophage CSF (GM-CSF) have been shown to increase human monocyte urokinase-type plasminogen-activator (u-PA) activity with possible consequences for cell migration and tissue remodeling; because monocyte u-PA activity is likely to be controlled in part also by the PA inhibitors (PAIs) made by the cell, the effect of M-CSF and GM-CSF on human monocyte PAI-2 and PAI-1 synthesis was investigated. To this end, elutriation-purified human monocytes were treated in vitro with purified recombinant human M-CSF and GM-CSF, and PAI-2 and PAI-1 antigen and mRNA levels measured by specific enzyme-linked immunosorbent assays and Northern blot, respectively. Each CSF could enhance the protein and mRNA levels of PAI-2 and PAI-1 at similar concentrations for each product. This similar regulation of monocyte PAI expression in response to the CSFs contrasted with that found for the effects of lipopolysaccharide, transforming growth factor-beta and a glucocorticoid. Therefore, PAIs may be modulating the effects of the CSFs on monocyte u-PA activity at sites of inflammation and tissue remodeling.

Dose-Response Relationship, Drug↗
PubMed1993

Effects of macrophage-colony stimulating factor on human monocytes: induction of expression of urokinase-type plasminogen activator, but not of secreted prostaglandin E2, interleukin-6, interleukin-1, or tumor necrosis factor-alpha.

It is often assumed that macrophage-colony stimulating factor (M-CSF) or CSF-1, as well as granulocyte macrophage-CSF (GM-CSF), can induce inflammatory mediator production by monocytes/macrophages. We demonstrate with elutriation-purified human monocytes that, in contrast to lipopolysaccharide, recombinant human CSF-1 does not induce secretion of prostaglandin E2, interleukin-6 (IL-6), IL-1 beta, or tumor necrosis factor alpha, as measured by immunoassay; however, increased urokinase-type plasminogen activator (u-PA) activity in cell lysates and mRNA was observed. Similar results were obtained when the monocytes were treated with recombinant human GM-CSF. Such increased u-PA expression may contribute to the function of CSF-1 at sites of inflammation.

Cells, Cultured↗
PubMed1993

Cytokine regulation of granulocyte-macrophage colony stimulating factor and macrophage colony-stimulating factor production in human arterial smooth muscle cells.

Smooth muscle cells (SMC) are the major cell type found in the walls of large blood vessels and appear to participate in local immune and inflammatory reactions, as well as in certain vascular diseases. We tested whether human arterial SMC can produce in vitro the colony stimulating factors (CSFs), granulocyte macrophage-CSF (GM-CSF) and macrophage CSF (M-CSF). Untreated internal mammary artery and aortic SMC produced no detectable GM-CSF but constitutively made M-CSF, measured by ELISA and radioimmunoassay, respectively. Interleukin-1 (IL-1) and, to a lesser extent, tumor necrosis factor alpha (TNF alpha) stimulated GM-CSF formation within 3 h; mRNA levels also increased particularly in the presence of the protein synthesis inhibitor, cycloheximide. IL-1, TNF alpha and, in addition, interferon-gamma (IFN-gamma) raised the M-CSF levels within 6 h; cycloheximide potentiated the effects of IL-1 and TNF alpha on mRNA levels. These results suggest that cytokine-stimulated human arterial SMC may be a source of the M-CSF found in atherosclerotic lesions. Since monocytes/macrophages can be activated by GM-CSF and M-CSF, while GM-CSF can also affect granulocyte function, SMC may participate in inflammatory reactions and vascular diseases by releasing these cytokines.

Aorta↗
PubMed1993

Contrasting effects of interleukin-4 on colony-stimulating factor and interleukin-6 synthesis by vascular endothelial cells.

Endothelial cells (EC) may regulate both local and systemic aspects of inflammation through the synthesis of cytokines such as granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), macrophage colony-stimulating factor (M-CSF), and interleukin-6 (IL-6). EC are known to synthesize these cytokines in response to interleukin-1 (IL-1 alpha), tumor necrosis factor-alpha (TNF-alpha) and lipopolysaccharide (LPS). In this paper, we illustrate the effect of interleukin-4 (IL-4) in reducing the synthesis of GM-CSF by EC stimulated with IL-1 alpha, TNF-alpha, or LPS. This is compared with the previously reported strong synergy between IL-4 and IL-1 alpha, TNF-alpha, or LPS in the synthesis of IL-6 by EC. No clear effect of IL-4 was seen in the synthesis of G-CSF or M-CSF. The range of concentrations of IL-4 at which these effects were seen was identical for both reduced GM-CSF synthesis and increased IL-6 synthesis. The effect of IL-4 on IL-6 synthesis was seen by 4 h of treatment, while that on GM-CSF was apparent between 4 and 8 h. It is suggested that these contrasting effects of IL-4 may reflect a biological role for this cytokine in the regulation of leukocytosis and the acute phase response.

Acute-Phase Reaction↗
PubMed1992

Plasminogen activator in granulocyte-macrophage-CSF transgenic mice.

The pattern of expression of urokinase type plasminogen activator (PA) in granulocyte-macrophage-CSF transgenic mice and their normal littermates was studied using RNAse protection assays and a plasminogen-dependent fibrinolytic assay for PA. Urokinase type PA mRNA was expressed at a high level in transgenic peritoneal cells and at a lower level in transgenic eye tissue and spleen, but not in equivalent tissue from the normal mice. Enzymically active PA was detectable in protein extracts from peritoneal cells taken from transgenic mice of less than 8 wk of age (young mice) but not from normals. Paradoxically, extracts from transgenic mice of more than 12 wk of age (old mice) showed little detectable PA activity despite continuing transcription in some mice of this age. The production of PA by peritoneal cells may be responsible for the spontaneous i.p. bleeding which is a feature of the transgenic mice and production in other tissues may help explain the local pathologic changes.

Age Factors↗