Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In inflammatory demyelinating diseases such as multiple sclerosis and experimental allergic encephalomyelitis, myelin destruction occurs in the vicinity of infiltrating mononuclear cells. The observations that myelin can be altered prior to phagocytosis and in areas not contiguous with inflammatory cells suggests a common mechanism for the initial stages of demyelination. Because stimulated macrophages secrete several neutral proteases, including plasminogen activator, we have investigated the possibility that myelinolysis could be mediated directly or indirectly by these enzymes. Isolated myelin was incubated with conditioned media from cultures of thioglycollate-stimulated mouse peritoneal macrophages in the presence and absence of plasminogen. Myelin appeared to be vulnerable to attack by at least two proteolytic activities secreted by the macrophages, a plasminogen-dependent and a plasminogen-independent activity; of the major proteins in myelin, the basic protein was most susceptible. The direct myelinolytic activity of macrophage-conditioned media was abolished by EDTA, and the plasminogen-dependent hydrolysis was abolished by p-nitrophenylguanidinobenzoate, an inhibitor of plasminogen activator and plasmin. These results suggest that the plasminogen activator released by the stimulated macrophages generated plasmin which hydrolyzed basic protein in intact myelin. This interpretation was confirmed by the observation that urokinase, a plasminogen activator, in the presence of plasminogen brought about marked degradation of basic protein in myelin. We propose that the release of neutral proteases by stimulated macrophages involved in cell-mediated reactions, and its amplification by the plasminogen-plasmin system, may play a significant role in the demyelination observed in several inflammatory demyelinating diseases.
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PMID:Degradation of basic protein in myelin by neutral proteases secreted by stimulated macrophages: a possible mechanism of inflammatory demyelination. 14 51

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory demyelinating disease of the central nervous system commonly used as a model for multiple sclerosis. In both of these diseases demyelination occurs association with perivascular infiltrates of T-cells and macrophages. The similarities in immunopathology suggest that these two diseases share common mechanisms of tissue destruction. We have proposed a general mechanism to explain the clinical and histopathological features of EAE. T-cells sensitized to the inducing antigen, myelin basic protein (MBP), react with antigen-presenting cells (possibly endothelial cells, microglia or astrocytes) in the central nervous system. As a consequence of this reaction, T-cells release lymphokines which activate macrophages, stimulate an augmenting inflammatory response, and, through the action of vasoactive amines, induce vasospasm and breakdown of the blood-brain barrier. The activated macrophages secrete inflammatory mediators, including plasminogen activator and other proteinases, which, in concert with serum plasminogen and complement, initiate myelin destruction. The macrophage products also serve to enhance the inflammatory response and vascular permeability. In support of this hypothesis we find that: (1) macrophage-secreted proteinases can degrade MBP in lyophilized myelin and that proteolysis is amplified in the presence of plasminogen; (2) proteolysis of proteins in fresh myelin by macrophage proteinases and plasminogen or by plasmin is potentiated by complement; (3) removal of macrophages from the circulation suppresses EAE; (4) proteinase inhibitors suppress EAE; and (5) prazosin, an alpha 1-adrenergic receptor antagonist, suppresses the clinical signs of EAE and the increased vascular permeability but only delays the inflammatory response. We believe that prazosin acts on the vascular alpha 1-adrenergic receptor to inhibit vasospasm and prevent opening of the blood-brain barrier. Thus it is possible to suppress both clinical signs and pathology by interceding at several steps of the cell-mediated immune reaction.
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PMID:Mechanisms and suppression of inflammatory demyelination. 213 Jun 45

Pokeweed-mitogen-induced IgG secretion, Con A suppression and T cell surface markers were measured in 30 chronic progressive multiple sclerosis (MS) patients and 21 healthy controls. Mean IgG secretion was higher in the MS patients than in the controls (2392 +/- 270 vs 1499 +/- 243); Con A suppression was lower (4 +/- 5% vs 24 +/- 4%) and the CD4/CD8 ratio was higher (4.1 +/- 0.4 vs 2.9 +/- 0.4). The above assays were used in vitro to monitor the effects of Wellferon (lymphoblastoid interferon) injections on this group of MS patients. Before treatment the INF-group (n = 14) did not differ from the PLA-group (n = 16). After 1 week of daily injections the level of IgG secreted was dramatically reduced in the INF group (629 +/- 96 ng/ml) compared to the PLA-group (1756 +/- 319 ng/ml). There was no change in either Con A suppression or T cell surface markers. IgG secretion remained lower in the INF-group for the 6 month treatment period. Following cessation of the injections and a 6 month washout period, IgG secretion in the INF-group rose and was equivalent to that observed in the PLA-group. A series of lymphocyte subset mixing experiments implicates the B lymphocyte subset as being directly affected by interferon injections in vitro.
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PMID:Reduction of immunoglobulin G secretion in vitro following long term lymphoblastoid interferon (Wellferon) treatment in multiple sclerosis patients. 295 31

Recent work has implicated plasminogen activator released from macrophages as a possible mediator of the demyelinating process in experimental allergic encephalomyelitis and multiple sclerosis (MS). We have studied the capacity of white matter and plaques from MS patients to break down fibrin clots, using a histochemical technique. Fibrinolytic activity was localized exclusively to areas around blood vessels and capillaries in both patients and controls. While there was marked variation between individuals, the unaffected white matter from MS patients was, on the average, not more active than that of controls, but plaques tended to show more numerous foci of lysis, often also more intense, than adjacent white matter; there was no correlation with disease activity or age of the plaques as determined by histological criteria. The localization and degree of fibrinolysis observed were not related to the presence of lymphocytic infiltrates, gliosis, or macrophages. However, the findings do not exclude an involvement of fibrinolytic enzymes (although originating from vascular endothelium rather than macrophages) in the genesis of the MS plaque, which commonly starts around a small vein.
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PMID:Fibrinolytic activity of plaques and white matter in multiple sclerosis. 721 4

In order to examine the plasminogen activator (PA) induction involved in the pathogenesis of acute disseminated encephalomyelitis (ADEM) and multiple sclerosis (MS), PA activity in peripheral blood lymphocytes derived from 5 ADEM and 3 MS patients was investigated. There was no PA induction in any ADEM, MS or control lymphocytes treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) alone. PA activity, however, in lymphocytes exposed to human interferon-gamma (HuIFN-gamma) prior to MNNG treatment was elevated during the active phase of ADEM and MS, whereas the PA induction disappeared in association with improvement of the neurologic symptoms. The PA activity was abolished by mixed treatment with HuIFN-gamma and anti-HuIFN-gamma antibody. No such PA induction by any HuIFN was observed in any normal controls or cases of other neurologic diseases. Among the cytokines tested other than HuIFN, tumor necrosis factor-alpha, in combination with MNNG, also induced PA activity in lymphocytes from ADEM and MS patients during the active phase. Thus, the PA induction observed in lymphocytes on combined treatment with MNNG and cytokines may be involved in the progression of neurologic disorders in these demyelinating diseases, and indicates the possibility of therapeutic strategies involving anticytokine usage.
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PMID:Involvement of cytokines in N-methyl-N'-nitro-N-nitrosoguanidine-induced plasminogen activator activity in acute disseminated encephalomyelitis and multiple sclerosis lymphocytes. 824 10

The expression of tissue-type plasminogen activator (t-PA) and a number of metalloproteases as well as plasminogen activator inhibitor-1 (PAI-1) and tissue inhibitor of metalloproteases-1 (TIMP-1) was analyzed in the central nervous system (CNS) of normal control and multiple sclerosis (MS) cases by immunohistopathology. The expression of t-PA was detectable only in the blood vessel matrix in control white matter, but positive infiltrating mononuclear cells were also observed in MS white matter and primary lesions. In active plaques this pattern converted to strong positivity of foamy macrophages in areas of demyelination, declining in chronic lesions. In general PAI-1 expression paralleled that of t-PA. Gelatinase A and B were detected predominantly in astrocytes and microglia throughout normal control white matter, with additional positive mononuclear cells in perivascular cuffs in MS white matter. In the demyelinating lesion there is widespread prominent expression of gelatinase B in reactive astrocytes and macrophages, which persists in astrocytes in the chronic lesion. TIMP-1 was also present in the vessel matrix and in lesional macrophages. These observations on the coexpression of enzymes and inhibitors of the matrix degrading cascade in CNS tissue pinpoint t-PA, a rate-limiting enzyme, and gelatinase B as therapeutic targets in MS.
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PMID:The expression of tissue-type plasminogen activator, matrix metalloproteases and endogenous inhibitors in the central nervous system in multiple sclerosis: comparison of stages in lesion evolution. 895 42

The serine proteinase tissue-type plasminogen activator (t-PA) and the metalloproteinase gelatinase B (MMP-9) have recently been demonstrated in MS lesions. Both enzymes are interconnected in an enzyme cascade which contributes to destruction of the blood brain barrier and demyelination and both enzymes are inhibited by D-penicillamine. Metacycline was shown in in vitro experiments to inhibit gelatinase B. The combination of peroral D-penicillamine plus metacycline was evaluated in a double-blind placebo-controlled way in two groups of 10 patients suffering from secondary progressive multiple sclerosis. The major objectives of this pilot trial were to examine the safety of this combination and the possibility of blinding, while the effect on disease progression was considered as a secondary endpoint. Over a follow-up period of 1 year and in this selected patient group, there was no significant improvement in the Expanded Disability Status Scale score (EDSS) as compared with that of the placebo-control group. Toxicity was too high to consider additional trials with this combination of metalloproteinase inhibitors. Although peroral treatment is by most MS patients acknowledged as a major improvement in treatment compliance, one has to await the development of more selective and efficacious protease inhibitors than those used in the combination therapy described here.
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PMID:Toxicity in a double-blind, placebo-controlled pilot trial with D-penicillamine and metacycline in secondary progressive multiple sclerosis. 959 37

Heparin-binding growth factors have been implicated in central nervous system development, regeneration and pathology. To assess the expression pattern and possible function in multiple sclerosis, the heparin-binding growth factors pleiotrophin (PTN), midkine (MK), basic fibroblast growth factor (FGF-2) and one of its receptors (FGFR1/flg) mRNA and protein levels were examined in an experimental autoimmune encephalomyelitis (EAE) model in the Lewis rat. We assessed the time course of expression of PTN, MK and FGF-2 during EAE and determined the cellular origin of FGF-2 and FGFR1 in normal spinal cord and during inflammatory demyelination. Basal expression of PTN and MK mRNAs in normal spinal cords was significantly upregulated after induction of EAE. MK expression was upregulated two to threefold correlating with disease progression, whereas PTN expression reached peak levels threefold above basal levels during the clinical recovery period. FGF-2 mRNA expression was low in normal spinal cord and dramatically increased in correlation with progressive demyelination. FGF-2 was confined to neurons in normal tissue and shifted dramatically to microglia, paralleling their activation during EAE. Double immunohistochemistry revealed colocalization of FGF-2 to activated microglia/macrophages with strongest expression in the macrophage-rich perivascular core area and microglial expression at the edges of white and gray matter perivascular regions. FGFR1, like its ligand, was induced in activated macrophages/microglia. Growth factor expression in demyelinating diseases could serve several functions, e.g., to modulate the activity of microglia/macrophage in an autocrine fashion, to induce the expression of other factors like insulin-like growth factor 1 or plasminogen activator, which can effect regeneration or degeneration, respectively, and finally to stimulate directly localized proliferation and/or regeneration of oligodendrocytes within the lesion area.
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PMID:Basic FGF and FGF receptor 1 are expressed in microglia during experimental autoimmune encephalomyelitis: temporally distinct expression of midkine and pleiotrophin. 981 19

Betaseron, an analogue of human beta-interferon where serine was genetically engineered to substitute for cysteine at position 17, is produced in E. coli. The molecule is a small polypeptide of 165 amino acids with a single disulphide bond, and is non-glycosylated. The site-specific substitution was made to obtain a product that is more stable upon storage. Similar to native IFN-beta, Betaseron is hydrophobic in nature and has been shown to have the same panel of biological activities which includes antiviral activity against a variety of viruses, inhibition of cell growth, activation of natural killer cells, and binding to interferon receptors on the cell surface. Betaseron has been tested in a wide variety of clinical settings since 1983. The pivotal trial for the treatment of relapsing-remitting multiple sclerosis began in 1988. A PLA was filed for this indication in 1992 by Berlex and Chiron, and FDA approval was received in 1993. Betaseron is synthesized in E. coli and deposited as inclusion bodies. The manufacturing process involves solubilization and reduction of the insoluble protein, followed by purification by organic extraction, cystine oxidation and size exclusion chromatographic steps. The purified Betaseron is formulated with human serum albumin to maintain solubility at neutral pH. The complete primary sequence of Betaseron was verified by amino and carboxy-terminal sequence analysis, peptide mapping, amino acid analysis and fragment analysis after chemical cleavages. Overlapping amino acid sequence information confirmed that the amino acid sequence is the same as predicted by the DNA sequence. The amino-terminal methionine of Betaseron is removed after synthesis in E. coli. An intramolecular disulphide bond between Cys 31 and Cys 141 formed during the manufacturing process is routinely confirmed by peptide map analysis. The purity of Betaseron is assessed using a panel of analytical methods including non-reducing and reducing SDS-PAGE and reversed phase HPLC analysis where minor product-related components can be identified. These minor species were characterized with respect to their biological and biochemical properties, and identified using a variety of approaches including construction of additional, beta-interferon analogs. There is significant redundancy in the release testing of Betaseron. The amount of characterization information available on this relatively simple molecule along with the extensive manufacturing experience would suggest that some redundant testing could be eliminated for this well-characterized protein.
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PMID:Betaseron. 989 May 22

The role of extracellular proteolysis in inflammatory demyelination, originally hypothesized as a mechanism for myelin degradation, is increasingly recognized as a pathogenetic step and as a target for therapy in human demyelinating disease. The activation of ubiquitous plasminogen by urokinase (u-PA) and tissue-type plasminogen activator (t-PA), which is associated with various neuropathologies, including multiple sclerosis (MS), is the key initiator of the activation cascade of the four classes of matrix metalloproteinases (MMPs): collagenases, stromelysins, membrane-type metalloproteinases and gelatinases. Spatiotemporal protein and mRNA expression of gelatinase B (MMP-9) and matrilysin (MMP-7) have been documented respectively in MS lesions and in the central nervous system (CNS) of animals developing experimental autoimmune encephalomyelitis (EAE). A close interaction between disease-promoting cytokines and extracellularly acting proteases is deduced from in vitro experiments. Cytokines regulate the balance between the proteases and their respective specific inhibitors at the transcriptional level, while proteolysis is a reciprocal mechanism to enhance (by activation) or downmodulate (by degradation) the specific activities of cytokines. In acute inflammation the contribution of chemokines is hierarchically organised, interleukin-8 (IL-8) and related CXC-chemokines inducing a rapid influx of neutrophils in the acute lesions and an instantaneous exocytosis of gelatinase B granules. This results in sudden and extensive damage to the CNS. In chronic disease involving autoimmune processes CC-chemokines that act mainly on mononuclear cell types appear to be more strictly regulated. As MMPs modify matrix components, promoting extravasation of lymphocytes and monocytes/macrophages and have the potential to generate encephalitogenic peptides from myelin basic protein, novel treatments for demyelinating diseases may be predicted by specific inhibition of these enzymes. Here we review plasminogen activators and the MMP family, in the context of their role in CNS inflammation and demyelination and highlight studies in which intervention in these protease cascades are and may be used to treat demyelinating diseases.
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PMID:Plasminogen activators and matrix metalloproteases, mediators of extracellular proteolysis in inflammatory demyelination of the central nervous system. 1037 31


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