Inflammatory mediators regulate cathepsin S in macrophages and microglia: A role in attenuating heparan sulfate interactions.
(9/980)
BACKGROUND: Cathepsin S is a member of the family of cysteine lysosomal proteases. The distribution of cathepsin S is restricted to cells from the mononuclear lineage both in the brain and in the periphery. Also, its protease activity is uniquely stable at neutral pH. MATERIALS AND METHODS: We compared the expression of cathepsin S, B, and L mRNAs in various undifferentiated and differentiated cells of mononuclear origin, and examined the modulation of these mRNAs by inflammatory mediators (lipopolysaccharide and various cytokines). In addition, the effect of these agents on cathepsin S protein levels and protease activity was also determined. Lastly, the ability of cathepsin S to process basement membrane components such as heparan sulfate proteoglycans in vitro and in vivo was assessed. RESULTS: Cathepsin S, B, and L mRNAs are expressed in mature macrophages and microglial cells and not in undifferentiated monocytes. Activators of macrophages negatively regulate all three transcripts. Consistent with this, treatment with these agents leads to a decrease in intracellular cathepsin S protein levels and activity. However, the same treatments result in stimulation of secreted cathepsin S activity. Cathepsin S is capable of degrading heparan sulfate proteoglycans in vitro. Also, when expressed in endothelial cells, cathepsin S autocrinely attenuates the basic fibroblast growth factor (bFGF)-mediated binding of FGF receptor containing cells to endothelial cells, by acting on basement membrane proteoglycans. CONCLUSIONS: Taken together, these data imply that cathepsin S is a regulatable cysteine protease that plays a role in the degradation of extracellular proteins, whose secretion from macrophages and microglia is increased by signals that lead to activation of these cells, and may be important in regulating extracellular matrix interactions. http://link.springer-ny. com/link/service/journals/00020/bibs/5n5p320.html (+info)
Neurotrophic factors regulate cathepsin S in macrophages and microglia: A role in the degradation of myelin basic protein and amyloid beta peptide.
(10/980)
BACKGROUND: Cathepsin S is a member of the family of cysteine lysosomal proteases preferentially expressed in macrophages and microglia and is active after prolonged incubation in neutral pH. Upon activation of macrophages by a number of inflammatory mediators, there is an increase in secreted cathepsin S activity accompanied by a decrease in cellular cathepsin S activity and protein content, as well as a decrease in cathepsin S mRNA. The decrease in cathepsin S mRNA and protein at the cellular level is in contrast to the response observed in some in vivo scenarios. MATERIALS AND METHODS: We investigated the effect of basic fibroblast growth factor (bFGF) and nerve growth factor (NGF), two growth factors present during cell injury and inflammation but not known to activate macrophages and microglia, on the expression of cathepsin S, cathepsin B, and cathepsin L mRNAs in these cells, and on cathepsin S activity. We then tested the ability of cathepsin S to degrade myelin basic protein, and amyloid beta peptide at both acidic and neutral pH. RESULTS: Basic FGF and NGF treatment of macrophages and microglia significantly increased the levels of cathepsin S, B, and L mRNAs (2- to 5-fold). Basic FGF also increased cathepsin S activity intra- and extracellularly. Recombinant human cathepsin S was able to degrade myelin basic protein and monomeric and dimeric amyloid beta peptide at both acidic and neutral pH, as well as to process human amyloid precursor protein generating amyloidogenic fragments. CONCLUSIONS: These data suggest that bFGF and NGF may be the molecular signals that positively regulate the expression and activity of cysteine lysosomal proteases (cathepsin S in particular) in macrophages and microglia in vivo, and that there is an interplay between these factors and the activators of inflammation. Disruption of the balance between these two categories of signals may underlie the pathological changes that involve cysteine proteases. http://link.springer-ny.com/link/service/journals/00020/bibs /5n5p334. html (+info)
Cathepsin expression during skeletal development.
(11/980)
Cysteine proteinases, cathepsins B, H, K, L and S, have been implicated in several proteolytic processes during development, growth, remodeling and aging, as well as in a variety of pathological processes. For systematic analysis of cathepsin gene expression we have produced cDNA clones for mouse and human cysteine cathepsins. Northern analysis of a panel of total RNAs isolated from 16-19 different human and mouse tissues revealed the presence of mRNAs for cathepsin B, H, K, L and S in most tissues, but each with a distinct profile. Of the different cathepsin mRNAs, those for cathepsin K were clearly the highest in bone and cartilage. However, relatively high mRNA levels for the other cathepsins were also present in these tissues. To better understand the roles of different cathepsins during endochondral ossification in mouse long bones, cathepsin mRNAs were localized by in situ hybridization. Cathepsin K mRNAs were predominantly seen in multinucleated chondroclastic and osteoclastic cells at the osteochondral junction and on the surface of bone spicules. The other cathepsin mRNAs were also seen in osteoclasts, and in hypertrophic and proliferating chondrocytes. These observations were confirmed by immunohistochemistry and suggest that all cysteine cathepsins are involved in matrix degradation during endochondral ossification. (+info)
Stimulation of angiogenesis through cathepsin B inactivation of the tissue inhibitors of matrix metalloproteinases.
(12/980)
The tissue inhibitors of matrix metalloproteinases (MMPs), TIMP-1 and TIMP-2, are also angiogenesis inhibitors. Cathepsin B and MMPs are found at sites of neovascularization in pathologies such as cancer and osteoarthritis. Treatment of TIMP-1, TIMP-2, and of a mixture of both inhibitors from human articular chondrocytes with cathepsin B resulted in their fragmentation, whereby they lost their MMP-inhibitory and anti-angiogenic activities. Our data suggest that, besides directly participating in tissue destruction, cathepsin B can be harmful for two further reasons: it raises the activity of the MMPs also in the absence of mechanisms up-regulating these enzymes, and it stimulates angiogenesis. This is a prerequisite for blood vessel invasion in a variety of pathological situations of which cancer and osteoarthritis are prominent examples. (+info)
Expression of cathepsin K messenger RNA in giant cells and their precursors in human osteoarthritic synovial tissues.
(13/980)
OBJECTIVE: To investigate the expression of cathepsin K messenger RNA (mRNA) in the giant cells found in human osteoarthritic (OA) synovium and associated reparative connective tissues, and to compare this with mRNA expression of cathepsins B, L, and S, which are cysteine proteases known to be highly expressed by cells of the monocyte/macrophage lineage. METHODS: Sections of human OA synovium were processed for in situ hybridization and probed for cathepsins K, B, L, and S. Serial sections were reacted for tartrate-resistant acid phosphatase (TRAP) and nonspecific esterase (NSE) activity, which are selective markers for the osteoclast and cells of the macrophage/monocyte lineage, respectively. RESULTS: At 3 sites of monocyte infiltration/giant cell formation (granulation tissue, the intimal and subintimal synovial layers, and deep stroma extending to the periphery of osteophytic tissue), both TRAP-positive mono- and multinucleated cells and TRAP-negative, NSE-positive mononuclear precursors were identified. Cells containing both enzyme activities were also found, potentially indicating an intermediate stage of differentiation. The TRAP-positive mononuclear/giant cells, and the occasional NSE-positive precursor, expressed an intense signal for cathepsin K mRNA, but did not express cathepsins B, L, and S. In contrast, the deep zone of phagocytic-like cells adjacent to sites of ossification expressed high levels of mRNA for cathepsins L, B, and S as well as cathepsin K mRNA. CONCLUSION: Giant cells that form within OA synovial tissue express high levels of cathepsin K mRNA. It appears that cathepsin K acts principally to digest the bone (and cartilage) fragments sheered from the joint surface during OA. The high TRAP activity and the undetectable expression of the macrophage-associated degradative proteases (cathepsins B, L, and S) by synovial giant cells strengthens the hypothesis that cathepsin K is the primary protease involved in bone degradation. At sites of synovial osteogenesis, a population of phagocytic-like cells expressed TRAP and cathepsins B, L, S, and K, and may represent blood-derived macrophages pushed toward an osteoclast phenotype. (+info)
Exocytosis of active cathepsin B enzyme activity at pH 7.0, inhibition and molecular mass.
(14/980)
Lysosomal cathepsin B has been implicated in parasitic, inflammatory and neoplastic diseases. Most of these pathologies suggest a role for cathepsin B outside the cells, although the origin of extracellular active enzyme is not well defined. The activity of extracellular cathepsin B is difficult to assess because of the presence of inhibitors and inactivation of the enzyme by oxidizing agents. Therefore, we have developed a continuous assay for measurement of cathepsin B activity produced pericellularly by living cells. The kinetic rate of Z-Arg-Arg-NHMec conversion was monitored and the assay optimized for enzyme stability, cell viability and sensitivity. To validate the assay, we determined that human liver cathepsin B was stable and active under the conditions of the assay and its activity could be inhibited by the selective epoxide derivative CA-074. Via this assay, we were able to demonstrate that active cathepsin B was secreted pericellularly by viable cells. Both preneoplastic and malignant cells secreted active cathepsin B. Pretreatment of cells with the membrane-permeant proinhibitor CA-074Me completely abolished pericellular and total cathepsin B activity whereas pretreatment with the active drug CA-074 had no effect. Immunoprecipitation and immunoblotting experiments suggested that the active enzyme species was 31-kDa single-chain cathepsin B. Exocytosis of cathepsin B was not related to secretion of proenzyme or secretion from mature lysosomes. Our results suggest an alternative pathway for exocytosis of active cathepsin B. (+info)
Importance of thioredoxin in the proteolysis of an immunoglobulin G as antigen by lysosomal Cys-proteases.
(15/980)
For disulphide-bonded antigens, reduction has been postulated to be a prerequisite for proteolytic antigen processing, with subsequent production of major histocompatibility complex (MHC) class II binding fragments. The murine monoclonal immunoglobulin G (IgG) CE25/B7 was used as a multimeric antigen in a human model. Native IgG is highly resistant to proteolysis and has been previously found to be partially reduced at early steps of cell processing to become a suitable substrate for endopeptidases. The role of the oxidoreductase thioredoxin (Trx) was assessed in the reduction of the IgG by cleavage of H-L and H-H disulphide bonds. Recombinant human Trx (rTrx) has been assayed in a proteolytic in vitro system on IgG using endosomal and lysosomal subcellular fractions from B lymphoblastoid cells. rTrx is required in a dose-dependent manner for development of efficient proteolysis, catalysed by thiol-dependent Cys-proteases, such as cathepsin B. We demonstrated that cathepsin B activity was stimulated by the addition of rTrx. Thus, we propose that Trx-dependent IgG proteolysis occurred, on the one hand by means of the unfolding of the IgG after disulphide reduction, becoming a substrate of lysosomal proteases, and on the other hand by Cys-proteases such as cathepsin B that are fully active upon the regeneration of their activity by hydrogen donors. (+info)
WF14861, a new cathepsins B and L inhibitor produced by Colletotrichum sp. I. Taxonomy, production, purification and structure elucidation.
(16/980)
WF14861, a novel cathepsins B and L inhibitor, was obtained from the culture mycelium of a fungus strain Colletotrichum sp. No. 14861. Spectroscopic analysis showed that WF14861 consisted of trans-epoxysuccinic acid, L-tyrosine and spermidine, WF14861 inhibited cathepsins B and L selectively. (+info)