Studies on bone enzymes. The assay of acid hydrolases and other enzymes in bone tissue

The effect of dibutyryl cyclic AMP and PGE2 on lysosomal enzyme release and lactate production in relation to bone resorption in vitro

The effect of dibutyryl cyclic AMP (dbc AMP) and PGE2 on the content and release of lysosomal and non-lysosomal enzymes was studied in a bone organ culture system using half calvaria from 6-7 day-old mice. In parallel the effect of dbc AMP and PGE2 on the release of calcium (Ca2+) and inorganic phosphate (Pi), glucose consumption and lactate production was also followed. DbcAMP (2.5 X 10(-4) M) decreased the release of beta-glucuronidase, beta-N-acetyl-glucosaminidase, acid phosphatase, Ca2+ and Pi during the first day of culture. During the 3rd and 4th day of dbcAMP increased all these parameters. In contrast no changes in the release of lactate dehydrogenase (LDH) and alanine aminotransferase (ALAT) were seen. Glucose consumption and lactate production was not stimulated by dbcAMP until the 3rd and 4th day. On the other hand, PGE2 (10(-7) M) stimulated the release of beta-glucuronidase, beta-N-acetylglucosaminidase, Ca2+ and Pi as well as glucose consumption and lactate production already after 24 h and this stimulation was maintained throughout the culture period. No effect by PGE2 on the release of LDH and ALAT was registered. The activities of LDH in the bone explants after 96 h of culture were significantly augmented by both dbcAMP and PGE2. It is concluded that bone resorption stimulated by dbcAMP and PGE2, is associated lysosomal enzyme release and lactate production.

Relationship between bone resorption and lysosomal enzyme release as demonstrated by the effect of 1 alpha-hydroxy-vitamin D-3 in an organ culture system

The effect of 1 alpha-hydroxy-vitamin D-3 on the release of calcium (40Ca, 45Ca), inorganic phosphate and lysosomal enzymes, on glucose consumption and lactate production was studied in a bone organ culture system using half calvaria from 6--7-day-old mice. 1 alpha-Hydroxy-vitamin D-3 stimulated the mobilization of minerals and increased the release of beta-glucuronidase, beta-N-acetylglucosaminidase and acid phosphatase, while no effect on the release of lactate dehydrogenase was seen. 1 alpha-Hydroxy-vitamin D-3 also caused a significant increase in the total activities of acid phosphatase in the bones after culture, indicating increased enzyme synthesis. The stimulatory effect on the release of Pi and beta-glucuronidase was also obtained after a temporary exposure to 1 alpha-hydroxy-vitamin D-3. The stimulation by 1 alpha-hydroxy-vitamin D-3 on the release of Ca2+, Pi and beta-glucuronidase was suppressed by a protein synthesis inhibitor, cycloheximide. No effect by 1 alpha-hydroxy-vitamin D-3 on glucose consumption and lactate production was registered, suggesting that increased mineral mobilization does not require increased lactate production. It is concluded that although the data in the present paper do not prove a cause-and-effect relationship between lysosomal enzyme release and bone resorption, they give further support to the concept that the processes are intimately associated.

Quantitative measurements of human bone enzymes

Up to now quantitative analysis of human bone enzymes is a part of osteology which is not evaluated sufficiently. The lack of standardized methods, fresh bone and reliable methods of bone disintegration seem to impede these experiments mainly. The authors have elaborated a complex method for quantitative measurements of human bone enzymes and they describe the practical use of this method. The importance of quantitative bone enzyme measurements is pointed out.

Influence of diphenylhydantoin on lysosomal enzyme release during bone resorption in vitro

The effect of diphenylhydantoin (DPH) on the release of lysosomal enzymes during resorption of cultured mouse calvarial bone was studied. The enzyme activities of beta-glucuronidase and beta-galactosidase in the culture medium was taken as indicators for lysosomal enzyme release. In concentrations 50 micrograms/ml or higher, DPH inhibited the release of beta-glucuronidase and beta-galactosidase in parallel with bone resorption as indicated by reduced release of 45Ca, Ca2+, Pi and hydroxyproline. The release of the cytosolic enzyme lactate dehydrogenase was not influenced by concentrations of DPH up to 50 micrograms/ml but higher concentrations caused an increased release indicating cell injury. When bone resorption was stimulated by prostaglandin E2, DPH (50 micrograms/ml) also reduced the mobilization of bone mineral and the release of beta-glucuronidase without influencing the release of lactate dehydrogenase. It is suggested that DPH by interfering with cellular release processes reduces the resorption of bone.

Stable acid phosphatase: I. Demonstration and distribution

After a pH-dependent reactivation a highly stable form of acid phosphatase (SAPhase) could be demonstrated in active cells of the macrophage/giant cell/osteoclast series and also in epiphyseal chondrocytes, in cells lining bone undergoing resorption and in hamster eosinophils. Because acid phosphatases of epithelial cells in rat, hamster and Macaca sp. tissues did not possess this stability, SAPhase served as a useful cell marker for the above mesenchymal cell types in paraffin and glycol-methacylate sections even after rapid demineralization in acidic buffers. Conformational alterations appear to occur in the enzyme during formaldehyde fixation, embedding, and reactivation. The granular staining of SAPhase and the successful use of a non-aqueous fixative suggest an association of SAPhase with lysosomes and their membranes. Cells of mesencymal origin that are actively engaged in intra- and/or extracellular digestion contain high levels of SAPhase. The distribution and properties of SAPhase indicate an interrelationship between mononuclear and mutinuclear cell types actively engaged in such digestive processes.

Indomethacin inhibits bone resorption and lysosomal enzyme release from bone in organ culture

The effect of indomethacin on bone resorption was studied in an organ culture system, using calvarial bones from 6--7-day-old mice. It was found that indomethacin inhibited spontaneous bone resorption, as estimated by decreased release of 45Ca, Ca2+ and Pi. Indomethacin reduced the release of beta-glucuronidase, beta-galactosidase and beta-N-acetylglucosaminidase, diminished glucose consumption and lactate production, but showed no effect on the release of lactate dehydrogenase. No inhibitory effect of indomethacin on the release of 45Ca stimulated by parathyroid hormone, prostaglandin E2 or 1 alpha(OH)D3 could be registered. 5,8,11,14-eicosatetraynoic acid, an inhibitor of both cyclo- and lipoxygenase pathway of arachidonate metabolism, reduced the spontaneous release of 45Ca, whereas the selective lipoxygenase inhibitor 5,8,11-eicosatriynoic acid was without effect. The results presented indicate that indomethacin may have an inhibitory effect upon the osteoclasts, probably by decreased metabolism of arachidonic acid via the cyclo-oxygenase pathway. A possible relationship between this finding and the pathogenesis of rapid destruction of articular bone in osteoarthritic patients treated with indomethacin is discussed.

Stable acid phosphatase: II. Effects of pH and inhibitors

Microdensitometry demonstrated that stable acid phosphatase (SAPhase) in rat and hamster osteoclasts, chondroclasts, and chondrocytes has very similar properties. The differences that were observed suggest that conformational alterations in the enzymes may be responsible for inhibition by some agents such as tartrate. These differences in response to inhibitors depend on the method of embedding as well as on species differences. SAPhase appears to correspond to acid nitrophenyl posphatase, as shown by its pH dependent re-activation, resistance to fluoride inhibition at near-neutral pH, and the inverse effect of pH on inhibition by zinc versus aluminium ions. That proportion of SAPhase resistant to fluoride is an acid phosphatase with activity at near-neutral pH rather than a strict neutral phosphatase. The difference between fluoride sensitive and fluoride resistant SAPhase may relate to the varying association of a single enzyme with cell or lysosomal membranes. The close similarity of acid and neutral SAPhase suggests that both may represent a single enzyme in two forms rather than two distinct enzymes.

Collagenase, procollagenase and bone resorption. Effects of heparin, parathyroid hormone and calcitonin

1. The addition of heparin to the culture fluid of mouse tibiae or calvaria did not cause any significant resorption of bone collagen or mineral. However, heparin (or analogue sulfated polyanions), enhanced greatly the amount of latent, trypsin-activatable collagenase (i.e. procollagenase) released by the bones in the medium without influencing that of directly active collagenase which was always very low. Heparin appeared to act by increasing the production of the enzyme which is immediately excreted. Procollagenase and collagenase are not stored in bone tissue, even under conditions where it is in active resorption. 2. Parathyroid hormone induced in the explants a resorption of both mineral and collagen that was inhibited by calcitonin. These hormones, however, had no influence on the release of procollagenase or collagenase either in the presence or in the absence of heparin. 3. Once activated, bone collagenase digested the collagen of the bone explants, and more extensively after their demineralization. Thus the latent collagenase that accumulates around non-resorbing bones has to be considered as a precursor, (and not as a residue), of active enzyme. 4. Active collagenase added to incipient cultures of bones disappeared with a half-life of 24 h. The lost enzyme could, however, not be reactivated by trypsin and thus was not transformed into latent procollagenase.

Levamisole inhibits mineral mobilisation, lactate production and lysosomal enzyme release from cultured bones

Levamisole added to cultured calvarial bones inhibited spontaneous bone resorption, as indicated by reduced release of calcium and inorganic phosphate to the medium. In addition, levamisole reduced lactate production and release of lysosomal enzymes.

Cathepsin D: ultra-immunohistochemical localization in dentinogenesis

Cathepsin D was purified from rat liver using a new affinity chromatographic method, based on the coupling to the specific inhibitor pepstatin. This preparation was used for the production of specific antibodies from rabbit. The purified IgG fraction was conjugated to horseradish peroxidase in a two-step coupling procedure and used for electron microscopic immunohistochemistry of the odontoblast-predentine region of the rat incisor. Precipitates, indicating the presence of cathepsin D, were seen in the odontoblast, odontoblast process, and in the extracellular unmineralized matrix, the predentine. The observations are discussed in relation to proteoglycan degradation at the mineralization front simultaneous with crystal formation, and in relation to the function of lysosomal enzymes in the turnover of connective tissue.

Degradation of cartilage proteoglycans by a neutral proteinase secreted by rabbit bone-marrow macrophages in culture

When cultivated together with pieces of cartilage biosynthetically labelled with 35S in their proteoglycans, rabbit macrophages, differentiated in vitro from bone-marrow cells, cause the release of soluble 35S-labelled material into the culture medium. This process is inhibited by killing the macrophages or by cycloheximide treatment, and is due to the secretion by the cells of a metal-dependent neutral proteinase capable of degrading cartilage proteoglycan subunits into fragments of high molecular weight. Enzyme activity is optimum at about pH7, and is inhibited by EDTA, o-phenanthroline, cysteine or serum, but not by di-isopropyl phosphorofluoridate nor by 4-hydroxymercuribenzoate. The effect of EDTA is partially reversed by Co2+ or Zn2+ ions. The enzyme is eluted from Sephadex G-150 columns as a single peak of material (apparent mol.wt. 17000) that contains also most of the proteolytic activity exerted by culture media on Azocoll (denatured collagen) or on casein. The possible role of this metalloproteinase in chronic inflammatory processes is discussed, particularly in connection with joint erosions in rheumatoid arthritis.

Ultrahistochemical analysis of glycosaminoglycan hydrolysis in the rat periodontal ligament. II. Aryl sulfatase and bone resorption

The distribution of aryl sulfatase in the rat periodontal ligament was investigated by ultrastructural histochemistry. In the periodontal ligament aryl sulfatase was localized specifically in osteoclasts and in vicinal perivascular macrophages. Macrophages associated with bone formation did not stain. The authors interpret this specificity as a potential marker for osteoclast differentiation from macrophages--or as a further indication of the capacity of macrophages to modulate their enzymatic complement in response to the environment. To explain the absence of aryl sulfatase in areas of bone formation we suggest that different sulfate esters are mobilized from resorbing and mineralizing matrices, and that only the enzyme associated with bone resorption is histochemically detectable with the artificial substrates currently used.

Ultrastructural analysis of glycosaminoglycan hydrolysis in the rat periodontal ligament. I. Evidence for macrophage involvement in bone remodelling

We identified the cellular sites of glycosaminoglycan hydrolysis by localizing a key enzyme, N-acetyl-beta-glucosaminidase, in the rat periodonatal ligament. Reaction product was seen in osteoclasts, osteoblasts, fibroblasts, and in macrophages situated perivascularly in areas of bone remodelling. The preferential location of macrophages in areas of both bone formation and bone resorption, and their intense NAGase activity identified the macrophage as a significant participant in the total process of bone remodelling. We considered the presence of reaction product in the Golgi zone and the rough endoplasmic reticulum of osteoblasts and fibroblasts as possible localization of a NAG-transferase.

Cathepsin D activity in isolated odontoblasts

The presence of an acid proteinase with a high activity has been demonstrated in isolated odontoblast-predentine material from dentinogenically active rat incisors. The enzyme was identified as cathepsin D (EC 3.4.23.5). The possible significance of the enzymatic degradation of proteoglycans and glycosaminoglycans in the course of the calcification process is discussed.

Collagen gel in osseous defects. A preliminary study

In a preliminary study, the effects of a biodegradable collagen gel on the healing of osseous defects were examined. Histologic and biochemical observations made on the seventh day after placement revealed that the collagen gel is well tolerated by the recipient and might be an effective stimulator of the formation of reparative bone. However, between the seventh and fourteenth days after placement, the deposition of reparative osseous tissues at the site of implant was significantly retarded. The possible implication of these findings is discussed.

Chrysotile-induced asbestosis: changes in the free cell population, pulmonary surfactant and whole lung tissue of rats

Rats inhaling chrysotile asbestos contracted asbestosis and fibrosis of the lungs. Studies of biochemical and morphological changes (between normal and treated animals) show that chrysotile induces an increase in the lung free cell population and pulmonary surfactant levels. Lysosomal enzyme levels are elevated in both the whole lung and free cell population and there are considerable changes in macrophage morphology. It is suggested that the primary response of the lung to chrysotile is an increase in surfactant production coupled with an increase in free cell numbers, in order to prevent the cytotoxic effect of the dust.

Histochemical demonstration of acid hydrolase activity in internal dentinal resorption

The enzymes acid phosphatase (E.C. 3.133) and beta-glucuronidase (E.C. 3.2.1.31) have been demonstrated in dentin-resorbing cells by means of histochemistry. Addition of specific enzyme inhibitros revealed that the acid phosphatase of these cells was sensitive to fluride, copper, and m?OLYBDATE BUT RESISTANT TO Tartrate. The same pattern of enzyme activity has previously been found in bone-resorbing cells.

Acid hydrolases in the odontoblast-predentin region of dentinogenically active teeth

The presence of hyaluronoglucosidase (EC 3.2.1.35; hyaluronidase), beta-N-acetylglucosaminidase (EC 3.2.1.30), exo-1,4-beta-xylosidase (EC 3.2.1.37), and arylsulfatase (EC 3.1.6.1) in dentinogenically active odontoblasts isolated from the rat incisor has been demonstrated by means of biochemical methods. The possible function of these enzymes in relation to the calcification process is discussed.

Inadequacy of steroids in the treatment of severe hemorrhagic shock

Massive doses of methylprednisolone were given to dogs prior to severe, lethal, hemorrhagic shock. An untreated group of dogs subjected to hemorrhagic shock served as controls. No persistent significant differences were seen in cardiac output, mean arterial blood pressure, superior mesenteric artery flow, and survival. Calculated total peripheral resistance tended to be lower in the treated dogs and was significantly lower after reinfusion of shed blood. Pretreatment with methylprednisolone did not prevent plasma elevations of the lysosomal enzymes, cathepsin D and beta-glucuronidase. Stabilization of hepatic lysosomes in treated dogs subjected to hemorrhagic shock was not evident. The results failed to indicate significant salutary effects of methylprednisolone sodium succinate in this lethal hemorrhagic shock model.

The localisation of bovine sperm hyaluronidase

Hyaluronidase is a component of the acrosome of bovine spermatozoa. Utilizing fluorescein and peroxidase-labelled antibodies, the enzyme has been localised at both the light and electron microscopic levels. Antibodies against purified bovine testicular hyaluronidase were prepared in New Zealand white rabbits. Immunodiffusion, immunoelectrophoresis, and immuno-inhibition studies of the antiserum demonstrated the presence of an antibody specific for bovine sperm hyaluronidase with no cross reactivity to other sperm-associated antigens. Fluorescence microscopy of ejaculated bovine spermatozoa show the enzyme to be limited to the anterior portion of the acrosome with a sharp termination at the rostral border of the equatorial segment of the acrosome. Light microscopic studies with peroxidase-labelled antiserum were similar to the fluorescent findings. Fine structure studies revealed reaction product predominately associated with the matrix of the acrosome cap. Within the acrosome, more intense localisation was observed in the apical densities, while no product was visualised within the equatorial segment. These findings are compatible with the hypothesis that the enzyme functions to facilitate the passage of spermatozoa between cells.

Bone resorption in chronic otitis media. A light-microscopical and histochemical investigation of acid phosphatase activity

As a continuation of our previous work, where we have demonstrated that in chronic otitis media the picture in the submucosa-bone marginal zone is dominated by capillary proliferation and occurrence of a mononuclear, histiocyte-like cell containing lysosome-like cytoplasmatic bodies, we now report the presence of considerable activity of acid phosphatase in close relation to the eroded bone. The activity was localized both extracellularly, spread along the bony surface, as well as intracellularly in mononuclear, histiocyte-like cells. The acid phosphatase is the "marker" enzyme for lysosomes, and cells with these lysosomes guarantee the presence of enzymatic activity capable of attacking bone collagen. It is difficult to avoid the conclusion that the lysosomes and their enzymes are directly involved in the processes of bone resorption.

Distribution of biologically labelled radioactive hyaluronic acid injected into joints

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