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Biomedical subjects

Y Eeckhout

Publications and source records attributed to Y Eeckhout.

52 records · Page 3Linked to original sources
PubMed1985

Bisphosphonates and bone resorption: effects on collagenase and lysosomal enzyme excretion.

When added to cultures of parathyroid hormone (PTH)-stimulated bones, dichloromethylenebisphosphonate (C12MBP) and 3-amino-1-hydroxypropydilene-1,1-bisphosphonate (AHPrBP) inhibit completely and in a parallel manner the development of resorption lacunae, the loss of calcium by the explants and their PTH-induced excretion of lysosomal hydrolases (beta-glucuronidase and N-acetyl-beta-glucosaminidase). The loss of collagen (hydroxyproline) by the bones is usually less inhibited than their loss of calcium and their heparin-induced excretion of collagenase is unaffected. To interpret these data, it is proposed that these bisphosphonates act more on the activity of osteoclasts, suppressing simultaneously their excretion of lysosomal enzymes and their erosion of mineralized bone matrix, than on that of other cell types (osteoblasts ?) responsible for collagenase production and the removal of uncalcified collagen.

Acetylglucosaminidase↗
PubMed1984

In vivo and in vitro evidence for the involvement of cysteine proteinases in bone resorption.

The excretion of cathepsin B, a lysosomal cysteine proteinase, by parathyroid hormone-stimulated embryonic mouse calvaria in culture, correlates closely with the extent of bone resorption evaluated by the loss of hydroxyproline and calcium and by the extension of resorption lacunae. E-64, a specific inhibitor of cysteine proteinases, inhibits reversibly the resorption of cultured bones without affecting the hormone-induced secretion of lysosomal hydrolases. Given in vivo to rats, the proteinase inhibitors, E-64 and leupeptin, both induce a concomitant fall in the serum calcium level and in the urinary excretion of hydroxyproline. These results provide evidence that cysteine proteinases, possibly lysosomal cathepsins, are necessary for bone resorption.

Animals↗
PubMed1983

Co-operation between metastatic tumor cells and macrophages in the degradation of basement membrane (type IV) collagen.

The co-culture of mouse peritoneal macrophages and Lewis lung carcinoma cells induces the release of a metal-dependent type IV collagen-degrading proteinase which is not produced in detectable amounts by either cell type cultivated alone. Conditioned media of the co-cultures degrade both pepsin-extracted type IV collagen from human placenta and mouse type IV procollagen. Thus macrophages can interact with tumor cells to degrade basement membrane type IV collagen: this might be of importance to allow cancer invasion and metastasis.

Animals↗
PubMed1981

Immunoreactive collagenase and bone resorption.

1. Active mouse bone collagenase is excluded from its inhibitory antibody by preincubation of that antibody with various forms of inactive enzyme, e.g. 'procollagenase', some collagenase-inhibitor complexes or partially denatured or degraded collagenase. This property allows the detection of several enzymatically inactive forms of collagenase. 2. The accumulation of immunoreactive collagenase in the culture fluid of mouse bones occurred only in the presence of heparin and was not correlated with bone resorption induced by parathyroid hormone. These experiments provide further (see Lenaers-Claeys, G. and Vaes, G., Biochim. Biophys. Acta (1979) 584, 375-388), more conclusive evidence that the critical role in the resorption of the organic matrix of these explants may be due to another enzyme system than collagenase.

Animals↗
PubMed1980

Inhibition of bone resorption in culture by inhibitors of thiol proteinases.

Leupeptin, antipain, tosyl-lysylchloromethane (Tos-Lys-CH2Cl) and benzyloxy-carbonylphenylalanylalanyldiazomethane (Z-Phe-Ala-CHN2) inhibit reversibly the resorption induced by parathyroid hormone or heparin in cultured mouse bones. Leupeptin and antipain do not affect collagenase production and activity or the enhanced secretion of beta-glucuronidase induced by the bone-resorbing agents. They might thus act by a direct (extracellular?) inhibition of lysosomal thiol proteinases.

Animals↗
PubMed1978

The simultaneous release by bone explants in culture and the parallel activation of procollagenase and of a latent neutral proteinase that degrades cartilage proteoglycans and denatured collagen.

1. A latent neutral proteinase was found in culture media of mouse bone explants. Its accumulation during the cultures is closely parallel to that of procollagenase; both require the presence of heparin in the media. 2. Latent neutral proteinase was activated by several treatments of the media known to activate procollagenase, such as limited proteolysis by trypsin, chymotrypsin, plasmin or kallikrein, dialysis against 3 M-NaSCN at 4 degrees C and prolonged preincubation at 25 degrees C. Its activation often followed that of the procollagenase present in the same media. 3. Activation of neutral proteinase (as does that of procollagenase) by trypsin or plasmin involved two successive steps: the activation of a latent endogenous activator present in the media followed by the activation of neutral proteinase itself by that activator. 4. The proteinase degrades cartilage proteoglycans, denatured collagen (Azocoll) and casein at neutral pH; it is inhibited by EDTA, cysteine or serum. Collagenase is not inhibited by casein or Azocoll and is less resistant to heat or to trypsin than is the proteinase. Partial separation of the two enzymes was achieved by gel filtration of the media but not by fractional (NH4)2SO4 precipitation, by ion exchange or by affinity chromatography on Sepharose-collagen. These fractionations did not activate latent enzymes. 5. Trypsin activation decreases the molecular weight of both latent enzymes (60 000-70 000) by 20 000-30 000, as determined by gel filtration of media after removal of heparin. 6. The latency of both enzymes could be due either to a zymogen or to an enzyme-inhibitor complex. A thermostable inhibitor of both enzymes was found in some media. However, combinations of either enzyme with that inhibitor were not reactivated by trypsin, indicating that this inhibitor is unlikely to be the cause of the latency.

Animals↗
PubMed1977

Further studies on the activation of procollagenase, the latent precursor of bone collagenase. Effects of lysosomal cathepsin B, plasmin and kallikrein, and spontaneous activation.

1. Cathepsin B, a tissue (lysosomal) proteinase, and two humoral proteinases, plasmin and kallikrein, activate the latent collagenase ('procollagenase') which is released by mouse bone explants in culture. Other lysosomal proteinases (carboxypeptidase B, cathepsin C and D) and thrombin did not activate the procollagenase. Dialysis of the culture fluids against 3M-NaSCN at 4 degrees C and, for some culture fluids, prolonged preincubation at 25 degrees C also caused the activation of procollagenase. 2. In all these cases, activation of procollagenase involved at least two successive steps: the activation of an endogenous latent activator present in the culture fluids and the activation of procollagenase itself. 3. An assay method was developed for the endogenous activator. Human serum, bovine serum albumin, casein and cysteine inhibited the endogenous activator at concentrations that did not influence the collagenase activity. N-Ethylmaleimide and 4-hydroxy-mercuribenzoate stimulated the endogenous activator, but iodoacetate had no effect. 4. It is proposed that cathepsin B, kallikrein and plasmin may play a role in the physiological activation of latent collagenase and thus initiate degradation of collagen in vivo. This may occur whatever the molecular nature of procollagenase (zymogen or enzyme-inhibitor complex) might be.

Animals↗