Collagenolytic enzymes and their naturally occurring inhibitors

Hydroxyproline concentration in soluble and insoluble material from serum treated with trichloroacetic acid in postpartum mice

The hydroxyproline concentration in both the soluble and insoluble material from trichloroacetic acid-treated serum from postpartum mice was determined. The hydroxyproline concentration in the insoluble material increased, but that in the soluble material did not increase during the uterine involuting period.

Immunocytochemical staining of rat tissues with antibodies to denatured type I collagen: a technique for localizing areas of collagen degradation

Sheep were immunized with purified native collagen I and the antisera were fractionated by affinity chromatography on columns containing either native or heat-denatured forms of the antigen. Crossed immunoadsorption ensured complete removal of antibodies to terminal, non-helical regions resulting in antibodies that were specific for either native or central, non-helical determinants, as judged by ELISA and immunoblotting. Tissue immunostaining showed some areas, such as duodenal villus and blood vessels, where staining with antibodies against native and denatured collagen gave similar patterns, but other areas, such as pancreas, where immunolocalization of native collagen I was not accompanied by similar detection of the denatured form. Immunodetection on tissue sections of added human fibronectin showed similar staining patterns to those for denatured collagen. Areas of tissue showing the presence of denatured collagen were interpreted as an indication of collagen degradation, and the technique may therefore provide a means of assessing the pattern of collagen turnover within individual tissues.

Nerve-induced remodeling of muscle basal lamina during synaptogenesis

To identify mechanisms that regulate the deposition of the junctional basal lamina during synaptogenesis, immunocytochemical experiments were carried out on cultured nerve and muscle cells derived from Xenopus laevis embryos. In some experiments successive observations were made on individual muscle cells after pulse-labeling with a fluorescent monoclonal antibody specific for a basal lamina proteoglycan. In others, old and new proteoglycan molecules were differentially labeled with antibody conjugated to contrasting fluorochromes. These observations revealed that surface deposits of antibody-labeled proteoglycan remain morphologically stable for several days on developing muscle cells. Over the same period, however, new sites of proteoglycan accumulation formed that contained primarily those antigenic sites recently exposed at the cell surface. When muscle cells became innervated by cholinergic neurites, new proteoglycan accumulations were induced at the developing neuromuscular junctions, and these too were composed almost exclusively of recently deposited antigen. In older muscle cultures, where many cells possessed relatively high background concentrations of antigen over their surfaces, developing neuromuscular junctions initially showed a markedly reduced proteoglycan site-density compared with the adjacent, extrajunctional muscle surface. Much of this perineural region eventually became filled with dense, nerve induced proteoglycan plaques at later stages of synapse development. Motoneurons thus appear to have two, superficially paradoxical effects on muscle basal lamina organization. They first cause the removal of any existing, extrajunctional proteoglycan from the path of cell contact, and then induce the deposition of dense plaques of recently synthesized proteoglycan within the developing junctional basal lamina. This observation suggests that the proteolytic enzyme systems that have already been implicated in tissue remodeling may also contribute to the inductive interaction between nerve and muscle cells during synaptogenesis.

The promotion and inhibition of collagen-breakdown in organ cultures of pig synovium: the requirement for serum components and the involvement of cyclic adenosine 3':5'-monophosphate (cAMP)

In many pathological situations connective tissue cells acquire the ability to degrade the macromolecular components of their extracellular matrix. To study the destruction of collagen we used organ cultures of porcine synovial tissue. In the presence of 15% rabbit serum explants shrink considerably during 10-14 days, owing to early loss of interfibrillar material followed by retraction and local destruction of collagen fibres, partly by phagocytosis. These changes, and the release of latent collagenase into the medium, are largely inhibited by cortisol and partially by indomethacin. Collagen destruction can be greatly accelerated by the addition to the culture medium of one of the following: sodium fluoride, 3-isobutyl-1-methylxanthine, dibutyryl cyclic adenosine 3':5'-monophosphate or forskolin; these agents are known to affect cyclic adenosine monophosphate metabolism and our results suggest strongly that a change in the intracellular levels of cyclic adenosine monophosphate is a key-step in the process leading to the increased catabolism of collagen. With these compounds the destruction of collagen is largely extracellular; the histological changes and the increased levels of collagenase associated with the destruction can be prevented by cortisol and, except in the case of dibutyryl cyclic adenosine monophosphate, at least partially by indomethacin. Without serum only 3-isobutyl-1-methylxanthine sometimes causes drastic breakdown of collagen. This model system should be of great benefit in exploring the mechanisms involved in collagen destruction.

Sequence of human tissue inhibitor of metalloproteinases and its identity to erythroid-potentiating activity

Collagen fibres form the stable architecture of connective tissues and their breakdown is a key irreversible step in many pathological conditions. The destruction of collagen is usually initiated by proteinases, the best known of which is the metalloproteinase collagenase (EC 3.4.24). Collagenase and related metalloproteinases are regulated at the level of their synthesis and secretion, through the action of specific stimuli such as hormones and cytokines, and also at the level of their extracellular activity through the action of a specific inhibitor, TIMP (tissue inhibitor of metalloproteinases), which irreversibly forms inactive complexes with metalloproteinases. Although the mechanisms governing the production of TIMP are unknown, immunologically identical forms of this glycoprotein have been detected in a wide variety of human body fluids and cell and tissue culture media. We therefore suggested that under physiological conditions this ubiquitous inhibitor predominates over active metalloproteinases and that tissue destruction may arise when any perturbation of this controlling excess arises. However, further progress towards testing this theory has been hindered by a lack of knowledge about the structure of TIMP and insufficient material for studying it in model systems. Here we describe the structure of TIMP predicted from its complementary DNA, its synthesis in Escherichia coli and transfected animal cells, and the finding that it is identical to a protein recently reported to have erythroid-potentiating activity (EPA).

Early decrease in suture line breaking strength. The effect of proposed collagenase inhibition

Rats were subjected to end-to-end intestinal anastomosis. Breaking strength with the sutures in place, i.e., suture-holding capacity, was measured in different groups immediately after suture and after 24 h. The synthetic kallikrein-plasmin inhibitor S-2441, the inhibitor of plasminogen activation tranexamic acid (Cyklokapron), and the metalloprotease inhibitor tiopronin (Thiola), were studied regarding their effect on breaking strength of the intestinal anastomoses. There was a marked decrease in breaking strength at 24 h in the controls. This decrease was diminished by all of the substances tested. Their effect was probably due to an inhibition of collagenase.

The alkali burned cornea: electron microscopical, enzyme histochemical, and biochemical observations

The early phase of wound healing after small central alkali burns of the guinea pig cornea was studied using electron microscopical, enzyme histochemical, and biochemical techniques. In the first phase, which was morphologically characterized by the destruction of the epithelium and keratocytes and by the infiltration of the cornea with polymorphonuclear leukocytes, an increase in the activity of lysosomal phosphatases and glycosidases (beta-D-glucuronidase, acid beta-D-galactosidase, beta-D-N-acetylglucosaminidase) was noticed. In the second phase, the cornea was invaded by capillaries and fibroblasts. In this phase, the activity of proteases (aminopeptidase M, dipeptidyl peptidase IV) increased intra- and extracellularly, suggesting that these enzymes may be involved in the turnover of the collagenous matrix and the ground substance. Using synthetic 4-methoxy-2-naphthylamine substrates and fluorescence-band detection techniques after isoelectric focusing, an increase in the activity of endopeptidases was demonstrated. The decreased activity of gamma-glutamyl transpeptidase may be linked with the activation of latent collagenase.

Beneficial effect on intestinal anastomoses of S-2441, a synthetic kallikrein-kinin antagonist. Experimental studies in the rat

The effects of two protease inhibitors on breaking strength of an intestinal anastomosis were studied. The inhibitors tested were aprotinin and S-2441, a synthetic triple-peptide kallikrein-kinin antagonist. Rats were subjected to an end-to-end anastomosis in the small intestine. The breaking strength, or suture-holding capacity, was measured immediately after suture and after 24 hours. The loss of mechanical strength found in untreated rats was substantially, but not fully, prevented by S-2441. Aprotinin in the dose given was not effective.

Collagenase synthesis by osteoblast-like cells

Cultures of osteoblast-like cells from a rat sarcoma and osteoblast-enriched populations of rat calvarial cells synthesize and secrete a true collagenase and collagenase inhibitor. The enzyme, which is produced in a latent form, appears to be similar to the enzyme produced by fibroblasts.

Synthesis of collagenase and collagenase inhibitors by osteoblast-like cells in culture

A rat osteosarcoma cell clone (ROS 17/2), and osteoblast-enriched populations from rat calvaria cultured in the presence of concanavalin A, have been shown to produce latent collagenase and collagenase inhibitors. The enzymes and inhibitor activities from the ROS 17/2 cells were concentrated by ammonium sulphate precipitation and separated by gel filtration on AcA 54 resin. The size of the latent collagenase (Mr approximately equal to 58000) was reduced on conversion to active enzyme (Mr approximately equal to 48000) by p-aminophenylmercuric acetate. Latent and active forms of gelatinase activity, similar in size to the corresponding forms of collagenase, were also resolved. The collagenase inhibitor activity, which was sensitive to organomercurials, was recovered in two peaks (Mr approximately equal to 68000 and 30000). The active collagenase cleaved interstitial collagens (type I = III greater than II) producing typical 3/4 and 1/4 fragments. This activity was inhibited by the metal ion chelators ethylenediaminetetraacetic acid and o-phenanthroline. Additional specific cleavages of native collagen were also observed which, from the susceptibility of this activity to phenylmethylsulphonyl fluoride, leupeptin and antipain, suggested the presence of a second collagenolytic enzyme. This synthesis of collagenolytic enzymes by these osteoblast-like cells suggests that individual osteoblasts, like fibroblasts, are capable of both synthesizing and degrading their respective organic matrices in vivo.

Induction of collagenase synthesis in chondrocytes by a factor synthesized by inflamed synovial tissue

Rabbit inflamed synovial tissue grown in culture synthesizes a factor that induces collagenase synthesis in chondrocytes and in cartilage. Synthesis of this factor by the synovial tissue is inhibited by cycloheximide but not by indomethacin. The factor has an apparent molecular weight of 30,000, is stable to heat and to trypsin treatment but is inactivated by acid. Induction of collagenase synthesis in chondrocytes occurs after a lag period of 6 hours.