Release of proteases from cartilage cells as a result of activation by a macrophage factor--effects of some anti-inflammatory drugs

Production of collagenase and tissue inhibitor of metalloproteinases (TIMP) by rat growth plates in culture

Growth plate cartilage from normal and vitamin D-phosphate deficient (-VDP) rats was cultured to study the production of collagenase and tissue inhibitor of metalloproteinases (TIMP) in vitro. All tissues secreted latent collagenase into the medium at a constant rate during the 5 days in culture. Microdissected-VDP growth plates, containing predominatly hypertrophic cells, released up to 8-fold more collagenase into the medium than either intact-VDP or normal growth plates. TIMP was also secreted during the culture, but its rate of production was not as dependent on tissue type as collagenase. The tissue level of collagenase and TIMP before culture was compared with that found in conditioned medium and remnant tissue after culture. During the 5 day culture period microdissected-VDP growth plates, containing predominatly hypertrophic cells, produced 3-times more collagenase/microgram DNA over the starting level than either intact-VDP or normal growth plates. TIMP was never found in tissues after they had been cultured, but was present in all tissues before culture except those containing predominatly hypertrophic cells. The amount of TIMP required to block collagenase was calculated. Growth plates in culture produced enough TIMP to block all collagenase found in the medium and remnant tissue, while extracts of uncultured intact -VDP growth plates, and those divided to contain hypertrophic cells, had an excess of collagenase over TIMP. The results suggest that hypertrophic cells produce far more collagenase than other cells in the growth plate, but all cell types have about the same capacity to synthesize TIMP. As a result, increased collagenase synthesis by hypertrophic cells may surpass increases in TIMP synthesis and lead to collagen removal. This would allow for thinning of the longitudinal septa and expansion of the hypertrophic cells.

Triamcinolone impairs the synthesis of collagen and noncollagen proteins in condylar cartilage of newborn mice

The effects of triamcinolone hexacetonide (TH) on the synthesis of collagen and noncollagen proteins were tested in mandibular condylar cartilage of newborn mice. Four-day-old ICR mice received a single i.p. injection of TH at doses ranging from 0.4 to 4.0 mg/kg body weight. Hydrocortisone, deoxycorticosterone, dexamethasone, and progesterone were administered at a dose of 4.0 mg/kg. Test animals and nontreated and vehicle-treated controls were sacrificed after 24, 48, and 72 hours and were processed for electron microscopy. Additional animals were injected with 5 microCi of 3H-proline 2 hours before sacrifice. The specimens were extracted with 5% TCA containing 1 mM proline followed by 5% TCA, acetone, and ether, homogenized and digested with purified bacterial collagenase, and the amounts of radioactivity in collagenase digestible (CDP) and noncollagen proteins (NCP) were determined. The present results revealed that triamcinolone led to a significant dose-dependent decrease in the protein content of the tissue that lasted for 3 days (12-14% at the dose of 4 mg/kg). The incorporation of 3H-proline into CDP was reduced by 39, 57, and 42% at 24, 48, and 72 hours, respectively whereas the incorporation into NCP was reduced by 20, 35, and 23%, respectively. When compared with other steroids, dexamethasone revealed a similar inhibitory effect, whereas hydrocortisone and deoxycorticosterone had no significant effect. Progesterone, on the other hand, showed a transient (24 hours) stimulatory effect on the synthesis of collagen synthesis (21%, P less than 0.05). Electron microscopy showed an atypical arrangement of collagen fibers and accumulation of large aggregates of collagen that filled the entire matrical space between cartilage cells.

Interleukin-1 and osteoarthritis

Il-1, a multifunctional monokine, can stimulate both synoviocytes and articular chondrocytes to release neutral proteases and prostaglandin E2. It is also capable of promoting bone resorption. Therefore, this molecule (or family of molecules) is likely to play an important role in the mechanism of articular cartilage destruction that occurs in degenerative arthropathies. The synovial tissue itself can produce Il-1 (Catabolin) in some conditions, such as a slight traumatism, so that the presence of local inflammation is not necessary for "Il-1-cartilage" interaction to occur. Fundamental macromolecules of cartilage (collagens, proteoglycans) exert a stimulatory effect on Il-1 production, either as such or in the form of immune complexes. Some activated complement fractions (C3a and C5a) may also be actively involved. Studies on the mechanisms which regulate Il-1 synthesis and release, as well as investigations on the response of target cells to Il-1, are presently fascinating goals that could lead to new strategies in therapeutic research.

Modulation of cartilage destruction by select nonsteroidal antiinflammatory drugs. In vitro effect on the synthesis and activity of catabolism-inducing cytokines produced by osteoarthritic and rheumatoid synovial tissue

Non-enzymatic factors produced by synovial tissue can potentially mediate cartilage destruction by inducing the synthesis and release of matrix-degrading proteinases from chondrocytes. Pharmacologic control of this process is of potential clinical relevance. The in vitro effect of therapeutic concentrations of select nonsteroidal antiinflammatory drugs on the synthesis and activity of catabolism-inducing cytokines produced by 6-day explant cultures of osteoarthritic and rheumatoid synovial tissue was studied. Piroxicam regularly suppressed such factor synthesis by both types of tissue without significantly affecting total protein synthesis. This did not occur using sodium salicylate or indomethacin in osteoarthritis tissue cultures and was observed only occasionally in rheumatoid arthritis cultures. None of the nonsteroidal antiinflammatory drugs studied consistently blocked catabolism-inducing activity in osteoarthritis tissue, whereas piroxicam more consistently inhibited activity produced by rheumatoid arthritis tissue. Results suggest that the catabolism-inducing factors produced by the 2 tissue sources may differ.

Neutral proteases in human osteoarthritic synovium

The activities of neutral collagenolytic enzymes (CE) and neutral proteoglycan-degrading enzymes (PE) in the synovial membranes of osteoarthritis (OA) patients were determined. The total neutral metallo-CE activity showed a significantly higher level of activity when the membranes of OA patients were compared with those of controls. The severely and moderately inflamed synovia had significantly more enzyme activity than did either mildly inflamed or control synovia. Steroids reduced the total metallo-CE activity. In specimens with severe inflammation, the active form of the neutral metallo-CE was significantly elevated over that found in controls. The serine-CE activity was also significantly elevated in OA synovia with severe inflammation and synovial hypertrophy. The total and active neutral metallo-PE was significantly elevated in synovial membranes of OA patients with severe inflammation. Moreover, the serine-PE showed much more activity in OA patients than in controls. The enzyme activity remained at a significantly high level in the OA synovium, regardless of the presence or absence of macroscopic synovial hypertrophy or the histologic grading of the synovium (mild, moderate, severe). Our data indicate that, in OA, an increased level of neutral proteases in the synovia could be involved in the local tissue destruction of the periarticular structures. Because of the very high level of serine proteases, their diffusion may render plausible a degradative action on the cartilage surface.

Porcine heart valves produce a protein that induces cell-mediated connective tissue degradation: I. Biological properties

Cultured porcine heart valves secrete a factor that induces cells to degrade their extracellular matrix. This activity was routinely monitored by measuring the release of glycosaminoglycans from proteoglycan in cultured bovine nasal cartilage. It was observed that factor-mediated matrix degradation was dose dependent and required live target cells, while factor production by valves was inhibited by cycloheximide and declined with reduced cell viability. The effect of various steroidal and nonsteroidal anti-inflammatory drugs on the production and activity of the factor is discussed with reference to similar cytokines. It is concluded that there is a close similarity between the cardiac catabolic factor described here and catabolin, a protein isolated from porcine synovia and leukocytes, as shown by the neutralization of biological activity with antisera raised to porcine catabolin (interleukin-1).

Effects of 1-hydroxyethylidene-1,1 bisphosphonate and (chloro-4 phenyl) thiomethylene bisphosphonic acid (SR 41319) on the mononuclear cell factor-mediated release of neutral proteinases by articular chondrocytes and synovial cells

Articular chondrocytes and synovial cells were stimulated to produce collagenase, neutral casein and proteoglycan-degrading proteinases by conditioned medium from human peripheral blood mononuclear cells. Collagenase, neutral casein and proteoglycan-degrading proteinase secretion was inhibited by SR 41319, a new bisphosphonate, in a concentration-dependent manner. Complete inhibition was achieved at about 0.3 mM. EHDP exhibited the same general profile but was about 10-fold less active and never completely inhibited the enzyme secretion. When added before MCF, SR 41319 had a protective effect against subsequent activation of the cells by MCF. SR 41319 also inhibited the increase of enzyme secretion by cells previously stimulated with MCF. The results suggest that the ability of SR 41319 to inhibit the MCF-mediated secretion of neutral enzymes involved in cartilage destruction could be valuable in the management of connective tissue damage in rheumatoid arthritis.

Nonsteroidal anti-inflammatory drugs and modulation of cartilaginous changes in osteoarthritis and rheumatoid arthritis. Clinical implications

Nonsteroidal anti-inflammatory drugs have a potential for modifying the complex pathophysiologic events leading to cartilage destruction in various forms of arthritis. Following an evaluation of basic mechanisms in the pathogenesis of cartilaginous destructive lesions, the effects of nonsteroidal anti-inflammatory drugs on normal chondrocyte metabolism are discussed. Their capacity to modulate cartilage and bone lesions in experimental forms of arthritis is addressed, as is the manner in which they may modify the pathophysiology of cartilage destruction in human forms of arthritis. Different classes of nonsteroidal anti-inflammatory drugs produce different effects in certain in vivo or in vitro settings.

Enhanced production of prostaglandins and plasminogen activator during activation of human articular chondrocytes by products of mononuclear cells

We have examined the way in which products of cultured human blood mononuclear cells activate human articular chondrocytes. Conditioned medium from mononuclear cells enhanced the production of prostaglandin E by cultured human chondrocytes and also stimulated fibrinolytic activity in these cultures. These two effects may be interrelated, since the increased fibrinolysis in response to products of mononuclear cells was partially inhibited by indomethacin, an inhibitor of prostaglandin biosynthesis. The increased fibrinolysis is probably attributable to plasminogen activator, since it was strongly dependent on the presence of plasminogen. Increased amounts of PGE and chondroitin sulphate were also released from intact fragments of cartilage exposed to medium from cultured mononuclear cells. The time course and dose dependence of these effects were studied. The addition of exogenous arachidonic acid markedly enhanced production of PGE2. Ultrogel AcA54 was used to fractionate medium from cultured mononuclear cells and the chondrocyte-stimulating activity eluted with an apparent molecular weight between 12 000 and 25 000 daltons. Adherent and non-adherent mononuclear blood cells were also partially separated and conditioned medium from each was assayed for chondrocyte-stimulating factors. Both populations released factor(s) which increased the production of prostaglandin E by chondrocytes, but more activity came from the adherent mononuclear cells. The possible interrelationship between the chondrocyte activating factor studied here and others described in the literature is discussed.

The effects of razoxane (ICRF 159) on the production of collagenase and inhibitor (TIMP) by stimulated rabbit articular chondrocytes

Monolayer cultures of rabbit chondrocytes were stimulated to produce collagenase with conditioned medium from human peripheral blood mononuclear cells (MCM), and the ability of Razoxane to modulate the production of collagenase and specific tissue inhibitor of metalloproteinases (TIMP) was studied. Collagenase production was inhibited and TIMP increased by Razoxane, in a dose-dependent manner, when cells were treated daily for 3 days. Over this period the effect of Razoxane was progressive; 50 micrograms/ml or less had no effect at day 1 but 50 micrograms/ml was effective by day 3. The effectiveness of Razoxane was inversely related to the degree of MCM stimulation and the confluency of the culture. On removal of the drug, chondrocytes stimulated with MCM recovered their ability to produce collagenase, and TIMP production returned to near normal. The results suggest that the ability of Razoxane to reduce collagenase and increase TIMP production may correlate with its effectiveness in treating psoriatic arthritis.

Phospholipase C activity in plasma membranes isolated from lapine synovial cells in monolayer culture

Plasma membranes were isolated from lapine synovial cells grown in monolayer culture using discontinuous sucrose gradient centrifugation techniques. 5'nucleotidase was detected in great abundance while glucose-6 phosphate dehydrogenase and cytochrome oxidase were present at low to undetectable levels. Plasma membranes incubated at 37 degrees C for 60 min with [3H]-arachidonyl-phosphatidylinositol/phosphatidylserine synthesized [3H]-diacylglycerides. Little if any [3H]-diacylglyceride synthesis was measured when [3H]-arachidonyl-phosphatidylcholine or [3H]-arachidonyl-phosphatidylethanolamine were used as substrates. These results are consistent with a plasma membrane-associated phosphatidylinositol-specific phospholipase C from lapine synovial cells in culture.

The production in culture of metalloproteinases and an inhibitor by joint tissues from normal rabbits, and from rabbits with a model arthritis. II. Articular cartilage

During the development of proliferative arthritis in the knee joints of rabbits, there was a large increase in the ability of articular cartilage explants to produce latent collagenase in culture. In parallel, the normally high levels of collagenase inhibitor produced by cartilage in culture fell, but active collagenase was never detectable. Characterisation of the collagenase and other proteinase activities produced by rabbit articular cartilage in culture showed that two activities could be separated by gel filtration, one with activities on gelatin and cartilage proteoglycan and the other degrading collage. Under the conditions employed in this paper no resolution of the gelatin and proteoglycan activities could be achieved. All the activities were in a latent form, activated by 4-aminophenylmercuric acetate (APMA), and inhibited by 1,10-phenanthroline or EDTA, but not by di-isopropylfluorophosphate (DFP), indicating that they are metalloproteinases. Characterization of the collagenase inhibitor showed a single peak of activity of apparent molecular weight of 28,000 on gel filtration. The inhibitor was sensitive to APMA and also inhibited other rabbit metalloproteinases, analogous to the system described for rabbit bone. The physiological significance of the synthesis by articular cartilage of proteinases that destroy connective tissue macromolecules and the presence of an enzyme-inhibitor control system is discussed.

Cell-to-cell interactions in the secretion of enzymes of connective tissue breakdown, collagenase and proteoglycan-degrading neutral proteases. A review

Cell and tissue culture techniques provide valuable tools for investigating cell-to-cell interactions leading to the secretion of connective-tissue degrading enzymes, collagenase and proteoglycan-degrading neutral proteases, in inflammatory situations. These interactions, which might constitute a major regulatory mechanism, are reviewed here. Taken together, the available data strongly suggest that fibroblasts and related mesenchymal cells (such as chondrocytes, fibroblast-like or type B synovial lining cells, corneal stromal cells, etc.) could be the main suppliers of collagenase within tissues. These cells can secrete collagenase in response to factors produced by other cells, mainly macrophages and related cells (monocytes, synovial cells - presumably the macrophage like, type A synovial lining cells), possibly also epithelial cells. Lymphocytes are able to modulate factor production by macrophages so that, through the macrophage link the secretory behavior of the fibroblastic cells may be under the control of the immune defense system and serve as an effector of immune reactions leading to connective tissue destruction.