Inhibition of gelatinase activity in human airway epithelial cells and fibroblasts by dexamethasone and beclomethasone.

The effects of dexamethasone and beclomethasone on gelatinase activity released from lung epithelial cells (A549, NCI-H292 and Calu-3 cell lines and NHBE primary cultures) and human lung fibroblasts (HLF) were investigated. All cells spontaneously released gelatin-degrading activity but the amounts were unaffected by treatment with glucocorticoids. Phorbol myristate acetate (PMA) increased the amount of gelatinase activity in conditioned media prepared from all cell types examined. In epithelial cells, PMA induced the expression of gelatinase B, whereas in HLF the increased gelatinase activity resulted from increased activation of gelatinase A. Dexamethasone and beclomethasone produced concentration-dependent inhibition of PMA-induced gelatinase activity in HLF and epithelial cell lines. In the epithelial cell lines, the inhibition of activity was associated with an attenuation of enzyme induction by PMA. In contrast, primary cultures of human bronchial epithelial cells were unresponsive to dexamethasone at concentrations that were maximally effective at inhibiting gelatinase activity induced in other cells.

Preclinical and clinical studies of MMP inhibitors in cancer.

The role of matrix metalloproteinases in tumor angiogenesis and growth is now well recognized for models of both human and animal cancer. Clinical studies currently under way with the prototype matrix metalloproteinase inhibitor, marimastat, will establish whether inhibitors of these enzymes are of benefit in the treatment of different types of human cancer. On chronic therapy in humans, marimastat induces a reversible tendinitis that can also be detected in certain animal species. This paper compares the ability of broad-spectrum and various types of selective matrix metalloproteinase inhibitors to induce tendinitis and to exhibit anticancer effects in an animal cancer model. Under conditions in which both systemic exposure and inhibitor potency are controlled, selective inhibitors are less pro-tendinitic, but are weaker anticancer agents than broad-spectrum agents such as marimastat. The clinical relevance of these findings is discussed.

Results of single and repeat dose studies of the oral matrix metalloproteinase inhibitor marimastat in healthy male volunteers.

AIMS: To assess the tolerability and pharmacokinetic profile of single and repeat doses of the oral matrix metalloproteinase inhibitor marimastat in healthy male volunteers. METHODS: A total of 31 subjects participated in two placebo-controlled, rising-dose studies. The first study assessed the pharmacokinetics and tolerability of single doses of marimastat of 25, 50, 100, 200, 400 and 800 mg. In the second study, continuous dosing over 6.5 days with three incremental dose levels of 50, 100 and 200 mg twice daily was assessed. Full pharmacokinetic profiles were obtained on days 0 and 6, and trough concentrations were measured on all days. For each pharmacokinetic profile in the studies, summary measures including Cmax, tmax, elimination half-life and AUC were calculated. Urinary drug weights were also measured. All adverse events were documented, and haematological and biochemical variables, vital signs and ECGs were monitored throughout the study. RESULTS: Peak plasma concentrations were observed at 1.5-3 h for all subjects at all doses. Peak levels were approximately proportional to dose, as was drug exposure as calculated by AUC. Data from both studies indicate that the terminal elimination half-life is of the order of 8-10 h, and that there is no unexpected drug accumulation. Marimastat was well-tolerated, with adverse effects being mild and occurring with similar frequency to placebo. Small but reversible elevations in liver transaminases were noted with repeat dosing of marimastat, the most significant of these occurring at a dose of 200 mg twice daily. CONCLUSION: Single and repeat oral doses of marimastat in healthy male subjects appear to be well-tolerated. The drug is rapidly absorbed with high peak levels achieved. It has a terminal elimination half-life of 8-10 h which would support twice daily dosing in further clinical trials.

Anti-arthritic activity of hydroxamic acid-based pseudopeptide inhibitors of matrix metalloproteinases and TNF alpha processing.

OBJECTIVE AND DESIGN: The effects of two hydroxamate inhibitors of metalloproteinase and tumor necrosis factor alpha (TNF alpha) processing on endotoxin-induced plasma TNF alpha and arthritic lesions in adjuvant-induced arthritic (AA) rats were determined. MATERIAL AND TREATMENT: BB-1101 and BB-1433 were administered orally twice daily to AA Lewis rats with an established disease (days 13 to 22). AA rats (day 16) or normal rats were injected with bacterial endotoxin and plasma levels of TNF alpha were also determined. METHODS: Hindpaw swelling was measured plethysmographically. Bone degradation was determined by radiography and bone mineral densitometry. TNF alpha was quantified using a sandwich ELISA. RESULTS: The hydroxamic-acid pseudopeptides inhibited plasma. TNF alpha levels in vivo and significantly reduced swelling and bone degradation of the tibiotarsal joints of AA rats in the range of 10-50 mg/kg given orally (p < 0.01 by Student's t-test). CONCLUSIONS: Thus, these novel compounds offer a new disease modifying therapy for arthritis and the results also suggest that inhibition of TNF alpha production may contribute, at least in part, to their anti-arthritic activity.

Matrix metalloproteinases and processing of pro-TNF-alpha.

Tumor necrosis factor-alpha (TNF-alpha) is released from a cell membrane-anchored precursor by proteolytic cleavage. We have shown that broad spectrum synthetic inhibitors of matrix metalloproteinases (MMPs) prevent the processing of the TNF precursor but do not inhibit the release of other cytokines. Purified MMPs, stromelysin, matrilysin, collagenase, and the gelatinases can all cleave a recombinant pro-TNF substrate to yield mature TNF. MMP inhibitors prevent the rise in blood levels of TNF after endotoxin administration in rats and are effective in animal models of inflammatory disease such as adjuvant arthritis. Drugs that inhibit MMP action and TNF release show great promise for the treatment of autoimmune inflammatory diseases.

Processing of tumour necrosis factor-alpha precursor by metalloproteinases.

Tumour necrosis factor-alpha (TNF-alpha) is a potent pro-inflammatory and immunomodulatory cytokine implicated in inflammatory conditions such as rheumatoid arthritis, Crohn's disease, multiple sclerosis and the cachexia associated with cancer or human immunodeficiency virus infection. TNF-alpha is initially expressed as a 233-amino-acid membrane-anchored precursor which is proteolytically processed to yield the mature, 157-amino-acid cytokine. The processing enzyme(s) which cleave TNF-alpha are unknown. Here we show that the release of mature TNF-alpha from leukocytes cultured in vitro is specifically prevented by synthetic hydroxamic acid-based metalloproteinase inhibitors, which also prevent the release of TNF-alpha into the circulation of endotoxin challenged rats. A recombinant, truncated TNF-alpha precursor is cleaved to biologically active, mature TNF-alpha by several matrix metalloproteinase enzymes. These results indicate that processing of the TNF-alpha precursor is dependent on at least one matrix metalloproteinase-like enzyme, inhibition of which represents a novel therapeutic mechanism for interfering with TNF-alpha production.

Metalloproteinase inhibitors as therapeutics.

Matrix metalloproteinases (MMPs) are a family of enzymes which contain zinc at their active site and can degrade most of the matrix macromolecules found in connective tissues. These MMPs are secreted by connective tissue cells and infiltrating leucocytes in response to inflammatory mediators. There is now widespread recognition that MMPs are the major class of proteinases responsible for the excessive degradation of cartilage that leads to joint dysfunction in rheumatoid arthritis. The properties of the MMPs are reviewed and a therapeutic role for synthetic, zinc-binding pseudopeptide MMP inhibitors in the treatment of arthritis is proposed.

The interaction of purified rabbit bone collagenase with purified rabbit bone metalloproteinase inhibitor.

1. Pure rabbit bone metalloproteinase inhibitor (TIMP) bound tightly to pure rabbit bone collagenase with an apparent Kd of 1.4 X 10(-10) M. 2. The molecular weight of the enzyme-inhibitor complex was found to be 54 000, but no enzyme activity could be recovered from the complex after treatment with either mercurials or proteinases. The complex thus differed from latent collagenase in terms of size, susceptibility to mercurials and behaviour on concanavalin A-Sepharose. 3. The interaction of the purified components was compared with that of crude collagenase and crude inhibitor in culture medium. Mercurial treatment partially reversed the inhibition in the crude system, but not when the purified components were used. 4. The significance of the results is discussed in relation to the extracellular control of the activity of collagenase.

Purification and characterization of a rabbit bone metalloproteinase that degrades proteoglycan and other connective-tissue components.

A metalloproteinase, 'proteoglycanase', that degrades proteoglycan and insoluble type IV collagen as well as casein was purified to homogeneity from rabbit bone culture medium. The major form of this proteinase had a final specific activity of 2400 micrograms of casein degraded/min per mg of enzyme protein, and Mr 24 500 by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis or 12 500 by gel-filtration chromatography. It was active over the pH range 5.0-9.0 against a number of substrates, and the rates of degradation were almost constant over the whole of this range. The products generated from proteoglycan-aggregate degradation by this enzyme indicated cleavage at multiple chondroitin sulphate-binding sites along the protein core. In a new assay to detect degradation of insoluble type IV collagen, the proteoglycanase generated large fragments, probably by cleavage in the non-helical regions. The enzyme degraded laminin, fibronectin and procollagen, removing the extension peptides of the last-mentioned. It also cleaved the 'weak region' of the type III collagen helix in a manner analogous to trypsin. The synthetic substrate 2,4-dinitrophenyl-Pro-Leu-Gly-Ile-Ala-Gly-Arg-NH2 was cleaved exclusively at the Gly-Ile bond. The proteoglycanase was inhibited by tissue inhibitors of metalloproteinases from rabbit bone culture medium, human amniotic fluid and bovine nasal-cartilage extracts, forming essentially irreversible inactive complexes. The importance of this tissue-derived enzyme, with such a wide-ranging degradative capacity, in normal and pathological connective-tissue matrix degradation is discussed.

Metalloproteinases from rabbit bone culture medium degrade types IV and V collagens, laminin and fibronectin.

Gel-filtration chromatography of culture medium from rabbit bone explants separates three latent metalloproteinases with activities against collagen, proteoglycan and gelatin respectively. The fractions degrading proteoglycan also degrade laminin, fibronectin and the polymeric products of pepsin-solubilized type IV collagen and can also solubilize insoluble type IV collagen. The fractions degrading gelatin are capable of degrading solubilized type V and 1 alpha,2 alpha,3 alpha (cartilage) collagens, as well as the lower-molecular-weight products of pepsin-solubilized type IV collagen. All activities can be inhibited by 1,10-phenanthroline and occur in either partially or totally latent forms that can be activated by 4-aminophenylmercuric acetate.

Purification of rabbit bone inhibitor of collagenase.

1. Rabbit bones in tissue culture synthesize an inhibitor of collagenase during the first 4 days of culture. 2. The inhibitor was purified by a combination of gel filtration, concanavalin A--Sepharose chromatography, ion-exchange chromatography and zinc-chelate affinity chromatography. 3. The purified inhibitor migrated as a single band on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and had a mol.wt. of 28000. 4. The inhibitor blocked the activity of the metalloproteinases collagenase, gelatinase, neutral proteinase III (proteoglycanase), human leucocyte collagenase and gelatinase, but not thermolysin or bacterial collagenase. The serine proteinases plasmin and trypsin were not inhibited. 5. The inhibitor interacted with purified rabbit bone collagenase with 1:1 stoichiometry. 6. The inhibitory activity was lost after incubation for 1 h at 90 degrees C, after treatment with trypsin (250 micrograms/ml) at 37 degrees C for 30 min and after reduction and alkylation.

Zinc metalloenzyme properties of active and latent collagenase from rabbit bone.

1. Inhibition of collagenase from rabbit bone cultures by the chelating agents 1,10-phenanthroline and EDTA is almost completely reversed by Zn2+; other metal cations are less effective in reversing the inhibition. Optimal restoration of activity is achieved at Zn2+ concentrations below that of the chelator, but excess of Zn2+ is inhibitory. 2. Prolonged incubation of collagenase with either chelator causes irreversible inactivation. This inactivation is prevented by Zn2+ at the same concentrations needed to reverse the primary inhibition. 3. Collagenase incorporates 65Zn by exchange when incubated with 1,10-phenanthroline and Zn2+ containing this radioactive isotope. The 65Zn2+ can be removed from its binding site in collagenase by 1,10-phenanthroline or EDTA. Irreversible inactivation of collagenase by chelators destroys its ability to incorporate 65Zn2+. 4. Latent collagenase, the inhibited form in which collagenase first appears in culture, behaves similarly to the active enzyme in 65Zn2+-exchange experiments, but is resistant to irreversible inactivation by chelators. 5. It is concluded that collagenase is a zinc metalloenzyme that forms an inactive and unstable apoenzyme on treatment with chelators. The bound inhibitor component of latent collagenase evidently stabilizes the apoenzyme.