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Biomedical subjects

R A Greenwald

Publications and source records attributed to R A Greenwald.

At least 37 records · Page 2Linked to original sources
PubMed1995

Tenidap and flurbiprofen enhance uptake of matrix metalloproteinase inhibitor 4-dedimethylaminotetracycline in inflamed joints of adjuvant arthritic rats.

OBJECTIVE: To identify a mechanism by which a matrix metalloproteinase (MMP) inhibitor might act synergistically with other agents to decrease MMP activity and thereby lessen the radiologic severity of adjuvant arthritis. METHODS: Rats with adjuvant arthritis were treated with either flurbiprofen (FBP) or tenidap (TDP), along with 4-dedimethylaminotetracycline (CMT-1), a potent MMP inhibitor. Indices of inflammatory severity and of radiologic destruction were assessed and compared to serum and bone levels of the MMP inhibitor. RESULTS: Combination therapy with the MMP inhibitor plus either of the other drugs led to synergistic improvement in radiologic severity. For example, CMT-1 combined with TDP reduced radiologic severity 45% while decreasing collagenase and gelatinase activities by 61 and 72%, respectively, more than doubling bone CMT-1 levels (7.6 micrograms/g to 16.4 micrograms/g). FBP had similar effects. CONCLUSION: MMP inhibitors need access to the arthritic joint to interact with their target enzymes. Concomitant antiinflammatory therapy is required to assure drug entry into the inflamed tissues.

Animals↗
PubMed1994

Doxycycline disrupts chondrocyte differentiation and inhibits cartilage matrix degradation.

OBJECTIVE: The effects of doxycycline were tested in an in vitro system in which the cartilages of embryonic avian tibias are completely degraded. METHODS: Tibias were cultured with 5, 20, or 40 microgram/ml doxycycline. Control tibias were cultured without doxycycline. Conditioned media and tissue sections were examined for enzyme activity and matrix loss. RESULTS: Cartilages were not resorbed in the presence of doxycycline, whereas control cartilages were completely degraded. Collagen degradation was reduced in association with treatment with doxycycline at all doses studied. Higher concentrations of doxycycline reduced collagenase and gelatinase activity and prevented proteoglycan loss, cell death, and deposition of type X collagen in the cartilage matrix; in addition, treatment with doxycycline at higher concentrations caused increases in the length of the hypertrophic region. CONCLUSION: The effects of doxycycline extend beyond inhibition of the proteolytic enzymes by stimulating cartilage growth and disrupting the terminal differentiation of chondrocytes.

Animals↗
PubMed1994

Elevated plasma stromelysin levels in arthritis.

OBJECTIVE: To determine whether plasma concentrations of stromelysin-1 and gelatinase A are increased in patients with various forms of arthritis. METHODS: A sensitive and specific sandwich enzyme linked immunosorbent assay (ELISA), which employs a murine monoclonal antibody and a rabbit polyclonal antibody to human stromelysin-1, was used to measure plasma stromelysin-1 in 53 healthy subjects, 113 patients with various forms of arthritis and connective tissue diseases, and 65 patients with cancer. Gelatinase A was also measured in these patients using specific polyclonal and monoclonal antibodies to gelatinase A in an ELISA: RESULTS: The plasma concentration of stromelysin-1 (X +/- SEM) was significantly increased (p < 0.001) in patients with rheumatoid arthritis (RA) (187 +/- 14 ng/ml) and systemic lupus erythematosus (SLE) (258 +/- 35 ng/ml) as compared to both healthy control subjects (50 +/- 4 ng/ml) or patients with cancer (61 +/- 20 ng/ml). Plasma stromelysin-1 was also significantly increased in smaller groups of men with osteoarthritis (OA) and gout. In contrast, plasma concentrations of gelatinase A were not significantly increased in patients with RA, OA or gout. In healthy subjects, the concentration of stromelysin-1 was significantly higher in men than women. No correlation was noted between plasma stromelysin-1 levels and age. CONCLUSION: The detection of elevated plasma levels of stromelysin-1 in patients with RA is consistent with increased stromelysin-1 concentrations in inflamed synovial tissues in this disease. The origin of increased plasma stromelysin-1 in SLE is speculative. Measurement of plasma stromelysin-1 may be useful in the diagnosis and management of patients with various forms of arthritis.

Adult↗
PubMed1994

Detailed immunohistologic evaluation of a methotrexate-induced nodule.

Accelerated nodulosis in patients with rheumatoid arthritis who are receiving methotrexate has become a well-recognized phenomenon, and it appears to occur in both individuals with seropositive and seronegative findings. No histologic differences permit a distinction between seronegative and seropositive nodulosis--either occurring during the natural history of rheumatoid arthritis or when "induced" by methotrexate. We examined such a nodule in a man with seronegative rheumatoid arthritis. Results of immunofluorescence examination were not contributory, but studies of the inflammatory cell populations within the nodule showed 5% of the cells to be lymphocytes with a CD4/CD8 ratio of 25:1. Of the total mononuclear cells, 85% were reactive for Leu-10 (HLA-DQ) and 95% were reactive for HLA-DR, and about 75% of the macrophages were reactive for CD4+. The strong expression of CD4, in conjunction with macrophage markers, and the high T-helper/suppression ratio are of note. We discuss the implications of these findings and the role that they play in the pathogenesis of methotrexate-induced nodules.

Arthritis, Rheumatoid↗
PubMed1993

Reactive oxygen species activate and tetracyclines inhibit rat osteoblast collagenase.

Recent studies have demonstrated that tetracyclines (TCs) scavenge reactive oxygen species (ROS). Hypochlorous acid (HOCl), an ROS produced by neutrophils, has been shown to activate neutrophil procollagenase. The objective of the present study was to determine whether (1) HOCl also activated osteoblast procollagenase and (2) TCs inhibited this enzyme in the presence of HOCl. HOCl (5 microM) activated the proenzyme approximately sixfold (P < 0.01) from the medium of PTH-treated UMR-106-01 osteoblastic osteosarcoma cells as determined by functional collagenase assay (3H-methyl-labeled collagen substrate). Doxycycline (50-400 microM) and chemically modified tetracycline, CMT-1 (100-400 microM), significantly inhibited collagenase activity 50-90% and 40-80%, respectively, in the presence of 5 microM HOCl. Concentrations of 6-25 microM doxycycline and 10-50 microM CMT-1 had no significant effect. Furthermore, an excess concentration of cation (50 mM CaCl2 or 50 microM ZnCl2) added to the incubation mixtures containing either doxycycline or CMT-1 did not restore collagenase activity, as demonstrated by SDS-PAGE-fluorography. These data suggested that TCs reduced available HOCl and thus prevented the hypochlorous acid conversion of the osteoblast proenzyme to active collagenase. TCs may have therapeutic potential in the treatment of periodontitis and other diseases by several mechanisms that inhibit pathologic collagen breakdown.

Animals↗
PubMed1993

Effect of tetracyclines which have metalloproteinase inhibitory capacity on basal and heparin-stimulated bone resorption by chick osteoclasts.

Several tetracyclines (TETs) are potent inhibitors of collagenase (CGase) and can inhibit connective tissue degradation in a variety of inflammatory and degenerative disorders. The role of CGase in bone resorption by osteoclasts (OC) remains unclear. Disaggregated OCs from chick embryos were cultured for 24 h on devitalized bovine cortical bone +/- heparin in the presence of various TETs. Doxycycline (Dox) inhibited pit formation in a dose-dependent manner. CMT, a TET derivative which inhibits matrix metalloproteinases (MMPs) but is not antimicrobial, also inhibited chick OC bone resorption. Heparin markedly stimulated bone resorption at 5 micrograms/ml, which was reversed by Dox, 5 micrograms/ml. TETs can reversibly inhibit both basal and heparin-stimulated bone resorption by chick OCs. These findings suggest that MMPs may play a role in osteoclastic bone resorption, and that safe and effective inhibitors of MMPs, including certain TETs, might have a potential therapeutic role.

Animals↗
PubMed1992

Tetracyclines inhibit intracellular muscle proteolysis in vitro.

Tetracycline antibiotics (TETs) have a recently discovered novel action: inhibition of extracellular metalloproteinase activity, especially that of collagenase and gelatinase. This property, now confirmed in 8 different laboratories using > 40 tissue sources, includes natural and semi-synthetic TETs as well as a chemically modified TET (CMT) devoid of antimicrobial activity. We have used 14C-Tyr biosynthetically labelled intracellular proteins in L-6 myoblast culture as a test system to assess intracellular proteolysis. Starvation accelerates proteolysis, which can be suppressed by agents such as insulin or serum. Minocycline, doxycycline, and CMT all retarded the rate of intracellular protein degradation in a dose dependent manner. These agents also demonstrated marked synergism with insulin. A CMT derivative (pyrazole) stripped of one of its metal chelation sites and lacking anti-collagenase activity, also lost its antiproteolytic effect. CMT at physiologic concentrations (< or = 5 micrograms/ml) had no effect on protein synthesis, but at 15 micrograms/ml (pharmacologic), a suppressive effect was noted. These findings demonstrate that TETs can inhibit protein degradation as well as synthesis in a mammalian muscle-derived cell line.

Animals↗
PubMed1992

Inhibition of enzymatic activity of phospholipases A2 by minocycline and doxycycline.

Extracellular phospholipases A2 play an important role in articular and extra-articular inflammatory processes. Secretory non-pancreatic phospholipase A2 (PLA2) has been implicated in the pathogenesis of articular inflammation in rheumatoid arthritis, whereas pancreatic PLA2 contributes to the tissue damage associated with acute pancreatitis. Since in experimental models lipophilic tetracyclines such as minocycline and doxycycline are antiinflammatory, we examined their effects on PLA2 activity using two assay systems in vitro. We found that minocycline and to a lesser degree doxycycline were markedly inhibitory to both pancreatic and non-pancreatic PLA2. Using [14C]oleic acid labeled Escherichia coli membrane phospholipids as substrate, the IC50 values for minocycline and doxycycline were 3.6 x 10(-5) M (18 micrograms/mL) and 0.98 x 10(-4) M (47 micrograms/mL), respectively. In a scooting mode assay using the synthetic phospholipid 1-palmitoyl-2-(10-pyrenedecanoyl)-3-L-phosphatidylmethanol as substrate, IC50 values for minocycline were 5 microM (2.47 micrograms/mL) for non-pancreatic PLA2 and 8 microM (3.95 micrograms/mL) for pancreatic PLA2. Addition of excess calcium up to 50 mM did not reverse the inhibitory activity of tetracyclines. We conclude that lipophilic tetracyclines inhibit PLA2, probably by interaction with the substrate, and may be a useful adjunct in the therapy of inflammatory conditions in which PLA2 is implicated pathogenetically.

Animals↗
PubMed1992

Tetracyclines suppress matrix metalloproteinase activity in adjuvant arthritis and in combination with flurbiprofen, ameliorate bone damage.

Tetracyclines are potent inhibitors of 2 major matrix metalloproteinases which have been implicated in connective tissue degradation: collagenase and Type IV collagenase/gelatinase. We directly identified these enzyme activities in extracts of inflamed paw tissue from rats with adjuvant arthritis. Oral tetracycline therapy suppressed metalloproteinase activity in arthritic tissue, but even very high doses failed to exhibit substantial antiinflammatory efficacy (reduced joint swelling and paw diameter). Flurbiprofen, a conventional nonsteroidal antiinflammatory drug, reduced inflammatory indices as expected. The combination of the 2 agents administered orally completely inhibited collagenase activity, significantly inhibited gelatinase activity and produced substantial normalization of radiographic joint damage, far greater than either drug alone. Tetracycline inhibition curves in vitro suggest that the collagenase in this tissue is not of fibroblast origin. Tetracycline derivatives might be useful adjuncts to prevention of tissue damage in chronic inflammatory arthritides.

Administration, Oral↗
PubMed1992

The philatelic rheumatologist.

Many postage stamps illustrate themes, persons, or topics with rheumatologic connections. Examples include scientists from related disciplines, victims of rheumatic diseases, drugs used for arthritis, and stamps commemorating events such as World Rheumatism Year. A brief orientation to postage stamps and philately is given, and a small collection of rheumatologically related stamps is illustrated.

Global Health↗