minocycline and Osteoarthritis

To evaluate the capacity of doxycycline and minocycline to inhibit NO production and N-nitrosation reactions in vitro.. Synovial cells obtained from 6 patients with osteoarthritic joint disease were incubated for 24 hours with (i) or without (ii) IL-1beta (1 ng/ml), TNF-alpha (500 pg/ml), IFN-gamma (10(4) U/ml) plus minocycline or doxycycline (10(-4) to 10(-6) M), diclofenac (10(-5) M), or cortisol (10(-5) M). Nitrosothiols were determined by fluorimetry, nitrite by the Griess reaction, nitrate by a spectrophotometric assay using oxidation by nitrate reductase and iNOS by immunoblotting.. After 24 hours of stimulation, the level of NO production was much higher than that in untreated cells: about 5.5 times higher for nitrosothiols, 5.2 times higher for nitrate and about 3.5 times higher for nitrite. Doxycycline and minocycline induced a dose-dependent decrease in the production of nitrosothiols, nitrate and nitrite, and inhibited the synthesis of the iNOS protein. Doxycycline and minocycline inhibited the N-nitrosation reaction of DAN effectively, with IC50 values close to 100 microM. Diclofenac and cortisol had no effect.. This study provides new information on the mechanism by which tetracyclines exert anti-inflammatory effects, via inhibiting nitrosothiols.

Topics: Anti-Bacterial Agents; Anti-Inflammatory Agents; Anti-Inflammatory Agents, Non-Steroidal; Cell Survival; Cells, Cultured; Cytokines; Doxycycline; Humans; Immunoblotting; Minocycline; Nitrates; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitrites; Osteoarthritis; Ovalbumin; S-Nitrosothiols; Serine Proteinase Inhibitors; Steroids; Synovial Membrane; Tetracyclines

Tetracyclines (doxycycline and minocycline) augmented (one- to twofold) the PGE2 production in human osteoarthritis-affected cartilage (in the presence or absence of cytokines and endotoxin) in ex vivo conditions. Similarly, bovine chondrocytes stimulated with LPS showed (one- to fivefold) an increase in PGE2 accumulation in the presence of doxycycline. This effect was observed at drug concentrations that did not affect nitric oxide (NO) production. In murine macrophages (RAW 264.7) stimulated with LPS, tetracyclines inhibited NO release and increased PGE2 production. Tetracycline(s) and L-N-monomethylarginine (L-NMMA) (NO synthase inhibitor) showed an additive effect on inhibition of NO and PGE2 accumulation, thereby uncoupling the effects of tetracyclines on NO and PGE2 production. The enhancement of PGE2 production in RAW 264.7 cells by tetracyclines was accompanied by the accumulation of both cyclooxygenase (COX)-2 mRNA and cytosolic COX-2 protein. In contrast to tetracyclines, L-NMMA at low concentrations (< or = 100 microM) inhibited the spontaneous release of No in osteoarthritis-affected explants and LPS-stimulated macrophages but had no significant effect on the PGE2 production. At higher concentrations, L-NMMA (500 microM) inhibited NO release but augmented PGE2 production. This study indicates a novel mechanism of action of tetracyclines to augment the expression of COX-2 and PGE2 production, an effect that is independent of endogenous concentration of NO.

Topics: Animals; Cartilage, Articular; Cattle; Cell Line; Cyclooxygenase 2; Cytokines; Dinoprostone; Doxycycline; Endotoxins; Humans; Isoenzymes; Macrophages; Membrane Proteins; Mice; Minocycline; Nitric Oxide; Nitric Oxide Synthase; omega-N-Methylarginine; Organ Culture Techniques; Osteoarthritis; Prostaglandin-Endoperoxide Synthases; RNA, Messenger; Tetracycline; Up-Regulation

Tetracyclines have recently been shown to have "chondroprotective" effects in inflammatory arthritides in animal models. Since nitric oxide (NO) is spontaneously released from human cartilage affected by osteoarthritis (OA) or rheumatoid arthritis in quantities sufficient to cause cartilage damage, we evaluated the effect of tetracyclines on the expression and function of human OA-affected nitric oxide synthase (OA-NOS) and rodent inducible NOS (iNOS). Among the tetracycline group of compounds, doxycycline > minocycline blocked and reversed both spontaneous and interleukin 1 beta-induced OA-NOS activity in ex vivo conditions. Similarly, minocycline > or = doxycycline inhibited both lipopolysaccharide- and interferon-gamma-stimulated iNOS in RAW 264.7 cells in vitro, as assessed by nitrite accumulation. Although both these enzyme isoforms could be inhibited by doxycycline and minocycline, their susceptibility to each of these drugs was distinct. Unlike acetylating agents or competitive inhibitors of L-arginine that directly inhibit the specific activity of NOS, doxycycline or minocycline has no significant effect on the specific activity of iNOS in cell-free extracts. The mechanism of action of these drugs on murine iNOS expression was found to be, at least in part, at the level of RNA expression and translation of the enzyme, which would account for the decreased iNOS protein and activity of the enzyme. Tetracyclines had no significant effect on the levels of mRNA for beta-actin and glyceraldehyde-3-phosphate dehydrogenase nor on levels of protein of beta-actin and cyclooxygenase 2 expression. These studies indicate that a novel mechanism of action of tetracyclines is to inhibit the expression of NOS. Since the overproduction of NO has been implicated in the pathogenesis of arthritis, as well as other inflammatory diseases, these observations suggest that tetracyclines should be evaluated as potential therapeutic modulators of NO for various pathological conditions.

Topics: Animals; Arthritis, Rheumatoid; Cartilage; Cell Line; DNA Primers; Doxycycline; Enzyme Induction; Humans; Interferon-gamma; Kinetics; Lipopolysaccharides; Macrophages; Mice; Minocycline; Nitric Oxide Synthase; Organ Culture Techniques; Osteoarthritis; Polymerase Chain Reaction; Tetracyclines