minocycline and 4-des-dimethylaminotetracycline

We report the effects of tetracycline analogues on cytosolic Ca2+ transients resulting from application of ionic nickel (Ni2+), a potent surrogate agonist of the osteoclast Ca2+ "receptor". Preincubation with minocycline (1 mg/l) or a chemically modified tetracycline, 4-dedimethyl-aminotetracycline (CMT-1) (1 or 10 mg/l), resulted in a significant attenuation of the magnitude of the cytosolic [Ca2+] response to an application of 5 mM-[Ni2+]. Preincubation with doxycycline (1 or 10 mg/l) failed to produce similar results. In addition, application of minocycline alone (0.1-100 mg/l) resulted in a 3.5-fold elevation of cytosolic [Ca2+]. The results suggest a novel action of tetracyclines on the osteoclast Ca2+ "receptor".

Topics: Animals; Calcium; Cytosol; Doxycycline; Minocycline; Nickel; Osteoclasts; Rats; Receptors, Cytoplasmic and Nuclear; Tetracycline

We report the effects of the tetracycline analogues 4-dedimethylaminotetracycline (CMT-1) and minocycline on osteoclast spreading and motility. Both agents influenced the morphometric descriptor of cell spread area, rho, producing cellular retraction or an R effect (half-times: 30 and 44 minutes for CMT-1 and minocycline, respectively). At the concentrations employed, the tetracycline-induced R effects were significantly slower than, but were qualitatively similar to, those resulting from Ca2+ "receptor" activation through the application of 15 mM-[Ca2+] (slopes: -1.25, -0.18, and -4.40/minute for 10 mg/l-[CMT-1], 10 mg/l-[minocycline] and 15 mM-[Ca2+], respectively). In contrast, the same tetracycline concentrations did not influence osteoclast margin ruffling activity as described by mu, a motility descriptor known to be influenced by elevations of cellular cyclic AMP. Thus, the tetracyclines exert morphometric effects comparable to changes selectively activated by occupancy of the osteoclast Ca2+ "receptor" which may act through an increase in cytosolic [Ca2+].

Topics: Animals; Calcium; Image Processing, Computer-Assisted; Linear Models; Microscopy, Phase-Contrast; Minocycline; Osteoclasts; Rats; Rats, Wistar; Receptors, Cytoplasmic and Nuclear; Tetracycline

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.

Topics: Administration, Oral; Animals; Arthritis, Experimental; Bone and Bones; Cartilage, Articular; Collagenases; Dose-Response Relationship, Drug; Doxycycline; Drug Therapy, Combination; Electrophoresis, Polyacrylamide Gel; Extracellular Matrix; Flurbiprofen; Matrix Metalloproteinase 9; Metalloendopeptidases; Minocycline; Rats; Tetracycline; Tetracyclines

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.

Topics: Animals; Carbon Radioisotopes; Cell Line; Doxycycline; Insulin; Kinetics; Minocycline; Muscles; Proteins; Radioisotope Dilution Technique; Recombinant Proteins; Tetracycline; Tetracyclines; Tyrosine

Diabetes induces osteopenia, which is characterized by a deficiency of osteoid and decreased activity of osteoblasts. We recently found that tetracyclines prevent the loss of osteoid and bone matrix and the degeneration of osteoblasts in diabetic rats by a mechanism independent of their antimicrobial efficacy. However, bone remodeling requires the activity of osteoclasts as well as osteoblasts. To determine the in vivo effects of tetracycline on osteoclasts in long bones, either a tetracycline (minocycline, TC) or its chemically modified non-antibiotic analogue (CMT), 4-de-dimethylaminotetracycline, was administrated daily to streptozotocin-induced diabetic rats by oral intubation. After 21 days, the rats were perfusion-fixed with a mixture of formaldehyde and glutaraldehyde, and the humeri were dissected and processed for ultracytochemical demonstration of acid trimetaphosphatase (ACPase) activity. In untreated non-diabetic (control) rats, the osteoclasts at the zone of provisional ossification exhibited abundant mitochondria and cisterns of rough endoplasmic reticulum (RER) throughout the cytoplasm, prominent stacks of Golgi membranes, and lysosomes in the perinuclear cytoplasm, and numerous various pale vacuoles in the cytoplasmic area adjacent to well-developed ruffled border. Intense ACPase activity was observed in the Golgi saccules, lysosomes, pale vacuoles, and the extracellular canals of ruffled border. The reaction products were also noted along the resorbing bone surfaces associated with the osteoclast ruffled border. The osteoclasts in the untreated diabetic rats showed a cytoplasmic organization similar to that of the non-diabetic control rats, but showed little or no ruffled border which was replaced by a broad clear zone in some of these cells. However, most of the osteoclasts on bone matrix in the diabetics were devoid of both a ruffled border and a clear zone. ACPase activity was detected in the osteoclast cytoplasm of diabetic rat, as in the controls, but to a much lesser extent along the broad clear zone facing the resorbing bone surfaces. The osteoclasts in TC-treated diabetic rats possessed both a clear zone and a small ruffled border. However, in some cases, they lacked both structures reminiscent of the untreated diabetic cells. The osteoclasts of CMT-treated diabetic rats exhibited structural and enzymatic features essentially identical to those of the non-diabetic control rats. These results suggest that the diabetes-induced osteo

Topics: Acid Phosphatase; Administration, Oral; Animals; Diabetes Mellitus, Experimental; Male; Microbial Collagenase; Microscopy, Electron; Minocycline; Osteoclasts; Rats; Rats, Inbred Strains; Streptozocin; Tetracycline

Tetracyclines (including the semi-synthetic analogues, minocycline and doxycycline) are considered useful adjuncts in periodontal therapy because they suppress Gram-negative periodontopathogens. Recently, these antibiotics were found to inhibit mammalian collagenase activity, a property which may also be of therapeutic value. It has been suggested that the anti-collagenase properties of the tetracyclines are independent of their antibiotic efficacy. To advance this hypothesis further, we chemically converted tetracycline hydrochloride to its non-antimicrobial analogue, de-dimethylaminotetracycline. This chemically-modified tetracycline (CMT), although no longer an effective antibiotic, was found to inhibit the in vitro activity of collagenase from partially purified extracts of human rheumatoid synovial tissue and rachitic rat epiphysis. In a preliminary in vivo study, pathologically-excessive collagenase in skin and gingiva was induced by rendering adult male rats diabetic, and the oral administration of CMT to these rats significantly reduced the excessive collagenase activity in both tissues. Moreover, CMT administration did not affect the severe hyperglycemia in these rats but did prevent, at least in part, the diabetes-induced loss of body weight, skin weight, and skin collagen mass; these effects suggest a lack of toxicity in this animal model. A proposed clinical advantage of CMT over conventional tetracyclines, in the treatment of diseases characterized by excessive collagenolytic activity, is the lack of development of antibiotic-resistant micro-organisms during prolonged use. However, the consideration of clinical trials to support this hypothesis must await further laboratory and extensive toxicity tests.

Topics: Animals; Arthritis, Rheumatoid; Cartilage, Articular; Diabetes Mellitus, Experimental; Humans; Male; Metronidazole; Microbial Collagenase; Minocycline; Rats; Rats, Inbred Strains; Rickets; Skin; Streptozocin; Tetracycline; Tetracyclines