tetracycline and sancycline

Melanogenesis is regulated by melanocytes, which synthesize the pigment melanin inside melanosomes; these melanosomes are exported through dendritic extensions to adjacent keratinocytes and result in skin coloration. Chemically modified tetracyclines (CMTs) are nonantimicrobial tetracyclines that retain the capacity to inhibit matrix metalloproteinases (MMPs) and have shown several biological benefits; in particular, CMT-3 [(4-dedimethylamino sancycline (SAN)] has emerged as a candidate for therapeutic benefits in our previous studies. However, to date, studies of the effects of CMT-3 or SAN on melanogenesis are lacking. We have previously reported the anti-melanogenic activity of CMT-308 (the 9-amino derivative of CMT-3). Herein, we have compared the three tetracycline analogs, doxycycline (DOX), SAN, and CMT-3, for their effects on melanogenesis using B16F10 mouse melanoma cells and have validated results in primary human melanocytes (HEMn-DP). DOX did not show any significant effects on intracellular melanin or melanosome export in DP cells while SAN was cytotoxic at high doses but without effects on melanogenesis at lower doses. However, CMT-3 showed a robust suppression of dendricity parameters (dendrite number, dendrite length, and proportion of dendritic cells) in DP cells which was associated, at least in part, with a significant reduction of intracellular tyrosinase activity. In spite of its inhibition of tyrosinase activity, CMT-3 had no significant effects on intracellular melanin levels, suggesting that it selectively targets melanosome export. Our results demonstrate a unique structure-activity relationship (SAR) for the effects of these compounds on melanogenesis and support the conclusion that removal of the 4-dimethylamino moiety confers the selective capacity to suppress melanosome export. Collectively, these results indicate that CMT-3 might be a candidate for diminishing hyperpigmentation skin disorders.

Topics: Animals; Anti-Bacterial Agents; Doxycycline; Humans; Melanins; Melanocytes; Mice; Monophenol Monooxygenase; Tetracycline; Tetracyclines

A mixture of five tetracycline (TC) derivatives: minocycline (MC), demeclocycline (DMCTC), doxycycline (DC), and sancycline (SC), as well as each TC derivative from its main degradation product were separated by capillary zone electrophoresis (CZE). The influence of the pH and the concentration and nature of the background electrolyte (BGE) on the separations was investigated. Ethylenediaminetetraacetic acid (EDTA; 1 mM) was used as additive in a 25 mM phosphate buffer (pH 2.3) because this BGE enabled the rapid separation of the TC derivatives and of each TC derivative from its respective degradation product in less than 6 min. After optimization of the separation conditions, the analytical characteristics of the method were investigated. The parameters involved were linearity, precision (repeatability and reproducibility), and limits of detection (LODs). LODs obtained for the five TC derivatives studied were about 3 microg/mL. Finally, the CZE method developed was applied to study the stability of TC derivatives and to analyze the TC derivative content in three different pharmaceutical preparations.

Topics: Anti-Bacterial Agents; Demeclocycline; Doxycycline; Electrophoresis, Capillary; Minocycline; Molecular Structure; Pharmaceutical Preparations; Tetracycline; Tetracyclines; Time Factors

A thin-layer chromatography (TLC) method using UV and fluoresecence densitometry is described for the assay and purity control of minocycline (MC). With a mobile phase dichloromethane-methanol-water (57:35:8, v/v/v) and a silica gel thin-layer, previously sprayed with 10% m/v sodium edetate adjusted to pH 9.0, 4-epiminocycline and 7-didemethylminocycline were well separated from MC and from each other, 7-monodemethylminocycline and 6-deoxy-6-demethyltetracycline (6-DODMTC) were not separated from each other and were only partially separated from minocycline. 6-DODMTC was selectively determined by fluorescence densitometry, while quantification of other impurities and the assay of MC were performed by UV densitometry. Results obtained with qualitative TLC were compared with those obtained by a liquid chromatography (LC) method using a poly(styrene-divinylbenzene) copolymer stationary phase. The correlation coefficient for TLC and LC results was > 0.999. For TLC the relative standard deviation for the assay of MC at 1.25 mg ml-1 was < 3.0% (n = 4), while for LC it was < 1.0% (n = 4).

Topics: Anti-Bacterial Agents; Chromatography, Liquid; Chromatography, Thin Layer; Densitometry; Fluorescence; Minocycline; Tetracycline; Ultraviolet Rays

Endometriosis appears under a wide array of morphologies, and early microscopic disease escapes visual inspection. To improve endoscopic diagnosis, we studied the optical properties of ectopic endometrial tissue, in particular laser-induced fluorescence. Photosensitive drugs were used to obtain a selective signal. Five groups of four rabbits underwent surgical induction of endometriosis and were treated with estrogens for 5 weeks to stimulate growth of the implants. Intramuscular injections of vehicle, tetracycline hydrochloride, 6-demethyl-6-deoxytetracycline hydrochloride, tamoxifen citrate, and clomiphene citrate were given 24 hours before exposure of the tissues to argon-ion laser (351.1 nm + 363.8 nm; power density approximately 1.5 mW/cm2). Fluorescence was documented on photographic film. In controls, peritoneum and ovaries showed a dim, white-yellow fluorescence, whereas other tissues exhibited blue tones. Animals treated with tetracycline hydrochloride or tamoxifen citrate showed yellow fluorescence of active endometrial implants and the uterotomy site. Two implants, histologically without viable glandular tissue, did not fluoresce. Treatment with 6-demethyl-6-deoxytetracycline hydrochloride yielded signals of lower intensity. Clomiphene citrate caused fluorescence of the uterotomy site only. This experiment demonstrates that, of the compounds used, tamoxifen is the best selective photoenhancer for endometriotic implants and clomiphene is best for the uterotomy site. This study establishes the potential of these drugs for photoradiation diagnosis and possible treatment of diseases involving ectopic endometrium.

Topics: Animals; Clomiphene; Endometriosis; Female; Fluorescence; Lasers; Pelvic Neoplasms; Rabbits; Tamoxifen; Tetracycline; Tetracyclines

Effects of metal ion-tetracycline (TC) interactions on both gastrointestinal absorption and pharmacological activity of these drugs are well documented. In particular, recent simulation studies based on newly determined complex stability constants have drawn attention to the potential influence of Ca2+ and Mg2+ ions on the bioavailability of various TC derivatives in blood plasma. Contrary to previous thoughts, it was demonstrated in these studies that the fraction of antibiotic not bound to proteins almost exclusively occurs as calcium and magnesium complexes. Among this fraction, predominant binuclear species are electrically charged, and as such cannot passively diffuse through cell membranes. It was thus postulated that the partial blocking of one of the potential coordination sites of the TC molecule, which would favor the formation of neutral mononuclear complexes, should result in a better tissue penetration of the drug. Such correlations were recently established for specific derivatives. Before possible modifications of the TC molecule can be envisaged, it is necessary that all the chelating sites involved in the relevant complexes be properly assigned. As tetracyclines are very complex ligands, the present paper first deals with the coordination of calcium and magnesium with two simpler parent substances, i.e., 4-dedimethylamino-tetracycline (DTC) and 6-desoxy-6-demethyl-tetracycline (DSC). After the quantitative investigation of the proton and metal complex equilibria involved, UV and circular dichroism spectroscopies are used to study the corresponding structural aspects. In DTC complexes, the BCD ring system acts as the exclusive coordination site for both metals. For DSC, however, the N4 atom plays a leading role in the metal binding and would be the only donor involved in 1:1 species; in ML2 complexes, the second ligand is thought to bind through the BCD ring system.

Topics: Calcium; Circular Dichroism; Humans; Magnesium; Potentiometry; Spectrophotometry; Tetracycline; Tetracyclines

Topics: Anti-Bacterial Agents; Chemistry, Pharmaceutical; Protein Synthesis Inhibitors; Research; Tetracycline; Tetracyclines