Green tea polyphenols are reported to possess substantial antiinflammatory and chemopreventive properties. However, the molecular mechanism of chemopreventive activity of green tea polyphenols is not fully understood. An abnormally elevated level of cyclooxygenase-2 (COX-2) is implicated in the pathogenesis of carcinogenesis. In the present study, we found that pretreatment of the green tea extract enriched with catechin and epigallocatechin gallate (EGCG) by gavage inhibited COX-2 expression induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) in mouse skin. Similarly, EGCG downregulated COX-2 in TPA-stimulated human mammary epithelial cells (MCF-10A) in culture. To further elucidate the underlying mechanism of COX-2 inhibition by green tea extract and EGCG, we examined their effects on the activation of extracellular signal-regulated protein kinase (ERK) and p38 mitogen-activated protein kinase (MAPK), which are upstream enzymes known to regulate COX-2 expression in many cell types. Pretreatment with EGCG as well as green tea extract caused a decrease in the activation of ERK. In addition, EGCG inhibited the catalytic activity of ERK and p38 MAPK, suggesting that these signal-transducing enzymes could be potential targets for previously reported antitumor promoting activity of EGCG.
Chitosadcalcium-alginate beads were prepared by a coacervation method in aqueous medium. Their swelling properties and morphologies were studied. Complexed beads with a mean diameter of 500 pm were obtained by dropwise addition of a sodium alginate solution into a chitosan-calcium chloride solution. From scanning electron microscopic studies, we observed that chitosan modifies the morphology of calcium-alginate beads. The swelling properties of chitosadcalcium-alginate beads are different from those of calcium-alginate beads. In the case of calcium-alginate beads, the swelling volume increases as the pH of the medium increases. However, chitosadcalcium-alginate beads show a maximum swelling volume at pH 9.0.
This study introduces a new approach for producing highly monosized polymer microcapsules. The technique employs an impressive process in which the solute, dissolved freely in a solvent, is diffused uniformly into the preexisting monosized polymer particles in the form of a fine emulsion. The solvent is then eliminated, resulting consequently in solute-loaded polymer microcapsules. We named it a solute co-diffusion method, SCM. The loading efficiency of the solute was predicted successfully by a thermodynamic equation. In the experiment, the indomethacin-loaded poly(methyl methacrylate) microparticles were produced via SCM. From our results, SCM is expected to expand significantly the drug-loading technology in related fields.
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