ABSTRACT
Lysosomes are membrane-bound subcellular organelles involved in the degradation of macromolecules and pathogens in diverse processes, including endocytosis, phagocytosis, and autophagy. A red fluorescent probe was developed that is selectively sequestered in acidic organelles. U20S cells pretreated with 64 microM chloroquine for as little as 5 h show a dramatic increase in lysosome-like vesicle number and volume. The probe can be employed for highlighting lysosome-like organelles under conditions wherein cells produce vacuoles that contain most of the degradative enzymes of the lysosome but are not as acidic as the parent organelle. Using a conventional fluorescence microplate reader, the half-maximal effective concentration (EC(50)) of chloroquine was estimated. The high Z' score obtained using the assay demonstrated excellent signal-to-noise ratios. The fluorescence microplate assay was successfully employed to screen a small-molecule compound library for agents that increase lysosomal volume and number. One potential application of the new assay is in the toxicology portion of preclinical drug safety assessment (ADME-Tox) workflows, using in vitro cell culture models to aid in the drug development process.
Subject(s)
Drug Evaluation, Preclinical/instrumentation , Drug Evaluation, Preclinical/methods , Luminescent Measurements/methods , Pharmaceutical Preparations/analysis , Small Molecule Libraries/toxicity , Vacuoles/drug effects , Vacuoles/metabolism , Cell Line, Tumor , Cell Survival/drug effects , Chloroquine/pharmacology , Humans , Luminescent Measurements/instrumentation , Macrolides/pharmacology , Microscopy, Fluorescence , Phospholipids/metabolism , Small Molecule Libraries/analysisABSTRACT
The dihydroisoxazole nucleosides as well as their phosphonate derivatives were efficiently prepared via 1,3-dipolar cycloaddition reactions of nitrile oxides with corresponding vinyl nucleoside bases for antiviral studies.
ABSTRACT
Enantioselective syntheses of beta-D-isoxazolidinyl pyrimidine and purine nucleosides are described. Michael addition of N-methylhydroxylamine to alpha,beta-unsaturated esters was investigated. Both E- and Z-esters 10E and 10Z produced the same intermediates which were cyclized to isoxazolidin-5-ones 8 with high diastereoselectivity. The major isoxazolidin-5-one 8a was reduced and acetylated to acetate 11 for the preparation of nucleosides. The coupling reaction of acetate 11 with silylated thymine, uracil, and N(4)-benzoylcytosine using TMSOTf as a Lewis acid yielded the corresponding nucleoside derivatives. The related purine analogue was produced by the BF(3).Et(2)O-catalyzed condensation of acetate 11 with silylated 6-chloropurine. The predominant formation of the cis isomers for both pyrimidine and purine analogues was unexpected and the reaction mechanism was investigated. The nucleoside intermediates were converted to the corresponding 1,2-diols, which were latter oxidized and reduced to the desired monoalcohol products such as 14, 16, 19, and 24.
