ABSTRACT
6-Hydroxydopamine (6-OHDA), a neurotoxic substrate of the dopamine transporter (DAT), is widely used in Parkinson's disease models. However, the molecular mechanisms underlying 6-OHDA's selectivity for dopamine neurons and the injurious sequelae that it triggers are not well understood. We tested whether ectopic expression of DAT induces sensitivity to 6-OHDA in non-dopaminergic rat cortical neurons and evaluated the contribution of voltage-dependent potassium channel (Kv)-dependent apoptosis to the toxicity of this compound in rat cortical and midbrain dopamine neurons. Cortical neurons expressing DAT accumulated dopamine and were highly vulnerable to 6-OHDA. Pharmacological inhibition of DAT completely blocked this toxicity. We also observed a p38-dependent Kv current surge in DAT-expressing cortical neurons exposed to 6-OHDA, and p38 antagonists and Kv channel blockers were neuroprotective in this model. Thus, DAT-mediated uptake of 6-OHDA recruited the oxidant-induced Kv channel dependent cell death pathway present in cortical neurons. Finally, we report that 6-OHDA also increased Kv currents in cultured midbrain dopamine neurons and this toxicity was blocked with Kv channel antagonists. We conclude that native DAT expression accounts for the dopamine neuron specific toxicity of 6-OHDA. Following uptake, 6-OHDA triggers the oxidant-associated Kv channel-dependent cell death pathway that is conserved in non-dopaminergic cortical neurons and midbrain dopamine neurons.
Subject(s)
Adrenergic Agents/pharmacology , Dopamine Plasma Membrane Transport Proteins/physiology , Neurons/drug effects , Oxidopamine/pharmacology , Potassium Channels, Voltage-Gated/physiology , Analysis of Variance , Animals , Apoptosis/drug effects , Cells, Cultured , Cerebral Cortex/cytology , Dopamine/metabolism , Dose-Response Relationship, Drug , Drug Interactions , Electric Stimulation/methods , Embryo, Mammalian , Green Fluorescent Proteins/metabolism , Membrane Potentials/drug effects , Membrane Potentials/physiology , Membrane Potentials/radiation effects , Neurons/physiology , Patch-Clamp Techniques/methods , Potassium Channel Blockers/pharmacology , Rats , Tetraethylammonium/pharmacology , Transfection/methodsABSTRACT
3-Acetyl analogues of thiolactomycin, a thiotetronic acid natural product, were synthesized and profiled against livestock pathogens. Some analogues showed improved activity over thiolactomycin against Staphylococcus aureus and comparable activity against Pasteurella multocida. Several semisynthetically modified analogues of thiolactomycin showed no improvement in activity over thiolactomycin.
Subject(s)
Anti-Bacterial Agents/chemical synthesis , Thiophenes/chemical synthesis , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Microbial Sensitivity Tests , Staphylococcus aureus/drug effects , Structure-Activity Relationship , Thiophenes/chemistry , Thiophenes/pharmacologyABSTRACT
Some novel 6-fluoro-7-substituted-1,4-dihydro-4-oxoquinoline-3-carboxylic acids have been prepared. At the N-1 position "standard" substitution was employed with the ethyl, cyclopropyl, and p-fluorophenyl groups being used. At C-7 the introduction of some novel piperazines was made. Most notably, 2-(fluoromethyl)piperazine (10) and hexahydro-6-fluoro-1H-1,4-diazepine (16, fluorohomopiperazine) at the quinolone C-7 position produced products with similar in vitro antibacterial activity as the ciprofloxacin reference. The in vivo efficacy of 1-cyclopropyl-6-fluoro-7-[3-(fluoromethyl)piperazinyl]-1,4-dihydro-4- oxoquinoline-3-carboxylic acid (20) was excellent with better oral absorption than ciprofloxacin (2).
Subject(s)
Anti-Bacterial Agents , Anti-Infective Agents/pharmacology , Piperazines/pharmacology , 4-Quinolones , Animals , Anti-Infective Agents/chemical synthesis , Anti-Infective Agents/therapeutic use , Chemical Phenomena , Chemistry , Enterobacter/drug effects , Enterococcus faecalis/drug effects , Escherichia coli/drug effects , Escherichia coli Infections/drug therapy , Female , Mice , Molecular Structure , Piperazines/chemical synthesis , Piperazines/therapeutic use , Proteus/drug effects , Pseudomonas aeruginosa/drug effects , Staphylococcal Infections/drug therapy , Staphylococcus aureus/drug effects , Structure-Activity RelationshipABSTRACT
A series of polyfluoro-3-quinolonecarboxylic acids have been synthesized and their in vitro antibacterial activity evaluated. The desired 7-(substituted amino) derivatives were prepared from the 5,6,7,8-tetrafluoroquinolone acids. Conversely, amine displacement occurred primarily at the 5-position when the ester was used. Structure-activity studies indicated that the antibacterial activity was greatest when the N-1 substituent was cyclopropyl and the 7-substituent was 4-methyl-1-piperazinyl. All 5-(substituted amino) derivatives showed poor in vitro activity.
