ABSTRACT
Atypical dopamine reuptake inhibitors, such as modafinil, are used for the treatment of sleeping disorders and investigated as potential therapeutics against cocaine addiction and for cognitive enhancement. Our continuous effort to find modafinil analogues with higher inhibitory activity on and selectivity toward the dopamine transporter (DAT) has previously led to the promising thiazole-containing derivatives CE-103, CE-111, CE-123, and CE-125. Here, we describe the synthesis and activity of a series of compounds based on these scaffolds, which resulted in several new selective DAT inhibitors and gave valuable insights into the structure-activity relationships. Introduction of the second chiral center and subsequent chiral separations provided all four stereoisomers, whereby the S-configuration on both generally exerted the highest activity and selectivity on DAT. The representative compound of this series was further characterized by in silico, in vitro, and in vivo studies that have demonstrated both safety and efficacy profile of this compound class.
Subject(s)
Dopamine Plasma Membrane Transport Proteins/antagonists & inhibitors , Dopamine Uptake Inhibitors/pharmacology , Modafinil/analogs & derivatives , Modafinil/pharmacology , Serotonin and Noradrenaline Reuptake Inhibitors/pharmacology , Thiazoles/pharmacology , Animals , Dopamine Plasma Membrane Transport Proteins/metabolism , Dopamine Uptake Inhibitors/chemical synthesis , Dopamine Uptake Inhibitors/metabolism , Dopamine Uptake Inhibitors/pharmacokinetics , HEK293 Cells , Humans , Male , Modafinil/metabolism , Modafinil/pharmacokinetics , Molecular Docking Simulation , Molecular Structure , Norepinephrine Plasma Membrane Transport Proteins/antagonists & inhibitors , Protein Binding , Rats, Sprague-Dawley , Serotonin Plasma Membrane Transport Proteins/metabolism , Serotonin and Noradrenaline Reuptake Inhibitors/chemical synthesis , Serotonin and Noradrenaline Reuptake Inhibitors/metabolism , Serotonin and Noradrenaline Reuptake Inhibitors/pharmacokinetics , Stereoisomerism , Structure-Activity Relationship , Thiazoles/chemical synthesis , Thiazoles/metabolism , Thiazoles/pharmacokineticsABSTRACT
PURPOSE: In the present study, enhancement of the the antibacterial activity of ceftriaxone against Gram-positive (meticillin-resistant Staphylococcus aureus; MRSA) and Gram-negative (Escherichia coli) bacteria with a biodegradable polymer was attempted. METHODOLOGY: MRSA and E. coli were collected and identified by biochemical and molecular tests. Blank and ceftriaxone-loaded chitosan nanoparticles (CNPs) were prepared by the ionic gelation method. In vitro antibiotic-susceptibility studies were performed by disc diffusion, agar well plate method, Etest and time-kill assay. In vivo activity was assessed using the neutropenic mouse thigh model and cytotoxicity was estimated by MTT (methylthiazolyldiphenyl tetrazolium bromide) assay with the MCF-7 cancer cell line. RESULTS: MRSA showed 97â% and E. coli 83â% resistance against ceftriaxone in the disc diffusion test. The isolates showing a ≥1024 mg l-1 MIC value for ceftriaxone were selected for further evaluation. In the agar well plate method, the mean zones of inhibition for blank and ceftriaxone-loaded CNPs were 17 and 23 mm, respectively, for MRSA isolates and 15 and 25 mm, respectively, for E. coli isolates. In the time-kill assay, ~1 log10 to ~2.5 log10 reduction in viability was seen with both isolates when treated with ceftriaxone-loaded CNPs over 24 h. The in vivo studies also showed the enhanced antibacterial activity of ceftriaxone-loaded CNPs, with a 41â% reduction in MRSA and a 27â% reduction in E. coli burden. A low cytotoxicity of blank and ceftriaxone-loaded CNPs was seen, with a slight reduction in the percentage viability of cells from 87 to 83â% and from 88 to 81â%, respectively. CONCLUSION: The synergistic effect of ceftriaxone-loaded CNPs is a useful finding for the treatment of MRSA and E. coli infections.
