Synthesis and evaluation of chloramphenicol homodimers: molecular target, antimicrobial activity, and toxicity against human cells.
As fight against antibiotic resistance must be strengthened, improving old drugs that have fallen in reduced clinical use because of toxic side effects and/or frequently reported resistance, like chloramphenicol (CAM), is of special interest. Chloramphenicol (CAM), a prototypical wide-spectrum antibiotic has been shown to obstruct protein synthesis via binding to the bacterial ribosome. In this study we sought to identify features intensifying the bacteriostatic action of CAM. Accordingly, we synthesized a series of CAM-dimers with various linker lengths and functionalities and compared their efficiency in inhibiting peptide-bond formation in an Escherichia coli cell-free system. Several CAM-dimers exhibited higher activity, when compared to CAM. The most potent of them, compound 5, containing two CAM bases conjugated via a dicarboxyl aromatic linker of six successive carbon-bonds, was found to simultaneously bind both the ribosomal catalytic center and the exit-tunnel, thus revealing a second, kinetically cryptic binding site for CAM. Compared to CAM, compound 5 exhibited comparable antibacterial activity against MRSA or wild-type strains of Staphylococcus aureus, Enterococcus faecium and E. coli, but intriguingly superior activity against some CAM-resistant E. coli and Pseudomonas aeruginosa strains. Furthermore, it was almost twice as active in inhibiting the growth of T-leukemic cells, without affecting the viability of normal human lymphocytes. The observed effects were rationalized by footprinting tests, crosslinking analysis, and MD-simulations.
Department of Biochemistry, School of Medicine, University of Patras, Patras, Greece.
Ourania N
ON
Kostopoulou
Laboratory of Synthetic Organic Chemistry, Department of Chemistry, University of Patras, Patras, Greece.
George E
GE
Magoulas
Department of Biochemistry and Biotechnology, University of Thessaly, Ploutonos, Larissa, Greece.
Georgios E
GE
Papadopoulos
Division of Hematology, Department of Internal Medicine, School of Medicine, University of Patras, Patras, Greece.
Athanasia
A
Mouzaki
Department of Biochemistry, School of Medicine, University of Patras, Patras, Greece.
George P
GP
Dinos
Laboratory of Synthetic Organic Chemistry, Department of Chemistry, University of Patras, Patras, Greece.
Dionissios
D
Papaioannou
Department of Biochemistry, School of Medicine, University of Patras, Patras, Greece.
Dimitrios L
DL
Kalpaxis
D000890:Anti-Infective Agents / Q000737:chemistry* / Q000627:therapeutic use; D002474:Cell-Free System / Q000187:drug effects; D002701:Chloramphenicol / Q000737:chemistry* / Q000627:therapeutic use; D019281:Dimerization; D004352:Drug Resistance, Microbial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000472:pathogenicity; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects; D056004:Molecular Dynamics Simulation; D014176:Protein Biosynthesis / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D012270:Ribosomes / Q000235:genetics; D013211:Staphylococcus aureus / Q000187:drug effects
D000890:Anti-Infective Agents; D002701:Chloramphenicol