Design of New Antibacterial Enhancers Based on AcrB’s Structure and the Evaluation of Their Antibacterial Enhancement Activity

Abstract

Previously, artesunate (AS) and dihydroartemisinine 7 (DHA7) were found to have antibacterial enhancement activity against Escherichia coli via inhibition of the efflux pump AcrB. However, they were only effective against E. coli standard strains. This study aimed to develop effective antibacterial enhancers based on the previous work. Our results demonstrate that 86 new antibacterial enhancers were designed via 3D-SAR and molecular docking. Among them, DHA27 had the best antibacterial enhancement activity. It could potentiate the antibacterial effects of ampicillin against not only E. coli standard strain but also clinical strains, and of β-lactam antibiotics, not non-β-lactamantibiotics. DHA27 could increase the accumulation of daunomycin and nile red within E. coli ATCC 35218, but did not increase the bacterial membrane permeability. DHA27 reduced acrB’s mRNA expression of E. coli ATCC 35218 in a dose-dependent manner, and its antibacterial enhancement activity is related to the degree of acrB mRNA expression in E. coli clinical strains. The polypeptides from AcrB were obtained via molecular docking assay; the pre-incubated polypeptides could inhibit the activity of DHA27. Importantly, DHA27 had no cytotoxicity on cell proliferation. In conclusion, among newly designed antibacterial enhancers, DHA27 had favorable physical and pharmacological properties with no significant cytotoxicity at effective concentrations, and might serve as a potential efflux pump inhibitor in the future.

Artemisinin derivative DHA27 enhances the antibacterial effect of aminoglycosides against Pseudomonas aeruginosa by inhibiting mRNA expression of aminoglycoside-modifying enzymes

“…DHA27 was synthesized by College of Pharmacy, Zunyi Medical University and College of Pharmacy, Army Medical University (the Third Military Medical University) ( Song et al, 2016 ). Gentamicin, tobramycin (TOB), and amikacin were purchased from Beijing Solarbio Science & Technology Co., Ltd. whereas daunorubicin (DNR) was purchased from Med Chem Express (USA).…”

“…DNR, an antitumor drug, shows spontaneous fluorescence that is easily observable and therefore is often used as a tracer agent ( Li et al, 2011 ; Song et al, 2016 ). The concentration of the activated bacterial solution was adjusted to 1.0 × 10 6 CFU/mL.…”

“…Thirteen PA clinical isolates that had antibacterial sensitization of DHA27 in combination with tobramycin were cultured at 37°C with shaking until the OD 600 value was 0.3–0.8, and the bacteria were collected after centrifugation at 537 g for 5 min. RNA extraction and reverse transcription were performed using previously described protocols ( Song et al, 2016 ). Target genes were amplified by real-time fluorescence quantitative PCR using specific primers ( Table 1 ).…”

“…Our research group has been conducting long-term studies on the antibacterial sensitization of artemisinin derivatives. Previous studies have found that artemisinin derivative DHA27 combined with β -lactam antibiotics have antibacterial sensitization effect on E. coli ( Song et al, 2016 ). However, its antibacterial sensitizing effect has not been studied in other bacteria.…”

Antibacterial Photodynamic Treatment of Porphyromonas gingivalis with Toluidine Blue O and a NonLaser Red Light Source Enhanced by Dihydroartemisinin

“…Artemisinin is mainly used for the treatment of malaria (22) and plays an important role in antitumor (23), anti-inflammatory (24) and antibacterial effects (25). DHA and artesunate are the main active components of artemisinin.…”