The Natural Alkaloid Berberine Can Reduce the Number of Pseudomonas aeruginosa Tolerant Cells

Abstract

The eradication of recurrent Pseudomonas aeruginosa (PA) lung infection in cystic fibrosis (CF) patients may be hampered by the development of persistent bacterial forms, which can tolerate antibiotics through efflux pump overexpression. After demonstrating the efflux pump inhibitory effect of the alkaloid berberine on the PA MexXY-OprM efflux pump, in this study, we tested its ability (80/320 μg/mL) to enhance tobramycin (20xMIC/1000xMIC) activity against PA planktonic/biofilm cultures. Preliminary investigations of the involvement of MexY in PA tolerance to tobramycin treatment, performed on the isogenic pair PA K767 (wild type)/K1525 (ΔmexY) growing in planktonic and biofilm cultures, demonstrated that the ΔmexY mutant K1525 produced a lower (100 and 10 000 times, respectively) amount of tolerant cells than that of the wild type. Next, we grew broth cultures of PAO1, PA14, and 20 PA clinical isolates (of which 13 were from CF patients) in the presence of 20xMIC tobramycin with and without berberine 80 μg/mL. Accordingly, most strains showed a greater (from 10-to 1000-fold) tolerance reduction in the presence of berberine. These findings highlight the involvement of the MexXY-OprM system in the tobramycin tolerance of PA and suggest that berberine may be used in new valuable therapeutic combinations to counteract persister survival.

Berberine Derivatives as Pseudomonas aeruginosa MexXY-OprM Inhibitors: Activity and In Silico Insights

“…In this work, we evaluated the interaction between berberine and its three aromatic derivatives with the access to the periplasmic site between the periplasmic loop of TM7 and TM8 of the MexY protein, the inner transmembrane channel of the P. aeruginosa MexXY-OprM efflux pump, which is responsible for aminoglycoside extrusion. This site was selected because it is involved in the recruitment of lipophilic and small-sized substrates directly from the periplasmic space and it has been investigated in our previous research [11,12,41]. Indeed, a ligand that can bind strongly at this fissure could hamper the binding of natural substrates by hindering the conformational change in protomers in the MexY homotrimer in a non-competitive mechanism.…”

“…In previous studies, we optimized a full 3D model of the MexY structure using the highly similar models of the membrane channels P. aeruginosa MexB and Escherichia coli AcrB [9][10][11]. From a structural point of view, MexXY-OprM is a tripartite system characterized by a drug extrusion mechanism via a proton gradient as in all RND efflux systems [12]. MexY is the inner membrane protein, organized as a homotrimer presenting a transmembrane (TM) domain, with 12 alpha helices and a periplasmic domain, which is directly involved in the access, binding, and extrusion of substrates.…”

“…Although the MexY inhibitory activity of the natural alkaloid berberine was extensively assessed by in silico modeling [11,12,18], the association between berberine and tobramycin resulted in a strain-dependent variable behavior [11]. Previous studies showed that the introduction of an aromatic substituent in position 13 can improve both the synergism of the combination berberine-fluconazole against Candida albicans [19] (Scheme 1) and the antimicrobial activity of the alkaloid itself against multidrug-resistant (MDR) Staphylococcus aureus [20].…”

In Vitro Synergistic Inhibitory Activity of Natural Alkaloid Berberine Combined with Azithromycin against Alginate Production by Pseudomonas aeruginosa PAO1

“…Therefore, it is imperative to adopt effective measures to prevent biofilm propagation and control the associated infection successfully. Previous studies reported the inhibitory effects of BER against biofilm and MexXY-OprM efflux pump of clinical strains of Pseudomonas aeruginosa to some extent [47][48][49][50]; however, PAO1 is allowedly considered a model microorganism for biofilm research and the results obtained from this strain are more persuasive. In this study, sub-MIC doses of the BER-AZM combination treatment considerably inhibited the biomass, EPS, and total protein of PAO1 biofilm.…”

Scientometric Analysis of Medicinal and Edible Plant Coptis

“…Berberine is the alkaloid present in the highest concentrations in the rhizomes of C. chinensis. It has antipathogen (Yan et al, 2008;Mangiaterra et al, 2021), antibacterial toxin, anti-inflammatory (Cuellar et al, 2001), hypoglycemic (Lee et al, 2006), anti-gastric ulcer, antitumor, and positive muscle strength effects and exerts a negative frequency on the myocardium. With further research, an increasing number of pharmacological effects induced by berberine have been discovered, and the corresponding mechanisms of action have also been explained.…”