[Reserpine Is the New Addition into the Repertoire of AcrB Efflux Pump Inhibitors].

Acriflavine resistance protein B (AcrB) serves as prototype for multidrug resistance (MDR) efflux transporters of resistance nodulation division (RND) superfamily. AcrB has been proven as potential drug target with many synthetic and natural inhibitors have been identified such as those belonging to pyranopyridine, naphthamide and pimozide classes. The plant derived alkaloid inhibitors represented by reserpine has been found to inhibit both ATP binding cassette and major facilitator efflux transporters. In this study we report the reserpine induced inhibition of RND transporter AcrB. The preliminary docking analysis hints that reserpine shares its binding site with ciprofloxacin, a known substrate of AcrB and could possibly act as competitive inhibitor. For in vitro validation, AcrB from Salmonella typhi was cloned under the control of tac promoter and resulting vector was introduced into E. coli C41(DE3). Under autoinduced conditions, cells overexpressing AcrB transporter were subjected to combined dose of ciprofloxacin and reserpine. The combined exposure resulted in enhanced ciprofloxacin-induced growth inhibition of cells expressing AcrB transporter as compared to control cells transformed with vector of backbone sequence. Time kill analysis further confirmed these findings. To the best of our knowledge, this is first study to show that exposure to reserpine induces inhibition of AcrB. The assay developed in this study allows simple and reproducible detection of substrate/inhibitor effects upon AcrB and related efflux transporters.

Restraining the multidrug efflux transporter STY4874 of Salmonella Typhi by reserpine and plant extracts.

Efflux-mediated multidrug resistance is a well-known phenomenon facilitated by multidrug resistant (MDR) transporters. One of the approaches to counteract efflux-mediated resistance is the use of MDR pump inhibitors, and thus be used in combination with the conventional antibiotics to treat deadly diseases like typhoid fever. We have previously reported that STY4874, an efflux transporter of Salmonella serotype Typhi, exhibited promising characteristics as MDR pump. In this study, we aimed to get an insight into possible STY4874 inhibitors of plant origin. STY4874 was overexpressed in Escherichia coli and extracts from pomegranate peel, milk thistle seeds and reserpine, a synthetic plant alkaloid, were screened for inhibition of ciprofloxacin efflux. The extracts of milk thistle seeds and reserpine when incubated with ciprofloxacin showed statistically significant STY4874-mediated inhibitory activity, rendering the efflux pump inactive and hence early growth inhibition of host cells compared with cells expressing efflux pump and incubated only with ciprofloxacin. This efflux pump inhibitory activity was further confirmed by time-kill experiments. This study is the first to report on efflux pump inhibition of S. Typhi STY4874 and results can be extended towards its close homologues such as MdfA and MdtM from E. coli. SIGNIFICANCE AND IMPACT OF THE STUDY: Understanding and combating resistance governed by multidrug efflux transporters is an ongoing research intensive area, affecting treatment of various nosocomial and endemic/epidemic infections. Confronting drug resistance requires that inhibitors debilitating the underlying mechanisms should be included in combination therapy. One such example is the prescription of clavulanic acid as combination therapy with amoxicillin, collectively called as co-amoxiclav to combat ß-lactamase-mediated resistance. However, research related to finding the inhibitors of efflux transporters, the resistance mechanism distinct from ß-lactamase mediated resistance is at an early stage. The current study finds that plant-derived inhibitors can be an option towards restraining efflux-mediated resistance.

Pharmacokinetics and pharmacodynamics of dapagliflozin in children and adolescents with type 2 diabetes mellitus.

AIMS: To evaluate the pharmacokinetic (PK)/pharmacodynamic (PD) and safety profile of dapagliflozin in paediatric patients aged 10-17 years with type 2 diabetes mellitus (T2DM). METHODS: Patients were randomized to a single oral dose of dapagliflozin 2.5, 5 or 10 mg. The PK characteristics for individual patients were derived by non-compartmental methods. Urinary glucose excretion (UGE), fasting plasma glucose (FPG) and ease of swallowing were also evaluated. RESULTS: A total of 24 patients with a mean (range) body weight of 99.7 (61.5-169.5) kg received dapagliflozin. Dapagliflozin was rapidly absorbed after oral administration (median time to maximum plasma concentration ∼1.5 h) and systemic exposures to dapagliflozin and its 3-O-glucuronide metabolite appeared dose-proportional. The mean 24-h UGE increased in a dose-related manner (52.8, 62.4 and 89.0 g for the 2.5, 5 and 10 mg groups, respectively). Mean FPG concentrations were lower for all dose groups on day 2 (6.9, 6.2 and 6.8 mmol/l for 2.5, 5 and 10 mg groups, respectively) than they were predose on day 1 (9.5, 8.5 and 8.2 mmol/l for 2.5, 5 and 10 mg groups, respectively). Six patients (25%) experienced ≥1 adverse event (AE), however, there was no dose-related pattern. All AEs occurred only once and most were mild in intensity. Nearly all patients (n = 23; 95.8%) reported easy swallowing of the dapagliflozin tablets. CONCLUSIONS: Dapagliflozin was well tolerated in this paediatric population, with no significant safety findings. PK/PD characteristics were similar to those observed in adults with T2DM, thereby supporting the hypothesis that the same dapagliflozin dosage as that used in adults can be evaluated in future phase III paediatric studies.