During the screening of compounds that potentiate the effect of antimicrobial agents against methicillin-resistant Staphylococcus aureus (MRSA), we found that an extract of thyme (Thymus vulgaris L) leaves greatly reduced the minimum inhibitory concentration (MIC) of tetracycline against MRSA. We isolated the effective compound and identified it as baicalein (5, 6, 7-trihydroxyflavone). One of the clinically isolated MRSA strains possessed tetK, a gene encoding active efflux pump for tetracycline. We examined the effect of baicalein on the efflux of tetracycline, using Escherichia coli KAM32/pTZ1252 carrying the tetK. The E. coli KAM32/pTZ1252 showed 8 to 16 times higher MIC than E. coli KAM32. We observed strong inhibition of transport of tetracycline by baicalein with membrane vesicles prepared from E. coli KAM32/pTZ1252. Baicalein also showed synergy with tetracycline in a MRSA strain that doesn't possess tetK, or with ␤-lactams. Thus, mechanisms of the synergies seem to be versatile.

No abstract

No abstract

No abstract

Cisplatin (CDDP)-induced acute kidney injury (AKI) is a major clinical concern. CDDP treatment is generally conducted with multiple cycles; the magnitude of the CDDP-induced AKI may be altered by these cycles. Moreover, sub-chronic kidney injury (sCKI) induced by repeated CDDP treatment is often associated with renal interstitial fibrosis, potentially leading to chronic kidney disease. Therefore, it is suggested that the management of not only AKI but also sCKI induced by CDDP in multiple cycles plays an important role in the outcome of CDDP-based chemotherapy. This study investigated the alteration in pharmacokinetics and toxicodynamics of CDDP that was repeatedly administered for three cycles in rats; a cycle consisted of CDDP (5.0 mg/kg, bolus injection) followed by a 21-d washout period. AKI and sCKI were evaluated by plasma creatinine concentration. In repeated multiple administration of CDDP, renal clearance was decreased and the amounts of accumulated Pt in kidneys increased by the cycle. AKI and sCKI were similarly exacerbated by the cycle, whereas the degree of AKI showed a large inter-and intra-individual variation in each cycle. However, the degree of sCKI constantly increased (creatinine increasing ratio in any cycle is about 150%), suggesting that the degree of sCKI in any given cycle was predictable by monitoring the initial creatinine baseline. In this study, therefore, it is suggested that the evaluation of sCKI by monitoring creatinine concentration at base is important for the estimation of CDDP-induced nephrotoxicity. These results may provide useful information for more effective and safe CDDP-based chemotherapy with evidence-based dose adjustment.Key words cisplatin; repeated administration; pharmacokinetics; creatinine; kidney injury Cisplatin [cis-diamminedichloroplatinum (II), CDDP] is widely used as a key antitumor agent. However, despite its clinical usefulness, CDDP-induced nephrotoxicity is one of the dose-limiting side effects and a major clinical concern; recent retrospective studies have reported that approximately one-third of patients treated with CDDP-based chemotherapy experience acute kidney injury (AKI), even with plausible renoprotective strategies such as co-administration with hydration.1,2) Therefore, the prediction and prevention of CDDPinduced AKI still remain a challenge.The pharmacokinetics (PK) of CDDP and the pathophysiology of CDDP-induced AKI have been intensively investigated. A unique feature of CDDP PK is the non-specific and irreversible binding of CDDP to proteins; after administration, CDDP rapidly and irreversibly binds to plasma proteins to form inactive CDDP complexes.3,4) Therefore, irreversible binding of CDDP to plasma proteins should be considered as metabolic inactivation. Unbound CDDP is excreted mainly by glomerular filtration and partially by active transport mediated via organic cation transporter (OCT)-2 and multi-drug and toxin extrusion transporter 2.5,6) During distribution and excretion processes, CDDP accumulates in proximal tubular epithel...