Human oligopeptide transporter 2 (PEPT2) mediates cellular uptake of polymyxins.
OBJECTIVE
Polymyxins are a last-line therapy to treat MDR Gram-negative bacterial infections. Nephrotoxicity is the dose-limiting factor for polymyxins and recent studies demonstrated significant accumulation of polymyxins in renal tubular cells. However, little is known about the mechanism of polymyxin uptake into these cells. Oligopeptide transporter 2 (PEPT2) is a solute carrier transporter (SLC) expressed at the apical membrane of renal proximal tubular cells and facilitates drug reabsorption in the kidney. In this study, we examined the role of PEPT2 in polymyxin uptake into renal tubular cells.


METHODS
We investigated the inhibitory effects of colistin and polymyxin B on the substrate uptake mediated through 15 essential SLCs in overexpressing HEK293 cells. The inhibitory potency of both polymyxins on PEPT2-mediated substrate uptake was measured. Fluorescence imaging was employed to investigate PEPT2-mediated uptake of the polymyxin fluorescent probe MIPS-9541 and a transport assay was conducted with MIPS-9541 and [(3)H]polymyxin B1.


RESULTS
Colistin and polymyxin B potently inhibited PEPT2-mediated [(3)H]glycyl-sarcosine uptake (IC50 11.4 ± 3.1 and 18.3 ± 4.2 μM, respectively). In contrast, they had no or only mild inhibitory effects on the transport activity of the other 14 SLCs evaluated. MIPS-9541 potently inhibited PEPT2-mediated [(3)H]glycyl-sarcosine uptake (IC50 15.9 μM) and is also a substrate of PEPT2 (Km 74.9 μM). [(3)H]polymyxin B1 was also significantly taken up by PEPT2-expressing cells (Km 87.3 μM).


CONCLUSIONS
Our study provides the first evidence of PEPT2-mediated uptake of polymyxins and contributes to a better understanding of the accumulation of polymyxins in renal tubular cells.
Faculty of Pharmacy, The University of Sydney, Camperdown, NSW 2006, Australia.
Xiaoxi
X
Lu
Faculty of Pharmacy, The University of Sydney, Camperdown, NSW 2006, Australia.
Ting
T
Chan
Faculty of Pharmacy, The University of Sydney, Camperdown, NSW 2006, Australia.
Chenghao
C
Xu
Retinal Therapeutics Research Group, Save Sight Institute, The University of Sydney, Sydney, NSW 2000, Australia.
Ling
L
Zhu
Department of Industrial and Physical Pharmacy, College of Pharmacy, Purdue University, West Lafayette, IN 47907-2091, USA.
Qi Tony
QT
Zhou
Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, VIC 3052, Australia.
Kade D
KD
Roberts
Faculty of Pharmacy, The University of Sydney, Camperdown, NSW 2006, Australia.
Hak-Kim
HK
Chan
Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, VIC 3052, Australia.
Jian
J
Li
Faculty of Pharmacy, The University of Sydney, Camperdown, NSW 2006, Australia fanfan.zhou@sydney.edu.au.
Fanfan
F
Zhou
D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics*; D002460:Cell Line; D006801:Humans; D061848:Optical Imaging; D011113:Polymyxins / Q000493:pharmacokinetics*; D027981:Symporters / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D011113:Polymyxins; D027981:Symporters; C093694:hydrogen-coupled oligopeptide transporter PepT2