Characterization of the Inhibitory Effects ofN-Butylpyridinium Chloride and Structurally Related Ionic Liquids on Organic Cation Transporters 1/2 and Human Toxic Extrusion Transporters 1/2-K In Vitro and In Vivo

Abstract

ABSTRACT:Ionic liquids (ILs) are a class of salts that are expected to be used as a new source of solvents and for many other applications. Our previous studies revealed that selected ILs, structurally related organic cations, are eliminated exclusively in urine as the parent compound, partially mediated by renal transporters. This study investigated the inhibitory effects of N-butylpyridinium chloride (NBuPy-Cl) and structurally related ILs on organic cation transporters (OCTs) and multidrug and toxic extrusion transporters (MATEs) in vitro and in vivo. After Chinese hamster ovary cells expressing rat (r) OCT1, rOCT2, human (h) OCT2, hMATE1, or hMATE2-K were constructed, the ability of NBuPy-Cl, 1-methyl-3-butylimidazolium chloride (Bmim-Cl), N-butyl-N-methylpyrrolidinium chloride (BmPyCl), and alkyl substituted pyridinium ILs to inhibit these transporters was determined in vitro. NBuPy-Cl (0, 0.5, or 2 mg/kg per hour) was also infused into rats to assess its effect on the pharmacokinetics of metformin, a substrate of OCTs and MATEs. NBuPy-Cl, Bmim-Cl, and BmPy-Cl displayed strong inhibitory effects on these transporters (IC 50 ‫؍‬ 0.2-8.5 M). In addition, the inhibitory effects of alkyl-substituted pyridinium ILs on OCTs increased dramatically as the length of the alkyl chain increased. The IC 50 values were 0.1, 3.8, 14, and 671 M (hexyl-, butyl-, and ethyl-pyridinium and pyridinium chloride) for rOCT2-mediated metformin transport. Similar structurally related inhibitory kinetics were also observed for rOCT1 and hOCT2. The in vivo coadministration study revealed that NBuPy-Cl reduced the renal clearance of metformin in rats. These results demonstrate that ILs compete with other substrates of OCTs and MATEs and could alter the in vivo pharmacokinetics of such substrates.

Substrate-Dependent Inhibition of Human MATE1 by Cationic Ionic Liquids

“…NBuPy can block both the OCT2-mediated entry of metformin into RPT cells and the MATE1-mediated exit of metformin from these cells (rat kidney expresses MATE1 but not MATE2-K; (Ohta et al, 2006;Klaassen and Aleksunes, 2010)), but the observation that the NBuPy-induced reduction in plasma clearance of metformin was accompanied by an increase in metformin content (3.7-fold) (Cheng et al, 2011) in renal tissue suggests that NBuPy exerted its principal inhibitory effect on the MATE1-mediated exit step. It should be noted that the doses of NBuPy required to inhibit metformin clearance were quite high and most likely resulted in blood levels that would not be achieved in humans exposed orally or dermally to environmental or occupational levels of NBuPy-Cl or other ILs (Cheng et al, 2011). Nevertheless, the results presented here indicate that ILs are potentially capable of interfering with MATE-mediated OC transport and, consequently, of influencing the distribution and pharmacokinetics of cationic compounds that rely on renal (or hepatic) secretory pathways.…”

“…Previous studies showed that the three aforementioned model ILs are, in fact, actively secreted in urine of both mice and rats Knudsen et al, 2009), and they both inhibit and serve as substrate for the human and rat orthologs of OCT2 (Cheng et al, , 2011Knudsen et al, 2009). Although it might reasonably be inferred that secreted ILs are substrates for MATE transporters, the nature of the interaction of ILs with the MATEs has not been fully examined.…”

“…Environmental chemicals, like the model ILs, can also exert unwanted interactions at the level of renal secretion. Cheng et al (2011) recently showed that infusion of NBuPy reduced the plasma clearance of metformin by 65% in rats (with an associated increase in the plasma metformin concentration). NBuPy can block both the OCT2-mediated entry of metformin into RPT cells and the MATE1-mediated exit of metformin from these cells (rat kidney expresses MATE1 but not MATE2-K; (Ohta et al, 2006;Klaassen and Aleksunes, 2010)), but the observation that the NBuPy-induced reduction in plasma clearance of metformin was accompanied by an increase in metformin content (3.7-fold) (Cheng et al, 2011) in renal tissue suggests that NBuPy exerted its principal inhibitory effect on the MATE1-mediated exit step.…”

“…Cheng et al (2011) recently showed that infusion of NBuPy reduced the plasma clearance of metformin by 65% in rats (with an associated increase in the plasma metformin concentration). NBuPy can block both the OCT2-mediated entry of metformin into RPT cells and the MATE1-mediated exit of metformin from these cells (rat kidney expresses MATE1 but not MATE2-K; (Ohta et al, 2006;Klaassen and Aleksunes, 2010)), but the observation that the NBuPy-induced reduction in plasma clearance of metformin was accompanied by an increase in metformin content (3.7-fold) (Cheng et al, 2011) in renal tissue suggests that NBuPy exerted its principal inhibitory effect on the MATE1-mediated exit step. It should be noted that the doses of NBuPy required to inhibit metformin clearance were quite high and most likely resulted in blood levels that would not be achieved in humans exposed orally or dermally to environmental or occupational levels of NBuPy-Cl or other ILs (Cheng et al, 2011).…”

Expression of Organic Anion Transporter 2 in the Human Kidney and Its Potential Role in the Tubular Secretion of Guanine-Containing Antiviral Drugs

“…The cellular accumulation of compound (at each concentration tested) in the parental (control) HEK Flp-In cells was subtracted from uptake into the cells expressing the individual transporters; this was done to account for potential endogenous transport activity in the control cells. Kinetic parameters, K m (Michaelis constant) and J max (maximal rate of transport), were determined as described previously (Cheng et al, 2011).…”