Coexistence of Passive and Proton Antiporter-Mediated Processes in Nicotine Transport at the Mouse Blood–Brain Barrier

Abstract

Abstract. Nicotine, the main tobacco alkaloid leading to smoking dependence, rapidly crosses the bloodbrain barrier (BBB) to become concentrated in the brain. Recently, it has been shown that nicotine interacts with some organic cation transporters (OCT), but their influence at the BBB has not yet been assessed in vivo. In this study, we characterized the transport of nicotine at the mouse luminal BBB by in situ brain perfusion. Its influx was saturable and followed the Michaelis-Menten kinetics (K m 02.60 mM, V max 037.60 nmol/s/g at pH 7.40). At its usual micromolar concentrations in the plasma, most (79%) of the net transport of nicotine at the BBB was carrier-mediated, while passive diffusion accounted for 21%. Studies on knockout mice showed that the OCT Oct1-3, P-gp, and Bcrp did not alter [3 H]-nicotine transport at the BBB. Neither did inhibiting the transporters Mate1, Octn, or Pmat. The in vivo manipulation of intracellular and/or extracellular pH, the chemical inhibition profile, and the transstimulation experiments demonstrated that the nicotine transporter at the BBB shared the properties of the clonidine/proton antiporter. The molecular features of this proton-coupled antiporter have not yet been identified, but it also transports diphenhydramine and tramadol and helps nicotine cross the BBB at a faster rate and to a greater extent. The pharmacological inhibition of this nicotine/proton antiporter could represent a new strategy to reduce nicotine uptake by the brain and thus help curb addiction to smoking.

Proton-Coupled Organic Cation Antiporter-Mediated Uptake of Apomorphine Enantiomers in Human Brain Capillary Endothelial Cell Line hCMEC/D3

“…Several drugs have been reported to be proton-coupled organic cation antiporter substrates, including pramipexole, 13) oxycodone, 6) pyrilamine, 4,6) 3,4-methylenedioxymethamphetamine, 9) clonidine, 10) diphenhydramine, 4,7,14) nicotine, 15,16) and propranolol.…”

Development of a Rat Plasma and Brain Extracellular Fluid Pharmacokinetic Model for Bupropion and Hydroxybupropion Based on Microdialysis Sampling, and Application to Predict Human Brain Concentrations

“…The net uptake asymmetry observed is similar to oxycodone BBB transport in rats, (Boström et al, 2006), which showed a net 3-fold asymmetry favoring rat brain ECF relative to unbound plasma concentrations. Subsequent in vitro studies with oxycodone (Okura et al, 2008)-as well as more recent in vitro transport or in situ brain perfusion studies with several other low molecular weight weakly basic drugs, such as apomorphine (Okura et al, 2014), clonidine (André et al, 2009), codeine (Fischer et al, 2010), diphenhydramine (Shimomura et al, 2013), and nicotine (Cisternino et al, 2013)-implicate a pH-dependent proton-coupled antiporter at the BBB (Gharavi et al, 2015). It is possible that this transporter may also apply to bupropion and hydroxybupropion.…”

“…It is possible that this transporter may also apply to bupropion and hydroxybupropion. Moreover, the proton-coupled antiporter has been suggested to be capable of bidirectional transport (Cisternino et al, 2013). It is possible that the overshoot in bupropion K p,uu , which was modeled as a timedependent distributional clearance, may have been due to eventual replacement of protons by bupropion and/or hydroxybupropion on the abluminal side.…”

Transporter-Mediated Disposition of Opioids: Implications for Clinical Drug Interactions

“…In addition, codeine uptake in intestinal and brain endothelial cells was found to be pH dependent and possibly mediated through a yet to be identified proton-coupled antiporter that my incur a number of DDIs (109). In vivo evidence from an in situ mouse brain perfusion study supported this finding, as codeine was found to significantly inhibit the BBB transport of nicotine (29% reduction in transport rate at a concentration of 10 mM), which may also be a substrate of this same proton-coupled antiporter (20). The clinical relevance of these reported interactions is unclear however, as they appear to occur at supratherapeutic concentrations (182).…”

“…These transporters of interest are P-glycoprotein (P-gp/MDR1, ABCB1), Breast Cancer Resistance Protein (BCRP, ABCG2), the hepatic uptake Organic Anion Transporting Polypeptides (OATP) 1B1 and 1B3, and the renal Organic Anion Transporter (OAT) 1 and 3, and Organic Cation Transporter 2 (OCT2) (16). In addition, there are multiple emerging transporters of interest, such as members of the multidrug and toxic compound extrusion (MATE) family, as well as a number of yet to be fully identified transporters (18)(19)(20) (Fig. 1).…”