Probenecid, an organic anion transporter 1 and 3 inhibitor, increases plasma and brain exposure of N-acetylcysteine

Abstract

1. N-acetylcysteine (NAC) is being investigated as an antioxidant for several conditions including traumatic brain injury, but the mechanism by which it crosses membrane barriers is unknown. We have attempted to understand how the transporter inhibitor, probenecid, affects NAC pharmacokinetics and to evaluate the interaction of NAC with transporters.

2. Juvenile Sprague-Dawley rats were administered NAC alone or in combination with probenecid intraperitoneally. Plasma and brain samples were collected serially and NAC concentrations were measured. Transporter studies were conducted with human embryonic kidney-293 cells that overexpress organic anion transporter (OAT)1 or OAT3 and with human multi-drug resistance-associated protein (MRP)1 or MRP4 membrane vesicles.

3. NAC area under the curve was increased in plasma (1.65-fold) and brain (2.41-fold) by probenecid. The apparent plasma clearance was decreased by 65%. Time- and concentration-dependent NAC uptake that was inhibitable by probenecid was observed with OAT1 and OAT3. No uptake of NAC was observed with MRP1 or MRP4.

4. Our results indicate for the first time that NAC is substrate for OAT1 and OAT3 and that probenecid increases NAC plasma and brain exposure in vivo. These data provide insight regarding how NAC crosses biological barriers and suggest a promising therapeutic strategy to increase NAC exposure.

• Antioxidant
• inhibitor
• n-acetylcysteine
• organic anion tranporter
• pharmacokinetics
• probenecid
• transporter

Acknowledgements

The authors would like to thank Professor Kathleen Giacomini (University of California, San Francisco, CA, USA), who provided us with the human embryonic kidney cell lines stably transfected with human OAT3 (HEK-OAT3), human OAT1 (HEK-OAT1), and the corresponding HEK-empty vector (HEK-EV, control cells).

Declaration of interest

This work was supported by the National Institutes of Health NS069247 and TR000146. The authors have no conflicts of interest related to this study.