Probenecid Increases the Concentration of 7-Chlorokynurenic Acid Derived from the Prodrug 4-Chlorokynurenine within the Prefrontal Cortex

Abstract

Recent advances in the understanding of depression have led to increasing interest in ketamine and the role that N-methyl-d-aspartate (NMDA) receptor inhibition plays in depression. l-4-Chlorokynurenine (4-Cl-KYN, AV-101), a prodrug, has shown promise as an antidepressant in preclinical studies, but this promise has not been realized in recent clinical trials. We sought to determine if transporters in the CNS could be playing a role in this clinical response. We used radiolabeled uptake assays and microdialysis studies to determine how 4-Cl-KYN and its active metabolite, 7-chlorokynurenic acid (7-Cl-KYNA), cross the blood–brain barrier (BBB) to access the brain and its extracellular fluid compartment. Our data indicates that 4-Cl-KYN crosses the blood–brain barrier via the amino acid transporter LAT1 (SLC7A5) after which the 7-Cl-KYNA metabolite leaves the brain extracellular fluid via probenecid-sensitive organic anion transporters OAT1/3 (SLC22A6 and SLC22A8) and MRP4 (ABCC4). Microdialysis studies further validated our in vitro data, indicating that probenecid may be used to boost the bioavailability of 7-Cl-KYNA. Indeed, we found that coadministration of 4-Cl-KYN with probenecid caused a dose-dependent increase by as much as an 885-fold increase in 7-Cl-KYNA concentration in the prefrontal cortex. In summary, our data show that 4-Cl-KYN crosses the BBB using LAT1, while its active metabolite, 7-Cl-KYNA, is rapidly transported out of the brain via OAT1/3 and MRP4. We also identify a hitherto unreported mechanism by which the brain extracellular concentration of 7-Cl-KYNA may be increased to produce significant boosting of the drug concentration at its site of action that could potentially lead to an increased therapeutic effect.

AV-101, a Pro-Drug Antagonist at the NMDA Receptor Glycine Site, Reduces L-Dopa Induced Dyskinesias in MPTP Monkeys

“…For this reason, in the main experiment, AV-101 was administered 1.5 h before and at the same time of L-Dopa to extend the duration of the effect of AV-101. A recent study also reported that 7-Cl-KYNA, which binds to the GlyB co-agonist site of NMDA-R, leaves the brain extracellular fluid via probenecid-sensitive organic anion transporters [ 24 ]. Indeed, the co-administration of probenecid with AV-101 increased the brain concentration of 7-Cl-KYNA [ 24 ].…”

“…A recent study also reported that 7-Cl-KYNA, which binds to the GlyB co-agonist site of NMDA-R, leaves the brain extracellular fluid via probenecid-sensitive organic anion transporters [ 24 ]. Indeed, the co-administration of probenecid with AV-101 increased the brain concentration of 7-Cl-KYNA [ 24 ]. Whether the co-administration of AV-101 and probenecid could have a beneficial effect on LID remains to be investigated.…”

“…L-type amino acid transporter 1 (LAT1, SLC7A5) transport assay was carried out as described previously [ 22 , 23 , 24 ]. [ 3 H]-L-Dopa (specific activity 4 Ci/mmol) was acquired from American Radiolabeled Chemicals, Inc.…”

“…The transporter buffer was comprised of 1 µM L-Dopa (Hellobio, Bristol, UK); 25 mM HEPES (Sigma-Aldrich, Gillingham, UK); pH 7.4; Hank’s buffered saline solution (HBSS) (Sigma-Aldrich, Gillingham, UK); and 0.1% w / v BSA (Sigma-Aldrich, Gillingham, UK). Individual amino acids used to make up the physiological amino acid solution were purchased from Sigma-Aldrich and reconstituted, as described previously [ 24 ]. Cells were incubated with 0.15 µCi/mL [ 3 H]-L-Dopa as a radiotracer in the transport buffer with or without AV-101 (1, 2.5, 5 or 10 mM) for 3 min at 37 °C.…”

The evidence from clinical trials on Gout medicines effect on COVID‐19: A protocol for systematic review and meta‐analysis

“…Colchicine prevents acute gout flares because of its anti‐inflammatory properties (Dalbeth et al, 2014 ), while allopurinol and febuxostat inhibit xanthine oxidase and thus reduce the synthesis of uric acid (UA) (Strilchuk et al, 2019 ), febuxostat and allopurinol lower the UA levels and attenuate the expression of an inflammatory marker, monocyte chemoattractant protein (MCP)‐1(Nakagomi et al, 2015 ). On the other hand, probenecid facilitates the excretion of uric acid by suppressing renal tubular transport (inhibits pannexin 1 channels) and blocking its reuptake (Patel et al, 2021 ). While, indomethacin inhibits the prostaglandins' synthesis by cyclooxygenase (COX) enzymes, thus reducing the amount of serum inflammatory mediators (Munjal & Allam, 2022 ).…”