Search

The Blood-Brain Barrier P-glycoprotein (P-gp) function can be altered in several neurodegenerative diseases and due to the administration of different drugs which may cause alterations in drug concentrations and consequently lead to a reduced effectiveness or increased side-effects. The novel PET radiotracer [ 18 F]MC225 is a weak P-gp substrate that may show higher sensitivity to detect small changes in P-gp function than previously developed radiotracers. This study explores the sensitivity of [ 18 F]MC225 to measure the dose-dependent effect of P-gp inhibitor tariquidar. Twenty-three rats were intravenously injected with different doses of tariquidar ranging from 0.75 to 12 mg/kg, 30-min before the dynamic [ 18 F]MC225-PET acquisition with arterial sampling. Tissue and blood data were fitted to a 1-Tissue-Compartment-Model to obtain influx constant K 1 and distribution volume V T , which allow the estimation of P-gp function. ANOVA and post-hoc analyses of K 1 values showed significant differences between controls and groups with tariquidar doses >3 mg/kg; while applying V T the analyses showed significant differences between controls and groups with tariquidar doses >6 mg/kg. Dose-response curves were fitted using different models. The four-parameter logistic sigmoidal curve provided the best fit for K 1 and V T data. Half-maximal inhibitory doses (ID 50 ) were 2.23 mg/kg (95%CI: 1.669-2.783) and 2.93 mg/kg (95%CI: 1.135-3.651), calculated with K 1 or V T values respectively. According to the dose-response fit, differences in [ 18 F]MC225-K 1 values could be detected at tariquidar doses ranging from 1.37 to 3.25 mg/kg. Our findings showed that small changes in the P-gp function, caused by low doses of tariquidar, could be detected by [ 18 F]MC225-K 1 values, which confirms the high sensitivity of the radiotracer. The results suggest that [ 18 F]MC225 may allow the quantification of moderate P-gp impairments, which may allow the detection of P-gp dysfunctions at the early stages of a disease and potential transporter-mediated drug-drug interactions., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)