Effect of Long-term In Vitro Lithium Exposure on mRNA Levels of Claudin-3, CYP1A1, ABCG2 and GSTM3 Genes in the hCMEC/D3 Human Brain Endothelial Cell Line

Lithium chloride (LiCl) has been shown to improve the tightness of brain endothelial cell monolayers in vitro by inhibition of the GSK-3 beta enzyme, activation of the Wnt/beta-catenin pathway and regulation of tight junction (TJ) protein expression. However, the effect of LiCl on the drug transporters and drug-metabolizing enzymes has not been addressed so far. The hCMEC/D3 cell line is a validated in vitro BBB model expressing transporters and drug-metabolizing enzymes (phase 1 and 2). The present study was conducted to compare the mRNAs levels corresponding to several BBB endothelial markers in hCMEC/D3 cells with and without incubation in LiCl. We used quantitative real-time polymerase chain reaction (qRT-PCR) to quantify the mRNA expression of 5 tight junction (TJ) proteins, 4 adhesion proteins, 5 solute carriers, 7 ATP-binding cassette (ABC) transporters, 8 cytochrome P450 (CYP) and 17 phase 2 conjugation enzymes in hCMEC/D3 cells with and without incubation in LiCl. Our study showed that LiCl treatment for 6 days at a concentration of 10 mM induced the TJ protein claudin-3, the ABC transporter BCRP/ABCG2, the cytochrome P-450 CYP1A1 and the glutathione-S-transferase GSTM3, while the other selected markers were not significantly affected. Our findings provide new insights into the effects of lithium on some drug transporters and drug-metabolizing enzymes in the BBB that may have consequences in pharmacotherapy.