Stereoselective Regulation of P-gp Activity by Clausenamide Enantiomers in Caco-2, KB/KBv and Brain Microvessel Endothelial Cells

Abstract

The (−)- and (+)-clausenamide (CLA) enantiomers have different pharmacokinetic effects in animals, but their association with putative stereoselective regulation of P-glycoprotein (P-gp) remains unclear. Using three cells expressing P-gp—Caco-2, KBv and rat brain microvessel endothelial cells(RBMEC), this study investigated the association of CLA enantiomers with P-gp. The results showed that the rhodamine 123 (Rh123) accumulation, an indicator of P-gp activity, in Caco-2, KBv and RBMECs was increased by (−)CLA (1 or 5 μmol/L) at 8.2%–28.5%, but reduced by (+)CLA at 11.7%–25.9%, showing stereoselectivity in their regulation of P-gp activity. Following co-treatment of these cells with each CLA enantiomer and verapamil as a P-gp inhibitor, the (+)-isomer clearly antagonized the inhibitory effects of verapamil on P-gp efflux, whereas the (−)-isomer had slightly synergistic or additive effects. When higher concentrations (5 or 10 μmol/L) of CLA enantiomers were added, the stimulatory effects of the (+)-isomer were converted into inhibitory ones, leading to an enhanced intracellular uptake of Rh123 by 24.5%–58.2%; but (−)-isomer kept its inhibition to P-gp activity, causing 30.0%–63.0% increase in the Rh123 uptake. The biphasic effects of (+)CLA were confirmed by CLA uptake in the Caco-2 cells. (+)CLA at 1 μmol/L had significantly lower intracellular uptake than (−)CLA with a ratio[(−)/(+)] of 2.593, which was decreased to 2.167 and 1.893 after CLA concentrations increased to 2.5 and 5 μmol/L. Besides, in the non-induced KB cells, (+)CLA(5 μmol/L) upregulated P-gp expression at 54.5% relative to vehicle control, and decreased Rh123 accumulation by 28.2%, while (−)CLA(5 μmol/L) downregulated P-gp expression at 15.9% and increased Rh123 accumulation by 18.0%. These results suggested that (−)CLA could be a P-gp inhibitor and (+)CLA could be a modulator with concentration-dependent biphasic effects on P-gp activity, which may result in drug—drug interactions when combined with other P-gp substrate drugs.

Chiral Thioxanthones as Modulators of P-glycoprotein: Synthesis and Enantioselectivity Studies

“…This result highlights the existence of enantioselectivity in what concerns to induction mechanism, which is not a consequence of a direct interaction with P-gp. Previously, a similar behavior was described for the H1 anti-histaminic cetirizine, which was also ascribe to effects on P-gp expression [ 54 ]; the ( R )-cetirizine upregulates P-gp expression, while ( S )-cetirizine down-regulates it [ 54 , 65 ]; although, this library of compounds did not display any direct stereoselective modulation of P-gp, as previously observed for other substrates [ 54 , 55 , 63 , 64 ].…”

“…Although, some examples of enantioselective modulation of P-gp with other class of compounds have been described [ 54 , 55 , 63 , 64 ], no studies were reported focusing the enantioselectivity of chiral thioxanthones in modulating P-gp. Comparing the results obtained for the studied enantiomeric pairs (ATxs 1 (+) and 2 (−), ATxs 3 (+) and 4 (−), ATxs 5 (+) and 6 (−), and ATxs 7 (+) and 8 (−)), no significant differences were observed in P-gp activity.…”

Targeting P-glycoprotein: Investigation of piperine analogs for overcoming drug resistance in cancer

“…To elucidate the possible reason for drug resistance, both the parental (KB and SW480) and resistant (KB Ch R 8–5 and SW480-VCR) cells were checked for the P-gp expression by western blot analysis using mouse monoclonal antibody, which binds to 1040–1280 amino acids of P-gp of human origin 45 . The results showed that there was a significant overexpression of P-gp in drug resistant KB Ch R 8–5 and SW480-VCR cells, compared to the parental KB and SW480 cells (supplementary result Fig.…”

Chiral analysis of ammuxetine enantiomers in dog plasma using online SPE/liquid chromatography with tandem mass spectrometric detection after precolumn chiral derivatization

“…Chiral compounds usually exhibit discriminative properties, which display stereoselectivity in targeting specific molecules and in the process of absorption, distribution, metabolism, and excretion. Therefore, varying pharmacological, toxicological, and pharmacokinetic characteristics may occur as well . Moreover, there is a possibility that chiral compounds might undergo stereoconversion or racemization in vitro or in vivo .…”

“…Therefore, varying pharmacological, toxicological, and pharmacokinetic characteristics may occur as well. [1][2][3] Moreover, there is a possibility that chiral compounds might undergo stereoconversion or racemization in vitro or in vivo. 4,5 In accordance with the US Food and Drug Administration (FDA) guidelines, the relative contributions of each enantiomer to the pharmacological and toxicological activities of a new drug candidate must be studied.…”