Intracellular accumulation of Praziquantel in T lymphoblastoid cell lines, CEM (parental) and CEMVBL(P-gp-overexpressing)

Abstract

Background: Praziquantel (PZQ) is an antihelminthic drug whose P-glycoprotein (P-gp) substrate specificity has not been conclusively characterized. We investigated its specificity by comparing its in vitro intracellular accumulation in CEM (parental), and CEMVBL cells which over express P-gp, a drug efflux transporter. Saquinavir (SQV), a known substrate of efflux transporters was used as control.

Methods: A reversed phase liquid chromatography method was developed to simultaneously quantify PZQ and SQV in cell culture media involving involved a liquid - liquid extraction followed by ultra-high performance liquid chromatography using a Hypurity C18 column and ultraviolet detection set at a wavelength of 215 nm. The mobile phase consisted of ammonium formate, acetonitrile and methanol (57:38:5 v/v). Separation was facilitated via isocratic elution at a flow rate of 1.5 ml/min, with clozapine (CLZ) as internal standard. This was validated over the concentration range of 1.6 to 25.6 μM for all analytes. Intracellular accumulation of SQV in CEMVBL was significantly lower compared to that in CEM cells (0.1 ± 0.031 versus 0.52 ± 0.046, p = 0.03 [p <0.05]).

Results: Accumulation of PZQ in both cell lines cells were similar (0.05 ± 0.005 versus 0.04 ± 0.009, p = 0.4) suggesting that it is not a substrate of P-gp in CEM cells. In presence tariquidar, a known inhibitor of P-gp, the intracellular accumulation of SQV in CEMVBL cells increased (0.52 ± 0.068 versus 0.61 ± 0.102, p = 0.34 in CEM cells and 0.09 ± 0.015 versus 0.56 ± 0.089, p = 0.029 [p < 0.05] in CEMVBL cells). PZQ did not significantly affect the accumulation of SQV in either CEM (0.52 ± 0.068 versus 0.54 ± 0.061, p = 0.77), or in CEMVBL cells (0.09 ± 0.015 versus 0.1 ± 0.031, p = 0.89) cells compared to tariquidar, implying that PZQ is not an inhibitor of P-gp in CEMVBL cells.

Conclusions: PZQ is neither a substrate nor an inhibitor of the efflux drug transporter P-gp in T-lymphoblastoid cells, CEM and CEMVBL. We also report a simple, accurate and precise method for simultaneous quantification of PZQ and SQV.

Keywords: Characterization; P-glycoprotein; Pharmacokinetics; Praziquantel.

Fig. 1

Chromatogram depicting the retention times of CLZ (internal standard), PZQ and SQV at a concentration of 19.2 μM for both drugs

Fig. 2

Plots of the calibration curves showing the concentration response relationships of a (PZQ) and b (SQV) on the same run

Fig. 3

Chromatogram of the blank extract (DMEM), showing the injection peak and absence of any other interfering peaks

Fig. 4

Chromatograms showing the extracellular accumulation of SQV/PZQ in CEM parental (a), and CEMvbl cells (b); and intracellular accumulation in CEMvbl cells (c)

Fig. 5

Intracellular accumulation of SQV and PZQ in CEM and CEMvbl cells, Mean ± SD (n = 4)

Fig. 6

Effect of PZQ and tariquidar on the intracellular accumulation of SQV in CEM and CEMvbl cells, Mean ± SD (n = 4)