P-glycoprotein expression and pharmacological modulation in larval stages of Echinococcus granulosus

Abstract

P-glycoprotein (Pgp) is an ATP-dependent transporter involved in the efflux of a wide variety of lipophilic substrates, such as toxins and xenobiotics, out of cells. Pgp expression level is associated with the ineffective therapeutic treatment of cancer cells and microbial pathogens which gives it high clinical importance. Research on these transporters in helminths is limited. This work describes for the first time the Echinococcus granulosus Pgp (Eg-Pgp) expression, in a model cestode parasite and an important human pathogen. Based on calcein efflux assays in the presence of common Pgp modulators, we demonstrated the occurrence of active Eg-Pgp in protoscoleces and metacestodes. Eg-Pgp, which showed a molecular mass of ~130 kDa in western blots, is localized in the suckers and the tegument of control protoscoleces as well as in the subtegument or all parenchymatous cells of protoscoleces treated with Pgp-interfering agents. We also identified five genes encoding Pgp which are constitutively expressed in protoscoleces and metacestodes. We showed that the Eg-pgp1 and Eg-pgp2 transcripts were up-regulated in response to in vitro drug treatment with amiodarone and loperamide, in agreement with the increased polypeptide levels. Finally, in vitro treatment of protoscoleces and metacestodes with trifluoperazine and loperamide was lethal to the parasites. This indicates that both drugs as well as cyclosporine A negatively modulate the E. granulosus Pgp efflux activity, favoring the retention of these drugs in the larval tissue. These events could be associated with the reduction in protoscolex and metacestode viability.