Anthelmintics Are Substrates and Activators of Nematode P Glycoprotein

Abstract

P glycoproteins (Pgp), members of the ABC transporter superfamily, play a major role in chemoresistance. In nematodes, Pgp are responsible for resistance to anthelmintics, suggesting that they are Pgp substrates, as they are in mammalian cells. However, their binding to nematode Pgp and the functional consequences of this interaction have not been investigated. Our study showed that levamisole and most of the macrocyclic lactones (MLs) are Pgp substrates in nematodes. Ivermectin, although a very good substrate in mammalian cells, is poorly transported. In contrast to their inhibitory effect on mammalian Pgp, these drugs had a stimulatory effect on the transport activity of the reference Pgp substrate rhodamine 123 (R123) in the nematode. This may be due to a specific sequence of nematode Pgp, which shares only 44% identity with mammalian Pgp. Other factors, such as the affinity of anthelmintics for Pgp and their concentration in the Pgp microenvironment, could also differ in nematodes, as suggested by the specific relationship observed between the octanol-water partition coefficient (log P) of MLs and R123 efflux. Nevertheless, some similarities were also observed in the functional activities of the mammalian and nematode Pgp. As in mammalian cells, substrates known to bind the H site (Hoechst 33342 and colchicine) activated the R site, resulting in an increased R123 efflux. Our findings thus show that ML anthelmintics, which inhibit Pgp-mediated efflux in mammals, activate transport activity in nematodes and suggest that several substituents in the ML structure are involved in modulating the stimulatory effect.

Differential effects of mitogen-activated protein kinase pathway inhibitors on P-glycoprotein activation

“…Sterz et al reported that some substances are activators of P-gp [22]. Further, Kerboeuf et al reported that macrocyclic lactone anthelmintics activate P-gp in nematodes and suggested that several substituents in the macrocyclic lactone structure are involved in modulating P-gp activation [23].…”

The role of drug efflux systems in anthelmintic resistance in parasitic nematodes

“…contortus, it has been shown that LEV and MLs other than IVM are highly stimulatory of P-gps (Kerboeuf and Guegnard, 2011). However, it was recently described that IVM markedly inhibited rhodamine-123 (R-123; a fluorescent substrate) transport through pgp-2, pgp-9.1 and pgp-16 from adult worms of H. contortus expressed in mammalian cells (Godoy et al, 2015a;Godoy et al, 2015b;Godoy et al, 2016), whereas moxidectin caused less inhibition of R-123 efflux as compared to IVM.…”

“…Several agents identified as inhibitors of the transport proteins using efflux / accumulation assays have potential applications in chemotherapy of drug resistance in human cancers and livestock parasitic nematodes (Scala et al, 1997;Kerboeuf and Guegnard, 2011). In nematodes, R-123 accumulation/ efflux has been examined using eggs of H.…”

“…Therefore, ABC transporters might be involved in active efflux of anthelmintic drugs away from their target sites, resulting in decreased drug concentration and increased parasite survival. It has been suggested that commonly used anthelmintics such as ivermectin (IVM), levamisole (LEV) and thiabendazole are substrates of ABC transporters (Kerboeuf and Guegnard, 2011;Falasca and Linton, 2012), and there is inconsistent evidence that exposure to anthelmintics modulates the expression patterns of different ABC transporters in nematodes Areskog et al, 2013;. Modulation of the abundance or activity of these transport proteins (particularly Pglycoprotein) has been suggested as a possible mechanism of AR in nematodes (Blackhall et al, 1998a).…”

“…Since LEV acts a substrate of P-gps (Kerboeuf and Guegnard, 2011), there might be a possible contribution from P-gps towards LEV resistance. However, further work is required to test this hypothesis.…”