High-Affinity Binding of Silybin Derivatives to the Nucleotide-Binding Domain of a Leishmania tropica P-Glycoprotein-Like Transporter and Chemosensitization of a Multidrug-Resistant Parasite to Daunomycin

Abstract

In order to overcome the multidrug resistance mediated by P-glycoprotein-like transporters in Leishmania spp., we have studied the effects produced by derivatives of the flavanolignan silybin and related compounds lacking the monolignol unit on (i) the affinity of binding to a recombinant C-terminal nucleotide-binding domain of the L. tropica P-glycoprotein-like transporter and (ii) the sensitization to daunomycin on promastigote forms of a multidrug-resistant L. tropica line overexpressing the transporter. Oxidation of the flavanonol silybin to the corresponding flavonol dehydrosilybin, the presence of the monolignol unit, and the addition of a hydrophobic substituent such as dimethylallyl, especially at position 8 of ring A, considerably increased the binding affinity. The in vitro binding affinity of these compounds for the recombinant cytosolic domain correlated with their modulation of drug resistance phenotype. In particular, 8-(3,3-dimethylallyl)-dehydrosilybin effectively sensitized multidrug-resistant Leishmania spp. to daunomycin. The cytosolic domains are therefore attractive targets for the rational design of inhibitors against P-glycoprotein-like transporters.

Alkyl-Lysophospholipid Resistance in Multidrug-Resistant Leishmania tropica and Chemosensitization by a Novel P-Glycoprotein-Like Transporter Modulator

“…After 72 h of incubation at 28°C, cell densities were determined as described above. The sensitization of the resistant parasites to daunomycin in the presence of the reversal agent was expressed as the percentage of growth inhibition with respect to the control cells, as described previously (31,33). Control of the sesquiterpene toxicity in Leishmania was done in parallel tubes by incubating the wild-type parasite with the same concentration of reversal agent, as described previously (31)(32)(33).…”

“…Classical modulators of mammalian Pgp such as verapamil and cyclosporine poorly revert the MDR phenotype in Leishmania (5,18,32). Conversely, we have recently described that natural compounds such as sesquiterpenes and flavonoids, as well as hemisynthetic derivatives, constitute promising new classes of modulators due to their ability to increase drug accumulation and reverse the MDR phenotype in Leishmania parasites (31)(32)(33).…”

Leishmania: papel de la glicoproteína P en la mediación de resistencia a medicamentos y estrategias de reversión.

“…Son moduladores naturales de diferentes proteínas transportadoras al unirse a ellas (140)(141)(142)(143); en el caso de la Pgp, al parecer, los flavonoides interactúan al contrario de los sesquiterpenos, con el sitio de fijación del ATP o dominio NBD y con una región hidrofóbica adyacente a este dominio (144)(145)(146). Varios de estos compuestos son capaces de inhibir el eflujo de medicamentos y revierten el fenotipo MDR en una línea de L. tropica resistente a la daunomicina (147,148).…”

“…Entre los flavonoides naturales y sintéticos promisorios por presentar afinidad de fijación a la Pgp en diferentes líneas celulares, se encuentran algunos flavonoides como el kaempferol y la quercetina, isoflavones como la genisteína, chalconas halogenadas, flavonoides que contienen una cadena de N-benzilpiperazina y el flavanolignano derivado del silibin denominado 8-(3,3-dimetilalil)-dehidro-silibin (144,145,148).…”

Combination of Suboptimal Doses of Inhibitors Targeting Different Domains of LtrMDR1 Efficiently Overcomes Resistance of Leishmania spp. to Miltefosine by Inhibiting Drug Efflux

“…In contrast, two different families of natural compounds, flavonoids and dihydro-␤-agarofuran sesquiterpenes, are able to efficiently overcome the Leishmania MDR phenotype, probably by acting at different levels (35). Some flavonoid derivatives bind to a purified recombinant NBD from LtrMDR1 and interact with both the ATP-binding site and a vicinal hydrophobic region (7,11,34) with an affinity that correlates with their abilities to modulate drug accumulation and to reverse the resistance phenotype of a Leishmania tropica MDR line (34,37). On the other hand, some sesqui-terpenes efficiently overcome the Leishmania MDR phenotype (21,38,39) by increasing drug accumulation (21,38); their binding to the TMDs of human Pgp has been suggested recently (27).…”