Characterization of anti-Toxoplasma activity of SDZ 215-918, a cyclosporin derivative lacking immunosuppressive and peptidyl-prolyl-isomerase-inhibiting activity: possible role of a P glycoprotein in Toxoplasma physiology

Abstract

The immunosuppressive agent cyclosporin A (CsA) also possesses broad-spectrum antimicrobial activity. Previous investigators have reported that the obligate intracellular protozoan Toxoplasma gondii is sensitive to CsA. We have measured the sensitivity of Toxoplasma to 26 CsA derivatives that maintain only a subset of the parent compound's activity. We identified one compound, SDZ 215-918, that is a particularly potent inhibitor of parasite invasion and replication, with a 50% inhibitory concentration of 0.45 microg/ml, which is 10-fold lower than that of CsA. Kinetic studies demonstrate that activity has a rapid onset (half-life, < or = 20 min) and is initially reversible, although long-term exposure (> 24 h) to 5 microg/ml is lethal; in contrast, this concentration had no effect on host cell protein synthesis or cell division. SDZ 215-918 acts directly on the parasite, as demonstrated by inhibition of macromolecular synthesis in host-free extracellular parasites. Inhibition of invasion is due to a reduction in parasite motility. SDZ 215-918 does not bind to cyclophilins, the ubiquitous cyclosporin-binding proteins, but is a potent inhibitor of the mammalian P glycoprotein, a member of the ATP binding cassette transporter superfamily and the pump responsible for multidrug resistance in cancer and parasite cell lines. SDZ 215-918 blocks the efflux of rhodamine 123 from extracellular parasites, consistent with inhibition of a P glycoprotein-like pump. We suggest that a P glycoprotein or a related transporter plays a crucial role in the biology of Toxoplasma and may be a novel target for antiparasitic compounds. Preliminary studies with animals indicate that SDZ 215-918 inhibits parasite growth in vivo; its relationship to CsA may make it suitable for clinical development.

In vitro anti-parasitic activity of Cyclosporin A analogs on Trypanosoma cruzi

“…26 In our study, H-7-94 and F-7-62 CsA derivatives, have strongly bound to TcCyP19 but both compounds proved to exhibit a negligible immunosuppressive activity, 11 unlike CsA and other CsA analogs, which showed a physical and functional interaction with calcineurin, suppressing IL-2 gene expression.…”

The P-glycoprotein Inhibitor GF120918 Modulates Ca2+-Dependent Processes and Lipid Metabolism in Toxoplasma Gondii

“…Previous studies based on efflux analyses in the presence of P-gp inhibitors suggested that an active P-gp homologue is present in T. gondii [6], [7]. Recently, two P-gp homologues with the typical P-gp structure have been identified in the genome of the parasite (TgABC.B1 and TgABC.B2) and found to be constitutively expressed in both the vegetative and quiescent stages of T. gondii 's life cycle [8].…”

“…Further molecular characterization revealed that TgABC.B1 is coded by a single copy gene, expressed as a membrane-associated protein of ∼150 kDa, and constitutively present in different parasite strains [9]. Indications that T. gondii P-gp may be involved in key biological processes, such as replication and host cell invasion were provided by early works using P-gp inhibitors [6], [10]. However, given that these studies used host cells containing P-gp, it was not possible to discriminate between the contribution of T. gondii and host cell P-gp.…”

Molecular aspects of cyclophilins mediating therapeutic actions of their ligands

“…It is possible that anti-parasitic activity of CsA could be due to its binding to other targets such as P-glycoprotein (P-gP), in which the some CsA analogues proved to be potent modifiers of its activity [123,137,142]. It was suggested, however, that calcineurin was the target of CsA complexed to the cytosolic cyclophilin expressed in E. histolytica [140].…”