title: Resistance mechanism development to the topoisomerase-I inhibitor Hoechst 33342 by Leishmania donovani.
abstract: The bisbenzimidazole compound Hoechst 33342 (Ho342) has been identified as a specific Topoisomerase-I (Topo-I) inhibitor in mammalian cells. More recently, we have reported the ability of Ho342 to target L. donovani Topo-I, leading to parasite growth inhibition in vitro by mechanisms involving DNA breakage and apoptosis-like phenomenon. As the Ho342 lead molecule (2,5'-Bi-1H-benzimidazole) can be used as a starting structure for derivative compounds more effective against Leishmania, defining the Ho342 resistance mechanism(s) in Leishmania represents an important strategic tool. In the present study, we selected resistant parasites to Ho342 (LdRHo.300). While we observed an increase of the Topo-I gene expression correlated by a higher Topo-I DNA relaxation activity, the Topo-I genes (LdTOP1A and LdTOP1B) sequencing did not reveal any mutation for the resistant parasites. Moreover, our results on Ho342 cellular accumulation suggested the presence of a potential energy-dependent Ho342 transporter in the wild-type parasite, and that an alteration of this transporter has occurred in LdRHo.300, leading to an altered drug accumulation. Collectively, Ho342 resistance characterization provided results supporting that the resistance developed by LdRHo.300 involves complex mechanisms, most likely dominated by an altered drug accumulation, providing new insight in the Ho342 resistance mechanisms.
authors.affiliation: Centre for the Study of Host Resistance and the Research Institute of McGill University Health Centre, Department of Experimental Medicine, McGill University, Montreal, Quebec, Canada.
authors.forename: J F
authors.initials: JF
authors.lastname: Marquis
authors.forename: I
authors.initials: I
authors.lastname: Hardy
authors.forename: M
authors.initials: M
authors.lastname: Olivier
mesh_terms: D000818:Animals; D000981:Antiprotozoal Agents / Q000378:metabolism / Q000494:pharmacology*; D001562:Benzimidazoles / Q000378:metabolism / Q000494:pharmacology*; D001692:Biological Transport; D004264:DNA Topoisomerases, Type I / Q000235:genetics / Q000378:metabolism; D004351:Drug Resistance / Q000235:genetics*; D015870:Gene Expression / Q000187:drug effects; D007893:Leishmania donovani / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D059004:Topoisomerase I Inhibitors
chemical_list: D000981:Antiprotozoal Agents; D001562:Benzimidazoles; D059004:Topoisomerase I Inhibitors; D004264:DNA Topoisomerases, Type I; C017807:bisbenzimide ethoxide trihydrochloride