title: Resistance of Entamoeba histolytica to the cysteine proteinase inhibitor E64 is associated with secretion of pro-enzymes and reduced pathogenicity.
abstract: Cysteine proteinases (CPs) have been considered suitable targets for the development of antiparasitic drugs. To assess the importance of CPs for the growth and pathogenicity of the protozoan parasite Entamoeba histolytica we have cultured amoebae in the presence of various cysteine proteinase inhibitors (CPIs). It was found that broad range CPIs, which are membrane permeable and rapidly enter the cell, are highly toxic at micromolar concentrations, and all attempts to generate E. histolytica mutants resistant to these CPIs were unsuccessful. In contrast, the broad range CPI E64, which does not permeate membranes as well, was deleterious at much higher concentrations, and amoebae rapidly developed resistance to this inhibitor. Compared with sensitive wild-type cells, E64-resistant E. histolytica were substantially reduced in the expression of various CP genes and were able to secrete unprocessed enzyme into the culture medium. Moreover, E64 resistance was associated with a significant reduction in virulence, because these cells were greatly impaired in the ability to generate liver abscesses in experimentally infected gerbils.
authors.affiliation: Bernhard Nocht Institute for Tropical Medicine, 20359 Hamburg, Germany.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Nowak
authors.forename: Hannelore
authors.initials: H
authors.lastname: Lotter
authors.forename: Egbert
authors.initials: E
authors.lastname: Tannich
authors.forename: Iris
authors.initials: I
authors.lastname: Bruchhaus
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D016466:CHO Cells; D002455:Cell Division; D006224:Cricetinae; D003470:Culture Media / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D015180:Electrophoresis, Gel, Two-Dimensional; D004748:Entamoeba histolytica / Q000378:metabolism*; D005849:Gerbillinae; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism / Q000469:parasitology; D008101:Liver Abscess, Amebic / Q000469:parasitology; D008854:Microscopy, Electron; D009154:Mutation; D012313:RNA / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013997:Time Factors
chemical_list: D003470:Culture Media; D015853:Cysteine Proteinase Inhibitors; D012313:RNA; D007930:Leucine; C108192:aloxistatin