title: New azasterols against Trypanosoma brucei: role of 24-sterol methyltransferase in inhibitor action.
abstract: A series of azasterol derivatives, designed as potential inhibitors of the Delta(24)-sterol methyltransferase enzyme (24-SMT), were synthesized and evaluated for their activities against parasitic protozoa. Values in the nanomolar range were obtained for 50% effective dose against the Trypanosoma brucei subsp. rhodesiense bloodstream form cultured in vitro. In order to investigate the mode of action, Trypanosoma brucei subsp. brucei 24-SMT was cloned and overexpressed and compounds were assayed for inhibitory activity. None of the inhibitors tested appeared to be active against the enzyme. Sterol composition analysis showed that only cholestane type sterols are present in membranes of bloodstream forms while ergosterol is a major component of procyclic sterol extracts. Interestingly, Northern blot analysis showed the presence of 24-SMT mRNA in both the procyclic and the bloodstream forms of the parasite, although levels of mRNA were threefold lower in the latter. Likewise, Western blot analysis and activity determinations evidenced the existence of active enzyme in both forms of the parasite. We conclude that the designed compounds act at sites other than 24-SMT in Trypanosoma brucei.
authors.affiliation: Welsh School of Pharmacy, Cardiff University, UK.
authors.forename: Ludovic
authors.initials: L
authors.lastname: Gros
authors.forename: Victor Manuel
authors.initials: VM
authors.lastname: Castillo-Acosta
authors.forename: Carmen
authors.initials: C
authors.lastname: Jiménez Jiménez
authors.forename: Marco
authors.initials: M
authors.lastname: Sealey-Cardona
authors.forename: Sofia
authors.initials: S
authors.lastname: Vargas
authors.forename: Antonio
authors.initials: A
authors.lastname: Manuel Estévez
authors.forename: Vanessa
authors.initials: V
authors.lastname: Yardley
authors.forename: Lauren
authors.initials: L
authors.lastname: Rattray
authors.forename: Simon L
authors.initials: SL
authors.lastname: Croft
authors.forename: Luis M
authors.initials: LM
authors.lastname: Ruiz-Perez
authors.forename: Julio A
authors.initials: JA
authors.lastname: Urbina
authors.forename: Ian H
authors.initials: IH
authors.lastname: Gilbert
authors.forename: Dolores
authors.initials: D
authors.lastname: González-Pacanowska
mesh_terms: D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D001372:Aza Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D008780:Methyltransferases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry; D013261:Sterols / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D014344:Trypanocidal Agents / Q000494:pharmacology*; D014346:Trypanosoma brucei brucei / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development
chemical_list: D000981:Antiprotozoal Agents; D001372:Aza Compounds; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D013261:Sterols; D014344:Trypanocidal Agents; D008780:Methyltransferases