Glucose 6-Phosphate Dehydrogenase from Trypanosomes: Selectivity for Steroids and Chemical Validation in Bloodstream Trypanosoma brucei.
Ortiz, C., Moraca, F., Laverriere, M., Jordan, A., Hamilton, N. and Comini, M. A.
Redox Biology of Trypanosomes, Institut Pasteur de Montevideo, Mataojo 2020, Montevideo 11400, Uruguay.
Dipartimento di Biotecnologie, Chimica e Farmacia, Universita degli Studi di Siena, Via Aldo Moro 2, 53100 Siena, Italy.
Instituto de Investigaciones Biotecnologicas, Instituto Tecnologico de Chascomus (IIB-INTECH, UNSAM-CONICET), Av. General Paz 5445, INTI, San Martin 1650, Pcia de Buenos Aires, Argentina.
Drug Discovery Unit, Cancer Research UK Manchester Institute, Universi
Glucose 6-phosphate dehydrogenase (G6PDH) fulfills an essential role in cell physiology by catalyzing the production of NADPH(+) and of a precursor for the de novo synthesis of ribose 5-phosphate. In trypanosomatids, G6PDH is essential for in vitro proliferation, antioxidant defense and, thereby, drug resistance mechanisms. So far, 16alpha-brominated epiandrosterone represents the most potent hit targeting trypanosomal G6PDH. Here, we extended the investigations on this important drug target and its inhibition by using a small subset of androstane derivatives. In Trypanosoma cruzi, immunofluorescence revealed a cytoplasmic distribution of G6PDH and the absence of signal in major organelles. Cytochemical assays confirmed parasitic G6PDH as the molecular target of epiandrosterone. Structure-activity analysis for a set of new (dehydro)epiandrosterone derivatives revealed that bromination at position 16alpha of the cyclopentane moiety yielded more potent T. cruzi G6PDH inhibitors than the corresponding beta-substituted analogues. For the 16alpha brominated compounds, the inclusion of an acetoxy group at position 3 either proved detrimental or enhanced the activity of the epiandrosterone or the dehydroepiandrosterone derivatives, respectively. Most derivatives presented single digit muM EC50 against infective T. brucei and the killing mechanism involved an early thiol-redox unbalance. This data suggests that infective African trypanosomes lack efficient NADPH(+)-synthesizing pathways, beyond the Pentose Phosphate, to maintain thiol-redox homeostasis.
Molecules 26(2): en prensa (2021)