Unravelling the effects of proline analogues against Trypanosoma cruzi

Background Proline is a fundamental amino acid for T. cruzi , the etiological agent of Chagas disease. Proline is mainly incorporated from the extracellular medium by amino acid transport systems. Different proline analogues proved to interact with the proline permease TcAAAP069 and inhibit proline uptake by T. cruzi . Methods Decyl- ( 1 ), oleyl- ( 2 ) and farnesyl- ( 3 ) substituted proline analogues were evaluated on 6 T. cruzi DTUs. Effects on cell death and cell cycle were determined by flow cytometry. A fluorescent tag was incorporated to compound 1 ( 1-NBD ), in order to follow-up its fate through fluorescence microscopy and to determine its localization. The structure–activity relationship (SAR) was extended in order to understand the role of the proline and triazole motifs (compounds 4 – 13 ). Results The compounds showed broad-spectrum activity against all DTUs. Compound 2 induced an apoptosis-like cell death phenotype, while compounds 1 and 3 induced cell cycle arrest at G1. The fluorescent labelling ( 1-NBD ) and subsequent microscopy showed that compound 1 can be taken up by epimastigotes. SAR showed that triazole is crucial for activity, while proline grants selectivity, being the proline-triazole hybrid being essential for their activity, and the nature of the alkyl chains significantly influences their mode of action. Conclusion These findings contribute to a deeper understanding of the role of proline uptake and metabolism in T. cruzi survival.