Combinations of chloroquine with tigecycline and telithromycin induce early onset of apoptosis in Plasmodium falciparum in vitro

ABSTRACT

OBJECTIVE: This study aimed to demonstrate that apoptosis in Plasmodium falciparum can be measured using kits originally designed for mammalian cells. The antimalarial chloroquine and antibiotics tigecycline and telithromycin were used to show the performance of the assays. METHODS: Nuclear stain DAPI fluorescence was used to estimate cytotoxicity. Apoptotic assays used were CaspaTag™ for caspase activation, acridine orange for nuclear condensation, and TUNEL for DNA fragmentation. RESULTS: The IC50 values (95% confidence interval) for telithromycin (TL), tigecycline (TG) and chloroquine (CQ) were found to be 1.00 (0.47-1.53) µM, 4.56 (2.32-6.80) µM, and 0.019 (0.0089-0.029) µM, respectively. Activated caspase-like molecules seemed to be present in all erythrocytic stages, appearing to rise and fall with cell cycle progression with drug exposure appearing to dysregulate this pattern. Nuclear condensation and DNA fragmentation occurred late in the untreated erythrocytic life cycle of the parasite but were advanced by drug exposure. CONCLUSION: The study shows that drug-induced apoptosis can be measured in Plasmodium falciparum using the methods. These assays could be used for drug discovery, in particular, using high throughput flow cytometry.