Lycorine is an Amaryllidaceae alkaloid that presents anti-Trichomonas vaginalis activity. T. vaginalis causes trichomoniasis, the most common non-viral sexually transmitted infection. The modulation of T. vaginalis purinergic signaling through the ectonucleotidases, nucleoside triphosphate diphosphohydrolase (NTPDase), and ecto-5'-nucleotidase represents new targets for combating the parasite. With this knowledge, the aim of this study was to investigate whether NTPDase and ecto-5'-nucleotidase inhibition by lycorine could lead to extracellular ATP accumulation. Moreover, the lycorine effect on the reactive oxygen species (ROS) production by neutrophils and parasites was evaluated as well as the alkaloid toxicity. The metabolism of purines was assessed by HPLC. ROS production was measured by flow cytometry. Cytotoxicity against epithelial vaginal cells and fibroblasts was tested, as well as the hemolytic effect of lycorine and its in vivo toxicity in Galleria mellonella larvae. Our findings showed that lycorine caused ATP accumulation due to NTPDase inhibition. The alkaloid did not affect the ROS production by T. vaginalis; however, it increased ROS levels in neutrophils incubated with lycorine-treated trophozoites. Lycorine was cytotoxic against vaginal epithelial cells and fibroblasts; conversely, it was not hemolytic neither exhibited toxicity against the in vivo model of G. mellonella larvae. Overall, besides having anti-T. vaginalis activity, lycorine modulates ectonucleotidases and stimulates neutrophils to secrete ROS. This mechanism of action exerted by the alkaloid could enhance the susceptibility of T. vaginalis to host immune cell, contributing to protozoan clearance.
Keywords: Amaryllidaceae; Galleria mellonella; Lycorine; NTPDase; Reactive oxygen species; Trichomonas vaginalis.