Effect of the flavonoid compound glabridin on tachyzoites and bradyzoites of Toxoplasma gondii.

Abstract

Background: Toxoplasma gondii (T. gondii) is one of the most prevalent parasites worldwide. At present, the majority of drugs used for the treatment of toxoplasmosis target the tachyzoite stage of T. gondii and are largely ineffective against bradyzoites. Furthermore, these treatments are typically accompanied by adverse events. Consequently, there is an urgent need for the development of novel drugs that are both safe and effective against T. gondii.

Methods: A total of 20 flavonoids were preliminarily screened for their anti-T. gondii activity using microscopy. Next, the cell counting kit (CCK)-8 method was employed to assess the toxicity of glabridin (GLA) to host cells, while the RH strain of T.0gondii, which expresses β-galactosidase, was utilized to evaluate the inhibitory, anti-invasive, and antiproliferative effects of GLA on T. gondii. In addition, the Prugniaud (PRU) strain was employed to investigate the impact of GLA on the bradyzoites of T. gondii. Subsequently, the effect of GLA on the ultrastructure of T. gondii was examined via transmission electron microscopy (TEM), followed by an assessment of the influence of GLA on the autophagy and mitochondria of T. gondii through monodansylcadaverine (MDC), MitoTracker^™ red CMXRos, and CM-HDCFDA and MitoSOX Red staining.

Results: Among the 20 flavonoids assessed, GLA exhibited the most potent anti-T. gondii activity. Indeed, it significantly inhibited both the invasive and proliferative abilities of T. gondii, thereby disrupting its lytic cycle. Moreover, GLA markedly reduced the number of bradyzoites and concurrently inhibited cyst growth. Meanwhile, ultrastructural analysis revealed that GLA induced mitochondrial swelling, membrane rupture, and autophagy in T. gondii. Finally, fluorescent probe staining provided further evidence that GLA triggers mitochondrial dysfunction and autophagy in this parasite.

Conclusions: Our findings collectively indicate that the flavonoid compound GLA exhibits significant activity against both T. gondii tachyzoites and bradyzoites. The underlying mechanism of action potentially involves the induction of autophagy and mitochondrial dysfunction and the disruption of the membrane of T. gondii, thereby offering new avenues for treating toxoplasmosis and establishing a theoretical reference for future research.