Effects of (+)-usnic acid and (+)-usnic acid-liposome on Toxoplasma gondii.

Toxoplasma gondii pathogen is a threat to human health that results in economic burden. Unfortunately, there are very few high-efficiency and low-toxicity drugs for toxoplasmosis in the clinic. (+)-Usnic acid derived from lichen species has been reported to have anti-inflammatory, antibacterial, anti-parasitology, and even anti-cancer activities. Herein, the systematic effect of (+)-usnic acid and (+)-usnic acid-liposome on toxoplasma were studied in vitro and in vivo. The viability of toxoplasma tachyzoite was assayed with trypan blue and Giemsa staining; while the invasive capability of tachyzoite to cardiofibroblasts was detected using Giemsa staining. The survival time of mice and the changes in tachyzoite ultrastructure were studied in vivo. The results showed that (+)-usnic acid inhibited the viability of tachyzoite; pretreatment with (+)-usnic acid significantly decreased the invasion of tachyzoite to cardiofibroblasts in vitro; (+)-usnic acid and (+)-usnic acid-liposome extensively prolonged the survival time of mice about 90.9% and 117%, respectively; and improved the ultrastructural changes of tachyzoite, especially in dense granules, rhoptries, endoplasmic reticulum, mitochondria and other membrane organelles. In summary, these results demonstrate that (+)-usnic acid and (+)-usnic acid-liposome with low toxicity have an inhibitory effect on the viability of toxoplasma tachyzoite, and mainly destructed membrane organelles which are connected with the virulence of toxoplasma. These findings provide the basis for further study and development of usnic acid as a potential agent for treating toxoplasmosis.