[An In Vitro Study on Sonodynamic Therapy of Leishmania tropica Using Curcumin]

Leishmaniasis is an infectious disease that is transmitted by Phlebotomus, 400 thousand new cases appearing every year, and approximately 350 million people are at risk, and accepted by the World Health Organization as one of the six important tropical diseases. Cutaneous leishmaniasis is a disease that occurs on exposed areas of the body and is characterized by long-term non-healing skin lesions. Although the treatment methods applied today vary according to the clinical picture of the patient, the immune system of the person and the causative agent Leishmania species, there is still no standard treatment scheme that has few side effects and can be used in the treatment of leishmaniasis. Therefore, alternative treatment methods with less side effects are being tried. Sonodynamic therapy (SDT) has also emerged as an active antimicrobial research area in recent years. SDT, a new modality for antibacterial therapy, aims to increase antibacterial effects with the simultaneous combination of low-intensity ultrasound and sonosensitizer. There is no information in the literature about the effect of SDT on parasites. In this study, it was aimed to demontrate the anti-leishmanial effect and possible mechanisms of curcumin mediated SDT on L.tropica promastigotes in vitro. Parasites were incubated with 0.25, 1.0, 4.0 and 15.6 micromolar (μM) of curcumin for one hour and subjected to 1 MHz frequency, 50% duty cycle and 3 W/cm2 intensity ultrasound irradiation. XTT assay was used to evaluate the viability of the cells and morphological changes were analyzed by Giemsa staining. Flow cytometry was used to quantify the fluorescence emitted by intracellular reactive oxygen species (ROS) signal, JC-1, cell cycle, Annexin V/PI staining reagents. With the combination of curcumin (15.6 μM) and ultrasound (3 W/cm2 intensity, seven minutes), L.tropica promastigote viability was found to be significantly decreased compared to the control group. Giemsa staining results showed that 15.6 μM curcumin mediated SDT induced several morphological alterations in L.tropica promastigotes typical for apoptosis. Late apoptosis was observed in 15.6 μM curcumin combined SDT treated parasites according to Annexin/PI staining. Besides, curcumin mediated SDT caused mitochondrial membrane potential (∆ᴪm) loss. Cell cycle analysis data indicated that curcumin based SDT caused an subG1 arrest in the cell cycle of L.tropica promastigotes. The generation of intracellular ROS detected by flow cytometry was increased in L.tropica promastigotes treated with curcumin mediated SDT. This study provided new data elucidating the molecular mechanism underlying the anti-leishmanial effect of curcumin mediated SDT. Curcumin mediated SDT has the potential to inactivate L.tropica promastigotes. However, further testing with amastigote or animal models is needed.