[The Effects of Temoporfin-Mediated Photodynamic Inactivation on Leishmania tropica Promastigotes and Molecular...

Leishmaniasis is a serious and endemic infectious disease reported in over 90 countries and regions. Cutaneous leishmaniasis (CL) manifests on exposed areas of the body, with its main symptoms being single or multiple ulcerative or nodular lesions on the skin, which can become chronic within six months after a bite from the Phlebotomus vector or heal spontaneously. Although not fatal, the disease can leave permanent scars. Conventional treatment methods present a range of issues, including challenges in administration, the development of resistance and side effects. Photodynamic therapy (PDT) shows significant potential as an effective, easy-to-apply, and non-invasive treatment for CL. As a new modality for antileishmanial treatment, PDT aims to enhance antileishmanial effects through the concurrent combination of light and a photosensitizer. In this study, the aim was to investigate the antileishmanial effect and possible mechanisms of temoporfin-mediated photodynamic inactivation on Leishmania tropica promastigotes in vitro. Parasites were incubated with temoporfin at concentrations of 0.5, 1, 2, 4, 8, and 16 (μM) for 50 minutes and then exposed to red light at a flux of 1.71 J/cm² for 50 minutes. The MTT assay was used to assess cell viability and morphological changes were analyzed using Giemsa staining. Molecular docking was employed to identify the highest binding affinity to overexpressed receptors in L.tropica promastigotes. It was found that the combination of temoporfin and red light significantly reduced the viability of L.tropica promastigotes compared to the group treated with temoporfin alone. The IC50 value observed for L.tropica in the temoporfin and red light combination group was 1.924 μM. At this concentration (1.924 μM), neither temoporfin alone nor red light alone had a significant effect on the viability of L.tropica promastigotes. Additionally, typical morphological features, such as loss of fusiform shape, flagella and nucleus, were observed in the temoporfin-mediated red light group. According to the molecular docking analysis, Amphotericin B and temoporfin exhibited binding affinities of -7.4 kcal/mol and -6.9 kcal/mol, respectively, to the three-dimensional model of the 5WB5 protein. Temoporfin combined red light has the potential to inactivate L.tropica promastigotes as a non-invasive treatment. The absence of any cytotoxic effects from the PDT components, red light and temoporfin in the treatment group provides an important opportunity for further studies with amastigote or animal models, paving the way for potential clinical applications.