The photodynamic effects of protoporphyrin IX, protoporphyrin IX dimethyl ester or metallated protoporphyrin IX on Leishmania tarentolae in culture

Leishmania are parasites that cause leishmaniasis for which there are currently few treatments. Protoporphyrin IX (PIX), PIX-ester, PIX-Zn, and PIX-Sn were used at various concentrations to test their ability to inhibit growth of axenic Leishmania tarentolae. The compounds (in dimethyl sulfoxide, DMSO) were added at different concentrations to the cell cultures and control cells were exposed to DMSO only. Cells were exposed to 2 hours of direct fluorescent light (350-750 nm, 750 Lux) or kept in the dark. The cells were evaluated by microscopy, the MTT viability assay, and confocal microscopy. After 48 hours in culture, some compounds were observed to have negative effects on Leishmania promastigote growth when compared to DMSO controls depending on the concentration and light exposure. The amastigote form was more negatively affected by PIX-Sn relative to PIX. A MitoSOX™ probe was used to identify the presence of superoxide, suggesting a mechanism for cell inhibition. This research suggests that PIX especially with metallation shows potential to treat leishmaniasis.