The antidepressant clomipramine induces programmed cell death in Leishmania amazonensis through a mitochondrial pathway.

Despite many efforts, the currently available treatments for leishmaniasis are not fully effective. To discover new medications, drug repurposing arises as a promising strategy. We present data that supports the use of the antidepressant clomipramine against Leishmania amazonensis. The drug presented selective activity at micromolar range against both the parasite forms and stimulated nitric oxide production in host macrophages. Regarding the mechanism of action, clomipramine led parasites do mitochondrial depolarization, which coupled with the inhibition of trypanothione reductase induced strong oxidative stress in the parasites. The effects observed in promastigotes included lipoperoxidation, plasma membrane permeabilization, and apoptosis hallmarks (i.e., DNA fragmentation, phosphatidylserine exposure, and cell shrinkage). The mechanism of action in both parasitic forms was quite similar, but amastigotes also exhibited energetic stress, reflected by a reduction of adenosine triphosphate levels. Such differential effects might be attributable to the metabolic particularities of each form of the parasitic. Ultrastructural alterations of the endomembrane system and autophagy were also observed, possibly indicating an adaptive response to oxidative stress. Our results suggest that clomipramine interferes with the redox metabolism of L. amazonensis. In spite of the cellular responses to recover the cellular homeostasis, parasites underwent programmed cell death.

The photodynamic action of pheophorbide a induces cell death through oxidative stress in Leishmania amazonensis.

Leishmaniasis is a disease caused by hemoflagellate protozoa, affecting millions of people worldwide. The difficulties of treating patients with this parasitosis include the limited efficacy and many side effects of the currently available drugs. Therefore, the search for new compounds with leishmanicidal action is necessary. Photodynamic therapy has been studied in the medical field because of its selectivity, utilizing a combination of visible light, a photosensitizer compound, and singlet oxygen to reach the area of treatment. The continued search for selective alternative treatments and effective targets that impact the parasite and not the host are fundamentally important for the development of new drugs. Pheophorbide a is a photosensitizer that may be promising for the treatment of leishmaniasis. The present study evaluated the in vitro biological effects of pheophorbide a and its possible mechanisms of action in causing cell death in L. amazonensis. Pheophorbide a was active against promastigote and amastigote forms of the parasite. After treatment, we observed ultrastructural alterations in this protozoan. We also observed changes in promastigote macromolecules and organelles, such as loss of mitochondrial membrane potential [∆Ψm], lipid peroxidation, an increase in lipid droplets, DNA fragmentation, phosphatidylserine exposure, an increase in caspase-like activity, oxidative imbalance, and a decrease in antioxidant defense systems. These findings suggest that cell death occurred through apoptosis. The mechanism of cell death in intracellular amastigotes appeared to involve autophagy, in which we clearly observed an increase in reactive oxygen species, a compromised ∆Ψm, and an increase in the number of autophagic vacuoles. The present study contributes to the development of new photosensitizers against L. amazonensis. We also elucidated the mechanism of action of pheophorbide a, mainly in intracellular amastigotes, which is the most clinically relevant form of this parasite.