Atividade leishmanicida do nerolidol e de um surfactante: associação com rigidez de membrana em Leishmania amazonensis e macrófagos infectados

Abstract

Leishmaniasis is a neglected parasitic disease that affects millions of people, especially in tropical regions such as Brazil. Transmitted by sand flies, currently available treatments have important limitations, such as high toxicity, high cost and increased parasite resistance. In view of this scenario, the leishmanicidal effects of nerolidol, a natural sesquiterpene, and the zwitterionic surfactant HPS (N-hexadecyl-N,N-dimethyl-3-ammonium-1-propanesulfonate) against Leishmania amazonensis were investigated. Using the electron paramagnetic resonance (EPR) spectroscopy of spin labeling, it was found that both compounds altered the fluidity of the parasite's plasma membrane, promoting an initial increase followed by rigidity after 24 h of exposure. IC50 values ??were estimated at approximately 74 ?M for nerolidol and 10 ?M for HPS. At concentrations ranging from one to three times their respective IC50 values, they induced significant membrane stiffness, attributed to the formation of reactive oxygen species (ROS), with consequent lipid peroxidation and/or protein oxidation. In uninfected J774A.1 macrophages, no membrane stiffening was observed, possibly due to the protective action of endogenous nitric oxide, capable of neutralizing oxidative stress. On the other hand, in macrophages previously infected with Leishmania, there was an increase in membrane stiffness after 72 h of treatment, suggesting that the infection sensitizes these cells to oxidative damage. To complement the evaluation of the selectivity and safety of the compounds, their cytotoxicity in macrophages derived from the THP-1 cell line, a more representative model of the human immune system in a state of differentiation, was also analyzed. In this approach, it was observed that the mean CC50 values ??were approximately nine times higher than those recorded in J774A.1 cells, indicating lower toxicity in a model of greater physiological relevance and reinforcing the selective profile of the compounds for the parasite. The data obtained indicate that the antileishmanial activity of nerolidol and HPS is strongly associated with their direct action on the parasite's plasma membrane. The initial increase in fluidity may favor ionic leakage and depolarization of the cell membrane, causing mitochondrial hyperpolarization and increased ROS production, which triggers a sequence of events, including membrane rigidification, resulting in irreversible structural damage and death of the parasite.