Correlation between glucose uptake and membrane potential in Leishmania parasites isolated from DCL patients with therapeutic failure: a proof of concept

Abstract

Besides infection with drug-resistant parasites, therapeutic failure in leishmaniasis may be caused by altered drug pharmacokinetics, re-infection, and host immunologic compromise. Our aim has been to evaluate if relapses that occur in patients suffering from diffuse cutaneous leishmaniasis (DCL) associate with changes in the fitness of infecting organisms. Therefore, in isolates from patients suffering DCL, we correlated glucose uptake and plasma membrane potential and compared the results with those obtained from reference strains. The data demonstrate that Leishmania parasites causing DCL incorporate glucose at an efficient rate, albeit without significant changes in the plasma membrane potential as their corresponding reference strains. The isolate that did not change its accumulation rate of glucose compared to its reference strain expressed a less polarized membrane potential that was insensitive to mitochondrial inhibitors, suggesting a metabolic dysfunction that may result in glycolysis being the main source of ATP. The results constitute a proof of concept that indicates that parasites causing DCL adapted well to drug pressure and expressed an increased fitness. That is, that in Leishmania mexicana and Leishmania amazonensis, parasites isolated from DCL patients, a strong modification of the parasite physiology might occur. As consequences, the parasites adapted well to drug pressure, increased their fitness, and they had an efficient glucose uptake rate albeit not significant changes in membrane potential as their corresponding reference strains. Further validation of the concepts herein established and whether or not the third isolate corresponds with a drug-resistant phenotype need to be demonstrated at the genetic level.

Leishmanicidal Activity of Betulin Derivatives in Leishmania amazonensis; Effect on Plasma and Mitochondrial Membrane Potential, and Macrophage Nitric Oxide and Superoxide Production

“…To evaluate the plasma membrane potential (∆Ψp), the fluorescent compound, bisoxonol, bis[1,3-diethylthiobarbituric acid] trimethine oxonol, was used, as well as a method [41] optimized by Padrón-Nieves et al [42][43][44]. Initially, calibration curves for each strain, using increasing concentrations of KCl (0.5 to 75 mM), were performed in the late log growth phase Leishmania promastigotes in the presence of the potassium ionophore valinomycin.…”

“…At least two independent experiments were performed in duplicate. Compounds used as depolarizing controls were: FCCP, an oxidative phosphorylation inhibitor and ionophore, which acts by decoupling the respiratory chain, interrupting the synthesis of ATP by transporting hydrogen ions through the mitochondrial membrane before they can be used as a source of energy; and oligomycin, an antibiotic that inhibits mitochondrial ATPase by binding to the F0 subunit and interfering with the transport of H + , thus inhibiting the synthesis of ATP [43].…”