The Paradoxical Leishmanicidal Effects of Superoxide Dismutase (SOD)-Mimetic Tempol in Leishmania braziliensis Infection in vitro

Abstract

Leishmaniasis is an infectious disease caused by protozoans of the genus Leishmania . The macrophage is the resident cell in which the parasite replicates and it is important to identify new compounds that can aid in parasite elimination since the drugs used to treat leishmaniasis are toxic and present side effects. We have previously shown that treatment of Leishmania braziliensis -infected macrophages with DETC (Diethyldithiocarbamate) induces parasite killing, in vivo . Thus, the objective of this study was to further evaluate the effect of oxidants and antioxidants in L. braziliensis- infected macrophages, following treatment with either oxidizing Hydrogen Peroxide, Menadione, DETC, or antioxidant [NAC (N-Acetyl-Cyteine), Apocynin, and Tempol] compounds. We determined the percentage of infected macrophages and number of amastigotes. Promastigote survival was also evaluated. Both DETC (SOD-inhibitor) and Tempol (SOD-mimetic) decreased the percentage of infected cells and parasite load. Hydrogen peroxide did not interfere with parasite burden, while superoxide-generator Menadione had a reducing effect. On the other hand, NAC (GSH-replenisher) and Apocynin (NADPH-oxidase inhibitor) increased parasite burden. Tempol surfaces as an interesting candidate for the chemotherapy of CL with an IC 50 of 0.66 ± 0.08 mM and selectivity index of 151. While it remains obscure how a SOD-mimetic may induce leishmanicidal effects, we suggest the possibility of developing Tempol-based topical applications for the treatment of cutaneous leishmaniasis caused by L. braziliensis .

Nitric Oxide Resistance in Leishmania (Viannia) braziliensis Involves Regulation of Glucose Consumption, Glutathione Metabolism and Abundance of Pentose Phosphate Pathway Enzymes

“…braziliensis amastigotes survive and replicate much better in the absence of ROS, identifying these molecules as important regulators of the parasite proliferation inside the host cells [ 48 ]. In addition, supplementation of cell cultures with pro-oxidants and antioxidants modulates Leishmania infection, resulting in a reduced parasite load in stressful conditions [ 49 ]. Moreover, sensitivity to distinct reactive species may vary in the parasite stages, with H 2 O 2 being more toxic to Leishmania amastigotes than O 2 •− [ 43 , 50 ].…”

“…In contrast, O 2 •− metabolism might be essential for NO-resistant strain because only SOD-treated cells showed reduction in the parasite load. The use of tempol, an antioxidant able to promote O 2 •− dismutation at rates similar to SOD, pointed to the dual role of this free radical to control the infection, highlighting differences in the pathogenesis of cutaneous leishmaniasis caused by different species of Leishmania [ 49 , 51 , 52 ].…”

Fe-S cofactors in the SARS-CoV-2 RNA-dependent RNA polymerase are potential antiviral targets

“…TEMPOL exhibited strong antiviral activity at concentrations above 0.2 mM. Viral titers were reduced by more than 5 log 10 in the presence of 0.4 mM TEMPOL, which is reported to have a 50% cytotoxic concentration (CC50) greater than 100 mM (50). Our studies present a molecular basis for pursuing TEMPOLwith its low cytotoxicity and known access to tissues relevant for COVID-19 infection (51, 52)-and other related stable nitroxides as potential SARS-CoV-2 therapies during active viral infection.…”

Heme oxygenase-1 in protozoan infections: A tale of resistance and disease tolerance

“…The first study to evaluate the role of HO-1 on leishmaniasis, using L. mexicana pifanoi, showed that amastigotes induce high HO-1 expression early after macrophage infection [55]. Inhibition of HO-1 activity with SnPPIX increased ROS production after amastigote phagocytosis, while induction of HO-1 with CoPPIX reduced the amounts of superoxide, an important ROS associated to Leishmania control inside macrophages [101]. However, these authors did not study the effects of manipulating HO-1 on parasite burden.…”