Authors

S M Acuña¹; A J Kowaltowski²; J M Zanatta²; S M Muxel¹;  ¹ University of São Paulo, Brazil;  ² Universidade de São Paulo, Brazil

Discussion

Macrophages need to be fuelled to cope with activating stimuli, like Leishmania amazonensis infection. This protozoan parasite induces macrophage expression of a blended phenotype, between pro and anti-inflammatory (M1 and M2, respectively). Cytosolic reactive oxygen/nitrogen species production associated with activation can promote redox imbalance if antioxidant systems are not sufficiently active. Mitochondria express Nicotinamide Nucleotide Transhydrogenase (NNT), which produces NADPH from NADH using H⁺ transmembrane transport from intermembrane space to the matrix as a driving force. This NADPH can be used to recycle glutathione or thioredoxin systems in the organellar matrix. The absence of this enzyme does not make mice unviable but reduces their mitochondrial antioxidant capacity. Indeed, mice with mutant Nnt are prone to develop metabolic syndromes. Since infection with L. amazonensis induces the production of reactive species, we hypothesized that the Nnt absence would negatively impact on parasite clearance, promoting its survival. Using C57BL/6Tac (Nnt^WT), C57BL/6J (Nnt^-/-) and B6.129P2-Nos2^tm/Lau/J (Nos2^-/- - a susceptible control) mouse strains; we infected macrophages with L. amazonensis and monitored the infection after 4, 24, 48 and 72 h. We observed that Nnt^-/-and Nos2^-/- macrophages showed a similar rate of infected macrophages, differing after 24 h when Nnt^-/- reduced this rate, although the number of amastigotes per infected macrophage was higher than Nnt^WT, and lower than Nos2^-/-. We also accompanied the in vivo infection of these mice strains for 8 weeks.  Both mutant mice presented similar footpad thickness during all tested times. Our data suggest that the imbalanced redox environment promoted by NNT absence is comparable to nitric oxide synthase 2 (NOS2) absence, worsening parasite clearance ability. The data presented brings forward a new aspect regarding the relationship between host and parasite, indicating that mitochondrial redox balance is an essential player in this process.