NTPDase 1 de Leishmania braziliensis como um alvo terapêutico: imunolocalização em formas promastigotas e amastigotas e susceptibilidade à Leishmanicidas

Abstract

Nucleoside triphosphate diphosphohydrolase (NTPDase) activity was recently characterized in Leishmania (Viannia) braziliensis promastigotes (Lb), and an antigenic conserved B domain (r82-121) from the specific NTPDase 1 isoform was identified. In this work, mouse polyclonal antibodies produced against two synthetic peptides belonging to this domain (LbB1LJ, r82-103; LbB2LJ, r102-121), and antibodies produced against peptides potB1LJ and potB2LJ, with high identity to the LbB1LJ and LbB2LJ respectively, were used as tools for studies of this protein. The anti-LbB1LJ or anti-LbB2LJ antibody, immobilized on Protein A-Sepharose, immunoprecipitated the NTPDase 1 of 48 kDa and depleted approximately 40% of the phosphohydrolytic activity from detergent-homogenized Lb preparation. By ultrastructural immunocytochemical microscopy, using anti-LbB1LJ, anti-LbB2LJ or anti-potB1LJ antibody, the NTPDase 1 was identified on the surface, subcellular cytoplasmic vesicles, mitochondria, kinetoplast, flagellum and flagellar pocket, and nucleus of promastigotes. In addition, the NTPDase 1 was isolated from the promastigotes mitochondrial fraction by nondenaturing gel, and its expression and identity were confirmed by enzyme activity measurements, Western blots and mass spectrometry. The ATPase and ADPase activities of detergent-homogenized preparation were partially inhibited by anti-LbB1LJ or anti-potB1LJ antibody (43-79%), which was more effective than that inhibition by anti-LbB2LJ or anti-potB1LJ antibody (18-60%). In addition, the immune sera anti-LbB1LJ or anti-potB1LJ (67-73%) and anti-LbB2LJ or anti-potB2LJ (33-40%) were cytotoxic, and significantly reduce the promastigotes growth in vitro. By Western blots and confocal microscopy laser scanning analyses, the antibodies produced against B domain confirmed the expression and identity of the intracellular amastigotes NTPDase 1 and, also, in free amastigotes recovered from Vero cells. All taken together, the results appoint the conserved B domain from the L. (V.) braziliensis NTPDase 1 as an important target for inhibitor design and the potential application of these biomolecules in experimental protocols of disease control. The N-alkylaminoalkanethiosulfuric acids, which did not have in vitro or in vivo cytotoxic effect, reduced in vitro intracellular amastigotes proliferation, the most effective being the SIPA, SSEC and IBSS, with IC50 24-35 μM. The NPSO, SXIP and TBSO were less effective, with IC50 54 to >100 μM. TBSO exception, all the other AAATs partially inhibited the ATPase and/or ADPase activity from the promastigotes preparation. The SIPA also was an effective antileishmanial when tested on the amastigotes recovered from the Vero cells, with IC50 20 μM and, in addition, it was capable to reduce the ATPase and ADPase activities from the homogenized of these parasites suggesting a Ki 10-100 μM. Furthermore, SIPA 30 μM significantly reduced 28% of the mitochondrial membrane potential, and it could be one of the mechanisms by which AAATs are antileishmanial compounds. The NTPDase 1 may play a key role in the mitochondrial activity, a new hypothesis to be explored, and target of AAATs, which were tested for the first time on the trypanosomatids and characterized in this work as new antileishmanial compounds.