European propolis is highly active against trypanosomatids including Crithidia fasciculata.

Extracts of 35 samples of European propolis were tested against wild type and resistant strains of the protozoal pathogens Trypanosoma brucei, Trypanosoma congolense and Leishmania mexicana. The extracts were also tested against Crithidia fasciculata a close relative of Crithidia mellificae, a parasite of bees. Crithidia, Trypanosoma and Leishmania are all members of the order Kinetoplastida. High levels of activity were obtained for all the samples with the levels of activity varying across the sample set. The highest levels of activity were found against L. mexicana. The propolis samples were profiled by using liquid chromatography with high resolution mass spectrometry (LC-MS) and principal components analysis (PCA) of the data obtained indicated there was a wide variation in the composition of the propolis samples. Orthogonal partial least squares (OPLS) associated a butyrate ester of pinobanksin with high activity against T. brucei whereas in the case of T. congolense high activity was associated with methyl ethers of chrysin and pinobanksin. In the case of C. fasciculata highest activity was associated with methyl ethers of galangin and pinobanksin. OPLS modelling of the activities against L. mexicana using the mass spectrometry produced a less successful model suggesting a wider range of active components.

Screening of the MMV and GSK open access chemical boxes using a viability assay developed against the kinetoplastid Crithidia fasciculata.

Diseases caused by the pathogenic kinetoplastids continue to incapacitate and kill hundreds of thousands of people annually throughout the tropics and sub-tropics. Unfortunately, in the countries where these neglected diseases occur, financial obstacles to drug discovery and technical limitations associated with biochemical studies impede the development of new, safe, easy to administer and effective drugs. Here we report the development and optimisation of a Crithidia fasciculata resazurin viability assay, which is subsequently used for screening and identification of anti-crithidial compounds in the MMV and GSK open access chemical boxes. The screening assay had an average Z' factor of 0.7 and tolerated a maximum dimethyl sulfoxide concentration of up to 0.5%. We identified from multiple chemical boxes two compound series exhibiting nanomolar potency against C. fasciculata, one centred around a 5-nitrofuran-2-yl scaffold, a well-known moiety in several existing anti-infectives, and another involving a 2-(pyridin-2-yl) pyrimidin-4-amine scaffold which seems to have pan-kinetoplastid activity. This work facilitates the future use of C. fasciculata as a non-pathogenic and inexpensive biological resource to identify mode of action/protein target(s) of potentially pan-trypanocidal potent compounds. This knowledge will aid in the development of new treatments for African sleeping sickness, Chagas disease and leishmaniasis.

Chemical and Antimicrobial Profiling of Propolis from Different Regions within Libya.

Extracts from twelve samples of propolis collected from different regions of Libya were tested for their activity against Trypanosoma brucei, Leishmania donovani, Plasmodium falciparum, Crithidia fasciculata and Mycobacterium marinum and the cytotoxicity of the extracts was tested against mammalian cells. All the extracts were active to some degree against all of the protozoa and the mycobacterium, exhibiting a range of EC50 values between 1.65 and 53.6 µg/ml. The toxicity against mammalian cell lines was only moderate; the most active extract against the protozoan species, P2, displayed an IC50 value of 53.2 µg/ml. The extracts were profiled by using liquid chromatography coupled to high resolution mass spectrometry. The data sets were extracted using m/z Mine and the accurate masses of the features extracted were searched against the Dictionary of Natural Products (DNP). A principal component analysis (PCA) model was constructed which, in combination with hierarchical cluster analysis (HCA), divided the samples into five groups. The outlying groups had different sets of dominant compounds in the extracts, which could be characterised by their elemental composition. Orthogonal partial least squares (OPLS) analysis was used to link the activity of each extract against the different micro-organisms to particular components in the extracts.

The effect of tunicamycin on the glucose uptake, growth, and cellular adhesion in the protozoan parasite Crithidia fasciculata.

Crithidia fasciculata represents a very interesting model organism to study biochemical, cellular, and genetic processes unique to members of the family of the Trypanosomatidae. Thus, C. fasciculata parasitizes several species of insects and has been widely used to test new therapeutic strategies against parasitic infections. By using tunicamycin, a potent inhibitor of glycosylation in asparaginyl residues of glycoproteins (N-glycosylation), we demonstrate that N-glycosylation in C. fasciculata cells is involved in modulating glucose uptake, dramatically impacting growth, and cell adhesion. C. fasciculata treated with tunicamycin was severely affected in their ability to replicate and to adhere to polystyrene substrates and losing their ability to aggregate into small and large groups. Moreover, under tunicamycin treatment, the parasites were considerably shorter and rounder and displayed alterations in cytoplasmic vesicles formation. Furthermore, glucose uptake was significantly impaired in a tunicamycin dose-dependent manner; however, no cytotoxic effect was observed. Interestingly, this effect was reversible. Thus, when tunicamycin was removed from the culture media, the parasites recovered its growth rate, cell adhesion properties, and glucose uptake. Collectively, these results suggest that changes in the tunicamycin-dependent glycosylation levels can influence glucose uptake, cell growth, and adhesion in the protozoan parasite C. fasciculata.

Differential effects of paromomycin on ribosomes of Leishmania mexicana and mammalian cells.

Paromomycin, an aminoglycoside antibiotic having low mammalian cell toxicity, is one of the drugs currently used in the chemotherapy of cutaneous and visceral leishmaniasis. In order to understand the mode of action of this antibiotic at the molecular level, we have investigated the effects of paromomycin on protein synthesis in Leishmania and its mammalian hosts. We were able to demonstrate that in vivo protein synthesis in the promastigote stage of the parasite and its proliferation rate are markedly inhibited by paromomycin while being only slightly affected by other aminoglycoside antibiotics, such as streptomycin and neomycin B. Furthermore, both in vitro polypeptide synthesis induced by poly(U) as mRNA and accuracy of translation are significantly decreased by paromomycin in cell-free systems containing ribosomal particles of Leishmania promastigotes. Conversely, when ribosomes from mammalian cells are used instead of the protozoan particles, polyphenylalanine synthesis is only barely reduced by the antibiotic and the translation misreading remains almost unaltered. Surface plasmon resonance analysis of the interaction between paromomycin and protozoan or mammalian cell ribosomal RNAs shows a strong binding of antibiotic to the parasite ribosomal decoding site and practically no interaction with the mammalian cell counterpart. Our results indicating differential effects of paromomycin on the translation processes of the Leishmania parasite and its mammalian hosts can explain the therapeutic efficiency of this antibiotic as an antileishmaniasis agent.

Trypanosoma cruzi: high ribosomal resistance to trichosanthin inactivation.

Trypanosoma cruzi is the parasite causing Chagas Disease. Several results already published suggest that T. cruzi ribosomes have remarkable differences with their mammalian counterparts. In the present work, we showed that trypanosomatid (T. cruzi and Crithidia fasciculata) ribosomes are highly resistant to inactivation by trichosanthin (TCS), which is active against mammalian ribosomes. Differential resistance is an intrinsic feature of the ribosomal particles, as demonstrated by using assays where the only variable was the ribosomes source. Because we have recently described that TCS interacts with the acidic C-terminal end of mammalian ribosomal P proteins, we assayed the effect of a TCS variant, which is unable to interact with P proteins, on trypanosomatid ribosomes. This mutant showed similar shifting of IC(50) values on rat, T. cruzi and C. fasciculata ribosomes, suggesting that the resistance mechanism might involve other ribosomal components rather than the C-terminal end of P proteins.

[Inhibitory action of Fenton systems on topoisomerase I from Trypanosoma cruzi and Crithidia fasciculata]]. / Acción inhibitoria de sistemas Fenton sobre la topoisomerasa I de Trypanosoma cruzi y Crithidia fasciculata.

Fenton systems (H2O2/Fe(II) or H2O2/Cu(II)) inhibited Trypanosoma cruzi and Crithidia fasciculata topoisomerase I activity. About 61-71% inactivation was produced by 25 mM Fe(II) or Cu(II) with 3 mM H2O2. Thiol compounds and free radicals scavengers prevented the Fenton systems effects, depending on the topoisomerase assayed. With the T. cruzi enzyme, reduced glutathione, DL-dithiothreitol, cysteine and N-acetyl-L-cysteine entirely prevented the effect of the H2O2/Fe(II) system, mannitol protected 37%, whereas histidine and ethanol were ineffective. With C. fasciculata topoisomerase, reduced glutathione, DL-dithiothreitol and N-acetyl-L-cysteine protected 100%, cysteine, histidine and mannitol protected 28, 34 and 48% respectively, whereas ethanol was ineffective. With the H2O2/Cu(II) system and T. cruzi topoisomerase, DL-dithiothreitol and histidine protected 100% and 60%, respectively but the other assayed protectors were less effective. Similar results were obtained with the C. fasciculata enzyme. Topoisomerase inactivation by H2O2/Fe(II) or H2O2/Cu(II) systems was irreversible since they were not reverted by the more effective enzyme protectors. It is suggested that topoisomerases could act either as scavengers of "reactive oxygen species" (ROS) generated by Fenton systems or bind the corresponding metal ions, whose redox cycling would generate reactive oxygen species "in situ".

Spermidine is essential for normal proliferation of trypanosomatid protozoa.

Trypanosomatid parasites containing a metabolically unstable ornithine decarboxylase (ODC) are naturally resistant to high levels of alpha-difluoromethylornithine (DFMO) because this ODC inhibitor, though causing a drastic reduction of intracellular putrescine, elicits only a moderate decrease of the spermidine endogenous pool. In this study we have used a combination of DFMO with cyclohexylamine (CHA; bis-cyclohexylammonium sulfate), an inhibitor of spermidine synthase, to reach a more complete depletion of spermidine. Under these conditions we have observed the arrest of proliferation not only in trypanosomatids with stable ODC but also in parasites with an enzyme of high turnover rate. In all cases the reinitiation of proliferation occurred only after the addition of exogenous spermidine, and neither putrescine nor spermine were able to induce the same effect.

Effect of dyskinetoplastic agents on ultrastructure and oxidative phosphorylation in Crithidia fasciculata.

Ethidium bromide (EB) is an intercalating agent which binds specifically to the kinetoplast (mitochondrial) DNA (kDNA) of trypanosomatids. Accordingly, EB inhibits DNA replication, thus inducing dyskinetoplasty. Since in eukariotic organisms mitochondrial DNA encodes the genetic information for cytochromes b, aa3 and F0F1 ATPase, it seemed of interest to establish whether a similar effect occurs in Crithidia fasciculata, a trypanosomatid used for assay of potential trypanocidal drugs. Culturing of C. fasciculata in the presence of EB inhibited growth and induced dyskinetoplasty, as confirmed by electron microscopy. The kinetoplast of EB-cultured crithidia lost its characteristic arc shape, it was misplaced in the cell cytoplasm its matrix structure and membrane differentiation were specifically modified. Dyskinetoplasty decreased crithidia respiration and oxidative phosphorylation, as indicated by the lower ATP level, ATP/ADP ratio and adenylate energy charge. The interference of EB with kinetoplastic constituents synthesis was confirmed by the lack of action of EB on crithidia in the stationary phase of growth, that ruled out direct inhibition of oxidative phosphorylation enzymes. The lipophilic o-naphthoquinone beta-lapachone produced structural alterations in kinetoplast membranes, that correlated with inhibition of oxidative phosphorylation. These latter effects involved free radicals since they were prevented by free radical scavengers.

Effect of dyskinetoplastic agents on ultrastructure and oxidative phosphorylation in Crithidia fasciculata

Ethidium bromide (EB) is an intercalating agent which binds specifically to the kinetoplast (mitochondrial) DNA (kDNA) of trypanosomatids. Accordingly, EB inhibits DNA replication, thus inducing dyskinetoplasty. Since in eukariotic organisms mitochondrial DNA encodes the genetic information for cytochromes b, aa3 and F0F1 ATPase, it seemed of interest to establish whether a similar effect occurs in Crithidia fasciculata, a trypanosomatid used for assay of potential trypanocidal drugs. Culturing of C. fasciculata in the presence of EB inhibited growth and induced dyskinetoplasty, as confirmed by electron microscopy. The kinetoplast of EB-cultured crithidia lost its characteristic arc shape, it was misplaced in the cell cytoplasm its matrix structure and membrane differentiation were specifically modified. Dyskinetoplasty decreased crithidia respiration and oxidative phosphorylation, as indicated by the lower ATP level, ATP/ADP ratio and adenylate energy charge. The interference of EB with kinetoplastic constituents synthesis was confirmed by the lack of action of EB on crithidia in the stationary phase of growth, that ruled out direct inhibition of oxidative phosphorylation enzymes. The lipophilic o-naphthoquinone beta-lapachone produced structural alterations in kinetoplast membranes, that correlated with inhibition of oxidative phosphorylation. These latter effects involved free radicals since they were prevented by free radical scavengers.(AU)

Sensitivity of trypanosomatid protozoa to DFMO and metabolic turnover of ornithine decarboxylase.

alpha-Difluoromethylornithine (DFMO), the specific and irreversible inhibitor of ornithine decarboxylase (ODC), was able to induce the arrest of proliferation in Leishmania mexicana and ODC-transformed Trypanosoma cruzi cultures grown in a semi-defined medium essentially free of polyamines. Conversely, Crithidia fasciculata and Phytomonas 274 were not affected by the inhibitor. The drug-resistance of Crithidia and Phytomonas was neither caused by an impairment of DFMO uptake nor by a decrease of the enzyme affinity for the inhibitor. We were also able to rule out the possibility of ODC overexpression in the drug-tolerant parasites. The measurements of ODC metabolic turnover indicated that the enzymes from Crithidia and Phytomonas have a short half-life of 20-40 min, while ODC from Leishmania and transgenic Trypanosoma cruzi are rather stable with a half-life longer than 6 hours. Analyses of polyamine internal pools under different growth conditions have shown that DFMO was able to markedly decrease the levels of putrescine and spermidine in all parasites, but the depletion of spermidine was higher in trypanosomatids containing an ODC with slow turnover. Our results suggest that in these parasites cultivated in the presence of the drug, spermidine might decrease below critical levels needed to maintain trypanothione concentrations or other conditions essential for normal proliferation.

Phenothiazine inhibitors of trypanothione reductase as potential antitrypanosomal and antileishmanial drugs.

Given the role of trypanothione in the redox defenses of pathogenic trypanosomal and leishmanial parasites, in contrast to glutathione for their mammalian hosts, selective inhibitors of trypanothione reductase are potential drug leads against trypanosomiasis and leishmaniasis. In the present study, the rational drug design approach was used to discover tricyclic neuroleptic molecular frameworks as lead structures for the development of inhibitors, selective for trypanothione reductase over host glutathione reductase. From a homology-modeled structure for trypanothione reductase, replaced in the later stages of the study by the X-ray coordinates for the enzyme from Crithidia fasciculata, a series of inhibitors based on phenothiazine was designed. These were shown to be reversible inhibitors of trypanothione reductase from Trypanosoma cruzi, linearly competitive with trypanothione as substrate and noncompetitive with NADPH, consistent with ping-pong bi bi kinetics. Analogues, synthesized to define structure-activity relationships for the active site, included N-acylpromazines, 2-substituted phenothiazines, and trisubstituted promazines. Analysis of Ki and I50 data, on the basis of calculated log P and molar refractivity values, provided evidence of a specially favored fit of small 2-substituents (especially 2-chloro and 2-trifluoromethyl), with a remote hydrophobic patch on the enzyme accessible for larger, hydrophobic 2-substituents. There was also evidence of an additional hydrophobic enzymic region available to suitable N-substituents of the promazine nucleus. Ki data also indicated that the phenothiazine nucleus can adopt more than one inhibitory orientation in its binding site. Selected compounds were tested for in vitro activity against Trypanosoma brucei, T. cruzi, and Leishmania donovani, with selective activities in the micromolar range being determined for a number of them.

Effects of cationic diamidines on polyamine metabolism in the trypanosomatid Crithidia fasciculata.

The effect of a series of five recently synthesized cationic diamidines on cell proliferation and polyamine metabolism was studied on cultures of the model Trypanosomatid Crithidia fasciculata. Compounds displaying two arylic moieties (CGP039937A and CGP040215A) were ten fold more cytostatic than those displaying only one arylic residue (CGP033829A, CGP035753A and CGP036958A). The depletion of intracellular polyamine, putrescine and spermidine, pools and the effect of these compounds on S-adenosylmethionine decarboxylase and putrescine uptake suggest the requirement of two arylic groups in their chemical structure to obtain measurable effects on both polyamine metabolism and cell growth.

[Inhibition of oxidative phosphorylation in Crithidia fasciculata and Trypanosoma cruzi by lipophilic o-quinones and nifurtimox]. / Inhibición de la oxidación fosforilante en Crithidia fasciculata y Trypanosoma cruzi por o-quinonas lipofílicas y nifurtimox.

ATP and ADP levels were determined in Crithidia fasciculata and Trypanosoma cruzi. The nucleotide levels in crithidia or epimastigotes at the stationary phase of growth were, in nmol/10(8) cells, 15-40, and 3-7, for ATP and ADP, respectively. Incubation with the lipophilic o-naphthoquinones CG 8-935, CG 9-442 and CG 10-248 or the anti-chagasic nitrofuran nifurtimox, significantly decreased ATP level, with non-significant variations of the ADP level. The kinetics of ATP variation showed an initial 1-2 h lag and the diminution of the ATP level reached maximum value after 4-6 h incubation. Addition of L-glutamate or D-glucose as energy sources produced 2- or 3-fold increase of ATP level, after incubation the protozoa for 4-6 h with the corresponding substrates. Quinones and nifurtimox strongly depressed D-glucose or L-glutamate effects. Buthionine sulfoximine an inhibitor of glutathione biosynthesis, enhanced the effect of nifurtimox on ATP level in Crithidia fasciculata. It is concluded that by inhibiting ATP synthesis, either directly or-through oxygen radicals, the assayed drugs produced their cytotoxic action.

Effect of polyamines on mitochondrial F-ATPase from Crithidia fasciculata and Trypanosoma cruzi.

ATP hydrolysis by Crithidia fasciculata mitochondrial ATPase was studied through the use of submitochondrial particles and the soluble enzyme. (a) ATP hydrolysis by these preparations was inhibited by spermine but not by spermidine or putrescine. (b) The ATPase activity inhibited by spermine was partially recovered when excess Mg2+ was added to the reaction mixture. (c) When polyamines were present throughout the preparation of the mitochondrial membranes, the membrane-bound ATPase was irreversibly inactivated. The polyamine effect decreased in the order spermine > putrescine > spermidine. (d) The spermidine or putrescine pre-treated membranes oxidized succinate at a faster rate than the control ones. (e) Trypanosoma cruzi F-ATPase was inhibited by polyamines in the same manner as the C. fasciculata enzyme.

Differential regulation of putrescine uptake in Trypanosoma cruzi and other trypanosomatids.

Putrescine uptake in Trypanosoma cruzi epimastigotes is 10 to 50-fold higher than in Leishmania mexicana or Crithidia fasciculata. Polyamine transport in all these trypanosomatids is an energy-dependent process strongly inhibited by the presence of 2,4-dinitrophenol or KCN. Putrescine uptake in T. cruzi and L. mexicana was markedly decreased by the proton ionophore carbonylcyanide m-chlorophenylhydrazone but it was not affected by ouabain, a Na(+)-K+ pump inhibitor. The depletion of intracellular polyamines by treatment of parasite cultures with alpha-difluoromethylornithine elicited a marked induction of putrescine uptake in L. mexicana and C. fasciculata by increasing considerably the Vmax of this process. Conversely, the uptake of putrescine in T. cruzi was essentially unchanged by the same treatment. The differential regulation of putrescine transport in T. cruzi might be related to some distinctive features of polyamine metabolism in this parasite.

Kinetoplast-associated DNA topoisomerase in Crithidia fasciculata: crosslinking of mitochondrial topoisomerase II to both minicircles and maxicircles in cells treated with the topoisomerase inhibitor VP16.

The mitochondrial DNA of the trypanosomatid Crithidia fasciculata consists of thousands of copies of a 2.5 kb minicircle and a small number of 37kb maxicircles catenated into a single enormous network. Treatment of C. fasciculata with the type II DNA topoisomerase inhibitor VP16 produces cleavable complexes of a type II DNA topiosomerase with both minicircles and maxicircles. A combined Southern and Western blot analysis of the cleaved DNA species released from the network by SDS treatment has identified topollmt, the kinetoplast-associated topisomerase, in covalent complexes with linear forms of minicircle and maxicircle DNAs. These results directly implicate topollmt in the topological reactions required for the duplication of the kinetoplast network.

Efecto de orto-naftoquinonas lipofílicas sobre el crecimiento y la producción de peróxidos por Leptomonas seymouri y Crithidia fasciculata / Effect of lipophilic ortho-naphthoquinones on the growth and production of peroxides by Leptomonas seymouri and Crithidia fasciculata

Las §-naftoquinonas CG 8-935, CG 9-442, CG 10-248 y las mansonomas A, C, E y F inhiben el crecimiento de L. seymouri (LS) y C. fasciculata (CF). Las mansononas más activas fueron E y F (I50, 0.1 y 0.4 *M con LS y 0.3-1.2 *M con CF), con actividades citotóxicas iguales o superiores a las de las o-quinonas CG. La incubación de los protozoarios con las quinonas CG y las quinonas E y F indujo la producción de H2O2 y O2. Menor producción se obtuvo con la perezona y la priminina (p-benzoquinonas utilizadas como testigo). El efecto de las o-quinonas fue proprocional a su concentración y con las mansononas E y F la producción de O2 fue 4-5 veces mayor que la de H2O2. Diferencias menores se observaron con las quinonas CG. La producción de peróxidos resultó de un ciclo redox, iniciado por una fase anaeróbica (I) en la que se formaron los quinoles, seguida por una fase aeróbica (II) en la que se formó O2 y H2O2. Con las mansononas E y F, y las quinonas CG, la velocidad de la fase II fue superior o igual a la de la fase I pero, con las mansononas A y C, la velocidad de oxidación de los quinoles fue 8-10 veces menor que la de reducción de las quinonas. Esas diferencias concuerdan con a) la oxidación in vitro de los quinoles; b) su capacidad para producir O2 y c) su capacidad para inducir la quimiluminiscencia de la lucigenina. Los resultados descriptos demuestran la intervención de oxi-radicales en la citotoxicidad de las §-quinonas, no obstante la existencia de catalasa y otras enzimas protectoras en LS y CF, pero no se descartan otros mecanismos. La sensibilidad de ambos organismos a las quinonas estudiadas, similar o superior a la del T. cruzi, autoriza a utilizar a LS y CF como modelos para el ensayo de quimioterápicos antichagásicos

Efecto de orto-naftoquinonas lipofílicas sobre el crecimiento y la producción de peróxidos por Leptomonas seymouri y Crithidia fasciculata / Effect of lipophilic ortho-naphthoquinones on the growth and production of peroxides by Leptomonas seymouri and Crithidia fasciculata

Las º-naftoquinonas CG 8-935, CG 9-442, CG 10-248 y las mansonomas A, C, E y F inhiben el crecimiento de L. seymouri (LS) y C. fasciculata (CF). Las mansononas más activas fueron E y F (I50, 0.1 y 0.4 *M con LS y 0.3-1.2 *M con CF), con actividades citotóxicas iguales o superiores a las de las o-quinonas CG. La incubación de los protozoarios con las quinonas CG y las quinonas E y F indujo la producción de H2O2 y O2. Menor producción se obtuvo con la perezona y la priminina (p-benzoquinonas utilizadas como testigo). El efecto de las o-quinonas fue proprocional a su concentración y con las mansononas E y F la producción de O2 fue 4-5 veces mayor que la de H2O2. Diferencias menores se observaron con las quinonas CG. La producción de peróxidos resultó de un ciclo redox, iniciado por una fase anaeróbica (I) en la que se formaron los quinoles, seguida por una fase aeróbica (II) en la que se formó O2 y H2O2. Con las mansononas E y F, y las quinonas CG, la velocidad de la fase II fue superior o igual a la de la fase I pero, con las mansononas A y C, la velocidad de oxidación de los quinoles fue 8-10 veces menor que la de reducción de las quinonas. Esas diferencias concuerdan con a) la oxidación in vitro de los quinoles; b) su capacidad para producir O2 y c) su capacidad para inducir la quimiluminiscencia de la lucigenina. Los resultados descriptos demuestran la intervención de oxi-radicales en la citotoxicidad de las º-quinonas, no obstante la existencia de catalasa y otras enzimas protectoras en LS y CF, pero no se descartan otros mecanismos. La sensibilidad de ambos organismos a las quinonas estudiadas, similar o superior a la del T. cruzi, autoriza a utilizar a LS y CF como modelos para el ensayo de quimioterápicos antichagásicos (AU)

[Effect of lipophilic ortho-naphthoquinones on the growth of and production of peroxides by Leptomonas seymouri and Crithidia fasciculata]. / Efecto de orto-naftoquinonas lipofilicas sobre el crecimiento y la producción de peróxidos por Leptomonas seymouri y Crithidia fasciculata.

The lipophilic o-naphthoquinones CG 8-935, CG 9-442, CG 10-248 and mansonones A, C, E and F inhibit growth of the trypanosomatids Leptomonas seymouri (LS) and Crithidia fasciculata (CF). The most active mansonones were E and F (I50, 0.1-0.4 microM with LS; 0.3-1.2 microM with CF) with cytotoxic activities equal to or higher than quinones CG, as reported previously. Incubation of LS or CF with the CG-quinones and mansonones E and F caused the release of H2O2 and O2-. from the whole cells to the suspending medium, as detected by the microperoxidase and adrenochrome assays, respectively. Lower O2-. and H2O2 production values were obtained with perezone and primine, two p-benzoquinones used as controls. Quinones effect on O2-. and H2O2 production was closely related to their concentration and with mansonones E and F, O2-. production was 4-5-fold higher than H2O2 production. Smaller differences were observed with the CG-quinones. Peroxide production in the assayed organisms was the result of quinone redox-cycling, which involved an anaerobic, reductive phase producing quinols, and an aerobic phase (II), in which quinol oxidation and peroxide production (O2-., H2O2) occurred. With mansonones E and F, and quinone CG, phase II rate was faster than or similar to phase I rate, but with mansonones A and C, the quinols oxidation rate was 8-10-fold slower than the quinones reduction rate. These differences fit in well with a) the quinol oxidation rates, measured in vitro; b) O2-. production by quinols oxidation and c) quinols capability for producing lucigenin chemiluminescence. These results support the assumption that oxyradicals play a relevant role in o-naphthoquinones cytotoxic action, despite the presence of catalase and other protective enzymes in CF and LS. Other effects are not, however, ruled out. CF and LS sensitivity towards the assayed o-quinones was similar or higher than that of Trypanosoma cruzi, thus allowing the use of those organisms for preliminary screening of antichagasic drugs.