Relevance of hemin for in vitro differentiation of Trypanosoma cruzi

Heme crystallization in a Chagas disease vector acts as a redox-protective mechanism to allow insect reproduction and parasite infection

Heme crystallization as hemozoin represents the dominant mechanism of heme disposal in blood feeding triatomine insect vectors of the Chagas disease. The absence of drugs or vaccine for the Chagas disease causative agent, the parasite Trypanosoma cruzi, makes the control of vector population the best available strategy to limit disease spread. Although heme and redox homeostasis regulation is critical for both triatomine insects and T. cruzi, the physiological relevance of hemozoin for these organisms remains unknown. Here, we demonstrate that selective blockage of heme crystallization in vivo by the antimalarial drug quinidine, caused systemic heme overload and redox imbalance in distinct insect tissues, assessed by spectrophotometry and fluorescence microscopy. Quinidine treatment activated compensatory defensive heme-scavenging mechanisms to cope with excessive heme, as revealed by biochemical hemolymph analyses, and fat body gene expression. Importantly, egg production, oviposition, and total T. cruzi parasite counts in R. prolixus were significantly reduced by quinidine treatment. These effects were reverted by oral supplementation with the major insect antioxidant urate. Altogether, these data underscore the importance of heme crystallization as the main redox regulator for triatomine vectors, indicating the dual role of hemozoin as a protective mechanism to allow insect fertility, and T. cruzi life-cycle. Thus, targeting heme crystallization in insect vectors represents an innovative way for Chagas disease control, by reducing simultaneously triatomine reproduction and T. cruzi transmission.

Chagas disease is a fatal illness caused by Trypanosoma cruzi parasites, which are transmitted by blood sucking triatomine insect vectors. Although blood is a natural food source for these insects, its digestion releases toxic products, which poses a dietary challenge for both triatomine insects and trypanosomes. To overcome this, triatomines eliminate these toxic blood products by a unique process of heme crystallization into hemozoin that take place in their digestive tract. Here we describe that this detoxification process represents the major mechanism for redox balance control, and is necessary to allow triatomine insect reproduction, and Trypanosoma cruzi infection. Disruption of heme crystallization in triatomine insects thus represents a new venue for Chagas disease control, by targeting at the same time insect reproduction and parasite transmission.

Trypanosomatid essential metabolic pathway: new approaches about heme fate in Trypanosoma cruzi

Trypanosoma cruzi, the causal agent of Chagas disease, has a complex life cycle and depends on hosts for its nutritional needs. Our group has investigated heme (Fe-protoporphyrin IX) internalization and the effects on parasite growth, following the fate of this porphyrin in the parasite. Here, we show that epimastigotes cultivated with heme yielded the compounds α-meso-hydroxyheme, verdoheme and biliverdin (as determined by HPLC), suggesting an active heme degradation pathway in this parasite. Furthermore, through immunoprecipitation and immunoblotting assays of epimastigote extracts, we observed recognition by an antibody against mammalian HO-1. We also detected the localization of the HO-1-like protein in the parasite using immunocytochemistry, with antibody staining primarily in the cytoplasm. Although HO has not been described in the parasite's genome, our results offer new insights into heme metabolism in T. cruzi, revealing potential future therapeutic targets.

Biological characterization of a beta-galactosidase expressing clone of Trypanosoma cruzi CL strain

Clone CL B5 of Trypanosoma cruzi is a beta-galactosidase expressing organism that was genetically transfected to be used for in vitro pharmacological screening. Biological parameters were determined, evaluating growth kinetics of epimastigotes, metacyclogenesis, infectivity to mammalian cell lines, parasitemia kinetics in mice and sensibility to nifurtimox and benznidazole. Differences in relation to other strains and CL parental strain were found, the most important being the incapability to produce death to mice in spite of the high inoculum used. However, it possesses the required features to be used for in vitro drug screening. Data obtained demonstrate that heterogeneity of T. cruzi appears even among clones of the same strain, and that these differences found do not prevent the use of clone CL B5 for the purpose that was engineered.

Biological characterization and genetic diversity of Mexican isolates of Trypanosoma cruzi

The present work reports the in vitro biological characterization of 17 Trypanosoma cruzi isolates from southern and central México, and compares these results to those of four South American strains and one clone from Brazil. The parameters evaluated were growth rates, percentage of parasites undergoing transformation from epimastigotes to trypomastigotes, infectivity to, and in vitro killing of cultured Vero and P388 cells. Isoenzyme patterns of 11 enzymatic systems and 16 loci were also determined for the Mexican isolates. The parasites showed differences in growth, depending if they were cultured in LIT with hemin or in Grace's media. Transformation was obtained only in Grace's medium and differences were observed between the stocks. Stocks Z10 and Z21 showed the highest percentage of transformation within the Mexican isolates (39 and 41%, respectively). A second group showed percentages of transformation between 15 and 28%. In contrast, the South American strains showed higher rates of transformation (36-65%). Infection of cultured cells by isolates Z10 and H5 was evaluated in both Vero and P388 cells. Differences were observed both in the percentage of infected cells as well as in the number of amastigotes per cell. Differences in the ability to cause in vitro killing of P388 cells were also observed among the isolates. Isoenzyme analysis revealed genetic variation between the isolates, each of them with an unique zymodeme. This genetic analysis revealed, in general, a clustering based on the geographical origin of the isolates. Finally, correlation with clinical symptoms is discussed.

Biological characterization of Trypanosoma cruzi zymodemes: in vitro differentiation of epimastigotes and infectivity of culture metacyclic trypomastigotes to mice

Thirty-one Trypanosoma cruzi isolates from Chile, Peru, and Bolivia were studied in their capacity to differentiate in vitro from epimastigotes to metacyclic trypomastigotes on TAU-3AAG medium. Zymodeme 1 parasites displayed the best level of differentiation, which ranges from 60 to 90% depending on the isolate. Zymodeme 2 parasites exhibited highly heterogenous differentiation rates. This differentiation method permits the obtention of large amounts of metacyclic trypomastigotes from zymodeme 1 parasites. Metacyclic trypomastigotes obtained in vitro were infective to nude Balb/c hybrid mice. Zymodeme 1 parasites produced high parasitemias in this murine model; in contrast, zymodeme 2 parasites displayed lower parasitemias. Of a total of 27 T. cruzi isolates, 20 proved to be infective to mice, 12 gave enough parasites for further studies, and 8 of these were used for biological characterization. Results are compared with the infective clone Dm28 and Tulahuén strains maintained since 1954 in mice.