Tryp-ing Up Metabolism: Role of Metabolic Adaptations in Kinetoplastid Disease Pathogenesis

The effect of nutritional and oxidative stress on the metabolome of Trypanosoma cruzi

Trypanosoma cruzi, a flagellated protozoan, is the causative agent of Chagas disease. The parasite has developed various mechanisms to get through its intricate life cycle and adapt to different evolutionary phases. T. cruzi proliferates in the insect vector's digestive tract as an epimastigote form, encountering fluctuating nutrient availability and oxidative stress caused by the digestion of red blood cells from the mammalian host blood meal. To unravel how the parasite's metabolism adapts to these changing conditions, we conducted an analysis of the chemical species present in epimastigote forms. This involved comparing cultured parasites with those subjected to nutritional deficiency or oxidative stress using untargeted metabolomics. We looked at 21 samples: seven biological copies of parasites that were actively growing, seven samples that were put in a medium without nutrients for 3 h, and seven samples that were treated with glucose oxidase for 30 min to make H2O2 continuously. Importantly, in all conditions, parasite viability was maintained when the samples were collected. Upon nutrient removal, we observed a substantial decrease in amino acids and carbohydrate metabolites, accompanied by the accumulation of fatty acids and steroids, with the predominance of inositol and sphingolipid metabolism, along with a simultaneous decrease in the levels of H2O2. In the presence of H2O2, a significant rise in components of the pentose pathway and specific amino acids such as methionine and serine occurred, along with pathways related to an increase in antioxidant species metabolism such as ribulose 5-phosphate and glyceric acid. Conversely, fatty acid and steroid levels decrease. We found no common increase in metabolites or lipids. In contrast, eight species (succinic acid, glutamic acid, valine, 2-hydroxyisocaproic acid, alanine, indolelactic acid, proline, and lanosterol) were consumed under both stresses. These findings underscore the rapid and distinct enrichment responses in amino acids, lipids, and carbohydrates required to cope with each different environmental condition. We concluded that T. cruzi presents a flexible metabolism that rapidly adapts to variable changes in the environment.

The intersection of host in vivo metabolism and immune responses to infection with kinetoplastid and apicomplexan parasites

SUMMARYProtozoan parasite infection dramatically alters host metabolism, driven by immunological demand and parasite manipulation strategies. Immunometabolic checkpoints are often exploited by kinetoplastid and protozoan parasites to establish chronic infection, which can significantly impair host metabolic homeostasis. The recent growth of tools to analyze metabolism is expanding our understanding of these questions. Here, we review and contrast host metabolic alterations that occur in vivo during infection with Leishmania, trypanosomes, Toxoplasma, Plasmodium, and Cryptosporidium. Although genetically divergent, there are commonalities among these pathogens in terms of metabolic needs, induction of the type I immune responses required for clearance, and the potential for sustained host metabolic dysbiosis. Comparing these pathogens provides an opportunity to explore how transmission strategy, nutritional demand, and host cell and tissue tropism drive similarities and unique aspects in host response and infection outcome and to design new strategies to treat disease.

Localized cardiac small molecule trajectories and persistent chemical sequelae in experimental Chagas disease

Post-infectious conditions present major health burdens but remain poorly understood. In Chagas disease (CD), caused by Trypanosoma cruzi parasites, antiparasitic agents that successfully clear T. cruzi do not always improve clinical outcomes. In this study, we reveal differential small molecule trajectories between cardiac regions during chronic T. cruzi infection, matching with characteristic CD apical aneurysm sites. Incomplete, region-specific, cardiac small molecule restoration is observed in animals treated with the antiparasitic benznidazole. In contrast, superior restoration of the cardiac small molecule profile is observed for a combination treatment of reduced-dose benznidazole plus an immunotherapy, even with less parasite burden reduction. Overall, these results reveal molecular mechanisms of CD treatment based on simultaneous effects on the pathogen and on host small molecule responses, and expand our understanding of clinical treatment failure in CD. This link between infection and subsequent persistent small molecule perturbation broadens our understanding of infectious disease sequelae.

Impact of Visceral Leishmaniasis on Local Organ Metabolism in Hamsters

Leishmania is an intracellular parasite with different species pathogenic to humans and causing the disease leishmaniasis. Leishmania donovani causes visceral leishmaniasis (VL) that manifests as hepatosplenomegaly, fever, pancytopenia and hypergammaglobulinemia. If left without treatment, VL can cause death, especially in immunocompromised people. Current treatments have often significant adverse effects, and resistance has been reported in some countries. Determining the metabolites perturbed during VL can lead us to find new treatments targeting disease pathogenesis. We therefore compared metabolic perturbation between L. donovani-infected and uninfected hamsters across organs (spleen, liver, and gut). Metabolites were extracted, analyzed by liquid chromatography-mass spectrometry, and processed with MZmine and molecular networking to annotate metabolites. We found few metabolites commonly impacted by infection across all three sites, including glycerophospholipids, ceramides, acylcarnitines, peptides, purines and amino acids. In accordance with VL symptoms and parasite tropism, we found a greater overlap of perturbed metabolites between spleen and liver compared to spleen and gut, or liver and gut. Targeting pathways related to these metabolite families would be the next focus that can lead us to find more effective treatments for VL.

Chemical Cartography Approaches to Study Trypanosomatid Infection

Pathogen tropism and disease tropism refer to the tissue locations selectively colonized or damaged by pathogens, leading to localized disease symptoms. Human-infective trypanosomatid parasites include Trypanosoma cruzi, the causative agent of Chagas disease; Trypanosoma brucei, the causative agent of sleeping sickness; and Leishmania species, causative agents of leishmaniasis. Jointly, they affect 20 million people across the globe. These parasites show specific tropism: heart, esophagus, colon for T. cruzi, adipose tissue, pancreas, skin, circulatory system and central nervous system for T. brucei, skin for dermotropic Leishmania strains, and liver, spleen, and bone marrow for viscerotropic Leishmania strains. A spatial perspective is therefore essential to understand trypanosomatid disease pathogenesis. Chemical cartography generates 3D visualizations of small molecule abundance generated via liquid chromatography-mass spectrometry, in comparison to microbiological and immunological parameters. This protocol demonstrates how chemical cartography can be applied to study pathogenic processes during trypanosomatid infection, beginning from systematic tissue sampling and metabolite extraction, followed by liquid chromatography-tandem mass spectrometry data acquisition, and concluding with the generation of 3D maps of metabolite distribution. This method can be used for multiple research questions, such as nutrient requirements for tissue colonization by T. cruzi, T. brucei, or Leishmania, immunometabolism at sites of infection, and the relationship between local tissue metabolic perturbation and clinical disease symptoms, leading to comprehensive insight into trypanosomatid disease pathogenesis.

Decreased glutamate transport in acivicin resistant Leishmania tarentolae

Studies of drug resistance in the protozoan parasites of the genus Leishmania have been helpful in revealing biochemical pathways as potential drug targets. The chlorinated glutamine analogue acivicin has shown good activity against Leishmania cells and was shown to target several enzymes containing amidotransferase domains. We selected a Leishmania tarentolae clone for acivicin resistance. The genome of this resistant strain was sequenced and the gene coding for the amidotransferase domain-containing GMP synthase was found to be amplified. Episomal expression of this gene in wild-type L. tarentolae revealed a modest role in acivicin resistance. The most prominent defect observed in the resistant mutant was reduced uptake of glutamate, and through competition experiments we determined that glutamate and acivicin, but not glutamine, share the same transporter. Several amino acid transporters (AATs) were either deleted or mutated in the resistant cells. Some contributed to the acivicin resistance phenotype although none corresponded to the main glutamate transporter. Through sequence analysis one AAT on chromosome 22 corresponded to the main glutamate transporter. Episomal expression of the gene coding for this transporter in the resistant mutant restored glutamate transport and acivicin susceptibility. Its genetic knockout led to reduced glutamate transport and acivicin resistance. We propose that acivicin binds covalently to this transporter and as such leads to decreased transport of glutamate and acivicin thus leading to acivicin resistance.

Studies of drug resistance in the protozoan parasites of the genus Leishmania have been helpful in revealing biochemical pathways as potential drug targets. Here we report on the characterization at the genomics and metabolomics levels of a L. tarentolae strain made resistant to acivicin, an analogue of glutamine with activity against this parasite. We found that resistance to acivicin is accompanied by a reduced uptake and intracellular levels of glutamate and that both are expected to share the same transporter. Through gene overexpression and disruption studies we identified the main amino acid transporter responsible for glutamate uptake.

Metabolic flexibility in Trypanosoma cruzi amastigotes: implications for persistence and drug sensitivity

Throughout their life cycle, parasitic organisms experience a variety of environmental conditions. To ensure persistence and transmission, some protozoan parasites are capable of adjusting their replication or converting to distinct life cycle stages. Trypanosoma cruzi is a 'generalist' parasite that is competent to infect various insect (triatomine) vectors and mammalian hosts. Within the mammalian host, T. cruzi replicates intracellularly as amastigotes and can persist for the lifetime of the host. The persistence of the parasites in tissues can lead to the development of Chagas disease. Recent work has identified growth plasticity and metabolic flexibility as aspects of amastigote biology that are important determinants of persistence in varied growth conditions and under drug pressure. A better understanding of the link between amastigote and host/tissue metabolism will aid in the development of new drugs or therapies that can limit disease pathology.