Association between altered tryptophan metabolism, plasma aryl hydrocarbon receptor agonists, and inflammatory Chagas disease

Introduction

Chagas disease causes a cardiac illness characterized by immunoinflammatory reactions leading to myocardial fibrosis and remodeling. The development of Chronic Chagas Cardiomyopathy (CCC) in some patients while others remain asymptomatic is not fully understood, but dysregulated inflammatory responses are implicated. The Aryl hydrocarbon receptor (AhR) plays a crucial role in regulating inflammation. Certain tryptophan (Trp) metabolites have been identified as AhR ligands with regulatory functions.

Methods results and discussion

We investigated AhR expression, agonist response, ligand production, and AhR-dependent responses, such as IDO activation and regulatory T (Treg) cells induction, in two T. cruzi-infected mouse strains (B6 and Balb/c) showing different polymorphisms in AhR. Furthermore, we assessed the metabolic profile of Trp catabolites and AhR agonistic activity levels in plasma samples from patients with chronic Chagas disease (CCD) and healthy donors (HD) using a luciferase reporter assay and liquid chromatography-mass spectrophotometry (LC-MS) analysis. T. cruzi-infected B6 mice showed impaired AhR-dependent responses compared to Balb/c mice, including reduced IDO activity, kynurenine levels, Treg cell induction, CYP1A1 up-regulation, and AhR expression following agonist activation. Additionally, B6 mice exhibited no detectable AhR agonist activity in plasma and displayed lower CYP1A1 up-regulation and AhR expression upon agonist activation. Similarly, CCC patients had decreased AhR agonistic activity in plasma compared to HD patients and exhibited dysregulation in Trp metabolic pathways, resulting in altered plasma metabolite profiles. Notably, patients with severe CCC specifically showed increased N-acetylserotonin levels in their plasma. The methods and findings presented here contribute to a better understanding of CCC development mechanisms and may identify potential specific biomarkers for T. cruzi infection and the severity of associated heart disease. These insights could be valuable in designing new therapeutic strategies. Ultimately, this research aims to establish the AhR agonistic activity and Trp metabolic profile in plasma as an innovative, non-invasive predictor of prognosis for chronic Chagas disease.

An in silico analysis revealed a novel evolutionary lineage of putative mitoviruses

Mitoviruses (family Mitoviridae) are small capsid-less RNA viruses that replicate in the mitochondria of fungi and plants. However, to date, the only authentic animal mitovirus infecting an insect was identified as Lutzomyia longipalpis mitovirus 1 (LulMV1). Public databases of transcriptomic studies from several animals may be a good source for identifying the often missed mitoviruses. Consequently, a search of mitovirus-like transcripts at the NCBI transcriptome shotgun assembly (TSA) library, and a search for the mitoviruses previously recorded at the NCBI non-redundant (nr) protein sequences library, were performed in order to identify new mitovirus-like sequences associated with animals. In total, 10 new putative mitoviruses were identified in the TSA database and 8 putative mitoviruses in the nr protein database. To our knowledge, these results represent the first evidence of putative mitoviruses associated with poriferan, cnidarians, echinoderms, crustaceans, myriapods and arachnids. According to different phylogenetic inferences using the maximum likelihood method, these 18 putative mitoviruses form a robust monophyletic lineage with LulMV1, the only known animal-infecting mitovirus. These findings based on in silico procedures provide strong evidence for the existence of a clade of putative mitoviruses associated with animals, which has been provisionally named 'kvinmitovirus'.

A Survey of Mycoviral Infection in Fusarium spp. Isolated from Maize and Sorghum in Argentina Identifies the First Mycovirus from Fusarium verticillioides

Mycoviruses appear to be widespread in Fusarium species worldwide. The aim of this work was to identify mycoviral infections in Fusarium spp., isolated from maize and sorghum grown in Argentina, and to estimate their potential effects on the pathogenicity and toxigenesis of the host fungus towards maize. Mycoviruses were identified in 2 out of 105 isolates analyzed; Fusarium verticillioides strain Sec505 and Fusarium andiyazi strain 162. They were characterized as members of the genus Mitovirus by high-throughput sequencing and sequence analysis. The F. verticillioides mitovirus was a novel mycovirus whereas the F. andiyazi mitovirus was found to be a new strain of a previously identified mitovirus. We have named these mitoviruses, Fusarium verticillioides mitovirus 1 (FvMV1) and Fusarium andiyazi mitovirus 1 strain 162 (FaMV1-162). To our knowledge, FvMV1 is the first mycovirus reported as naturally infecting F. verticillioides, the major causal agent of ear rot and fumonisin producer in corn. Both mitoviruses exhibited 100% vertical transmission rate to microconidia. The Fa162 strain infected with FaMV1-162 did not show phenotypic alterations. In contract, F. verticillioides Sec505 infected with FvMV1 showed increased virulence as well as microconidia and fumonisin-B1 production, compared with two uninfected strains. These results suggest that FvMV1 could have a role in modulating F. verticillioides pathogenicity and toxin production worth further exploring.

Microscopic and PCR-based detection of microsporidia spores in human stool samples

Microsporidia are obligate intracellular fungi with a remarkable ability to infect a wide range of invertebrate and vertebrate hosts. Namely, Enterocytozoon bieneusi is the most frequently microsporidia reported worldwide, and mainly associated with chronic diarrhea and wasting syndrome in AIDS patients. Microscopy and PCR-based detection techniques are effective for diagnosis and identification of species and genotypes; however, these methods should be standardized in each laboratory. In this study, we performed microscopy and nested PCR techniques with PCR product sequencing to detect E. bieneusi in human stool samples. These techniques, if applied together, might prove useful for diagnosis and future epidemiological studies of intestinal microsporidiosis in Argentina.

Deficiency of CD73 activity promotes protective cardiac immunity against Trypanosoma cruzi infection but permissive environment in visceral adipose tissue

Damaged cells release the pro-inflammatory signal ATP, which is degraded by the ectonucleotidases CD39 and CD73 to the anti-inflammatory mediator adenosine (ADO). The balance between ATP/ADO is known to determine the outcome of inflammation/infection. However, modulation of the local immune response in different tissues due to changes in the balance of purinergic metabolites has yet to be investigated. Here, we explored the contribution of CD73-derived ADO on the acute immune response against Trypanosoma cruzi parasite, which invades and proliferates within different target tissues. Deficiency of CD73 activity led to an enhanced cardiac microbicidal immune response with an augmented frequency of macrophages with inflammatory phenotype and increased CD8+ T cell effector functions. The increment of local inducible nitric oxide (NO) synthase (iNOS)⁺ macrophages and the consequent rise of myocardial NO production in association with reduced ADO levels induced protection against T. cruzi infection as observed by the diminished cardiac parasite burden compared to their wild-type (WT) counterpart. Unexpectedly, parasitemia was substantially raised in CD73KO mice in comparison with WT mice, suggesting the existence of tissue reservoir/s outside myocardium. Indeed, CD73KO liver and visceral adipose tissue (VAT) showed increased parasite burden associated with a reduced ATP/ADO ratio and the lack of substantial microbicidal immune response. These data reveal that the purinergic system has a tissue-dependent impact on the host immune response against T. cruzi infection.

Subchronic mycotoxicoses in rats. Histopathological changes and modulation of the sphinganine to sphingosine (Sa/So) ratio imbalance induced by Fusarium verticillioides culture material, due to the coexistence of aflatoxin B1 in the diet

Mycotoxicoses are diseases caused by consumption of diets contaminated with mycotoxins, a special class of fungal secondary metabolites. Fumonisin B1 (FB1) and aflatoxin B1 (AFB1), the main toxins synthesized by toxicogenic stocks of Fusarium spp. and Aspergillus spp., respectively, can coexist in grains and in its by-products. We investigated a probable synergism of a fumonisins-containing Fusarium verticillioides culture material and AFB1 in the induction of hepatocyte apoptosis in rats subchronically fed on a mixture of them. Furthermore, the possibility of modifications in the fumonisins-induced Sa/So ratio imbalance in tissues and urine from rats poisoned with this mycotoxin, due to the presence of AFB1 in the diet, was evaluated. The co-exposure to fumonisins and AFB1 produced a higher liver toxicity, with respect to their individual administration, inducing apoptosis and mitotic hepatocytes. There was an inversion of the typical Sa/So ratio in rats fed on the culture material as well as in those subjected to a diet co-contamined with fumonisins and AFB1. Moreover, the later had a synergistic effect in the induction of Sa/So variations in kidneys. Therefore, the mixture of fumonisins and AFB1 induced toxic responses which could not be considered a sum of the effects caused individually by these mycotoxins.

Aromatic plants essential oils activity on Fusarium verticillioides Fumonisin B1 production in corn grain

The minimum inhibitory concentration (MIC) of Origanum vulgare, Aloysia triphylla, Aloysia polystachya and Mentha piperita essential oils (EOs) against Fusarium verticillioides M 7075 (F. moniliforme, Sheldon) were assessed, using the semisolid agar antifungal susceptibility (SAAS) technique. O. vulgare, A. triphylla, A. polystachya and M. piperita EOs were evaluated at final concentrations of 10, 20, 40, 50, 100, 200, 250, 500, 1000 and 1500 epsilonl per litre (epsilonl/l) of culture medium. A. triphylla and O. vulgare EOs showed the highest inhibitory effects on F. verticillioides mycelial development. This inhibition was observed at 250 and 500 epsilonl/l for EOs coming from Aloysia triphylla and O. vulgare, respectively. Thus, the effects of EOs on FB(1) production were evaluated using corn grain (Zea mays) as substrate. The EOs were inserted on the 5th, 10th, 15th and 20th day of maize postinoculation with a conidia suspension of F. verticillioides. O. vulgare and A. triphylla were applied to give final concentrations of 30 ppm and 45 ppm, respectively. Different effects were observed in the toxicogenicity at the 20th day treatment. The O. vulgare EO decreased the production level of FB(1) (P < 0.01) while A. triphyla EO increased it (P < 0.001) with respect to those obtained in the inoculated maize, not EOs treated. Results obtained in the present work indicate that fumonisin production could be inhibited or stimulated by some constituents of EOs coming from aromatic plants. Further studies should be performed to identify the components of EOs with modulatory activity on the growth and fumonisins production of Fusarium verticillioides.

Immunobiological effects of AFB1 and AFB1-FB1 mixture in experimental subchronic mycotoxicoses in rats

Maize co-contamination with aflatoxin B1 (AFB1) and fumonisin B1 (FB1) is frequently found in several countries. Although the alterations on nutritional and immunologic parameters induced by these mycotoxins, when administered individually, are partially characterised, little is known about the effects induced in animals by a subchronic administration of both toxins mixtures. We have studied the nutritional and immunological alterations induced in rats fed during 90 days with a diet without mycotoxins, containing 40 ppb AFB1, and with a diet containing a mixture of 40 ppb AFB1 and 100 ppm FB1. Animals fed with the mixture of toxins obtained lower body weight than the control ones. The mitogenic response of spleen mononuclear cells (SMC) in vivo was higher in animals fed with AFB1. In in vitro studies, lower proliferations of SMC pre-exposed to AFB1 and to the mixture of toxins were detected. The SMC of animals fed with AFB1 produced lower levels of IL-2, higher of IL-4 and equal levels of IL-10. The SMC of animals fed with both toxins produced higher levels of IL-4, lower of IL-10 and equal levels of IL-2. The SMC preincubated with an AFB1-FB1 mixture produced higher concentrations of IL-4, lower of IL-10 and equal levels of IL-2. The peritoneal macrophages of animals that consumed AFB1 released less H(2)O(2), while animals fed with the mixture of toxins produced higher levels. In in vitro studies, macrophages pre-exposed to the mixture of toxins released less H(2)O(2). These results show different immunobiological effects produced by a mixture of mycotoxins in comparison to the individual action of the same toxins.

Immunobiological effects of fumonisin B1 in experimental subchronic mycotoxicoses in rats

Fumonisin B1 (FB1), the principal secondary metabolite produced by the fungus Fusarium verticillioides (Gibberella fujikuroi mating population A), is a potent toxin that can be found in fungus-contaminated corn and corn-based food products. We have investigated the immunobiological effects of subchronic dietary exposure to FB1 in male Wistar rats. Animals were fed with diets containing 0 (control) or 100 ppm of FB1 for 12 weeks. The total FB1 intake on day 90 was 810 mg/kg of body weight. Food consumption, body weight, and body weight gain on day 90 were reduced in animals exposed to FB1. Histopathologic changes consisted of histiocytic perivascular infiltrate and an increased number of Kupffer cells in the liver, necrosis and apoptosis of tubular epithelial cells in the kidney, and increased mitotic figures and lymphocytic infiltrate in the small intestine. Serum enzyme alkaline phosphatase was significantly elevated in rats fed FB1, while triglyceride levels decreased compared to controls. Treatment with FB1 in vivo or in vitro did not have a significant effect on mitogen-induced proliferation of spleen mononuclear cells. However, increased levels of interleukin-4 (IL-4) and decreased levels of IL-10 were released by these cells in culture compared to controls. FB1 in vivo or in vitro decreased the hydrogen peroxide (H(2)O(2)) released by peritoneal macrophages, while no changes in levels of superoxide anion produced by total peritoneal cells were detected. The results from the present work demonstrate that subchronic FB1 intake could affect the small intestine and alter the interleukin profile and some main functions of macrophages in antitumor activity.