Could angiotensin-modulating drugs be relevant for the treatment of Trypanosoma cruzi infection? A systematic review of preclinical and clinical evidence.

Although leucocytes are targets of renin-angiotensin system (RAS) effector molecules and RAS-modulating drugs exert immunomodulatory effects, their impact on Trypanosoma cruzi infection remains poorly understood. By using the framework of a systematic review, we integrated the preclinical and clinical evidence to investigate the relevance of angiotensin-inhibiting drugs on T. cruzi infections. From a comprehensive and structured search in biomedical databases, only original studies were analysed. In preclinical and clinical studies, captopril, enalapril and losartan were RAS-modulating drugs used. The main in vitro findings indicated that these drugs increased parasite uptake per host cells, IL-12 expression by infected dendritic cells and IFN-γ by T lymphocytes, in addition to attenuating IL-10 and IL-17 production by CD8 + T cells. In animal models, reduced parasitaemia, tissue parasitism, leucocytes infiltration and mortality were often observed in T. cruzi-infected animals receiving RAS-modulating drugs. In patients with Chagas' disease, these drugs exerted a controversial impact on cytokine and hormone levels, and a limited effect on cardiovascular function. Considering a detailed evaluation of reporting and methodological quality, the current preclinical and clinical evidence is at high risk of bias, and we hope that our critical analysis will be useful in mitigating the risk of bias in further studies.

Could diet composition modulate pathological outcomes in schistosomiasis mansoni? A systematic review of in vivo preclinical evidence.

Schistosomiasis and malnutrition are often overlapped in poor communities, resulting in disproportionately high mortality rates. Currently, fragmented data make it difficult to define the relationship between diet and schistosomiasis. Thus, we systematically review the preclinical evidence on the impact of diet in Schistosoma mansoni infection. From a structured search, we recovered 27 original articles. All studies used mice and most of them investigated hypoproteic (70.37%), hyperlipidic (22.22%) or vitamin-deficient (7.41%) diets. Diets based on carbohydrate, zinc or milk supplementation were investigated at a reduced frequency (3.70% each). Hypoproteic diets attenuated parasitic load and granulomatous inflammation, but also reduced host resistance to S. mansoni infection, determining higher mortality rates. By stimulating steatohepatitis, parasitic load and granulomatous inflammation, hyperlipidic diets increase organ damage and mortality in infected animals. Although a high-sugar diet and vitamin restriction potentiate and zinc supplementation attenuates S. mansoni infection, the current evidence for these diets remains inconclusive. Analysis of methodological quality indicated that the current evidence is at high risk of bias due to incomplete characterization of the experimental design, diet composition and treatment protocols. From the bias analysis, we report methodological limitations that should be considered to avoid systematic reproduction of inconsistent and poorly reproducible experimental designs.

Lipopolysaccharide-induced acute lung injury in mice chronically infected by Schistosoma mansoni.

We used a murine model of Schistosoma mansoni (SM) infection and lipopolysaccharide (LPS)-induced endotoxicity to investigate if these conditions can interact to modify the pathological manifestations typically observed in each condition. Swiss mice were randomized into four groups: SAL, uninfected; SM, infected; LPS, uninfected + LPS; and SM + LPS, infected + LPS. S. mansoni infection developed over 120 days, after which blood samples and lungs were collected, peritoneal leukocytes were isolated and cultivated for 6 and 24 h after LPS inoculation (1 mL/kg). Infected animals presented marked granulomatous inflammation. LPS exposure transiently modified the profile of leucocyte migration into the lung tissue and increased NO production by isolated leukocytes, without inducing any acute effect on the structure of schistosomiasis granulomas. Beyond modifying lung morphology, S. mansoni and LPS interacted to modulate the circulating levels of cytokines. S. mansoni infection restricted INF-γ upregulation 6 and 24 h after LPS administration. Conversely, 24 h after inoculation, LPS increased IL-2 and IL-5 levels. Our findings indicate that LPS impaired the lung microenvironment by acutely disrupting inflammatory homeostatic mechanisms that control lung schistosomiasis. As schistosomiasis develops as a chronic condition, long-term exposure to endotoxins could aggravate the granulomatous process, an issue that requires further investigation.

Schistosoma mansoni co-infection modulates Chagas disease development but does not impair the effect of benznidazole-based chemotherapy.

The adequate management of parasite co-infections represents a challenge that has not yet been overcome, especially considering that the pathological outcomes and responses to treatment are poorly understood. Thus, this study aimed to evaluate the impact of Schistosoma mansoni infection on the efficacy of benznidazole (BZN)-based chemotherapy in Trypanosoma cruzi co-infected mice. BALB/c mice were maintained uninfected or co-infected with S. mansoni and T. cruzi, and were untreated or treated with BZN. Body weight, mortality, parasitemia, cardiac parasitism, circulating cytokines (Th1/Th2/Th17); as well as heart, liver and intestine microstructure were analyzed. The parasitemia peak was five times higher and myocarditis was more severe in co-infected than T. cruzi-infected mice. After reaching peak, parasitemia was effectively controlled in co-infected animals. BZN successfully controlled parasitemia in both co-infected and T. cruzi-infected mice and improved body mass, cardiac parasitism, myocarditis and survival in co-infected mice. Co-infection dampened the typical cytokine response to either parasite, and BZN reduced anti-inflammatory cytokines in co-infected mice. Despite BZN normalizing splenomegaly and liver cellular infiltration, it exacerbated hepatomegaly in co-infected mice. Co-infection or BZN exerted no effect on hepatic granulomas, but increased pulmonary and intestinal granulomas. Marked granulomatous inflammation was identified in the small intestine of all schistosomiasis groups. Taken together, our findings indicate that BZN retains its therapeutic efficacy against T. cruzi infection even in the presence of S. mansoni co-infection, but with organ-specific repercussions, especially in the liver.

Dietary glycemic and energy load differentially modulates Schistosoma mansoni-induced granulomatous inflammation and response to antiparasitic chemotherapy.

The impact of diet composition and energy content on schistosomiasis evolution and treatment efficacy is still controversial. This study compared the impact of sucrose-rich diet and intermittent fasting on Schistosoma mansoni infection and praziquantel (PZQ)-based chemotherapy response in mice. BALB/c mice were infected with S. mansoni and followed for 15 weeks. The animals were randomized into nine groups receiving high glycemic load (high-sucrose diet - HSD), low caloric load (standard chow alternate-day fasting - ADF), and standard chow ad libitum (AL). Eight weeks after S. mansoni infection, these groups remained untreated or were treated with PZQ (300 mg/kg/day) for 3 days. Our results indicated that parasite load (S. mansoni eggs and parasite DNA levels), granulomatous inflammation (granulomas number and size), and liver microstructural damage (reduction in hepatocytes number, increase in nucleus-cytoplasm ratio, connective stroma expansion and fibrosis) were increased in ADF-treated animals. These animals also showed decreased eggs retention, granulomatous inflammation and collagen accumulation in the small intestine. Conversely, HSD diet and PZQ treatment attenuated all these parameters and stimulated hepatic regenerative response. PZQ also stimulated fibrosis resolution in HSD-treated mice, effect that was limited ADF-exposed mice. Our findings indicate that dietary glycemic and energy load can modulate schistosomiasis progression and the severity of hepatic and intestinal granulomatous inflammation in untreated and PZQ-treated mice. Thus, lower intestinal eggs retention may potentially be linked to worsening liver disease in ADF, while attenuation of hepatic and intestinal granulomatous inflammation is consistent with reduced parasite load in HSD- and PZQ-treated animals.

Oxidative stress, cardiomyocytes premature senescence and contractile dysfunction in in vitro and in vivo experimental models of Chagas disease.

AIMS: The relationship between redox imbalance and cardiovascular senescence in infectious myocarditis is unknown. Thus, the aim of this study was to investigate whether cardiomyocytes parasitism, oxidative stress and contractile dysfunction can be correlated to senescence-associated ß-galactosidase (SA-ß-Gal) activity in Trypanosoma cruzi-infection in vitro and in vivo. METHODS: Uninfected, T. cruzi-infected untreated and benznidazole (BZN)-treated H9c2 cardiomyocytes and rats were investigated. Parasitological, prooxidant, antioxidant, microstructural, and senescence-associated markers were quantified in vitro and in vivo. RESULTS: T. cruzi infection triggered intense cardiomyocytes parasitism in vitro and in vivo, which was accompanied by reactive oxygen species (ROS) upregulation, lipids, proteins and DNA oxidation in cardiomyocytes and cardiac tissue. Oxidative stress was parallel to microstructural cell damage (e.g., increased cardiac toponin I levels) and contractile dysfunction in cardiomyocytes in vitro and in vivo, whose severity accompanied a premature cellular senescence-like phenotype revealed by increased senescence-associated ß-galactosidase (SA-ß-Gal) activity and DNA oxidation (8-OHdG). Cellular parasitism (e.g., infection rate and parasite load), myocarditis and T. cruzi-induced prooxidant responses were attenuated by early BZN administration to interrupt the progression of T. cruzi infection, protecting against SA-ß-gal-based premature cellular senescence, microstructural damage and contractile deterioration in cardiomyocytes from T. cruzi-infected animals. CONCLUSION: Our findings indicated that cell parasitism, redox imbalance and contractile dysfunction were correlated to SA-ß-Gal-based cardiomyocytes premature senescence in acute T. cruzi infection. Therefore, in addition to controlling parasitism, inflammation and oxidative stress; inhibiting cardiomyocytes premature senescence should be further investigated as an additional target of specific Chagas disease therapeutics.

Pharmacological potential of new metronidazole/eugenol/dihydroeugenol hybrids against Trypanosoma cruzi in vitro and in vivo.

AIMS: From well-delimited immunomodulatory, redox and antimicrobial properties; metronidazole and eugenol were used as structural platforms to assembly two new molecular hybrids (AD06 and AD07), whose therapeutic relevance was analyzed on T. cruzi infection in vitro and in vivo. METHODS: Non-infected, T. cruzi-infected H9c2 cardiomyocytes, and mice non-treated and treated with vehicle, benznidazole (Bz - reference drug), AD06 and AD07 were investigated. Parasitological, prooxidant, antioxidant, microstructural, immunological, and hepatic function markers were analyzed. RESULTS: Our findings indicated that in addition to having a direct antiparasitic effect on T. cruzi, metronidazole/eugenol hybrids (especially AD07) attenuated cellular parasitism, reactive species biosynthesis and oxidative stress in infected cardiomyocytes in vitro. Although AD06 and AD07 exerted no relevant impact on antioxidant enzymes activity (CAT, SOD, GR and GPx) in host cells, these drugs (especially AD07) attenuated trypanothione reductase activity in T. cruzi, which increased parasite's susceptibility to in vitro pro-oxidant challenge. AD06 and AD07 were well tolerated and do not determine humoral response suppression, mortality (100 % survival) or hepatotoxicity in mice, as indicated by transaminases plasma levels. AD07 also induced relevant in vivo antiparasitic and cardioprotective effects, attenuating parasitemia, cardiac parasite load and myocarditis in T. cruzi-infected mice. Although this cardioprotective response is potentially related to AD07 antiparasitic effect, a direct anti-inflammatory potential of this molecular hybrid cannot be ruled out. CONCLUSION: Taken together, our findings indicated that the new molecular hybrid AD07 stood out as a potentially relevant candidate for the development of new, safe and more effective drug regimens for T. cruzi infection treatment.

Chronic rapamycin pretreatment modulates arginase/inducible nitric oxide synthase balance attenuating aging-dependent susceptibility to Trypanosoma cruzi infection and acute myocarditis.

Considering the efficacy of rapamycin in increasing lifespan and healthspan, attenuating the aging-dependent immunological decline, we compared the evolution of Trypanosoma cruzi infection and acute myocarditis in young and elderly mice untreated and chronically treated with this drug. Five groups were investigated: young uninfected and infected, elderly uninfected and infected with Trypanosoma cruzi untreated and treated with rapamycin (4 mg/kg every 3 days) from the 8th to the 96th week of age. Seven days after the last treatment, elderly mice were inoculated with T. cruzi. Young animals were infected at 8-weeks-old. Untreated elderly mice exhibited increase parasitemia, parasite load and myocarditis, which were associated to down-regulation in IL-2, IL-6, IFN-γ, TNF, anti-T. cruzi immunoglobulin G (IgG) total, IgG1 and IgG2a plasma levels, inducible nitric oxide synthase (iNOS) gene expression and nitric oxide (NO) cardiac production, as well as upregulation in Arginase-1 gene expression and arginase activity compared to young animals. These parameters were improved in rapamycin-pretreated elderly mice, which exhibited a better parasitological control, reduced heart inflammation and microstructural damage. These responses were associated with a better balance between Th1 and Th2 effectors similar to that observed in young animals, including an improved activation of Th1 cytokines and the iNOS pathway that positively regulates NO biosynthesis, contradicting the predominant activation of the arginase pathway in untreated elderly animals. Thus, our findings suggest that chronic pretreatment with rapamycin can attenuate immunosenescence in mice, contributing to prolong parasite resistance and attenuate acute myocarditis in elderly host challenged by T. cruzi.

The Tapeworm Hymenolepis diminuta as an Important Model Organism in the Experimental Parasitology of the 21st Century.

The tapeworm Hymenolepis diminuta is a common parasite of the small intestine in rodents but it can also infect humans. Due to its characteristics and ease of maintenance in the laboratory, H. diminuta is also an important model species in studies of cestodiasis, including the search for new drugs, treatments, diagnostics and biochemical processes, as well as its host-parasite interrelationships. A great deal of attention has been devoted to the immune response caused by H. diminuta in the host, and several studies indicate that infection with H. diminuta can reduce the severity of concomitant disease. Here, we present a critical review of the experimental research conducted with the use of H. diminuta as a model organism for over more than two decades (in the 21st century). The present review evaluates the tapeworm H. diminuta as a model organism for studying the molecular biology, biochemistry and immunology aspects of parasitology, as well as certain clinical applications. It also systematizes the latest research on this species. Its findings may contribute to a better understanding of the biology of tapeworms and their adaptation to parasitism, including complex correlations between H. diminuta and invertebrate and vertebrate hosts. It places particular emphasis on its value for the further development of modern experimental parasitology.

Impact of Trypanosoma cruzi infection on nitric oxide synthase and arginase expression and activity in young and elderly mice.

Elderly organisms are more susceptible to infectious diseases. However, the impact of aging on antiparasitic mechanisms, especially the nitric oxide pathway, is poorly understood. Using an integrated in vivo and in vitro model, we compared the severity of Trypanosoma cruzi infection in young and elderly (8 or 72 weeks old) mice. Forty C57BL/6 mice were randomized into four groups: Y-inf, young infected; Yn-inf, young uninfected; A-inf, aged infected; An-inf, aged uninfected. Parasitemia was measured daily, and animals were euthanized after 15 days of infection. Trypanosoma cruzi-induced inflammatory processes were analyzed in blood and heart samples, as well as in bone marrow-derived macrophages (BMDMs) co-cultured with splenocytes isolated from young or elderly mice. Our results indicated upregulated IgG2b and IL-17 production in elderly animals, which was not sufficient to reduce parasitemia, parasitic load and myocarditis to levels observed in young animals. The higher susceptibility of elderly mice to T. cruzi infection was accompanied by reduced cardiac inducible nitric oxide synthase (iNOS) gene expression, nitric oxide (NO) and IFN-γ levels, as well as an antagonistic upregulation of arginase-1 expression and arginase activity. The same responses were observed when BMDMs co-cultured with splenocytes from elderly mice were stimulated with T. cruzi antigens. Our findings indicate that elderly mice were more susceptible to T. cruzi infection, which was potentially related to an attenuated response to antigenic stimulation, inhibition of iNOS gene expression and NO production, and antagonistic upregulation of arginase gene expression and activity, which created favorable conditions for heart parasitism and myocarditis development.