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Trypomastigote forms of Trypanosoma cruzi, the causative agent of Chagas disease, shed extracellular vesicles (EVs) that promote the susceptibility of host cells to infection. During T. cruzi infection, the immune response of the host is important for controlling parasitism, which is necessary for survival. Macrophages produce inflammatory mediators, such as eicosanoids and nitric oxide (NO), with trypanocidal effects that control the parasite load in the early stages of the disease. In this study, we evaluated the contribution of host cyclooxygenase (COX) to the actions of EVs shed by T. cruzi strain Y (EVs-Y) in infected macrophages. RAW 264.7 macrophages exposed to EVs-Y and then infected with trypomastigote forms of T. cruzi produced less NO, and an increased number of trypomastigote forms were internalized in the cell compared to the controls, indicating that the effects exerted by EVs-Y favor the parasite. Interestingly, when macrophages were pretreated with acetylsalicylic acid, a dual COX inhibitor, before exposure to EVs-Y and subsequent infection with trypomastigote forms, there was an increase in NO production and a decrease in trypomastigote uptake compared to the controls. These results suggest that EVs-Y modulates the macrophage response in favor of T. cruzi and indicate a role for COX in the effects of EVs.

Chagas disease, caused by the protozoan Trypanosoma cruzi, is one of the main causes of death due to cardiomyopathy and heart failure in Latin American countries. The treatment of Chagas disease is directed at eliminating the parasite, decreasing the probability of cardiomyopathy and disrupting the disease transmission cycle. Benznidazole (BZ) and nifurtimox (Nfx) are recognized as effective drugs for the treatment of Chagas disease by the World Health Organization, but both have high toxicity and limited efficacy, especially in the chronic disease phase. At low doses, aspirin (ASA) has been reported to protect against T. cruzi infection. We evaluated the effectiveness of BZ in combination with ASA at low doses during the acute disease phase and evaluated cardiovascular aspects and cardiac lesions in the chronic phase. ASA treatment prevented the cardiovascular dysfunction (hypertension and tachycardia) and typical cardiac lesions. Moreover, BZ+ASA-treated mice had a smaller cardiac fibrotic area than BZ-treated mice. These results were associated with an increase in numbers of eosinophils and reticulocytes and levels of nitric oxide in the plasma and cardiac tissue of ASA-treated mice relative to respective controls. These effects of ASA and BZ+ASA in chronically infected mice were inhibited by pretreatment with the lipoxin A(4) (LXA(4)) receptor antagonist Boc-2, indicating that the protective effects of ASA are mediated by ASA-triggered lipoxin. These results emphasize the importance of exploring new drug combinations for treatments of the acute phase of Chagas disease that are beneficial for patients with chronic disease.

Aims Sepsis is a potentially fatal systemic inflammatory response and its underlying pathophysiology is still poorly understood. Studies suggest that obesity, a component of metabolic syndrome (MS), is associated with sepsis survival. Therefore, this study focused on investigating the influence of MS on mortality and cardiovascular dysfunction induced by sublethal cecal ligation and puncture (SL-CLP). Main methods Newborn Swiss mice received monosodium glutamate (MSG) (4 mg kg−1 day−1, s.c.) during the first 5 d of life for MS induction, while the control pups received equimolar saline solution. On the 75th day, SL-CLP was used to induce mild sepsis (M-CLP) in the MS (MS-M-CLP) and control (SAL-M-CLP) mice. The effect of MS on sepsis in mice was assessed by determining the survival rate and quantification of nitric oxide (NO) in the plasma, and associating this data with hematological and cardiovascular parameters. Key findings MS improved the survival of septic mice, preventing impairment to hematological and cardiovascular parameters. In addition, MS attenuated plasmatic NO increase, which is a typical feature of sepsis. Significance These findings provide new insights into the relationship between obesity and mild sepsis in mice, thus revealing an approach in favor of the “obesity paradox.”

Cell invasion by Trypanosoma cruzi and its intracellular replication are essential for progression of the parasite life cycle and development of Chagas disease. Prostaglandin E2 (PGE 2 ) and other eicosanoids potently modulate host response and contribute to Chagas disease progression. In this study, we evaluated the effect of aspirin (ASA), a non-selective cyclooxygenase (COX) inhibitor on the T. cruzi invasion and its influence on nitric oxide and cytokine production in human monocytes. The pretreatment of monocytes with ASA or SQ 22536 (adenylate-cyclase inhibitor) induced a marked inhibition of T. cruzi infection. On the other hand, the treatment of monocytes with SQ 22536 after ASA restored the invasiveness of T. cruzi. This reestablishment was associated with a decrease in nitric oxide and PGE 2 production, and also an increase of interleukin-10 and interleukin-12 by cells pre-treated with ASA. Altogether, these results reinforce the idea that the cyclooxygenase pathway plays a fundamental role in the process of parasite invasion in an in vitro model of T. cruzi infection.

Long-chain omega-3 polyunsaturated fatty acids (LC n-3 PUFA) are known to modulate a variety of immune cell functions. On occasion, this has led to diminished host resistance to certain viral and bacterial infections. Little is known about the impact of n-3 PUFA on host resistance to parasitic infection, however, based on results from a small study conducted more than two decades ago, we hypothesized that providing mice LC n-3 PUFA will diminish host resistance to Trypanosoma cruzi, the parasitic pathogen responsible for Chagas disease. To investigate this, C57BL/6 mice were supplemented by gavage (0.6% v/w) with phosphate-buffered saline, corn oil (CO), or menhaden fish oil (FO, a fat source rich in LC n-3 PUFA) for 15 days prior to T cruzi (Y strain) challenge and throughout the acute phase of infection. FO supplementation was associated with a transient 2-fold greater peak of blood parasitemia at 7 days postinfection (dpi), whereas subsequent cardiac parasitemia was ~60% lower at 12 dpi. FO treatment also ameliorated the leukopenia and thrombocytopenia observed in the early stages of a T cruzi infection. FO supplementation reduced circulating and cardiac nitric oxide at 7 and 12 dpi, respectively. FO supplementation altered ex vivo prostaglandin E2 and cytokine and chemokine production by splenocytes isolated from uninfected and infected mice. Overall, our results suggest that oral administration of LC n-3 PUFA from FO can have beneficial effects on the host in the early course of a T cruzi infection.

We evaluated the influence of metabolic syndrome (MS) on acute Trypanosoma cruzi infection. Obese Swiss mice, 70 days of age, were subjected to intraperitoneal infection with 5 × 102 trypomastigotes of the Y strain. Cardiovascular, oxidative, inflammatory, and metabolic parameters were evaluated in infected and non-infected mice. We observed higher parasitaemia in the infected obese group (IOG) than in the infected control group (ICG) 13 and 15 days post-infection. All IOG animals died by 19 days post-infection (dpi), whereas 87.5% of the ICG survived to 30 days. Increased plasma nitrite levels in adipose tissue and the aorta were observed in the IOG. Higher INF-γ and MCP-1 concentrations and lower IL-10 concentrations were observed in the IOG compared to those in the ICG. Decreased insulin sensitivity was observed in obese animals, which was accentuated after infection. Higher parasitic loads were found in adipose and hepatic tissue, and increases in oxidative stress in cardiac, hepatic, and adipose tissues were characteristics of the IOG group. Thus, MS exacerbates experimental Chagas disease, resulting in greater damage and decreased survival in infected animals, and might be a warning sign that MS can influence other pathologies.

Chagas disease (Cd) or American human trypanosomiasis is caused by Trypanosoma cruzi and affects ~7 million people, mostly in Latin America. The infective trypomastigote forms of the parasite can invade several human blood cell populations, including monocytes and dendritic cells (DC). Although these cells display a wide functional diversity, their interactions with T. cruzi via cyclooxygenase (COX) and cyclic adenosine monophosphate (cAMP) dependent pathways have not been analyzed. To exploiting this mechanism, DC-enriched peripheral human blood mononuclear cell populations (DC-PBMC) were used as our model. Our results showed that the treatment of these cell populations with celecoxib (CEL), a cyclooxygenase-2 selective inhibitor or SQ 22,536, an adenilate cyclase inhibitor, significantly caused marked inhibition of T. cruzi infection. In contrast, aspirin (ASA, a non-selective COX-1 and COX-2 inhibitor) treatment did not inhibit the infection of the cells by the parasite and was independent of nitric oxide (NO) production. The expression of co-stimulatory molecules CD80 and CD86 were similar on cells treated or not with both COX-inhibitors. The infection stimulated the release of TNF-α, IL-1β, IL-6, IL-8, and IL-10 production by infected cells. Treatment with ASA or CEL did not affect TNF-α, IL-6, IL-8, IL-10, and NO production by infected cells, but increased IL-1β production by them. Our results suggest a key role of COX-2 and cAMP pathways in T. cruzi invasion process of human blood cells and these pathways may represent targets of new therapeutic options for Cd.

The intracellular protozoan parasite Trypanosoma cruzi is the etiologic agent of Chagas disease, a serious disorder that affects millions of people in Latin America. Cell invasion by T. cruzi and its intracellular replication are essential to the parasite's life cycle and for the development of Chagas disease. Here, we present evidence suggesting the involvement of the host's cyclooxygenase (COX) enzymes during T. cruzi invasion. Pharmacological antagonists for COX-1 (aspirin) and COX-2 (celecoxib) caused marked inhibition of T. cruzi infection when rat cardiac cells were pretreated with these nonsteroidal anti-inflammatory drugs (NSAIDs) for 60 min at 37°C before inoculation. This inhibition was associated with an increase in the production of NO and interleukin-1β and decreased production of transforming growth factor β (TGF-β) by cells. Taken together, these results indicate that COX-1 more than COX-2 is involved in the regulation of anti- T. cruzi activity in cardiac cells, and they provide a better understanding of the influence of TGF-β-interfering therapies on the innate inflammatory response to T. cruzi infection and may represent a very pertinent target for new therapeutic treatments of Chagas disease.

Sugar cane molasses is a cheaper carbon source alternative than glucose traditionally used in fermentation processes. In the present study a biopolymer soluble from Agrobacterium radiobacter k84 (ARB) was obtained by fermentation using sugar cane molasses as a carbon source in a process with yield of 10.0 g.L-1. The ARB is composed by minerals (40%), carbohydrate (35%) and protein (15%). In vitro test of the cytotoxic effect of ARB at concentrations 2.5 mg/mL, 5.0 mg/mL and 10.0 mg/mL in LLC MK2 (Rhesus Monkey Kidney) cells revealed a 50% cytotoxic concentration (CC50) of 9.32 mg/mL. In a 30-day in vivo oral toxicity study, Swiss mice were administered ARB by gavage at 5 mg/mL, 15 mg/mL, 50 mg/mL and 150 mg/mL (approximately 25 mg/kg/day, 75 mg/kg/day, 250 mg/kg/day and 750 mg/kg/day). The results did not present any hematological or histopathological signs of adverse effects, leading us to define the no observed adverse effect level (NOAEL) as 150 mg/mL (approximately 750 mg/kg/day).

Sugar cane molasses is a cheaper carbon source alternative than glucose traditionally used in fermentation processes. In the present study a biopolymer soluble from Agrobacterium radiobacter k84 (ARB) was obtained by fermentation using sugar cane molasses as a carbon source in a process with yield of 10.0 g.L-1. The ARB is composed by minerals (40%), carbohydrate (35%) and protein (15%). In vitro test of the cytotoxic effect of ARB at concentrations 2.5 mg/mL, 5.0 mg/mL and 10.0 mg/mL in LLC MK2 (Rhesus Monkey Kidney) cells revealed a 50% cytotoxic concentration (CC50) of 9.32 mg/mL. In a 30-day in vivo oral toxicity study, Swiss mice were administered ARB by gavage at 5 mg/mL, 15 mg/mL, 50 mg/mL and 150 mg/mL (approximately 25 mg/kg/day, 75 mg/kg/day, 250 mg/kg/day and 750 mg/kg/day). The results did not present any hematological or histopathological signs of adverse effects, leading us to define the no observed adverse effect level (NOAEL) as 150 mg/mL (approximately 750 mg/kg/day).O melaço de cana-de-açúcar é uma fonte de carbono alternativa de menor custo que a glicose tradicionalmente utilizada em processos fermentativos. No presente estudo, um biopolímero solúvel de Agrobacterium radiobacter k84 (ARB) foi obtido por fermentação utilizando melaço de cana de açúcar como fonte de carbono em um processo com rendimento de 10,0 g.L-1. O ARB é composto de minerais (40%), carboidratos (35%) e proteínas (15%). O teste do efeito citotóxico do ARB in vitro nas concentrações de 2,5 mg/mL, 5,0 mg/mL e 10,0 mg/mL em células LLC MK2 (Rim de Macaco Rhesus) revelou uma concentração citotóxica 50% (CC50) de 9,32 mg/mL. Em estudo in vivo de toxicidade oral durante 30 dias, camundongos Swiss receberam por gavagem soluções de ARB nas concentrações de 5 mg/mL, 15 mg/mL, 50 mg/mL e 150 mg/mL (aproximadamente 25 mg/kg/dia, 75 mg/kg/dia, 250 mg/ kg/dia e 750 mg/kg/dia). Os resultados não apresentaram sinais hematológicos ou histopatológicos de efeitos adversos, levando a definir a dose sem efeito adverso observado (NOAEL) como 150 mg/mL (aproximadamente 750 mg/kg/dia).

Chagas' disease is accompanied by severe anemia and oxidative stress, which may contribute to mortality. In this study, we investigated the role of 5-lipoxygenase (5-LO) in the control of parasitism and anemia associated with oxidative damage of erythrocytes in experimental Trypanosoma cruzi infection. Wild-type C57BL/6, 129Sv mice treated or not with nordihydroguaiaretic acid (NDGA, 5-LO inhibitor), mice lacking the 5-LO enzyme gene (5-LO(-/-)) and inducible nitric oxide synthase gene (iNOS(-/-)) were infected with the Y strain of T. cruzi. Impairment of 5-LO resulted in increased numbers of trypomastigote forms in the blood and amastigote forms in the heart of infected mice. We assessed oxidative stress in erythrocytes by measuring oxygen uptake, induction time and chemiluminescence following treatment with tert-butyl hydroperoxide (TBH). Our results show that 5-LO metabolites increased lipid peroxidation levels in erythrocytes during the early phase of murine T. cruzi infection. NDGA treatment reduced oxidative damage of erythrocytes in C57BL/6 T. cruzi-infected mice but not in C57BL/6 iNOS(-/-) infected mice, showing that the action of NDGA is dependent on endogenous nitric oxide (NO). In addition, our results show that 5-LO metabolites do not participate directly in the development of anemia in infected mice. We conclude that 5-LO products may not only play a major role in controlling heart tissue parasitism, i.e., host resistance to acute infection with T. cruziin vivo, but in the event of an infection also play an important part in erythrocyte oxidative stress, an NO-dependent effect.

Trypanosoma cruzi is the causative agent of Chagas disease. Approximately 8 million people are thought to be affected with this disease worldwide. T. cruzi infection causes an intense inflammatory response, which is critical for the control of parasite proliferation and disease development. Nitric oxide-donating nonsteroidal anti-inflammatory drugs (NO-NSAIDs) are an emergent class of pharmaceutical derivatives with promising utility as chemopreventive agents. In this study, we investigated the effect of NO-indomethacin on parasite burden, cell invasion, and oxidative stress in erythrocytes during the acute phase of infection. NO-indomethacin was dissolved in dimethyl formamide followed by i.p. administration of 50 ppm into mice 30 min after infection with 5×10(3) blood trypomastigote forms (Y strain). The drug was administered every day until the animals died. Control animals received 100 μL of drug vehicle via the same route. Within the NO-indomethacin-treatment group, parasitemia and mortality (100%) were higher and oxidative stress in erythrocytes, anemia, and entry of parasites into macrophages were significantly greater than that seen in controls. Increase in the entry and survival of intracellular T. cruzi was associated with inhibition of nitric oxide production by macrophages treated with NO-indomethacin (2.5 μM). The results of this study provide strong evidence that NO-NSAIDs potently inhibit nitric oxide production, suggesting that NO-NSAID-based therapies against infections would be difficult to design and would require caution.

Trypanosoma cruzi, the causative agent of Chagas’ disease (CD), is a substantial public health concern in Latin America. Laboratory mice inoculated with T. cruzi have served as important animal models of acute CD. Host hypoferremic responses occur during T. cruzi infection; therefore, it has been hypothesized that T. cruzi requires iron for optimal growth in host cells and, unlike extracellular pathogens, may benefit from host hypoferremic responses. Recent technological improvements of X-ray fluorescence are useful for diagnostics or monitoring in biomedical applications. The goal of our study was to determine whether the iron availabilities in Swiss and C57BL/6 mice differ during the acute phase of T. cruzi infection and whether the availability correlates with oxidative stress in the susceptible and resistant phenotypes identified in these mice. Our results showed that the decrease in iron levels in the skin of resistant infected mice correlated with the increase in oxidative stress associated with anemia and the reduction in parasite burden.

Prostaglandins are known to be produced by macrophages when challenged with Trypanosoma cruzi, the etiological agent of Chagas' disease. It is not known whether these lipid mediators play a role in oxidative stress in host defenses against this important protozoan parasite. In this study, we demonstrated that inducible cyclooxygenase-mediated prostaglandin production is a key chemical mediator in the control of parasite burden and erythrocyte oxidative stress during T. cruzi infection in C57BL/6 and BALB/c mice, prototype hosts for the study of resistance and susceptibility in murine Chagas' disease. The results suggested the existence of at least two mechanisms of oxidative stress, dependent or independent with regard to the nitric oxide and cyclooxygenase pathway, where one or the other is more evident depending on the mouse strain.

Trypanosoma cruzi infection in mice is associated with severe hematological changes, including anemia, which may contribute to mortality. TNF-alpha and nitric oxide (NO) play a critical role in establishing host resistance to this pathogen. We hypothesized that phagocyte-derived NO damages erythrocytes and contributes to the anemia observed during T. cruzi infection. To test this hypothesis, two strains of mice that differed in susceptibility and NO response to T. cruzi infection were used in these studies. We also blocked endogenous NO production by aminoguanidine (AG) treatment or blocked TNF-alpha with a neutralizing antibody and used mice that cannot produce phagocyte-derived NO (C57BL/6 iNOS(-/-)). Following infection with T. cruzi, resistant (C57BL/6) and susceptible (Swiss) mice displayed a parasitemia that peaked at the same time (i.e., day 9), yet parasitemia was 3-fold higher in Swiss mice (P0.05). All Swiss mice were dead by day 23 post-infection, while no C57BL/6 mice died during the study. At 14 days post-infection anemia in C57BL/6 mice was more severe than in Swiss mice. Treatment of both strains with the NO inhibitor, AG (50 mg/kg), and the use of iNOS(-/-) mice, revealed that the anemia in T. cruzi-infected mice is not caused by NO. However, the reticulocytosis that occurs during infection was significantly reduced after treatment with AG in both Swiss and C57BL/6 mice (P0.05). In addition, we showed that neutralization of TNF-alpha in vivo induced a significant increase in circulating reticulocytes in T. cruzi-infected C57BL/6 mice (P0.05), but did not modify other hematologic parameters in these mice. The evaluation of the oxidative stress after induction by t-butyl hydroperoxide (t-BHT) revealed that the treatment with AG completely protected against NO-mediated haemoglobin oxidation. Further, treatment with AG, but not with anti-TNF-alpha, protected against the infection-induced reduction of antioxidant capacity of erythrocytes as assessed by oxygen uptake and induction time. In summary, this is the first report showing the participation of NO and TNF-alpha in the oxidative stress to erythrocytes in acute T. cruzi infection. Further, our data suggest that NO does not play a direct role in development of the anemia. However, NO may contribute to other hematological changes noted during T. cruzi infection, such as the elevation of circulating reticulocytes and the reduction in circulating leukocytes and neutrophils.

Mice infected with Trypanosoma cruzi, the agent of Chagas disease, rapidly develop anemia and thrombocytopenia. These effects are partially promoted by the parasite trans-sialidase (TS), which is shed in the blood and depletes sialic acid from the platelets, inducing accelerated platelet clearance and causing thrombocytopenia during the acute phase of disease. Here, we demonstrate that oral immunization of C57BL/6 mice with Phytomonas serpens, a phytoflagellate parasite that shares common antigens with T. cruzi but has no TS activity, reduces parasite burden and prevents thrombocytopenia and leukopenia. Immunization also reduces platelet loss after intraperitoneal injection of TS. In addition, passive transfer of immune sera raised in mice against P. serpens prevented platelet clearance. Thus, oral exposure to P. serpens attenuates the progression of thrombocytopenia induced by TS from T. cruzi. These findings are not only important for the understanding of the pathogenesis of T. cruzi infection but also for developing novel approaches of intervention in Chagas disease.