15d-PGJ(2) modulates acute immune responses to Trypanosoma cruzi infection

Administration of artinm lectin reduces the severity of the acute phase infection with Trypanosoma cruzi

The acute phase of experimental Trypanosoma cruzi infection is associated with a strong inflammatory reaction, physiological changes, amastigote nests in tissues, and hematological alterations. ArtinM, a lectin extracted from Artocarpus heterophyllus seeds, is a homotetramer exhibiting immunomodulatory properties that promotes Th1 immune responses against intracellular pathogens, including the induction of neutrophil migration and increase in IL‐12 production. This study aimed to evaluate the effects of ArtinM on experimental Chagas disease in mice. We evaluated mouse survival curves, parasitemia, hematological parameters including quantification of inflammatory infiltrates, and amastigote nests in cardiac tissue during infection. The results showed a reduced number of parasites in the blood, an increase in animal survival, improvements in hematological parameters, and decrease in inflammatory infiltrates and amastigote nests in the group treated with ArtinM. Collectively, these data suggest that the administration of ArtinM can lower the number of parasites in peak parasitemia caused by the Colombian strain of T. cruzi and can increase survival of infected mice. The observed reduction in cardiac tissue injury may be due to fewer T. cruzi amastigote nests and lower levels of inflammatory infiltrates. This study highlights the need for further investigation into the use of ArtinM as a potential alternative therapeutic for treating Chagas disease.

Acellular Human Amniotic Membrane Scaffold with 15d-PGJ2 Nanoparticles in Postinfarct Rat Model

The difficulty in the regeneration of cardiomyocytes after myocardial infarction is a major cause of heart failure. Together, the amniotic membrane and 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ₂) can help in the recovery of cardiomyocyte, as they present many growth factors and anti-inflammatory effect, respectively. The objective of this study is to compare the efficacy of Human Decellularized Amniotic Membrane Scaffold (AHAS) loaded with 15d-PGJ₂ in improving ventricular function in a rat model of postinfarct ventricular dysfunction. Myocardial infarction was induced in 24 rats by left coronary occlusion. After a week, the animals were subjected to echocardiography for evaluation of left ventricle ejection fraction (LVEF), left ventricle end diastolic volume (LVEDV), and left ventricle end systolic volume (LVESV). Animals with ejection fraction <40% were included in the study and were randomized into three groups: control (n = 8), AHAS (n = 8) and AHAS +15d-PGJ₂ (n = 8). In the AHAS group only the membrane was implanted, whereas in the AHAS +15d-PGJ₂ the membrane +15d-PGJ₂ was implanted on myocardial infarction. Echocardiographic evaluation was performed after 1 month. For histological analysis, heart tissue was stained with Gomori trichome, Sirius Red, the antibody against CD31 and connexin 43 (Cx43). There were no significant differences in the baseline LVEF, LVEDV, and LVESV in all groups. After 1 month, ejection fraction decreased in the control group but increased in the AHAS group and in the AHAS +15d-PGJ₂ group in comparison with the control group. The LVEDV and LVESV in the AHAS and AHAS +15d-PGJ₂ groups decreased compared with the control group, featuring a ventricular antiremodeling effect. Histopathology of the infarcted area identified the reduction of infarct size and collagen type 1 in the AHAS and AHAS +15d-PGJ₂ groups. New blood vessels and cardiomyocytes have been identified in an infarcted area by CD31 and Cx43. AHAS +15d-PGJ₂ provided an increase in the ejection fraction and prevented ventricular dilation in this postinfarction ventricular dysfunction model. Impact Statement Our study demonstrated reduction of myocardial fibrosis, proliferation of cardiomyocytes and increase in ejection fraction in rats after experimental acellular amniotic membrane scaffold (AHAS) carrying nanoparticles of 15d-PGJ2 scaffold engraftment in infarcted myocardium. AHAS grafts facilitated colonization of fibrotic myocardium regions with new contractile cells, in addition to preventing reduction of left ventricle wall thickness. This contribution is theoretically and practically relevant as current literature describes experimental studies performed on cardiac ischemic models which present conflicting results concerning cell types used in a research model.

Pyridinecarboxylic Acid Derivative Stimulates Pro-Angiogenic Mediators by PI3K/AKT/mTOR and Inhibits Reactive Nitrogen and Oxygen Species and NF-κB Activation Through a PPARγ-Dependent Pathway in T. cruzi-Infected Macrophages

Chagas disease is caused by Trypanosoma cruzi infection and represents an important public health concern in Latin America. Macrophages are one of the main infiltrating leukocytes in response to infection. Parasite persistence could trigger a sustained activation of these cells, contributing to the damage observed in this pathology, particularly in the heart. HP₂₄, a pyridinecarboxylic acid derivative, is a new PPARγ ligand that exerts anti-inflammatory and pro-angiogenic effects. The aim of this work was to deepen the study of the mechanisms involved in the pro-angiogenic and anti-inflammatory effects of HP₂₄ in T. cruzi-infected macrophages, which have not yet been elucidated. We show for the first time that HP₂₄ increases expression of VEGF-A and eNOS through PI3K/AKT/mTOR and PPARγ pathways and that HP₂₄ inhibits iNOS expression and NO release, a pro-inflammatory mediator, through PPARγ-dependent mechanisms. Furthermore, this study shows that HP₂₄ modulates H₂O₂ production in a PPARγ-dependent manner. It is also demonstrated that this new PPARγ ligand inhibits the NF-κB pathway. HP₂₄ inhibits IKK phosphorylation and IκB-α degradation, as well as p65 translocation to the nucleus in a PPARγ-dependent manner. In Chagas disease, both the sustained increment in pro-inflammatory mediators and microvascular abnormalities are crucial aspects for the generation of cardiac damage. Elucidating the mechanism of action of new PPARγ ligands is highly attractive, given the fact that it can be used as an adjuvant therapy, particularly in the case of Chagas disease in which inflammation and tissue remodeling play an important role in the pathophysiology of this disease.

Immune-endocrine interactions related to a high risk of infections in chronic metabolic diseases: The role of PPAR gamma

Diverse disturbances in immune-endocrine circuitries are involved in the development and aggravation of several chronic metabolic diseases (CMDs), including obesity, diabetes, and metabolic syndrome. The chronic inflammatory syndrome observed in CMDs culminates in dysregulated immune responses with low microbial killing efficiency, by means low host innate immune response, and loss of ability to eliminate the pathogens, which results in a high prevalence of infectious diseases, including pneumonia, tuberculosis, and sepsis. Herein, we review evidence pointing out PPARγ as a putative player in immune-endocrine disturbances related to increased risk of infections in CMDs. Cumulated evidence indicates that PPARγ activation modulates host cells to control inflammation during CMDs because of PPARγ agonists have anti-inflammatory and pro-resolutive properties, increasing host ability to eliminate pathogen, modulating hormone production, and restoring glucose and lipid homeostasis. As such, we propose PPARγ as a putative therapeutic adjuvant for patients with CMDs to favor a better infection control.

Inflammatory and Pro-resolving Lipids in Trypanosomatid Infections: A Key to Understanding Parasite Control

Pathogenic trypanosomatids (Trypanosoma cruzi, Trypanosoma brucei, and Leishmania spp.) are protozoan parasites that cause neglected diseases affecting millions of people in Africa, Asia, and the Americas. In the process of infection, trypanosomatids evade and survive the immune system attack, which can lead to a chronic inflammatory state that induces cumulative damage, often killing the host in the long term. The immune mediators involved in this process are not entirely understood. Most of the research on the immunologic control of protozoan infections has been focused on acute inflammation. Nevertheless, when this process is not terminated adequately, permanent damage to the inflamed tissue may ensue. Recently, a second process, called resolution of inflammation, has been proposed to be a pivotal process in the control of parasite burden and establishment of chronic infection. Resolution of inflammation is an active process that promotes the normal function of injured or infected tissues. Several mediators are involved in this process, including eicosanoid-derived lipids, cytokines such as transforming growth factor (TGF)-β and interleukin (IL)-10, and other proteins such as Annexin-V. For example, during T. cruzi infection, pro-resolving lipids such as 15-epi-lipoxin-A4 and Resolvin D1 have been associated with a decrease in the inflammatory changes observed in experimental chronic heart disease, reducing inflammation and fibrosis, and increasing host survival. Furthermore, Resolvin D1 modulates the immune response in cells of patients with Chagas disease. In Leishmania spp. infections, pro-resolving mediators such as Annexin-V, lipoxins, and Resolvin D1 are related to the modulation of cutaneous manifestation of the disease. However, these mediators seem to have different roles in visceral or cutaneous leishmaniasis. Finally, although T. brucei infections are less well studied in terms of their relationship with inflammation, it has been found that arachidonic acid-derived lipids act as key regulators of the host immune response and parasite burden. Also, cytokines such as IL-10 and TGF-β may be related to increased infection. Knowledge about the inflammation resolution process is necessary to understand the host–parasite interplay, but it also offers an interesting opportunity to improve the current therapies, aiming to reduce the detrimental state induced by chronic protozoan infections.

Hepatic injury associated with Trypanosoma cruzi infection is attenuated by treatment with 15-deoxy-Δ12,14 prostaglandin J2

Trypanosoma cruzi, the etiological agent of Chagas' disease, causes an intense inflammatory response in several tissues, including the liver. Since this organ is central to metabolism, its infection may be reflected in the outcome of the disease. 15-deoxy-Δ^12,14 prostaglandin J₂ (15dPGJ2), a natural agonist of peroxisome-proliferator activated receptor (PPAR) γ, has been shown to exert anti-inflammatory effects in the heart upon T. cruzi infection. However, its role in the restoration of liver function and reduction of liver inflammation has not been studied yet. BALB/c mice were infected with T. cruzi. The effects of in vivo treatment with 15dPGJ2 on liver inflammation and fibrosis, as well as on the GOT/GPT ratio were studied and the role of NF-κB pathway on 15dPGJ2-mediated effects was analysed. 15dPGJ2 reduced liver inflammatory infiltrates, proinflammatory enzymes and cytokines expression, restored the De Ritis ratio values to normal, reduced the deposits of interstitial and perisinusoidal collagen, reduced the expression of the pro-fibrotic cytokines and inhibited the translocation of the p65 NF-κB subunit to the nucleus. Thus, we showed that 15dPGJ2 is able to significantly reduce the inflammatory response and fibrosis and reduced enzyme markers of liver damage in mice infected with T. cruzi.

Are reactive oxygen species always detrimental to pathogens?

Reactive oxygen species (ROS) are deadly weapons used by phagocytes and other cell types, such as lung epithelial cells, against pathogens. ROS can kill pathogens directly by causing oxidative damage to biocompounds or indirectly by stimulating pathogen elimination by various nonoxidative mechanisms, including pattern recognition receptors signaling, autophagy, neutrophil extracellular trap formation, and T-lymphocyte responses. Thus, one should expect that the inhibition of ROS production promote infection. Increasing evidences support that in certain particular infections, antioxidants decrease and prooxidants increase pathogen burden. In this study, we review the classic infections that are controlled by ROS and the cases in which ROS appear as promoters of infection, challenging the paradigm. We discuss the possible mechanisms by which ROS could promote particular infections. These mechanisms are still not completely clear but include the metabolic effects of ROS on pathogen physiology, ROS-induced damage to the immune system, and ROS-induced activation of immune defense mechanisms that are subsequently hijacked by particular pathogens to act against more effective microbicidal mechanisms of the immune system. The effective use of antioxidants as therapeutic agents against certain infections is a realistic possibility that is beginning to be applied against viruses.

PPARγ ligand treatment inhibits cardiac inflammatory mediators induced by infection with different lethality strains of Trypanosoma cruzi

Trypanosoma cruzi (T. cruzi), the etiological agent of Chagas' disease, causes cardiac alterations in the host. Although the main clinical manifestations arise during the chronic stage, the mechanisms leading to heart damage develop early during infection. In fact, an intense inflammatory response is observed from acute stage of infection. Recently, peroxisome proliferator-activated receptors (PPARs) have attracted research interest due to their participation in the modulation of inflammation. In this work we addressed the role of 15-Deoxy-∆(12,14) ProstaglandinJ2 (15dPGJ2), a PPARγ natural ligand in the regulation of inflammatory mediators, in acute and chronic experimental mouse models of Chagas' disease with the RA and K98 T. cruzi strains, respectively. This work demonstrates that 15dPGJ2 treatment inhibits the expression and activity of inducible nitric oxide synthase (NOS2) as well as TNF-α and IL-6 mRNA levels. Also, expression and activity of metalloproteinases 2 (MMP-2) and 9 (MMP9) were inhibited by 15dPGJ2. Moreover GW9662, a specific PPARγ antagonist, revealed the participation of other signaling pathways since, in GW9662 presence, 15dPJG2 had a partial effect on the inhibition of inflammatory parameters in the acute model of infection. Accordingly, NF-κB activation was demonstrated, assessing p65 nuclear translocation in the hearts of infected mice with both T. cruzi strains. Such effect was inhibited after 15dPGJ2 treatment. Our findings support the concept that in vivo PPARγ and NF-κB pathways are implicated in the inhibitory effects of 15dPGJ2 on inflammatory mediators at different times depending on whether the infection is caused by the lethal or non-lethal T. cruzi strain.

Oxidative stress fuels Trypanosoma cruzi infection in mice

Oxidative damage contributes to microbe elimination during macrophage respiratory burst. Nuclear factor, erythroid-derived 2, like 2 (NRF2) orchestrates antioxidant defenses, including the expression of heme-oxygenase-1 (HO-1). Unexpectedly, the activation of NRF2 and HO-1 reduces infection by a number of pathogens, although the mechanism responsible for this effect is largely unknown. We studied Trypanosoma cruzi infection in mice in which NRF2/HO-1 was induced with cobalt protoporphyrin (CoPP). CoPP reduced parasitemia and tissue parasitism, while an inhibitor of HO-1 activity increased T. cruzi parasitemia in blood. CoPP-induced effects did not depend on the adaptive immunity, nor were parasites directly targeted. We also found that CoPP reduced macrophage parasitism, which depended on NRF2 expression but not on classical mechanisms such as apoptosis of infected cells, induction of type I IFN, or NO. We found that exogenous expression of NRF2 or HO-1 also reduced macrophage parasitism. Several antioxidants, including NRF2 activators, reduced macrophage parasite burden, while pro-oxidants promoted it. Reducing the intracellular labile iron pool decreased parasitism, and antioxidants increased the expression of ferritin and ferroportin in infected macrophages. Ferrous sulfate reversed the CoPP-induced decrease in macrophage parasite burden and, given in vivo, reversed their protective effects. Our results indicate that oxidative stress contributes to parasite persistence in host tissues and open a new avenue for the development of anti-T. cruzi drugs.

Role of PPARs in Trypanosoma cruzi Infection: Implications for Chagas Disease Therapy

Chagas disease, which is caused by Trypanosoma cruzi (T. cruzi), remains a substantial public health concern and an important cause of morbidity and mortality in Latin America. T. cruzi infection causes an intense inflammatory response in diverse tissues by triggering local expression of inflammatory mediators, which results in the upregulation of the levels of cytokines and chemokines, and important cardiac alterations in the host, being one of the most characteristic damages of Chagas disease. Therefore, controlling the inflammatory reaction becomes critical for the control of the proliferation of the parasite and of the evolution of Chagas disease. The nuclear receptors known as peroxisome proliferator-activated receptors (PPARs) have emerged as key regulators of lipid metabolism and inflammation. The precise role of PPAR ligands in T. cruzi infection or in Chagas disease is poorly understood. This review summarizes our knowledge about T. cruzi infection as well as about the activation of PPARs and the potential role of their ligands in the resolution of inflammation, with the aim to address a new pharmacological approach to improve the host health.

Bioactive lipids in Trypanosoma cruzi infection

Chagas disease is caused by Trypanosoma cruzi, a protozoan parasite. Chagas disease remains a serious health problem in large parts of Mexico and Central and South America, where it is a major cause of morbidity and mortality. This disease is being increasingly recognized in non-endemic regions due to immigration. Heart disease develops in 10-30% of infected individuals. It is increasingly clear that parasite- and host-derived bioactive lipids potently modulate disease progression. Many of the changes that occur during acute and chronic Chagas disease can be accounted for by the effects of arachidonic acid (AA)-derived lipids such as leukotrienes, lipoxins, H(P)ETEs, prostaglandins (PGs) and thromboxane. During the course of infection with T. cruzi, changes in circulating levels of AA metabolites are observed. Antagonism of PG synthesis with cyclooxygenase (COX) inhibitors has both beneficial and adverse effects. Treatment with COX inhibitors during acute infection may result in increased parasite load and mortality. However, treatment instituted during chronic infection may be beneficial with no increase in mortality and substantial improvement with cardiac function. Recently, T. cruzi infection of mice deficient in AA biosynthetic enzymes for various pathways has yielded more insightful data than pharmacological inhibition and has highlighted the potential deleterious effects of inhibitors due to "off-target" actions. Using COX-1 null mice, it was observed that parasite biosynthesis is dependent upon host metabolism, that the majority of TXA(2) liberated during T. cruzi infection is derived from the parasite and that this molecule may act as a quorum sensor to control parasite growth/differentiation. Thus, eicosanoids present during acute infection may act as immunomodulators aiding the transition to, and maintenance of, the chronic stage of the disease. It is also likely that the same mediators that initially function to ensure host survival may later contribute to cardiovascular damage. Collectively, the eicosanoids represent a new series of targets for therapy in Chagas disease with defined potential therapeutic windows in which to apply these agents for greatest effect. A deeper understanding of the mechanism of action of non-steroidal anti-inflammatory drugs may provide clues to the differences between host responses in acute and chronic T. cruzi infection.