Does L-arginine availability during the early pregnancy alters the immune response of Trypanosoma cruzi infected and pregnant Wistar rats?

L-Arginine supplementation in pregnancy: a systematic review of maternal and fetal outcomes

BACKGROUND/AIM OF THE STUDY

L-Arginine (L-Arg)/Nitric Oxide (NO) system is involved in the pathophysiology of relevant Obstetric conditions. This review aims at summarizing the effects of L-Arg supplementation in pregnancy looking at safety and efficacy.

METHODS

We conducted a systematic review of the literature utilizing PubMed for studies published from inception to September 2022. The search included human and animal studies where L-Arg was supplemented pre-conceptionally or during pregnancy, by either oral or intravenous route. The main perinatal outcomes were focused.

RESULTS

Among 1028 publications, 51 studies were eligible for inclusion, 25 were performed in women, and the remnant in animals. Compared to controls/placebo, the supplementation with L-Arg reduced the development of pre-eclampsia (four studies), decreased blood pressure, and reduced the need for antihypertensive drugs in women with Hypertensive Disorders of Pregnancy (HDP, eight studies). In women carrying growth retarded fetuses, L-Arg improved fetoplacental circulation, birth weight and neonatal outcomes (five studies), while in the case of threatened preterm birth, L-Arg reduced uterine contractions (two studies). In several animal species, L-Arg supplementation in pregnancy improved reproductive performance by increasing the litter number and size. Moreover, in pre-eclamptic and metabolic syndrome experimental models, maternal hypertension and fetal growth were improved.

CONCLUSION

L-Arg displays biological activities in pregnancies complicated by HDP and growth restriction, both in women and animal models. L-Arg administration is safe and could be a candidate as an intervention beneficial to maternal and fetal outcomes, at least in moderate clinical disorders.

Myeloid-Derived Suppressor Cells in Trypanosoma cruzi Infection

Myeloid-derived suppressor cells (MDSCs) are immature heterogeneous myeloid cells that expand in pathologic conditions as cancer, trauma, and infection. Although characterization of MDSCs is continuously revisited, the best feature is their suppressor activity. There are many markers for MDSC identification, it is distinctive that they express inducible nitric oxide synthase (iNOS) and arginase 1, which can mediate immune suppression. MDSCs can have a medullary origin as a result of emergency myelopoiesis, but also can have an extramedullary origin. Early studies on Trypanosoma cruzi infection showed severe immunosuppression, and several mechanisms involving parasite antigens and host cell mediators were described as inhibition of IL-2 and IL-2R. Another mechanism of immunosuppression involving tumor necrosis factor/interferon γ-dependent nitric oxide production by inducible nitric oxide synthase was also described. Moreover, other studies showed that nitric oxide was produced by CD11b⁺ Gr-1⁺ MDSCs in the spleen, and later iNOS and arginase 1 expressed in CD11b⁺Ly6C⁺Ly6G^lo monocytic MDSC were found in spleen and heart of T. cruzi infected mice that suppressed T cell proliferation. Uncontrolled expansion of monocytic MDSCs leads to L-arginine depletion which hinders nitric oxide production leading to death. Supplement of L-arginine partially reverts L-arginine depletion and survival, suggesting that L-arginine could be administered along with anti-parasitical drugs. On the other hand, pharmacological inhibition of MDSCs leads to death in mice, suggesting that some expansion of MDSCs is needed for an efficient immune response. The role of signaling molecules mediating immune suppression as reactive oxygen species, reactive nitrogen species, as well as prostaglandin E2, characteristics of MDSCs, in T. cruzi infection is not fully understood. We review and discuss the role of these reactive species mediators produced by MDSCs. Finally, we discuss the latest results that link the SLAMF1 immune receptor with reactive oxygen species. Interaction of the parasite with the SLAMF1 modulates parasite virulence through myeloid cell infectivity and reactive oxygen species production. We discuss the possible strategies for targeting MDSCs and SLAMF1 receptor in acute Trypanosoma cruzi infection in mice, to evaluate a possible translational application in human acute infections.

L-arginine supplementation increases cardiac collagenogenesis in mice chronically infected with Berenice-78 Trypanosoma cruzi strain

Chagas disease, caused by Trypanosoma cruzi, is a major neglected tropical disease that occurs mainly as chronic infection and systemic infection. Currently, there is no suitable and effective drug to treat this parasitic disease. Administration of nutrients with immunomodulatory properties, such as arginine and nitric oxide radicals, may be helpful as antiparasitic therapy. In this study, we evaluated the effects of arginine supplementation during the acute phase of infection under the development of chronic Chagas' heart disease in Swiss mice inoculated with the Berenice-78 strain of T. cruzi. The effectiveness of arginine was determined by daily detection of the parasite in the blood and long-term serum levels of nitric oxide and tumor necrosis factor-alpha, in addition to evaluation of heart tissue damage. Arginine could flatten parasitemia and prevent elevation of tumor necrosis factor-alpha in T. cruzi-infected mice. Regarding chronic inflammatory myocardial derangements, similar findings were verified among T. cruzi-infected groups. Arginine promoted collagenogenesis in the heart muscle tissue of T. cruzi-infected arginine-supplemented group. These data show the paradoxical benefits of arginine in improving the outcome of Chagas chronic cardiomyopathy.

Prenatal Amino Acid Supplementation to Improve Fetal Growth: A Systematic Review and Meta-Analysis

Aberrant fetal growth remains a leading cause of perinatal morbidity and mortality and is associated with a risk of developing non-communicable diseases later in life. We performed a systematic review and meta-analysis combining human and animal studies to assess whether prenatal amino acid (AA) supplementation could be a promising approach to promote healthy fetal growth. PubMed, Embase, and Cochrane libraries were searched to identify studies orally supplementing the following AA groups during gestation: (1) arginine family, (2) branched chain (BCAA), and (3) methyl donors. The primary outcome was fetal/birth weight. Twenty-two human and 89 animal studies were included in the systematic review. The arginine family and, especially, arginine itself were studied the most. Our meta-analysis showed beneficial effects of arginine and (N-Carbamyl) glutamate (NCG) but not aspartic acid and citrulline on fetal/birth weight. However, no effects were reported when an isonitrogenous control diet was included. BCAA and methyl donor supplementation did not affect fetal/birth weight. Arginine family supplementation, in particular arginine and NCG, improves fetal growth in complicated pregnancies. BCAA and methyl donor supplementation do not seem to be as promising in targeting fetal growth. Well-controlled research in complicated pregnancies is needed before ruling out AA supplements or preferring arginine above other AAs.

Effects of ghrelin supplementation on the acute phase of Chagas disease in rats

Background

Trypanosoma cruzi is the causative agent of Chagas disease, which is endemic to subtropical and tropical Americas. The disease treatment remains partially ineffective, involving therapies directed to the parasite as well as palliative strategies for the clinical manifestations. Therefore, novel candidates for disease control are necessary. Additionally, strategies based on parasite inhibition via specific targets and application of compounds which improve the immune response against the disease is welcomed. Ghrelin is a peptide hormone pointed as a substance with important cardioprotective, vasodilatory, anti-apoptotic, anti-oxidative and immune modulatory functions. The aims of this study were to evaluate the immunomodulatory effects of ghrelin in male Wistar rats infected with the Y strain of T. cruzi.

Methods

In order to delineate an immune response against T. cruzi mediated by ghrelin, we evaluated the following parameters: quantification of blood and cardiac parasites; analysis of cell markers (CD3⁺, CD8⁺, NK, NKT, CD45RA⁺, macrophage and RT1B⁺); nitric oxide (NO) production; lymphoproliferation assays; splenocyte apoptosis; and INF-γ, IL-12 and IL-6 quantification in sera.

Results

The animals infected with T. cruzi and supplemented with ghrelin demonstrated an upregulated pattern in macrophage and NO production, whereas an anti-inflammatory response was observed in T cells and cytokines. The low response against T. cruzi mediated by T cells probably contributed to a higher colonization of the cardiac tissue, when compared to infected groups. On the other side, the peptide decreased the inflammatory infiltration in cardiac tissue infected with T. cruzi.

Conclusions

Ghrelin demonstrated a dual function in animals infected with T. cruzi. Further studies, especially related to the decrease of cardiac tissue inflammation, are needed in order to determine the advantages of ghrelin supplementation in Chagas disease, mostly for populations from endemic areas.

Regulatory Lymphoid and Myeloid Cells Determine the Cardiac Immunopathogenesis of Trypanosoma cruzi Infection

Chagas disease is a multisystemic disorder caused by the protozoan parasite Trypanosoma cruzi, which affects ~8 million people in Latin America, killing 7,000 people annually. Chagas disease is one of the main causes of death in the endemic area and the leading cause of infectious myocarditis in the world. T. cruzi infection induces two phases, acute and chronic, where the infection is initially asymptomatic and the majority of patients will remain clinically indeterminate for life. However, over a period of 10–30 years, ~30% of infected individuals will develop irreversible, potentially fatal cardiac syndromes (chronic chagasic cardiomyopathy [CCC]), and/or dilatation of the gastro-intestinal tract (megacolon or megaesophagus). Myocarditis is the most serious and frequent manifestation of chronic Chagas heart disease and appears in about 30% of infected individuals several years after infection occurs. Myocarditis is characterized by a mononuclear cell infiltrate that includes different types of myeloid and lymphoid cells and it can occur also in the acute phase. T. cruzi infects and replicates in macrophages and cardiomyocytes as well as in other nucleated cells. The pathogenesis of the chronic phase is thought to be dependent on an immune-inflammatory reaction to a low-grade replicative infection. It is known that cytokines produced by type 1 helper CD4+ T cells are able to control infection. However, the role that infiltrating lymphoid and myeloid cells may play in experimental and natural Chagas disease pathogenesis has not been completely elucidated, and several reports indicate that it depends on the mouse genetic background and parasite strain and/or inoculum. Here, we review the role that T cell CD4+ subsets, myeloid subclasses including myeloid-derived suppressor cells may play in the immunopathogenesis of Chagas disease with special focus on myocarditis, by comparing results obtained with different experimental animal models.

L-arginine supplementation reduces mortality and improves disease outcome in mice infected with Trypanosoma cruzi

Chagas disease caused by Trypanosoma cruzi is a neglected disease that affects about 7 million people in Latin America, recently emerging on other continents due to migration. As infection in mice is characterized by depletion of plasma L-arginine, the effect on infection outcome was tested in mice with or without L-arginine supplementation and treatment with 1400W, a specific inhibitor of inducible nitric oxide synthase (iNOS). We found that levels of L-arginine and citrulline were reduced in the heart and plasma of infected mice, whereas levels of asymmetric dimethylarginine, an endogenous iNOS inhibitor, were higher. Moreover, L-arginine supplementation decreased parasitemia and heart parasite burden, improving clinical score and survival. Nitric oxide production in heart tissue and plasma was increased by L-arginine supplementation, while pharmacological inhibition of iNOS yielded an increase in parasitemia and worse clinical score. Interestingly, electrocardiograms improved in mice supplemented with L-arginine, suggesting that it modulates infection and heart function and is thus a potential biomarker of pathology. More importantly, L-arginine may be useful for treating T. cruzi infection, either alone or in combination with other antiparasitic drugs.

Trypanosoma cruzi is the causative agent of the neglected Chagas disease in humans. During infection in mice, depletion of plasma L-arginine is correlated with mortality. L-arginine is a semi-essential amino acid needed for cell proliferation, and is the substrate of arginase 1 (Arg-1) and inducible nitric oxide synthase (iNOS), which is involved in the immune response against infections. Observed L-arginine depletion is likely caused by increased Arg-1 activity, but the effect on immune response are still unknown. Our hypothesis is that L-arginine depletion may block nitric oxide (NO) production by iNOS, which is needed for parasite killing. To test this hypothesis, mice were supplemented with and without L-arginine, and the differential effect of treatment with an iNOS inhibitor was determined. L-arginine supplement was beneficial to the mice, lowering mortality and improving disease outcome and heart function. The beneficial effect was associated with increased levels of NO, thus low levels of L-arginine and NO are considered candidate markers of pathology. Finally, as L-arginine is a common dietary supplement, it may be useful for treatment of Chagas patients, either alone or in combination with antiparasitic drugs.

Application of the amniotic fluid metabolome to the study of fetal malformations, using Down syndrome as a specific model

Although monitoring and diagnosis of fetal diseases in utero remains a challenge, metabolomics may provide an additional tool to study the etiology and pathophysiology of fetal diseases at a functional level. In order to explore specific markers of fetal disease, metabolites were analyzed in two separate sets of experiments using amniotic fluid from fetuses with Down syndrome (DS) as a model. Both sets included 10–15 pairs of controls and cases, and amniotic fluid samples were processed separately; metabolomic fingerprinting was then conducted using UPLC-MS. Significantly altered metabolites involved in respective metabolic pathways were compared in the two experimental sets. In addition, significantly altered metabolic pathways were further compared with the genomic characters of the DS fetuses. The data suggested that metabolic profiles varied across different experiments, however alterations in the 4 metabolic pathways of the porphyrin metabolism, bile acid metabolism, hormone metabolism and amino acid metabolism, were validated for the two experimental sets. Significant changes in metabolites of coproporphyrin III, glycocholic acid, taurochenodeoxycholate, taurocholate, hydrocortisone, pregnenolone sulfate, L-histidine, L-arginine, L-glutamate and L-glutamine were further confirmed. Analysis of these metabolic alterations was linked to aberrant gene expression at chromosome 21 of the DS fetus. The decrease in coproporphyrin III in the DS fetus may portend abnormal erythropoiesis, and unbalanced glutamine-glutamate concentration was observed to be closely associated with abnormal brain development in the DS fetus. Therefore, alterations in amniotic fluid metabolites may provide important clues to understanding the etiology of fetal disease and help to develop diagnostic testing for clinical applications.

Expression of arginase I and inducible nitric oxide synthase in the peripheral blood and lymph nodes of HIV‑positive patients

Arginase I (Arg I) and inducible nitric oxide synthase (iNOS) are important in regulating immune functions through their metabolites. Previous studies have revealed that the expression of Arg I is increased and the expression of iNOS is reduced in the serum and peripheral blood mononuclear cells of human immunodeficiency virus (HIV)-infected patients. As one of the most important immune organs and HIV replication sites, whether similar changes are present in the lymph nodes following HIV infection remains to be elucidated. To investigate this, the present study collected lymph node and blood specimens from 52 HIV-infected patients to measure the expression levels of Arg I and iNOS by immunohistochemistry and fluoresence-based flow cytometry. Compared with control subjects without HIV infection, the patients with HIV had significantly higher expression levels of Arg I in the lymph nodes and higher frequencies of Arg I⁺ CD4⁺ T cells and CD8⁺ T cells in the blood and lymph nodes, and these results were contrary the those of iNOS in the corresponding compartments. The expression levels of Arg I in the lymph nodes and blood were negatively associated with peripheral CD4⁺ T cell count and positively associated with viral load. However, the expression levels of iNOS in the lymph nodes and blood were positively associated with peripheral CD4⁺ T cell count and negatively associated with viral load. These results showed that alterations in the expression levels of Arg I and iNOS in the peripheral T cells and peripheral nodes of HIV infected patients are associated with disease progression in these patients. These results indicate a potential to therapeutic strategy for delaying disease progression through regulating and manipulating the expression levels of Arg I and iNOS in patients infected with HIV.