The Aryl Hydrocarbon Receptor Modulates Production of Cytokines and Reactive Oxygen Species and Development of Myocarditis during Trypanosoma cruzi Infection

The role of the AHR in host-pathogen interactions

Host-microorganism encounters take place in many different ways and with different types of outcomes. Three major types of microorganisms need to be distinguished: (1) pathogens that cause harm to the host and must be controlled; (2) environmental microorganisms that can be ignored but must be controlled at higher abundance; and (3) symbiotic microbiota that require support by the host. Recent evidence indicates that the aryl hydrocarbon receptor (AHR) senses and initiates signalling and gene expression in response to a plethora of microorganisms and infectious conditions. It was originally identified as a receptor that binds xenobiotics. However, it was subsequently found to have a critical role in numerous biological processes, including immunity and inflammation and was recently classified as a pattern recognition receptor. Here we review the role of the AHR in host-pathogen interactions, focusing on AHR sensing of different microbial classes, the ligands involved, responses elicited and disease outcomes. Moreover, we explore the therapeutic potential of targeting the AHR in the context of infection.

Therapeutic Potential of Nutritional Aryl Hydrocarbon Receptor Ligands in Gut-Related Inflammation and Diseases

A solid scientific foundation is required to build the concept of personalized nutrition developed to promote health and a vision of disease prevention. Growing evidence indicates that nutrition can modulate the immune system through metabolites, which are either generated via microbiota metabolism or host digestion. The aryl hydrocarbon receptor (AhR) plays a crucial role in regulating immune responses, particularly in the gut, and has emerged as a key modulator of gut-mediated inflammation and related diseases. AhR is a ligand-activated transcription factor that responds to environmental, dietary, and microbial-derived signals, influencing immune balance and maintaining intestinal homeostasis. Nutritional AhR ligands play a significant role in modulating intestinal immunity and the function of mucosal immune cells, thereby exerting clinical effects on colitis and innate immunity. Additionally, they have the capacity to orchestrate autophagy, phagocytic cell function, and intestinal epithelial tight junctions. Therapeutic strategies aimed at enhancing AhR activity, restoring gut integrity, and optimizing immune responses hold promise as avenues for future research and potential treatments for critically ill patients.

Kynurenine-AhR reduces T-cell infiltration and induces a delayed T-cell immune response by suppressing the STAT1-CXCL9/CXCL10 axis in tuberculosis

Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), is a critical global health issue that is complicated by the ability of the pathogen to delay the host's T-cell immune response. This delay in T-cell recruitment to the site of infection is a pivotal survival strategy for Mtb, allowing it to establish a persistent chronic infection. To investigate the underlying mechanisms, this study focused on Mtb's exploitation of host tryptophan metabolism. Mtb upregulates indoleamine 2,3-dioxygenase 1 (IDO1) in inflammatory macrophages, thereby increasing kynurenine (Kyn) production. Kyn then activates the aryl hydrocarbon receptor (AhR), leading to the upregulation of suppressor of cytokine signaling 3 and subsequent inhibition of the JAK-STAT1 signaling pathway. This results in reduced secretion of the chemokines CXCL9 and CXCL10, which are crucial for T-cell recruitment to the lungs. Supported by in vivo mouse models, our findings reveal that disrupting this pathway through AhR knockout significantly enhances T-cell infiltration and activity, thereby undermining Mtb-induced immunosuppression. In contrast, additional Kyn injection obviously inhibited T-cell infiltration and activity. These results highlight potential therapeutic targets of AhR and IDO1, offering new avenues for enhancing the host immune response against tuberculosis and guiding future vaccine development efforts.

Kynurenic Acid/AhR Signaling at the Junction of Inflammation and Cardiovascular Diseases

Persistent systemic chronic inflammatory conditions are linked with many pathologies, including cardiovascular diseases (CVDs), a leading cause of death across the globe. Among various risk factors, one of the new possible contributors to CVDs is the metabolism of essential amino acid tryptophan. Proinflammatory signals promote tryptophan metabolism via the kynurenine (KYN) pathway (KP), thereby resulting in the biosynthesis of several immunomodulatory metabolites whose biological effects are associated with the development of symptoms and progression of various inflammatory diseases. Some participants in the KP are agonists of aryl hydrocarbon receptor (AhR), a central player in a signaling pathway that, along with a regulatory influence on the metabolism of environmental xenobiotics, performs a key immunomodulatory function by triggering various cellular mechanisms with the participation of endogenous ligands to alleviate inflammation. An AhR ligand with moderate affinity is the central metabolite of the KP: KYN; one of the subsequent metabolites of KYN-kynurenic acid (KYNA)-is a more potent ligand of AhR. Understanding the role of AhR pathway-related metabolites of the KP that regulate inflammatory factors in cells of the cardiovascular system is interesting and important for achieving effective treatment of CVDs. The purpose of this review was to summarize the results of studies about the participation of the KP metabolite-KYNA-and of the AhR signaling pathway in the regulation of inflammation in pathological conditions of the heart and blood vessels and about the possible interaction of KYNA with AhR signaling in some CVDs.

Role of aryl hydrocarbon receptors in infection and inflammation

The aryl hydrocarbon receptor (AhR) is a transcription factor that is activated by various ligands, including pollutants, microorganisms, and metabolic substances. It is expressed extensively in pulmonary and intestinal epithelial cells, where it contributes to barrier defense. The expression of AhR is pivotal in regulating the inflammatory response to microorganisms. However, dysregulated AhR expression can result in endocrine disorders, leading to immunotoxicity and potentially promoting the development of carcinoma. This review focuses on the crucial role of the AhR in facilitating and limiting the proliferation of pathogens, specifically in relation to the host cell type and the species of etiological agents involved in microbial pathogen infections. The activation of AhR is enhanced through the IDO1-AhR-IDO1 positive feedback loop, which is manipulated by viruses. AhR primarily promotes the infection of SARS-CoV-2 by inducing the expression of angiotensin-converting enzyme 2 (ACE2) and the secretion of pro-inflammatory cytokines. AhR also plays a significant role in regulating various types of T-cells, including CD4+ T cells and CD8+ T cells, in the context of pulmonary infections. The AhR pathway plays a crucial role in regulating immune responses within the respiratory and intestinal barriers when they are invaded by viruses, bacteria, parasites, and fungi. Additionally, we propose that targeting the agonist and antagonist of AhR signaling pathways could serve as a promising therapeutic approach for combating pathogen infections, especially in light of the growing prevalence of drug resistance to multiple antibiotics.

Indoleamine 2,3-Dioxygenase 1 Deletion-Mediated Kynurenine Insufficiency Inhibits Pathological Cardiac Hypertrophy

BACKGROUND

Aberrant amino acid metabolism is implicated in cardiac hypertrophy, while the involvement of tryptophan metabolism in pathological cardiac hypertrophy remains elusive. Herein, we aimed to investigate the effect and potential mechanism of IDO1 (indoleamine 2,3-dioxygenase) and its metabolite kynurenine (Kyn) on pathological cardiac hypertrophy.

METHODS

Transverse aortic constriction was performed to induce cardiac hypertrophy in IDO1-knockout (KO) mice and AAV9-cTNT-shIDO1 mice. Liquid chromatography-mass spectrometry was used to detect the metabolites of tryptophan-Kyn pathway. Chromatin immunoprecipitation assay and dual luciferase assay were used to validate the binding of protein and DNA.

RESULTS

IDO1 expression was upregulated in both human and murine hypertrophic myocardium, alongside with increased IDO1 activity and Kyn content in transverse aortic constriction-induced mice's hearts using liquid chromatography-mass spectrometry analysis. Myocardial remodeling and heart function were significantly improved in transverse aortic constriction-induced IDO1-KO mice, but were greatly exacerbated with subcutaneous Kyn administration. IDO1 inhibition or Kyn addition confirmed the alleviation or aggravation of hypertrophy in cardiomyocyte treated with isoprenaline, respectively. Mechanistically, IDO1 and metabolite Kyn contributed to pathological hypertrophy via the AhR (aryl hydrocarbon receptor)-GATA4 (GATA binding protein 4) axis.

CONCLUSIONS

This study demonstrated that IDO1 deficiency and consequent Kyn insufficiency can protect against pathological cardiac hypertrophy by decreasing GATA4 expression in an AhR-dependent manner.

Modified Linggui Zhugan Decoction protects against ventricular remodeling through ameliorating mitochondrial damage in post-myocardial infarction rats

Introduction

Modified Linggui Zhugan Decoction (MLZD) is a Traditional Chinese Medicine prescription developed from Linggui Zhugan Decoction (LZD) that has been used for the clinical treatment of ischemic cardiovascular diseases. However, the cardioprotective mechanism of MLZD against post-myocardial infarction (MI) ventricular remodeling remains unclear.

Methods

We explored the effects of MLZD on ventricular remodeling and their underlying mechanisms, respectively, in SD rats with MI models and in H9c2 cardiomyocytes with oxygen-glucose deprivation (OGD) models. The cardiac structure and function of rats were measured by echocardiography, HE staining, and Masson staining. Apoptosis, inflammation, mitochondrial structure and function, and sirtuin 3 (SIRT3) expression were additionally examined.

Results

MLZD treatment significantly ameliorated cardiac structure and function, and thus reversed ventricular remodeling, compared with the control. Further research showed that MLZD ameliorated mitochondrial structural disruption, protected against mitochondrial dynamics disorder, restored impaired mitochondrial function, inhibited inflammation, and thus inhibited apoptosis. Moreover, the decreased expression level of SIRT3 was enhanced after MLZD treatment. The protective effects of MLZD on SIRT3 and mitochondria, nevertheless, were blocked by 3-TYP, a selective inhibitor of SIRT3.

Discussion

These findings together revealed that MLZD could improve the ventricular remodeling of MI rats by ameliorating mitochondrial damage and its associated apoptosis, which might exert protective effects by targeting SIRT3.

Platelets, Macrophages, and Thromboinflammation in Chagas Disease

Chagas disease (CD) is a major health problem in the Americas and an emerging health problem in Europe and other nonendemic countries. Several studies have documented persistence of the protozoan parasite Trypanosoma cruzi, and oxidative and inflammatory stress are major pathogenic factor. Mural and cardiac thrombi, cardiac arrhythmias, and cardiomyopathy are major clinical features of CD. During T. cruzi infection, parasite-released factors induce endothelial dysfunction along with platelet (PLT) and immune-cell activation. PLTs have a fundamental role in maintaining hemostasis and preventing bleeding after vascular injury. Excessive activation of PLTs and coagulation cascade can result in thrombosis and thromboembolic events, which are recognized to occur in seropositive individuals in early stages of CD when clinically symptomatic heart disease is not apparent. Several host and parasite factors have been identified to signal hypercoagulability and increase the risk of ischemic stroke in early phases of CD. Further, PLT interaction with immune cells and their role in host defense against pathogens and inflammatory processes have only recently been recognized and evolving. In the context of parasitic diseases, PLTs function in directly responding to T. cruzi infection, and PLT interactions with immune cells in shaping the proinflammatory or immunoregulatory function of monocytes, macrophages, and neutrophils remains elusive. How T. cruzi infection alters systemic microenvironment conditions to influence PLT and immune-cell interactions is not understood. In this review, we discuss the current literature, and extrapolate the mechanistic situations to explain how PLT and innate immune cell (especially monocytes and macrophages) interactions might be sustaining hypercoagulability and thromboinflammation in chronic CD.

Melatonin regulates antioxidant defense and inflammatory response by activating Nrf2-dependent mechanisms and inhibiting NFkappaB expression in middle-aged T. cruzi infected rats

Oxidative stress with higher levels of leptin and inflammatory response are key processes related to pathogenesis of both T. cruzi infection and aging. Nuclear factor erythroid 2-related factor 2 (Nrf2) controls the expression of several genes implicated in the oxidative stress response in many pathological conditions. Melatonin is a pleiotropic hormone with_, antioxidant, anti-inflammatory and anti-aging actions. Then, we hypothesized that Nrf2 response is impaired during the acute T. cruzi (9 days) infection and that melatonin rescues Nrf2 responses. Young (5 weeks-old) and middle-aged (18 months-old) male Wistar rats were infected with T. cruzi. Nrf2 translocation and markers of inflammation and oxidative stress were analyzed in blood and spleen. Increased apoptosis levels and oxidative stress indicators were observed in the rat spleen during T. cruzi infection. These responses were accompanied by decreased Nrf2 expression and increased expression of nuclear factor kappa B (NFκB). Melatonin (5 mg/kg/day; p.o. gavage) attenuated the superoxide anion (O₂^-) and hydrogen peroxide (H₂O₂) production induced by T. cruzi infection. Increased expressions of catalase and superoxide dismutase (SOD) were detected in the spleen of melatonin-treated rats infected with T. cruzi. Melatonin treatment inhibited the spleen NF-κB activation and downregulates the levels of circulating interleukin (IL)-4, IL-10 and tumor necrosis factor (TNF)-α in T. cruzi middle-aged infected rats. Increased levels of the chemokine CXCL1 in middle-aged control rats was observed, confirming that aging alters the production of this chemokine. In T. cruzi infected young animals, CXCL1 was up-regulated when compared to non-infected young ones. For young or middle-aged animals, melatonin treatment had no significant effect on CXCL1 levels. Our findings demonstrate an important role for Nrf2/NF-kB regulation as a possible mechanism by which melatonin attenuates oxidative stress, and provide new insights for further studies of this indoleamine as a therapeutic co-adjuvant agent against T. cruzi infection.

Reshaping the tumor microenvironment with oncolytic viruses, positive regulation of the immune synapse, and blockade of the immunosuppressive oncometabolic circuitry

BACKGROUND

Oncolytic viruses are considered part of immunotherapy and have shown promise in preclinical experiments and clinical trials. Results from these studies have suggested that tumor microenvironment remodeling is required to achieve an effective response in solid tumors. Here, we assess the extent to which targeting specific mechanisms underlying the immunosuppressive tumor microenvironment optimizes viroimmunotherapy.

METHODS

We used RNA-seq analyses to analyze the transcriptome, and validated the results using Q-PCR, flow cytometry, and immunofluorescence. Viral activity was analyzed by replication assays and viral titration. Kyn and Trp metabolite levels were quantified using liquid chromatography-mass spectrometry. Aryl hydrocarbon receptor (AhR) activation was analyzed by examination of promoter activity. Therapeutic efficacy was assessed by tumor histopathology and survival in syngeneic murine models of gliomas, including Indoleamine 2,3-dioxygenase (IDO)-/- mice. Flow cytometry was used for immunophenotyping and quantification of cell populations. Immune activation was examined in co-cultures of immune and cancer cells. T-cell depletion was used to identify the role played by specific cell populations. Rechallenge experiments were performed to identify the development of anti-tumor memory.

RESULTS

Bulk RNA-seq analyses showed the activation of the immunosuppressive IDO-kynurenine-AhR circuitry in response to Delta-24-RGDOX infection of tumors. To overcome the effect of this pivotal pathway, we combined Delta-24-RGDOX with clinically relevant IDO inhibitors. The combination therapy increased the frequency of CD8+ T cells and decreased the rate of myeloid-derived suppressor cell and immunosupressive Treg tumor populations in animal models of solid tumors. Functional studies demonstrated that IDO-blockade-dependent activation of immune cells against tumor antigens could be reversed by the oncometabolite kynurenine. The concurrent targeting of the effectors and suppressors of the tumor immune landscape significantly prolonged the survival in animal models of orthotopic gliomas.

CONCLUSIONS

Our data identified for the first time the in vivo role of IDO-dependent immunosuppressive pathways in the resistance of solid tumors to oncolytic adenoviruses. Specifically, the IDO-Kyn-AhR activity was responsible for the resurface of local immunosuppression and resistance to therapy, which was ablated through IDO inhibition. Our data indicate that combined molecular and immune therapy may improve outcomes in human gliomas and other cancers treated with virotherapy.

Human Adult Microbiota in a Static Colon Model: AhR Transcriptional Activity at the Crossroads of Host–Microbe Interaction

Functional symbiotic intestinal microbiota regulates immune defense and the metabolic processing of xenobiotics in the host. The aryl hydrocarbon receptor (AhR) is one of the transcription factors mediating host–microbe interaction. An in vitro static simulation of the human colon was used in this work to analyze the evolution of bacterial populations, the microbial metabolic output, and the potential induction of AhR transcriptional activity in healthy gut ecosystems. Fifteen target taxa were explored by qPCR, and the metabolic content was chromatographically profiled using SPME-GC-MS and UPLC-FLD to quantify short-chain fatty acids (SCFA) and biogenic amines, respectively. Over 72 h of fermentation, the microbiota and most produced metabolites remained stable. Fermentation supernatant induced AhR transcription in two of the three reporter gene cell lines (T47D, HepG2, HT29) evaluated. Mammary and intestinal cells were more sensitive to microbiota metabolic production, which showed greater AhR agonism than the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) used as a positive control. Some of the SCFA and biogenic amines identified could crucially contribute to the potent AhR induction of the fermentation products. As a fundamental pathway mediating human intestinal homeostasis and as a sensor for several microbial metabolites, AhR activation might be a useful endpoint to include in studies of the gut microbiota.

Qiliqiangxin Modulates the Gut Microbiota and NLRP3 Inflammasome to Protect Against Ventricular Remodeling in Heart Failure

Aims: Pathological left ventricular (LV) remodeling induced by multiple causes often triggers fatal cardiac dysfunction, heart failure (HF), and even cardiac death. This study is aimed to investigate whether qiliqiangxin (QL) could improve LV remodeling and protect against HF via modulating gut microbiota and inhibiting nod-like receptor pyrin domain 3 (NLRP3) inflammasome activation.

Methods: Rats were respectively treated with QL (100 mg/kg/day) or valsartan (1.6 mg/kg/day) by oral gavage after transverse aortic constriction or sham surgery for 13 weeks. Cardiac functions and myocardial fibrosis were assessed. In addition, gut microbial composition was assessed by 16S rDNA sequencing. Furthermore, rats’ hearts were harvested for histopathological and molecular analyses including immunohistochemistry, immunofluorescence, terminal-deoxynucleotidyl transferase-mediated 2’-deoxyuridine 5’-triphosphated nick end labeling, and Western blot.

Key findings: QL treatment preserved cardiac functions including LV ejection fractions and fractional shortening and markedly improved the LV remodeling. Moreover, HF was related to the gut microbial community reorganization like a reduction in Lactobacillus, while QL reversed it. Additionally, the protein expression levels like IL-1β, TNF-α, NF-κB, and NLRP3 were decreased in the QL treatment group compared to the model one.

Conclusion: QL ameliorates ventricular remodeling to some extent in rats with HF by modulating the gut microbiota and NLRP3 inflammasome, which indicates the potential therapeutic effects of QL on those who suffer from HF.

Indoxyl Sulfate Activates NLRP3 Inflammasome to Induce Cardiac Contractile Dysfunction Accompanied by Myocardial Fibrosis and Hypertrophy

In patients with chronic kidney diseases (CKD), high serum indoxyl sulfate (IS) levels correlate with cardiac fibrosis and hypertrophy and thus a critical risk factor for heart failure. The aim of this study was to determine the effects of IS on cardiac function and inflammasome pathway in a rat model of CKD. We assessed the physiological and pathological changes and measured biomarkers of fibrosis and hypertrophy in the hearts of Dahl salt-sensitive (DS), DS hypertensive (DH), and DH IS-treated rats (DH + IS). Low left ventricular (LV) ejection fraction, LV dilatation, and advanced myocardial fibrosis and hypertrophy were observed in DH + IS, which resemble changes found in uremic cardiomyopathy. These changes were independent of renal function and blood pressure. RT-PCR and western blotting analysis showed upregulation of fibrosis and hypertrophy-related biomarkers and adhesion molecules in the hearts of DH + IS rats. IS activated aryl hydrocarbon receptor (AHR) pathway, nuclear factor kappa B p65 (NF-κB p65), and inflammasome in the myocardium of DH + IS rat. Moreover, IS upregulated the expression of critical NLRP3 inflammasome components (NLRP3, ASC, and procaspase-1) and increased production of IL-1β and IL-18. Finally, IS upregulated various inflammatory cytokines, such as MCP-1, TNF-α, IL-6, and TGFβ1, in the myocardium. Our results suggested that IS induced cardiac fibrosis and hypertrophy and impaired LV function through activation of cardiac NLRP3 inflammasome via the AHR/NF-κB pathway.

SOCS2 expression in hematopoietic and non-hematopoietic cells during Trypanosoma cruzi infection: Correlation with immune response and cardiac dysfunction

Chagas disease has a complex pathogenesis wherein the host immune response is essential for controlling its development. Suppressor of cytokine signaling(SOCS)2 is a crucial protein that regulates cytokine production. In this study, SOCS2 deficiency resulted in an initial imbalance of IL12- and IL-10-producing neutrophils and dendritic cells (DCs), which caused a long-lasting impact reducing inflammatory neutrophils and DCs, and tolerogenic DCs at the peak of acute disease. A reduced number of inflammatory and pro-resolving macrophages, and IL17A-producing CD4⁺ T cells, and increased lymphocyte apoptosis was found in SOCS2-deficient mice. Electrocardiogram analysis of chimeric mice showed that WT mice that received SOCS2 KO bone marrow transplantation presented increased heart dysfunction. Taken together, the results demonstrated that SOCS2 is a crucial regulator of the immune response during Trypanosoma cruzi infection, and suggest that a SOCS2 genetic polymorphism, or failure of its expression, may increase the susceptibility of cardiomyopathy development in Chagasic patients.

Role of formyl peptide receptor 2 (FPR2) in modulating immune response and heart inflammation in an experimental model of acute and chronic Chagas disease

Chagas disease is an important disease of the heart. Lipoxins have important regulatory functions in host immune response (IR). Herein, we examined whether the receptor for lipoxin A4, the formyl peptide receptor (FPR) 2, had an effect on Trypanosoma cruzi infection. In vitro, FPR2 deficiency or inhibition improved the activity of macrophages against T. cruzi. In vivo, during the acute phase, the absence of FPR2 reduced parasitemia and increased type 2 macrophages, type 2 neutrophils, and IL-10-producing dendritic cells. Moreover, the acquired IR was characterized by greater proportions of Th1/Th2/Treg, and IFNγ-producing CD8⁺T cells, and reductions in Th17 and IL-17-producing CD8⁺T cells. However, during the chronic phase, FPR2 deficient mice presented and increased inflammatory profile regarding innate and acquired IR cells (Th1/IFN-γ-producing CD8⁺T cells). Notably, FPR2 deficiency resulted in increased myocarditis and impaired heart function. Collectively, our data suggested that FPR2 is important for the orchestration of IR and prevention of severe T. cruzi-induced disease.

4-Chlorophenylthioacetone-derived thiosemicarbazones as potent antitrypanosomal drug candidates: Investigations on the mode of action

Chagas disease (ChD), caused by Trypanosoma cruzi, remains a challenge for the medical and scientific fields due to the inefficiency of the therapeutic approaches available for its treatment. Thiosemicarbazones and hydrazones present a wide spectrum of bioactivities and are considered a platform for the design of new anti-T. cruzi drug candidates. Herein, the potential antichagasic activities of [(E)-2-(1-(4-chlorophenylthio)propan-2-ylidene)-hydrazinecarbothioamides] (C1, C3), [(E)-N'-(1-((4-chlorophenyl)thio)propan-2-ylidene)benzohydrazide] (C2), [(E)-2-(1-(4-, and [(E)-2-(1-((4-chlorophenyl)thio)propan-2-ylidene)hydrazinecarboxamide] (C4) were investigated. Macrophages (MOs) from C57BL/6 mice stimulated with C1 and C3, but not with C2 and C4, reduced amastigote replication and trypomastigote release, independent of nitric oxide (NO) and reactive oxygen species production and indoleamine 2,3-dioxygenase activity. C3, but not C1, reduced parasite uptake by MOs and potentiated TNF production. In cardiomyocytes, C3 reduced trypomastigote release independently of NO, TNF, and IL-6 production. C1 and C3 were non-toxic to the host cells. A reduction of parasite release was found during infection of MOs with trypomastigotes pre-incubated with C1 or C3 and MOs pre-stimulated with compounds before infection. Moreover, C1 and C3 acted directly on trypomastigotes, killing them faster than Benznidazole, and inhibited T. cruzi proliferation at various stages of its intracellular cycle. Mechanistically, C1 and C3 inhibit parasite duplication, and this process cannot be reversed by inhibiting the DNA damage response. In vivo, C1 and C3 attenuated parasitemia in T. cruzi-infected mice. Moreover, C3 loaded in a lipid nanocarrier system (nanoemulsion) maintained anti-T. cruzi activity in vivo. Collectively, these data suggest that C1 and C3 are candidates for the treatment of ChD and present activity in both the host and parasite cells.

Tityus serrulatus scorpion venom as a potential drug source for Chagas' disease: Trypanocidal and immunomodulatory activity

Current chemical therapies for Chagas Disease (CD) lack ability to clear Trypanosoma cruzi (Tc) parasites and cause severe side effects, making search for new strategies extremely necessary. We evaluated the action of Tityus serrulatus venom (TsV) components during Tc infection. TsV treatment increased nitric oxide and pro-inflammatory cytokine production by Tc-infected macrophages (MØ), decreased intracellular parasite replication and trypomastigotes release, also triggering ERK1/2, JNK1/2 and p38 activation. Ts7 demonstrated the highest anti-Tc activity, inducing high levels of TNF and IL-6 in infected MØ. TsV/Ts7 presented synergistic effect on p38 activation when incubated with Tc antigen. KPP-treatment of MØ also decreased trypomastigotes releasing, partially due to p38 activation. TsV/Ts7-pre-incubation of Tc demonstrated a direct effect on parasite decreasing MØ-trypomastigotes releasing. In vivo KPP-treatment of Tc-infected mice resulted in decreased parasitemia. Summarizing, this study opens perspectives for new bioactive molecules as CD-therapeutic treatment, demonstrating the TsV/Ts7/KPP-trypanocidal and immunomodulatory activity during Tc infection.

The aryl hydrocarbon receptor and the gut-brain axis

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor initially identified as the receptor for dioxin. Almost half a century after its discovery, AHR is now recognized as a receptor for multiple physiological ligands, with important roles in health and disease. In this review, we discuss the role of AHR in the gut-brain axis and its potential value as a therapeutic target for immune-mediated diseases.

Pulmonary paracoccidioidomycosis in AhR deficient hosts is severe and associated with defective Treg and Th22 responses

AhR is a ligand-activated transcription factor that plays an important role in the innate and adaptive immune responses. In infection models, it has been associated with host responses that promote or inhibit disease progression. In pulmonary paracoccidioidomycosis, a primary fungal infection endemic in Latin America, immune protection is mediated by Th1/Th17 cells and disease severity with predominant Th2/Th9/Treg responses. Because of its important role at epithelial barriers, we evaluate the role of AhR in the outcome of a pulmonary model of paracoccidioidomycosis. AhR^−/− mice show increased fungal burdens, enhanced tissue pathology and mortality. During the infection, AhR^−/− mice have more pulmonary myeloid cells with activated phenotype and reduced numbers expressing indoleamine 2,3 dioxygenase 1. AhR-deficient lungs have altered production of cytokines and reduced numbers of innate lymphoid cells (NK, ILC3 and NCR IL-22). The lungs of AhR^−/− mice showed increased presence Th17 cells concomitant with reduced numbers of Th1, Th22 and Foxp3⁺ Treg cells. Furthermore, treatment of infected WT mice with an AhR-specific antagonist (CH223191) reproduced the main findings obtained in AhR^−/− mice. Collectively our data demonstrate that in pulmonary paracoccidioidomycosis AhR controls fungal burden and excessive tissue inflammation and is a possible target for antifungal therapy.

Intestinal microbiota regulates tryptophan metabolism following oral infection with Toxoplasma gondii

INTRODUCTION

The intestinal microbiota plays an important role in modulating host immune responses. Oral Toxoplasma gondii infection can promote intestinal inflammation in certain mice strains. The IDO-AhR axis may control tryptophan (Trp) metabolism constituting an important immune regulatory mechanism in inflammatory settings.

AIMS

In the present study, we investigated the role of the intestinal microbiota on Trp metabolism during oral infection with T gondii.

METHODS AND RESULTS

Mice were treated with antibiotics for four weeks and then infected with T gondii by gavage. Histopathology and immune responses were evaluated 8 days after infection. We found that depletion of intestinal microbiota by antibiotics contributed to resistance against T gondii infection and led to reduced expression of AhR on dendritic and Treg cells. Mice depleted of Gram-negative bacteria presented higher levels of systemic Trp, downregulation of AhR expression and increased resistance to infection whereas depletion of Gram-positive bacteria did not affect susceptibility or expression of AhR on immune cells.

CONCLUSION

Our findings indicate that the intestinal microbiota can control Trp availability and provide a link between the AhR pathway and host-microbiota interaction in acute infection with T gondii.

RETRACTED: Bone marrow mesenchymal stem cells-derived exosomal microRNA-185 represses ventricular remolding of mice with myocardial infarction by inhibiting SOCS2

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Concern was raised about the integrity of the images in Figures 5B and 7C, which appear to contain suspected duplications, as detailed here: https://pubpeer.com/publications/C968FDCECE2069D7FF43B346B261ED and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. Numerous additional suspected image duplications were detected within Figures 5 and 6. Most of these image duplications involve either pasting portions of one image into another, or rotating/flipping the image. The journal requested the corresponding author comment on these concerns and provide the raw data. The authors did not respond to this request and therefore the Editor-in-Chief decided to retract the article.

Immunity and vaccine development efforts against Trypanosoma cruzi

Trypanosoma cruzi (T. cruzi) is the causative agent for Chagas disease (CD). There is a critical lack of methods for prevention of infection or treatment of acute infection and chronic disease. Studies in experimental models have suggested that the protective immunity against T. cruzi infection requires the elicitation of Th1 cytokines, lytic antibodies and the concerted activities of macrophages, T helper cells, and cytotoxic T lymphocytes (CTLs). In this review, we summarize the research efforts in vaccine development to date and the challenges faced in achieving an efficient prophylactic or therapeutic vaccine against human CD.

Benzo(a)pyrene facilitates dermatophagoides group 1 (Der f 1)-induced epithelial cytokine release through aryl hydrocarbon receptor in asthma

BACKGROUND

Environmental pollutants, which coexist with allergens, have been associated with the exacerbation of asthma. However, the underlying molecular mechanisms remain elusive. We sought to determine whether benzo(a)pyrene (BaP) co-exposure with dermatophagoides group 1 allergen (Der f 1) can potentiate Der f 1-induced asthma and its underlying mechanisms.

METHODS

The effect of BaP was investigated in Der f 1-induced mouse model of asthma, including airway hyper-responsiveness, allergic inflammation, and epithelial-derived cytokines. The impact of BaP on Der f 1-induced airway epithelial cell oxidative stress (ROS) and cytokine release was further analyzed. The role of aryl hydrocarbon receptor (AhR) signaling in BaP-promoted Der f 1-induced ROS, cytokine production, and allergic inflammation was also investigated.

RESULTS

Compared with Der f 1, BaP co-exposure with Der f 1 led to airway hyper-responsiveness and increased lung inflammation in mouse model of asthma. Increased expression of TSLP, IL-33, and IL-25 was also found in the airways of these mice. Moreover, BaP co-exposure with Der f 1 activated AhR signaling with increased expression of AhR and CYP1A1 and promoted airway epithelial ROS generation and TSLP and IL-33, but not IL-25, expression. Interestingly, AhR antagonist CH223191 or cells with AhR knockdown abrogated the increased expression of ROS, TSLP, and IL-33. Furthermore, ROS inhibitor N-acetyl-L-cysteine (NAC) also suppressed BaP co-exposure-induced expression of epithelial TSLP, IL-33, and IL-25. Finally, AhR antagonist CH223191 and NAC inhibited BaP co-exposure with Der f 1-induced lung inflammation.

CONCLUSIONS

Our findings suggest that BaP facilitates Der f 1-induced epithelial cytokine release through the AhR-ROS axis.

Nutritional Modulation of Immune and Central Nervous System Homeostasis: The Role of Diet in Development of Neuroinflammation and Neurological Disease

The gut-microbiome-brain axis is now recognized as an essential part in the regulation of systemic metabolism and homeostasis. Accumulating evidence has demonstrated that dietary patterns can influence the development of metabolic alterations and inflammation through the effects of nutrients on a multitude of variables, including microbiome composition, release of microbial products, gastrointestinal signaling molecules, and neurotransmitters. These signaling molecules are, in turn, implicated in the regulation of the immune system, either promoting or inhibiting the production of pro-inflammatory cytokines and the expansion of specific leukocyte subpopulations, such as Th17 and Treg cells, which are relevant in the development of neuroinflammatory and neurodegenerative conditions. Metabolic diseases, like obesity and type 2 diabetes mellitus, are related to inadequate dietary patterns and promote variations in the aforementioned signaling pathways in patients with these conditions, which have been linked to alterations in neurological functions and mental health. Thus, maintenance of adequate dietary patterns should be an essential component of any strategy aiming to prevent neurological pathologies derived from systemic metabolic alterations. The present review summarizes current knowledge on the role of nutrition in the modulation of the immune system and its impact in the development of neuroinflammation and neurological disease.

Role of Aryl Hydrocarbon Receptor (AhR) in the Regulation of Immunity and Immunopathology During Trypanosoma cruzi Infection

Resistance to Trypanosoma cruzi infection is dependent on a rapid induction of Th1-type and CD8+ T cell responses that should be promptly balanced to prevent immunopathology. T. cruzi-infected B6 mice are able to control parasite replication but show a limited expansion of Foxp3+regulatory T (Treg) cells that results in the accumulation of effector immune cells and the development of acute liver pathology. AhR is a ligand-activated transcription factor that promotes Treg cell development and suppression of pro-inflammatory cytokine production in dendritic cells, altering the course of adaptive immune response and the development of immunopathology. Here, we used different AhR-dependent activation strategies aiming to improve the Treg response, and B6 congenic mice carrying a mutant AhR variant with low affinity for its ligands (AhRd) to evaluate the role of AhR activation by natural ligands during experimental T. cruzi infection. The outcome of TCDD or 3-HK plus ITE treatments indicated that strong or weak AhR activation before or during T. cruzi infection was effective to regulate inflammation improving the Treg cell response and regularizing the ratio between CD4+ CD25- to Treg cells. However, AhR activation shifted the host-parasite balance to the parasite replication. Weak AhR activation resulted in Treg promotion while strong activation differentially modulated the susceptibility and resistance of cell death in activated T and Treg cells and the increase in TGF-β-producing Treg cells. Of note, T. cruzi-infected AhRd mice showed low levels of Treg cells associated with strong Th1-type response, low parasite burden and absence of liver pathology. These mice developed a Treg- and Tr1-independent mechanism of Th1 constriction showing increased levels of systemic IL-10 and IL-10-secreting CD4+ splenocytes. In addition, AhR activation induced by exogenous ligands had negative effects on the development of memory CD8+ T cell subsets while the lack/very weak activation in AhRd mice showed opposite results, suggesting that AhR ligation restricts the differentiation of memory CD8+T cell subsets. We propose a model in which a threshold of AhR activation exists and may explain how activation or inhibition of AhR-derived signals by infection/inflammation-induced ligands, therapeutic interventions or exposure to pollutants can modulate infections/diseases outcomes or vaccination efficacy.

The Role of the Aryl Hydrocarbon Receptor (AHR) in Immune and Inflammatory Diseases

The aryl hydrocarbon receptor (AHR) is a nuclear receptor that modulates the response to environmental stimuli. It was recognized historically for its role in toxicology but, in recent decades, it has been increasingly recognized as an important modulator of disease—especially for its role in modulating immune and inflammatory responses. AHR has been implicated in many diseases that are driven by immune/inflammatory processes, including major depressive disorder, multiple sclerosis, rheumatoid arthritis, asthma, and allergic responses, among others. The mechanisms by which AHR has been suggested to impact immune/inflammatory diseases include targeted gene expression and altered immune differentiation. It has been suggested that single nucleotide polymorphisms (SNPs) that are near AHR-regulated genes may contribute to AHR-dependent disease mechanisms/pathways. Further, we have found that SNPs that are outside of nuclear receptor binding sites (i.e., outside of AHR response elements (AHREs)) may contribute to AHR-dependent gene regulation in a SNP- and ligand-dependent manner. This review will discuss the evidence and mechanisms of AHR contributions to immune/inflammatory diseases and will consider the possibility that SNPs that are outside of AHR binding sites might contribute to AHR ligand-dependent inter-individual variation in disease pathophysiology and response to pharmacotherapeutics.

Regulation of the Immune Response by the Aryl Hydrocarbon Receptor

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is activated by small molecules provided by the diet, microorganisms, metabolism, and pollutants. AhR is expressed by a number of immune cells, and thus AhR signaling provides a molecular pathway that integrates the effects of the environment and metabolism on the immune response. Studies have shown that AhR signaling plays important roles in the immune system in health and disease. As its activity is regulated by small molecules, AhR also constitutes a potential target for therapeutic immunomodulation. In this review we discuss the role of AhR in the regulation of the immune response in the context of autoimmunity, infection, and cancer, as well as the potential opportunities and challenges of developing AhR-targeted therapeutics.

Aryl Hydrocarbon Receptor: A New Player of Pathogenesis and Therapy in Cardiovascular Diseases

The aryl hydrocarbon receptor (AhR) is a DNA binding protein that acts as a nuclear receptor mediating xenobiotic metabolism and environmental responses. Owing to the evolutionary conservation of this gene and its widespread expression in the immune and circulatory systems, AhR has for many years been almost exclusively studied by the pharmacological/toxicological field for its role in contaminant toxicity. More recently, the functions of AhR in environmental adaption have been examined in the context of the occurrence, development, and therapy of cardiovascular diseases. Increasing evidence suggests that AhR is involved in maintaining homeostasis or in triggering pathogenesis by modulating the biological responses of critical cell types in the cardiovascular system. Here, we describe the structure, distribution, and ligands of AhR and the AhR signaling pathway and review the impact of AhR on cardiovascular physiology. We also discuss the potential contribution of AhR as a new potential factor in the targeted treatment of cardiovascular diseases.

ROS and Trypanosoma cruzi: Fuel to infection, poison to the heart

The activation of macrophage respiratory burst in response to infection with Trypanosoma cruzi inflicts oxidative damage to the host’s tissues. For decades, the role of reactive oxygen species (ROS) in the elimination of T. cruzi was taken for granted, but recent evidence suggests parasite growth is stimulated in oxidative environments. It is still a matter of debate whether indeed oxidative environments provide ideal conditions (e.g., iron availability in macrophages) for T. cruzi growth and whether indeed ROS signals directly to stimulate growth. Nitric oxide (NO) and ROS combine to form peroxynitrite, participating in the killing of phagocytosed parasites by activated macrophages. In response to infection, mitochondrial ROS are produced by cardiomyocytes. They contribute to oxidative damage that persists at the chronic stage of infection and is involved in functional impairment of the heart. In this review, we discuss how oxidative stress helps parasite growth during the acute stage and how it participates in the development of cardiomyopathy at the chronic stage.

Aryl hydrocarbon receptor (AHR): "pioneer member" of the basic-helix/loop/helix per-Arnt-sim (bHLH/PAS) family of "sensors" of foreign and endogenous signals

The basic-helix/loop/helix per-Arnt-sim (bHLH/PAS) family comprises many transcription factors, found throughout all three kingdoms of life; bHLH/PAS members "sense" innumerable intracellular and extracellular "signals" - including endogenous compounds, foreign chemicals, gas molecules, redox potential, photons (light), gravity, heat, and osmotic pressure. These signals then initiate downstream signaling pathways involved in responding to that signal. The term "PAS", abbreviation for "per-Arnt-sim" was first coined in 1991. Although the mouse Arnt gene was not identified until 1991, evidence of its co-transcriptional binding partner, aryl hydrocarbon receptor (AHR), was first reported in 1974 as a "sensor" of foreign chemicals, up-regulating cytochrome P450 family 1 (CYP1) and other enzyme activities that usually metabolize the signaling chemical. Within a few years, AHR was proposed also to participate in inflammation. The mouse [Ah] locus was shown (1973-1989) to be relevant to chemical carcinogenesis, mutagenesis, toxicity and teratogenesis, the mouse Ahr gene was cloned in 1992, and the first Ahr(-/-) knockout mouse line was reported in 1995. After thousands of studies from the early 1970s to present day, we now realize that AHR participates in dozens of signaling pathways involved in critical-life processes, affecting virtually every organ and cell-type in the animal, including many invertebrates.