Caspase-1/ASC inflammasome-mediated activation of IL-1β-ROS-NF-κB pathway for control of Trypanosoma cruzi replication and survival is dispensable in NLRP3-/- macrophages

Molecular regulation of NLRP3 inflammasome activation during parasitic infection

Parasitic diseases are a serious global health concern, causing many common and severe infections, including Chagas disease, leishmaniasis, and schistosomiasis. The NLRP3 inflammasome belongs to the NLR (nucleotide-binding domain leucine-rich-repeat-containing proteins) family, which are cytosolic proteins playing key roles in the detection of pathogens. NLRP3 inflammasomes are activated in immune responses to Plasmodium, Leishmania, Toxoplasma gondii, Entamoeba histolytica, Trypanosoma cruzi, and other parasites. The role of NLRP3 is not fully understood, but it is a crucial component of the innate immune response to parasitic infections and its functions as a sensor triggering the inflammatory response to the invasive parasites. However, while this response can limit the parasites' growth, it can also result in potentially catastrophic host pathology. This makes it essential to understand how NLRP3 interacts with parasites to initiate the inflammatory response. Plasmodium hemozoin, Leishmania glycoconjugate lipophosphoglycan (LPG) and E. histolytica Gal/GalNAc lectin can stimulate NLRP3 activation, while the dense granule protein 9 (GRA9) of T. gondii has been shown to suppress it. Several other parasitic products also have diverse effects on NLRP3 activation. Understanding the mechanism of NLRP3 interaction with these products will help to develop advanced therapeutic approaches to treat parasitic diseases. This review summarizes current knowledge of the NLRP3 inflammasome's action on the immune response to parasitic infections and aims to determine the mechanisms through which parasitic molecules either activate or inhibit its action.

Activation of Inflammasome complex in nasopharyngeal epithelial cells from patients with Coronavirus disease 2019 contributes to inflammatory state and worse disease outcomes

Pathogenesis of Coronavirus disease 2019 (COVID-19) has been associated with dysregulation of both adaptive and innate immune systems. Hence, we determined the contribution of inflammasome in the nasopharyngeal epithelial cells isolated from COVID-19 subjects to disease pathogenesis and outcomes. Epithelial cells from 150 COVID-19 patients and 150 healthy controls were yielded through nasopharyngeal swab sampling. Patients were categorized into three groups of those with clinical presentations/need hospitalization, with clinical presentations/no need hospitalization and cases without clinical symptoms/no need hospitalization. Finally, the transcriptional amount of inflammasome related genes were assessed in the nasopharyngeal epithelial cells using qPCR. There was a significant upregulation of nod-like receptor (NLR) family pyrin domain containing 1 (NLRP1), nod-like receptor (NLR) family pyrin domain containing 3 (NLRP3), Apoptosis-associated speck-like protein containing a CARD (ASC) and Caspase-1 mRNA expressions in patients compared to controls. NLRP1, NLRP3, ASC and Caspase-1 were upregulated in epithelial cells of patients with clinical symptoms/need hospitalization and cases with clinical symptoms/no need hospitalization when compared to controls. There was a correlation between expression of inflammasome-related genes and clinicopathological features. Abnormal expression of inflammasome-related genes in the nasopharyngeal epithelial cells obtained from COVID-19 patients may be of prognostic value to determine the intensity of the disease's outcomes and requirement for alternative supports in hospitals.

Global scientific trends update on macrophage polarization in rheumatoid arthritis: A bibliometric and visualized analysis from 2000 to 2022

The goal of this work was to use bibliometric analysis to help guide future research on macrophage polarization in RA. We looked for studies on macrophage polarization in RA published between January 1, 2000, and December 31, 2022, in the WoSCC database. Research trends and hotspots were shown and assessed using VOSviewer and CiteSpace. A total of 181 articles were gathered. Belgium was among the early adopters of the field. Chinese institutes have produced the most research. Researchers such as Angel Luis Corb, Amaya Puig-Kröger, and Lizbeth Estrada-Capetillo have made major contributions to the field. Frontiers in Immunology has published the most study findings. According to VOSviewer, the most investigated immune cells, biomarkers, and signaling pathways in the previous three years have been "T cells", "gm-csf", and "nf-κb" in that order. We discovered that the most often used terms in the previous three years were "pathway", "oxidative stress", "extracellular capsule" and "nlrp3 inflammasome" using Citespace. We emphasize these concepts in our findings, presenting the exact mechanisms of pathophysiology related to macrophage polarization in RA, as well as current breakthroughs in therapy strategies.

Mitochondrial dysfunction and mitophagy: crucial players in burn trauma and wound healing

Burn injuries are a significant cause of death worldwide, leading to systemic inflammation, multiple organ failure and sepsis. The progression of burn injury is explicitly correlated with mitochondrial homeostasis, which is disrupted by the hyperinflammation induced by burn injury, leading to mitochondrial dysfunction and cell death. Mitophagy plays a crucial role in maintaining cellular homeostasis by selectively removing damaged mitochondria. A growing body of evidence from various disease models suggest that pharmacological interventions targeting mitophagy could be a promising therapeutic strategy. Recent studies have shown that mitophagy plays a crucial role in wound healing and burn injury. Furthermore, chemicals targeting mitophagy have also been shown to improve wound recovery, highlighting the potential for novel therapeutic strategies based on an in-depth exploration of the molecular mechanisms regulating mitophagy and its association with skin wound healing.

Effect and mechanism of reactive oxygen species-mediated NOD-like receptor family pyrin domain-containing 3 inflammasome activation in hepatic alveolar echinococcosis

BACKGROUND

The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is a significant component of the innate immune system that plays a vital role in the development of various parasitic diseases. However, its role in hepatic alveolar echinococcosis (HAE) remains unclear.

AIM

To investigate the NLRP3 inflammasome and its mechanism of activation in HAE.

METHODS

We assessed the expression of NLRP3, caspase-1, interleukin (IL)-1β, and IL-18 in the marginal zone and corresponding normal liver of 60 patients with HAE. A rat model of HAE was employed to investigate the role of the NLRP3 inflammasome in the marginal zone of HAE. Transwell experiments were conducted to investigate the effect of Echinococcus multilocularis (E. multilocularis) in stimulating Kupffer cells and hepatocytes. Furthermore, immunohistochemistry, Western blotting, and enzyme-linked immunosorbent assay were used to evaluate NLRP3, caspase-1, IL-1β, and IL-18 expression; flow cytometry was used to detect apoptosis and reactive oxygen species (ROS).

RESULTS

NLRP3 inflammasome activation was significantly associated with ROS. Inhibition of ROS production decreased NLRP3-caspase-1-IL-1β pathway activation and mitigated hepatocyte damage and inflammation.

CONCLUSION

E. multilocularis induces hepatocyte damage and inflammation by activating the ROS-mediated NLRP3-caspase-1-IL-1β pathway in Kupffer cells, indicating that ROS may serve as a potential target for the treatment of HAE.

Monocytes educated by cancer-associated fibroblasts secrete exosomal miR-181a to activate AKT signaling in breast cancer cells

BACKGROUND

Cancer-associated fibroblasts (CAFs), one of the major components of the tumor stroma, contribute to an immunosuppressive tumor microenvironment (TME) through the induction and functional polarization of protumoral macrophages. We have herein investigated the contribution of CAFs to monocyte recruitment and macrophage polarization. We also sought to identify a possible paracrine mechanism by which CAF-educated monocytes affect breast cancer (BC) cell progression.

METHODS

Monocytes were educated by primary CAFs and normal fibroblast (NF); the phenotypic alterations of CAF- or NF-educated monocytes were measured by flow cytometry. Exosomes isolated from the cultured conditioned media of the educated monocytes were characterized. An in vivo experiment using a subcutaneous transplantation tumor model in athymic nude mice was conducted to uncover the effect of exosomes derived from CAF- or NF-educated monocytes on breast tumor growth. Gain- and loss-of-function experiments were performed to explore the role of miR-181a in BC progression with the involvement of the AKT signaling pathway. Western blotting, enzyme-linked immunosorbent assay, RT-qPCR, flow cytometry staining, migration assay, immunohistochemical staining, and bioinformatics analysis were performed to reveal the underlying mechanisms.

RESULTS

We illustrated that primary CAFs recruited monocytes and established pro-tumoral M2 macrophages. CAF may also differentiate human monocyte THP-1 cells into anti-inflammatory M2 macrophages. Besides, we revealed that CAFs increased reactive oxygen species (ROS) generation in THP-1 monocytes, as differentiating into M2 macrophages requires a level of ROS for proper polarization. Importantly, T-cell proliferation was suppressed by CAF-educated monocytes and their exosomes, resulting in an immunosuppressive TME. Interestingly, CAF-activated, polarized monocytes lost their tumoricidal abilities, and their derived exosomes promoted BC cell proliferation and migration. In turn, CAF-educated monocyte exosomes exhibited a significant promoting effect on BC tumorigenicity in vivo. Of clinical significance, we observed that up-regulation of circulating miR-181a in BC was positively correlated with tumor aggressiveness and found a high level of this miRNA in CAF-educated monocytes and their exosomes. We further clarified that the pro-oncogenic effect of CAF-educated monocytes may depend in part on the exosomal transfer of miR-181a through modulating the PTEN/Akt signaling axis in BC cells.

CONCLUSIONS

Our findings established a connection between tumor stromal communication and tumor progression and demonstrated an inductive function for CAF-educated monocytes in BC cell progression. We also proposed a supporting model in which exosomal transfer of miR-181a from CAF-educated monocytes activates AKT signaling by regulating PTEN in BC cells.

Mitochondrial oxidative stress in the tumor microenvironment and cancer immunoescape: foe or friend?

The major concept of "oxidative stress" is an excess elevated level of reactive oxygen species (ROS) which are generated from vigorous metabolism and consumption of oxygen. The precise harmonization of oxidative stresses between mitochondria and other organelles in the cell is absolutely vital to cell survival. Under oxidative stress, ROS produced from mitochondria and are the major mediator for tumorigenesis in different aspects, such as proliferation, migration/invasion, angiogenesis, inflammation, and immunoescape to allow cancer cells to adapt to the rigorous environment. Accordingly, the dynamic balance of oxidative stresses not only orchestrate complex cell signaling events in cancer cells but also affect other components in the tumor microenvironment (TME). Immune cells, such as M2 macrophages, dendritic cells, and T cells are the major components of the immunosuppressive TME from the ROS-induced inflammation. Based on this notion, numerous strategies to mitigate oxidative stresses in tumors have been tested for cancer prevention or therapies; however, these manipulations are devised from different sources and mechanisms without established effectiveness. Herein, we integrate current progress regarding the impact of mitochondrial ROS in the TME, not only in cancer cells but also in immune cells, and discuss the combination of emerging ROS-modulating strategies with immunotherapies to achieve antitumor effects.

Regulatory Effects of Quercetin on M1/M2 Macrophage Polarization and Oxidative/Antioxidative Balance

Macrophage polarization plays essential and diverse roles in most diseases, such as atherosclerosis, adipose tissue inflammation, and insulin resistance. Homeostasis dysfunction in M1/M2 macrophage polarization causes pathological conditions and inflammation. Neuroinflammation is characterized by microglial activation and the concomitant production of pro-inflammatory cytokines, leading to numerous neurodegenerative diseases and psychiatric disorders. Decreased neuroinflammation can be obtained by using natural compounds, including flavonoids, which are known to ameliorate inflammatory responses. Among flavonoids, quercetin possesses multiple pharmacological applications and regulates several biological activities. In the present study, we found that quercetin effectively inhibited the expression of lipocalin-2 in both macrophages and microglial cells stimulated by lipopolysaccharides (LPS). The production of nitric oxide (NO) and expression levels of the pro-inflammatory cytokines, inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, were also attenuated by quercetin treatment. Our results also showed that quercetin significantly reduced the expression levels of the M1 markers, such as interleukin (IL)-6, tumor necrosis factor (TNF)-α, and IL-1β, in the macrophages and microglia. The M1 polarization-associated chemokines, C–C motif chemokine ligand (CCL)-2 and C-X-C motif chemokine ligand (CXCL)-10, were also effectively reduced by the quercetin treatment. In addition, quercetin markedly reduced the production of various reactive oxygen species (ROS) in the microglia. The microglial phagocytic ability induced by the LPS was also effectively reduced by the quercetin treatment. Importantly, the quercetin increased the expression levels of the M2 marker, IL-10, and the endogenous antioxidants, heme oxygenase (HO)-1, glutamate-cysteine ligase catalytic subunit (GCLC), glutamate-cysteine ligase modifier subunit (GCLM), and NAD(P)H quinone oxidoreductase-1 (NQO1). The enhancement of the M2 markers and endogenous antioxidants by quercetin was activated by the AMP-activated protein kinase (AMPK) and Akt signaling pathways. Together, our study reported that the quercetin inhibited the effects of M1 polarization, including neuroinflammatory responses, ROS production, and phagocytosis. Moreover, the quercetin enhanced the M2 macrophage polarization and endogenous antioxidant expression in both macrophages and microglia. Our findings provide valuable information that quercetin may act as a potential drug for the treatment of diseases related to inflammatory disorders in the central nervous system.

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.

The First Contact of Human Dendritic Cells With Trypanosoma cruzi Reveals Response to Virus as an Unexplored Central Pathway

Chagas disease is a debilitating and neglected disease caused by the protozoan Trypanosoma cruzi. Soon after infection, interactions among T. cruzi and host innate immunity cells can drive/contribute to disease outcome. Dendritic cells (DCs), present in all tissues, are one of the first immune cells to interact with Trypanosoma cruzi metacyclic trypomastigotes. Elucidating the immunological events triggered immediately after parasite-human DCs encounter may aid in understanding the role of DCs in the establishment of infection and in the course of the disease. Therefore, we performed a transcriptomic analysis of a 12 h interaction between T. cruzi and MoDCs (monocyte-derived DCs) from three human donors. Enrichment analyses of the 468 differentially expressed genes (DEGs) revealed viral infection response as the most regulated pathway. Additionally, exogenous antigen processing and presentation through MHC-I, chemokine signaling, lymphocyte co-stimulation, metallothioneins, and inflammasome activation were found up-regulated. Notable, we were able to identify the increased gene expression of alternative inflammasome sensors such as AIM2, IFI16, and RIG-I for the first time in a T. cruzi infection. Both transcript and protein expression levels suggest proinflammatory cytokine production during early T. cruzi-DCs contact. Our transcriptome data unveil antiviral pathways as an unexplored process during T. cruzi-DC initial interaction, disclosing a new panorama for the study of Chagas disease outcomes.

Ex vivo infection of canine and ovine placental explants with Trypanosoma cruzi and Toxoplasma gondii: differential activation of NF kappa B signaling pathways

Chagas disease and toxoplasmosis, caused by Trypanosoma cruzi and Toxoplasma gondii, respectively, are important zoonotic diseases affecting humans, companion animals, and livestock, responsible for major health and economic burden. Both parasites can be transmitted vertically in different mammalian species through the placenta. Of note, the transmission rate of T. cruzi is low in dogs, whereas that of T. gondii is high in sheep. The probability of congenital infection depends on complex parasite-host interactions; parasite factors, maternal and fetal immune responses and placental responses all have a role in infection establishment. Since the innate immune response is regulated, at least partially, by NF-κB signaling pathways, our main objective was to determine the effect of ex vivo infection of canine (CPE) and ovine (OPE) placental explants with both parasites, on the activation of canonical and non-canonical NF-κB pathways and its relation to infection. Here, we show that T. cruzi activates both the NF-κB canonical and non-canonical pathways in CPE and OPE, unlike T. gondii, that activates only the canonical pathway in CPE and has no effect on the non-canonical pathway in both explants. Moreover, the inhibition of either or both NF-κB pathways increases the DNA load of T. cruzi in both explants, modulates, on the other hand, T. gondii infection in a differential fashion. Overall, we conclude that the differential modulation of the NF-κB pathways by both pathogens in placental explants might explain, at least partially, the differences in transmission rates of T. cruzi and T. gondii in different mammalian species.

Activation of NLRP3 by uropathogenic Escherichia coli is associated with IL-1β release and regulation of antimicrobial properties in human neutrophils

The NLRP3 inflammasome and IL-1β have recently been linked to the severity of uropathogenic Escherichia coli (UPEC)-mediated urinary tract infection (UTI). However, not much is known about the contribution of NLRP3 to the antimicrobial properties of neutrophils and the release of IL-1β during UPEC infection. The purpose of this study was to elucidate the mechanisms behind UPEC-induced IL-1β release from human neutrophils, and to investigate the contribution of the NLRP3 inflammasome in neutrophil-mediated inhibition of UPEC growth. We found that the UPEC strain CFT073 increased the expression of NLRP3 and increased caspase-1 activation and IL-1β release from human neutrophils. The IL-1β release was mediated by the NLRP3 inflammasome and by serine proteases in an NF-κB-and cathepsin B-dependent manner. The UPEC virulence factors α-hemolysin, type-1 fimbriae and p-fimbriae were all shown to contribute to UPEC mediated IL-1β release from neutrophils. Furthermore, inhibition of caspase-1 and NLRP3 activation increased neutrophil ROS-production, phagocytosis and the ability of neutrophils to suppress UPEC growth. In conclusion, this study demonstrates that UPEC can induce NLRP3 and serine protease-dependent release of IL-1β from human neutrophils and that NLRP3 and caspase-1 can regulate the antimicrobial activity of human neutrophils against UPEC.

ROS-mediated NLRP3 inflammasome activation participates in the response against Neospora caninum infection

Background

Neospora caninum is an obligate intracellular protozoan that causes neosporosis, N. caninum infection is a major cause of abortion in cattle worldwide. Currently, specific treatment for neosporosis is not available. The NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is a cytoplasmic protein complex that plays an important role in host defense against N. caninum infection, but the underlying mechanisms are poorly understood.

Methods

The reactive oxygen species (ROS) inhibitor and the ROS inducer, wild-type (WT) and NLRP3-deficient peritoneal macrophages or mice were used to investigate the role of ROS in NLRP3 inflammasome activation and controlling parasite burdens. ROS production, cell death and cell viability, production of inflammasome-mediated IL-1β or IL-18, cleavage of caspase-1 and NLRP3 expression, as well as parasite burdens were detected.

Results

In vitro, N. caninum induced ROS generation in a dose-dependent manner in peritoneal macrophages. The pretreatment of ROS inhibitor N-acetyl-l-cysteine (NAC) significantly attenuated N. caninum-induced ROS production, LDH release, IL-1β secretion and NLRP3 expression, whereas N. caninum proliferation was notably increased. In contrary, the ROS inducer pyrogallol (PG) significantly enhanced ROS production and NLRP3 inflammasome activity and decreased the parasite burden in N. caninum-infected peritoneal macrophages. NADPH-dependent ROS-mediated NLRP3 inflammasome activation induced by N. caninum can also be confirmed by using the NADPH oxidase inhibitor diphenyleneiodonium chloride (DPI). However, the NAC or DPI pre-treatment or PG treatment did not significantly alter N. caninum-induced inflammasome activities and parasite proliferation in Nlrp3^−/− peritoneal macrophages. In vivo, IL-18 releases in serum and parasite burdens in peritoneal exudate cells were significantly increased in PG-treated WT mice after infection with N. caninum; however, IL-18 productions and parasite burdens were not changed in PG-treated Nlrp3^−/− mice. Furthermore, PG treatment in WT mice infected with N. caninum significantly decreased the mortality, weight loss and parasite burdens in tissues and histopathological lesions.

Conclusions

Neospora caninum-induced NADPH-dependent ROS generation plays an important role in NLRP3 inflammasome activation and controlling parasites. The ROS inducer PG can control N. caninum infection mainly by promoting NLRP3 inflammasome activation. ROS-mediated NLRP3 inflammasome axis can be a potential therapeutic target for neosporosis.

Gene expression network analyses during infection with virulent and avirulent Trypanosoma cruzi strains unveil a role for fibroblasts in neutrophil recruitment and activation

Chagas disease is caused by Trypanosoma cruzi, a protozoan parasite that has a heterogeneous population composed of a pool of strains with distinct characteristics, including variable levels of virulence. In previous work, transcriptome analyses of parasite genes after infection of human foreskin fibroblasts (HFF) with virulent (CL Brener) and non-virulent (CL-14) clones derived from the CL strain, revealed a reduced expression of genes encoding parasite surface proteins in CL-14 compared to CL Brener during the final steps of the intracellular differentiation from amastigotes to trypomastigotes. Here we analyzed changes in the expression of host genes during in vitro infection of HFF cells with the CL Brener and CL-14 strains by analyzing total RNA extracted from cells at 60 and 96 hours post-infection (hpi) with each strain, as well as from uninfected cells. Similar transcriptome profiles were observed at 60 hpi with both strains compared to uninfected samples. However, at 96 hpi, significant differences in the number and expression levels of several genes, particularly those involved with immune response and cytoskeleton organization, were observed. Further analyses confirmed the difference in the chemokine/cytokine signaling involved with the recruitment and activation of immune cells such as neutrophils upon T. cruzi infection. These findings suggest that infection with the virulent CL Brener strain induces a more robust inflammatory response when compared with the non-virulent CL-14 strain. Importantly, the RNA-Seq data also exposed an unexplored role of fibroblasts as sentinel cells that may act by recruiting neutrophils to the initial site of infection. This role for fibroblasts in the regulation of the inflammatory response during infection by T. cruzi was corroborated by measurements of levels of different chemokines/cytokines during in vitro infection and in plasma from Chagas disease patients as well as by neutrophil activation and migration assays.

Trypanosoma cruzi is the causative agent of Chagas disease, a debilitating and often life-threatening illness that affects 6 to 7 million people mainly in Latin America. The parasite, transmitted to humans by an insect vector, needs to invade different cells from the infected person in order to multiply and spread the infection to various organs, including the heart and the gut. In this study, we investigated how the host cell responds to the infection by analyzing changes in the expression of human genes in fibroblasts infected with the CL Brener and CL-14 strains, which are strains that present highly distinct virulent phenotypes during infection in mice. We showed that human fibroblasts build a strong immune response upon infection by T. cruzi and that this response is different depending on the parasite strain: infection with the virulent CL Brener strain induces a more robust inflammatory response compared with the infection with the avirulent CL-14 strain. We also showed that, in response to the infection, fibroblasts produce molecules that can recruit and activate neutrophils, which are important immune cells that controls the infection.

ASC Modulates CTL Cytotoxicity and Transplant Outcome Independent of the Inflammasome

The adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD) is known to facilitate caspase-1 activation, which is essential for innate host immunity via the formation of the inflammasome complex, a multiprotein structure responsible for processing IL1β and IL18 into their active moieties. Here, we demonstrated that ASC-deficient CD8⁺ T cells failed to induce severe graft-versus-host disease (GVHD) and had impaired capacity for graft rejection and graft-versus-leukemia (GVL) activity. These effects were inflammasome independent because GVHD lethality was not altered in recipients of caspase-1/11-deficient T cells. We also demonstrated that ASC deficiency resulted in a decrease in cytolytic function, with a reduction in granzyme B secretion and CD107a expression by CD8⁺ T cells. Altogether, our findings highlight that ASC represents an attractive therapeutic target for improving outcomes of clinical transplantation.

Activation of the Nrf2/HO-1 Pathway by Amomum villosum Extract Suppresses LPS-Induced Oxidative Stress In Vitro and Ex Vivo

Despite its deleterious effects on living cells, oxidative stress plays essential roles in normal physiological processes and provides signaling molecules for cell growth, differentiation, and inflammation. Macrophages are equipped with antioxidant mechanisms to cope with intracellular ROS produced during immune response, and Nrf2 (NF-E2-related factor 2)/HO-1 (heme oxygenase-1) pathway is an attractive target due to its protective effect against ROS-induced cell damage in inflamed macrophages. We investigated the effects of ethanol extract of A. villosum (AVEE) on lipopolysaccharide- (LPS-) stimulated inflammatory responses generated via the Nrf2/HO-1 signaling pathway in murine peritoneal macrophages and RAW 264.7 cells. AVEE was found to suppress the NF-κB signaling pathway, thus, to reduce proinflammatory cytokine, nitric oxide, and prostaglandin levels in peritoneal macrophages and Raw 264.7 cells treated with LPS, and to enhance HO-1 expression by activating Nrf2 signaling. Furthermore, these anti-inflammatory effects of AVEE were diminished when cells were pretreated with SnPP (a HO-1 inhibitor). HPLC analysis revealed AVEE contained quercetin, a possible activator of the Nrf2/HO-1 pathway. These results show A. villosum ethanol extract exerts anti-inflammatory effects by activating the Nrf2/HO-1 pathway in LPS-stimulated macrophages.

PARP1-cGAS-NF-κB pathway of proinflammatory macrophage activation by extracellular vesicles released during Trypanosoma cruzi infection and Chagas disease

Trypanosoma cruzi (T. cruzi) is the etiological agent of Chagas cardiomyopathy. In the present study, we investigated the role of extracellular vesicles (Ev) in shaping the macrophage (Mφ) response in progressive Chagas disease (CD). We purified T. cruzi Ev (TcEv) from axenic parasite cultures, and T. cruzi-induced Ev (TEv) from the supernatants of infected cells and plasma of acutely and chronically infected wild-type and Parp1-/- mice. Cultured (Raw 264.7) and bone-marrow Mφ responded to TcEV and TEv with a profound increase in the expression and release of TNF-α, IL-6, and IL-1β cytokines. TEv produced by both immune (Mφ) and non-immune (muscle) cells were proinflammatory. Chemical inhibition or genetic deletion of PARP1 (a DNA repair enzyme) significantly depressed the TEv-induced transcriptional and translational activation of proinflammatory Mφ response. Oxidized DNA encapsulated by TEv was necessary for PARP1-dependent proinflammatory Mφ response. Inhibition studies suggested that DNA-sensing innate immune receptors (cGAS>>TLR9) synergized with PARP1 in signaling the NFκB activation, and inhibition of PARP1 and cGAS resulted in >80% inhibition of TEv-induced NFκB activity. Histochemical studies showed intense inflammatory infiltrate associated with profound increase in CD11b+CD68+TNF-α+ Mφ in the myocardium of CD wild-type mice. In comparison, chronically infected Parp1-/- mice exhibited low-to-moderate tissue inflammation, >80% decline in myocardial infiltration of TNF-α+ Mφ, and no change in immunoregulatory IL-10+ Mφ. We conclude that oxidized DNA released with TEv signal the PARP1-cGAS-NF-κB pathway of proinflammatory Mφ activation and worsens the chronic inflammatory pathology in CD. Small molecule antagonists of PARP1-cGAS signaling pathway would potentially be useful in reprogramming the Mφ activation and controlling the chronic inflammation in CD.

Inflammasome Activation in Response to Intracellular Protozoan Parasites

Inflammasomes are cytosolic complexes that assemble in response to cellular stress or upon sensing microbial molecules, culminating in cytokine processing and an inflammatory form of cell death called pyroptosis. Inflammasomes are usually composed of a sensor molecule, an adaptor protein, and an inflammatory caspase, such as Caspase-1, which cleaves and activates multiple substrates, including Gasdermin-D, pro-IL-1β, and pro-IL-18. Ultimately, inflammasome activation promotes inflammation and restriction of the microbial infection. In recent years, many studies have addressed the role of inflammasomes during fungal, bacterial, viral, and parasitic diseases, revealing sophisticated aspects of the host-pathogen interaction. In this review, we summarize recent advances on inflammasome activation in response to intracellular parasites, including Leishmania spp., Plasmodium spp., Trypanosoma cruzi, and Toxoplasma gondii.

MGL1 Receptor Plays a Key Role in the Control of T. cruzi Infection by Increasing Macrophage Activation through Modulation of ERK1/2, c-Jun, NF-κB and NLRP3 Pathways

Macrophage galactose-C type lectin (MGL)1 receptor is involved in the recognition of Trypanosoma cruzi (T. cruzi) parasites and is important for the modulation of the innate and adaptive immune responses. However, the mechanism by which MGL1 promotes resistance to T. cruzi remains unclear. Here, we show that MGL1 knockout macrophages (MGL1^-/- Mφ) infected in vitro with T. cruzi were heavily parasitized and showed decreased levels of reactive oxygen species (ROS), nitric oxide (NO), IL-12 and TNF-α compared to wild-type macrophages (WT Mφ). MGL1^-/- Mφ stimulated in vitro with T. cruzi antigen (TcAg) showed low expression of TLR-2, TLR-4 and MHC-II, which resulted in deficient splenic cell activation compared with similar co-cultured WT Mφ. Importantly, the activation of p-ERK1/2, p-c-Jun and p-NF-κB p65 were significantly reduced in MGL1^-/- Mφ exposed to TcAg. Similarly, procaspase 1, caspase 1 and NLRP3 inflammasome also displayed a reduced expression that was associated with low IL-β production. Our data reveal a previously unappreciated role for MGL1 in Mφ activation through the modulation of ERK1/2, c-Jun, NF-κB and NLRP3 signaling pathways, and to the development of protective innate immunity against experimental T. cruzi infection.

Origin of Monocytes/Macrophages Contributing to Chronic Inflammation in Chagas Disease: SIRT1 Inhibition of FAK-NFκB-Dependent Proliferation and Proinflammatory Activation of Macrophages

BACKGROUND

Trypanosoma cruzi (Tc) causes Chagas disease (CD) that is the most frequent cause of heart failure in Latin America. TNF-α+ monocytes/macrophages (Mo/Mφ) are associated with inflammatory pathology in chronic CD. In this study, we determined the progenitor lineage of Mo/Mφ contributing to inflammation and examined the regulatory role of SIRT1 in modulating the Mo/Mφ response in Chagas disease.

METHODS AND RESULTS

C57BL/6 mice were infected with Tc, treated with SIRT1 agonist (SRT1720) after control of acute parasitemia, and monitored during chronic phase (150 days post-infection). Flow cytometry studies showed an increase in maturation of bone marrow hematopoietic stem cell (HSC)-derived Mo of proinflammatory and anti-inflammatory phenotype in acutely- and chronically-infected mice; however, these cells were not increased in splenic compartment of infected mice. Instead, yolk-sac-derived CD11b+ F4/80+ Mo/Mφ were increased in sinusoidal compartment of Chagas mice. The splenic CD11b+ F4/80+ Mo/Mφ of Chagas (vs. control) mice exhibited increased mRNA, protein, and surface expression of markers of proinflammatory phenotype (CD80+/CD64+ > CD200+/CD206+) associated with proinflammatory cytokines response (IL-6+TNF-α >> Arg-1+IL-10), and these were also detected in the myocardium of chronically infected mice. Infected mice treated with SRT1720 (vs. infected/untreated) exhibited decreased splenic expansion and myocardial infiltration of proinflammatory Mo/Mφ. SRT1720 did not alter the inherent capability of splenic Mo/Mφ of Chagas mice to respond to pathogen stimulus. Instead, SRT1720 dampened the Tc-induced increase in the expression and/or phosphorylation of focal adhesion kinase (FAK) and downstream transcription factors (Pu.1, c-Myb, and Runx1) involved in Mφ proliferation and migration and Notch1 involved in functional activation. Studies in cultured Mφ confirmed the agonistic effects of SIRT1 in controlling the Tc-induced, FAK-dependent increase in the expression of transcription factors and showed that SIRT1 agonist and FAK inhibitor abrogated the NF-κB transcriptional activity and inflammatory cytokine gene expression in Tc-infected Mφ.

CONCLUSIONS

The proinflammatory Mo/Mφ of yolk sac origin drive the splenic and tissue inflammatory response in chronic CD. SRT1720 reprogrammed the Tc-induced FAK-dependent transcription factors involved in Mφ proliferation and proinflammatory activation in Chagas disease.

Immuno-metabolic profile of human macrophages after Leishmania and Trypanosoma cruzi infection

Macrophages can reprogram their metabolism in response to the surrounding stimuli, which affects their capacity to kill intracellular pathogens. We have investigated the metabolic and immune status of human macrophages after infection with the intracellular trypanosomatid parasites Leishmania donovani, L. amazonensis and T. cruzi and their capacity to respond to a classical polarizing stimulus (LPS and IFN-γ). We found that macrophages infected with Leishmania preferentially upregulate oxidative phosphorylation, which could be contributed by both host cell and parasite, while T. cruzi infection did not significantly increase glycolysis or oxidative phosphorylation. Leishmania and T. cruzi infect macrophages without triggering a strong inflammatory cytokine response, but infection does not prevent a potent response to LPS and IFN-γ. Infection appears to prime macrophages, since the cytokine response to activation with LPS and IFN-γ is more intense in infected macrophages compared to uninfected ones. Metabolic polarization in macrophages can influence infection and immune evasion of these parasites since preventing macrophage cytokine responses would help parasites to establish a persistent infection. However, macrophages remain responsive to classical inflammatory stimuli and could still trigger inflammatory cytokine secretion by macrophages.

Ex vivo infection of human placental explants with Trypanosoma cruzi and Toxoplasma gondii: Differential activation of NF kappa B signaling pathways

Trypanosoma cruzi (T. cruzi) and Toxoplasma gondii (T. gondii) are the causative agents of Chagas disease and Toxoplasmosis. T. cruzi and T. gondii present, respectively, low and high congenital transmission rates and induce a distinctive cytokine/chemokine profile in ex vivo infected human placental explants (HPE). Since the innate immune response is regulated, at least partially, by NF-κB signaling pathways, our main objective was to determine the effect of ex vivo infection with both parasites on the activation of canonical and non-canonical NF-κB pathways and its relation to parasite infection. T. cruzi activates both, the canonical and non-canonical pathways of NF-κB, unlike T. gondii, which has no effect on the canonical pathway and inhibits the non-canonical pathway. The inhibition of both pathways of NF-κB increases the DNA load of T. cruzi and T. gondii in HPE. Therefore, the differential modulation of NF-κB signal transduction pathways by both parasites might explain, at least partially, the low and high congenital transmission rates of T. cruzi and T. gondii.

Macrophage-Driven Biomaterial Degradation Depends on Scaffold Microarchitecture

In situ tissue engineering is a technology in which non-cellular biomaterial scaffolds are implanted in order to induce local regeneration of replaced or damaged tissues. Degradable synthetic electrospun scaffolds are a versatile and promising class of biomaterials for various in situ tissue engineering applications, such as cardiovascular replacements. Functional in situ tissue regeneration depends on the balance between endogenous neo-tissue formation and scaffold degradation. Both these processes are driven by macrophages. Upon invasion into a scaffold, macrophages secrete reactive oxygen species (ROS) and hydrolytic enzymes, contributing to oxidative and enzymatic biomaterial degradation, respectively. This study aims to elucidate the effect of scaffold microarchitecture, i.e., μm-range fiber diameter and fiber alignment, on early macrophage-driven scaffold degradation. Electrospun poly-ε-caprolactone-bisurea (PCL-BU) scaffolds with either 2 or 6 μm (Ø) isotropic or anisotropic fibers were seeded with THP-1 derived human macrophages and cultured in vitro for 4 or 8 days. Our results revealed that macroph age-induced oxidative degradation in particular was dependent on scaffold microarchitecture, with the highest level of ROS-induced lipid peroxidation, NADPH oxidase gene expression and degradation in the 6 μm Ø anisotropic group. Whereas, biochemically polarized macrophages demonstrated a phenotype-specific degradative potential, the observed differences in macrophage degradative potential instigated by the scaffold microarchitecture could not be attributed to either distinct M1 or M2 polarization. This suggests that the scaffold microarchitecture uniquely affects macrophage-driven degradation. These findings emphasize the importance of considering the scaffold microarchitecture in the design of scaffolds for in situ tissue engineering applications and the tailoring of degradation kinetics thereof.

Cytosolic Recognition of Microbes and Pathogens: Inflammasomes in Action

Infection is a dynamic biological process underpinned by a complex interplay between the pathogen and the host. Microbes from all domains of life, including bacteria, viruses, fungi, and protozoan parasites, have the capacity to cause infection. Infection is sensed by the host, which often leads to activation of the inflammasome, a cytosolic macromolecular signaling platform that mediates the release of the proinflammatory cytokines interleukin-1β (IL-1β) and IL-18 and cleavage of the pore-forming protein gasdermin D, leading to pyroptosis. Host-mediated sensing of the infection occurs when pathogens inject or carry pathogen-associated molecular patterns (PAMPs) into the cytoplasm or induce damage that causes cytosolic liberation of danger-associated molecular patterns (DAMPs) in the host cell. Recognition of PAMPs and DAMPs by inflammasome sensors, including NLRP1, NLRP3, NLRC4, NAIP, AIM2, and Pyrin, initiates a cascade of events that culminate in inflammation and cell death. However, pathogens can deploy virulence factors capable of minimizing or evading host detection. This review presents a comprehensive overview of the mechanisms of microbe-induced activation of the inflammasome and the functional consequences of inflammasome activation in infectious diseases. We also explore the microbial strategies used in the evasion of inflammasome sensing at the host-microbe interaction interface.

NLRP3 Inflammasome and Caspase-1/11 Pathway Orchestrate Different Outcomes in the Host Protection Against Trypanosoma cruzi Acute Infection

Infection with protozoan parasite Trypanosoma cruzi results in activation of nucleotide-binding domain and leucine-rich repeat containing receptors (NLRs). NLR activation leads to inflammasome formation, the activation of caspase-1, and the subsequent cleavage of IL-1β and IL-18. Considering that inflammasome activation and IL-1β induction by macrophages are key players for an appropriate T cell response, we investigated the relevance of NLR pyrin domain-containing 3 (NLRP3) and caspase-1/11 to elucidate their roles in the induction of different T cell phenotypes and the relationship with parasite load and hepatic inflammation during T. cruzi-Tulahuen strain acute infection. We demonstrated that infected nlrp3-/- and C57BL/6 wild type (WT) mice exhibited similar parasitemia and survival, although the parasite load was higher in the livers of nlrp3-/- mice than in those of WT mice. Increased levels of transaminases and pro-inflammatory cytokines were found in the plasma of WT and nlrp3-/- mice indicating that NLRP3 is dispensable to control the parasitemia but it is required for a better clearance of parasites in the liver. Importantly, we have found that NLRP3 and caspase-1/11-deficient mice differentially modulate T helper (Th1, Th2, and Th17) and cytotoxic T lymphocyte phenotypes. Strikingly, caspase-1/11-/- mice showed the most dramatic reduction in the number of IFN-γ- and IL-17-producing CD4+ and CD8+ T cells associated with higher parasitemia and lower survival. Additionally, caspase-1/11-/- mice demonstrated significantly reduced liver inflammation with the lowest alanine aminotransferase (ALT) levels but the highest hepatic parasitic load. These results unequivocally demonstrate that caspase-1/11 pathway plays an important role in the induction of liver adaptive immunity against this parasite infection as well as in hepatic inflammation.

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.

Pathogenesis of Chronic Chagas Disease: Macrophages, Mitochondria, and Oxidative Stress

PURPOSE OF REVIEW

Trypanosoma cruzi is the causative agent of Chagas disease. Decades after initial infection, ~30% of individuals can develop chronic chagasic cardiomyopathy. There are several proposed mechanisms for pathogenesis of Chagas disease, including parasite persistence, immune responses against parasite or self that continue in the heart, vascular compromise, and involvement of autonomous and central nervous system. Herein, we will focus on the significance of macrophages, mitochondrial dysfunction, and oxidative stress in progression of chagasic cardiomyopathy.

RECENT FINDINGS

The current literature suggests that T. cruzi prevents cytotoxic activities of the innate immune cells and persists in the host, contributing to mitochondrial oxidative stress. We discuss how the neoantigens generated due to cellular oxidative damage contribute to chronic inflammatory stress in chagasic disease.

SUMMARY

We propose that metabolic regulators, PARP-1/SIRT1, determine the disease outcome by modulating the mitochondrial and macrophage stress and antioxidant/oxidant imbalance, and offer a potential new therapy against chronic Chagas disease.

Mammalian Target of Rapamycin Inhibition in Trypanosoma cruzi-Infected Macrophages Leads to an Intracellular Profile That Is Detrimental for Infection

The causative agent of Chagas’ disease, Trypanosoma cruzi, affects approximately 10 million people living mainly in Latin America, with macrophages being one of the first cellular actors confronting the invasion during T. cruzi infection and their function depending on their proper activation and polarization into distinct M1 and M2 subtypes. Macrophage polarization is thought to be regulated not only by cytokines and growth factors but also by environmental signals. The metabolic checkpoint kinase mammalian target of rapamycin (mTOR)-mediated sensing of environmental and metabolic cues influences macrophage polarization in a complex and as of yet incompletely understood manner. Here, we studied the role of the mTOR pathway in macrophages during T. cruzi infection. We demonstrated that the parasite activated mTOR, which was beneficial for its replication since inhibition of mTOR in macrophages by different inhibitors decreased parasite replication. Moreover, in rapamycin pretreated and infected macrophages, we observed a decreased arginase activity and expression, reduced IL-10 and increased interleukin-12 production, compared to control infected macrophages treated with DMSO. Surprisingly, we also found a reduced iNOS activity and expression in these macrophages. Therefore, we investigated possible alternative mechanisms involved in controlling parasite replication in rapamycin pretreated and infected macrophages. Although, cytoplasmic ROS and the enzyme indoleamine 2, 3-dioxygenase (IDO) were not involved, we observed a significant increase in IL-6, TNF-α, and IL-1β production. Taking into account that IL-1β is produced by activation of the cytoplasmic receptor NLRP3, which is one of the main components of the inflammasome, we evaluated NLRP3 expression during mTOR inhibition and T. cruzi infection. We observed that rapamycin-pretreated and infected macrophages showed a significant increase in NLRP3 expression and produced higher levels of mitochondrial ROS (mtROS) compared with control cells. Moreover, inhibition of mtROS production partially reversed the effect of rapamycin on parasite replication, with there being a significant increase in parasite load in rapamycin pretreated and infected macrophages from NLRP3 KO mice compared to wild-type control cells. Our findings strongly suggest that mTOR inhibition during T. cruzi infection induces NLRP3 inflammasome activation and mtROS production, resulting in an inflammatory-like macrophage profile that controls T. cruzi replication.

New Insights into the Immunobiology of Mononuclear Phagocytic Cells and Their Relevance to the Pathogenesis of Cardiovascular Diseases

Macrophages are the primary immune cells that reside within the myocardium, suggesting that these mononuclear phagocytes are essential in the orchestration of cardiac immunity and homeostasis. Independent of the nature of the injury, the heart triggers leukocyte activation and recruitment. However, inflammation is harmful to this vital terminally differentiated organ with extremely poor regenerative capacity. As such, cardiac tissue has evolved particular strategies to increase the stress tolerance and minimize the impact of inflammation. In this sense, growing evidences show that mononuclear phagocytic cells are particularly dynamic during cardiac inflammation or infection and would actively participate in tissue repair and functional recovery. They respond to soluble mediators such as metabolites or cytokines, which play central roles in the timing of the intrinsic cardiac stress response. During myocardial infarction two distinct phases of monocyte influx have been identified. Upon infarction, the heart modulates its chemokine expression profile that sequentially and actively recruits inflammatory monocytes, first, and healing monocytes, later. In the same way, a sudden switch from inflammatory macrophages (with microbicidal effectors) toward anti-inflammatory macrophages occurs within the myocardium very shortly after infection with Trypanosoma cruzi, the causal agent of Chagas cardiomyopathy. While in sterile injury, healing response is necessary to stop tissue damage; during an intracellular infection, the anti-inflammatory milieu in infected hearts would promote microbial persistence. The balance of mononuclear phagocytic cells seems to be also dynamic in atherosclerosis influencing plaque initiation and fate. This review summarizes the participation of mononuclear phagocyte system in cardiovascular diseases, keeping in mind that the immune system evolved to promote the reestablishment of tissue homeostasis following infection/injury, and that the effects of different mediators could modulate the magnitude and quality of the immune response. The knowledge of the effects triggered by diverse mediators would serve to identify new therapeutic targets in different cardiovascular pathologies.

15-Deoxy-Δ12,14-Prostaglandin J2 Exerts Proresolving Effects Through Nuclear Factor E2-Related Factor 2-Induced Expression of CD36 and Heme Oxygenase-1

AIMS

15-Deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) has been shown to rescue cells from inflammatory insults and to participate in the resolution of acute inflammation. In this study, we investigated molecular mechanisms underlying proresolving effects of 15d-PGJ₂.

RESULTS

15d-PGJ₂ injected into the peritoneum of mice facilitated the resolution of zymosan A-induced peritonitis. 15d-PGJ₂ administration reduced the number of total leukocytes and attenuated polymorphonuclear leukocyte infiltration. Furthermore, 15d-PGJ₂ increased the proportion of macrophages engulfing apoptotic neutrophils, a process called efferocytosis. In addition, when the thioglycollate-elicited mouse peritoneal macrophages were stimulated with 15d-PGJ₂, their efferocytic activity was amplified. In another experiment, RAW264.7 murine macrophages exposed to 15d-PGJ₂ conducted phagocytic clearance of apoptotic cells to a greater extent than the control cells. Under these conditions, expression of CD36 and heme oxygenase-1 (HO-1) was enhanced along with increased accumulation of the nuclear factor E2-related factor 2 (Nrf2) in the nucleus. Knockdown of Nrf2 abolished 15d-PGJ₂-induced expression of CD36 and HO-1, and silencing of CD36 and HO-1 attenuated 15d-PGJ₂-induced efferocytosis. Moreover, peritoneal macrophages isolated from Nrf2-null mice failed to upregulate 15d-PGJ₂-induced expression of CD36 and HO-1 and to mediate efferocytosis. Unlike 15d-PGJ₂, its nonelectrophilic analog 9,10-dihydro-15d-PGJ₂ lacking the α,β-unsaturated carbonyl group could not induce CD36 expression and efferocytosis.

INNOVATION

15d-PGJ₂, as one of the terminal products of cyclooxygenase-2, exerts proresolving effects through induction of efferocytosis. The results of this study suggest that 15d-PGJ₂ possesses a therapeutic value in the management of inflammatory disorders.

CONCLUSION

15d-PGJ₂ facilitates resolution of inflammation by inducing Nrf2-induced expression of CD36 and HO-1 in macrophages. Antioxid. Redox Signal. 27, 1412-1431.

Therapeutic effects of sphingosine kinase inhibitor N,N-dimethylsphingosine (DMS) in experimental chronic Chagas disease cardiomyopathy

Chagas disease cardiomyopathy is a parasite-driven inflammatory disease to which there are no effective treatments. Here we evaluated the therapeutic potential of N,N-dimethylsphingosine(DMS), which blocks the production of sphingosine-1-phosphate(S1P), a mediator of cellular events during inflammatory responses, in a model of chronic Chagas disease cardiomyopathy. DMS-treated, Trypanosoma cruzi-infected mice had a marked reduction of cardiac inflammation, fibrosis and galectin-3 expression when compared to controls. Serum concentrations of galectin-3, IFNγ and TNFα, as well as cardiac gene expression of inflammatory mediators were reduced after DMS treatment. The gene expression of M1 marker, iNOS, was decreased, while the M2 marker, arginase1, was increased. DMS-treated mice showed an improvement in exercise capacity. Moreover, DMS caused a reduction in parasite load in vivo. DMS inhibited the activation of lymphocytes, and reduced cytokines and NO production in activated macrophage cultures in vitro, while increasing IL-1β production. Analysis by qRT-PCR array showed that DMS treatment modulated inflammasome activation induced by T. cruzi on macrophages. Altogether, our results demonstrate that DMS, through anti-parasitic and immunomodulatory actions, can be beneficial in the treatment of chronic phase of T. cruzi infection and suggest that S1P-activated processes as possible therapeutic targets for the treatment of Chagas disease cardiomyopathy.

NLRP3 inflammasome activation in murine macrophages caused by Neospora caninum infection

Background

Neospora caninum is an intracellular parasite that causes significant economic losses in cattle industry. Understanding the host resistance mechanisms in the innate immune response to neosporosis could facilitate the exploration of approaches for controlling N. caninum infection. The NLR inflammasome is a multiprotein platform in the cell cytoplasm and plays critical roles in the host response against microbes.

Methods

Neospora caninum-infected wild-type (WT) macrophages and Nlrp3^−/− macrophages, and inhibitory approaches were used to investigate inflammasome activation and its role in N. caninum infection. Inflammasome RT Profiler PCR Arrays were used to identify the primary genes involved in N. caninum infection. The expression of the sensor protein NLRP3, processing of caspase-1, secretion of IL-1β and cell death were detected. Neospora caninum replication in macrophages was also assessed.

Results

Many NLR molecules participated in the recognition of N. caninum, especially the sensor protein NLRP3, and further study revealed that the NLRP3 distribution became punctate in the cell cytoplasm, which facilitated inflammasome activation. Inflammasome activation-mediated caspase-1 processing and IL-1β cleavage in response to N. caninum infection were observed and were correlated with the time of infection and number of infecting parasites. LDH-related cell death was also observed, and this death was regarded as beneficial for the clearance of N. caninum. Treatment of N. caninum-infected macrophages with caspase-1, pan-caspase and NLRP3 inhibitors led to the impaired release of active IL-1β and a failure to restrict parasite replication. And Neospora caninum infected peritoneal macrophages from Nlrp3-deficient mice displayed greatly decreased release of active IL-1β and the failure of caspase-1 cleavage.

Conclusions

The NLRP3 inflammasome can be activated in N. caninum-infected macrophages, and plays a protective role in the host response to control N. caninum.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2197-2) contains supplementary material, which is available to authorized users.

Gene Expression Profiling and Functional Characterization of Macrophages in Response to Circulatory Microparticles Produced during Trypanosoma cruzi Infection and Chagas Disease

BACKGROUND

Chronic inflammation and oxidative stress are hallmarks of chagasic cardiomyopathy (CCM). In this study, we determined if microparticles (MPs) generated during Trypanosoma cruzi (Tc) infection carry the host's signature of the inflammatory/oxidative state and provide information regarding the progression of clinical disease.

METHODS

MPs were harvested from supernatants of human peripheral blood mononuclear cells in vitro incubated with Tc (control: LPS treated), plasma of seropositive humans with a clinically asymptomatic (CA) or symptomatic (CS) disease state (vs. normal/healthy [NH] controls), and plasma of mice immunized with a protective vaccine before challenge infection (control: unvaccinated/infected). Macrophages (mφs) were incubated with MPs, and we probed the gene expression profile using the inflammatory signaling cascade and cytokine/chemokine arrays, phenotypic markers of mφ activation by flow cytometry, cytokine profile by means of an ELISA and Bioplex assay, and oxidative/nitrosative stress and mitotoxicity by means of colorimetric and fluorometric assays.

RESULTS

Tc- and LPS-induced MPs stimulated proliferation, inflammatory gene expression profile, and nitric oxide (∙NO) release in human THP-1 mφs. LPS-MPs were more immunostimulatory than Tc-MPs. Endothelial cells, T lymphocytes, and mφs were the major source of MPs shed in the plasma of chagasic humans and experimentally infected mice. The CS and CA (vs. NH) MPs elicited >2-fold increase in NO and mitochondrial oxidative stress in THP-1 mφs; however, CS (vs. CA) MPs elicited a more pronounced and disease-state-specific inflammatory gene expression profile (IKBKB, NR3C1, and TIRAP vs. CCR4, EGR2, and CCL3), cytokine release (IL-2 + IFN-γ > GCSF), and surface markers of mφ activation (CD14 and CD16). The circulatory MPs of nonvaccinated/infected mice induced 7.5-fold and 40% increases in ∙NO and IFN-γ production, respectively, while these responses were abolished when RAW264.7 mφs were incubated with circulatory MPs of vaccinated/infected mice.

CONCLUSION

Circulating MPs reflect in vivo levels of an oxidative, nitrosative, and inflammatory state, and have potential utility in evaluating disease severity and the efficacy of vaccines and drug therapies against CCM.

Macrophages Promote Oxidative Metabolism To Drive Nitric Oxide Generation in Response to Trypanosoma cruzi

Trypanosoma cruzi is the causative agent of chronic chagasic cardiomyopathy. Why macrophages (mφs), the early responders to infection, fail to achieve parasite clearance is not known. Mouse (RAW 264.7) and human (THP-1 and primary) mφs were infected for 3 h and 18 h with T. cruzi TcI isolates, SylvioX10/4 (SYL, virulent) and TCC (nonpathogenic), which represent mφ stimulation and infection states, respectively. Mφs incubated with lipopolysaccharide and gamma interferon (LPS/IFN-γ) and with interleukin-4 (IL-4) were used as controls. We monitored the cytokine profile (using enzyme-linked immunosorbent assay [ELISA]), reactive oxygen species (ROS; fluorescent probes), nitric oxide (·NO; Griess assay), and metabolic state using a custom-designed mitoxosome array and Seahorse XF24 Analyzer. LPS/IFN-γ treatment of mφs elicited a potent increase in production of tumor necrosis alpha (TNF-α) at 3 h and of ROS and ·NO by 18 h. Upon SYL infection, murine mφs elicited an inflammatory cytokine profile (TNF-α ≫ TGF-β + IL-10) and low levels of ·NO and ROS production. LPS/IFN-γ treatment resulted in the inhibition of oxidative metabolism at the gene expression and functional levels and a switch to the glycolytic pathway in mφs, while IL-4-treated mφs utilized oxidative metabolism to meet energy demands. SYL infection resulted in an intermediate functional metabolic state with increased mitoxosome gene expression and glycolysis, and IFN-γ addition shut down the oxidative metabolism in SYL-infected mφs. Further, TCC- and SYL-stimulated mφs exhibited similar levels of cell proliferation and production of TNF-α and ROS, while TCC-stimulated mφs exhibited up to 2-fold-higher levels of oxidative metabolism and ·NO production than SYL-infected mφs. Inhibiting ATP-coupled O₂ consumption suppressed the ·NO generation in SYL-infected mφs. Mitochondrial oxygen consumption constitutes a mechanism for stimulating ·NO production in mφs during T. cruzi infection. Enhancing the oxidative metabolism provides an opportunity for increased ·NO production and pathogen clearance by mφs to limit disease progression.

Differential inflammasome activation signatures following intracellular infection of human macrophages with Mycobacterium bovis BCG or Trypanosoma cruzi

Pathogens frequently exploit or evade inflammasome activation in order to survive and proliferate. Alternatively, inadequate inflammasome activation by attenuated microorganisms or adjuvanted subunit vaccines may contribute to poor longevity of protection. To further understand these pathways, we determined the differential inflammasome transcriptome of human THP monocyte-derived macrophages in response to Mycobacterium bovis BCG, as compared to LPS or Trypanosoma cruzi. The results identify the highly specific innate recognition programs associated with inflammasome activation by human macrophages exposed to these microbial stimuli. BCG, T. cruzi, and LPS strongly induced expression of both unique and overlapping genes downstream of TLR signaling pathways including cytokines and chemokines that mediate inflammation and regulate cell death pathways. Compared to LPS, BCG failed to directly activate anti-apoptotic molecules and multiple NLR and inflammasome complex components including caspase-1, and actively repressed important signaling intermediates in AP-1 and NFκB transcription factor pathways. Both BCG and T. cruzi repressed expression of TXNIP, an anti-oxidant inhibitor that recruits caspase-1 to the NLRP3 inflammasome, while T. cruzi infection uniquely failed to activate TNF-α. These results identify unique pathogen specific strategies to activate inflammation and modulate cell death that may drive inflammatory outcomes and suggest avenues of investigation to optimize host immunity.

S-Nitrosylation Proteome Profile of Peripheral Blood Mononuclear Cells in Human Heart Failure

Nitric oxide (NO) protects the heart against ischemic injury; however, NO- and superoxide-dependent S-nitrosylation (S-NO) of cysteines can affect function of target proteins and play a role in disease outcome. We employed 2D-GE with thiol-labeling FL-maleimide dye and MALDI-TOF MS/MS to capture the quantitative changes in abundance and S-NO proteome of HF patients (versus healthy controls, n = 30/group). We identified 93 differentially abundant (59-increased/34-decreased) and 111 S-NO-modified (63-increased/48-decreased) protein spots, respectively, in HF subjects (versus controls, fold-change | ≥1.5|, p ≤ 0.05). Ingenuity pathway analysis of proteome datasets suggested that the pathways involved in phagocytes' migration, free radical production, and cell death were activated and fatty acid metabolism was decreased in HF subjects. Multivariate adaptive regression splines modeling of datasets identified a panel of proteins that will provide >90% prediction success in classifying HF subjects. Proteomic profiling identified ATP-synthase, thrombospondin-1 (THBS1), and vinculin (VCL) as top differentially abundant and S-NO-modified proteins, and these proteins were verified by Western blotting and ELISA in different set of HF subjects. We conclude that differential abundance and S-NO modification of proteins serve as a mechanism in regulating cell viability and free radical production, and THBS1 and VCL evaluation will potentially be useful in the prediction of heart failure.

Allicin prevents oxidized low-density lipoprotein-induced endothelial cell injury by inhibiting apoptosis and oxidative stress pathway

Background

Vascular endothelial apoptosis is significantly associated with atherosclerosis and cardiovascular diseases, for which oxidized low-density lipoprotein (ox-LDL) is a major risk factor. Allicin, the primary active ingredient of garlic, has been found to have cardiovascular protective effect by changing the fatty-acid composition, but its effect on ox-LDL-induced vascular endothelial injury remains unclear. We investigated the protective effect of allicin on cell viability, LDH release, apoptosis and apoptotic signaling in human umbilical vein endothelial cells (HUVECs).

Methods

In cultured HUVEC cell line, ox-LDL induced injury was investigated. The cell viability and injury were evaluated by using cell proliferation Assay kit and LDH release assay. The apoptosis was evaluated by the Annexin V-FITC kit. The activity of caspase-3 was assessed using a colorimetric caspase-3 assay kit. The ROS production was evaluated by fluorometric assay and NADPH oxidase activity was assessed with a GENMED kit.

Results

Exposure of HUVECs to ox-LDL (150 μg/ml) reduced cell viability, induced apoptosis and increased activity of caspase-3, NADPH oxidase, and reactive oxygen species (ROS) production. The pretreatment with allicin (30 and 100 μM) significantly rescued the cell viability, inhibited ox-LDL-induced apoptosis and activity of caspase-3, NADPH oxidase and ROS production in HUVECs, and the protective effect is concentration-dependent. The allicin (100 μM) alone did not show significant difference from control. Our study demonstrated that allicin protected HUVECs from ox-LDL-induced endothelial injury by reducing the apoptosis, mediated by inhibition of caspase-3 and NADPH oxidase related apoptotic signaling.

Conclusions

Allicin prevents ox-LDL-induced endothelial cell injury by inhibiting apoptosis and oxidative stress pathway.

The Reactive Oxygen Species in Macrophage Polarization: Reflecting Its Dual Role in Progression and Treatment of Human Diseases

High heterogeneity of macrophage is associated with its functions in polarization to different functional phenotypes depending on environmental cues. Macrophages remain in balanced state in healthy subject and thus macrophage polarization may be crucial in determining the tissue fate. The two distinct populations, classically M1 and alternatively M2 activated, representing the opposing ends of the full activation spectrum, have been extensively studied for their associations with several disease progressions. Accumulating evidences have postulated that the redox signalling has implication in macrophage polarization and the key roles of M1 and M2 macrophages in tissue environment have provided the clue for the reasons of ROS abundance in certain phenotype. M1 macrophages majorly clearing the pathogens and ROS may be crucial for the regulation of M1 phenotype, whereas M2 macrophages resolve inflammation which favours oxidative metabolism. Therefore how ROS play its role in maintaining the homeostatic functions of macrophage and in particular macrophage polarization will be reviewed here. We also review the biology of macrophage polarization and the disturbance of M1/M2 balance in human diseases. The potential therapeutic opportunities targeting ROS will also be discussed, hoping to provide insights for development of target-specific delivery system or immunomodulatory antioxidant for the treatment of ROS-related diseases.

Changes in Proteome Profile of Peripheral Blood Mononuclear Cells in Chronic Chagas Disease

Trypanosoma cruzi (Tc) infection causes chagasic cardiomyopathy; however, why 30-40% of the patients develop clinical disease is not known. To discover the pathomechanisms in disease progression, we obtained the proteome signature of peripheral blood mononuclear cells (PBMCs) of normal healthy controls (N/H, n = 30) and subjects that were seropositive for Tc-specific antibodies, but were clinically asymptomatic (C/A, n = 25) or clinically symptomatic (C/S, n = 28) with cardiac involvement and left ventricular dysfunction. Protein samples were labeled with BODIPY FL-maleimide (dynamic range: > 4 orders of magnitude, detection limit: 5 f-mol) and resolved by two-dimensional gel electrophoresis (2D-GE). After normalizing the gel images, protein spots that exhibited differential abundance in any of the two groups were analyzed by mass spectrometry, and searched against UniProt human database for protein identification. We found 213 and 199 protein spots (fold change: |≥ 1.5|, p< 0.05) were differentially abundant in C/A and C/S individuals, respectively, with respect to N/H controls. Ingenuity Pathway Analysis (IPA) of PBMCs proteome dataset identified an increase in disorganization of cytoskeletal assembly and recruitment/activation and migration of immune cells in all chagasic subjects, though the invasion capacity of cells was decreased in C/S individuals. IPA predicted with high probability a decline in cell survival and free radical scavenging capacity in C/S (but not C/A) subjects. The MYC/SP1 transcription factors that regulate hypoxia and oxidative/inflammatory stress were predicted to be key targets in the context of control of Chagas disease severity. Further, MARS-modeling identified a panel of proteins that had >93% prediction success in classifying infected individuals with no disease and those with cardiac involvement and LV dysfunction. In conclusion, we have identified molecular pathways and a panel of proteins that could aid in detecting seropositive individuals at risk of developing cardiomyopathy.