Toxoplasma gondii Dense Granule Antigen 1 stimulates apoptosis of monocytes through autocrine TGF-β signaling

Toxoplasma gondii activates NLRP12 inflammasome pathway in the BALB/c murine model

The host resistance against Toxoplasma gondii (T. gondii) infection is related to the initiation of the immune response. The study aimed to investigate the role of the leucine-rich repeat family, pyrin domain -containing protein 12 (NLRP12), and cytoplasmic nucleotide-binding domain in the inflammasome-mediated cell death during murine toxoplasmosis. Groups of BALB/c mice (n = 10) were inoculated intraperitoneally with live tachyzoites, excretory-secretory antigens (ESAs) of T. gondii RH strain, and RPMI. The gene expression levels of NLRP12, caspase-3, caspase-1, IL-1β, IL-18, ASC, and Bcl-2 were measured in the peritoneal cells using quantitative real-time PCR, while the determination of NLRP12 protein level was measured by Western blot. Also, the intracellular reactive oxygen species (ROS) production was investigated. Quantitative and comparative analyses showed that injection of tachyzoites significantly increased NLRP12, caspase-3, caspase-1, IL-1β, IL-18, and ASC genes mRNA expression levels (p<0.01). Contrary to the acute infection, the Bcl-2 gene was significantly expressed in the ESAs group (p<0.0001). The level of NLRP12 protein was significantly higher in the mice that received tachyzoites and ESAs in comparison to the control group (p<0.0001). These findings provide an inside into the host-T. gondii interaction and NLRP12 regulation, which is important for the modulation of the immunological response.

BEWO trophoblast cells and Toxoplasma gondii infection modulate cell death mechanisms in THP-1 monocyte cells by interference in the expression of death receptor and intracellular proteins

Crosstalk between trophoblast and monocytes is essential for gestational success, and it can be compromised in congenital toxoplasmosis. Cell death is one of the mechanisms involved in the maintenance of pregnancy, and this study aimed to evaluate the role of trophoblast in the modulation of monocyte cell death in the presence or absence of Toxoplasma gondii infection. THP-1 cells were stimulated with supernatants of BeWo cells and then infected or not with T. gondii. The supernatants were collected and analyzed for the secretion of human Fas ligand, and cells were used to determine cell death and apoptosis, cell death receptor, and intracellular proteins expression. Cell death and apoptosis index were higher in uninfected THP-1 cells stimulated with supernatants of BeWo cells; however, apoptosis index was reduced by T. gondii infection. Macrophage migration inhibitory factor (MIF) and transforming growth factor (TGF)-β1, secreted by BeWo cells, altered the cell death and apoptosis rates in THP-1 cells. In infected THP-1 cells, the expression of Fas/CD95 and secretion of FasL was significantly higher; however, caspase 3 and phosphorylated extracellular-signal-regulated kinase (ERK1/2) were downregulated. Results suggest that soluble factors secreted by BeWo cells induce cell death and apoptosis in THP-1 cells, and Fas/CD95 can be involved in this process. On the other hand, T. gondii interferes in the mechanism of cell death and inhibits THP-1 cell apoptosis, which can be associated with active caspase 3 and phosphorylated ERK1/2. In conclusion, our results showed that human BeWo trophoblast cells and T. gondii infection modulate cell death in human THP-1 monocyte cells.

The effects of FAR1 and TGFBRAP1 on the proliferation and apoptosis of follicular granulosa cells in goose (Anser cygnoides)

The low laying performance of geese seriously damages the growth of the poultry industry, and is related to the development of pre- hierarchical follicles. Our previous studies have revealed that FAR1 and TGFBRAP1 were involved in follicular development, but the exact regulation mechanism still kept unclear. In recent studies, the expression of FAR1 and TGFBRAP1 mRNA were detected, and we found that their expression levels were relatively higher in hierarchical follicles than in pre-hierarchical follicles (P < 0.05). Moreover, generally the level of FAR1 and TGFBRAP1 mRNA gradually increased in hierarchical follicles. In addition, the proliferation and apoptosis of granulosa cells were assayed with overexpression or knockdown technology. The results showed that by the knockdown of FAR1 mRNA level, the proliferation rate of follicular granulosa cells increased significantly, the apoptosis rate decreased (P < 0.05), and the apoptosis rate also reduced obviously by transfecting TGFBRAP1-siRNA (P < 0.05). Finally, the overexpression of FAR1 or TGFBRAP1 resulted in the inhabitation to the secretion of E2 and P4 in granulosa cells, while the knockdown of FAR1 or TGFBRAP1 enhanced the secretion of E2 and P4. In conclusion, the results indicated that FAR1 and TGFBRAP1 regulated the apoptosis of follicular granulosa cells and cut the secretion of E2 and P4 in geese, which provided basic data for the understanding of the regulating process of goose reproduction.

Transcriptomic analyses reveal distinct response of porcine macrophages to Toxoplasma gondii infection

Toxoplasma gondii is an obligate protozoan parasite infecting diverse hosts. Studies have demonstrated that different hosts respond differently to Toxoplasma infection. Pigs are among the most susceptible hosts of T. gondii, but the host-pathogen interactions that shape the outcome of infection in pigs are completely unknown. Here, we used dual RNA-seq to profile the transcriptomic changes of porcine alveolar macrophages (PAMs) upon Toxoplasma infection. Our results indicated that PAMs initiated different responses to Toxoplasma infection compared with mouse macrophages. First, although infected PAMs upregulated numerous pro-inflammatory factors, IL-12, which plays critical roles in IL-12~IFN-γ-mediated immunity against Toxoplasma infection in mice, was found unchanged during PAM infection. Second, the gene encoding iNOS that is responsible for nitric oxide (NO) production was also not induced in infected PAMs. Consistently, there was no NO level change in PAMs after infection. Third, it seems like Toxoplasma infection inhibited apoptosis in PAMs. On the parasite side, the most obvious change is the upregulation of genes involved in metabolism and macromolecule synthesis, such as the type II fatty acid synthesis in the apicoplast. Together, these results revealed distinct responses of PAMs to Toxoplasma infection and provide novel insights into Toxoplasma-pig interactions.

Downmodulation of Effector Functions in NK Cells upon Toxoplasma gondii Infection

The obligate intracellular parasite Toxoplasma gondii can actively infect any nucleated cell type, including cells from the immune system. The rapid transfer of T. gondii from infected dendritic cells to effector natural killer (NK) cells may contribute to the parasite's sequestration and shielding from immune recognition shortly after infection. However, subversion of NK cell functions, such as cytotoxicity or production of proinflammatory cytokines, such as gamma interferon (IFN-γ), upon parasite infection might also be beneficial to the parasite. In the present study, we investigated the effects of T. gondii infection on NK cells. In vitro, infected NK cells were found to be poor at killing target cells and had reduced levels of IFN-γ production. This could be attributed in part to the inability of infected cells to form conjugates with their target cells. However, even upon NK1.1 cross-linking of NK cells, the infected NK cells also exhibited poor degranulation and IFN-γ production. Similarly, NK cells infected in vivo were also poor at killing target cells and producing IFN-γ. Increased levels of transforming growth factor β production, as well as increased levels of expression of SHP-1 in the cytosol of infected NK cells upon infection, were observed in infected NK cells. However, the phosphorylation of STAT4 was not altered in infected NK cells, suggesting that transcriptional regulation mediates the reduced IFN-γ production, which was confirmed by quantitative PCR. These data suggest that infection of NK cells by T. gondii impairs NK cell recognition of target cells and cytokine release, two mechanisms that independently could enhance T. gondii survival.

Toxoplasma Modulates Signature Pathways of Human Epilepsy, Neurodegeneration & Cancer

One third of humans are infected lifelong with the brain-dwelling, protozoan parasite, Toxoplasma gondii. Approximately fifteen million of these have congenital toxoplasmosis. Although neurobehavioral disease is associated with seropositivity, causality is unproven. To better understand what this parasite does to human brains, we performed a comprehensive systems analysis of the infected brain: We identified susceptibility genes for congenital toxoplasmosis in our cohort of infected humans and found these genes are expressed in human brain. Transcriptomic and quantitative proteomic analyses of infected human, primary, neuronal stem and monocytic cells revealed effects on neurodevelopment and plasticity in neural, immune, and endocrine networks. These findings were supported by identification of protein and miRNA biomarkers in sera of ill children reflecting brain damage and T. gondii infection. These data were deconvoluted using three systems biology approaches: "Orbital-deconvolution" elucidated upstream, regulatory pathways interconnecting human susceptibility genes, biomarkers, proteomes, and transcriptomes. "Cluster-deconvolution" revealed visual protein-protein interaction clusters involved in processes affecting brain functions and circuitry, including lipid metabolism, leukocyte migration and olfaction. Finally, "disease-deconvolution" identified associations between the parasite-brain interactions and epilepsy, movement disorders, Alzheimer's disease, and cancer. This "reconstruction-deconvolution" logic provides templates of progenitor cells' potentiating effects, and components affecting human brain parasitism and diseases.

Pyrimidinergic Receptor Activation Controls Toxoplasma gondii Infection in Macrophages

Infection by the protozoan parasite Toxoplasma gondii is highly prevalent worldwide and may have serious clinical manifestations in immunocompromised patients. T. gondii is an obligate intracellular parasite that infects almost any cell type in mammalian hosts, including immune cells. The immune cells express purinergic P2 receptors in their membrane--subdivided into P2Y and P2X subfamilies--whose activation is important for infection control. Here, we examined the effect of treatment with UTP and UDP in mouse peritoneal macrophages infected with T. gondii tachyzoites. Treatment with these nucleotides reduced parasitic load by 90%, but did not increase the levels of the inflammatory mediators NO and ROS, nor did it modulate host cell death by apoptosis or necrosis. On the other hand, UTP and UDP treatments induced early egress of tachyzoites from infected macrophages, in a Ca2+-dependent manner, as shown by scanning electron microscopy analysis, and videomicroscopy. In subsequent infections, prematurely egressed parasites had reduced infectivity, and could neither replicate nor inhibit the fusion of lysosomes to the parasitophorous vacuole. The use of selective agonists and antagonists of the receptor subtypes P2Y2 and P2Y4 and P2Y6 showed that premature parasite egress may be mediated by the activation of these receptor subtypes. Our results suggest that the activity of P2Y host cell receptors controls T. gondii infection in macrophages, highlighting the importance of pyrimidinergic signaling for innate immune system response against infection. Finally the P2Y receptors should be considered as new target for the development of drugs against T. gondii infection.

Levels of Transforming Growth Factor-Beta After Immunization of Mice With in vivo prepared Toxoplasma gondii Excretory/Secretory Proteins

BACKGROUND

Zoonotic parasite Toxoplasma gondii has a high prevalence in human populations. A suitable vaccine for animals can stop the transmission of infection between animal and human.

OBJECTIVES

The aim of this study was to evaluate in vivo prepared excretory/secretory antigens (E/SA) as a potential candidate for immunization against the parasite and its effect on the production of transforming growth factor-beta (TGF-β).

MATERIALS AND METHODS

Toxoplasma gondii tachyzoites were inoculated in the peritoneal cavity of mice and E/SA was harvested and used in animal immunization with and without adjuvant. Serum levels of anti-E/SA antibodies and TGF-β were measured in days 0, 3, 7, 14, 28 and 56 after immunization using ELISA technique. The measurements were statistically analyzed.

RESULTS

Our results showed that the serum levels of anti-E/SA immunoglobulins significantly increased in all of the immunized groups. The differences of the serum levels of TGF-β between the groups were statistically significant at days 28 and 56 after immunization with E/SA.

CONCLUSIONS

Based on our study, in vivo prepared E/SA may be considered as a good candidate for animal immunization.

Involvement of PI 3 kinase/Akt-dependent Bad phosphorylation in Toxoplasma gondii-mediated inhibition of host cell apoptosis

Toxoplasma gondii-infected cells are resistant to various apoptotic stimuli, however, the role of the pro-apoptotic BH3-only Bad protein in T. gondii-imposed inhibition of host cell apoptosis in connection with the phosphoinositide 3-kinase (PI3K)-PKB/Akt pathway was not well delineated. Here, we investigated the signaling patterns of Bad, Bax and PKB/Akt in T. gondii-infected and uninfected THP-1 cells treated with staurosporine (STS) or PI3K inhibitors. STS treatment, without T. gondii infection, reduced the viability of THP-1 cells in proportion to STS concentration and triggered many cellular death events such as caspase-3 and -9 activation, Bax translocation, cytochrome c release from host cell mitochondria into cytosol, and PARP cleavage in the host cell. However, T. gondii infection eliminated the STS-triggered mitochondrial apoptotic events described above. Additionally, T. gondii infection in vitro and in vivo induced the phosphorylation of PKB/Akt and Bad in a parasite-load-dependent manner which subsequently inhibited Bax translocation. The PI3K inhibitors, LY294002 and Wortmannin, both blocked parasite-induced phosphorylation of PKB/Akt and Bad. Furthermore, THP-1 cells pretreated with these PI3K inhibitors showed reduced phosphorylation of Bad in a dose-dependent manner and subsequently failed to inhibit the Bax translocation, also these cells also failed to overcome the T. gondii-imposed inhibition of host cell apoptosis. These data demonstrate that the PI3K-PKB/Akt pathway may be one of the major route for T. gondii in the prevention of host cell apoptosis and T. gondii phosphorylates the pro-apoptotic Bad protein to prevent apoptosis.