B7-H4 reduction induced by Toxoplasma gondii infection results in dysfunction of decidual dendritic cells by regulating the JAK2/STAT3 pathway

Impact of the Immunomodulatory Factor Soluble B7-H4 in the Progress of Preeclampsia by Inhibiting Essential Functions of Extravillous Trophoblast Cells

A key aspect of preeclampsia pathophysiology is the reduced invasiveness of trophoblasts and the impairment of spiral artery remodelling. Understanding the causes of altered trophoblast function is critical to understand the development of preeclampsia. B7-H4, a checkpoint molecule, controls a wide range of processes, including T-cell activation, cytokine release, and tumour progression. Our previous findings indicated that B7-H4 levels are elevated in both maternal blood and placental villous tissue during the early stages of preeclampsia. Here, we investigated the function of B7-H4 in trophoblast physiology. Recombinant B7-H4 protein was used to treat human SGHPL-5 extravillous trophoblast cells. Biological functions were investigated using MTT, wound healing, and transwell assays. Signalling pathways were analysed by immunoblotting and immunofluorescence. The functionality of B7-H4 was further confirmed by immunoblotting and immunohistochemical analysis in placental tissues from control and preeclamptic patients following therapeutic plasma exchange (TPE) or standard of care treatment. This study showed that B7-H4 inhibited the proliferation, migration, and invasion capacities of SGHPL-5 extravillous cells while promoting apoptosis by downregulating the PI3K/Akt/STAT3 signalling pathway. These results were consistently confirmed in placental tissues from preterm controls compared to early-onset preeclamptic placental tissues from patients treated with standard of care or TPE treatment. B7-H4 may play a role in the development of preeclampsia by inhibiting essential functions of extravillous trophoblast cells during placental development. One possible mechanism by which TPE improves pregnancy outcomes in preeclampsia is through the elimination of B7-H4 amongst other factors.

Decidual natural killer cells dysfunction is caused by IDO downregulation in dMDSCs with Toxoplasma gondii infection

Myeloid-derived suppressor cells (MDSCs) play a crucial role in maintaining maternal-fetal tolerance by expressing some immune-suppressive molecules, such as indoleamine 2,3-dioxygenase (IDO). Toxoplasma gondii (T. gondii) infection can break the immune microenvironment of maternal-fetal interface, resulting in adverse pregnancy outcomes. However, whether T. gondii affects IDO expression in dMDSCs and the molecular mechanism of its effect are still unclear. Here we show, the mRNA level of IDO is increased but the protein level decreased in infected dMDSCs. Mechanistically, the upregulation of transcriptional levels of IDO in dMDSCs is regulated through STAT3/p52-RelB pathway and the decrease of IDO expression is due to its degradation caused by increased SOCS3 after T. gondii infection. In vivo, the adverse pregnancy outcomes of IDO-/- infected mice are more severe than those of wide-type infected mice and obviously improved after exogenous kynurenine treatment. Also, the reduction of IDO in dMDSCs induced by T. gondii infection results in the downregulation of TGF-β and IL-10 expression in dNK cells regulated through Kyn/AhR/SP1 signal pathway, eventually leading to the dysfunction of dNK cells and contributing the occurrence of adverse pregnancy outcomes. This study reveals a novel molecular mechanism in adverse pregnancy outcome induced by T. gondii infection.

Single-cell transcriptomic analysis of decidual immune cell landscape in the occurrence of adverse pregnancy outcomes induced by Toxoplasma gondii infection

BACKGROUND

Toxoplasma gondii is an obligate intracellular parasite that can lead to adverse pregnancy outcomes, particularly in early pregnancy. Previous studies have illustrated the landscape of decidual immune cells. However, the landscape of decidual immune cells in the maternal-fetal microenvironment during T. gondii infection remains unknown.

METHODS

In this study, we employed single-cell RNA sequencing to analyze the changes in human decidual immune cells following T. gondii infection. The results of scRNA-seq were further validated with flow cytometry, reverse transcription-polymerase chain reaction, western blot, and immunofluorescence staining.

RESULTS

Our results showed that the proportion of 17 decidual immune cell clusters and the expression levels of 21 genes were changed after T. gondii infection. Differential gene analysis demonstrated that T. gondii infection induced the differential expression of 279, 312, and 380 genes in decidual NK cells (dNK), decidual macrophages (dMφ), and decidual T cells (dT), respectively. Our results revealed for the first time that several previously unknown molecules in decidual immune cells changed following infection. This result revealed that the function of maternal-fetal immune tolerance declined, whereas the killing ability of decidual immune cells enhanced, eventually contributing to the occurrence of adverse pregnancy outcomes.

CONCLUSIONS

This study provides valuable resource for uncovering several novel molecules that play an important role in the occurrence of abnormal pregnancy outcomes induced by T. gondii infection.

Increased serum IL-12 levels are associated with adverse IVF outcomes

Interleukin-12 (IL-12) is involved in the occurrence and development of many diseases, such as preeclampsia, intrauterine growth restriction, preterm labor, and recurrent pregnancy losses. This study aimed to determine whether a high serum level of IL-12 was associated with adverse in vitro fertilization (IVF) outcomes. Included infertile women with high serum IL-12 levels who underwent IVF cycles and infertile controls with pure tubal etiology. The impact of serum IL-12 on baseline and clinical characteristics, immune-related indicators, IVF laboratory, and pregnancy outcomes were compared. In addition, the correlation of follicular fluid IL-12 and serum IL-12 level and the role of IL-12 in apoptosis of granulosa cells (GCs) was investigated. Women with high serum IL-12 levels had lower numbers of retrieved oocytes, embryos, perfect and available embryos, lower rates of perfect and available embryos, and blastocyst formation. Additionally, significantly higher levels of serum Th1, Th2, and Th17-related cytokines were observed in women with high serum IL-12 levels than in the controls. Meanwhile, the follicular fluid IL-12 levels were positively correlated with serum IL-12 levels, and IL-12 promoted apoptosis of GCs in vitro. We concluded that women with serum high IL-12 levels may have adverse IVF outcomes, partly by promoting apoptosis of GCs. Therefore, early screening for cytokines, especially IL-12, and appropriate consultation for couples receiving IVF-ET should be considered. In addition, specific immune and inflammatory mechanisms associated with high serum IL-12 levels should be further explored.

LILRB4 regulates the function of decidual MDSCs via the SHP-2/STAT6 pathway during Toxoplasma gondii infection

BACKGROUND

Toxoplasma gondii infection can cause adverse pregnancy outcomes, such as recurrent abortion, fetal growth restriction and infants with malformations, among others. Decidual myeloid-derived suppressor cells (dMDSCs) are a novel immunosuppressive cell type at the fetal-maternal interface which play an important role in sustaining normal pregnancy that is related to their high expression of the inhibitory molecule leukocyte immunoglobulin-like receptor B4 (LILRB4). It has been reported that the expression of LILRB4 is downregulated on decidual macrophages after T. gondii infection, but it remains unknown whether T. gondii infection can induce dMDSC dysfunction resulting from the change in LILRB4 expression.

METHODS

LILRB4-deficient (LILRB4^-/-) pregnant mice infected with T. gondii with associated adverse pregnancy outcomes, and anti-LILRB4 neutralized antibodies-treated infected human dMDSCs were used in vivo and in vitro experiments, respectively. The aim was to investigate the effect of LILRB4 expression on dMDSC dysfunction induced by T. gondii infection.

RESULTS

Toxoplasma gondii infection was observed to reduce STAT3 phosphorylation, resulting in decreased LILRB4 expression on dMDSCs. The levels of the main functional molecules (arginase-1 [Arg-1], interleukin-10 [IL-10]) and main signaling molecules (phosphorylated Src-homology 2 domain-containing protein tyrosine phosphatase [p-SHP2], phosphorylated signal transducer and activator of transcription 6 [p-STAT6]) in dMDSCs were all significantly reduced in human and mouse dMDSCs due to the decrease of LILRB4 expression induced by T. gondii infection. SHP-2 was found to directly bind to STAT6 and STAT6 to bind to the promoter of the Arg-1 and IL-10 genes during T. gondii infection.

CONCLUSIONS

The downregulation of LILRB4 expression on dMDSCs induced by T. gondii infection could regulate the expression of Arg-1 and IL-10 via the SHP-2/STAT6 pathway, resulting in the dysfunction of dMDSCs, which might contribute to adverse outcomes during pregnancy by T. gondii infection.

Modeling the human placental barrier to understand Toxoplasma gondii´s vertical transmission

Toxoplasma gondii is a ubiquitous apicomplexan parasite that can infect virtually any warm-blooded animal. Acquired infection during pregnancy and the placental breach, is at the core of the most devastating consequences of toxoplasmosis. T. gondii can severely impact the pregnancy’s outcome causing miscarriages, stillbirths, premature births, babies with hydrocephalus, microcephaly or intellectual disability, and other later onset neurological, ophthalmological or auditory diseases. To tackle T. gondii’s vertical transmission, it is important to understand the mechanisms underlying host-parasite interactions at the maternal-fetal interface. Nonetheless, the complexity of the human placenta and the ethical concerns associated with its study, have narrowed the modeling of parasite vertical transmission to animal models, encompassing several unavoidable experimental limitations. Some of these difficulties have been overcome by the development of different human cell lines and a variety of primary cultures obtained from human placentas. These cellular models, though extremely valuable, have limited ability to recreate what happens in vivo. During the last decades, the development of new biomaterials and the increase in stem cell knowledge have led to the generation of more physiologically relevant in vitro models. These cell cultures incorporate new dimensions and cellular diversity, emerging as promising tools for unraveling the poorly understood T. gondii´s infection mechanisms during pregnancy. Herein, we review the state of the art of 2D and 3D cultures to approach the biology of T. gondii pertaining to vertical transmission, highlighting the challenges and experimental opportunities of these up-and-coming experimental platforms.

Effect of B7-H4 downregulation induced by Toxoplasma gondii infection on dysfunction of decidual macrophages contributes to adverse pregnancy outcomes

BACKGROUND

Toxoplasma gondii infection during pregnancy can lead to fetal defect(s) or congenital complications. The inhibitory molecule B7-H4 expressed on decidual macrophages (dMφ) plays an important role in maternal-fetal tolerance. However, the effect of B7-H4 on the function of dMφ during T. gondii infection remains unclear.

METHODS

Changes in B7-H4 expression on dMφ after T. gondii infection were explored both in vivo and in vitro. B7-H4^-/- pregnant mice (pregnant mice with B7-H4 gene knockout) and purified primary human dMφ treated with B7-H4 neutralizing antibody were used to explore the role of B7-H4 signaling on regulating the membrane molecules, synthesis of arginine metabolic enzymes and cytokine production by dMφ with T. gondii infection. Also, adoptive transfer of dMφ from wild-type (WT) pregnant mice or B7-H4^-/- pregnant mice to infected B7-H4^-/- pregnant mice was used to examine the effect of B7-H4 on adverse pregnancy outcomes induced by T. gondii infection.

RESULTS

The results illustrated that B7-H4^-/- pregnant mice infected by T. gondii had poorer pregnancy outcomes than their wild-type counterparts. The expression of B7-H4 on dMφ significantly decreased after T. gondii infection, which resulted in the polarization of dMφ from the M2 toward the M1 phenotype by changing the expression of membrane molecules (CD80, CD86, CD163, CD206), synthesis of arginine metabolic enzymes (Arg-1, iNOS) and production of cytokines (IL-10, TNF-α) production. Also, we found that the B7-H4 downregulation after T. gondii infection increased iNOS and TNF-α expression mediated through the JAK2/STAT1 signaling pathway. In addition, adoptive transfer of dMφ from a WT pregnant mouse donor rather than from a B7-H4^-/- pregnant mouse donor was able to improve adverse pregnancy outcomes induced by T. gondii infection.

CONCLUSIONS

The results demonstrated that the downregulation of B7-H4 induced by T. gondii infection led to the dysfunction of decidual macrophages and contributed to abnormal pregnancy outcomes. Moreover, adoptive transfer of B7-H4⁺ dMφ could improve adverse pregnancy outcomes induced by T. gondii infection.

Tim-3 downregulation by Toxoplasma gondii infection contributes to decidual dendritic cell dysfunction

Background

Women in early pregnancy infected by Toxoplasma gondii may have severe adverse pregnancy outcomes, such as spontaneous abortion and fetal malformation. The inhibitory molecule T cell immunoglobulin and mucin domain 3 (Tim-3) is highly expressed on decidual dendritic cells (dDCs) and plays an important role in maintaining immune tolerance. However, whether T. gondii infection can cause dDC dysfunction by influencing the expression of Tim-3 and further participate in adverse pregnancy outcomes is still unclear.

Methods

An abnormal pregnancy model in Tim-3-deficient mice and primary human dDCs treated with Tim-3 neutralizing antibodies were used to examine the effect of Tim-3 expression on dDC dysfunction after T. gondii infection.

Results

Following T. gondii infection, the expression of Tim-3 on dDCs was downregulated, those of the pro-inflammatory functional molecules CD80, CD86, MHC-II, tumor necrosis factor-α (TNF-α), and interleukin-12 (IL-12) were increased, while those of the tolerant molecules indoleamine 2,3-dioxygenase (IDO) and interleukin-10 (IL-10) were significantly reduced. Tim-3 downregulation by T. gondii infection was closely associated with an increase in proinflammatory molecules and a decrease in tolerant molecules, which further resulted in dDC dysfunction. Moreover, the changes in Tim-3 induced by T. gondii infection further reduced the secretion of the cytokine IL-10 via the SRC-signal transducer and activator of transcription 3 (STAT3) pathway, which ultimately contributed to abnormal pregnancy outcomes.

Conclusions

Toxoplasma gondii infection can significantly downregulate the expression of Tim-3 and cause the aberrant expression of functional molecules in dDCs. This leads to dDC dysfunction, which can ultimately contribute to abnormal pregnancy outcomes. Further, the expression of the anti-inflammatory molecule IL-10 was significantly decreased by Tim-3 downregulation, which was mediated by the SRC-STAT3 signaling pathway in dDCs after T. gondii infection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05506-1.