Protective role of IL33 signaling in negative pregnancy outcomes associated with lipopolysaccharide exposure

IL-33 Signaling Inhibition Leads to a Preeclampsia-Like Phenotype in Pregnant Rats

PROBLEM

Preeclampsia (PE) is a hypertensive pregnancy disorder that is a leading cause of maternal and fetal morbidity and mortality characterized by maternal vascular dysfunction, oxidative stress, chronic immune activation, and excessive inflammation. No cure exists beyond delivery of the fetal-placental unit and the mechanisms driving pathophysiology are not fully understood. However, aberrant immune responses have been extensively characterized in clinical studies and shown to mediate PE pathophysiology in animal studies. One pathway that may mediate aberrant immune responses in PE is deficiencies in the IL-33 signaling pathway. In this study, we aim to investigate the impact of IL-33 signaling inhibition on cNK, TH17, and TReg populations, vascular function, and maternal blood pressure during pregnancy.

METHOD OF STUDY

In this study, IL-33 signaling was inhibited using two different methods: intraperitoneal administration of recombinant ST2 (which acts as a decoy receptor for IL-33) and administration of a specific IL-33 neutralizing antibody. Maternal blood pressure, uterine artery resistance index, renal and placental oxidative stress, cNK, TH17, and TReg populations, various cytokines, and pre-proendothelin-1 levels were measured.

RESULTS

IL-33 signaling inhibition increased maternal blood pressure, uterine artery resistance, placental and renal oxidative stress. IL-33 signaling inhibition also increased placental cNK and TH17 and renal TH17 cells while decreasing placental TReg populations. IL-33 neutralization increased circulating cNK and TH17s and decreased circulating TRegs in addition to increasing pre-proendothelin-1 levels.

CONCLUSIONS

Data presented in this study demonstrate a role for IL-33 signaling in controlling vascular function and maternal blood pressure during pregnancy possibly by mediating innate and adaptive immune inflammatory responses, identifying the IL-33 signaling pathway as a potential therapeutic target for managing preeclampsia.

IL-33 supplementation improves uterine artery resistance and maternal hypertension in response to placental ischemia

Preeclampsia (PE), a leading cause of maternal/fetal morbidity and mortality, is a hypertensive pregnancy disorder with end-organ damage that manifests after 20 wk of gestation. PE is characterized by chronic immune activation and endothelial dysfunction. Clinical studies report reduced IL-33 signaling in PE. We use the Reduced Uterine Perfusion Pressure (RUPP) rat model, which mimics many PE characteristics including reduced IL-33, to identify mechanisms mediating PE pathophysiology. We hypothesized that IL-33 supplementation would improve blood pressure (BP), inflammation, and oxidative stress (ROS) during placental ischemia. We implanted intraperitoneal mini-osmotic pumps infusing recombinant rat IL-33 (1 µg/kg/day) into normal pregnant (NP) and RUPP rats from gestation day 14 to 19. We found that IL-33 supplementation in RUPP rats reduces maternal blood pressure and improves the uterine artery resistance index (UARI). In addition to physiological improvements, we found decreased circulating and placental cytolytic Natural Killer cells (cNKs) and decreased circulating, placental, and renal TH17s in IL-33-treated RUPP rats. cNK cell cytotoxic activity also decreased in IL-33-supplemented RUPP rats. Furthermore, renal ROS and placental preproendothelin-1 (PPET-1) decreased in RUPP rats treated with IL-33. These findings demonstrate a role for IL-33 in controlling vascular function and maternal BP during pregnancy by decreasing inflammation, renal ROS, and PPET-1 expression. These data suggest that IL-33 may have therapeutic potential in managing PE.NEW & NOTEWORTHY Though decreased IL-33 signaling has been clinically associated with PE, the mechanisms linking this signaling pathway to overall disease pathophysiology are not well understood. This study provides compelling evidence that mechanistically links reduced IL-33 with the inflammatory response and vascular dysfunction observed in response to placental ischemia, such as in PE. Data presented in this study submit the IL-33 signaling pathway as a possible therapeutic target for the treatment of PE.

Ingenuity pathway analysis of gingival epithelial cells stimulated with estradiol and progesterone

OBJECTIVE

Periodontal disease is a risk factor for preterm delivery, and elevated female hormone levels during pregnancy promote hormone-dependent periodontopathogenic bacterial growth and gingivitis. Although the saliva of pregnant women contains female hormones at elevated levels, their effects on the gingiva are poorly understood. Therefore, in this study, we investigated the effects of estradiol and progesterone stimulation on gingival epithelial cells via ingenuity pathway analysis.

METHODS

Human gingival epithelial progenitors were cultured in a CnT-Prime medium; 17β-estradiol (E2) and progesterone (P4) were used as the reagents. Cells treated with dimethyl sulfoxide alone were used as the control group. Cells in the control and experimental groups were incubated for 12 h. RNA was extracted from the cultured cells, RNA-Seq was performed, and pathway analysis was conducted.

RESULTS

Differentially expressed genes were detected for 699 (over 2-fold increase) and 348 (decrease) genes in group E2 and for 1448 (increase) and 924 (decrease) genes in group P4 compared with those in the control group (FDR <0.05, n = 4). The z-scores of the pathways suggest that E2 and P4 increased the activity of the wound healing signaling pathway. The activation of this pathway was higher in the E2 and P4 groups than that in the control group.

CONCLUSIONS

The results of this study suggest that estradiol and progesterone may affect gingival homeostasis and wound healing.

Conditionally mutant animal model for investigating the invasive trophoblast cell lineage

Placental development involves coordinated expansion and differentiation of trophoblast cell lineages possessing specialized functions. Among the differentiated trophoblast cell lineages are invasive trophoblast cells, which exit the placenta and invade the uterus, where they restructure the uterine parenchyma and facilitate remodeling of uterine spiral arteries. The rat exhibits deep intrauterine trophoblast cell invasion, a feature shared with human placentation, and is also amenable to gene manipulation using genome-editing techniques. In this investigation, we generated a conditional rat model targeting the invasive trophoblast cell lineage. Prolactin family 7, subfamily b, member 1 (Prl7b1) is uniquely and abundantly expressed in the rat invasive trophoblast cell lineage. Disruption of Prl7b1 did not adversely affect placental development. We demonstrated that the Prl7b1 locus could be effectively used to drive the expression of Cre recombinase in invasive trophoblast cells. Our rat model represents a new tool for investigating candidate genes contributing to the regulation of invasive trophoblast cells and their roles in trophoblast-guided uterine spiral artery remodeling.

Paternal lipopolysaccharide exposure induced intrauterine growth restriction via the inactivation of placental MEST/PI3K/AKT pathway in mice

Maternal lipopolysaccharide (LPS) exposure during pregnancy has been related to IUGR. Here, we explored whether paternal LPS exposure before mating impaired fetal development. All male mice except controls were intraperitoneally injected with LPS every other day for a total of five injections. The next day after the last LPS, male mice were mated with untreated female mice. Interestingly, fetal weight and crown-rump length were reduced, while the incidence of IUGR was increased in paternal LPS exposure group. Additionally, paternal LPS exposure leaded to poor placental development through causing cell proliferation inhibition and apoptosis. Additional experiment demonstrated that the inactivation of placental PI3K/AKT pathway might be involved in paternal LPS-induced cell proliferation inhibition and apoptosis of trophoblast cells. Furthermore, the mRNA and protein levels of mesoderm specific transcript (MEST), a maternally imprinted gene with paternal expression, were significantly decreased in mouse placentas from paternal LPS exposure. Further analysis showed that paternal LPS exposure caused the inactivation of placental PI3K/AKT pathway and then cell proliferation inhibition and apoptosis might be via down-regulating placental MEST. Overall, our results provide evidence that paternal LPS exposure causes poor placental development and subsequently IUGR may be via down-regulating MEST/PI3K/AKT pathway, and then inducing cell proliferation inhibition and apoptosis in placentas.

The Reparative Roles of IL-33

When discovered in the early 2000s, interleukin-33 (IL-33) was characterized as a potent driver of type 2 immunity and implicated in parasite clearance, as well as asthma, allergy, and lung fibrosis. Yet research in other models has since revealed that IL-33 is a highly pleiotropic molecule with diverse functions. These activities are supported by elusive release mechanisms and diverse expression of the IL-33 receptor, STimulation 2 (ST2), on both immune and stromal cells. Interestingly, IL-33 also supports type 1 immune responses during viral and tumor immunity and after allogeneic hematopoietic stem cell transplantation. Yet the IL-33-ST2 axis is also critical to the establishment of systemic homeostasis and tissue repair and regeneration. Despite these recent findings, the mechanisms by which IL-33 governs the balance between immunity and homeostasis or can support both effective repair and pathogenic fibrosis are poorly understood. As such, ongoing research is trying to understand the potential reparative and regulatory versus pro-inflammatory and pro-fibrotic roles for IL-33 in transplantation. This review provides an overview of the emerging regenerative role of IL-33 in organ homeostasis and tissue repair as it relates to transplantation immunology. It also outlines the known impacts of IL-33 in commonly transplanted solid organs and covers the envisioned roles for IL-33 in ischemia-reperfusion injury, rejection, and tolerance. Finally, we give a comprehensive summary of its effects on different cell populations involved in these processes, including ST2 + regulatory T cells, innate lymphoid cell type 2, as well as significant myeloid cell populations.

Conservation at the uterine-placental interface

The hemochorial placentation site is characterized by a dynamic interplay between trophoblast cells and maternal cells. These cells cooperate to establish an interface required for nutrient delivery to promote fetal growth. In the human, trophoblast cells penetrate deep into the uterus. This is not a consistent feature of hemochorial placentation and has hindered the establishment of suitable animal models. The rat represents an intriguing model for investigating hemochorial placentation with deep trophoblast cell invasion. In this study, we used single-cell RNA sequencing to characterize the transcriptome of the invasive trophoblast cell lineage, as well as other cell populations within the rat uterine-placental interface during early (gestation day [gd] 15.5) and late (gd 19.5) stages of intrauterine trophoblast cell invasion. We identified a robust set of transcripts that define invasive trophoblast cells, as well as transcripts that distinguished endothelial, smooth muscle, natural killer, and macrophage cells. Invasive trophoblast, immune, and endothelial cell populations exhibited distinct spatial relationships within the uterine-placental interface. Furthermore, the maturation stage of invasive trophoblast cell development could be determined by assessing gestation stage-dependent changes in transcript expression. Finally, and most importantly, expression of a prominent subset of rat invasive trophoblast cell transcripts is conserved in the invasive extravillous trophoblast cell lineage of the human placenta. These findings provide foundational data to identify and interrogate key conserved regulatory mechanisms essential for the development and function of an important compartment within the hemochorial placentation site that is essential for a healthy pregnancy.

Maternal IL-33 critically regulates tissue remodeling and type 2 immune responses in the uterus during early pregnancy in mice

The pregnant uterus is an immunologically rich organ, with dynamic changes in the inflammatory milieu and immune cell function underlying key stages of pregnancy. Recent studies have implicated dysregulated expression of the interleukin-1 (IL-1) family cytokine, IL-33, and its receptor, ST2, in poor pregnancy outcomes in women, including recurrent pregnancy loss, preeclampsia, and preterm labor. How IL-33 supports pregnancy progression in vivo is not well understood. Here, we demonstrate that maternal IL-33 signaling critically regulates uterine tissue remodeling and immune cell function during early pregnancy in mice. IL-33-deficient dams exhibit defects in implantation chamber formation and decidualization, and abnormal vascular remodeling during early pregnancy. These defects coincide with delays in early embryogenesis, increased resorptions, and impaired fetal and placental growth by late pregnancy. At a cellular level, myometrial fibroblasts, and decidual endothelial and stromal cells, are the main IL-33⁺ cell types in the uterus during decidualization and early placentation, whereas ST2 is expressed by uterine immune populations associated with type 2 immune responses, including ILC2s, Tregs, CD4⁺ T cells, M2- and cDC2-like myeloid cells, and mast cells. Early pregnancy defects in IL-33-deficient dams are associated with impaired type 2 cytokine responses by uterine lymphocytes and fewer Arginase-1⁺ macrophages in the uterine microenvironment. Collectively, our data highlight a regulatory network, involving crosstalk between IL-33-producing nonimmune cells and ST2⁺ immune cells at the maternal-fetal interface, that critically supports pregnancy progression in mice. This work has the potential to advance our understanding of how IL-33 signaling may support optimal pregnancy outcomes in women.

Modeling Trophoblast Cell-Guided Uterine Spiral Artery Transformation in the Rat

The rat possesses hemochorial placentation with deep intrauterine trophoblast cell invasion and trophoblast-guided uterine spiral artery remodeling, which resembles human placentation. Uterine spiral arteries are extensively remodeled to deliver sufficient supply of maternal blood and nutrients to the developing fetus. Inadequacies in these key processes negatively impact fetal growth and development. Recent innovations in genome editing combined with effective phenotyping strategies have provided new insights into placental development. Application of these research approaches has highlighted both conserved and species-specific features of hemochorial placentation. The review provides foundational information on rat hemochorial placental development and function during physiological and pathological states, especially as related to the invasive trophoblast cell-guided transformation of uterine spiral arteries. Our goal is to showcase the utility of the rat as a model for in vivo mechanistic investigations targeting regulatory events within the uterine-placental interface.

Inherent maternal type 2 immunity: Consequences for maternal and offspring health

An inherent elevation in type 2 immunity is a feature of maternal and offspring immune systems. This has diverse implications for maternal and offspring biology including influencing success of pregnancy, offspring immune development and maternal and offspring ability to control infection and diseases such as allergies. In this review we provide a broad insight into how this immunological feature of pregnancy and early life impacts both maternal and offspring biology. We also suggest how understanding of this axis of immune influence is and may be utilised to improve maternal and offspring health.