Lipopolysaccharide and cAMP modify placental calcitriol biosynthesis reducing antimicrobial peptides gene expression

In Vitro Culturing of Human Trophoblasts from Term Placenta

Since the early 1960s, researchers began culturing placental cells to establish an in vitro model to study the biology of human trophoblasts, including their ability to differentiate into syncytiotrophoblasts and secrete steroid and peptide hormones that help sustain a viable pregnancy. This task was addressed by testing different serum concentrations, cell culture media, digestive enzymes, growth factors, substrate coating with diverse proteins from the extracellular matrix, and so on. Among the many methodological challenges, the contamination of trophoblasts with other cell types, such as immune and stromal cells, was a matter of concern. However, introducing the Percoll gradient to isolate cytotrophoblasts was an excellent contribution, and later, the depletion of contaminating cells by using magnetic bead-conjugated antibodies also helped increase the purity of cytotrophoblasts. Herein, with some modifications, we describe a rapid and easy method for cytotrophoblast isolation from the term human placenta based on the previously reported method by Harvey Kliman et al. (Endocrinology 118:1567-1582, 1986). This method yields about 40-90 million cells from a single placenta, with a purity of around 85-90%.

High Glucose Promotes Inflammation and Weakens Placental Defenses against E. coli and S. agalactiae Infection: Protective Role of Insulin and Metformin

Placentas from gestational diabetes mellitus (GDM) patients undergo significant metabolic and immunologic adaptations due to hyperglycemia, which results in an exacerbated synthesis of proinflammatory cytokines and an increased risk for infections. Insulin or metformin are clinically indicated for the treatment of GDM; however, there is limited information about the immunomodulatory activity of these drugs in the human placenta, especially in the context of maternal infections. Our objective was to study the role of insulin and metformin in the placental inflammatory response and innate defense against common etiopathological agents of pregnancy bacterial infections, such as E. coli and S. agalactiae, in a hyperglycemic environment. Term placental explants were cultivated with glucose (10 and 50 mM), insulin (50–500 nM) or metformin (125–500 µM) for 48 h, and then they were challenged with live bacteria (1 × 105 CFU/mL). We evaluated the inflammatory cytokine secretion, beta defensins production, bacterial count and bacterial tissue invasiveness after 4–8 h of infection. Our results showed that a GDM-associated hyperglycemic environment induced an inflammatory response and a decreased beta defensins synthesis unable to restrain bacterial infection. Notably, both insulin and metformin exerted anti-inflammatory effects under hyperglycemic infectious and non-infectious scenarios. Moreover, both drugs fortified placental barrier defenses, resulting in reduced E. coli counts, as well as decreased S. agalactiae and E. coli invasiveness of placental villous trees. Remarkably, the double challenge of high glucose and infection provoked a pathogen-specific attenuated placental inflammatory response in the hyperglycemic condition, mainly denoted by reduced TNF-α and IL-6 secretion after S. agalactiae infection and by IL-1β after E. coli infection. Altogether, these results suggest that metabolically uncontrolled GDM mothers develop diverse immune placental alterations, which may help to explain their increased vulnerability to bacterial pathogens.

Compartmentalized Innate Immune Response of Human Fetal Membranes against Escherichia coli Choriodecidual Infection

An infectious process into the uterine cavity represents a major endangered condition that compromises the immune privilege of the maternal-fetal unit and increases the risk for preterm birth (PTB) and premature rupture of membranes (PROM). Fetal membranes are active secretors of antimicrobial peptides (AMP), which limit bacterial growth, such as Escherichia coli. Nevertheless, the antibacterial responses displayed by chorioamniotic membranes against a choriodecidual E. coli infection have been briefly studied. The objective of this research was to characterize the profile of synthesis, activity, and spatial distribution of a broad panel of AMPs produced by fetal membranes in response to E. coli choriodecidual infection. Term human chorioamniotic membranes were mounted in a two independent compartment model in which the choriodecidual region was infected with live E. coli (1 × 10⁵ CFU/mL). Amnion and choriodecidual AMP tissue levels and TNF-α and IL-1β secretion were measured by the enzyme-linked immunosorbent assay. The passage of bacterium through fetal membranes and their effect on structural continuity was followed for 24 h. Our results showed that E. coli infection caused a progressive mechanical disruption of the chorioamniotic membranes and an activated inflammatory environment. After the challenge, the amnion quickly (2-4 h) induced production of human beta defensins (HBD)-1, HBD-2, and LL-37. Afterwards (8-24 h), the amnion significantly produced HBD-1, HBD-2, HNP-1-3, S100A7, sPLA2, and elafin, whereas the choriodecidua induced LL-37 synthesis. Therefore, we noticed a temporal- and tissue-specific pattern regulation of the synthesis of AMPs by infected fetal membranes. However, fetal membranes were not able to contain the collagen degradation or the bacterial growth and migration despite the battery of produced AMPs, which deeply increases the risk for PTB and PROM. The mixture of recombinant HBDs at low concentrations resulted in increased bactericidal activity compared to each HBD alone in vitro, encouraging further research to study AMP combinations that may offer synergy to control drug-resistant infections in the perinatal period.

Cord Serum Calcitriol Inversely Correlates with Maternal Blood Pressure in Urinary Tract Infection-Affected Pregnancies: Sex-Dependent Immune Implications

Urinary tract infections (UTI) during pregnancy are frequently associated with hypertensive disorders, increasing the risk of perinatal morbidity. Calcitriol, vitamin D₃’s most active metabolite, has been involved in blood pressure regulation and prevention of UTIs, partially through modulating vasoactive peptides and antimicrobial peptides, like cathelicidin. However, nothing is known regarding the interplay between placental calcitriol, cathelicidin, and maternal blood pressure in UTI-complicated pregnancies. Here, we analyzed the correlation between these parameters in pregnant women with UTI and with normal pregnancy (NP). Umbilical venous serum calcitriol and its precursor calcidiol were significantly elevated in UTI. Regardless of newborn’s sex, we found strong negative correlations between calcitriol and maternal systolic and diastolic blood pressure in the UTI cohort (p < 0.002). In NP, this relationship was observed only in female-carrying mothers. UTI-female placentas showed higher expression of cathelicidin and CYP27B1, the calcitriol activating-enzyme, compared to male and NP samples. Accordingly, cord-serum calcitriol from UTI-female neonates negatively correlated with maternal bacteriuria. Cathelicidin gene expression positively correlated with gestational age in UTI and with newborn anthropometric parameters. Our results suggest that vitamin D deficiency might predispose to maternal cardiovascular risk and perinatal infections especially in male-carrying pregnancies, probably due to lower placental CYP27B1 and cathelicidin expression.

Immunoendocrine Dysregulation during Gestational Diabetes Mellitus: The Central Role of the Placenta

Gestational Diabetes Mellitus (GDM) is a transitory metabolic condition caused by dysregulation triggered by intolerance to carbohydrates, dysfunction of beta-pancreatic and endothelial cells, and insulin resistance during pregnancy. However, this disease includes not only changes related to metabolic distress but also placental immunoendocrine adaptations, resulting in harmful effects to the mother and fetus. In this review, we focus on the placenta as an immuno-endocrine organ that can recognize and respond to the hyperglycemic environment. It synthesizes diverse chemicals that play a role in inflammation, innate defense, endocrine response, oxidative stress, and angiogenesis, all associated with different perinatal outcomes.

Placentas associated with female neonates from pregnancies complicated by urinary tract infections have higher cAMP content and cytokines expression than males

PROBLEM

The cAMP pathway is involved in important biological processes including immune regulation and hormone signaling. At the feto-maternal unit, cAMP participates in placental function/physiology and the establishment of immunoendocrine networks. Low cAMP in male fetuses cord blood has been linked to poorer perinatal outcomes; however, cAMP placental content and its relationship with immune factors and fetal sex in an infectious condition have not been investigated.

METHOD OF STUDY

Sex-dependent changes in cAMP content and its association with cytokines and antimicrobial peptides expression were studied in human placentas collected from normal pregnancies and with urinary tract infections (UTI). Radioimmunoassay was used to quantify cAMP in placental tissue, while immune markers expression was studied by qPCR. Additionally, cAMP effect on antimicrobial peptides expression was studied in cultured trophoblasts challenged with lipopolysaccharide, to mimic an infection.

RESULTS

In UTI, placentas from female neonates had higher cAMP tissue content and increased expression of TNFA, IL1B, and IL10 than those from males, where IFNG was more elevated. While cAMP negatively correlated with maternal bacteriuria and IFNG, it positively correlated with the antimicrobial peptide S100A9 expression in a sex-specific fashion. In cultured trophoblasts, cAMP significantly stimulated β-defensin-1 while reduced the lipopolysaccharide-dependent stimulatory effect on β-defensin-2, β-defensins-3, and S100A9.

CONCLUSION

Our results showed higher cAMP content and defense cytokines expression in placentas associated with female neonates from pregnancies complicated by UTI. The associations between cAMP and bacteriuria/immune markers, together with cAMP's ability to differentially regulate placental antimicrobial peptides expression, suggest a dual modulatory role for cAMP in placental immunity.

Prolactin decreases LPS-induced inflammatory cytokines by inhibiting TLR-4/NFκB signaling in the human placenta

Prolactin (PRL) plays an important role in trophoblast growth, placental angiogenesis and immunomodulation within the feto-maternal interface, where different cell types secrete PRL and express its receptor. During pregnancy, inflammatory signalling is a deleterious event that has been associated with poor fetal outcomes. The placenta is highly responsive to the inflammatory stimulus; however, the actions of PRL in placental immunity and inflammation remain largely unknown. The aim of this study was to evaluate PRL effects on the TLR4/NFkB signalling cascade and associated inflammatory targets in cultured explants from healthy term human placentas. An in utero inflammatory scenario was mimicked using lipopolysaccharides (LPS) from Escherichia coli. PRL significantly reduced LPS-dependent TNF-α, IL-1β and IL-6 secretion and intracellular levels. Mechanistically, PRL prevented LPS-mediated upregulation of TLR-4 expression and NFκB phosphorylation. In conclusion, PRL limited inflammatory responses to LPS in the human placenta, suggesting that this hormone could be critical in inhibiting exacerbated immune responses to infections that could threaten pregnancy outcome. This is the first evidence of a mechanism for anti-inflammatory activity of PRL in the human placenta, acting as a negative regulator of TLR-4/NFkB signaling.

Innate Immune Cells and Toll-like Receptor-Dependent Responses at the Maternal-Fetal Interface

During pregnancy, the placenta, the mother and the fetus exploit several mechanisms in order to avoid fetal rejection and to maintain an immunotolerant environment throughout nine months. During this time, immune cells from the fetal and maternal compartments interact to provide an adequate defense in case of an infection and to promote a tolerogenic milieu for the fetus to develop peacefully. Trophoblasts and decidual cells, together with resident natural killer cells, dendritic cells, Hofbauer cells and other macrophages, among other cell types, contribute to the modulation of the uterine environment to sustain a successful pregnancy. In this review, the authors outlined some of the various roles that the innate immune system plays at the maternal-fetal interface. First, the cell populations that are recruited into gestational tissues and their immune mechanisms were examined. In the second part, the Toll-like receptor (TLR)-dependent immune responses at the maternal-fetal interface was summarized, in terms of their specific cytokine/chemokine/antimicrobial peptide expression profiles throughout pregnancy.

Variations in maternal adenylate cyclase genes are associated with congenital Zika syndrome in a cohort from Northeast, Brazil

BACKGROUND

Vertical transmission of Zika virus (ZIKV) is associated with congenital malformations but the mechanism of pathogenesis remains unclear. Although host genetics appear to play a role, no genetic association study has yet been performed to evaluate this question. In order to investigate if maternal genetic variation is associated with Congenital Zika Syndrome (CZS), we conducted a case-control study in a cohort of Brazilian women infected with ZIKV during pregnancy.

METHODS

A total of 100 women who reported symptoms of zika during pregnancy were enrolled and tested for ZIKV. Among 52 women positive for ZIKV infection, 28 were classified as cases and 24 as controls based on the presence or absence of CZS in their infants. Variations in the coding region of 205 candidate genes involved in cAMP signaling or immune response were assessed by high throughput sequencing and tested for association with development of CZS.

RESULTS

From the 817 single nucleotide variations (SNVs) included in association analyses, 22 SNVs in 17 genes were associated with CZS under an additive model (alpha = 0.05). Variations c.319T>C (rs11676272) and c.1297G>A, located at ADCY3 and ADCY7 genes showed the most prominent effect. The association of ADCY3 and ADCY7 genes was confirmed using a Sequence Kernel Association Test to assess the joint effect of common and rare variations, and results were statistically significant after adjustment for multiple comparisons (P < 0.002).

CONCLUSION

These results suggest that maternal ADCY genes contribute to ZIKV pathogenicity and influence the outcome of CZS, being promising candidates for further replication studies and functional analysis.