Effects of low-dose lipopolysaccharide (LPS) pretreatment on LPS-induced intra-uterine fetal death and preterm labor

Melatonin alleviates high temperature exposure induced fetal growth restriction via the gut-placenta-fetus axis in pregnant mice

INTRODUCTION

Global warming augments the risk of adverse pregnancy outcomes in vulnerable expectant mothers. Pioneering investigations into heat stress (HS) have predominantly centered on its direct impact on reproductive functions, while the potential roles of gut microbiota, despite its significant influence on distant tissues, remain largely unexplored. Our understanding of deleterious mechanisms of HS and the development of effective intervention strategies to mitigate the detrimental impacts are still limited.

OBJECTIVES

In this study, we aimed to explore the mechanisms by which melatonin targets gut microbes to alleviate HS-induced reproductive impairment.

METHODS

We firstly evaluated the alleviating effects of melatonin supplementation on HS-induced reproductive disorder in pregnant mice. Microbial elimination and fecal microbiota transplantation (FMT) experiments were then conducted to confirm the efficacy of melatonin through regulating gut microbiota. Finally, a lipopolysaccharide (LPS)-challenged experiment was performed to verify the mechanism by which melatonin alleviates HS-induced reproductive impairment.

RESULTS

Melatonin supplementation reinstated gut microbiota in heat stressed pregnant mice, reducing LPS-producing bacteria (Aliivibrio) and increasing beneficial butyrate-producing microflora (Butyricimonas). This restoration corresponded to decreased LPS along the maternal gut-placenta-fetus axis, accompanied by enhanced intestinal and placental barrier integrity, safeguarding fetuses from oxidative stress and inflammation, and ultimately improving fetal weight. Further pseudo-sterile and fecal microbiota transplantation trials confirmed that the protective effect of melatonin on fetal intrauterine growth under HS was partially dependent on gut microbiota. In LPS-challenged pregnant mice, melatonin administration mitigated placental barrier injury and abnormal angiogenesis via the inactivation of the TLR4/MAPK/VEGF signaling pathway, ultimately leading to enhanced nutrient transportation in the placenta and thereby improving the fetal weight.

CONCLUSION

Melatonin alleviates HS-induced low fetal weight during pregnancy via the gut-placenta-fetus axis, the first time highlighting the gut microbiota as a novel intervention target to mitigate the detrimental impact of global temperature rise on vulnerable populations.

Impact of Prenatal LPS and Early-life Constant Light Exposure on Circadian Gene Expression Profiles in Various Rat Tissues

Exposure to lipopolysaccharide (LPS) during prenatal development leads to various changes in neurobiological and behavioural patterns. Similarly, continuous exposure to constant light (LL) during the critical developmental period of the circadian system affects gene expression in various tissues in adulthood. Given the reciprocal nature of the interaction between the circadian and the immune systems, our study primarily investigated the individual effects of both interventions and, more importantly, their combined effect. We aimed to explore whether there might be a potential synergistic effect on circadian rhythms and their parameters, focussing on the expression of clock genes, immune-related genes, and specific genes in the hippocampus, pineal gland, spleen and adrenal gland of rats at postnatal day 30. Our results show a significant influence of prenatal LPS and postnatal LL on the expression profiles of all genes assessed. However, the combination of prenatal LPS and postnatal LL only revealed an enhanced negative effect in a minority of the comparisons. In most cases, it appeared to attenuate the changes induced by the individual interventions, restoring the measured parameters to values closer to those of the control group. In particular, genes such as Nr1d1, Aanat and Tph1 showed increased amplitude in the pineal gland and spleen, while the kynurenine enzymes Kynu and KatII developed circadian rhythmicity in the adrenal glands only after the combined interventions. Our data suggest that a mild immunological challenge during prenatal development may play a critical role in triggering an adaptive response of the circadian clock later in life.

Effects of maternal LPS and developmental exposure to an environmentally relevant phthalate mixture on neuron number in the rat medial prefrontal cortex

The brain is especially vulnerable to environmental influences during the perinatal period. While the effects of environmental factors are usually studied in isolation, it is more typical to be exposed to multiple influences during early development, necessitating study of synergistic actions on the developing brain. Both maternal infection and endocrine disrupting phthalates can decrease cell number in the medial prefrontal cortex (mPFC), a region critical for executive functioning. In the present study, groups of pregnant Long Evans rats were treated with either (1) 100 μg/kg (i.p.) lipopolysaccharide (LPS) on embryonic days 15 and 16 combined with a low-dose (1 mg/kg) phthalate mixture throughout gestation and the neonatal period, (2) LPS alone, (3) phthalates alone, or (4) neither phthalates nor LPS (control). Neurons and glial cells were stereologically quantified in the mPFC. The adult offspring previously exposed to LPS or phthalates alone had reduced mPFC neuron number in exposed males, but not females, while the combination treatment did not produce significant effects. In males, LPS alone also reduced the number of glia in the mPFC. Additionally, the combination of LPS and phthalates resulted in fewer pregnancies to term and decreased litter size. These results provide insight into how common environmental factors can interact to alter the developmental trajectory of the mPFC.

The dangerous liaisons in innate immunity involving recombinant proteins and endotoxins: Examples from the literature and the Leptospira field

Endotoxins, also known as lipopolysaccharides (LPS), are essential components of cell walls of diderm bacteria such as Escherichia coli. LPS are microbe-associated molecular patterns that can activate pattern recognition receptors. While trying to investigate the interactions between proteins and host innate immunity, some studies using recombinant proteins expressed in E. coli reported interaction and activation of immune cells. Here, we set out to provide information on endotoxins that are highly toxic to humans and bind to numerous molecules, including recombinant proteins. We begin by outlining the history of the discovery of endotoxins, their receptors and the associated signaling pathways that confer extreme sensitivity to immune cells, acting alone or in synergy with other microbe-associated molecular patterns. We list the various places where endotoxins have been found. Additionally, we warn against the risk of data misinterpretation due to endotoxin contamination in recombinant proteins, which is difficult to estimate with the Limulus amebocyte lysate assay, and cannot be completely neutralized (e.g., treatment with polymyxin B or heating). We further illustrate our point with examples of recombinant heat-shock proteins and viral proteins from severe acute respiratory syndrome coronavirus 2, dengue and HIV, for which endotoxin contamination has eventually been shown to be responsible for the inflammatory roles previously ascribed. We also critically appraised studies on recombinant Leptospira proteins regarding their putative inflammatory roles. Finally, to avoid these issues, we propose alternatives to express recombinant proteins in nonmicrobial systems. Microbiologists wishing to undertake innate immunity studies with their favorite pathogens should be aware of these difficulties.

Determining zebrafish dorsal organizer size by a negative feedback loop between canonical/non-canonical Wnts and Tlr4/NFκB

In vertebrate embryos, the canonical Wnt ligand primes the formation of dorsal organizers that govern dorsal-ventral patterns by secreting BMP antagonists. In contrast, in Drosophila embryos, Toll-like receptor (Tlr)-mediated NFκB activation initiates dorsal-ventral patterning, wherein Wnt-mediated negative feedback regulation of Tlr/NFκB generates a BMP antagonist-secreting signalling centre to control the dorsal-ventral pattern. Although both Wnt and BMP antagonist are conserved among species, the involvement of Tlr/NFκB and feedback regulation in vertebrate organizer formation remains unclear. By imaging and genetic modification, we reveal that a negative feedback loop between canonical and non-canonical Wnts and Tlr4/NFκB determines the size of zebrafish organizer, and that Tlr/NFκB and Wnts switch initial cue and feedback mediator roles between Drosophila and zebrafish. Here, we show that canonical Wnt signalling stimulates the expression of the non-canonical Wnt5b ligand, activating the Tlr4 receptor to stimulate NFκB-mediated transcription of the Wnt antagonist frzb, restricting Wnt-dependent dorsal organizer formation.

Lipopolysaccharide-induced sickness behavior is not altered in male Fmr1-deficient mice

OBJECTIVES

Fragile X syndrome is the main monogenetic cause of intellectual disability and autism. Alterations in the immune system are commonly found in these developmental disorders. We and others have demonstrated that Fmr1 mutant mice present an altered response to immune stimuli. However, whether this altered immune response can influence the Fmr1 mutant behavioral outcomes in response to inflammation has not been fully investigated.

MATERIALS AND METHODS

In the current study, we examine the behavioral sickness response of male wildtype and knockout  mice to the innate immune stimulus lipopolysaccharide (LPS) (0.1 mg/kg) to determine if Fmr1 mutants have altered sickness behavior. We used an enzyme-linked immunosorbent assay (ELISA) to measure changes in the cytokine interleukin-6 (IL-6) to determine that inflammation was induced in the mice. Sickness behavior was assessed in a wheel-running paradigm, and a tail suspension test was used to assess the depressive-like phenotype that follows sickness behavior in response to LPS.

RESULTS

The ELISA using blood serum confirmed a significant increase in IL-6 in mice that were treated with LPS. Treated Fmr1 mutants exhibited decreased distance traveled in the wheel running after LPS administration, similar to treated controls. Another cohort of animals treated with LPS were tested in the tail suspension test and exhibited no alterations in immobility time in response to LPS.

CONCLUSION

Together, our data suggest that Fmr1 mutant mice do not have altered sickness behavior in response to a low dose of LPS.

LPS Administration during Fertilization Affects Epigenetic Inheritance during Embryonic Development

Intrauterine inflammation can cause infertility by disrupting reproductive function. The pathogenesis underlying this process may primarily involve endotoxins from lipopolysaccharides (LPS), which are produced by Gram-negative bacteria. However, the long-term effects of endotoxins in mammalian pregnancy following LPS exposure during fertilization have not been clarified. In this study, we performed experiments to analyze the influence of LPS on early embryonic development and fetal development in mice. Mice uteruses were examined for the expression of genes related to the inflammatory response. The expression of Il-1β and Il-6 increased following the administration of 200 and 1000 µg/kg LPS. Exposure to LPS using in vitro fertilization (IVF) significantly decreased the embryonic developmental rate. A concentration of 100 µg/kg LPS significantly increased the placental weight and fetal crown -rump length (CRL), whereas a concentration of 200 µg/kg LPS significantly decreased the placenta weight and fetal weight in vivo. These findings indicate that maternal LPS during fertilization affects fetal development until the late stage of pregnancy. Thus, maternal endotoxins may affect epigenetic inheritance during embryonic development from the early to late stages of pregnancy.

Distribution of endotoxin in maternal and fetal body with intrahepatic cholestasis of pregnancy and its association with adverse fetal outcome

BACKGROUND

Intrahepatic cholestasis of pregnancy is a pregnancy-specific liver disease. In this study, we sought to explore the distribution of lipopolysaccharide in the maternal body, and its effect on the fetal body in the intrahepatic cholestasis of pregnancy mice. It provides a new sight for the clinical treatment of women with intrahepatic cholestasis of pregnancy.

METHODS

The serum levels of lipopolysaccharide and lipopolysaccharide binding protein in women with intrahepatic cholestasis of pregnancy were analyzed. To assess the association between lipopolysaccharide levels and adverse fetal outcomes, ursodeoxycholic acid, resveratrol, and phosphatidylinositol-3-kinase inhibitor were employed in intrahepatic cholestasis of pregnancy mice, and we studied the fluorescence intensity and distribution of lipopolysaccharide in mice with intrahepatic cholestasis of pregnancy.

RESULTS

Our data indicated significantly elevated levels of lipopolysaccharide and lipopolysaccharide binding protein in women with intrahepatic cholestasis of pregnancy. In vivo fluorescence imaging revealed that the intensity of lipopolysaccharide in mice with intrahepatic cholestasis of pregnancy was higher than that in the control group, and decreased after ursodeoxycholic and resveratrol treatment. The fluorescence intensity analysis indicated that lipopolysaccharide levels in maternal liver, placenta, fetal brain and fetal liver were significantly higher in the intrahepatic cholestasis pregnancy mice group than in the control group.

CONCLUSIONS

This study provided evidence of endotoxin distribution in maternal liver, placenta, fetal liver and fetal brain in mice with intrahepatic cholestasis of pregnancy. Ursodeoxycholic acid and resveratrol treatment effectively reduced lipopolysaccharide levels in pregnant mice with intrahepatic cholestasis of pregnancy.

Astaxanthin ameliorates the impairment consequence of prenatal bacterial lipopolysaccharide exposure in adult male offspring NMRI mice

In this study, the potential effects of astaxanthin (AST) were investigated on preventing the prenatal LPS-induced injures in mothers and adult male offspring of NMRI mice. Pregnant mice were randomly divided into four groups: 1. Saline + vehicle; 2. Saline + AST: received astaxanthin (4 mg/kg for 3 days, ip) on 11-13 gestation days; 3. LPS + vehicle (LPS-treated group): injected with LPS (20 µg/kg, sc) on gestation day 11; 4. LPS + AST: administrated LPS and astaxanthin on gestation days 11 and 11-13, respectively. In each group, maternal care behaviors and TNF-α serum levels were examined until weaning of male offspring at 23 days. At 60 days old, male pups underwent analysis of body weight and length, serum gonadotropins and testosterone hormone levels, sperm quality, gonadal and brain tissues morphologies, and the expression of SOX9 and GnRH genes by real-time PCR. Serum TNF-α level increased significantly in mothers treated with LPS, while AST reduced it. In adult male offspring, serum hormone levels, sperm quality, and the number of spermatocytes and Leydig cells in the testes improved when AST was administrated. According to histological studies of the brain, neurons in the LPS-treated group were smaller and less active, whereas neurons in the LPS + AST group were larger, more numerous, and more active. LPS significantly reduced GnRH expression, while AST induction improved its expression. AST administration during pregnancy prevented the adverse effects of prenatal exposure to LPS, presumably through its genomic and non-genomic effects, in adult male offspring.

Hepcidin Gene Co-Option Balancing Paternal Immune Protection and Male Pregnancy

Viviparity has originated independently more than 150 times in vertebrates, while the male pregnancy only emerged in Syngnathidae fishes, such as seahorses. The typical male pregnancy seahorses have closed sophisticated brood pouch that act as both uterus and placenta, representing an excellent model system for studying the evolutionary process of paternal immune protection. Phylogenetic analysis indicated that the hampII gene family has multiple tandem duplicated genes and shows independent lineage-specific expansion in seahorses, and they had the highest ratio of nonsynonymous substitutions to synonymous substitutions (dN/dS) in the seahorse phylogenetic branch. The expression levels of hampIIs in the brood pouch placenta were significantly higher during pregnancy than non-pregnancy. Both LPS stimulation test in vivo and cytotoxicity test in vitro proved the immunological protection function of hampIIs against pathogen infection in seahorse. Besides, seahorse hampII peptides exhibit weaker antibacterial function, but stronger agglutination and free endotoxin inhibition. We assumed that the modified immunological function seemed to be a trade-off between the resistance to microbial attack and offspring protection. In brief, this study suggests that the rapid co-option of hampIIs contributes to the evolutionary adaption to paternal immune care during male pregnancy.

LPS vs. Poly I:C Model: Comparison of Long-Term Effects of Bacterial and Viral Maternal Immune Activation (MIA) on the Offspring

A prominent health issue nowadays is the COVID-19 pandemic, which poses acute risks to human health. However, the long-term health consequences are largely unknown and cannot be neglected. An especially vulnerable period for infection is pregnancy, when infections could have long-term health effect on the child. Evidence suggests that maternal immune activation (MIA) induced by either bacteria or viruses presents various effects on the offspring, leading to adverse phenotypes in many organ systems. This review compares the mechanisms of bacterial and viral MIA and the possible long-term outcomes for the offspring by summarizing the outcome in animal LPS and Poly I:C models. Both models are activated immune responses mediated by Toll-like receptors. The outcomes for MIA offspring include neurodevelopment, immune response, circulation, metabolism, and reproduction. Some of these changes continue to exist until later life. Besides different doses and batches of LPS and Poly I:C, the injection day, administration route, and also different animal species influence the outcomes. Here, we specifically aim to support colleagues when choosing their animal models for future studies.

Placental extracellular vesicles-associated microRNA-519c mediates endotoxin adaptation in pregnancy

BACKGROUND

Pregnancy represents a unique challenge for the maternal-fetal immune interface, requiring a balance between immunosuppression, which is essential for the maintenance of a semiallogeneic fetus, and proinflammatory host defense to protect the maternal-fetal interface from invading organisms. Adaptation to repeated inflammatory stimuli (endotoxin tolerance) may be critical in preventing inflammation-induced preterm birth caused by exaggerated maternal inflammatory responses to mild or moderate infections that are common during pregnancy. However, the exact mechanisms contributing to the maintenance of tolerance to repeated infections are not completely understood. MicroRNAs play important roles in pregnancy with several microRNAs implicated in gestational tissue function and in pathologic pregnancy conditions. MicroRNA-519c, a member of the chromosome 19 microRNA cluster, is a human-specific microRNA mainly expressed in the placenta. However, its role in pregnancy is largely unknown.

OBJECTIVE

This study aimed to explore the role of "endotoxin tolerance" failure in the pathogenesis of an exaggerated inflammatory response often seen in inflammation-mediated preterm birth. In this study, we investigated the role of microRNA-519c, a placenta-specific microRNA, as a key regulator of endotoxin tolerance at the maternal-fetal interface.

STUDY DESIGN

Using a placental explant culture system, samples from term and second-trimester placentas were treated with lipopolysaccharide. After 24 hours, the conditioned media were collected for analysis, and the placental explants were re-exposed to repeated doses of lipopolysaccharide for 3 days. The supernatant was analyzed for inflammatory markers, the presence of extracellular vesicles, and microRNAs. To study the possible mechanism of action of the microRNAs, we evaluated the phosphodiesterase 3B pathway involved in tumor necrosis factor alpha production using a microRNA mimic and phosphodiesterase 3B small interfering RNA transfection. Finally, we analyzed human placental samples from different gestational ages and from women affected by inflammation-associated pregnancies.

RESULTS

Our data showed that repeated exposure of the human placenta to endotoxin challenges induced a tolerant phenotype characterized by decreased tumor necrosis factor alpha and up-regulated interleukin-10 levels. This reaction was mediated by the placenta-specific microRNA-519c packaged within placental extracellular vesicles. Lipopolysaccharide treatment increased the extracellular vesicles that were positive for the exosome tetraspanin markers, namely CD9, CD63, and CD81, and secreted primarily by trophoblasts. Primary human trophoblast cells transfected with a microRNA-519c mimic decreased phosphodiesterase 3B, whereas a lack of phosphodiesterase 3B, achieved by small interfering RNA transfection, led to decreased tumor necrosis factor alpha production. These data support the hypothesis that the anti-inflammatory action of microRNA-519c was mediated by a down-regulation of the phosphodiesterase 3B pathway, leading to inhibition of tumor necrosis factor alpha production. Furthermore, human placentas from normal and inflammation-associated pregnancies demonstrated that a decreased placental microRNA-519c level was linked to infection-induced inflammatory pathologies during pregnancy.

CONCLUSION

We identified microRNA-519c, a human placenta-specific microRNA, as a novel regulator of immune adaptation associated with infection-induced preterm birth at the maternal-fetal interface. Our study serves as a basis for future experiments to explore the potential use of microRNA-519c as a biomarker for infection-induced preterm birth.

Hyperactivation of the amygdala correlates with impaired social play behavior of prepubertal male rats in a maternal immune activation model

Maternal infection during pregnancy is an environmental risk factor for neurodevelopmental dysfunction, such as autism spectrum disorder (ASD). This study investigated the effect of maternal immune activation (MIA) on the behavior profile of prepubertal offspring and whether MIA alters the neuronal activation pattern of brain areas related to social play behavior. Pregnant Wistar rats received 500 μg/kg of lipopolysaccharide or saline solution on gestational day 16. Their offspring were tested using behavioral tasks to capture some of the core and associated ASD-like symptoms. Neuronal activation, indexed via c-fos expression after social play behavior, was evaluated in several brain areas. MIA had a number of adverse effects on dams and reduced the number of successful births and litter size. MIA induced sex-specific autistic-like features by a reduction in ultrasonic vocalizations in response to separation from the mother and nest, reduction in discrimination between neutral odors and their nest odor, moderate effect in stereotypies in the hole-board test, impaired risk assessment phenotype, and reduction in social play behavior without changes in locomotor activity only in prepubertal male offspring. A decrease in social play behavior may be associated with a decrease in the number of c-fos-positive cells in the prefrontal cortex and striatum, but hyperactivation of the basolateral and basomedial amygdala. Prenatal immune challenge results in ASD-like symptoms such as impaired risk assessment behavior, communication, and social interactions in male prepubertal offspring. Impaired social play behavior is correlated with neuronal hyperactivation in the amygdala.

Dysbacteriosis induces abnormal neurogenesis via LPS in a pathway requiring NF-κB/IL-6

In this study, we identified elevated levels of LPS and suppressed neurogenesis in a successfully established mouse model of gut microbiota dysbiosis. We mimicked these phenotypes using mouse and chicken embryos exposed to LPS and found that dramatic variation in gene expression was due to changes in the dorsal-ventral patterning of the neural tube. Cell survival and excess ROS were also involved in this process. Antioxidant administration alleviated LPS-activated NF-κB signaling, while directly blocking NF-κB signaling altered the LPS-induced inhibition of neurogenesis. Furthermore, IL-6 was proven to play a vital role in the expression of crucial neurogenesis-related genes and NF-κB. In summary, we found that the suppression of neurogenesis induced by dysbacteriosis-derived LPS was significantly reversed in mice with fecal microbiota transplantation. This study reveals that gut dysbacteriosis-derived LPS impairs embryonic neurogenesis, and that the NF-κB/IL-6 pathway could be one of the main factors triggering the downstream signaling cascade.

A role for 4-hydroxy-2-nonenal in premature placental senescence in preeclampsia and intrauterine growth restriction

Premature placental senescence is a hallmark of pregnancy-related disorders such as intrauterine growth restriction (IUGR) and preeclampsia (PE), two major cause of maternal and neonatal morbidity and mortality. Oxidative stress and lipid peroxidation are involved in the pathogenesis of PE and IUGR, and may play a role in placental aging. In this study, we investigated whether 4-hydroxy-2-nonenal (HNE), a lipid peroxidation-derived aldehyde present in preeclamptic placentas, may contribute to premature senescence in placenta-related complications. Placentas from PE-affected women, exhibited several senescence patterns, such as an increased expression of phosphorylated (serine-139) histone γH2AX, a sensitive marker of double-stranded DNA breaks, the presence of lipofuscin granules, and an accumulation of high molecular weight cross-linked and ubiquitinated proteins. PE placentas showed an accumulation of acetylated proteins consistent with the presence of HNE-adducts on sirtuin 1 (SIRT1). Likewise, oxidative stress and senescence markers together with SIRT1 modification by HNE, were observed in murine placentas from mice treated with lipopolysaccharide during gestation and used as models of IUGR. The addition of HNE and ONE (4-oxo-2-nonenal), to cultured HTR-8/SVneo human trophoblasts activated the senescence-associated- β-galactosidase, and generated an accumulation of acetylated proteins, consistent with a modification of SIRT1 by HNE. Altogether, these data emphasize the role of HNE and lipid peroxidation-derived aldehydes in premature placental senescence in PE and IUGR, and more generally in pathological pregnancies.

Diet Supplementation with Pomegranate Peel Improves Embryonic Survival in a Mouse Model of Early Pregnancy Loss

The peel of pomegranate fruit is a rich source of polyphenolic compounds with powerful antioxidant properties. We evaluated the therapeutic potential of pomegranate peel (PP) in the prevention of early pregnancy loss in a mouse model of embryonic mortality and abortion (female CBA/J x male DBA/2). CBA/J mice were divided into 3 groups: mice in control group (CONT group) were fed a standard diet, whereas mice in groups 2 and 3 were fed a standard diet supplemented with 1% PP (PP1% group) and 5% PP (PP5% group), respectively. All the mice were fed their diets for 10 days before mating and continued with the same diets for a further 14 days after mating. At day 14 of pregnancy the female mice were sacrificed and the placentas and maternal livers were harvested for measurement of the content of thiols and thiobarbituric acid reactive substances (TBARS), as biomarkers of oxidative stress, and the enzymatic activities of total superoxide dismutase (TSOD), copper/zinc SOD (SOD1), manganese SOD (SOD2), selenium glutathione peroxidase (GPX) and glutathione reductase (GR). Diet supplemented with 5% PP improved embryonic survival and reduced embryonic mortality from 28.2% (CONT) to 8.5% (PP5%). This was accompanied by increased activities of placental TSOD, SOD1 and SOD2, and thiol content. Diet supplemented with 5% PP also reduced placental oxidative stress as demonstrated by a decrease of placental TBARS content. This study highlights the potential of interventions with PP-supplemented diet before and during early pregnancy, in order to ameliorate embryonic survival and prevent early pregnancy loss.

Verbascoside-Rich Abeliophyllum distichum Nakai Leaf Extracts Prevent LPS-Induced Preterm Birth Through Inhibiting the Expression of Proinflammatory Cytokines from Macrophages and the Cell Death of Trophoblasts Induced by TNF-α

Background: Preterm birth is a known leading cause of neonatal mortality and morbidity. The underlying causes of pregnancy-associated complications are numerous, but infection and inflammation are the essential high-risk factors. However, there are no safe and effective preventive drugs that can be applied to pregnant women. Objective: The objectives of the study were to investigate a natural product, Abeliophyllum distichum leaf (ADL) extract, to examine the possibility of preventing preterm birth caused by inflammation. Methods: We used a mouse preterm birth model by intraperitoneally injecting lipopolysaccharides (LPS). ELISA, Western blot, real-time PCR and immunofluorescence staining analyses were performed to confirm the anti-inflammatory efficacy and related mechanisms of the ADL extracts. Cytotoxicity and cell death were measured using Cell Counting Kit-8 (CCK-8) analysis and flow cytometer. Results: A daily administration of ADL extract significantly reduced preterm birth, fetal loss, and fetal growth restriction after an intraperitoneal injection of LPS in mice. The ADL extract prevented the LPS-induced expression of TNF-α in maternal serum and amniotic fluid and attenuated the LPS-induced upregulation of placental proinflammatory genes, including IL-1β, IL-6, IL-12p40, and TNF-α and the chemokine gene CXCL-1, CCL-2, CCL3, and CCL-4. LPS-treated THP-1 cell-conditioned medium accelerated trophoblast cell death, and TNF-α played an essential role in this effect. The ADL extract reduced LPS-treated THP-1 cell-conditioned medium-induced trophoblast cell death by inhibiting MAPKs and the NF-κB pathway in macrophages. ADL extract prevented exogenous TNF-α-induced increased trophoblast cell death and decreased cell viability. Conclusions: We have demonstrated that the inhibition of LPS-induced inflammation by ADL extract can prevent preterm birth, fetal loss, and fetal growth restriction.

Quantitative assessment of morphology and sub-cellular changes in macrophages and trophoblasts during inflammation

In pregnancy during an inflammatory condition, macrophages present at the feto-maternal junction release an increased amount of nitric oxide (NO) and pro-inflammatory cytokines such as TNF-α and INF-γ, which can disturb the trophoblast functions and pregnancy outcome. Measurement of the cellular and sub-cellular morphological modifications associated with inflammatory responses are important in order to quantify the extent of trophoblast dysfunction for clinical implication. With this motivation, we investigated morphological, cellular and sub-cellular changes in externally inflamed RAW264.7 (macrophage) and HTR-8/SVneo (trophoblast) using structured illumination microscopy (SIM) and quantitative phase microscopy (QPM). We monitored the production of NO, changes in cell membrane and mitochondrial structure of macrophages and trophoblasts when exposed to different concentrations of pro-inflammatory agents (LPS and TNF-α). In vitro NO production by LPS-induced macrophages increased 22-fold as compared to controls, whereas no significant NO production was seen after the TNF-α challenge. Under similar conditions as with macrophages, trophoblasts did not produce NO following either LPS or the TNF-α challenge. Super-resolution SIM imaging showed changes in the morphology of mitochondria and the plasma membrane in macrophages following the LPS challenge and in trophoblasts following the TNF-α challenge. Label-free QPM showed a decrease in the optical thickness of the LPS-challenged macrophages while TNF-α having no effect. The vice-versa is observed for the trophoblasts. We further exploited machine learning approaches on a QPM dataset to detect and to classify the inflammation with an accuracy of 99.9% for LPS-challenged macrophages and 98.3% for TNF-α-challenged trophoblasts. We believe that the multi-modal advanced microscopy methodologies coupled with machine learning approach could be a potential way for early detection of inflammation.

Transcriptome, Spliceosome and Editome Expression Patterns of the Porcine Endometrium in Response to a Single Subclinical Dose of Salmonella Enteritidis Lipopolysaccharide

Endometrial infections at a young age can lead to fertility issues in adulthood. Bacterial endotoxins, such as lipopolysaccharide (LPS), can participate in long-term molecular changes even at low concentrations. Lipopolysaccharide plays a crucial role in the progression of septic shock, inflammation and auto-immune diseases. The aim of this study was to describe transcriptomic modulations in the porcine endometrium, induced in vivo by a single subclinical dose of LPS from Salmonella Enteritidis. which did not produce clinical symptoms of toxicity. The RNA-seq methodology was applied to reveal 456 differentially expressed regions, including 375 genes, four long noncoding RNAs, and 77 other unclassified transcripts. Two independent methods confirmed 118 alternatively spliced genes that participate i.a., in the formation of the MHC-I complex and the adaptive immune response. Single nucleotide variant-calling algorithms supported the identification of 3730 allele-specific expression variants and 57 canonical A-to-I RNA editing sites. The results demonstrated that the differential expression of genes involved in inflammation, immune response, angiogenesis and endometrial development may be maintained for up to 7 days after exposure to LPS. RNA editing sites and long noncoding RNAs (lncRNAs) play an important role in transcriptional regulatory machinery in the porcine endometrium in response to LPS administration.

Insight Into TLR4-Mediated Immunomodulation in Normal Pregnancy and Related Disorders

Unlike organ transplants where an immunosuppressive environment is required, a successful pregnancy involves an extremely robust, dynamic, and responsive maternal immune system to maintain the development of the fetus. A specific set of hormones and cytokines are associated with a particular stage of pregnancy. Any disturbance that alters this fine balance could compromise the development and function of the placenta. Although there are numerous underlying causes of pregnancy-related complications, untimely activation of Toll-like receptors (TLR), primarily TLR4, by intrauterine microbes poses the greatest risk. TLR4 is an important Pattern Recognition Receptor (PRR), which activates both innate and adaptive immune cells. TLR4 activation by LPS or DAMPs leads to the production of pro-inflammatory cytokines via the MyD88 dependent or independent pathway. Immune cells modulate the materno–fetal interface by TLR4-mediated cytokine production, which changes at different stages of pregnancy. In most pregnancy disorders, such as PTB, PE, or placental malaria, the TLR4 expression is upregulated in immune cells or in maternal derived cells, leading to the aberrant production of pro-inflammatory cytokines at the materno–fetal interface. Lack of functional TLR4 in mice has reduced the pro-inflammatory responses, leading to an improved pregnancy, which further strengthens the fact that abnormal TLR4 activation creates a hostile environment for the developing fetus. A recent study proposed that endothelial and perivascular stromal cells should interact with each other in order to maintain a homeostatic balance during TLR4-mediated inflammation. It has been reported that depleting immune cells or supplying anti-inflammatory cytokines can prevent PTB, PE, or fetal death. Blocking TLR4 signaling or its downstream molecule by inhibitors or antagonists has proven to improve pregnancy-related complications to some extent in clinical and animal models. To date, there has been a lack of knowledge regarding whether TLR4 accessories such as CD14 and MD-2 are important in pregnancy and whether these accessory molecules could be promising drug targets for combinatorial treatment of various pregnancy disorders. This review mainly focuses on the activation of TLR4 during pregnancy, its immunomodulatory functions, and the upcoming advancement in this field regarding the improvement of pregnancy-related issues by various therapeutic approaches.

Dysbacteriosis-Derived Lipopolysaccharide Causes Embryonic Osteopenia through Retinoic-Acid-Regulated DLX5 Expression

Growing evidence suggests an adverse impact of gut microbiota dysbiosis on human health. However, it remains unclear whether embryonic osteogenesis is affected by maternal gut dysbacteriosis. In this study, we observed that elevated lipopolysaccharide (LPS) levels led to skeletal developmental retardation in an established mouse model of gut microbiota dysbiosis. Using chick embryos exposed to dysbacteriosis-derived LPS, we found restriction in the development of long bones as demonstrated by Alcian blue and alizarin red staining. Micro-CT and histological analysis exhibited decreased trabecular volume, bone mineral density, and collagen production, as well as suppressed osteoblastic gene expression (Ocn, Runx2, Osx, and Dlx5) in chick embryonic phalanges following LPS treatment. Atomic force microscopy manifested decreased roughness of MC3T3-E1 cells and poorly developed matrix vesicles (MVs) in presence of LPS. The expression of the aforementioned osteoblastic genes was suppressed in MC3T3-E1 cells as well. High-throughput RNA sequencing indicated that retinoic acid (RA) may play an important role in LPS-induced osteopenia. The addition of RA suppressed Dlx5 expression in MC3T3-E1 cells, as was also seen when exposed to LPS. Quantitative PCR, Western blot, and immunofluorescent staining showed that retinoic acid receptor α (RARα) was upregulated by LPS or RA treatment, while the expression of DLX5 was downregulated. CYP1B1 expression was increased by LPS treatment in MC3T3-E1 cells, which might be attributed to the increased inflammatory factors and subsequently activated NF-κB signaling. Eventually, blocking RA signals with AGN193109 successfully restored LPS-inhibited osteoblastic gene expression. Taken together, our data reveals that maternal gut microbiota dysbiosis can interfere with bone ossification, in which Dlx5 expression regulated by RA signaling plays an important role.

Dysbacteriosis-induced LPS elevation disturbs the development of muscle progenitor cells by interfering with retinoic acid signaling

Whether myogenesis is affected by the maternal gut dysbacteriosis still remains ambiguous. In this study, first we show the elevated level of lipopolysaccharides (LPS) in a gut microbiota dysbiosis mouse model. Second, we demonstrate that the diameter of muscle fibers, limb development, and somitogenesis were inhibited in both the gut microbiota dysbiosis and LPS exposed mice and chicken embryos. These might be due to LPS disturbed the cell survival and key genes which regulate the somitogenesis and myogenesis. RNA sequencing and subsequent validation experiments verified that retinoic acid (RA) signaling perturbation was mainly responsible for the aberrant somite formation and differentiation. Subsequently, we found that LPS-induced reactive oxygen species (ROS generation and antioxidant genes such as Nrf2, AKR1B10) contributed to the above -mentioned interference with RA signaling. These findings highlight that the gut microbiota homeostasis is also involved in regulating the development of muscle progenitor cells during pregnancy.

Bone marrow stem cells accelerate lung maturation and prevent the LPS-induced delay of morphological and functional fetal lung development in the presence of ErbB4

ErbB4 is a regulator in lung development and disease. Prenatal infection is an important risk factor for the delay of morphologic lung development, while promoting the maturation of the surfactant system. Bone marrow-derived mesenchymal stem cells (BMSCs) have the potential to prevent lung injury. We hypothesized that BMSCs in comparison with hematopoietic control stem cells (HPSCs) minimize the lipopolysaccharide (LPS)-induced lung injury only when functional ErbB4 receptor is present. We injected LPS and/or murine green fluorescent protein-labeled BMSCs or HPSCs into the amniotic cavity of transgenic ErbB4^heart mothers at gestational day 17. Fetal lungs were analyzed 24 h later. BMSCs minimized significantly LPS-induced delay in morphological lung maturation consisting of a stereologically measured increase in mesenchyme and septal thickness and a decrease of future airspace and septal surface. This effect was more prominent and significant in the ErbB4^heart+/- lungs, suggesting that the presence of functioning ErbB4 signaling is required. BMSC also diminished the LPS induced increase in surfactant protein (Sftp)a mRNA and decrease in Sftpc mRNA is only seen if ErbB4 is present. The reduction of morphological delay of lung development and of levels of immune-modulating Sftp was more pronounced in the presence of the ErbB4 receptor. Thus, ErbB4 may be required for the protective signaling of BMSCs.

Maternal lipopolysaccharide exposure results in glucose metabolism disorders and sex hormone imbalance in male offspring

An adverse intrauterine environment may be an important factor contributing to the development of type 2 diabetes in later life. The present study investigated the longitudinal effects of maternal lipopolysaccharide (LPS) exposure during the third trimester on glucose metabolism and sex hormone balance in the offspring. Pregnant mice were intraperitoneally injected with LPS (50 μg/kg) daily from gestational day (GD) 15 to GD17. Glucose tolerance test (GTT) and insulin tolerance test (ITT) were assessed at postnatal day (PND) 60 and PND120. Sex hormones, their receptors, and metabolic enzymes (aromatase) were measured in male offspring at different phases of development (PND14: juvenile; PND35: adolescence; PND60: adulthood; and PND120: middle age). LPS-exposed male offspring exhibited glucose intolerance and insulin resistance by GTT and ITT at middle age, accompanied by an increase in fasting blood glucose and reductions in serum insulin levels and hepatic phosphorylated (p) -AKT/AKT ratio. However, glucose intolerance and insulin resistance were not observed in LPS-exposed female offspring. Maternal LPS exposure upregulated hepatic aromatase proteins and mRNA levels in male offspring at all time points. At adolescence, the testosterone/estradiol ratio (T/E2) was markedly reduced in LPS-exposed male offspring. Moreover, maternal LPS exposure significantly increased hepatic estrogen receptor (ER) α expressions and decreased hepatic androgen receptor (AR) expressions in male offspring. At adulthood, maternal LPS exposure increased serum estradiol levels, decreased serum testosterone levels and elevated hepatic ERβ expressions in male offspring. In conclusion, maternal LPS exposure upregulated aromatase expressions, followed by a reduction in the T/E2 ratio and an alteration in sex hormone receptor activity, which might be involved in the development of glucose metabolism disorders in middle-aged male offspring. This study provides a novel clue and direction to clarify the pathogenesis of maternal infection-related diabetes in male offspring.

Folic Acid Promotes Wound Healing in Diabetic Mice by Suppression of Oxidative Stress

The aim of this study was to investigate the effects of folic acid on impaired wound healing in diabetic mice. Male mice were divided into three groups: group 1, the non-diabetic mice (control); group 2, the streptozotocin (STZ)-induced type 1 diabetic mice; and group 3, the diabetic mice that received a daily dose of 3 mg/kg folic acid via oral gavage. Full-thickness excision wounds were created with 8-mm skin biopsy punches. Each wound closure was continuously evaluated until the wound healed up. Wound healing was delayed in diabetic mice compared with the non-diabetic mice. There were significantly reduced levels of hydroxyproline content (indicator of collagen deposition) and glutathione in diabetic wounds, whereas levels of lipid peroxidation and protein nitrotyrosination were increased. Daily supplementation with folic acid restored diabetes-induced healing delay. Histopathology showed that folic acid supplementation accelerated granulation tissue formation, proliferation of fibroblasts, and tissue regeneration in diabetic mice. Interestingly, folic acid alleviated diabetes-induced impaired collagen deposition in wounds. Moreover, folic acid significantly decreased levels of lipid peroxidation, protein nitrotyrosination and glutathione depletion in diabetic wounds. In conclusion, our results indicate that folic acid supplementation may improve impaired wound healing via suppressing oxidative stress in diabetic mice.

Microbiota-derived lipopolysaccharide retards chondrocyte hypertrophy in the growth plate through elevating Sox9 expression

Accumulating data show that the cytotoxicity of bacterial lipopolysaccharides (LPS) from microbiota or infection is associated with many disorders observed in the clinics. However, it is still obscure whether or not embryonic osteogenesis is affected by the LPS exposure during gestation. Using the early chicken embryo model, we could demonstrate that LPS exposure inhibits chondrogenesis of the 8-day chicken embryos by Alcian Blue-staining and osteogenesis of 17-day by Alcian Blue and Alizarin Red staining. Further analysis of the growth plates showed that the length of the proliferating zone (PZ) increases whereas that of the hypertrophic zone (HZ) decreased following LPS exposure. However there is no significant change on cell proliferation in the growth plates. Immunofluorescent staining, western blot analysis, and quantitive polymerase chain reaction revealed that Sox9 and Col2a1 are highly expressed at the messenger RNA level and their protein products are also abundant. LPS exposure causes a downregulation of Runx2 and Col10a1 expression in 8-day hindlimbs, and a suppression of Runx2, Col10a1, and Vegfa expression in 17-day phalanges. Knocking down Sox9 in ATDC5 cells by small interfering RNA transfection lead to the expression reduction of Col2a1, Runx2, and Col10a1, implying the vital role of Sox9 in the process of LPS-induced delay in the transition from proliferating chondrocytes to hypertrophic chondrocytes in the growth plate. In the presence of LPS, the antioxidant defense regulator nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is highly expressed, and the activities of superoxide dismutase 1 (SOD1), SOD2, and glutaredoxin rise in 17-day phalanges and ADTC5 cells. Simultaneously, an increase of intracellular ROS is observed. When Nrf2 expression was knocked down in ATDC5 cells, the expressions of Sox9, Col2a1, Runx2, Col10a1, and Vegfa were also going down as well. Taken together, our current data suggest that LPS exposure during gestation could restrict the chondrocytes conversion from proliferating to hypertrophic in the growth plate, in which LPS-induced Sox9 plays a crucial role to trigger the cascade of downstream genes by excessive ROS production and Nrf2 elevation.

Characterization of C-C motif chemokine ligand 4 in the porcine endometrium during the presence of the maternal-fetal interface

Chemokines and their receptors play a crucial role in embryo implantation at the maternal-fetal interface during pregnancy. In this study, we investigated the role of CCL4 in development of the porcine endometrium in the early gestational period. Porcine CCL4 showed high similarity with the human counterpart, and mRNA expression of CCL4 and its receptor (CCR5) was predominantly present in the endometrium during early pregnancy. Treatment with CCL4 increased proliferation of porcine uterine luminal epithelial (pLE) cells by activation of PI3K and MAPK signal transduction. In addition, CCL4 recovered the endoplasmic-reticulum stress-reduced proliferation and decreased the unfolded protein response in pLE cells. Besides, the lipopolysaccharide-activated NF-κB pathway was suppressed in response to CCL4 in pLE cells. Inhibition of CCR5 decreased the proliferation of pLE cells and activation of the PI3K and MAPK pathways by CCL4. Furthermore, CCL4 enhanced conceptus-maternal interactions between porcine trophectoderm (pTr) cells and pLE cells during early pregnancy by activating expression of migration and implantation-related genes. Collectively, the results suggest that CCL4 may improve successful implantation in early pregnancy in pigs.

Disruption of female reproductive function by endotoxins

Endotoxemia can be caused by obesity, environmental chemical exposure, abiotic stressors and bacterial infection. Circumstances that deleteriously impact intestinal barrier integrity can induce endotoxemia, and controlled experiments have identified negative impacts of lipopolysaccharide (LPS; an endotoxin mimetic) on folliculogenesis, puberty onset, estrus behavior, ovulation, meiotic competence, luteal function and ovarian steroidogenesis. In addition, neonatal LPS exposures have transgenerational female reproductive impacts, raising concern about early life contacts to this endogenous reproductive toxicant. Aims of this review are to identify physiological stressors causing endotoxemia, to highlight potential mechanism(s) by which LPS compromises female reproduction and identify knowledge gaps regarding how acute and/or metabolic endotoxemia influence(s) female reproduction.

The upregulation of pro-inflammatory cytokines in the rabbit uterus under the lipopolysaccaride-induced reversible immunoresponse state

The reproductive organs are more likely to develop gram-negative bacterial infection than other internal organs because of direct access to the body surface. The objective of this study was (1) to provide a suitable intravenous injection dose of lipopolysaccharides (LPS) instead of gram-negative bacterial infection in order to induce a reversible immunoresponse state and (2) to examine the expression levels of pro-inflammatory cytokines in the uterus of rabbits while in an immunoresponse state. Two series of experiments were performed to accomplish these objectives. In the first series, 20 healthy New Zealand White female rabbits were divided into 5 homogeneous groups (n=4), and intravenously injected with 0, 0.5, 1, 2, or 4mg/kg body weight (BW) of LPS derived from Escherichia coli dissolved in 2ml of sterile saline (LPS carrier). The control group received only saline. The concentrations of IL-1β, IL-6, and TNF-α in serum and the white blood cell count changed with time after LPS stimulation, and certain doses of LPS led to the death of some rabbits. The results suggested that a dose of 0.5mg/kg of LPS induced a reversible immunoresponse state. In the second series, 4 rabbits were not injected (0h), 16 rabbits were injected with 0.5mg/kg LPS, and 16 rabbits in the control group were injected with 2ml of sterile saline. Tissues of the uterine horn, uterine body, and cervix from the 36 rabbits were collected at 0, 1.5, 3, 6, and 12h (n=4) postinjection for examination of the expression levels of IL-1β, IL-6, and TNF-α by quantitative real-time PCR (qRT-PCR). The results suggested that 0.5mg/kg of LPS upregulated the expression levels of IL-1β, IL-6 and TNF-α in the uterine body and uterine horn, and IL-6 in the cervix. In conclusion, the expression levels of IL-1β, IL-6 and TNF-α were upregulated in the uterus of rabbits under the reversible immunoresponse state induced by 0.5mg/kg of LPS-injection.

Human thioredoxin-1 attenuates the rate of lipopolysaccharide-induced preterm delivery in mice in association with its anti-inflammatory effect

BACKGROUND

Maternal intrauterine infection/inflammation represents the major etiology of preterm delivery and the leading cause of neonatal mortality and morbidity. The aim of this study was to investigate the anti-inflammatory properties of thioredoxin-1 in vivo and its potential ability to attenuate the rate of inflammation-induced preterm delivery.

METHODS

Two intraperitoneal injections of lipopolysaccharide from Escherichia coli were administered in pregnant mice on gestational day 15, with a 3-h interval between the injections. From either 1 h before or 1 h after the first lipopolysaccharide injection, mice received three intravenous injections of either recombinant human thioredoxin-1, ovalbumin, or vehicle, with a 3-h interval between injections.

RESULTS

Intraperitoneal injection of lipopolysaccharide induced a rise of tumor necrosis factor-α, interferon-γ, monocyte chemotactic protein 1, and interleukin-6 in maternal serum levels and provoked preterm delivery. Recombinant human thoredoxin-1 prevented the rise in these proinflammatory cytokine levels. After the inflammatory challenge, placentas exhibited severe maternal vascular dilatation and congestion and a marked decidual neutrophil activation. These placental pathological findings were ameliorated by recombinant human thioredoxin-1, and the rate of inflammation-induced preterm delivery was attenuated.

CONCLUSION

Thioredoxin-1 may thus represent a novel effective treatment to delay inflammation-induced preterm delivery.

Rosiglitazone pretreatment protects against lipopolysaccharide-induced fetal demise through inhibiting placental inflammation

Peroxisome proliferator-activated receptor (PPAR)-γ is highly expressed in human and rodent placentas. Nevertheless, its function remains obscure. The present study investigated the effects of rosiglitazone, a PPAR-γ agonist, on LPS-induced fetal death. All pregnant mice except controls were intraperitoneally injected with LPS (150 μg/kg) daily from gestational day (GD)15 to GD17. As expected, maternal LPS injection caused placental inflammation and resulted in 63.6% fetal death in dams that completed the pregnancy. Interestingly, LPS-induced fetal mortality was reduced to 16.0% when pregnant mice were pretreated with RSG. Additional experiment showed that rosiglitazone pretreatment inhibited LPS-induced expressions of tumor necrosis factor (Tnf)-α, interleukin (Il)-1β, Il-6, macrophage inflammatory protein (Mip)-2 and keratinocyte-derived chemokine (Kc) in mouse placenta. Although rosiglitazone had little effect on LPS-evoked elevation of IL-10 in amniotic fluid, it alleviated LPS-evoked release of TNF-α and MIP-2 in amniotic fluid. Further analysis showed that pretreatment with rosiglitazone, which activated placental PPAR-γ signaling, simultaneously suppressed LPS-evoked nuclear factor kappa B (NF-κB) activation and blocked nuclear translocation of NF-κB p65 and p50 subunits in trophoblast giant cells of the labyrinth layer. These results provide a mechanistic explanation for PPAR-γ-mediated anti-inflammatory activity in the placentas. Overall, the present study provides additional evidence for roles of PPAR-γ as an important regulator of placental inflammation.

Prenatal maternal lipopolysaccharide administration leads to age- and region-specific oxidative stress in the early developmental stage in offspring

Prenatal exposure to lipopolysaccharide (LPS) has been exploited to simulate brain disorder in animal model. Prenatal LPS-exposure has shown elevated levels of pro-inflammatory cytokines in the early stages of the postnatal period. This study determines the effect of prenatal LPS-exposure on oxidative stress (OS) in the distinct brain regions in the early postnatal stages. LPS (50 μg/kg, i.p.) and water for injection (100 μl, i.p.) were given to the experimental (n=5) and control (n=5) group of pregnant Swiss albino mice respectively on gestational day (GD)-16 and 17. Animals were decapitated on postnatal day (PnD) - 1, 7, 14 and 21 to assay levels of oxidative markers from 6 distinct brain regions. When compared with the control, prenatal LPS-exposure alters levels of OS markers: (i) on PnD-1, glutathione (GSH) level is raised and superoxide dismutase (SOD) activity is dropped, (ii) on PnD-7, advanced oxidation of protein product (AOPP) level is elevated, (iii) on PnD-14, lipid peroxidation (MDA) and activity of catalase (CAT) are enhanced, (iv) on PnD-21, increased MDA continued. The hippocampus (HC) and cerebellum (CB) were mostly susceptible to OS in the early postnatal development. Levels of MDA and activity of CAT enzyme were increased on PnD-14 in the cortex, HC and CB. Except MDA, all OS markers recovered and returned to the level of control animals on PnD-21. Taken together, these results suggest that prenatal LPS-exposure induces age- and region-specific OS in the early postnatal stage.

The effect of maternal Inflammation on foetal programming of metabolic disease

Maternal obesity during pregnancy increases the child's risk of developing obesity and obesity-related diseases later in life. Key components in foetal programming of metabolic risk remain to be identified; however, chronic low-grade inflammation associated with obesity might be responsible for metabolic imprinting in the offspring. We have therefore surveyed the literature to evaluate the role of maternal obesity-induced inflammation in foetal programming of obesity and related diseases. The literature on this topic is limited, so this review also includes animal models where maternal inflammation is mimicked by single injections with lipopolysaccharide (LPS). An LPS challenge results in an immunological response that resembles the obesity-induced immune profile, although LPS injections provoke a stronger response than the subclinical obesity-associated response. Maternal LPS or cytokine exposures result in increased adiposity and impaired metabolic homeostasis in the offspring, similar to the phenotype observed after exposure to maternal obesity. The cytokine levels might be specifically important for the metabolic imprinting, as cytokines are both transferable from maternal to foetal circulation and have the capability to modulate placental nutrient transfer. However, the immune response associated with obesity is moderate and therefore potentially weakened by the pregnancy-driven immune modulation, dominated by anti-inflammatory Treg and Th2 cells. We know from other low-grade inflammatory diseases, such as rheumatoid arthritis, that pregnancy can improve disease state. If pregnancy is also capable of suppressing the obesity-associated inflammation, the immunological markers might be less likely to affect metabolic programming in the developing foetus than otherwise implied.

Specific Lipopolysaccharide Serotypes Induce Differential Maternal and Neonatal Inflammatory Responses in a Murine Model of Preterm Labor

Intrauterine inflammation is recognized as a key mediator of both normal and preterm birth but is also associated with neonatal neurological injury. Lipopolysaccharide (LPS) is often used to stimulate inflammatory pathways in animal models of infection/inflammation-induced preterm labor; however, inconsistencies in maternal and neonatal responses to LPS are frequently reported. We hypothesized that LPS serotype-specific responses may account for a portion of these inconsistencies. Four different Escherichia coli LPS serotypes (O111:B4, O55:B5, O127:B8, and O128:B12) were administered to CD1 mice via intrauterine injection at gestational day 16. Although control animals delivered at term 60 ± 15 hours postinjection (p.i.), those administered with O111:B4 delivered 7 ± 2 hours p.i., O55:B5 delivered 10 ± 3 hours p.i., O127:B8 delivered 16 ± 10 hours p.i., and O128:B12 delivered 17 ± 2 hours p.i. (means ± SD). A correlation between the onset of preterm labor and myometrial activation of the inflammatory transcription factor, activator protein 1, but not NF-κB was observed. Specific LPS serotypes induced differential activation of downstream contractile and inflammatory pathways in myometrium and neonatal pup brain. Our findings demonstrate functional disparity in inflammatory pathway activation in response to differing LPS serotypes. Selective use of LPS serotypes may represent a useful tool for targeting specific inflammatory response mechanisms in these models.

Endotoxin exposure and puberty in female rats: the role of nitric oxide and caspase-1 inhibition in neonates

Bacterial toxins are widespread in the environment as well as in the digestive system of humans and animals. Toxin from Gram-negative bacteria (endotoxin or lipopolysaccharide; LPS) has a life-long programming effect on reproduction in rats, but the mediators have not been well-documented, so we investigated the effects of LPS on the timing of puberty in female rats. Because the levels of nitric oxide (NO) and interleukin 1β (IL-1β) increase following injection of LPS, we injected neonates (post-natal day (pnd) 7) with LPS, with or without NO or IL-1β inhibitors. Half of the prepubescent (pnd 30) animals received an additional LPS injection. Vaginal opening, number of ovarian follicles, and serum anti-LPS antibodies were determined. A single LPS injection was sufficient to reduce the primordial follicle pool, but puberty was delayed when rats received 2 LPS injections (at pnd 7 and 30). NO or IL-1β inhibitors improved both of these parameters, suggesting that the early detrimental effects of LPS on puberty and primordial follicle pool are mediated by NO and IL-1β.

Supplementation with vitamin D3 during pregnancy protects against lipopolysaccharide-induced neural tube defects through improving placental folate transportation

Several reports demonstrated that maternal lipopolysaccharide (LPS) exposure at middle gestational stage caused neural tube defects (NTDs). This study investigated the effects of supplementation with vitamin D3 (VitD3) during pregnancy on LPS-induced NTDs. Pregnant mice except controls were ip injected with LPS (25 μg/kg) daily from gestational day (GD)8 to GD12. In LPS+VitD3 group, pregnant mice were orally administered with VitD3 (25 μg/kg) before LPS injection. As expected, a 5-day LPS injection resulted in 62.5% (10/16) of dams and 20.3% of fetuses with NTDs. Additional experiment showed that a 5-day LPS injection downregulated placental proton-coupled folate transporter (pcft) and reduced folate carrier 1 (rfc1), 2 major folate transporters in placentas. Consistent with downregulation of placental folate transporters, folate transport from maternal circulation into embryos was disturbed in LPS-treated mice. Interestingly, VitD3 not only inhibited placental inflammation but also attenuated LPS-induced downregulation of placental folate transporters. Correspondingly, VitD3 markedly improved folate transport from maternal circulation into the embryos. Importantly, supplementation with VitD3 during pregnancy protected mice from LPS-induced NTDs. Taken together, these results suggest that supplementation with VitD3 during pregnancy prevents LPS-induced NTDs through inhibiting placental inflammation and improving folate transport from maternal circulation into the embryos.

Maternal lipopolysaccharide alters the newborn oxidative stress and C-reactive protein levels in response to an inflammatory stress

Maternal infection is associated with oxidative stress (OS) and inflammatory responses. We have previously shown that maternal exposure to lipopolysaccharide (LPS) at E18 alters the subsequent offspring immune response. As immune responses are mediated, in part, by OS, we sought to determine if maternal inflammation during pregnancy programs offspring OS and C-reactive protein (CRP) levels. Pregnant Sprague-Dawley rats received intraperitoneal (i.p.) injections of saline or LPS at 18 days' gestation (n = 4), and pups delivered spontaneously at term. At postnatal day 24, male and female offspring received i.p. injection of LPS. Serum lipid peroxides formation (PD) and CRP levels were determined before and at 4 h following the LPS injection. Pups of LPS-exposed dams had significantly higher basal OS (PD 29.4 ± 5.4 v. 10.1 ± 4.8 nmol/ml) compared with controls. In response to LPS, CRP levels (20.4 ± 2.8 v. 5.7 ± 1.0 ng/ml) were significantly higher among pups of LPS-exposed dams than controls. Prenatal maternal exposure to LPS increases baseline OS levels in neonates and CRP levels in response to LPS. These results suggest that maternal inflammation during the antenatal period may induce long-term sequelae in the offspring that may predispose to adult disease.

Effects of maternal LPS exposure during pregnancy on metabolic phenotypes in female offspring

It is increasingly recognized that intra-uterine growth restriction (IUGR) is associated with an increased risk of metabolic disorders in late life. Previous studies showed that mice exposed to LPS in late gestation induced fetal IUGR. The present study investigated the effects of maternal LPS exposure during pregnancy on metabolic phenotypes in female adult offspring. Pregnant mice were intraperitoneally injected with LPS (50 µg/kg) daily from gestational day (GD)15 to GD17. After lactation, female pups were fed with standard-chow diets (SD) or high-fat diets (HFD). Glucose tolerance test (GTT) and insulin tolerance test (ITT) were assessed 8 and 12 weeks after diet intervention. Hepatic triglyceride content was examined 12 weeks after diet intervention. As expected, maternal LPS exposure during pregnancy resulted in fetal IUGR. Although there was an increasing trend on fat mass in female offspring whose dams were exposed to LPS during pregnancy, maternal LPS exposure during pregnancy did not elevate the levels of fasting blood glucose and serum insulin and hepatic triglyceride content in female adult offspring. Moreover, maternal LPS exposure during pregnancy did not alter insulin sensitivity in adipose tissue and liver in female adult offspring. Further analysis showed that maternal LPS exposure during pregnancy did not exacerbate HFD-induced glucose tolerance and insulin resistance in female adult offspring. In addition, maternal LPS exposure during pregnancy did not aggravate HFD-induced elevation of hepatic triglyceride content in female adult offspring. In conclusion, LPS-induced IUGR does not alter metabolic phenotypes in adulthood.

Orally administered melatonin prevents lipopolysaccharide-induced neural tube defects in mice

Lipopolysaccharide (LPS) has been associated with adverse pregnant outcomes, including fetal demise, intra-uterine growth restriction (IUGR), neural tube defects (NTDs) and preterm delivery in rodent animals. Previous studies demonstrated that melatonin protected against LPS-induced fetal demise, IUGR and preterm delivery. The aim of the present study was to investigate the effects of melatonin on LPS-induced NTDs. All pregnant mice except controls were intraperitoneally injected with LPS (25 µg/kg) daily from gestational day (GD)8 to GD12. Some pregnant mice were orally administered with melatonin (MT, 50 mg/kg) before each LPS injection. A five-day LPS injection resulted in 27.5% of fetuses with anencephaly, exencephaly or encephalomeningocele. Additional experiment showed that maternal LPS exposure significantly down-regulated placental proton-coupled folate transporter (pcft) and disturbed folate transport from maternal circulation through the placentas into the fetus. Interestingly, melatonin significantly attenuated LPS-induced down-regulation of placental pcft. Moreover, melatonin markedly improved the transport of folate from maternal circulation through the placentas into the fetus. Correspondingly, orally administered melatonin reduced the incidence of LPS-induced anencephaly, exencephaly or encephalomeningocele. Taken together, these results suggest that orally administered melatonin prevents LPS-induced NTDs through alleviating LPS-induced disturbance of folate transport from maternal circulation through the placenta into the fetus.

Nicotine, an α7 nAChR agonist, reduces lipopolysaccharide-induced inflammatory responses and protects fetuses in pregnant rats

OBJECTIVE

The objective of the study was to examine the effects of nicotine, an α7 nicotinic acetylcholine receptor agonist, on lipopolysaccharide (LPS)-induced inflammatory responses in rats during pregnancy.

STUDY DESIGN

Pregnant Sprague Dawley rats were randomly divided into groups (n = 6 rats/group): group 1 rats each received a single intraperitoneal injection of LPS (25 μg/kg) on gestation day 16; group 2 rats were first pretreated with nicotine (1 mg/kg per day, subcutaneously) on gestation days 14 and 15 and then were treated with single injections of LPS on gestational day 16; group 3 rats were treated with the vehicle (saline) used for groups 2 and 3 (controls). Maternal blood was collected at 6 hours and 24 hours after LPS and vehicle treatments and assayed for tumor necrosis factor (TNF)-α, interleukin-6 (IL-6), and interleukin-10 (IL-10). In addition, the number of live pups and pup weights were obtained at the time of delivery.

RESULTS

LPS treatment significantly (P < .001) elevates maternal blood levels of TNF-α and IL-6 but not IL-10 (P > .05). Nicotine treatment significantly reduces LPS-induced TNF-α and IL-6 concentrations (P < .001) but does not change (P > .05) IL-10 levels. The number of live pups in the LPS group are significantly lower (P < .001) than the vehicle treated controls, and nicotine treatment significantly (P < .011) reverses this change. Similarly, fetal weights are lower following LPS (P < .016) and higher (P < .024) in the group treated with nicotine plus LPS.

CONCLUSION

Nicotine reduces the LPS-induced inflammatory responses and rescues the fetus in rats during pregnancy. Thus, nicotine exerts dramatic antiinflammatory effects. These observations have important implications for control of inflammatory responses during pregnancy.

Maternal LPS exposure during pregnancy impairs testicular development, steroidogenesis and spermatogenesis in male offspring

Lipopolysaccharide (LPS) is associated with adverse developmental outcomes including embryonic resorption, fetal death, congenital teratogenesis and fetal growth retardation. Here, we explored the effects of maternal LPS exposure during pregnancy on testicular development, steroidogenesis and spermatogenesis in male offspring. The pregnant mice were intraperitoneally injected with LPS (50 µg/kg) daily from gestational day (GD) 13 to GD 17. At fetal period, a significant decrease in body weight and abnormal Leydig cell aggregations were observed in males whose mothers were exposed to LPS during pregnancy. At postnatal day (PND) 26, anogenital distance (AGD), a sensitive index of altered androgen action, was markedly reduced in male pups whose mothers were exposed to LPS daily from GD13 to GD 17. At PND35, the weight of testes, prostates and seminal vesicles, and serum testosterone (T) level were significantly decreased in LPS-treated male pups. At adulthood, the number of sperm was significantly decreased in male offspring whose mothers were exposed to LPS on GD 13-17. Maternal LPS exposure during gestation obviously diminished the percent of seminiferous tubules in stages I-VI, increased the percent of seminiferous tubules in stages IX-XII, and caused massive sloughing of germ cells in seminiferous tubules in mouse testes. Moreover, maternal LPS exposure significantly reduced serum T level in male mice whose mothers were exposed to LPS challenge during pregnancy. Taken together, these results suggest that maternal LPS exposure during pregnancy disrupts T production. The decreased T synthesis might be associated with LPS-induced impairments for spermatogenesis in male offspring.

Prenatal exposure to lipopolysaccharide combined with pre- and postnatal high-fat diet result in lowered blood pressure and insulin resistance in offspring rats

Background

Adult metabolic syndrome may in part have origins in fetal or early life. This study was designed to explore the effect of prenatal exposure to lipopolysaccharide and high-fat diet on metabolic syndrome in offspring rats.

Methods

32 pregnant rats were randomly divided into four groups, including Control group; LPS group (pregnant rats were injected with LPS 0.4 mg/kg intraperitoneally on the 8^th, 10^th and 12^th day of pregnancy); High-fat group (maternal rats had high-fat diet during pregnancy and lactation period, and their pups also had high-fat diet up to the third month of life); LPS + High-fat group (rats were exposed to the identical experimental scheme with LPS group and High-fat group).

Results

Blood pressure elevated in LPS group and High-fat group, reduced in LPS+High-fat group, accompanied by the increase of serum leptin level in LPS and High-fat group and increase of serum IL-6, TNF-a in High-fat group; both serum insulin and cholesterol increased in High-fat and LPS+High-fat group, as well as insulin in LPS group. HOMA-IR value increased in LPS, High-fat and LPS+High-fat group, and QUICKI decreased in these groups; H-E staining showed morphologically pathological changes in thoracic aorta and liver tissue in the three groups. Increased serum alanine and aspartate aminotransferase suggest impaired liver function in LPS+High-fat group.

Conclusion/Significance

Prenatal exposure to lipopolysaccharide combined with pre- and postnatal high-fat diet result in lowered blood pressure, insulin resistance and impaired liver function in three-month old offspring rats. The lowered blood pressure might benefit from the predictive adaptive response to prenatal inflammation.

Folic acid protects against lipopolysaccharide-induced preterm delivery and intrauterine growth restriction through its anti-inflammatory effect in mice

Increasing evidence demonstrates that maternal folic acid (FA) supplementation during pregnancy reduces the risk of neural tube defects, but whether FA prevents preterm delivery and intrauterine growth restriction (IUGR) remains obscure. Previous studies showed that maternal lipopolysaccharide (LPS) exposure induces preterm delivery, fetal death and IUGR in rodent animals. The aim of this study was to investigate the effects of FA on LPS-induced preterm delivery, fetal death and IUGR in mice. Some pregnant mice were orally administered with FA (0.6, 3 or 15 mg/kg) 1 h before LPS injection. As expected, a high dose of LPS (300 μg/kg, i.p.) on gestational day 15 (GD15) caused 100% of dams to deliver before GD18 and 89.3% of fetuses dead. A low dose of LPS (75 μg/kg, i.p.) daily from GD15 to GD17 resulted in IUGR. Interestingly, pretreatment with FA prevented LPS-induced preterm delivery and fetal death. In addition, FA significantly attenuated LPS-induced IUGR. Further experiments showed that FA inhibited LPS-induced activation of nuclear factor kappa B (NF-κB) in mouse placentas. Moreover, FA suppressed LPS-induced NF-κB activation in human trophoblast cell line JEG-3. Correspondingly, FA significantly attenuated LPS-induced upregulation of cyclooxygenase (COX)-2 in mouse placentas. In addition, FA significantly reduced the levels of interleukin (IL)-6 and keratinocyte-derived cytokine (KC) in amniotic fluid of LPS-treated mice. Collectively, maternal FA supplementation during pregnancy protects against LPS-induced preterm delivery, fetal death and IUGR through its anti-inflammatory effects.

Progesterone is essential for protecting against LPS-induced pregnancy loss. LIF as a potential mediator of the anti-inflammatory effect of progesterone

Lipopolysaccharide (LPS) administration to mice on day 7 of gestation led to 100% embryonic resorption after 24 h. In this model, nitric oxide is fundamental for the resorption process. Progesterone may be responsible, at least in part, for a Th2 switch in the feto-maternal interface, inducing active immune tolerance against fetal antigens. Th2 cells promote the development of T cells, producing leukemia inhibitory factor (LIF), which seems to be important due to its immunomodulatory action during early pregnancy. Our aim was to evaluate the involvement of progesterone in the mechanism of LPS-induced embryonic resorption, and whether LIF can mediate hormonal action. Using in vivo and in vitro models, we provide evidence that circulating progesterone is an important component of the process by which infection causes embryonic resorption in mice. Also, LIF seems to be a mediator of the progesterone effect under inflammatory conditions. We found that serum progesterone fell to very low levels after 24 h of LPS exposure. Moreover, progesterone supplementation prevented embryonic resorption and LPS-induced increase of uterine nitric oxide levels in vivo. Results show that LPS diminished the expression of the nuclear progesterone receptor in the uterus after 6 and 12 h of treatment. We investigated the expression of LIF in uterine tissue from pregnant mice and found that progesterone up-regulates LIF mRNA expression in vitro. We observed that LIF was able to modulate the levels of nitric oxide induced by LPS in vitro, suggesting that it could be a potential mediator of the inflammatory action of progesterone. Our observations support the view that progesterone plays a critical role in a successful pregnancy as an anti-inflammatory agent, and that it could have possible therapeutic applications in the prevention of early reproductive failure associated with inflammatory disorders.

Zinc supplementation during pregnancy protects against lipopolysaccharide-induced fetal growth restriction and demise through its anti-inflammatory effect

LPS is associated with adverse developmental outcomes, including preterm delivery, fetal death, teratogenicity, and intrauterine growth restriction (IUGR). Previous reports showed that zinc protected against LPS-induced teratogenicity. In the current study, we investigated the effects of zinc supplementation during pregnancy on LPS-induced preterm delivery, fetal death and IUGR. All pregnant mice except controls were i.p. injected with LPS (75 μg/kg) daily from gestational day (GD) 15 to GD17. Some pregnant mice were administered zinc sulfate through drinking water (75 mg elemental Zn per liter) throughout the pregnancy. As expected, an i.p. injection with LPS daily from GD15 to GD17 resulted in 36.4% (4/11) of dams delivered before GD18. In dams that completed the pregnancy, 63.2% of fetuses were dead. Moreover, LPS significantly reduced fetal weight and crown-rump length. Of interest, zinc supplementation during pregnancy protected mice from LPS-induced preterm delivery and fetal death. In addition, zinc supplementation significantly alleviated LPS-induced IUGR and skeletal development retardation. Further experiments showed that zinc supplementation significantly attenuated LPS-induced expression of placental inflammatory cytokines and cyclooxygenase-2. Zinc supplementation also significantly attenuated LPS-induced activation of NF-κB and MAPK signaling in mononuclear sinusoidal trophoblast giant cells of the labyrinth zone. It inhibited LPS-induced placental AKT phosphorylation as well. In conclusion, zinc supplementation during pregnancy protects against LPS-induced fetal growth restriction and demise through its anti-inflammatory effect.

Gonadal and nongonadal FSHR and LHR dysfunction during lipopolysaccharide induced failure of blastocyst implantation in mouse

PURPOSE

The purpose of the present study was to investigate the impact of lipopolysaccharide (LPS) on follicle-stimulating hormone (FSH), luteinizing hormone (LH) and their receptors during preimplantation days of pregnancy.

METHOD

The PBS or lipopolysaccharide (LPS) was injected intraperitoneally in the pregnant females on day 0.5 of pregnancy and serum, embryos, ovaries and uterine horns were collected on days 1.5, 2.5, 3.5, 4.0, 4.125, 4.33 and 4.42 of pregnancy.

RESULT(S)

In the LPS-treated pregnant females, the secretion of FSH and LH is disturbed with respect to normal pregnancy. Furthermore, the expression of FSHR mRNA in embryos and ovaries, LHR mRNA in embryos and uterus get modulated in response to LPS during preimplantation days of pregnancy.

CONCLUSION(S)

The disturbance in the serum level of FSH and LH in response to LPS leads implantation failure in mouse which suggests that these gonadotropins plays an integral role in the process of the successful implantation. This study also suggests a possible nongonadal role of FSHR and LHR in LPS-induced implantation failure in the mouse.

N-acetyl-cysteine (NAC) attenuates LPS-induced maternal and amniotic fluid oxidative stress and inflammatory responses in the preterm gestation

OBJECTIVE

Maternal infection is associated with oxidative stress and inflammation. We sought to determine whether N-acetyl-cysteine can decrease maternal oxidative stress and the inflammatory response in preterm gestation.

STUDY DESIGN

Pregnant rats 16 days, were treated with (1) lipopolysaccharide, (2) N-acetyl-cysteine 120 minutes after lipopolysaccharide, or (3) saline solution (intraperitoneal). Six hours after lipopolysaccharide administration, serum lipid peroxide formation (LPO), tumor necrosis factor-α, interleukin-6, and interleukin-1β levels in maternal serum and amniotic fluid were determined.

RESULTS

Lipopolysaccharide significantly increased maternal serum lipid peroxide formation (24-118.5 nmol/mL; P < .05), and maternal serum and amniotic fluid tumor necrosis factor-α, interleukin-6, and interleukin-1β. N-acetyl-cysteine treatment after lipopolysaccharide significantly attenuated lipid peroxide formation (47.5 nmol/mL) and proinflammatory cytokines response in maternal serum and amniotic fluid.

CONCLUSION

Maternal and amniotic fluid oxidative stress and inflammatory stimulation are attenuated by N-acetyl-cysteine even when administered after lipopolysaccharide. These results suggest that N-acetyl-cysteine may protect the fetus from adverse sequelae associated with inflammatory stimulation.

Tocolytic effect of delta9-tetrahydrocannabinol in mice model of lipopolysaccharide--induced preterm delivery: role of nitric oxide

INTRODUCTION

In this study, we explained that exogenous cannabinoid, Delta(9)-tetrahydrocannabinol (THC), has a preventive effect in a murine model of lipopolysaccharide (LPS)-induced preterm delivery and the contribution of nitric oxide (NO) pathway as a mechanism involved in this process.

STUDY DESIGN

Preterm delivery was induced by double dose of 35 microg/kg LPS with 3-hour interval on gestational day (gd) 15. Delta(9)-tetrahydrocannabinol was administered with (a) double dose (0.02, 0.05, 0.1, 0.5, 1, and 5 mg/kg) 1 hour before each LPS injection, on gd 15 and (b) single administration (0.05, 0.1, and 0.5 mg/kg,) on gds 13 and 14, and the double administration, 1 hour before each LPS injection. To assess the involved mechanism, either AM281 (CB1 receptor antagonist, 2 mg/kg) and AM630 (CB2 receptor antagonist, 5 mg/kg) or N(omega)-nitro-L-arginine methyl ester (L-NAME, 2 mg/kg) was administered 1 hour before each THC injection on gds 13, 14, and 15. The main outcome measurement was the incidence of preterm delivery after injection of last LPS dose. Any interaction in the incidence and time of preterm delivery was ruled out by administration of AM281, AM630, or L-NAME alone.

RESULTS

Chronic THC treatment (0.5 mg/kg) significantly decreased the incidence of LPS-induced premature labor and increased the delivery time. Both AM281 and L-NAME reversed THC-induced attenuation of preterm delivery rate and pregnancy duration. Unlike AM281, AM630 did not influence the rate of preterm delivery in THC-treated mice.

CONCLUSION

Delta(9)-Tetrahydrocannabinol contributes to the regulation of gestational duration in LPS-induced preterm delivery probably by NO coupling through the CB1 receptor.