Inflammatory mechanisms of preterm labor and emerging anti-inflammatory interventions

Preterm birth is a major public health concern, requiring a deeper understanding of its underlying inflammatory mechanisms and to develop effective therapeutic strategies. This review explores the complex interaction between inflammation and preterm labor, highlighting the pivotal role of the dysregulation of inflammation in triggering premature delivery. The immunological environment of pregnancy, characterized by a fragile balance of immune tolerance and resistance, is disrupted in preterm labor, leading to a pathological inflammatory response. Feto-maternal infections, among other pro-inflammatory stimuli, trigger the activation of toll-like receptors and the production of pro-inflammatory mediators, promoting uterine contractility and cervical ripening. Emerging anti-inflammatory therapeutics offer promising approaches for the prevention of preterm birth by targeting key inflammatory pathways. From TLR-4 antagonists to chemokine and interleukin receptor antagonists, these interventions aim to modulate the inflammatory environment and prevent adverse pregnancy outcomes. In conclusion, a comprehensive understanding of the inflammatory mechanisms leading to preterm labor is crucial for the development of targeted interventions in hope of reducing the incidence of preterm birth and improving neonatal health outcomes.

The role of neutrophils and neutrophil extracellular traps (NETs) in stages, outcomes and pregnancy complications

Neutrophils are the main components of innate immunity to eliminate infectious pathogens. Neutrophils play a role in several stages of the reproductive cycle, and their presence in the female reproductive system is highly regulated, so their function may change during pregnancy. Emerging evidence suggests that neutrophils are important at all stages of pregnancy, from implantation, placentation, and connective tissue regeneration to birth, as well as birth itself. Neutrophil extracellular traps (NETs) are defined as extracellular strands of unfolded DNA together with histone complexes and neutrophil granule proteins. NET formation is a new mechanism of these cells for their defense function. These strands containing DNA and antimicrobial peptides were initially recognized as one of the defense mechanisms of neutrophils, but later it was explained that they are involved in a variety of non-infectious diseases. Since the source of inflammation and tissue damage is the irregular activity of neutrophils, it is not surprising that NETosis are associated with a number of inflammatory conditions and diseases. The overexpression of NET components or non-principled NET clearance is associated with the risk of production and activation of autoantibodies, which results in participation in autoinflammatory and autoimmune disorders (SLE, RA), fibrosis, sepsis and other disorders such as vascular diseases, for example, thrombosis and atherosclerosis. Recent published articles have shown the role of neutrophils and extracellular traps (NETs) in pregnancy, childbirth and pregnancy-related diseases. The aim of this study was to identify and investigate the role of neutrophils and neutrophil extracellular traps (NETs) in the stages of pregnancy, as well as the complications caused by these cells.

Role of IL-6, IL-10 and TNFα Gene Variants in Preterm Birth

Background: The association of gene variants for interleukin 6 (IL-6) (rs1800796), interleukin 10 (IL-10) (rs1800896) and tumor necrosis factorα (TNFα (rs1800629) with the occurrence of spontaneous preterm birth (PTB) was investigated to determine whether these genetic variants are a risk factor. Methods: A total of 199 blood samples from pregnant women who had given birth prematurely and 200 control blood samples were analyzed to determine single nucleotide polymorphisms (SNPs) of genes for IL-6 (rs1800796), IL-10 (rs1800896) and TNFα (rs1800629). The control samples were samples from pregnant women with term delivery. The isolation of DNA was performed on mini-spin columns according to the manufacturer's protocol. The quality and purity of the isolated DNA were tested using a Qubit 3 fluorometer. Genotyping was performed with an ABI PRISM 7500 SDS using TaqMan SNP genotyping assays. The genotypes obtained were analyzed using the 7500 Software v2.3 package. Results: Carriers of the A/A genotype for the rs1800629 SNP of the TNFα gene have a 4.81 times greater chance of late-onset PTB compared to carriers of the G/G and A/G genotypes in the recessive inheritance model. The presence of the G/G genotype in the recessive inheritance model compared with the G/A and A/A genotypes for the rs1800896 SNP of the IL-10 gene represents a potentially protective factor, with mothers in the term-birth group having an almost 2-fold lower odds of PTB in general and an almost 10-fold lower odds of early PTB. On the other hand, carriers of the A/G genotype of rs1800896 have a 1.54-fold higher chance of preterm birth in general and a 1.6-fold higher chance of late preterm birth in the superdominant inheritance model compared to the A/A and G/G genotypes in the group of mothers with PTB. In this study, no association was found between PTB and the rs1800796 SNP of the IL-6 gene. Conclusions: rs1800629 in mothers was associated with PTB. rs1800896 shows a potentially protective effect for the occurrence of PTB in this study. No association was found between PTB and rs1800796.

Raspberry Leaves and Extracts-Molecular Mechanism of Action and Its Effectiveness on Human Cervical Ripening and the Induction of Labor

The gestational period is an incredibly stressful time for a pregnant woman. Pregnant patients constantly seek effective and reliable compounds in order to achieve a healthy labor. Nowadays, increasing numbers of women use herbal preparations and supplements during pregnancy. One of the most popular and most frequently chosen herbs during pregnancy is the raspberry leaf (Rubus idaeus). Raspberry extracts are allegedly associated with a positive effect on childbirth through the induction of uterine contractions, acceleration of the cervical ripening, and shortening of childbirth. The history of the consumption of raspberry leaves throughout pregnancy is vast. This review shows the current status of the use of raspberry leaves in pregnancy, emphasizing the effect on the cervix, and the safety profile of this herb. The majority of women apply raspberry leaves during pregnancy to induce and ease labor. However, it has not been possible to determine the exact effect of using raspberry extracts on the course of childbirth and the perinatal period. Additionally, it is unclear whether this herb has only positive effects. The currently available data indicate a weak effect of raspberry leaf extracts on labor induction and, at the same time, their possible negative impact on cervical ripening.

IL-6 and IL-8: An Overview of Their Roles in Healthy and Pathological Pregnancies

Interleukin-6 (IL-6) is an acknowledged inflammatory cytokine with a pleiotropic action, mediating innate and adaptive immunity and multiple physiological processes, including protective and regenerative ones. IL-8 is a pro-inflammatory CXC chemokine with a primary function in attracting and activating neutrophils, but also implicated in a variety of other cellular processes. These two ILs are abundantly expressed at the feto-maternal interface over the course of a pregnancy and have been shown to participate in numerous pregnancy-related events. In this review, we summarize the literature data regarding their role in healthy and pathological pregnancies. The general information related to IL-6 and IL-8 functions is followed by an overview of their overall expression in cycling endometrium and at the feto-maternal interface. Further, we provide an overview of their involvement in pregnancy establishment and parturition. Finally, the implication of IL-6 and IL-8 in pregnancy-associated pathological conditions, such as pregnancy loss, preeclampsia, gestational diabetes mellitus and infection/inflammation is discussed.

Impact of Oxidative Stress on Molecular Mechanisms of Cervical Ripening in Pregnant Women

Uterine cervix is one of the essential factors in labor and maintaining the proper course of pregnancy. During the last days of gestation, the cervix undergoes extensive changes manifested by transformation from a tight and rigid to one that is soft and able to dilate. These changes can be summarized as “cervical ripening”. Changes in the cervical tissue can be referred to as remodeling of the extracellular matrix. The entire process is the result of a close relationship between biochemical and molecular pathways, which is strictly controlled by inflammatory and endocrine factors. When the production of reactive oxygen species exceeds the antioxidant capacity, oxidative stress occurs. A physiologic increase of reactive oxygen species (ROS) and reactive nitrogen species (RNS) is observed through pregnancy. ROS play important roles as second messengers in many intracellular signaling cascades contributing to the course of gestation. This review considers their involvement in the cervical ripening process, emphasizing the molecular and biochemical pathways and the clinical implications.

Functional and pathological role of 15-Lipoxygenase and its metabolites in pregnancy and pregnancy-associated complications

Maternal lipid metabolism status during pregnancy may have pivotal effects on a healthy pregnancy, the progression of labor, and childbirth. Based on evidence, changes in maternal lipid profile and metabolism is related to various alterations in fetal metabolic status, fat mass, birth weight and can result in serious maternal and fetal complications. 15-lipoxygenase accounts as a key enzyme in metabolizing polyunsaturated fatty acids that generate various inflammatory lipid metabolites. The possible involvement of 15- lipoxygenase and its metabolites in the inflammatory process, cell proliferation and death, and immune response has been postulated. The indicative role of the 15- lipoxygenase enzymatic pathway in the implantation process, stages of pregnancy, embryogenesis, organogenesis, progression of labor, pregnancy period, and pregnancy-associated complications is remarkable. Accordingly, this study will review the research conducted on the role of 15- lipoxygenase in different reproductive tissues, and its pathological role in pregnancy-related diseases to provide more insight regarding the emerging role of 15-lipoxygenase in normal pregnancy.

Risk of Adverse Birth Outcomes in Two Cohorts of Pregnant Women With HIV in Zambia

BACKGROUND

A trial of progesterone to prevent preterm birth among HIV-infected Zambian women [Improving Pregnancy Outcomes with Progesterone (IPOP)] found no treatment effect, but the risk of the primary outcome was among the lowest ever documented in women with HIV. In this secondary analysis, we compare the risks of preterm birth (<37 weeks), stillbirth, and a composite primary outcome comprising the two in IPOP versus an observational pregnancy cohort [Zambian Preterm Birth Prevention Study (ZAPPS)] in Zambia, to evaluate reasons for the low risk in IPOP.

METHODS

Both studies enrolled women before 24 gestational weeks, during August 2015-September 2017 (ZAPPS) and February 2018-January 2020 (IPOP). We used linear probability and log-binomial regression to estimate risk differences and risk ratios (RR), before and after restriction and standardization with inverse probability weights.

RESULTS

The unadjusted risk of composite outcome was 18% in ZAPPS (N = 1450) and 9% in IPOP (N = 791) (RR = 2.0; 95% CI = 1.6, 2.6). After restricting and standardizing the ZAPPS cohort to the distribution of IPOP baseline characteristics, the risk remained higher in ZAPPS (RR = 1.6; 95% CI = 1.0, 2.4). The lower risk of preterm/stillbirth in IPOP was only partially explained by measured risk factors.

CONCLUSIONS

Possible benefits in IPOP of additional monetary reimbursement, more frequent visits, and group-based care warrant further investigation.

Inflammatory factors, genetic variants, and predisposition for preterm birth

Preterm birth is a major clinical and public health challenge, with a prevalence of 11% worldwide. It is the leading cause of death in children younger than 5 years old and represents 70% of neonatal deaths and 75% of neonatal morbidity. Despite the clinical and public health significance, this condition's etiology is still unclear, and most of the cases are spontaneous. There are several known preterm birth risk factors, including inflammatory diseases and the genetic background, although the underlying molecular mechanisms are far from understood. The present review highlights the research advances on the association between inflammatory-related genes and the increased risk for preterm delivery. The most associated genetic variants are the TNFα rs1800629, the IL1α rs17561, and the IL1RN rs2234663. Moreover, many of the genes discussed in this review are also implicated in pathologies involving inflammatory or autoimmune systems, such as periodontal disease, bowel inflammatory disease, and autoimmune rheumatic diseases. This review presents evidence suggesting a common genetic background to preterm birth, autoimmune and inflammatory diseases susceptibility.

Mid-pregnancy maternal blood nitric oxide-related gene and miRNA expression are associated with preterm birth

Aim: The nitric oxide (NO) pathway modulates inflammation and may influence birth timing. Patients & methods: Case-control analysis of 136 pregnant women with RNA obtained <28 weeks; n = 212 mRNAs and n = 108 miRNAs in the NO pathway were evaluated. NO-pathway mRNA and miRNA transcript counts in women delivering preterm versus at term were compared, miRNA-mRNA expression levels correlated and prediction models generated. Results: Fourteen genes were differentially expressed in women delivering <37 weeks; 13/14 were also differentially expressed in those delivering <34 weeks (q <0.10) versus term births. Multiple miRNA-mRNA pairs were correlated. Models with gene expression better predicted prematurity than models with only clinical or nongenomic predictors. Conclusion: Maternal blood NO pathway-related mRNA and miRNA expression is associated with prematurity.

Evolutionary transcriptomics implicates HAND2 in the origins of implantation and regulation of gestation length

The developmental origins and evolutionary histories of cell types, tissues, and organs contribute to the ways in which their dysfunction produces disease. In mammals, the nature, development and evolution of maternal-fetal interactions likely influence diseases of pregnancy. Here we show genes that evolved expression at the maternal-fetal interface in Eutherian mammals play essential roles in the evolution of pregnancy and are associated with immunological disorders and preterm birth. Among these genes is HAND2, a transcription factor that suppresses estrogen signaling, a Eutherian innovation allowing blastocyst implantation. We found dynamic HAND2 expression in the decidua throughout the menstrual cycle and pregnancy, gradually decreasing to a low at term. HAND2 regulates a distinct set of genes in endometrial stromal fibroblasts including IL15, a cytokine also exhibiting dynamic expression throughout the menstrual cycle and gestation, promoting migration of natural killer cells and extravillous cytotrophoblasts. We demonstrate that HAND2 promoter loops to an enhancer containing SNPs implicated in birth weight and gestation length regulation. Collectively, these data connect HAND2 expression at the maternal-fetal interface with evolution of implantation and gestational regulation, and preterm birth.

Antenatal pentoxifylline therapy to prevent endotoxin-induced fetal injury in the preterm goat model

Objective:

Pentoxifylline (PTX) has immunomodulatory properties and is known to reduce sepsis-associated infant mortality. We aimed to evaluate maternal oral and intra-amniotic administration of PTX for the prevention of fetal inflammation and injury in a caprine model.

Materials and Methods:

Inflammation-mediated fetal injury was induced with maternal granulocyte-colony stimulating factor and intra-amniotic endotoxin at 0.76 of gestation in date-mated pregnant goats. Eight groups were formed (n=4 each): Control, fetal injury, oral 30 mg/kg/day and 60 mg/kg/day PTX for 15 days + fetal injury, intra-amniotic 400 mg/kg and 800 mg/kg estimated fetal weight single-dose PTX with and without fetal injury. Preterm delivery by hysterotomy was performed at 0.80 of gestation to evaluate the fetal and placental effects. Immunochemistry for various markers including interleukins, caspases, cyclooxygenases, vimentin, myelin basic protein, and surfactant proteins were carried out in the fetal lungs, fetal brain, and placenta. Fetal plasma and amniotic fluid interleukins were also evaluated. Kruskal-Wallis H test and Mann-Whitney U test were used for comparisons.

Results:

High-dose (60 mg/kg/day) maternal prophylactic oral treatment attenuated endotoxin-related histological injury and was related to low inflammatory marker expressions comparable to the controls (p>0.05 except cyclooxygenase 2). Following maternal oral administration, fetal plasma and amniotic fluid levels of the studied interleukins were also lower than the untreated endotoxin-exposed animals (p<0.05 for all comparisons). Intra-amniotic PTX was associated with inconsistent results and increased inflammatory markers in some fetuses.

Conclusion:

Oral PTX before preterm birth mitigates intrauterine inflammation with neuroprotective effects in the fetus. PTX can be considered as a candidate drug for fetal brain injury prevention in the preterm period.

Experimental drugs for the inhibition of preterm labor

INTRODUCTION

Preterm birth is the leading cause of neonatal morbidity and mortality globally and poses a substantial economic burden. Consequently, there is a need for the identification of therapeutic targets and novel experimental drugs for the inhibition of preterm labor to improve neonatal outcomes.

AREAS COVERED

The authors review the pathophysiology of labor and the inflammatory pathways underpinning it. The interruption of these pathways forms the basis of therapeutic targets to inhibit preterm labor. Current drugs available for the treatment of preterm labor are reviewed, followed by experimental drugs including toll-like receptor 4 (TLR-4) antagonists, cytokine suppressive anti-inflammatory drugs (CSAIDs), N-acetyl cysteine (NAC), Sulfasalazine (SSZ), tumor necrosis factor-alpha (TNF-α) antagonists, interleukin-1 receptor (IL-1) inhibitors, omega-3 polyunsaturated fatty acids and lipid metabolites, and the polyphenols.

EXPERT OPINION

A number of new therapeutic strategies for the prevention of preterm labor are being investigated. These have the potential to improve neurodevelopmental outcomes and survival in babies born preterm, reducing the economic and healthcare costs of caring for the complex needs of these children in the immediate and long term. It is likely that over the next decade there will be a new treatment option that targets the pathological inflammatory processes involved in preterm labor.

Neutrophils in preterm birth: Friend or foe?

Preterm birth is a serious global health problem that affects 5-18% of pregnancies worldwide. In addition to being the major cause of neonatal mortality and morbidity, preterm birth is associated with short term and long term complications in the offspring. Despite this, the causes and pathogenesis of preterm birth remain unclear. Neutrophils are innate immune cells that infiltrate the maternal-fetal interface during normal parturition and their accumulation is dramatically increased during preterm birth, especially in the presence of an infection. Indeed, a defining feature of chorioamnionitis (inflammation of the chorioamnionic fetal membranes) that is associated with more than 40% of preterm births, is neutrophil accumulation. While these cells may play an important role during normal term parturition as well as preterm birth, their functions at the maternal-fetal interface are unclear. This review will provide a broad overview of the relevant studies to enable a better understanding of the roles of neutrophils during normal parturition and preterm birth.

Aldehyde dehydrogenase isoforms and inflammatory cell populations are differentially expressed in term human placentas affected by intrauterine growth restriction

OBJECTIVE

Intrauterine growth restriction (IUGR) is a complication of pregnancy that has both short- and long-term sequelae for affected mothers and offspring. The pathophysiology of disease stems from poor nutrient and oxygen provision to the fetus, resulting in increased oxidative stress within the placenta. As the milieu within the local microenvironment alters macrophage differentiation, we hypothesized that macrophage plasticity may be altered in placentas associated with IUGR, and that macrophages would show hallmarks of lipid peroxidation including altered aldehyde metabolism.

METHODS

In human placentas taken from normal pregnancies resulting in appropriate-for-gestational-age (AGA) newborns and placentas associated with IUGR, placental macrophages were evaluated by immunohistochemistry and shown in IUGR to resemble pro-inflammatory activated M1-type macrophages. To link oxidative stress to macrophages, the expression of aldehyde dehydrogenase (ALDHs) isozymes ALDH1, ALDH2, and ALDH3 was assessed.

RESULTS

All three isozymes displayed preferential staining for distinct cellular populations within the term human placenta. ALDH1 and ALDH2 were strongly expressed in placental Hofbauer and decidual stromal cells. ALDH3, in contrast, was present in extravillous trophoblasts. Comparing AGA and IUGR-associated placentas, ALDH1 and ALDH2 trended to have greater expression in macrophage populations but lower expression in decidual cell populations in IUGR-associated placentas. ALDH3 had higher expression in IUGR-associated placentas but localized specifically to extravillous trophoblast populations.

CONCLUSION

Therefore, we speculate that specific ALDH isozymes have cell-specific functions related to differentiation, inflammation, or oxidative stress responses that are altered in IUGR-associated term human placentas. This family of isozymes may be a novel method to identify human placentas affected by placental insufficiency/IUGR.

Propofol Suppresses LPS-Induced Inflammation in Amnion Cells via Inhibition of NF-κB Activation

Background

Preterm labor is a leading risk factor for neonatal death and long-term impairment and linked closely with inflammation. Non-obstetric surgery is occasionally needed during pregnancy and the anesthetic drugs or surgery itself can give rise to inflammation. Here, we examined the influence of propofol pretreatment on the expression of cyclooxygenase-2 (COX-2) and prostaglandin E₂ (PGE₂) after lipopolysaccharide (LPS) stimulation. In addition, we evaluated the expression of pro-inflammatory cytokines and nuclear factor kappa B (NF-κB).

Methods

Human amnion-derived WISH cells were used to investigate the effect of propofol on the LPS-induced expression of inflammatory substances involved in preterm labor. For the experiment, WISH cells were pretreated with various concentrations propofol (0.01-10 μg/ml) for 1 h and then treated with LPS (1 μg/ml) for 24 h. Cytotoxicity was evaluated using MTT assay. PGE₂ concentration was assessed by ELISA. Protein expressions of COX-2, PGE₂ and NF-κB were analyzed by western blotting analysis. RT-PCR was used for analysis of mRNA expression of COX-2, PGE₂, interlukin (IL)-1β and tumor necrosis factor (TNF)-α.

Results

Propofol showed no cytotoxicity on the WISH cells. LPS-induced PGE₂ production and COX-2 and PGE₂ expression were decreased after propofol pretreatment. Propofol also attenuated the LPS-induced mRNA expression of IL-1β and TNF-α. Moreover, the activation of NF-κB was inhibited by propofol pretreatment on LPS-stimulated WISH cells.

Conclusion

We demonstrated that propofol suppresses the expression of inflammatory substances enhanced by LPS stimulation. Furthermore, this inhibitory effect of propofol on the inflammatory substance expression is mediated by suppression of NF-κB activation.

Omega-3 polyunsaturated fatty acids reduce preterm labor by inhibiting trophoblast cathepsin S and inflammasome activation

Preterm labor is associated with inflammation and infection. The mechanisms underlying the role of omega-3 fatty acid in inflammasome activation and prevention of preterm labor remain unknown. We hypothesized that omega-3 fatty acid can reduce the rate of preterm birth induced by infection and trophoblast inflammation. In the present study, we found that inflammasome-related molecules and IL-1β in trophoblasts were activated by TNF-α derived from lipopolysaccharide (LPS)-stimulated THP-1 cell-conditioned medium (CM) and recombinant TNF-α protein. The results demonstrated that stimulation with TNF-α caused lysosomal rupture in trophoblasts, which accelerated cathepsin S (CTSS) diffusion from lysosomes to the cytosol and activated NLRP1 (nacht domain-leucine-rich repeat, and pyd-containing protein 1) and absent in melanoma 2 (AIM2) inflammasomes, thereby increasing IL-1β secretion. Moreover, in response to LPS challenge, TNF-α increased trophoblast cell death and decreased cell viability through inflammasome and CTSS activation. Stearidonic acid (SDA; 18:4n-3) and docosahexaenoic acid (DHA; 22:6n-3) inhibited inflammasome-related molecule synthesis and CTSS and caspase-1 activation, which further reduced the preterm delivery rate of pregnant mice induced by LPS (92.9 compared with 69.7% (DHA); 92.9 compared with 53.5% (SDA)). Higher expression of TNF-α, IL-1β, prostaglandin E2, and CTSS, but lower resolvin D1 expression, was observed in preterm pregnant mice than in controls. Similarly, resolvin D1 was highly expressed in women with term delivery compared with women with preterm delivery. Thus, SDA and DHA may attenuate macrophage-derived TNF-α inducing CTSS and inflammasome activation, IL-1β secretion, and placental trophoblast cell death. These functions are implicated in the preventive effects of SDA and DHA on preterm labor.

Repurposing simvastatin as a therapy for preterm labor: evidence from preclinical models

Preterm birth (PTB), the leading cause of neonatal morbidity and mortality, urgently requires novel therapeutic agents. Spontaneous PTB, resulting from preterm labor, is commonly caused by intrauterine infection/inflammation. Statins are well-established, cholesterol-lowering drugs that can reduce inflammation and inhibit vascular smooth muscle contraction. We show that simvastatin reduced the incidence of PTB in a validated intrauterine LPS-induced PTB mouse model, decreased uterine proinflammatory mRNA concentrations (IL-6, Cxcl1, and Ccl2), and reduced serum IL-6 concentration. In human myometrial cells, simvastatin reduced proinflammatory mediator mRNA and protein expression (IL-6 and IL-8) and increased anti-inflammatory cytokine mRNA expression (IL-10 and IL-13). Critically, simvastatin inhibited myometrial cell contraction, basally and during inflammation, and reduced phosphorylated myosin light chain concentration. Supplementation with mevalonate and geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate, abolished these anticontractile effects, indicating that the Rho/Rho-associated protein kinase pathway is critically involved. Thus, simvastatin reduces PTB incidence in mice, inhibits myometrial contractions, and exhibits key anti-inflammatory effects, providing a rationale for investigation into the repurposing of statins to treat preterm labor in women.—Boyle, A. K., Rinaldi, S. F., Rossi, A. G., Saunders, P. T. K., Norman, J. E. Repurposing simvastatin as a therapy for preterm labor: evidence from preclinical models.

Oxidative stress induces p38MAPK-dependent senescence in the feto-maternal interface cells

OBJECTIVE

This study tested the mechanism of the oxidative stress (OS)-induced senescence pathway at the feto-maternal interface cells.

METHODS

Primary amnion mesenchymal cells (AMCs), chorion and decidual cells isolated from the placental membranes of women at normal term (not in labor) were exposed to OS-inducing cigarette smoke extract (CSE) for 48 h. Reactive oxygen species (ROS) was measured using 2'7'-dichlorodihydrofluorescein. Western blot analysis determined phosphorylated (P) p38MAPK and p53 expression. Senescence-associated β-Galactosidase (SA-β-Gal) and matrix metallopeptidase 9 (MMP9) histochemistry were used to measure senescence and inflammation respectively. Cotreatment of cells with the antioxidant, N-acetyl cysteine (NAC), or the p38MAPK inhibitor, SB203580 (SB), verified the activation specificity.

RESULTS

CSE increased ROS production from AMCs, chorion cells, and decidual cells (P < 0.05) compared to controls. Western blot analysis determined that CSE induced p38MAPK activation (P < 0.05) and cotreatment with NAC inhibited ROS production and p38MAPK activation (P < 0.05) in all cell types. CSE did not increase p53 phosphorylation in any of the cells; however, AMCs showed constitutive P-p53 expression. CSE increased senescence in AMCs and chorion cells compared to controls (P = 0.01 and P = 0.003, respectively); however, senescence was not observed in decidual cells. Senescence was significantly reduced following cotreatment with SB and NAC (AMCs; P = 0.01 and chorion; P = 0.009). CSE increased MMP9 in all cells that was reduced by NAC.

CONCLUSION

OS induced p38MAPK activation and inflammation in all cell types that was associated with senescence in fetal cells but not in maternal cells.

Immune cell and transcriptomic analysis of the human decidua in term and preterm parturition

STUDY QUESTION

Is labour, both at term and preterm, associated with alterations in decidual lymphocyte densities and widespread changes to the decidual transcriptome?

SUMMARY ANSWER

The onset of parturition, both at term and preterm, is associated with widespread gene expression changes in the decidua, many of which are related to inflammatory signalling, but is not associated with changes in the number of any of the decidual lymphocyte populations examined.

WHAT IS KNOWN ALREADY

Given its location, directly at the maternal–foetal interface, the decidua is likely to play a pivotal role in the onset of parturition, however, the molecular events occurring in the decidua in association with the onset of labour, both at term and preterm, remain relatively poorly defined. Using flow cytometry and microarray analysis, the present study aimed to investigate changes to the immune cell milieu of the decidua in association with the onset of parturition and define the decidual gene signature associated with term and preterm labour (PTL).

STUDY DESIGN, SIZE, DURATION

This study used decidual samples collected from 36 women across four clinical groups: term (38–42 weeks of gestation) not in labour, TNL; term in labour, TL; preterm (<35 weeks of gestation)not in labour, PTNL; and preterm in labour, PTL.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Decidual lymphocytes were isolated from fresh decidual tissue collected from women in each of our four patient groups and stained with a panel of antibodies (CD45, CD3, CD19, CD56, CD4, CD8 and TCRVα24-Jα18) to investigate lymphocyte populations present in the decidua (TNL, n = 8; TL, n = 7; PTNL, n = 5; PTL, n = 5). RNA was extracted from decidual tissue and subjected to Illumina HT-12v4.0 BeadChip expression microarrays (TNL, n = 11; TL, n = 8; PTNL, n = 7; PTL, n = 10). Quantitative real-time PCR (qRT-PCR) was used to validate the microarray results.

MAIN RESULTS AND THE ROLE OF CHANCE

The relative proportions of decidual lymphocytes (T cells, NK cells, B cells and invariant natural killer (iNKT) cells) were unaffected by either gestation or labour status. However, we found elevated expression of the non-classical MHC-protein, CD1D, in PTL decidua samples (P < 0.05), suggesting the potential for increased activation of decidual invariant NKT (iNKT) cells in PTL. Both term and PTL were associated with widespread gene expression changes, particularly related to inflammatory signalling. Up-regulation of candidate genes in TL (IL-6, PTGS2, ATF3, IER3 and TNFAIP3) and PTL (CXCL8, MARCO, LILRA3 and PLAU) were confirmed by qRT-PCR analysis.

LARGE SCALE DATA

Microarray data are available at www.ebi.ac.uk/arrayexpress under accession number E-MTAB-5353.

LIMITATIONS REASONS FOR CAUTION

Whilst no changes in lymphocyte number were observed across our patient samples, we did not investigate the activation state of any of the immune cell sub-populations examined, therefore, it is possible that the function of these cells may be altered in association with labour onset. Additionally, the results of our transcriptomic analyses are descriptive and at this stage, we cannot prove direct causal link with the up-regulation of any of the genes examined and the onset of either term or PTL.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings demonstrate that the onset of parturition is associated with widespread changes to the decidual transcriptome, and there are distinct gene expression changes associated with term and PTL. We confirmed that an inflammatory signature is present within the decidua, and we also report the up-regulation of several genes involved in regulating the inflammatory response. The identification of genes involved in regulating the inflammatory response may provide novel molecular targets for the development of new, more effective therapies for the prevention of preterm birth (PTB). Such targets are urgently required.

STUDY FUNDING AND COMPETING INTEREST(S)

This work was supported by Medical Research Council (grant number MR/L002657/1) and Tommy's, the baby charity. Jane Norman has had research grants from the charity Tommy's and from the National Institute for Health Research on PTB during the lifetime of this project. Jane Norman also sits on a data monitoring committee for GSK for a study on PTB prevention and her institution receives financial recompense for this. The other authors do not have any conflicts of interest to declare.

Yogurt consumption during pregnancy and preterm delivery in Mexican women: A prospective analysis of interaction with maternal overweight status

Preterm delivery is an important cause of perinatal morbidity and mortality, often precipitated by maternal infection or inflammation. Probiotic-containing foods, such as yogurt, may reduce systemic inflammatory responses. We sought to evaluate whether yogurt consumption during pregnancy is associated with decreased preterm delivery. We studied 965 women enrolled at midpregnancy into a clinical trial of prenatal docosahexaenoic acid supplementation in Mexico. Yogurt consumption during the previous 3 months was categorized as ≥5, 2-4, or <2 cups per week. Preterm delivery was defined as delivery of a live infant before 37 weeks gestation. We used logistic regression to evaluate the association between prenatal yogurt consumption and preterm delivery and examined interaction with maternal overweight status. In this population, 25.4%, 34.2%, and 40.4% of women reported consuming ≥5, 2-4, and <2 cups of yogurt per week, respectively. The prevalence of preterm delivery was 8.9%. Differences in preterm delivery were non-significant across maternal yogurt consumption groups; compared with women reporting <2 cups of yogurt per week, those reporting 2-4 cups of yogurt per week had adjusted odds ratio (aOR) for preterm delivery of 0.81 (95% confidence interval, CI [.46, 1.41]), and those reporting ≥5 cups of yogurt per week had aOR of 0.94 (95% CI [.51, 1.72]). The association between maternal yogurt consumption and preterm delivery differed significantly for nonoverweight women compared with overweight women (p for interaction = .01). Compared with nonoverweight women who consumed <2 cups of yogurt per week, nonoverweight women who consumed ≥5 cups of yogurt per week had aOR for preterm delivery of 0.24 (95% CI [.07, .89]). Among overweight women, there was no significant association. In this population, there was no overall association between prenatal yogurt consumption and preterm delivery. However, there was significant interaction with maternal overweight status; among nonoverweight women, higher prenatal yogurt consumption was associated with reduced preterm delivery.

Endogenous hydrogen sulfide contributes to uterine quiescence during pregnancy

Recent evidence suggests that uterine activation for labor is associated with inflammation within uterine tissues. Hydrogen sulfide (H₂S) plays a critical role in inflammatory responses in various tissues. Our previous study has shown that human myometrium produces H₂S via its generating enzymes cystathionine-γ-lyase (CSE) and cystathionine-β-synthetase (CBS) during pregnancy. We therefore explored whether H₂S plays a role in the maintenance of uterine quiescence during pregnancy. Human myometrial biopsies were obtained from pregnant women at term. Uterine smooth muscle cells (UMSCs) isolated from myometrial tissues were treated with various reagents including H₂S. The protein expression of CSE, CBS and contraction-associated proteins (CAPs) including connexin 43, oxytocin receptor and prostaglandin F_2α receptor determined by Western blot. The levels of cytokines were measured by ELISA. The results showed that CSE and CBS expression inversely correlated to the levels of CAPs and activated NF-κB in pregnant myometrial tissues. H₂S inhibited the expression of CAPs, NF-κB activation and the production of interleukin (IL)-1β, IL-6 and tumor necrosis factor α (TNFα) in cultured USMCs. IL-1β treatment reversed H₂S inhibition of CAPs. Knockdown of CSE and CBS prevented H₂S suppression of inflammation. H₂S modulation of inflammation is through K_ATP channels and phosphoinositide 3-kinase (PI3K) and extracellular signal-regulated kinase (ERK) signaling pathways. H₂S activation of PI3K and ERK signaling is dependent on K_ATP channels. Our data suggest that H₂S suppresses the expression of CAPs via inhibition of inflammation in myometrium. Endogenous H₂S is one of the key factors in maintenance of uterine quiescence during pregnancy.

The Potential Functions of Small Heat Shock Proteins in the Uterine Musculature during Pregnancy

The small heat shock protein B (HSPB) family is comprised of eleven members with many being induced by physiological stressors. In addition to being molecular chaperones, it is clear these proteins also play important roles in cell death regulation, cytoskeletal rearrangements, and immune system activation. These processes are important for the uterine smooth muscle or myometrium during pregnancy as it changes from a quiescent tissue, during the majority of pregnancy, to a powerful and contractile tissue at labor. The initiation and progression of labor within the myometrium also appears to require an inflammatory response as it is infiltrated by immune cells and it produces pro-inflammatory mediators. This chapter summarizes current knowledge on the expression of HSPB family members in the myometrium during pregnancy and speculates on the possible roles of these proteins during myometrial programming and transformation of the myometrium into a possible immune regulatory tissue.

Preterm birth: Inflammation, fetal injury and treatment strategies

Preterm birth (PTB) is the leading cause of childhood mortality in children under 5 and accounts for approximately 11% of births worldwide. Premature babies are at risk of a number of health complications, notably cerebral palsy, but also respiratory and gastrointestinal disorders. Preterm deliveries can be medically indicated/elective procedures or they can occur spontaneously. Spontaneous PTB is commonly associated with intrauterine infection/inflammation. The presence of inflammatory mediators in utero has been associated with fetal injury, particularly affecting the fetal lungs and brain. This review will outline (i) the role of inflammation in term and PTB, (ii) the effect infection/inflammation has on fetal development and (iii) recent strategies to target PTB. Further research is urgently required to develop effective methods for the prevention and treatment of PTB and above all, to reduce fetal injury.

HoxA13 Stimulates Myometrial Cells to Secrete IL-1β and Enhance the Expression of Contraction-Associated Proteins

Bipedalism in humans requires regionalization of myometrial function with a contracted lower uterine segment and a relaxed fundus during pregnancy to prevent fetal pressure on the cervix and reversal of this phenotype during labor. The HoxA13 gene is highly expressed in the lower uterine segment before term labor and regulates the regionalization of myometrium contractility. However, how HoxA13 regulates signal pathways to exert its functions remains unclear. Using a gene microarray technique, we profiled HoxA13 transcriptome in myometrial cells containing immune response genes (eg, IL-1β, IL-6, and IL-8) and contraction-associated proteins (CAPs) such as cyclooxygenase-2 (Cox-2) and connexin-43. IL-1β is responsible for mediating HoxA13 actions in up-regulating IL-6, IL-8, Cox-2, and connexin-43 expression. Blocking IL-1β with its inhibitor abolishes these HoxA13 actions. HoxA13-induced IL-1β stimulates the recruitment of activated THP-1 monocytes to myometrial cells, which in turn amplify the secretion of IL-1β, IL-6, and IL-8 through a mutual feed-forward loop between these cell types. As a result, Cox-2 expression is dramatically enhanced. These findings lead us to conclude that HoxA13 increases myometrial cell contractility by enhancing the secretion of IL-1β, resulting in an up-regulation of CAP and other proinflammatory cytokine expression. HoxA13-induced IL-1β in myometrial cells also prompts leukocyte recruitment and further amplifies CAP expression.

A critical role of interleukin-1 in preterm labor

Preterm birth (PTB) is a leading cause of neonatal mortality and morbidity worldwide, and represents a heavy economic and social burden. Despite its broad etiology, PTB has been firmly linked to inflammatory processes. Pro-inflammatory cytokines are produced in gestational tissues in response to stressors and can prematurely induce uterine activation, which precedes the onset of preterm labor. Of all cytokines implicated, interleukin (IL)-1 has been largely studied, revealing a central role in preterm labor. However, currently approved IL-1-targeting therapies have failed to show expected efficacy in pre-clinical studies of preterm labor. Herein, we (a) summarize animal and human studies in which IL-1 or IL-1-targeting therapeutics are implicated with preterm labor, (b) focus on novel IL-1-targeting therapies and diagnostic tests, and (c) develop the case for commercialization and translation means to hasten their development.

Specific inhibition of c-Jun N-terminal kinase delays preterm labour and reduces mortality

Preterm labour (PTL) is commonly associated with infection and/or inflammation. Lipopolysaccharide (LPS) from different bacteria can be used to independently or mutually activate Jun N-terminal kinase (JNK)/AP1- or NF-κB-driven inflammatory pathways that lead to PTL. Previous studies using Salmonella abortus LPS, which activates both JNK/AP-1 and NF-κB, showed that selective inhibition of NF-κB delays labour and improves pup outcome. Where labour is induced using Escherichia coli LPS (O111), which upregulates JNK/AP-1 but not NF-κB, inhibition of JNK/AP-1 activation also delays labour. In this study, to determine the potential role of JNK as a therapeutic target in PTL, we investigated the specific contribution of JNK signalling to S. Abortus LPS-induced PTL in mice. Intrauterine administration of S. Abortus LPS to pregnant mice resulted in the activation of JNK in the maternal uterus and fetal brain, upregulation of pro-inflammatory proteins COX-2, CXCL1, and CCL2, phosphorylation of cPLA2 in myometrium, and induction of PTL. Specific inhibition of JNK by co-administration of specific D-JNK inhibitory peptide (D-JNKI) delayed LPS-induced preterm delivery and reduced fetal mortality. This is associated with inhibition of myometrial cPLA2 phosphorylation and proinflammatory proteins synthesis. In addition, we report that D-JNKI inhibits the activation of JNK/JNK3 and caspase-3, which are important mediators of neural cell death in the neonatal brain. Our data demonstrate that specific inhibition of TLR4-activated JNK signalling pathways has potential as a therapeutic approach in the management of infection/inflammation-associated PTL and prevention of the associated detrimental effects to the neonatal brain.

Crosstalk between monocytes and myometrial smooth muscle in culture generates synergistic pro-inflammatory cytokine production and enhances myocyte contraction, with effects opposed by progesterone

Both term and preterm parturition are characterized by an influx of macrophages and neutrophils into the myometrium and cervix, with co-incident increased peripheral blood monocyte activation. Infection and inflammation are strongly implicated in the pathology of preterm labour (PTL), with progesterone considered a promising candidate for its prevention or treatment. In this study, we investigated the effect of monocytes on myometrial smooth muscle cell inflammatory cytokine production both alone and in response to LPS, a TLR4 agonist used to trigger PTL in vivo. We also investigated the effect of monocytes on myocyte contraction. Monocytes, isolated from peripheral blood samples from term pregnant women, were cultured alone, or co-cultured with PHM1-41 myometrial smooth muscle cells, for 24 h. In a third set of experiments, PHM1-41 myocytes were cultured for 24 h in isolation. Cytokine secretion was determined by ELISA or multiplex assays. Co-culture of monocytes and myocytes led to synergistic secretion of pro-inflammatory cytokines and chemokines including IL-6, IL-8 and MCP-1, with the secretion being further enhanced by LPS (100 ng/ml). The synergistic secretion of IL-6 and IL-8 from co-cultures was mediated in part by direct cell–cell contact, and by TNF. Conditioned media from co-cultures stimulated contraction of PHM1-41 myocytes, and the effect was inhibited by progesterone. Both progesterone and IL-10 inhibited LPS-stimulated IL-6 and IL-8 secretion from co-cultures, while progesterone also inhibited chemokine secretion. These data suggest that monocytes infiltrating the myometrium at labour participate in crosstalk that potentiates pro-inflammatory cytokine secretion, an effect that is enhanced by LPS, and can augment myocyte contraction. These effects are all partially inhibited by progesterone.

Drugs to block cytokine signaling for the prevention and treatment of inflammation-induced preterm birth

Preterm birth (PTB) at less than 37 weeks of gestation is the leading cause of neonatal morbidity and mortality. Intrauterine infection (IUI) due to microbial invasion of the amniotic cavity is the leading cause of early PTB (<32 weeks). Commensal genital tract Ureaplasma and Mycoplasma species, as well as Gram-positive and Gram-negative bacteria, have been associated with IUI-induced PTB. Bacterial activation of Toll-like receptors and other pattern recognition receptors initiates a cascade of inflammatory signaling via the NF-κB and p38 mitogen-activated protein kinase (MAPK) signaling pathways, prematurely activating parturition. Antenatal antibiotic treatment has had limited success in preventing PTB or fetal inflammation. Administration of anti-inflammatory drugs with antibiotics could be a viable therapeutic option to prevent PTB and fetal complications in women at risk of IUI and inflammation. In this mini-review, we will discuss the potential for anti-inflammatory drugs in obstetric care, focusing on the class of drugs termed “cytokine suppressive anti-inflammatory drugs” or CSAIDs. These inhibitors work by specifically targeting the NF-κB and p38 MAPK inflammatory signaling pathways. Several CSAIDs are discussed, together with clinical and toxicological considerations associated with the administration of anti-inflammatory agents in pregnancy.

Ultrasound-guided intrauterine injection of lipopolysaccharide as a novel model of preterm birth in the mouse

Mouse models are used to study mechanisms that link intrauterine infection and preterm birth (PTB). To mimic intrauterine infection, lipopolysaccharide (LPS) is commonly injected into the uterus via minilaparotomy, which is invasive, and can cause PTB in control animals. We hypothesized that less-invasive ultrasound-guided intrauterine LPS injection or intravaginal LPS administration could induce PTB by stimulating an inflammatory response of the uteroplacental tissues, while minimizing PTB in control animals. On day 17 of gestation mice received LPS intravaginally (10 to 240 μg; n = 3 to 8) or into the uterus (20 μg) under ultrasound guidance (n = 7) or via laparotomy (n = 7). Control animals received phosphate-buffered saline (PBS; n = 5 to 7). Intrauterine administration of LPS, both under ultrasound guidance and via laparotomy, induced delivery earlier than in PBS control groups (P < 0.01). Intravaginal LPS administration did not stimulate PTB. Quantitative real-time PCR and immunohistochemistry of tissues harvested 6 hours after treatment confirmed that ultrasound-guided LPS administration induced a localized inflammatory response. Ultrasound-guided intrauterine LPS injection reliably induces PTB in the mouse and mimics the local inflammatory and immune responses observed in the more-invasive laparotomy model of inflammation-induced PTB. Ultrasound-guided intrauterine LPS injection is a useful novel model of PTB for future studies and concords with the principles of reduction, replacement, and refinement.

Biological functions of thyroid hormone in placenta

The thyroid hormone, 3,3,5-triiodo-l-thyronine (T₃), modulates several physiological processes, including cellular growth, differentiation, metabolism, inflammation and proliferation, via interactions with thyroid hormone response elements (TREs) in the regulatory regions of target genes. Infection and inflammation are critical processes in placental development and pregnancy-related diseases. In particular, infection is the leading cause of neonatal mortality and morbidity worldwide. However, to date, no successful approach has been developed for the effective diagnosis of infection in preterm infants. Pre-eclampsia (PE) is a serious disorder that adversely affects ~5% of human pregnancies. Recent studies identified a multiprotein complex, the inflammasome, including the Nod-like receptor (NLR) family of cytosolic pattern recognition receptors, the adaptor protein apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and caspase-1, which plays a vital role in the placenta. The thyroid hormone modulates inflammation processes and is additionally implicated in placental development and disease. Therefore, elucidation of thyroid hormone receptor-regulated inflammation-related molecules, and their underlying mechanisms in placenta, should facilitate the identification of novel predictive and therapeutic targets for placental disorders. This review provides a detailed summary of current knowledge with respect to identification of useful biomarkers and their physiological significance in placenta.

15-epi-lipoxin A4 reduces the mortality of prematurely born pups in a mouse model of infection-induced preterm birth

Preterm birth remains the leading cause of neonatal mortality and morbidity worldwide. There are currently few effective therapies and therefore an urgent need for novel treatments. Although there is much focus on trying to alter gestation of delivery, the primary aim of preterm birth prevention therapies should be to reduce prematurity related mortality and morbidity. Given the link between intrauterine infection and inflammation and preterm labour (PTL), we hypothesized that administration of lipoxins, key anti-inflammatory and pro-resolution mediators, could be a useful novel treatment for PTL. Using a mouse model of infection-induced PTL, we investigated whether 15-epi-lipoxin A₄ could delay lipopolysaccharide (LPS)-induced PTL and reduce pup mortality. On D17 of gestation mice (n = 9–12) were pretreated with vehicle or 15-epi-lipoxin A₄ prior to intrauterine administration of LPS or PBS. Although pretreatment with 15-epi-lipoxin A₄ did not delay LPS-induced PTL, there was a significant reduction in the mortality amongst prematurely delivered pups (defined as delivery within 36 h of surgery) in mice treated with 15-epi-lipoxin A₄ prior to LPS treatment, compared with those receiving LPS alone (P < 0.05). Quantitative real-time (QRT)-PCR analysis of utero-placental tissues harvested 6 h post-treatment demonstrated that 15-epi-lipoxin A₄ treatment increased Ptgs2 expression in the uterus, placenta and fetal membranes (P < 0.05) and decreased 15-Hpgd expression (P < 0.05) in the placenta and uterus, suggesting that 15-epi-lipoxin A₄ may regulate the local production and activity of prostaglandins. These data suggest that augmenting lipoxin levels could be a useful novel therapeutic option in the treatment of PTL, protecting the fetus from the adverse effects of infection-induced preterm birth.

Preterm birth, intrauterine infection, and fetal inflammation

Preterm birth (PTB) (delivery before 37 weeks’ gestation) is a leading cause of neonatal death and disease in industrialized and developing countries alike. Infection (most notably in high-risk deliveries occurring before 28 weeks’ gestation) is hypothesized to initiate an intrauterine inflammatory response that plays a key role in the premature initiation of labor as well as a host of the pathologies associated with prematurity. As such, a better understanding of intrauterine inflammation in pregnancy is critical to our understanding of preterm labor and fetal injury, as well as on-going efforts to prevent PTB. Focusing on the fetal innate immune system responses to intrauterine infection, the present paper will review clinical and experimental studies to discuss the capacity for a fetal contribution to the intrauterine inflammation associated with PTB. Evidence from experimental studies to suggest that the fetus has the capacity to elicit a pro-inflammatory response to intrauterine infection is highlighted, with reference to the contribution of the lung, skin, and gastrointestinal tract. The paper will conclude that pathological intrauterine inflammation is a complex process that is modified by multiple factors including time, type of agonist, host genetics, and tissue.

Chemotactic activity of gestational tissues through late pregnancy, term labor, and RU486-induced preterm labor in Guinea pigs

PROBLEM

Is increased leukocyte chemotactic activity (CA) from gestational tissues necessary for term or preterm labor in guinea pigs?

METHOD OF STUDY

Tissue extracts were prepared from pregnant guinea pig decidua-myometrium, cervix, fetal membranes (amniochorion), and placenta during early third trimester (n = 8), term not in labor (TNL, n = 5), and term spontaneous labor (TL, n = 6), RU486-induced preterm labor (PTL, n = 6), or controls (cPTL, n = 5). Leukocyte CA was assessed using a modified Boyden chamber assay. Extract chemokine and maternal progesterone concentrations were quantified by enzyme immunoassay.

RESULTS

Only the extracts from amniochorion demonstrated increased CA through late gestation and labor. In contrast, CA was decreased in extracts from amniochorion and cervix from animals after RU486-induced PTL. Maternal progesterone concentrations remained high in all groups.

CONCLUSION

Leukocyte CA of intrauterine tissues is increased in term spontaneous labor. However, RU486-induced preterm labor occurs in the absence of increased CA.

Decidual neutrophil infiltration is not required for preterm birth in a mouse model of infection-induced preterm labor

Parturition is associated with a leukocyte influx into the intrauterine tissues; however, the exact role these leukocytes play in the onset of labor remains unclear. Neutrophil infiltration of the uteroplacental tissues has been particularly associated with infection-associated preterm labor (PTL) in both women and mouse models. In this study, we investigated the role of neutrophils in a mouse model of infection-induced PTL. Intrauterine administration of LPS on day 17 of gestation resulted in a 7-fold increase in the number of decidual neutrophils compared with control mice receiving PBS (p < 0.01; n = 8–11). We hypothesized that neutrophil influx is necessary for PTL and that neutrophil depletion would abolish preterm birth. To test this hypothesis, mice were depleted of neutrophils by treatment with anti–Gr-1, anti–Ly-6G, or the appropriate IgG control Ab on day 16 of gestation prior to LPS on day 17 (n = 6–7). Successful neutrophil depletion was confirmed by flow cytometry and immunohistochemistry. Neutrophil depletion with Gr-1 resulted in reduced uterine and placental Il-1β expression (p < 0.05). Neutrophil depletion with Ly-6G reduced uterine Il-1β and Tnf-α expression (p < 0.05). However, neutrophil depletion with either Ab did not delay LPS-induced preterm birth. Collectively, these data show that decidual neutrophil infiltration is not essential for the induction of infection-induced PTL in the mouse, but that neutrophils contribute to the LPS-induced inflammatory response of the uteroplacental tissues.

Systemic increase in human maternal circulating CD14+CD16- MCP-1+ monocytes as a marker of labor

OBJECTIVES

To study the influence of pregnancy and labor on the proportion and level of activation of monocyte subpopulations in human pregnancy.

STUDY DESIGN

Peripheral blood samples were obtained from healthy nonpregnant women (n = 6); women in the third-trimester of healthy pregnancies (n = 18) and women with preterm premature rupture of membranes (n = 46), just before delivery for the last 2 groups. Monocyte subpopulations were characterized by flow cytometry using CD14, CD16, and activation level using macrophage chemoattractant protein-1 (MCP-1) and CCR2 antibodies.

RESULTS

The relative proportion of each monocyte subset in nonpregnant women was similar to that in women with healthy or complicated pregnancies. However, pregnancy was associated with a significant decrease in MCP-1 expressing monocytes (79.5% ± 19.8% vs 9.3% ± 6.8% and 11.9% ± 8.3% for nonpregnant, healthy pregnancy, and preterm premature rupture of membranes (respectively, P < .05). Spontaneous labor was associated with a return to nonpregnant values for the proportion of MCP-1 expressing monocytes in both normal (74.4% ± 16.9) and preterm premature rupture of membranes pregnancy (68.4% ± 35.6), irrespective of the mode of delivery (vaginal or cesarean section). This was not observed in women who delivered without spontaneous labor onset. CCR-2 (MCP-1 receptor) expression was not modified in monocytes at the time of labor, but was significantly increased in granulocytes (3646 ± 1080 vs 7338 ± 2718 for nonlaboring and laboring preterm premature rupture of membranes, respectively, P < .05) CONCLUSION: In light of previous reports of a role for MCP-1 in labor, our results suggest the downregulation of activation levels of monocytes, via MCP-1 expression might be involved in maternofetal immune tolerance. Monocyte reactivation might be associated with labor.

Infiltration of myeloid cells into decidua is a critical early event in the labour cascade and post-partum uterine remodelling

Leucocyte infiltration in the decidua (maternal–foetal interface) before, during and after term (TL) and preterm labour (PTL) was studied in mouse. We also investigated the mechanism of peripheral leucocyte recruitment into decidua by analysing the tissue cytokine profiles. Decidual tissues were collected during late gestation, TL and post-partum (PP). PTL was initiated on gestational day 15 by intrauterine injection of Lipopolysaccharide (LPS, 125 μg) or progesterone signalling antagonism by RU486. Animals were killed during PTL or PP. Decidua basalis was analysed using FACS and immunohistochemistry. Markers of myeloid cell differentiation (Gr1, Ly6G, Neu7/4, F4/80) were assessed to define tissue monocytes (M), neutrophils (N) and macrophages (Macs). Flow cytometry revealed a significant (P < 0.05) increase in decidual Macs prior to TL; M and N numbers increased during TL and further increased during PP, which correlated with immunohistochemistry data. Massive influx of N, but not Macs and M, was detected by FACS during LPS-PTL (P < 0.05) but not RU486-PTL. Highest levels of N infiltration into the decidua occurred PP in both LPS and RU486 groups. Decidual infiltration during TL and RU486-PTL was accompanied by an increase in pro-inflammatory cytokines (IL1b and IL6) and CCL2 chemokine; LPS-PTL showed increases in multiple cytokines. PP period following TL and PTL was associated with further up-regulation of multiple cytokines/chemokines (P < 0.05). Our data suggest a programme of myeloid cells involvement in parturition with the pre-partum influx of Macs into the decidua contributing to the progression of labour, whereas the later influx of M and N contribute to PP decidual involution.

Myometrial immune cells contribute to term parturition, preterm labour and post-partum involution in mice

This study aimed to determine the mechanism of uterine activation during labour, both term (TL) and preterm (PTL). We hypothesized that the peripheral leucocytes are recruited to uterine tissues by locally produced cytokines where they contribute to the initiation of parturition. Mouse uteri were collected (i) during gestation, TL and post-partum (PP), (ii) during PTL initiated by intrauterine infusion of LPS (125 μg) or (iii) injection of the progesterone receptor antagonist RU486 and analysed for multiple cytokine expression levels by real-time polymerase chain reaction (RT-PCR) and 23-plex Cytokine assay or enzymatically dispersed for assessment of immune cell populations. Markers of myeloid cell differentiation (Gr1, Neu7/4 and F4/80) were evaluated by FACS to define tissue macrophages (Macs), monocytes (M) and neutrophils (N) and by immunohistochemistry to detect tissue Macs and N. Our results indicate that: (1) Macs were elevated in mouse myometrium before TL (P < 0.05) followed by an increase in M and N; these changes were accompanied by an increase in multiple pro-inflammatory cytokines/chemokines genes. The expression of corresponding proteins increased PP. (2) TL and RU486-PTL models showed similar gene/protein expression profiles, (3) LPS-PTL was characterized by strong pro-inflammatory response and massive influx of N in myometrial tissues showing a pattern different from TL and RU486-PTL, (4) The PP period appears similar in all three models, with elevated myometrial cytokine levels and high infiltration of immune cells. We concluded that leucocytes infiltrate myometrium around the time of parturition implicating their potential role in labour activation (both term and preterm) and major role in PP uterine involution.

Peroxisome proliferator-activated receptor alpha expression changes in human pregnant myometrium

Peroxisome proliferator-activated receptor alpha (PPARα) has been demonstrated to exhibit anti-inflammatory activities that are hypothesized to play a key role in labor suppression and maintenance of uterine quiescence. The aim of this study was to identify pregnancy- and labor-associated changes in PPARα in human myometrium. For this investigation, human myometrium was obtained from premenopausal women, and the study participants were categorized into the following 4 groups: nonpregnant (NP; n = 10), preterm not in labor (PNL; n = 10, gestation range 20-35 weeks), term not in labor (TNL; n = 20, gestation range 37-41 weeks), and term in labor (TL; n = 20, gestation range 37-41 weeks). Immunohistochemistry was used to locate and confirm the expression of PPARα. Relative quantitative real-time polymerase chain reaction (PCR) and Western blotting were employed to study the expression of anti-inflammatory PPARα and proinflammatory interleukin 1β (IL-1β). Immunohistochemistry indicated that PPARα was located in the nucleus of uterine smooth muscle cells. Compared to other groups, in PNL group, the PPARα messenger RNA (mRNA) and protein increased significantly. Decreased PPARα mRNA and protein expressions in myometrium were associated with labor while IL-1β increased remarkably. There were negative correlations between PPARα and IL-1β on mRNA (r = -.765, P < .01) and protein (r = -.624, P < .01) levels analyzed using Pearson test. In conclusion, human pregnancy is associated with changes in expression of PPARα and IL-1β in myometrium. The changes observed suggest that PPARα may play a role in maintaining pregnancy or initiating labor through inhibiting the expression of IL-1β in human myometrium.

Term and preterm labor: decreased suppressive activity and changes in composition of the regulatory T-cell pool

Regulatory T cells (Tregs) exert a key role in tolerance induction to the semi-allogeneic fetus. Currently, it is not known whether immunological rejection processes are involved in the induction of normal term or irresistible preterm labor. In this study, we examined whether there were differences in the percentage of the total CD4(+)CD127(low+/-)CD25(+)FoxP3(+)-Treg-cell pool, its suppressive activity and its composition with distinct Treg subsets (HLA-DR(low+)-, HLA-DR(high+)-, HLA-DR(-)- and naive CD45RA(+)-Tregs) between preterm and term laboring women. We found that its percentage was decreased neither in term nor in preterm laboring women. Its suppressive activity was strongly diminished in preterm laboring women and to a lesser extent in spontaneously term laboring women. During the normal course of pregnancy, its composition changed in such a way that the percentage of naive CD45RA(+)-Tregs increased while the percentage of the highly suppressive HLA-DR(low+)- and HLA-DR(high+)-Tregs decreased significantly until term. With the onset of spontaneous term labor this phenomenon was reversed and reached significant values postpartum. In addition, we confirmed that both the decreased percentage of HLA-DR(+)-Tregs within the total Treg-cell pool and their decreased level of HLA-DR expression (depending on the percentage of HLA-DR(low+)- and HLA-DR(high+)-Tregs) had a reducing effect on the suppressive activity of the total Treg cell pool in preterm laboring women. However, spontaneous term delivery was associated with increasing percentages of HLA-DR(+)-Tregs and increasing HLA-DR expression of this Treg subset. Therefore, it becomes apparent that the mechanisms inducing term or preterm labor may be completely different.

Physiologic uterine inflammation and labor onset: integration of endocrine and mechanical signals

The mechanisms underlying the preparation of the uterus for labor are not fully understood. Our previous studies have shown that during pregnancy, the uterine muscle (myometrium) undergoes dramatic phenotypic modulation culminating in term labor. The current review will discuss the cellular mechanisms involved in the regulation of myometrial activity and its modulation by endocrine signals and by mechanical stimulation of the uterus by the growing fetus. In particular, the contribution of uterine inflammation to the onset of labor will be described. We provide evidence that increased production of cytokines/chemokines in pregnant myometrium is associated with uterine occupancy and regulated by progesterone, suggesting the integration of mechanical and endocrine signals. Myometrial cells can actively participate in the inflammatory process in the uterus through the release of multiple proinflammatory cytokines and chemokines, providing a strong signal for activation of immune cells, their subsequent infiltration into pregnant uterus, and the initiation of labor.