Progesterone control of myometrial contractility

During pregnancy, the primary function of the uterus is to be quiescent and not contract, which allows the growing fetus to develop and mature. A uterine muscle layer, myometrium, is composed of smooth muscle cells (SMCs). Before the onset of labor contractions, the uterine SMCs experience a complex biochemical and molecular transformation involving the expression of contraction-associated proteins. Labor is initiated when genes in SMCs are activated in response to a combination of hormonal, inflammatory and mechanical signals. In this review, we provide an overview of molecular mechanisms regulating the process of parturition in humans, focusing on the hormonal control of the myometrium, particularly the steroid hormone progesterone. The primary reason for discussing the regulation of myometrial contractility by progesterone is the importance of the clinical problem of preterm birth. It is thought that the hormonal mechanisms regulating premature uterine contractions represent an untimely triggering of the normal events occurring during term parturition. Yet, our knowledge of the complex and redundant hormonal pathways controlling uterine contractile activity leading to delivery of the neonate remains incomplete. Finally, we introduce recent animal studies using a novel class of drugs, Selective Progesterone Receptor Modulators, targeting progesterone signaling to prevent premature myometrial contractions.

Protein interaction networks define the genetic architecture of preterm birth

The likely genetic architecture of complex diseases is that subgroups of patients share variants in genes in specific networks sufficient to express a shared phenotype. We combined high throughput sequencing with advanced bioinformatic approaches to identify such subgroups of patients with variants in shared networks. We performed targeted sequencing of patients with 2 or 3 generations of preterm birth on genes, gene sets and haplotype blocks that were highly associated with preterm birth. We analyzed the data using a multi-sample, protein–protein interaction (PPI) tool to identify significant clusters of patients associated with preterm birth. We identified shared protein interaction networks among preterm cases in two statistically significant clusters, p < 0.001. We also found two small control-dominated clusters. We replicated these data on an independent, large birth cohort. Separation testing showed significant similarity scores between the clusters from the two independent cohorts of patients. Canonical pathway analysis of the unique genes defining these clusters demonstrated enrichment in inflammatory signaling pathways, the glucocorticoid receptor, the insulin receptor, EGF and B-cell signaling, These results support a genetic architecture defined by subgroups of patients that share variants in genes in specific networks and pathways which are sufficient to give rise to the disease phenotype.

The short-chain fatty acids butyrate and propionate protect against inflammation-induced activation of mediators involved in active labor: implications for preterm birth

Spontaneous preterm birth is a global health issue affecting up to 20% of pregnancies and leaves a legacy of neurodevelopmental complications. Inflammation has been implicated in a significant proportion of preterm births, where pro-inflammatory insults trigger production of additional pro-inflammatory and pro-labor mediators. Thus, novel therapeutics that can target inflammation may be a novel avenue for preventing preterm birth and improving adverse fetal outcomes. Short-chain fatty acids (SCFAs), such as butyrate and propionate, are dietary metabolites produced by bacterial fermentation of fiber in the gut. SCFAs are known to possess anti-inflammatory properties and have been found to function through G-coupled-receptors and histone deacetylases. Therefore, this study aimed to investigate the effect of SCFAs on pro-inflammatory and pro-labor mediators in an in vitro model of preterm birth. Primary human cells isolated from myometrium and fetal membranes (decidua, amnion mesenchymal and amnion epithelial cells) were stimulated with the pro-inflammatory cytokines tumor necrosis factor alpha (TNF) or interleukin 1B (IL1B). The SCFAs butyrate and propionate suppressed inflammation-induced expression of pro-inflammatory cytokines and chemokines, adhesion molecules, the uterotonic prostaglandin PGF2alpha and enzymes involved in remodeling of myometrium and degradation of the fetal membranes. Notably, propionate and butyrate also suppressed inflammation-induced prostaglandin signaling and myometrial cell contraction. These effects appear to be mediated through suppression of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) activation. These results suggest that the SCFAs may be able to prevent myometrial contractions and rupture of membranes. Further in vivo studies are warranted to identify the efficacy of SCFAs as a novel anti-inflammatory therapeutic to prevent inflammation-induced spontaneous preterm birth.

In vitro selenium supplementation suppresses key mediators involved in myometrial activation and rupture of fetal membranes

Spontaneous preterm birth, which can affect up to 20% of all pregnancies, is the greatest contributor to perinatal morbidity and mortality. Infection is the leading pathological cause of spontaneous preterm birth. Infection activates the maternal immune system, resulting in the upregulation of pro-inflammatory and pro-labor mediators that activate myometrial contractions and rupture of fetal membranes. Anti-inflammatory agents therefore have the potential for the prevention of spontaneous preterm birth. Selenium, an essential micronutrient, has been shown to be a potent anti-inflammatory regulator. Notably, clinical and epidemiological studies have suggested a link between selenium and preterm birth. Thus, the aim of this study was to assess the effect of selenite (an inorganic form of selenium) on the expression of pro-inflammatory and pro-labor mediators in human gestational tissues. Human fetal membranes and myometrium were pre-incubated with or without selenite before incubation with the bacterial product lipopolysaccharide (LPS) to stimulate inflammation associated with preterm birth. Selenite blocked LPS-induced expression of pro-inflammatory cytokines and chemokines and enzymes involved in remodelling of myometrium and degradation of fetal membranes. Of note, selenite also suppressed myometrial activation induced by inflammation as evidenced by a decrease in LPS-induced prostaglandin signalling and myometrial cell contractility. These effects of selenite were mediated by the MAPK protein ERK as selenite blunted LPS induced activation of ERK. In conclusion, selenite suppresses key mediators involved in inflammation induced activation of mediators involved in active labor in human fetal membranes and myometrium. These findings support recent clinical studies demonstrating selenium supplementation is associated with decreased incidence of spontaneous preterm birth.

Transcriptional control of parturition: insights from gene regulation studies in the myometrium

The onset of labour is a culmination of a series of highly coordinated and preparatory physiological events that take place throughout the gestational period. In order to produce the associated contractions needed for foetal delivery, smooth muscle cells in the muscular layer of the uterus (i.e. myometrium) undergo a transition from quiescent to contractile phenotypes. Here, we present the current understanding of the roles transcription factors play in critical labour-associated gene expression changes as part of the molecular mechanistic basis for this transition. Consideration is given to both transcription factors that have been well-studied in a myometrial context, i.e. activator protein 1, progesterone receptors, oestrogen receptors, and nuclear factor kappa B, as well as additional transcription factors whose gestational event-driving contributions have been demonstrated more recently. These transcription factors may form pregnancy- and labour-associated transcriptional regulatory networks in the myometrium to modulate the timing of labour onset. A more thorough understanding of the transcription factor-mediated, labour-promoting regulatory pathways holds promise for the development of new therapeutic treatments that can be used for the prevention of preterm labour in at-risk women.

NF-κB and Its Regulators During Pregnancy

The transcriptional factor NF-κB is a nuclear factor involved in both physiological and pathological processes. This factor can control the transcription of more than 400 genes, including cytokines, chemokines, and their modulators, immune and non-immune receptors, proteins involved in antigen presentation and cell adhesion, acute phase and stress response proteins, regulators of apoptosis, growth factors, other transcription factors and their regulators, as well as different enzymes; all these molecules control several biological processes. NF-κB is a tightly regulated molecule that has also been related to apoptosis, cell proliferation, inflammation, and the control of innate and adaptive immune responses during onset of labor, in which it has a crucial role; thus, early activation of this factor may have an adverse effect, by inducing premature termination of pregnancy, with bad outcomes for the mother and the fetus, including product loss. Reviews compiling the different activities of NF-κB have been reported. However, an update regarding NF-κB regulation during pregnancy is lacking. In this work, we aimed to describe the state of the art around NF-κB activity, its regulatory role in pregnancy, and the effect of its dysregulation due to invasion by pathogens like Trichomonas vaginalis and Toxoplasma gondii as examples.

GIT2 deficiency attenuates inflammation-induced expression of pro-labor mediators in human amnion and myometrial cells†

Untimely activation of the inflammatory response by sterile or infective insults in uterine tissues can result in preterm birth. Pro-inflammatory cytokines and pathogenic activation of toll-like receptors (TLRs) initiate a biochemical cascade of events leading to myometrial activation and contractility, cervical dilatation, and rupture of the chorioamniotic membranes. GIT2 is a signaling protein known to play a role in innate and adaptive immunity; however, its role in the inflammatory pathways of human labor is not known. In this article, we report that GIT2 expression is lower in human myometrium and fetal membranes with term labor, and in preterm amnion with histological chorioamnionitis. GIT2 knockdown by siRNA in primary myometrial and amnion cells exhibited reduced expression of pro-inflammatory cytokines and chemokines in response to inflammatory challenge by cytokines or TLR ligands. In addition, the pro-inflammatory cytokines IL1B and TNF could not induce the expression of extracellular matrix degrading enzymes in GIT2-deficient amnion cells. Myometrial activation in response to pro-inflammatory cytokines was also significantly suppressed in GIT2-deficient cells as evidenced by decreased prostaglandin release and expression of contraction-associated proteins. Further to this, collagen gel assays demonstrated that TNF had a reduced ability to induce myometrial contractility in situ in GIT2-deficient myometrial cells compared to control-transfected cells. In summary, the loss of GIT2 diminishes the effects inflammatory mediators have in promoting myometrial contraction and fetal membrane rupture in vitro, suggesting that GIT2 could be a possible target for preterm birth therapies.

Novel anti-inflammatory actions of TIPE2 in human primary amnion and myometrial cells

Inflammation plays a pivotal role in the terminal process of human labor and delivery, including myometrial contractions and membrane rupture. TNF-alpha-induced protein 8-like-2 (TIPE2) is a novel inflammation regulator; however, there are no studies on the role of TIPE2 in human labor. We report that in myometrium, there is decreased TIPE2 mRNA expression during late gestation which was further decreased in labor. In fetal membranes, TIPE2 mRNA expression was decreased with both term and preterm labor compared to no labor samples. Knockdown of TIPE2 by siRNA in primary myometrium and amnion cells was associated with an augmentation of IL1B and TNF-induced expression of pro-inflammatory cytokines and chemokines; expression of contraction-associated proteins and secretion of the uterotonic prostaglandin PGF2α and expression of extracellular matrix degrading enzymes. In TIPE2-deficient myometrial cells treated with inhibitors of NF-κB or ERK1/2, the secretion of pro-labor mediators was reduced back to control levels. In conclusion, these in vitro experiments indicate that loss of TIPE2 exacerbates the inflammatory response.

CPPED1-targeting microRNA-371a-5p expression in human placenta associates with spontaneous delivery

MicroRNAs (miRNAs) are important regulators of gene expression, and their expression is associated with many physiological conditions. Here, we investigated potential associations between expression levels of miRNAs in human placenta and the onset of spontaneous term birth. Using RNA sequencing, we identified 54 miRNAs differentially expressed during spontaneous term labor compared to elective term births. Expression levels of 23 miRNAs were upregulated, whereas 31 were downregulated at least 1.5-fold. The upregulated miRNA miR-371a-5p putatively targets CPPED1, expression of which decreases during spontaneous birth. We used a luciferase reporter–based assay to test whether a miR-371a-5p mimic affected translation when it bound to the 3′ untranslated region of CPPED1. In this setting, the miR-371a-5p mimic resulted in lower luciferase activity, which suggests that miR-371a-5p regulates levels of CPPED1. In conclusion, inversely correlated levels of miR-371a-5p and CPPED1 suggest a role for both in spontaneous delivery.

Targeting bromodomain-containing proteins to prevent spontaneous preterm birth

Preterm birth is a global healthcare challenge. Spontaneous preterm birth (sPTB) is commonly caused by inflammation, yet there are currently no effective therapies available. The Bromodomain and Extra-Terminal motif (BET) proteins, Bromodomain-containing protein (Brd) 2 (Brd2), Brd3 and Brd4 regulate inflammation in non-gestational tissues. The roles of Brd2-4 in human pregnancy are unknown. Using human and mouse models, the present study has identified the Brd proteins part of the process by which inflammation induces parturition. Using human clinical samples, we demonstrate that labor and infection increase the expression of Brds in the uterus and fetal membranes. In primary human myometrial, amnion and decidual cells, we found that global Brd protein inhibition, as well as selective inhibition of Brds, suppressed inflammation-induced expression of mediators involved in myometrial contractions and rupture of fetal membranes. Importantly, studies in the mouse model demonstrate that the pan-Brd inhibitor JQ1 reduced intrauterine inflammation induced by bacterial endotoxin LPS as well as decreasing the effectiveness of LPS to induce parturition. These results implicate BET proteins as novel therapeutic targets for reducing inflammation associated with spontaneous preterm labor.

Inhibition of GPR91 Reduces Inflammatory Mediators Involved in Active Labor in Myometrium

Results

GPR91 mRNA expression was significantly higher in myometrium from women during term spontaneous labor compared to no labor. Likewise, in mice, GPR91 mRNA expression was significantly upregulated in myometrium during inflammation-induced preterm labor compared to preterm no labor. In myometrial cells, IL1B and TNF significantly increased GPR91 mRNA expression. Knockdown of GPR91 by siRNA in myometrial cells significantly suppressed the secretion and/or expression of IL1B- and TNF-induced proinflammatory cytokines (GM-CSF, IL1A, IL1B, and IL6) and chemokines (CXCL8 and CCL2), myometrial contractility (expression of the contraction-associated proteins PTGFR and CX43, secretion of the uterotonic PGF_2α, and in situ collagen gel contraction), and the transcription factor NF-κB.

Conclusion

Our findings demonstrate that GPR91 is involved in the genesis of proinflammatory and prolabor mediators induced by IL1B or TNF and collectively suggest that GPR91 may contribute to augmentation of the labor processes.

Transcriptomic analysis reveals the key regulators and molecular mechanisms underlying myometrial activation during equine placentitis†

The key event in placentitis-induced preterm labor is myometrial activation with the subsequent initiation of labor. However, the molecular mechanisms underlying myometrial activation are not fully understood in the mares. Therefore, the equine myometrial transcriptome was characterized during placentitis (290.0 ± 1.52 days of GA, n = 5) and the prepartum period (330 days of GA, n = 3) in comparison to normal pregnant mares (289.8 ± 2.18 days of GA, n = 4). Transcriptome analysis identified 596 and 290 DEGs in the myometrium during placentitis and the prepartum period, respectively, with 138 DEGs in common. The placentitis DEGs included eight genes (MMP1, MMP8, S100A9, S100A8, PI3, APOBEC3Z1B, RETN, and CXCL2) that are exclusively expressed in the inflamed myometrium. Pathway analysis elucidated that inflammatory signaling, Toll-like receptor signaling, and apoptosis pathways dominate myometrial activation during placentitis. The prepartum myometrium was associated with overexpression of inflammatory signaling, oxidative stress, and 5-hydroxytryptamine degradation. Gene ontology enrichment analysis identified several chemoattractant factors in the myometrium during placentitis and prepartum period, including CCL2, CXCL1, CXCL3, and CXCL6 in common. Upstream regulator analysis revealed 19 potential upstream regulators in placentitis dataset including transcription regulators (E2F1, FOXM1, HIF1A, JUNB, NFKB1A, and STAT1), transmembrane receptors (FAS, ICAM1, SELP, TLR2, and TYROBP), growth factors (HGF and TGFB3), enzymes (PTGS2 and PRKCP), and others (S100A8, S100A9, CD44, and C5AR1). Additionally, three upstream regulators (STAT3, EGR1, and F2R) were identified in the prepartum dataset. These findings revealed the key regulators and pathways underlying myometrial activation during placentitis, which aid in understanding the disease and facilitate the development of efficacious therapies.

Role of IRG1 in Regulating Pro-inflammatory and Pro-labor Mediators in Human Myometrium

Preterm birth is a major contributor to neonatal deaths and associated long-term morbidities for the survivors, yet therapies remain elusive, given our incomplete understanding of the mechanisms driving human labor and delivery. Human labor is an inflammatory process, and we investigated whether IRG1 (immunoresponsive gene-1) plays a role in these processes. We demonstrate that IRG1 mRNA and protein expression is significantly increased in myometrium with human term labor, compared to no labor samples, and with preterm (LPS) labor in a mouse model. Pro-labor mediators such as pro-inflammatory cytokines TNF and IL1B, and TLR ligands fsl-1, flagellin, LPS, and poly(I:C) also increased IRG1 mRNA expression in myometrial explants. IRG1 silencing, using siRNA in primary myometrial cells, displayed a decrease in the expression of inflammation-induced pro-inflammatory cytokines (IL1A, IL6), chemokines (CCL2, CXCL1, CXCL8), adhesion molecules (ICAM1, VCAM1), and contractility (PTGFR mRNA expression, prostaglandin F_2α release, and in situ gel contraction assay). Our results suggest that IRG1 is involved when pro-labor mediators activate the inflammatory processes of human labor, warranting further investigation.

Expression and function of macrophage-inducible C-type lectin (Mincle) in inflammation driven parturition in fetal membranes and myometrium

The pivotal role of inflammatory processes in human parturition is well known, but not completely understood. We have performed a study to examine the role of macrophage-inducible C-type lectin (Mincle) in inflammation-associated parturition. Using human samples, we show that spontaneous labour is associated with up-regulated Mincle expression in the myometrium and fetal membranes. Mincle expression was also increased in fetal membranes and myometrium in the presence of pro-labour mediators, the proinflammatory cytokines interleukin (IL)-1B and tumour necrosis factor (TNF), and Toll-like receptor (TLR) ligands fsl-1, poly(I:C), lipopolysaccharide (LPS) and flagellin. These clinical studies are supported by mouse studies, where an inflammatory challenge in a mouse model of preterm birth increased Mincle expression in the uterus. Importantly, elimination of Mincle decreased the effectiveness of proinflammatory cytokines and TLR ligands to induce the expression of pro-labour mediators; namely, proinflammatory cytokines and chemokines, contraction-associated proteins and prostaglandins, and extracellular matrix remodelling enzymes, matrix metalloproteinases. The data presented in this study suggest that Mincle is required when inflammatory activation precipitates parturition.

PARK7 regulates inflammation-induced pro-labour mediators in myometrial and amnion cells

Preterm birth is a prevalent cause of neonatal deaths worldwide. Inflammation has been implicated in spontaneous preterm birth involved in the processes of uterine contractility and membrane rupture. Parkinson protein 7 (PARK7) has been found to play an inflammatory role in non-gestational tissues. The aims of this study were to determine the expression of PARK7 in myometrium and fetal membranes with respect to term labour onset and to elucidate the effect of PARK7 silencing in primary myometrium and amnion cells on pro-inflammatory and pro-labour mediators. PARK7 mRNA expression was higher in term myometrium and fetal membranes from women in labour compared to non-labouring samples and in amnion from preterm deliveries with chorioamnionitis. In human primary myometrial cells transfected with PARK7 siRNA (siPARK7), there was a significant decrease in IL1B, TNF, fsl-1 and poly(I:C)-induced expression of pro-inflammatory cytokine IL6, chemokines (CXCL8, CCL2), adhesion molecule ICAM1, prostaglandin PGF_2α and its receptor PTGFR. Similarly, amnion cells transfected with siPARK7 displayed a decrease in IL1B-induced expression of IL6, CXCL8 and ICAM1. In myometrial cells transfected with siPARK7, there was a significant reduction of NF-κB RELA transcriptional activity when stimulated with fsl-1, flagellin and poly(I:C), but not with IL1B or TNF. Collectively, our novel data describe a role for PARK7 in regulating inflammation-induced pro-inflammatory and pro-labour mediators in human myometrial and amnion cells.

Potent anti-inflammatory effects of honokiol in human fetal membranes and myometrium

BACKGROUND

Preterm birth is the most prominent complication attributing to poor pregnancy and neonatal outcome. Infection is most commonly implicated in preterm birth; it initiates a cascade of inflammatory events that leads to the rupture of fetal membranes and spontaneous uterine contractions. Anti-inflammatory agents may thus be a therapeutic approach to prevent the premature rupture of fetal membranes and block contractions. In non-gestational tissues, the polyphenol honokiol has been shown to possess potent anti-inflammatory properties.

PURPOSE

The aim of this study was to investigate the effect of honokiol on pro-inflammatory mediators in human gestational tissues.

METHODS

Fetal membranes, myometrium and freshly isolated amnion cells and primary myometrial cells were treated with honokiol in the absence or presence of the products lipopolysaccharide (LPS) and fibroblast-stimulating lipopeptide-1 (fsl-1), the viral dsRNA analogue polyinosinic:polycytidylic acid (poly(I:C)) or the pro-inflammatory cytokines TNF or IL1B. A luciferase assay was used to determine the effect of honokiol on nuclear factor kappa B (NF-κB) RelA transcriptional activity.

RESULTS

Honokiol significantly decreased pro-inflammatory cytokine (IL1A, IL6) and chemokine (CXCL8, CXCL1, CCL2) mRNA expression and secretion from fetal membranes (amnion and choriodecidua) and myometrium stimulated with LPS, fsl-1 or poly(I:C). In amnion cells, honokiol also significantly decreased the expression and secretion of the extracellular matrix degrading enzyme MMP9. Moreover, in myometrium, honokiol significantly suppressed the expression of the contraction associated protein PTGFR, the secretion of the uterotonic prostaglandins PGE₂ and PGF_2α, and blocked TNF-induced myometrial cell contractility. Finally, honokiol significantly suppressed IL1B- and TNF-induced NF-κB RelA transcriptional activity in primary amnion and myometrial cells.

CONCLUSIONS

Honokiol reduced the expression of pro-inflammatory and pro-labour mediators in human amnion, choriodecidua and myometrium and that this may be facilitated through the suppression of NF-κB activation. These results indicate that the polyphenol honokiol may be a potent therapeutic for the prevention of preterm birth.

Identification of SMAD3 as a Novel Mediator of Inflammation in Human Myometrium In Vitro

Preterm birth remains the primary cause of early neonatal death and is a major determinant for long-term health consequences. Aberrant intrauterine inflammation and infection are known to augment the synthesis of proinflammatory cytokines and induce uterine contractions, which can subsequently lead to preterm birth. The transforming growth factor-β (TGF-β) superfamily members regulate numerous cellular processes through the activation of intracellular mediators known as mothers against decapentaplegic homolog (SMADs). Studies in nongestational tissues have shown that SMAD3 plays a role in immune regulation and inflammation; however, its role in human labour remains unknown. Thus, the present study aimed at (i) characterising the expression of SMAD3 in the human myometrium; (ii) determining the effect of bacterial and viral products and proinflammatory cytokines on SMAD3 transcriptional activity in primary human myometrial cells; and (iii) investigating the effect of SMAD3 siRNA knockdown on the production of prolabour mediators in primary human myometrial cells. Phosphorylated (i.e., active) SMAD3 protein expression was lower in the myometrium after spontaneous term labour compared to the myometrium from nonlabouring women. Using a luciferase assay, the proinflammatory cytokines IL-1β and TNF, and viral analogue polyinosinic : polycytidylic acid (poly(I : C)) significantly reduced SMAD3 transcriptional activity in human primary myometrial cells. Loss-of-function studies found that SMAD3 knockdown in myometrial cells significantly increased IL-1β- and poly(I : C)-induced proinflammatory cytokines (IL-1A, IL-6), chemokines (IL-8, MCP-1), the adhesion molecule ICAM-1, COX-2 mRNA expression, and subsequent PGF2α release. In conclusion, SMAD3 deficiency is associated with increased production of proinflammatory and prolabour mediators in the human myometrium.

Runt-related transcription factor 1 (RUNX1) deficiency attenuates inflammation-induced pro-inflammatory and pro-labour mediators in myometrium

Identifying new targets that regulate myometrial activation are required to develop effective treatments to stop preterm labor. Inflammation, which can be induced by sterile or infective insults, plays a role in initiating and maintaining uterine contractions. Several high throughput transcription screening studies have identified an upregulation of runt-related transcription factor 1 (RUNX1) mRNA expression in myometrium with labor. The role of RUNX1 in labor, however, is not known. We report increased RUNX1 during late gestation which was further augmented in labor, suggesting that RUNX1 may be involved in the transition of the myometrium from a quiescent into a contractile state in preparation for labor. By inhibiting the expression of RUNX1, we have established that RUNX1 induces the expression of pro-inflammatory cytokines, chemokines, adhesion molecules, contraction-associated proteins OXR and PTGFR, the uterotonic PGF_2α, and the ECM remodelling enzyme MMP9. Targeting RUNX1 may be a novel approach to prevent preterm labor.

Markers of protein synthesis are increased in fetal membranes and myometrium after human labour and delivery

Preterm birth remains one of the leading causes of neonatal death. Inflammation and maternal infection are two of the leading aetiological factors for preterm birth. Labour is associated with increased production of proinflammatory cytokines, chemokines and prolabour mediators in human gestational tissues. In non-gestational tissues, synthesis of proinflammatory and prolabour mediators is regulated by components of the protein synthesis machinery. Therefore, in the present study we investigated the effect of human labour on the expression of three protein synthesis markers, namely eukaryotic elongation factor 2 kinase (EEF2K), mitogen-activated protein kinase interacting protein kinase 1 (MKNK1) and eukaryotic translation initiation factor 4E (EIF4E), and their role in regulating inflammation in human gestational tissues. In fetal membranes and myometrium, EEF2K expression was significantly lower, whereas MKNK1 expression was significantly higher withterm and preterm labourcompared to term nolabour. In contrast, EIF4E expression did not change in fetal membranes or myometrium with labour. In primary myometrial cells, loss-of-function studies using specific chemical inhibitors of EEF2K (A484954) and MKNK1 (CGP57380) demonstrated that MKNK1, but not EEF2K, was required for polyinosinic-polycytidylic acid (poly(I:C); a viral double-stranded RNA mimetic) and interleukin (IL)-1β-induced production of IL6, C-X-C motif chemokine ligand 8 (CXCL8), prostaglandin-endoperoxide synthase 2 (PTGS2) and prostaglandin F2α. In conclusion, spontaneous term and preterm labour is associated with decreased EEF2K and increased MKNK1 expression in fetal membranes and myometrium. Moreover, MKNK1 is involved in the genesis of proinflammatory and prolabour mediators that is mediated by inflammation or infection. However, further studies are required to elucidate the role of EEF2K in human labour.

IRF5 is increased in labouring myometrium and regulates pro-labour mediators

Preterm birth continues to be the leading cause of neonatal mortality and morbidities that can extend into adult life. Few treatment options stem from our incomplete understanding of the mechanisms of human labour and delivery. Activation of the inflammatory response in gestational tissues by inflammation and/or infection leads to the production of pro-inflammatory and pro-labour mediators, thus preterm birth. Interferon regulatory factor 5 (IRF5) has recently emerged as an important pro-inflammatory transcription factor involved in acute and chronic inflammation. The aims of this study were to determine the expression of IRF5 in human myometrium from labouring and non-labouring women, and whether IRF5 is involved in the genesis of pro-inflammatory and pro-labour mediators induced by pro-inflammatory cytokines or toll-like receptor (TLR) ligands. IRF5 mRNA and protein expression was significantly higher in human myometrium after spontaneous term labour, compared to non-labouring tissues. IRF5 mRNA expression was also significantly higher in primary myometrial cells treated with the pro-inflammatory cytokines IL1B or TNF. In primary myometrial cells, IRF5 knockdown by siRNA (siIRF5) was associated with significantly decreased expression and or secretion of pro-inflammatory cytokines (IL1A, IL6), chemokines (CXCL8, CCL2), adhesion molecules (ICAM1, VCAM1) and contraction-associated proteins PTGS2, PGF_2α and PTGFR when in the presence of IL1B, TNF, fsl-1 (TLR2/6 ligand) or flagellin (TLR5 ligand). siIRF5-transfected cells also displayed decreased NF-κB RELA transcriptional activity in the presence of these preterm birth mediators. Our study suggests a novel role for IRF5 in the regulation of the inflammatory response in human myometrium.

The immunoproteasome inhibitor ONX-0914 regulates inflammation and expression of contraction associated proteins in myometrium

There are currently no effective treatments to prevent spontaneous preterm labor. The precise upstream biochemical pathways that regulate the transition between uterine quiescence during pregnancy and contractility during labor remain unclear. It is well known however that intrauterine inflammation, including infection, is commonly associated with preterm labor. In this study, we identified the immunoproteasome subunit low-molecular-mass protein (LMP)7 mRNA expression to be significantly upregulated in laboring human myometrium. Silencing LMP7 using siRNA-targeted knockdown of LMP7 and its inhibitor ONX-0914 in human myometrial cells and tissues decreased proinflammatory cytokines (IL-6), cell chemotaxis (CXCL8, CCL2 expression, and THP-1 migration), cell to cell adhesion (ICAM1 expression and myometrial adhesion), contraction-associated proteins (PTGS2, FP, PGE2, and PGF2α), as well as suppressing contractions in myometrial cells and in myometrial tissues obtained from laboring women. In addition, LMP7 silencing reduced NF-κB RelA activity. ONX-0914 alleviated inflammation (CCL3, CXCL1, PTGS2, and IL-6) in myometrium, placenta, fetal brain, amniotic fluid, and maternal serum induced by LPS in pregnant mice. Collectively, our data suggest a novel role for ONX-014 to suppress uterine activation and contractility associated with preterm labor.

A20, an essential component of the ubiquitin-editing protein complex, is a negative regulator of inflammation in human myometrium and foetal membranes

STUDY QUESTION

Does A20 regulate mediators involved in the terminal processes of human labour in primary myometrial and amnion cells?

SUMMARY ANSWER

A20 is a nuclear factor-kappa B (NF-κB) responsive gene that acts as a negative regulator of NF-κB-induced expression of pro-labour mediators.

WHAT IS KNOWN ALREADY

Inflammation is commonly implicated in spontaneous preterm birth and the processes involved in rupture of foetal membranes and uterine contractions. In myometrium and foetal membranes, the pro-inflammatory transcription factor NF-κB regulates the transcription of pro-labour mediators in response to inflammatory stimuli. In non-gestational tissues, A20 is widely recognised as an anti-inflammatory protein that inhibits inflammation-induced NF-κB signalling.

STUDY DESIGN, SIZE, DURATION

Primary human amnion and myometrial cells were used to determine the effect of pro-inflammatory mediators on A20 expression and the effect of A20 siRNA on the expression and secretion of pro-labour mediators. The expression of A20 was assessed in myometrium and foetal membranes from non-labouring and labouring women at preterm and or term (n = 8 or nine samples per group).

PARTICIPANTS/MATERIALS, SETTING, METHODS

The effects of pro-inflammatory mediators and of A20 siRNA in cell cultures were determined by quantitative RT-PCR (qRT-PCR), western blots, immunoassays, gelatin zymography and luciferase assays. A20 expression in tissue samples was assessed by qRT-PCR. Statistical significance was ascribed to a P value < 0.05.

MAIN RESULTS AND THE ROLE OF CHANCE

In primary cells isolated from myometrium and or amnion, the pro-inflammatory cytokines IL1B and TNF, the bacterial products flagellin and fsl-1, and the viral double stranded RNA analogue poly(I:C) significantly increased A20 mRNA expression via NF-κB. A20 siRNA studies in primary myometrial and amnion cells demonstrated an augmentation of inflammation-induced expression and or secretion of pro-inflammatory cytokines (IL1A, IL6), chemokines (CXCL1, CXCL8, CCL2), adhesion molecules (ICAM1, VCAM1), contraction-associated proteins (PTGS2, PTGFR, PGF2α) and the extracellular matrix degrading enzyme MMP9, as well as NF-κB activation. Inhibition of NF-κB activity significant attenuated inflammation-induced expression of pro-labour mediators in A20 siRNA transfected cells. Finally, A20 mRNA expression was decreased in myometrium and foetal membranes with labour, and in foetal membranes with chorioamnionitis.

LARGE SCALE DATA

Not applicable.

LIMITATIONS, REASONS FOR CAUTION

The conclusions of this study are solely reliant on the data from in vitro experiments using cells isolated from myometrium and amnion.

WIDER IMPLICATIONS OF THE FINDINGS

The results of this study raise the possibility that targeting A20 may be a therapeutic approach to reduce inflammation associated with spontaneous preterm birth.

STUDY FUNDING AND COMPETING INTEREST(S)

Associate Professor Martha Lappas is supported by a Career Development Fellowship from the National Health and Medical Research Council (NHMRC; grant no. 1047025). Funding for this study was provided by the NHMRC (grant no. 1058786), Norman Beischer Medical Research Foundation and the Mercy Research Foundation. There are no competing interests.

Effect of spontaneous term labour on the expression of the NR4A receptors nuclear receptor related 1 protein (Nurr1), neuron-derived clone 77 (Nur77) and neuron-derived orphan receptor 1 (NOR1) in human fetal membranes and myometrium

Inflammation has been implicated in the mechanisms responsible for human labour. Emerging evidence indicates that nuclear receptor subfamily 4A (NR4A) receptors regulate the transcription of genes involved in inflammation. The aim of the present study was to determine the effect of spontaneous term labour, Toll-like receptor (TLR) ligands and nucleotide-binding oligomerisation domain-containing (NOD) ligands on the expression of nuclear receptor related 1 protein (Nurr1), neuron-derived clone 77 (Nur77) and neuron-derived orphan receptor 1 (NOR1) in human fetal membranes and myometrium. Human fetal membranes and myometrium were collected from term non-labouring women and women after spontaneous labour onset. Tissue explants were used to determine the effect of the bacterial products lipopolysaccharide (LPS; TLR4 ligand), flagellin (TLR5 ligand), fibroblast-stimulating lipopeptide (FSL-1) (TLR2 ligand), γ-D-glutamyl-meso-diaminopimelic acid (iE-DAP) (NOD1 ligand) or minimal peptidoglycan muramyl dipeptide (MDP; NOD2 ligand) on Nurr1, Nur77 and NOR1 expression. Term labour was associated with significantly higher Nurr1 and Nur77, but not NOR1, expression in fetal membranes and myometrium. LPS and MDP increased Nurr1, Nur77 and NOR in fetal membranes; flagellin increased Nurr1 in fetal membranes and the myometrium, as well as NOR1 in the myometrium; and FSL-1 increased Nurr1 expression in fetal membranes. In summary, human labour and bacterial products increase Nurr1, Nur77 and/or NOR1 expression in human fetal membranes and myometrium. This increase in NR4A receptors may contribute to the expression of proinflammatory and pro-labour genes associated with fetal membrane rupture and myometrial contractions.

NOD-like receptor pyrin domain-containing-3 (NLRP3) regulates inflammation-induced pro-labor mediators in human myometrial cells

PROBLEM

Inflammation plays a major role in preterm birth. Nucleotide-binding oligomerization domain-like receptor pyrin domain-containing-3 (NLRP3) plays a role in inflammatory diseases. The aims of this study were to determine the effect of term labor on the expression of NLRP3 in human myometrium and the effect of NLRP3 silencing on pro-labor mediators in myometrial cells.

METHOD OF STUDY

NLRP3 expression was assessed in myometrium from non-laboring and laboring women by qRT-PCR and Western blotting. Human primary myometrial cells were transfected with NLRP3 siRNA (siNLRP3), treated with pro-inflammatory cytokines and toll-like receptor (TLR) ligands, and assayed for pro-inflammatory mediators' expression.

RESULTS

NLRP3 expression was higher in myometrium after term spontaneous labor and by TNF, IL1B, fsl-1, and flagellin. In siNLRP3-transfected cells, there was a significant decrease in the expression of pro-inflammatory cytokines (IL1A, IL6), chemokines (CXCL8, CCL2), and adhesion molecules (ICAM1 and VCAM1) stimulated with IL1B, TNF, or TLR ligands; decrease in IL1B-stimulated PTGS2 and PTGFR mRNA expression and PGF_2α release; and increase in TNF-stimulated myometrial gel shrinkage as assessed by an in vitro cell contraction assay.

CONCLUSION

NLRP3 is increased with labor in myometrial, and knockdown of NLRP3 is associated with an attenuation of inflammation-induced expression of pro-inflammatory and pro-labor mediators in human myometrium.

The IL-1β signalling pathway and its role in regulating pro-inflammatory and pro-labour mediators in human primary myometrial cells

Interleukin (IL)-1β plays a central role in the processes of human labour and delivery. The adaptor proteins involved in the IL-1β signalling pathway in human myometrium are not known. This study sought to determine the role of the adaptor proteins myeloid differentiation primary response 88 (MyD88), tumour necrosis factor receptor-associated factor 6 (TRAF6), IL-1 receptor-associated kinase 4 (IRAK4) and transforming growth factor beta-activated kinase 1 (TAK1) in IL-1β-induced formation of pro-inflammatory and pro-labour mediators in human myometrium. Human primary myometrial cells were transfected with siRNA against MyD88 (siMYD88), TRAF6 (siTRAF6), IRAK4 (siIRAK4) or TAK1 (siTAK1), treated with IL-1β, and assayed for the mRNA expression and or secretion of pro-inflammatory and pro-labour mediators. Transfection of primary myometrial cells with siMYD88, siTRAF6, siIRAK4 and siTAK1 significantly decreased IL-1β-induced IL-1α, IL-6, growth-regulated alpha protein (GRO-α), IL-8, monocyte chemoattractant protein (MCP)-1, intercellular adhesion molecule (ICAM)-1 and cyclooxygenase (COX)-2 mRNA expression and release of IL-6, GRO-α, IL-8, MCP-1, ICAM-1 and prostaglandin PGF_2α. The expression and secretion of the extracellular matrix remodelling enzyme matrix metalloproteinase (MMP)-9 was significantly lower with siMYD88 and siTRAF6. Finally, IL-1β-induced nuclear factor κB (NF-κB) transcriptional activity was significantly attenuated by transfection with siMyD88, siTRAF6 and siIRAK4; there was no effect of siTAK1 transfection on NF-κB transcriptional activity. Collectively, these findings suggest that MyD88, TRAF6, IRAK4 and TAK1 are involved in IL-1β signalling in human myometrium. Further studies are required to determine if inhibition of these proteins can prevent preterm birth.

RKIP is decreased in laboring myometrium and modulates inflammation-induced pro-labor mediators

Nuclear factor-kappa B (NF-κB)-induced inflammation plays a central role in the terminal process of human labor and delivery. Our previous studies show that IL1B induces NF-κB signaling through extracellular signal-regulated kinase (ERK; official gene symbol MAPK1), whereas TNF induces NF-κB-driven transcription of pro-labor mediators via an MAPK1-independent mechanism. Raf kinase inhibitor protein (RKIP) negatively regulates inflammation by inhibiting NF-κB activation directly or indirectly by inhibiting MAPK1. The role of RKIP in the processes of human labor and delivery is not known. The present study was performed to investigate the expression of RKIP in laboring and non-laboring human myometrium and determine the effect of siRNA knockdown of RKIP (siRKIP) on pro-labor mediators in human myometrial primary cells. Term labor was associated with a decrease in RKIP expression. Furthermore, RKIP expression was decreased in myometrial cells treated with IL1B and TNF, two likely factors contributing to preterm birth. The effect of siRKIP in primary myometrial cells was a significant augmentation of IL1B- and TNF-induced CXCL1 and CXCL8 mRNA abundance and secretion; PTGS2 mRNA levels and prostaglandin PGF_2α release and MMP9 mRNA abundance and pro-MMP9 secretion. There was no effect of siRKIP on MAPK1 activation. On the other hand, RKIP knockdown was associated with increased activation of NF-κB RELA in the presence of IL1B and TNF. In conclusion, in human primary myometrial cells, RKIP negatively regulates IL1B- and TNF-induced expression and or secretion of pro-inflammatory and pro-labor mediators by inhibiting NF-κB RELA activation.

The Adaptor Protein p62 Mediates Nuclear Factor κB Activation in Response to Inflammation and Facilitates the Formation of Prolabor Mediators in Human Myometrium

Preventing spontaneous preterm birth is one of the most important issues facing perinatal medicine today. The pathophysiology of preterm labor, the single biggest cause of preterm birth, is poorly understood. Inflammation, however, plays a significant role in the terminal processes of human labor, which include myometrial contractions. Nuclear factor κB (NF-κB) drives the transcription of proinflammatory mediators involved in the terminal effector pathways of human labor and delivery. Recent studies in nongestational tissues have shown that the adaptor protein p62 interacts with NF-κB to induce inflammation. The aim of this study was to determine the role of p62 in the genesis of NF-κB-induced proinflammatory and prolabur mediators. Human spontaneous term labor was associated with increased p62 messenger RNA (mRNA) and protein expression in myometrium. Myometrial cells treated with proinflammatory cytokines interleukin 1β (IL-1β) and tumor necrosis factor alpha (TNF-α) also significantly increased p62 mRNA and protein expression. Functional studies using p62 small interfering RNA (siRNA) demonstrated a significant attenuation of TNF-α- and IL-1β-induced proinflammatory cytokines (IL-6) and chemokine (IL-8 and monocyte chemoattractant protein 1 [MCP-1]) mRNA expression and secretion, expression of cyclooxygenase 2, release of prostaglandin F_2α (PGF_2α), and expression of the prostaglandin F receptor (FP). In addition, siRNA knockdown of p62 significantly suppressed IL-1β- and TNF-α-induced NF-κB activation. Collectively, these studies suggest that p62 is involved in the genesis of NF-κB-induced proinflammatory and prolabor mediators.

RAF1 is increased in labouring myometrium and modulates inflammation-induced pro-labour mediators

Inflammation plays a central role in the terminal process of human labour and delivery, including myometrial contractions. RAF1 proto-oncogene serine/threonine-protein kinase (RAF1) can activate ERK (official gene symbolMAPK1) and/or nuclear factor-kappa B (NF-κB) to regulate genes involved in inflammation. There are, however, no studies on the role of RAF1 in the processes of human labour and delivery. Thus, the aims of this study were to determine the effect of i) human labour and pro-inflammatory cytokines interleukin 1 beta (IL1B) and tumour necrosis factor (TNF) alpha on RAF1 protein expression in myometrium and ii) siRNA knockdown ofRAF1on pro-inflammatory and pro-labour mediators in human myometrial primary cells. Term labour was associated with an increase in RAF1 protein expression. Furthermore, RAF1 protein expression was increased in myometrial cells treated with IL1B and TNF, two likely factors contributing to preterm birth. Knockdown ofRAF1by siRNA in primary myometrial cells significantly decreased IL1B- and TNF-inducedIL1A, IL1B, IL6,(C-X-C motif) ligand 8 (CXCL8)and chemokine (C-C motif) ligand 2 (CCL2) mRNA abundance and IL6, IL8 and CCL2; prostaglandin-endoperoxide synthase 2 (PTGS2) mRNA levels and prostaglandin PGF2αrelease; and NF-κB activation. Furthermore,RAF1knockdown was associated with decreased activation of ERK in the presence of IL1B but not TNF. Concordantly, the ERK inhibitor U0126 significantly decreased IL1B-inducedIL6,CXCL8,CCL2andPTGS2mRNA abundance; IL6, CXCL8, CCL2 and PGF2αrelease; and NF-κB activation. In conclusion, IL1B induces the expression and secretion of pro-labour mediators through the RAF1–MAPK1–NF-κB signalling pathway. TNF, on the other hand, regulates pro-labour mediators through the RAF1–NF-κB signalling pathway via an MAPK1-independent mechanism.

KLF5 regulates infection- and inflammation-induced pro-labour mediators in human myometrium

The transcription factor Kruppel-like factor 5 (KLF5) has been shown to associate with nuclear factor kappa B (NFκB) to regulate genes involved in inflammation. However, there are no studies on the expression and regulation of KLF5 in the processes of human labour and delivery. Thus, the aims of this study were to determine the effect of i) human labour on KLF5 expression in both foetal membranes and myometrium; ii) the pro-inflammatory cytokine interleukin 1 beta (IL1β), bacterial product flagellin and the viral dsRNA analogue poly(I:C) on KLF5 expression and iii) KLF5 knockdown by siRNA in human myometrial primary cells on pro-inflammatory and pro-labour mediators. In foetal membranes, there was no effect of term or preterm labour on KLF5 expression. In myometrium, the term labour was associated with an increase in nuclear KLF5 protein expression. Moreover, KLF5 expression was also increased in myometrial cells treated with IL1β, flagellin or poly(IC), likely factors contributing to preterm birth. KLF5 silencing in myometrial cells significantly decreased IL1β-induced cytokine expression (IL6 and IL8 mRNA expression and release), COX2 mRNA expression, and subsequent release of prostaglandins PGE2 and PGF2α. KLF5 silencing also significantly reduced flagellin- and poly(I:C)-induced IL6 and IL8 mRNA expression. Lastly, IL1β-, flagellin- and poly(I:C)-stimulated NFκB transcriptional activity was significantly suppressed in KLF5-knockout myometrial cells. In conclusion, this study describes novel data in which KLF5 is increased in labouring myometrium, and KLF5 silencing decreased inflammation- and infection-induced pro-labour mediators.

Differential expression of AP-1 proteins in human myometrium after spontaneous term labour onset

OBJECTIVES

The aims of this study were (i) to determine the localisation of activator protein (AP)-1 family members (cFos, FosB, cJun, JunB and JunD) in human myometrium; and (ii) to determine the effect of human term labour on the expression of AP-1 family of transcription factors in myometrium.

STUDY DESIGN

This localised the AP-1 family members cFos, FosB, cJun, JunB and JunD in human myometrium was performed by immunohistochemistry. The effect of term labour on the expression of these family members at the mRNA and protein level was assessed by qRT-PCR and Western blotting, respectively. The effect of pro-inflammatory stimuli on AP-1 transcriptional activity was assessed using a luciferase assay in primary human myometrial cells.

RESULTS

Immunohistochemical expression of cFos, FosB, cJun, JunB and JunD were all present in human myometrial tissue and displayed cytoplasmic staining. FosB and JunD also displayed nuclear staining. Term labour was associated with an increase in cFos and JunB mRNA and protein expression. On the other hand, JunD mRNA and protein expression was decreased with labour. FosB mRNA was increased with labour, but there was no change at the protein level. There was no change in cJun mRNA or protein expression. AP-1 transcriptional activity was increased in human myometrial cells by the pro-inflammatory cytokine TNF-α. There was, however, no effect of the bacterial products lipopolysaccharide (LPS; TLR4 ligand), iE-DAP (NOD1 ligand), MDP (NOD2 ligand), FSL-1 (TLR2 ligand) or flagellin (TLR5 ligand) on AP-1 transcriptional activity.

CONCLUSION

This study shows that human labour is associated with changes in AP-1 family members. Further studies are required to determine the exact role of the AP-1 family members in myometrium.

Effect of silibinin in reducing inflammatory pathways in in vitro and in vivo models of infection-induced preterm birth

Infection-induced preterm birth is the largest cause of infant death and of neurological disabilities in survivors. Silibinin, from milk thistle, exerts potent anti-inflammatory activities in non-gestational tissues. The aims of this study were to determine the effect of silibinin on pro-inflammatory mediators in (i) human fetal membranes and myometrium treated with bacterial endotoxin lipopolysaccharide (LPS) or the pro-inflammatory cytokine IL-1β, and (ii) in preterm fetal membranes with active infection. The effect of silibinin on infection induced inflammation and brain injury in pregnant mice was also assessed. Fetal membranes and myometrium (tissue explants and primary cells) were treated with 200 μM silibinin in the presence or absence of 10 μg/ml LPS or 1 ng/ml IL-1β. C57BL/6 mice were injected with 70 mg/kg silibinin with or without 50 μg LPS on embryonic day 16. Fetal brains were collected after 6 h. In human fetal membranes, silibinin significantly decreased LPS-stimulated expression of IL-6 and IL-8, COX-2, and prostaglandins PGE2 and PGF2α. In primary amnion and myometrial cells, silibinin also decreased IL-1β-induced MMP-9 expression. Preterm fetal membranes with active infection treated with silibinin showed a decrease in IL-6, IL-8 and MMP-9 expression. Fetal brains from mice treated with silibinin showed a significant decrease in LPS-induced IL-8 and ninjurin, a marker of brain injury. Our study demonstrates that silibinin can reduce infection and inflammation-induced pro-labour mediators in human fetal membranes and myometrium. Excitingly, the in vivo results indicate a protective effect of silibinin on infection-induced brain injury in a mouse model of preterm birth.

The TLR2 ligand FSL-1 and the TLR5 ligand Flagellin mediate pro-inflammatory and pro-labour response via MyD88/TRAF6/NF-κB-dependent signalling

PROBLEM

Toll-like receptors (TLRs) 2 and 5 induce inflammation via the adapter proteins myeloid differentiation factor 88 (MyD88) and TNFR-associated factor 6 (TRAF6) and the transcription factor nuclear factor-kappa B (NF-κB). The aims of this study were to determine the effects of the TLR5 ligand flagellin and the TLR2 ligand FSL-1 on pro-inflammatory and pro-labour mediators in human fetal membranes and myometrium, and to establish whether their actions are dependent on MyD88, TRAF6 and NF-κB.

METHOD OF STUDY

Tissue explants were performed to determine the effect of flagellin and FSL-1 on pro-labour mediators in fetal membranes and myometrium. siRNA knockdown was performed in primary amnion and myometrium cells to determine the role of MyD88, TRAF6 and NF-κB.

RESULTS

Flagellin and FSL-1 increased pro-inflammatory cytokines (IL-6 and IL-8), MMP-9 expression and activity, and COX-2 expression and prostaglandin release. siRNA knockdown of TLR2 decreased FSL-1 induced production of IL-6, IL-8, COX-2, prostaglandins and MMP-9; similarly, siRNA knockdown of TLR5 decreased flagellin induced production of these pro-labour mediators. The effects of flagellin and FSL-1 are mediated by MyD88 and TRAF6, as siRNA knockdown of MyD88 and TRAF6 decreased flagellin and FSL-1 induced pro-labour mediators. Additionally, the effects of flagellin and FSL-1 are mediated via NF-κB, as flagellin and FSL-1 increased NF-κB transcriptional activity, and the NF-κB inhibitor BAY 11-7082 attenuated flagellin and FSL-1 induced expression and secretion of pro-labour mediators.

CONCLUSION

TLR2 engagement by the synthetic lipoprotein FSL-1 and TLR5 engagement by bacterial flagellin enhances pro-inflammatory and pro-labour mediators in human fetal membranes and myometrium via MyD88/TRAF6/NF-κB.