The effect of interleukin-1 in rabbit cervical ripening

The Role of the NLRP3 Inflammasome in the Molecular and Biochemical Mechanisms of Cervical Ripening: A Comprehensive Review

The uterine cervix is one of the key factors involved in ensuring a proper track of gestation and labor. At the end of the gestational period, the cervix undergoes extensive changes, which can be summarized as a transformation from a non-favorable cervix to one that is soft and prone to dilation. During a process called cervical ripening, fundamental remodeling of the cervical extracellular matrix (ECM) occurs. The cervical ripening process is a derivative of many interlocking and mutually driving biochemical and molecular pathways under the strict control of mediators such as inflammatory cytokines, nitric oxide, prostaglandins, and reactive oxygen species. A thorough understanding of all these pathways and learning about possible triggering factors will allow us to develop new, better treatment algorithms and therapeutic goals that could protect women from both dysfunctional childbirth and premature birth. This review aims to present the possible role of the NLRP3 inflammasome in the cervical ripening process, emphasizing possible mechanisms of action and regulatory factors.

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.

Signaling Pathways Regulating Human Cervical Ripening in Preterm and Term Delivery

At the end of gestation, the cervical tissue changes profoundly. As a result of these changes, the uterine cervix becomes soft and vulnerable to dilation. The process occurring in the cervical tissue can be described as cervical ripening. The ripening is a process derivative of enzymatic breakdown and inflammatory response. Therefore, it is apparent that cervical remodeling is a derivative of the reactions mediated by multiple factors such as hormones, prostaglandins, nitric oxide, and inflammatory cytokines. However, despite the research carried out over the years, the cellular pathways responsible for regulating this process are still poorly understood. A comprehensive understanding of the entire process of cervical ripening seems crucial in the context of labor induction. Greater knowledge could provide us with the means to help women who suffer from dysfunctional labor. The overall objective of this review is to present the current understanding of cervical ripening in terms of molecular regulation and cell signaling.

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.

Decreased type III collagen expression in human uterine cervix of prolapse uteri

The precise mechanism of prolapse uteri is not fully understood. There is evidence to suggest that abnormalities of collagen, the main component of extracellular matrix, or its repair mechanism, may predispose women to prolapse. To investigate the characteristic structure of human uterine cervix of patients with prolapse uteri, various types of collagen expression in the uterine cervix tissues of the prolapse uteri were compared to those of normal uterine cervix. After informed consent, 36 specimens of uterine cervical tissues were obtained at the time of surgery from 16 postmenopausal women with prolapse uteri (stage III-IV by the Pelvic Organ Prolapse Quantification examination) and 20 postmenopausal women without prolapse uteri (control group). Collagens were extracted from the uterine cervix tissues by salt precipitation methods. The relative levels of various collagens were evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The uterine cervix was longer in the patients with prolapse uteri than those of postmenopausal controls without prolapse uteri. The ratios of type III to type I collagen in the uterine cervical tissues were significantly decreased in the prolapse uteri, as compared to those of the postmenopausal uterine cervix without prolapse. These results suggest that decreased type III collagen expression may play an important role in determing the physiology and structure of the uterine cervix tissues of prolapse uteri.

A novel isoform of microphthalmia-associated transcription factor inhibits IL-8 gene expression in human cervical stromal cells

Cervical ripening during pregnancy is a profound change in cervix structure and function characterized by increases in the proinflammatory cytokine IL-8 and dissolution of the cervical extracellular matrix. Relatively little is known about the molecular mechanisms that underlie these events. Here, we report identification of a novel isoform of micropthalmia-associated transcription factor in human cervical stromal cells (MiTF-CX) that is down-regulated 12-fold during cervical ripening and that represses expression of IL-8. Ectopic expression of MiTF-CX in human cervical stromal cells resulted in substantial suppression of endogenous IL-8 mRNA and protein expression, whereas expression of dominant negative MiTF-CX mutants with impaired DNA binding resulted in dramatic increases in IL-8 production. Gel shift, reporter gene, and chromatin immunoprecipitation assays revealed one strong binding site (E-box (-397) CACATG(-391)) in the human IL-8 promoter that was crucial for mediating transcriptional repression by MiTF-CX. Moreover, we show that MiTF-CX expression in the cervix was itself positively autoregulated via two E-box motifs within a 2.1-kb promoter fragment. We therefore propose that maintenance of cervical competency during pregnancy is an active process maintained through suppression of IL-8 by the transcription factor MiTF-CX. During cervical ripening, loss of MiTF-CX would result in significant up-regulation of IL-8 mRNA and protein synthesis, thereby leading to recruitment and activation of leukocytes within the cervix and dissolution of the extracellular matrix.

PREMATURE CERVICAL CHANGE AND THE USE OF CERVICAL CERCLAGE

Preterm birth and its subsequent consequences continue to be a major challenge worldwide. In the United States in 2004, 12.5% of infants were born preterm, making the annual societal economic burden associated with preterm birth in excess of $26.2 billion (and this is a modest estimate). Spontaneous preterm birth accounts for about 75% of all preterm births; however, at earlier gestations iatrogenic preterm birth accounts for a greater proportion of all preterm births; at 27–28 weeks 50% are iatrogenic. The proportion of babies transferred to the neonatal unit is more than 90% for those born before 33 completed weeks of gestation compared with 31% at 36 weeks; delivery between 33 completed weeks and 36 completed weeks has a relatively low morbidity and mortality. Nonetheless, 1 in 3 children born preterm but beyond 32 weeks have educational and behavioural problems at the age of 7, with 1 in 4 children born between 32 and 35 weeks requiring support from non-teaching assistants at school. Although more than 40% of babies at 35 completed weeks show signs of maturity, some still need ventilation at 38 completed weeks. Almost one-fifth of all infants born at less than 32 weeks gestation do not survive the first year of life.

Involvement of nuclear factor-kB activation through RhoA/Rho-kinase pathway in LPS-induced IL-8 production in human cervical stromal cells

Interleukin-8 (IL-8) is a chemokine that recruits and activates neutrophils in stromal tissue and plays an essential role in cervical ripening. Nuclear factor-kB (NF-kB) is known to be important for the up-regulation of IL-8 gene expression. We examined the molecular mechanisms responsible for NF-kB activation in IL-8 production in cervical stromal cells. Lipopolysaccharide (LPS) and IL-1beta stimulated IL-8 production by cervical stromal cells in a dose-dependent manner. Pretreatment of cervical stromal cells with inhibitors of RhoA (C3 transferase exoenzyme), Rho-kinase (Y-27632) or NF-kB (BAY11-7082) effectively blocked LPS-induced IL-8 release. In contrast, IL-1beta-induced IL-8 production was significantly blocked by BAY11-7082, but not by C3 transferase exoenzyme or Y-27632. Pull-down assays showed that LPS activated RhoA, but IL-1beta caused only a lower level of activation. Transfection of the cervical stromal cells with RhoA small interfering RNA (siRNA) inhibited LPS-stimulated IL-8 production, whereas IL-1beta-induced IL-8 production was not significantly inhibited by knockdown of RhoA with siRNA. Using an NF-kB transcription reporter vector, luciferase assays demonstrated that incubation with LPS or IL-1beta induced the activation of NF-kB in cervical stromal cells. Activation of NF-kB by LPS was inhibited by treatment with C3 exoenzyme, Y-27632 or RhoA siRNA. However, inhibition of the RhoA/Rho-kinase pathway did not attenuate the activation of NF-kB by IL-1beta. These results suggest that LPS-induced IL-8 production is accompanied by enhanced NF-kB activation through the RhoA/Rho-kinase pathway in human cervical cells.

Utilization of different aquaporin water channels in the mouse cervix during pregnancy and parturition and in models of preterm and delayed cervical ripening

Biochemical changes of cervical connective tissue, including progressive disorganization of the collagen network and increased water content, occur during gestation to allow for cervical dilatation during labor, but the mechanisms that regulate cervical fluid balance are not fully understood. We examined whether aquaporins (AQPs), a family of membrane channel proteins that facilitate water transport, help mediate fluid balance in the mouse cervix during parturition. Of the 13 known murine AQPs, AQP0-2, 6, 7, 9, 11, and 12 were absent or at the limits of detection. By Northern blot and real-time PCR, AQP3 expression was low in nongravid and mid-pregnancy cervices with peak expression on d 19 and postpartum d 1 (PP1). AQP4 expression was generally low throughout pregnancy but showed a small upward trend at the time of parturition. AQP5 and AQP8 expression were significantly increased on d 12-15 but fell to nongravid/baseline by d 19 and PP1. By in situ hybridization and immunohistochemistry, AQP3 was preferentially expressed in basal cell layers of the cervical epithelium, whereas AQP4, 5, and 8 were primarily expressed in apical cell layers. Females with LPS-induced preterm labor had similar trends in AQP4, 5, and 8 expression to mice with natural labor at term gestation. Mice with delayed cervical remodeling due to deletion of the steroid 5alpha-reductase type 1 gene showed significant reduction in the levels of AQP3, 4, and 8 on d 19 or PP1. Together, these studies suggest that AQPs 3, 4, 5, and 8 regulate distinct aspects of cervical water balance during pregnancy and parturition.

Interleukin-8 is involved in cervical dilatation but not in prelabour cervical ripening

Our aim was to determine the amount and source of interleukin (IL)-8 and to study IL-8 receptor expression in the human cervix during pregnancy and after labour. Cervical biopsies were obtained from six non-pregnant women, eight women undergoing pregnancy termination, 17 women undergoing elective caesarean section and 11 women after vaginal delivery. IL-8 levels were compared in women with and without a ripe cervix, as determined by cervical Bishop score and cervicovaginal fetal fibronectin levels. Levels of IL-8 and IL-1beta, a regulator of IL-8 expression, were determined by enzyme-linked immunosorbent assay (ELISA). IL-8, IL-1beta and IL-8 receptor proteins were localized by immunohistochemistry. Compared with late pregnancy, IL-8 levels increased after labour and vaginal delivery (P < 0.01) but there was no correlation with cervical ripening. IL-8 was localized to stromal cells, macrophages and granulocytes. There were no significant differences in IL-1beta levels between groups. IL-8 receptors were expressed primarily on granulocytes and macrophages after vaginal delivery. We conclude that IL-8 is involved in cervical dilatation but not in cervical ripening.

Interleukin-1beta induces glycosaminoglycan synthesis via the prostaglandin E2 pathway in cultured human cervical fibroblasts

The aim of this study was to identify, in cultured human cervical fibroblasts, the mechanisms by which interleukin (IL)-1beta induces the synthesis of glycosaminoglycans (GAG) and to explore the putative role of prostaglandin E(2) (PGE(2)) in this process. Exposure of the cells for 24 h to IL-1beta induced a significant (P < 0.05) dose-dependent increase in GAG synthesis. IL-1beta (1 ng/ml) induced the expression of cyclooxygenase-2 (COX-2) protein 6 h after treatment, accompanied by a 7.5-fold increase in PGE(2) production. We confirmed that NS398, a selective COX-2 inhibitor, dose-dependently blocked PGE(2) augmentation following IL-1beta treatment. AH23848, the selective EP(4) receptor antagonist, completely abolished IL-1beta-induced GAG synthesis, whereas AH6809, an EP(2) receptor antagonist, had no effect on the stimulatory effects of IL-1beta. Furthermore, we demonstrated that 6 h exposure to IL-1beta induced a notable increase in EP(4) receptor mRNA expression and a decrease in EP(1) receptor mRNA but had no effect on the expression of EP(2) and EP(3) receptor transcripts. In conclusion, these findings indicate that IL-1beta not only induced GAG synthesis by increasing COX-2 protein expression and the subsequent PGE(2) production but also enhanced the responsiveness of cervical fibroblasts to PGE(2) by selectively up-regulating EP(4) receptor mRNA expression. These results suggest that PGE(2) may regulate human cervical ripening in an autocrine/paracrine manner via EP(4) receptors.

Changes in the number of polymorphonuclear leukocytes and concentrations of IL-8 and granulocyte elastase in the vaginas of normal pregnant women

PROBLEM

It is unknown whether the number of vaginal polymorphonuclear leukocytes (vPMNs) of healthy pregnant women changes during pregnancy.

METHOD OF STUDY

We studied 23 women after 14.7 +/- 3.6 weeks, 37 women after 25.2 +/- 3.1 weeks, and 26 women after 32.9 +/- 2.0 weeks of gestation. Numbers of total vPMNs, viable vPMNs, dead vPMNs, percentage viability of vPMNs, and concentrations of IL-8 and elastase activity were determined in vaginal washings.

RESULTS

The vPMNs, including viable and dead vPMNs, significantly increased with advancing gestation from 9.9 +/- 8.6 x 10(5) to 13.1 +/- 13.4 x 10(5), and to 27.1 +/- 26.6 x 10(5) (r=0.315, P < 0.01). Vaginal IL-8 significantly increased with advancing gestation. However, increases in vaginal elastase activity did not occur.

CONCLUSIONS

These results suggested that an increase in vPMNs is an early event, and that the increase in vaginal elastase activity is a late event in relation to the ripening of the uterine cervix.

Anatomy and physiology of the uterine cervix

The human uterine cervix undergoes extensive changes during pregnancy. Collagen is reorganized and consolidated early in gestation with proliferation and hyperplasia of the cellular component. As term approaches, multiple factors work together in complex interactions that cause collagen dispersion and the cervix to ripen (clinically become softer). Increases in decorin levels, hyaluronic acid, and physiologic cell death are in part responsible for this remodeling process. As the collagen bundles disperse and lose strength, cytokines, hyaluronic acid, collagenases, and elastase possibly work together to allow effacement. Then, the mechanical forces of uterine contractions extend the elastin and allow dilatation. During dilation, levels of cytokines and hyaluronic acid begin to decrease, which may serve to decrease collagenolytic activity and allow the cervix to begin the process of repairing itself. Despite this advance knowledge of cervical ripening, the signals responsible for the initiation of these changes remain to be elucidated. If we can understand the exact mechanisms that affect these changes, then we may be better able to address such complex issues as cervical incompetence, preterm delivery, postterm delivery, and proper "ripening" of the cervix to avoid surgical delivery for arrest disorders of the active phase.

Chemokines and human reproduction

OBJECTIVE

To review the available information regarding chemotactic cytokines and their possible implications in human reproduction.

DESIGN

A thorough literature and MEDLINE search was conducted to identify studies relating to the role of chemokines in ovulation, menstruation, implantation, cervical ripening and preterm labor, and endometriosis.

RESULT(S)

Chemokines mediate leukocyte traffic through their specific receptors in various tissues. Although four families have been described to date, two remain the major subfamilies: alpha-chemokines (with interleukin-8 as representative for this group), and beta-chemokines (with monocyte chemotactic protein-1 as representative). Interleukin-8, monocyte chemotactic protein-1, and growth-regulated oncogene-alpha are involved in follicular development and atresia, ovulation, steroidogenesis, and corpus luteum function. Interleukin-8 showed cycle-dependent expression in human endometrium, and at the same time, stimulated endometrial stromal cell growth, acting as an autocrine growth factor. Interleukin-8 has been identified in human amnion, chorion, decidua, and villous placenta, and its level increases during labor. Levels of interleukin-8 correlate with the release of collagenases, a crucial step that regulates the process of cervical extracellular matrix remodeling. The levels of monocyte chemotactic protein-1; regulated on activation, normal T-expressed and secreted (RANTES); interleukin-8; and growth-regulated oncogene-alpha are elevated in the peritoneal fluid of women with endometriosis, and they correlate with the stage of the disease.

CONCLUSION(S)

Chemokines play a relevant role in many physiologic and pathologic situations, such as ovulation, menstruation, implantation, cervical ripening and preterm labor, and endometriosis. Their regulation soon may provide new therapeutic strategies.

Pro-inflammatory cytokines induce expression of matrix-metabolizing enzymes in human cervical smooth muscle cells

The process of cervical ripening has been likened to an inflammatory reaction associated with the catabolism of cervical extracellular matrix by enzymes released from infiltrating leukocytes. We hypothesized that smooth muscle cells in the cervix also participate in this process and that pro-inflammatory cytokines act on cervical smooth muscle cells (CSMC) to provoke the expression of matrix-degrading enzymes. We treated primary cultures of human CSMC with tumor necrosis factor-alpha (TNF-alpha) and examined expression of the elastinolytic enzyme, cathepsin S, the collagen metabolizing matrix metalloproteinases (MMP)-1, -3, -9, and the tissue inhibitor of metalloproteinase (TIMP)-1 and -2. A time course analysis revealed that 10 ng/ml of TNF-alpha induced cathepsin S, MMP-1, -3, and -9 mRNA expression with the maximal response observed after 24-48 hours. TNF-alpha induced cathepsin S, MMP-1, -3, and -9 mRNA expression in a dose-dependent manner: the maximal effect was observed at a concentration of 10 ng/ml, with appreciable increases observed at concentrations of 0.1 to 1.0 ng/ml. In contrast, TIMP-1 and -2 mRNAs were not significantly increased by TNF-alpha treatment. Interleukin-1beta produced a pattern of gene expression in the CSMC similar to that observed following TNF-alpha treatment. Western blot analysis and zymography confirmed the induction of proMMP-1, -3, and -9 in response to TNF-alpha, but MMP-2 immunoreactivity and zymographic activity were unaffected. TNF-alpha increased secretion of procathepsin S, but did not affect TIMP-1 and reduced TIMP-2 production. We conclude that CSMC are targets of pro-inflammatory cytokines, which induce a repertoire of enzymes capable of degrading the cervical extracellular matrix. The induction of these enzymes may facilitate the normal ripening of the cervix at term and participate in the premature cervical changes associated with preterm labor.

Interleukin-8 potentiates the effect of interleukin-1-induced uterine contractions

The aim of this research was to study the effect of exogenous interleukin (IL)-8, IL-1 and IL-8 + IL-1 on uterine contractions in rabbits. Four equal groups of non-pregnant rabbits (n = 24) were investigated using either placebo or experimental drugs in the form of vaginal suppositories. The suppositories contained human recombinant IL-8 (200 ng), IL-1 (200 ng), IL-8 (200 ng) + IL-1 (200 ng) or vehicle Witepsol base, 500 microliters). Subsequently, the plasma concentration of prostaglandin (PG) E2 was estimated 3 h after the last dose of treatment. Neutrophil infiltration in the endometrial tissue was studied with anti-rabbit RT2 staining. Suppositories with IL-1 and IL-8 + IL-1 produced contractile responses with increased frequency (P < 0.003, P < 0.0005) and amplitude (P < 0.0001) in vivo, compared with vehicle. IL-1 and IL-8 + IL-1 also caused similar contractile effects with increased frequency (P < 0.01, P < 0.0007) and amplitude (P < 0.0001) in an in-vitro experiment than vehicle. The frequency and amplitude of uterine contractions were more significant with IL-8 + IL-1 than that of IL-1, both in vivo (P < 0.002, P < 0.05) and in vitro (P < 0.005, P < 0.01). IL-8 did not induce any contractions. Prostaglandin concentration was increased approximately 8-fold with IL-8 + IL-1 (P < 0.0001) and 2.5-fold with IL-1 treatment (P < 0.0001). Neutrophil numbers were significantly increased with IL-8 + IL-1 > IL-8 > IL-1 (P < 0.002, P < 0.0003 and P < 0.008) compared with vehicle. Our data suggest that IL-8 stimulates IL-1-induced uterine contractions through PGE2 production and could be an important process during labour and delivery.

Interleukin-1beta and interleukin-8 in cervicovaginal fluid during pregnancy

OBJECTIVE

We investigated the usefulness of cervicovaginal interleukin-1beta and interleukin-8 levels during pregnancy as markers of preterm and term parturition.

STUDY DESIGN

Cervicovaginal fluids were obtained from 119 pregnant women at 24 to 41 weeks' gestation. Cytokine concentrations were measured by enzyme-linked immunoassay.

RESULTS

Interleukin-1beta and interleukin-8 concentrations in cervicovaginal fluids obtained from women not in labor increased exponentially as gestational age increased. Interleukin-1beta and interleukin-8 concentrations were significantly correlated. These cytokine concentrations were significantly higher in patients in preterm labor than in patients at preterm not in labor and were significantly higher in women at term in labor than in women at term not in labor. These cytokine levels were significantly correlated with the degree of cervical dilation and tocolytic index.

CONCLUSIONS

These findings suggest that cervicovaginal interleukin-1beta and interleukin-8 contribute to term and preterm parturition. Measurement of cervicovaginal concentrations of these cytokines may be clinically useful in patients with threatened premature delivery.

Usefulness of a new tactile sensor for measurement of uterine cervical ripening in mice in a quantitative and noninvasive manner

OBJECTIVE

The purpose of this study was to establish a method with a new tactile sensor for determining in a quantitative and noninvasive manner the extent of uterine cervical ripening.

STUDY DESIGN

We used a newly designed tactile sensor to measure the softness of the cervix in untreated nonpregnant, pregnant, parturient, and nursing mice and then on day 15 of gestation in pregnant mice treated with dehydroepiandrosterone sulfate or Escherichia coli lipopolysaccharide. Additionally, to elucidate the correlation between the extent of cervical softness and its morphologic changes, we observed microscopically the uterine cervices.

RESULTS

The hardness of the murine cervix decreased with the progression of pregnancy and became minimal at delivery. We demonstrated for the first time with a tactile sensor for measuring hardness that dehydroepiandrosterone sulfate and lipopolysaccharide significantly decreased the stiffness of the murine cervix. These findings were supported by the morphologic observations on the cervices.

CONCLUSIONS

These results show that the tactile sensor for measuring hardness makes it possible to determine the extent of cervical ripening quantitatively rather than qualitatively. We consider that cervical ripening determined objectively in this manner is a good parameter to predict the onset of preterm delivery.