Elevated plasma interleukin 6: a biochemical marker of human preterm labour

The contribution of the immune system to parturition

The immune system plays a central role before and during parturition, including the main physiological processes of parturition: uterine contractions and cervical ripening. The immune system comprises white blood cells and their secretions. Polymorphonuclear cells and macrophages invade the cervical tissue and release compounds, such as oxygen radicals and enzymes, which break down the cervical matrix to allow softening and dilatation. During this inflammatory process, white blood cells undergo chemotaxis, adherence to endothelial cells, diapedesis, migration and activation. Factors that regulate white blood cell invasion and secretion include cytokines such as tumour necrosis factor and interleukins. Glucocorticoids, sex hormones and prostaglandins, affect cytokine synthesis. They also modulate the target cells, resulting in altered responses to cytokines. On the other hand, the immune system has profound effects on the hormonal system and prostaglandin synthesis. In animals, nitric oxide has marked effects on uterine quiescence during gestation. At the same time, it plays an important role in regulating the vascular tone of uterine arteries and has anti-adhesive effects on leukocytes. Cytokines are found in amniotic fluid, and in maternal and foetal serum at term and preterm. Several intrauterine cells have been shown to produce these cytoldnes. Since neither white blood cells, cytokines nor nitric oxide seem to be the ultimate intermediate for human parturition, the immune system is an additional but obligatory and underestimated component in the physiology of delivery. Scientists, obstetricians and anaesthesiologists must thus be aware of these processes.

Maternal plasma interleukin-6, interleukin-1beta and C-reactive protein as indicators of tocolysis failure and neonatal outcome after preterm delivery

OBJECTIVE

To investigate whether maternal serum interleukin-6 (IL-6), interleukin-1beta (IL-1beta) and high sensitive C-reactive protein (CRP) could be used as markers of tocolysis failure and adverse neonatal outcome in pregnancies with preterm labor (PL).

METHODS

Forty-seven maternal blood samples taken because of PL at admission and delivery were analyzed. Control samples were taken from 20 gravidas with normal pregnancies. Differences in interleukins and CRP levels with or without chorioamnionitis, connatal infection or periventricular leukomalacia (PVL) were analyzed. Cut-off values were estimated for prediction of tocolysis failure and adverse neonatal outcome.

RESULTS

All three parameters were significantly higher in patients delivering prematurely than in patients delivering at term. All three parameters were significantly higher with than without histologic chorioamnionitis (p < 0.001), with than without connatal infection (p < 0.01), with than without PVL (p < 0.01 for IL-6 and IL-1beta, p < 0.05 for CRP), and in pregnancies with preterm premature rupture of membranes (PPROM) delivered within 48 hours compared to those more prolonged (p < 0.01). Choosing 50.9 pg/mL of IL-6 and a CRP of 19.7 as cut-offs in maternal blood admission concentrations for neonatal PVL, resulted in sensitivity of 81% and specificity of 91% and sensitivity of 91% and specificity of 81%, respectively. At respective maternal blood admission cut-off levels of 27.8 pg/mL of IL-6 and 8.9 of CRP, both parameters were effective predictors of connatal infection.

CONCLUSIONS

Maternal blood IL-6 and CRP could become useful in predicting tocolysis failure and intrauterine treat for the fetus.

Early second-trimester inflammatory markers and short cervical length and the risk of recurrent preterm birth

This study aimed to analyze the associations between serum and cervicovaginal inflammatory markers and recurrent spontaneous preterm birth in a cohort study of 62 pregnant women with > or =1 prior early spontaneous birth. Serum samples and cervicovaginal swabs from the women were obtained at enrollment in early second trimester (week 12-25). Cervical length was measured by ultrasound and dicotomized in to short (< or =25 mm) and long cervices (>25 mm). The study endpoints were spontaneous preterm birth before 35 weeks and secondarily<37 weeks. Multiple inflammatory markers in serum (IL-1beta, IL-2, IL-5, IL-6, IL-8, IL-12, IL-18, TNF-alpha, TGF-beta, sTNF-R1, GM-CSF and TREM-1) and cervicovaginal secretions (IL-18, sTNF-RI and sIL-6) were individually associated with spontaneous preterm birth. Short cervical length did not explain associations between inflammatory markers and spontaneous preterm birth. Serum and cervicovaginal inflammatory markers did not correlate. In a combined prediction model using both serum and vaginal inflammatory markers, serum TNF-alpha, cervicovaginal sIL-6Ralpha and cervical length predicted 69% of all recurrent spontaneous preterm birth at a 5% false-positive rate. In conclusion, cervical length, serum TNF-alpha and cervicovaginal sIL-6Ralpha provide a clinically useful prediction of recurrent preterm birth in early second-trimester in women with a prior spontaneous preterm birth.

Pre-B-cell colony-enhancing factor, a novel cytokine of human fetal membranes

OBJECTIVE

Our purpose was to determine whether pre-B-cell colony-enhancing factor (PBEF) is expressed in the human fetal membranes during normal gestation and parturition in the absence of infection and to show its effects on the expression of interleukin (IL)-6 and IL-8.

STUDY DESIGN

PBEF was immunolocalized in the fetal membranes from early pregnancy, at preterm, and at term. Its expression was quantitated by Northern analysis in separated uninfected amnion, chorion, decidua, and placenta of patients at term before labor and in full-thickness membranes before and after spontaneous labor at preterm and at term. Amnion-like epithelial (WISH) cells and fetal membrane explants were treated with recombinant PBEF (rhPBEF), and the expression of IL-6 and IL-8 was quantitated.

RESULTS

PBEF was immunolocalized throughout gestation in the amniotic epithelium and mesenchymal cells as well as the chorionic cytotrophoblast and parietal decidua. Northern analysis showed significantly more (P <.01) PBEF expressed in the amnion than in either chorion or placenta. Its expression increased after labor at both preterm and term and correlated with that of IL-8 (r = 0.87). rhPBEF treatment of WISH cells significantly increased IL-6 (P <.05) and IL-8 (P <.01) gene expression after 4 hours and of IL-8 protein after 24 hours (P <.01); similar 4-hour treatment of fetal membrane explants significantly increased IL-6 (P <.01) and IL-8 (P <.05) gene expression.

CONCLUSION

PBEF is a novel cytokine constitutively expressed by the fetal membranes during pregnancy. It increased the expression of IL-6 and IL-8 and may be important in both normal spontaneous labor and infection-induced preterm labor.

Molecular epidemiology of preterm delivery: methodology and challenges

Preterm delivery (PTD) appears to be a complex trait determined by both genetic and environmental factors. Few studies have examined genetic influence on PTD. The overall goal of our study is to examine major candidate genes of PTD and to test gene-environment interactions. Our study includes 500 preterm trios, including 500 preterm babies and their parents and 500 maternal age-matched term controls. We will perform the transmission/disequilibrium test (TDT) on candidate genes thought to be important in each of the four biological pathways of PTD: (1) decidual chorioamionotic inflammation: interleukin 1 (IL-1), IL-6, and tumour necrosis factor (TNF); (2) maternal and fetal stress: corticotropin-releasing hormone (CRH); (3) uteroplacental vascular lesions: methylenetereahydrofolate reductase (MTHFR); and (4) susceptibility to environmental toxins: GSTM1, GSTT1, CYP1A1, CYP2D6, CYP2E1, NAT2, NQO1, ALDH2, and EPHX. We will also perform standard case-control analyses on the 500 preterm cases and 500 term controls to examine gene-environment interactions. The major environmental, nutritional and social factors as well as clinical variables known or suspected to be associated with PTD will be used to test for gene-environment interactions. This study integrates epidemiological and clinical data as well as genetic markers along major pathogenic pathways of PTD. The findings from this study should improve our understanding of genetic influences on PTD and gene-environment interactions.

Immune activation in the early puerperium is related to postpartum anxiety and depressive symptoms

The pathophysiology of the postpartum blues, common transient mood disorders in the first week postpartum, has remained elusive. Recently, however, it has been shown that depression and anxiety disorders are accompanied by activation of the inflammatory response system (IRS). This study was developed to determine whether the postnatal blues is associated with IRS activation. Serum concentrations of interleukin-6 (IL-6), IL-6 receptor (IL-6R), gp130 (the IL-6 signaling protein), IL-1R antagonist (IL-1RA) and leukemia inhibitory factor receptor (LIFR) were assayed in 22 nonpregnant women and in 91 pregnant women before delivery and 1 and 3 days after delivery. On each occasion the parturient women completed the State version of the Spielberger State-Trait-Anxiety-Inventory (STAI) and the Zung Depression Rating Scale (ZDS). Serum IL-6, IL-1RA and LIFR were significantly higher in pregnant women at the end of term than in nonpregnant women.

Patterns of inflammatory cytokine serum concentrations during the perinatal period

Inflammatory cytokines interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) were measured in the serum of healthy, term neonates on the first (N1), fifth (N5) and 40th (N40) day after birth, compared with those in maternal serum (MS), umbilical cord (UC) and in adult controls. All three cytokines were significantly elevated in N1 and N5, compared with those in UC and adults (P < 0.0001). IL-1beta and IL-6 declined significantly from N1 to N40 (P < 0.0001), while TNF-alpha increased significantly from N1 to N5 and declined thereafter. TNF-alpha values in UC were significantly higher than in adults, but lower than in N40 (P < 0.0001), while IL-1beta and IL-6 values in UC did not differ from those in N40 and in adults. IL-1beta and IL-6, but not TNF-alpha values in MS were significantly higher than those in controls (P < 0.0001). IL-1beta values in MS were significantly higher than those in N1 (P < 0.0001), while those of IL-6 and TNF-alpha were significantly lower (P < 0.0001). Moreover, IL- 1beta values were dependent on the mode of delivery in N1 (P < 0.001), in MS (P < 0.02) and in UC (0.03), while IL-1beta and TNF-alpha values in N1 were strongly interrelated (r = 0.7; P < 0.01). In conclusion, the increased values of IL-1beta, IL-6 and TNF-alpha during the perinatal period might reflect a newborn immune response to the stress of delivery and to environmental changes after birth.

Inflammatory cytokines in newborn infants

Serum levels of IL-1beta, IL-6 and TNF-alpha were measured in 48 healthy, termed neonates on the 1st (N1), 5th (N5) and 40th (N40) day after birth, compared with those in maternal serum (MS), umbilical cord (UC) and adult controls. Cytokine values in N1 and N5 were significantly elevated, than those in UC and in controls (P<0.0001). IL-1beta and IL-6 declined significantly from N1 to N40 (P<0.0001), while TNF-alpha increased significantly from N1 to N5 and declined thereafter. MS infinity IL-1beta and IL-6, but not MS infinity TNF-alpha, were significantly higher than those of controls (P<0.0001). IL-1beta values depended on the mode of delivery. In conclusion, the increased concentrations of IL-1beta, IL-6 and TNF-alpha during the perinatal period might suggest their involvement in an inflammation-like process during normal parturition, and reflect also a newborn immune response to the stress of delivery and environmental changes.

Differential secretion of chemokines from peripheral blood in pregnant compared with non-pregnant women

The maintenance of a normal pregnancy is dependent on the delicate interaction between the endocrine and the immune systems. Cytokines are thought to play a key role in pregnancy by way of local modulation of the immune system at the level of peripheral leukocytes. This study examined the potential of peripheral venous blood cultures from pregnant women throughout gestation and from non-pregnant women to produce the chemokines monocyte chemotactic protein-1 (MCP-1), interleukin-8 (IL-8) and RANTES. Significantly (P = < 0.001), higher levels of MCP-1 were released from peripheral blood cultures from pregnant women at term than during the first trimester or from women who were not pregnant. This could not be accounted for by differences in differential blood counts. Significantly higher levels (P = < 0.05) of MCP-1 were released from PBMC preparations from pregnant compared with non-pregnant women. No 'rebound' increase in MCP-1 was observed on withdrawing progesterone support to the PBMC preparations. MCP-1 was secreted predominately from CD14+ cells with those from pregnant women producing more than those from non-pregnant women. There was no statistical difference in release of IL-8 or RANTES from either peripheral blood or PBMC preparations from pregnant or non-pregnant women. IL-8 and RANTES were secreted from CD14+ and CD14- cells, respectively. The hypothesis proposed is that the monocytes are fundamentally different in pregnancy and that measurement of MCP-1 has the potential to act as a marker of pregnancy status.

Prenatal determinants of motor disorders

Cerebral palsies (CP) are the commonest childhood motor disorders, originating in early childhood as a result of interference in the developing brain. Identifying prenatal factors in CP is a challenge because there is a considerable period of time (years) between the causal event(s) and diagnosis. Four fascinating "natural" situations provided a unique opportunity to identify and measure prenatal exposures in relation to motor disorders, thus establishing the unequivocal role of some factors. However, the majority of studies determining adverse reproductive effects of environmental factors require a retrospective case-control approach, which present considerable problems. Studies based on the Western Australian CP register suggest that prenatal factors singly or in complex sequences are more common as causes than those occurring perinatally or postnatally. In future, better diagnosis of motor disorders, use of sophisticated scientific techniques to identify markers of neuronal development and the accurate linkage of these findings to clinical patterns of motor dysfunction are required.

Interleukin-6 and neopterin levels in serum of patients with preterm labour with and without infection

We estimated the levels of interleukin 6 (IL-6) and neopterin, in serum of twelve nonpregnant (group A) and 28 pregnant women between 28-36 weeks of pregnancy. Group B consisted of eight patients with uncomplicated pregnancy, group C consisted of thirteen pregnant women with clinical signs of preterm labour and without laboratory markers of infection and group D consisted of seven pregnant women with signs of preterm labour and with laboratory markers of infection. The levels of IL-6 and neopterin were significantly higher in group D compared to groups A, B and C (p < 0.05). Similarly, the level of C-reactive protein (CRP) and total white blood cell count (the laboratory markers of infection) were significantly higher in group D than in groups A, B and C. Total white blood cell count was significantly lower in group A than in group B and D (p < 0.05). There were no significant differences in values of IL-6, neopterin and CRP between groups A, B and C (p > 0.05). In all groups, significant correlations were found between IL-6 and neopterin as well as total white blood cell count and CRP. Our results suggest that IL-6 and neopterin may be the markers of preterm labour caused by infection. On the other hand, cell-mediated immune response may be involved in the mechanisms of preterm labour.

Inflammatory cytokine (interleukins 1, 6 and 8 and tumor necrosis factor-alpha) release from cultured human fetal membranes in response to endotoxic lipopolysaccharide mirrors amniotic fluid concentrations

OBJECTIVE

This study was conducted to quantitate and compare the amount of cytokines released from human fetal membranes in response to treatment with bacterial lipopolysaccharide and to compare this with amniotic fluid levels.

STUDY DESIGN

Amniochorionic membranes were collected from women undergoing elective repeat cesarean section and showing no signs of infection- or pregnancy-related complications. Membranes were maintained in an organ explant system and stimulated with bacterial lipopolysaccharide for 24 hours. Media samples were collected and stored at -20 degrees C until cytokine levels were assayed by enzyme-linked immunosorbent assay.

RESULTS

Enzyme-linked immunosorbent assay results demonstrated that lipopolysaccharide stimulated production of interleukins 1, 6 and 8 and tumor necrosis factor-alpha by the fetal membranes in comparison with the control cultures. A greater release of interleukin-6 and interleukin-8 compared with interleukin-1 and tumor necrosis factor-alpha was noticed. The relationships between cytokine concentrations observed in culture mirror those seen in amniotic fluid.

CONCLUSION

Amniochorionic membranes can respond to an infectious process with increased secretion of interleukins 1, 6 and 8 and tumor necrosis factor-alpha. Cytokines produced from both amnion and chorion (interleukin-6 and interleukin-8) are released in greater quantities than those cytokines produced from chorion or amnion alone (interleukin-1 and tumor necrosis factor-alpha). These studies support a major role for amnion in infection-induced preterm labor.

Lewis phenotype in women with preterm labor and premature rupture of the membranes

Objective: The purpose of this study was to evaluate the possible association between Lewis phenotype status in pregnant women and preterm labor (PTL) or preterm rupture of the membranes (PROM).

Methods: Red blood cell (RBC) Lewis phenotype was determined in 113 pregnant women admitted for PTL or PROM and in 121 controls. The results were controlled for the influence of race on Lewis phenotype.

Results: Pregnancy was associated with a higher frequency in women with the a–b– phenotype. There was no association between RBC Lewis phenotype and the occurrence of PTL or PROM.

Conclusions: A susceptibility to PTL or PROM is not due to a lack of Lewis antigen expression on the plasma membrane of the vaginal mucosa.