IL-6Trans-Signaling System in Intra-Amniotic Inflammation, Preterm Birth, and Preterm Premature Rupture of the Membranes

Abstract

Classic IL-6 signaling is conditioned by the transmembrane receptor (IL-6R) and homodimerization of gp130. During trans-signaling, IL-6 binds to soluble IL-6R (sIL-6R) enabling activation of cells expressing solely gp130. Soluble gp130 (sgp130) selectively inhibits IL-6 trans-signaling. To characterize amniotic fluid IL-6 trans-signaling molecules (IL-6, sIL-6R, sgp130) in normal gestations and pregnancies complicated by intra-amniotic inflammation (IAI) we studied 301 women during second trimester (n=39), third trimester (n=40) and preterm labor with intact (n=131, 85 IAI negative & 46 IAI positive) or preterm premature rupture of membranes (PPROM: n=91, 61 IAI negative & 30 IAI positive). ELISA, Western blotting and RT-PCR were used to investigate amniotic fluid, placenta and amniochorion for protein and mRNA expression of sIL-6R, sgp130, IL-6R and gp130. Tissues were immunostained for IL-6R, gp130, CD15+ (polymorphonuclear) and CD3+ (T-cell) inflammatory cells. The ability of sIL-6R and sgp130 to modulate basal and LPS-stimulated release of amniochorion matrix-metalloprotease-9 (MMP-9) was tested ex-vivo. We showed that in physiologic gestations amniotic fluid sgp130 decreases toward term. Amniotic fluid IL-6 and sIL-6R were elevated in IAI whereas sgp130 was decreased in PPROM. Our results suggested that fetal membranes are the probable source of amniotic fluid sIL-6R and sgp130. Immunohistochemistry and RT-PCR revealed increased IL-6R and decreased gp130 expression in amniochorion of women with IAI. Ex-vivo, sIL-6R and LPS augmented amniochorion MMP-9 release whereas sgp130 opposed this effect. We conclude that IL-6 trans-signaling molecules are physiologic constituents of the amniotic fluid regulated by gestational age and inflammation. PPROM likely involves functional loss of sgp130.

Vaginal Lactoferrin Administration before Genetic Amniocentesis Decreases Amniotic Interleukin-6 Levels

“…The proinflammatory cytokine IL-6 was measured and quantified in the AF supernatants (100 µl), aliquoted and stored at -70°C until analysis, by an enzyme-linked immunoabsorbent assay using a Quantikine Elisa Human IL-6 Kit (R & R Systems, Minneapolis, Minn., USA), according to the manufacturer's instructions. For all assays, full or diluted (1:10 to 1:100) AF samples (tested in duplicates) were done to fall within the range of the standard curves as previously described [11]. The interassay and intra-assay coefficients of variation were <10% for all the analytes.…”

Endocrine, paracrine, and autocrine placental mediators in labor

“…IL-6 also induces production of metalloproteinases that promote cervical ripening and rupture of membranes, as observed in ex vivo studies. 25 …”

Use of amniotic fluid for determining pregnancies at risk of preterm birth and for studying diseases of potential environmental etiology

“…IL-6 has consistently been found to be the most predictive and best candidate as a diagnostic tool for detecting pre-clinical chorioamnion inflammation and intra-amniotic inflammation (IAI) leading to PTB (Table 2) (El-Bastawissi et al, 2000; Harirah et al, 2002; Krupa et al, 2006; Lee et al, 2011; Thomakos et al, 2010; Vrachnis et al, 2012; Weissenbacher et al, 2012; Wenstrom et al, 1997). IL-6 stimulates production of proteins involved in the inflammatory process and of enzymes involved in prostaglandin synthesis.…”