Occurrence of a RAGE-Mediated Inflammatory Response in Human Fetal Membranes

Abstract

Context: Sterile inflammation has been shown to play a key role in the rupture of the fetal membranes (FMs). Moreover, an early and exacerbated runaway inflammation can evolve into a preterm premature rupture of membranes and lead to potential preterm birth. In this context, we investigated the receptor for advanced glycation end products (RAGE), an axis implied in physiological sterile inflammation, in conjunction with two major ligands: AGEs and High-Mobility Group Box 1 (HMGB1). Our first objective was to determine the spatiotemporal expression profiles of the different actors of the RAGE-signaling axis in human FMs, including its intracellular adaptors Diaphanous-1 and Myd88. Our second goal was to evaluate the functionality of RAGE signaling in terms of FMs inflammation. Methods The presence of the actors (RAGE, HMGB1, Myd88, and Diaphanous-1) at the mRNA level was investigated by reverse transcription quantitative polymerase chain reaction (RT-qPCR) in the human amnion and choriodecidua at the three trimesters and at term. Measurements were conducted at two distinct zones: the zone of intact morphology (ZIM) and the zone of altered morphology (ZAM). Then, proteins were quantified using Western blot analysis, and their localization was evaluated by immunofluorescence in term tissues. In addition, pro-inflammatory cytokine secretion was quantified using a Multiplex assay after the treatment of amnion and choriodecidua explants with two RAGE ligands (AGEs and HMGB1) in the absence or presence of a RAGE inhibitor (SAGEs). Results The FMs expressed the RAGE-signaling actors throughout pregnancy. At term, RNA and protein overexpression of the RAGE, HMGB1, and Diaphanous-1 were found in the amnion when compared to the choriodecidua, and the RAGE was overexpressed in the ZAM when compared to the ZIM. The two RAGE ligands (AGEs and HMGB1) induced differential cytokine production (IL1β and TNFα) in the amnion and choriodecidua. Conclusion Considered together, these results indicate that RAGE signaling is present and functional in human FMs. Our work opens the way to a better understanding of FMs weakening dependent on a RAGE-based sterile inflammation.

High‐mobility group box 1 is a driver of inflammation throughout pregnancy

“…54 A recent study detected HMGB1 gene and protein expressed throughout pregnancy in human fetal membranes and also showed increased gene and protein expression of HMGB1 in amnion compared to choriodecidua within the zone of altered morphology (ZAM) area. 42 These data further support the idea that HMGB1 may be an important contributor to the initiation of fetal membrane weakening in rupture of membranes (ROM) and pPROM.…”

“…Therefore, although the assessment of the precise mechanisms of pregnancy complications is often not studied until the fetus is born, there are few situations in which samples can be collected from less invasive approaches such as the assessment of maternal plasma or serum 71 . However, two recent publications were able to elegantly measure the levels of HMGB1 over all of three trimesters and at delivery, the first assessing levels from cultured fetal membranes 42 and the other levels in the maternal circulation throughout pregnancy 43 …”

“…The increased concentration or expression of HMGB1 has been detected in term tissues 35‐38 ; however, there is evidence to suggest HMGB1 also has an adverse role that promotes and contributes to pregnancy complications that include preterm premature rupture of the membranes (pPROM) and infection‐initiated inflammation (Table 1). 39‐49 …”

“…3 The increased concentration or expression of HMGB1 has been detected in term tissues [35][36][37][38] ; however, there is evidence to suggest HMGB1 also has an adverse role that promotes and contributes to pregnancy complications that include preterm premature rupture of the membranes (pPROM) and infection-initiated inflammation (Table 1). [39][40][41][42][43][44][45][46][47][48][49] Therefore, the aims of this review are threefold: (a) to describe how important HMGB1 is to drive inflammation in the different stages of pregnancy, (b) to describe the current knowledge of HMGB1 in pregnancy pathologies driven by inflammation, and (c) to highlight the potential of HMGB1 as a biomarker and therapeutic target in pregnancy.…”

Cigarette Smoke Condensate Exposure Induces Receptor for Advanced Glycation End-Products (RAGE)-Dependent Sterile Inflammation in Amniotic Epithelial Cells

“…Our team already reported that RAGE is overexpressed, not only in the amnion compared to choriodecidua, but also in the rupture zone compared to the intact one. In parallel, a previous study demonstrated that FM are sensitive to RAGE ligands: the AGEs and HMGB1 [ 37 ]. This preferential expression of RAGE in the amnion could be exacerbated by contact with smoking compounds, explaining such amniotic susceptibility to CSC.…”