Targeting Inhibitor of κB Kinase β Prevents Inflammation-Induced Preterm Delivery by Inhibiting IL-6 Production from Amniotic Cells

Abstract

Preterm delivery (PTD) remains a serious challenge in perinatology. Intrauterine infection and/or inflammation, followed by increased inflammatory cytokines, represented by IL-6, are involved in this pathology. Our aim was to identify IL-6-producing cells in the placenta and to analyze the potential of targeting IκB kinase β (IKKβ) signaling to suppress IL-6 production for the treatment of PTD. Immunohistochemical analyses using placentas complicated with severe chorioamnionitis revealed that IL-6 is mainly expressed in human amniotic mesenchymal stromal cells (hAMSCs). Primary hAMSCs were collected, and strong IL-6 expression was confirmed. In hAMSCs, the treatment of tumor necrosis factor-α or IL-1β drastically induced IL-6 production, followed by the phosphorylation of IKKs. A novel IKKβ inhibitor, IMD-0560, almost completely inhibited IL-6 production from hAMSCs. Using an experimental lipopolysaccharide-induced PTD mouse model, the therapeutic potential of IMD-0560 was examined. IMD-0560 was delivered vaginally 4 hours before lipopolysaccharide administration. Mice in the IMD-0560 (30 mg/kg, twice a day) group had a significantly lower rate of PTD [10 of 22 (45%)] without any apparent adverse events on the mice and their pups. In uteri collected from mice, IMD-0560 inhibited not only IL-6 production but also production of related cytokines, such as keratinocyte-derived protein chemokine/CXCL1, macrophage inflammatory protein-2/CXCL2, and monocyte chemoattractant protein-1/chemokine ligand 2. Targeting IKKβ signaling shows promising effects through the suppression of these cytokines and can be explored as a future option for the prevention of PTD.

Prevention of lipopolysaccharide-induced preterm labor by the lack of CX3CL1-CX3CR1 interaction in mice

“…In support of this notion, IL-1 and TNF-α administration induced both preterm labor and intermediate steps in the labor cascade, and genetic disruption of IL-1 or TNF-α receptors significantly prevented LPS-induced PTL [ 59 – 61 ]. In addition, the inhibition of IL-6 signaling or IL-6 production suppressed LPS-induced PTL [ 30 , 62 ]. On the contrary, the absence of IL-10, a major anti-inflammatory cytokine, exaggerated LPS-induced PTL with elevated expression of inflammatory cytokines such as IL-1, IL-6 and TNF-α [ 63 ].…”

IL-37 Exerts Anti-Inflammatory Effects in Fetal Membranes of Spontaneous Preterm Birth via the NF-κB and IL-6/STAT3 Signaling Pathway

“…Previous studies have shown that the resident cells of the chorion and decidua are capable of synthesizing and secreting IL-6, and its production is stimulated by LPS or proinflammatory factors such as IL-1 β and TNF- α [ 35 ]. Furthermore, another study has demonstrated that IL-6 secretion is upregulated in fetal membranes of preterm pregnancies, indicating that IL-6 might be a key factor in accelerating the events of preterm birth [ 36 ]. Therefore, it is understandable that the change of IL-6 is the most obvious one among these markers.…”

Porphyromonas gingivalis, a cause of preterm birth in mice, induces an inflammatory response in human amnion mesenchymal cells but not epithelial cells

“…These findings indicate that amnion mesenchymal cells can mediate immune responses. Immunohistochemical analyses have shown that infected placentas contain mesenchymal cells with high levels of IL-6 expression [10]. Moreover, stimuli such as IL-1β, IL-6, thrombin, fibronectin and LPS from Escherichia coli have been reported to activate NF-κB, enhance COX-2 mRNA expression and increase prostaglandin E 2 production in mesenchymal cells but not epithelial cells [9][10][11][12][13][14][15].…”

“…Amnion cells were characterized using antibodies specific for two different filament proteins: cytokeratin-18 (a marker of epithelial cells) and vimentin (a marker of mesenchymal cells). Immunostaining was performed using primary antibodies against cytokeratin-18 (1:15,000; Abcam, Cambridge, UK) and vimentin (1:3000; Cell Signaling Technology, Danvers, MA, USA), as described in a previous report [10]. Amnion epithelial cells displayed a cobblestone-like morphology and were positive for cytokeratin-18 and negative for vimentin.…”

“…The amnion is the load-bearing structure of the fetal membrane and comprises an avascular layer of epithelial cells, underlying mesenchymal cells and extracellular matrix proteins [8]. Primary cultures of epithelial cells and mesenchymal cells isolated from the amnion have been studied to characterize their normal function and role during inflammation [9][10][11][12][13][14][15].…”