Moderate Hypoxia Down-Regulates Interleukin-6 Secretion and TLR4 Expression in Human Sw.71 Placental Cells

Abstract

Background/Aims: The placenta is a vital organ for pregnancy. Many in vitro placental experiments are conducted under 21% O₂; however, O₂ tension could influence cellular functions, including cytokine secretion. We investigated the effects of oxygen tension between moderate hypoxia (5% O₂) and normoxia (21% O₂) by testing the hypothesis that moderate hypoxia regulates cellular phenotypes differently from normoxia in human trophoblast cells. Methods and Results: Sw.71 trophoblast cells were incubated under normoxic or moderately hypoxic conditions. Cells were also treated with lipopolysaccharide (LPS) as a Toll-like receptor 4 (TLR4) ligand inducing inflammation. Interleukin-6 (IL-6) as an inflammatory cytokine was determined, and TLR4, hypoxia-induced factor-1α (HIF1α), and reactive oxygen species (ROS) production were detected. Moderate hypoxia increased HIF1α expression and cell proliferation and acted by two different mechanisms to decrease IL-6 secretion compared with normoxia: it limits the TLR4 expression and ROS production. Treatment with cobalt chloride as an HIF1 activator inhibited IL-6 secretion and TLR4 expression; this effect was reversed on treatment with PX-12 as an HIF1 suppressor. Conclusion: IL-6 secretion, TLR4 expression, and ROS production, classical markers of inflammation, are down-regulated by moderate hypoxia, and HIF1α and ROS have a potential to regulate these responses in human trophoblast cells.

Palmitic acid induces interleukin-1β secretion via NLRP3 inflammasomes and inflammatory responses through ROS production in human placental cells

“…Recently, we demonstrated that ROS inhibition clearly suppressed NLRP3 inflammasome activation and inflammatory responses in vivo and in vitro (Shirasuna et al, 2015c). We also examined the effects of ROS induction by rotenone and pyocianin in Sw.71 cells, and found that both ROS inducers stimulated IL-6 secretion in a dosedependent manner (Shirasuna et al, 2015b). There are two main sources of cellular ROS including the phagocyte NADPH oxidase, which generates superoxide anions and mitochondria that generate reactive oxidants.…”

LPS Promotes Vascular Smooth Muscle Cells Proliferation Through the TLR4/Rac1/Akt Signalling Pathway

“…Moreover, blocking the progress of atherosclerosis by inhibiting TLR4-mediated signalling has been verified in different animal models [22-25]. LPS has been shown to activate TLR4 and induce various signalling cascades, including PI3K/Akt [13], mitogen-activated protein kinase [26, 27] and interleukin-1 receptor associated kinase (IRAK) [28, 29]; each of which participates in cell proliferation [30]. However, the underlying molecular mechanisms controlling VSMCs proliferation after LPS stimulation remain to be identified.…”

Crocetin Inhibits Lipopolysaccharide-Induced Inflammatory Response in Human Umbilical Vein Endothelial Cells

“…Specifically, previous studies indicated it is mediated by upstream regulator toll-like receptor (TLR) family, especially TLR4. As a ligand of TLR [31], we applied LPS stimulation to activate IκBα kinase (IKK) via tumor necrosis factor receptor (TNFR), and interleukin-1 receptor (IL-1R), which further phosphorylates and signals for degrading the cytoplasmic IκBα subunit of the IκBα-p65-p50 complex. Upon IκBα degradation, p65 subunit is released and translocated into the nucleus, where it activates downstream inflammatory gene translational activity.…”