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


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.


CONCLUSIONS
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.
Laboratory of Animal Reproduction, Department of Agriculture, Tokyo University of Agriculture, Atsugi, Kanagawa, Japan.
Koumei
K
Shirasuna
Narumi
N
Shimamura
Kotomi
K
Seno
Ayaka
A
Ohtsu
Shogo
S
Shiratsuki
Akihide
A
Ohkuchi
Hirotada
H
Suzuki
Shigeki
S
Matsubara
Shiho
S
Nagayama
Hisataka
H
Iwata
Takehito
T
Kuwayama
D015687:Cell Hypoxia / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D007249:Inflammation / Q000473:pathology; D015850:Interleukin-6 / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D010920:Placenta / Q000166:cytology*; D011247:Pregnancy; D017382:Reactive Oxygen Species / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D014327:Trophoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000378:metabolism
D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C508600:IL6 protein, human; D015850:Interleukin-6; D008070:Lipopolysaccharides; D017382:Reactive Oxygen Species; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; C501162:FLT1 protein, human; D040281:Vascular Endothelial Growth Factor Receptor-1