title: Expression of hypoxia-inducible factor-1 by trophectoderm cells in response to hypoxia and epidermal growth factor.
abstract: The low oxygen environment in the uterine environment requires pre-implantation embryos to adapt to oxygen deficiency. Hypoxia-inducible factor (HIF)-1 is a master regulator whereby cells adapt to changes in oxygen concentrations. In addition to hypoxic conditions, non-hypoxic stimuli such as growth factors also activate expression of HIF-1. In this study, the mechanisms underlying low oxygen-dependent and epidermal growth factor (EGF)-dependent expression of HIF-1α were explored using porcine trophectoderm (pTr) cells. The results indicated that expression of HIF-1α and HIF-1β mRNAs was not affected by low concentrations of oxygen; however, hypoxic conditions markedly increased the abundance of HIF-1α protein, especially in nuclei of pTr cells. Even under normoxic conditions, the abundance of HIF-1α protein increased in response to EGF. This EGF-mediated increase in HIF-1α protein was blocked through inhibition of translation by cycloheximide. The inhibitors LY294002 (PI3K-AKT inhibitor), U0126 (inhibitor of ERK1/2) and rapamycin (mTOR inhibitor) also blocked the ability of EGF to increase HIF-1α protein and to phosphorylate AKT, ERK1/2 and mTOR proteins. Both hypoxia and EGF induced proliferation of pTr cells. This ability of EGF to stimulate proliferation of pTr cells was suppressed by EGFR siRNA, but not HIF-1α siRNA, but a significant decrease in EGF-induced HIF-1α protein occurred when pTr cells were transfected with HIF-1α siRNA. The results of the present study suggest that pTr cells adapt to oxygen deficiency and proliferate in response to an oxygen-dependent HIF-1 system, and that EGF at maternal-conceptus interface can increase the abundance of HIF-1α protein via translational regulation through AKT, ERK1/2 and mTOR signaling cascades.
authors.affiliation: Department of Animal Resources Science, Dankook University, Cheonan, Republic of Korea.
authors.forename: Wooyoung
authors.initials: W
authors.lastname: Jeong
authors.affiliation: Center for Animal Biotechnology and Genomics and Department of Animal Science, Texas A&M University, College Station, TX, USA.
authors.forename: Fuller W
authors.initials: FW
authors.lastname: Bazer
authors.affiliation: Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea. Electronic address: ghsong@korea.ac.kr.
authors.forename: Gwonhwa
authors.initials: G
authors.lastname: Song
authors.affiliation: Department of Animal Resources Science, Dankook University, Cheonan, Republic of Korea. Electronic address: jinyoungkim@dankook.ac.kr.
authors.forename: Jinyoung
authors.initials: J
authors.lastname: Kim
mesh_terms: D000818:Animals; D015687:Cell Hypoxia / Q000502:physiology; D002460:Cell Line; D049109:Cell Proliferation / Q000502:physiology; D004815:Epidermal Growth Factor / Q000378:metabolism*; D051793:Hypoxia-Inducible Factor 1 / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D013552:Swine; D014327:Trophoblasts / Q000166:cytology* / Q000502:physiology*
chemical_list: D051793:Hypoxia-Inducible Factor 1; D004815:Epidermal Growth Factor; D010100:Oxygen
keywords: Cell signaling; EGF; HIF-1; Hypoxia; Proliferation; Trophectoderm