title: Sphingosine 1‑phosphate induced by hypoxia increases the expression of PAI‑1 in HepG2 cells via HIF‑1α.
abstract: Our group has recently reported that in the immortal human HepG2 liver cell line, sphingosine 1‑phosphate (S1P) increases transcription of plasminogen activator inhibitor type‑1 (PAI‑1), the major physiological inhibitor of fibrinolysis, within 4 h. The present study aimed to elucidate the molecular mechanisms underlying this effect. PAI‑1 expression was measured by reverse transcription‑quantitative polymerase chain reaction and immunoblotting. It was demonstrated that S1P increased PAI‑1 promoter activity but did not increase the activity of promoters lacking the hypoxia responsive element (HRE) 2. In addition, S1P transiently increased the concentration of hypoxia inducible factor (HIF)‑1α, a transcription factor capable of binding to HRE. When HIF‑1α was knocked down, the induction of transcription of PAI‑1 by S1P was no longer observed. Sphingosine kinase (SPHK) activity is increased by hypoxia. It was demonstrated that increases in the concentration of the HIF‑1α protein induced by hypoxia were prevented by treatment with SPHK inhibitor or S1P receptor antagonists. Thus, modification of the induction of HIF‑1α by S1P, leading to increased transcription of PAI‑1, may be an attractive therapeutic target for thrombosis and consequent inhibition of fibrinolysis associated with hypoxia.
authors.affiliation: Department of Molecular and Cellular Pathobiology and Therapeutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Aichi 467‑8603, Japan.
authors.forename: Akimasa
authors.initials: A
authors.lastname: Sanagawa
authors.affiliation: Department of Molecular and Cellular Pathobiology and Therapeutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Aichi 467‑8603, Japan.
authors.forename: Soichiro
authors.initials: S
authors.lastname: Iwaki
authors.affiliation: Department of Molecular and Cellular Pathobiology and Therapeutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Aichi 467‑8603, Japan.
authors.forename: Moyoko
authors.initials: M
authors.lastname: Asai
authors.affiliation: Department of Molecular and Cellular Pathobiology and Therapeutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Aichi 467‑8603, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sakakibara
authors.affiliation: Department of Molecular and Cellular Pathobiology and Therapeutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Aichi 467‑8603, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Norimoto
authors.affiliation: Cardiovascular Research Institute, University of Vermont, Colchester, VT 05446, USA.
authors.forename: Burton E
authors.initials: BE
authors.lastname: Sobel
authors.affiliation: Department of Molecular and Cellular Pathobiology and Therapeutics, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Aichi 467‑8603, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Fujii
mesh_terms: D019898:Autocrine Communication; D015972:Gene Expression Regulation, Neoplastic; D056945:Hep G2 Cells; D006801:Humans; D000860:Hypoxia / Q000235:genetics* / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D008246:Lysophospholipids / Q000096:biosynthesis*; D019899:Paracrine Communication; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics*; D011401:Promoter Regions, Genetic; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D015533:Transcriptional Activation
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008246:Lysophospholipids; D017395:Plasminogen Activator Inhibitor 1; D018719:Erb-b2 Receptor Tyrosine Kinases; D013110:Sphingosine; C060506:sphingosine 1-phosphate