title: Progestin isoforms provide different levels of protein S expression in HepG2 cells.
abstract: BACKGROUND
  Use of combined oral contraceptives (COCs) results in acquired protein S (PS) deficiency, a well-established risk factor for venous thromboembolism (VTE). The risk of VTE due to COCs containing newer-generation progestins is double compared with COCs containing older-generation progestins, although there is little difference in estrogen contents between the generations. In contrast, progestin-only contraceptives do not confer an increased risk of VTE. In this study, we aimed to investigate how different isoforms of progestin in COCs affect the risk of VTE by measuring PS expression.
  
  
  METHODS
  The effect of progestin, levonorgestrel (LNG) or drospirenone (DRSP), on PS mRNA expression in HepG2 cells was measured using reverse transcription-quantitative PCR; PS level was determined using Western blot analysis. PROS1 promoter activity, PS mRNA stability, and de novo synthesis of PS mRNA were examined in HepG2 cells after treatment with progestin.
  
  
  CONCLUSIONS
  In the presence of progestins, PS mRNA and protein expressions were significantly upregulated in HepG2 cells due to the augmentation of de novo PS mRNA expression modulated by RNA polymerase II (Pol II), thereby facilitating PS transcription elongation. Moreover, the transcription elongation inhibitor blocked progestin-mediated de novo PS mRNA expression. Conversely, progestin did not affect PROS1 promoter activity and PS mRNA stability. Pol II elongation efficiency in the newer-generation progestin (DRSP) treatment was not as strong compared with older-generation progestin (LNG), suggesting the difference in VTE risk between COC generations.
authors.affiliation: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Kozuka
authors.affiliation: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Tamura
authors.affiliation: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Japan.
authors.forename: Nami
authors.initials: N
authors.lastname: Kawamura
authors.affiliation: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Nakata
authors.affiliation: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Hasebe
authors.affiliation: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Japan.
authors.forename: Ayumi
authors.initials: A
authors.lastname: Makiyama
authors.affiliation: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Takagi
authors.affiliation: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Japan.
authors.forename: Moe
authors.initials: M
authors.lastname: Murata
authors.affiliation: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Mizutani
authors.affiliation: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Takagi
authors.affiliation: Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Japan. Electronic address: kojima@met.nagoya-u.ac.jp.
authors.forename: Tetsuhito
authors.initials: T
authors.lastname: Kojima
mesh_terms: D056945:Hep G2 Cells; D006801:Humans; D011372:Progestins / Q000009:adverse effects*; D020033:Protein Isoforms / Q000378:metabolism*; D017293:Protein S / Q000378:metabolism*; D012307:Risk Factors; D054556:Venous Thromboembolism / Q000139:chemically induced*
chemical_list: D011372:Progestins; D020033:Protein Isoforms; D017293:Protein S
keywords: Combined oral contraceptive; Progestin; Protein S; Transcription elongation; Venous thromboembolism