title: Antiproliferative property of sphingosine 1-phosphate in rat hepatocytes involves activation of Rho via Edg-5.
abstract: OBJECTIVE
  Sphingosine 1-phosphate (S1P), a ligand for G protein-coupled endothelial differentiation gene-1 (Edg-1), Edg-3, Edg-5, Edg-6, and Edg-8, elicits a variety of responses by cells. Prominent among these is cell proliferation. S1P is abundantly stored in platelets and released upon their activation, suggesting that S1P plays a pathophysiologic role in vivo. Because the major part of injected S1P was distributed into the liver in mice, we wondered whether the liver would be one of its targets. The effects of S1P on hepatocytes, the major constituent cells in the liver, were examined.
  
  
  RESULTS
  Northern blot analysis revealed the expression of Edg-1 and Edg-5 messenger RNA (mRNA) in cultured rat hepatocytes, in which S1P decreased DNA synthesis induced by hepatocyte growth factor (HGF) or epidermal growth factor (EGF) without affecting total protein synthesis. This inhibitory effect was attenuated by inactivation of small GTPase Rho with C3 exotoxin but not by inactivation of G(i) with pertussis toxin. Moreover, in the presence of JTE-013, a newly developed and specific binding antagonist for Edg-5, the inhibitory effect was also cancelled. Finally, the administration of S1P after 70% partial hepatectomy in rats reduced the peak of DNA synthesis in hepatocytes with increased Rho activity. Furthermore, Edg-5 but not Edg-1 mRNA expression was enhanced in hepatocytes 24-72 hours after partial hepatectomy, which coincides with decreasing hepatocyte proliferation.
  
  
  CONCLUSIONS
  S1P has an antiproliferative property in rat hepatocytes by activating Rho via Edg-5. Our results raise the possibility that S1P is a negative regulator in liver regeneration.
authors.affiliation: Department of Gastroenterology, University of Tokyo, Japan. ikeda-1im@h.u-tokyo.ac.jp
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Ikeda
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Satoh
authors.forename: Mikio
authors.initials: M
authors.lastname: Yanase
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Inoue
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Tomiya
authors.forename: Masahiro
authors.initials: M
authors.lastname: Arai
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Tejima
authors.forename: Kayo
authors.initials: K
authors.lastname: Nagashima
authors.forename: Hisato
authors.initials: H
authors.lastname: Maekawa
authors.forename: Naohisa
authors.initials: N
authors.lastname: Yahagi
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yatomi
authors.forename: Soutaro
authors.initials: S
authors.lastname: Sakurada
authors.forename: Yoh
authors.initials: Y
authors.lastname: Takuwa
authors.forename: Itsuro
authors.initials: I
authors.lastname: Ogata
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kimura
authors.forename: Kenji
authors.initials: K
authors.lastname: Fujiwara
mesh_terms: D036002:ADP Ribose Transferases / Q000494:pharmacology; D000818:Animals; D001905:Botulinum Toxins / Q000494:pharmacology; D016466:CHO Cells; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D006224:Cricetinae; D004247:DNA / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D022781:Hepatocytes / Q000166:cytology* / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008115:Liver Regeneration / Q000502:physiology; D008246:Lysophospholipids; D008297:Male; D037342:Pertussis Toxin / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled; D049312:Receptors, Lysophospholipid; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000502:physiology*
chemical_list: C471998:JTE 013; D008246:Lysophospholipids; D011720:Pyrazoles; D011725:Pyridines; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D049312:Receptors, Lysophospholipid; C060506:sphingosine 1-phosphate; D004247:DNA; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D037342:Pertussis Toxin; D001905:Botulinum Toxins; D020741:rho GTP-Binding Proteins; D013110:Sphingosine