title: Possible Involvement of Sphingosine-1-Phosphate/G(i)/RhoA pathways in adherence of eosinophils to pulmonary endothelium.
abstract: BACKGROUND
  Sphingosine-1-phosphate (S1P), a lysophospholipid released from inflammatory cells, causes cell migration by increasing cytokines and chemokines. This study was designed to determine whether S1P causes adherence of eosinophils to pulmonary endothelial cells via enhancement of adhesion molecule expression.
  
  
  METHODS
  Expression of VCAM-1 and ICAM-1 was assessed by RT-PCR and Western blot analysis in human pulmonary microvasucular endothelial cells (HPMVECs). The number of adherent eosinophils to HPMVECs was calculated according to adhesion assay.
  
  
  RESULTS
  Pre-treatment of HPMVECs with S1P increased mRNA and protein expression of VCAM-1, in contrast, did not dramatically increase those expression of ICAM-1. The maximal expression of these adhesion molecules in mRNA and protein was observed 4 and 8h after exposure to S1P, respectively. Pre-treatment with S1P also activated RhoA, a monomeric G protein; the ability of S1P to enhance the expression of VCAM-1 was attenuated by RhoA related inhibitors such as Y-27632, C3 exoenzyme, and GGTI-286. The effects of S1P on VCAM-1 were attenuated by pre-incubation with pertussis toxin, which catalyzes the ADP-ribosylation of G(i), a heterotrimeric G protein. After HPMVECs were treated with S1P, adhesion of human eosinophilic leukemic cell line (EoL-1) cells to HPMVECs was enhanced in a concentration-dependent manner. Augmented adherence of EoL-1 cells by S1P was also attenuated by Y-27632 and pertussis toxin. S1P causes adherence of eosinophils to pulmonary endothelium via RhoA activation.
  
  
  CONCLUSIONS
  S1P may act as a lipid mediator in asthma. The RhoA/Rho-kinase pathway may be a therapeutic target for preventing eosinophil infiltration to the airway.
authors.affiliation: Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Aichi, Japan.
authors.forename: Toyokazu
authors.initials: T
authors.lastname: Sashio
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kume
authors.forename: Naoya
authors.initials: N
authors.lastname: Takeda
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Asano
authors.forename: Seita
authors.initials: S
authors.lastname: Tsuji
authors.forename: Masashi
authors.initials: M
authors.lastname: Kondo
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Hasegawa
authors.forename: Kaoru
authors.initials: K
authors.lastname: Shimokata
mesh_terms: D036002:ADP Ribose Transferases / Q000494:pharmacology; D000577:Amides / Q000494:pharmacology; D001905:Botulinum Toxins / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects / Q000276:immunology; D002460:Cell Line; D004730:Endothelium, Vascular / Q000187:drug effects; D004804:Eosinophils / Q000187:drug effects / Q000276:immunology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D008168:Lung / Q000473:pathology; D008246:Lysophospholipids / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019010:Vascular Cell Adhesion Molecule-1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000276:immunology / Q000378:metabolism*
chemical_list: D000577:Amides; C437105:GGTI 286; D008246:Lysophospholipids; D011725:Pyridines; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1; C108830:Y 27632; C060506:sphingosine 1-phosphate; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D001905:Botulinum Toxins; D020742:rhoA GTP-Binding Protein; D007930:Leucine; D013110:Sphingosine