Endothelial barrier protection by FTY720 under hyperglycemic condition: involvement of focal adhesion kinase, small GTPases, and adherens junction proteins.
Recently, sphingosine 1-phosphate (S1P) has been highlighted as an endothelial barrier-stabilizing mediator. FTY720 is a S1P analog originally developed as a novel immunosuppressant. The phosphorylated form of FTY720 binds to S1P receptors to exert S1P-like biological effects, suggesting endothelial barrier promotion by FTY720. To elucidate whether FTY720 induces signaling events related to endothelial barrier enhancement under hyperglycemic conditions, human microvascular endothelial cells (HMVECs) preincubated with hyperglycemic (30 mM) medium were treated with 100 nM FTY720 for 3 h. Immunofluorescent microscopy and coprecipitation study revealed FTY720-induced focal adhesion kinase (FAK)-associated adherens junction (AJ) assembly at cell-cell contacts coincident with formation of a prominent cortical actin ring. FTY720 also induced transmonolayer electrical resistance (TER) augmentation in HMVEC monolayers in both normoglycemic and hyperglycemic conditions, implying endothelial barrier enhancement. Similar to S1P, site-specific FAK tyrosine phosphorylation analysis revealed FTY720-induced FAK [Y576] phosphorylation without phosphorylation of FAK [Y397/Y925]. Furthermore, FTY720 conditioned the phosphorylation profile of FAK [Y397/Y576/Y925] in hyperglycemic medium to the same pattern observed in normoglycemic medium. FTY720 challenge resulted in small GTPase Rac activation under hyperglycemic conditions, whereas increased Rho activity in hyperglycemic medium was restored to the basal level. Rac protein depletion by small interfering RNA (siRNA) technique completely abolished FTY720-induced FAK [Y576] phosphorylation. These findings strongly suggest the barrier protective effect of FTY720 on HMVEC monolayers in hyperglycemic medium via S1P signaling, further implying the possibility of FTY720 as a therapeutic agent of diabetic vascular disorder.
Sarai
Kei
K
Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan. shikata@md.okayama-u.ac.jp
Shikata
Kenichi
K
Shikata
Yasushi
Y
Omori
Kazuyoshi
K
Watanabe
Naomi
N
Sasaki
Motofumi
M
Nishishita
Shingo
S
Wada
Jun
J
Goda
Noriko
N
Kataoka
Noriyuki
N
Makino
Hirofumi
H
D000199:Actins / Q000378:metabolism; D022005:Adherens Junctions / Q000187:drug effects / Q000502:physiology*; D015820:Cadherins / Q000502:physiology*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002478:Cells, Cultured; D017097:Electric Impedance; D042783:Endothelial Cells / Q000187:drug effects / Q000502:physiology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D000068876:Fingolimod Hydrochloride; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000502:physiology*; D006801:Humans; D006943:Hyperglycemia / Q000378:metabolism*; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008246:Lysophospholipids / Q000378:metabolism; D055806:Microvessels / Q000166:cytology; D020559:Monomeric GTP-Binding Proteins / Q000502:physiology*; D010766:Phosphorylation; D011409:Propylene Glycols / Q000494:pharmacology*; D049349:Receptors, Lysosphingolipid / Q000502:physiology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D020744:rac GTP-Binding Proteins / Q000502:physiology; D020741:rho GTP-Binding Proteins / Q000502:physiology
D000199:Actins; D015820:Cadherins; D015815:Cell Adhesion Molecules; D007166:Immunosuppressive Agents; D008246:Lysophospholipids; D011409:Propylene Glycols; D049349:Receptors, Lysosphingolipid; C060506:sphingosine 1-phosphate; D051416:Focal Adhesion Protein-Tyrosine Kinases; D020559:Monomeric GTP-Binding Proteins; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins; D000068876:Fingolimod Hydrochloride; D013110:Sphingosine