Sphingosylphosphorylcholine is a novel messenger for Rho-kinase-mediated Ca2+ sensitization in the bovine cerebral artery: unimportant role for protein kinase C.
Although recent investigations have suggested that a Rho-kinase-mediated Ca2+ sensitization of vascular smooth muscle contraction plays a critical role in the pathogenesis of cerebral and coronary vasospasm, the upstream of this signal transduction has not been elucidated. In addition, the involvement of protein kinase C (PKC) may also be related to cerebral vasospasm. We recently reported that sphingosylphosphorylcholine (SPC), a sphingolipid, induces Rho-kinase-mediated Ca2+ sensitization in pig coronary arteries. The purpose of this present study was to examine the possible mediation of SPC in Ca2+ sensitization of the bovine middle cerebral artery (MCA) and the relation to signal transduction pathways mediated by Rho-kinase and PKC. In intact MCA, SPC induced a concentration-dependent (EC50=3.0 micromol/L) contraction, without [Ca2+]i elevation. In membrane-permeabilized MCA, SPC induced Ca2+ sensitization even in the absence of added GTP, which is required for activation of G-proteins coupled to membrane receptors. The SPC-induced Ca2+ sensitization was blocked by a Rho-kinase inhibitor (Y-27632) and a dominant-negative Rho-kinase, but not by a pseudosubstrate peptide for conventional PKC, which abolished the Ca2+-independent contraction induced by phorbol ester. In contrast, phorbol ester-induced Ca2+ sensitization was resistant to a Rho-kinase inhibitor and a dominant-negative Rho-kinase. In primary cultured vascular smooth muscle cells, SPC induced the translocation of cytosolic Rho-kinase to the cell membrane. We propose that SPC is a novel messenger for Rho-kinase-mediated Ca2+ sensitization of cerebral arterial smooth muscle and, therefore, may play a pivotal role in the pathogenesis of abnormal contraction of the cerebral artery such as vasospasm. The SPC/Rho-kinase pathway functions independently of the PKC pathway.
Shirao
Satoshi
S
Department of Molecular Physiology, Yamaguchi University School of Medicine, Ube, Japan.
Kashiwagi
Shiro
S
Sato
Masafumi
M
Miwa
Saori
S
Nakao
Fumiaki
F
Kurokawa
Tetsu
T
Todoroki-Ikeda
Natsuko
N
Mogami
Kimiko
K
Mizukami
Yoichi
Y
Kuriyama
Shinichi
S
Haze
Kyousuke
K
Suzuki
Michiyasu
M
Kobayashi
Sei
S
D000818:Animals; D020013:Calcium Signaling; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D002536:Cerebral Arteries / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism* / Q000502:physiology; D046508:Culture Techniques; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004928:Escin / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000032:analysis / Q000037:antagonists & inhibitors / Q000502:physiology*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D054460:rho-Associated Kinases
D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; C005356:sphingosine phosphorylcholine; D010767:Phosphorylcholine; D015240:Phorbol 12,13-Dibutyrate; D004928:Escin; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D013110:Sphingosine