title: Syringaresinol causes vasorelaxation by elevating nitric oxide production through the phosphorylation and dimerization of endothelial nitric oxide synthase.
abstract: Nitric oxide (NO) produced by endothelial NO synthase (eNOS) plays an important role in vascular functions, including vasorelaxation. We here investigated the pharmacological effect of the natural product syringaresinol on vascular relaxation and eNOS-mediated NO production as well as its underlying biochemical mechanism in endothelial cells. Treatment of aortic rings from wild type, but not eNOS(-/-) mice, with syringaresinol induced endothelium-dependent relaxation, which was abolished by addition of the NOS inhibitor N(G)-monomethyl-L-arginine. Treatment of human endothelial cells and mouse aortic rings with syringaresinol increased NO production, which was correlated with eNOS phosphorylation via the activation of Akt and AMP kinase (AMPK) as well as elevation of intracellular Ca(2+) levels. A phospholipase C (PLC) inhibitor blocked the increases in intracellular Ca(2+) levels, AMPK-dependent eNOS phosphorylation, and NO production, but not Akt activation, in syringaresinol- treated endothelial cells. Syringaresinol-induced AMPK activation was inhibited by co-treatment with PLC inhibitor, Ca(2+) chelator, calmodulin antagonist, and CaMKKβ siRNA. This compound also increased eNOS dimerization, which was inhibited by a PLC inhibitor and a Ca(2+)-chelator. The chemicals that inhibit eNOS phosphorylation and dimerization attenuated vasorelaxation and cGMP production. These results suggest that syringaresinol induces vasorelaxation by enhancing NO production in endothelial cells via two distinct mechanisms, phosphatidylinositol 3-kinase/Akt- and PLC/Ca(2+)/CaMKKβ-dependent eNOS phosphorylation and Ca(2+)-dependent eNOS dimerization.
authors.affiliation: Vascular System Research Center, School of Medicine, Kangwon National University, Chuncheon 200-701, Korea.
authors.forename: Byung-Hee
authors.initials: BH
authors.lastname: Chung
authors.forename: Sookon
authors.initials: S
authors.lastname: Kim
authors.forename: Jong-Dai
authors.initials: JD
authors.lastname: Kim
authors.forename: Jung Joon
authors.initials: JJ
authors.lastname: Lee
authors.forename: Yi-Yong
authors.initials: YY
authors.lastname: Baek
authors.forename: Dooil
authors.initials: D
authors.lastname: Jeoung
authors.forename: Hansoo
authors.initials: H
authors.lastname: Lee
authors.forename: Jongseon
authors.initials: J
authors.lastname: Choe
authors.forename: Kwon-Soo
authors.initials: KS
authors.lastname: Ha
authors.forename: Moo-Ho
authors.initials: MH
authors.lastname: Won
authors.forename: Young-Guen
authors.initials: YG
authors.lastname: Kwon
authors.forename: Young-Myeong
authors.initials: YM
authors.lastname: Kim
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D005663:Furans / Q000494:pharmacology*; D017353:Gene Deletion; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D017705:Lignans / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D054801:Phosphoinositide Phospholipase C / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D055503:Protein Multimerization / Q000187:drug effects*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D005663:Furans; D017705:Lignans; C042192:syringaresinol; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D054801:Phosphoinositide Phospholipase C