Exp Mol Med.  2012 Mar;44(3):191-201. 10.3858/emm.2012.44.3.014.

Syringaresinol causes vasorelaxation by elevating nitric oxide production through the phosphorylation and dimerization of endothelial nitric oxide synthase

• Chung BH
• Kim S
• Kim JD
• Lee JJ
• Baek YY
• Jeoung D
• Lee H
• Choe J
• Ha KS
• Won MH
• Kwon YG
• Kim YM

• KMID: 1245262
• DOI: http://doi.org/10.3858/emm.2012.44.3.014

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 NG-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 Ca2+ levels. A phospholipase C (PLC) inhibitor blocked the increases in intracellular Ca2+ 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, Ca2+ chelator, calmodulin antagonist, and CaMKKbeta siRNA. This compound also increased eNOS dimerization, which was inhibited by a PLC inhibitor and a Ca2+-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/Ca2+/CaMKKbeta-dependent eNOS phosphorylation and Ca2+-dependent eNOS dimerization.

Keyword

nitric oxide synthase type III; phosphorylation; protein multimerization; syringaresinol; type C phospholipases; vasodilation

MeSH Terms

Animals
Aorta/*drug effects/physiology
Enzyme Activation/drug effects
Furans/*pharmacology
Gene Deletion
Human Umbilical Vein Endothelial Cells/drug effects/metabolism
Humans
Lignans/*pharmacology
Mice
Mice, Inbred C57BL
Nitric Oxide/metabolism
Nitric Oxide Synthase Type III/genetics/*metabolism
Phosphatidylinositol 3-Kinases/metabolism
Phosphoinositide Phospholipase C/metabolism
Phosphorylation/drug effects
Protein Multimerization/*drug effects
Proto-Oncogene Proteins c-akt/metabolism
Vasodilation/*drug effects