Molecular mechanism of endothelial nitric-oxide synthase activation by Platycodon grandiflorum root-derived saponins.
Nitric oxide (NO) produced by endothelial nitric-oxide synthase (eNOS) has antithrombotic and antiatherosclerotic properties in the vasculature. Previously, we demonstrated that saponins derived from the roots of Platycodon grandiflorum (CKS) inhibited the tumor necrosis factor-alpha-induced expression of adhesion molecules in human endothelial cells. In this study, we found that CKS increased eNOS phosphorylation and NO production in human endothelial cells. Treatment with CKS increased the phosphorylation of Akt, p38/MAPK, AMP-activated protein kinase (AMPK), and calmodulin-dependent protein kinase II (CaMK II) leading to increased NO production in human endothelial cells. Moreover, inhibitors of Akt (LY294002), p38/MAPK (SB203580), AMPK (compound C), and CaMK II (W7) failed to suppress CKS-induced eNOS phosphorylation. In addition, CKS-induced eNOS phosphorylation was inhibited by the overexpression of a dominant-negative mutant form of AMPK (DN-AMPK). Taken together, these results indicate that CKS stimulates eNOS phosphorylation and NO production via the activation of PI3K/Akt, p38/MAPK, AMPK, and CaMK II.
Department of Toxicology, College of Pharmacy, Chungnam National University, 220 Gung-dong, Yuseong-Gu, Daejeon 305-764, Republic of Korea.
Hyung Gyun
HG
Kim
Tran Thi
TT
Hien
Eun Hee
EH
Han
Young Chul
YC
Chung
Hye Gwang
HG
Jeong
D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010936:Plant Extracts / Q000737:chemistry; D018517:Plant Roots / Q000737:chemistry; D031238:Platycodon / Q000737:chemistry*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012503:Saponins / Q000737:chemistry / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D010936:Plant Extracts; D012503:Saponins; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; D055372:AMP-Activated Protein Kinases