Tannin 1-alpha-O-galloylpunicalagin induces the calcium-dependent activation of endothelial nitric-oxide synthase via the phosphatidylinositol 3-kinase/Akt pathway in endothelial cells.
Many polyphenols have been found to increase endothelial nitric oxide (NO) production. In our present study, we investigated the effects of 1-alpha-O-galloylpunicalagin upon endothelial nitric oxide synthase (eNOS) activity in endothelial cells (ECs). Both 1-alpha-O-galloylpunicalagin and punicalagin induced NO production in a dose-dependent manner in ECs. Despite having similar chemical structures, punicalagin induced lower levels of NO production than 1-alpha-O-galloylpunicalagin. After 1-alpha-O-galloylpunicalagin addition, a rise in the intracellular Ca(2+) concentration preceded NO production. The Ca(2+) ionophore A23187 stimulated eNOS phosphorylation and augmented NO production. Pretreatment with Ca(2+) chelators inhibited 1-alpha-O-galloylpunicalagin-induced eNOS phosphorylation and NO production. Treatment with 1-alpha-O-galloylpunicalagin did not alter the eNOS protein levels but, unlike punicalagin, induced a sustained activation of eNOS Ser(1179) phosphorylation. 1-alpha-O-galloylpunicalagin was also found to activate ERK1/2, JNK and Akt in ECs. Moreover, simultaneous treatment of these cells with specific phosphatidylinositol-3-kinase inhibitors significantly inhibited the observed increases in eNOS activity and phosphorylation levels. In contrast, the inhibition of (ERK)1/2, JNK and p38 had no influence on eNOS Ser(1179) phosphorylation. Our present results thus indicate that the 1-alpha-O-galloylpunicalagin-induced calcium-dependent activation of eNOS is primarily mediated via a phosphatidylinositol 3-kinase/Akt-dependent increase in eNOS activity, and occurs independently of the eNOS protein content.
Chen
Lih-Geeng
LG
Institute of Biomedical and Biopharmaceutical Sciences, National Chiayi University, Chiayi, Taiwan.
Liu
Yen-Chin
YC
Hsieh
Chia-Wen
CW
Liao
Being-Chyuan
BC
Wung
Being-Sun
BS
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000378:metabolism*; D004789:Enzyme Activation; D005419:Flavonoids / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D047348:Hydrolyzable Tannins / Q000378:metabolism*; D007476:Ionophores / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D010636:Phenols / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D059808:Polyphenols; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D029766:Terminalia / Q000737:chemistry
D005419:Flavonoids; D047348:Hydrolyzable Tannins; D007476:Ionophores; D010636:Phenols; D059808:Polyphenols; C534358:tannin 1-alpha-O-galloylpunicalagin; D009569:Nitric Oxide; D006861:Hydrogen Peroxide; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D002118:Calcium