Ginkgo biloba extract reduces high-glucose-induced endothelial reactive oxygen species generation and cell adhesion molecule expression by enhancing HO-1 expression via Akt/eNOS and p38 MAP kinase pathways.
OBJECTIVE
Hyperglycemia is one of the major risk factors leading to vascular complications in clinical diabetes mellitus. Ginkgo biloba extract (GBE), an antioxidant herbal medicine, possesses anti-inflammatory effects. We examined whether GBE can reduce high glucose-induced endothelial adhesiveness to monocytes, an in vitro sign mimicking in vivo early atherogenesis, through selective regulation of heme oxygenase (HO)-1 expression.


METHODS
Human aortic endothelial cells (HAECs) were cultured with normal glucose or high glucose (25 mM) for 4 days and subsequently combined with GBE (EGb761, Dr. Willmar Schwabe, Karlsruhe, Germany) treatment in the last 18 h of the 4-day period. The endothelial reactive oxygen species (ROS) generation, adhesion molecule expression and the adhesiveness to monocytes were examined. The specific signal pathways such as HO-1 were also examined.


RESULTS
High glucose increased ROS generation, adhesion molecule expression and the adhesiveness to monocytes in HAECs. These high glucose-induced phenomena could be suppressed by GBE (100 μg/ml)-induced HO-1 expression in a dose-dependent and time-dependent manner. In addition, jun N-terminal kinases inhibitor or phosphoinositide 3 kinase inhibitor could reduce GBE-induced HO-1 expression. Furthermore, HO-1 inhibitor, HO-1 siRNA, endothelial nitric oxide synthase (eNOS) siRNA, or nuclear factor erythroid 2-related factor (Nrf) 2 siRNA blocked the cytoprotective effects of GBE. Meanwhile, p38/mitogen-activated protein kinase (MAPK) inhibitor could also reduce the effects of GBE on HO-1 induction.


CONCLUSIONS
GBE could reduce high glucose-induced endothelial adhesion via enhancing HO-1 expression through the Akt/eNOS and p38/MAPK pathways. Our findings suggest a potential strategy targeting on HO-1 induction by GBE for endothelial protection in the presence of high glucose such as that in diabetes mellitus.
Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan.
Hsiao-Ya
HY
Tsai
Po-Hsun
PH
Huang
Feng-Yen
FY
Lin
Jia-Shiong
JS
Chen
Shing-Jong
SJ
Lin
Jaw-Wen
JW
Chen
D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D042783:Endothelial Cells / Q000187:drug effects* / Q000502:physiology; D055785:Gene Knockdown Techniques; D020441:Ginkgo biloba; D005947:Glucose; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009000:Monocytes / Q000187:drug effects / Q000502:physiology; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D010936:Plant Extracts / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism*
D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D010936:Plant Extracts; D017382:Reactive Oxygen Species; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1; D009569:Nitric Oxide; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D020928:Mitogen-Activated Protein Kinases; D005947:Glucose