Ginkgo biloba extract attenuates oxLDL-induced endothelial dysfunction via an AMPK-dependent mechanism

Author:

Ou Hsiu-Chung1,Hsieh Yueh-Ling1,Yang Nae-Cherng23,Tsai Kun-Ling1,Chen Kai-Ling1,Tsai Chiou-Sheng4,Chen I-Ju5,Wu Bor-Tsang1,Lee Shin-Da16

Affiliation:

1. Department of Physical Therapy and Graduate Institute of Rehabilitation Science, China Medical University, Taichung, Taiwan;

2. School of Nutrition, Chung Shan Medical University, Taichung, Taiwan;

3. Department of Nutrition, Chung Shan Medical University Hospital, Taichung, Taiwan;

4. Department of Pathology and Laboratory Medicine, Taichung Veterans General Hospital, Taichung, Taiwan;

5. Department of Physical Education, Asia University, Taichung, Taiwan; and

6. Department of Healthcare Administration, Asia University, Taichung, Taiwan

Abstract

Atherosclerosis is a complex inflammatory arterial disease, and oxidized low-density lipoprotein (oxLDL) is directly associated with chronic vascular inflammation. Previous studies have shown that Ginkgo biloba extract (GbE) acts as a therapeutic agent for neurological and cardiovascular disorders. However, the mechanisms mediating the actions of GbE are still largely unknown. In the present study, we tested the hypothesis that GbE protects against oxLDL-induced endothelial dysfunction via an AMP-activated protein kinase (AMPK)-dependent mechanism. Human umbilical vein endothelial cells were treated with GbE, followed by oxLDL, for indicated time periods. Results from Western blot showed that GbE inhibited the membrane translocation of the NADPH oxidase subunits p47phox and Rac-1 and attenuated the increase in protein expression of membrane subunits gp91 and p22phox caused by oxLDL-induced AMPK dephosphorylation and subsequent PKC activation. AMPK-α1-specific small interfering RNA-transfected cells that had been exposed to GbE followed by oxLDL revealed elevated levels of PKC and p47phox. In addition, exposure to oxLDL resulted in reduced AMPK-mediated Akt/endothelial nitric oxide (NO) synthase signaling and the induction of phosphorylation of p38 mitogen-activated protein kinase, which, in turn, activated NF-κB-mediated inflammatory responses, such as the release of interleukin-8, the expression of the adhesion molecule, and the adherence of monocytic cells to human umbilical vein endothelial cells. Furthermore, oxLDL upregulated the expression of inducible NO synthase, thereby augmenting the formation of NO and protein nitrosylation. Pretreatment with GbE, however, exerted significant cytoprotective effects in a dose-dependent manner. Results from this study may provide insight into a possible molecular mechanism by which GbE protects against oxLDL-induced endothelial dysfunction.

Publisher

American Physiological Society

Subject

Physiology (medical),Physiology

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