Autophagic effects of Hibiscus sabdariffa leaf polyphenols and epicatechin gallate (ECG) against oxidized LDL-induced injury of human endothelial cells

• Published in: European journal of nutrition Vol. 56; no. 5; pp. 1963 - 1981
• Main Authors: Chen, Jing-Hsien, Lee, Ming-Shih, Wang, Chi-Ping, Hsu, Cheng-Chin, Lin, Hui-Hsuan
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-08-2017; Springer Nature B.V
• Subjects: 1-Phosphatidylinositol 3-kinase; Adenine - analogs & derivatives; Adenine - pharmacology; AKT protein; Antioxidants - pharmacology; Apoptosis; Apoptosis - drug effects; Arteriosclerosis; Autophagy; Autophagy - drug effects; Beclin-1 - metabolism; Catechin - analogs & derivatives; Catechin - analysis; Catechin - pharmacology; Cell injury; Cell proliferation; Cell Proliferation - drug effects; Cell Survival - drug effects; Cells, Cultured; Chemistry; Chemistry and Materials Science; Chloroquine; Cytotoxicity; Electrocardiography; Endothelial cells; Epicatechin; Flavonoids; Hibiscus - chemistry; Human Umbilical Vein Endothelial Cells - drug effects; Human Umbilical Vein Endothelial Cells - metabolism; Humans; Leaves; Lipoproteins, LDL - toxicity; Low density lipoprotein; Nutrition; Organelles; Original Contribution; Phagocytosis; Phenanthrenes - pharmacology; Phosphatidylinositol 3-Kinases - antagonists & inhibitors; Phosphatidylinositol 3-Kinases - metabolism; Plant Leaves - chemistry; Polymerase chain reaction; Polyphenols; Polyphenols - analysis; Polyphenols - pharmacology; PTEN Phosphohydrolase - antagonists & inhibitors; PTEN Phosphohydrolase - metabolism; PTEN protein; Umbilical vein; Western blotting; leaf polyphenols; Oxidized low-density lipoprotein; Autophagy; Endothelial cells; (−)-Epicatechin gallate; Apoptosis; Hibiscus sabdariffa leaf polyphenols
• ISSN: 1436-6207; 1436-6215
• DOI: 10.1007/s00394-016-1239-4

Purpose
Oxidized low-density lipoprotein (ox-LDL) contributes to the pathogenesis of atherosclerosis by promoting vascular endothelial cell injury.
Hibiscus sabdariffa
leaf polyphenols (HLP), rich in flavonoids, have been shown to possess antioxidant and antiatherosclerotic activities. In this study, we examined the protective role of HLP and its main compound (−)-epicatechin gallate (ECG) in human umbilical vein endothelial cells (HUVECs) exposed to ox-LDL in vitro.
Methods
In a model of ox-LDL-impaired HUVECs, assessments of cell viability, cytotoxicity, cell proliferation, apoptosis, and autophagy were detected. To highlight the mechanisms of the antiapoptotic effects of HLP and ECG, the expressions of molecular proteins were measured by Western blotting, real-time PCR, and so on.
Results
HLP or ECG improved the survival of HUVECs from ox-LDL-induced viability loss. In addition, HLP or ECG showed potential in reducing ox-LDL-dependent apoptosis. Next, the ox-LDL-induced formation of acidic vesicular organelles and upregulation of the autophagy-related genes were increased by HLP or ECG. The HLP-triggered autophagic flux was further confirmed by increasing the LC3-II level under the pretreatment of an autophagy inhibitor chloroquine. Molecular data indicated the autophagic effect of HLP or ECG might be mediated via class III PI3K/Beclin-1 and PTEN/class I PI3K/Akt cascade signaling, as demonstrated by the usage of a class III PI3K inhibitor 3-methyladenine (3-MA) and a PTEN inhibitor SF1670.
Conclusions
Our data imply that ECG-enriched HLP upregulates the autophagic pathway, which in turn led to reduce ox-LDL-induced HUVECs injury and apoptosis and provide a new mechanism for its antiatherosclerotic activity.