Abstract
The endothelial integrity is the cornerstone of the atherogenic process. Low-density lipoprotein (LDL) oxidation occurring within atheromatous plaques leads to deleterious vascular effects including endothelial cell cytotoxicity. The aim of this study was to evaluate the vascular antioxidant and cytoprotective effects of polyphenol-rich extracts from two medicinal plants from the Reunion Island: Antirhea borbonica (A. borbonica), Doratoxylon apetalum (D. apetalum). The polyphenol-rich extracts were obtained after dissolving each dry plant powder in an aqueous acetonic solution. Quantification of polyphenol content was achieved by the Folin–Ciocalteu assay and total phenol content was expressed as g gallic acid equivalent/100 g plant powder (GAE). Human vascular endothelial cells were incubated with increasing concentrations of polyphenols (1–50 µM GAE) before stimulation with oxidized low-density lipoproteins (oxLDLs). LDL oxidation was assessed by quantification of hydroperoxides and thiobarbituric acid reactive substances (TBARS). Intracellular oxidative stress and antioxidant activity (catalase and superoxide dismutase) were measured after stimulation with oxLDLs. Cell viability and apoptosis were quantified using different assays (MTT, Annexin V staining, cytochrome C release, caspase 3 activation and TUNEL test). A. borbonica and D. apetalum displayed high levels of polyphenols and limited LDL oxidation as well as oxLDL-induced intracellular oxidative stress in endothelial cells. Polyphenol extracts of A. borbonica and D. apetalum exerted a protective effect against oxLDL-induced cell apoptosis in a dose-dependent manner (10, 25, and 50 µM GAE) similar to that observed for curcumin, used as positive control. All together, these results showed significant antioxidant and antiapoptotic properties for two plants of the Reunion Island pharmacopeia, A. borbonica and D. apetalum, suggesting their therapeutic potential to prevent cardiovascular diseases by limiting LDL oxidation and protecting the endothelium.
Highlights
Reunion Island widely used by the population for their anti-inflammatory properties, namely D. apetalum and A. borbonica
Results are expressed as means ± SEM of at least 3 independent experiments. ** p < 0.01, *** p < 0.001, compared to control (LDL) [A]; ** p < 0.01, *** p < 0.001, compared to oxidized LDLs (oxLDLs) [B] using one-way analysis of variance (ANOVA) with posthoc Tukey’s test
Our results demonstrate that polyphenol-rich extracts exerted a potent cytoprotective effect on endothelial cells exposed to oxLDLs, suggesting that they could limit the atherogenic process
Summary
Among the different risk factors of cardiovascular disease, high levels of low-density lipoprotein cholesterol (LDL-C) remain the major determinant of lipid accumulation within the arterial wall and subsequent atherosclerotic plaque formation. LDL oxidation is responsible for their unregulated uptake by phagocytes, thereby forming foam cells [1]. In the subendothelial space of large arteries, LDL undergo oxidation via different mechanisms involving reactive oxygen species produced by vascular cells and leukocytes in the presence of transition metals such as iron contained in hemin [2]. In the first steps of atherogenesis, oxidized LDLs (oxLDLs) induce the expression of adhesion molecules such
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