Flavanone metabolites decrease monocyte adhesion to TNF-α-activated endothelial cells by modulating expression of atherosclerosis-related genes

Abstract

Flavanones are found specifically and abundantly in citrus fruits. Their beneficial effect on vascular function is well documented. However, little is known about their cellular and molecular mechanisms of action in vascular cells. The goal of the present study was to identify the impact of flavanone metabolites on endothelial cells and decipher the underlying molecular mechanisms of action. We investigated the impact of naringenin and hesperetin metabolites at 0·5, 2 and 10 mM on monocyte adhesion to TNF-a-activated human umbilical vein endothelial cells (HUVEC) and on gene expression. Except hesperetin-7-glucuronide and naringenin-7-glucuronide (N7G), when present at 2 mM, flavanone metabolites (hesperetin-3 0 -sulphate, hesperetin-3 0 -glucuronide and naringenin-4 0 -glucuronide (N4 0 G)) significantly attenuated monocyte adhesion to TNF-a-activated HUVEC. Exposure of both monocytes and HUVEC to N4 0 G and N7G at 2 mM resulted in a higher inhibitory effect on monocyte adhesion. Gene expression analysis, using TaqMan Low-Density Array, revealed that flavanone metabolites modulated the expression of genes involved in atherogenesis, such as those involved in inflammation, cell adhesion and cytoskeletal organisation. In conclusion, physiologically relevant concentrations of flavanone metabolites reduce monocyte adhesion to TNF-a-stimulated endothelial cells by affecting the expression of related genes. This provides a potential explanation for the vasculoprotective effects of flavanones.Key words: Flavanones: Metabolites: Monocyte adhesion: Gene expression: Endothelial cellsAtherosclerosis, a multifactorial disease of the large arteries and the leading cause of CVD, is characterised by inflammatory and oxidative stress involving chronic dysfunction of the endothelium. This altered function of endothelial cells is associated with both an imbalance in the production of vasodilators/vasoconstrictors and an increase in the expression of pro-inflammatory, chemotactic and adhesion molecules (1,2) .These changes facilitate the adhesion of circulating immune cells to the activated endothelium, and their subsequent migration into the arterial wall constitutes early events in the atherogenic process. Once in the intima, monocytes differentiate into activated macrophages, which take up oxidised lipoproteins, leading to the formation of foam cells (3) . A positive association between a high consumption of fruits and vegetables and a reduced risk of CVD has been described (4,5) . Among the protective bioactive compounds found in fruits and vegetables, polyphenols seem to be of particular interest. Indeed, epidemiological studies have established an inverse relationship between the intake of flavonoids, a subclass of polyphenols, and mortality from CVD (6) . Animal * Corresponding author: C. Morand, email christine.morand@clermont.inra.fr Abbreviations: ACTR, actin-related protein; CCL2, chemokine (C-C motif) ligand 2; EZR, ezrin; H3 0 G, hesperetin-3 0 -glucuronide; H3 0 S, hesperetin-3 0 -sulphate; H7G, hesperetin-7-...

Polyphenols: Benefits to the Cardiovascular System in Health and in Aging

“…The levels of circulating Ang II were significantly reduced, which otherwise leads to vasoconstriction. Flavanones can also modulate inflammatory process in atherosclerosis by reducing the binding of monocytes treated with Naringenin and Hesperitin, flavanones found primarily in citrus fruits, to TNFα activated endothelial cells [215]. …”

Dietary Flavanols Modulate the Transcription of Genes Associated with Cardiovascular Pathology without Changes in Their DNA Methylation State

“…In vitro , polyphenols impact the expression of genes in various cell types. It has been demonstrated that flavanone metabolites at physiological concentrations can modulate the expression of genes involved in inflammation in tumor necrosis factor (TNF)-α-stimulated human umbilical vein endothelial cells (HUVECs) [8]. Exposure of human monocytes to green tea polyphenols affected the expression of genes related to atherosclerosis development, such as CD36 , LXR-α , MYC or LDL-R [9].…”

Effects of naringenin and its phase II metabolites onin vitrohuman macrophage gene expression

“…In order to understand the role of naringenin and its phase II metabolites on macrophage cholesterol intake and potential of foam cell formation (Chanet et al, 2013), the expression of the scavenger receptor CD36, a multiligand scavenger receptor responsible for the recognition and internalisation of oxidatively modified LDL, was evaluated. This gene was downregulated in untreated M1 cells -naringenin and its 7-glucuronide were able to significantly counteract this downregulation.…”

“…Several studies have reported an active role of various polyphenols within in vitro macrophage models Hämäläinen et al, 2007;Raso et al, 2001;Tsai et al, 1999), and recently, naringenin was also evaluated in macrophage/monocyte cultures, suggesting a role in the inhibition of inflammatory and atherosclerosis-related pathways (Chanet et al, 2013;Chao et al, 2010;Vafeiadou et al, 2009). Despite this interest in understanding the effect that phenolic substances could elicit on macrophages, specific molecular actions as well as the role of metabolites instead of parent plant compounds require further elucidation (Del Rio et al, 2013).…”