A Dietary Mixture of Oxysterols Induces In Vitro Intestinal Inflammation through TLR2/4 Activation: The Protective Effect of Cocoa Bean Shells

Abstract

Background: Exaggerated Toll-like receptor (TLR)-mediated immune and inflammatory responses play a role in inflammatory bowel diseases. This report deals with the ability of a mixture of oxysterols widely present in cholesterol-rich foods to induce in vitro intestinal inflammation through TLR up-regulation. The anti-inflammatory action of four cocoa bean shell (CBS) extracts with different polyphenol content, was tested. Methods: Differentiated intestinal CaCo-2 cells were treated with a dietary oxysterol mixture (Oxy-mix) (60 µM). The expression and activation of TLR2 and TLR4, as well as the production of their downstream signaling effectors IL-8, IFNβ and TNFα were analyzed in the presence or absence of TLR antibodies. Honduras CBS extracts were characterized for their polyphenol contents; their anti-inflammatory action was analyzed in CaCo-2 cells treated with Oxy-mix. Results: Oxysterol-dependent TLR-2 and TLR4 over-expression and activation together with cytokine induction were abolished by blocking TLRs with specific antibodies. Polyphenol-rich CBS extracts consisting of high quantities of (−)-epicatechin and tannins also prevented TLR induction. Conclusions: TLR2 and TLR4 mainly contribute to inducing oxysterol-dependent intestinal inflammation. The fractionation method of CBS allowed the recovery of fractions rich in (−)-epicatechin and tannins able to counteract oxysterol-induced inflammation, thus highlighting the beneficial biological potential of specific CBS extracts.

Keywords

• dietary oxysterols
• Toll-like receptors
• IL-8
• IFNβ
• TNFα
• phenolic extract
• cocoa bean shell
• Honduras cocoa
• (−)-epicatechin
• tannins