Polyphenol-Mediated Beneficial Effects in Healthy Status and Disease with Special Reference to Immune-Based Mechanisms

Polyphenols are natural products of vegetal origin endowed with many biological activities when ingested in appropriate amounts. In this chapter, the focus is on the bioavailability of polyphenols as well as on their capacity to interact with an array of receptors on various cell types. Particularly, immune and non-immune cells of the gut represent the major targets of dietary polyphenols and their metabolites. Regular polyphenol intake with food (vegetables and fruit) and beverages (e.g., red wine, green tea and orange juice) has been shown to prevent cardiovascular risk. Release of nitric oxide, a well-known vasodilator, from endothelial cells as well as from monocytes upon stimulation with polyphenols seems to represent the key event in the induction of cardioprotection. Moreover, red wine polyphenols in vitro stimulate human peripheral blood mononuclear cell response with a release of both pro-inflammatory and anti-inflammatory cytokines, thus maintaining a condition of immune homeostasis. In this framework, polyphenols also present in fermented grape marc (FGM) are able to induce expression of FoxP3 in human CD4+ cells, thus leading to the generation of T regulatory cells that, in turn, produce interleukin-10, an anti-inflammatory cytokine. On these grounds, mitigation of experimental colitis and asthma in mice seems to reside on the ability of FGMs to downregulate noxious immune responses into the host. Moreover, the interaction of polyphenols with intestinal microbiota has been shown to generate beneficial effects in the host. Finally, potential clinical application of polyphenols in the prevention of age-related diseases will be discussed. © 2014 Elsevier Inc. All rights reserved.