[Polyphenols of natural origin against age-related disorders of tissue homeostasis.]

Aging-related disorders of tissue homeostasis may lead to excessive cell proliferation in the form of cancer and to extracellular matrix expansion in the form of fibroses. Death rates attributed to both of the conditions are decreased, according to epidemiological evidence, upon increased dietary intakes of polyphenols, including flavonoids, stilbenes, lignans, and curcuminoids. That is, polyphenols, although they have very different structures, unidirectionally influence the two opposite sides of balance in tissue homeostasis: the cells, which are able, and the extracellular matrix, which is unable to proliferate. The common features of fibroses and cancer are the transformation of fibroblasts into myofibroblasts (MF) and the epithelial- and endothelial-to-mesenchymal transitions (EMT and EndMT), which shift cell proportions in tissues toward MF. The increased ability of MF to produce collagen promotes fibroses in non-cancerous tissues, and EMT and EndMT enhance cancer progression. These processes are influenced by not polyphenols themselves due to their interactions with different sterically suitable targets, but by polyphenol oxidation products, which are all highly electrophilic. By binding to the SH-groups of the KEAP1 protein complexed with the NRF2 protein, they release NRF2, which is generally known as a transcription factor involved in activating the genes implicated in cell antioxidant defenses. In the present review, attention is drawn to the published data about NRF2 ability to attenuate TGFβ1 signaling, which promotes fibroblasts conversion into MF and enhances EMP and EndMP, that is increases the phenotypic instability of cells. Thus, the anticarcinogenic and antifibrotic effects of polyphenols may both involve cell phenotype stabilization, which may contribute to the geroprotector effects of polyphenols.