Modulation of human keratinocyte responses to solar UV by plant polyphenols as a basis for chemoprevention of non-melanoma skin cancers.

Excessive exposure to solar UVA and UVB radiation is widely considered to cause skin cancers such as squamous cell carcinoma and basalioma. Direct UVB damage to skin cell DNA as well as UV-induced chronic skin inflammation, accelerated keratinocyte proliferation, inhibited apoptosis, and immunosuppression seem to underlie the UV-induced carcinogenesis. Also, UVB induces cytochrome P450 subfamilies (CYP1A1 and CYP1B1) involved in metabolic activation of organic pro-carcinogens and their conversion to ultimate carcinogens. Here, the effects of several glycosylated and non-glycosylated plant polyphenols (verbascoside, resveratrol, polydatin, rutin, and quercetin) on the inflammatory, apoptotic, metabolic, and proliferative responses of cultured human epidermal keratinocytes (HEK) to non-cytotoxic doses of solar-simulated UVA+UVB and chemical mediators of UV signalling in HEK, 6-formylindolo[3,2-b]carbazole and squalene isolated from photo-oxidized skin surface lipids (SSL), were evaluated. We showed that the stilbenes and quercetin being exposed to UV were photo-destroyed within a short period of time, while verbascoside and rutin were photo-stable. When SSL were exposed to UV, the stilbenes and quercetin remarkably accelerated photo-oxidation of alpha-tocopherol, squalene, and cholesterol fractions, whilst verbascoside protected them. Verbascoside invariably inhibited molecular pathways in HEK leading to inflammatory cytokine expression (NFkappaB and EGFR/ERK phosphorylation), and cell proliferation (EGFR nuclear translocation), and displayed a stimulus-specific effect on the metabolic axis aryl hydrocarbon receptor (AhR)-CYP1A1/CYP1B1. By contrast, the stilbenes inhibited UV-connected inflammatory cytokines excluding IL-8, but they prevalently stimulated NFkappaB, EGFR nuclear translocation and the AhR-CYP pathway. We conclude that, among the PPs investigated, verbascoside does interfere with multiple UV-sensitive signalling in HEK in a way that it could have a major impact on skin cancer chemoprevention.

alpha-Fetoprotein as a modulator of the pro-inflammatory response of human keratinocytes.

BACKGROUND AND PURPOSE: The immunomodulatory effects of alpha-fetoprotein (AFP) on lymphocytes and macrophages have been described in vitro and in vivo. Recombinant forms of human AFP have been proposed as potential therapeutic entities for the treatment of autoimmune diseases. We examined the effects of embryonic and recombinant human AFP on the spontaneous, UVA- and cytokine-induced pro-inflammatory responses of human keratinocytes. EXPERIMENTAL APPROACH: Cultures of primary and immortalized human keratinocytes (HaCaT) and human blood T lymphocytes were used. The effects of AFP on cytokine expression were studied by bioplexed elisa and quantitative reverse transcriptase polymerase chain reaction assay. Kinase and nuclear factor kappa B (NFkappaB) phosphorylation were quantified by intracellular elisa. Nuclear activator protein 1 and NFkappaB DNA binding activity was measured by specific assays. Nitric oxide and H(2)O(2) production and redox status were assessed by fluorescent probe and biochemical methods. KEY RESULTS: All forms of AFP enhanced baseline expression of cytokines, chemokines and growth factors. AFP dose-dependently increased tumour necrosis factor alpha-stimulated granulocyte macrophage colony stimulating factor and interleukin 8 expression and decreased tumour necrosis factor alpha-induced monocyte chemotactic protein 1 and IP-10 (interferon gamma-produced protein of 10 kDa) expression. AFP induced a marked activator protein 1 activation in human keratinocytes. AFP also increased H(2)O(2) and modulated nitrite/nitrate levels in non-stimulated keratinocytes whereas it did not affect these parameters or cytokine release from UVA-stimulated cells. Phosphorylation of extracellular signal-regulated kinase (ERK1/2) and Akt1 but not NFkappaB was activated by AFP alone or by its combination with UVA. CONCLUSIONS AND IMPLICATIONS: Exogenous AFP induces activation of human keratinocytes, with de novo expression of a number of pro-inflammatory mediators and modulation of their pro-inflammatory response to cytokines or UVA. AFP may modulate inflammatory events in human skin.