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Oxidative stress and inflammatory tissue damage are two major events frequently implicated in carcinogenesis. Numerous polyphenolic compounds derived from plants possess antioxidant and anti-inflammatory activities and are hence effective in preventing cancer. Oligonol is a polyphenol formulation enriched with catechin-type oligomers. As an initial approach to assess the chemopreventive potential of oligonol, we have determined its effects on inflammatory as well as oxidative damage in mouse skin irradiated with UVB. Topical application of oligonol onto the dorsal skin of male HR-1 hairless mice 30 min prior to UVB exposure diminished epidermal hyperplasia and formation of 4-hydroxynonenal, a biochemical hallmark of lipid peroxidation. Topical application of oligonol also significantly inhibited UVB-induced cyclooxygenase (COX-2) expression in mouse skin. Oligonol diminished the DNA binding of activator protein-1 (AP-1) and CCAAT/enhancer binding protein (C/EBP), and the expression of C/EBPdelta in mouse skin exposed to UVB. Our study also revealed that oligonol attenuated UVB-induced catalytic activity as well as expression of p38 mitogen-activated protein (MAP) kinase. Moreover, UVB-induced phosphorylation of another upstream kinase Akt was attenuated by oligonol. Taken together, oligonol showed antioxidative and anti-inflammatory effects in UVB-irradiated mouse skin by inhibiting COX-2 expression via blockade of the activation of AP-1 and C/EBP, and upstream kinases including p38 MAP kinase and Akt.

Exposure to ultraviolet B (UVB) radiation is known to cause inflammatory tissue damage and skin cancer. One of the molecular links between inflammation and cancer is the eukaryotic transcription factor nuclear factor-kappaB (NF-κB), which is known to regulate expression of various pro-inflammatory genes including inducible nitric oxide synthase (iNOS). The present study was aimed at elucidating the molecular mechanisms underlying UVB-induced NF-κB activation and iNOS expression in hairless mouse skin. Irradiation of male HR-1 hairless mouse skin with UVB (5 kJ/m(2) ) resulted in increased degradation of IκBα, nuclear translocation of p65 and p50, and the DNA binding of NF-κB. Exposure to UVB radiation induced the phosphorylation and the catalytic activity of an upstream kinase IκB kinase-β (IKKβ). Pharmacological inhibition of IKKβ attenuated UVB-induced NF-κB activation in mouse skin. Irradiation of mouse skin with UVB also increased phosphorylation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein (MAP) kinase. Pretreatment with SC-514, a specific inhibitor of IKKβ, attenuated UVB-induced phosphorylation of ERK and p38 MAP kinase. A kinetic study showed that UVB significantly increased the expression of iNOS in mouse skin at 6 h postirradiation, which was abrogated by pretreatment with SC-514. In conclusion, the upstream kinase IKKβ is involved in UVB-induced activation of MAP kinases and NF-κB, and expression of iNOS in mouse skin.

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