Inhibition of contact dermatitis in animal models and suppression of proinflammatory gene expression by topically applied flavonoid, wogonin.

Wogonin (5,7-dihydroxy-8-methoxyflavone) is a down-regulator of cyclooxygenase-2 and inducible nitric oxide synthase expression, contributing to anti-inflammatory activity in vivo. For further characterization of modulatory activity on proinflammatory gene expression in vivo, the effect of wogonin was examined in this experiment using animal models of skin inflammation. By topical application, wogonin inhibited an edematic response as well as proinflammatory gene expression against contact dermatitis in mice. Wogonin inhibited ear edema (19.4-22.6%) at doses of 50-200 microg/ear and down-regulated interleukin-1beta induction (23.1%) at 200 microg/ear in phenol-induced simple irritation. Wogonin (2x50-2x200 microg/ear) also inhibited edematic response (51.2-43.9%) and down-regulated proinflammatory gene expression of cyclooxygenase-2, interleukin-1beta, interferon-gamma, intercellular adhesion molecule-1 and inducible nitric oxide synthase with some different sensitivity against picryl chloride-induced delayed hypersensitivity reaction. All these results clearly demonstrate that wogonin is a down-regulator of proinflammatory gene expression in animal models of skin inflammation. Therefore, wogonin may have potential for a new anti-inflammatory agent against skin inflammation.