Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/9/2010
Publication Date: 9/30/2010
Citation: Choi, S., Kim, S., Kang, M., Nam, S., Friedman, M. 2010. Protective effects of black rice bran against chemically-induced inflammation of mouse skin. Journal of Agriculture and Food Chemistry. 58:10007-10015. Interpretive Summary: Rice (Oryza sativa L.) is a basic food for a large part of the world’s population, especially in Asia. Rice bran is a rich source of a large number of bioactive secondary metabolites. Major bioactive components of black rice are anthocyanin pigments, whereas those in brown rice are simple phenolic compounds. These rice bran ingredients and dark rice brans have been shown to possess a number of health-promoting functions. To further demonstrate the beneficial potential of dark rice brans, we are collaborating with colleagues at Korean universities and at the Rice Research Unit, ARS, Beaumont, Texas on the antimicrobial, antitoxin, and other beneficial effects of pigmented rice brans obtained from newly developed genetic rice varieties. The results of the present study carried out in Korea show that oral feeding of a standard mice diet supplemented with 10% black rice bran significantly suppressed chemically-induced inflammation of the ear skin in mice as compared to that observed with the diet without black rice bran. By contrast, the diet with 10% brown rice bran did not suppress the inflammation. Because prolonged inflammation is associated with the development of allergies, atherosclerosis, cancer, heart and infectious diseases, it would be of interest to evaluate the potential of black rice bran-containing foods to prevent or treat these disorders.
Technical Abstract: We investigated the inhibitory effects of black rice (cv. LK1-3-6-12-1-1) bran against 12-O-tetradecanolylphorbol-13-acetate (TPA)-induced skin edema and 2,4-dinitroflurobenzene (DNFB)-induced allergic contact dermatitis (ACD) in inflammatory mouse models. We also determined the effects of the bran extract on the following biomarkers: pro-inflammatory cytokines tumor necrosis factor-a (TNF-a), interleukin-1ß (IL-1ß), interleukin-6 (IL-6), eicosanoids leukotriene B4 (LTB4), and prostaglandin E2 (PGE2). Topical application of TPA to ears of CD-1 mice induced inflammation accompanied with substantial increase in TNF-a, IL-1ß, IL-6, LTB4 and PGE2 levels and an elevation in intercellular adhesion molecule-1 (ICAM-1) gene expressions in ear skin tissues. Intraperitoneal injection of black rice bran extract prior to TPA application in mice significantly suppressed TPA-induced inflammation (edema) and induced a marked decrease in the production of TNF-a, IL-1ß, IL-6, and LTB4. Feeding mice a standard diet with added 10% black rice bran also significantly suppressed DFNB-induced allergic contact dermatitis on the skin of the mice. By contrast, a non-pigmented brown rice bran extract did not inhibit the TPA-induced edema and failed to significantly suppress production of pro-inflammatory biomarkers (mediators). These in vivo findings further demonstrate the potential value of black rice bran as an anti-inflammatory and anti-allergic food ingredient and possibly also as a therapeutic agent for the treatment and prevention of diseases associated with chronic inflammation.