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Suppression of azoxymethane-induced preneoplastic lesions and inhibition of cyclooxygenase-2 activity in the colonic mucosa of rats drinking a crude green tea extract

Metz, N., Lobstein, A., Schneider, Y., Gosse, F., Schleiffer, R., Anton, R., Raul, F.
Nutrition and cancer 2000 v.38 no.1 pp. 60-64
tea, plant extracts, intestinal mucosa, diet, experimental diets, colon, oxygenases, enzyme activity, rats, animal models
We determined the effects of a crude green tea extract given as drinking fluid on the promotion/progression phase of colon carcinogenesis in rats after induction of the neoplastic process by azoxymethane. Adult Wistar rats were given azoxymethane (15 mg/kg ip) once a week for two weeks. One week after the second injection, the rats were randomly divided into two groups. One group (n = 8) received daily prepared aqueous solutions of green tea extracts (GTE; 0.02%, wt/vol); the control group (n = 8) received tap water. After six weeks, rats receiving GTE showed a 60% reduction in the number of colonic preneoplastic lesions (aberrant crypts). The number of individual crypts per aberrant crypt focus (crypt multiplicity) was significantly reduced in the GTE group; the majority (80%) of the remaining aberrant foci contained only one or two preneoplastic crypts. A significant and selective decrease of cyclooxygenase (COX)-2 activity was observed in the colon of rats receiving GTE (23 +/- 3 vs. 117 +/- 30 mU/mg protein in controls), whereas COX-1 showed no alterations. Our data demonstrate that GTE reduces COX-2 and suppresses the formation of colonic preneoplastic lesions. They provide new insights into the mechanism of chemopreventive and anti-inflammatory properties of green tea.