Suppression of azoxymethane-induced preneoplastic lesions and inhibition of cyclooxygenase-2 activity in the colonic mucosa of rats drinking a crude green tea extract.
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 i.p.) 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.
Metz
N
N
Laboratoire du Contrôle Métabolique et Nutritionnel en Oncologie Digestive de l'Université Louis Pasteur, Institut de Recherche contre les Cancers de l'Appareil Digestif, 67091 Strasbourg, France.
Lobstein
A
A
Schneider
Y
Y
Gossé
F
F
Schleiffer
R
R
Anton
R
R
Raul
F
F
D000818:Animals; D001397:Azoxymethane / Q000633:toxicity; D002273:Carcinogens / Q000633:toxicity; D003106:Colon / Q000187:drug effects / Q000201:enzymology*; D003110:Colonic Neoplasms / Q000139:chemically induced / Q000517:prevention & control*; D051546:Cyclooxygenase 2; D007413:Intestinal Mucosa / Q000187:drug effects / Q000201:enzymology; D007527:Isoenzymes / Q000037:antagonists & inhibitors*; D008297:Male; D010936:Plant Extracts / Q000494:pharmacology / Q000627:therapeutic use*; D011230:Precancerous Conditions / Q000139:chemically induced / Q000517:prevention & control*; D011451:Prostaglandin-Endoperoxide Synthases; D051381:Rats; D017208:Rats, Wistar; D013662:Tea / Q000737:chemistry*
D002273:Carcinogens; D007527:Isoenzymes; D010936:Plant Extracts; D013662:Tea; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D001397:Azoxymethane