Chemoprevention of Colon Carcinogenesis by Oleanolic Acid and Its Analog in Male F344 Rats and Modulation of COX-2 and Apoptosis in Human Colon HT-29 Cancer Cells
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To assess the chemopreventive effect of oleanolic acid (ONA) and its synthetic analog 18α-olean-12-ene-3β-23,28-triol (OT) on azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) in F344 rats and understand anti-inflammatory properties and apoptosis effects in HT29 colon cancer cells and Raw 264.7 macrophage cell lines.
Five week-old male F344 rats were fed a control diet or experimental diets containing two doses of ONA (750 and 1,500 ppm) and OT (250 and 500 ppm). After 1 week, all animals were s.c. injected with AOM (15 mg/kg body weight, once weekly for 2 weeks). At 14 weeks of age, all rats were killed and colons were evaluated for ACF. Cyclooxygenase (COX)-2, inducible nitric oxide synthase (iNOS) expressions and apoptosis were assessed in cell lines exposed to OT using western blots and 4’,6-diamidino-2-phenylindole staining.
Administration of ONA and OT inhibited mean colonic ACF and multi-crypt AC/foci in a dose dependent manner (p < 0.001–0.0001). OT blocked the COX-2 expression induced by phorbol 12-myristate 13-acetate in a dose-dependent manner and induced apoptosis in HT-29 cancer cells, and suppressed iNOS activation in RAW264.7 macrophages.
ONA and OT possess chemopreventive activity against colon carcinogenesis in rat and OT inhibits the COX-2 and iNOS and induces apoptosis in cell lines.