| Objective: The aim of this part was to establish a close colorectal cancer(CRC) model of Sprague-Dawley(S-D) rats resemble to human disease and detect the changes of host immune in the process of experimental CRC formation .Method: CRC was induced consistently in experimental S-D rats by carcinogen DMH. Ten rats were randomly divided into two groups and five of each: (1) Control groups, (2) DMH groups. DMH groups received s.c. DMH at the dose of 20mg/kg body weight once weekly for 20 weeks, and Control groups received equal volume of 1mmol/L ethylene diamine tetraacetic acid (EDTA). Tumorigenesis of rat colorectal was observed and further proved by pathology in 21 weeks. CD3+,CD3+CD4+,CD3+CD8+,CD3+CD25+ in peripheral blood were ere analyzed by flow cytometry (FCM) in 16 weeks and 21 weeks. CD3+,CD3+CD4+,CD3+CD8+,CD3+CD25+ in spleen and interferon-γ(IFN-γ) from PHA-stimulated splenocyte were ere analyzed by FCM and enzyme linked immunosorbent assay(ELISA) respectively in 21 weeks.Results: All rats in DMH groups developed CRC and only two adenomas were found in one rat of control group at the end of the experiment. CRC incidence of DMH group was 100%(5/5). The ratio of CD3+ and CD3+CD4+of DMH group in peripheral blood was lower than that of control group in 16 weeks, but no significantly different was found(P>0.05).In 21 weeks, CD3+CD4+, CD4/CD8 in peripheral blood and CD3+CD4+, CD3+CD25+, CD4/CD8 in spleen of DMH groups were significantly lower than that of control groups(P<0.05). The secretion of IFN-γfrom splenocytes after phytohemagglutinin (PHA) stimulation for 72 hours was significantly lower in DMH group than that of control group in 21 weeks (P<0.01). Conclusion: A model of CRC was established. And immune suppression is associated with DMH induced rat CRC which resemble to hunman CRC.Objective: Evidence indicates that tea polyphenols(TPs) could enhance host immune functions .As we have proved in partâ… that immune suppression is associated with DMH induced rat CRC which resemble to hunman CRC.In this part we studied immune influence and evaluated chemoprevention effects of TPs in experimental CRC formation.Method: CRC was induced consistently in experimental S-D rats by the carcinogen DMH. Ten rats were randomly divided into two groups and five of each: (1) DMH groups, (2)TPs groups. Rats in both groups received s.c. DMH at the dose of 20mg/kg body weight once weekly for 20 weeks. Throughout the experiment, rats in TPs groups were supplied with 0.1%(W/V) tea polyphenols in tap water as the sole source of drinking fluid, and DMH groups were supplied with the same tap water. Tumour formation of rat colorectal was observed and further proved by Pathology in 21 weeks. CD3+,CD3+CD4+,CD3+CD8+,CD3+CD25+ in peripheral blood were ere analyzed by FCM in 16 weeks and 21 weeks. CD3+,CD3+CD4+,CD3+CD8+,CD3+CD25+ in spleen and IFN-γfrom PHA-stimulated splenocyte were ere analyzed by FCM and ELISA respectively in 21 weeks.Results: All rats in DMH groups and TPs groups developed large bowel neoplasm in 21 weeks. The average number of large bowel neoplasmat and CRC in TPs groups was significantly lower than that of DMH groups(P<0.05). CRC incidence of DMH group and TPs groups was 100%(5/5) and 80%(4/5) respectively which was proved by pathology. Dukes' stage of TPs groups has a better appearance than DMH groups. Most rats in TPs groups is B-C while most in DMH group is D.CD3+CD25+ of TPs groups in peripheral blood was significantly higher than that of DMH group in 16 weeks(P<0.05). In 21 weeks, CD3+CD4+, CD4/CD8 in peripheral blood and CD3+CD4+, CD3+CD25+, CD4/CD8 in spleen of TPs groups were significantly higher than that of DMH group(P<0.05). The secretion of IFN-γfrom splenocytes after PHA stimulation for 72 hours was significantly higher in TPs groups than that of DMH groups in 21 weeks(P<0.01).Conclusion: (1)TPs have properties of up-regulating host cellular immune functions. (2)TPs have been shown to inhibit the development of DMH induced rat CRC. |
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