Masao Inagake

Inhibition of 1,2-dimethylhydrazine-induced oxidative DNA damage by green tea extract in rat.

Following subcutaneous injection of 1,2‐dimethylhydrazine (DMH), which is carcinogenic to rat colon and liver, to Sprague‐Dawley rats, a significant increase of 8‐hydroxydeoxyguanosine (8‐OHdG) was observed in the DNA of colonic mucosa and liver. The 8‐OHdG formation reached the maximal level at about 24 h after the DMH injection. On the other hand, no increase of 8‐OHdG was observed in the DNA of the kidney. Drinking green tea extract (GTE) for ten days prior to the DMH injection significantly inhibited the formation of 8‐OHdG in the colon. These findings demonstrate that DMH causes oxidative damage to the DNA of its target organ, and that GTE protects colonic mucosa from this oxidative damage.

Inhibition of mucosal lipid hyperoxidation by green tea extract in 1,2-dimethylhydrazine-induced rat colonic carcinogenesis

Phosphatidylcholine hydroperoxide (PCOOH) measured using a chemiluminescence detector to examine colonic mucosal lipid hyperoxidation increased after injection of 1,2-dimethylhydrazine and green tea extract (GTE), which we previously showed inhibited carcinogenesis and oxidative DNA damage in the gastrointestinal tract. Therefore, the hyperoxidation of membrane phospholipids reflected well the degree of DNA damage and carcinogenic alteration, and may be a useful intermediate biomarker for initiation of carcinogenesis.

Immunohistochemical staining and activity of ornithine decarboxylase in colorectal cancer

Using a new anti-human ornithine decarboxylase (anti-hODC) monoclonal antibody, the relationship between the immunoreactivity of ODC and its activity was analyzed in 21 human colorectal cancer tissues, 42 adjacent non-tumorous mucosa specimens, and 10 normal rectal mucosa samples from frozen sections and paraffin-embedded samples. A statistical significant correlation was found between the antibody reaction and the enzymic activity (P < 0.01). The immunohistochemical staining for ODC provides a new and simplified procedure for studying the activity of ODC as compared to previous methods using radioisotopes. It offers the advantages of retrospectively determining the amount of ODC in samples previously embedded in paraffin.

Inhibitory Effect of Green Tea Extract Against Azoxymethane-Induced Colon Carcinogenesis in Rat

We investigated the effect of green tea polyphenol (GTP) on azoxymethane(AOM)-induced colon carcinogenesis in male Fisher rats. AOM was given (7.4mg/kg body weight) s.c. once a week for ten weeks. A week after the treatment, they were divided into three groups. AOM-GTP1 and AOM-GTP2 groups received 0.01 and 0.1% GTP in drinking water respectively from weeks 11 to 26. The AOM-control group received tap water. The tumor incidence in the AOM-GTP1 and AOM-GTP2 groups was significandy lower than that of the AOM-control group. We concluded that GTP supprssed AOM-induced colon carcinogenesis.