Hideki Mori

Silymarin, a naturally occurring polyphenolic antioxidant flavonoid, inhibits azoxymethane‐induced colon carcinogenesis in male F344 rats

The modifying effect of dietary administration of the polyphenolic antioxidant flavonoid silymarin, isolated from milk thistle [Silybum marianum (L.) Gaertneri], on AOM‐induced colon carcinogenesis was investigated in male F344 rats. In the short‐term study, the effects of silymarin on the development of AOM‐induced colonic ACF, being putative precursor lesions for colonic adenocarcinoma, were assayed to predict the modifying effects of dietary silymarin on colon tumorigenesis. Also, the activity of detoxifying enzymes (GST and QR) in liver and colonic mucosa was determined in rats gavaged with silymarin. Subsequently, the possible inhibitory effects of dietary feeding of silymarin on AOM‐induced colon carcinogenesis were evaluated using a long‐term animal experiment. In the short‐term study, dietary administration of silymarin (100, 500 and 1,000 ppm in diet), either during or after carcinogen exposure, for 4 weeks caused significant reduction in the frequency of colonic ACF in a dose‐dependent manner. Silymarin given by gavage elevated the activity of detoxifying enzymes in both organs. In the long‐term experiment, dietary feeding of silymarin (100 and 500 ppm) during the initiation or postinitiation phase of AOM‐induced colon carcinogenesis reduced the incidence and multiplicity of colonic adenocarcinoma. The inhibition by feeding with 500 ppm silymarin was significant (p < 0.05 by initiation feeding and p < 0.01 by postinitiation feeding). Also, silymarin administration in the diet lowered the PCNA labeling index and increased the number of apoptotic cells in adenocarcinoma. β‐Glucuronidase activity, PGE2 level and polyamine content were decreased in colonic mucosa. These results clearly indicate a chemopreventive ability of dietary silymarin against chemically induced colon tumorigenesis and will provide a scientific basis for progression to clinical trials of the chemoprevention of human colon cancer.

Neuronal degradation in mouse retina after a transient ischemia and protective effect of hypothermia

Abstract Temporal profile of neuronal deaths in the mouse retina evoked by a transient retinal ischemia and the protective effect of hypothermia on such deaths were evaluated. A transient ischemic insult was induced in the mouse retina by elevating the intra-ocular pressure. The retina tissue responses after reperfusion were histopathologically detected by monitoring the retinal cell death in the ganglion cell layer and inner nuclear layer, using a sequential TUNEL-staining technique, and by measuring the inner retinal thickness. Elevation of intra-ocular pressure induced a time-related appearance of TUNEL-positive cells in the mouse inner retinas. Peak TUNEL staining occurred 12 h after reperfusion. Lowering mice body temperature to 35°C, 33°C and 29°C during the ischemia period significantly inhibited DNA fragmentation of retinal neurons in a lowering temperature dependent manner. In this experiment, the inner retinal thickness was preserved in 29°C group compared with that in 37°C group. From these results, the 45-min transient ischemia and histopathological examination 12 h later provided a reproducible number of retinal neuronal deaths. Furthermore, hypothermic intervention showed a protective effect to salvage retinal neuronal cells from a transient ischemic insult.

A bitter diterpenoid furanolactone columbin from Calumbae Radix inhibits azoxymethane-induced rat colon carcinogenesis

The modifying effect of dietary administration of a diterpenoid furanolactone columbin isolated from the crude drug Calumbae Radix (the root of Jateorhiza columba MIERS, Menispermacea) on azoxymethane (AOM)-induced was investigated in male F344 rats. Animals were initiated with AOM (three weekly subcutaneous injections of 15 mg/kg body weight) to induce colonic neoplasms. They were fed the experimental diets mixed with columbin (4, 20, and 100 ppm) for 4 weeks, starting 1 week before the first dosing of AOM and thereafter maintained on the basal diet without columbin. Additional experimental groups included the AOM alone group, the columbin alone group (100 ppm in diet for 4 weeks), and the untreated control group. Dietary feeding of columbin (4, 20, and 100 ppm) during the initiation phase of AOM-induced colon carcinogenesis reduced the incidence and multiplicity of colonic adenocarcinoma and the inhibition by feeding of 20 ppm (incidence: 20%, P=0.0242 and multiplicity: 0.20+/-0.40, P<0.02) and 100 ppm (incidence: 10%, P=0.0029 and multiplicity: 0.10+/-0.30, P<0.002) columbin was significant when compared with the AOM alone group (incidence: 55% and multiplicity: 0.55+/-0.50). Also, columbin administration in diet lowered the number of argyrophilic nucleolar organizer regions protein per nucleus in non-lesional colonic crypts and the blood polyamine content, which are reflected in cell proliferation activity. These results indicate chemopreventive ability of dietary columbin against chemically induced colon tumorigenesis when fed during the initiation phase, providing a scientific basis for chemopreventive ability of columbin against human colon cancer.

Induction of Apoptosis by Sulindac in Azoxymethane‐induced Possible Colonic Premalignant Lesions in Rats

We have reported that β‐catenin‐accumulated crypts (BCAC), which do not have the appearance of aberrant crypt foci (ACF) are possible colonic premalignant lesions in rats. Suppression of the occurrence and advancement of such lesions should have critical relevance to cancer prevention. This study examined whether sulindac, a chemopreventive nonsteroidal anti‐inflammatory drug is able to induce apoptosis in such premalignant lesions. At 6 weeks of age, rats groups 1–3 were given azoxymethane (AOM) (15 mg/kg‐body weight) once weekly for 3 weeks. Two groups were given sulindac in the diet (200 and 400 ppm), starting at 9 weeks of age. The rats were sacrificed at the termination, and the colons were carefully examined. The incidence and crypt multiplicity of BCAC and ACF were significantly less than those of the control group. The effect of sulindac on the expression of BCAC was greater than that on ACF. Exposure to sulindac significantly increased the apoptotic index (terminal deoxynucleotide transferase dUTP nick‐end labeling (TUNEL)‐positive cells) in BCAC. However, no significant increase of the index was found in the case of ACF. These results suggest that the chemopreventive effect of sulindac in rats is related to the induction of apoptosis in premalignant lesions. Our results also provide additional evidence that BCAC are premalignant lesions in colon carcinogenesis in rodents.