Among ethanol extracts of 10 edible berries, bilberry extract was found to be the most effective at inhibiting the growth of HL60 human leukemia cells and HCT116 human colon carcinoma cells in vitro. Bilberry extract induced apoptotic cell bodies and nucleosomal DNA fragmentation in HL60 cells. The proportion of apoptotic cells induced by bilberry extract in HCT116 was much lower than that in HL60 cells, and DNA fragmentation was not induced in the former. Of the extracts tested, that from bilberry contained the largest amounts of phenolic compounds, including anthocyanins, and showed the greatest 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. Pure delphinidin and malvidin, like the glycosides isolated from the bilberry extract, induced apoptosis in HL60 cells. These results indicate that the bilberry extract and the anthocyanins, bearing delphinidin or malvidin as the aglycon, inhibit the growth of HL60 cells through the induction of apoptosis. Only pure delphinidin and the glycoside isolated from the bilberry extract, but not malvidin and the glycoside, inhibited the growth of HCT116 cells.
We investigated the growth inhibitory activity of several flavonoids, including apigenin, luteolin, kaempherol, quercetin, butein, isoliquiritigenin, naringenin, genistein, and daizein against B16 mouse melanoma 4A5 cells. Isoliquiritigenin and butein, belonging to the chalcone group, markedly suppressed the growth of B16 melanoma cells and induced cell death. The other flavonoids tested showed little growth inhibitory activity and scarcely caused cell death. In cells treated with isoliquiritigenin or butein, condensation of nuclei and fragmentation of nuclear DNA, which are typical phenomena of apoptosis, were observed by Hoechst 33258 staining and by agarose gel electrophoresis of DNA. Flowcytometric analysis showed that isoliquiritigenin and butein increased the proportion of hypodiploid cells in the population of B16 melanoma cells. These results demonstrate that isoliquiritigenin and butein inhibit cell proliferation and induce apoptosis in B16 melanoma cells. Extracellular glucose decreased the proportion of hypodiploid cells that appeared as a result of isoliquiritigenin treatment. p53 was not detected in cells treated with either of these chalcones, however, protein of the Bcl-2 family were detected. The level of expression of Bax in cells treated with either of these chalcones was markedly elevated and the level of Bcl-XL decreased slightly. Isoliquiritigenin did not affect Bcl-2 expression, but butein down-regulated Bcl-2 expression. From these results, it seems that the pathway by which the chalcones induce apoptosis may be independent of p53 and dependent on proteins of the Bcl-2 family. It was supposed that isoliquiritigenin induces apoptosis in B16 cells by a mechanism involving inhibition of glucose transmembrane transport and promotion of Bax expression. On the other hand, it was suggested that butein induces apoptosis via down-regulation of Bcl-2 expression and promotion of Bax expression. This mechanism differs from the isoliquiritigenin induction pathway.
The effect of dietary flavonoids (flavone, isoflavone, flavanone, chalcone, flavonol, and flavonol derivatives) on the differentiation of 3T3-L1 adipocytes was investigated. Glycerol-3-phosphate dehydrogenase (GPDH) activity, which is a hallmark of 3T3-L1 differentiation, was measured. The GPDH activity in the cells treated with quercetin, kaempferol, and isorhamnetin was significantly lower than that in the control cells. A low lipid accumulation in cells stained with Oil-Red O was observed following treatment of these flavonols. The anti-differentiation action of quercetin was more potent than that of its derivatives. Quercetin directly inhibited the activity of GPDH extracted from mature 3T3-L1 adipocytes. The inhibitory action of quercetin on the differentiation of 3T3-L1 cells may involve the direct inhibition of GPDH, which is a key enzyme lipid synthesis.
The activities of hepatic cytosolic glutathione S-transferases (GSTs) towards 1,2-dichloro-4-nitrobenzene in male rats were higher than those in females, however, the enzyme activities towards 1-chloro-2,4-dinitrobenzene were not significantly different between the two sexes. SDS-PAGE analysis of GSTs purified from male and female rat hepatic cytosols by affinity column chromatography showed that there was a significant difference in the subunit composition between the two sexes. With regard to the several isozymes of GSTs in male and female rats, isozymes with basic and neutral/acidic isoelectric points were separated into seven molecular species by chromatofocusing. These sex differences in the quantitative proportions of GST isozymes were also confirmed by immunotitration using anti-GST-BL and -AC antibodies. On the other hand, glutathione peroxidase (GSH-Px) activities in rat hepatic cytosol towards hydrogen peroxide and cumene hydroperoxide were markedly higher in females than in males. Of the two types of GSH-Px, selenoenzyme (Se-GSH-Px) and the Se-independent enzyme (non-Se-GSH-Px), the former was found to be mainly responsible for the sex difference in the enzyme activities. Moreover, the GSH-Px activity of GSTs, non-Se-GSH-Px, was also higher in females than that in males. Since GST isozymes of the BL type are known to possess GSH-Px activity towards cumene hydroperoxide, the increased activities of non-Se-GSH-Px in the female hepatic cytosol seemed to be mainly due to the increased transferase activities of the isozymes, GST-L2 and -BL.
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