Flavonoids are a group of plant polyphenols and are ubiquitously found in plants. 1,2) Fruits and vegetables, as well as popular beverages such as wine, tea, and coffee, are the main dietary sources of flavonoids. It has been reported that flavonoids show pharmacological effects such as antioxidant, 3,4) antiviral, 5) antitumor, 6) and antiinflammatory activities. 7) In particular, their antioxidant activity has attracted much attention as a possible dietary preventive against cardiovascular and neurodegenerative diseases. 6,8) There are many reports that flavonoids act as antioxidants and protect various cell types from oxidative stress-mediated cell injury. We reported that flavonoids have protective effects on human umbilical vein endothelial (HUVE) cells and rat neuronal cells (PC12) exposed to the highly toxic lipid peroxide linoleic acid hydroperoxide. [9][10][11] In addition, it has been observed that flavonoids suppress the cytotoxicity of hydrogen peroxide toward Chinese hamster cells (V79) 12) and oxidized low-density lipoproteins in human lymphoid cell lines, 13) glucose oxidase-mediated apoptosis in mouse thymocytes, 14) and metal-induced lipid hydroperoxide-dependent lipid peroxidation in a-linoleic acid-loaded rat hepatocytes. 15)On the other hand, it has been suggested that flavonoids act as mutagens, prooxidants, and enzyme inhibitors.16) Further, it has been reported that they exert cytotoxicity at higher concentrations and in the presence of oxidation-catalyzing factors such as transition metal ions. The cytotoxicity of flavonoids toward human promyelocytic leukemia cells (HL-60), 17) human acute myelogeneous leukemia cells (KG1, KG1a, THP-1, and U937), 18) rhesus monkey kidney cells (LLC-MK2), rat glial tumor cells (C6), 19) bovine leukemia virus-transformed lamb embryo kidney fibroblasts (FLK), 20) mouse and hamster pancreatic b-cells (b TC1 and HIT), 21) human fibroblasts (HFK-2), human keratinocytes (HaCaT), human breast cancer adenocarcinoma cells (MCF-7), human neuroblastoma cells (SHEP and WAC-2), and bovine capillary endothelial cells 22) has been found. As shown above, however, there are only a few reports on the cytotoxicity of flavonoids toward human normal cells.If flavonoids are used as dietary factors for health maintenance, relatively large amounts may be ingested. Thus the potentially toxic effects of excessive flavonoid intake must be clarified. 16) In the present paper, we describe the cytotoxicity of nine flavonoids, including the two flavones apigenin and luteolin, the three flavonols 3-hydroxyflavone, kaempherol, and quercetin, the flavonol glycoside rutin, the two flavanones eriodictyol and naringenin, and the flavanol taxifolin (Table 1 and Fig. 1), toward cultured normal human cells, TIG-1 cells and HUVE cells. Further, we examined the intracellular levels of ROS in flavonoid-treated TIG-1 cells using DCF-DA 23) and their incorporation of flavonoids in culture medium. The cytotoxicity of flavonoids, including apigenin, eriodictyol, 3-hydroxyflavone, kaempherol, luteolin,...

We have screened the p53 status of 156 human cell lines, including 142 tumor cell lines from 27 different tumor types and 14 cell lines from normal tissues by using functional analysis of separated alleles in yeast. This assay enables us to score wild-type p53 expression on the basis of the ability of expressed p53 to transactivate the reporter gene HIS3 via the p53-responsive GAL1 promotor in Saccharomyces cerevisiae. Of 142 tumor cell lines, at least 104 lines (73.2%) were found to express the mutated p53 gene: 94 lines (66.2%) were mutated in both alleles, three lines (2.1%) were heterozygous, and no p53 cDNA was amplified from seven lines (4.9%). Of the 14 cell lines originating from normal tissues, all the transformed or immortalized cell lines expressed mutant p53 only. Yeast cells expressing mutant p53 derived from 94 cell lines were analyzed for temperature-sensitive growth. p53 cDNA from eight cell lines showed p53-dependent temperature-sensitive growth, growing at 30 degrees C but not at 37 degrees C. Four temperature-sensitive p53 mutations were isolated: CAT-->CGT at codon 214 (H214R), TAC-->TGC at codon 234 (Y234C), GTG-->ATG at codon 272 (V272M), and GAG-->AAG (E285K). Functionally wild-type p53 was detected in 38 tumor cell lines (26.8%) and all of the diploid fibroblasts at early and late population doubling levels. These results strongly support the previous findings that p53 inactivation is one of the most frequent genetic events that occurs during carcinogenesis and immortalization.

No abstract

Although it has been reported that hypoxia inducible factor 2 α (Hif2a), a major transcriptional factor inducible by low oxygen tension, is expressed in the mouse uterus during embryo implantation, its role in pregnancy outcomes remains unclear. This study aimed to clarify functions of uterine HIF using transgenic mouse models. Mice with deletion of Hif2a in the whole uterus (Hif2a-uKO mice) showed infertility due to implantation failure. Supplementation with progesterone (P4) and leukemia inhibitory factor (LIF) restored decidual growth arrest and aberrant position of implantation sites in Hif2a-uKO mice, respectively, but did not rescue pregnancy failure. Histological analyses in Hif2a-uKO mice revealed persistence of the intact luminal epithelium, which blocked direct contact between stroma and embryo, inactivation of PI3K-AKT pathway (embryonic survival signal), and failed embryo invasion. Mice with stromal deletion of Hif2a (Hif2a-sKO mice) showed infertility with impaired embryo invasion and those with epithelial deletion of Hif2a (Hif2a-eKO mice) showed normal fertility, suggesting the importance of stromal HIF2α in embryo invasion. This was reflected in reduced expression of membrane type 2 metalloproteinase (MT2-MMP), lysyl oxidase (LOX), VEGF, and adrenomedullin (ADM) in Hif2a-uKO stroma at the attachment site, suggesting that stromal HIF2α regulates these mediators to support blastocyst invasion. These findings provide new insight that stromal HIF2α allows trophoblast invasion through detachment of the luminal epithelium and activation of an embryonic survival signal.

The effects of atmospheric oxygen on the life span and aging rate of the nematode Caenorhabditis elegans were examined. The mean and maximum life spans of both the wild type and mev-1(kn1) mutant, whose cytoplasmic superoxide dismutase activity level is about half of the wild type, were increased and decreased under low and high concentrations of oxygen, respectively. The Gompertz component, a parameter of aging rate, of the wild type was smaller under 1% oxygen than under 2% or more oxygen. Further, the Gompertz component of the mutant increased with an increase in oxygen concentration. These effects of oxygen on the perturbation of life span and aging rate were more pronounced in the mev-1(kn1) mutant than in the wild type. The oxygen-dependent perturbation of life span and aging rate seems to be enhanced by a genetic defect of the mutant in antioxidant defense. A 1% oxygen exposure at the early phase of life span was ineffective for life span extension in the mutant, suggesting that the effect of oxygen concentrations on life span is not secondary to the effects of development and maturation. These results show that changes in oxygen concentration perturb aging rate, and hence oxygen is involved in the specification of life span of the nematode.