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Biomedical subjects

Kiyoshi Egawa

Publications and source records attributed to Kiyoshi Egawa.

9 recordsLinked to original sources
PubMed2007

Induction of matrix metalloproteinase gene expression in an endothelial cell line by direct interaction with malignant cells.

Mouse endothelial TKD2 cells in monolayers were cocultured with various human cell lines for 24 h, and the expression of several secreted matrix metalloproteinases (MMP) and cell adhesion molecules was examined by real-time reverse transcription-polymerase chain reaction using mouse-specific primers. Coculture with normal fibroblasts did not elicit the expression of these molecules, but coculture with cancer cells induced the expression of MMP-3, MMP-9 and MMP-10 mRNA in endothelial cells, and in normal mouse embryonic fibroblasts. The induction of MMP mRNA was dependent on direct cell adhesion, as separate culture of A549 cells in Boyden chambers did not induce MMP mRNA, and neutralizing antibody against VLA-4 abolished the induction. An inhibitor of phosphatidylinositol-3-phosphate kinase strongly suppressed the induction of MMP-3, MMP-9 and MMP-10 mRNA, and expression of the dominant-negative mutant of phosphatidylinositol-3-phosphate kinase also decreased the induction. It was suggested that intracellular reactive oxygen species (ROS) levels were increased in TKD2 cells following adhesion to cancer cells. ROS scavengers decreased the levels of MMP induction, and roterone, an inhibitor of mitochondrial complex I, strongly suppressed the induction of MMP-3, MMP-9 and MMP-10. The depletion of mitochondria in TKD2 cells decreased the induction of MMP-9, but the induction of MMP-3 and MMP-10 was not affected. These results indicate that the adhesion of cancer cells to endothelial cells activates several distinct signaling pathways to induce MMP gene expression, and the pathways for MMP-3, MMP-9 and MMP-10 are partly different. For the induction of MMP-9, mitochondria participate in induction, possibly through the production of ROS.

Animals↗
PubMed2006

Inhibition of angiogenesis and HIF-1alpha activity by antimycin A1.

We identified antimycin A1 as an inhibitor of the hypoxia-response element (HRE) from screening using a reporter under the control of HRE under hypoxic conditions. Antimycin A1 was effective at 20 pg/ml in inhibiting the reporter activity. The expression of vascular endothelial growth factor (VEGF) mRNA during hypoxia was also inhibited by antimycin A1. Angiogenesis induced by implantation of mouse sarcoma-180 cells was significantly inhibited by non-toxic doses of antimycin A1. Hypoxia inducible factor (HIF)-1alpha protein levels were significantly decreased by antimycin A1, but its mRNA level was not affected. Antimycin A1 is known to be an inhibitor of mitochondrial electron transport system, and depletion of mitochondria abolished antimycin A1-effect, at least in part. Inhibitors of proteasome or protein synthesis did not affect the decrease in HIF-1alpha level induced by antimycin A1. These results indicate that antimycin A1 inhibited angiogenesis through decrease in VEGF production caused by inhibition of HIF-1alpha activation.

Animals↗
PubMed2006

Anthracyclines, small-molecule inhibitors of hypoxia-inducible factor-1 alpha activation.

Hypoxia-inducible factor-1 (HIF-1) is a central mediator of cellular responses to low oxygen and has recently become an important therapeutic target for solid tumor therapy. To identify small molecule inhibitors of the HIF-1 transcriptional activation, we have established a high through-put assay system using a stable transformant of mammalian cells that express the luciferase reporter gene construct containing a HIF-1 binding site. Using this system, we screened 5000 cultured broths of microorganisms, and we found that cinerubin (1-hydroxy aclacinomycin B) showed a significant inhibition of the reporter activity induced by hypoxic conditions. In addition, we demonstrated that aclarubicin also inhibited the HIF-1 transcriptional activity under hypoxic conditions, but neither doxorubicin nor daunorubicin inhibited it. Consistent with these results, cinerubin and aclarubicin inhibited the hypoxic induction of the vascular endothelial growth factor (VEGF) protein in HepG2 cells, but neither doxorubicin nor daunorubicin affected it. Thus, our results suggested that some anthracyclines are also acting as angiogenesis inhibitors.

Animals↗
PubMed2005

Dynamic statistical parametric mapping for analyzing the magnetoencephalographic epileptiform activity in patients with epilepsy.

Our current purpose is to evaluate the applicability of dynamic statistical parametric mapping, a novel method for localizing epileptiform activity recorded with magnetoencephalography in patients with epilepsy. We report four pediatric patients with focal epilepsies. Magnetoencephalographic data were collected with a 306-channel whole-head helmet-shaped sensor array. We calculated equivalent current dipoles and dynamic statistical parametric mapping movies of the interictal epileptiform discharges that were based in the minimum-L2 norm estimate, minimizing the square sum of the dipole element amplitudes. The dynamic statistical parametric mapping analysis of interictal epileptiform discharges can demonstrate the rapid change and propagation of interical epileptiform discharges. According to these findings, specific epileptogenic lesion-focal cortical dysplasia could be found and patients could be operated on successfully. The presurgical analysis of interictal epileptiform discharges using dynamic statistical parametric mapping seems to be promising in patients with a possible underlying focal cortical dysplasia and might help to guide the placement of invasive electrodes.

Adolescent↗
PubMed2003

Specific inhibition of hypoxia-inducible factor (HIF)-1 alpha activation and of vascular endothelial growth factor (VEGF) production by flavonoids.

Screening using a reporter under the control of the hypoxia-response element (HRE) identified several flavonoids and homoisoflavonoids that inhibit the activation of HRE under hypoxic conditions. Among various compounds, isorhamnetin, luteolin, quercetin, and methyl ophiopogonanone B (MOB) were effective at 3 to 9 microg/ml in inhibiting the reporter activity. The expression of vascular endothelial growth factor (VEGF) mRNA during hypoxia was also inhibited by MOB in HepG2 cells, but the effective doses were 10 to 20 microg/ml. MOB caused destabilization of hypoxia-inducible factor (HIF)-1alpha, as revealed by Western blotting, that was dependent on proteasome activity and the tumor suppressor, p53. The tubular formation and migration of human umbilical vein endothelial cells was also inhibited by MOB. MOB is expected to act as an inhibitor of angiogenesis.

Animals↗
PubMed2003

HIF-1-dependent VEGF reporter gene assay by a stable transformant of CHO cells.

For the establishment of a screening system to detect inhibitors of vascular endotherial growth factor (VEGF) expression, a stable transformant of Chinese hamster ovary cells was isolated and cloned by transfection of a hypoxia-inducible factor 1 (HIF-1)-dependent VEGF promoter reporter gene. The expression of the reporter gene in the clone cells, as measured by luciferase activity, was stable. Hypoxic responses were best observed at an initial cell density of 2 x 10(4)/well. The maximal increase of luciferase activity was 30 fold. In the highest cell density of 8 x 10(4)/well (2.1 x 10(5)/cm(2)), basal activity was increased 13-15 fold compared to that at the lower cell densities, and did not respond to hypoxia. Addition of CoCl(2), which is known to mimic hypoxia, increased luciferase activity more than 10 times in normoxia. Nitric oxide donors, which are known to suppress the activation of HIF-1, inhibited expression of the VEGF promoter reporter gene under hypoxia. Histone deacetylase inhibitors, trichostatin A and sodium n-butyrate which are known to stimulate transcription of many genes enhanced its transcription in hypoxia. These results indicate that the stable transformant is a useful tool for screening of HIF-1 modifiers.

Animals↗
PubMed2002

Induction of p16/INK4a gene expression and cellular senescence by toyocamycin.

We constructed an assay system of a luciferase reporter with p16/lNK4a gene transcriptional regulatory domain to identify p16-inducing substances, and found toyocamycin to induce gene expression from the screening of culture fluids of Streptomyces. Toyocamycin is a nucleoside analog, and it increased the p16 mRNA level in human normal fibroblasts or synovial cells as assessed by Northern blot hybridization or real time RT-PCR. It also induced cellular senescence in normal human fibroblasts. The transcriptional regulatory regions of human p16 gene that were responsible for the induction were analyzed using deletion mutants of the transcriptional regulatory region of p16 linked to the luciferase gene. The DNA fragment -111 to +1 bp from the cap site was sufficient to drive toyocamycin-activated transcription of p16/luciferase reporter. Nucleotide sequences within this domain contained the Sp1- and Ets-binding sequences. Mutations were introduced into these sequences, and the Sp1 sequence was found to be critical for the induction, and this notion was confirmed from gel-mobility shift assay.

Base Sequence↗
PubMed2002

Induction of p16INK4a transcription and of cellular senescence by aclacinomycin-derivatives and cardiac glycosides.

Stable transformants of Saos-2 cells that contain the luciferase reporter gene under the control of the human p16INK4a transcriptional regulatory region were established, and were used to identify growth-inhibiting substances from culture broths of actinomycetes and extracts of plants. Among the active substances so far identified were an aclacinomycin-derivative, cenerubin B, and a cardiac glycoside, periplocin. These substances inhibited growth of normal human fibroblasts, and induced senescent phenotypes including a flattened morphology and increased acidic beta-galactosidase activity, although the activities of their derivatives to induce p16CDKN2 and beta-galactosidase did not coincided with each other. These results suggest that the reporter system using the p16CDKN2 transcriptional regulatory region is a useful means for screening growth inhibiting substances that are potential anti-tumor agents.

Aclarubicin↗