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Biomedical subjects

Shinji Tamura

Publications and source records attributed to Shinji Tamura.

10 recordsLinked to original sources
PubMed2003

Angiotensin II stimulates the nuclear translocation of Smad2 and induces PAI-1 mRNA in rat hepatic stellate cells.

It has recently been reported that angiotensin II (ANGII) stimulates gene expression of transforming growth factor-beta1 (TGF-beta1) and is involved in hepatic fibrosis. This effect is thought to be caused through ANGII type 1 receptor (ATR1). However, a role of ANGII at the postreceptor levels of TGF-beta1 signaling has not been identified. To clarify the role of ANGII on hepatic fibrosis, we investigated the effect of ANGII on rat hepatic stellate cells (HSCs). HSCs were isolated from male Sprague-Dawley rats. TGF-beta1 and matrix protein gene expression in HSCs was assessed by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) using SYBR Green I. The nuclear translocation of Smad2 in HSCs after 20 min ANGII stimulation was analyzed by Western blotting. ANGII was found to induce TGF-beta1 and matrix protein gene expression in HSCs. The nuclear translocation of Smad2 in HSCs was also induced by ANGII stimulation. These effects of ANGII were almost completely blocked by the ATR1 antagonist, CS-866. ANGII induces TGF-beta1 and matrix protein mRNA, and stimulates rapid nuclear translocation of Smad2 in rat HSCs through ATR1, which indicates that the ATR1 blockade represents a novel approach for the possible prevention of hepatic fibrosis.

Journal Article↗
PubMed2003

Liver regeneration in heparin-binding EGF-like growth factor transgenic mice after partial hepatectomy.

BACKGROUND & AIMS: Heparin-binding epidermal growth factor-like growth factor (HB-EGF), a member of the EGF family, is synthesized in the form of a membrane-anchored precursor (proHB-EGF), which subsequently is processed proteolytically to mature HB-EGF. This study describes the effects of HB-EGF on liver regeneration after 70% partial hepatectomy in proHB-EGF transgenic mice with liver-specific expression. METHODS & RESULTS: No significant differences in liver/body weight ratios and in bromodeoxyuridine (BrdU)-labeling index (the ratios of BrdU-positive hepatocyte nuclei) were found between adult transgenic and wild-type mice. However, in regenerating liver after partial hepatectomy, transgenic mice had higher liver/body weight ratios than wild-type mice and at 120 hours reached a level equal to that before partial hepatectomy. The BrdU-labeling index was about 5 times higher in the livers of transgenic mice compared with the wild type (51.5% vs. 10.2%, respectively; P < 0.01) at 48 hours after partial hepatectomy. Activation of microtubule-associated protein kinase after partial hepatectomy was higher and earlier in the transgenic mice as compared with the wild-type mice. Soluble HB-EGF was increased in the liver (at 8 min) after partial hepatectomy, indicating that the shedding of proHB-EGF occurred after partial hepatectomy. CONCLUSIONS: The transgenic expression of HB-EGF accelerates the proliferation of hepatocytes after partial hepatectomy, suggesting that HB-EGF functions as a hepatotrophic factor in vivo.

Animals↗
PubMed2003

[Roles of beta-catenin overexpression and adenomatous polyposis coli mutation in head and neck cancer].

Beta-catenin is an undercoat protein of cadherin, a cellular adhesion molecule. Beta-catenin also functions as a transcriptional activator downstream of the Wnt signaling pathway. Intracellular beta-catenin is regulated by the formation of a complex with APC (adenomatous polyposis coli) protein. The activation of this pathway by stabilization with beta-catenin has been shown to be an important step in the development of colorectal carcinoma, which is mainly caused by inactivating mutations in the APC tumor suppressor gene or by activating mutations in exon 3 of the beta-catenin gene. This study was conducted to clarify the contribution of beta-catenin accumulation and the mutation of the beta-catenin gene to the carcinogenesis of head and neck cancer. Beta-catenin accumulation was examined immunohistochemically in 49 frozen or formalin-fixed, paraffin-embedded samples of head and neck tumors. We also performed a direct sequence analysis of APC and beta-catenin to examine the cause of beta-catenin accumulation. Genomic DNA was extracted and purified from fresh tissue samples of head and neck cancers. We examined the APC mutation cluster region in 15 samples and analyzed beta-catenin exon 3 mutations in 31 cases. Twelve out of 49 (24.5%) cases exhibited beta-catenin accumulation in our histochemical study. The 5 year survival rate was 0% in the beta-catenin accumulation group, compared to 50% in the non-accumulation group, (p < 0.01). This finding strongly suggests that beta-catenin may play an important role in the carcinogenesis or progression of head and neck cancer. One of the 15 cases exhibited an APC missense mutation that led to the replacement of amino acids; this case died in 12 months. Regarding the beta-catein mutation, non of the 31 samples exhibited a gene mutation in beta-catenin exon 3. Thus, the rate of APC and beta-catenin mutation in head and neck cancer may be very low.

Adult↗
PubMed2002

Frequent impairment of the spindle assembly checkpoint in hepatocellular carcinoma.

BACKGROUND: Chromosomal instability (CI) leading to aneuploidy is one form of genetic instability, a characteristic feature of various types of cancers. Recent work has suggested that CI can be induced by a spindle assembly checkpoint defect. The aim of the current study was to determine the frequency of a defect of the checkpoint in hepatocellular carcinoma (HCC) and to establish whether alterations of genes encoding the checkpoint were associated with CI in HCC. METHODS: Aneuploidy and the function of the spindle assembly checkpoint were examined using DNA flow cytometry and morphologic analysis with microtubule disrupting drugs. To explore the molecular basis, the authors examined the expression and alterations of the mitotic checkpoint gene, BUB1, using Northern hybridization and direct sequencing in 8 HCC cell lines and 50 HCC specimens. Furthermore, the authors examined the alterations of other mitotic checkpoint genes, BUBR1, BUB3, MAD2B, and CDC20, using direct sequencing in HCC cell lines with aneuploidy. RESULTS: An impaired spindle assembly checkpoint was found in five (62.5%) of the eight aneuploid cell lines. Transcriptional expressions of the BUB1 gene appeared in all cell lines. While some polymorphic base changes were noted in BUB1, BUBR1, and CDC20, no mutations responsible for impairment of the mitotic checkpoint were found in either the HCC cell lines or HCC specimens, which suggests that these genes did not seem to be involved in tumor development in HCC. CONCLUSIONS: The loss of spindle assembly checkpoint occurred with a high frequency in HCC with CI. However, other mechanisms might also contribute to CI in HCC.

Adult↗
PubMed2002

Activation of signal transducer and activator transcription 3 and expression of suppressor of cytokine signal 1 during liver regeneration in rats.

BACKGROUND/AIMS: Recent work has shown that the signal transducer and activator of transcription (STAT) 3 activation is important for the initiation of the proliferative response following partial hepatectomy (PH). However, the issue of where STAT3 is activated and how it is regulated is unclear. The aims of this study were to identify STAT3-activated cells and to clarify the expression of suppressor of cytokine signal (SOCS), a negative feedback molecule of STAT3, after PH. METHODS: STAT3-activated cells and SOCS1-positive cells were identified by immunohistochemistry after a two-thirds PH in rats. SOCS mRNA was examined by Northern analysis. RESULTS: STAT3 was activated in hepatocytes from those localized in the periportal zones of hepatic lobules after PH. STAT3 activation was also detected in Kupffer cells and sinusoidal endothelial cells prior to its detection in hepatocytes. After STAT3 activation, SOCS1 protein in response to PH was detected immunohistochemically in regenerating liver. SOCS1 and SOCS3 mRNA were induced in regenerating liver after PH. CONCLUSIONS: STAT3 signaling can occur in Kupffer cells and sinusoidal endothelial cells prior to in hepatocytes from those localized in the periportal zones. SOCS1 as well as SOCS3 may regulate STAT3 signaling negatively after PH.

Animals↗
PubMed2002

NF-kappaB activation in non-parenchymal liver cells after partial hepatectomy in rats: possible involvement in expression of heparin-binding epidermal growth factor-like growth factor.

BACKGROUND/AIMS: Nuclear factor (NF) B activation plays a critical role in the initiation of liver growth after partial hepatectomy (PH). However, the issue of where specifically NF-B is activated is unclear. We previously reported that heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a hepatotrophic factor. The aims of this study were to identify NF-B-activated cells and to clarify their involvement in HB-EGF expression after PH. METHODS: Using rats, a two-thirds PH was performed, after which NF-B-activated cells and HB-EGF-positive cells were identified by Southwestern histochemistry or immunohistochemistry. NF-B binding activity and HB-EGF gene expression were analyzed in rat hepatocytes and non-parenchymal cells (NPC) in primary culture. RESULTS: NF-B was activated in Kupffer cells and sinusoidal endothelial cells prior to activation in hepatocytes. HB-EGF immunoreactivity was detected after NF-B activation in the sinusoidal cells from those localized in the periportal zones of hepatic lobules. HB-EGF gene expression by tumor necrosis factor was accompanied by an increase in NF-B binding activity in NPC but not in hepatocytes in primary culture, which was abolished by pyrrolidine dithiocarbamate, an inhibitor of NF-B activation. CONCLUSIONS; NF-B was activated in NPC prior to activation in hepatocytes. NF-B activation may be involved in HB-EGF expression in NPC after PH.

Animals↗
PubMed2002

Characterization of mac25/angiomodulin expression by high endothelial venule cells in lymphoid tissues and its identification as an inducible marker for activated endothelial cells.

Previous results have indicated that mac25/angiomodulin (AGM) is expressed in lymph node (LN) high endothelial venules (HEV), the specialized venules that support efficient lymphocyte transendothelial migration. How mac25/AGM's endothelial expression pattern is regulated in situ remains unknown. Here, we demonstrate that in mouse LN blood vessels, including HEV, mac25/AGM is localized, unlike previous reports, not to the luminal or lateral regions bordering the endothelial cells (EC), but exclusively to the basal lamina that is in direct association with EC. In the spleen, mac25/AGM was expressed in the vascular basal lamina, in direct association with smooth muscle cells and pericytes, but not with EC. In addition, we report herein that mac25/AGM is an inducible marker for activated EC. In inflamed tissues, mac25/AGM expression was strongly induced in the abluminal region of blood vessels. In vitro, mac25/AGM was readily induced in EC upon activation with pro-inflammatory cytokines such as tumor necrosis factor-alpha, indicating that mac25/AGM is an activated EC marker. mac25/AGM binds vascular endothelial growth factor and, together with its strict abluminal localization, it is suggested that mac25/AGM has a specific function(s) in the subendothelium of activated blood vessels such as capturing humoral factors produced in the vicinity of HEV.

Animals↗