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Takafumi Naiki

Publications and source records attributed to Takafumi Naiki.

9 recordsLinked to original sources
PubMed2006

Actin organization and hepatocyte differentiation are regulated by extracellular matrix via PI-4,5-bisphosphate in the rat.

Cell adhesion to the extracellular matrix (ECM) plays vital roles in both morphogenesis and regulation of gene expression in cells of adult organisms. How intracellular, cytoskeletal, and signaling factors connect and communicate with the ECM is a fundamental question. Using a cDNA microarray analysis, we identified phosphatidylinositol 4,5-bisphosphate (PI[4,5]P2) phosphatase mRNA as being up-regulated in hepatocytes cultured on a basement membrane matrix, Engelbreth-Holm-Swarm (EHS) gel, which led to the finding that the PI(4,5)P2 levels of hepatocytes decreased on EHS gel. These changes in hepatocytes on EHS gel were accompanied by promotion of actin depolymerization and differentiated phenotypes of the hepatocytes. Treatment with PI(4,5)P2 or a phospholipase C inhibitor, U73122, resulted in decreased mRNA expressions of albumin and hepatocyte nuclear factor 4 (HNF-4) in hepatocytes. In contrast, actin-disrupting agent gelsolin increased mRNA expressions of albumin and HNF-4. In conclusion, organization of the actin cytoskeleton via PI(4,5)P2 is involved in the regulation of hepatocyte differentiation by the ECM.

Actins↗
PubMed2005

Prospective study on early virologic response to treatment with interferon alpha-2b plus ribavirin in patients with chronic hepatitis C genotype 1b.

To evaluate the predictive value of early virologic response (EVR) of achieving a sustained virologic response (SVR), an open, prospective trial including 42 patients with chronic hepatitis C genotype 1b was performed with directly observed 24-week treatment with interferon alpha-2b plus ribavirin. We assessed the predictive values of EVR at days 3, 7, 14, and weeks 4, 8, and 12 of the SVR. The SVR in an intention-to-treat analysis was 19.0%. Patients who reached SVR presented a significantly faster reduction in plasma viral load. Stepwise multiple logistic regression analysis of the factors (gender, age, IFN dosage, ribavirin dosage, HCV RNA, ISDR, and loss of HCV RNA at week 4) revealed that loss of HCV RNA at week 4 was the only independent variable of treatment outcome (P=0.0039). A viral load at treatment day 3 above 100kIU/ml, at day 7 above 50kIU/ml, and at day 14 above 10kIU/ml was 100% predictive for virologic non-response in all except 1 patient. The cutoff levels for HCV RNA at days 3 and 14 of treatment were associated with an algorithm of the failure to detect HCV RNA after 12 weeks of treatment. In conclusions, a very early virologic response assessment could be useful for prediction of later outcome of combination therapy in chronic hepatitis C genotype 1b.

Journal Article↗
PubMed2005

Adenovirus-mediated hepatocyte nuclear factor-4alpha overexpression maintains liver phenotype in cultured rat hepatocytes.

Hepatocyte nuclear factor 4alpha (HNF-4alpha) is a transcription factor that controls embryonal liver development and that maintains and regulates gene expression in adult liver cells. We have previously demonstrated that transient overexpression of HNF-4alpha up-regulates a number of liver-specific genes in hepatoma cell lines. In this study, we extend these studies by assessing the functional role of HNF-4alpha in regulating cellular viability and liver-specific functions of primary rat hepatocytes. In cells transfected with an adenovirus vector carrying rat HNF-4alpha cDNA, induction and maintenance of liver-specific genes and functions were observed over a long-term culture, which might be associated with the prevention of a rapid loss of the mitochondrial membrane potential. In addition, we demonstrated that transthyretin mRNA was up-regulated by HNF-4alpha in primary hepatocytes, but not in hepatoma cells. These results indicate that HNF-4alpha plays a role in the maintenance of morphologically and biochemically functional hepatocytes and that the difference in expression of liver-specific genes induced by HNF-4alpha may depend on a differentiation state of cells.

Adenoviridae↗
PubMed2005

Normal liver regeneration and liver cell apoptosis after partial hepatectomy in tumor necrosis factor-alpha-deficient mice.

AIMS/BACKGROUND: Tumor necrosis factor-alpha (TNF-alpha) is known as a proinflammatory cytokine that has been implicated as a contributing factor in a number of disease processes. TNF-alpha also influences liver repair following hepatotoxic damage, and regeneration following partial hepatectomy (PH). The aim of this study was to assess the mechanism by which TNF-alpha influences liver cell apoptosis and regeneration following PH in TNF-alpha-deficient (TNF-alpha(-/-)) mice. METHODS: PH was performed in wild mice and TNF-alpha(-/-) mice. RESULTS: In both groups, serum alanine aminotransferase and serum total bilirubin levels comparably peaked at 6 and 48 h after PH, respectively. No differences were observed in hepatocyte proliferation, as determined by mitotic and the proliferating cell nuclear antigen labeling indices, between TNF-alpha(+/+) and TNF-alpha(-/-) mice. Few terminal deoxynucleotidyl transferase nick end-labeling-positive hepatocytes were seen in either type of mice. Nuclear factor-kappa B DNA binding activity in the remaining liver of TNF-alpha(-/-) mice after PH was similar to that of control mice. Ribonuclease protection assay showed that transforming growth factor beta1 mRNA was up-regulated comparably in the livers of the two groups, and that other cytokines were hardly seen in either. Interleukin-6/ signal transducer and activator of transcription-3-dependent pathway was not affected in TNF-alpha(-/-) mice. CONCLUSIONS: These findings suggest that TNF-alpha has little influence on liver regeneration and liver cell apoptosis after PH in mice.

Alanine Transaminase↗
PubMed2004

Leflunomide protects from T-cell-mediated liver injury in mice through inhibition of nuclear factor kappaB.

Leflunomide is a novel immunosuppressive and anti-inflammatory agent for the treatment of autoimmune disease. The aim of this study was to investigate whether leflunomide protects from liver injury induced by concanavalin A (Con A), a T-cell-dependent model of liver damage. BALB/c mice were injected with 25 mg/kg Con A in the presence or absence of 30 mg/kg leflunomide. Liver injury was assessed biochemically and histologically. Levels of circulating cytokines and expressions of cytokine messenger RNA (mRNA) in the liver and the spleen were determined. Treatment with leflunomide markedly reduced serum transaminase activities and the numbers of dead liver cells. Leflunomide significantly inhibited increases in plasma tumor necrosis factor alpha (TNF-alpha) and interleukin 2 concentrations, and also reduced TNF-alpha mRNA expression in the liver after administration of Con A. These findings were supported by the results in which leflunomide administration decreased the number of T lymphocytes infiltrating the liver as well as inhibiting their production of TNF-alpha. Activation of nuclear factor kappaB (NF-kappaB), which regulates TNF-alpha production, was inhibited in the liver of mice treated with leflunomide, resulting in a reduction of TNF-alpha production from lymphocytes infiltrating the liver. In conclusion, leflunomide is capable of regulating T-cell-mediated liver injury in vivo and that this event may depend on the decrease of TNF-alpha production in the liver through inhibition of NF-kappaB activation caused by leflunomide.

Animals↗
PubMed2004

Functional activity of human hepatoma cells transfected with adenovirus-mediated hepatocyte nuclear factor (HNF)-4 gene.

Fulminant hepatic failure (FHF) is still associated with high mortality despite recent advances in medical management. There is need of an effective and safe bioartificial liver (BAL) support to help keep patients with FHF alive until an organ becomes available for transplantation or the native liver recovers. The aim of this study was to establish highly functional liver cells by means of transfecting hepatocyte nuclear factor (HNF)-4 gene for the development of BAL. We constructed adenovirus vector carrying rat HNF-4 cDNA, and transfected to hepatoma-derived cell lines, HepG2 and HuH-7, to enforce expression of the exogenous HNF-4 gene. We analyzed expression of HNF-4, HNF-1, and liver-specific genes in cells infected by the adenovirus vector expressing HNF-4. Adenovirus-mediated HNF-4 gene transfer resulted in increases in expressions of HNF-4, HNF-1, and liver-specific genes such as apolipoproteins, alpha1-antitrypsin (alpha1-AT), phosphoenolpyruvate carboxy-kinase, cytochrome P450 families, and glutamine synthetase in transfected hepatoma cells. Cells overexpressing HNF-4 removed ammonia from medium supplemented with NH4Cl to a greater extent than control cells. These findings demonstrated that transfected cell lines restored differentiated gene expressions and liver-specific function by the overproduction of HNF-4. HNF-4-overexpressing hepatocyte cell lines are useful for bioreactor of BAL systems.

Adenoviridae↗
PubMed2003

Inhibition of nuclear factor kappaB and phosphatidylinositol 3-kinase/Akt is essential for massive hepatocyte apoptosis induced by tumor necrosis factor alpha in mice.

BACKGROUND/AIMS: Tumor necrosis factor (TNF)-alpha itself does not induce liver injury in normal mice or hepatocytes. Rather, this event, especially in vitro, is explained by the fact that the TNF-alpha/TNF receptor system not only triggers downstream signals leading to apoptosis but also induces an antiapoptotic pathway through the activation of nuclear factor (NF)-kappaB. The aim of this study was to determine whether inhibition of antiapoptotic pathways influences the susceptibility of mice to TNF-alpha. Here, we focused on the roles of NF-kappaB and phosphatidylinositol 3-kinase (PI3K)-regulated serine/threonine kinase Akt. METHODS: TNF-alpha was administered to BALB/c mice after treatment with an adenovirus expressing a mutant form IkappaBalpha (Ad5IkappaB), the PI3K inhibitor wortmannin, or both. Liver injury was assessed biochemically and histologically. The expression of Bcl-2 family members and caspase activity were examined. RESULTS: In the mice livers, treatment with Ad5IkappaB or the wortmannin suppressed the activation of NF-kappaB or Akt, respectively. Suppression of either NF-kappaB or Akt showed a slight increase in transaminase levels and focal liver cell death after TNF-alpha administration. However, in mice treated with both Ad5IkappaB and wortmannin, TNF-alpha administration resulted in massive hepatocyte apoptosis and hemorrhagic liver destruction in mice. The combination of Ad5IkappaB, wortmannin, and TNF-alpha markedly increased the activation of caspase-3 and -9, and activated caspase-8 to a lesser degree, suggesting that TNF-alpha-induced hepatocyte apoptosis is dependent on type II cell death signaling pathway, probably through the mitochondria. Inhibition of the NF-kappaB and PI3K/Akt pathways had no effect on expression of Bcl-2 families. CONCLUSION: The inducible activation of NF-kappaB and constitutive activation of Akt regulate hepatocyte survival against TNF-alpha, which occurs independent of Bcl-2 families.

Androstadienes↗
PubMed2002

Analysis of gene expression profile induced by hepatocyte nuclear factor 4alpha in hepatoma cells using an oligonucleotide microarray.

Hepatocyte nuclear factor 4alpha (HNF-4alpha), a liver-specific transcription factor, plays a significant role in many liver-specific functions, including lipid, glucose, drug, and ammonia metabolism, and also in embryonal liver development. However, its functions and regulation are not yet clearly understood. In this study, we constructed an adenovirus vector carrying rat HNF-4alpha cDNA and transfected the adenovirus to human hepatoma cells, HuH-7, to enforce expression of the exogenous HNF-4alpha gene. We analyzed HNF-4alpha-induced genes using cDNA microarray technology, which included over 9000 genes. As a result, 62 genes showed a greater than 2.0-fold change in expression level after the viral transfection. Fifty-six genes were consistently induced by HNF-4alpha overexpression, and six genes were repressed. To assess HNF-4alpha function, we attempted to classify the genes, which had been classified by their encoding protein functions in a previous report. We could classify 45 genes. The rest of the HNF-4alpha-sensitive genes were unclassified (4 genes) or not identified (13 genes). Among the classified genes, almost half of the induced genes (26 of 40) were related to metabolism genes and particularly to lipid metabolism-related genes. This cDNA microarray analysis showed that HNF-4alpha is one of the central liver metabolism regulators.

Adenoviridae↗