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Hitoshi Takagi

Publications and source records attributed to Hitoshi Takagi.

At least 73 records · Page 4Linked to original sources
PubMed2004

Leptin stimulates ischemia-induced retinal neovascularization: possible role of vascular endothelial growth factor expressed in retinal endothelial cells.

Diabetic retinopathy is the leading cause of new blindness in adults in developed countries. Leptin, an adipocyte-derived hormone, stimulates endothelial proliferation and angiogenesis. This study was designed to elucidate the pathophysiologic role of leptin in the progression of retinal neovascularization. Using the retinopathy of prematurity model, a mouse model of ischemia-induced retinal neovascularization, we have demonstrated more pronounced retinal neovascularization in 17-day-old transgenic mice overexpressing leptin than in age-matched wild-type littermates. Ischemia-induced retinal neovascularization was markedly suppressed in 17-day-old leptin-deficient ob/ob mice. Western blot analysis revealed that a biologically active leptin receptor isoform is expressed in mouse retinal endothelial cells. Leptin receptor expression was also detected in primary cultures of porcine retinal endothelial cells, where it upregulated vascular endothelial growth factor (VEGF) mRNA expression. This effect was thought to be mediated at least partly through the activation of signal transducers and activators of transcription (STAT)3, because adenoviral transfection of the dominant-negative form of STAT3 abolished the leptin-induced upregulation of VEGF mRNA expression in retinal endothelial cells. This study provides evidence that leptin stimulates the ischemia-induced retinal neovasucularization possibly through the upregulation of endothelial VEGF, thereby suggesting that leptin antagonism may offer a novel therapeutic strategy to prevent or treat diabetic retinopathy.

Animals↗
PubMed2003

Metallothionein is a potential negative regulator of apoptosis.

Apoptotic resistance can either be desirable or undesirable, depending on the conditions. In cancer chemotherapy, it is critical that tumor cells are selectively and effectively killed while leaving normal cells undamaged. Since acquisition of apoptotic resistance appears to be a common occurrence during malignant transformation, elucidating the mechanisms underlying apoptotic resistance is an area of intense study. Previous studies have revealed that metallothionein (MT) can protect cells from apoptosis induced by oxidative stress and metals. In the present study, we tested the hypothesis that the presence of MT may somehow modulate apoptosis. Our results revealed a strong linear negative correlation between basal MT levels and etoposide-induced apoptosis in the human tumor cell lines PLC/PRF/5, H460, and HepG2 (r = -0.991). In HepG2 cells, 24 h pretreatment with cadmium resulted in concentration-dependent increases in MT levels and marked decreases in etoposide-induced apoptosis. Zinc pretreatment also resulted in increased MT synthesis and decreased etoposide-induced apoptosis. More importantly, induced MT levels were negatively correlated with sensitivity to etoposide-induced apoptosis (r = -0.965). These suggest that MT may play a role in regulating apoptosis and that modulating MT expression may provide a strategy for altering cellular resistance to chemotherapeutic compounds.

Apoptosis↗
PubMed2003

Pilot clinical trial of the use of alpha-tocopherol for the prevention of hepatocellular carcinoma in patients with liver cirrhosis.

Patients with chronic hepatitis C virus (HCV) infection often develop liver cirrhosis and hepatocellular carcinoma (HCC). The purpose of this study was to test the chemopreventive effect of alpha-tocopherol on hepatocarcinogenesis in patients with liver cirrhosis and a history of HCV infection. Eighty-three patients with liver cirrhosis and with positive history of HCV infection were divided at random into two groups. Forty-four patients were treated with alpha-tocopherol (Vit E group) while the other 39 were followed as controls. The clinical background (gender, age, and laboratory data) was similar in the two groups. Serum levels of alpha-tocopherol, albumin, alanine aminotransferase (ALT), and total cholesterol and platelet count were measured serially over a period of five years. The mean serum concentration of alpha-tocopherol was low in both groups at entry and was significantly higher in the Vit E group than in the control group one month after treatment. Platelet count, serum albumin, ALT, and total cholesterol were not different between the two groups during the five-year period. Cumulative tumor-free survival and cumulative survival rate tended to be higher in the Vit E group than in controls, albeit statistically insignificant. The serum level of alpha-tocopherol was low in patients with liver cirrhosis and positive for HCV. Although the administration of alpha-tocopherol normalized the level one month later, it could neither improve liver function, suppress hepatocarcinogenesis, nor improve cumulative survival. Patients treated with alpha-tocopherol tended to live longer without development of HCC but the difference was not statistically significant.

Alanine Transaminase↗
PubMed2003

Fatal pneumonia caused by Burkholderia cepacia 9 months after resection of aspergilloma.

A 69-year-old man developed an episode of severe community-acquired pneumonia 9 months after resection of aspergilloma. Although Aspergillus fumigatus was also isolated in the pleural cavity, it did not invade the remaining lung parenchyma. The patient developed progressive bilateral pneumonia leading to death from respiratory failure. Burkholderia cepacia was considered as prime pathogen, as it was repeatedly cultured from sputum and tracheal secretions, as well as the autopsy lung. B. cepacia is resistant to most antibiotics, and seldom causes pneumonia in patients without cystic fibrosis or chronic granulomatous disease. The precise reason that this apparently immunocompetent patient developed B. cepacia pneumonia remains unknown.

Aged↗
PubMed2003

Potential role of the angiopoietin/tie2 system in ischemia-induced retinal neovascularization.

PURPOSE: Ischemia-induced neovascularization can cause catastrophic loss of vision in retinal disorders such as diabetic retinopathy. Recent studies have shown that the angiopoietin-Tie2 system is a major regulator of vascular integrity and is involved in pathologic angiogenesis. In the study described herein, the role of these molecules in ischemic retinal disorders was investigated. METHODS: Human epiretinal membranes were examined by immunohistochemistry, In situ hybridization, and reverse transcription-polymerase chain reaction (RT-PCR) analysis. Effects of angiopoietins on tube formation were studied in vitro in bovine retinal capillary endothelial cells (BRECs) and in a murine model of ischemia-induced retinal neovascularization. RESULTS: In human epiretinal membranes surgically obtained from eyes with ischemic retinal disorders, substantial upregulation of angiopoietin 2 (Ang2) and the receptor Tie2 was recorded than in those from eyes with nonischemic diseases, whereas expression of Ang1 was constant in all membranes. Both Ang1 and Ang2 promoted tube-forming activity and enhanced the effects of vascular endothelial growth factor (VEGF) in cultured BRECs. Soluble Tie2 fusion protein (sTie2-Fc), which precluded modulation of VEGF-dependent tube formation by the angiopoietins, suppressed both VEGF and hypoxia-conditioned, medium-induced tube-forming activity in BRECs. Intravitreal injection of sTie2-Fc, soluble Flt-1 fusion protein (sFlt-1-Fc), and both chimeric proteins suppressed retinal angiogenesis in a murine model of retinal ischemia in the order of sTie2-Fc < sFlt-1-Fc < sTie2-Fc+sFlt-1-Fc. CONCLUSIONS: These results reinforce the substantial role of the angiopoietins/Tie2 system in ischemia-induced angiogenesis as well as the VEGF system and suggest that combined inhibition of Tie2 and VEGF signaling may be more effective in halting or preventing pathologic angiogenesis in ischemic retinal disorders.

Adult↗
PubMed2002

CCl4-induced acute liver injury in mice is inhibited by hepatocyte growth factor overexpression but stimulated by NK2 overexpression.

Hepatocyte growth factor (HGF) inhibits acute liver injury. NK2 acts as an antagonist to HGF in vitro, but its in vivo function has reached no consensus conclusions. We have investigated in vivo effects of HGF and NK2 on CCl4-induced acute liver injury. Elevation of the serum alanine aminotransferase level and extension of centrilobular necrosis were inhibited in HGF transgenic mice but were promoted in NK2 transgenic mice. Hepatocyte proliferation after liver injury was not inhibited in NK2 transgenic mice. Thus, this study indicates that HGF inhibits liver injury, and NK2 antagonizes HGF on liver injury, however, NK2 may not antagonize HGF on hepatocyte proliferation.

Alanine Transaminase↗
PubMed2002

Transforming growth factor alpha protects against Fas-mediated liver apoptosis in mice.

The Fas/Fas ligand interaction plays a crucial role in various liver diseases, and administration of agonistic anti-Fas antibody to mice causes massive hepatic apoptosis and fulminant hepatic failure. Several growth factors have recently been found to function in preventing apoptosis. In this study, we demonstrated that overexpression of transforming growth factor alpha (TGFalpha) has a dramatic protective effect on Fas-mediated hepatic apoptosis at the biochemical and histological levels. Moreover, 85.7% (six out of seven) of TGFalpha transgenic mice survived the lethal liver damage, whereas all wild-type mice died. Expression of Bcl-xL, an anti-apoptotic protein, was greatly increased in the transgenic mice. Taken together, our findings suggest that TGFalpha protects against Fas-mediated liver apoptosis in vivo and up-regulation of Bcl-xL may participate in protective effect of TGFalpha.

Alanine Transaminase↗
PubMed2002

Identification of a defect in the UGT1A1 gene promoter and its association with hyperbilirubinemia.

The UDP-glucuronosyltransferase UGT1A1 plays a critical role in the detoxification of potentially neurotoxic bilirubin by conjugating it with glucuronic acid. We identified a polymorphism that results in a T to G substitution at nucleotide number -3263 of the phenobarbital-responsive enhancer module of the UGT1A1 gene, thereby significantly decreasing transcriptional activity as indicated by the luciferase-reporter assay. At least one T-3263G allele was found in 21 of 25 subjects with mild hyperbilirubinemia (Gilbert's syndrome); this frequency (0.58) was significantly higher than that in normobilirubinemic controls (0.17; n = 8 of 27). Homozygous mutations in the TATA element (A[TA](7)TAA) or at nucleotide 211 of exon 1 (G to A substitution) were found in 5 and 2 of the hyperbilirubinemic group, respectively, while 12 of these subjects were double heterozygotes for the T-3263G and G211A mutations. Plasma total bilirubin levels in these double heterozygotes were significantly higher than those in control subjects carrying one or other of these mutations singly, indicating that compound heterozygous mutations may result in more strongly reduced UGT1A1 activity. Our results indicate that homozygosity and compound heterozygosity for mutations in the UGT1A1 gene promoter (T-3263G and A[TA](7)TAA) and/or exon 1 of the gene (G211A) could explain the hyperbilirubinemia seen in the majority of individuals with Gilbert's syndrome.

Adult↗
PubMed2002

Hepatocyte growth factor promotes hepatocarcinogenesis through c-Met autocrine activation and enhanced angiogenesis in transgenic mice treated with diethylnitrosamine.

Hepatocyte growth factor (HGF) is a mitogen for hepatocytes, but it is not clear whether HGF stimulates or inhibits hepatocarcinogenesis. We previously reported that HGF transgenic mice under the metallothionein gene promoter developed benign and malignant liver tumors spontaneously after 17 months of age. To elucidate the role of HGF in hepatocarcinogenesis, diethylnitrosamine (DEN) was administered to HGF transgenic mice. HGF overexpression accelerated DEN-induced hepatocarcinogenesis, often accompanied by abnormal blood vessel formation. In this study, 59% of transgenic males (versus 20% of wild-type males) and 39% of transgenic females (versus 2% of wild-type females) developed either benign or malignant liver tumors by 48 weeks (P<0.005, P<0.001, respectively). Moreover, 33% of males and 23% of female transgenic mice developed hepatocellular carcinoma (HCC), while none of the wild-type mice developed HCC (P<0.001, P<0.005, respectively). Enhanced kinase activity of the HGF receptor, Met, was detected in most of these tumors. Expression of vascular endothelial growth factor (VEGF) was up-regulated in parallel with HGF transgene expression. Taken together, our results suggest that HGF promotes hepatocarcinogenesis through the autocrine activation of the HGF-Met signaling pathway in association with stimulation of angiogenesis by HGF itself and/or indirectly through VEGF.

Alkylating Agents↗
PubMed2002

Severe manifestation of acute hepatitis A recently found in Gunma, Japan.

BACKGROUND: The incidence of acute hepatitis A infection in Japan peaked 10 years ago and has been decreasing since then. However, an increase in severe cases of the disease has been documented recently. We experienced an outbreak in 1998-1999, and compared the clinical features of the disease in 1998-1999 (recent outbreak) and in 1987-1988 (past outbreak) in our prefecture (Gunma). METHODS: Forty patients with acute hepatitis A were admitted to nine Gunma hospitals from October 1998 to September 1999. Their clinical features were compared with those of 100 patients with acute hepatitis A admitted to the same hospitals in 1987-1988. RESULTS: Both outbreaks occurred mostly during the winter-spring season. Secondary familial infection was significantly decreased in the recent outbreak. Patients in the recent outbreak were 7 years older than those in the past outbreak. Laboratory findings, such as serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and prothrombin time, were worse in the recent than in the past outbreak. Severe-type hepatitis and fulminant hepatitis occurred in 5 patients (12.5%) in the recent outbreak but in only 2 patients (2.0%) in the past outbreak. CONCLUSIONS: Clinical data and manifestations were more severe in the recent outbreak than in the past outbreak of acute hepatitis A. It is important to be aware of hepatitis A virus infection and to take into account the available vaccination against hepatitis A virus in Japan.

Acute Disease↗
PubMed2002

Absence of specific symptoms in chronic hepatitis C.

BACKGROUND: No systematic research has been carried out on the symptoms of chronic hepatitis C, although the disease is believed to induce subjective symptoms such as fatigue or dullness in the legs. METHODS: The Todai Health Index has been developed as a symptom checklist that is used for screening particular diseases or for health management. The index was chosen as the most suitable questionnaire for measuring characteristic symptoms of chronic hepatitis C. Sixty patients with chronic hepatitis C who did not have any severe complications were compared with healthy control subjects who were selected randomly from the residents of Isesaki City, Gunma, Japan. RESULTS: The major findings were as follows: (1) male and female patients with chronic hepatitis C had no characteristic subjective physical symptoms when compared with the healthy controls, except for a significant difference in aggression, and (2) the severity of the hepatitis was not associated with the patients' symptoms after adjusting for age and treatments. CONCLUSIONS: Patients with chronic hepatitis C who did not have any severe complications did not show specific subjective physical symptoms.

Adult↗
PubMed2002

Simple liver cyst with spontaneous regression.

We report a-55-year-old woman with spontaneous regression of simple liver cyst. The size of the cyst gradually became reduced without any treatment, and a reduction in diameter from 77 mm to 10 mm was observed after 8 years of follow-up. Spontaneous regression of congenital cysts of the liver in an adult seems to be very rare, and its mechanism is discussed.

Cysts↗
PubMed2002

Inhibitory mechanism of vascular endothelial growth factor (VEGF) by bucillamine.

1. Vascular endothelial growth factor (VEGF) plays an important role in the neovascularization of ischaemic retinal diseases such as proliferative diabetic retinopathy. We determined that bucillamine, an anti-rheumatic drug, inhibits the VEGF production induced by hypoxia in bovine retinal microcapillary endothelial cells (BREC). To further clarify the inhibitory mechanism, we investigated the possible mechanism by which bucillamine exerts this inhibitory effect. 2. Bucillamine (100 micro M) decreased the hypoxia-induced increase of VEGF mRNA by 54.5% (P<0.001). Bucillamine (100 micro M) reduced the hypoxia-induced VEGF content in culture media by 29.0% (P<0.001), while monosulfydryl drugs, N-acetylcysteine and D-penicillamine, did not. 3. Bucillamine (100 micro M) did not affect VEGF mRNA half-life (hypoxia, 4.3 h; hypoxia+bucillamine, 3.9 h; normoxia, 2.7 h; normoxia+bucillamine, 2.7 h). 4. Reporter gene studies revealed that bucillamine reduced transcriptional activity in the 5'-flanking region of the VEGF gene by 74.0%. Hypoxia stimulated binding activity of BREC nuclear protein to a hypoxia responsive element (HRE), which was decreased by bucillamine. 5. Bucillamine inhibited hypoxic-induction of HIF-1alpha mRNA by 73.1% (P<0.001). Bucillamine also inhibited spontaneous VEGF mRNA expression by 26.6%. Furthermore, it inhibited activity of VEGF promoter and decreased binding activity to Sp1 and HRE, but did not alter AP1 and AP2 activity in normoxia. 6. These data suggest that bucillamine inhibits hypoxic induction of VEGF through inhibition of HIF-1 induction and binding activity in BREC. Bucillamine also inhibits the spontaneous expression of VEGF mRNA by its effect on Sp1 and HRE binding.

Animals↗