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Yuko Kageyama,
Hitoshi Ikeda, Naoko Watanabe,
Masakazu Nagamine,
Yoshika Kusumoto,
Mitsuru Yashiro,
Yumiko Satoh,
Tatsuo Shimosawa,
Koji Shinozaki,
Tomoaki Tomiya, [......],
Takako Nishikawa,
Natsuko Ohtomo,
Yasushi Tanoue,
Hiromitsu Yokota,
Takatoshi Koyama,
Kazuhiro Ishimaru,
Yasuo Okamoto,
Yoh Takuwa,
Kazuhiko Koike,
Yutaka Yatomi
[show abstract]
[hide abstract]
ABSTRACT: Sinusoidal vasoconstriction, in which hepatic stellate cells operate as contractile machinery, has been suggested to play a pivotal role in the pathophysiology of portal hypertension. We investigated whether sphingosine 1-phosphate (S1P) stimulates contractility of those cells and enhances portal vein pressure in isolated perfused rat livers with Rho activation by way of S1P receptor 2 (S1P(2) ). Rho and its effector, Rho kinase, reportedly contribute to the pathophysiology of portal hypertension. Thus, a potential effect of S1P(2) antagonism on portal hypertension was examined. Intravenous infusion of the S1P(2) antagonist, JTE-013, at 1 mg/kg body weight reduced portal vein pressure by 24% without affecting mean arterial pressure in cirrhotic rats induced by bile duct ligation at 4 weeks after the operation, whereas the same amount of S1P(2) antagonist did not alter portal vein pressure and mean arterial pressure in control sham-operated rats. Rho kinase activity in the livers was enhanced in bile duct-ligated rats compared to sham-operated rats, and this enhanced Rho kinase activity in bile duct-ligated livers was reduced after infusion of the S1P(2) antagonist. S1P(2) messenger RNA (mRNA) expression, but not S1P(1) or S1P(3) , was increased in bile duct-ligated livers of rats and mice and also in culture-activated rat hepatic stellate cells. S1P(2) expression, determined in S1P 2LacZ/+ mice, was highly increased in hepatic stellate cells of bile duct-ligated livers. Furthermore, the increase of Rho kinase activity in bile duct-ligated livers was observed as early as 7 days after the operation in wildtype mice, but was less in S1P 2-/- mice. Conclusion: S1P may play an important role in the pathophysiology of portal hypertension with Rho kinase activation by way of S1P(2) . The S1P(2) antagonist merits consideration as a novel therapeutic agent for portal hypertension. (HEPATOLOGY 2012).
Hepatology 04/2012; 56(4):1427-38. · 11.66 Impact Factor
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Hayato Nakagawa,
Hitoshi Ikeda,
Kazuhiro Nakamura,
Ryunosuke Ohkawa,
Ryota Masuzaki,
Ryosuke Tateishi,
Haruhiko Yoshida, Naoko Watanabe,
Kazuaki Tejima,
Yukio Kume, [......],
Tomoaki Tomiya,
Yukiko Inoue,
Takako Nishikawa,
Natsuko Ohtomo,
Yasushi Tanoue,
Masao Omata,
Koji Igarashi,
Junken Aoki,
Kazuhiko Koike,
Yutaka Yatomi
[show abstract]
[hide abstract]
ABSTRACT: The clinical significance of autotaxin (ATX), a key enzyme for the production of the bioactive lysophospholipid lysophosphatidic acid remains unknown. Serum ATX enzymatic activity reportedly increases in parallel with liver fibrosis and exhibits a gender difference.
Serum ATX antigen level, measured easier than the activity, was evaluated as a marker of liver fibrosis in 2 cohorts of chronic liver disease caused by hepatitis C virus.
In the first cohort, serum ATX level correlated significantly with liver fibrosis stage and was the best parameter for prediction of cirrhosis with an area under the receiver operating characteristic curve (AUROC) of 0.756 in male and 0.760 in female, when compared with serum hyaluronic acid and aminotransferase-to-platelet ratio index, an established marker of liver fibrosis. In another cohort, serum ATX level correlated significantly with liver stiffness, a novel reliable marker of liver fibrosis, being the second-best parameter in male (AUROC, 0.799) and in female (AUROC, 0.876) for prediction of significant fibrosis, and the best parameter in male (AUROC, 0.863) and the third-best parameter in female (AUROC, 0.872) for prediction of cirrhosis, both of which were judged by liver stiffness.
Serum ATX level may be a novel marker of liver fibrosis.
Clinica chimica acta; international journal of clinical chemistry 03/2011; 412(13-14):1201-6. · 2.54 Impact Factor
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Hitoshi Ikeda,
Ryunosuke Ohkawa, Naoko Watanabe,
Kazuhiro Nakamura,
Yukio Kume,
Hayato Nakagawa,
Haruhiko Yoshida,
Shigeo Okubo,
Hiromitsu Yokota,
Tomoaki Tomiya,
Yukiko Inoue,
Takako Nishikawa,
Natsuko Ohtomo,
Yasushi Tanoue,
Kazuhiko Koike,
Yutaka Yatomi
[show abstract]
[hide abstract]
ABSTRACT: Bioactive lipid mediator S1P has been suggested to play pathophysiological roles in various fields of clinical science as a circulating paracrine mediator. We previously established a reliable method of measuring plasma S1P concentration, and reported that the one in healthy subjects has a gender difference and a correlation with red blood cell (RBC)-parameters, however, the reports of S1P measurements in the blood in patients with a specific disease have been scarce. Because our previous evidence suggests that S1P is involved in liver pathophysiology, we examined plasma S1P concentration in chronic hepatitis C patients.
S1P assay was performed using a high-performance liquid chromatography system.
Plasma S1P concentrations were reduced in chronic hepatitis C patients compared with in healthy subjects with the same hemoglobin concentration, irrespective of gender. Among the blood parameters, serum hyaluronic acid concentration, a surrogate marker for liver fibrosis, was most closely and inversely correlated with plasma S1P concentration. Furthermore, plasma S1P concentration decreased throughout the progression of carbon tetrachloride-induced liver fibrosis in rats.
Plasma S1P concentration was reduced in chronic hepatitis C patients, and liver fibrosis might be involved, at least in part, in the mechanism responsible for this reduction.
Clinica chimica acta; international journal of clinical chemistry 02/2010; 411(9-10):765-70. · 2.54 Impact Factor
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Naoko Watanabe,
Hitoshi Ikeda,
Yukio Kume,
Yumiko Satoh,
Makoto Kaneko,
Daiya Takai,
Kazuaki Tejima,
Masakazu Nagamine,
Hirosato Mashima,
Tomoaki Tomiya,
Eisei Noiri,
Masao Omata,
Masanori Matsumoto,
Yoshihiro Fujimura,
Yutaka Yatomi
[show abstract]
[hide abstract]
ABSTRACT: Although hepatic stellate cells, endothelial cells, glomerular podocytes and plateles were reported to be a source of ADAMTS13, it is not clarified which source is involved in the regulation of plasma ADAMTS13 activity. It was demonstrated previously that selective hepatic stellate cell damage in rats caused decreased plasma ADAMTS13 activity. To further elucidate the potential contribution of hepatic stellate cells to the regulation of plasma ADAMTS13 activity, this study examined plasma ADAMTS13 activity when hepatic stellate cells proliferate during the process of liver fibrosis by employing rat models of liver fibrosis due to cholestasis, bile duct ligation, and steatohepatitis, a choline-deficient L-amino acid-defined-diet. ADAMTS13 expression was increased with co-localisation with smooth muscle alpha-actin, a marker of hepatic stellate cells, in bile duct-ligated livers up to four weeks, in which a close correlation between ADAMTS13 and smooth muscle alpha-actin mRNA expressions was determined. Plasma ADAMTS13 activity, measured by a sandwich ELISA involving a specific substrate to ADAMTS13, was increased in bile duct-ligated rats with a significant correlation with ADAMTS13 mRNA expression levels in the liver. Furthermore, ADAMTS13 mRNA expression was increased with enhanced mRNA expression in smooth muscle alpha-actin in the livers of rats fed a choline-deficient L-amino acid-defined-diet for 16 weeks, in which increased plasma ADAMTS13 activity was determined. Thus, increased plasma ADAMTS13 activity in cholestasis and steatohepatitis in rats may be due, at least in part, to enhanced ADAMTS13 production in the liver, suggesting a significant role of hepatic stellate cells in the regulation of plasma ADAMTS13 activity.
Thrombosis and Haemostasis 09/2009; 102(2):389-96. · 5.04 Impact Factor
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ABSTRACT: Autotaxin (ATX), discovered in human melanoma cells, has been gaining attention because it could be involved in cancer invasion and metastasis as an autocrine motility factor. Recent evidence has indicated that ATX is a key enzyme in the synthesis of lysophosphatidic acid, a lipid mediator with a wide range of biological actions including the stimulation of proliferation and contraction in hepatic stellate cells, a pivotal player in hepatic fibrosis. Serum ATX activity was found to be enhanced in relation to hepatic fibrosis in chronic liver disease due to hepatitis virus C infection, and the possible contribution of ATX to the pathogenesis of hepatic fibrosis should be further clarified. Although an enhanced activity of serum ATX was noted in patients with hepatocellular carcinoma, this may be due to hepatic fibrosis from which hepatocellular carcinoma often arises. It is worth further evaluating whether serum ATX activity is significantly enhanced in patients with cancers of the digestive system other than hepatocellular carcinoma.
Rinsho byori. The Japanese journal of clinical pathology 06/2009; 57(5):445-9.
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Hitoshi Ikeda, Naoko Watanabe,
Isao Ishii,
Tatsuo Shimosawa,
Yukio Kume,
Tomoaki Tomiya,
Yukiko Inoue,
Takako Nishikawa,
Natsuko Ohtomo,
Yasushi Tanoue,
Satoko Iitsuka,
Ryoto Fujita,
Masao Omata,
Jerold Chun,
Yutaka Yatomi
[show abstract]
[hide abstract]
ABSTRACT: Sphingosine 1-phosphate (S1P), a bioactive lipid mediator, stimulates proliferation and contractility in hepatic stellate cells, the principal matrix-producing cells in the liver, and inhibits proliferation via S1P receptor 2 (S1P(2)) in hepatocytes in rats in vitro. A potential role of S1P and S1P(2) in liver regeneration and fibrosis was examined in S1P(2)-deficient mice. Nuclear 5-bromo-2'-deoxy-uridine labeling, proliferating cell nuclear antigen (PCNA) staining in hepatocytes, and the ratio of liver weight to body weight were enhanced at 48 h in S1P(2)-deficient mice after a single carbon tetrachloride (CCl(4)) injection. After dimethylnitrosamine (DMN) administration with a lethal dose, PCNA staining in hepatocytes was enhanced at 48 h and survival rate was higher in S1P(2)-deficient mice. Serum aminotransferase level was unaltered in those mice compared with wild-type mice in both CCl(4)- and DMN-induced liver injury, suggesting that S1P(2) inactivation accelerated regeneration not as a response to enhanced liver damage. After chronic CCl(4) administration, fibrosis was less apparent, with reduced expression of smooth-muscle alpha-actin-positive cells in the livers of S1P(2)-deficient mice, suggesting that S1P(2) inactivation ameliorated CCl(4)-induced fibrosis due to the decreased accumulation of hepatic stellate cells. Thus, S1P plays a significant role in regeneration and fibrosis after liver injury via S1P(2).
The Journal of Lipid Research 11/2008; 50(3):556-64. · 5.56 Impact Factor
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ABSTRACT: Amino acids regulate cellular functions in a variety of cell types. Most notably, leucine stimulates protein production through the mammalian target of rapamycin (mTOR)-dependent signaling pathway. We investigated the effect of amino acids on hepatocyte growth factor (HGF) production. Treatment with glutamine and proline, as well as leucine, increased HGF levels in the culture medium of a rat hepatic stellate cell clone in a dose-dependent manner. Up-regulation of phosphorylation of 70 kDa ribosomal protein S6 kinase and eukaryotic initiation factor 4E-binding protein 1 was not apparent in the cells after treatment with glutamine or proline. When rats received injections of glutamine or proline, hepatic and circulating HGF levels increased and peaked around 12h after treatment. Glutamine and proline may have the potential to stimulate HGF production but the mechanism underlying this stimulation seems not to be through the mTOR-dependent signaling pathway.
Biochemical and Biophysical Research Communications 12/2007; 363(4):978-82. · 2.48 Impact Factor
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Kazuaki Tejima,
Masahiro Arai,
Hitoshi Ikeda,
Tomoaki Tomiya,
Mikio Yanase,
Yukiko Inoue,
Takako Nishikawa, Naoko Watanabe,
Natsuko Ohtomo,
Masao Omata,
Kenji Fujiwara
[show abstract]
[hide abstract]
ABSTRACT: To elucidate the mechanisms of hepatocyte preconditioning by H2O2 to better understand the pathophysiology of ischemic preconditioning.
The in vitro effect of H2O2 pretreatment was investigated in rat isolated hepatocytes subjected to anoxia/reoxygenation. Cell viability was assessed with propidium iodide fluorometry. In other experiments, rat livers were excised and subjected to warm ischemia/reperfusion in an isolated perfused liver system to determine leakage of liver enzymes. Preconditioning was performed by H2O2 perfusion, or by stopping the perfusion for 10 min followed by 10 min of reperfusion. To inhibit Kupffer cell function or reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, gadolinium chloride was injected prior to liver excision, or diphenyleneiodonium, an inhibitor of NADPH oxidase, was added to the perfusate, respectively. Histological detection of oxygen radical formation in Kupffer cells was performed by perfusion with nitro blue tetrazolium.
Anoxia/reoxygenation decreased hepatocyte viability compared to the controls. Pretreatment with H2O2 did not improve such hepatocyte injury. In liver perfusion experiments, however, H2O2 preconditioning reduced warm ischemia/reperfusion injury, which was reversed by inhibition of Kupffer cell function or NADPH oxidase. Histological examination revealed that H2O2 preconditioning induced oxygen radical formation in Kupffer cells. NADPH oxidase inhibition also reversed hepatoprotection by ischemic preconditioning.
H2O2 preconditioning protects hepatocytes against warm ischemia/reperfusion injury via NADPH oxidase in Kupffer cells, and not directly. NADPH oxidase also mediates hepatoprotection by ischemic preconditioning.
World Journal of Gastroenterology 11/2007; 13(38):5071-8. · 2.47 Impact Factor
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Hitoshi Ikeda,
Yukio Kume,
Kazuaki Tejima,
Tomoaki Tomiya,
Takako Nishikawa, Naoko Watanabe,
Natsuko Ohtomo,
Masahiro Arai,
Chihiro Arai,
Masao Omata,
Kenji Fujiwara,
Yutaka Yatomi
[show abstract]
[hide abstract]
ABSTRACT: A protective effect of Rho-kinase inhibitor on various organ injuries is gaining attention. Regarding liver injury, Rho-kinase inhibitor is reported to prevent carbon tetrachloride (CCl4)- or dimethylnitrosamine-induced liver fibrosis and hepatic ischemia-reperfusion injury in rats. Because Rho-kinase inhibitor not only improved liver fibrosis but also reduced serum alanine aminotransferase (ALT) level in CCl4-induced liver fibrosis, we wondered whether Rho-kinase inhibitor might exert a direct hepatocyte-protective effect. We examined this possibility in acute CCl4 intoxication in rats. Rho-kinase inhibitor, HA-1077, reduced serum alanine ALT level in rats with acute liver injury induced by CCl4 with the improvement of histological damage and the reduction of the number of apoptotic cells. In cultured rat hepatocytes in serum-free condition, HA-1077 reduced apoptosis evaluated by quantitative determination of cytoplasmic histone-associated DNA oligonucleosome fragments with the reduction of caspase-3 activity and the enhancement of Bcl-2 expression. HA-1077 stimulated phosphorylation of Akt, and wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3-kinase)/Akt pathway, abrogated the reduction of hepatocyte apoptosis by HA-1077 in vitro. Furthermore, wortmannin abrogated the reduction of serum ALT level by HA-1077 in rats with acute liver injury induced by CCl4, suggesting that the activation of PI3-kinase/Akt pathway may be involved in the hepatocyte-protective effect by Rho-kinase inhibitor in vivo. In conclusion, Rho-kinase inhibitor prevented hepatocyte damage in acute liver injury induced by CCl4 in rats and merits consideration as a hepatocyte-protective agent in liver injury, considering its direct antiapoptotic effect on hepatocytes in vitro.
AJP Gastrointestinal and Liver Physiology 11/2007; 293(4):G911-7. · 3.43 Impact Factor
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Naoko Watanabe,
Hitoshi Ikeda,
Kazuhiro Nakamura,
Ryunosuke Ohkawa,
Yukio Kume,
Tomoaki Tomiya,
Kazuaki Tejima,
Takako Nishikawa,
Masahiro Arai,
Mikio Yanase,
Junken Aoki,
Hiroyuki Arai,
Masao Omata,
Kenji Fujiwara,
Yutaka Yatomi
[show abstract]
[hide abstract]
ABSTRACT: Lysophosphatidic acid (LPA) is a lipid mediator with multiple biological actions. We have reported that LPA stimulates hepatic stellate cell proliferation and inhibits DNA synthesis in hepatocytes, suggesting that LPA might play some role in the liver. We have found that plasma LPA level and serum autotaxin (ATX) activity were increased in patients with chronic hepatitis C. However, the clinical significance of LPA and its synthetic enzyme, autotaxin (ATX), is still unclear. To determine whether the increase of plasma LPA level and serum ATX activity might be found generally in liver injury, we examined the possible modulation of them in the blood in rats with various liver injuries. Plasma LPA level and serum ATX activity were increased in carbon tetrachloride-induced liver fibrosis correlatively with fibrosis grade, in dimethylnitrosamine-induced acute liver injury correlatively with serum alanine aminotransferase level or in 70% hepatectomy as early as 3 h after the operation. Plasma LPA level was correlated with serum ATX activity in rats with chronic and acute liver injury. ATX mRNA in the liver was not altered in carbon tetrachloride-induced liver fibrosis. Plasma LPA level and serum ATX activity are increased in various liver injuries in relation to their severity. Whether increased ATX and LPA in the blood in liver injury is simply a result or also a cause of the injury should be further clarified.
Life Sciences 10/2007; 81(12):1009-15. · 2.53 Impact Factor
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Naoko Watanabe,
Hitoshi Ikeda,
Kazuhiro Nakamura,
Ryunosuke Ohkawa,
Yukio Kume,
Junken Aoki,
Kotaro Hama,
Shinichi Okudaira,
Masayuki Tanaka,
Tomoaki Tomiya,
Mikio Yanase,
Kazuaki Tejima,
Takako Nishikawa,
Masahiro Arai,
Hiroyuki Arai,
Masao Omata,
Kenji Fujiwara,
Yutaka Yatomi
[show abstract]
[hide abstract]
ABSTRACT: Recent accumulating evidence indicates that lysophosphatidic acid (LPA) is a lipid mediator, abundantly present in blood, with a wide range of biologic actions including the regulation of proliferation and contraction in liver cells. Although it is speculated that LPA might play a role in pathophysiologic processes in vivo, not only its role but also even a possible alteration in its blood concentration under specific diseases is essentially unknown. Autotaxin (ATX), originally purified as an autocrine motility factor for melanoma cells, was revealed to be a key enzyme in LPA synthesis. We determined LPA and ATX levels in the blood of patients with liver disease.
ATX activity was measured by determining choline with the substrate of lysophosphatidylcholine, and the LPA level by an enzymatic cycling method in 41 patients with chronic hepatitis C.
The serum ATX activity and plasma LPA level were significantly increased in patients, and were correlated positively with serum hyaluronic acid, and negatively with platelets, albumin, and prothrombin time. The plasma LPA level was strongly correlated with serum ATX activity. There were significant correlations between the histologic stage of fibrosis and both the serum ATX activity and plasma LPA level.
The serum ATX activity and plasma LPA level are increased in chronic hepatitis C in association with liver fibrosis. Our study may provide the first evidence showing a significant increase of both ATX and LPA in the blood under a specific disease.
Journal of Clinical Gastroenterology 08/2007; 41(6):616-23. · 3.16 Impact Factor
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ABSTRACT: Branched chain amino acids modulate various cellular functions in addition to providing substrates for the production of proteins. We examined the mechanism underlying the stimulation by leucine of hepatocyte growth factor (HGF) production by hepatic stellate cells. Both p70 S6 kinase activity and phosphorylation of eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) were up-regulated rapidly after leucine treatment of a rat hepatic stellate cell clone. No such activation was observed following treatment with valine or isoleucine. Rapamycin, an inhibitor of mammalian target of rapamycin (mTOR), suppressed leucine-induced activation of p70 S6 kinase and 4E-BP1 and negated the stimulatory effect of leucine on HGF production. An mTOR-dependent signaling pathway mediates the stimulatory effect of leucine on the production of HGF by hepatic stellate cells.
Biochemical and Biophysical Research Communications 07/2007; 358(1):176-80. · 2.48 Impact Factor
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Masahiro Arai,
Kazuaki Tejima,
Hitoshi Ikeda,
Tomoaki Tomiya,
Mikio Yanase,
Yukiko Inoue,
Kayo Nagashima,
Takako Nishikawa, Naoko Watanabe,
Masao Omata,
Kenji Fujiwara
[show abstract]
[hide abstract]
ABSTRACT: Brief periods of tissue ischemia produced tissue resistance to prolonged ischemia and reperfusion, a phenomenon called ischemic preconditioning. The mechanisms of ischemic preconditioning were examined in a rat warm ischemia-reperfusion model as well as the effect of ischemic preconditioning on liver regeneration. Ischemic preconditioning decreased liver injury after warm ischemia-reperfusion, which was reversed by Kupffer cell depletion. Ischemic preconditioning stimulated Kupffer cells to produce reactive oxygen species. Scavengers of reactive oxygen species reversed the effect of ischemic preconditioning, and pretreatment with sublethal dose of hydrogen peroxide mimicked ischemic preconditioning effect. Rat livers were preconditioned by ischemia and subjected to 70% partial hepatectomy. Liver regeneration was then evaluated serially. Ischemic preconditioning promoted liver regeneration, which was reversed by adenosine A2 receptor antagonism and mimicked by adenosine A2 receptor agonism. Promotion of liver regeneration by ischemic preconditioning and adenosine A2 receptor agonism were reversed by Kupffer cell depletion. In conclusion, ischemic preconditioning stimulates Kupffer cells to produce reactive oxygen species, leading to hepatocyte protection against warm ischemia-reperfusion injury; and ischemic preconditioning promoted liver regeneration via adenosine A2 receptor pathway in Kupffer cells.
Journal of Gastroenterology and Hepatology 07/2007; 22 Suppl 1:S65-7. · 2.87 Impact Factor
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Yukio Kume,
Hitoshi Ikeda,
Morihiro Inoue,
Kazuaki Tejima,
Tomoaki Tomiya,
Takako Nishikawa, Naoko Watanabe,
Tatsuya Ichikawa,
Makoto Kaneko,
Shigeo Okubo,
Hiromitsu Yokota,
Masao Omata,
Kenji Fujiwara,
Yutaka Yatomi
[show abstract]
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ABSTRACT: ADAMTS13 is gaining attention, because its deficiency causes thrombotic thrombocytopenic purpura. Although its regulatory mechanism is not fully understood, we wondered if hepatic stellate cells (HSCs) play a role, because ADAMTS13 mRNA is exclusively expressed in the liver and primarily in HSCs. Plasma ADAMTS13 activity was markedly reduced in dimethylnitrosamine-treated rats, where HSC apoptosis is an essential event, but not in carbon tetrachloride- or thioacetamide-treated rats without HSC apoptosis. Furthermore, plasma ADAMTS13 activity was also reduced in 70% hepatectomized rats, where HSC loss occurs. These results suggest that HSC may be involved in the regulation of plasma ADAMTS13 activity.
FEBS Letters 05/2007; 581(8):1631-4. · 3.54 Impact Factor
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Tomoaki Tomiya,
Miho Yamaoka,
Yukiko Inoue,
Takako Nishikawa,
Mikio Yanase,
Hitoshi Ikeda,
Kazuaki Tejima,
Kayo Nagashima, Naoko Watanabe,
Masao Omata,
Kenji Fujiwara
[show abstract]
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ABSTRACT: Background: Rapamycin is a specific inhibitor of the mammalian target of rapamycin (mTOR). The effect of rapamycin on proliferation and cellular function was studied in hepatocytes stimulated by hepatocyte growth factor (HGF) or transforming growth factor-alpha (TGFalpha). Methods and Results: When isolated rat hepatocytes were cultured at low density, the addition of HGF or TGFalpha increased DNA synthesis but did not affect albumin or fibrinogen concentrations in the medium. In contrast, in hepatocytes cultured at high density, the albumin and fibrinogen concentrations, but not DNA synthesis, were increased by HGF or TGFalpha. The HGF- or TGFalpha-induced increase in DNA synthesis and in albumin or fibrinogen concentrations was suppressed by the addition of rapamycin, as well as wortmannin, a phosphatidylinositol-3 kinase inhibitor. Conclusion: HGF and TGFalpha stimulate proliferation and function of hepatocytes depending upon the conditions, and rapamycin inhibited these stimulatory effects, possibly by inhibiting the mTOR-dependent signaling pathway.
Chemotherapy 02/2007; 53(1):59-69. · 1.82 Impact Factor
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Hitoshi Ikeda,
Kayo Nagashima,
Mikio Yanase,
Tomoaki Tomiya,
Masahiro Arai,
Yukiko Inoue,
Kazuaki Tejima,
Takako Nishikawa, Naoko Watanabe,
Kazuya Kitamura,
Tomomi Isono,
Naohisa Yahagi,
Eisei Noiri,
Mie Inao,
Satoshi Mochida,
Yukio Kume,
Yutaka Yatomi,
Kazuhiko Nakahara,
Masao Omata,
Kenji Fujiwara
[show abstract]
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ABSTRACT: Use of herbal remedies in the treatment of various diseases has a long tradition in Eastern medicine and the liver diseases are not an exception. In their use, lack of elucidation of mechanism(s) as well as randomized, placebo-controlled clinical trials has been a problem. Recently, we and others reported that inchin-ko-to (TJ-135), one of herbal remedies, suppressed hepatic fibrosis in animal models. In the course of clarifying the mechanism, we directed our focus on hepatic stellate cells (HSCs), playing a pivotal role in hepatic fibrosis, and found that rat HSCs cultured with TJ-135 changed their morphology to star-like configuration with thin, slender and dendritic processes with fewer stress fibers, which might be the features in apoptosis. In fact, TJ-135 induced HSC apoptosis in a time- and concentration-dependent manner as judged by the nuclear morphology, quantitation of cytoplasmic histone-associated DNA oligonucleosome fragments and caspase 3 activity. In HSCs treated with TJ-135, increased expression of p53 and decreased expression of Bcl-2 and phosphorylated Akt and Bad were determined. HSC apoptosis is shown to be involved in the mechanisms of spontaneous resolution of rat hepatic fibrosis and the agent which induces HSC apoptosis has been shown to reduce experimental hepatic fibrosis in rats. Thus, the induction of HSC apoptosis could be the mechanism how TJ-135 works on the resolution of hepatic fibrosis. Our current data may shed light on the novel effect of the herbal remedy.
Life Sciences 05/2006; 78(19):2226-33. · 2.53 Impact Factor
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Kazuaki Tejima,
Masahiro Arai,
Hitoshi Ikeda,
Tomoaki Tomiya,
Mikio Yanase,
Yukiko Inoue,
Kayo Nagashima,
Takako Nishikawa, Naoko Watanabe,
Masao Omata,
Kenji Fujiwara
[show abstract]
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ABSTRACT: Hepatic ischemic preconditioning decreases sinusoidal endothelial cell injury and Kupffer cell activation after cold ischemia/reperfusion, leading to improved survival of liver transplant recipients in rats. Ischemic preconditioning also protects livers against warm ischemia/reperfusion injury, in which hepatocyte injury is remarkable. We aimed to determine whether ischemic preconditioning directly protects hepatocytes and to elucidate its mechanisms.
Rats were injected with gadolinium chloride to deplete Kupffer cells or with N -acetyl- l -cysteine, superoxide dismutase, or catalase to scavenge reactive oxygen species. Livers were then preconditioned by 10 minutes of ischemia and 10 minutes of reperfusion. Subsequently, livers were subjected to 40 minutes of warm ischemia and 60 minutes of reperfusion in vivo or in a liver perfusion system. In other rats, livers were preconditioned by H(2)O(2) perfusion instead of ischemia. In the other experiments, livers were perfused with nitro blue tetrazolium to detect reactive oxygen species formation.
Ischemic preconditioning decreased injury in hepatocytes, but not in sinusoidal endothelial cells. Kupffer cell depletion itself did not change hepatocyte injury after ischemia/reperfusion, indicating no contribution of Kupffer cells to ischemia/reperfusion injury. However, Kupffer cell depletion reversed hepatoprotection by ischemic preconditioning. Reactive oxygen species formation occurred in Kupffer cells after ischemic preconditioning. Scavenging of reactive oxygen species reversed the effect of ischemic preconditioning, and H(2)O(2) preconditioning mimicked ischemic preconditioning.
Ischemic preconditioning directly protected hepatocytes after warm ischemia/reperfusion, which is not via suppression of changes in sinusoidal cells as in cold ischemia/reperfusion injury. This hepatocyte protection was mediated by reactive oxygen species produced by Kupffer cells.
Gastroenterology 12/2004; 127(5):1488-96. · 11.68 Impact Factor
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Tomoaki Tomiya,
Yukiko Inoue,
Mikio Yanase,
Masahiro Arai,
Hitoshi Ikeda,
Kazuaki Tejima,
Kayo Nagashima,
Takako Nishikawa, Naoko Watanabe,
Masao Omata,
Kenji Fujiwara
[show abstract]
[hide abstract]
ABSTRACT: Hepatocyte growth factor (HGF) has pleiotropic effects. Up-regulation of HGF activity in vivo may be beneficial. Branched-chain amino acids (BCAAs) are known to modulate various cellular functions. When starved rats received intraperitoneal injections of valine, leucine or isoleucine, only leucine treatment increased both hepatic and circulating levels of HGF in a dose-dependent manner, up to 1.5 and 2.3 times higher, respectively, than in controls. When young growing rats with free access to food were injected with leucine once a day for a week, HGF levels and liver weights were significantly higher than those of control rats. Furthermore, 1 week of leucine treatment of adult rats resulted in elevated serum albumin levels with an increase in HGF levels. Taken together with our previous report showing that leucine stimulates HGF production by hepatic stellate cells in culture, leucine, among BCAAs, may induce an increase in HGF production by the liver in vivo.
Biochemical and Biophysical Research Communications 10/2004; 322(3):772-7. · 2.48 Impact Factor
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Hitoshi Ikeda,
Kayo Nagashima,
Mikio Yanase,
Tomoaki Tomiya,
Masahiro Arai,
Yukiko Inoue,
Kazuaki Tejima,
Takako Nishikawa, Naoko Watanabe,
Masao Omata,
Kenji Fujiwara
[show abstract]
[hide abstract]
ABSTRACT: Although structural changes are most important to determine vascular resistance in portal hypertension, vasoactive mediators also contribute to its regulation. Hepatic stellate cells (HSCs) are assumed to play a role in modulating intrahepatic vascular resistance based on their residence in the space of Disse and capacity to contract. Because sphingosine 1-phosphate (S1P) has been shown to stimulate HSC contractility, we wondered if S1P could regulate portal pressure. S1P at 0.5-5 microM increased portal pressure in isolated rat perfused liver. This effect was abrogated in the presence of a binding antagonist for S1P2, JTE-013. Perfusion of isolated rat liver with 5 microM S1P increased Rho activity in the liver, and co-perfusion with JTE-013 cancelled S1P-induced Rho activation. Because S1P is present in human plasma at approximately 0.2 microM, S1P might readily regulate portal vascular tone in physiological and pathological status. The antagonist for S1P2 merits consideration for treatment of portal hypertension.
Biochemical and Biophysical Research Communications 08/2004; 320(3):754-9. · 2.48 Impact Factor
