Shotaro Sakisaka

Genomic Structure of the Canalicular Multispecific Organic Anion–Transporter Gene (MRP2/cMOAT) and Mutations in the ATP-Binding–Cassette Region in Dubin-Johnson Syndrome

Summary Dubin-Johnson syndrome (DJS) is an autosomal recessive disease characterized by conjugated hyperbilirubinemia. Previous studies of the defects in the human canalicular multispecific organic anion transporter gene ( MRP2/cMOAT ) in patients with DJS have suggested that the gene defects are responsible for DJS. In this study, we determined the exon/intron structure of the human MRP2/cMOAT gene and further characterized mutations in patients with DJS. The human MRP2/cMOAT gene contains 32 exons, and it has a structure that is highly conserved with that of another ATP–binding–cassette gene, that for a multidrug resistance–associated protein. We then identified three mutations, including two novel ones. All mutations identified to date are in the cytoplasmic domain, which includes the two ATP-binding cassettes and the linker region, or adjacent putative transmembrane domain. Our results confirm that MRP2/cMOAT is the gene responsible for DJS. The finding that mutations are concentrated in the first ATP-binding–cassette domain strongly suggests that a disruption of this region is a critical route to loss of function.

Expression and Role of Vascular Endothelial Growth Factor in Liver Regeneration After Partial Hepatectomy in Rats

Vascular endothelial growth factor (VEGF) plays a major role in angiogenesis, which is essential for both healing of injured tissue and proliferation of carcinoma cells. In this study we elucidated the expression and role of VEGF in rat liver regeneration after partial hepatectomy. VEGF expression was mainly detected in periportal hepatocytes and reached a maximal level 48–72 hr after partial hepatectomy by both immunohistochemistry and in situ hybridization. Similarly, immunohistochemistry for Ki-67 showed that the proliferative activity of sinusoidal endothelial cells was highest in the periportal area and reached a maximal level 72 hr after partial hepatectomy. Moreover, neutralization of VEGF significantly inhibited proliferative activity of hepatocytes (p < 0.0001), as well as sinusoidal endothelial cells (p < 0.001), at 48 and 96 hr after partial hepatectomy. Conversely, injection of VEGF significantly promoted proliferative activity of hepatocytes (p < 0.0001) as well as sinusoidal endothelial cells (p < 0.0005) at 48 hr after partial hepatectomy. These results suggest that VEGF promotes proliferation of hepatocytes through reconstruction of liver sinusoids by proliferation of sinusoidal endothelial cells. Furthermore, these data point to a new therapeutic strategy, the use of VEGF and other hepatocyte growth factors in fulminant or severe acute hepatitis.

Vascular Endothelial Growth Factor in Patients with Rheumatoid Arthritis

To examine the role of vascular endothelial growth factor (VEGF), an endothelial cell specific growth factor, in rheumatoid arthritis (RA), serum concentration of VEGF was examined in patients with RA, osteoarthritis (OA), systemic lupus erythematosus (SLE), systemic sclerosis (SS) and control subjects. Serum C-reactive protein (CRP) level, erythrocyte sedimentation rate, white blood cell count and rheumatoid factor titer were also determined in patients with RA. The serum concentration of VEGF was significantly higher in patients with RA than in controls (p < 0.01), and patients with OA (p < 0.05), SLE (p < 0.05), and SS (p < 0.05). The serum concentration of VEGF correlated with serum levels of CRP (r = 0.698, p < 0.0001). The serum concentration of VEGF before treatment was significantly higher than that after treatment in patients with RA who experienced clinical remission (p < 0.05). Our data suggest that VEGF is involved in the pathogenesis of RA and that measurement of serum concentration of VEGF is a noninvasive, useful method for monitoring the disease activity of RA.

Role of hepatocytes in direct clearance of lipopolysaccharide in rats

BACKGROUND & AIMS The liver is the clearance organ for lipopolysaccharide (LPS). The aim of this study was to investigate the biliary excretion of LPS using fluorescein isothiocyanate (FITC)-labeled LPS. METHODS After FITC-LPS was injected intravenously into rats, the cellular localization of fluorescence in the liver was examined and the biliary excretion of fluorescence was measured. The effects of gadolinium chloride, a blocker of Kupffer cells, and colchicine, an inhibitor of microtubules, on the biliary excretion of fluorescence was investigated, and bile was analyzed using high-performance liquid chromatography. RESULTS Laser scanning confocal microscopy showed that fluorescence was taken up by hepatocytes 5 minutes after injection of FITC-LPS into the portal vein. When FITC-LPS was injected into the portal vein, fluorescence was rapidly secreted into bile, peaking at 20 minutes, and 25.1% of the injected dose appeared in bile within 60 minutes. When the same dose of FITC-LPS was injected into the tail vein, 15.8% appeared in bile within 60 minutes. Chromatography showed that FITC-LPS was excreted into bile in an unchanged form over a period of 20 minutes after injection. Colchicine significantly reduced the biliary excretion of fluorescence, but gadolinium chloride had no effect. CONCLUSIONS LPS was directly and effectively processed by hepatocytes and secreted into the bile canalicular system via a microtubule-dependent vesicular pathway.

Abnormal accumulation of endotoxin in biliary epithelial cells in primary biliary cirrhosis and primary sclerosing cholangitis

BACKGROUNDS/AIMS Previous studies have revealed the involvement of Kupffer cells and hepatocytes in the metabolism of endotoxin in the liver. The aim of this study was to investigate the in vivo localization of endotoxin in liver cells, including Kupffer cells, hepatocytes, and biliary epithelial cells, in primary biliary cirrhosis and primary sclerosing cholangitis. We also examined the effect of ursodeoxycholic acid on the intrahepatic distribution of endotoxin in primary biliary cirrhosis. METHODS The immunohistochemical localization of endotoxin was examined in liver specimens from 30 cases of primary biliary cirrhosis and seven of primary sclerosing cholangitis using a monoclonal antibody against lipid A. Controls were seven cases of obstructive jaundice, ten of hepatitis C virus-related liver cirrhosis, 14 of chronic hepatitis C, and five histologically normal liver cases. Semi-quantitative analysis of endotoxin accumulation was performed to measure the intensity of fluorescence for endotoxin. Nine of the 30 patients with primary biliary cirrhosis underwent a second liver biopsy for evaluation of the ursodeoxycholic acid treatment. RESULTS In primary biliary cirrhosis and primary sclerosing cholangitis, biliary epithelial cells showed strong immunostaining for endotoxin as well as hepatocytes and Kupffer cells. Biliary epithelial cells of primary biliary cirrhosis and primary sclerosing cholangitis showed more intense immunoreactivity than those of other controls. In primary biliary cirrhosis, ursodeoxycholic acid reduced the immunoreactivity to endotoxin in biliary epithelial cells, and increased the immunoreactivity to endotoxin in Kupffer cells, but did not affect that in hepatocytes. CONCLUSIONS Our results revealed that in primary biliary cirrhosis and primary sclerosing cholangitis, endotoxin accumulates abnormally in biliary epithelial cells. In addition, we found that ursodeoxycholic acid treatment in primary biliary cirrhosis may provide a beneficial effect on the intrahepatic metabolism of endotoxin.

Guidelines for the treatment of chronic hepatitis and cirrhosis due to hepatitis B virus infection for the fiscal year 2008 in Japan

In the 2008 guidelines for the treatment of patients with cirrhosis, who are infected with hepatitis B virus (HBV), the main goal is to normalize levels of alanine and aspartate aminotransferases by eliminating HBV or reducing viral loads. In patients with compensated cirrhosis, the clearance of HBV from serum is aimed for by entecavir, as the main resort, for histological improvement toward the prevention of hepatocellular carcinoma (HCC). In patients with decompensated cirrhosis, by contrast, meticulous therapeutic strategies are adopted for the reversal to compensation, toward the eventual goal of decreasing the risk of HCC. For maintaining liver function and preventing HCC, branched chain amino acids and nutrient supplements are applied, in addition to conventional liver supportive therapies. For patients with chronic hepatitis B, separate guidelines are applied to those younger than 35 years and those aged 35 years or older. Even for patients with chronic hepatitis who are negative for hepatitis e antigen (HBeAg), but who harbor HBV DNA in titers of 7 log copies/mL or more, a “drug‐free state” is aimed for by sequential treatment with interferon (IFN) plus entecavir as the first line. For patients with chronic hepatitis B aged 35 years or older, who are HBeAg‐negative and carry HBV DNA in titers of less than 7 log copies/mL, long‐term IFN for 24–48 weeks is adopted anew. To HBeAg‐negative patients who have either or both platelet counts of less than 150 × 103/mm3 and less than 7 log copies of HBV DNA, also, long‐term IFN for 24–48 weeks is indicated.

The endothelin-1 binding site in rat liver tissue: Light- and electron-microscopic autoradiographic studies

BACKGROUND Endothelin (ET) is known as a vasoconstrictive substance. The receptors for ET have been shown in various organs. However, little is known about the endothelin-1 (ET-1) binding sites in the liver. The aim of this study was to examine ET-1 binding sites in the liver. METHODS ET-1 binding sites in rat liver were studied in vivo by light- and electron-microscopic autoradiography using 125I-ET-1. RESULTS Light-microscopic autoradiographic observation revealed strong localization of grains in the sinusoidal lining cells of the hepatic lobule and a small number of grains in the luminal space of the portal vein and central vein. In the hepatic lobule, more grains were located in the periportal region, and the quantity tended to decrease from the midzonal to the pericentral region. Electron-microscopic autoradiographic observation revealed grains in Ito cells and in the endothelial cells of the portal vein, central vein, and hepatic sinusoids. CONCLUSIONS These results suggest that ET-1 acts on Ito cells and on endothelial cells of the hepatic sinusoids, portal vein, and central vein and that its action is related to hemodynamics of the liver, particularly regulation of the microcirculation of the hepatic sinusoids.

High prevalence of anticardiolipin antibodies in hepatitis C virus infection: lack of effects on thrombocytopenia and thrombotic complications

Abstract: Hepatitis C virus (HCV) causes various extrahepatic immunologic abnormalities. Recently, an association between HCV infection and antiphospholipid syndrome, including thrombocytopenia, has been reported. However, the precise relationship between thrombocytopenia and anticardiolipin antibodies in patients with chronic HCV infection is not fully understood; likewise, the association of antiphospholipid syndrome and various liver diseases is not well understood. To evaluate the prevalence and importance of antiphospholipid antibodies in various chronic liver diseases, we determined the levels of anticardiolipin antibodies, platelet numbers, and levels of platelet-associated immunoglobulin G (PA-IgG) and thrombin-antithrombin III complex (TAT) in patients with chronic HCV infection, chronic hepatitis B virus (HBV) infection, and primary biliary cirrhosis (PBC). The prevalence of anticardiolipin antibodies in patients with HCV infection was significantly higher than that in control subjects or individuals with the other liver diseases examined. However, there was no significant correlation between anticardiolipin antibodies and platelet counts or TAT. The frequency of thrombotic complications was similar in anticardiolipin antibody-positive and -negative patients with chronic HCV infection. Further, sera from all but one anticardiolipin antibody-positive HCV patient were negative for phospholipid-dependent anti-β2 glycoprotein I antibodies. Our results suggest that anticardiolipin antibodies are frequently found in patients with chronic HCV infection, but they do not appear to be of clinical importance. Immunologic disturbances induced by HCV or prolonged tissue damage in systemic organs as a result of the extrahepatic manifestations of HCV infection may induce the production of antibodies to various cardiolipin-binding proteins or phospholipids.

PTEN/Akt signaling through epidermal growth factor receptor is prerequisite for angiogenesis by hepatocellular carcinoma cells that is susceptible to inhibition by gefitinib.

Hepatocellular carcinoma (HCC) is one of the most common tumor-related causes of death worldwide for which there is still no satisfactory treatment. We previously reported the antiangiogenic effect of gefitinib, a selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor that has been used successfully to treat lung cancer. In this study, we investigated the effects of gefitinib on tumor-induced angiogenesis by using HCC cell lines (HCC3, CBO12C3, and AD3) in vitro as well as in vivo. Oral administration of gefitinib inhibited angiogenesis induced by HCC3 and CBO12C3, but not by AD3 in the mouse dorsal air sac model. Production of both vascular endothelial growth factor (VEGF) and chemokine C-X-C motif ligand 1 (CXCL1) by EGF-stimulated HCC was more markedly inhibited by gefitinib in HCC3 and CBO12C3 cells than in AD3 cells. EGF stimulated the phosphorylation of EGFR, Akt, and extracellular signal-regulated kinase 1/2 (ERK1/2) in HCC3 and CBO12C3 cells, whereas EGF stimulated phosphorylation of EGFR and ERK1/2, but not Akt in AD3 cells. In fact, Akt was constitutively activated in the absence of EGF in AD3 cells. Gefitinib inhibited Akt phosphorylation in all three cell lines, but it was about five times less effective in AD3 cells. The concentration of PTEN in AD3 cells was about a half that in HCC3 and CBO12C3 cells. Transfection of HCC3 cells with PTEN small interfering RNA reduced their sensitivity to gefitinib in terms of its inhibitory effect on both Akt phosphorylation and the production of VEGF and CXCL1. In conclusion, effect of gefitinib on HCC-induced angiogenesis depends on its inhibition of the production of angiogenic factors, probably involving a PTEN/Akt signaling pathway.

Role of ATP7B in biliary copper excretion in a human hepatoma cell line and normal rat hepatocytes

BACKGROUND & AIMS Wilsons disease is a genetic disorder characterized by the accumulation of copper in the body caused by a defect of biliary copper excretion. The Wilsons disease gene has been cloned; however, the precise localization of the gene product (ATP7B) and its role in biliary copper excretion have not been clarified. METHODS We constructed a chimeric protein between green fluorescent protein (GFP) and ATP7B (GFP-ATP7B) and expressed it in a human hepatoma cell line (Huh7) and isolated rat hepatocytes. The Golgi apparatus, late endosomes, lysosomes, and bile canaliculus were visualized by fluorescence microscopy. Brefeldin A and nocodazole were used to redistribute the Golgi proteins. Bafilomycin A1 was used to analyze the association between GFP-ATP7B and the late endosomes. RESULTS GFP-ATP7B colocalized with rhodamine-dextran and late endosome markers but not with the Golgi markers, lysosome markers, or a tight junction protein. Brefeldin A and nocodazole redistributed the Golgi proteins, but they did not affect the distribution of ATP7B. CONCLUSIONS Although it is widely believed that ATP7B is located at the Golgi apparatus, its main localization is in late endosomes. ATP7B seems to translocate copper from the cytosol to the late endosomal lumen, thus participating in biliary copper excretion via lysosomes.