Riko Ogata

Integrin α6β1 plays a significant role in the attachment of hepatoma cells to laminin

Abstract Background/Aims: Tumor invasion and metastasis consist of a series of complex events. During this process, the ability of tumor cells to adhere to laminin, a major component of basement membranes, is required at various steps. The expression of laminin-binding integrins and the extent of tumor metastasis and progression appear to be related. In hepatocellular carcinoma, increased expression of laminin-binding integrins is observed. However, little is known concerning the possible functional interactions between laminin-binding integrins and laminin. Therefore, we investigated the participation of laminin-binding integrins in the attachment of hepatoma cells to laminin. Methods: Human hepatoma cell lines (KIM-1, KYN-1,2) were used. We investigated the expression of integrin α 1 , α 2 , α 3 , α 6 , β 1 and β 4 subunits on hepatoma cells by immunocytochemical and flow cytometric analysis. Participation of these integrin subunits in the attachment of hepatoma cells to laminin was evaluated by an inhibition of cell adhesion assay. Results: Integrin α 1 , α 2 , α 3 , α 6 and β 1 subunits were expressed at the marginal areas of hepatoma cells, while the integrin β 4 subunit was scarcely detected. Laminin promoted the attachment of hepatoma cells in a dose-dependent manner. Although anti-integrin α 1 , α 2 , α 3 and β 4 subunit antibodies did not inhibit cell attachment to laminin, anti-integrin α 6 and β 1 subunit antibodies inhibited the attachment by 50% or more. Conclusions: These findings indicate that integrin α 6 β 1 is very important in the attachment of hepatoma cells to laminin, suggesting the participation of this integrin in metastasis and invasion of hepatoma cells.

Estrogen upregulates nitric oxide synthase expression in cultured rat hepatic sinusoidal endothelial cells

BACKGROUND/AIMS Estrogen receptor (ER) is present in vascular endothelial cells and estrogen promotes nitric oxide (NO) synthesis, which relaxes smooth muscle cells. It is also speculated that NO is synthesized by estrogen in hepatic sinusoidal endothelial cells (SECs). Here we investigated the localization of ER and endothelial cell nitric oxide synthase (ecNOS), and determined 17beta-estradiol (E2)-induced ecNOS expression in normal rat SECs. METHODS Cultured SECs were used. Fluorescence intensities of ecNOS were measured by immunofluorescence using a confocal laser-scanning microscope. E2 was added (100 pg/ml) to the culture medium, and the expressions of ecNOS mRNA and protein were analyzed by reverse-transcription polymerase chain reaction and Western blotting. NO production in cultured SECs was examined using diaminofluorescein-2 diacetate as a fluorescent indicator for NO. RESULTS Immunolocalization of ER and ecNOS in normal liver was demonstrated in endothelial cells lining the hepatic sinusoids. ER and ecNOS were localized in the nuclei and cytoplasm of cultured SECs, respectively. The mRNA expression of ecNOS in cultured SECs was increased after 6 h, and the protein expression of ecNOS was increased 24 h after E2 stimulation. The fluorescence intensity of NO in cultured SECs was increased by E2 stimulation compared with untreated control cells. CONCLUSIONS These results suggested that ER is present in SECs, and estrogen upregulates NO production in SECs. E2 may be involved in the regulation of the hepatic sinusoidal microcirculation.

Erythropoietic protoporphyria with fatal liver failure.

Abstract: A 33-year-old woman with a history of photosensitivity, persistent abdominal pain, and liver dysfunction was admitted to our department because of abdominal pain and progression of liver dysfunction. On admission, levels of protoporphyrin and coproporphyrin within erythrocytes were markedly increased. Autofluorescent erythrocytes were also detected, leading to a diagnosis of erythropoietic protoporphyria. A liver biopsy specimen revealed cirrhosis with dark brown granules filling hepatocytes, bile canaliculi, and bile ductules. Transfusion of washed erythrocytes, hemodialysis, and administration of cholestyramine and beta-carotene transiently improved levels of porphyrins and liver function. The patient died of rupture of esophageal varices followed by multiple organ failure. However, the treatments were believed to have extended survival.

VEGF Participates in Neovascularization and Sinusoidal Capillarization in HCC

Early in hepatocarcinogenesis, hepatocellular carcinomas do not show hypervascularity, but at later stages they require abundant arterial blood supply. Vascular endothelial growth factor is one of the most direct-acting angiogenic factors. We have clarified the participation of vascular endothelial growth factor in the development of neovascularization and sinusoidal capillarization in hepatocellular carcinoma.

Contraction and Relaxation of Ito Cells

Ito cells (hepatic stellate cells) are localized around liver sinusoidal endothelial cells. The cytoplasm of these cells contains contractile proteins such as actin and myosin, suggesting that microcirculation of liver sinusoids is regulated by the contraction and relaxation of these cells.

Diagnosis and Treatment of Hepatic Fibrosis and Hepatic Sinusoidal Cells

Hepatic fibrosis is a common response to chronic liver injury from many causes, including alcohol, chronic viral infections, metabolic liver disorders, and autoimmune hepatitis. Hepatic fibrosis results from an imbalance in extracellular matrix (ECM) synthesis (fibrogenesis) and ECM degradation (fibrolysis). The dynamic process of hepatic fibrosis and the cells producing ECM or matrix metalloproteinases (MMP) have largely been elucidated; it is mainly hepatic stellate cells (HSCs) and Kupffer cells which are involved in fibrogenesis and fibrolysis, respectively. Based on an understanding of connective tissue metabolism, new perspectives for specific antifibrotic therapy in hepatic fibrosis are been developed. The new potential strategies for this therapy are the inhibition of ECM synthesis, augmentation of ECM degradation, inhibition of HSC activation, neutralization of proliferative or fibrogenic mediators, and gene therapy. These approaches are expected to prevent progressive hepatic fibrosis and cirrhosis in the future.