Enhanced Expression of Endothelin B Receptor at Protein and Gene Levels in Human Cirrhotic Liver

Abstract

Endothelin (ET) has been implicated in the regulation of hepatic microcirculation and development of portal hypertension. This study examined the localization of ETA receptor (ETAR) and ETB receptor (ETBR) in cirrhotic liver tissues from patients with hepatocellular carcinoma with hepatitis C-related cirrhosis, and normal liver samples from patients with metastatic liver carcinoma. Anti-ETAR and ETBR antibodies were used for immunohistochemistry and Western blot. Immunoelectron microscopy was conducted using immunoglobulin-gold and silver staining. For in situ hybridization (ISH), human ETAR and ETBR peptide nucleic acid probes were used with the catalyzed signal amplification system. In normal liver tissue, immunohistochemistry revealed that ETBR was predominantly expressed on hepatic sinusoidal lining cells, particularly on sinusoidal endothelial (SECs) and hepatic stellate cells (HSCs), and ETAR was scantily expressed. These findings were confirmed by Western blot and ISH. In cirrhotic liver tissue, overexpression of ETBR was demonstrated by Western blot and ISH. Morphometric analysis showed significant increase of ETBR expression on HSCs and SECs in cirrhotic liver, particularly on HSCs. ETAR expression was increased but remained low. Enhanced ETBR expression in cirrhosis may intensify the effect of endothelin on HSCs and increase hepatic microvascular tone.

In situ hybridisation in filamentous fungi using peptide nucleic acid probes

“…Less abundant mRNAs may need the use of multiple probes hybridising to the same mRNA. The use of catalysed signal enhancement of PNA probes in fungi, as was done in mammalian systems (Larsen et al, 2003;Yokomori et al, 2001) will be hampered by the presence of the cell wall, as is the case with DNA probes.…”

“…Peptide nucleic acid (PNA) probes have been used to detect rRNA in situ in bacteria and yeasts (PerryOÕKeefe et al, 2001;Rigby et al, 2002;Worden et al, 2000) and mRNA in mammalian cells (Larsen et al, 2003;Yokomori et al, 2001).…”

Localization of the 31-amino-acid endothelin-1 in hamster tissue

“…Recently, it is reported that ET-1(1-31) more strongly bind to ET B or ET B -like receptor (Kitamura et al, 2003). Moreover, ET B receptor dominantly expressed in sinusoidal cells in the human and rat liver (Anand et al, 2001;Yokomori et al, 2001). It was not possible to identify ET-1(1-31)-like IR on stellate cells.…”

Comparison of endothelin receptors in normal versus cirrhotic human liver and in the liver from endothelial cell-specific ETB knockout mice

“…In rats with cirrhosis, expression of both receptors on hepatic stellate cells was reported to be up-regulated, but receptor (Yokomori et al, 2001a). Using immunohistochemistry, ET B expression was also reported to be up-regulated in human cirrhotic liver, with low ET A expression detected in both normal and diseased liver (Yokomori et al, 2001b). Endothelin may also be an important regulator of sinusoid vascular resistance mediated by vasoconstriction of stellate cells, the main effector of sinusoid calibre (Rockey and Weisiger, 1996).…”