A.M. Jezequel

Acute carbon tetrachloride feeding induces damage of large but not small cholangiocytes from BDL rat liver

Bile duct damage and/or loss is limited to a range of duct sizes in cholangiopathies. We tested the hypothesis that CCl4damages only large ducts. CCl4 or mineral oil was given to bile duct-ligated (BDL) rats, and 1, 2, and 7 days later small and large cholangiocytes were purified and evaluated for apoptosis, proliferation, and secretion. In situ, we measured apoptosis by morphometric and TUNEL analysis and the number of small and large ducts by morphometry. Two days after CCl4 administration, we found an increased number of small ducts and reduced number of large ducts. In vitro apoptosis was observed only in large cholangiocytes, and this was accompanied by loss of proliferation and secretion in large cholangiocytes and loss of choleretic effect of secretin. Small cholangiocytes de novo express the secretin receptor gene and secretin-induced cAMP response. Consistent with damage of large ducts, we detected cytochrome P-4502E1 (which CCl4 converts to its radicals) only in large cholangiocytes. CCl4induces selective apoptosis of large ducts associated with loss of large cholangiocyte proliferation and secretion.

Chronic ethanol feeding increases apoptosis and cell proliferation in rat liver

The present study was conducted to evaluate if the increased rate of apoptosis previously reported in the liver of ethanol-treated rats was accompanied by increased cell renewal. A quantitative analysis of apoptosis was performed in rats fed an ethanol-containing liquid diet for 5 weeks. S-phase cells were demonstrated by immunohistochemistry, using the Bromodeoxyuridine/anti-Bromodeoxyuridine method. In ethanol-fed rats apoptosis was five times greater than in pair-fed controls. Bromodeoxyuridine-labelled hepatocytes increased from 0.07 +/- 0.009% in controls to 0.17 +/- 0.013% (p < 0.001) and Bromodeoxyuridine-labelled lipocytes (desmin-positive sinusoidal cells) increased from 3.43 +/- 0.28% to 6.60 +/- 1.04% (p < 0.001). The lobular distribution of labelled cells was modified with a shift towards the perivenular areas. The results of this study suggest that the replacement of liver cells lost by ethanol-induced apoptosis is not impaired in intact (non-operated) animals. The impaired regeneration following partial hepatectomy reported in ethanol-fed rats is possibly due to differences in the extent of parenchymal loss, to altered relationships between hepatocytes and blood supply and to the modalities of regeneration involved.

Dimethylnitrosamine-induced cirrhosis: Evidence for an immunological mechanism

The present study is concerned with the early events associated with the development of cirrhosis induced by dimethylnitrosamine (DMN). The antigenic expression of MHC class II components (Ia) and of some intermediate filament proteins (vimentin and desmin) have been studied by immunohistochemistry and the findings correlated with ultrastructural data. Micronodular cirrhosis developed after 3 weeks of treatment with DMN but enhanced expression of Ia antigen on macrophages and on infiltrating lymphocytes was observed after 1 week, before the formation of septa, suggesting that immune-mediated mechanisms are involved in the response to DMN-induced liver injury. The expression of vimentin and of desmin also increased at an early stage and at 3 weeks the septa were outlined by cellular elements showing positivity for both intermediate filament proteins. In keeping with these observations, ultrastructural data showed active division of macrophages in situ, infiltration of the parenchyma by T and B lymphocytes, activation of lipocytes (Ito cells) showing evidence of mitosis, and the presence of transitional elements between lipocytes, myofibroblasts and fibroblasts. This experimental model may be helpful in understanding the relationship between immune-mediated response to liver injury and development of hepatic fibrosis.

Modulation of extracellular matrix components during dimethylnitrosamine-induced cirrhosis

Liver fibrosis was induced in rats after administration of dimethylnitrosamine (DMN) intraperitoneally three times a week for 3 weeks. Incomplete septa appeared after 7 days and evidence of nodulation of the parenchyma was observed after 21 days. Both distribution of extracellular matrix components (collagen type I, type III and type IV, laminin, fibronectin, heparan sulphate proteoglycan) and the distribution of desmin as a marker of lipocytes (Ito cells) and of iso-alpha-smooth muscle actin were studied with immunoperoxidase. Changes in the distribution of extracellular matrix components outlined both the formation of septa and the development of nodules with changes in the sinusoidal pattern evoking aspects of capillarization. The number of desmin-positive cells increased in DMN-treated animals, showing a prominent reaction in the fibrous septa. In the normal liver, lipocytes were positive for laminin and negative for actin, but septal and juxta-septal lipocytes were positive for both antigens, suggesting the presence of transitional cells with mixed immunoreactivity. This was confirmed by ultrastructural studies which showed typical intraseptal myofibroblasts and other elements exhibiting the structural features of both myofibroblasts and lipocytes.

Cell proliferation following extrahepatic biliary obstruction: Evaluation by immunohistochemical methods

The aim of the present investigation was to conduct an immunohistochemical study using bromodeoxyuridine (BrdU) incorporation as a marker of S-phase cells and cytokeratins as markers of biliary epithelial cells, in bile-duct-ligated rats at intervals of 1, 3, 7, 14 and 21 days after total biliary obstruction. Data obtained using only BrdU incorporation by S-phase nuclei were compared with those obtained by the simultaneous demonstration of S-phase nuclei and cytoplasmic cytokeratins. The labelling index of parenchymal liver cells and of biliary epithelial cells was evaluated as an index of the cellular growth pattern after total biliary obstruction. Our data show that following total biliary obstruction: (a) cell proliferation follows a similar pattern for biliary epithelial cells hepatocytes with a peak on the 3rd day; (b) the labelling index is significantly higher in biliary epithelial cells than in hepatocytes; and (c) sequential immunohistochemical staining using cytokeratin as a marker allows better identification of biliary epithelial cells, especially when the ductular lumen is not clearly outlined, or in isolated biliary cells which appear as components of the wall of the ducts of Hering.

Primary biliary cirrhosis: modalities of injury and death in biliary epithelium.

BACKGROUND/AIM Despite the number of studies on primary biliary cirrhosis, contrasting data remain concerning modalities of cholangiocyte death. Liver biopsies obtained from 40 patients with anti mitochondrial antibody-positive primary biliary cirrhosis, at various stages of the disease, were examined, and special attention was paid to the expression of subcellular damage and evidence of apoptosis. METHODS Liver sections were stained with haematoxylin/eosin or Sirius red. Ductular mass was evaluated on sections after cytokeratin 7 staining. Apoptosis was evaluated on haematoxylin/eosin stained material or after processing for terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling assay. In 16 patients, part of the biopsy was processed for electron microscopy. Twenty histologically normal liver biopsies were used for control purposes. RESULTS According to Scheuers classification, 29 patients were classified as stage I-II, and 11 as stage III-IV. A strong staining of bile ducts was evident after immunohistochemistry for cytokeratin 7, often associated with ductular metaplasia in lobular zone 1. Cytokeratin 7-positive cells occupied 3.0+/-1.3% of liver mass as compared to 0.25+/-0.03% in controls. Ductular metaplasia accounted for 1.4+/-0.07% of all cytokeratin 7-positive cells. Regardless of staging, apoptotic bodies were seen only exceptionally in epithelial wall of bile ducts, whereas cholangiocyte damage leading to extensive lytic necrosis appeared responsible for most of the bile duct mass loss, as also confirmed by ultrastructural studies. A few terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling-positive nuclei were occasionally associated with the inflammatory infiltrate and evidence of apoptosis in hepatocytes was frequent, especially in zone 1. CONCLUSION Regardless of staging, lytic necrosis and not apoptosis accounts for most of the bile duct loss in primary biliary cirrhosis. Furthermore, ductular metaplasia appears as a late event with highly variable pattern being observed between patients.

Differential expression of ras isoforms in hepatic stellate cells

DIFFERENTIAL EXPRESSION OF RAS ISOFORMS IN HEPATIC STELLATE CELLS E Ridolfi, A. Benedetti, A. Di Sario, S. Saccomanno, L. Marucci, E. Bendia, A.M. Jezequel, G. Sve~liati Baroni Dept. of Gastroenterology and Inst. of Exp. Pathology, University of Ancona, Ancona, Italy. Ras proteins represent the products of three different Ras genes (H-, K-, and N-ms) and are plasma membrane-associated GTPases that function as relay switches transducing biological information from extracellular signals to the nucleus. One or the other isoform may predominate in a different cell type where they play a key role in transforming activity and regulating cell proliferation. Hepatic stellate cell (HSC) proliferation close to area of necrosis represent a key event in liver fibrosis and PDGF represents the main mitogen. Aims of the present study ware thus:l)to evaluate the expression of Ras isoforms in activated HSC;2)to determine the effect of blocking Ras signaling on HSC proliferation;3)to determine the intracellular pathways which transduce extracellular signal to the nucleus via Ras proteins. By immunoprecipitation, the H-Ras isoform only was detected in total HSC lysate. This was confirmed by immunohistochemisffy by which the H-Ras isofonn was detected preferentially in the cytoplasmic area. PDGF-stimulated HSC showed a 4-fold increase in cell proliferation as determined by BrdU incorporation in S-phase nuclei. This was blocked by chaetomellic acid (a H-Ras processing inhibitor) which reduced cell proliferation down to control value starting at 2 pM. In addition, chaetomellic acid reduced PDGF-induced ERKll2 phosphorylation while had no effect on 70 kD

Phenotypic analysis of inflammatory infiltrate in rats with dimethylnitrosamine-induced cirrhosis

6 kinase (a downstream component of the PI3Kinase pathway) activation as determined by Western blot. This study thus indicates that PDGF-induced HSC proliferation is driven by H-Res. Since a non toxic inhibition of Ras processing has been obtained in vivo, H-Ras represents a plausible target for the experimental therapy of hepatic fibrosis. [ P/C03/38 ]

A morphological study of the early stages of hepatic fibrosis induced by low doses of dimethylnitrosamine in the rat

The present study is concerned with the immunohistochemical characterization in situ of the mononuclear infiltrate accompanying the formation of septa and the development of cirrhosis in the liver of rats treated with dimethylnitrosamine (DMN), i.p. (10 microliters/kg, 3 days a week for 3 weeks). Monoclonal antibodies against macrophages, pan T cells, T cell subsets and B cells have been applied on cryostat sections of animals given DMN for 7, 14 and 21 days. The maximum increase of macrophages and lymphocytes was observed at days 7 and 14 respectively. At all times T lymphocytes appeared as the major component of the inflammatory infiltrate with a largely predominant population of cytotoxic/suppressor T cells. At day 21, with evidence of nodulation of parenchyma, macrophages levelled off while T cells remained numerous without changes in the inducer-helper T cells/cytotoxic-suppressor T cells ratio which remained always less than 1. B cells were always few. These findings illustrate the early influx of lymphocytes in DMN-induced liver injury and help to define the lymphocyte subsets associated with inflammation and fibrosis in a reproducible animal model.