Apical membrane rupture and backward bile flooding in acetaminophen-induced hepatocyte necrosis

Morphological changes of hepatocyte death have so far only been described on cells in culture or in tissue sections. Using a high-resolution and high-magnification multiphoton microscopic system, we recorded in living mice serial changes of acetaminophen (APAP)-induced hepatocyte necrosis in relevance to metabolism of a fluorogenic bile solute. Initial changes of hepatocyte injury included basal membrane disruption and loss of mitochondrial membrane potential. An overwhelming event of rupture at adjacent apical membrane resulting in flooding of bile into these hepatocytes might ensue. Belbs formed on basal membrane and then dislodged into the sinusoid circulation. Transmission electron microscopy disclosed a necrotic hepatocyte depicting well the changes after apical membrane rupture and bile flooding. Administration of the antidote N-acetylcysteine dramatically reduced the occurrence of apical membrane rupture. The present results demonstrated a hidden but critical step of apical membrane rupture leading to irreversible APAP-induced hepatocyte injury.

Less reversal of liver fibrosis after prolonged carbon tetrachloride injection

BACKGROUND/AIMS

It was generally believed, but not proved, that early cirrhosis may be reversible, while advanced cirrhosis may not. This present study is to compare in mice the spontaneous regression of liver fibrosis between early and more advanced stage.

METHODOLOGY

Liver fibrosis in mice was induced by intraperitoneal injection of carbon tetrachloride for 4, 10, and 16 weeks. After the last dose of each schedule, mice were sacrificed 1 day later (progression model) or left untreated for 10, 20, and 60 days (regression model). Tissue sections were stained by Sirius red. Liver hydroxyproline levels were determined to assess severity of fibrosis. Gelatinases in tissue extracts were assayed by zymography.

RESULTS

During regression, diminution of fibrotic bands was more prominent in the 4-week group than in the others. Liver hydroxyproline levels in the progression model increased and resolution of liver fibrosis in the regression model decreased as carbon tetrachloride injection was prolonged. Liver matrix metalloproteinase-2 and -9 activities in the progression model also decreased as the injection was prolonged.

CONCLUSIONS

These data demonstrated that reversibility of liver fibrosis would be gradually lost as liver injuries were prolonged. Gradual loss of the expression of matrix metalloproteinases may be responsible for the loss of reversibility.

Expression of matrix metalloproteinases in spontaneous regression of liver fibrosis

BACKGROUND/AIMS

Spontaneous regression of liver fibrosis would depend on the degradation of the excessive matrix in the liver. In this study, we tried to determine the kinetics of the expression of genes for matrix metalloproteinase-2 and -13.

METHODOLOGY

Liver fibrosis induced by carbon tetrachloride was resolved after withdrawal of this toxin. Histological staining for fibrous septa and determination of liver collagen content were used to evaluate the extent of liver fibrosis. Expression in liver of matrix metalloproteinase-2 and -13 was determined by reverse transcription-polymerase chain reaction.

RESULTS

The fibrous septa became thinner and interrupted and liver fibrosis resolved rapidly within 10 days. Expression of matrix metalloproteinase-2 and -13 was elevated to 2.5- and 8.7-fold, respectively, at peak fibrosis. The former was maintained at 88%-76% and the later dropped rapidly to 30%-20% in the recovery periods.

CONCLUSIONS

Resolution of liver fibrosis began within 10 days but only to 70%. Gene expression kinetics suggested metalloproteinase-13 might play a more important role in the resolution because it surged more markedly at peak fibrosis and returned to nearly basal levels in the recovery periods in parallel with liver collagen content.

Correlation of E-cadherin expression and recurrence of hepatocellular carcinoma

BACKGROUND/AIMS

We performed this study to clarify the relationship between E-cadherin expression and recurrence of hepatocellular carcinoma.

METHODOLOGY

Forty-five surgically resected specimens of hepatocellular carcinoma were collected. The patients included 35 men and 10 women. The ages were between 30 and 77 years, with a mean age of 54 years. Western blotting and/or immunohistochemical staining of the tumor and non-tumor tissues for detection of E-cadherin were performed. Reverse transcription-polymerase chain reaction to check the levels of mRNA for E-cadherin and nucleotide sequencing of putative calcium binding domains were done if the tumor tissues showed negative E-cadherin expression.

RESULTS

Three (6.7%) tumor tissues were negative for E-cadherin with both Western blotting and immunohistochemical staining. Of the 3, two showed decreased mRNA in tumor tissues while the other 10 randomly selected samples did not show this phenomenon. No mutation of nucleotide sequence in the putative calcium binding domains was found. Two of the 3 patients had invasive cancers by histological studies while 13 out of the other 42 E-cadherin positive cases showed invasive cancers.

CONCLUSIONS

E-cadherin underexpression might have some contribution to the early recurrence of hepatocellular carcinoma. Transcriptional or post-transcriptional down-regulation may be the mechanism of underexpression of E-cadherin in hepatocellular carcinoma.

Tissue hepatocyte growth factor and proliferating cell nuclear antigen in hepatocellular carcinoma

To better understand the roles of hepatocyte growth factor (HGF) and proliferating cell nuclear antigen (PCNA) in hepatocellular carcinoma (HCC), 37 surgically resected HCCs and corresponding nontumorous liver tissue specimens were collected and the expression of these two factors was quantified by Western blot analysis. Both HGF and PCNA expression levels were significantly higher in tumor tissue than in nontumorous liver tissue. However, their expression levels in HCC tissue and nontumorous tissue did not show any significant correlation with the recurrence of HCC. In addition, HGF and PCNA did not correlate with Edmondson's grade, invasiveness of tumor, presence of tumor capsule, or tumor size. No correlation was found between the expression levels of HGF and PCNA in HCC tissue. We conclude that, although both HGF and PCNA are present at higher levels in HCC tissue than in nontumorous liver tissue, they play little role in the clinicopathologic manifestations of this tumor. HGF appears to contribute little, if at all, to the proliferative activity of HCC cells.

Telomerase activity and telomere length in human hepatocellular carcinoma

Telomerase activity is activated and telomere length altered in various types of cancers, including hepatocellular carcinoma (HCC). A total of 39 HCC tissues and the corresponding non-tumour livers were analysed and correlated with clinical parameters. Telomere length was determined by terminal restriction fragment assay, and telomerase activity was assayed by telomeric repeat amplification protocol. Telomerase activity was positive in 24 of the 39 tumour tissues (1.15-285.13 total product generated (TPG) units) and in six of the 39 non-tumour liver tissues (1.05-1.73 TPG units). In the 28 cases analysed for telomere length, telomere length was shortened in 11 cases, lengthened in six cases, and unaltered in 11 cases compared with non-tumour tissues. Neither telomere length nor telomerase activity was correlated to any clinical parameters.

Lack of critical domains in the beta-chain of hepatocyte growth factor

Hepatocyte growth factor (HGF) is a cytokine with pleiotropic effects on many different cell types. Its biological activities depend on the disulfide-linked alpha beta heterodimeric molecule. To study the functions of the beta-chain of HGF, insect cell-expressed HGFs prepared from nested deletions from C-terminus of beta-chain were studied for their biological activities and ligand-binding functions. The results demonstrated that the functions of HGF are dependent on the intactness of its beta-chain. The loss of HGF activities is correlated with the progressive deletion of beta-chain. There is not a single critical domain in the beta-chain that is essential for the functions of HGF. We propose that beta-chain may act to stabilize the ligand-receptor binding or contribute to the proper conformation of HGF to interact with its receptor.

Characterization of hepatocyte growth factor expressed by baculovirus

To express recombinant hepatocyte growth factor (HGF), we cloned the cDNA by polymerase chain reaction. Functional recombinant HGF was expressed in insect cells by a baculovirus expression system. The recombinant HGF is a mixture of a single-chain precursor and a two-chain heterodimer. Under non-reducing conditions, they migrate together as a single band with MW 67 kDa on Western blots. Under reducing conditions, the precursor migrates at 91 kDa, alpha-chain at 64 kDa and beta-chain at 34 kDa. About 25% of the expressed HGF is in the expression medium, which does have scatter activity on HepG2 and MDCK cells and proliferation activity on BN CL.2 cells (a mouse hepatocytes cell line) in a dose-dependent manner.