Journal of Gastroenterology and Hepatology (Australia)

Abstract  The management of primary and secondary malignant liver tumors poses a great challenge to clinicians. Although surgical resection is the gold‐standard treatment, most patients have unresectable malignant liver tumors. Over the past decade, various modalities of loco‐regional therapy have gained much interest. Among them, thermal ablative therapy, including cryotherapy, microwave coagulation, interstitial laser therapy, and radiofrequency ablation (RFA), have been proven to be safe and effective. Despite the effective tumor eradication achieved within cryotherapy, the underlying freeze/thaw mechanism has resulted in serious complications that include bleeding from liver cracking and the ‘cryoshock’ phenomenon. Thermal ablation using microwave and laser therapy for malignant liver tumors is curative and is associated with minimal complications. However, this treatment modality is effective only for tumors <3 cm diameter. Radiofrequency ablation seems to be the most promising form of thermal ablative therapy in terms of a lower complication rate and a larger volume of ablation. However, its use is restricted by the difficulty encountered when using imaging studies to monitor the areas of ablation during and after the procedure. Moreover, the techniques of RFA need to be refined in order to achieve the same oncological radicality of malignant liver tumors as achieved by surgical resection. As each of the loco‐regional therapies has its own advantages and limitations, a multidisciplinary approach using a combination of therapies will be the future trend for the management of malignant liver tumors.

Hepatitis C virus (HCV) infection can be detected by using immunoassay techniques that measure reactivity to viral protein antigens. In this study seven discreet proteins derived from HCV genomic coding sequences have been expressed, purified and characterized. Six proteins represent the structural regions of the core (C22‐3), the envelope (E1 and E2), and the non‐structural regions NS3 (C33C), NS3–NS4 (C100‐3) and NS5. The seventh, C25, is a chimeric fusion protein containing C33C, C100‐3 and C22‐3 regions. Using these recombinant proteins, multi‐antigen radioimmunoassays and enzyme immunoassays (EIA) were designed. The fusion protein, C25, was demonstrated to be an improved antigen for serodiagnosis of HCV antibody. Use of the C25 protein accelerated HCV antibody detection by 3–46 weeks in non‐A, non‐B hepatitis seroconversion cases and significantly increased the rate of detection in a paid donor population by 20%. The C25 assay also demonstrated excellent specificity in 2446 randomly selected low prevalence samples. The repeated reactive rate in this group of samples was 0.5%.

Samples from volunteer blood donors pre‐selected for repeat reactivity with the first generation C100‐3‐based HCV antibody tests (n= 175) were tested using the C25 assay. The C25 assay detected 37.7% samples as reactive and 53.1% samples as non‐reactive. This result was in agreement with all other supplementary tests that include RIBA^TM, multi‐antigen assay, Abbott neutralization and peptide assay. The other 9.2% samples were classified as ‘indeterminant’ because these samples were only partially in agreement with some of the above supplementary tests.

The C25 enzyme‐linked immunosorbent assay (ELISA), with its improved assay sensitivity, can identify additional HCV antibody reactive cases in both hepatocellular carcinoma and cryptogenic cirrhosis patients. The C25 and multi‐antigen EIA assays were used to investigate the vertical transmission of HCV. It was observed that these improved assays are able to detect antibodies in a vertical transmission case. The C25 ELISA was also compared with a synthetic peptide assay. The C25 assay was found to be superior to the peptide assay that performed poorly in the detection of the C33C only reactive samples.

Mitochondria play a central role in cellular energy metabolism. Oxidative phosphorylation occurs in the electron transport system of the inner mitochondrial membrane. Cytochrome aa3, b and c1 are encoded by mitochondrial DNA whereas cytochrome c is encoded by the nuclear gene, and these mitochondrial‐DNA dependent cytochromes are decreased and electron transport at complex II, III and IV is disturbed in liver carcinomas and during carcinogenesis. The more the decreased cytochrome and oxidase activity are seen, the more significant is the increase in reactive oxygen species (ROS) production. ROS produced in mitochondria may be the main cause of nuclear‐gene mutation in carcinogenesis. The mitochondrial dysfunction and overproduction of ROS plays a key role in progression of chronic hepatitis C and ethanol‐induced liver injury. Ethanol also causes bacterial translocation in the intestine and the resulting lipopolysaccharides (LPS) activates Kupffer cells to produce pro‐inflammatory cytokines. We suspect that non‐alcoholic steatohepatitis (NASH) also is the result of increased ROS production in Kupffer cells and hepatocytes.

During the prereplicative period of liver regeneration the changes in the levels of mRNA for tumour necrosis factor‐α (TNF‐α) and its receptors were nearly synchronous. The mRNA levels reached their maximum 1 – 3 h after operation and exceeded the values for intact animals about tenfold. Lipopolysaccharide stimulation induced an increase in TNF‐α and TNF receptor production comparable with that occurring during regeneration.

Nitric oxide (NO) production in the regenerating liver was determined by electron paramagnetic resonance (EPR) spectroscopy. The first increase in NO production occurred approximately 1 h after partial hepatectomy (PHE). The second and more pronounced peak of NO production was observed about 6 h after PHE when the hepatocytes entered the first cell cycle; it originated mainly from these cells. The consequent minimum of NO synthesis coincided with the maximal rate of DNA synthesis. The third gradual rise of NO production was seen at the transit from the first to the second cell cycle of the hepatocytes and the entrance of the non‐parenchymal cells into proliferation.

Hepatocytes, Kupffer and endothelial cells were isolated from livers after PHE. They were found to start their main NO production in the described sequence at the times corresponding to their respective entrance into the cell cycle. The maxima of NO synthesis were inversely correlated to the DNA‐synthesizing activity of the individual cell type.

Epstein‐Barr virus (EBV) is part of the herpesvirus family that infects up to 90% of the population. Initial infection is often subclincal in children but will generally result in symptomatic infectious mononucleosis in adolescents and adults. Ganciclovir has been utilized in immunocompromised patients with EBV encephalitis and post‐liver transplant for EBV fulminant hepatitis. Herein, the successful use of ganciclovir in two immunocompetent patients with severe EBV hepatitis is reported.

Quiescent hepatic stellate cells (HSCs) in healthy liver store 80% of total liver retinols and release them depending on the extracellular retinol status. However, HSCs activated by liver injury lose their retinols and produce a considerable amount of extracellular matrix, subsequently leading to liver fibrosis. Emerging evidence suggests that retinols and their metabolites such as retinoic acids (RAs) contribute to liver regeneration, fibrosis and tumor. However, it is not clear yet why HSCs lose retinol, which enzymes are involved in the retinol metabolism of HSCs and what function of retinol metabolites on HSCs upon liver injury. Recently, our group and collaborators have demonstrated that during activation, HSCs not only lose retinols but also metabolize them into RAs by alcohol dehydrogenases and retinaldehyde dehydrogenases. As transcriptional factors, metabolized RAs induce retinoic acid early inducible‐1 and suppressor of cytokine signaling 1 in HSCs, which plays an important role in the interaction between HSCs and natural killer cells. In addition, RAs released from HSCs may induce hepatic cannabinoid receptor 1 expression in alcoholic liver steatosis or regulate immune responses upon liver inflammation. The present review summarizes the role of endogenous metabolized RAs on HSCs themselves and on other liver cells including hepatocytes and immune cells. Moreover, the effects of exogenous retinol and RA treatments on HSCs and liver disease are discussed.