Karim Hamesch

The intravenous injection of the plant lectin concanavalin A (ConA) is a widely used model for acute immune-mediated hepatitis in mice. In contrast to several other models for acute hepatic damage, ConA-induced injury is primarily driven by the activation and recruitment of T cells to the liver. Hence, the ConA model has unique features with respect to its pathogenesis and important similarities to immune-mediated hepatitis in humans, such as autoimmune hepatitis, acute viral hepatitis or distinct entities of drug toxicity leading to immune activation. However, the ConA model has considerable variability, depending on the preparation of the compound, genetic background of the mice, sex, age and microbial environment of the animal facility barrier. This standard operating procedure (SOP) comprises a detailed protocol for the ConA application, including preparation of ConA working solution, handling of the animals, choice of the appropriate conditions and endpoints, as well as efficient dose-finding.

In addition to carbon tetrachloride (CCl4), thioacetamide (TAA) represents a second widely used model for the induction of experimental liver fibrosis, but can also be employed for the development of acute liver failure and liver tumours. While TAA itself is not hepatotoxic, its reactive metabolites covalently bind to proteins and lipids thereby causing oxidative stress and centrilobular necrosis. Compared with CCl4, TAA leads to more periportal infiltrates and more pronounced ductal proliferation. While TAA has been shown to induce liver fibrosis development in several different mouse strains, wide variations in the administration routes, doses and treatment durations have been reported. Therefore, an adoption of a universal standard operating procedure for the administration of TAA is urgently needed. For that purpose, we are presenting here two TAA models (intraperitoneal administration of 150 mg/kg of TAA three times per week for 11 weeks in rats, and TAA administration in drinking water at 300 mg/L for 2-4 months in mice) with which we have had success in reliably and reproducibly developing chronic liver injury and fibrosis.

The intraperitoneal application of lipopolysaccharide (LPS) alone or in combination with other hepatotoxins is an experimental model for inducing systemic and hepatic inflammation in rodents applied worldwide. The endotoxin is recognized by the LPS-binding protein. This complex binds together with the lymphocyte antigen 96 (MD2) and the pattern-recognition receptor CD14 to members of the toll-like receptor family. The activated receptor complex in turn transduces signals to well characterized intracellular cascades that result in a multifaceted network of intracellular responses ending in inflammation. The most prominent among these is the activation of the NF-κB pathway and the production of a multitude of inflammatory cytokines. Although the application of LPS is in general easy to perform, unintended variations in preparation of the injection solution or in handling of the animals might affect the reproducibility or the outcome of a specific experiment. Here, we present a well-standardized protocol that allows for an induction of highly reproducible acute hepatic inflammation in mice. Furthermore, examples of appropriate readouts for the resulting inflammatory response are given.

OBJECTIVE: Homozygous alpha1-antitrypsin (AAT) deficiency increases the risk for developing cirrhosis, whereas the relevance of heterozygous carriage remains unclear. Hence, we evaluated the impact of the two most relevant AAT variants ('Pi*Z' and 'Pi*S'), present in up to 10% of Caucasians, on subjects with non-alcoholic fatty liver disease (NAFLD) or alcohol misuse. DESIGN: We analysed multicentric case-control cohorts consisting of 1184 people with biopsy-proven NAFLD and of 2462 people with chronic alcohol misuse, both cohorts comprising cases with cirrhosis and controls without cirrhosis. Genotyping for the Pi*Z and Pi*S variants was performed. RESULTS: The Pi*Z variant presented in 13.8% of patients with cirrhotic NAFLD but only in 2.4% of counterparts without liver fibrosis (p<0.0001). Accordingly, the Pi*Z variant increased the risk of NAFLD subjects to develop cirrhosis (adjusted OR=7.3 (95% CI 2.2 to 24.8)). Likewise, the Pi*Z variant presented in 6.2% of alcohol misusers with cirrhosis but only in 2.2% of alcohol misusers without significant liver injury (p<0.0001). Correspondingly, alcohol misusers carrying the Pi*Z variant were prone to develop cirrhosis (adjusted OR=5.8 (95% CI 2.9 to 11.7)). In contrast, the Pi*S variant was not associated with NAFLD-related cirrhosis and only borderline with alcohol-related cirrhosis (adjusted OR=1.47 (95% CI 0.99 to 2.19)). CONCLUSION: The Pi*Z variant is the hitherto strongest single nucleotide polymorphism-based risk factor for cirrhosis in NAFLD and alcohol misuse, whereas the Pi*S variant confers only a weak risk in alcohol misusers. As 2%-4% of Caucasians are Pi*Z carriers, this finding should be considered in genetic counselling of affected individuals.