Human keratin 8 variants predispose to acetaminophen toxicity

Abstract

Background and Aims: Keratins 8 and 18 (K8/K18) are the intermediate filaments of digestive epithelia and display an important cytoprotective function. Accordingly, K8/K18 variants predispose humans to chronic liver disease development/progression and to acute acetaminophen toxicity. Given that K8 G62C and K8 R341H are the most common K8 variants in Caucasians, we studied their hitherto unknown molecular effects in the newly generated transgenic K8 R341H overexpressors as well as in the previously described K8 G62C mouse. Methods: Alterations in gene expression profile were quantified by microarray analysis. Analyses in disease-relevant mouse models (acetaminophen, concavacain A and Fas induced liver injury) were complemented by experiments in primary hepatocyte cultures. Immunostaining, histological staining, immunoblotting, real time RT-PCR as well as serological analysis were used to evaluate the results of the experiments. Results: Under basal conditions, K8 G62C/K8 R341H mice did not show any obvious liver phenotype or altered keratin distribution pattern. Unlike in K18 R90C mice, isolated hepatocytes did not display any mechanical fragility. The presence of K8 G62C/R341H variants resulted in profoundly different gene expression profile alterations, while both variants predisposed to acetaminophen liver toxicity. On the other hand, the extent of concavacain A-induced liver injury was comparable to non-transgenic littermates and K8 G62C, but not K8 R341H predisposed to Fas-induced liver injury. Conclusion: Transgenic mice overexpressing K8 G62C/R341H represent a great tool to validate the findings of human association studies as well as to evaluate the underlying pathomechanisms. Our results suggest that K8 G62C/R341H variants exhibit some common properties, but also result in distinct liver phenotypes.