Understanding the role of microRNA expression in the response to phenobarbital toxicity in the rat

New chemical entities that humans and animals are likely to be exposed to are tested using various in vitro and in vivo toxicological assays to understand the potential for harm. The increasing power of in silico analysis in combination with in vitro techniques is being exploited for the ability to predict in vivo outcomes such as toxicity, thereby reducing the requirement for animal testing. Previous studies in our laboratory have found that dietary phenobarbital treatment of rats results in dysregulation of the hepatic miRNAome, including prominent alteration of the expression of the miR-200a/b/429 cluster and miR-182/96 cluster. In this thesis I explore the use of a cell culture system, rat hepatocyte-like B13/H cells, to interrogate the underlying mechanisms of phenobarbital-mediated toxicity. Through this model I explore the function of phenobarbital-dysregulated microRNAs to determine their roles as markers of phenobarbital treatment in the rat. We find that the B13/H cells provide a useful system for studying the phenobarbital response in vitro, and how these responses relate to the effects of oral exposure to phenobarbital in vivo in the rat. In this respect, the B13/H cells appear representative of the rat response to phenobarbital, which is different to that of the mouse. With a focus on the phenobarbital-mediated dysregulation of the miR-182/96 cluster, I have explored the consequences of phenobarbital treatment on the B13/H cell model and related this to the in vivo effects. The data suggest that these microRNAs appear to control phenobarbital-mediated perturbation of glycolysis, cell transformation and methylation patterns.