The study of troglitazone liver toxicity via in vitro and in silico approaches

Background: Drug-induced liver injury (DILI) is rare but potentially lethal, and it can cause liver disease attributable to all types of drugs. The adverse impact of most of the DILI incidents is mild, and it recovers after the removal of drugs. The harmful agents should be identified and removed as early as possible to avoid the development of chronic liver damage. Troglitazone (TGZ) was a derivative of a thiazolidinedione drug produced for the treatment of type 2 diabetes, in the late 1990s. However, it was withdrawn from the market due to reported cases of liver toxicities. Several molecular mechanisms have been proposed to underlie TGZ-induced liver toxicity. Understanding the interactions between these mechanisms could aid drug developers in predicting DILI more vigorously. Aim: This thesis is aimed at using a combination of in silico and in vitro approaches to evaluate the interaction of TGZ with multiple biological systems and predict the emergent biological pathways in TGZ-induced liver toxicity. Method: To evaluate TGZ toxicity pathways, a model was constructed using Petri net software termed "SNOOPY" to reconstruct the putative cellular effects of TGZ, including activation of PPARy, interaction with mitochondria, and activation of apoptosis. The model was imported into the MUFINS software suite and simulated. Activation of apoptosis was validated against the published systems biology markup language (SBML) model downloaded from BIOMODELS, upon which the model was created. The effects of TGZ on cellular activities were determined through an in vitro approach. Results: The model created in SNOOPY and simulated in MUFINS could reproduce the behaviour of the original submission of BIOMODELS simulated in COPASI, validating the reconstruction. Other possible TGZ toxicity pathways have been predicted. TGZ-induced apoptosis is done through the activation of caspase 3/7 and 9, in a concentration-dependent manner. Also, a dose-dependent decrease in cellular processes has been recorded. However, caspase-8 activation in TGZ-treated cells has not been recorded. Conclusion: These data support the activation of apoptosis via the intrinsic route. The in sillico model reproduces the original model, and it can therefore be used to predict TGZ induced-liver toxicity. The in vitro assays were useful tools to elucidate TGZ-induced toxicity, making it a suitable model for this study.