Investigating the protective properties of dimethyl fumarate and Nrf2 signalling in response to drug toxicity

Abstract

Liver disease represents a major cause of mortality and morbidity. Despite the regenerative capacity of the liver, maintained injury or acute injury can lead to loss of liver function and disease. The most common cause of acute liver damage is drug-induced liver injury (DILI).

This can lead to organ failure and possible death. Therefore, new therapies to reduce the severity of the injury are required. Stimulation of anti-inflammatory and anti-oxidative stress pathways during the resolution of the injury have been proposed as powerful approaches to reduce organ injury and to enhance regeneration.

A main transcription factor which regulates anti-inflammatory and anti-oxidative stress is ‘nuclear factor erythroid-derived 2-like 2’ (Nrf2). Therefore, pharmacological activation of the Nrf2 pathway offers the potential to exert a cytoprotective effect promoting tissue regeneration.

Dimethyl fumarate (DMF) is a drug approved for some forms of multiple sclerosis. DMF’s protection is due in part by activation of the Nrf2 pathway. We hypothesize that DMF could be used to reduce the severity of DILI via Nrf2 activation. This thesis explores the protective effects of DMF and Nrf2 signalling during paracetamol-induced hepatotoxicity using in vitro and in vivo models.

For the in vitro studies, a semi-automated platform to produce hepatocytes-like cells (HLCs) from human pluripotent stem cells was employed. Single-cell high content image analysis was performed to understand Nrf2 nuclear translocation dynamics following DMF administration. The protective properties of DMF were tested in three different combinations: pre-treatment prior to paracetamol incubation, co-treatment or post-treatment following paracetamol injury. In all cases, DMF protected HLCs from paracetamol exposure. These findings were validated in a Zebrafish model of paracetamol injury. A zebrafish liver GFP reporter line was employed to detect fluorescence changes upon paracetamol exposure. Pre-treatment with DMF prior to paracetamol injury reduced the level of GFP loss.

RNA sequencing from both models identified that DMF protection was mediated via Nrf2 pathway stimulation. This was mainly by an increase in cell metabolism and oxidative stress management as well as reducing pro-inflammatory pathways activation. In summary, the findings of this work provide new understanding on the effects of DMF in the modulation of the Nrf2 pathway during paracetamol-induced liver injury. These studies may provide a platform to develop new treatment regimes for patients with acute liver disease.