Biography
Biography: Lisa BG Tee
Abstract
Background: It is well known that paracetamol can induce hepatotoxicity when an excessive amount is consumed. Quantities above the recommended therapeutic dose cause the production of the toxic metabolite, NAPQI, which causes the generation of radicals resulting in the depletion of glutathione stores. Subsequently, the hepatocyte is vulnerable to injury. However the mechanism of destruction is still not fully understood and as a result, the field of drug-induced liver damage requires further study to further understand the impact paracetamol has on a liver cell. With new technology and live cell imaging via confocal microscopy, this study was able to document the morphological changes in isolated hepatocytes exposed to paracetamol. Methodology and Results: This study investigates the effect of dithiotreitol and N-acetylcysteine in reversing paracetamol toxicity. Cultured AML12 mouse hepatocytes were pre-incubated with 0 or 2.5mM paracetamol. At 4.5 h, toxicity was evident in paracetamol-treated but not control cells. Hepatocytes exposed to paracetamol exhibited mitochondrial depolarisation and decreased cell viability. Confocal microscopy studies with bright-field microscopy and MitoTracker dye indicated that changes in cell morphology and mitochondria occurred as a result of the paracetamol-induced toxicity. Conclusion and Significance: This data is consistent with the hypothesis that at excessive concentration, paracetamol is metabolised into N-acetyl-p-benzoquinone imine (NAPQI) within 90 minutes. Addition of 1.5mM dithiothreitol (DTT), a reducing agent, or 1.25mM N-acetylcysteine (NAC), a glutathione precursor, after paracetamol preincubation increased cell viability and reduced mitochondrial depolarisation. Live imaging indicated that cell injury was lower after the addition of DTT and NAC. DTT and NAC showed no toxicity to hepatocytes when added individually. These data support the hypothesis that DTT reverses oxidative stress induced by NAPQI, probably by reducing oxidised disulphide groups found in essential mitochondrial proteins into thiols.