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Paracetamol-stimulated lipid peroxidation in isolated rat and mouse hepatocytes
Abstract:
Treatment of isolated hepatocytes from 3-methylcholanthrene induced rats with 1 mM paracetamol has been found to greatly decrease cellular reduced glutathione (GSH) content and to promote lipid peroxidation, evaluated as malonaldehyde (MDA) production and conjugated diene absorbance. A similar dosing of hepatocytes from phenobarbital-induced or normal rats is ineffective in that respect. On the other hand, the aspecific stimulation of the cytochrome P-450-mediated paracetamol activation due to acetone addition further increases GSH depletion as well as MDA production. Isolated hepatocytes with basal low GSH content are also more susceptible to paracetamol-induced lipid peroxidation, indicating that the rate of the drug metabolism and the cellular GSH content are critical factors in the determination of such peroxidative attack. In isolated mouse liver cells paracetamol does not require preliminary cytochrome P-450 induction to stimulate MDA formation, even at concentrations ineffective in rat cells. However, 5 mM paracetamol, despite a great depletion of cellular GSH content, does not promote MDA formation either in the rat or in the mouse hepatocytes. This effect may be due to the ability of paracetamol to scavenge lipid peroxides under defined conditions, as tested in various lipid peroxidizing systems. Membrane leakage of lactate dehydrogenase (LDH) is evident in paracetamol treated cells undergoing lipid peroxidation, but not when MDA formation is inhibited by high doses of the drug or by addition of anti-oxidants such as alpha-tocopherol and diphenylphenylenediamine (DPPD). Nevertheless in these conditions the covalent binding of activated paracetamol metabolites is not affected, suggesting that lipid peroxidation might play a role in the pathogenesis of liver damage following paracetamol overdose.
Insights
Paracetamol treatment depletes cellular glutathione (GSH) and promotes lipid peroxidation in rat hepatocytes, especially when cytochrome P-450 is induced. Low GSH levels increase susceptibility to this damage, suggesting GSH
Area of Science:
- Hepatology
- Toxicology
- Biochemistry
Background:
- Paracetamol (acetaminophen) overdose is a leading cause of acute liver failure.
- The mechanism of paracetamol-induced liver injury involves oxidative stress and cellular damage.
- Reduced glutathione (GSH) plays a critical role in cellular defense against oxidative stress.
Purpose of the Study:
- To investigate the role of cytochrome P-450 induction and cellular GSH levels in paracetamol-induced lipid peroxidation.
- To determine the susceptibility of isolated hepatocytes to paracetamol-induced oxidative damage under varying conditions.
- To explore the potential protective mechanisms of paracetamol against lipid peroxidation.
Main Methods:
- Treatment of isolated rat and mouse hepatocytes with varying concentrations of paracetamol.
- Assessment of cellular reduced glutathione (GSH) content.
- Evaluation of lipid peroxidation via malonaldehyde (MDA) production and conjugated diene absorbance.
- Measurement of lactate dehydrogenase (LDH) leakage as an indicator of membrane damage.
- Inclusion of cytochrome P-450 induction (3-methylcholanthrene, phenobarbital) and antioxidant treatments.
Main Results:
- Paracetamol (1 mM) significantly decreased GSH content and increased lipid peroxidation in 3-methylcholanthrene-induced rat hepatocytes.
- Hepatocytes from phenobarbital-induced or normal rats showed no such effects at similar doses.
- Acetone addition enhanced paracetamol-induced GSH depletion and MDA production.
- Hepatocytes with low basal GSH content were more susceptible to paracetamol-induced lipid peroxidation.
- In mouse hepatocytes, paracetamol induced MDA formation without prior cytochrome P-450 induction.
- High paracetamol doses (5 mM) inhibited MDA formation in both rat and mouse hepatocytes, potentially by scavenging lipid peroxides.
- Membrane leakage (LDH) occurred during lipid peroxidation but was inhibited by high paracetamol doses or antioxidants.
Conclusions:
- Drug metabolism rate and cellular GSH content are critical factors in paracetamol-induced lipid peroxidation.
- Lipid peroxidation appears to play a significant role in the pathogenesis of liver damage following paracetamol overdose.
- Paracetamol may possess antioxidant properties at higher concentrations, scavenging lipid peroxides.