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Microsomal oxidative damage promoted by acetaminophen metabolism
María Eugenia Letelier1, Miguel López-Valladares, Liliana Peredo-Silva
1Laboratory of Pharmacology and Toxicology, Department of Pharmacological and Toxicological Chemistry, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago 8380492, Chile. mel@ciq.uchile.cl
Acetaminophen adverse reactions linked to oxidative stress may stem from NAD(P)H oxidase (NOX) activity, not just cytochrome P450. NOX inhibitors blocked reactive oxygen species generation, suggesting NOX as a primary driver.
Area of Science:
- Biochemistry
- Toxicology
- Drug Metabolism
Background:
- Acetaminophen (APAP) adverse reactions are linked to oxidative stress, potentially caused by reactive oxygen species (ROS) and/or the metabolite NAPQI.
- Both ROS and NAPQI production are associated with the liver cytochrome P450 (CYP450) system, but their relative contributions remain unclear.
- NADPH oxidase (NOX) activity has been proposed in rat liver microsomes, suggesting a potential role in ROS generation.
Purpose of the Study:
- To investigate the specific roles of NAD(P)H oxidase (NOX) and cytochrome P450 (CYP450) in acetaminophen-induced oxidative stress.
- To differentiate the contributions of NOX and CYP450 activities to reactive oxygen species (ROS) generation during acetaminophen biotransformation.
Main Methods:
- Rat liver microsomes were incubated with acetaminophen and NADPH.
- Specific inhibitors for NOX (apocynin, plumbagin) and CYP450 (SKF-525A) were used to assess their effects on oxidative stress markers.
- Assessed outcomes included lipid peroxidation, thiol content, and glutathione-S-transferase (GST) activity.
Main Results:
- Incubation with acetaminophen and NADPH induced lipid peroxidation and decreased thiol content and GST activity.
- NOX inhibitors (apocynin, plumbagin) prevented lipid peroxidation and GST activity reduction, but not thiol content decrease.
- The CYP450 inhibitor SKF-525A specifically prevented the decrease in thiol content.
Conclusions:
- Reactive oxygen species (ROS) generation during acetaminophen incubation with NADPH in rat liver microsomes is primarily mediated by NAD(P)H oxidase (NOX) activity.
- Cytochrome P450 (CYP450) activity is responsible for the observed decrease in thiol content, indicating a distinct role in acetaminophen's effects.
- These findings help clarify the mechanisms underlying acetaminophen-induced oxidative stress and toxicity.
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