A 16-year-old girl has taken an overdose of acetaminophen. Which mechanism leads to hepatic toxicity?

• A. Activation of protein kinases
• B. Depletion of glycogen stores
• C. Increased conversion of triglycerides
• D. Peroxidation of lipids in cell membranes

Answer: (D)

In cases of acetaminophen overdose, hepatotoxicity primarily arises due to the formation of a toxic metabolite known as N-acetyl-p-benzoquinone imine (NAPQI). Under normal circumstances, acetaminophen is metabolized primarily through conjugation with sulfate and glucuronide, leading to safe and non-toxic products. However, when taken in excess, the metabolic pathways become saturated, resulting in increased production of NAPQI.

NAPQI is highly reactive and can bind to cellular macromolecules, including proteins and phospholipids within the hepatocyte cell membranes. This binding leads to oxidative stress and ultimately causes lipid peroxidation, which damages the integrity of cell membranes and contributes to cellular necrosis. The peroxidation of lipids is especially detrimental because it disrupts cellular function, alters membrane fluidity, and can lead to cell death, resulting in hepatic toxicity.

Thus, the mechanism of hepatic toxicity in acetaminophen overdose is closely tied to the peroxidation of lipids, which is a direct consequence of the oxidative stress induced by NAPQI and its interaction with cellular components. Recognizing this mechanism is crucial for understanding the pathological process underlying liver damage in such cases.