Ultrastructural Changes during Acute Acetaminophen-Induced Hepatotoxicity in the Mouse: A Time and Dose Study

Abstract

This study was undertaken to evaluate the early ultrastructural changes during the development of acetaminophen hepatotoxicity. Doses at or near the threshold for hepatotoxicity were selected to permit comparison of early reversible effects to those which ultimately progressed to necrosis in the absence of early agonal effects or drug-induced mortality. Both 300- and 600-mg/kg doses resulted in similar declines in hepatic glutathione levels to 14 and 22% of control values, respectively, by 2 hours, with more rapid recovery after the low dose. Plasma sorbitol dehydrogenase activity was elevated after 600 mg/kg but not after 300 mg/kg. During the first 2 hours after acetaminophen there was cytomegaly with rapid progression to necrosis after 600 mg/kg but minimal progression after 300 mg/kg. Ultrastructurally, vesiculation, vacuolation and mitochondrial and plasma membrane degeneration culminated in scattered single cell death by 4 hours and widespread centrilobular necrosis by 8 hours after 600 mg/kg. The time course of lesion development was slower after 300 mg/kg with damage restricted to the first two to three rows of centrilobular cells and limited numbers of isolated necrotic cells by 8 hours. By 18 to 24 hours livers of mice given 300 mg/kg appeared normal. Results are consistent with the endoplasmic reticulum being the site of acetaminophen activation and initial attack. However, early ultrastructural changes in mitochondria and plasma membrane observed after the high dose were not prominent after the low dose. This suggests that early acetaminophen damage to these organelles may play a critical role in acetaminophen hepatotoxicity.

The mechanism underlying acetaminophen-induced hepatotoxicity in humans and mice involves mitochondrial damage and nuclear DNA fragmentation

“…Mitochondrial dysfunction after toxic doses of APAP has been recognized in rodents since the 1980s, when inhibition of mitochondrial respiration and depletion of ATP were first described (15,16,44). More recent studies have shown the development of oxidative and nitrosative stress within mitochondria and occurrence of the mitochondrial MPT after APAP treatment (18)(19)(20)(21).…”

“…The additional reactive metabolite depletes liver GSH and binds to proteins (11)(12)(13)(14). Ultrastructural and biochemical studies demonstrated that toxic doses of APAP could cause changes in the morphology and function of liver mitochondria (15,16). While it was clear from these data that mitochondrial injury occurs after treatment with large doses of APAP, it was not known how this developed.…”

“…This suggested that NAPQI binding to mitochondrial proteins leads to mitochondrial oxidative stress. It is now known that this causes the mitochondrial membrane permeability transition (MPT) pore opening (19)(20)(21), matrix swelling, and outer membrane lysis in rodent models (15). The permeabilization and lysis result in the release of apoptosis-inducing factor (AIF) and endonuclease G (EndoG) from mitochondria.…”

Chromatin breakdown by deoxyribonuclease1 promotes acetaminophen-induced liver necrosis: an ultrastructural and histochemical study on male CD-1 mice

“…It was suggested by Ruepp et al (2002) that the toxic cascade activates a number of genes involved in apoptosis, but energy-depletion and mitochondrial failure might divert the cell death program to necrosis. Similarly, Placke et al (1987) described that beside GSH-depletion oxidative stress also plays a central role in liver damage, since they observed ultrastructural changes in mitochondria early after application of high doses of APAP. Indeed, a recent quantitative analysis led Gujral et al (2002) to conclude that necrosis and not apoptosis was the principal mechanism of hepatocyte death after APAP-intoxication.…”

Effects of Hepatoprotective Compounds from the Leaves of <i>Lumnitzera racemosa</i> on Acetaminophen-Induced Liver Damage <i>in Vitro</i>

“…6,7) Therefore, studies on scavenging free radicals or reactive oxygen species (ROS) as well as reducing oxidative stress, and thereby avoiding hepatotoxicity, have received much attention in human health sciences. Biochemical studies suggested that toxic doses of APAP could cause changes in the morphology and function of liver mitochondria, 8,9) because of the binding of APAP more frequently to mitochondrial proteins, 10) which causes mitochondrial oxidative stress. 11) In the search for hepatoprotective agents from the natural sources, the closely relevant model system to human liver toxicosis could be an effective way to identify therapeutically applicable agents using most widely used drugs in the world, APAP.…”