Pretreatment of mice with macrophage inactivators decreases acetaminophen hepatotoxicity and the formation of reactive oxygen and nitrogen species.
Hepatotoxic doses of acetaminophen to mice produce not only acetaminophen-protein adducts in the centrilobular cells of the liver, but nitrotyrosine-protein adducts in the same cells, the site of the necrosis. Nitration of tyrosine occurs with peroxynitrite, a species formed by reaction of nitric oxide (NO.) with superoxide (O2. -). Because NO. and O2.- may be produced by activated Kupffer cells and/or infiltrated macrophages, we pretreated mice with the macrophage inactivators/depeleters gadolinium chloride (7 mg/kg, intravenously [iv]) or dextran sulfate (10 mg/kg, iv) 24 hours before administration of acetaminophen (300 mg/kg). Mice treated with acetaminophen plus gadolinium chloride, or acetaminophen plus dextran sulfate, had significantly less evidence of hepatotoxicity as evidenced by lower serum alanine transaminase (ALT) levels (28 +/- 1 IU/L and 770 +/- 240 IU/L, respectively) at 8 hours compared with acetaminophen (6,380 +/- 408 IU/L). Analysis of hepatic homogenates for acetaminophen-protein adducts at 2 hours, a time of maximal covalent binding and before hepatocyte lysis, indicated that these pretreatments did not decrease covalent binding. Western blot analysis for the macrophage marker protein F4/80 in homogenates revealed not only the expected decrease by the macrophage inactivators/depleters, but also an apparent increase in acetaminophen-only-treated mice. At 8 hours nitrotyrosine-protein adducts were present in the acetaminophen-only-treated mice, but not in the acetaminophen plus gadolinium chloride-treated mice, or acetaminophen plus dextran sulfate-treated mice. High levels of heme-protein adducts, a measure of oxidative stress, were detected in livers of the 8 hour acetaminophen-only-treated mice. These data suggest that acetaminophen hepatotoxicity is mediated by an initial metabolic activation and covalent binding, and subsequent activation of macrophages to form O2.-, NO., and peroxynitrite. Nitration of tyrosine correlates with toxicity.
Michael
S L
SL
Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
Pumford
N R
NR
Mayeux
P R
PR
Niesman
M R
MR
Hinson
J A
JA
D000082:Acetaminophen / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics / Q000633:toxicity*; D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D001219:Aspartate Aminotransferases / Q000097:blood; D016264:Dextran Sulfate / Q000494:pharmacology*; D005682:Gadolinium / Q000494:pharmacology*; D007728:Kupffer Cells / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D008099:Liver / Q000187:drug effects* / Q000473:pathology; D008262:Macrophage Activation / Q000187:drug effects*; D008264:Macrophages / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009336:Necrosis; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D016877:Oxidants / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism
D000893:Anti-Inflammatory Agents; D009566:Nitrates; D016877:Oxidants; D017382:Reactive Oxygen Species; D013481:Superoxides; C039642:peroxynitric acid; D009569:Nitric Oxide; D000082:Acetaminophen; D016264:Dextran Sulfate; D005682:Gadolinium; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; C038958:gadolinium chloride