Acetaminophen-induced oxidant stress and cell injury in cultured mouse hepatocytes: protection by N-acetyl cysteine.
The increase in cellular and mitochondrial glutathione disulfide (GSSG) levels and the GSSG:GSH ratio after acetaminophen (AAP) overdose suggest the involvement of an oxidant stress in the pathophysiology. However, the initial severe depletion of hepatocellular glutathione makes quantitative assessment of the oxidant stress difficult. Therefore, we tested the hypothesis that oxidant stress precedes the onset of cell injury in a cell culture model using 2',7'-dichlorofluorescein (DCF) fluorescence as a marker for intracellular oxidant stress. Cultured primary murine hepatocytes were exposed to 5 mM AAP. DCF fluorescence, XTT reduction, lactate dehydrogenase (LDH) release, and trypan blue uptake were determined from 0 to 12 h. After glutathione depletion at 3 h, DCF fluorescence increased by 16-fold and was maintained at that level up to 12 h. At 1.5 h after AAP, a significant decrease of the cellular XTT reduction capacity was observed, which continued to decline until 9 h. Cell necrosis (LDH release, trypan blue uptake) was detectable in 20% of cells at 6 h, with a significant further increase at later time points. Pretreatment with 20 mM N-acetylcysteine (NAC) 1 h before AAP enhanced cellular glutathione content, prevented or attenuated the AAP-induced decrease of GSH levels and XTT reduction capacity, respectively, and reduced the loss of cell viability. Additionally, treatment with NAC 2 h after AAP exposure prevented further deterioration of XTT reduction at 3 h and later, and attenuated cell necrosis. Thus, AAP-induced oxidant stress precedes cell necrosis and, in cultured hepatocytes, the oxidant stress is involved in the propagation of cell injury.
Bajt
Mary Lynn
ML
Liver Research Institute, University of Arizona, College of Medicine, Tucson, Arizona 85724, USA.
Knight
Tamara R
TR
Lemasters
John J
JJ
Jaeschke
Hartmut
H
D000082:Acetaminophen / Q000037:antagonists & inhibitors* / Q000633:toxicity*; D000111:Acetylcysteine / Q000494:pharmacology*; D018712:Analgesics, Non-Narcotic / Q000633:toxicity*; D000818:Animals; D002469:Cell Separation; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D005452:Fluoresceins; D016166:Free Radical Scavengers / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D018384:Oxidative Stress / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013778:Tetrazolium Salts; D014343:Trypan Blue
D018712:Analgesics, Non-Narcotic; D005452:Fluoresceins; D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D013778:Tetrazolium Salts; C059087:2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-((phenylamino)carbonyl)-2H-tetrazolium hydroxide; D000082:Acetaminophen; C037631:2',7'-dichlorofluorescein; D007770:L-Lactate Dehydrogenase; D005978:Glutathione; D014343:Trypan Blue; D000111:Acetylcysteine