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  Hepatic ATP-Depletion Precedes Thioacetamide-Induced Liver Damage

Gottschalk, S., Chan, T., Raymond, V.-A., Leibfritz, D., Zwingmann, C., & Bilodeau, M. (2008). Hepatic ATP-Depletion Precedes Thioacetamide-Induced Liver Damage. Poster presented at 10th European Regional International Society for the Study of Xenobiotics Meeting (ISSX 2008), Vienna, Austria. doi:10.1080/03602530801949332.

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Gottschalk, S1, Author              
Chan , TS, Author
Raymond, V-A, Author
Leibfritz, D, Author
Zwingmann, C, Author
Bilodeau, M, Author
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1External Organizations, ou_persistent22              

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 Abstract: Introduction: Acute thioacetamide (TAA; CH3-CS-NH2) administration is widely used in animal models to investigate mechanisms of toxin-induced liver injury, regeneration and fibrosis. TAA is metabolized by micosomal CYP2E1 to TAA-S-oxide, which in turn is oxidized by CYP2E1 to TAA-S,S-dioxide. This highly reactive metabolite covalently modifies macromolecules in all cell compartments. It has been shown that TAA-bioactivation is subject to saturation kinetics and CYP2E1 has less specificity for TAA-S-oxide than for TAA. However, the exact cause leading to cell death and whether covalent binding to macromolecules is responsible for hepatic necrosis still remains unclear. Aim: Cellular energy metabolism in mouse liver after TAA-administration was followed to elucidate a mechanism that may pre-dispose liver cells to die from necrosis. Methods: BALB/c mice were injected with a non-lethal hepatotoxic dose of TAA (200 mg/kg, ip) and sacrificed 1-6, 12, 18 and 24hrs after TAA-injection. Standard assays were used for serum-ALT/AST and caspase-3 determinations. ATP/ADP/AMP and GSH/GSSG were analyzed by HPLC. NMR analysis: Mice were injected with [U-13C]glucose (500 mg/kg, ip) 45 min prior to sacrifice. Ex vivo 13C-NMR-spectra of water soluble metabolites from liver-extracts were recorded. Flux of 13C through pyruvate carboxylase (PC) and pyruvate dehydrogenase (PDH) was followed up by 13C-isotopomer analysis. Results: One hour after TAA-injection the hepatic energy charge ([ATP]+[ADP]/2)/([ATP]+[ADP]+[AMP]) dropped to 68±8%control (P<0.001) as indicated by decreased ATP (63±13%control, P<0.005) and increased ADP and AMP (130±4, P<0.01 and 214±28, P<0.001; %controls, respectively). Neither the energy charge nor the ATP-levels recovered at any time-point up to 24hrs. In fact, ATP further declined to 27±4%control (P<0.001) at 24hrs. Analysis of 13C-NMR spectra suggests diminished flux trough PC (65±17%control) and decreased glycolytic activity (fractional enrichments in [3-13C]lactate and [3-13C]alanine: 72±3 and 35±4%controls, respectively) at 1hr, while PDH-flux was at control-level. GSH-levels were unchanged up to 12hrs and decreased at 18 and 24 hrs (37±9 and 28±7%controls, P<0.001, respectively). The ratio GSH/GSSG was not different from controls at any time-point. Histological evidence and serum-ALT/AST activities indicate that TAA-induced liver injury does not occur before 6 hrs after injection. No significant Caspase-3 activity was found up to 24 hrs after TAA-treatment, ruling out the involvement of apoptosis. Conclusions: Our results demonstrate a deterioration in hepatic energy status and energy metabolism early and prior to any identifiable signs of TAA-induced liver damage. We suggest that the decrease of ATP – due to an unknown mechanism – pre-disposes livers cells to undergo necrosis (through energy failure) instead of apoptosis (which requires well maintained ATP-stores). The absence of any evidence for a redox status change also supports this hypothesis.

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 Dates: 2008-12
 Publication Status: Published online
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 Identifiers: BibTex Citekey: GottschalkCRLZB2008_2
DOI: 10.1080/03602530801949332
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Title: 10th European Regional International Society for the Study of Xenobiotics Meeting (ISSX 2008)
Place of Event: Vienna, Austria
Start-/End Date: 2008-05-18 - 2008-05-21

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Title: Drug Metabolism Reviews
  Other : Drug Metab. Rev.
Source Genre: Journal
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Publ. Info: New York : Marcel Dekker
Pages: - Volume / Issue: 40 (Supplement 1) Sequence Number: 167 Start / End Page: 117 - 118 Identifier: ISSN: 0360-2532
CoNE: https://pure.mpg.de/cone/journals/resource/954925521667