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Event: 1393

Key Event Title

A descriptive phrase which defines a discrete biological change that can be measured. More help

Hepatocytotoxicity

Short name
The KE short name should be a reasonable abbreviation of the KE title and is used in labelling this object throughout the AOP-Wiki. More help
Hepatocytotoxicity
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Biological Context

Structured terms, selected from a drop-down menu, are used to identify the level of biological organization for each KE. More help
Level of Biological Organization
Cellular

Cell term

The location/biological environment in which the event takes place.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help
Cell term
hepatocyte

Organ term

The location/biological environment in which the event takes place.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help
Organ term
liver

Key Event Components

The KE, as defined by a set structured ontology terms consisting of a biological process, object, and action with each term originating from one of 14 biological ontologies (Ives, et al., 2017; https://aopwiki.org/info_pages/2/info_linked_pages/7#List). Biological process describes dynamics of the underlying biological system (e.g., receptor signalling).Biological process describes dynamics of the underlying biological system (e.g., receptor signaling).  The biological object is the subject of the perturbation (e.g., a specific biological receptor that is activated or inhibited). Action represents the direction of perturbation of this system (generally increased or decreased; e.g., ‘decreased’ in the case of a receptor that is inhibited to indicate a decrease in the signaling by that receptor).  Note that when editing Event Components, clicking an existing Event Component from the Suggestions menu will autopopulate these fields, along with their source ID and description.  To clear any fields before submitting the event component, use the 'Clear process,' 'Clear object,' or 'Clear action' buttons.  If a desired term does not exist, a new term request may be made via Term Requests.  Event components may not be edited; to edit an event component, remove the existing event component and create a new one using the terms that you wish to add.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help

Key Event Overview

AOPs Including This Key Event

All of the AOPs that are linked to this KE will automatically be listed in this subsection. This table can be particularly useful for derivation of AOP networks including the KE. Clicking on the name of the AOP will bring you to the individual page for that AOP. More help
AOP Name Role of event in AOP Point of Contact Author Status OECD Status
Cyp2E1 Activation Leading to Liver Cancer KeyEvent Francina Webster (send email) Open for citation & comment WPHA/WNT Endorsed

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KE.In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available in relation to this KE. More help
Term Scientific Term Evidence Link
rodents rodents High NCBI
Homo sapiens Homo sapiens High NCBI

Life Stages

An indication of the the relevant life stage(s) for this KE. More help
Life stage Evidence
All life stages High

Sex Applicability

An indication of the the relevant sex for this KE. More help
Term Evidence
Mixed High

Key Event Description

A description of the biological state being observed or measured, the biological compartment in which it is measured, and its general role in the biology should be provided. More help

Taxonomic Applicability: Hepatotoxicity can occur in any species that has a liver.

Sex applicability: It can occur in both sexes

How it works: Hepatotoxicity occurs through three main mechanisms: apoptosis, necrosis, and necroptosis. (1) During programmed cell death, apoptotic cells are ‘disassembled’ and cellular components ‘bleb’ off as large vacuoles, which can be eliminated by phagocytosis. Apoptosis is activated via the extrinsic pathway (mediated through a death receptor, Tumor Necrosis Factor Receptor; TNFR) or intrinsic pathway (mediated through the mitochondria), each of which activate the caspase cascade (Riedl and Shi 2004). (2) Necrosis is an unregulated, accidental form of cell death that occurs when severe damage to cellular components causes the cell to die abruptly and spill its contents into the extracellular space.  Released cellular components include damage-associated molecular patterns (DAMPs) that trigger an inflammatory response. (3) The third type of cell death is necroptosis, or programmed necrosis, which uses the same death receptor that is upstream to the extrinsic pathway of apoptosis, but signaling results in a necrotic outcome. The decision for TNFR to signal for apoptosis or necroptosis is thought to depend on the receptor protein kinases 1 and 3 (RIP1, RIP3), which are part of the protein complex that forms on the intra-cellular portion of the TNFR. Activation of caspase-8 cleaves the RIP1-RIP3 complex and favours apoptosis, whereas inhibition of caspase-8 favours the RIP1-RIP3 complex (called the ‘necrosome’). As per standard necrosis, necroptosis results in DAMP release, which triggers inflammation. Necroptosis has been reviewed (Vandenabeele, et al. 2010). Cell death mechanisms in the liver and in liver disease have also been reviewed (Eguchi, et al. 2014, Luedde, et al. 2014).

The mitochondrial permeability transition (MPT) is an important process that leads to necrosis or apoptosis. When the mitogen activated protein kinase (MAPK) cascade is triggered (ASK1MKK4JNK), Bcl-2-associated X protein (Bax)  is recruited to the outer mitochondrial membrane (Youle and Strasser 2008). Bax triggers the opening of the mitochondrial permeability transition pore (MTP), through which cytochrome c is released, which triggers the caspase cascade and apoptosis. Alternatively, when the MTP opens across the inner and outer mitochondrial membranes, mitochondrial swelling and decoupling of oxidative phosphorylation (i.e., loss of ATP generation) leads to cell death by necrosis (Pessayre, et al. 2010, Rasola and Bernardi 2007).

How It Is Measured or Detected

A description of the type(s) of measurements that can be employed to evaluate the KE and the relative level of scientific confidence in those measurements.These can range from citation of specific validated test guidelines, citation of specific methods published in the peer reviewed literature, or outlines of a general protocol or approach (e.g., a protein may be measured by ELISA). Do not provide detailed protocols. More help

In vivo (liver):

  • Hematoxylin and eosin (H&E)-stained liver sections can be examined by a pathologist for the presence of cytotoxicity;
  • Serum levels of alanine aminotransferase (ALT) can be used as an indicator of hepatotoxicity. Serum levels of aspartate aminotransferase (AST) can also be used; however, AST is considered to be less ‘liver specific’ than ALT. Therefore, an AST/ALT ratio is often used. ALT and AST are typically measured using a commercial kit (e.g., from Sigma Aldrich or Roche); protocol: www.bio-protocol.org/e931;
  • Additional serum biomarkers of liver cell death have been reviewed in: (Eguchi, et al. 2014), and include: miRNAs (including mir-122), soluble death receptors (sTNFR, sTRAIL, sFas), microparticles (small vesicles released from dying cells), and other soluble proteins (including High mobility group box 1, HMGB1, and cleaved keratin 18, K18);

In vivo or in vitro:

  • Lactate dehydrogenase (LDH) leakage. LDH leakage is a measure of necrotic cell death, which can be detected using a colorimetric absorbance assay based on MTT reduction (Chan, et al. 2013).
  • Trypan Blue Exclusion. Trypan blue is a commercially available dye that only stains dead cells;
  • Apoptosis can be assayed by measuring caspase activation. There are a number of commercially available caspase assay kits:
    • The TUNEL assay is commonly used to measure DNA fragmentation that results from apoptotic signaling cascades (Lozano, et al. 2009)
      • This assay measures the presence of nicks in the DNA that are identified by terminal deoxynucleotidyl transferase or TdT, an enzyme that catalyzes the addition of dUTPs that are secondarily labeled with a marker;
  • In the MTT assay in which viable cells (with active metabolism) convert MTT into a purple compound (formazan), whereas dead cells remain colourless (Riss, et al. 2004);
  • Trypan blue assay: non –viable cells take-up trypan blue, whereas viable cells remain colourless (Strober 2015).

Domain of Applicability

A description of the scientific basis for the indicated domains of applicability and the WoE calls (if provided).  More help

Cytotoxicity can occur in any species from bacteria through to humans. Hepatocytotoxicity can occur in any species with a liver.

References

List of the literature that was cited for this KE description. More help

Chan, F.K., Moriwaki, K., De Rosa, M.J., 2013. Detection of necrosis by release of lactate dehydrogenase activity. Methods Mol. Biol. 979, 65-70.

Eguchi, A., Wree, A., Feldstein, A.E., 2014. Biomarkers of liver cell death. J. Hepatol. 60, 1063-1074.

Lozano, G.M., Bejarano, I., Espino, J., Gonzalez, D., Ortiz, A., Garcia, J.F., Rodriguez, A.B., Pariente, J.A., 2009. Relationship between caspase activity and apoptotic markers in human sperm in response to hydrogen peroxide and progesterone. J. Reprod. Dev. 55, 615-621.

Luedde, T., Kaplowitz, N., Schwabe, R.F., 2014. Cell death and cell death responses in liver disease: mechanisms and clinical relevance. Gastroenterology 147, 765-783.e4.

Pessayre, D., Mansouri, A., Berson, A., Fromenty, B., 2010. Mitochondrial involvement in drug-induced liver injury. Handb. Exp. Pharmacol. (196):311-65. doi, 311-365.

Rasola, A., Bernardi, P., 2007. The mitochondrial permeability transition pore and its involvement in cell death and in disease pathogenesis. Apoptosis 12, 815-833.

Riedl, S.J., Shi, Y., 2004. Molecular mechanisms of caspase regulation during apoptosis. Nat. Rev. Mol. Cell Biol. 5, 897-907.

Riss, T.L., Moravec, R.A., Niles, A.L., Duellman, S., Benink, H.A., Worzella, T.J., Minor, L., 2004. Cell Viability Assays, in: Sittampalam, G.S., Coussens, N.P., Nelson, H., Arkin, M., Auld, D., Austin, C., Bejcek, B., Glicksman, M., Inglese, J., Iversen, P.W., Li, Z., McGee, J., McManus, O., Minor, L., Napper, A., Peltier, J.M., Riss, T., Trask OJ, J., Weidner, J. (Eds.), Assay Guidance Manual, Bethesda (MD).

Strober, W., 2015. Trypan Blue Exclusion Test of Cell Viability. Curr. Protoc. Immunol. 111, A3.B.1-3.

Vandenabeele, P., Galluzzi, L., Vanden Berghe, T., Kroemer, G., 2010. Molecular mechanisms of necroptosis: an ordered cellular explosion. Nat. Rev. Mol. Cell Biol. 11, 700-714.

Youle, R.J., Strasser, A., 2008. The BCL-2 protein family: opposing activities that mediate cell death. Nat. Rev. Mol. Cell Biol. 9, 47-59.