Upstream eventActivation, Caspase 8 pathway
Key Event Relationship Overview
AOPs Referencing Relationship
|AOP Name||Adjacency||Weight of Evidence||Quantitative Understanding|
|IKK complex inhibition leading to liver injury||adjacent||High||High|
Life Stage Applicability
Key Event Relationship Description
After recruitment, dimerization and activation of Caspase8, the active caspase will clear executioner caspases (3,6,7) or activate the intrinsic apoptotic pathway via BID. (McIlwain et al. 2015)
Evidence Supporting this KER
It has been well established that caspase activation leads to cell death. In the caspase 8 pathway, the TRADD adaptor protein recruits FADD and forms a complex together with pro-caspase 8. Then caspase 8 can directly activate caspase-3, -6, or -7, which leads to apoptosis. Furthermore, Caspase8 can also splice Bid to tBid which promotes disruption of the membrane of mitochondria. Cytochrome C will be released and forms an apoptosome with followed by activation of Caspase 9 and Apaf1. These can stimulate procaspases 3,6,7 which can induce apoptosis. (Murphy 2012; Melino & Vaux 2010)
Evidence caspase 8 leads to cell death:
Reviewed by (McIlwain et al. 2015)
Cells from caspase 8 deficient mice are resistant to death receptor induced apoptosis.
Cells from FADD or TRADD deficient mice are resistant for TNFa mediated apoptosis.
Inactivating Caspase 8 mutations are associated with cancers.
A selective caspases inhibitor in patients with hepatitis virus C infection showed reduced ALT levels and CK-18 fragments through reduction of apoptosis in the liver, according to authors (Manns et al. 2010)
Hepatocyte specific Caspase 8 KO protects from LPS or Fas mediated apoptosis. However, increased necrotic damage is observed. Double KO Caspase8 and NEMO were protected against steatosis and hepatocarcinogenesis but have massive liver necrosis, cholestasis and biliary lesions, caused RIP complex accumulation(Liedtke et al. 2011)
Uncertainties and Inconsistencies
Hepatocellular deletion of Caspase 8 in mice show less apoptosis after DCC treatment (model hepatocholestasis)(Chaudhary et al. 2013)
Quantitative Understanding of the Linkage
Known modulating factors
Known Feedforward/Feedback loops influencing this KER
Domain of Applicability
McIlwain, D.R., Berger, T. & Mak, T.W., 2015. Caspase Functions in Cell Death and Disease: Figure 1. Cold Spring Harbor Perspectives in Biology, 7(4), p.a026716. Available at: http://cshperspectives.cshlp.org/lookup/doi/10.1101/cshperspect.a026716.
Melino, G. & Vaux, D., 2010. Cell Death G. Melino & D. Vaux, eds.,
Murphy, K., 2012. Jayneway’s Immunology 8th ed.,
Manns, M.P. et al., 2010. 273 Short Term Safety, Tolerability, Pharmacokinetics and Preliminary Activity of Gs-9450, a Selective Caspase Inhibitor, in Patients With Chronic Hcv Infection. Journal of Hepatology, 52, pp.S114–S115. Available at: http://linkinghub.elsevier.com/retrieve/pii/S0168827810602759.
Liedtke, C. et al., 2011. Loss of caspase-8 protects mice against inflammation-related hepatocarcinogenesis but induces non-apoptotic liver injury. Gastroenterology, 141(6), pp.2176–2187. Available at: http://dx.doi.org/10.1053/j.gastro.2011.08.037.
Chaudhary, K. et al., 2013. Caspase 8 differentially controls hepatocytes and non-parenchymal liver cells during chronic cholestatic liver injury in mice. Journal of Hepatology, 59(6), pp.1292–1298. Available at: http://dx.doi.org/10.1016/j.jhep.2013.07.026.