title: RIP1-Dependent Programmed Necrosis is Negatively Regulated by Caspases During Hepatic Ischemia-Reperfusion.
abstract: Programmed necrosis (necroptosis), a newly discovered form of cell death, is mediated by receptor-interacting protein 1 (RIP1) and plays a pivotal role after myocardial, renal, and cerebral ischemia-reperfusion (I/R). The relevance of necroptosis in the postischemic liver remains, however, unclear. The aim of this study was to analyze the role of programed necrosis during hepatic I/R. C57BL6 mice were subjected to warm hepatic I/R (90 min/240 min). The animals were pretreated with either the RIP1 inhibitor necrostatin-1 (Nec-1, 3.5 μg kg) or vehicle (Nec-1inactive, 3.5 μg kg) administered systemically before ischemia. Sham-operated animals served as controls (n = 6 each group). The inflammatory response was evaluated by intravital microscopy. The hepatic transaminases alanine aminotransferase/aspartate aminotransferase in plasma as well as the activity of caspase-3 in tissue were determined as markers of hepatocellular injury. Leukocyte recruitment to the liver, sinusoidal perfusion failure, as well as the transaminase activities were strongly increased on I/R as compared with the sham-operated mice. Inhibition of the RIP1-dependent pathway with Nec-1, however, did not attenuate I/R-induced leukocyte migration, perfusion failure, and hepatocellular injury. Western blot analysis showed a baseline RIP1 expression in livers from sham-operated mice, whereas RIP1 expression was not detectable in both Nec-1-treated and vehicle-treated I/R group. Caspase-3 activity was significantly elevated after I/R in both postischemic groups. Our in vivo data show that RIP1-mediated necroptosis is not present in the postischemic liver and that I/R-induced caspase activation is associated with loss of RIP1 expression. Because caspases are able to cleave RIP1, we hypothesize that I/R-triggered caspase activation negatively regulates necroptosis and, thereby, determines apoptosis as a preferred route of cell death after hepatic I/R.
authors.affiliation: *Department of General, Visceral, Transplantation, Vascular and Thoracic Surgery, Klinikum der Universität München, and †Walter-Brendel Centre for Experimental Medicine, Ludwig-Maximilians-University of Munich, Munich, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Rosentreter
authors.forename: Dominik
authors.initials: D
authors.lastname: Funken
authors.forename: Jörg
authors.initials: J
authors.lastname: Reifart
authors.forename: Konstantin
authors.initials: K
authors.lastname: Mende
authors.forename: Markus
authors.initials: M
authors.lastname: Rentsch
authors.forename: Andrej
authors.initials: A
authors.lastname: Khandoga
mesh_terms: D000818:Animals; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism*; D002465:Cell Movement / Q000187:drug effects; D005260:Female; D020690:GTPase-Activating Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D022781:Hepatocytes / Q000378:metabolism* / Q000473:pathology; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007962:Leukocytes / Q000378:metabolism / Q000473:pathology; D008099:Liver / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D009336:Necrosis; D015427:Reperfusion Injury / Q000235:genetics / Q000378:metabolism* / Q000473:pathology
chemical_list: D020690:GTPase-Activating Proteins; D007093:Imidazoles; D007211:Indoles; C490620:Ralbp1 protein, mouse; C507699:necrostatin-1; C505409:Casp3 protein, mouse; D053148:Caspase 3