Clinical Studies Intrahepatic activation of caspases in human fulminant hepatic failure Ludger Leifeld, Jacob Nattermann, Magdalene Fielenbach, Volker Schmitz, Tilman Sauerbruch and Ulrich Spengler Department of Internal Medicine I, University of Bonn, Germany Leifeld L, Nattermann J, Fielenbach M, Schmitz V, Sauerbruch T, Spengler U. Intrahepatic activation of caspases in human fulminant hepatic failure. Liver International 2006: 26: 872–879. r2006 The Authors. Journal compilation r 2006 Blackwell Munksgaard Abstract: Background/Aims: Apoptosis has been implicated in the pathogenesis of fulminant hepatic failure (FHF) potentially involving caspases. Thus far, apoptosis in FHF has mainly been studied in animal models while human data are sparse. Methods: Caspases-3, -8 and -9 activities and Fas expression were analyzed in correlation to TdT-mediated dUTP nick end labelling (TUNEL) positive apoptotic cells in livers of patients with FHF (n 5 26), chronic liver disease (CLD) (n 5 60) and normal controls (NC) (n 5 10). Results: Numbers of TUNEL-positive cells were higher in FHF than in CLD and NC (Po0.001) correlating to the intrahepatic activities of caspase-3. The highest caspase-3 activities were found in fulminant hepatitis B, significantly surpassing those in FHF of any other etiology. In fulminant hepatitis B, caspase-9 activity was also higher than in controls, while caspase-8 activation was not higher than in NC. Unlike caspase-3, caspases -8 and -9 activities were not correlated to the numbers of TUNEL positive cells. Fas expression was also the highest in FHF but did not differ between hepatitis B virus-FHF and other FHF. Conclusions: Our data indicate differential activation of intrahepatic caspases in FHF depending on the underlying etiology. Massive activation of caspases in fulminant hepatitis B confirms a pivotal role of apoptotic pathways in the pathogenesis of human fulminant hepatitis B. Key words: apoptosis – caspases – fulminant hepatic failure – hepatitis B Privatdozent Dr. med. Ludger Leifeld, Department of Internal Medicine I, Sigmund Freud Strae 25, D-53105 Bonn, Germany. Tel: 10049 228 287 5259 Fax: 10049 228 287 4323 e-mail: ludger.leifeld@ukb.uni-bonn.de Received 7 December 2005, accepted 4 May 2006                                                                                   Apoptosis of hepatocytes is supposed to be the major underlying pathomechanism, that leads to fulminant hepatic failure (FHF). This hypothesis has been extensively studied in murine models. For instance, systemic application of the agonistic Fas- antibody Jo2 leads to hepatocellular apoptosis and death of the mice within several hours due to liver failure, while other organs are not significantly affected by systemic Fas activation (1). This pro- cess is mediated by a sequence of intracellular events mainly involving activation of proteases of the caspase family. In general, caspase-3 is the central effector caspase leading to cleavage of different cellular substrates and finally to apopto- tic cell death. Caspase-3 can be directly activated via the extrinsic (‘death receptor’) pathway via activation of the initiator caspase-8. Caspase-8 is the most proximal caspase and can be activated by ligation of death factors such as Fas or TNF-a. Alternatively, caspase-3 is activated via the intrin- sic mitochondrial pathway of apoptosis: first, caspase-8 activates BID (‘BH3 interacting domain death agonist’) and initializes cytochrome c release from the mitochondria into the cytosol. Cytosolic cytochrome c activates caspase-9, which in turn activates the effector caspase-3. In addition to experimental FHF induced by Fas antibody, apoptosis has been demonstrated to be a part of the pathomechanism in several other murine models of FHF such as galactosa- mine-LPS induced liver failure (2, 3), galactosa- mine-endotoxine-induced liver failure (4), herpes simplex hepatitis (5) and the concanavalin A model of FHF (6, 7). However, only few data are available on the induction of apoptosis in human FHF (8–13). In particular, intrahepatic activation of caspases has not yet been studied . Therefore, we analyzed activation of caspases-3, Abbreviations: FHF, fulminant hepatic failure; CLD, chronic liver disease; NC, normal controls. Liver International 2006: 26: 872–879 r 2006 The Authors Journal compilation r 2006 Blackwell Munksgaard DOI: 10.1111/j.1478-3231.2006.01300.x 872