8% pre-run TBEpolyacrylamid gel and electrophoresis was continued at 80 V for 90120 minutes. The signal was then detected and quantified with Odyssey infrared imaging system. trigger a cytokine response with significant TNF-serum levels, we were curious A-83-01 cost whether the loss of RelA/p65 within hepatocytes would lead to enhanced liver injury after PH. To our surprise, we did not observe significantly different ALT levels in RelaF/FAlbCre animals as compared to control animals when followed over 7 days after 2/3 PH. Moreover, tissue integrity was not disturbed and no significant apoptotic cell death could be detected at any time point as assessed by histology and TUNEL-staining. Overall mortality after 2/3 PH did not differ significantly between groups and could be attributed to technical complications during surgery. These results suggest that the main NF-kB subunit RelA/p65 is not essential to protect hepatocytes form cell death after 2/3 PH. Statistics Data are expressed as mean 6 standard error. Differences between groups were analyzed by Student’s t-test where appropriate. In all cases, sample sizes were chosen to produce statistically unambiguous results. A P value of 0.05 or less was considered significant. Results Hepatocyte-specific Loss of RelA/p65 does not Result in Enhanced Liver Damage after 2/3 PH To study the functional role of the transactivating NF-kB subunit RelA/p65 in liver regeneration, RelaF/FAlbCre animals were subjected to 2/3 PH. Livers of these mice lack a functional RelA/p65 specifically in hepatocytes and loss of NF-kB binding activity upon LPS- or TNF-stimulation renders them highly sensitive to TNF-induced apoptosis. Because PH is known to RelA/p65 in Liver Regeneration Hepatocyte-specific Inactivation of RelA/p65 Causes an Accelerated Cell Cycle Progression without Altering Liver Mass Regeneration after 2/3 PH We next asked, whether the regenerative response would be altered in RelaF/FAlbCre animals after 2/3 PH as assessed by BrdU uptake as a measure for DNA-synthesis. Controls and mutant mice displayed similar kinetics of BrdU-uptake, however, the onset of BrdU uptake started earlier in RelaF/FAlbCre animals with significantly higher levels at 36 hours after PH. Consistent with histological findings, G1/S-phase-specific Cyclin D1 mRNA expression at 24 hours after PH was higher in RelaF/ F AlbCre animals as was Cyclin D1 expression on protein 
level at 2448 hours after PH. Moreover, WB analysis showed more pronounced PCNA and Cyclin A expression at 36 and 48 hours post PH. Theses findings suggest that hepatocyte loss of a functional RelA/p65 leads to an accelerated cell cycle progression after PH. As JNK signalling is suppressed by NF-kB signals and Cyclin D1 expression is known to be regulated by JNK/AP1, we analyzed early phosphorylation of JNK during the priming phase at 1, 4 and 6 hours after PH. While control animals did not display significant phospho-JNK levels, phosphorylation of p54-JNK was clearly induced in liver lysates from RelaF/ F AlbCre after PH. Furthermore, we found enhanced levels phospho-STAT3 in livers of RelaF/FAlbCre animals as compared to controls. However, serum levels of the gp130 ligand and inducer of the JAK/STAT signalling pathway IL-6 or induction of IL-6 mRNA were not significantly different between the groups, indicating and confirming that NF-kB signals within hepatocytes negatively regulate STAT3 activation. Of note, we were unable to detect any TNF-serum levels by ELISA in sera