or liver lysates of control or mutant mice at 1, 4, 6 or 12 hours after PH. mRNA expression levels of TNF were hardly detected in liver samples and not different in RelaF/FAlbCre livers at 1 and 4 h after PH. Despite the above findings indicating a slight but robust acceleration of cell cycle progression in RelA/p65 LY341495 cost deficient hepatocytes, the time course of liver mass regeneration was not different between groups and all animals almost fully reached the initial liver mass within 7 days after 2/3 PH irrespective of the genotype. Our results from 2/3 and 80% PH support the concept that genetic loss of intact NF-kB signalling within in the parenchymal cellular compartment of the liver does not particularly sensitize this organ to enhanced cell death after liver resection but rather leads to a certain proliferation advantage that however does not significantly alter overall restoration of the total number and mass of hepatocytes. Genetic Inactivation of RelA/p65 in Both Parenchymal and Non-parenchymal Cells Neutralizes the Proliferative Advantage Seen after Hepatocyte-specific Deletion of RelA/p65 and Leads to a Normal Regenerative Response after PH In contrast to previous reports that attribute PH-induced NFkB-activation to parenchymal cells, a more recent concept proposes that Kupffer cells are the main source of NF-kBactivation that also orchestrate the early cytokine response after PH. Therefore, to additionally inactivate canonical NFkB signalling in Kupffer cells, we used RelaF/FMxCre animals to study liver regeneration after PH. Effective deletion of wildtype RelA/p65 was confirmed by WB analysis of lysates from Kupffer cells isolated form control and RelaF/FMxCre animals 7 days after i.p. injection with polyIC. To verify that nuclear translocation of RelA/p65 as a prerequisite for NF-kB activation does not occur 
in both parenchymal and non-parenchymal cellular compartments in the livers of RelaF/FMxCre animals, RelaF/FMxCre and control animals were challenged with an i.p. injection of TNF and subjected to anti-p65-IHC analysis. TNF is a strong inducer of NF-kB and consequently, at 45 min after TNF-injection RelA/p65 translocation can be observed in hepatocytes and non-parenchymal cells in control animals. In RelaF/FAlbCre animals nuclear staining of RelA/p65 is restricted to non-parenchymal cells while nuclear staining of RelA/p65 is virtually absent in all cells in the livers of TNF-treated RelaF/FMxCre animals. Consequently and as previously reported, RelaF/FMxCre mice display a blunted LPS-induced TNF-response because nuclear translocation of RelA/p65 in Kupffer cells as the main source of LPS-induced NF-kB-dependent TNF-production is inhibited. Accordingly, stimulation of the NF-kB target gene A20 after LPS-challenge was abolished in RelaF/FMxCre mice. PH-induced induction of A20 was only attenuated in RelaF/FAlbCre mice but abolished in RelaF/FMxCre animals. However, PH-induced A20mRNA induction in control animals was very low when compared to LPS injection, suggesting that liver NF-kB activation is very weak after PH. Similarly, the magnitude of PHinduced induction of the NF-kB target gene IkBa in controls was mild, but completely inhibited in RelaF/FMxCre mice. The assumption that NF-kB activation was only mild after PH under our experimental conditions was confirmed by anti-p65-IHC where nuclear staining was only occasionally observed mainly in non-parenchymal cells of control animals when analyzed at 1 h and 4 h post PH. Fu
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