The appearance of the bands representing cleaved caspase-3 was prominent in cytoplasmic liver samples 120 minutes after TNFα/D-galN treatment in WT mice but only after 480 minutes in NS3/4A-Tg mice

to a much lower degree (Fig. 2A). This could be confirmed in liver sections from LPS/D-galN–treated mice using immunohistochemistry. Whereas a significant staining for cleaved caspase-3 was visible in WT mice 6 hours after application of LPS/D-galN, only a weak staining for cleaved caspase-3 was evident in NS3/4A-Tg mice (Fig. 2B). Furthermore, we analyzed the degree of apoptosis and necrosis in murine liver samples taken at different time points after LPS/D-galN administration through TUNEL staining. Again, liver sections from WT mice taken 6 hours after LPS/D-galN injection

had a significantly (P < 0,0001) higher PD0332991 research buy number of TUNEL-positive cells per 10 mm2 of liver compared with NS3/4A-Tg mice (Fig. 3A, upper right). Additionally, WT mice showed extensive and severe changes in the liver parenchyma with a high infiltration of inflammatory cells 6 hours after LPS/D-galN application (Fig. 3A, lower right). Thus, NS3/4A-Tg mice are less sensitive to TNFα-induced apoptosis compared with WT mice. These antiapoptotic effects might be exerted by the NS3/4A-related increase in NFκB activation. Activated NFκB is known both to protect hepatocytes from apoptosis and to PF-562271 purchase promote liver regeneration.13 We therefore determined the total number of hepatocyte nuclei and the number of dividing hepatocyte nuclei per 10 mm2 of liver in hematoxylin-eosin–stained liver sections from WT and NS3/4A-Tg mice left untreated or treated with LPS/D-galN. The total number of hepatocyte nuclei decreased during LPS/D-galN treatment in both WT and NS3/4A-Tg mice, with a more pronounced reduction in WT mice, compared with NS3/4A-Tg mice illustrating LPS/D-galN–mediated liver injury (Fig. 3B, left). In order to investigate liver regeneration, the amount of actively dividing hepatocyte nuclei was determined. Interestingly, this showed that, whereas the number of dividing hepatocyte

Orotic acid nuclei decreased in WT mice, NS3/4A-Tg mice revealed an increase in the number of dividing hepatocyte nuclei during LPS/D-galN treatment (Fig. 3B, right). Furthermore, after staining for the proliferation marker Ki67, liver sections from NS3/4A-Tg mice treated with LPS/D-galN had a significantly higher number of Ki67-positive nuclei compared with WT mice treated the same way (19.20 ± 2.49 versus 5.60 ± 1.65 positive nuclei per 10 mm2 of liver; P < 0.0001 [Mann-Whitney]) (Fig. 3C). Thus, NS3/4A not only exerts antiapoptotic effects but also promotes hepatocyte regeneration, most likely by increasing NFκB activation. NFκB regulates the transcription of an exceptionally large number of genes, many of which participate in immune and inflammatory responses, including TNFα, IL-1α, and IL-6.