15 Therefore, we also studied fibrogenesis by measuring mRNA expression of collagen and metalloprotease inhibitor (Timp 1), which decreased in p38α KO after they underwent BDL (Fig. 4D), showing that these KO mice exhibited a lower profibrotic stage. Moreover, collagen deposition in the liver by the Sirius Red staining method showed that p38α KO mice did not exhibit more fibrosis than WT mice in chronic cholestasis (Fig. 4E,F). Consequently, liver fibrosis does not seem to account for the reduced life span of p38α KO BDL mice. Albumin is considered a marker of hepatic function, and hence a decrease in its synthesis
could indicate impairment of the liver capacity for protein synthesis. p38α KO sham mice already showed decreased albumin mRNA levels before inducing the illness (Fig.
5A). In WT mice, the decrease in albumin mRNA expression began when BDL Selleck TSA HDAC was performed, so the reduction in the albumin mRNA levels was seen at 12 days of cholestasis, and kept on descending until 28 days (Fig. 5A). In the p38α KO group, mRNA expression of albumin ACP-196 manufacturer remained at the same low level during evolution of the illness, showing also no significant differences with the p38α sham group at 12 and 28 days (Fig. 5A). Albumin immunohistochemical staining showed the same profile (Fig. 5B). Since activation of p70 S6 kinase and subsequent phosphorylation of S6 ribosomal protein are involved in protein synthesis PIK3C2G and are downstream MAPK, we assessed activation of this pathway. Figure 6 and Supporting Fig. S6 show significantly reduced phosphorylation of p70 S6 kinase and S6 only in p38-deficient mice after BDL. Since endoplasmic reticulum stress might also contribute to the reduced
albumin synthesis, we measured GADD 153 and phosphorylation of eIF2a. Supporting Fig. S7 shows that liver-specific p38-deficient mice did not exhibit more endoplasmic reticulum stress than WT mice. On the other hand, looking for cellular structure alterations we investigated HSP27, a phosphorylation target of MK2, and found a significant increase (P < 0.01) in phospho-HSP27 by western blotting only in BDL WT mice but not in p38α KO mice (Fig. 5C; Supporting Fig. S3). Interestingly, p38α KO BDL mice had higher expression of HSP27 in comparison with WT BDL mice (Fig. 5C). This result was confirmed by confocal image analysis (Fig. 5D,E). At this point, considering all the parameters that were indicating that p38α KO BDL mice exhibited worse liver conditions and could suffer from the illness more than the WT BDL mice, we decided to study the evolution of hepatomegaly and cell size in the progress of the illness. Comparing the hepatocyte size at the very beginning, we found differences between WT sham and p38α KO sham (Fig. 6A). In addition, when mice underwent BDL a different phenomenon was observed. In a WT liver, cell growth tried to compensate for liver injury and loss of function.