Increases in p53 expression induce CTGF synthesis by mouse and human hepatocytes and result in liver fibrosis in mice

Abstract

The tumor suppressor p53 has been implicated in the pathogenesis of non-cancer-related conditions such as insulin resistance, cardiac failure, and early aging. In addition, accumulation of p53 has been observed in the hepatocytes of individuals with fibrotic liver diseases, but the significance of this is not known. Herein, we have mechanistically linked p53 activation in hepatocytes to liver fibrosis. Hepatocyte-specific deletion in mice of the gene encoding Mdm2, a protein that promotes p53 degradation, led to hepatocyte synthesis of connective tissue growth factor (CTGF; the hepatic fibrogenic master switch), increased hepatocyte apoptosis, and spontaneous liver fibrosis; concurrent removal of p53 completely abolished this phenotype. Compared with wild-type controls, mice with hepatocyte-specific p53 deletion exhibited similar levels of hepatocyte apoptosis but decreased liver fibrosis and hepatic CTGF expression in two models of liver fibrosis. The clinical significance of these data was highlighted by two observations. First, p53 upregulated CTGF in a human hepatocellular carcinoma cell line by repressing miR-17-92. Second, human liver samples showed a correlation between CTGF and p53-regulated gene expression, which were both increased in fibrotic livers. This study reveals that p53 induces CTGF expression and promotes liver fibrosis, suggesting that the p53/CTGF pathway may be a therapeutic target in the treatment of liver fibrosis.

Mcl-1 and Bcl-xL regulate Bak/Bax-dependent apoptosis of the megakaryocytic lineage at multistages

“…Western blot was performed as previously described. 41 For immunodetection, the following antibodies were used: rabbit polyclonal antibody to stat5 (Santa Cruz Biotechnology), rabbit polyclonal antibody pf4-Cre mice, respectively. The reticulated platelet proportion was determined by staining with thiazole orange, three mice per group; statistical analysis was performed using Mann-Whitney's U-test (e).…”

Activation of the Mitochondrial Apoptotic Pathway Produces Reactive Oxygen Species and Oxidative Damage in Hepatocytes That Contribute to Liver Tumorigenesis

“…Primary hepatocytes were isolated from C57BL/6J mice (Charles River Japan) by a two-step collagenase-pronase perfusion of mouse livers as previously described (12). Isolated hepatocytes were maintained at 37 C under 5% CO 2 in William's Eagle medium containing 10% FCS (Sigma-Aldrich Japan), 100 nmol/L dexamethasone, 100 nmol/L insulin (Sigma-Aldrich Japan) and L-glutamine (Invitrogen).…”

Retinoid X receptor α in human liver is regulated by miR-34a

“…Previous studies have revealed that miR-34a is regulated by p53, a tumor suppressor gene [12,13]. It was recently reported that p53 induces the expression of connective tissue growth factor (CTGF), a hepatic fibrogenic master switch, and promotes liver fibrosis [14]. From these finding, we hypothesized that miR-34a might also lead to liver fibrosis.…”