The novel growth factor, progranulin, stimulates mouse cholangiocyte proliferation via sirtuin-1-mediated inactivation of FOXO1

Abstract

Progranulin (PGRN), a secreted growth factor, regulates the proliferation of various epithelial cells. Its mechanism of action is largely unknown. Sirtuin 1 (Sirt1) is a protein deacetylase that is known to regulate the transcriptional activity of the forkhead receptor FOXO1, thereby modulating the balance between proapoptotic and cell cycle-arresting genes. We have shown that PGRN is overexpressed in cholangiocarcinoma and stimulates proliferation. However, its effects on hyperplastic cholangiocyte proliferation are unknown. In the present study, the expression of PGRN and its downstream targets was determined after bile duct ligation (BDL) in mice and in a mouse cholangiocyte cell line after stimulation with PGRN. The effects of PGRN on cholangiocyte proliferation were assessed in sham-operated (sham) and BDL mice treated with PGRN or by specifically knocking down endogenous PGRN expression using Vivo-Morpholinos or short hairpin RNA. PGRN expression and secretion were upregulated in proliferating cholangiocytes isolated after BDL. Treatment of mice with PGRN increased biliary mass and cholangiocyte proliferation in vivo and in vitro and enhanced cholangiocyte proliferation observed after BDL. PGRN treatment decreased Sirt1 expression and increased the acetylation of FOXO1, resulting in the cytoplasmic accumulation of FOXO1 in cholangiocytes. Overexpression of Sirt1 in vitro prevented the proliferative effects of PGRN. Conversely, knocking down PGRN expression in vitro or in vivo inhibited cholangiocyte proliferation. In conclusion, these data suggest that the upregulation of PGRN may be a key feature stimulating cholangiocyte proliferation. Modulating PGRN levels may be a viable technique for regulating the balance between ductal proliferation and ductopenia observed in a variety of cholangiopathies.

Fine‐Tuning of Sirtuin 1 Expression Is Essential to Protect the Liver From Cholestatic Liver Disease

“…As cholestatic disease progresses, cholangiocytes lose their proliferative capacity in advanced disease, contributing to bile duct loss (ductopenia) . Our results point to the contribution of SIRT1 to this process and support the previously described ability of mild SIRT1 overexpression to inhibit the proliferative effect of growth factors like progranulin in vitro …”

“…(3) Our results point to the contribution of SIRT1 to this process and support the previously described ability of mild SIRT1 overexpression to inhibit the proliferative effect of growth factors like progranulin in vitro. (38) Ultimately, the apparent differences in severity of the damaging phenotype observed in SIRT1overexpressing mice when compared to SIRT1 hep-/mice, despite the similarly attenuation of FXR signaling, support that apoptotic cell death associated with increased SIRT1 expression play a key role in contributing to liver injury during cholestasis.…”

FOXO1, a Potential Therapeutic Target, Regulates Autophagic Flux, Oxidative Stress, Mitochondrial Dysfunction, and Apoptosis in Human Cholangiocarcinoma QBC939 Cells

“…SIRT1 is a NAd+ dependent deacetylation enzyme. Frampton G et al have demonstrated that treatment with progranulin, a secreted growth factor, decreased Sirt1 expression and increased the acetylation of FOXO1, resulting in the cytoplasmic accumulation of FOXO1 and enhanced proliferation in cholangiocytes [35]. However the effect of resveratrol on cholangiocarcinoma is far from clear.…”

Sirtuin 1 activation alleviates cholestatic liver injury in a cholic acid–fed mouse model of cholestasis

“…Despite the ability of Sirt1 in modulating BA metabolism, very few studies have investigated the Sirt1 pathway in cholestasis. Bile‐duct–ligated models of cholestasis demonstrate decreased hepatic Sirt1 protein expression . However, no further studies have been performed to determine how this down‐regulation affects cholestatic liver injury and whether activation of Sirt1 can alleviate cholestatic liver injury.…”

“…Bile-duct-ligated models of cholestasis demonstrate decreased hepatic Sirt1 protein expression. (22,23) However, no further studies have been performed to determine how this down-regulation affects cholestatic liver injury and whether activation of Sirt1 can alleviate cholestatic liver injury. The current study aims to: (1) confirm the decrease in expression and activity of Sirt1 in mouse models of cholestasis, (2) determine whether activation of Sirt1 through oral administration of SRT1720 alleviates cholestatic liver injury, and, if so, (3) by what mechanism.…”