Saturated Free Fatty Acids Induce Cholangiocyte Lipoapoptosis

Authors

Sathish Kumar Natarajan, University of Nebraska - LincolnFollow
Sally A. Ingham, University of Nebraska Medical Center
Ashley M. Mohr, University of Nebraska Medical Center
Cody J. Wehrkamp, University of Nebraska Medical Center
Anuttoma Ray, University of Nebraska Medical Center
Sohini Roy, University of Nebraska Medical Center
Sophie C. Cazanave, Virginia Commonwealth University
Mary Anne Phillippi, University of Nebraska Medical Center
Justin L. Mott, University of Nebraska Medical Center

Document Type

Article

Date of this Version

2014

Citation

Hepatology. 2014 December ; 60(6): 1942–1956.

Comments

Copyright 2014 by the American Association for the Study of Liver Diseases.

Abstract

Recent studies have identified a cholestatic variant of nonalcoholic fatty liver disease (NAFLD) with portal inflammation and ductular reaction. Based on reports of biliary damage, as well as increased circulating free fatty acids (FFAs) in NAFLD, we hypothesized the involvement of cholangiocyte lipoapoptosis as a mechanism of cellular injury. Here, we demonstrate that the saturated FFAs palmitate and stearate induced robust and rapid cell death in cholangiocytes. Palmitate and stearate induced cholangiocyte lipoapoptosis in a concentration-dependent manner in multiple cholangiocyte-derived cell lines. The mechanism of lipoapoptosis relied on the activation of caspase 3/7 activity. There was also a significant up-regulation of the proapoptotic BH3-containing protein, PUMA. In addition, palmitate-induced cholangiocyte lipoapoptosis involved a time-dependent increase in the nuclear localization of forkhead family of transcription factor 3 (FoxO3). We show evidence for posttranslational modification of FoxO3, including early (6 hours) deacetylation and dephosphorylation that coincide with localization of FoxO3 in the nuclear compartment. By 16 hours, nuclear FoxO3 is both phosphorylated and acetylated. Knockdown studies confirmed that FoxO3 and its downstream target, PUMA, were critical for palmitate- and stearate-induced cholangiocyte lipoapoptosis. Interestingly, cultured cholangiocyte-derived cells did not accumulate appreciable amounts of neutral lipid upon FFA treatment.