Potential conflict of interest: Nothing to report.
Steatohepatitis/Metabolic Liver Disease
Saturated free fatty acids induce cholangiocyte lipoapoptosis
Article first published online: 20 JUN 2014
© 2014 by the American Association for the Study of Liver Diseases
Volume 60, Issue 6, pages 1942–1956, December 2014
How to Cite
Natarajan, S. K., Ingham, S. A., Mohr, A. M., Wehrkamp, C. J., Ray, A., Roy, S., Cazanave, S. C., Phillippi, M. A. and Mott, J. L. (2014), Saturated free fatty acids induce cholangiocyte lipoapoptosis. Hepatology, 60: 1942–1956. doi: 10.1002/hep.27175
Supported by the Fred and Pamela Buffett Cancer Center and the College of Medicine Student Summer Research Program, University of Nebraska Medical Center. The contents of the article are solely the responsibility of the authors.
See Editorial on Page 1809
- Issue published online: 24 NOV 2014
- Article first published online: 20 JUN 2014
- Accepted manuscript online: 18 APR 2014 10:44AM EST
- Manuscript Accepted: 16 APR 2014
- Manuscript Received: 8 NOV 2013
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. Conclusion: Our data show that the saturated FFAs palmitate and stearate induced cholangiocyte lipoapoptosis by way of caspase activation, nuclear translocation of FoxO3, and increased proapoptotic PUMA expression. These results suggest that cholangiocyte injury may occur through lipoapoptosis in NAFLD and nonalcoholic steatohepatitis patients. (Hepatology 2014;60:1941–1955)