Tricyclic Antidepressants Promote Ceramide Accumulation to Regulate Collagen Production in Human Hepatic Stellate Cells

Sci Rep. 2017 Mar 21:7:44867. doi: 10.1038/srep44867.

Abstract

Activation of hepatic stellate cells (HSCs) in response to injury is a key step in hepatic fibrosis, and is characterized by trans-differentiation of quiescent HSCs to HSC myofibroblasts, which secrete extracellular matrix proteins responsible for the fibrotic scar. There are currently no therapies to directly inhibit hepatic fibrosis. We developed a small molecule screen to identify compounds that inactivate human HSC myofibroblasts through the quantification of lipid droplets. We screened 1600 compounds and identified 21 small molecules that induce HSC inactivation. Four hits were tricyclic antidepressants (TCAs), and they repressed expression of pro-fibrotic factors Alpha-Actin-2 (ACTA2) and Alpha-1 Type I Collagen (COL1A1) in HSCs. RNA sequencing implicated the sphingolipid pathway as a target of the TCAs. Indeed, TCA treatment of HSCs promoted accumulation of ceramide through inhibition of acid ceramidase (aCDase). Depletion of aCDase also promoted accumulation of ceramide and was associated with reduced COL1A1 expression. Treatment with B13, an inhibitor of aCDase, reproduced the antifibrotic phenotype as did the addition of exogenous ceramide. Our results show that detection of lipid droplets provides a robust readout to screen for regulators of hepatic fibrosis and have identified a novel antifibrotic role for ceramide.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antidepressive Agents, Tricyclic / pharmacology*
  • Ceramides / metabolism*
  • Collagen / biosynthesis*
  • Drug Discovery / methods
  • Extracellular Matrix / drug effects
  • Extracellular Matrix / metabolism
  • Gene Expression Regulation / drug effects
  • Hepatic Stellate Cells / drug effects*
  • Hepatic Stellate Cells / metabolism*
  • High-Throughput Screening Assays
  • Humans
  • Liver Cirrhosis / drug therapy
  • Liver Cirrhosis / etiology
  • Liver Cirrhosis / metabolism
  • Liver Cirrhosis / pathology
  • Myofibroblasts / drug effects
  • Myofibroblasts / metabolism
  • Signal Transduction / drug effects

Substances

  • Antidepressive Agents, Tricyclic
  • Ceramides
  • Collagen