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Amplified inhibition of stellate cell activation pathways by PPAR-γ, RAR and RXR agonists

Efrat Sharvit1, Shirley Abramovitch, Shimon Reif

  • 1Institute of Gastroenterology and Liver Diseases, Tel Aviv Sourasky Medical Center, and Sackler Faculty of Medicine, Tel Aviv, Israel ; Pediatric Gastroenterology Unit, Dana Children's Hospital, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel ; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.

Plos One
|October 8, 2013
PubMed

Insights

Combined treatment with PJ, ATRA, and 9-cis ligands inhibits liver fibrosis by halting hepatic stellate cell proliferation and reducing fibrotic markers. This multi-ligand approach offers a potent strategy against liver disease progression.

Area of Science:

  • Hepatology
  • Molecular Biology
  • Cell Biology

Background:

  • Peroxisome proliferator activator receptor (PPAR) ligands like 15-Δ12,13-prostaglandin L(2) (PJ) and all-trans retinoic acid (ATRA) show anti-fibrotic effects in the liver.
  • The role of retinoic acid X receptor (RXR) ligands, including 9-cis, in liver fibrosis remains less understood.

Purpose of the Study:

  • To investigate the synergistic effects of combined PJ, ATRA, and 9-cis treatment on key liver fibrosis events.
  • To evaluate the impact of these ligands on hepatic stellate cell (HSC) proliferation and activation.

Main Methods:

  • Primary rat hepatic stellate cells (HSCs) were treated with PJ, ATRA, and 9-cis.
  • Cell cycle progression was analyzed using FACS analysis.
  • Protein and gene expression of fibrotic markers (collagen Iα1, αSMA), cell cycle regulators (cyclin D1, p21, p27), and signaling pathways (mTOR, p70S6K) were assessed via Western blot and real-time PCR.

Main Results:

  • Combined PJ, ATRA, and 9-cis treatment additively inhibited HSC proliferation through G0/G1 cell cycle arrest.
  • This inhibition was associated with reduced cyclin D1 and increased p21/p27 protein levels.
  • The combined ligands downregulated mTOR and p70S6K phosphorylation, inhibited HSC activation (indicated by reduced vitamin A lipid droplet depletion), and markedly suppressed collagen Iα1 and αSMA expression.

Conclusions:

  • Combined treatment with PJ, ATRA, and 9-cis significantly inhibits HSC proliferation and activation.
  • This multi-ligand approach effectively downregulates key fibrotic markers, suggesting a potent therapeutic strategy for liver fibrosis.
  • The additive anti-proliferative and anti-fibrotic effects highlight the potential of combining these ligands for enhanced efficacy compared to single-agent treatments.

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