Rapamycin ameliorates inflammation and fibrosis in the early phase of cirrhotic portal hypertension in rats through inhibition of mTORC1 but not mTORC2

PLoS One. 2014 Jan 3;9(1):e83908. doi: 10.1371/journal.pone.0083908. eCollection 2014.

Abstract

Objective: Hepatic stellate cells (HSCs) transdifferentiation and subsequent inflammation are important pathological processes involved in the formation of cirrhotic portal hypertension. This study characterizes the pathogenetic mechanisms leading to cholestatic liver fibrosis and portal hypertension, and focuses on mammalian target of rapamycin (mTOR) pathway as a potential modulator in the early phase of cirrhotic portal hypertension.

Methods: Early cirrhotic portal hypertension was induced by bile duct ligation (BDL) for three weeks. One week after operation, sham-operated (SHAM) and BDL rats received rapamycin (2 mg/kg/day) by intraperitoneal injection for fourteen days. Vehicle-treated SHAM and BDL rats served as controls. Fibrosis, inflammation, and portal pressure were evaluated by histology, morphometry, and hemodynamics. Expressions of pro-fibrogenic and pro-inflammatory genes in liver were measured by RT-PCR; alpha smooth muscle actin (α-SMA) and antigen Ki67 were detected by immunohistochemistry; expressions of AKT/mTOR signaling molecules, extracellular-signal-regulated kinase 1/2 (ERK1/2), p-ERK1/2, and interleukin-1 beta (IL-1β) were assessed by western blot.

Results: The AKT/mTOR signaling pathway was markedly activated in the early phase of cirrhotic portal hypertension induced by BDL in rats. mTOR blockade by rapamycin profoundly improved liver function by limiting inflammation, fibrosis and portal pressure. Rapamycin significantly inhibited the expressions of phosphorylated 70KD ribosomal protein S6 kinase (p-P70S6K) and phosphorylated ribosomal protein S6 (p-S6) but not p-AKT Ser473 relative to their total proteins in BDL-Ra rats. Those results suggested that mTOR Complex 1 (mTORC1) rather than mTORC2 was inhibited by rapamycin. Interestingly, we also found that the level of p-ERK1/2 to ERK1/2 was significantly increased in BDL rats, which was little affected by rapamycin.

Conclusions: The AKT/mTOR signaling pathway played an important role in the early phase of cirrhotic portal hypertension in rats, which could be a potential target for therapeutic intervention in the early phase of such pathophysiological progress.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Extracellular Matrix / metabolism
  • Fibrosis
  • Hemodynamics
  • Inflammation / genetics
  • Inflammation / metabolism
  • Inflammation / pathology
  • Liver / drug effects
  • Liver / metabolism
  • Liver / pathology
  • Liver Cirrhosis / complications
  • Liver Cirrhosis / drug therapy
  • Liver Cirrhosis / metabolism*
  • Liver Cirrhosis / pathology*
  • Liver Function Tests
  • Male
  • Mechanistic Target of Rapamycin Complex 1
  • Mechanistic Target of Rapamycin Complex 2
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Multiprotein Complexes / antagonists & inhibitors*
  • Portal Pressure / drug effects
  • Proto-Oncogene Proteins c-akt / metabolism
  • Rats
  • Signal Transduction / drug effects
  • Sirolimus / pharmacology*
  • Splenomegaly / pathology
  • TOR Serine-Threonine Kinases / antagonists & inhibitors*
  • TOR Serine-Threonine Kinases / metabolism

Substances

  • Multiprotein Complexes
  • Mechanistic Target of Rapamycin Complex 1
  • Mechanistic Target of Rapamycin Complex 2
  • Proto-Oncogene Proteins c-akt
  • TOR Serine-Threonine Kinases
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Sirolimus

Grants and funding

This study was jointly supported by the Foundation of Shanghai Natural Science (09ZR1418600) and the National Natural Science (81070358) of China. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.