title: The Effects of Combined Treatment with an HMG-CoA Reductase Inhibitor and PPARγ Agonist on the Activation of Rat Pancreatic Stellate Cells.
abstract: OBJECTIVE
  Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) and peroxisome proliferator-activated receptor gamma (PPARγ) ligands can modulate cellular differentiation, proliferation, and apoptosis through various pathways. It has been shown that HMG-CoA reductase inhibitors and PPARγ agonists separately inhibit pancreatic stellate cell (PaSC) activation. We studied the effects of a combination of both types of drugs on activated PaSCs via platelet-derived growth factor (PDGF), which has not previously been reported. The present study was performed to elucidate the underlying mechanisms of these effects by focusing on the impact of the signaling associated with cell-cycle progression.
  
  
  METHODS
  Primary cultures of rat PaSCs were exposed to simvastatin and troglitazone. Proliferation was quantified using the BrdU method, and cell-cycle analysis was performed using a fluorescent activated cell sorter. The protein expression levels of smooth muscle actin (SMA), extracellular signal-regulated kinase (ERK), and a cell cycle machinery protein (p27Kip1) were investigated using Western blot analysis.
  
  
  RESULTS
  Simvastatin reversed the effects of PDGF on cell proliferation in a dose-dependent manner. The combination of a low concentration of simvastatin (1 mM) and troglitazone (10 mM) synergistically reversed the effects of PDGF on cell proliferation but had no effect on cell viability. The expression of a-SMA was markedly attenuated by combining the two drugs, which blocked the cell cycle beyond the G0/G1 phase by reducing the levels of phosphorylated ERK and reversed the expression of p27Kip1 interrupted by PDGF.
  
  
  CONCLUSIONS
  Simvastatin and troglitazone synergistically inhibited cell proliferation in activated PaSCs by blocking the cell cycle beyond the G0/G1 phase. This inhibition was due to the synergistic modulation of the ERK pathway and the cell cycle machinery protein p27Kip1.
authors.affiliation: Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Beom Jae
authors.initials: BJ
authors.lastname: Lee
authors.forename: Hong Sik
authors.initials: HS
authors.lastname: Lee
authors.forename: Chang Duck
authors.initials: CD
authors.lastname: Kim
authors.forename: Sung Woo
authors.initials: SW
authors.lastname: Jung
authors.forename: Yeon Seok
authors.initials: YS
authors.lastname: Seo
authors.forename: Yong Sik
authors.initials: YS
authors.lastname: Kim
authors.forename: Yoon Tae
authors.initials: YT
authors.lastname: Jeen
authors.forename: Hoon Jai
authors.initials: HJ
authors.lastname: Chun
authors.forename: Soon Ho
authors.initials: SH
authors.lastname: Um
authors.forename: Sang Woo
authors.initials: SW
authors.lastname: Lee
authors.forename: Jai Hyun
authors.initials: JH
authors.lastname: Choi
authors.forename: Ho Sang
authors.initials: HS
authors.lastname: Ryu