Effects of peroxisome proliferators-activated receptor γ agonists on transforming growth factor-β1 and Smads signal pathway:experiment with hepatic stellate cell

Objective: To study the effects of peroxisome proliferators-activated receptorγ(PPARγ) agonists on transforming growth factor(TGF)-β1-induced fibrotic responses in liver fibrosis,so as to investigate its effects in prevention of liver fibrosis.Methods:Hepatic stellate cell(HSC) were cultured and divided into groups.In Group 1 TGFβ1 of the concentrations of 0,1,2,5,and 10ng/ml were added and co-cultured for 24h.In Group 2 TGFβ1 of the concentration of 5ng/ml was added and co-cultured for 0,6,12,and 24h respectively.Groups 3,4,and 5 were pretreated with 10μmol/L15d-PGJ2,PPARγ ligand,10μmol/L troglitazone,agonist of and 10μmol/L ciglitazone,both PPARγ agonists,respectively for 2h,then treated with 5ng/mlTGFβ1.A blank control group was set up.The cultured cells were collected.RT-PCR was used to detect the mRNA expression of TGF-β1-induedfibronectin(FN).Western blotting was used to detect the expression of TGF-β1-induced FN,Smad,and phosphorylated Smad(p-Smad) proteins.Results: TGF-β1 enhanced the FN mRNA expression in a dose-and time-dependent manner.The FN mRNA expression of the 5ng/mlTGF-β1 group was 3.7 times higher than that of the control group(P0.05).The FN mRNA expressions of the 15d-PGJ2,troglitazone-,and ciglitazone-pretreated groups were lower than those of the 5ng/ml TGF-β1 group by 37.4%,41.1%,and 21.7% respectively(all P0.05).The FN expression of that was lower than that of the 5ng/ml TGF-β1 group by 24.7%,37.1% and 27.1% respectively(allP0.05).The p-Smad2/3 protein expression levels of the TGF-β1 group began to increase 15 minutes after stimulation,increased in a time-dependent manner,peaked 1 hour after,and began to decrease 2 hours later.However,the levels of protein expression of total Smad2 and Smad3 did not change significantly in all the groups.Both 2ng/ml TGFβ1 and 5 ng/mlTGFβ1 significantly induced the increase of protein expression of p-Smad2/3(allP0.05).The levels of protein expression of p-Smad2 and p-Smad3 of the 5ng/ml TGFβ1 group were 3.42 and 0.98 times higher than those of the 2 ng/mlTGFβ1(both P 0.05).The levels of protein expression of p-Smad2/3 of the 15d-PGJ2,troglitazone-,and ciglitazone-pretreated groups were all significantly lower than those of the 5 ng/mlTGFβ1 group by 61.1%,53.4%,and 59.4%(allP0.05).However,there was no significant difference among different drug-treated groups(allP0.05).Conclusion:Through abrogating TGF-β1/Smads signaling pathway,PPARγ agonists inhibitTGF-β1-induced HSC and may play a potential role in preventing liver fibrosis as a novel approach to prevent the progress of liver fibrosis.