Abstract:

BACKGROUND: One of important mechanisms underlying myocardial fibrosis is that transforming growth factor β1(TGF-β1) stimulates the proliferation and differentiation of cardiac fibroblasts via Smads signaling pathway. Previous studies have confirmed that tanshinone ⅡA can effectively inhibit myocardial fibrosis. But whether blockage of TGF-β1/Smads signaling pathway is involved in this process remains unclear.
OBJECTIVE: To investigate the effects of tanshinone ⅡA on TGF-β1 signal transduction in rat cardiac fibroblasts.
METHODS: Neonatal rat cardiac fibroblasts were harvested by trypsin digestion and differential attachment and treated with 5 μg/L TGF-β1 and different concentrations of tanshinone ⅡA (10^-6, 10^-5 and 10^-4 mol/L). At 6, 12, and 24 hours after TGF-β1 application, fibronectin expression was detected by reverse transcription-polymerase chain reaction and Western blot analysis. At 15, 30, 60, and 120 minutes after TGF-β1 application, Smads protein expression was determined by Western blot analysis.
RESULTS AND CONCLUSION: Fibronectin mRNA and protein expression began to increase at 6 hours after TGF-β1 application and was 1.3 and 1.8 times higher than initial level, respectively (P < 0.01), at 24 hours after TGF-β1 application. Phosphorylated Smad2/3 protein expression began to increase at 15 minutes after TGF-β1 application, peaked at 1 hour, decreased at 2 hours, but it was still 3.9 times higher than initial level (P < 0.01). Tanshinone ⅡA (10^-5 and 10^-4 mol/L) pretreatment downregulated fibronectin and phosphorylated Smad2/3 expression (P < 0.05 or P < 0.01) in a dose-dependent manner. These findings demonstrate that TGF-β1 induced fibronectin protein and mRNA expression and Smad2/3 protein expression in a time-dependent manner. Tanshinone ⅡA against myocardial fibrosis was likely related to its inhibition of TGF-β1-induced Smad2/3 phosphorylation and blockage of TGF-β1/Smads signaling pathways within cardiac fibroblasts.