ABSTRACT
The proliferation and differentiation of cardiac fibroblasts (CFs) is central to cardiac fibrosis. Betulinic acid (BA) is an active compound isolated from the bark of the birch tree Betula spp. (Betulaceae) and has been shown to attenuate hepatic fibrosis. However, the effect of BA on the high glucoseinduced fibrosis response in CFs remains to be elucidated, therefore, the present study investigated the effect of BA on high glucoseinduced CFs and examined the possible mechanism underlying the effect of BA on CF transdifferentiation. CFs were preincubated with various concentrations of BA for 24 h and then stimulated with high glucose (25 mM) for various times. Cell proliferation was evaluated using an MTT assay. The mRNA expression levels of αsmooth muscle actin (SMA) and transforming growth factor (TGF)ß1 were determined using reverse transcriptionquantitative polymerase chain reaction analysis. The protein expression levels of αSMA, collagen I, collagen III, fibronectin, TGFß1, small mothers against decapentaplegic (Smad)2/3, phosphorylated (p)Smad2 and pSmad3 and were detected using western blot analysis. The data revealed that BA attenuated the CF proliferation and myofibroblast differentiation induced by high glucose. In addition, BA inhibited the expression of extracellular matrix (ECM) in the CFs induced by high glucose. It was also found that BA inhibited the high glucoseinduced phosphorylation of Smad2/3 in the CFs. Taken together, BA suppressed the high glucoseinduced increase in the proliferation of CFs and expression of ECM via inhibition of the TGFß1/Smad signaling pathway. Thus, BA may offer therapeutic potential towards the treatment of cardiac fibrosis.