Effects of breviscapine on epithelial-mesenchymal transition induced by transforming growth factor-β2 in human lens epithelial cells

Abstract

Background Epithelial-mesenchymal transition (EMT) is a major event in the pathogenesis of posterior capsular opacification (PCO),and the expressions of α-smooth muscle actin (α-SMA) is the marker of EMT.Previous studies showed that breviscapine plays an important role in anti-fibrosis and suppression EMT,however,the mechanism of its effect on EMT in LECs is unclear.Objective Present study was to investigate the effect of breviscapine on the expression of α-SMA and fibronectin (FN) in human LECs induced by transforming growth factor-β2 (TGF-β2).Methods Human LECs strain,HLE-B3,was cultured and passaged in DMEM containing 10％ fetal bovine serum.Different concentrations of breviscapine (6.75,12.75,25.00,50.00 and 100.00 mg/L)were added into the medium for 24,48 and 72 hours respectively,and then cell cunting kit-8 (CCK-8) was used to evaluate the half maximal inhibitory concentration (IC50) of breviscapine to HLE-B3.In addition,HLE-B3 was subcultured at the density of 1 × 106/hole and divided into 4 groups.The cells were in free-serum medium as the normal control;the cells were exposed in 10 μg/L TGF-β2 as TGF-β2 group;while in the breviscapine group,10 mg/L of breviscapine was added into the culture medium and another group was the combination of 10 mg/L breviscapine and 10 μg/L of TGF-β2 treatment.Real-time PCR and Western blot were used to detect the mRNA expressions of α-SMA and FN as well as their protein in HLE-B3 72 hours after cultured.Results The inhibitory rate of breviscapine to HLE-B3 proliferation was gradually elevated with the increase of concentration of breviscapine,showing a significant inhibition of the cell proliferation among the different groups and at various time points (F =292.851,P=0.000;F =65.037,P=0.000).IC50 of HLE-B3 at 72 hours was 22 mg/L,and therefore,in rest of experiment 10 mg/L of breviscapine was used which was 1/2 only half of the IC50.α-SMA and FN were expressed in cultured normal HLE-B3.The expressing level of α-SMA mRNA and FN mRNA in the HLE-B3 was significantly different among the normal group,TGF-β22 group,breviscapine treatment group and combination group as well as at various time points (F =105.490,P =0.000 ; F =1041.414,P =0.000).Similarly,the protein expressions of α-SM A and FN in the HLE-B3 was significantly different among the four groups and different time points (F=136.872,P=0.000;F=119.820,P=0.000).The expression levels of α-SMA and FN mRNA and their proteins in HLE-B3 were remarkably increased in the 10 μg/L TGF-β2 group compared with the normal control group (at all P=0.000),and those in the combination group were obviously declined in comparison to the TGF-β2 group (P =0.001,0.001,0.001,0.010).No significant difference was found in the expressions of α-SMA and FN in the HLE-B3 between the breviscapine group and normal control group in both transcriptional level and protein level (P =0.551,0.292,0.551,0.360).Conclusions 10 mg/L breviscapine can arrest the proliferation and EMT of human LECs.This result suggests that using breviscapine may be a potential prophylactic approach in the prevention of PCO. Key words: Breviscapine; Lens epithelial cell; Epithelial-mesenchymal transition; Posterior capsular opacification