Inhibitory effect of transforming growth factor-β1 on expression of N-myc downstream regulatory gene 2 in human renal tubular epithelial cell line HK-2 and its significance

Objective To investigate the effect of transforming growth factor-β1 (TGF-β1) on the expression of N-myc downstream regulatory gene 2 (NDRG2) in human renal tubular epithelial cell line HK-2. Methods The control group and the experimental group were set up according to whether or not the TGF-β1 was incubated. Western blotting and real-time quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) were applied to detect the expression of E-cadherin, α-smooth muscle actin (α-SMA), Vimentin and Snail protein in epithelial cells. The expression of NDRG2 in human renal tubular epithelial cells (HK-2) treated with different concentrations of TGF-β1 was detected by Western blotting and RT-qPCR. Results The results showed that the protein expression level expression of E-cadherin in the control group and the experimental group was (1.0±0.2) vs. (0.3±0.2) (t=4.850, P=0.008), that of α-SMA was (1.0±0.1) vs. (2.6±0.4) (t=6.721, P=0.003), that of Vimentin was (1.0±0.1) vs. (2.6±0.4) (t=6.721, P=0.003), and that of Snail was (1.0±0.1) vs. (2.5±0.2) (t=11.620, P=0.000). In the control group and the experimental group, the mRNA expression level of E-cadherin was (1.0±0.2) vs. (0.2±0.1) (t=7.686, P=0.002), that of α-SMA was (1.0±0.3) vs. (2.4±0.3) (t=5.715, P=0.005), that of Vimentin was (1.1±0.15) vs. (2.6±0.5) (t=4.977, P=0.008), and that of Snail was (0.9±0.2) vs. (1.9±0.2) (t=6.124, P=0.004). At the same time, after incubation with TGF-β1, NDRG2 in HK-2 cells was significantly down-regulated at both protein and mRNA levels. The levels of protein expression in each group were (1.00±0.04 vs. 0.80±0.03 vs. 0.50±0.05 vs. 0.30±0.03 vs. 0.20±0.02) (P=0.019), and mRNA expression in each group were (1.00±0.05 vs. 0.70±0.03 vs. 0.50±0.04 vs. 0.30±0.02 vs. 0.20±0.05) (P=0.021). Especially when incubated with TGF-β1 concentration greater than 10 ng/ml, the difference was statistically significant. Conclusion TGF-β1 can promote the process of EMT in HK-2 cells, and TGF-β1 can down-regulate the expression of NDRG2 in protein and RNA in HK-2 cells. Key words: N-myc downstream regulatory gene 2; Transforming growth factor-β1; Renal tubular epithelial cells; Epithelial-mesenchymal transition