Inhibitory effect of vascular endothelial growth factor on transforming growth factor β1-induced epithelial-mesenchymal transition of HK2 cells and its relationship with connective tissue growth factor and PI3K-Akt pathway

Objective To examine the relationship of the inhibitory effect of vascular endothelial growth factor(VEGF) on epithelial-mesenchymal transition (EMT) induced by TGF-β1 in HK2 cells with the expression of connective tissue growth factor (CTGF) and PI3K-Akt pathway. Methods The cultured HK2 cells were divided into the following groups: normal control group, TGF-β1 (5 μg/L) group, VEGF (100 μg/L) group, TGF-β1 plus VEGF group. LY294002 (25 μmol/L), the blocker of PI3K-Akt pathway, was added to each of above-mentioned groups for the second part of the study, α-smooth muscle actin (α-SMA) and E-cadherin expressions of HK2 cells were assessed with double-stain immunocytochemistry method. The mRNA and protein expressions of α-SMA and CTGF of cells were assessed with RT-PCR and Western blot. The expressions of fibronectin (FN) and collagen Ⅰ (Col Ⅰ) in medium were assessed with ELISA. Results The expressions of α-SMA and CTGF significantly increased in HK2 cells treated with TGF-β1 compared with those in normal control (P<0.05), while significantly decreased in cells co-treated with TGF-β1 and VEGF compared with those treated with TGF-β1 alone (P<0.05, respectively). The expression of E-cadherin was exactly opposite to that of α-SMA. When LY294002 was added to TGF-β1 and VEGF co-treated cells, the expressions of α-SMA, CTGF, FN and Col Ⅰ were markedly up-regulated, when compared with those without LY294002 treatment (P<0.05). Conclusion Inhibitory effect of VEGF on TGF-β1-induced EMT of HK2 ceils in vitro may be related to down-regulation of CTGF expression and reduction of FN and Col Ⅰ, which may be partly dependent on PI3K-Akt pathway.