To examine the effects of monocyte chemoattractant protein-1 (MCP-1) on epithelial-myofibroblast transition (EMT) of renal proximal tubular epithelial cells and the possible mechanism involved.
Human renal proximal tubular epithelial cells of the line HK-2 were cultured and divided into three groups: negative control group; positive control group, treated with transforming growth factor (TGF)-beta1 5 microg/L, and MPC-1 group, treated with MCP-1 0.1, 1, 10, and 100 microg/L for 24 h, 36 h, 48 h, and 72 h respectively. The expressions of alpha-smooth muscle actin (alpha-SMA) mRNA and protein of cells were detected by s. Western blotting and RT-PCR were used to detect the expression of P-Erk1/2, Erk1/2, P-P38MAPK, P38MAPK, and RhoA protein levels of the HK-2 cells, and RT-PCR was used to detect the expression of RhoC and Snail mRNA. Specific inhibitors of the Erk, P38MAPK, and Rho signal transduction pathways PD98059, SB203580, and Y27632 were added into the culture fluid of HK-2 cells respectively, 1 h later MCP-1 microg/L was added for 48 h, and Western blotting was used to detect the protein expression of alpha-small muscle actin (SMA).
The expression levels of alpha-SMA protein and mRNA significantly increased in the MCP-1 treated HK-2 cells,and these expression levels were the highest in the HK-2 cells treated with MCP-1 1 microg/L for 48 h. The ratios of (P-Erk1/2)/ (Erk1/2) and P-P38MAPK/P38MAPK were significantly increased (all P < 0.05) in the MCP-1 treated HK-2 cells with the highest ratios seen in the HK-2 cells treated by 100 microg/L of MCP-1. The expression levels of RhoA protein and RhoC mRNA of the HK-2 cells stimulated with MCP-1 of different concentrations were not significantly different (all P > 0.05). MCP-1 induced expression of a-SMA was only partly inhibited by PD98059 but not by SB203587 or Y27632. MCP-1 dose-dependently increased the expression of Snail mRNA of the HK-2 cells compared with those of the negative control cells. The level of Snail mRNA was the highest in the HK-2 cells treated with 100 microg/L MCP-1.
MCP-1 may induce the EMT of renal proximal tubular epithelial cells in vitro, and this effect may involve upregulation of Erk1/2 Map kinase signal pathways and Snail mRNA expression. P38MAPK or Rho kinase signal pathways can not be proven to be involved in MCP-1 induced EMT.