Figure 6.

Fingolimod (FTY720) inhibited the synthesis of extracellular matrix in normal rat kidney (NRK)‐49F cells by binding with S1P1. Rat renal fibroblast NRK‐49F cells were incubated with FTY720 (5 μM), transforming growth factor (TGF)‐β (2 μg/ml) or TGF‐β plus FTY720 for 12 h. The cells were lysed, and total protein was extracted for Western blot analysis. The expression levels of α‐smooth muscle actin (SMA) and collagen IV were increased after 12 h of TGF‐β treatment, indicating activation of the NRK‐49F cells, and this activation was inhibited by FTY720 (a). The optical densities of α‐SMA and collagen IV were normalized to that of glyceraldehyde 3‐phosphate dehydrogenase (GAPDH) (a). Cells were then pretreated with either S1P1‐siRNA or negative control siRNA before TGF‐β and FTY720 treatment. The inhibitory effect of FTY720 on fibronectin and α‐SMA was reversed significantly after S1P1 blockage (b). The optical densities of fibronectin, α‐SMA and S1P1 were normalized to that of GAPDH (b). The data are presented as the mean ± standard error of the mean (s.e.m.). **P < 0·01 relative to the control or FTY720‐treated groups. ***P < 0·001 relative to the control or FTY720‐treated groups. The data represent the results from at least three independent experiments.