JNK1/β-catenin axis regulates H2O2-induced epithelial-to-mesenchymal transition in human lens epithelial cells.

Epithelial-mesenchymal transition (EMT) is the main cause of fibrotic cataracts. Oxidative stress was recently shown to trigger epithelial-mesenchymal transition in human lens epithelial cells (hLECs). However, the underlying mechanism is not fully understood. Here we reported that exposure to low doses (100 μM) of H2O2 led to EMT in hLECs, as indicated by simultaneous down-regulated of E-cadherin and ZO-1, and up-regulated of alpha smooth muscle actin (α-SMA). H2O2-induced EMT was accompanied by accumulation of phosphorylated JNK1. In contrast, knockdown of JNK1 via siRNA reversed H2O2-induced EMT. Of interest, in human lens capsules of anterior subcapsule cataracts, the expressions of JNK1, as well as β-catenin and its downstream effectors cyclin D and c-Myc, were augmented compared to that in normal lens capsules. Mechanistically, activated JNK1 dislodged β-catenin from the cell membrane, which subsequently translocated to the nuclei and triggered transcription of its effectors. Nuclei β-catenin, cyclin D and c-Myc were accumulated in H2O2-induced EMT and JNK1 depletion abrogated these trend in hLECs. In conclusion, our data suggest that JNK1 is essential for H2O2-induced EMT in hLECs via mediating the translocation of β-catenin.