LYTAK1 attenuates proliferation of retinal pigment epithelial cells through TGF-β-mediated epithelial-mesenchymal transition via the ERK/AKT signaling pathway

Retinal pigment epithelial (RPE) cells have crucial roles in the initiation and development of human ophthalmic diseases. Our previous study suggested that transforming growth factor-beta (TGF-beta)-activated kinase 1 (TAK1) is a potential target in the progression and pathogenesis of human proliferative vitreoretinopathy disease. The present study further analyzed the role of TAK1 inhibitor, LYTAK1, in human RPE cells and explored the potential molecular mechanism of LYTAK1-mediated proliferation of human RPE cells. Proliferation of human RPE cells was investigated following treatment with LYTAK1 and knockdown of TGF-beta. TGF-beta-mediated epithelial-mesenchymal transition (EMT) through regulation of the extracellular signal-regulated kinase (ERK)/protein kinase B (AKT) signaling pathway was also explored to analyze the LYTAK1-mediated mechanism of proliferation in human RPE cells. The present results demonstrated that LYTAK1 administration suppressed TAK1 gene and protein expression in human RPE cells. LYTAK1 administration also inhibited proliferation and migration of human RPE cells in vitro. Outcomes indicated that LYTAK1 treatment downregulated expression levels of TGF-beta 1 and EMT markers, including cadherin, fibronectin and alpha-smooth muscle actin in human RPE cells. Notably, results demonstrated that the ERK/AKT signal pathway was blocked by LYTAK1 in human RPE cells. Knockdown of TGF-beta markedly inhibited phosphorylation and activity of TAK1 and suppressed the LYTAK1-mediated ERK/AKT signaling pathway in RPE cells, which further canceled inhibition of RPE cell proliferation by LYTAK1. In conclusion, these findings indicated that LYTAK1 may inhibit RPE cell proliferation through the TGF-beta-mediated EMT/ERK/AKT signaling pathway, suggesting that TAK1 may be a potential target for the treatment of RPE diseases.