JNK inhibitor SP600125 alleviates TGF-β2-induced epithelial-mesenchymal transition in RPE cell via TGF-βR2/Smad2/3 and JNK/c-Jun pathway

To explore the effect of SP600125, a c-Jun N-terminal kinases (JNK) inhibitor, on epithelial-mesenchymal transition (EMT) in retinal pigment epithelial (RPE) cell caused by transforming growth factor-beta 2 (TGF-β2).

Human RPE cell line (ARPE-19) cells were treated with TGF-β2 and JNK inhibitor SP600125 in vitro. Cellular viability, migration and proliferation in ARPE-19 cells were examined by cell counting kit-8 (CCK-8) assay, wound scratch, and bromodeoxyuridine (BrdU) staining assay, respectively. Transforming growth factor-beta receptor 2 (TGF-βR2), Smad2/3, JNK, c-Jun, alpha-smooth muscle actin (α-SMA), N-cadherin, and vimentin proteins were analyzed by immunoblotting. Moreover, TGF-βR2 was detected by immunofluorescence assay.

TGF-β2 significantly enhanced viability, migration, and proliferation in ARPE‑19 cells, induced phosphorylation of TGF-βR2, Smad2/3, JNK, and c‑Jun, and upregulated α‑SMA, N‑cadherin, and vimentin expression. SP600125 inhibited these cellular processes and reduced the expression/phosphorylation of the above proteins; notably, it blocked TGF-β2‑induced effects, including cell viability, migration, proliferation, phosphorylation of TGF-βR2, Smad2/3, JNK, and c‑Jun, as well as upregulation of α‑SMA, N‑cadherin, and vimentin.

JNK inhibitor SP600125 suppresses TGF-β2-induced the increases in cell viability, migration, proliferation, and EMT in RPE cells via the TGF-βR2/Smad2/3 and JNK/c-Jun signaling pathways.