NF kappa B-Mediated Expression of Phosphoinositide 3-Kinase delta Is Critical for Mesenchymal Transition in Retinal Pigment Epithelial Cells

Epithelial mesenchymal transition (EMT) plays a vital role in a variety of human diseases including proliferative vitreoretinopathy (PVR), in which retinal pigment epithelial (RPE) cells play a key part. Transcriptomic analysis showed that the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway was up-regulated in human RPE cells upon treatment with transforming growth factor (TGF)-beta 2, a multifunctional cytokine associated with clinical PVR. Stimulation of human RPE cells with TGF-beta 2 induced expression of p110 delta (the catalytic subunit of PI3K delta) and activation of NF kappa B/p65. CRISPR-Cas9-mediated depletion of p110 delta or NF kappa B/p65 suppressed TGF-beta 2-induced fibronectin expression and activation of Akt as well as migration of these cells. Intriguingly, abrogating expression of NF kappa B/p65 also blocked TGF-beta 2-induced expression of p110 delta, and luciferase reporter assay indicated that TGF-beta 2 induced NF kappa B/p65 binding to the promoter of the PIK3CD that encodes p110 delta. These data reveal that NF kappa B/p65-mediated expression of PI3K delta is essential in human RPE cells for TGF-beta 2-induced EMT, uncovering hindrance of TGF-beta 2-induced expression of p110 delta as a novel approach to inhibit PVR.