Abstract
Purpose: :
Proliferation and dedifferentiation of retinal pigment epithelial (RPE) cells known as epithelial mesenchymal transition (EMT) are associated in pathogenesis in proliferative vitreoretinopathy (PVR). TGFβ is a critical factor to induce RPE-EMT formation. Recently, it is reported that toll-like receptor (TLR) 4 signaling that acts as receptor for lipopolysaccharide (LPS) enhances TGFβ pathway. In this study, we therefore investigated the effect of TLR4 signaling on human RPE treated with TGFβ.
Methods: :
ARPE-19 cell lines were used as human RPE cells, and treated with human recombinant TGFβ2 to induce RPE-EMT formation. The expressions of TLR4, TGFβ receptor (TGFβR), and TGFβ pseudoreceptor (BAMBI) on RPE were analyzed by flow cytometry or RT-PCR. The proliferation of TGFβ-treated RPE stimulated with LPS were assessed by [3H]-thymidine incorporation. Cytokine productions by RPE with LPS stimulation were also measured by cytokine beads array.
Results: :
RPE-EMT formation was observed morphologically in TGFβ-treated RPE cells. TLR4 was expressed on both RPE and TGFβ-treated RPE, and the expression of TLR4 on the cells was enhanced by LPS stimulation. With stimulus by LPS, cell proliferation and IL-6 production were also enhanced in TGFβ-treated RPE. TGFβ-treated RPE exposed to LPS highly expressed TGFβR. Moreover, BAMBI transcript was downregulated in RPE exposed to LPS.
Conclusions: :
TLR4 signaling promotes cell proliferation and inflammatory cytokine production of dedifferentiated RPE by TGFβ. Thus, TLR4 enhances TGFβ signaling and RPE dedifferentiation in pathogenic mechanisms of PVR.
Keywords: inflammation • retinal pigment epithelium • proliferative vitreoretinopathy