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Zeev Dvashi, Orit Adir, Keren Ben Yaakov, Ayala Pollack; TNFα Directly Activates the TGFβ1 Signaling pathways in Retinal Pigment Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5781.
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© ARVO (1962-2015); The Authors (2016-present)
This study aimed to investigate a possible cross-talk between TNFα and TGFβ1 in the inflammatory response of RPE cells. Inflammation and fibrosis are the hallmarks of many retinal pathologies and are mediated by cytokines and chemokines such as tumor necrosis factor α (TNFα), transforming growth factor β1 (TGFβ1), monocyte chemoattractant protein-1 (MCP-1) and interleukins. Inflammatory response of the retinal pigment epithelium (RPE) cells is mainly characterized by the transformation of RPE cells into myofibroblasts cells, a process which is manifested by increased motility and contractility, enhanced expression of α- Smooth muscle actin (αSMA) and secretion of Matrix metalloproteinases (MMPs). TNFα and TGFβ1 are known to play a key role in inflammatory response in RPE cells.
ARPE-19 cells were treated with SB431542 (TGFβ1 receptor kinase inhibitor) followed by TNFα (20ng/ml) stimulation at all experiments, as well as TGFβ1 (2.5ng/ml). Smad2, p38 and p65 activation was determined by western blot analysis; αSMA expression was detected by immunofluorescence staining; cell migration was determined using scratch assay; cell contractility was examined using collagen contraction assay; MMPs levels were quantified by gelatin zymography assay.
Stimulation of RPE cells with TGFβ1 activates Smad2/3 protein, a specific TGFβ1 substrate. Treatment with TNFα also increases Smad2/3 activation. Moreover, TNFα treatment increases αSMA expression, cell migration and contractility, all are inflammation features. However, addition of TGFβ1 receptor specific inhibitor of abolishes all these processes. A synergistic effect was observed in the combine treatments of TNFα and TGFβ1 induced MMP9 secretion, in addition to elevation in MMP2 secretion.
The data presented hereby, demonstrates that TGFβ1 is trans-activated by TNFα, and that TNFα- induced inflammatory response is TGFβ1- dependent. Thus, a better understanding of the cross- talk between TNFα and TGFβ1 might be used to reduce the inflammatory and the fibrotic response underlies many retinal pathologies.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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