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Wenwen Chen, Qing Chang, Fangyuan Hu, Juan Zhang, Peijun Zhang, Tingting Jiang; TLR4-MAP4K4 Signaling Pathway in Retinal Vascular Endothelial Cells. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1457.
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© ARVO (1962-2015); The Authors (2016-present)
Mechanisms of retinal angiogenesis, particularly the signaling pathways independent of vascular endothelial grows factor (VEGF), remain elusive. Under disease conditions, inflammation and innate immunity likely play important roles in influencing the structure and integrity of retinal vasculature. Toll-like receptor 4 (TLR4) is expressed by endothelial cells and respond to various ligands, such as fatty acids and extracellular matrix components, that are relevant to retinal angiogenesis. The goals of our study were to explore TLR4-mediated signaling pathway in retinal microvascular endothelial cells (RMVECs) and to examine the effects of TLR4 antagonists in models of angiogenesis.
Cultured human RMVECs were stimulated with TLR 4 agonist lipopolysaccharide (LPS) at 100ng/ml. Its downstream mitogen-activated protein kinase 4 (MAP4K4) was depleted by transducing cells with shRNA in lentiviral vector. The rates of cell proliferation and migration were measured by EdU, transwell, scratch wound healing and matrigel tube formation assays. The in vivo effect of TLR 4 antagonist, TAK-242, was examined in mouse model of oxygen-induced retinopathy (OIR), by intravitreal injection. Lucentis was used as positive control.
LPS stimulated the expression of TLR4 and MAP4K4 in HRMVECs, enhanced the ability of cell proliferation, migration and angiogenesis. Down-regulation of MAP4K4 in HRMEVECs markedly decreased the phosphorylation level of its downstream substrate protein moesin, redistributed VE-adherin to cytoplasmic membrane and suppressed the proliferation, migration and tube formation of HRMVEC induced by LPS. Intravitreal injection of TAK-242 significantly decreased the expression of MAP4K4, and reduced non-perfusion area and angiogenesis of retina in OIR mouse. Similar effects were achieved by Lucentis.
TLR4-MAP4K4 pathway takes part in the process of retina angiogenesis through regulating the proliferation and migration of RMVECs, and is a potential target for intervention via mechanisms independent of VEGF.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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