Hypoxia and inflammation in the release of VEGF and interleukins from human retinal pigment epithelial cells

• Published in: Graefe's archive for clinical and experimental ophthalmology Vol. 255; no. 9; pp. 1757 - 1762
• Main Authors: Arjamaa, Olli, Aaltonen, Vesa, Piippo, Niina, Csont, Tamás, Petrovski, Goran, Kaarniranta, Kai, Kauppinen, Anu
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2017; Springer Nature B.V
• Subjects: Basic Science; Enzyme-linked immunosorbent assay; Epithelium; Hypoxia; Inflammation; Interleukin 1; Interleukin 18; Interleukin 6; Interleukin 8; Lipopolysaccharides; Medicine; Medicine & Public Health; Ophthalmology; Oxygenation; Retina; Retinal pigment epithelium; Toll-like receptors; Vascular endothelial growth factor; Vascularization; Human RPE cells; Hypoxia; Inflammation; Interleukins; VEGF
• ISSN: 0721-832X; 1435-702X
• DOI: 10.1007/s00417-017-3711-0

Purpose Retinal diseases are closely associated with both decreased oxygenation and increased inflammation. It is not known if hypoxia-induced vascular endothelial growth factor (VEGF) expression in the retina itself evokes inflammation, or whether inflammation is a prerequisite for the development of neovascularization. Methods Human ARPE-19 cell line and primary human retinal pigment epithelium (RPE) cells were used. ARPE-19 cells were kept either under normoxic (24 h or 48 h) or hypoxic conditions (1% O 2 , 24 h). Part of the cells were re-oxygenated (24 h). Some ARPE-19 cells were additionally pre-treated with bacterial lipopolysaccharide (LPS). The levels of IL-6, IL-8, IL-1β, and IL-18 were determined from medium samples by an enzyme-linked immunosorbent assay (ELISA) method. Primary human RPE cells were exposed to hypoxia for 24 h, and the subsequent release of IL-6 and IL-8 was measured with ELISA. VEGF secretion from ARPE-19 cells was determined up to 24 h. Results Hypoxia induced significant ( P  < 0.01) increases in the levels of both IL-6 and IL-8 in ARPE-19 cells, and LPS pre-treatment further enhanced these responses. Hypoxia exposure did not affect the IL-1β or IL-18 release irrespective of LPS pre-treatment. If primary RPE cells were incubated for 4 h in hypoxic conditions, IL-6 and IL-8 concentrations were increased by 7 and 8-fold respectively. Hypoxia increased the VEGF secretion from ARPE-19 cells in a similar manner with or without pre-treatment with LPS. Conclusions Hypoxia causes an inflammatory reaction in RPE cells that is potentiated by pre-treatment with the Toll-like receptor-activating agent, LPS. The secretion of VEGF from these cells is regulated directly by hypoxia and is not mediated by inflammation.