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

Graefes Arch Clin Exp Ophthalmol. 2017 Sep;255(9):1757-1762. doi: 10.1007/s00417-017-3711-0. Epub 2017 Jun 19.


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% O2, 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.

Keywords: Human RPE cells; Hypoxia; Inflammation; Interleukins; VEGF.

MeSH terms

  • Cells, Cultured
  • Enzyme-Linked Immunosorbent Assay
  • Humans
  • Hypoxia / metabolism*
  • Hypoxia / pathology
  • Inflammation / metabolism*
  • Inflammation / pathology
  • Interleukins / metabolism*
  • Retinal Diseases / metabolism*
  • Retinal Diseases / pathology
  • Retinal Pigment Epithelium / metabolism*
  • Retinal Pigment Epithelium / pathology
  • Vascular Endothelial Growth Factor A / metabolism*


  • Interleukins
  • Vascular Endothelial Growth Factor A