Hyperosmolarity-enhanced COX-2 expression contributes to high glucose-induced angiogenesis

Abstract

Aim/hypothesis: Diabetic hyperglycemia increases plasma osmolarity, leading to adaptive cellular responses. Cycloxygenase-2 (COX-2) plays a role in angiogenesis and plaque stability. We tested the hypothesis that glucose-induced hyperosmolarity promotes angiogenesis through activation of COX-2 expression, thus orchestrating endothelial sprouting and migration. Methods: Human aortic endothelial cells (HAEC) and dermal microvascular endothelial cells (HMVEC) were incubated with 5.5 mmol/L glucose (normoglycemia), high glucose (HG, at 12.5, 25 and 45 mmol/L), or equimolar concentrations of the hyperosmolar controls mannitol (HM). Results: Both HG and HM increased the expression of the water channel aquaporin-1 (AQP1) and of COX-2. HG and HM for 1 h increased the nuclear accumulation of Tonicity enhancer binding protein (TonEBP) and its binding to Tonicity enhancer element at electrophoretic mobility shift assay. HG and HM induced endothelial migration at a fluorimetric assay, and tubulization in Matrigel. Targeting the osmosignaling pathway with small interfering RNAs to AQP1 and to TonEBP both reverted the inducing effects of HG and HM on COX-2 expression as well as angiogenic activities. Compared with age- and sex-matched C57/BL6 control mice, the aorta of D2.B6-Ins2 Akita diabetic mice (3 months old, male) showed lipid accumulation as visualized with Oil red O staining (Figure, panel A), and slight increase of AQP1 (panel B) and COX-2 (panel C) expression. ![Figure][1] Conclusion/interpretation: By activating the water channels AQP1 and TonEBP, hyperosmolarity caused by HG or HM induces COX-2 expression and angiogenesis in human endothelial cells, which may be relevant for vascular complications of diabetes. [1]: pending:yes