Hydrocortisone decreases retinal endothelial cell water and solute flux coincident with increased content and decreased phosphorylation of occludin

Abstract

Corticosteroids provide an effective treatment to reduce edema for conditions in which the blood-brain or blood-retinal barrier is compromised. However, little is known about the mechanism by which these hormones affect endothelial cell function. We hypothesized that hydrocortisone would reduce transport of water and solutes across bovine retinal endothelial cell (BREC) monolayers coincident with changes to the tight junction protein occludin. Treatment of BREC with 103 nM hydrocortisone for two days significantly decreased water and solute transport across cell monolayers. Immunoblot analysis of occludin extracted in SDS or urea based buffers revealed a 1.65-or 2.57-fold increase in content, respectively. A similar two-fold increase in occludin mRNA was observed by real-time PCR. Immunocytochemistry revealed hydrocortisone dramatically increased both occludin and ZO-1 staining at the cell border. Additionally, 4 h of hydrocortisone treatment significantly reduced occludin phosphorylation. To our knowledge, this is the first example of a regulated decrease in occludin phosphorylation associated with increased barrier properties. In conclusion, hydrocortisone directly affects retinal endothelial cell barrier properties coincident with changes in occludin content, phosphorylation and tight junction assembly. Localized hydrocortisone therapy may be developed as a treatment option for patients suffering from retinal edema due to diabetes.

A Novel Model for Brain Iron Uptake: Introducing the Concept of Regulation

“…15 We obtained CSF from healthy, iron-sufficient, and anemic iron-deficient infant monkeys. The results from this experiment are shown in Figure 3A and clearly show increased iron release from ECs upon exposure to CSF from iron-deficient monkeys versus CSF from iron sufficient monkeys.…”

Intravitreal bevacizumab for choroidal neovascularisation secondary to causes other than age-related macular degeneration

“…Mechanisms of intravitreal corticosteroids include reduction of retinal capillary permeability by increasing the activity and/or density of tight junctions in the retinal capillary endothelium, 64 inhibition of the VEGF gene expression, inhibition of the VEGF metabolic pathway, 65 and suppression of intracellular adhesion molecule-1 (ICAM-1)-mediated leucocyte adhesion to vessel walls. 66 Corticosteroids help keep vision stable, but increase the incidence of cataracts and glaucoma.…”

Signal Transduction Pathways in use of Dexamethasone Implant in the Eye

“…Glucocorticoids also develop the properties of the Blood-Retinal Barrier (BRB) [114]. It has been observed that occludin phosphorylation was reduced after 4 hours following the initiation of glucocorticoid treatment, and occludin expression was increased simultaneously in the bovine retinal endothelial cell layer [114].…”

“…Occludin increases in the in vitro vascular endothelial barrier models, and it was observed that occludin mRNA increased. It was also shown that it was hydrocortisone that caused occludin dephosphorylation [114].…”

“…TEER reflects the para-cellular permeability and confluence in cell layers in vivo and in vitro; therefore, it provides a measure of the integrity of the tight junction complexes [113]. Hydrocortisone decreases the transport of water and solutes in bovine retinal endothelial mono-layer cells, and increases the expression of ZO-1 and occludin tight junction proteins in the cell margins [114]. In human endothelial cells, dexamethasone suppresses the down-regulation of claudin-5 mainly induced by thapsigargin, TEER reduction, and leakage with FITC dextrane addition [115].…”