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Dexamethasone Inhibits High Glucose–, TNF-–, and IL-1β–Induced Secretion of Inflammatory and Angiogenic Mediators from Retinal Microvascular Pericytes

From the Department of Biological Sciences, Allergan Inc., Irvine, California.

PURPOSE. To characterize the effects of dexamethasone in human retinal pericytes (HRMPs), monocytes (THP-1), and retinal endothelial cells (HRECs) treated with high glucose, TNF-, or IL-1β.

METHODS. HRMP and HREC phenotypes were verified by growth factor stimulation of intracellular calcium–ion mobilization. Glucocorticoid receptor phosphorylation was assessed with an anti-phospho-Ser²¹¹ glucocorticoid receptor antibody. Secretion of 89 inflammatory and angiogenic proteins were compared in cells incubated with (1) normal (5 mM) or high (25 mM) D-glucose and (2) control medium, TNF- (10 ng/mL), or IL-1β (10 ng/mL), with or without dexamethasone (1 nM to 1 µM). The proteins were compared by using multianalyte profile testing.

RESULTS. HRMPs and HRECs expressed functional PDGFB-R and VEGFR-2, respectively. Dexamethasone induction of glucocorticoid receptor phosphorylation was dose-dependent in all cell types. High glucose increased secretion of inflammatory mediators in HRMPs, but not in HRECs. Dexamethasone dose dependently inhibited secretion of these mediators in HRMPs. For all cells, TNF- and IL-1β induced a fivefold or more increase in inflammatory and angiogenic mediators; HRMPs secreted the greatest number and level of mediators. Dexamethasone dose dependently inhibited the secretion of multiple proteins from HRMPs and THP-1 cells, but not from HRECs (IC₅₀ 2 nM to 1 µM).

CONCLUSIONS. High glucose, TNF-, and IL-1β induced an inflammatory phenotype in HRMPs, characterized by hypersecretion of inflammatory and angiogenic mediators. Dexamethasone at various potencies blocked hypersecretion of several proteins. Pericytes may be a key therapeutic target in retinal inflammatory diseases, including diabetic retinopathy. Inhibition of pathologic mediators may depend on delivering high levels (1 µM) of glucocorticoid to the retina.