Purchase this article with an account.
Carolina Franco Nitta, Finny Monickaraj, Paul McGuire, Arup Das; The Sphingosine-1-Phosphate pathway is significantly altered in diabetic retinopathy. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5185.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The leading cause of vision loss in diabetic retinopathy is increased retinal vascular permeability. Sphingosine-1-phosphate (S1P) is a bioactive lipid with multiple functions, including the maintenance of vascular barrier integrity. S1P is synthesized by two kinases (Sphk1 and Sphk2) and signals through GPCRs (S1PR1-5), which are in turn regulated by RGSs (Regulators of G-protein signaling). We have previously indicated a role for S1P in diabetic retinopathy. The purpose of this study was to further analyze the signaling components of the S1P pathway in models of diabetic retinopathy, and find potential therapeutic targets.
Brown Norway rats were made diabetic with streptozotocin (50mg/kg) and retinas harvested after 2 weeks. RNA and protein was extracted, and the levels of Sphk1, Sphk2, and S1PR1 were quantified by real-time PCR and western blot. Retinal vascular permeability was measured by albumin protein levels by western blot. Additionally, human retinal pericytes (HRPs) were cultured in presence of low (5mM), high (30mM), or alternating daily low and high glucose (glucose flux) for 7 days. RNA was isolated and the levels of RGS1-4 were quantified by real-time PCR. Human retinal endothelial cells (HRECs) were treated with a S1PR1 agonist (SEW2871) to determine its effect on cell barrier by ECIS (Electric Cell-substrate Impedance Sensing).
Diabetic rats had increased retinal vascular leakiness, and exhibited significantly lower levels of Sphk1, Sphk2, and S1PR1 mRNA and protein levels in retinas. High glucose and glucose flux treatment of HRPs significantly decreased the levels of RGS1 and RGS4. The agonist SEW2871 significantly increased the HREC barrier.
Increased retinal vascular permeability in diabetic rats can be due to decreased production of S1P from lower levels of sphingosine kinases. RGS proteins, responsible for regulating S1PRs, are altered in high glucose treated HRPs, demonstrating that multiple components of the S1P pathway are altered in diabetes. S1P is typically secreted by pericytes or circulating blood cells and binds to receptors on endothelial cells. By selectively activating S1PR1 with SEW2871 treatment, HRECs increased barrier tightness, in a similar fashion to S1P alone. Targeting the activation of S1PR1 component of the S1P pathway can be a potential therapeutic target in diabetic retinopathy.
This PDF is available to Subscribers Only