TITLE PAGE C-type natriuretic peptide protects the retinal pigment epithelium against advanced glycation end-product-induced barrier dysfunction

This article has not been copyedited and formatted. The final version may differ from this version. ABSTRACT In diabetic retinopathy, vision loss is usually secondary to macular edema, which is thought to depend on the functional integrity of the blood-retina barrier. The levels of advanced glycation end-products in the vitreous correlate with the progression of diabetic retinopathy. Natriuretic peptides (NP) are expressed in the eye and their receptors are present in the RPE. Here, we investigated the effect of glycated-albumin (Glyc-alb), an AGE model, on RPE barrier function and the ability of NP to suppress this response. Transepithelial electrical resistance (TEER) measurements were utilized to assess the barrier function of ARPE-19 and human fetal RPE monolayers. The monolayers were treated with 0.1 μ g/mL to 100 μ g/mL Glyc-alb in the absence or presence of 1 pM to 100 nM of apical ANP, BNP or CNP. Glyc-alb induced a significant reduction in TEER within two hours. This response was concentration-dependent (EC 50 =2.3 μ g/mL) with a maximal reduction of 40±2% for ARPE-19 and 27±7% for hfRPE at 100 μ g/mL six hours post treatment. One hour pretreatment with ANP, BNP or CNP blocked the reduction in TEER induced by Glyc-alb (100 μ g/mL). The suppression of the Glyc-alb response by NP was dependent upon the generation of cGMP and exhibited a rank order of agonist potency consistent with the activation of NPR2 subtype (CNP>>BNP≥ANP). Our data demonstrate that Glyc-alb is effective in reducing RPE barrier function and this response is suppressed by NP. Moreover, these studies support the idea that NPR2 agonists can be potential candidates for treating retinal edema in diabetic patients. This article has not been copyedited and formatted. The final version may differ from this version.