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Finny Monickaraj, Paul McGuire, Arup Das; Role of Cathepsin-D in alteration of Endothelium-Pericyte interaction in Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4038.
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© ARVO (1962-2015); The Authors (2016-present)
Previously, we have demonstrated the effect of Cathepsin D (CD) on the mechanical disruption of retinal endothelial cell junctions and increased vaso-permeability, and increased levels of cathepsin D in retinas of diabetic mice. Here we have further examined the effect of CD on the endothelial-pericyte interaction, and the effect of Dipeptidyl peptidase-4 (DPP-4) inhibitor on CD in the endothelial-pericyte interaction. The DPP-4 inhibitor has been shown to alter the function of the IGF2 receptor, which is the presumed binding site for CD on endothelial cells.
Human retinal endothelial cells (HREC) and human retinal pericytes (HRP) were co-cultured and treated overnight with 25ug/ml of recombinant pro-CD along with 250nM DPP-4 inhibitor. Western blots were performed to check the levels of PDGFR-β, N-Cad, PKC-α and phosphor-PKC-α. Real-time PCR was used to measure angiopoietin-2 (Ang-2) levels in the treated co-cultured cells. GFP-HRP cells were co-cultured with HRECs to check the binding efficiency in treated conditions.
Co-cultured cells treated with pro-CD showed a significant decrease in the expression of PDGFR- β, a tyrosine kinase receptor required for pericyte cell survival and N-Cad, the key adherens junction protein between endothelium and pericytes, and also increase in the vessel destabilizing agent, Ang-2. The effect was reversed in the cells treated with DPP-4 inhibitor along with pro-CD. With pro-CD treatment, there was a significant increase in the downstream signaling protein PKC-α, which disrupts tight junction structure and function, and this was significantly reduced with DPP-4 inhibitor treatment. We observed significantly increased binding of endothelial cells and pericytes when cells were treated with the DPP-4 inhibitor and pro-CD.
The cathepsin D decreases N-cad and PDGFR- β in the endothelium-pericyte alteration in the blood-retinal barrier, and the drug DPP-4 inhibitor can significantly diminish this effect. Thus, the DPP-4 inhibitor may be used as a potential adjuvant therapeutic strategy for treating diabetic macular edema.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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