neuropeptide-y and Retinal-Neovascularization

Diabetic retinopathy (DR) is one of the most severe clinical manifestations of diabetes mellitus and a major cause of blindness. DR is principally a microvascular disease, although the pathogenesis also involves metabolic reactive intermediates which induce neuronal and glial activation resulting in disruption of the neurovascular unit and regulation of the microvasculature. However, the impact of neural/glial activation in DR remains controversial, notwithstanding our understanding as to when neural/glial activation occurs in the course of disease. The objective of this study was to determine a potential protective role of neuropeptide Y (NPY) using an established model of DR permissive to N-methyl-D-aspartate (NMDA)-induced excitotoxic apoptosis of retinal ganglion cells (RGC) and vascular endothelial growth factor (VEGF)-induced vascular leakage. In vitro evaluation using primary retinal endothelial cells demonstrates that NPY promotes vascular integrity, demonstrated by maintained tight junction protein expression and reduced permeability in response to VEGF treatment. Furthermore, ex vivo assessment of retinal tissue explants shows that NPY can protect RGC from excitotoxic-induced apoptosis. In vivo clinical imaging and ex vivo tissue analysis in the diabetic model permitted assessment of NPY treatment in relation to neural and endothelial changes. The neuroprotective effects of NPY were confirmed by attenuating NMDA-induced retinal neural apoptosis and able to maintain inner retinal vascular integrity. These findings could have important clinical implications and offer novel therapeutic approaches for the treatment in the early stages of DR.

Topics: Animals; Apoptosis; Cellular Microenvironment; Diabetes Mellitus, Experimental; Diabetic Retinopathy; Endothelial Cells; Humans; Mice; N-Methylaspartate; Neuropeptide Y; Rats; Retina; Retinal Ganglion Cells; Retinal Neovascularization; Vascular Endothelial Growth Factor A

In this study, we investigated whether the proangiogenic neuropeptides secretoneurin (SN), substance P (SP), and neuropeptide Y (NPY) contribute to the development of abnormal neovascularization in the oxygen-induced retinopathy (OIR) model in mice. By exposing litters of C57Bl/6N mice to 75% oxygen from postnatal day 7 (P7) until postnatal day 11 (P11) and then returning them to normoxic conditions, retinal ischemia and subsequent neovascularization on the retinal surface were induced. Retinae were dissected on P9, P11, P12-P14, P16 and P20, and the concentrations of SN, SP, NPY and VEGF determined by radioimmunoassay or ELISA. The levels of SN and SP increased in controls from P9 until P16 and from P9 until P14, respectively, whereas the levels of NPY were high at P9 and decreased thereafter until P20, suggesting that NPY may participate in the development of the retina. However, dipeptidyl peptidase IV (DPPIV) and the NPY-Y2 receptor were not detectable in the immature retina indicating that NPY is not involved in the physiological vascularization in the retina. Compared to controls, OIR had no effect on the levels of SN, whereas levels of both SP and NPY slightly decreased during hyperoxia. Normalization of the levels of SP, and to a more pronounced extent of NPY, was significantly delayed during relative hypoxia. This clearly indicates that these three neuropeptides are not involved in the pathogenesis of neovascularization in OIR. Moreover, since there were no differences in the expression of two vessel markers in the retina of NPY knockout mice versus controls at P14, NPY is also not involved in the delayed development of the intermediate and deep vascular plexus in the retina in this animal model.

Topics: Animals; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Hyperoxia; Mice; Mice, Inbred C57BL; Mice, Knockout; Neuropeptide Y; Neuropeptides; Radioimmunoassay; Retina; Retinal Neovascularization; Secretogranin II; Substance P

Neuropeptide Y is a sympathetic neurotransmitter, a potent endothelium-derived angiogenic factor and a vascular mitogen. We have studied the role of the functional leucine7 to proline7 polymorphism of the signal peptide region of preproneuropeptide Y (prepro-NPY) as a genetic susceptibility factor for diabetic retinopathy. In addition, we investigated the role of the NPY Y2-receptor as a putative mediator of angiogenic NPY signaling in the retina.. Frequencies of proline7 (Pro7) carriers in the prepro-NPY were determined in type 1 and type 2 diabetes patients having retinopathy, in type 2 diabetes patients without retinopathy and in healthy control subjects. The role of Y2-receptor in hyperoxemia-induced retinal neovascularization was investigated in Y2-receptor knockout mice (Y2-/-) and in rats administered Y2-receptor mRNA antisense oligonucleotide.. The carriers having Pro7 in the preproNPY are markedly over-represented among type 2 diabetes patients with retinopathy compared to type 2 diabetes patients without retinopathy and to the population control. Neonatal exposure to hyperoxia resulted in development of retinal neovascularization that was prevented in Y2(-1-) -mice, and significantly inhibited in rats treated with the Y2-receptor antisense oligonucleotide.. NPY and Y2-receptor play important roles in diabetic retinopathy and retinal neovascularization and are thus potential new targets for drug molecules for treatment of retinopathy.

Topics: Adult; Aged; Animals; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Diabetic Retinopathy; Female; Humans; Male; Mice; Middle Aged; Neuropeptide Y; Rats; Receptors, Neuropeptide Y; Retinal Neovascularization

Neuropeptide Y (NPY) is a potent vaso-constrictor and angiogenic agent that is found in the retina. The goal of this study was to determine the expression of NPY and its receptors, NPY Y1 and NPY Y2, in a mouse model of oxygen-induced retinopathy.. Retinal NPY, NPY Y1, and NPY Y2 mRNA expression were evaluated using reverse transcriptase-polymerase chain reaction. Neuropeptide Y cellular localization was determined using immunohistochemistry.. Retinal NPY mRNA expression was increased by 2.3-fold from P7 to P12, and 2.8-fold from P7 to P17 in oxygen-reared animals. Retinal NPY Y1 was increased 1.9-fold from P7 to P12 in room-air-reared animals. There was no change in NPY Y1 expression following exposure to oxygen. Retinal NPY Y2 expression in oxygen-reared animals increased by 2.8-fold from P7 to P12 and by 2.7-fold from P12 to P17. There was no change in NPY Y2 expression in room-air-reared animals. Retinal NPY and NPY Y2 expression increased concomitant with vasoconstriction and neovascularization seen in this model by evaluation of retinal whole mounts. Neuropeptide Y protein was detectable by immunohistochemistry mainly between the inner and outer nuclear layers and increased with hyperoxic exposure at P12 and also increased during the period of relative retinal hypoxia at P17.. Retinal NPY and NPY Y2 receptor expression are altered in the development of oxygen-induced retinopathy of the mouse, during both the hyperoxic vasoconstrictive phase and the period of retinal neovascularization. Alteration in the production of NPY and the NPY Y2 receptor may be avenues for potential modification in the development of retinopathy.

Topics: Animals; Disease Models, Animal; Humans; Immunoenzyme Techniques; Infant, Newborn; Mice; Mice, Inbred C57BL; Neuropeptide Y; Oxygen; Receptors, Neuropeptide Y; Retinal Neovascularization; Retinal Vessels; Retinopathy of Prematurity; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger