Immunohistochemical localization of NGF, BDNF, and their receptors in a normal and AMD-like rat retina

Darya V Telegina,Nataliya G Kolosova,Oyuna S Kozhevnikova

doi:10.1186/s12920-019-0493-8

Darya V Telegina, Nataliya G Kolosova + Show 1 more

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https://doi.org/10.1186/s12920-019-0493-8

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Abstract

BackgroundAge-related macular degeneration (AMD) is a major cause of blindness in developed countries, and the molecular pathogenesis of AMD is poorly understood. A large body of evidence has corroborated the key role of neurotrophins in development, proliferation, differentiation, and survival of retinal cells. Neurotrophin deprivation has been proposed to contribute to retinal-cell death associated with neurodegenerative diseases. Little is known about the expression of the immature form of neurotrophins (proneurotrophins) and their mature form [e.g., nerve growth factor (proNGF and mNGF) and brain-derived neurotrophic factor (proBDNF and mBDNF)] in the retina during physiological aging and against the background of AMD. In addition, cell-specific localization of proteins NGF and BDNF in the retina during AMD development is not clear. Here, we evaluated contributions of the age-related alterations in the neurotrophin system to the development of AMD-like retinopathy in OXYS rats.MethodsMale OXYS rats at preclinical (20 days), early (3 months), and late (18 months) stages of the disease and age-matched male Wistar rats (as controls) were used. We performed immunohistochemical localization of NGF, BDNF, and their receptors TrkA, TrkB, and p75NTR by fluorescence microscopy in retinal sections from OXYS and Wistar rats.ResultsWe found increased NGF staining in Muller cells in 18-month-old OXYS rats (progressive stage of retinopathy). In contrast, we observed only subtle changes in the labeling of mature BDNF (mBDNF) and TrkB during the development of AMD-like retinopathy in OXYS rats. Using colocalization with vimentin and NeuN, we detected a difference in the cell type–specific localization of mBDNF between OXYS and Wistar rats. We showed that the mBDNF protein was located in Muller cells in OXYS rats, whereas in the Wistar retina, mBDNF immunoreactivity was detected in Muller cells and ganglion cells. During the development of AMD-like retinopathy, proBDNF dominated over mBDNF during increasing cell loss in the OXYS retina.ConclusionsThese data indicate that alterations in the balance of neurotrophic factors in the retina are involved in the development of AMD-like retinopathy in OXYS rats and confirm their participation in the pathogenesis of AMD in humans.

Highlights

Age-related macular degeneration (AMD) is a major cause of blindness in developed countries, and the molecular pathogenesis of AMD is poorly understood
nerve growth factor (NGF) and tropomyosin-receptor kinase A (TrkA) staining was observed in the ganglion cell layer (GCL) and inner nuclear retinal layer (INL) of 3-month-old Wistar rats, while in OXYS rats, proteins NGF and TrkA localized in the GCL at this age
In the Wistar retina, the staining of NGF was detectable in the GCL and TrkA expression was detectable in the GCL and INL, but colocalization of proteins NGF and TrkA decreased as compared to age 3 months and age-matched OXYS rats (Fig. 1a)

Summary

Introduction

Age-related macular degeneration (AMD) is a major cause of blindness in developed countries, and the molecular pathogenesis of AMD is poorly understood. Little is known about the expression of the immature form of neurotrophins (proneurotrophins) and their mature form [e.g., nerve growth factor (proNGF and mNGF) and brain-derived neurotrophic factor (proBDNF and mBDNF)] in the retina during physiological aging and against the background of AMD. Neurotrophins like nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are known to play an important role in aging and development of neurodegenerative diseases such as Alzheimer’s disease and AMD [2, 3]. Mature NGF and BDNF (mNGF and mBDNF) are derived from their precursors (proNGF and proBDNF) after proteolytic cleavage in the extracellular space. The exact localization of proteins NGF and BDNF in the retinal cells involved in the process of AMD development and their functional significance are not clear [4]

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