Implication of N-Methyl-d-Aspartate Receptor in Homocysteine-Induced Age-Related Macular Degeneration

Int J Mol Sci. 2021 Aug 28;22(17):9356. doi: 10.3390/ijms22179356.

Abstract

Age-related macular degeneration (AMD) is a leading cause of vision loss. Elevated homocysteine (Hcy) (Hyperhomocysteinemia) (HHcy) has been reported in AMD. We previously reported that HHcy induces AMD-like features. This study suggests that N-Methyl-d-aspartate receptor (NMDAR) activation in the retinal pigment epithelium (RPE) is a mechanism for HHcy-induced AMD. Serum Hcy and cystathionine-β-synthase (CBS) were assessed by ELISA. The involvement of NMDAR in Hcy-induced AMD features was evaluated (1) in vitro using ARPE-19 cells, primary RPE isolated from HHcy mice (CBS), and mouse choroidal endothelial cells (MCEC); (2) in vivo using wild-type mice and mice deficient in RPE NMDAR (NMDARR-/-) with/without Hcy injection. Isolectin-B4, Ki67, HIF-1α, VEGF, NMDAR1, and albumin were assessed by immunofluorescence (IF), Western blot (WB), Optical coherence tomography (OCT), and fluorescein angiography (FA) to evaluate retinal structure, fluorescein leakage, and choroidal neovascularization (CNV). A neovascular AMD patient's serum showed a significant increase in Hcy and a decrease in CBS. Hcy significantly increased HIF-1α, VEGF, and NMDAR in RPE cells, and Ki67 in MCEC. Hcy-injected WT mice showed disrupted retina and CNV. Knocking down RPE NMDAR improved retinal structure and CNV. Our findings underscore the role of RPE NMDAR in Hcy-induced AMD features; thus, NMDAR inhibition could serve as a promising therapeutic target for AMD.

Keywords: N-methyl-d-aspartate receptor; age-related macular degeneration; blood retinal barrier; cystathionine-β-synthase; homocysteine; mouse.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Animals
  • Cell Line
  • Choroidal Neovascularization / etiology
  • Cystathionine beta-Synthase / blood
  • Disease Models, Animal
  • Endothelial Cells / metabolism
  • Female
  • Homocysteine / adverse effects*
  • Homocysteine / blood*
  • Humans
  • Hyperhomocysteinemia / complications
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism
  • Macular Degeneration / chemically induced
  • Macular Degeneration / diagnostic imaging
  • Macular Degeneration / genetics
  • Macular Degeneration / metabolism*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Middle Aged
  • Neovascularization, Pathologic / etiology
  • Primary Cell Culture
  • Receptors, N-Methyl-D-Aspartate / genetics*
  • Receptors, N-Methyl-D-Aspartate / metabolism*
  • Retinal Pigment Epithelium / metabolism
  • Vascular Endothelial Growth Factor A / metabolism

Substances

  • Hif1a protein, mouse
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Receptors, N-Methyl-D-Aspartate
  • Vascular Endothelial Growth Factor A
  • vascular endothelial growth factor A, mouse
  • Homocysteine
  • Cystathionine beta-Synthase