title: Pressure-Induced Alterations in PEDF and PEDF-R Expression: Implications for Neuroprotective Signaling in Glaucoma.
abstract: BACKGROUND
  Alterations in neuron-glia signaling are implicated in glaucoma, a neurodegenerative disease characterized by retinal ganglion cell (RGC) death. Pigment epithelium derived factor (PEDF) is a secreted protein with potential neuroprotective qualities in retinal disease, including chronic ocular hypertension. Here we sought to determine whether moderate, short-term elevations in IOP alter PEDF signaling and whether pressure-induced PEDF signaling directly impacts RGC apoptosis.
  
  
  METHODS
  In retina from naïve mice and mice with unilateral, microbead-induced glaucoma, we examined expression and cell type-specific localization of PEDF and its receptor (PEDF-R), using quantitative PCR and immunohistochemistry. Using primary cultures of purified RGCs and Müller cells, we examined cell type-specific expression of PEDF in response to 48 hours of elevated hydrostatic pressure, using multiplex ELISA and immunocytochemistry. We also measured pressure-induced apoptosis of RGCs in the presence or absence of atglistatin, a potent and selective inhibitor of PEDF-R, and recombinant PEDF, using TUNEL assays.
  
  
  RESULTS
  PEDF and PEDF-R are constitutively expressed in naïve retina, primarily in the ganglion cell and nerve fiber layers. Elevated IOP increases PEDF and PEDF-R expression, particularly associated with RGCs and Müller cells. Elevated pressurein vitroincreased PEDF secretion by 6-fold in RGCs and trended towards an increase in expression by Müller cells, as compared to ambient pressure. This was accompanied by changes in the subcellular localization of PEDF-R in both cell types. Inhibition of PEDF signaling with atglistatin increased pressure-induced apoptosis in RGCs and treatment with recombinant PEDF inhibited pressure-induced apoptosis, both in a dose-dependent manner.
  
  
  CONCLUSIONS
  Our findings suggest that moderate, short-term elevations in IOP promote PEDF signaling via up-regulation of both PEDF and PEDF-R. Based onin vivoandin vitrostudies, this PEDF signaling likely arises from both Müller cells and RGCs, and has the potential to directly inhibit RGC apoptosis.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Vanderbilt Eye Institute, USA.
authors.forename: Sean J
authors.initials: SJ
authors.lastname: Lee
authors.affiliation: Department of Ophthalmology and Visual Sciences, Vanderbilt Eye Institute, USA.
authors.forename: D'Anne S
authors.initials: DS
authors.lastname: Duncan
authors.affiliation: Department of Ophthalmology and Visual Sciences, Vanderbilt Eye Institute, USA.
authors.forename: Franklin D
authors.initials: FD
authors.lastname: Echevarria
authors.affiliation: Department of Ophthalmology and Visual Sciences, Vanderbilt Eye Institute, USA.
authors.forename: William M
authors.initials: WM
authors.lastname: McLaughlin
authors.affiliation: Department of Ophthalmology and Visual Sciences, Vanderbilt Eye Institute, USA.
authors.forename: Jeremy B
authors.initials: JB
authors.lastname: Hatcher
authors.affiliation: Department of Ophthalmology and Visual Sciences, Vanderbilt Eye Institute, USA; Department of Pharmacology, Vanderbilt University Medical Center, USA.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Sappington
keywords: Apoptosis; Glaucoma; Glia; Microbead occlusion model; Neuroinflammation; Pigmented epithelial growth factor; Retinal ganglion cell