title: Regulation of pigment epithelium-derived factor production and release by retinal glial (Müller) cells under hypoxia.
abstract: OBJECTIVE
  To assess the regulation of pigment epithelium-derived factor (PEDF) production by retinal Müller glial cells, especially under ischemic or hypoxic conditions.
  
  
  METHODS
  PEDF was determined in surgically excised retinal tissue originating from patients with ischemic diabetic retinopathy and in primary guinea pig Müller cell cultures exposed to the protein synthesis inhibitor cycloheximide (CHX) and to hypoxia. PEDF production and secretion were studied by immunohistochemistry, quantitative RT-PCR, ELISA, fluorescence-activated cell sorter analysis, and Western blotting.
  
  
  RESULTS
  Gliotic Müller cells displayed decreased PEDF immunoreactivity in fibrovascular tissue from patients with diabetes compared with tissue from subjects with pathologic myopia. In Müller cell cultures, CHX treatment resulted in an increase, whereas mild hypoxia (2.5%-10% O(2)) induced a decrease, of PEDF mRNA and protein levels. However, strong hypoxia (0.2% O(2)) induced an upregulation of PEDF mRNA expression and resulted in only slightly reduced PEDF levels after 24 hours, detected as either a released, soluble, or cell surface-linked protein.
  
  
  CONCLUSIONS
  These results suggest that under certain conditions including mild hypoxia, Müller cells synthesize a protein factor that downregulates PEDF expression or its turnover. Generally, the cells appear to generate a biphasic response to hypoxia. In moderate hypoxia, PEDF is downregulated such that the VEGF-to-PEDF ratio increases (and angiogenesis is facilitated). During severe (or chronic) oxygen deficiency, however, the PEDF decline is arrested or even reversed; thus, the neurotrophic effects of PEDF remain available.
authors.affiliation: University of Leipzig, Eye Hospital, Leipzig, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Lange
authors.forename: Yousef
authors.initials: Y
authors.lastname: Yafai
authors.forename: Andreas
authors.initials: A
authors.lastname: Reichenbach
authors.forename: Peter
authors.initials: P
authors.lastname: Wiedemann
authors.forename: Wolfram
authors.initials: W
authors.lastname: Eichler
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003930:Diabetic Retinopathy / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005136:Eye Proteins / Q000096:biosynthesis / Q000235:genetics*; D015870:Gene Expression; D006168:Guinea Pigs; D006801:Humans; D000860:Hypoxia / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D015151:Immunoblotting; D007150:Immunohistochemistry; D009414:Nerve Growth Factors / Q000096:biosynthesis / Q000235:genetics*; D009457:Neuroglia / Q000378:metabolism* / Q000473:pathology; D010857:Pigment Epithelium of Eye / Q000294:innervation* / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015843:Serpins / Q000096:biosynthesis / Q000235:genetics*; D000099174:Pigment Epithelium-Derived Factor
chemical_list: D005136:Eye Proteins; D009414:Nerve Growth Factors; D012333:RNA, Messenger; D015843:Serpins; D000099174:Pigment Epithelium-Derived Factor