title: Increased expression and activity of 12-lipoxygenase in oxygen-induced ischemic retinopathy and proliferative diabetic retinopathy: implications in retinal neovascularization.
abstract: OBJECTIVE
  Arachidonic acid is metabolized by 12-lipoxygenase (12-LOX) to 12-hydroxyeicosatetraenoic acid (12-HETE) and has an important role in the regulation of angiogenesis and endothelial cell proliferation and migration. The goal of this study was to investigate whether 12-LOX plays a role in retinal neovascularization (NV).
  
  
  METHODS
  Experiments were performed using retinas from a murine model of oxygen-induced ischemic retinopathy (OIR) that was treated with and without the LOX pathway inhibitor, baicalein, or lacking 12-LOX. We also analyzed vitreous samples from patients with and without proliferative diabetic retinopathy (PDR). Western blotting and RT-PCR were used to assess the expression of 12-LOX, vascular endothelial growth factor (VEGF), and pigment epithelium-derived factor (PEDF). Liquid chromatography-mass spectrometry was used to assess the amounts of HETEs in the murine retina and human vitreous samples. The effects of 12-HETE on VEGF and PEDF expression were evaluated in Müller cells (rMCs), primary mouse retinal pigment epithelial cells, and astrocytes.
  
  
  RESULTS
  Retinal NV during OIR was associated with increased 12-LOX expression and 12-, 15-, and 5-HETE production. The amounts of HETEs also were significantly higher in the vitreous of diabetic patients with PDR. Retinal NV was markedly abrogated in mice treated with baicalein or mice lacking 12-LOX. This was associated with decreased VEGF expression and restoration of PEDF levels. PEDF expression was reduced in 12-HETE-treated rMCs, astrocytes, and the retinal pigment epithelium. Only rMCs and astrocytes showed increased VEGF expression by 12-HETE.
  
  
  CONCLUSIONS
  12-LOX and its product HETE are important regulators of retinal NV through modulation of VEGF and PEDF expression and could provide a new therapeutic target to prevent and treat ischemic retinopathy.
authors.affiliation: Department of Oral Biology and Anatomy, Medical College of Georgia, Augusta, Georgia, USA. malshabrawey@mcg.edu
authors.forename: Mohamed
authors.initials: M
authors.lastname: Al-Shabrawey
authors.forename: Rene
authors.initials: R
authors.lastname: Mussell
authors.forename: Khalid
authors.initials: K
authors.lastname: Kahook
authors.forename: Amany
authors.initials: A
authors.lastname: Tawfik
authors.forename: Mohamed
authors.initials: M
authors.lastname: Eladl
authors.forename: Vijay
authors.initials: V
authors.lastname: Sarthy
authors.forename: Julian
authors.initials: J
authors.lastname: Nussbaum
authors.forename: Ahmed
authors.initials: A
authors.lastname: El-Marakby
authors.forename: Sun Young
authors.initials: SY
authors.lastname: Park
authors.forename: Zafer
authors.initials: Z
authors.lastname: Gurel
authors.forename: Nader
authors.initials: N
authors.lastname: Sheibani
authors.forename: Krishna Rao
authors.initials: KR
authors.lastname: Maddipati
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000378:metabolism*; D015153:Blotting, Western; D003930:Diabetic Retinopathy / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism; D044950:Flavanones / Q000494:pharmacology; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000378:metabolism; D007150:Immunohistochemistry; D007511:Ischemia / Q000378:metabolism*; D013058:Mass Spectrometry; D051379:Mice; D009414:Nerve Growth Factors / Q000235:genetics / Q000378:metabolism; D015861:Retinal Neovascularization / Q000235:genetics / Q000378:metabolism*; D012171:Retinal Vessels / Q000187:drug effects / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015843:Serpins / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism; D014822:Vitreous Body / Q000378:metabolism; D000099174:Pigment Epithelium-Derived Factor
chemical_list: D001092:Arachidonate 12-Lipoxygenase; D004791:Enzyme Inhibitors; D005136:Eye Proteins; D044950:Flavanones; D006893:Hydroxyeicosatetraenoic Acids; D009414:Nerve Growth Factors; D015843:Serpins; D042461:Vascular Endothelial Growth Factor A; D000099174:Pigment Epithelium-Derived Factor; C006680:baicalein