title: High glucose induced differential expression of lysyl oxidase and its isoform in ARPE-19 cells.
abstract: OBJECTIVE
  Lysyl oxidase (LOX) stabilizes the extracellular matrix (ECM) by cross-linking collagen and elastin molecules. In proliferative diabetic retinopathy (PDR), there is ECM remodeling with neovascularization and basement membrane changes. While protease activities are well reported, the role of LOX in the pathogenesis of diabetic retinopathy is less studied. This study was done to see the effect of high glucose on the activity and expression of LOX and its isoforms in ARPE-19 cells.
  
  
  METHODS
  ARPE-19 cells were exposed to high glucose up to 48 h, and LOX activity was determined by N-acetyl-3,7-dihydroxyphenoxazine assay. The mRNA expression of LOX and its isoforms was done by real-time PCR and the protein expression by ELISA. Immunohistochemistry for LOX was done in epiretinal membrane from PDR.
  
  
  RESULTS
  With an increase in glucose concentration LOX activity and protein was reduced significantly at 30 mM glucose at 48 h. mRNA expression of LOX, LOXL1, and LOXL2 varied with time and concentration of glucose. Vascular endothelial growth factor (VEGF) increased the LOX activity as well as the mRNA expression. Pigment epithelium-derived factor (PEDF) downregulated the mRNA expression of LOX, LOXL1, and LOXL2. The matrix metalloprotease (MMP) activity increased significantly with the increase in glucose concentration. The diabetic neovascular membrane showed increased immunostaining of LOX.
  
  
  CONCLUSIONS
  This study suggests that although the LOX activity, which is composite of all the isoforms, was reduced under high glucose conditions, there was a differential mRNA expression with increased LOX and LOXL1 and decreased LOXL2 expression.
authors.affiliation: Department of Biochemistry and Cell Biology, Vision and Medical Research Foundation, Chennai, India.
authors.forename: Karunakaran
authors.initials: K
authors.lastname: Coral
authors.forename: Jagadeesan
authors.initials: J
authors.lastname: Madhavan
authors.forename: Rishi
authors.initials: R
authors.lastname: Pukhraj
authors.forename: Narayanasamy
authors.initials: N
authors.lastname: Angayarkanni
mesh_terms: D001786:Blood Glucose / Q000378:metabolism; D002478:Cells, Cultured; D003930:Diabetic Retinopathy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D004797:Enzyme-Linked Immunosorbent Assay; D015971:Gene Expression Regulation, Enzymologic; D020022:Genetic Predisposition to Disease; D006801:Humans; D007150:Immunohistochemistry; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics; D008249:Protein-Lysine 6-Oxidase / Q000096:biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D055213:Retinal Pigment Epithelium / Q000201:enzymology / Q000473:pathology*
chemical_list: D001786:Blood Glucose; D020033:Protein Isoforms; D012333:RNA, Messenger; D008249:Protein-Lysine 6-Oxidase