title: Disruption of the association of integrin-associated protein (IAP) with tyrosine phosphatase non-receptor type substrate-1 (SHPS)-1 inhibits pathophysiological changes in retinal endothelial function in a rat model of diabetes.
abstract: OBJECTIVE
  We have previously shown that the association of integrin-associated protein (IAP) with tyrosine phosphatase non-receptor type substrate-1 (SHPS-1) regulates the response of cells, including osteoclasts, osteoblasts, smooth muscle and retinal endothelial cells, to IGF-I. Here we sought to: (1) determine whether the regulation of IGF-I responsiveness by the association of IAP with SHPS-1 is a generalised response of endothelial cells; (2) identify the mechanism by which this association contributes to changes in endothelial cell responses to IGF-I; and (3) determine whether inhibition of this association alters pathophysiological changes occurring in vivo.
  
  
  METHODS
  Endothelial cells were maintained in 5 mmol/l glucose and at hyperglycaemic levels, and exposed to an anti-IAP antibody that disrupts the association between IAP and SHPS-1. A rodent model of diabetes with endothelial cell dysfunction was used to investigate the role of the association of IAP with SHPS-1 in endothelial cell function in vivo.
  
  
  RESULTS
  Endothelial cells maintained in 5 mmol/l glucose showed constitutive cleavage of the extracellular domain of IAP (which contains the SHPS-1 binding site), with no association between IAP and SHPS-1 being detected. In contrast, hyperglycaemia inhibited IAP cleavage, allowing IAP to associate with SHPS-1 and IGF-I to stimulate SHPS-1 tyrosine phosphorylation. Exposure to the anti-IAP antibody inhibited IGF-I-stimulated tube formation and increased permeability. In the rodent model, basal IAP-SHPS-1 association was not detected in retinal extracts from normal rats, but was fully restored in rats with diabetes. The anti-IAP antibody inhibited the association of IAP with SHPS-1, and reduced retinal vascular permeability and leucocyte adherence to levels similar to those in non-diabetic rats. The antibody also significantly inhibited the aberrant neovascularisation induced by hypoxia.
  
  
  CONCLUSIONS
  Our results demonstrate that the increased association of IAP with SHPS-1 contributes to the pathophysiological changes in the endothelium that are induced by hyperglycaemia and hypoxia.
authors.affiliation: Departments of Medicine and Ophthalmology, School of Medicine, University of North Carolina at Chapel Hill, NC, USA. laura_maile@med.unc.edu
authors.forename: L A
authors.initials: LA
authors.lastname: Maile
authors.forename: K
authors.initials: K
authors.lastname: Gollahon
authors.forename: C
authors.initials: C
authors.lastname: Wai
authors.forename: G
authors.initials: G
authors.lastname: Byfield
authors.forename: M E
authors.initials: ME
authors.lastname: Hartnett
authors.forename: D
authors.initials: D
authors.lastname: Clemmons
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D051928:CD47 Antigen / Q000737:chemistry / Q000378:metabolism*; D002199:Capillary Permeability; D002448:Cell Adhesion; D002478:Cells, Cultured; D003930:Diabetic Retinopathy / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology*; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D018922:HL-60 Cells; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism; D006801:Humans; D007231:Infant, Newborn; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007962:Leukocytes / Q000378:metabolism; D008297:Male; D009389:Neovascularization, Pathologic / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011971:Receptors, Immunologic / Q000378:metabolism*; D012160:Retina / Q000378:metabolism / Q000473:pathology; D012171:Retinal Vessels / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D012178:Retinopathy of Prematurity / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology
chemical_list: D051928:CD47 Antigen; D011971:Receptors, Immunologic; C501924:Sirpa protein, rat; D007334:Insulin-Like Growth Factor I