title: The Chemokine Platelet Factor-4 Variant (PF-4var)/CXCL4L1 Inhibits Diabetes-Induced Blood-Retinal Barrier Breakdown.
abstract: OBJECTIVE
  To investigate the expression of platelet factor-4 variant (PF-4var/CXCL4L1) in epiretinal membranes from patients with proliferative diabetic retinopathy (PDR) and the role of PF-4var/CXCL4L1 in the regulation of blood-retinal barrier (BRB) breakdown in diabetic rat retinas and human retinal microvascular endothelial cells (HRMEC).
  
  
  METHODS
  Rats were treated intravitreally with PF-4var/CXCL4L1 or the anti-vascular endothelial growth factor (VEGF) agent bevacizumab on the first day after diabetes induction. Blood-retinal barrier breakdown was assessed in vivo with fluorescein isothiocyanate (FITC)-conjugated dextran and in vitro in HRMEC by transendothelial electrical resistance and FITC-conjugated dextran cell permeability assay. Occludin, vascular endothelial (VE)-cadherin, hypoxia-inducible factor (HIF)-1α, VEGF, tumor necrosis factor (TNF)-α, receptor for advanced glycation end products (RAGE), caspase-3 levels, and generation of reactive oxygen species (ROS) were assessed by Western blot, enzyme-linked immunosorbent assays, or spectrophotometry.
  
  
  RESULTS
  In epiretinal membranes, vascular endothelial cells and stromal cells expressed PF-4var/CXCL4L1. In vitro, HRMEC produced PF-4var/CXCL4L1 after stimulation with a combination of interleukin (IL)-1β and TNF-α, and PF-4var/CXCL4L1 inhibited VEGF-mediated hyperpermeability in HRMEC. In rats, PF-4var/CXCL4L1 was as potent as bevacizumab in attenuating diabetes-induced BRB breakdown. This effect was associated with upregulation of occludin and VE-cadherin and downregulation of HIF-1α, VEGF, TNF-α, RAGE, and caspase-3, whereas ROS generation was not altered.
  
  
  CONCLUSIONS
  Our findings suggest that increasing the intraocular PF-4var/CXCL4L1 levels early after the onset of diabetes protects against diabetes-induced BRB breakdown.
authors.affiliation: Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia Dr Nasser Al-Rashid Research Chair in Ophthalmology, King Saud University, Riyadh, Saudi Arabia.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Abu El-Asrar
authors.affiliation: Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: Ghulam
authors.initials: G
authors.lastname: Mohammad
authors.affiliation: Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: Mohd Imtiaz
authors.initials: MI
authors.lastname: Nawaz
authors.affiliation: Department of Oral Biology, Cellular Biology and Anatomy, Culver Vision Discovery Institute and Department of Ophthalmology, Georgia Regents University, Augusta, Georgia, United States.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Abdelsaid
authors.affiliation: Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: Mohammad Mairaj
authors.initials: MM
authors.lastname: Siddiquei
authors.affiliation: Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: Kaiser
authors.initials: K
authors.lastname: Alam
authors.affiliation: Laboratory of Histochemistry and Cytochemistry, University of Leuven, KU Leuven, Leuven, Belgium.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Van den Eynde
authors.affiliation: Laboratory of Histochemistry and Cytochemistry, University of Leuven, KU Leuven, Leuven, Belgium.
authors.forename: Gert
authors.initials: G
authors.lastname: De Hertogh
authors.affiliation: Laboratory of Immunobiology, Rega Institute for Medical Research, Department of Microbiology and Immunology, University of Leuven, KU Leuven, Leuven, Belgium.
authors.forename: Ghislain
authors.initials: G
authors.lastname: Opdenakker
authors.affiliation: Department of Oral Biology, Cellular Biology and Anatomy, Culver Vision Discovery Institute and Department of Ophthalmology, Georgia Regents University, Augusta, Georgia, United States.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Al-Shabrawey
authors.affiliation: Laboratory of Molecular Immunology, Rega Institute for Medical Research, Department of Microbiology and Immunology, University of Leuven, KU Leuven, Leuven, Belgium.
authors.forename: Jo
authors.initials: J
authors.lastname: Van Damme
authors.affiliation: Laboratory of Molecular Immunology, Rega Institute for Medical Research, Department of Microbiology and Immunology, University of Leuven, KU Leuven, Leuven, Belgium.
authors.forename: Sofie
authors.initials: S
authors.lastname: Struyf
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001813:Blood-Retinal Barrier / Q000187:drug effects* / Q000502:physiology; D053148:Caspase 3 / Q000378:metabolism; D002478:Cells, Cultured; D003921:Diabetes Mellitus, Experimental / Q000150:complications*; D003930:Diabetic Retinopathy / Q000188:drug therapy* / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism; D019773:Epiretinal Membrane / Q000378:metabolism*; D006801:Humans; D008297:Male; D010978:Platelet Factor 4 / Q000378:metabolism / Q000502:physiology / Q000627:therapeutic use*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism / Q000494:pharmacology
chemical_list: D015415:Biomarkers; C064936:PF4V1 protein, human; D017382:Reactive Oxygen Species; D042461:Vascular Endothelial Growth Factor A; D010978:Platelet Factor 4; D053148:Caspase 3
keywords: blood-retinal barrier; diabetic retinopathy; platelet factor-4 variant (PF-4var CXCL4L1)