The chemokine platelet factor-4 variant (PF-4var)/CXCL4L1 inhibits diabetes-induced blood–retinal barrier breakdown

Ahmed M. Abu El-Asrar, Ghulam Mohammad, Mohd Imtiaz Nawaz, Mohammed Abdelsaid, Mohammad Mairaj Siddiquei, Kaiser Alam, Kathleen Van Den Eynde, Gert De Hertogh, Ghislain Opdenakker, Mohamed Al-Shabrawey, Jo Van Damme, Sofie Struyf

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


PURPOSE. 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.

Original languageEnglish (US)
Pages (from-to)1956-1974
Number of pages19
JournalInvestigative Ophthalmology and Visual Science
Issue number3
StatePublished - Feb 24 2015


  • Blood-retinal barrier
  • Diabetic retinopathy
  • Platelet factor-4 variant (PF-4var/CXCL4L1)

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience


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