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ABSTRACT
Purpose: To investigate the expression of the leukocyte proteins myeloid-related protein (MRP)-8 and MRP-14 in proliferative diabetic retinopathy (PDR) and the effect of MRP-8/MRP-14 (calprotectin) heterodimer on induction of proinflammatory factors in human retinal microvascular endothelial cells (HRMEC).
Methods: Epiretinal membranes from 20 patients with PDR and 10 patients with proliferative vitreoretinopathy (PVR), vitreous fluid samples from PDR and non-diabetic subjects and HRMEC were studied by immunohistochemistry and Western blot analysis.
Results: MRP-14 expression was localized in endothelial cells, leukocytes and myofibroblasts in all PDR membranes. MRP-8 expression was limited to intravascular leukocytes in 42% of the studied membranes. In PVR membranes, MRP-14 was expressed in leukocytes and myofibroblasts, whereas MRP-8 immunoreactivity was limited to leukocytes. MRP-14 was significantly upregulated in vitreous from PDR patients. MRP-8/MRP-14 (calprotectin) increased expression of intercellular adhesion molecule-1, but attenuated vascular cell adhesion molecule-1 expression in HRMEC.
Conclusions: Increased MRP-14 levels are associated with inflammation in PDR.
ACKNOWLEDGMENTS
The authors thank Mr. Wilfried Versin and Ms. Nathalie Volders for technical assistance; and Ms. Connie Unisa-Marfil for secretarial work.
DECLARATION OF INTEREST
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.
FUNDING
This work was supported by King Saud University, Riyadh, Saudi-Arabia through the Vice Deanship of Research Chair (Dr Nasser Al-Rashid Research Chair in Ophthalmology) and by the Fund for Scientific Research of Flanders (FWO-Vlaanderen) and the Concerted Research Actions (GOA 2013/014) in Belgium (GO).
