Interaction between VEGF and Calcium-Independent Phospholipase A₂ in Proliferation and Migration of Retinal Pigment Epithelium

Abstract

Purpose: Inhibition of VEGF in the eye is an important treatment modality for reducing proliferation and migration of retinal pigment epithelium (RPE) in age-related macular degeneration (AMD). Additionally, previous studies suggest calcium-independent phospholipase A₂ group VIA (iPLA₂-VIA) to be a potential regulator of cell proliferation and migration, and evidence show abundant expression of iPLA₂-VIA in RPE cells. The aim of the present study was to evaluate the potential role of iPLA₂-VIA in VEGF-induced proliferation and migration of RPE cells.

Materials and methods: The human RPE cell line, ARPE-19, was used in all assays. To explore the role of iPLA₂-VIA in VEGF-induced RPE proliferation and migration, iPLA₂-VIA inhibition by the iPLA₂-VIA specific inhibitor, bromoenol lactone, was done. RPE cell proliferation and migration were evaluated by measurements of incorporated radioactive thymidine in DNA and by a Boyden chamber technique, respectively. A luciferase assay monitored the VEGF-induced iPLA₂-VIA transcriptional activity. Western blot analysis and an activity assay were used to detect the protein levels and activity of iPLA₂-VIA respectively after treatment with VEGF.

Results: RPE cells treated with VEGF showed significant increased proliferation and migration. Furthermore, inhibition of iPLA₂-VIA significantly reduced the spontaneous proliferation and migration as well as the VEGF-induced proliferation and migration. Finally, inhibition of iPLA₂-VIA reduced the VEGF-induced iPLA₂-VIA-activity, -protein level, and -promoter activity.

Conclusions: A significant interaction between VEGF and iPLA₂-VIA in the regulation of RPE cells appears to be relevant in elucidating the exact mechanisms of action in the proliferative and migratory phenotype of RPE cells in AMD.

KEYWORDS::

• Retinal pigment epithelium
• VEGF
• iPLA2-VIA
• proliferation
• migration

ACKNOWLEDGEMENTS

The authors thank technician Charlotte Taul Brændstrup, Department of International Health, Immunology and Microbiology, University of Copenhagen, Denmark for skillful assistance to the study and Michael Gelb, Departments of Chemistry and Biochemistry, University of Washington, Seattle, for providing the cPLA₂ inhibitors Pyrrolidine and Wyeth-1. The study was supported by The Danish Eye Foundation, The Danish Eye Health Society, and The Lundbeck Foundation.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.