Inhibition of Calcium-Independent Phospholipase A2 Prevents Retinal Pigment Epithelium Cell Death

Abstract

Purpose: : The causal mechanisms of retinal pigment epithelium (RPE) cell death remain intriguing. We have previously identified calcium-independent phospholipase A₂ (iPLA₂-VIA) in the RPE cells and shown a role of iPLA₂-VIA in RPE proliferation. Since the proliferative phenotype of RPE is only seen during pathological conditions in which both proliferation and cell death takes place, the present study elucidates a potential role of iPLA₂-VIA in RPE cell death.

Methods: : ARPE-19 cells and primary mouse-RPE cultures were treated with sodium-iodate (SI) to induce cell death. Cells were transfected with an iPLA₂-VIA promoter-luciferase construct to evaluate the regulation of iPLA₂-VIA after exposure to SI. Activity assays and western blot analysis were performed to evaluate the protein level and activity levels of iPLA₂-VIA after SI-exposure. Inhibitors of iPLA₂-VIA were used to explore a potential protective role in cells exposed to SI. Primary RPE cell cultures were grown from iPLA₂-VIA knockout mice and wild type mice, respectively. The cultures were exposed to SI to investigate a possible increased protection against SI in iPLA₂-VIA KO mice compared to wild type mice.

Results: : The present study revealed an upregulation of iPLA₂-VIA promoter activity, iPLA₂-VIA protein as well as iPLA₂-VIA protein activity in ARPE-19 cells exposed o SI. SI-induced cell death could be ameliorated by iPLA₂-VIA specific inhibitors in both APRE-19 cells and in primary mice RPE cultures. RPE cultures from iPLA₂-VIA knockout mice were less vulnerable to SI-induced cell death compared to RPE cultures from wild type mice.

Conclusions: : SI -induced RPE cell death involves iPLA₂-VIA upregulation and activation and inhibition of SI-induced RPE cell death can be ameliorated by inhibitors of iPLA₂-VIA. Hence, the present study reveals a role of iPLA₂-VIA in RPE cell death, and it is tempting to suggest iPLA₂-VIA as a possible pharmaceutical target in retinal diseases.

Keywords: retinal pigment epithelium • cell survival • retinal culture