Impact of a reduction of plasmalogen levels on Müller cell metabolism

Abstract

Purpose : Retinopathy of Prematurity (ROP) is the leading cause of blindness in premature children resulting from abnormal vascular development. Previous studies have shown that omega-3 polyunsaturated fatty acids (PUFAs) can modulate physiologic and pathologic angiogenesis. Data from our laboratory suggest that plasmalogens, that are phospholipids that concentrate omega-3 PUFAs, are involved in the regulation of post-natal retinal vascular development through the action of a calcium-independent phospholipase A2 (iPLA2) (Saab et al PLoSONE 2014). In the retina, Müller cells are known to play crucial functions in retinal angiogenesis as well as to be rich in plasmalogens and to express phospholipases. The aim of this study is to investigate the roles of plasmalogens and omega-3 PUFAs on Müller cell metabolism.

Methods : Primary cultures of rat Müller cells were treated with siRNA against the major enzyme for plasmalogen biosynthesis (DHAP-AT) and/or with a chemical inhibitor of iPLA2, bromoenol lactone (BEL). Lipid profile of cells was determined by gas chromatography, cell proliferation by Ki67 assay and cell migration was evaluated by videomicroscopy. The expression of p38, ERK, JNK in their non-phosphorylated and phosphorylated forms was determined by western blotting.

Results : The use of siRNA against DHAP-AT led to a 50%-diminution of plasmalogens levels in cells. Decreasing the cell levels of plasmalogens and/or inhibiting iPLA2 had no impact on cellular viability. A reduction of the ability of cells to migrate was observed in samples treated with siRNA against DHAP-AT at 72 hours. The inhibition of the expression of DHAP-AT led to an increase in the rate of phosphorylation of ERK. No effect of BEL was observed on these parameters.

Conclusions : Plasmalogens seem to initiate a MAPK-dependent signalling cascade in retinal Müller cells that might impact cell phenotype. Alteration of Müller cell metabolism seems to be the consequence of a diminution of plasmalogens levels following siRNA treatment rather than that of an inhibition of iPLA2 by BEL.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.