Dietary Intake of Omega-3 Long-Chain Polyunsaturated Fatty Acids Modulates Arachidonic Acid Cascade Enzymes and Protects Against Pathogenic Retinal Neovascularization

Abstract

Purpose: : Lipid based molecules act as effectors of angiogenesis and inflammation; among the most potent are the eicosanoids, derived from the 20 carbon long chain polyunsaturated fatty acids (PUFAs), through the cyclooxygenase (COX) and lipoxygenase (LOX) pathways. We have found that dietary intake of ω-3 PUFAs suppresses proliferative retinopathy in a mouse model of oxygen-induced retinopathy (OIR). Here we demonstrate that ω-3 PUFAs may inhibit pathologic neovascularization through various mediators in the COX and LOX pathways.

Methods: : The diets of C57/Bl6 litters were enriched with ω-3 or ω-6 PUFA via maternal feed. Retinas of the pups reflected the change in ω-6/ω-3 ratio. To induce retinopathy the mothers and pups were placed in 75% oxygen for 5 days from P7 to P12 and then returned to room air. Isolated retinas were pooled across dietary groups, RNA was isolated, and converted to cDNA. Retinal mRNA expression was compared to cyclophilin and quantified using real time-PCR. Additionally, SC58236 (a specific COX-2 inhibitor) or NDGA (LOX inhibitor) was used to address the role of these enzymes in the pathogenesis of retinopathy through the modulation of downstream effectors.

Results: : LOX inhibition by NDGA resulted in a 17% reduction of retinal vaso-obliteration and a 27% reduction in neovascularization (NV). Similarly, low-dose COX-2 inhibition reduced NV by 50%. An ω-3 PUFA diet versus an ω-6 PUFA diet was associated with a 40% inhibition of retinal NV in the OIR mouse model at P17. During the hypoxia phase of the disease (P14), an ω-3 diet increased retinal mRNA levels of 12-LOX (+42%), and suppressed levels of 15-LOX (-86%), COX-2 (-60%), cytosolic phopholipase A₂ (-38%) and cytosolic prostaglandin E2 synthase (-22%). Ceramide kinase and 5-LOX and did not show conclusive variation with diet at the level of mRNA.

Conclusions: : These findings suggest that an ω-3 PUFA diet may inhibit retinal neovascularization in part through altering enzyme mRNA expression in eicosanoid lipid signaling pathways; thereby altering the levels of downstream lipid mediators.

Keywords: retinal neovascularization • lipids • inflammation