Interventional Treatment With 3-Pufas in the Proliferative Stage of Retinopathy Attenuates Pathologic Neovascularization Through Activation of Ppar

Abstract

Purpose: : Lipid-based mediators are powerful modulators of retinal neovascularization (NV). Previously, we showed that prophylactic supplementation of ω3 (vs. ω6) dietary long chain polyunsaturated fatty acids (PUFAs) decreases NV in a mouse model of oxygen-induced retinopathy (OIR) by enhancing re-growth of normal vessels without affecting vessel loss. Here, we addressed the direct effect of ω3-PUFAs on active neovascularization, as many interventions for proliferative retinopathies have opposite effects when applied to phase I (vessel loss) and phase II (neovessel proliferation) of the OIR mouse model.

Methods: : Retinopathy was induced in C57Bl/6 WT mice through exposure to 75% oxygen from P7 to P12. Upon return to room air, ω3 or ω6-PUFA intervention was started at P14, coinciding with the onset of neovessel formation. Maximal NV and vaso-obliteration (VO) were analyzed at P17. For late intervention of ω3-PUFAs to be quickly effective we postulated ω3-PUFA acting through a receptor. We therefore inhibited PPARγ, a known nuclear ω3-PUFA receptor, during ω3-PUFA intervention. Additionally, gene expression and protein levels of inflammatory mediators and VEGF levels were analyzed.

Results: : Mice with ω3-PUFA intervention from P14 - P17 have significantly attenuated retinal NV when compared to ω6-PUFA controls (5.2 +/- 0.5 vs. 9.1 +/- 0.5% NV area; p = 10-5). Inhibition of the ω3-PUFA receptor PPARγ largely reverses the beneficial effects of ω3-PUFA intervention. Both systemic and retinal TNFα protein levels are significantly reduced in mice with ω3-PUFA intervention, an effect that is partially reversed with inhibition of PPARγ. VEGF levels remain unchanged with ω3-PUFA intervention.

Conclusions: : Interventional treatment with ω3-PUFAs during the active neovascular phase of OIR attenuates the extent of retinopathy in a PPARγ-dependent fashion by reducing the detrimental inflammatory cytokines accompanying NV. Importantly, these findings have direct clinical implications for the active phase of proliferative retinopathies. In light of ω3-PUFA intervention not altering retinal VEGF levels, this treatment approach might be complementary to anti-VEGF therapies.

Keywords: retinal neovascularization • retinopathy of prematurity • lipids