Pharmacological Inhibition or Genetic Knockout of 5-LO Decreases Neovascularization in a Mouse Model of Oxygen-Induced Retinopathy

Abstract

Purpose: : Ocular neovascularization is the most common cause of blindness in all age groups. Previously, our lab demonstrated that this pathology is mediated in part through lipid based molecules. Omega3 long chain polyunsaturated fatty acids (omega3-LCPUFAs) are anti-angiogenic whereas omega6-LCPUFAs can aggravate neovascularization (NV) in a mouse model of oxygen-induced retinopathy. Both omega3- and omega6-LCPUFAs are substrates for the lipoxygenase (LO) pathway. LO constitutes a family consisting of 5-, 12-, or 15-LO which process eicosanoids into 5-, 12-, or 15-hydroxyeicosatetraenoic acid (HETE). These are transformed enzymatically into secondary products including leukotrienes and lipoxins which can act as signaling molecules.

Methods: : Retinopathy was induced in C57Bl/6 WT and 5-LO -/- mice through exposure to 75% oxygen from P7 to P12. After return to room air neovascularization (NV) was analyzed on P17 in 5-LO -/- mice and C57/Bl6 WT mice receiving the 5-LO inhibitor NDGA (25 µg/g/d). Expression of 5-LO and five lipoxygenase activating protein (FLAP) was studied using quantitative Real-time PCR and 5-HETE production was analyzed using LC/MS/MS-based lipidomics.

Results: : Expression of 5-LO as well as FLAP was elevated during the phase of pathologic retinal NV. Pharmacologic inhibition or genetic knockout of 5-LO decreased NV significantly. 5-LO gene expression did not change with dietary supplementation of omega3-LCPUFAs. However, the 5-LO metabolite 5-HETE was significantly reduced by omega3 supplementation.

Conclusions: : This data suggests that the downstream byproducts of the 5-LO pathway are important in modulating retinal angiogenesis. Pharmacologic inhibition or knockout of 5-LO signaling reduces hypoxia-induced neovascularization in the mouse retina. Our study suggests that omega3-LCPUFAs reduce the 5-LO metabolite 5-HETE, implying a functional role for 5-HETE in mediating the anti-angiogenic effect of omega3 supplementation.

Keywords: lipids • retinal neovascularization