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Ahmed S Ibrahim, Amany M Tawfik, Sally Elshafey, Elia J Duh, Sylvia B Smith, Mohamed Al-Shabrawey, ; Pro-inflammatory effect of 12/15-lipoxygenase derived lipid metabolites in retina: Role of Pigment epithelium-derived factor (PEDF) suppression. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2258.
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Retinal vascular homeostasis is regulated by a delicate balance between the levels of VEGF and PEDF. We recently demonstrated that 12/15-lipoxygenase (LOX)-derived eicosanoids (12- and 15-hydroxyeicosatetraenoic acids or HETEs) contribute to diabetic retinopathy (DR) via disrupting this balance. In addition, NADPH oxidase (NOX), a major source of oxidative stress during DR, is a downstream mediator from HETEs. The goal of this study was to portray the causal relationship between LOX-NOX system and PEDF during DR and to test whether PEDF restoration prevents HETEs-mediated retinal vascular injury.
Fluorescein angiogram (FA) was used to characterize the effect of intravitreal injection of 12- HETE (0.1μM) with or without PEDF on retinal vascular function in normal wild type (Wt) living mice. Retina, were then collected for further assessment of inflammatory markers. Rat Muller cells (rMC1) were treated with 12-HETE in the presence or absence of PEDF followed by analysis of pNFκB by Western blotting on cell lysates. Condition medium was collected for ELISA measurement of TNFα and IL6. Experimental diabetes was induced Wt and NOX2-deficient mice by streptozotocin. One group of the wt diabetic mice received NADPH oxidase inhibitor, apocynin (50mg/kg/day). Immunofluorescence and Western blotting were used to assess the retinal expression of PEDF
FA showed marked increase in the inflammatory response to the intravitreal injection of 12-HETE into the Wt control mice as evidenced by marked vascular leakage and increased VCAM-1 expression. Concurrent injection of PEDF showed less vascular inflammatory response to 12-HETE injection. Furthermore, in-vitro results showed that HETEs significantly suppressed PEDF expression while increased levels of p-NFκB, TNFα and IL6 in rMC1. All these effects were prevented in PEDF-treated cells. Since our previous studies linked the pro-inflammatory effect of HETEs to the NADPH oxidase activation, we also examined the impact of NADPH oxidase inhibition or deletion of NOX2 on retinal expression of PEDF. Retinal PEDF was preserved in diabetic mice treated with apocynin or lacking NOX2
Our findings suggest that interfering with LOX-NOX signaling system opens up an entirely new terrain for treating DR by restoring the endogenous PEDF that carries out multilevel neurovascular protective function.
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