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Mohamed A. Al-Shabrawey, Ahmed El-Marakby, Saif Ahmad, Sylvia Megyerdi, Krishna Maddipati; Inhibition Of 12/15 Lipoxygenase Reduces Oxidative Stress And Inflammatory Cytokines In Retina Of Diabetic Mouse. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4449.
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Diabetic retinopathy (DR) is characterized by an initial period of vascular inflammation and increased permeability followed by active proliferation of new vessels. These changes involve increases in the VEGF expression and inflammatory mediators. We have shown that diabetes-induced VEGF expression and leukocyte adhesion in retina are regulated by reactive oxygen species (ROS) derived from NADPH oxidase. Furthermore, our recent study demonstrated that the pathway mediated by 12-hydroxyeicosatetraenoic acids (HETEs), the product of 12/15 lipoxygenase (12/15-LOX) is involved in the pathogenesis of retinal neovascularization. The goal of the current study was to test the effect of 12/15-LOX pathway inhibition on diabetes-induced ROS generation, cytokines production and leukocyte adhesion in retina.
Experimental diabetes was induced in 6-8 weeks old mice by intraperitoneal injection of streptozotocin (55mg/kg). One group has been treated with 12/15-LOX inhibitor, baicalein (50mg/kg) in drinking water. Mice were sacrificed 10 weeks after the onset of diabetes and retinas were collected for 12/15LOX expression, cytokine array and LC/MS assay of 12 and 15-HETEs. An additional mouse group was injected with lipopolysacharide (LPS) and the effect of baicalein on intracellular adhesion molecule-1 (ICAM-1) expression was tested using Western blotting. Leukocyte adhesion was also tested in different mouse groups using Concavalin A lectin. Dihydroethedium staining was used to assess superoxide generation in retinal sections of normal and diabetic mice treated with or without baicalein and in bovine retinal endothelial cells (BRECs) treated with 12-HETE in the presence or absence of NADPH oxidase inhbitor, apocynin.
Diabetes significantly increased 12/15 LOX expression and the amount of 12- and 15-HETEs in mouse retina. This was associated with a significant increase in the levels of IL6, ICAM-1 and VCAM-1 and superoxide generation. This increase was prevented by baicalein which also reduced the number of adherent leukocytes (P<0.05). 12-HETE increased superoxide generation in BRECs, which blocked by NADPH oxidase inhibitor, apocynin. Additionally, baicalein significantly reduced LPS- induced ICAM-1 expression in retina (P<0.05).
12/15 lipoxygenase plays a role in diabetes-induced retinal inflammation probably through NADPH oxidase-derived ROS formation and represents a new therapeutic target for DR.
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