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Jinling Yang, Harumasa Yokota, Modesto A. Rojas, Sr., S Priya Narayanan, Zhimin Xu, M A. Behzadian, Ruth B. Caldwell; Involvement of p38 MAP Kinase Activation and uPAR Expression In the Blood-retinal Barrier Breakdown In Retinal Ischemia-reperfusion. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3572.
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To define the role of p38 MAP kinase in blood-retinal barrier dysfunction using an animal model of retinal ischemia-reperfusion injury. There is an increasing body of evidence showing that ischemia is a critical aspect in a number of retinal diseases including diabetic retinopathy. Studies showed that both VEGF protein and vascular permeability are increased in models of retinal ischemia reperfusion. We have shown previously that p38 MAP kinase inhibitor and dominant negative mutant of p38 block VEGF-induced GSK / beta-catenin signaling, uPAR expression and endothelial permeability increase in retinal endothelial cells. Here, we present data showing that activation of p38 is correlated with ischemia-reperfusion induced vascular permeability increase and inhibition of p38 preserves the blood-retinal barrier.
Retinal ischemia-reperfusion injury was achieved by increasing intraocular pressure above systolic blood pressure and then restoring normal pressure, thus transiently stopping retinal blood flow followed by reperfusion. Inhibitor of p38 was injected intravitreally 15 min before ischemia-reperfusion. Vascular permeability was measured by Evans blue extravasation into the retina. Western blotting and immuno-staining were used to analyze phosphorylation of p38 and its substrates. uPAR expression was measured by quantitative real-time PCR in addition to Western blotting and immuno-staining.
Increased phosphorylation and activation of p38 and increased uPAR expression were observed following ischemia-reperfusion injury. Retinal vascular permeability was also increased in this model. Moreover, intravitreal injection of p38 inhibitor blocked vascular permeability increase by ischemia-reperfusion.
Activation of p38 and increased uPAR expression are involved in blood-retinal barrier breakdown associated with ischemia-reperfusion injury. Moreover, blockade of p38 activation restores the blood-retinal barrier. These results indicate the involvement of p38 activation in retinal vascular permeability increase and offer a new strategy for developing potent and specific therapies for the treatment of retinal diseases associated with vascular barrier dysfunction.
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