Role of NADPH Oxidase in Retinal Vascular Inflammation
Mohamed Al-Shabrawey 1,
Modesto Rojas 2,
Tammy Sanders 1,
Ali Behzadian 2,
Azza El-Remessy 3,
Manuela Bartoli 4,
Abdul Kader Parpia 5,
Greg Liou 4,
and
Ruth B. Caldwell 6*
1 Oral Biology, Medical College of Georgia, Augusta, Georgia, United States
2 Vascular Biology Center, Medical College of Georgia, Augusta, Georgia, United States
3 College of Pharmacy, University of Georgia, Augusta, Georgia, United States
4 Medical College of Georgia, Augusta, Georgia, United States
5 Internal Medicine, Medical College of Georgia, Augusta, Georgia, United States
6 Vascular Biology Center, Medical College of Georgia, 1120 15 St, Augusta, Georgia, 30912, United States
* To whom correspondence should be addressed. E-mail: rcaldwel{at}mail.mcg.edu.
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Abstract |
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Purpose. We have demonstrated that NADPH oxidase-derived reactive oxygen species (ROS) are important for ischemia-induced increases in vascular endothelial growth factor (VEGF) and retinal neovascularization. We also have shown that diabetes-induced increases in retinal ROS, VEGF expression and vascular permeability are accompanied by increases in the NADPH oxidase catalytic subunit NOX2 within the retinal vessels. The goal of this study was to evaluate the potential role of NOX2 and NADPH oxidase activity in the development of retinal vascular inflammation.
Methods. Studies were performed using wild type mice, mice lacking NOX2 and mice treated with the NADPH oxidase inhibitor apocynin in models of endotoxemia and streptozotocin-induced diabetes. Intracellular adhesion molecule-1 (ICAM-1) expression was determined by Western blotting. Leukocyte adhesion was assessed by labeling adherent leukocytes with Concanavalin A. Vascular permeability was assessed by extravasation of FITC-conjugated albumin. ROS production was determined by dichlorofluroscein imaging.
Results. These studies showed that both endotoxemia- and diabetes-induced increases in ICAM-1 expression and leukostasis were significantly inhibited by deletion of NOX2, indicating that this enzyme is critically involved in both conditions. Moreover, apocynin treatment was as effective as deletion of NOX2 in preventing diabetes-induced increases in ICAM-1, leukostasis, and breakdown of the blood-retinal barrier, suggesting that NOX2 is primarily responsible for these early signs of diabetic retinopathy.
Conclusion. These data suggest that NOX2 activity has a primary role in retinal vascular inflammation during acute and chronic conditions associated with retinal vascular inflammatory reactions. Targeting this enzyme could be a novel therapeutic strategy for treatment of retinopathies associated with vascular inflammation.
Key Words:
blood-retinal barrier, cell adhesion, diabetic retinopathy, knockout animals, lipopolysaccharide, retinal vasculature
