Suppression of retinal peroxisome proliferator-activated receptor gamma in experimental diabetes and oxygen-induced retinopathy: role of NADPH oxidase.
OBJECTIVE
Recently, the authors have shown that NADPH oxidase is positively correlated with increased leukocyte adhesion and vascular leakage in diabetes and neovascularization in oxygen-induced retinopathy (OIR). Peroxisome proliferator-activated receptor gamma (PPARgamma) agonists have been shown to prevent vascular inflammation and leakage in an experimental model of diabetes. The goal of this study was to investigate whether there is a link between NADPH oxidase and PPARgamma that leads to vascular dysfunction in diabetic retina or OIR.


METHODS
Diabetes was induced with streptozotocin in wild-type mice or NOX2 knockout mice. One group of wild-type mice was treated with apocynin. Bovine retinal endothelial cells (BRECs) were treated with normal glucose (5 mM) or high glucose (25 mM) in the presence or absence of superoxide dismutase (SOD) or NADPH oxidase inhibitors (apocynin or diphenyleneiodonium [DPI]). Western blotting and immunofluorescence were used to evaluate PPARgamma expression. Activation of nuclear factor (NF)kappaB was measured using the transcription factor assay kit and Western blot analysis of phospho-NFkappaB. PPARgamma expression was also tested in OIR and lipopolysaccharide-induced retinal inflammation.


RESULTS
Retinal expression of PPARgamma was suppressed in experimental models of diabetes, OIR, and retinal inflammation. This was associated with the activation of NFkappaB in the diabetic retina. These effects were prevented by apocynin or deletion of NOX2. PPARgamma expression was also suppressed in endothelial cells treated with high glucose, and this was prevented by apocynin, DPI, and SOD.


CONCLUSIONS
Suppression of PPARgamma is involved in the pathogenesis of diabetic retinopathy and OIR. NADPH oxidase could be an upstream mediator of these changes.
Tawfik
Amany
A
Department of Oral Biology and Anatomy, School of Dentistry, Medical College of Georgia, Augusta, Georgia 30912, USA.
Sanders
Tammy
T
Kahook
Khalid
K
Akeel
Sara
S
Elmarakby
Ahmed
A
Al-Shabrawey
Mohamed
M
D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D018929:Cell Culture Techniques; D003921:Diabetes Mellitus, Experimental / Q000209:etiology / Q000378:metabolism*; D003930:Diabetic Retinopathy / Q000209:etiology / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020868:Gene Silencing / Q000502:physiology; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D007231:Infant, Newborn; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D016328:NF-kappa B / Q000378:metabolism; D009861:Onium Compounds / Q000494:pharmacology; D010100:Oxygen / Q000633:toxicity; D047495:PPAR gamma / Q000378:metabolism*; D012171:Retinal Vessels / Q000166:cytology; D012173:Retinitis / Q000378:metabolism; D012178:Retinopathy of Prematurity / Q000209:etiology / Q000378:metabolism*
D000098:Acetophenones; D004791:Enzyme Inhibitors; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D009861:Onium Compounds; D047495:PPAR gamma; C007517:diphenyleneiodonium; C056165:acetovanillone; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D005947:Glucose; D010100:Oxygen