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karishma M. choksi, Sylvia Megyerdi, Sara Akeel, Saif Ahmad, Amira othman, Gregory Liou, Mohamed A. Shabrawey; Interrelation Between NADPH Oxidase And BMP2/SMAD Pathway In Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5413.
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© ARVO (1962-2015); The Authors (2016-present)
Our previous studies demonstrated that NADPH oxidase-derived reactive oxygen species (ROS) play crucial role in the pathogenesis of diabetic retinopathy (DR) via enhancing inflammatory response and angiogenic pathway. Bone morphogenetic proteins (BMPs) are extracellular proteins which belong to the transforming growth factor-β superfamily. In addition to their ability to contribute to the bone development, induction and repair, they also regulate endothelial cell function through activation of SMAD or MAP Kinase pathway. Recently we showed that ROS mediate the biological effect of BMP2 (Akeel et al., 2011). The purpose of this study was to characterize the changes in the expression of BMP2/SMAD during diabetic retinopathy and to test whether NADPH oxidase plays a role in this process.
Experimental diabetes was induced in 6-8 weeks old mice by streptozotocin injection (85 mg/kg). Immunohistochemistry, Immunoflurosecnce (IF) and Western blotting (WB) were used to assess the expression of BMP2 and phospho-SMAD1/5/8 in retinal sections and homogenate of normal and diabetic mice and human subjects (eye donors). Retinal levels of BMP2 and p-SMAD1/5/8 were also measured in diabetic mice treated with NADPH oxidase inhibitor, apocynin (50mg/kg in drinking water) or lacking its catalytic subunit NOX2 using WB and IF. In vitro studies were performed using rat Muller cells (rMC) and bovine retinal endothelial cells (BRECs) treated with or without BMP2 (10ng/ml). WB was used to assess the changes in the expression of ICAM1 in BRECs and ELISA was used to measure the amount of VEGF in rMC condition medium.
There was marked increase in expression of BMP2/p-SMAD1/5/8 in mouse and human retina by diabetes. Inhibiting NADPH oxidase or deletion of NOX2 attenuated the effect of diabetes on BMP2/p-SMAD1/5/8 expression. BMP2 induced significant increase in ICAM1 (7+1.2 vs 5.7+0.4, P<0.05) and VEGF expression (228.8+16 vs 97+16.7 pg/ml, P<0.0001) in REC and rMC respectively compared to the non treated cells.
Our findings suggest that BMP2/SMAD pathway is regulated by NADPH oxidase and plays a role in DR probably via enhancing angiogenic and inflammatory pathways.
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