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L. A. Wiley, J. J. Steinle; The Effects of Advanced Glycation End Products (AGEs) on Primary Human Microvascular Retinal Endothelial Cells (HMRECs). Invest. Ophthalmol. Vis. Sci. 2007;48(13):1364.
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To determine the cellular pathways affected by treatment of HMRECs with AGEs.
HMRECs were maintained in high glucose (25mM glucose) media supplemented with 20% FBS. Prior to experiments, cells were kept in serum-reduced media (5% FBS) for at least 24 hours. 5% FBS was utilized because serum starvation is known to induce apoptosis. Cells were treated with AGEs (200 mg/L) and the lysates collected by scraping for immunoblotting of various cellular pathways and proteins.
Treatment of HMRECs increased the pro-apoptotic protein levels of Bax and p53, while also increasing the levels of the anti-apoptotic protein Bcl-2. AGEs also increased the phosphorylation of the stress-activated pathway p38 MAP Kinase. Surprisingly, AGEs also increased the expression of the mitogen VEGF. In addition, treatment with AGEs increased phosphorylation of the MAP Kinase/Erk pathway in a time-dependent manner.
Although the effect of AGEs in the retina has been well documented, their effects on HMRECs, to our knowledge, have not been elucidated. Here, we show that AGEs, which are thought to be primarily apoptotic, are also capable of activating mitogenic pathways. While they increased levels of pro-apoptotic markers, there was also a simultaneous increase in Bcl-2. This observation coupled with their activation of both VEGF and Erk show that AGEs could initially provide a protective effect on cells. Furthermore, there are increased levels of both AGEs and VEGF in patients with PDR. One possible explanation could be that AGEs promote VEGF activity, leading to the progression of PDR. Further evaluation of the role that AGEs have on VEGF could lead to novel treatments against PDR.
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