Purchase this article with an account.
S. Rangasamy, J. Maestas, A. Das, P. McGuire; Angiopoietin-2 Mediates Vascular Adhesion of Leukocytes: Implications in Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5612.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The early interaction between leukocytes and microvascular endothelial cells plays an important role in the progression of diabetic retinopathy. Our earlier studies have shown that angiopoietin-2 (Ang-2) mRNA and protein levels were increased in retinas during the early stages of diabetic retinopathy. Here in this study we have examined the role of Ang-2 in mediating leukocyte/endothelial interactions in diabetic retinopathy.
Human retinal endothelial cells (HRECs) were grown to confluence and treated with either 5.5 mM (low) or 30.5 mM (high) glucose for 5 days. Calcein-AM labeled U937 cells were incubated with HRECs cells for 30 minutes at 37°C. Non-adherent cells were removed by washing 4 times and the adherent cells were quantified by fluorescence measurement. RNA was extracted from the retina of 4 week diabetic and normal rats and from HRECs incubated with high and low glucose. ICAM-1 expression levels were analyzed by quantitative RT-PCR.
The adhesion of monocytes to the endothelial cells was significantly increased in HRECs treated with high glucose for 5 days (p<0.05). Interestingly we found that high glucose induced adhesion was significantly blocked by Ang-1 and Human Tie-2/Fc fusion protein which indicated a role for Ang-2 in the adhesion of U937 to HRECs (p<0.05). We also found that Ang-2 increases the adhesion of U937 to endothelial cells in a dose-dependent manner. ICAM-1 levels were significantly elevated in the retinas of rat with 4 weeks of diabetes comparing to the control group. Also, the ICAM-1 level was significantly increased in the retinas of rat with intraocular injection of Ang-2 comparing to sham injected rats. High glucose and Ang-2 treatment in HRECs also resulted in a significant increase in the level of ICAM-1 expression over control groups.
In this study we found that high glucose promotes adhesion of leukocytes to endothelial cells. Increased adhesion of leukocytes by high glucose is mediated by Ang-2, through the induced expression of endothelial ICAM-1. Thus a better understanding of Ang-2 as a proinflammatory molecule in the retina may help in the development of novel therapies for diabetic retinopathy.
This PDF is available to Subscribers Only