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T. Sato, A. Li, S. Roy; Reduced Expression of Occludin and ZO-1 in Microvascular Endothelial Cells Grown in High Glucose Medium and in Retinas of Diabetic Rat . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3910.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To investigate whether expression of tight junction proteins, occludin and ZO-1, is altered in cultured microvascular endothelial cells grown in high glucose condition and in retinas of diabetic rats. Methods: Rat microvascular endothelial cells (RMEC) were grown in normal (5 mM) or high (30 mM) D-glucose medium for 9 days. Total RNA and protein was extracted and RT-PCR and Western Blot analysis was performed to determine occludin and ZO-1 expression. To determine occludin and ZO-1 expression in retinas of streptozotocin-induced diabetic rats and age-matched control rats, RT-PCR and Western Blot analysis was performed with total RNA and protein isolated from retinas of control and diabetic rats. Measurements for glycohemoglobin and blood glucose level in control and diabetic rats (3.9±0.5 vs 5.9±0.9; 320±38 mg/dl vs. 124±14, respectively) confirmed the diabetic status of the animals. Results: RMEC grown in high glucose medium showed significant reduction in occludin and ZO-1 expression compared to cells grown in normal medium. Occludin mRNA and protein level was reduced (72±10% of control, P=0.021 and 85±14% of control, P=0.019, respectively; ZO-1 mRNA and protein level was reduced (73±15% of control, P=0.032 and 59±12% of control, P=0.002, respectively). Rats with 8 weeks of diabetes showed significant reduction in occludin and ZO-1 protein level compared to control rats. Occludin and ZO-1 protein level was reduced (74.4 ± 11% of control: P=0.006; 78±10% of control, P=0.03, respectively). Conclusions: The findings indicate that high glucose condition or diabetes may induce early biochemical and molecular changes with respect to tight junction protein, occludin and ZO-1, expression. Reduced occludin and ZO-1 expression are early biosynthetic changes that may contribute to blood-retinal barrier breakdown and increased vascular permeability in diabetic retinopathy.
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