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M. Rema, C. Premanand, P. Usatyuk, V. Natarajan; VEGF–Induced Human Retinal Endothelial Cell Permeability and Curcumin . Invest. Ophthalmol. Vis. Sci. 2006;47(13):950.
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This study evaluates the specific molecular action of curcumin on VEGF induced Human Retinal Endothelial Cell (HREC) permeability. Curcumin (diferuloylmethane), a small–molecular weight compound isolated from turmeric (Curcuma longa Linn) has been shown to have anti–inflammatory, antioxidant and anti–proliferative effects.
HRECs were isolated and cultured within 20 hours of postmortem from human donors. HRECs were exposed to varying concentrations of VEGF (2.5, 5, 10, 50 and 100 ng/ml) and the permeability changes were measured as Transendothelial Electrical Resistance (TER) by Electrical Cell–substrate Impedance Sensing system (ECIS). The effect of different doses of curcumin (1, 5 and 10µM) on VEGF induced TER changes were then measured. The expression of PKC is an index of the permeability induced by VEGF. Total PKC activity was measured by γ32P incorporation. Effect of 10µM curcumin on VEGF induced PKC ßII expression was analysed by western blot.
VEGF in a dose–dependent manner decreased TER that reflects the increase in HREC permeability. 10ng/ml VEGF showed a 27% decrease in the TER when compared to cells with no treatment. On addition of curcumin this decrease in the TER was reverted. Different concentrations of curcumin 1, 5 and 10µM suitably decreased this VEGF induced permeability by 3, 17 and 26.3% respectively. Total PKC activity was increased to 3.4 fold on exposure of HRECs to 10ng/ml VEGF and this effect was significantly attenuated by 10µM curcumin from 21 ± 2.75 pmoles of phosphate incorporation (VEGF control) to 9.1± 0.1 pmoles (p < 0.01). To measure the specific isoform involved, western blot analysis was carried out. VEGF induced the overexpression of PKC ß II in the membrane fraction of HRECs and this was significantly inhibited by 10µM curcumin (26.8% vs Vehicle control). However, no significant effect was seen with PKC α expression in the cytosol and membrane fractions of HRECs.
The VEGF induced HREC permeability was significantly inhibited by curcumin and the mechanism of its action seems to be through inhibition of VEGF–mediated PKC ß II expression/activity.
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