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K. G. Shadrach, A. Calabro, G. Hoppe, J. G. Hollyfield, P. Senanayake; Peroxisome Proliferator-Activated Receptor Gamma Pioglitazone Reduces Secretion of Interleukin-8 by Retinal Pigment Epithelium Cells Under Hyperglycemic Stress. Invest. Ophthalmol. Vis. Sci. 2008;49(13):472.
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To evaluate the secretion of Interleukin-6 (IL-6) and IL-8 by retinal pigment epithelium (RPE) cells and the effect of peroxisome proliferator-activated receptor gamma agonist pioglitazone under hyperglycemic stress.
ARP19 cells were cultured in DMEM: F12, 15 mM HEPES medium supplemented with 10% fetal bovine serum (FBS), penicillin-streptomycin-glutamine. At confluence, the medium was changed to 5.55 µmol glucose devoid of FBS for 24 hours. Thereafter, three glucose concentrations (5.55, 27.77 and 54.55 µmol), devoid of FBS with pioglitazone (1µmol) or vehicle were tested in six replicates. At the end of 24 hours, the culture medium was aspirated and cells and cell matrices were collected and stored at - 20º C. Measurement of IL-6 and IL-8 were performed using commercially available ELISA kits (R&D Systems, sensitivity 0.7 and 1.5 pg/ml, respectively). Glucose remaining in the medium was quantified by fluorophore assisted carbohydrate electrophoresis to determine the amount of glucose utilized by the cell cultures.
Levels of IL-8 were significantly increased in the RPE cells cultured in 27.77 and 54.55 µmol glucose, compared to 5.55 µmol (102 ± 5, 105 ± 4 vs 4.9 ±1.3 pg/ml, p< 0.01). Pioglitazone significantly reduced the levels of IL-8 in the RPE cultures (102 ± 5 to 29.1 ± 8 and 105 ± to 26 ± 5, p < 0.01; piogliatazone vs vehicle). Levels of IL-6 in culture medium from 5.55, 27.77 and 54.55 µmol cultures were similar. Piogliatazone reduced the secretion of IL- 6 by the RPE cells. Glucose remaining in the medium from RPE cells cultured in 5.5, 27.77 and 54.55 µmol glucose was in the nmol range: vehicle vs pioglitazone, 2.15 ± 0.19 vs 0.99 ± 0.09, 21.19 ± 0.96 vs 14.80 ± 1.14 and 24.62 ± 0.99 vs 15.92 ± 0.61respectively (mean±sem).
Pioglitazone may be effective against hyperglycemia induced IL-8 secretion by the RPE. RPE cells in culture have the capacity to utilize extensive amounts of glucose. Pioglitazone may increase the uptake of glucose by RPE cells.
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