An RPE cell line (ARPE-19) were cultured for 3 weeks in a medium supplemented with 10%fetal calf serum containing 5.5 mmol D-glucose (mimicking physiological conditions) or 25 mmol Dglucose (mimicking the hyperglycemia that occurs in diabetic patients). Occludin, ZO-1 and claudin-1 were studied by real-time polymerase chain reaction and Western blot at 14 and 21 days.
Occludin and ZO-1 mRNA levels and protein content were similar in cultures maintained at 5.5 mmol and 25 mmol of D-glucose. In contrast, high glucose concentration (25 mmol) induced a clear upregulation in claudin-1 mRNA expression and protein content at 21 days (mRNA level: 1.03 vs 2.29; protein content: 0.92 vs 1.14).
High glucose concentration leads to differential expression of tight junction proteins in ARPE-19 cells. In addition, our results suggest that the upregulation of claudin-1by glucose is involved in the increase of tight junction sealing function. The functional consequences and clinical applicability of these findings require further investigation.