Regulated Expression of PTPRJ by COX-2/PGE2 Axis in Endothelial Cells

Background: This study was designed to examine a novel role of COX-2/PGE(2) signaling as a regulator of PTPRJ expression in endothelial cells. Methods: A bioinformatics analysis of a whole genome array was carried out to search for regulators of PTPRJ expression in endothelial cells. PTPRJ expression was also measured in endothelial cells derived from a balloon injury-induced neointimal hyperplasia model in male New Zealand Rabbits. Changes in PTPRJ expression in HUVEC cells was examined by RT-PCR and western blotting after transfection of COX-2 plasmids or treatment with varying concentrations of a COX-2 inhibitor. Results: A significant correlation was identified between COX-2 and PTPRJ in GSE39264 (Pearson correlation coefficient = -0.87; n = 22; P < 0.01, two-tailed). PTPRJ expression was reduced during the progression of neointimal hyperplasia after balloon injury, which correlated with an increase in COX-2 expression. In HUVECs, after transfection with 1 mu g/ml, 0.5 mu g/ml, or 0.25 mg/ml COX-2 plasmids, PTPRJ protein expression was reduced to 0.60- (+/- 0.08), 0.75- (+/- 0.09), and 0.88- (+/- 0.04) fold, respectively, while mRNA expression was reduced to 0.15- (+/- 0.03), 0.26- (+/- 0.05), and 0.47- (+/- 0.09) fold, respectively. After treatment of HUVECs with 10 mmol/L or 20 mmol/L celecoxib, the reduction in PTPRJ expression induced by COX-2 over-expression was not only rescued but in fact increased by 2.05-fold (+/- 0.28) and 3.34-fold (+/- 0.37), respectively, compared with control. Conclusions: Our results suggest that COX-2/PGE2 signaling may function as a negative regulator of PTPRJ expression in endothelial cells both in vivo and vitro.