PI3K/Akt-mediated promotive effect of insulin on proliferation of retinal pigment epithelial cells and secretion of transforming growth factor-β2 / 中华实验眼科杂志

ABSTRACT

Background Insulin can promote the occurrence of myopia.It has been proven that insulin receptor exists in human retinal pigment epithelial (RPE) cells and can promote RPE cells to secrete transforming growth factor-β2(TGF-β2),which is one of the most important myopic signal molecules.Objective This study was to investigate if PI3K/Akt mediates the promotive effects of insulin on proliferation of human RPE cells and secretion of TGF-β2.Methods Human RPE cell line,ARPE-19 cells,were regularly cultured using DMEM containing 10％ fetal bovine serum,and 10× 103 U/ml insulin,LY294002,10× 103 U/ml insulin+LY294002,Wortmanin,10× 103 U/ml insulin+Wortmanin were added into the medium respectively for 48 hours,and the regularly cultured cells served as blank controls.The proliferation value (absorbance,A) of the cells was evaluated by MTS,and the TGF-β2 level in the cell supernatant was detected by ELISA.The relative expression of TGF-β2 mRNA in the cells was assayed using reverse transcription PCR (RT-PCT) 1 hour and 2 hours after the addition of reagents.Results MTS showed that the proliferation value of the cells in the insulin+LY294002 group was 0.75±0.03,which was significantly lower than that in the insulin group (0.98± 0.04).No significant difference was seen in the proliferative value between the insulin+Wortmanin group and the insulin group (0.97±0.07 versus 0.98± 0.04,P＞0.05).ELISA revealed that the content of TGF-β2 in the the cell supernatant was (11.59±2.85) pg/ml and (49.16± 10.94) pg/ml in the insulin + LY294002 group and the insulin + Wortmanin group,respectively,showing a significant decline in comparison with (548.50±35.18) pg/ml in the insulin group (both at P＜0.05).A significant difference was found in the TGF-β2 content between the insulin+LY294002 group and the insulin+Wortmanin group (t =8.131,P =0.000).The RT-PCR showed that 1 hour and 2 hours after addition of the reagents,the expression levels of TGF-β2 mRNA in the cells were lower in both insulin+LY294002 group and insulin+Wortmanin group than those in the insulin group (P＜0.05).The decline range of TGF-β2 mRNA expression level was more significant in the insulin+LY294002 group than that in the insulin+Wortmanin group at 1 hour (t=4.176,P=0.014) rather than at 2 hours (t=0.756,P=0.492).Conclusions Insulin can promote the proliferation of human RPE cells and secretion of TGF-β2 through PI3K/Akt pathway.This may be one of the mechanisms of insulin causes myopia.