Abstract
Purpose::
The retinal pigment epithelial(RPE) cells produce a vascular endothelial growth factor(VEGF) mRNA in the hyperglycemic condition. An advanced glycation end product(AGEP) is also produced in hyperglycemia. Previous studies have shown that an AGEP stimulates VEGF expression. The inhibitory action of aminoguanidine on the AGEP formation was also confirmed. The goal of current study was to examine the hypothesis that an inhibition of AGEP formation by aminoguanidine will suppress a glucose-induced VEGF mRNA expression. The study was designed in two steps. The first step was to verify a VEGF mRNA expresssion by glucose. The second step was to examine an inhibitory effect of aminoguanidine on the glucose-induced VEGF mRNA expression.
Methods::
The human RPE cells were cultured in the Dulbecco's modified Eagle's medium, and used for a study. The study consisted of three groups; control, comparison and aminoguanidine-treated group. For a control groups, the RPE cells were incubated in the media without any addition. In a comparison group, the RPE cells were incubated in the media containing each 5.5, 11 or 16.5mMol glucose. In the aminoguanidine-treated group, the RPE cells were incubated in the media containing mixture of each 5.5, 11 or 16.5mMol glucose and each 1, 3 or 10µMol aminoguanidine. All three groups were incubated for 5, 10 or 15 days. At each time point, the VEGF mRNA expression of the RPE cells was assayed by northrn blot analysis.
Results::
In the control group, no detectable VEGF mRNA expression was found at any time point. In the comparison group, the VEGF mRNA expressions showed proportional increase to both increased glucose concentration and also increased incubation periods. In the aminoguanidine-treated group, the VEGF mRNA expression decreased proportional to the concentration of aminoguanidine added in case of 5 or 10 days incubation. But in case of 15 days incubation, the decrease of VEGF mRNA expression was less prominent than those shown at 5 or 10 days incubation, and was shown at all the three concentrations of glucose media.
Conclusions::
A glucose-induced VEGF mRNA expression increased proportional to the glucose concentration of the culture media. The expressions were more prominent with increase of incubation periods. The aminoguanidine inhibited glucose-induced VEGF mRNA expression in concentration-dependent manner in cases of 5 or 10 days incubation. However, in case of 15 days incubation, the inhibitory effect of aminoguanidine on the glucose-induced VEGF mRNA expression was less prominent than those of 5 or 10 days incubation cases.
Keywords: drug toxicity/drug effects • growth factors/growth factor receptors • retinal pigment epithelium