Effects of simvastatin on CAT-1-mediated arginine transport and NO level under high glucose conditions in conditionally immortalized rat inner blood-retinal barrier cell lines (TR-iBRB)

- We hypothesized that l-arginine uptake would be increased by effect of simvastatin at high glucose conditions.
- We measured [3H]l-arginine uptake in inner blood-retinal barrier at control and high glucose conditions.
- The [3H]l-arginine uptake was decreased at high glucose and simvastatin pretreatment increased the [3H]l-arginine uptake.
- Simvastatin treatment elevated CAT-1 mRNA expression and NO levels by elevating eNOS mRNA expression.
- Simvastatin might be a good modulator for therapy of diabetic retinopathy by regulating NO levels.

ObjectiveHyperglycemia causes the breakdown of the blood-retinal barrier by impairing endothelial nitric oxide synthase (eNOS) function. Statins have many pleiotropic effects such as improving endothelial barrier permeability and increasing eNOS mRNA stability. The objective of this study was to determine effect of simvastatin on l-arginine transport and NO production under high-glucose conditions in conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB).MethodsChanges in l-arginine transport uptake and, expression levels of cationic amino acid transporter 1 (CAT-1) and eNOS mRNA were investigated after pre-treatment with simvastatin and NOS inhibitors (l-NMMA and l-NAME) under high-glucose conditions using TR-iBRB, an in vitro model of iBRB. The NO level released from TR-iBRB cells was examined using Griess reagents.ResultsUnder high glucose conditions, [3H]l-arginine uptake was decreased in TR-iBRB cells. Simvastatin pretreatment elevated [3H]l-arginine uptake, the expression levels of CAT-1 and eNOS mRNA, and NO production under high-glucose conditions. Moreover, the co-treatment with simvastatin and NOS inhibitors reduced [3H]l-arginine uptake compared to pretreatment with simvastatin alone.ConclusionOur results suggest that, in the presence of high-glucose levels, increased l-arginine uptake due to simvastatin treatment was associated with increased CAT-1 and eNOS mRNA levels, leading to higher NO production in TR-iBRB cells. Thus, simvastatin might be a good modulator for diabetic retinopathy therapy by increasing of the l-arginine uptake and improving endothelial function in retinal capillary endothelial cells.