Effects of simvastatin on the expression of heme oxygenase-1 in human RPE cells.
OBJECTIVE
Chronic oxidative stress can lead to the impairment of RPE cells, indicating it to be a risk factor for AMD. The cholesterol-independent, pleiotropic effects of statins have protective effects on several cell types via unknown mechanisms. This study examined the role of heme oxygenase-1 (HO-1) as a target and potential mediator of statins in cultured human RPE cells.


METHODS
The RPE cell viability was measured using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. After 24 hours incubation, RT-PCR and Western blot was performed to measure the levels of HO-1 mRNA and protein expression, respectively, in RPE cells. Intracellular reactive oxygen species (ROS) production was measured using a fluorescence-activated cell sorter.


RESULTS
In cultured human RPE cells, simvastatin showed no toxicity up to 10 μM. Simvastatin increased the HO-1 mRNA and protein levels in a concentration-dependent manner up to 10 μM. HO-1 protein induction by simvastatin was unaffected by mevalonate or N-nitro-L-arginine methyl ester, showing that the isoprenoid- and NO-dependent pathways are not involved. Simvastatin-dependent HO-1 protein induction was reduced significantly by pharmacological inhibition of the phosphotidylinositol-3-kinase (PI3K)/Akt pathways. The simvastatin-induced inhibition of free radical formation was recovered by the presence of an HO inhibitor, zinc protoporphyrin.


CONCLUSIONS
These results demonstrate that HO-1 is a target site and an antioxidant mediator of simvastatin in human RPE cells. Simvastatin-dependent upregulation of HO-1 is mainly via PI3K/Akt-dependent signaling pathways. Simvastatin may have some clinical benefits in preventing retinal diseases associated with oxidative stress, such as AMD.
Department of Ophthalmology and Inha Vision Science Laboratory, Inha University School of Medicine, Incheon, Republic of Korea.
Kyoung Jin
KJ
Kim
Kyong Sil
KS
Kim
Na Rae
NR
Kim
Hee Seung
HS
Chin
D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D005609:Free Radicals / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D051547:Heme Oxygenase-1 / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000633:toxicity; D018384:Oxidative Stress / Q000187:drug effects; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D015398:Signal Transduction / Q000187:drug effects; D019821:Simvastatin / Q000633:toxicity*; D018675:Toxicity Tests / Q000379:methods
D005609:Free Radicals; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D019821:Simvastatin; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D019869:Phosphatidylinositol 3-Kinases; C494918:AKT1 protein, human; D051057:Proto-Oncogene Proteins c-akt