Bilberry (Vaccinium myrtillus) anthocyanins modulate heme oxygenase-1 and glutathione S-transferase-pi expression in ARPE-19 cells

PURPOSE. To determine whether anthocyanin-enriched bilberry extracts modulate pre- or posttranslational levels of oxidative stress defense enzymes heme-oxygenase (HO)-1 and glutathione S-transferase-pi (GST-pi) in cultured human retinal pigment epithelial (RPE) cells. METHODS. Confluent ARPE-19 cells were preincubated with anthocyanin and nonanthocyanin phenolic fractions of a 25% enriched extract of bilberry (10(-6)-1.0 mg/mL) and, after phenolic removal, cells were oxidatively challenged with H2O2. The concentration of intracellular glutathione was measured by HPLC and free radical production determined by the dichlorofluorescin diacetate assay. HO-1 and GST-pi protein and mRNA levels were determined by Western blot and RT-PCR, respectively. RESULTS. Preincubation with bilberry extract ameliorated the intracellular increase of H2O2-induced free radicals in RPE, though H2O2 cytotoxicity was not affected. By 4 hours, the extract had upregulated HO-1 and GST-pi protein by 2.8- and 2.5-fold, respectively, and mRNA by 5.5- and 7.1-fold, respectively, in a dose-dependent manner. Anthocyanin and nonanthocyanin phenolic fractions contributed similarly to mRNA upregulation. CONCLUSIONS. Anthocyanins and other phenolics from bilberry upregulate the oxidative stress defense enzymes HO-1 and GST-pi in RPE, suggesting that they stimulate signal transduction pathways influencing genes controlled by the antioxidant response element.