Abstract
Purpose: :
Oxidative stress (OS) has been implicated in many ocular diseases in which the RPE is considered a primary target. Several studies have shown that miRNAs play roles in a broad range of biological processes, including AMD, retinitis pigmentosa, retinoblastoma, and diabetic retinopathy. Alterations in miRNA expression may occur following exposure to stress-inducing agents, including H2O2. This study has attempted to unravel whether curcumin, a polyphenolic compound with many biological activities, alters H2O2-induced expression profiles of miRNAs in ARPE-19 cells.
Methods: :
The effect of curcumin on the H2O2-induced miRNA expression profile was assessed in ARPE-19 cells, which were treated with curcumin (20 µM) for 6 h prior to H2O2 (200 µM) for 18 h. Control cells with or without H2O2 and curcumin treatments were also maintained. miRNA expression profiling was carried out through real-time PCR array (Qiagen). The array contains a panel of 88 miRNAs, plus four housekeeping genes. Also, the effect of curcumin on the expression levels of selected antioxidant genes and proteins was tested by qRT-PCR and western blotting, respectively.
Results: :
Given individually, curcumin and H2O2 significantly downregulated 20 and 18 miRNAs, and upregulated 6 and 29 miRNAs (p<0.05 compared with controls; fold change >2.0), respectively. Furthermore, curcumin pretreatment in cells exposed to H2O2 significantly reduced the expression of 17 H2O2-induced miRNAs. The members of the miR-30 family that are putative regulators of the antioxidant defense system were found to be reduced by curcumin. As determined by qRT-PCR and western blotting, curcumin increased the expression of catalase, GPx1, and GPx4 at the mRNA and protein levels, respectively.
Conclusions: :
The results demonstrated that curcumin can modulate the expression of H2O2-induced miRNAs that are putative regulators of the antioxidant defense system, as well as other genes that have been reported to be linked to ocular diseases.
Keywords: retinal pigment epithelium • age-related macular degeneration • diabetic retinopathy