Retracted Article: Sauchinone inhibits high glucose-induced oxidative stress and apoptosis in retinal pigment epithelial cells

Abstract

Diabetic retinopathy (DR) is a common complication of diabetes mellitus and results in acquired blindness among working-age adults. It has been demonstrated that high glucose (HG)-induced oxidative stress and cell apoptosis in retinal pigment epithelial (RPE) cells are major factors for the pathogenesis of DR. Sauchinone, one of the active lignan isolated from Saururus chinensis, was reported to possess anti-oxidant and anti-apoptosis effects. In the present study, we investigated the effects of sauchinone on HG-induced oxidative stress and apoptosis in ARPE-19 cells. Our results proved that sauchinone improved the cell viability of HG-induced ARPE-19 cells. Moreover, sauchinone treatment caused a decrease in intracellular reactive oxygen species (ROS) generation and an increase in the activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT). Besides, flow cytometry showed that the apoptotic rate in sauchinone-treated ARPE-19 cells obviously decreased as compared in the HG-treated cells. Western blot indicated that sauchinone treatment caused a significant decrease in bax expression and increase in bcl-2 expression in HG-treated ARPE-19 cells. Sauchinone treatment enhanced the HG-caused induction of p-Akt, nuclear factor erythroid 2-related factor (Nrf2), and heme oxygenase-1 (HO-1) expressions in ARPE-19 cells. However, the inhibitor of Akt, LY294002, reversed the effects of sauchinone on cell viability, oxidative stress, and cell apoptosis in HG-treated ARPE-19 cells. These findings suggested that sauchinone treatment prevented HG-induced oxidative stress and apoptosis via regulating the Akt/Nrf2/HO-1 pathway in HG-induced RPE cells. These findings suggested that sauchinone might be a therapeutic agent for the treatment and prevention of DR.

Fig. 1. Sauchinone improved cell viability of HG-induced ARPE-19 cells. (A) Effect of sauchinone on ARPE-19 cells viability. ARPE-19 cells were incubated with a series of concentrations of sauchinone (0, 5, 10, 20, 40 μM) for 48 h. (B) Effect of sauchinone on cell viability of HG-induced ARPE-19 cells. Cells were pretreated with different dosages of sauchinone (0, 5, 10 and 20 μM) for 2 h, followed by incubation in HG (25 mM) condition for 48 h. All results were expressed as means ± SEM of three independent replications. *p < 0.05 vs. control cells; ^#p < 0.05 vs. HG-induced ARPE-19 cells.

Fig. 2. Sauchinone ameliorated oxidative stress in HG-induced ARPE-19 cells. Cells were pretreated with a series of concentrations of sauchinone (0, 5, 10, 20 μM) for 2 h, followed by incubation in HG (25 mM) condition for 48 h. ROS generation (A) and the activities of antioxidant enzyme activities including SOD (B), GPx (C), and CAT (D) were determined to reflect oxidative stress. All results were expressed as means ± SEM of three independent replications. *p < 0.05 vs. control cells; ^#p < 0.05 vs. HG-induced ARPE-19 cells.

Fig. 3. Sauchinone ameliorated cell apoptosis in HG-induced ARPE-19 cells. After pretreatment with a series of concentrations of sauchinone (0, 5, 10, 20 μM) for 2 h, ARPE-19 cells were incubated in HG (25 mM) condition for 48 h. (A) Apoptotic rates of ARPE-19 cells were assessed using flow cytometry. (B) Expressions of bcl-2 and bax were detected using Western blot. All results were expressed as means ± SEM of three independent replications. *p < 0.05 vs. control cells; ^#p < 0.05 vs. HG-induced ARPE-19 cells.

Fig. 4. Sauchinone enhanced the HG-induced activation of Akt/Nrf2/HO-1 signaling pathway in ARPE-19 cells. ARPE-19 cells were incubated with or without sauchinone (20 μM) for 2 h in the presence or absence of HG (25 mM) condition. The expressions of Akt, p-Akt, nuclear Nrf2, and HO-1 were assessed using Western blot analysis. (A) Effect of sauchinone on the activation of Akt/Nrf2/HO-1 signaling pathway. (B) Quantification analysis was performed using Gel-Pro Analyzer version 4.0 software. Cells were pretreated with 5 μM LY294002 for 1 h, and then incubated with or without sauchinone (20 μM) for 2 h in the presence or absence of HG (25 mM) condition. (C) Effect of LY294002 on cell viability. (D) Effect of LY294002 on oxidative stress. (E) Effect of LY294002 on cell apoptosis. All results were expressed as means ± SEM of three independent replications. *p < 0.05 vs. control cells; ^#p < 0.05 vs. HG-induced ARPE-19 cells; &p < 0.05 vs. HG + sauchinone group.