Berberine-mediated REDD1 down-regulation ameliorates senescence of retinal pigment epithelium by interrupting the ROS-DDR positive feedback loop

Abstract

Background: Accumulation of age-associated senescent cells accompanied with increased reactive oxygen species (ROS) and inflammatory factors contributes to the progression of age-related macular degeneration (AMD), the main cause of blindness in the elderly. Berberine (BBR) has shown efficacy in the treatment of age-related diseases including diabetes and obesity by decreasing ROS. However, the pharmacological effect of BBR on alleviating retinal aging remains largely unknown.

Purpose: Our study aimed to investigate the pharmacological effect of BBR as an anti-aging agent in retinal aging and its further molecular mechanisms.

Methods: D-galactose (DG)-induced ARPE-19 cell senescence and retinal aging were employed to evaluate the anti-aging effect of BBR in vivo and in vitro. The siRNA transfection, Western-Blot analyses, SA-β-Gal assay and immunofluorescence were performed to investigate the potential mechanisms of BBR on anti-aging of RPE.

Results: In RPE-choroid of both natural aged and DG-induced accelerated aged mice, oxidative stress was increased along with the up-regulation of p21 expression, which was ameliorated by BBR treatment. BBR down-regulated the expression of REDD1 to decrease intracellular ROS content, attenuating DG-induced senescence in vitro and in vivo. Furthermore, p53 instead of HIF-1α was identified as the transcriptional regulator of REDD1 in DG-induced premature senescence. Importantly, NAC and BBR reversed the expression of p53 and the content of 8-OHdG, indicating that the positive feedback loop of ROS-DNA damage response (DDR) was formed, and BBR interrupted this feedback loop to alleviate DG-induced premature senescence by reducing REDD1 expression. In addition, BBR restored DG-damaged autophagy flux by up-regulating TFEB-mediated lysosomal biosynthesis by inhibiting REDD1 expression, thereby attenuating cellular senescence.

Conclusion: BBR down-regulates REDD1 expression to interrupt the ROS-DDR positive feedback loop and restore autophagic flux, thereby reducing premature senescence of RPE. Our findings elucidate the promising effects of REDD1 on cellular senescence and the great potential of BBR as a therapeutic approach.

Keywords: Autophagic flux; Berberine; REDD1; Retinal pigment epithelium; Senescence.