Department of Ophthalmology, The Fourth Affiliated Hospital of China Medical University, Eye Hospital of China Medical University, Key Lens Research Laboratory of Liaoning Province, Shenyang City, Liaoning Province, 110005, PR China.
Department of Ophthalmology and Vision Science, University of Arizona College of Medicine, Tucson, AZ 85710, USA; NeuVision Medical Institute, Tucson, AZ 85718, USA.
Exp Cell Res. 2022 Jan 1;410(1):112955. doi: 10.1016/j.yexcr.2021.112955. Epub 2021 Dec 5.
The retinal pigment epithelium cells (RPE) are sensitive to oxidative stimuli due to long-term exposure to various environmental stimuli. Thus, the oxidative injury of RPE cells caused by the imbalance of redox homeostasis is one of the main pathogenic factors of age-related macular degeneration (AMD). But the sophisticated mechanisms linking AMD to oxidative stress are not fully elucidated. Activation of Nrf2 signal pathway can protect RPE cells from oxidative damage. The present study investigated the regulating mechanism of miR-125b in Nrf2 cascade and evaluated its antioxidant capacity. The in vitro studies indicated that overexpression of miR-125b substantially inhibited Keap1 expression, enhanced Nrf2 expression and induced Nrf2 nuclear translocation. Importantly, functional studies demonstrated that forced expression of miR-125b could significantly elevate cell proliferation and superoxide dismutase (SOD) levels while reduce reactive oxygen species (ROS) overproduction and malondialdehyde (MDA) formation. Further studies showed that miR-125b had no effect when Nrf2 was silenced in ARPE-19 cells. Additionally, the results identified that Nrf2 silence induced ROS accumulation enhances HIF-1α protein expression, while miR-125b could offset this effect via promoting HIF-1α protein degradation. Subsequent in vivo studies demonstrated that sodium iodate induced outer retina thinner was reversed with exogenous supplementation of miR-125b, which was cancelled in Nrf2 knockout mice. In conclusion, this study illustrated that miR-125b can protect RPE from oxidative damage via targeting Nrf2/HIF-1α signal pathway and potentially may serve as a therapeutic agent of AMD.
视网膜色素上皮细胞 (RPE) 由于长期暴露于各种环境刺激物中，对氧化应激很敏感。因此，由于氧化还原平衡失调导致的 RPE 细胞氧化损伤是年龄相关性黄斑变性 (AMD) 的主要致病因素之一。但是，将 AMD 与氧化应激联系起来的复杂机制尚未完全阐明。激活 Nrf2 信号通路可以保护 RPE 细胞免受氧化损伤。本研究探讨了 miR-125b 在 Nrf2 级联中的调节机制，并评估了其抗氧化能力。体外研究表明，miR-125b 的过表达可显著抑制 Keap1 表达，增强 Nrf2 表达并诱导 Nrf2 核易位。重要的是，功能研究表明，miR-125b 的强制表达可以显著提高细胞增殖和超氧化物歧化酶 (SOD) 水平，同时减少活性氧 (ROS) 产生过多和丙二醛 (MDA) 形成。进一步的研究表明，当 ARPE-19 细胞中的 Nrf2 被沉默时，miR-125b 没有影响。此外，结果表明，Nrf2 沉默诱导的 ROS 积累增强 HIF-1α 蛋白表达，而 miR-125b 可以通过促进 HIF-1α 蛋白降解来抵消这种作用。随后的体内研究表明，外源性补充 miR-125b 可逆转碘酸钠诱导的外视网膜变薄，而在 Nrf2 敲除小鼠中这种作用被取消。总之，本研究表明，miR-125b 可以通过靶向 Nrf2/HIF-1α 信号通路来保护 RPE 免受氧化损伤，并且可能作为 AMD 的治疗剂。
