Department of Genetics and Molecular Biology, School of Medicine, Xi'an Jiaotong University, Xi'an 710061, China.
Neuroscience. 2013 Jan 3;228:1-12. doi: 10.1016/j.neuroscience.2012.10.002. Epub 2012 Oct 13.
The neuroprotective role of 17β-estradiol is well known; however, its mechanism of action remains unclear. In the present study, we applied light-induced apoptosis on the Sprague-Dawley rat retina to determine the neuroprotective effect of intravitreal administration of 17β-estradiol on retinal neurons and to demonstrate its underlying mechanism of action. Fourteen days after ovariectomy, adult female Sprague-Dawley rats received light damage. The functional and morphological changes of the retina were monitored by electroretinogram and hematoxylin and eosin staining, respectively. Retinal apoptosis was characterized by the presence of DNA laddering and positive terminal deoxyuridine triphosphate (dUTP) nick-end labeling. The phosphoinositide 3-kinase (PI3K)-specific inhibitor LY294002 was used to elucidate whether the PI3K/Akt signaling pathway was activated by 17β-estradiol. Western blotting was used to detect the activation of caspase 3 and Akt. Immunofluorescence was performed to determine the translocation of NF-κB. Our data showed that exposure to 8000lux white light for 12h resulted in functional damage to the rat retina, histological changes and retinal neuronal apoptosis. 17β-Estradiol significantly rescued retinal function by preventing neuronal apoptosis. Moreover, the inhibition of Akt activation by LY294002 increased retinal neuronal apoptosis, demonstrating that the PI3K/Akt signaling pathway is involved. Levels of cleaved caspase-3 were suppressed in the presence of 17β-estradiol, while LY294002 reversed the effects. It is noteworthy that NF-κB p65 also translocated from the cytoplasm to the nucleus after 17β-estradiol administration. This translocation was inhibited by pre-injection of LY294002. Taken together, these results indicate that 17β-estradiol intravitreal administration protects the function of the rat retina by preventing retinal neuronal apoptosis from light damage. In addition, the PI3K/Akt signaling pathway is activated, which inhibits caspase-3 activation and induces NF-κB p65 nuclear translocation.
17β-雌二醇的神经保护作用是众所周知的；然而，其作用机制仍不清楚。在本研究中，我们应用光诱导凋亡于 Sprague-Dawley 大鼠视网膜，以确定 17β-雌二醇玻璃体内给药对视网膜神经元的神经保护作用，并阐明其作用机制。卵巢切除术后 14 天，成年雌性 Sprague-Dawley 大鼠接受光损伤。视网膜的功能和形态变化分别通过视网膜电图和苏木精-伊红染色进行监测。通过 DNA 梯状带和末端脱氧核苷酸转移酶（dUTP）缺口末端标记法（TUNEL）阳性来鉴定视网膜细胞凋亡。使用磷酸肌醇 3-激酶（PI3K）特异性抑制剂 LY294002 来阐明 17β-雌二醇是否激活了 PI3K/Akt 信号通路。通过 Western blot 检测 caspase 3 和 Akt 的激活。通过免疫荧光检测 NF-κB 的易位。我们的数据表明，暴露于 8000lux 白光 12 小时导致大鼠视网膜功能损伤、组织学改变和视网膜神经元凋亡。17β-雌二醇通过阻止神经元凋亡显著挽救了视网膜功能。此外，LY294002 抑制 Akt 的激活增加了视网膜神经元凋亡，表明 PI3K/Akt 信号通路参与其中。在存在 17β-雌二醇的情况下，cleaved caspase-3 的水平被抑制，而 LY294002 逆转了这种作用。值得注意的是，NF-κB p65 在给予 17β-雌二醇后也从细胞质易位到细胞核。这种易位被预先注射 LY294002 所抑制。总之，这些结果表明，17β-雌二醇玻璃体内给药通过防止光损伤引起的视网膜神经元凋亡来保护大鼠视网膜的功能。此外，激活了 PI3K/Akt 信号通路，抑制了 caspase-3 的激活，并诱导了 NF-κB p65 的核易位。
