Does elevated intraocular pressure reduce retinal TRKB-mediated survival signaling in experimental glaucoma?
Does elevated intraocular pressure reduce retinal TRKB-mediated survival signaling in experimental glaucoma?
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DOI：
10.1016/j.exer.2009.08.003
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发表时间：
2009-12
影响因子：
3.4
通讯作者：
Morrison, John C.
中科院分区：
文献类型：
--
作者：
Guo, Ying;Johnson, Elaine;Cepurna, William;Jia, Lijun;Dyck, Jennifer;Morrison, John C.
神经营养因子(NT)及其受体的逆行转运减少被认为是青光眼视网膜神经节细胞(RGC)丢失的直接原因。然而，补充NT和NT受体的策略未能避免实验性青光眼RGC的最终死亡。本研究在大鼠青光眼模型中检测了NT系统的主要成分及其相互作用蛋白的反应。采用巩膜外静脉注射高渗盐水造成单侧慢性眼压升高(n=99)。收集视网膜，按视神经损伤程度分组。采用定量逆转录聚合酶链式反应、蛋白印迹分析和免疫组织化学方法检测基因和蛋白表达水平及蛋白定位。在RGC特异的三种Brn3蛋白(Brn3a、b和c)中，只有Brn3a在信息水平上显著下调至神经损伤最严重的同类值的35%±4%。随着眼压升高，视网膜组织中BDNF、NGF、NT-4/5、NT-3的表达水平无明显变化。视网膜成熟BDNF蛋白的丰度不受高眼压的影响，而ProBDNF蛋白的丰度随损伤程度的增加呈线性下降(R2=0.50)。在神经损伤最严重的视网膜，TrkB和TrkC受体的mRNA表达水平分别下降到67±9%和44±5%。然而，TrkB蛋白及其磷酸化形式的水平没有变化。随着损伤程度的增加，p75NTR的信使水平线性上调至219±26%(R2=0.46)，但在蛋白水平上无明显变化。在神经损伤最严重的视网膜，p75NTR凋亡适配蛋白Nade、NRIF和Lingo1的mRNA表达显著下调。损伤程度与Jun(R2=0.23)和JunB(R2=0.27)的消息水平呈正相关，激活的Jun蛋白的RGC标记增加。ATF3mRNA水平与损伤程度呈线性正相关(R2=0.53)，神经损伤最严重的眼的ATF3mRNA水平增加近5倍(482±76%)。在下游促生存信号成分中，ERK5mRNA的表达在神经损伤最严重的视网膜中线性上调(R2=0.32)，达到同行的157±15%(P<；0.01)。NF-κB表达水平与损伤程度呈轻度正相关(R2=0.12)。高眼压暴露后，损伤最严重的视网膜组织中BCL-XL基因表达水平显著降低至83±7%。ERK1/2、Akt1-3或Bcl2的消息水平似乎没有受到影响。升高的眼压不会改变促细胞凋亡的Bim、Bax或P53的mRNA水平。这项研究表明，高眼压暴露并不会导致视网膜BDNF或其受体TrkB水平的显著下降。这表明NT通路对高眼压的反应是复杂的，特别是关于p75NTR和ATF3的作用。更好地了解这些蛋白在眼压诱导的损伤中的作用，可能会为青光眼的神经保护提供明智的策略。
Reduced retrograde transport of neurotrophins (NT) and their receptors has been hypothesized to contribute directly to retinal ganglion cell (RGC) loss in glaucoma. However, strategies of supplementing NT and NT receptors have failed to avert ultimate RGC death in experimental glaucoma. This study examines the response of major components of the NT system and their interacting proteins in a rat glaucoma model. Unilateral chronic intraocular pressure (IOP) elevation was produced by episcleral vein injection of hypertonic saline (N = 99). Retinas were collected and grouped by extent of optic nerve injury. Quantitative reverse transcription PCR, western blot analysis and immunohistochemistry were used to determine mRNA and protein levels and protein localization. Out of three RGC-specific Brn3 proteins (Brn3a, b, and c), only Brn3a was significantly downregulated at the message level to 35 ± 4% of fellow values with the severest nerve injury. With IOP elevation, no significant alterations were found in retinal mRNA levels for BDNF, NGF, NT-4/5 or NT-3. The abundance of mature retinal BDNF protein was not significantly affected by elevated IOP, while proBDNF protein decreased linearly with increasing injury grade (r2 = 0.50). In retinas with the severest nerve injury, TrkB and TrkC receptor mRNA levels significantly declined to 67 ± 9% and 44 ± 5% of fellow values, respectively. However, the levels of TRKB protein and its phosphorylated form were unchanged. Message level for p75NTR was linearly upregulated up to 219 ± 26% with increasing injury (r2 = 0.46), but no alteration was detected at protein level. The mRNA expression of p75NTR apoptosis adaptor proteins NADE, NRIF, and Lingo1 were significantly downregulated in retinas with the greatest nerve injury. A positive correlation was found between injury extent and message levels for Jun (r2 = 0.23) as well as Junb (r2 = 0.27), and RGC labeling of activated JUN protein increased. Atf3 mRNA levels demonstrated a positive linear correlation to the extent of injury (r2 = 0.53), resulting in a nearly five-fold increase (482 ± 76%) in eyes with the greatest nerve damage. Among downstream pro-survival signaling components, Erk5 mRNA expression was linearly upregulated (r2 = 0.32) up to 157 ± 15% of fellow values in retinas with the severest nerve injury (p < 0.01). A slight positive correlation was found between NF-κB message levels and injury extent (r2 = 0.12). Bcl-xl mRNA levels in the most severely injured retinas were significantly reduced to 83 ± 7% by elevated IOP exposure. Message levels for Erk1/2, Akt1-3 or Bcl2 appeared unaffected. Elevated IOP did not alter mRNA levels of pro-apoptotic Bim, Bax, or p53. This study demonstrates that elevated IOP exposure does not result in a dramatic decrease in retinal levels of either BDNF or its receptor, TrkB. It shows that the responses of NT pathways to elevated IOP are complex, particularly with regard to the role of p75NTR and Atf3. A better understanding of the roles of these proteins in IOP-induced injury is likely to suggest informed strategies for neuroprotection in glaucoma.
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DOI：
10.1073/pnas.95.7.3978
发表时间：
1998-03-31
影响因子：
11.1
作者：
Di Polo, A;Aigner, LJ;Aguayo, AJ
通讯作者：
Aguayo, AJ
影响因子：
3.4
作者：
Johnson, Elaine C.;Cepurna, William O.;Morrison, John C.
通讯作者：
Morrison, John C.
影响因子：
16.2
作者：
COHENCORY, S;FRASER, SE
通讯作者：
FRASER, SE
影响因子：
16.2
作者：
Atwal, JK;Massie, B;Kaplan, DR
通讯作者：
Kaplan, DR
影响因子：
1.8
作者：
Clarke, DB;Bray, GM;Aguayo, AJ
通讯作者：
Aguayo, AJ