巴氯芬激活GABAb受体对糖尿病性视网膜病变的神经保护作用及机制研究

Retinal neural degeneration is the most important pathogenesis factor in the early stage of diabetic retinopathy (DR). Recent studies indicated that gamma-aminobutyric acid type B (GABAb) receptor participated in the regulation of neuroprotection in cerebellar granule neurons, but the effect was unclear in the DR. Our previous studies showed that baclofen, the special agonists of GABAb receptor, which attenuated the apoptosis of retinal ganglion cells (RGCs) under the high glucose and hypoxia conditions. To define the molecular mechanism of GABAb receptor in the occurrence and development process of DR, we put forward the relevant research hypothesis: GABAb receptor on the surface of RGCs will be activated using baclofen under the simulation of high glucose and hypoxia conditions in vitro and in vivo. GABAb receptor through the upregulation of PI3K/Akt signaling pathway, in turn, leads to PERK pathway inactivation and regulates the expression of apoptosis related factors to play a role of neuroprotective effect. To test this hypothesis, our research mainly divided into two parts: ①Using baclofen and RNAi interference to upregulate and silence GABAb genes, by which we detect apoptosis of RGCs in vivo and vitro; ②Exploring whether baclofen-GABAb receptors through PI3K/Akt-PERK pathways regulate the apoptosis of RGCs. This may help us demonstrate the potential therapeutic drug of DR.

视网膜神经退行性病变是糖尿病性视网膜病变（DR）早期重要的病理改变。新近研究表明，γ-氨基丁酸B型（GABAb）受体对小鼠小脑颗粒神经元具有重要的保护作用，但该作用在DR中尚未明确。我们前期结果显示GABAb受体的特异激动剂—巴氯芬可明显改善高糖/低氧下视网膜神经节细胞（RGCs）的凋亡。为进一步明确DR中巴氯芬的神经保护效应及作用机制，我们提出科研假说：体内外模拟糖尿病的高糖/低氧环境使用巴氯芬激活RGCs上的GABAb受体，通过活化PI3K/Akt通路继而阻断内质网PERK途径，最终调控凋亡相关因子的表达发挥神经保护作用。为验证此假说，我们的研究分为两部分：①使用巴氯芬上调GABAb基因并通过siRNA手段抑制该基因表达，观察高糖/低氧环境下RGCs的凋亡情况；②明确巴氯芬-GABAb受体是否通过PI3K/Akt-PERK调控RGCs凋亡。本研究将为延缓和控制DR发展提供潜在治疗药物。

视网膜神经退行性病变是糖尿病性视网膜病变（DR）早期重要的病理改变。新近研究表明，γ-氨基丁酸B型（GABAb）受体对小鼠小脑颗粒神经元具有重要的保护作用，我们前期也初步观察到GABAb受体的特异激动剂—巴氯芬可明显改善高糖/低氧下视网膜神经节细胞（RGCs）的凋亡，提示巴氯芬可降低DR环境下的RGCs的损伤，发挥对RGCs的保护作用，但巴氯芬在其中参与的相关调控机制仍缺乏相关研究。本研究为进一步明确DR中巴氯芬的神经保护效应及作用机制，我们通过体外模拟糖尿病缺氧环境，使用巴氯芬特异性激活RGCs上的GABAb2受体，发现巴氯芬可通过活化Akt通路继而阻断下游内质网的PERK/eIF2α/ATF-4途径，降低CHOP的表达，进一步下调促凋亡相关因子caspase-3及Bax的表达，增加抑凋亡因子Bcl-2的表达水平，减少RGCs凋亡的发生，发挥神经保护作用。同时，我们也在糖尿病大鼠中观察到给予巴氯芬药物后，可通过上调Akt通路、抑制下游的CHOP通路明显减少STZ大鼠视网膜神经节细胞的凋亡数量及caspase-3及Bax的表达。本研究揭示了巴氯芬对DR的神经保护作用，为延缓和控制DR发展提供潜在治疗药物。