Epicatechin blocks pro-nerve growth factor (proNGF)-mediated retinal neurodegeneration via inhibition of p75 neurotrophin receptor proNGF expression in a rat model of diabetes
Epicatechin blocks pro-nerve growth factor (proNGF)-mediated retinal neurodegeneration via inhibition of p75 neurotrophin receptor proNGF expression in a rat model of diabetes
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DOI：
10.1007/s00125-010-1994-3
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发表时间：
2011-03-01
期刊：
影响因子：
8.2
通讯作者：
El-Remessy, A. B.
中科院分区：
文献类型：
--
作者：
Al-Gayyar, M. M. H.;Matragoon, S.;El-Remessy, A. B.
在神经退行性疾病中已经检测到前神经生长因子（NGF）（NGF的前体形式）的积累。然而，proNGF在糖尿病视网膜中的作用以及proNGF引起视网膜神经变性的分子机制仍然未知。本研究的目的是阐明proNGF在神经胶质细胞活化中的作用，并研究表儿茶素，酪氨酸硝化的选择性抑制剂，在实验性糖尿病大鼠模型中的神经保护作用。proNGF及其受体的表达进行了检查，从链脲佐菌素诱导的糖尿病大鼠视网膜，视网膜Muller和视网膜神经节细胞（RGCs）。在糖尿病视网膜和细胞培养物中通过TUNEL和3-（4，5-二甲基噻唑-2-基）-2，5-二苯基四唑溴化物测定来评估RGC死亡。使用Slot-blot测定硝基酪氨酸。Western blot检测酪氨酸激酶A（TrkA）受体和p38丝裂原活化蛋白激酶（p38 MAPK）的激活，糖尿病诱导的过氧亚硝基阴离子通过酪氨酸硝化损伤TrkA-Y 490的磷酸化，激活胶质细胞，增加proNGF及其受体p75（NTR）的表达。这些作用与p38 MAPK、裂解的聚-（ADP-核糖）聚合酶和RGC死亡的激活有关。用表儿茶素治疗糖尿病动物（100 mg/kg/天，口服）可阻断这些作用，恢复神经元存活。RGC与活化的Muller细胞的条件培养基的共培养物显著降低RGC活力（44%）。通过使用小干扰RNA沉默p75（NTR）的表达保护RGC培养物免受高糖和proNGF诱导的细胞凋亡。糖尿病诱导的过氧亚硝酸盐刺激Muller细胞中p75（NTR）和proNGF的表达。它还损害TrkA受体磷酸化并激活RGC中的p75（NTR）凋亡途径，导致神经元细胞死亡。这些作用被表儿茶素阻断，表儿茶素是一种安全的膳食补充剂，表明其在糖尿病患者中的潜在治疗用途。
Accumulation of pro-nerve growth factor (NGF), the pro form of NGF, has been detected in neurodegenerative diseases. However, the role of proNGF in the diabetic retina and the molecular mechanisms by which proNGF causes retinal neurodegeneration remain unknown. The aim of this study was to elucidate the role of proNGF in neuroglial activation and to examine the neuroprotective effects of epicatechin, a selective inhibitor of tyrosine nitration, in an experimental rat model of diabetes.Expression of proNGF and its receptors was examined in retinas from streptozotocin-induced diabetic rats, and in retinal Muller and retinal ganglion cells (RGCs). RGC death was assessed by TUNEL and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays in diabetic retinas and cell culture. Nitrotyrosine was determined using Slot-blot. Activation of the tyrosine kinase A (TrkA) receptor and p38 mitogen-activated protein kinase (p38MAPK) was assessed by western blot.Diabetes-induced peroxynitrite impaired phosphorylation of TrkA-Y490 via tyrosine nitration, activated glial cells and increased expression of proNGF and its receptor, p75 neurotrophin receptor (p75(NTR)), in vivo and in Muller cells. These effects were associated with activation of p38MAPK, cleaved poly-(ADP-ribose) polymerase and RGC death. Treatment of diabetic animals with epicatechin (100 mg kg(-1) day(-1), orally) blocked these effects and restored neuronal survival. Co-cultures of RGCs with conditioned medium of activated Muller cells significantly reduced RGC viability (44%). Silencing expression of p75(NTR) by use of small interfering RNA protected against high glucose- and proNGF-induced apoptosis in RGC cultures.Diabetes-induced peroxynitrite stimulates p75(NTR) and proNGF expression in Muller cells. It also impairs TrkA receptor phosphorylation and activates the p75(NTR) apoptotic pathway in RGCs, leading to neuronal cell death. These effects were blocked by epicatechin, a safe dietary supplement, suggesting its potential therapeutic use in diabetic patients.