Structural features of the Nogo receptor signaling complexes at the neuron/myelin interface

Upon spinal cord injury, the central nervous system axons are unable to regenerate, partially due to the repulsive action of myelin inhibitors, such as the myelin-associated glycoprotein (MAG), Nogo-A and the oligodendrocyte myelin glycoprotein (OMgp). These inhibitors bind and signal through a single receptor/co-receptor complex that comprises of NgR1/LINGO-1 and either p75 or TROY, triggering intracellular downstream signaling that impedes the re-growth of axons. Structure–function analysis of myelin inhibitors and their neuronal receptors, particularly the NgRs, have provided novel information regarding the molecular details of the inhibitor/receptor/co-receptor interactions. Structural and biochemical studies have revealed the architecture of many of these proteins and identified the molecular regions important for assembly of the inhibitory signaling complexes. It was also recently shown that gangliosides, such as GT1b, mediate receptor/co-receptor binding. In this review, we highlight these studies and summarize our current understanding of the multi-protein cell-surface complexes mediating inhibitory signaling events at the neuron/myelin interface.     

黄连解毒汤有效部位抑制NogoA/NgR表达对脑缺血大鼠白质损伤的影响

目的:观察黄连解毒汤有效部位对脑缺血大鼠白质损伤的影响,探讨黄连解毒汤有效部位对轴突修复抑制信号勿动蛋白A(NogoA)和勿动蛋白受体(Nogo receptor, NgR)的调控作用。方法:将雄性SD大鼠随机分为假手术组、模型组、总生物碱组、总黄酮组、总环烯醚萜组。除假手术组外,其余各组大鼠采用线栓法建立大鼠大脑中动...     

嗅鞘细胞移植促进脊髓损伤修复：可通过抑制损伤区NogoA、NgR及RhoA表达实现？

目的：观察嗅鞘细胞移植前后脊髓损伤区勿动蛋白（NogoA）、NgR及RhoA的动态变化,探讨嗅鞘细胞移植治疗脊髓损伤的可能机制。 方法：实验于2006年9月/2007年5月在西安交大医学院环境与基因重点实验室完成。①实验动物：成年SD大鼠40只,随机数字表法分为正常组、模型组、嗅鞘细胞组、DF12对照组,10只/组。另取30只健康成年雄性SD大鼠作为嗅鞘细胞的来源。②实验方法：除正常组外,其余各组均建立全横切脊髓损伤模型。嗅鞘细胞组将原代培养12d的嗅鞘细胞悬液调整为1×1011 L-1,在距损伤缘上下各1mm处分4点应用微量注射器注射,深度1.0mm,每处各注射1μL。DF12对照组同法每点注射等量DF12培养液,模型组、正常组不进行任何处理。③实验评估：各组分别于移植后1, 4, 8周采用免疫组化技术及Western blot技术动态检测脊髓损伤区NogoA、NgR及RhoA表达的变化。同时在移植后8周行嗜银染色检测组织形态学变化及应用BBB法评价移植后各组动物下肢功能。 结果：①组织形态学变化。嗅鞘细胞移植8周后除正常组外,其余各组均可见明显的神经纤维再生,但模型组与DF12对照组大部分纤维排列紊乱,再生纤维方向性较差;嗅鞘细胞组可见明显的新生轴突,且神经纤维跨越损伤部位修复脊髓损伤,无论在数量还是质量上均优于模型组及DF12对照组。②移植后8周各组下肢运动功能检测BBB评分结果的比较：嗅鞘细胞组BBB评分均明显高于模型组、DF12对照组,且差异有显著性意义（P<0.01）。③免疫组化技术及Western blot技术均显示正常组NogoA、NgR及RhoA的表达明显低于其余3组（P<0.05）,而模型组和DF12对照组差异无显著性意义（P>0.01）;同时OECs组与模型组和DF12对照组比较亦有显著性差异（P<0.05）。结论：嗅鞘细胞移植可能通过降低脊髓损伤区NogoA、NgR及RhoA的表达,从而促进损伤脊髓的修复。     

NogoA在视觉发育期正常猫和斜视性弱视猫视皮层21a区的表达

背景 视觉发育可塑性的分子机制仍是目前研究的热点,有助于对视觉发育期视功能的异常进行解释和防治,目前轴索生长抑制因子NogoA在视觉发育可塑性中的作用日益受到关注. 目的 观察正常发育猫和斜视性弱视猫视皮层21a区神经元NogoA的表达变化,从分子水平探讨斜视性弱视的发病机制.方法 4周龄幼猫16只按随机数字表法分为正常组和斜视性弱视组,每组8只.斜视性弱视组手术离断右眼外直肌制备成人工内斜视模型,与正常组在同等视觉环境下饲养1周后进行视觉诱发电位(VEP)检测,VEP P100波幅下降及隐含时延长确定为弱视模型制作成功.确定弱视形成后用断颈法处死实验猫,制备猫视皮质区21a区组织切片,采用苏木精-伊红染色检测2个组猫视皮层区的发育情况,应用免疫组织化学法观察正常组和斜视性弱视组视皮层21a区NogoA的表达并进行定量比较. 结果 斜视性弱视组猫P-VEP P100隐含时为(108.50±6.95)ms,右眼/左眼P100振幅比值为0.35±0.09,正常组为(98.10±7.07)ms,右眼/左眼P100振幅比值为0.83±0.14,差异均有统计学意义(t=4.450,P=0.005；t=5.970,P=0.005).2个组视皮质21a区苏木精-伊红染色表明斜视性弱视组视皮质神经元的数目无明显减少,但神经元细胞质突起变短或消失.免疫组织化学染色表明,NogoA阳性细胞均存在于Ⅱ～Ⅵ层,呈棕黄色表达,位于神经元一侧.正常组视皮质21a区Ⅱ～Ⅵ层可见NogoA阳性染色细胞,斜视性弱视组Ⅱ/Ⅲ、Ⅳ、V/Ⅵ区NogoA表达的免疫阳性细胞密度分别为(387.37±2.01)、(354.58±1.85)、(289.68±1.81)个/mm2,明显高于正常组的(161.39±1.98)、(128.93±1.26)、(96.25±1.49)个/mm2,差异均有统计学意义(t=-160.400、-201.890、-164.740,P=0.000). 结论 NogoA在调控视觉发育敏感期及其可塑性中可发挥关键性作用.     

空肠弯曲菌脂多糖对大鼠脊髓髓鞘损伤的实验研究

目的 探讨空肠弯曲菌脂多糖(Cj-LPS)对大鼠脊髓髓鞘损伤的影响。方法 Wistar大鼠分为对照组(NC组)、脂多糖组(Cj-LPS组)和抗LPS组(Anti-LPS组)。NC组使用试剂为生理盐水混合完全弗氏佐剂(CFA);Cj-LPS组试剂则由Cj-LPS、CFA和生理盐水组成;抗LPS组试剂为特异性抗Cj-LPS IgG混合CFA。注射后第4周和第6周分别处死各组大鼠。光镜观察脊髓组织形态变化,RT-PCR检测神经营养因子-3(NT-3)及其受体TrkC和神经生长抑制因子NogoA及其受体NgR mRNA的表达。结果 Cj-LPS组大鼠出现脊髓髓鞘损伤, NT-3/TrkC mRNA的表达下降, NogoA/NgR mRNA的表达增加;与Cj-LPS组比较,抗LPS组脊髓髓鞘损伤减轻。结论 Cj-LPS可诱导大鼠脊髓髓鞘损伤,而抗LPS抗体可以改善由Cj-LPS诱导的大鼠脊髓髓鞘损伤。     

术后认知功能障碍老年小鼠海马内NogoA-NgR1通路的变化

目的观察术后认知功能障碍老年小鼠海马内神经生长抑制因子NogoA及其受体NgR1表达的变化,并探讨其可能机制。方法采用异氟醚麻醉+腹腔探查术建立POCD模型。老年雄性C57BL/6小鼠40只,随机分为四组:O_2+Saline组(OS组)、O_2+NEP1-40组(ON组)、异氟醚麻醉+腹腔探查术+Saline组(SS组)及异氟醚麻醉+腹腔探查术+NEP1-40组(SN组),每组10只。麻醉前7d行右侧脑室置管;麻醉前2h至行为学测试前2h每天侧脑室注射NEP1-40(20μg/2μl)或等容的无菌生理盐水,连续注射8d。术后第5天行旷场实验,第6、7天分别行场景性和条件性恐惧实验训练和测试。行为学测试后2h,取小鼠海马组织,采用Western blot法检测NogoA、NgR1、RhoA、ROCK2和GAP43含量变化;Golgi染色检测海马CA1区神经元树突棘数量改变。结果与OS和ON组比较,SS组在场景性恐惧实验测试中僵直反应百分比明显降低,海马内NogoA、NgR1、RhoA和ROCK2含量明显升高,GAP43含量和总的、新生的和成熟的树突棘数量明显减少(P0.05);与SS组比较,SN组在场景性恐惧实验测试中僵直反应百分比明显升高,海马内RhoA和ROCK2含量明显降低,GAP43含量和总的、新生的和成熟的树突棘数量明显增多(P0.05)。结论麻醉手术致老年小鼠认知功能损害与其海马内NogoA-NgR1通路过度激活有关。     

Olfactory ensheathing cell transplantation and inhibition of NogoA, NgR and RhoA expression in the damaged zone to ameliorate spinal cord injury

BACKGROUND:Olfactory ensheathing cell(OEC)transplantation promotes repair of spinal cord injury. Neural regeneration inhibits binding of the myelin protein Nogo to its receptor(NgR),activates downstream inhibitory signal RhoA, and leads to axonal degeneration.OBJECTIVE: To determine the relationship between OECs transplantation for spinal cord injury and NogoA, NgR, and RhoA protein expression in the damaged zone.DESIGN, TIME AND SETTING: A randomized, controlled, animal experiment was performed from September 2006 to May 2007 at the Key Laboratory of Environment and Genes in Xi'an Jiaotong University School of Medicine, China.MATERIALS: OECs were harvested from healthy, adult, male, Sprague Dawley rats aged 6 months. Mouse anti-rat NogoA, NgR, and RhoA monoclonal antibodies were utilized for detection.METHODS: A total of 40 adult Sprague Dawley rats were randomly assigned to four groups: normal, model, OECs, and DF12, with 10 animals in each group. Transverse section spinal cord injury was established in the OECs and DF12 groups, followed by injection of 1 μL OECs suspension(1×108/mL)or equivalent DF12 medium at 1 mm above and below the injury site.MAIN OUTCOME MEASURES: Immunohistochemistry and Western blot were utilized to detect NogoA, NgR, and RhoA expression in the spinal cord injury lesions. Morphological changes were observed by argyrophilia staining, and lower extremity function of the animals was assessed using Basso, Beattie, and Bresnahan scores.RESULTS: Eight weeks following OECs transplantation, a significant increase in new axons was observed in the OECs group, and nerve fibers crossed the injury site to repair spinal cord injury.Qualitative and quantitative results from the OECs group were superior to the model and DF12 groups. At 8 weeks after transplantation, Basso, Beattie, and Bresnahan scores were significantly greater in the OECs group compared with the model and DF12 groups(P< 0.01), but expression of NogoA, NgR, and RhoA protein was significantly decreased compared with the model and DF12 groups(P< 0.05).CONCLUSION: OEC transplantation could inhibit NogoA, NgR, and RhoA expression in spinal cord injury lesions, thereby promoting repair of spinal cord injury.     

补肾益髓方及其拆方调控实验性自身免疫性脑脊髓炎小鼠轴突再生抑制信号通路相关分子的实验研究

目的 观察补肾益髓方（Bushen Yisui formula,BSYSF）及其拆方补肾方（Bushen formula,BSF）和化痰活血方（Huatan Huoxue formula,HTHXF）对实验性自身免疫性脑脊髓炎（experimental autoimmune encephalomyelitis,EAE）小鼠轴突再生抑制信号通路NogoA/NgR/RhoA/ROCK的调控作用。方法 将雌性C57BL/6小鼠采用数字表法随机分为正常对照组（normal control,NC）、模型组（model,MO）、醋酸泼尼松组（prednisone acetate,PA,6 mg/kg）、梓醇组（catapol,CA,40 mg/kg）、BSYSF组（生药3.02 g/kg）、BSF组（生药1.44 g/kg）、HTHXF组（生药1.57 g/kg）,每组16只。用髓鞘少突胶质细胞糖蛋白_35-55（myelin oligodendrocyte glycoprotein_35-55,MOG_35-55）免疫小鼠制备EAE模型。NC和MO组小鼠灌服蒸馏水,各治疗组予相应药物灌胃,每日1次,共40 d。免疫第25天和40天,分别取小鼠脑和脊髓。应用实时荧光定量-PCR（quantitative real time-PCR,qRT-PCR）检测NogoA、NgR、RhoA和ROCKⅡmRNA表达;免疫组织化学（immunohistochemistry,IHC）和蛋白质印迹（Western blotting,WB）法测定上述指标蛋白的表达。结果 MO组小鼠脑和脊髓NogoA、NgR、RhoA和 ROCKⅡmRNA和蛋白表达较NC组明显上调（P<0.05,P<0.01,P<0.001）。经BSYSF及其拆方BSF和HTHXF治疗后,NogoA、NgR、RhoA和ROCKⅡmRNA和蛋白的表达均有不同程度的降低,BSYSF组的上述指标差异有统计学意义（P<0.05,P<0.01,P<0.001）。结论 BSYSF及其拆方BSF和HTHXF均具有调节EAE小鼠轴突抑制因子NogoA/NgR及其信号通路RhoA/ROCK作用,并且BSYSF作用明显。上述结果为阐释BSYSF促进轴突再生的作用机制提供了实验依据。