Structural and Ultrastructural Localization of NGF and NGF Receptors in the Thymus of Subjects Affected by Myasthenia Gravis

We have previously reported that the thymus of patients affected by myasthenia gravis (MG) is characterized by an elevated level of nerve growth factor (NGF), an endogenous polypeptide which plays a marked role in the cell biology of nervous and immune system. A consistent number of studies has shown altered expression of NGF in diseases associated with inflammatory and/or autoimmune responses. To evaluate the biochemical and molecular mechanisms implicated in NGF action in human myasthenic thymus, it is important to identify the cellular and structural organization of NGF receptors. To address this question, we investigated, both at light and electron microscopic levels, the cellular distribution of immunoreactivity for NGF and its low-affinity receptors, (p75) and its high-affinity receptor (TrkA) in the thymus of patients with MG. The present investigation shows that NGF and NGF receptors are overexpressed in the thymic cells of patients with MG compared to control subjects.     

甲状腺激素通过NGF及TrKA调节中枢胆碱能神经元发育

目的探索甲状腺激素通过神经生长因子(NGF)及其受体TrKA对大鼠顶叶皮层、海马部位中枢胆碱能神经元发育的作用。方法将Wistar大鼠分为3组:①甲状腺功能减退(甲减)组:从母鼠妊娠5～6d起饲以含0.02%的他巴唑饮用水;②甲状腺功能亢进(甲亢)组:仔鼠出生即日起,按体质量腹腔注射T4(0.4μg/g);③对照组:饲以普通饲料及饮用水。于出生后第14、21、28天,免疫组化法检测大鼠顶叶皮层、海马中胆碱乙酰转移酶(ChAT)阳性细胞,原位杂交法测定NGF、TrkA mRNA的表达。结果①出生后第21、28天顶叶皮层、海马中,甲减组(159.42±5.26、162.37±4.67,98.60±7.67、101.50±4.39)ChAT阳性细胞数较对照组(174.80±5.10、171.40±3.87,213.40±16.93、274.60±6.69)明显减少(P<0.05或<0.01),甲亢组(312.50±3.75、296.30±6.13,324.60±15.72、319.10±8.85)ChAT阳性细胞数较对照组明显增加(P<0.01);②对照组顶叶皮层、海马中,ChAT阳性细胞数、NGF、TrkA mR...     

神经生长因子对氧合血红蛋白诱导小鼠神经细胞凋亡及神经生长因子受体表达的影响

【目的】研究神经生长因子（NGF）对氧合血红蛋白（Oxynb）诱导的小鼠神经细胞凋亡以及P75NTR和TrkA表达的影响,并进一步探讨Oxynb诱导细胞凋亡及NGF对神经细胞保护作用的可能机制。【方法】雄性健康ICR小鼠随机分为损伤组（24只）、损伤给药组（24只）,脑皮层局部蛛网膜下腔注射Oxynb建立蛛网膜下腔出血的动物模型,尾静脉注射神经生长因子,使用TUNEL法检测细胞凋亡,免疫组织化学法检测P75NTR和Tr—kA表达的情况。【结果】注射0xy硒后出现神经细胞凋亡,P75NTR表达增加,TrkA表达无明显改变,在NGF给药组,神经细胞凋亡数明显减少,P75NTR表达明显降低,TrkA的表达无明显改变。【结论】P75NTR表达的增加提示,其参与了Oxynb诱导的小鼠神经细胞凋亡,而静脉注射NGF可以抑制OxyHb诱导的细胞凋亡,其机制可能是通过与受体结合,从而降低P75NTR表达水平以实现其保护作用。     

甲状腺激素调节脑组织中NGF及其受体

目的我们采用甲减、甲亢、正常对照3组大鼠动物模型,对出生后14天、21天、28天大鼠的海马、顶叶皮质中的NGFmRNA、NGF受体TrkAmRNA、及其阳性细胞进行观察,探索甲状腺激素对上述部位NGF及其受体的调节机制。方法①甲减组:从母鼠孕5～6天始饲含0.02%的他巴唑饮用水,至处死日;②甲亢组:仔鼠出生即日始,腹腔注射T4[0.4μg/(g.d)];③正常对照组:饲以普通饲料及饮用水;采用原位杂交法测定NGFmRNA及其受体TrkAmRNA的表达。结果①在海马及顶叶皮质中,NGFmRNA、TrkAmRNA最高表达时间分别为P21、P28;②在海马及顶叶皮质中,各时点P14、P21、P28,NGFmRNA、TrkAmR-NA表达甲减组均低于正常对照组(P<0.05或P<0.01);甲亢组与正常对照组相比,NGFmRNA于P14、P21有显著差异(P<0.05或P<0.01),TrkAmRNA各时点两组间均无统计学意义。结论甲状腺激素可能通过神经生长因子及其受体TrkA的表达调节海马及顶叶皮质中的神经细胞存活。     

Immunocytochemical evidence that most sensory neurons of the rat molar pulp express receptors for both glial cell line-derived neurotrophic factor and nerve growth factor

Most pulpal afferent neurons have cytochemical features in common with the class of nociceptors that express neuropeptides and respond to NGF, while very few bind the plant lectin IB4, a widely used marker for the class of nociceptors that respond to the GDNF family of neurotrophic factors. The present study was undertaken to determine whether the GDNF receptor, GFRalpha-1, is expressed by pulpal afferents, and, further, to determine whether tooth injury evokes changes in expression of the GDNF and NGF receptors among pulpal afferents. The tracer, fluoro-gold (FG), was applied to shallow cavities in dentin of first and second maxillary molars. After 4 weeks, the molars of one side received a test injury consisting of a deeper cavity that exposed pulp horns. Animals were perfusion fixed 2 days later, and sections of the trigeminal ganglia were double immunostained with combinations of antibodies against GFRalpha-1, and TrkA. Under control conditions, GFRalpha-1 immunostaining was observed in 72% of neurons that projected to the molar pulp, TrkA in 78%, and immunostaining for both receptors was observed in 65% of pulpal afferents. Tooth injury evoked up-regulation of GFRalpha-1 expression (to 93%) and a slight down-regulation of TrkA expression (67%) among tooth afferents, while there was no discernable change in the proportion of pulpal afferents that expressed both TrkA and GFRalpha-1 (to 61%).     

Local Administration of a Synthetic Cell-Penetrating Peptide Antagonizing TrkA Function Suppresses Inflammatory Pain in Rats

Novel agents that inhibit nerve growth factor signaling are required for the treatment of inflammatory pain. The present study investigated the effect of local administration of inhibitory peptide of TrkA (IPTRK3), a synthetic cell-penetrating peptide that antagonizes TrkA function, in complete Freund’s adjuvant (CFA)–induced hyperalgesia in rats. Three hours after subcutaneous injection of CFA into the plantar surface of the rat’s left hind paw, 10 mM IPTRK3 was injected at the same site. Thermal and mechanical hyperalgesia were tested in the ipsilateral hind paw until 7 days after CFA injection. The ipsilateral dorsal root ganglion (DRG) was dissected out for immunohistochemical analysis of transient receptor potential vanilloid subfamily member 1 (TRPV1) channels and TrkA. Local injection of this peptide significantly suppressed both thermal and mechanical hyperalgesia produced by CFA and also significantly reduced TRPV1 expression at the DRG. These results suggest that local administration of IPTRK3 is likely effective in the treatment of inflammatory pain in rats.     

脑出血患者血肿周围脑组织中P75NTR、TrkA的表达及其与细胞凋亡的关系

目的 通过对人脑出血后血肿周围不同区域组织中的P75NTR、TrkA表达的检测,探讨其在脑出血后血肿周围组织细胞凋亡中的作用. 方法采集脑出血血肿清除术患者的脑组织标本,分别运用DNA断裂原位末端标记(TUNEL)法及免疫组化技术检测血肿周围及远隔部位组织中细胞凋亡率与P75NTR、TrkA的表达. 结果相对于远隔部位组织,脑出血后血肿周围组织中的细胞凋亡率与P75NTR的表达水平明显增加(P<0.05),而TrkA的表达水平并没有明显变化(P>0.05).P75NTR的阳性细胞率与TUNEL阳性细胞率呈正相关(r=0.628,p=0.000). 结论脑出血后血肿周围组织中凋亡细胞明显增多,P75NTR介导的细胞凋亡通路可能发挥了重要的作用;TrkA在脑出血发生后并没有增量表达以增加细胞存活,未起到拮抗P75NTR介导的细胞凋亡作用.     

Ebselen, a redox regulator containing a selenium atom, induces neurofilament M expression in cultured rat pheochromocytoma PC12 cells via activation of mitogen-activated protein kinase

We found that ebselen [2-phenyl-1,2-benzisoselenazol-3(2H)-one] caused phosphorylation of mitogen-activated protein kinase (MAPK), followed by expression of neurofilament-M, a neuron-specific protein, in cultured PC12 rat pheochromocytoma cells. The ebselen-induced MAPK activation was suppressed by U0126, an inhibitor of MAPK kinase (MEK1/2), but not by K252a, a selective inhibitor of Trk family tyrosine kinases; AG1478, an antagonist of epidermal growth factor receptor (EGFR); pertussis toxin, an inhibitor of Gi/o; or GP antagonist-2A, an inhibitor of Gq. Furthermore, we observed that N-acetyl-L-cysteine, an inhibitor of tyrosine kinases, suppressed ebselen-induced MAPK activation and buthionine sulfoximine, an activator of protein tyrosine phosphatases, enhanced the effect, indicating that ebselen activated MEK1/2 through one or more tyrosine kinases. Based on these results, we propose that ebselen stimulated intracellular tyrosine kinase activity, thus activating a MAPK cascade (tyrosine kinase-MEK1/2-ERK1/2) in PC12 cells and that this activation resulted in their neuronal differentiation.