神经营养因子受体p75NTR可谓节肝脏修复

据医业网3月22日报道（原载Science 2007；315：1853—1856），肿瘤坏死因子受体家族成员神经营养因子受体p75NTR，对于指导肝脏纤维变性和硬化受损修复期间发生的肝星形细胞（HSCs）分化起重要作用。[第一段]     

肿瘤坏死因子受体p55、p75与急性胰腺炎

急性胰腺炎是一种常见疾病,尽管其诱发因素各不相同,但病理生理过程均始于胰腺细胞破坏。近年来的研究,特别是急性胰腺炎动物模型的研究表明,胰腺腺泡破坏之后,炎症局灶处细胞因子大量释放并逸入体循环,在严重病例可导致全身性炎症反应综合征(SIRS)和多器官衰竭(MOF)。肿瘤坏死因子(TNF)是细胞因子网络的启动因子,可诱导白细胞介素(IL)-6、IL-8等促炎细胞因子的产生,是一种重要的全身反应性介质,在急性胰腺炎中起关键作用;而TNF受体(TNFR)则是TNF发挥作用的重要相关受体,影响着疾病的严重程度和转归。本文对TNFR-p55、TNFR-p75这两种受体的结构、功能、性质及其与急性胰腺炎的关系作一综述。     

p75 神经营养因子受体在心血管系统中的作用

p75神经营养因子受体属于神经营养因子的受体之一。越来越多的研究表明,p75NTR在心血管系统自主神经中发挥重要的作用,不仅促进交感神经的生长发育,还调节心脏神经递质的释放。p75NTR还抑制新生血管形成,具有一定的抗血管生成作用,且介导平滑肌细胞凋亡,加重血管粥样硬化损伤。p75NTR这些特性表明其抑制剂存在重要的治疗潜能,或许能够改善缺血所致的损伤,如冠心病、急性心肌梗死、周围血管病变等。     

神经营养因子受体的研究进展

神经营养因子家族在神经细胞的生长发育、保护修复过程中起着极其重要的作用.而神经营养因子受体是启动信号转导,产生生物学效应的重要物质.根据同源性大小、基因表达部位和蛋白作用的专一性以及信号传递机制的不同,可将神经营养因子分为三个家族:神经生长因子家族、睫状神经营养因子家族和胶质细胞源性神经营养因子.本文从结构、功能、信号传递机制等方面,对其相应受体的最新研究进展作一综述.     

p75神经营养因子受体在脑缺血后神经元凋亡中的作用

p75神经营养因子受体(p75 neurotrophin receptor, p75 NTR)为肿瘤坏死因子受体超家族成员,通过与原肌球蛋白受体激酶(tropomyosin receptor kinase, Trk)受体相互作用或与神经营养因子结合,介导多种复杂的信号转导通路,诱导突触生长和影响细胞存亡。急性...     

神经营养因子研究进展

<正>神经营养因子(NTF)在神经元和非神经元细胞的增殖、存活、死亡方面起重要作用。NTF作为信号分子可能介导大脑的高级活动,例如学习、记忆、行为等。NTF还在神经系统中起调节突触连接、突触结构和神经递质的释放和增强等作用。NTF水平的改变可能会导致阿尔茨海默病(AD)或亨廷顿病等神经退行性疾病的发生,还会导致抑郁症、滥用药物等精神障碍〔1~3〕。本文就NTF研究进展作一综述。     

肿瘤坏死因子受体p55/p75在重症急性胰腺炎发病机制中的作用

目的探讨肿瘤坏死因子受体p55/p75(TNFR p55/TNFR p75)在重症急性胰腺炎(SAP)发病机制中的作用。方法36只雄性SD大鼠均分为对照组与SAP组。SAP组采用5%牛黄胆酸钠1ml/kg胰胆管逆行穿刺注射建立模型,对照组仅给予剖腹假手术。两组大鼠分别在造模后3、6和12h处死,收集外周血与胰腺标本。ELISA法检测血清TNFα水平,RT PCR法检测外周血单个核细胞(PBMC)与胰腺组织中TNFR p55/TNFR p75mRNA表达,采用血清淀粉酶与病理组织学评分作为SAP严重程度的指标。结果SAP组不同时间点血清淀粉酶、TNFα水平及胰腺组织炎症评分均显著高于对照组(P<0.01)。在PBMC中TNFR p55/TNFR p75mRNA的表达在各时间点均较对照组显著上调(P值均<0.01),且在6h达峰值,分别为1.32±0.07和0.95±0.04;而对照组在6h点为0.84±0.01和0.68±0.04。胰腺组织中TNFR p55/TNFR p75mRNA的表达在各时间点也均高于对照组(P值均<0.05)。结论TNFα是SAP病程中重要的细胞因子并可能通过结合胰腺组织中TNFR p55/TNFR p75参与胰腺组织损伤;同时,TNFα又可能通过与PBMC中TNFR p55/TNFR p75相互作用导致外周血中白细胞活化,从而加重胰腺炎的严重程度。     

神经营养因子及其受体与胰腺癌的关系

神经营养素(Neurotrophins,NTs)可在多种肿瘤细胞中表达,而且在不同的肿瘤中作用也不相同,主要取决与肿瘤细胞的类型。近年研究发现,NGF及其受体TrKA的表达在肿瘤发生、进展及预后评估等方面具有重要作用[1],因此NTs和它们的受体与癌基因的关系越来越受到人们的重视,现将近年来     

神经营养因子受体Trk小分子激动剂研究进展

神经营养因子作用于Trk受体酪氨酸激酶后能激活细胞内磷酸肌醇3-激酶、细胞外信号调节激酶等信号通路,促进神经元的存活和分化。开发非肽类小分子Trk激动剂以及神经营养因子模拟物,能够在激动Trk受体信号转导的同时避免神经营养因子的诸多缺点,为治疗神经系统疾病提供了新的治疗思路。     

阿尔茨海默病中脑源性神经营养因子及其受体的变化

阿尔茨海默病是一种进行性中攀神经系统神经变性疾病,脑源性神经营养因子为一类在脑内广泛分布的神经营养因子类物质。由于它所具有的神经保护作用,和／或其体的含量变化可能与阿尔海默病的发病有关,研究发现,阿尔茨海默病患者脑内脑源性神经营养因子及其受体的水平确有降低;阿尔茨海默病动物模型中,脑源性神经营养因子可以在一定程度上缓解神经元变性。     

Expression of the p75 neurotrophin receptor in acute leukaemia

The dLNGFR is a cytoplasmically deleted form of the low-affinity nerve growth factor receptor (LNGFR, also known as p75NTR). Recently, we observed a myeloid leukaemia in mice transplanted with dLNGFR-modified bone marrow cells. Retroviral-mediated expression of dLNGFR was suspected to contribute to the murine leukaemia. This led us to investigate the expression of p75NTR in human leukaemia. Expression of p75NTR was observed in nine of 119 (8%) adult patients with acute leukaemia by flow cytometry analysis, particularly in acute lymphoblastic leukaemia (26%). These results support further detailed analyses of neurotrophin receptors and downstream signalling pathways in haematological malignancies.     

Up-regulation of p75 neurotrophin receptor (p75NTR) is associated with apoptosis in chronic pancreatitis

Activation of apoptosis in chronic pancreatitis has been demonstrated. The low-affinity neurotrophin receptor p75 (p75NTR) mediates apoptosis in many cell types in vivo and in vitro. The aim of this study was to examine whether p75NTR is involved in the apoptotic process in chronic pancreatitis. The quantity and localization of the receptor was evaluated using northern blot analysis, in situ hybridization, immunohistochemistry, and western blot analysis. Apoptosis was determined by TUNEL assay. By northern blot analysis, p75NTR mRNA levels were increased 40-fold in chronic pancreatitis compared with normal pancreas (P < 0.01). in situ hybridization revealed weak p75NTR mRNA expression in some ductal cells in the normal pancreas. In contrast in chronic pancreatitis moderate p75NTR expression was present in acinar cells next to fibrosis, ductal cells, and cells of ductular structures as well as in some islet cells. Immunostaining of p75NTR in normal pancreas and chronic pancreatitis tissue samples showed a similar intensity and distribution pattern as found by in situ hybridization. Higher p75NTR protein levels could be confirmed by western blot analysis, which revealed an 8.6-fold increase of p75NTR in chronic pancreatitis. TUNEL staining showed, in chronic pancreatitis samples, positivity in some acinar cells next to fibrosis, some ductal cells, and cells of ductular structures. Also some islet cells were positive by TUNEL staining. The presence of p75NTR immunoreactivity was positively correlated (P < 0.05) with the apoptotic index in the exocrine and endocrine pancreas. In conclusion, p75NTR, the low-affinity receptor of neurotrophins which mediates apoptosis, is up-regulated in CP and is involved in the apoptotic process of the exocrine and endocrine pancreas.     

姜黄素对人肝星状细胞中神经生长因子及其低亲和力受体表达的影响

目的观察姜黄素对人肝星状细胞(HSC)中神经生长因子(NGF)及其低亲和力受体P75NTR表达的影响,探讨姜黄素逆转肝纤维化的可能机制。方法体外培养人HSC株LX-2,分别给予0~80μmol/L不同浓度的姜黄素作用于LX-2,MTT法检测细胞增殖;选取30~50μmol/L姜黄素分别作用于LX-2,细胞免疫化学染色检测NGF和P75NTR表达,计算阳性细胞率。结果 10~20μmol/L姜黄素作用下LX-2增殖与对照组相比,差异无统计学意义(P0.05);在30~80μmol/L浓度范围内,LX-2增殖显著降低(P0.05);在30~50μmol/L浓度范围内,NGF蛋白表达率分别为(46.59±8.15)%、(90.75±4.72)%、(83.32±4.78)%,对照组为(27.11±5.50)%;P75NTR为(37.17±4.71)%、(88.74±6.27)%、(83.79±4.70)%,对照组为(24.33±5.17)%,差异均有统计学意义(P0.01)。结论姜黄素可诱导人HSC中NGF和P75NTR的蛋白表达,这可能是姜黄素逆转肝纤维化的机制之一。     

大鼠肝纤维化自发逆转过程中肝星状细胞凋亡与p75的表达

肝星状细胞（HSC）凋亡是肝纤维化逆转的主要机制之一。人和大鼠的HSC表达低亲和力神经生长因子受体p75，当p75与神经生长因子（NGF）结合时可引起细胞凋亡。本研究通过建立四氯化碳（CCl4）肝纤维化大鼠模型，对肝纤维化自发逆转过程中HSC凋亡和p75表达进行了研究。     

Activated hepatic stellate cells overexpress p75NTR after partial hepatectomy and undergo apoptosis on nerve growth factor stimulation.

BACKGROUND: Expression of neurotrophins (NTs) and their receptors is increased during hepatic regeneration, but their role is not well understood. METHODS: NTs and their receptors were investigated by RT-PCR and immunostaining in regenerating livers after two-thirds hepatectomy (PH) and in hepatocytes and hepatic stellate cells (HSCs) isolated from regenerating livers in mice. Induction of apoptosis after treatment with NGF and the expression of alpha-smooth muscle actin (SMA), interleukin 6 (IL-6) and hepatocyte growth factor (HGF) were also investigated in regenerating HSCs. RESULTS: Nerve growth factor (NGF) and p75 NT receptor (p75NTR) mRNA were elevated after PH, while other NTs and NT receptors showed no remarkable change. NGF was detected in regenerating hepatocytes, but not in normal hepatocytes. Regenerating HSCs expressed increased p75NTR and SMA in vivo and showed an activated phenotype and the high expression of HGF and IL-6 in vitro. Enhanced cell death was seen in HSCs, both from normal and regenerating liver, after treatment with NGF. CONCLUSIONS: Although activated HSCs may produce the factors that regulate liver regeneration, the de novo NGF production by regenerating hepatocytes may induce the death of activated HSCs via p75NTR, leading to termination of hepatic regeneration.     

The neurotrophin receptor p75NTR modulates long-term depression and regulates the expression of AMPA receptor subunits in the hippocampus

Neurotrophins are involved in the modulation of synaptic transmission, including the induction of long-term potentiation (LTP) through the receptor TrkB. Because previous studies have revealed a bidirectional mode of neurotrophin action by virtue of signaling through either the neurotrophin receptor p75NTR or the Trk receptors, we tested the hypothesis that p75NTR is important for longterm depression (LTD) to occur. Although LTP was found to be unaffected in hippocampal slices of two different strains of mice carrying mutations of the p75NTR gene, hippocampal LTD was impaired in both p75NTR-deficient mouse strains. Furthermore, the expression levels of two (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits, GluR2 and GluR3, but not GluR1 or GluR4, were found to be significantly altered in the hippocampus of p75NTR-deficient mice. These results implicate p75NTR in activity-dependent synaptic plasticity and extend the concept of functional antagonism of the neurotrophin signaling system.     

Abnormal cell proliferation in the p75NTR‐positive basal cell compartment of the esophageal epithelium during squamous carcinogenesis

The low affinity neurotrophin receptor p75NTR is known to be expressed in the mitotically quiescent basal layer (BL) of the normal esophageal epithelium. The aim of the present study was to detect oncogenic changes in the p75NTR‐positive BL during esophageal squamous carcinogenesis. The normal epithelium (NE), low‐grade intraepithelial neoplasia (LGN), high‐grade intraepithelial neoplasia (HGN), and esophageal squamous carcinoma (SCC), in which invasion was limited to the muscularis mucosa, were obtained from surgically removed esophagi. The expression of p75NTR, the proliferation marker ki67, hTERT, p53, and p63 was examined immunohistochemically. The expression of p75NTR was detected in these tissues with average staining indexes (number of stained cells/100 nucleated cells; SI) of 1.00, 0.99, 0.81, and 0.73, respectively. The expression of ki67 in the BL significantly increased with the progression from LGN to HGN. The expression of hTERT and p53 significantly increased with the progression from NE to LGN, and then increased in a stepwise manner in HGN and SCC, with SI (hTERT/p53) of 0.10/0.11, 0.32/0.45, 0.50/0.72, and 0.65/0.61, respectively. The expression of p63 showed no significant difference among NE, LGN, HGN, and SCC, with SI of 0.82, 0.77, 0.85, and 0.87, respectively. A correlation was observed between the expression of ki67 and p53 (P = 0.005), while a negative correlation was found between p75NTR and hTERT (P = 0.01). Our results demonstrated that phenotypic changes from quiescent to active proliferation in the p75NTR‐positive BL occurred during the progression from LGN to HGN. The altered expression of hTERT and p53 in the BL was detected in LGN, which suggested that additional oncogenic events that disrupt mitotic regulation in the p75NTR‐positive quiescent BL may play a crucial role in malignant transformation. Further investigations using the isolation and tracing of p75NTR‐positive cells in precancerous epithelia may provide us with a better understanding of squamous carcinogenesis.     

Low-affinity nerve growth factor receptor p75NTR immunoreactivity in the myocardium with sympathetic hyperinnervation

INTRODUCTION: We previously demonstrated the relationship between sympathetic nerve density in myocardium and the occurrences of ventricular arrhythmia. Nerve growth factor (NGF) regulates myocardial sympathetic innervation. However, it is unclear whether the NGF high-affinity receptor tyrosine kinase A (TrkA) and the NGF low-affinity receptor p75NTR are altered in the state of sympathetic hyperinnervation in the heart. The aim of this study was to determine the density and location of TrkA and p75NTR in canine ventricles with sympathetic hyperinnervation. METHODS AND RESULTS: Myocardial sympathetic hyperinnervation was induced by local infusion of NGF into myocardium or left stellate ganglia, or chronic subthreshold electric stimulation to the left stellate ganglia. The results showed that TrkA immunoreactivity was absent in the myocardium. Low-affinity receptor p75NTR immunoreactivity was present in axons, Schwann cells, and interstitial cells of sympathetic nerves, as well as in interstitial cells of the myocardium. The density of p75NTR immunolabeled myocardial interstitial cells at the NGF infusion site was lower than that at the site remote from NGF infusion, yet the sympathetic nerve density was higher at the infusion site than the remote area. The density of p75NTR also was lower in the myocardium with high sympathetic nerve density, induced by NGF infusion or chronic electric stimulation of the left stellate ganglia, compared to control groups. CONCLUSION: The data indicate that p75NTR may be the main NGF receptor in the myocardium, and p75NTR immunopositive interstitial cells may have a role in regulating sympathetic nerve growth in canine heart.     

High nerve growth factor receptor (p75NTR) expression is a favourable prognostic factor in paediatric B cell precursor-acute lymphoblastic leukaemia

Nerve growth factor (NGF) plays a pivotal role in cellular survival/death decisions with the low affinity receptor p75NTR predominately transmitting anti-proliferative signals. In spite of its established role in B-cell function and identification as a prognostically favourable marker in a number of malignancies, little is known about the expression pattern and prognostic significance of p75NTR in B cell precursor-acute lymphoblastic leukaemia (BCP-ALL). p75NTR expression was prospectively studied on primary ALL-blasts in a cohort of paediatric patients with common ALL (n = 86) and preB-ALL (n = 34) treated within the Co-operative study group for childhood acute lymphoblastic leukaemia (CoALL) protocol, CoALL06-97. Flow cytometric analysis showed that almost half of the patients expressed no or negligible amounts of p75NTR (<10%). The median expression in patients expressing p75NTR beyond that threshold was 49% (range 11-100%). In patients classified as low-risk at diagnosis, p75NTR expression was significantly higher than in high-risk patients (P = 0.001). Of note, p75NTR expression was lower in the 21 patients who subsequently developed relapse compared with those remaining in remission (P = 0.038). Accordingly, relapse-free survival was significantly better in patients expressing high surface p75NTR (P = 0.041). Thus, in this prospective analysis, high p75NTR expression was a strong prognostic marker that identified a group of paediatric ALL patients with favourable outcome.