下调脑源性神经营养因子/酪氨酸受体激酶B信号通路可降低孤独症模型鼠海马神经元过度增殖并改善症状

目的:探讨脑源性神经营养因子(BDNF)/酪氨酸受体激酶B(TrkB)信号通路活性下调对孤独症大鼠模型海马神经干细胞增殖的影响及其治疗作用。方法:采用Wistar妊娠母鼠在孕期12.5 d时腹腔注射丙戊酸法建立子代孤独症大鼠模型,断乳后给予侧脑室注射K252a,以下调BDNF/TrkB通路活性,应用5-溴脱氧尿嘧啶核苷(BrdU)免疫荧光观察海马神经干细胞的增殖变化,并采用水迷宫检测子代孤独症大鼠模型的学习记忆行为。结果:与对照组比较,孤独症大鼠模型海马BDNF/TrkB通路活性上升,表现为其效应分子环磷酸腺苷反应元件结合蛋白(CREB)表达显著增加,模型组海马神经干细胞增殖也显著增加;BrdU免疫荧光显色显示,K252a处理能逆转大鼠模型海马神经干细胞的过度增殖,同时,水迷宫行为学检测显示,K252a处理显著改善大鼠模型的学习记忆能力。结论:下调BDNF/TrkB通路活性可以减轻孤独症模型大鼠海马神经干细胞过度增殖并改善症状,为孤独症的临床治疗提供了实验依据。     

仙茅苷对老年痴呆模型大鼠学习记忆能力及海马BDNF/TrkB表达的影响

目的探讨仙茅苷对老年痴呆模型大鼠学习记忆能力及海马脑源性神经营养因子/酪氨酸激酶受体B(BDNF/TrkB)表达的影响。方法 36只健康成年SD大鼠,随机分为对照组、模型组与仙茅苷组,每组l2只。采用皮下注射D-半乳糖联合双侧海马注射Aβ25-35构建痴呆模型大鼠,仙茅苷灌胃8周后,Morris水迷宫方法观察各组大鼠的学习记忆能力,免疫组织化学方法和Western Blot方法检测各组大鼠海马BDNF与TrkB的表达,real time PCR方法检测各组大鼠海马BDNF mRNA与TrkB mRNA的表达。结果与对照组相比,模型组大鼠的平均潜伏期明显延长,探索次数明显减少;与模型组相比,仙茅苷组大鼠的平均潜伏期明显缩短,探索次数明显增加。模型组大鼠海马BDNF与TrkB mRNA与蛋白表达水平显著低于对照组;而仙茅苷组大鼠在给予治疗后显著高于模型组。结论仙茅苷能够提高老年痴呆模型大鼠学习记忆能力,可能与激活BDNF/TrkB信号通路相关。     

老龄大鼠海马结构脑源性神经营养因子表达的改变

目的：探讨大鼠海马结构脑源性神经营养因子（BDNF）表达的老龄性改变，为脑衰老提供可靠的免疫组织化学资料。方法：选用雌性Wistar大鼠24只，分为青年组和老龄组。应用免疫组化方法结合图像分析技术对2组大鼠海马结构BDNF阳性产物进行定性、定量分析。结果：老龄组海马CA3和CA1区神经元BDNF含量比青年组分别下降了13．3％、10．4％，然而，齿状回从青年到老年变化不显著。结论：老龄时海马CA3和CA1区神经元的BDNF表达发生了明显的变化，其含量明显降低。提示老龄大鼠海马CA3和CA1区神经元BDNF表达的改变，可能是老龄动物海马结构营养及学习记忆障碍的形态学基础。     

侧脑室注射PP2对慢性复合应激大鼠学习记忆功能和海马内Fyn、BDNF和TrkB表达的影响

为了探讨酪氨酸激酶抑制剂PP2对慢性复合应激性学习记忆增强大鼠的学习记忆功能和海马内非受体酪氨酸激酶(Fyn)、脑源性神经营养因子(BDNF)和Trk酪氨酸激酶B(TrkB)表达的影响,本实验将成年雄性大鼠22只,随机分为三组:即慢性复合应激组(对照组)、慢性复合应激+注射盐水组(盐水组)和慢性复合应激+注射PP2组(PP2组)。全部动物暴露于复合应激原中6周后,盐水组和PP2组动物分别侧脑室注射生理盐水或PP2(1次/d,共11d)。实验结束后,用Morris水迷宫测试大鼠的空间学习记忆成绩;采用免疫组织化学方法检测Fyn、BDNF和TrkB在海马内蛋白表达的变化。结果显示:与对照组和盐水组相比,PP2组动物的学习与记忆成绩明显下降(P<0.05);海马内Fyn和BDNF蛋白阳性表达减弱(P<0.05);但3组动物海马内TrkB的蛋白表达无显著性差异(P>0.05)。上述结果表明:侧脑室注射PP2可抑制大鼠慢性复合应激性学习记忆能力的增强作用,下调Fyn和BDNF在海马内的表达;提示Fyn和BDNF/TrkB信号转导途径在慢性复合应激增强大鼠学习记忆能力的过程中发挥重要作用。     

脑源性神经营养因子与癫痫

癫痫发作可诱导海马内脑源性神经营养因子(BDNF)水平上调,进而激活海马门区及CA3区腔隙层的TrkB受体,通过促进兴奋性神经递质释放等效应加强海马通路尤其是苔状纤维的兴奋性突触传递,从而导致持续的高度兴奋状态;而阻断BDNF信号转导通路则可抑制癫痫发生.提示BDNF在癫痫发作过程中具有重要作用,进一步阐明其细胞分子机制将为探索癫痫治疗手段提供新途径.     

脑源性神经营养因子在衰老和神经系统退行性变中的作用研究进展

脑源性神经营养因子(brain-derived neurotrophic factor,BDNF)是神经营养因子家族中的一员,在维持神经元的生长、分化和神经损伤后的修复与再生中发挥重要作用.海马和大脑皮质被认为是认知、学习和记忆的高级中枢,而认知和记忆能力会随着衰老而逐渐减退,其原因与海马和大脑皮质内,特别是海马内神经元的突触可塑性改变有关.     

脑卒中后抑郁大鼠海马BDNF及其受体TrkB蛋白的表达变化

目的:探讨脑卒中后抑郁(PSD)大鼠海马脑源性神经营养因子(BDNF)及其高亲和力受体酪氨酸激酶B(TrkB)蛋白的表达变化。方法:24只雌性SD大鼠随机分为正常组、抑郁组、脑卒中组及PSD组,每组6只。采用线栓法建立局灶性脑缺血(卒中)模型;采用孤养方法建立抑郁模型;局灶性脑缺血模型加以慢性不可预见的中等应激刺激和孤养法建立PSD模型;并设正常组做为正常对照。应用免疫组化检测各组大鼠造模后第29天大鼠海马BDNF和TrkB免疫阳性细胞数的表达变化。结果:PSD组海马BDNF免疫阳性细胞数最少[(8.56±1.67)个/视野]。PSD组、抑郁组及脑卒中组与正常对照组相比BDNF阳性细胞数均明显减少(P0.05);PSD组海马TrkB免疫阳性细胞数最少[(6.44±1.13)个/视野],与各对照组相比,差异均有统计学意义(P0.05)。结论:PSD大鼠海马BDNF及其高亲和力受体TrkB蛋白表达减少可能在PSD发病过程中发挥了一定的作用。     

大鼠体神经-内脏神经吻合后脑源性神经营养因子及其受体的表达变化

为了研究大鼠体神经-内脏神经吻合后脑源性神经营养因子(BDNF)及其受体酪氨酸激酶B(TrkB)在脊髓前角神经元中的表达变化,以正常大鼠为对照,运用RT-PCR技术检测大鼠体神经-内脏神经吻合术后不同时间脊髓腰4(L4)前角神经元中BDNF及TrkB mRNA的表达变化。结果显示,在正常大鼠L4前角神经元中,BDNF及TrkB的mRNA均存在一定水平的表达;体神经-内脏神经吻合术后7d、14d、1m和2m,BDNF和TrkBm RNA的表达均升高,术后7d达到高峰,14d开始下降;2m时BD-NF mRNA的表达量仍显著高于正常组(P<0.01),而TrkB mRNA的表达量到2m时虽仍高,但与正常组相比,其差异已无统计学意义(P>0.05)。上述结果表明,大鼠体神经-内脏神经反射弧建立后,脊髓L4前角神经元的内源性BDNF及其受体TrkB的表达均增高,它们可能作为保护性因子有利于受损神经元的存活和再生。     

脑源性神经营养因子对学习和记忆作用的研究进展

脑源性神经营养因子(BDNF)在中枢神经系统中生物学效应非常广泛,本文探讨了BDNF通过胆碱能神经系统、海马LTP以及小脑等方面对学习和记忆所产生的作用,总结了近年来的研究进展.     

BDNF对慢性应激性大鼠海马神经元损伤的保护作用

目的研究脑源性神经营养因子(BDNF)对大鼠海马神经元的保护作用。方法40只成年Wistar大鼠随机分为对照组、应激组、BDNF低剂量组和高剂量组,每组10只。用电击足底结合噪声建立慢性应激大鼠模型,Morris水迷宫观察动物的空间学习和记忆能力,Nissl染色观察和计数海马神经元数量,Fara-2荧光法测海马突触体内游离钙浓度。结果在双海马注射BDNF后,对于因慢性应激引起的空间学习和记忆能力下降,海马神经元数量减少,海马突触体内游离钙浓度增高有明显保护作用。结论BDNF对应激海马损伤有保护作用,其机制可能是通过调节海马细胞内的钙浓度,防止海马神经细胞丢失有关。     

BDNF Meditated trkB and Synapsin I Changes within the Hippocampus after Mild Traumatic Brain Injury in Rat:Reflections of Injury-induced Neuroplasticity

1 IntroductionTraumatic brain injury (TBI) can produce chronic cognitive learning/memory deficits that are thought to be mediated, in part, by impaired hippocampal function. Brain-derived neurotrophic factor (BDNF), its signal transduction receptor trkB and its downstream effector synapsin I are involved in this period. BDNF, trkB and the slope of field excitatory post-synaptic potential(fEPSP) were measured in the hippocampus of rat after fluid percussion brain injury (FPI). Isofluorane anaesthe- tizeed 50...     

Spatial memory training modifies the expression of brain-derived neurotrophic factor tyrosine kinase receptors in young and aged rats

Aging leads to alterations in the function of the hippocampus, a brain structure largely involved in learning processes. This study aimed at examining the basal levels and the impact of a learning-associated task on brain-derived neurotrophic factor (BDNF), on BDNF full-length catalytic receptor (TrkB.FL) and on the truncated forms (TrkB.T1 and TrkB.T2) receptor expression (mRNA and protein) in the hippocampus of young (2-month-old) and aged (24-month-old) Wistar rats. Spatial memory was evaluated using a water-maze procedure involving visible and invisible platform location learning. Aged rats showed higher latencies during the first two training days but rapidly exhibited learning performances similar to patterns observed with young rats. Real-time PCR measurements showed that aged rats had significantly higher levels of trkB.FL mRNAs than young rats under basal conditions. In situ hybridization analysis indicated that the highest level of trkB.FL mRNA (mRNA encoding for TrkB.FL receptor) was noted in the dentate gyrus, and in the CA2 and CA3 hippocampal layers. In contrast, there was no marked difference in trkB.T1 signal in any hippocampal region. Training induced a significant reduction in trkB.FL mRNA levels solely in aged rats. In contrast, in young and aged rats, trkB.T2 mRNA levels were significantly increased after training. Measurements of proteins revealed that learning significantly increased TrkB.FL content in aged rats. Untrained aged rats presented higher levels of BDNF and brain-derived neurotrophic factor precursor (proBDNF) proteins than young rats. Training strongly increased precursor BDNF metabolism in young and aged rats, resulting in increased levels of proBDNF in the two groups but in old rats the mature BDNF level did not change. This study shows that Wistar rats present age-related differences in the levels of BDNF and TrkB isoforms and that spatial learning differentially modifies some of these parameters in the hippocampus.     

TrkB but not trkC receptors are necessary for postnatal maintenance of hippocampal spines

Dendritic spines are major sites of excitatory synaptic transmission and changes in their densities have been linked to alterations in learning and memory. The neurotrophins brain-derived neurotrophic factor and neurotrophin-3 and their receptors, trkB and trkC, are thought to be involved in learning, memory and long-term potentiation (LTP). LTP is known to induce trkB and trkC gene expression as well as spinogenesis in the hippocampus. In the aging hippocampus, declines in trkB and trkC mRNA levels may underlie, at least in part, impairments in spatial memory and reductions in spine densities. To determine the significance of trkB and trkC for the maintenance of dendritic spines, we have analyzed Golgi-impregnated hippocampi of adult and aged mice heterozygous for trkB, trkC, or both along with respective wildtype littermates. Deletion of one allele of trkB, but not trkC, significantly reduces spine densities of CA1 pyramidal neurons in both adult and aged mice, as compared to age-matched controls. This indicates that trkB, but not trkC, receptors are necessary for the maintenance of hippocampal spines during postnatal life.     

Expression of trkB in human neuroblastoma in relation to MYCN expression and retinoic acid treatment

Expression of full-length trkB can be found in some highly malignant neuroblastoma tumors with an amplified MYCN gene. This contrasts sympathetic neuroblasts, from which neuroblastomas are thought to arise, which neither express trkB nor are dependent on the p145(trkB) ligands, brain-derived neurotrophic factor (BDNF) or neurotrophin-4/5, for their normal development. In this study we show that trkB was expressed in two out of five neuroblastoma tumors with amplified MYCN, while no trkB expression was observed when the MYCN gene was overexpressed in a non-MYCN-amplified neuroblastoma cell line. This shows that MYCN overexpression per se is not sufficient to induce trkB expression. trkB expression and BDNF responsiveness in neuroblastoma cells can be induced by all-trans-retinoic acid (RA). When SH-SY5Y cells were stimulated with a combination of RA and BDNF, norepinephrine and tyrosine hydroxylase levels were unaltered, showing that the cells did not change toward a more catecholaminergic sympathetic phenotype. However, expression of growth-associated protein 43, indicative of a neuronal phenotype, was elevated. Vesicular acetylcholine transporter, choline acetyl transferase, and neuropeptide tyrosine mRNA levels also increased in RA-BDNF-treated cells, which could suggest that these cells develop into a sympathetic cholinergic phenotype. In addition, treatment with RA-induced expression of the platelet-derived growth factor receptor-alpha. As previously shown for BDNF, platelet-derived growth factor stimulated growth of the RA-treated cells, findings that could have clinical relevance. If these receptors mediate a mitogenic signal in vivo also, this might limit the effect of RA treatment on neuroblastoma patients.     

TrkB-like immunoreactivity in the song system of developing zebra finches

The neural song system in zebra finches develops for approximately the first 2 months after hatching. During that time, male-biased sexual dimorphisms emerge in the volume of song control nuclei as well as in the number and size of neurons within them. Brain derived neurotrophic factor (BDNF) has been documented in song control nuclei at various stages of development. Its high affinity receptor (tyrosine kinase B; trkB) is also in the song system, at least at around I month of age. The present study was designed to more completely describe the timing and potential location of BDNF action by investigating trkB expression during sexual differentiation of the song control nuclei. The pattern of immunoreactivity to a trkB antibody was examined in male and female zebra finches at post-hatching days 3-60. Labeling in somata and neuropil appeared to define the telencephalic components of the motor pathway (high vocal center and robust nucleus of the archistriatum) for song production in males from days 30 to 60, and in females on days 45 and 60 (high vocal center). These results are consistent with the hypothesis that the receptor, and its ligand BDNF, play a role in processes related to song learning in both sexes, including perhaps the motor component exhibited by developing males.     

Age-related changes in brain-derived neurotrophic factor and tyrosine kinase receptor isoforms in the hippocampus and hypothalamus in male rats

A large amount of aging individuals show diminished cognitive and endocrine capabilities. The main brain areas involved in these changes are the hippocampus and hypothalamus, two regions possessing high plasticity and implicated in cognitive and endocrine functions, respectively. Among neurotrophins (considered as genuine molecular mediators of synaptic plasticity), brain-derived neurotrophic factor (BDNF) exhibits in adult rats, the highest concentrations in the hippocampus and hypothalamus. Most of neuronal effects of BDNF are mediated through high-affinity cell surface BDNF tyrosine kinase receptors (TrkB). Different TrkB isoforms are issued by alternative splicing of mRNA encoding for TrkB (trkB mRNA) generating at least three different TrkB receptors with different signaling capabilities. The goal of this study was to examine simultaneously the expression (mRNAs and proteins) of BDNF and its three specific receptors, in the hippocampus and hypothalamus throughout lifespan in rats. We observed that BDNF essentially increased during the first 2 postnatal weeks in the hippocampus and hypothalamus, with no close correlation to its mRNA levels. In these regions, mRNA encoding for BDNF full-length catalytic receptor (trkB.FL mRNA) showed no important changes throughout life but of the mRNA truncated forms of TrkB receptors (trkB.T1 mRNA and trkB.T2 mRNA) trkB.T1 mRNA strongly increased after birth, then remaining stable during aging. trkB.T2 mRNA gradually decreased from 1 postnatal week becoming undetectable in the hippocampus in old-rats. Proteins issued from these mRNAs showed substantial quantitative modifications with aging. From 2 months old, the BDNF full-length catalytic receptor (TrkB.FL) gradually and significantly decreased in the hippocampus and the hypothalamus. Of the truncated forms of TrkB receptors (TrkB.T1 and TrkB.T2) TrkB.T1, which is essentially localized in glial cells, significantly increased from the first postnatal week in the hippocampus and in the hypothalamus, remaining stable during aging but reduced in old rats. TrkB.T2 which similarly to TrkB.FL has a neuronal localization also gradually decreased in the hippocampus and in the hypothalamus throughout lifespan. These reductions were significant at 21 and 30 days old, respectively. All the changes reported here could contribute to the reduced plasticity of these regions observed in old rats.     

去脑皮层血管对大鼠前脑大细胞基底核AChE、ChAT、BDNF、trkB及其mRNA表达的影响

本研究采用去除大鼠皮层血管建立的血管性痴呆模型。去除皮层血管后 ,发现大鼠前脑大细胞基底核胆碱能神经元的ACh E、Ch AT、BDNF、trk B及其 m RNA的表达明显降低。结果说明 ,去皮层血管后造成的大细胞基底核的损害是继发皮质损害的逆行性变性 ,大鼠去皮层血管后 ,皮质、海马等处神经元靶源性的 BDNF、trk B及其 m RNA的表达降低 ,逆行性运输到大细胞基底核的胆碱能神经元的 BDNF减少 ,导致大细胞基底核神经元的变性、坏死     

Differential regional expression patterns of α-synuclein, TNF-α, and IL-1β; and variable status of dopaminergic neurotoxicity in mouse brain after Paraquat treatment

Background

During inflammation, immune cells accumulate in damaged areas and release pro-inflammatory cytokines and neurotrophins. Brain-derived neurotrophic factor (BDNF) plays a neuromodulatory role in spinal cord dorsal horn via the post-synaptic tyrosine protein kinase B (trkB) receptor to facilitate pain transmission. However, the precise role of BDNF and trkB receptor in the primary sensory neurons of dorsal root ganglia (DRG) during inflammation remains to be clarified. The aim of this study was to investigate whether and how BDNF-trkB signaling in the DRG is involved in the process of inflammatory pain.

Methods

We used complete Freund's adjuvant- (CFA-) induced and tumor necrosis factor-α- (TNF-α-) induced inflammation in rat hindpaw as animal models of inflammatory pain. Quantification of protein and/or mRNA levels of pain mediators was performed in separate lumbar L3-L5 DRGs. The cellular mechanism of TNF-α-induced BDNF and/or trkB receptor expression was examined in primary DRG cultures collected from pooled L1-L6 DRGs. Calcitonin gene-related peptide (CGRP), BDNF and substance P release were also evaluated by enzyme immunoassay.

Results

CFA injection into rat hindpaw resulted in mechanical hyperalgesia and significant increases in levels of TNF-α in the inflamed tissues, along with enhancement of BDNF and trkB receptor as well as the pain mediators CGRP and transient receptor potential vanilloid receptor subtype 1 (TRPV1) in DRG. Direct injection of TNF-α into rat hindpaw resulted in similar effects with retrograde transport of TNF-α along the saphenous nerve to DRG during CFA-induced inflammation. Primary DRG cultures chronically treated with TNF-α showed significant enhancement of mRNA and protein levels of BDNF and trkB receptor, BDNF release and trkB-induced phospho-ERK1/2 signal. Moreover, CGRP and substance P release were enhanced in DRG cultures after chronic TNF-α treatment or acute BDNF stimulation. In addition, we found that BDNF up-regulated trkB expression in DRG cultures.

Conclusions

Based on our current experimental results, we conclude that inflammation and TNF-α up-regulate the BDNF-trkB system in DRG. This phenomenon suggests that up-regulation of BDNF in DRG may, in addition to its post-synaptic effect in spinal dorsal horn, act as an autocrine and/or paracrine signal to activate the pre-synaptic trkB receptor and regulate synaptic excitability in pain transmission, thereby contributing to the development of hyperalgesia.     

Modulation of neurotrophin and neurotrophin receptor expression in nasal mucosa after nasal allergen provocation in allergic rhinitis

Background: Patients with allergic rhinitis (AR) feature both allergic airway inflammation and a hyperresponsiveness to nonspecific stimuli which is partly neuronally controlled. Still, it is unclear whether or not neurotrophins are involved in airway pathophysiology of AR and in nasobronchial interaction. Methods: Nine AR patients with mono‐allergy to grass pollen and nine healthy controls underwent nasal allergen provocation (NP). Serum samples, nasal and bronchial biopsies were taken before (T₀) and 24 h after (T₂₄) NP. Pan‐neurotrophin receptor p75^NTR, tyrosine kinase A (trkA), trkB, nerve growth factor (NGF), and brain‐derived neurotrophic factor (BDNF) were assessed with immunohistochemistry, and NGF and BDNF levels with ELISA. Results: At T₂₄, BDNF and NGF were upregulated in nasal mucosa (P < 0.05) and increased in the peripheral blood of AR compared with T₀. The increase in nasal BDNF expression correlated positively with the maximum increase in total nasal symptom score in AR (P = 0.02). p75^NTR was expressed on peripheral nerves and epithelial layer, trkA on endothelial cells, and trkB on mast cells. trkB + mast cells significantly decreased after NP in AR (P < 0.01). NP did not modulate p75^NTR and trkA expression in nasal mucosa and had no effect on the expression of neurotrophins and receptors in bronchial mucosa. Conclusion: This study shows that neurotrophins and their receptors are expressed in human airways. Allergic rhinitis was characterized by a modulation of BDNF, NGF, and trkB in nasal mucosa after NP and a correlation of nasal BDNF with the maximal increase of total nasal symptom score. Therefore, our data suggest that neurotrophins participate in upper‐airway pathophysiology in AR, whereas their role in nasobronchial interaction remains unclear.     

Caloric restriction does not reverse aging-related changes in hippocampal BDNF

Caloric restriction (CR) can attenuate the aging-related decline in learning and memory in rats. Understanding the mechanisms underlying this effect could lead to therapies for human memory impairment. We tested the hypotheses that aging is associated with a decline in hippocampal brain-derived neurotrophic factor (BDNF), a growth factor that enhances learning and memory, and that CR increases hippocampal BDNF. We compared BDNF protein levels in hippocampal subregions of young, middle-aged and old rats fed CR or ad libitum (AL) diets. Mean BDNF levels in the dentate gyrus and CA3 did not differ with diet but increased with age. In CA1, BDNF levels were slightly higher in CR than AL rats at middle and old age but did not change across lifespan. These data suggest that mnemonic impairments with age do not reflect a decrease in hippocampal BDNF. Furthermore, if CRs attenuation of aging-related memory changes is mediated by BDNF, then it must be through a small, CA1-specific increase and does not involve reversal of an aging-related decline in BDNF.