BDNF及其受体TrkB在实验性癫痫中的作用及意义探讨

目的检测大鼠杏仁核点燃癫痫后不同脑区脑源性神经营养因子（BDNF）及其受体TrkB的表达与定位。方法建立大鼠杏仁核点燃癫痫模型，应用免疫组化方法观察点燃鼠不同脑区不同点燃时程BDNF及TrkB的表达及含量。结果点燃后大鼠颞叶及海马BDNF随着点燃次数的增加而升高，并持续至点燃后49d;TrkB的表达也随着点燃次数的增加而升高，并持续至点燃后7d（改变同BDNF），点燃1周后表达逐渐减少，至点燃后7周时基本恢复正常。结论BDNF及TrkB直接参与癫痫的发生与发展，早期具有保护作用，但随着表达的进一步增加，又促进癫痫的发生发展，并一定程度上促进了癫痫发作后的神经细胞凋亡及脑损伤过程。     

顽固性颞叶癫痫患者海马或颞叶BDNF及其受体TrkB的测定

目的检测脑源性神经营养因子(BDNF)及其受体酪氨酸激酶B受体(TrkB)在难治性颞叶癫痫(TLE)患者颞叶和/或海马中的含量,探讨其在癫痫发病机制中的作用。方法选取经手术治疗的82例难治性TLE患者术中切除的海马或颞叶脑组织,用免疫组化方法对BDNF及其受体TrkB含量进行检测,并与11例对照进行比较。结果在难治性TLE患者中,BDNF在颞叶和海马中含量明显增加(分别P<0.05,P<0.01),且海马中含量明显高于颞叶(P<0.01);TrkB在颞叶和海马中含量显著增加(P<0.01),且海马中含量高于颞叶(P<0.05)。结论难治性TLE患者海马和颞叶中BDNF和TrkB含量增高,可能在癫痫发生、发展中起重要作用。     

抑郁症大鼠海马BDNF及其受体TrkB和p75NTR的表达及米氮平的调节作用

目的观察抑郁症模型大鼠学习记忆力改变情况,研究海马脑源性神经营养因子(BDNF)、酪氨酸激酶受体B(TrkB)和神经营养因子低亲和力受体(p75NTR)蛋白的表达变化,以及米氮平的调节作用。方法制备抑郁症大鼠模型;采用Morris水迷宫实验方法记录大鼠游动距离变化;免疫组化染色方法测定海马BDNF、TrkB和p75NTR表达阳性区吸光度值。结果抑郁症模型大鼠在目标象限游动距离减少,海马BDNF及TrkB蛋白表达减少,p75NTR蛋白表达增加;米氮平逆转上述行为学异常及蛋白表达异常(p﹤0.01)。结论抑郁症模型大鼠可能存在BDNF-p75NTR通路信息传递增强,而抗抑郁治疗用药可能通过BDNFTrkB信号通路的改变引起相应行为学改善。     

BDNF及其受体TrkB mRNA在脑缺血后适应大鼠模型中的表达变化

目的检测脑源性性神经营养因子(BDNF)及其受体酪氨酸激酶B(TrkB)在脑缺血后适应大鼠模型再灌注不同时间窗的表达,探讨BDNF/TrkB在脑缺血后适应中的作用。方法 Wistar大鼠随机分成对照组、缺血-再灌注组(IR)和缺血后适应组(IP),后两组根据再灌注时间的不同各分为6h、12h、24h、48h、72h 5个亚组。线栓法建立局灶性脑缺血-再灌注模型。TTC染色测定脑梗死体积,原位杂交法检测BDNF/TrkB mRNA的表达。结果 IP组大鼠梗死体积较IR组明显减小(P0.05)。IP组各时间点BDNF mRNA及TrkB mRNA表达较IR组均明显升高(P0.05)。结论脑缺血后适应能增加脑缺血-再灌注后BDNF及TrkB的表达,减轻脑梗死体积,BDNF/TrkB在脑缺血后适应后脑缺血-再灌注损伤中发挥了重要保护作用。     

二氢睾酮联合ADSC对大鼠脊髓损伤BDNF及其受体TrkB的影响

目的 探讨二氢睾酮(DHT)与脂肪源性干细胞(ADSC)联合应用对大鼠脊髓损伤后脑源性神经营养因子(BDNF)及其受体酪氨酸激酶B(TrkB)的表达和功能恢复的影响.方法 30只成年SD大鼠制备脊髓挫伤模型,随机分为对照组、ADSC组和DHT+ADSC组.BBB行为学和电生理方法检测运动功能的恢复,Western bolt检测脊髓损伤灶BDNF及其受体TrkB的蛋白表达.HE染色观察脊髓损伤灶面积,免疫荧光示踪PKH26标记的移植ADSC.结果 与ADSC组比较,DHT+ADSC组脊髓损伤灶内BDNF和TrkB蛋白相对表达明显增高,PKH-26标记的ADSC数量显著增高(P<0.05).与对照组比较,ADSC组和DHT+ADSC组电生理波幅增高、神经传导速度增快、延迟期缩短,其中DHT+ADSC组神经功能恢复作用显著优于ADSC组(P<0.05),且DHT+ADSC组BBB指数高于对照组和ADSC组.结论 二氢睾酮联合ADSC移植对大鼠脊髓损伤后改善损伤灶和功能恢复的作用优于ADSC组,其机制可能与二氢睾酮促进损伤灶BDNF及其受体TrkB表达,进而促进移植的ADSC存活有关.     

BDNF/TrkB通路与β-淀粉样蛋白的关系研究进展

脑源性神经生长因子(brain-derived neurotrophic factor,BDNF)对维持神经元存活、生长、分化及神经损伤后的修复与再生具有十分重要的意义[1].近年研究发现大脑中BDNF水平的下降与阿尔茨海默病(Alzheimer disease,AD)的发病具有密切关系.BDNF与其受体酪氨酸激酶受体(tropomyosin-related kinase B,TrkB)结合发挥生物学作用,有文献报道β-淀粉样蛋白(Aβ)能负调节TrkB[2],因此BDNF/TrkB通路可能在生物学上与β-淀粉样蛋白相关,二者的关系可能会成为治疗AD的新方向.故本文综述二者关系研究进展如下.     

脑源性神经营养因子与癫痫研究进展

癫痫发作后 ,脑内BDNF的表达升高 ,其在时间和地域分布上有一定规律 ,这与其维持神经元存活和再生的功能紧密相关 ;BDNF对癫痫动物模型的痫性发作有阻止作用 ;痫性发作后 ,BDNF的表达受到多种分子的影响     

匹罗卡品致疒间大鼠海马GAP-43与TrkB基因表达及其意义

目的探讨生长相关蛋白(GAP-43)和脑源性神经营养因子(BDNF)受体TrkB基因在匹罗卡品致疒间大鼠海马的表达及其意义.方法应用原位杂交组织化学方法研究匹罗卡品(PILO)致疒间大鼠海马GAP-43及TrkB mRNA表达的变化.结果匹罗卡品致癫疒间持续状态后3～6小时,海马齿状回颗粒细胞、CA3区及CA1区锥体细胞层TrkB mRNA表达显著高于对照组(P<0.01或0.05);在慢性期第7～30天,呈现第2次表达增强.致疒间后6～12小时,正常状态下并不表达GAP-43的大鼠海马颗粒细胞其GAP-43 mRNA表达较对照组显著增高(P<0.01),24小时～7天表达减少,在癫疒间慢性期表达再次高于对照组.结论 GAP-43及TrkB是颞叶癫疒间病理基础--海马苔藓纤维出芽的重要分子机制;BDNF对苔藓纤维的作用部分是通过GAP-43实现的.     

头痛宁胶囊对偏头痛大鼠BDNF/TrkB信号通路表达的影响

目的观察头痛宁胶囊对偏头痛大鼠模型中脑源性神经营养因子(BDNF)及其信号通路上酪氨酸激酶(TrkB)受体、下游信号分子细胞外调节蛋白激酶(ERK)、磷酸化cAMP反应结合蛋白(p-CREB)表达的影响。方法将60只SD大鼠随机分为正常对照组、模型组、头痛宁干预组,依照Tassorelli法建立硝酸甘油实验性偏头痛SD大鼠模型,观察各组大鼠的行为学变化,第五次建模后用ELISA法检测血清BDNF水平及免疫组化法检测三叉神经组织中BDNF、TrkB受体、下游信号分子ERK和p-CREB的蛋白表达变化及其定位。结果行为学观察结果显示:模型组及干预组大鼠造模后出现挠头增多、双耳发红、爬笼活动频繁,但干预组大鼠的持续时间及挠头爬笼次数较模型组减少,差异具有统计学意义(P<0.05);对照组未出现上述行为学改变。ELISA结果显示:模型组大鼠发作期及间歇期血清BDNF水平高于干预组发作期及间歇期和对照组(P<0.05),无性别差异(P>0.05)。免疫组化结果显示:模型组大鼠发作期三叉神经节细胞内BDNF、TrkB、p-ERK、p-CREB的蛋白水平高于干预组发作期及间歇期和对照组(P<0.05),无性别差异(P>0.05)。结论头痛宁胶囊可能通过下调BDNF、TrkB、p-ERK、p-CREB蛋白的表达水平来达到防治偏头痛的作用。     

Increased truncated TrkB receptor expression and decreased BDNF/TrkB signaling in the frontal cortex of reeler mouse model of schizophrenia

Heterozygous reeler mouse has been used as an animal model for schizophrenia based on several neuropathological and behavioral abnormalities homologous to schizophrenia. Since some of these abnormalities are primarily associated with altered BDNF signaling we investigated BDNF signaling in the frontal cortex of reeler mice in order to shed some light on the neuropathology and treatment of schizophrenia. BDNF, TrkB receptor isoforms (full-length and truncated), reelin, GAD67, GAD65, p75NTR, and NRH-2 levels were measured in the frontal cortex samples from reeler (B6C3Fe a/a-Reln^rl/+) and wild-type (WT) mice. BDNF protein levels were significantly higher in reeler compared to WT. The protein levels of full-length TrkB were not altered in reeler mice, but both mRNA and protein levels of truncated TrkB were significantly higher. Protein analysis showed that TrkB activity, as indicated by the levels of tyrosine-phosphorylated TrkB, was lower in reeler mice. We did not find any significant change in the levels of p75NTR and NRH-2, regulatory proteins of TrkB signaling, in the reeler mice. Furthermore, we found significant reduction in reelin and GAD67 expressions, but not GAD65 expression in reeler compared to WT mice. In summary, molecular processes associated with defective BDNF signaling in reeler mice provide new therapeutic targets for neuroprotective pharmacotherapy for schizophrenia.     

Maternal micronutrient imbalance alters gene expression of BDNF,NGF, TrkB and CREB in the offspring brain at an adult age

Micronutrients like folate, vitamin B₁₂, and fatty acids which are interlinked in the one carbon cycle play a vital role in mediating epigenetic processes leading to an increased risk for neurodevelopmental disorders in the offspring. Our earlier study demonstrates that a micronutrient imbalanced diet adversely affects docosahexaenoic acid (DHA) and protein levels of neurotrophins like brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the brain and cognition in the offspring by 3 months of age. In this study we attempt to analyze if these effects are a consequence of a change in gene expression of these molecules. Further, we also examined the effect of either a postnatal control diet or a prenatal omega-3 fatty acid supplementation on gene expression in the cortex of the offspring. Pregnant rats were divided into control and five treatment groups at two levels of folic acid (normal and excess folate) in the presence and absence of vitamin B₁₂. Omega-3 fatty acid (eicosapentaenoic acid – EPA + DHA) supplementation was given to vitamin B₁₂ deficient groups. Following delivery, 8 dams from each group were shifted to control diet and remaining continued on the same treatment diet. Our results demonstrate that the imbalanced diet caused a marked reduction in the mRNA levels of BDNF, NGF, TrkB, and cAMP response element-binding protein (CREB). Prenatal omega-3 fatty acid supplementation to the maternal imbalanced diet was able to normalize the mRNA levels of all the above genes. This study demonstrates that a maternal diet imbalanced in micronutrients (folic acid, vitamin B₁₂) influences gene expression of neurotrophins and their signalling molecules and thereby adversely affects the brain of the offspring.     

Prelimbic BDNF and TrkB signaling regulates consolidation of both appetitive and aversive emotional learning

The medial prefrontal cortex (mPFC) is known to regulate executive decisions and the expression of emotional memories. More specifically, the prelimbic cortex (PL) of the mPFC is implicated in driving emotional responses via downstream targets including the nucleus accumbens and amygdala, but mechanisms are yet to be fully understood. Therefore, we investigated whether prelimbic cortical brain-derived neurotrophic factor (BDNF) signaling through the high-affinity tyrosine kinase receptor B (TrkB) receptor may serve as a molecular mechanism underlying emotional memory encoding. Here, we utilized viral-mediated inducible bdnf deletion within the PL, as well as TrkB^F616A mutant mice, wherein TrkB receptor point mutation results in its being highly sensitive to inhibition by small PP1-derivative molecules, serving as a specific TrkB inhibitor. The site-specific TrkB antagonism and viral-mediated bdnf deletion within the PL resulted in deficits in both cocaine-dependent associative learning and fear expression. Deficiencies were rescued by the novel TrkB agonist 7,8-dihydroxyflavone, indicating that PL BDNF expression and downstream signaling through the TrkB receptor are required for memory formation in both appetitive and aversive domains.     

KLF7联合脂肪源性干细胞对小鼠坐骨神经缺损后轴突再生的影响

目的探讨核转录因子KLF7与脂肪源性干细胞(ADSC)联合应用对小鼠脱细胞同种异体神经支架(ANA)移植坐骨神经缺损后轴突再生和功能恢复的影响。方法成年C57BL/6小鼠随机分为脱细胞神经支架(ANA)组、ADSC组和KLF7+ADSC组,每组10只。坐骨神经功能指数(SFI)和电生理方法检测神经运动功能的恢复,Western bolt检测神经移植体内KLF7、Trk A和Trk B的蛋白表达。NF200免疫荧光法检测神经支架中轴突再生,并示踪PKH26标记的移植ADSC。结果与ADSC组比较,KLF7+ADSC组神经移植体内KLF7、Trk A和Trk B蛋白表达明显增高,NF200表达增强,PKH-26标记的ADSC数量显著增高(P0.05)。与ANA组比较,ADSC组和KLF7+ADSC组电生理波幅增高、神经传导速度增快、延迟期缩短,SFI功能指数增高,其中KLF7+ADSC组神经恢复作用显著优于ADSC组(P0.05)。结论 KLF7联合ADSC移植对小鼠ANA修复坐骨神经缺损后轴突再生和功能恢复的作用优于ADSC组,其机制可能与KLF7高表达促进神经移植体内Trk A和Trk B表达,进而促进移植的ADSC存活有关。     

BDNF/NT4-5 receptor TrkB and cadherin participate in cell-cell adhesion

The neurotrophin receptor TrkB plays a key role in promoting cell survival and differentiation in the nervous system. Two adhesive motifs in the extracelluar domain of TrkB have been proposed based on its predicted secondary structure. To investigate the potential adhesive function of trkB, a full length trkB cDNA was stably transfected into NIH 3T3 cells and TrkB-expressing clones isolated. Transfectant clones producing different levels of TrkB protein were subjected to a homotypic aggregation assay. Results showed that parental cells were non-adhesive during the assay while TrkB-expressing cells displayed varying degrees of aggregation depending on the amount of TrkB protein expressed. The observed adhesion was Ca²⁺-, Mg²⁺-, and temperature-dependent, characteristics shared by the cadherin family of adhesion molecules. The transfected cell lines also expressed cadherin in proportion to TrkB expression and both molecules were required for cell adhesion. Double immunofluorescence staining studies showed that TrkB was colocalized with cadherin and catenin at cell-cell contact sites. Whether TrkB and cadherin mediate adhesion separately or synergistically remains to be determined. J. Neurosci. Res. 49:281–291, 1997. © 1997 Wiley-Liss, Inc.     

Cellular levels of TrkB and MAPK in the neuroprotective role of BDNF for embryonic rat cortical neurons against hypoxia in vitro

Intrauterine asphyxia often results in neonatal loss or mental retardation. Brain-derived neurotrophic factor (BDNF) has been shown to be a protective agent against hypoxic damage to neurons. To understand the signaling mechanism underling the neuroprotective function of BDNF and to find therapeutic interventions for intrauterine asphyxia, we utilized an immunofluorescent technique to measure the intracellular levels of tyrosine kinase B (TrkB), phosphorylated TrkB, and the mitogen-activated protein kinase (MAPK) in the rat embryonic cortical neurons cultured in hypoxic conditions with and without BDNF pretreatment. The results showed that the fluorescent intensity of TrkB and phosphorylated TrkB in the cytoplasm and the fluorescent intensity of MARK in both cytoplasma and nucleus of the neurons were significantly increased in the presence of BDNF. The results indicate that the neuroprotective function of BDNF against hypoxia-induced neurotoxicity requires the participation of TrkB and is transduced via the Ras-MAPK signaling pathway.     

BDNF/TrkB signaling regulates HNK-1 carbohydrate expression in regenerating motor nerves and promotes functional recovery after peripheral nerve repair

Functional recovery after peripheral nerve injury is often poor despite high regenerative capacity of peripheral neurons. In search for novel treatments, brief electrical stimulation of the acutely lesioned nerve has recently been identified as a clinically feasible approach increasing precision of axonal regrowth. The effects of this stimulation appear to be mediated by BDNF and its receptor, TrkB, but the down-stream effectors are unknown. A potential candidate is the HNK-1 carbohydrate known to be selectively reexpressed in motor but not sensory nerve branches of the mouse femoral nerve and to enhance growth of motor but not sensory axons in vitro. Here, we show that short-term low-frequency electrical stimulation (1 h, 20 Hz) of the lesioned and surgically repaired femoral nerve in wild-type mice causes a motor nerve-specific enhancement of HNK-1 expression correlating with previously reported acceleration of muscle reinnervation. Such enhanced HNK-1 expression was not observed after electrical stimulation in heterozygous BDNF or TrkB-deficient mice. Accordingly, the degree of proper reinnervation of the quadriceps muscle, as indicated by retrograde labeling of motoneurons, was reduced in TrkB+/- mice compared to wild-type littermates. Also, recovery of quadriceps muscle function, evaluated by a novel single-frame motion analysis approach, and axonal regrowth into the distal nerve stump, assessed morphologically, were considerably delayed in TrkB+/- mice. These findings indicate that BDNF/TrkB signaling is important for functional recovery after nerve repair and suggest that up-regulation of the HNK-1 glycan is linked to this phenomenon.