Are TrkB receptor agonists the right tool to fulfill the promises for a therapeutic value of the brain-derived neurotrophic factor?

Brain-derived neurotrophic factor signaling via its receptor tro pomyosin receptor kinase B regulates several crucial physiological processes.It has been shown to act in the brain,promoting neuronal survival,growth,and plasticity as well as in the rest of the body where it is involved in regulating for instance aspects of the metabolism.Due to its crucial and very pleiotro pic activity,reduction of brain-derived neurotrophic factor levels and alterations in the brain-derived neurotrophic factor/tropomyosin receptor kinase B signaling have been found to be associated with a wide spectrum of neurological diseases.Howeve r,because of its poor bioavailability and pharmacological properties,brain-derived neurotrophic factor itself has a very low therapeutic value.Moreover,the concomitant binding of exogenous brain-derived neurotrophic factor to the p75 neurotrophin receptor has the potential to elicit several unwanted and deleterious side effects.Therefo re,developing tools and approaches to specifically promote tropomyosin receptor kinase B signaling has become an important goal of translational research.Among the newly developed tools are different categories of tropomyosin receptor kinase B receptor agonist molecules.In this review,we give a comprehensive description of the diffe rent tro pomyosin receptor kinase B receptor agonist drugs developed so far and of the res ults of their application in animal models of several neurological diseases.Moreover,we discuss the main benefits of tropomyosin receptor kinase B receptor agonists,concentrating especially on the new tropomyosin receptor kinase B agonist antibodies.The benefits observed both in vitro and in vivo upon application of tropomyosin receptor kinase B receptor agonist drugs seem to predominantly depend on their general neuroprotective activity and their ability to promote neuronal plasticity.Moreover,tro pomyosin receptor kinase B agonist antibodies have been shown to specifically bind the tropomyosin receptor kinase B receptor and not p75 neurotrophin receptor.Therefore,while,based on the current knowledge,the tropomyosin receptor kinase B receptor agonists do not seem to have the potential to reve rse the disease pathology per se,promoting brainderived neurotrophic factor/tro pomyosin receptor kinase B signaling still has a very high therapeutic relevance.

Brain-derived neurotrophic factor signaling in the neuromuscular junction during developmental axonal competition and synapse elimination

During the development of the nervous system,there is an overproduction of neurons and synapses.Hebbian competition between neighboring nerve endings and synapses performing different activity levels leads to their elimination or strengthening.We have extensively studied the involvement of the brain-derived neurotrophic factor-Tropomyosin-related kinase B receptor neurotrophic retrograde pathway,at the neuromuscular junction,in the axonal development and synapse elimination process versus the synapse consolidation.The purpose of this review is to describe the neurotrophic influence on developmental synapse elimination,in relation to other molecular pathways that we and others have found to regulate this process.In particular,we summarize our published results based on transmitter release analysis and axonal counts to show the different involvement of the presynaptic acetylcholine muscarinic autoreceptors,coupled to downstream serine-threonine protein kinases A and C(PKA and PKC)and voltage-gated calcium channels,at different nerve endings in developmental competition.The dynamic changes that occur simultaneously in several nerve terminals and synapses converge across a postsynaptic site,influence each other,and require careful studies to individualize the mechanisms of specific endings.We describe an activity-dependent balance(related to the extent of transmitter release)between the presynaptic muscarinic subtypes and the neurotrophin-mediated TrkB/p75NTR pathways that can influence the timing and fate of the competitive interactions between the different axon terminals.The downstream displacement of the PKA/PKC activity ratio to lower values,both in competing nerve terminals and at postsynaptic sites,plays a relevant role in controlling the elimination of supernumerary synapses.Finally,calcium entry through L-and P/Q-subtypes of voltage-gated calcium channels(both channels are present,together with the N-type channel in developing nerve terminals)contributes to reduce transmitter release and promote withdrawal of the most unfavorable nerve terminals during elimination(the weakest in acetylcholine release and those that have already become silent).The main findings contribute to a better understanding of punishment-rewarding interactions between nerve endings during development.Identifying the molecular targets and signaling pathways that allow synapse consolidation or withdrawal of synapses in different situations is important for potential therapies in neurodegenerative diseases.

Effects of ginsenoside on brain-derived neurotrophic factor and tyrosine kinase B mRNA expression in the hippocampal formation of aged rats

BACKGROUND： There are a limited number of studies involving the effects of ginsenosides, the active component of ginseng, on expression of hippocampal TrkB mRNA in aged rats. OBJECTIVE： To observe expression of brain-derived neurotrophic factor （BDNF） and tyrosine kinase B （TrkB） mRNA in the hippocampal formation of aged rats, as well as changes after ginsenoside administrated. DESIGN, TIME AND SETTING： A randomized, controlled experiment was performed at the Department of Anatomy, College of Basic Medical Sciences, China Medical University in March 2005. MATERIALS： A total of 39 female, Wistar rats were randomly divided into 3 groups （n = 13 each）： young （3-5 months old）, aged （27 months old）, and ginsenoside group （received 25mg/kg/d ginsenoside in the drinking water between 17 and 27 months of age）. METHODS： Following anesthesia, the rats were exsanguinated and perfused transcardially with chilled, heparinized, 0.9% saline. The brains were removed and post-fixed in 40 g/L paraformaldehyde/phosphate buffer for 20 minutes, and further incubated in 30% sucrose/phosphate buffer overnight. MAIN OUTCOME MEASURES： In situ hybridization, immunohistochemistry, and image analysis were used to investigate expression of BDNF and TrkB mRNA in the hippocampal formation. RESULTS： The expression levels of BDNF in the hippocampal CA3 and CA1 of aged rats was significantly less than the young group （t = 2.879, 1.814, 1.984, P 〈 0.05）. BDNF expression was significantly greater in the dentate gyrus of the ginsenoside group, compared with the aging group （t = 1.943, P 〈 0.01）. The expression of TrkB mRNA in the hippocampal CA3, CA1, and dentate gyrus of aged rats was less than the young group （t = 3.540, 3.629, 17.905, P 〈 0.01）. TrkB mRNA expression in the CA3 region and dentate gyrus of the ginsenoside group was significantly greater compared with the aging group （t = 1.293, 3.386, P 〈 0.05, 0.01 ）. CONCLUSION： BDNF and TrkB mRNA expression in the hippocampal formation were reduced in the aged group. However, ginsenosides can increase BDNF and TrkB mRNA expression in the hippocampal formation.

Auditory deprivation modifies the expression of brain-derived neurotrophic factor and tropomyosin receptor kinase B in the rat auditory cortex

The development and plasticity of central auditory system can be influenced by the change of peripheral neuronal activity. However, the molecular mechanism participating in the process remains elusive. Brain-derived neurotrophic factor(BDNF) binding with its functional receptor tropomyosin receptor kinase B(TrkB) has multiple effects on neurons. Here we used a rat model of auditory deprivation by bilateral cochlear ablation, to investigate the changes in expression of BDNF and Trk B in the auditory cortex after auditory deprivation that occurred during the critical period for the development of central auditory system. Reverse transcription-quantitative polymerase chain reaction(RTqPCR) and immunohistochemistry methods were adopted to detect the m RNA and protein expression levels of BDNF and TrkB in the auditory cortex at 2, 4, 6 and 8 weeks after surgery, respectively. The change in the expression of BDNF and TrkB mRNAs and proteins followed similar trend. In the bilateral cochlear ablation groups, the BDNF-TrkB expression level initially decreased at 2 weeks but increased at 4 weeks followed by the reduction at 6 and 8 weeks after cochlear removal, as compared to the age-matched sham control groups. In conclusion, the BDNF-TrkB signaling is involved in the plasticity of auditory cortex in an activity-dependent manner.

Neuroprotective effects of exogenous brain-derived neurotrophic factor on amyloid-beta 1-40-induced retinal degeneration

Amyloid-beta(Aβ)-related alterations,similar to those found in the brains of patients with Alzheimer's disease,have been observed in the retina of patients with glaucoma.Decreased levels of brain-derived neurotrophic factor(BDNF)are believed to be associated with the neurotoxic effects of Aβpeptide.To investigate the mechanism underlying the neuroprotective effects of BDNF on Aβ_(1-40)-induced retinal injury in Sprague-Dawley rats,we treated rats by intravitreal administration of phosphate-buffered saline(control),Aβ_(1-40)(5 nM),or Aβ_(1-40)(5 nM)combined with BDNF(1μg/mL).We found that intravitreal administration of Aβ_(1-40)induced retinal ganglion cell apoptosis.Fluoro-Gold staining showed a significantly lower number of retinal ganglion cells in the Aβ_(1-40)group than in the control and BDNF groups.In the Aβ_(1-40)group,low number of RGCs was associated with increased caspase-3 expression and reduced TrkB and ERK1/2 expression.BDNF abolished Aβ_(1-40)-induced increase in the expression of caspase-3 at the gene and protein levels in the retina and upregulated TrkB and ERK1/2 expression.These findings suggest that treatment with BDNF prevents RGC apoptosis induced by Aβ_(1-40)by activating the BDNF-TrkB signaling pathway in rats.

Tropomyosin-related kinase B/brain derived-neurotrophicfactor signaling pathway as a potential therapeutic targetfor colorectal cancer

Colorectal cancer(CRC) is the second most common cause of cancer-related death in western countries. Approximately one-quarter of newly diagnosed patients for CRC have metastases, and a further 40%-50% experience disease recurrence or develop metastases after all standard therapies. Therefore, understanding the molecular mechanisms involved in the progression of CRC and subsequently developing novel therapeutic targets is crucial to improve management of CRC and patients' long-term survival. Several tyrosine kinase receptors have been implicated in CRC development, progression and metastasis, including epidermal growth factor receptor(EGFR) and vascular EGFR. Recently, tropomyosin-related kinase B(Trk B), a tyrosine kinase receptor, has been reported in CRC and found to clearly exert several biological and clinical features, such as tumor cell growth and survival in vitro and in vivo, metastasis formation and poor prognosis. Here we review the significance of Trk B and its ligand brain derived-neurotrophic factor in CRC. We focus on their expression in CRC tumor samples, and their functional roles in CRC cell lines and in in vivo models. Finally we discuss therapeutic approaches that can lead to the development of novel therapeutic agents for treating Trk B-expressing CRC tumors.

Brain-derived neurotrophic factor prevents beta-amyloid-induced apoptosis of pheochromocytoma cells by regulating Bax/Bcl-2 expression

Brain-derived neurotrophic factor was utilized in the present study to treat cell injury models induced by aggregated β-amyloid（25 35）. Methylthiazolyldiphenyl-tetrazolium bromide assay and western blot analysis showed that brain-derived neurotrophic factor provided neuroprotection against cellular apoptosis by suppressing the decline in β-amyloid（25 35）-induced cell activity and the increasing ratio of Bax/Bcl-2. After treating pheochromocytoma cells with tyrosine kinase receptor B receptor inhibitor K252a, brain-derived neurotrophic factor reverses the above- mentioned changes. The experimental findings suggested that brain-derived neurotrophic factor prevented β-amyloid peptide-induced cellular apoptosis by modulating Bax/Bcl-2 expression, and this effect was associated with binding to the specific tyrosine kinase receptor B receptor.

Therapeutic potential of brain-derived neurotrophic factor(BDNF)and a small molecular mimics of BDNF for traumatic brain injury

Traumatic brain injury（TBI） is a major health problem worldwide.Following primary mechanical insults,a cascade of secondary injuries often leads to further neural tissue loss.Thus far there is no cure to rescue the damaged neural tissue.Current therapeutic strategies primarily target the secondary injuries focusing on neuroprotection and neuroregeneration.The neurotrophin brain-derived neurotrophic factor（BDNF） has significant effect in both aspects,promoting neuronal survival,synaptic plasticity and neurogenesis.Recently,the flavonoid 7,8-dihydroxyflavone（7,8-DHF）,a small Trk B agonist that mimics BDNF function,has shown similar effects as BDNF in promoting neuronal survival and regeneration following TBI.Compared to BDNF,7,8-DHF has a longer half-life and much smaller molecular size,capable of penetrating the blood-brain barrier,which makes it possible for non-invasive clinical application.In this review,we summarize functions of the BDNF/Trk B signaling pathway and studies examining the potential of BDNF and 7,8-DHF as a therapy for TBI.

TrkB and p-trkB expression in brain-derived neurotrophic factor-pretreated rat retina following acute high intraocular pressure

BACKGROUND： Exogenous brain-derived neurotrophic factor （BDNF） promotes retinal ganglion cell survival. However, the protective mechanisms remain unclear. OBJECTIVE： To investigate changes in retinal tyrosine kinase receptor B （trkB） expression and effects of exogenous BDNF on trkB activation in a rat model of acute high intraocular pressure （HtOP）. DESIGN, TIME AND SETTING： A randomized, controlled, animal experiment was performed at the Department of Anatomy and Neurobiology, Xiangya Medical School, Central South University from January 2004 to August 2006. MATERIALS： Rabbit anti-BDNF and anti-trkB.FL（full-length） polyclonal antibodies were purchased from Santa Cruz Biotechnology, USA; rabbit anti-p-trkB polyclonal antibodies were purchased from Cellsignal, USA. METHODS： A total of 48 healthy, adult, Sprague Dawiey rats were randomly assigned to acute HIOP （without BDNF pre-treatment） and BDNF pre-treated groups, with 24 animals in each group. In the BDNF pre-treated group, the left eyes were intravitreally injected with 3 pg/kg BDNF 2 days prior to HIOP. Rats in the acute HIOP group were not pre-treated with BDNE HIOP models were established by increased intraocular pressure in the left eyes until the b-wave of flash electroretinogragh disappeared and pressure was maintained for 60 minutes. The right eyes of all rats were not treated and served as the normal controls. MAIN OUTCOME MEASURES： Retinal structure and cell numbers in the ganglion cell layer （GCL） were detected by Nissl staining; expression of trkB and phosphorylated trkB in the rat retina were determined by immunohistochemistry. RESULTS： A greater number of GCL neurons were observed in the pre-treated group compared to the acute HIOP group （P 〈 0.05）. TrkB expression was significantly increased following HIOP at days 1 and 3 （P 〈 0.05）, but expression varied between retinal areas. Although trkB expression decreased at 7 days, phosphorylated trkB dramatically decreased with increasing time （P 〈 0.05）. TrkB expression in BDNF pre-treated rats was similar to the acute HIOP group at early injury time points. Nevertheless, trkB expression was significantly decreased compared to the acute HIOP group at 7 days （P 〈 0.05）, and phosphorylated trkB expression was significantly greater compared to the acute HIOP group at each time point （P〈 0.05）. CONCLUSION： TrkB expression displayed temporal and spatial changes in the rat retina following acute HIOP, and trkB up-regulation suggested that more BDNF was required for treating the injured retina. Exogenous BDNF partially ameliorated decreased expression of phosphorylated trkB and provided protection to the injured retina, to a certain degree, following HIOP.

Levetiracetam induces tyrosine kinase receptor B expression in SH-SY5Y cells

Tyrosine kinase receptor B （TrkB） plays an important role in long-term potentiation and memory formation.The present study used all-trans retinoic acid to induce TrkB expression in SH-SY5Y cells,and observed the effects of levetiracetam （LEV） on TrkB expression.Following exposure to 10,50,and 100 μg/mL LEV,the number of TrkB-positive cells,and average absorbance value were increased.Results demonstrated that LEV can induce TrkB expression in SH-SY5Y cells.

Neurotrophic factor-based pharmacological approaches in neurological disorders

Aging is a physiological event dependent on multiple pathways that are linked to lifespan and processes leading to cognitive decline.This process represents the major risk factor for aging-related diseases such as Alzheimer’s disease,Parkinson’s disease,and ischemic stroke.The incidence of all these pathologies increases exponentially with age.Research on aging biology has currently focused on elucidating molecular mechanisms leading to the development of those pathologies.Cognitive deficit and neurodegeneration,common features of aging-related pathologies,are related to the alteration of the activity and levels of neurotrophic factors,such as brain-derived neurotrophic factor,nerve growth factor,and glial cell-derived neurotrophic factor.For this reason,treatments that modulate neurotrophin levels have acquired a great deal of interest in preventing neurodegeneration and promoting neural regeneration in several neurological diseases.Those treatments include both the direct administration of neurotrophic factors and the induced expression with viral vectors,neurotrophins’binding with biomaterials or other molecules to increase their bioavailability but also cell-based therapies.Considering neurotrophins’crucial role in aging pathologies,here we discuss the involvement of several neurotrophic factors in the most common brain aging-related diseases and the most recent therapeutic approaches that provide direct and sustained neurotrophic support.

Express=on of Brain-derived Neurotrophic Factor and Tyrosine Kinase B in Cerebellum of Poststroke Depression Rat Model

Background： The pathophysiology of poststroke depression （PSD） remains elusive because of its proposed multifactorial nature. Accumulating evidence suggests that brain-derived neurotrophic factor （BDNF） plays a key role in the pathophysiology of depression and PSD. And the cerebellar dysfunction may be important in the etiology of depression; it is not clear whether it also has a major effect on the risk of PSD. This study aimed to explore the expression of BDNF and high-affinity receptors tyrosine kinase B （TrkB） in the cerebellum of rats with PSD. Methods： The rat models with focal cerebral ischemic were made using a thread embolization method. PSD rat models were established with comprehensive separate breeding and unpredicted chronic mild stress （UCMS） on this basis. A normal control group, depression group, and a stroke group were used to compare with the PSD group. Thirteen rats were used in each group. Immunohistochemistry and reverse transcription-polymerase chain reaction （RT-PCR） for detecting the expression of BDNF and TrkB protein and mRNA in the cerebellum were used at the 29th day following the UCMS. Results： Compared with the normal control group and the stroke group, the number of BDNF immunoreactive （IR） positive neurons was less in the PSD group （P 〈 0.05）. Furthermore, the number ofTrkB 1R positive cells was significantly less in the PSD group than that in the normal control group （P 〈 0.05）. The gene expression of BDNF and TrkB in the cerebellum of PSD rats also decreased compared to the normal control group （P 〈 0.05）. Conclusions： These findings suggested a possible association between expression of BDNF and TrkB in the cerebellum and the pathogeuesis of PSD.

Uncoupling neurotrophic function from nociception of nerve growth factor: what can be learned from a rare human disease?

Nerve growth factor(NGF) is a powerful trophic factor that provides essential support for the survival and differentiation of sympathetic and sensory neurons during development. However, NGF also activates nociceptors contributing significantly to inflammatory pain and neuropathic pain after tissue injury. As such anti-NGF based therapies represent a promising strategy for pain management. Because of dose-dependent serious side effects such as back pain, injection site hyperalgesia, clinical trials of using NGF to treat various disorders such as diabetic neuropathies, chemotherapy-induced and human immunodeficiency virus-associated peripheral neuropathies were all discontinued. Thus far, worldwide clinical applications of NGF in treating patients are very limited except in China. Hereditary sensory autonomic neuropathy type V(HSAN V) is an extremely rare disease. Genetic analyses have revealed that HSAN V is associated with autosomal recessive mutations in NGF. One of the mutations occurred at the 100^(th) position of mature NGF resulting in a change of residue from arginine to tryptophan(R100W). Although those HSAN V patients associated with the NGF^(R100W) mutation suffer from severe loss of deep pain, bone fractures and joint destruction, interestingly patients with the NGF^(R100W) mutation do not show apparent cognitive deficits, suggesting important trophic support function is preserved. We believe that NGF^(R100W) provides an ideal tool to uncouple the two important functions of NGF: trophic versus nociceptive. Studies from investigators including ourselves have indeed confirmed in animal testing that the NGF^(R100W) no longer induced pain. More importantly, the trophic function seemed to be largely preserved in NGF harboring the R100W mutation. On the mechanistic level, we found that the NGF^(R100W) mutation was capable of binding to and signaling through the tyrosine receptor kinase A receptor. But its ability to bind to and activate the 75 kDa neurotrophic factor was significantly diminished. The significance of these findings is at least two folds: 1) the NGF^(R100W) mutation can be used as an alternative to the wildtype NGF to treat human conditions without eliciting pain; and 2) the 75 kDa neurotrophic factor may serve as a novel target for pain management. We will discuss all the details in this mini-review.

百会穴久留针法改善缺血性脑卒中小鼠神经功能的作用及机制

目的研究百会穴久留针法通过脑源性神经营养因子(BDNF)/酪氨酸受体激酶B(TrkB)通路改善缺血性脑卒中小鼠神经功能的作用及机制。方法选择雄性C57BL/6J小鼠48只,随机分为假手术1组、模型1组、久留针1组、普通留针组,每组12只。后3组采用线栓法制备缺血性脑卒中模型,手术造模后第1天起久留针1组和普通留针组分别给予百会穴久留针和普通留针治疗,连续14 d。另选择雄性C57BL/6J小鼠40只,随机分为假手术2组、模型2组、久留针2组、久留针3组,每组10只。后3组采用线栓法制备缺血性脑卒中模型,针灸治疗前分别给予腺相关病毒100μl单次尾静脉注射。采用改良神经功能缺损评分(mNSS)及水迷宫实验的逃避潜伏期、目标象限停留时间、穿越原平台次数评价神经功能。结果与假手术1组比较,模型1组mNSS评分、目标象限停留时间、穿越原平台次数及缺血脑组织BDNF、TrkB表达明显降低,细胞凋亡率及裂解型半胱氨酸天冬氨酸蛋白酶3(Caspase-3)表达明显增加,差异有统计学意义(P<0.05);与模型1组比较,久留针1组和普通留针组mNSS评分、目标象限停留时间、穿越原平台次数及缺血脑组织BDNF、TrkB表达明显增加,细胞凋亡率及裂解型Caspase-3表达明显降低,且久留针1组上述变化较普通留针组更为显著,差异有统计学意义(P<0.05)。与久留针2组比较,久留针3组mNSS评分、目标象限停留时间、穿越原平台次数及缺血脑组织中BDNF表达明显降低(P<0.05),细胞凋亡率及裂解型Caspase-3表达明显增加[(16.41±2.25)%vs(7.59±1.09)%;1.46±0.16 vs 0.94±0.12,P<0.05]。结论百会穴久留针治疗对缺血性脑卒中小鼠神经功能的改善作用更为显著,激活BDNF/TrkB通路是其发挥神经保护作用的相关分子机制。

卡马西平对三叉神经痛大鼠三叉神经节及血清中BDNF表达变化的影响

目的:三叉神经痛(trigeminal neuralgia,TN)是一种严重的慢性神经病理性疼痛,主要影响三叉神经分布区域,临床治疗效果不佳。TN的治疗方法众多,但目前临床上主要是通过服用卡马西平(carbamazepine,CBZ)来抑制疼痛。脑源性神经营养因子(brain-derived neurotrophic factor,BDNF)和慢性痛密切相关。本研究通过慢性压迫性损伤眶下神经(chronic constriction injury of the infraorbital nerve,ION-CCI)大鼠模型观察CBZ处理对TN大鼠三叉神经节(trigeminal ganglion,TG)和血清中BDNF表达的影响。方法:建立雄性SD大鼠ION-CCI模型,并将其随机分为假手术(sham)组、TN组、TN+低剂量(20 mg/kg)CBZ处理组、TN+中剂量(40 mg/kg)CBZ处理组、TN+高剂量(80 mg/kg)CBZ处理组。在手术前后定时测量各组大鼠的面部机械痛阈(mechanical pain threshold)。使用实时聚合酶链反应技术测定各组大鼠TG中BDNF及酪氨酸激酶受体B(tyrosine kinase receptor B,TrkB)的mRNA含量,免疫荧光技术观察各组大鼠TG中BDNF蛋白质在神经元上的表达情况,蛋白质印迹法检测各组大鼠TG中BDNF、TrkB、细胞外调节蛋白激酶(extracellular regulated protein kinases,ERK)及磷酸化的细胞外调节蛋白激酶(phospho-extracellular regulated protein kinases,p-ERK)的蛋白质表达变化,酶联免疫吸附试验(enzyme-linked immunosorbent assay,ELISA)检测各组大鼠血清中BDNF的表达变化。结果:行为学检测结果表明:手术前,各组大鼠右侧面部感觉区域的机械痛阈差异均无统计学意义(均P>0.05);术后第3天开始,TN组大鼠机械痛阈与sham组相比均明显降低(均P<0.01),TN+80 mg/kg CBZ处理组、TN+40 mg/kg CBZ处理组和TN+20 mg/kg CBZ处理组与TN组相比均升高(均P<0.05)。实时聚合酶链反应和蛋白质印迹法结果显示:TN组大鼠TG中的BDNF、TrkB的mRNA及蛋白质表达量均较sham组升高(均P<0.05),TN+20 mg/kg CBZ处理组、TN+40 mg/kg CBZ处理组、TN+80 mg/kg CBZ处理组均较TN组降低(均P<0.05);与TN组相比,TN+20 mg/kg CBZ处理组、TN+40 mg/kg CBZ处理组、TN+80 mg/kg CBZ处理组大鼠TG中的p-ERK水平均显著降低(均P<0.05)。免疫荧光双标结果表明:TN组TG中的BDNF和神经元特异性核蛋白(neuron-specific nuclear protein,NeuN)主要共表达在神经元上,与sham组比较BDNF和NeuN水平升高(P<0.05),TN+20 mg/kg CBZ处理组、TN+40 mg/kg CBZ处理组、TN+80 mg/kg CBZ处理组与TN组大鼠比较二者表达均降低(均P<0.05)。ELISA检测结果显示:TN组大鼠血清中BDNF的水平较sham组显著升高(P<0.05),TN+20 mg/kg CBZ处理组、TN+40 mg/kg CBZ处理组、TN+80 mg/kg CBZ处理组均较TN组大鼠降低(均P<0.05)。Spearman相关分析显示血清中BDNF水平与机械痛阈呈负相关(r=−0.650,P<0.01)。结论:CBZ处理可以抑制TN大鼠TG中BDNF及其受体TrkB的表达,降低TN大鼠血清中BDNF水平及ERK信号通路磷酸化水平,进而抑制TN。可以考虑将血清中BDNF水平作为诊断TN和评估预后的指标。

脑源性神经营养因子和神经营养因子-5在女性生殖内分泌领域的研究进展

脑源性神经营养因子(BDNF)和神经营养因子-5(NT-5)属于神经营养因子家族,是一类由神经支配的靶组织分泌的分泌型多肽,两者通过作用于相同的受体发挥作用。BDNF和NT-5在卵巢表达广泛,发挥着促进卵泡组装和发育、卵母细胞成熟、排卵、调节颗粒细胞和膜细胞类固醇激素分泌等多种生理作用。不孕症是由多种病因导致的一种生育障碍状态,不孕症患者卵巢局部的BDNF和NT-5存在异常分泌情况。因此,了解BDNF和NT-5在女性生殖内分泌领域的研究进展,可能为不孕症治疗提供新方向,为辅助生殖结局的预测提供新指标。

基于BDNF/TrkB/CREB通路研究六味地黄丸对丙戊酸钠诱导的孤独症谱系障碍模型仔鼠的作用机制

目的基于脑源性神经营养因子(brain-derived neurotrophic factor,BDNF)/酪氨酸激酶受体B(tyrosine kinase receptor B,TrkB)/cAMP反应元件结合蛋白(cAMP response element binding protein,CREB)通路,探讨六味地黄丸对丙戊酸钠(sodium valproate,VPA)诱导的孤独症谱系障碍(autism spectrum disorder,ASD)仔鼠的作用机制。方法将13只SD孕鼠随机分为两组,其中10只孕鼠在第12.5天时腹腔注射VPA溶液(600 mg·kg^(-1))为VPA组,另外3只孕鼠注射等体积生理盐水为对照组。第21天对两组雄性仔鼠开展行为学检测,筛选出符合ASD疾病模型的仔鼠30只,随机分为模型组(等体积生理盐水),维生素D组(1480 IU·kg^(-1)),六味地黄丸高(3 g·kg^(-1))、中(1.5 g·kg^(-1))、低(0.75 g·kg^(-1))剂量组,每组6只。正常雄性仔鼠6只,设为空白组(等体积生理盐水)。各组仔鼠连续灌胃14 d,1次/d,给药后再次开展行为学检测。尼氏染色观察各组仔鼠海马组织神经元形态学变化,比色法检测各组仔鼠海马组织中谷氨酸(glutamic acid,GLU)、γ-氨基丁酸(gamma-aminobutyric acid,GABA)含量;qRT-PCR检测各组仔鼠海马组织中BDNF、TrkB、CREB mRNA相对表达。结果与对照组比较,VPA组仔鼠体质量、身长、尾长更小(P<0.05)。与空白组比较,模型组社交障碍症状明显(P<0.01),焦虑障碍症状明显(P<0.01),重复刻板行为增多(P<0.05或P<0.01),海马神经元结构损伤,GLU升高(P<0.01)、GABA下降(P<0.01),BDNF、TrkB、CREB mRNA表达降低(P<0.05或P<0.01);与模型组比较,维生素D组及六味地黄丸中、低剂量组仔鼠社交能力增强(P<0.05或P<0.01),焦虑障碍减轻(P<0.05或P<0.01),重复刻板行为减少(P<0.01或P<0.05),海马神经元结构明显复原,GLU下降(P<0.01),BDNF、TrkB、CREB mRNA表达增加(P<0.05或P<0.01),六味地黄丸中、低剂量组GABA上升(P<0.05或P<0.01)。结论六味地黄丸能显著改善VPA诱导的ASD仔鼠行为表现,增强海马组织神经元的再生与修复,其机制可能与平衡GLU、GABA水平,上调仔鼠海马组织中BDNF/TrkB/CREB的表达有关。

腧穴“解郁方”对慢性不可预测轻度应激抑郁大鼠下丘脑-垂体-肾上腺轴及BDNF/TrkB/CREB通路的影响

目的:观察腧穴“解郁方”对慢性不可预测轻度应激(CUMS)抑郁大鼠下丘脑-垂体-肾上腺(HPA)轴和脑源性神经营养因子(BDNF)/酪氨酸激酶B受体(TrkB)/环磷酸腺苷反应元件结合蛋白(CREB)信号通路的影响。方法:40只无特定病原体(SPF)级Sprague Danley(SD)雄性大鼠随机分为空白组(10只)、模型组(10只)、西药组(10只)、针刺组(10只),除空白组外,其余3组连续28 d构建CUMS抑郁大鼠模型,造模成功后,西药组连续14 d灌胃盐酸帕罗西汀混悬液,每日1次;针刺组针刺百会、太冲、神门,每日1次,每次20 min,连续针刺14 d。苏木素-伊红(HE)染色观察大鼠海马病理变化,酶联免疫吸附法(ELISA)测定血清促肾上腺皮质激素释放激素(CRH)、促肾上腺皮质激素(ACTH)、皮质醇(CORT)水平;免疫组化(IHC)检测海马BDNF、TrkB表达情况,蛋白质免疫印迹法(Western Blot)及实时荧光定量-聚合酶链式反应(PCR)测定海马BDNF、TrkB、CREB蛋白及mRNA的表达。结果:与空白组比较,模型组血清CRH、ACTH和CORT含量上升(P<0.01),海马病理损伤严重,海马BDNF、TrkB平均光密度降低(P<0.01),BDNF、TrkB、CREB蛋白及mRNA明显下降(P<0.05或P<0.01)。与模型组比较,针刺组血清CRH、ACTH、CORT含量下降(P<0.05),海马病理损害明显减轻,BDNF、TrkB平均光密度明显增加(P<0.05),BDNF、CREB、TrkB蛋白及mRNA表达水平上升(P<0.05)。结论:腧穴“解郁方”可能通过调节HPA轴和调控BDNF/TrkB/CREB信号通路,改善CUMS诱导的大鼠抑郁样行为。

脑源性神经营养因子与抑郁症的关系研究进展

抑郁症是一种致残性疾病,严重损害患者的生活质量,然而,抑郁症的发病机制尚未完全明确。脑源性神经营养因子(BDNF)是神经营养因子家族中的重要成员,其在神经元的存活、分化、突触可塑性及认知、情绪和记忆中发挥重要作用。研究发现,BDNF在大脑皮质和海马中的含量与抑郁症密切相关,其可以通过不同信号通路调控抑郁症的发生发展,因此,其可以作为抑郁症治疗的重要靶点。本文就近年来关于BDNF与抑郁症的关系以及BDNF信号通路在抑郁症发病和治疗中的作用机制研究进行综述,以期为临床上抑郁症的研究及治疗提供新思路。

苦参碱对缺氧/复氧小鼠海马神经元HT22细胞活力、凋亡的影响及机制研究

目的探讨苦参碱对缺氧/复氧(H/R)小鼠海马神经元HT22细胞活力、凋亡及脑源性神经营养因子(BDNF)/酪氨酸激酶受体B(TrkB)信号通路的影响。方法将处于对数生长期的HT22细胞分为对照组、H/R组及苦参碱低、中、高浓度组。对照组HT22细胞用无血清DMEM培养基在正常环境下培养28 h;H/R组HT22细胞在缺氧培养箱中维持4 h后在常氧条件下培养24 h;苦参碱低、中、高浓度组的H/R处理同H/R组,同时给予浓度分别为10、20、30μmol/L的苦参碱进行干预,培养24 h。检测HT22细胞活力、凋亡情况及凋亡相关蛋白[B淋巴细胞瘤-2基因(Bcl-2)、Bcl-2相关X蛋白(Bax)、半胱氨酸天冬氨酸蛋白水解酶-3(Caspase-3)]和BDNF/TrkB信号通路蛋白水平。结果与对照组比较,H/R组HT22细胞吸光度值、存活率、Bcl-2、BDNF、TrkB蛋白水平降低,细胞凋亡率、Bax、Caspase-3蛋白水平升高,差异有统计学意义(P<0.05);与H/R组比较,苦参碱低、中、高浓度组HT22细胞吸光度值、存活率、Bcl-2、BDNF、TrkB蛋白水平依次升高,细胞凋亡率、Bax、Caspase-3蛋白水平依次降低,差异有统计学意义(P<0.05),呈浓度依赖性。结论苦参碱能减轻H/R导致的神经元HT22细胞活力的降低,抑制HT22细胞凋亡,其机制可能与激活BDNF/TrkB信号通路有关。