Brain-derived neurotrophic factor mediates an excitoprotective effect of dietary restriction in mice

Dietary restriction (DR; reduced calorie intake) increases the lifespan of rodents and increases their resistance to cancer, diabetes and other age-related diseases. DR also exerts beneficial effects on the brain including enhanced learning and memory and increased resistance of neurons to excitotoxic, oxidative and metabolic insults. The mechanisms underlying the effects of DR on neuronal plasticity and survival are unknown. In the present study we show that levels of brain-derived neurotrophic factor (BDNF) are significantly increased in the hippocampus, cerebral cortex and striatum of mice maintained on an alternate day feeding DR regimen compared to animals fed ad libitum. Damage to hippocampal neurons induced by the excitotoxin kainic acid was significantly reduced in mice maintained on DR, and this neuroprotective effect was attenuated by intraventricular administration of a BDNF-blocking antibody. Our findings show that simply reducing food intake results in increased levels of BDNF in brain cells, and suggest that the resulting activation of BDNF signaling pathways plays a key role in the neuroprotective effect of DR. These results bolster accumulating evidence that DR may be an effective approach for increasing the resistance of the brain to damage and enhancing brain neuronal plasticity.     

Brain-derived neurotrophic factor shows a protective effect and improves recovery of the ERG b-wave response in light-damage

We investigated the neuroprotective effects of brain-derived neurotrophic factor (BDNF) and its influence on the functional recovery of the retina following light-induced retinal damage by electroretinogram (ERG). Rats were exposed to constant fluorescent light for 2, 5, 7, or 14 days, then returned to a cyclic light environment for 14 days. The result indicated that BDNF had few effects on the a-wave amplitude, but there was a statistically significant difference in the b-wave amplitudes between BDNF-treated and control eyes from day 0-14 of the recovery period following 2 days of light exposure (p < 0.05). Our findings suggest that BDNF not only protects the retinal neuronal function but also enhances the recovery from retinal light damage.     

Brain-derived neurotrophic factor promotes proliferation and progesterone synthesis in bovine granulosa cells

Brain-derived neurotrophic factor (BDNF) is involved in regulating the growth of ovarian follicles, maturation of the oocyte, and development of the early embryo through its receptor, tyrosine kinase receptor B (TrkB). However, it is still unclear as to how BDNF influences proliferation and steroidogenesis of bovine granulosa cells (GCs). In this paper, we confirmed that BDNF and TrkB were expressed in bovine GCs, and that proliferation and steroidogenesis by bovine GCs were reduced by knockdown of BDNF or inhibition of TrkB. With respect to GC proliferation, BDNF enhanced cellular viability and the percentage of cells in the S phase. BDNF also activated both protein kinase B (PKB, also known as AKT) and the extracellular signal-regulated protein kinase 1/2 (ERK1/2)-signaling pathway. Through the AKT-signaling pathway, BDNF increased the expression of proliferation-related genes, including cyclin A1 (CCNA1), cyclin E2 (CCNE2), cyclin D1 (CCND1), and cyclin-dependent kinase 1 (CDK1). However, through the ERK1/2 signaling pathway, BDNF only increased the expression of CCNA1 and CCNE2. Regarding steroidogenesis by bovine GCs, BDNF promoted progesterone (P ₄) synthesis, but had no effect on estradiol; it also activated the AKT-signaling pathway and increased the expression of steroidogenesis-related genes, including steroidogenic acute regulatory protein (STAR) and hydroxy-δ-5-steroid dehydrogenase, 3β- and steroid δ-isomerase 1 (HSD3B1). In summary, our data are the first to show that BDNF promotes the proliferation of bovine GCs through TrkB–AKT and ERK1/2 signaling pathways and increases P₄ synthesis by bovine GCs through the TrkB–AKT signaling pathway.     

Brain-derived neurotrophic factor levels in the nervous system of wild-type and neurotrophin gene mutant mice

Although brain-derived neurotrophic factor is the most abundant and widely distributed neurotrophin in the nervous system, reproducible determinations of its levels have been hampered by difficulties in raising suitable monoclonal antibodies. Following immunization of mice with recombinant fish and mammalian brain-derived neurotrophic factor, monoclonal antibodies were generated and used in an immunoassay based on the recognition of two different epitopes. Neither antibody crossreacts with neurotrophin homodimers other than brain-derived neurotrophic factor, although reactivity was detected with brain-derived neurotrophic factor/neurotrophin-3 heterodimers. As both nerve growth factor and neurotrophin-3 are known to affect the development of a variety of neurons expressing the brain-derived neurotrophic factor (bdnf) gene, this assay was used to determine levels in tissues isolated from newborn mice carrying a null mutation in the nerve growth factor (ngf) or the neurotrophin-3 (nt3) gene. Marked differences were observed between mutants and wild-type littermates in the PNS, but not in the CNS, suggesting that neither nerve growth factor nor neurotrophin-3 is a unique regulator of brain-derived neurotrophic factor levels in the newborn mouse CNS.     

Brain-derived neurotrophic factor and risk of schizophrenia: an association study and meta-analysis

Brain-derived neurotrophic factor (BDNF) is the most widely distributed neurotrophin in the central nervous system (CNS), and performs many biological functions such as neural survival, differentiation, and plasticity. Previous studies have suggested that variants in the BDNF gene increase the risk of schizophrenia. In this study, we genotyped one (GT)n dinucleotide repeat and three SNPs (rs6265, rs2030324, and rs2883187) in a Chinese sample (617 cases and 672 controls). In addition, we performed an updated meta-analysis based on 16 population-based case-control studies examining association between rs6265 and schizophrenia. In single-locus analysis, no significant association was found between BDNF polymorphisms and schizophrenia in our subjects. The meta-analysis based on Asian and Caucasian subjects did not give positive result that rs6265 is associated with schizophrenia. However, haplotype analysis found a common four-locus haplotype is protective against schizophrenia (Case 3.1% vs Control 7%, p=0.0011). Our data provides evidence that BDNF is a susceptibility gene for schizophrenia in Chinese subjects.     

Brain-derived neurotrophic factor (Val66Met) polymorphism and olfactory ability in young adults

Background

Brain- derived neurotrophic factor (BDNF) is linked to neurodegenerative diseases (e.g. Alzheimer disease and Parkinson disease) which are often characterized by olfactory impairment. A specific single nucleotide polymorphism of the BDNF gene, the Val66Met, modulates intracellular trafficking and activity-dependent secretion of BDNF protein. The aim of this study was to investigate a possible association between brain- derived neurotrophic factor Val66Met polymorphism and olfactory function, a well-known biomarker for neurodegeneration, in healthy young adults. A total of 101 subjects (45 males, age 38.7 ± 9.4 years) were assessed using the Sniffin’ Sticks Extended Test, a highly reliable commercial olfactory test composed of three sub-parts, calculating olfactory threshold (sensitivity), odor discrimination and odor identification. The Val66Met polymorphism was determined by polymerase chain reaction -restriction fragment length polymorphism (PCR-RFLP) analysis.

Results

An impaired function in Met carriers was found, especially when compared to subjects with Val/Val genotype, in the threshold (5.5 ± 2.0 vs 6.5 ± 1.8, p = 0.009), discrimination (10.3± 2.5 vs 11.9 ± 2.2, p = 0.002), and identification task (13.3 ± 1.6 vs 14.1 ± 1.3, p = 0.007), as well as in the overall TDI Score (29.1 ± 4.5 vs 32.6 ± 3.9, p < 0.001).

Conclusions

These findings appear to have implications for the evaluation of olfactory function and the relation of its impairment to cognitive decline and neurodegenerative disease.     

Brain-derived neurotrophic factor over-expression in the forebrain ameliorates Huntington's disease phenotypes in mice

Huntington's disease (HD), a dominantly inherited neurodegenerative disorder characterized by relatively selective degeneration of striatal neurons, is caused by an expanded polyglutamine tract of the huntingtin (htt) protein. The htt mutation reduces levels of brain-derived neurotrophic factor (BDNF) in the striatum, likely by inhibiting cortical BDNF gene expression and anterograde transport of BDNF from cortex to striatum. However, roles of the BDNF reduction in HD pathogenesis have not been established conclusively. We reasoned that increasing striatal BDNF through over-expression would slow progression of the disease if BDNF reduction plays a pivotal role in HD pathogenesis. We employed a Bdnf transgene driven by the promoter for the alpha subunit of Ca²⁺/calmodulin-dependent kinase II to over-express BDNF in the forebrain of R6/1 mice which express a fragment of mutant htt with a 116-glutamine tract. The Bdnf transgene increased BDNF levels and TrkB signaling activity in the striatum, ameliorated motor dysfunction, and reversed brain weight loss in R6/1 mice. Furthermore, it normalized DARPP-32 expression of the 32 kDa dopamine and cAMP-regulated phosphoprotein, increased the number of enkephalin-containing boutons, and reduced formation of neuronal intranuclear inclusions in the striatum of R6/1 mice. These results demonstrate crucial roles of reduced striatal BDNF in HD pathogenesis and suggest potential therapeutic values of BDNF to HD.     

Brain-derived neurotrophic factor accelerates nitric oxide donor-induced apoptosis of cultured cortical neurons

Brain-derived neurotrophic factor (BDNF) is known to have important functions in neuronal survival, differentiation, and plasticity. In addition to its role as a survival-promoting factor, BDNF reportedly can enhance neuronal cell death in some cases, for example, the death caused by excitotoxicity or glucose deprivation. The cellular mechanism of the death-enhancing effect of BDNF remains unknown, in contrast to that of its survival-promoting effect. In this work, we found that BDNF markedly accelerated the nitric oxide (NO) donor-induced death of cultured embryonic cortical neurons. BDNF increased the number of cells with nuclear condensation and DNA fragmentation 24 h after treatment with the NO donor, but it did not change the number of those cells 36 h after the treatment. The BDNF-accelerated death of cortical neurons was inhibited by the addition of actinomycin D or cycloheximide. These results suggest that BDNF can accelerate apoptotic cell death elicited by NO donor. TrkB-IgG and K252a blocked the BDNF-induced acceleration of the death, indicating that the death-accelerating effect by BDNF is mediated by TrkB. In addition, the BDNF-accelerated apoptosis was inhibited by the addition of SB202190 and SB203580, specific inhibitors of p38 mitogen-activated protein kinase (MAPK), and U0126, a specific inhibitor of MAPK/ERK kinase 1, indicating that the activation of both p38 MAPK and ERK is involved in the signaling cascade of the BDNF-accelerated, NO donor-induced apoptosis.     

Brain-derived neurotrophic factor transiently stabilizes silent synapses on developing neuromuscular junctions

A general feature of the developing nervous system is the activity-dependent rearrangement of genetically defined, synaptic connections. A parallel process occurs at the developing neuromuscular junction as activity-dependent synapse withdrawal reduces the initial polyneuronal innervation of individual muscle fibers to a mononeuronal innervation within the first few weeks after birth. Because members of the neurotrophin gene family influence motor neuron differentiation and survival, we examined whether or not they also influence synaptic rearrangements in neonatal muscles. We found that treatment with brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), or neurotrophin-4/5 (NT-4/5) causes the transient retention of multiple synaptic contacts on neonatal myofibers. However, the combination of both electrophysiological and histological assays revealed that the majority of such supernumerary synaptic contacts are functionally inactive or “silent.” There also occurs an increase in the number of retracting axons. Because BDNF mRNA is expressed in developing muscle and the trkB tyrosine kinase receptor for BDNF is expressed by neonatal motor neurons, our results suggest that BDNF may play an endogenous role in the refinement of synaptic connectivity that occurs in skeletal muscles after birth. © 1996 John Wiley & Sons, Inc.     

Brain-derived neurotrophic factor facilitates maturation of mesenchymal stem cell-derived dopamine progenitors to functional neurons

The generation of dopamine (DA) neurons from stem cells holds great promise in the treatment of Parkinson's disease and other neural disease associated with dysfunction of DA neurons. Mesenchymal stem cells (MSCs) derived from the adult bone marrow show plasticity with regards to generating cells of other germ layers. In addition to reduced ethical concerns, MSCs could be transplanted across allogeneic barriers, making them desirable stem cells for clinical applications. We have reported on the generation of DA cells from human MSCs using sonic hedgehog (SHH), fibroblast growth factor 8 and basic fibroblast growth factor. Despite the secretion of DA, the cells did not show evidence of functional neurons, and were therefore designated DA progenitors. Here, we report on the role of brain-derived neurotrophic factor (BDNF) in the maturation of the MSC-derived DA progenitors. 9-day induced MSCs show significant tropomyosin-receptor-kinase B expression, which correlate with its ligand, BDNF, being able to induce functional maturation. The latter was based on Ca²⁺ imaging analyses and electrophysiology. BDNF-treated cells showed the following: increases in intracellular Ca²⁺ upon depolarization and after stimulation with the neurotransmitters acetylcholine and GABA and, post-synaptic currents by electrophysiological analyses. In addition, BDNF induced increased DA release upon depolarization. Taken together, these results demonstrate the crucial role for BDNF in the functional maturation of MSC-derived DA progenitors.     

睫状神经营养因子对大鼠去神经骨骼肌的营养作用

目的：了解睫状神经营养因子（CNTF）对去神经引起的肌肉萎缩的治疗作用。方法：离断SD大鼠一侧坐骨神经,连续给予CNTF20d,观察肌肉湿重、蛋白含量、肌纤维横截面积、收缩性能和残肢程度。结果：①给予0.2mg/kg的CNTF,可使损务侧肌纤维横截面积增加35％,肌肉湿重增加38％,胫前肌总蛋白含量增加24％,腓长肌强直收缩强度提高40％,显著改善肢残程度;②0.2mg/kg的CNTF作用明显强于0.05mg/kg的CNTF;③此目鱼肌（慢肌）比伸趾长肌（快肌）对CNTF更敏感。结论：CNTF能显著改善成年大鼠坐骨神经离断后骨骼肌的萎缩和功能丧失,该效应的强弱与用药剂量和肌肉类型有关。     

脑源性神经营养因子研究进展

脑源性神经营养因子是一种小分子二聚体蛋白质,在结构上与神经生长因子相关。对中枢神经系统的多种类型神经元的生长、发育、分化、维护和再生部具有重要作用,对于治疗运动神经元病变以及神经系统迟行性疾病有显疗效。本对其细胞与分子生物学特征、生物学功能进行阐述。     

Brain-derived neurotrophic factor (BDNF) mediates bone morphogenetic protein-2 (BMP-2) effects on cultured striatal neurones

Bone morphogenetic proteins are members of the transforming growth factor-beta superfamily that have multiple functions in the developing nervous system. One of them, bone morphogenetic protein-2 (BMP-2), promotes the differentiation of cultured striatal neurones, enhancing dendrite growth and calbindin-positive phenotype. Bone morphogenetic proteins have been implicated in cooperative interactions with other neurotrophic factors. Here we examined whether the effects of BMP-2 on cultured striatal neurones are mediated or enhanced by other neurotrophic factors. BMP-2 had a cooperative effect with low doses of brain-derived neurotrophic factor or neurotrophin-3 (but not with other neurotrophic factors such as glial cell line-derived neurotrophic factor, neurturin or transforming growth factor-beta 2) on the number of calbindin-positive striatal neurones. Moreover, BMP-2 induced phosphorylated Trk immunoreactivity in cultured striatal neurones, suggesting that neurotrophins are involved in BMP-2 neurotrophic effects. The addition of TrkB-IgG or antibodies against brain-derived neurotrophic factor abolished the effects of BMP-2 on the number and degree of differentiation of calbindin-positive striatal neurones. Indeed, BMP-2 treatment increased brain-derived neurotrophic factor protein levels in treated cultures media and BDNF immunocytochemistry revealed that this neurotrophin was produced by neuronal cells. Taken together, these results indicate that brain-derived neurotrophic factor mediates the effects of BMP-2 on striatal neurones.     

Precursor form of brain-derived neurotrophic factor and mature brain-derived neurotrophic factor are decreased in the pre-clinical stages of Alzheimer's disease

Brain-derived neurotrophic factor (BDNF) is critical for the function and survival of neurons that degenerate in the late stage of Alzheimer's disease (AD). There are two forms of BDNF, the BDNF precursor (proBDNF) and mature BDNF, in human brain. Previous studies have shown that BDNF mRNA and protein, including proBDNF, are dramatically decreased in end-stage AD brain. To determine whether this BDNF decrease is an early or late event during the progression of cognitive decline, we used western blotting to measure the relative amounts of BDNF proteins in the parietal cortex of subjects clinically classified with no cognitive impairment (NCI), mild cognitive impairment (MCI) or mild to moderate AD. We found that the amount of proBDNF decreased 21 and 30% in MCI and AD groups, respectively, as compared with NCI, consistent with our previous results of a 40% decrease in end-stage AD. Mature BDNF was reduced 34 and 62% in MCI and AD groups, respectively. Thus, the decrease in mature BDNF and proBDNF precedes the decline in choline acetyltransferase activity which occurs later in AD. Both proBDNF and mature BDNF levels were positively correlated with cognitive measures such as the Global Cognitive Score and the Mini Mental State Examination score. These results demonstrate that the reduction of both forms of BDNF occurs early in the course of AD and correlates with loss of cognitive function, suggesting that proBDNF and BDNF play a role in synaptic loss and cellular dysfunction underlying cognitive impairment in AD.     

Brain-derived neurotrophic factor regulates LYN kinase–mediated myosin light chain kinase activation to modulate nonmuscle myosin II activity in hippocampal neurons

Myosins belong to a large superfamily of actin-dependent molecular motors. Nonmuscle myosin II (NM II) is involved in the morphology and function of neurons, but little is known about how NM II activity is regulated. Brain-derived neurotrophic factor (BDNF) is a prevalent neurotrophic factor in the brain that encourages growth and differentiation of neurons and synapses. In this study, we report that BDNF upregulates the phosphorylation of myosin regulatory light chain (MLC2), to increases the activity of NM II. The role of BDNF on modulating the phosphorylation of MLC2 was validated by using Western blotting in primary cultured hippocampal neurons. This result was confirmed by injecting BDNF into the dorsal hippocampus of mice and detecting the phosphorylation level of MLC2 by Western blotting. We further perform coimmunoprecipitation assay to confirm that this process depends on the activation of the LYN kinase through binding with tyrosine kinase receptor B, the receptor of BDNF, in a kinase activity-dependent manner. LYN kinase subsequently phosphorylates MLCK, further promoting the phosphorylation of MLC2. Taken together, our results suggest a new molecular mechanism by which BDNF regulates MLC2 activity, which provides a new perspective for further understanding the functional regulation of NM II in the nervous system.     

The 712A/G polymorphism of Brain-derived neurotrophic factor is associated with Parkinson's disease but not Major Depressive Disorder in a Chinese Han population

Background: Overlaps in clinical, pathological and molecular characteristics of Parkinson’s disease (PD) and Major Depressive Disorder (MD-D) have promoted association studies in search of common genetic risk factors that may predispose or modify this spectrum of disorders. Experimental and clinical data suggest that genetic variations in Brain-derived neurotrophic factor (BDNF) gene may increase the risk for PD and MD-D. Methods: Two hundred and sixty-six PD, 83 MD-D and 400 controls were recruited for this study, assessed using a battery of neuropsychological tests, and genotyped for 11757C/G, 712A/G, 196A/G, and 270C/T in BDNF gene. Results: 712A/G was associated with 2.50-fold time risk of PD. By combining genotypes AG/AA with 712 GG genotype as reference (OR = 1) in stratification analysis, AG/AA genotypes were associated with PD (OR = 2.94, 95% CI = 1.88–4.61). Accordingly, the A allele was significantly overrepresented in PD compared with the G allele (OR = 3.16, 95% CI = 2.08–4.81). This distribution in females and males were similar. Conclusion: Our results suggested a novel association between BDNF 712A/G AG/AA genotypes and PD in a Chinese Han population.     

周围神经损伤后外源性GDNF对神经元的保护作用

采用硅管套接大鼠切断的坐骨神经模型 ,局部给予胶质细胞源性神经营养因子 (GDNF) ,应用尼氏染色、酶组织化学染色方法 ,观察到外源性GDNF能减少脊髓修复侧前角运动神经元死亡的数目 ,降低脊髓前角运动神经元及脊神经节感觉神经元中胆碱酯酶 (CHE)及酸性磷酸酶 (ACP)变化的幅度。这表明外源性GDNF能保护周围神经切断后引起的神经元损伤。     

睫状神经营养因子对应激引起大鼠海马神经元损伤的保护作用及其机制的研究

本实验用Ｎｉｓｓｌ染色法、Ｂｉｅｌｓｃｈｏｗｓｋｙ－Ｇｒｏｓ－Ｌａｗｒｅｎｔｊｅｗ染色法、常规透射电镜、行为活动测定、双侧海马微量给药、海马神经元原代培养、活细胞连续照相、全细胞膜片钳记录、细胞内游离Ｃａ＾２＋浓度测定及Ｐ５３蛋白免疫组化测定等方法,观察了睫状神经营养因子（ＣＮＴＦ）对应激引起动物行为变化和海马神经元形态学变化的影响,探讨了ＣＮＴＦ的部分作用机制。结果表明,急性应激不引起大鼠海马神