The Signaling Pathway of Neurotrophic Factor Biosynthesis

There are various neurotrophic factors, such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF) and interleukin-6 (IL-6), which are essential for the promotion of neuronal survival (prevention of apoptosis), differentiation and regeneration in the central nervous system. Neurotrophic factors, neurotrophic factor-like substances and inducers of neurotrophic factor biosynthesis have enormous therapeutic potential for serious neuronal diseases such as Alzheimer's disease or traumatic, chemical and ischemic lesions in the brain. The clarification of the mechanism in neurotrophic factor biosynthesis is important in understanding the development of the drugs that stimulate neurotrophic factor production. In this review, we describe these mechanisms in the biosynthesis of NGF, BDNF, GDNF and IL-6, and also discuss the drugs that could possibly promote neurotrophic factor biosynthesis. (c) 2002 Prous Science. All rights reserved.     

Plasma Brain-Derived Neurotrophic Factor in treatment-resistant depressed patients receiving electroconvulsive therapy

There is an increasing evidence that the Brain-Derived Neurotrophic Factor (BDNF) could be involved in the mode of action of antidepressants and, perhaps, of ECT. This study aimed to investigate whether the clinical course of medication-resistant depressed patients following a course of ECT might be associated with changes of plasma BDNF concentrations. Our findings showed that at T0 (baseline) plasma BDNF levels of patients were significantly lower than those of control subjects, and that at T2 (after ECT) were significantly increased in parallel with the decrease of the Hamilton Rating Scale for Depression (HRSD) total score. However, only remitter patients who showed higher baseline BDNF levels than non-remitters reached normalized BDNF levels after ECT. These findings would suggest the potential usefulness of baseline plasma BDNF levels as predictors of response to ECT in treatment-resistant depressed patients.     

甲基苯丙胺成瘾者戒断期的脑源性神经营养因子变化研究进展

脑源性神经营养因子(brain-derived neurotrophic factor,BDNF)参与了神经发生、神经可塑性及认知功能等多种神经活动,参与学习和记忆的过程,对神经可塑性的调节和损伤后修复具有重要影响,被认为是与成瘾行为相关的生物标志物.本文回顾了国内外BDNF与物质成瘾关系以及甲基苯丙胺成瘾者戒断期外周...     

Combined Use of Carboxyl-Directed Protein Pegylation and Vector-Mediated Blood-Brain Barrier Drug Delivery System Optimizes Brain Uptake of Brain-Derived Neurotrophic Factor Following Intravenous Administration

Purpose. Peptide drug delivery to the brain requires optimization of (a) plasma pharmacokinetics and (b) blood-brain barrier (BBB) permeability. In the present studies, plasma pharmacokinetics are improved with protein pegylation and BBB transport is facilitated with the use of vector-mediated drug delivery using the OX26 monoclonal antibody (MAb) to the rat transferrin receptor, which undergoes receptor-mediated transcytosis through the BBB in vivo. Methods. A conjugate of OX26 and streptavidin (SA), designated OX26/SA, was prepared in parallel with the carboxyl-directed pegylation of brain-derived neurotrophic factor (BDNF). A novel bifunctional polyethyleneglycol (PEG) was used in which a hydrazide (Hz) was attached at one end and a biotin moiety was attached to the other end. This allowed for conjugation of BDNF-PEG-biotin to OX26/SA. Results. The brain uptake of BDNF-PEG-biotin was increased following conjugation to OX26/SA to a level of 0.144 ± 0.004% injected dose per g brain and a BBB permeability-surface area product of 2.0 ± 0.2 L/min/g. Conclusions. These studies demonstrate that peptide drug delivery to the brain can be achieved with advanced formulation of protein-based therapeutics. The formulation is intended to (a) minimize rapid systemic clearance of the peptide, and (b) allow for vector-mediated drug delivery through the BBB in vivo. Following this dual formulation, the brain uptake of a neurotrophin such as BDNF achieves a value that is approximately 2-fold greater than that of morphine, a neuroactive small molecule.     

Kinetic and Safety Studies on Intrathecally Infused Recombinant-Methionyl Human Brain-Derived Neurotrophic Factor in Dogs

To define the kinetics and safety of spinally infused recombinant-methionylhuman brain-derived neurotrophic factor (r metHuBDNF), beagledogs were prepared with lumbar intrathecal catheters passedthrough the cisternal membrane to the L1-L4 lumbar level. Forkinetic studies, r-metHuBDNF was delivered by bolus or infusionthrough one catheter and lumbar CSF was sampled periodicallythrough a second. As a lumbar boles, r-metHuBDNF displayed abiphasic clearance with ta = 0.7 hr and tb = 7.9 hr. Lumbarto cisternal concentrations after bolus delivery were approximately60:1. For safety studies, dogs received continuous intrathecalinfusion (2.4 ml/day) for 28 days of saline (n = 6), r-metHuBDNFat 200 (n = 6), 800 (n = 6), or 2000 (n = 7) µg/day. Controldogs showed no changes. Intrathecally infused r-metHuBDNF produceda dose-dependent increase in muscle tone and decreased coordination.Low-dose r-metHuBDNF was associated with moderate increasesin muscle tone after 22–28 days of infusion. No clinicallyimportant changes were noted in rectal temperature, arterialpressure, respiration and heart rate, body weight, food consumption,stool or urine output, or change in blood chemistries measuredthroughout the study. Cisternal CSF protein and glucose sampledat 28 days were not different between dose groups and all cultureswere negative. Histopathological examination of the spinal cordtypically revealed some degree of chronic inflammation aroundthe catheter, including fibrotic adhesions and focal accumulationsof lymphoid and plasma cells, but these effects were not dosedependent. In other dogs receiving r-metHuBDNF (2000 or 4000µg/day), termination of infusion resulted in significantrecovery.     

Transport of Human Recombinant Brain-Derived Neurotrophic Factor (BDNF) Through the Rat Blood−Brain Barrier in Vivo Using Vector-Mediated Peptide Drug Delivery

The blood–brain barrier (BBB) transport of brain-derived neurotrophic factor (BDNF) in anesthetized rats was examined in the present studies using vector-mediated peptide drug delivery. Following tritiation, the BDNF was biotinylated via a disulfide linker and was coupled to a covalent conjugate of neutral avidin (NLA), which binds the biotinylated peptide with a high affinity, and the murine OX26 monoclonal antibody to the rat transferrin receptor. Owing to the abundance of transferrin receptors on brain capillary endothelium, the OX26 monoclonal antibody undergoes receptor-mediated transcytosis through the BBB, and the NLA–OX26 conjugate transports biotinylated peptide therapeutics through the BBB. The present studies show that while unconjugated BDNF was not transported through the BBB in vivo, the conjugation of biotinylated BDNF to the NLA–OX26 vector resulted in a marked increase in the brain delivery of BDNF, as defined by measurements of the percentage of the injected dose (ID) delivered per gram of brain. Although BDNF was not transported through the BBB in vivo, this cationic peptide was avidly bound by isolated human brain capillaries via a low-affinity, high-capacity system that was inhibited by protamine and by serum protein binding of BDNF. In conclusion, these studies show that the delivery of unconjugated BDNF to brain is nil owing to the combined effects of negligible BBB transport and rapid systemic clearance of intravenous administered BDNF. The brain delivery of BDNF may be augmented by conjugation of BDNF to BBB drug delivery vectors, such as the NLA–OX26 conjugate.     

Regional Differences in Brain-Derived Neurotrophic Factor Levels and Dendritic Spine Density Confer Resilience to Inescapable Stress

Background:

In the learned helplessness (LH) paradigm, approximately 35% of rats are resilient to inescapable stress.

Methods:

The roles of brain-derived neurotrophic factor (BDNF) and dendritic spine density in the brain regions of LH (susceptible) and non-LH rats (resilient) were examined. Western blot analysis and Golgi staining were performed.

Results:

BDNF levels in the medial prefrontal cortex, CA3, and dentate gyrus (DG) were significantly lower in the LH group than in the control and non-LH groups, whereas BDNF levels in the nucleus accumbens (NAc) in the LH group but not the non-LH group were significantly higher than those in the control group. Furthermore, spine density in the prelimbic cortex, CA3, and DG was significantly lower in the LH group than in the control and non-LH groups, although spine density in the NAc was significantly higher in the LH group than in the control and non-LH groups.

Conclusions:

The results suggest that regional differences in BDNF levels and spine density in rat brain may contribute to resilience to inescapable stress.     

Metal-Catalyzed Oxidation of Brain-Derived Neurotrophic Factor (BDNF): Analytical Challenges for the Identification of Modified Sites

Purpose. We examined the metal-catalyzed oxidation of brain-derivedneurotrophic factor (BDNF) using the Cu(II)/ascorbate/O₂ modeloxidative system. Methods. Electrospray ionization mass spectrometry, peptide mappingand amino acid analysis were utilized to determine the nature of thecovalent modification induced by the metal-catalyzed oxidative system.Additionally, analytical ultracentrifugation, the Bradford assay, circulardichroism and ANSA dye-binding were used to determine the natureof any conformational changes induced by the oxidation. Results. Exposure of BDNF to the Cu(II)/ascorbate/O₂ system led tothe modification of ca. 35% of Met⁹² to its sulfoxide, and to subsequentconformational changes. The proteolytic digestion procedure wassensitive to this conformational change, and was unable to detect themodification. Chemical digestion with CNBr, however, was not sensitive tothis change, and allowed for the identification of the site ofmodification. Conclusions. The modification of Met⁹² to its sulfoxide rendered theoxidized BDNF inaccessible to proteolytic digestion, due toconformational changes associated with the oxidation.     

Micellar Nanocarriers: Potential Nose-to-Brain Delivery of Zolmitriptan as Novel Migraine Therapy

Purpose  

The investigation was aimed at developing micellar nanocarriers for nose-to-brain delivery of zolmitriptan with the objective to investigate the pathway involved in the drug transport.     

Nose-to-Brain Delivery: Evaluation of Polymeric Nanoparticles on Olfactory Ensheathing Cells Uptake

The nasal route has received a great deal of attention as a convenient and reliable method for the brain target on administration of drugs. When drugs are loaded into nanoparticles (NPs) the interaction with mucosa transports directly into the brain, skipping the blood–brain barrier and achieving rapid cerebrospinal fluid levels. Poly-lactic acid (PLA), poly-lactic-co-glycolic acid (PLGA), and chitosan (CS) were chosen to prepare NPs. After optimization of CS nanocarriers, our goal was to evaluate the different type of NPs uptake into olfactory ensheathing cells (OECs). We then correlated obtained biological data to zeta potential measurements of cells treated with NPs. Rodhamine-loaded NPs were used to study the uptake of OECs carried out by confocal microscopy at different times (1, 2, and 4 h). Our results showed that uptake of rodhamine-NPs by OECs was time dependent and it was influenced by the carrier charge. Confocal imaging of OECs demonstrated that NPPLGA showed a higher increase in uptake compared with NPPLA and NPCS after 1 h and it increased at 2–4 h. Zeta potential values of treated cells were more amplified with respect to untreated cells. The highest values were showed by unloaded NPPLGA, confirming microscopy data.     

The Hypotonic Environmental Changes Affect Liposomal Formulations for Nose-to-Brain Targeted Drug Delivery

Systemic administration of drugs is ineffective in the treatment of central nervous system disorders because of the blood-brain barrier. Nasal administration has been suggested as an alternative administration route as drugs absorbed in the olfactory epithelium bypass the blood-brain barrier and reach the brain within minutes. However, the nasal mucosa properties (e.g., tonicity, pH) are not constant because of physiological and environmental factors, and this might limit the therapeutic outcome of nanocarrier-based formulations. To shine light on the impact of environmental ionic strength on nanocarrier-based formulations, we have studied how liposomal formulations respond to the change of tonicity of the external environment. Large unilamellar vesicles loaded with 6 different drugs were exposed to different hypotonic environments, creating an osmotic gradient within the inner core and external environment of the liposomes up to 650 mOsm/kg. Both size and polydispersity of liposomes were significantly affected by tonicity changes. Moreover, the release kinetics of hydrophilic and lipophilic drugs were largely enhanced by hypotonic environments. These results clearly demonstrate that the environmental ionic strength has an impact on liposomal formulation stability and drug release kinetics and it should be considered when liposomal formulations for nose-to-brain targeted drug delivery are designed.     

Adenoviral Vector-Mediated Delivery Of Glial Cell Line-Derived Neurotrophic Factor Provides Neuroprotection In The Aged Parkinsonian Rat

1. The long-term delivery of neurotrophic factors to specific regions of the central nervous system via gene therapy offers a new strategy for the treatment of neurodegenerative disorders. 2. The neurotrophic factor glial cell line-derived neurotrophic factor (GDNF) is a potent dopaminergic (DA) trophic factor that ameliorates the behavioural and histological consequences of lesioning DA neurons in rodent and primate models of Parkinson's disease. 3. Glial cell line-derived neurotrophic factor gene therapy may have a potential use in the clinical treatment of Parkinson's disease. 4. We examined whether injection of an adenoviral vector encoding human GDNF preproprotein (Ad GDNF) could protect the rat nigrostriatal DA system from progressive neuronal degeneration. Because Parkinson's disease occurs primarily in the elderly population, we studied the effect of GDNF gene delivery in an aged rat model of Parkinson's disease. 5. In the aged (20 month) Fischer 344 rat, Ad GDNF was injected either near DA cell bodies in the substantia nigra (SN) or at the DA terminals in the striatum. One week following gene delivery, the neurotoxin 6-hydroxydopamine (6-OHDA) was injected unilaterally into the striatum to cause progressive degeneration of the DA neurons. 6. Injection of GDNF vector into either the striatum or the SN provided significant cell protection against 6-OHDA. However, only striatal injection of Ad GDNF protected against the development of behavioural and neurochemical changes that occur in the DA-depleted brain. 7. The results of this study are reviewed here and the behavioural and cellular effects of GDNF gene delivery into striatal versus mesencephalic sites are discussed.     

A Single Brain-Derived Neurotrophic Factor Infusion into the Dorsomedial Prefrontal Cortex Attenuates Cocaine Self-Administration-Induced Phosphorylation of Synapsin in the Nucleus Accumbens during Early Withdrawal

Background:

Dysregulation in the prefrontal cortex-nucleus accumbens pathway has been implicated in cocaine addiction. We have previously demonstrated that one intra-dorsomedial prefrontal cortex brain-derived neurotrophic factor (BDNF) infusion immediately following the last cocaine self-administration session caused a long-lasting inhibition of cocaine-seeking and normalized the cocaine-induced disturbance of glutamate transmission in the nucleus accumbens after extinction and a cocaine prime. However, the molecular mechanism mediating the brain-derived neurotrophic factor effect on cocaine-induced alterations in extracellular glutamate levels is unknown.

Methods:

In the present study, we determined the effects of brain-derived neurotrophic factor on cocaine-induced changes in the phosphorylation of synapsin (p-synapsin), a family of presynaptic proteins that mediate synaptic vesicle mobilization, in the nucleus accumbens during early withdrawal.

Results:

Two hours after cocaine self-administration, p-synapsin Ser9 and p-synapsin Ser62/67, but not p-synapsin Ser603, were increased in the nucleus accumbens. At 22 hours, only p-synapsin Ser9 was still elevated. Elevations at both time points were attenuated by an intra-dorsomedial prefrontal cortex brain-derived neurotrophic factor infusion immediately after the end of cocaine self-administration. Brain-derived neurotrophic factor also reduced cocaine self-administration withdrawal-induced phosphorylation of the protein phosphatase 2A C-subunit, suggesting that brain-derived neurotrophic factor disinhibits protein phosphatase 2A C-subunit, consistent with p-synapsin Ser9 dephosphorylation. Further, co-immunoprecipitation demonstrated that protein phosphatase 2A C-subunit and synapsin are associated in a protein-protein complex that was reduced after 2 hours of withdrawal from cocaine self-administration and reversed by brain-derived neurotrophic factor.

Conclusions:

Taken together, these findings demonstrate that brain-derived neurotrophic factor normalizes the cocaine self-administration–induced elevation of p-synapsin in nucleus accumbens that may underlie a disturbance in the probability of neurotransmitter release or represent a compensatory neuroadaptation in response to the hypofunction within the prefrontal cortex-nucleus accumbens pathway during cocaine withdrawal.     

脑源性神经营养因子在抑郁症中的研究进展

脑源性神经营养因子（brain-derived neurotrophic factor,BDNF）是参与机体情绪和认知功能至关重要的调节因子,能够促进脑内神经发生和突触发育。在抑郁患者及抑郁动物模型中,BDNF前体（brain-derived neurotrophic factor precursor,proBDNF）和前肽水平升高,BDNF成熟体（mature brain-derived neurotrophic factor,mBDNF）水平降低;抗抑郁药物治疗后,能够抑制proBDNF以及BDNF前肽的表达,促进mBDNF/proBDNF蛋白比值的升高。目前临床常见抗抑郁药的抗抑郁作用多依赖于BDNF及相关蛋白的信号转导。本文通过查阅文献,对BDNF及其相关因子在抑郁症中的作用进行总结。     

Implementing Neuronal Plasticity in NeuroAIDS: the Experience of Brain-derived Neurotrophic Factor and other Neurotrophic Factors

Human immunodeficiency virus type-1 (HIV) causes mild or severe neurological problems, termed HIV-associated neurocognitive disorder (HAND), even when HIV patients receive antiretroviral therapy. Thus, novel adjunctive therapies are necessary to reduce or abolish the neurotoxic effect of HIV. However, new therapies require a better understanding of the molecular and cellular mechanisms of HIV-induced neurotoxicity. HAND subjects are characterized by being profoundly depressed, and they experience deficits in memory, learning and movements. Experimental evidence has also shown that HIV reduces neurogenesis. These deficits resemble those occurring in premature brain aging or in a brain with impaired neural repair properties. Thus, it appears that HIV diminishes neuronal survival, along with reduced neuronal connections. These two phenomena should not occur in the adult and developing brain when synaptic plasticity is promoted by neurotrophic factors, polypeptides that are present in adult synapses. This review will outline experimental evidence as well as present emerging concepts for the use of neurotrophic factors and in particular brain-derived neurotrophic factor as an adjunct therapy to prevent HIV-mediated neuronal degeneration and restore the loss of synaptic connections.     

人睫状神经营养因子基因的克隆及序列分析

目的：构建1例2型糖尿病足坏疽截肢患者睫状神经营养因子（hCNTF）cDNA的克隆，为进一步研究睫状神经营养因子与2型糖尿病及其并发症发病的关系奠定基础。方法：从糖尿病足坏疽截肢患者坐骨神经组织中提取总RNA，经逆转录-聚合酶链式反应（RT-PCR）扩增hCNTFcDNA完全编码区，扩增产物经纯化后克隆至pMD18-T载体，并进行测序及序列分析。结果：成功构建此患者CNTFcDNA的克隆，重组质粒（pMD18-T／CNTF）经测序与Genebank检索的hCNTFcDNA突变序列（Accession NM_S72921）100％符合。结论：构建的突变CNTFcDNA克隆为进一步研究CNTF与2型糖尿病及其并发症在发病上的关系提供线索。     

Using Polymer Chemistry to Modulate the Delivery of Neurotrophic Factors from Degradable Microspheres: Delivery of BDNF

Purpose  

Brain-derived neurotrophic factor (BDNF) plays an important role in neuroprotection and repair, but long-term delivery from polymer systems has been challenging. We investigated the role the chemistry of the polymer played in loading and delivery of BDNF via microspheres, which are suitable for minimally invasive administration.