Long-term Brain-derived Neurotrophic Factor Research Articles

Distinct Effects of BDNF and NT-3 on the Dendrites and Presynaptic Boutons of Developing Olfactory Bulb GABAergic Interneurons In Vitro.

Brain-derived neurotrophic factor (BDNF) and neurotrophin 3 (NT-3) are known to regulate neuronal morphology and the formation of neural circuits, yet the neuronal targets of each neurotrophin are still to be defined. To address how these neurotrophins regulate the morphological and synaptic differentiation of developing olfactory bulb (OB) GABAergic interneurons, we analyzed the effect of BDNF and NT-3 on GABA+-neurons and on different subtypes of these neurons: tyrosine hydroxylase (TH+); calretinin (Calr+); calbindin (Calb+); and parvalbumin (PVA+). These cells were generated from cultured embryonic mouse olfactory bulb neural stem cells (eOBNSCs) and after 14days in vitro (DIV), when the neurons expressed TrkB and/or TrkC receptors, BDNF and NT-3 did not significantly change the number of neurons. However, long-term BDNF treatment did produce a longer total dendrite length and/or more dendritic branches in all the interneuron populations studied, except for PVA+-neurons. Similarly, BDNF caused an increase in the cell body perimeter in all the interneuron populations analyzed, except for PVA+-neurons. GABA+- and TH+-neurons were also studied at 21 DIV, when BDNF produced significantly longer neurites with no clear change in their number. Notably, these neurons developed synaptophysin+ boutons at 21 DIV, the size of which augmented significantly following exposure to either BDNF or NT-3. Our results show that in conditions that maintain neuronal survival, BDNF but not NT-3 promotes the morphological differentiation of developing OB interneurons in a cell-type-specific manner. In addition, our findings suggest that BDNF and NT-3 may promote synapse maturation by enhancing the size of synaptic boutons.

Neuroprotection of Retinal Ganglion Cells with AAV2-BDNF Pretreatment Restoring Normal TrkB Receptor Protein Levels in Glaucoma.

Intravitreal delivery of brain-derived neurotrophic factor (BDNF) by injection of recombinant protein or by gene therapy can alleviate retinal ganglion cell (RGC) loss after optic nerve injury (ONI) or laser-induced ocular hypertension (OHT). In models of glaucoma, BDNF therapy can delay or halt RGCs loss, but this protection is time-limited. The decreased efficacy of BDNF supplementation has been in part attributed to BDNF TrkB receptor downregulation. However, whether BDNF overexpression causes TrkB downregulation, impairing long-term BDNF signaling in the retina, has not been conclusively proven. After ONI or OHT, when increased retinal BDNF was detected, a concomitant increase, no change or a decrease in TrkB was reported. We examined quantitatively the retinal concentrations of the TrkB protein in relation to BDNF, in a course of adeno-associated viral vector gene therapy (AAV2-BDNF), using a microbead trabecular occlusion model of glaucoma. We show that unilateral glaucoma, with intraocular pressure ( IOP) increased for five weeks, leads to a bilateral decrease of BDNF in the retina at six weeks, accompanied by up to four-fold TrkB upregulation, while a moderate BDNF overexpression in a glaucomatous eye triggers changes that restore normal TrkB concentrations, driving signaling towards long-term RGCs neuroprotection. We conclude that for glaucoma therapy, the careful selection of the appropriate BDNF concentration is the main factor securing the long-term responsiveness of RGCs and the maintenance of normal TrkB levels.

BDNF impact on synaptic dynamics: extra or intracellular long-term release differently regulates cultured hippocampal synapses

Brain Derived Neurotrophic Factor (BDNF) signalling contributes to the formation, maturation and plasticity of Central Nervous System (CNS) synapses. Acute exposure of cultured brain circuits to BDNF leads to up-regulation of glutamatergic neuro-transmission, by the accurate tuning of pre and post synaptic features, leading to structural and functional synaptic changes. Chronic BDNF treatment has been comparatively less investigated, besides it may represent a therapeutic option to obtain rescue of post-injury alterations of synaptic networks. In this study, we used a paradigm of BDNF long-term (4 days) incubation to assess in hippocampal neurons in culture, the ability of such a treatment to alter synapses. By patch clamp recordings we describe the augmented function of excitatory neurotransmission and we further explore by live imaging the presynaptic changes brought about by long-term BDNF. In our study, exogenous long-term BDNF exposure of post-natal neurons did not affect inhibitory neurotransmission. We further compare, by genetic manipulations of cultured neurons and BDNF release, intracellular overexpression of this neurotrophin at the same developmental age. We describe for the first-time differences in synaptic modulation by BDNF with respect to exogenous or intracellular release paradigms. Such a finding holds the potential of influencing the design of future therapeutic strategies.

Over-expression of BDNF in Primary Mouse B cells

Abstract Background Neuronal networks require significant neurotrophic support for recovery after stroke, but delivery of neurotrophins (NTs) failed in clinical trials due to short half-lives and limited brain permeability. B cells, however, infiltrate the post-stroke brain and possess the ability to produce NTs (e.g. brain-derived neurotrophic factor (BDNF)). Thus, we hypothesized that neurotrophic B cells could enhance neuroplasticity after stroke. Methods A CMV-BDNF-mCherry plasmid was transfected into HEK-293T cells or LPS-stimulated splenic B cells isolated from 6–10 week old C57Bl/6J mice. Transfected B cells were co-cultured with supporting splenocytes for 24, 48, or 72h. Flow cytometry assessed mCherry+ B cells and BDNF secretion was measured via ELISA. Graphpad Prism analyzed statistical differences. Significance was p<0.05. Results The CMV-BDNF-mCherry plasmid was successfully transfected into HEK-293T cells compared to non-transfected controls, and led to long-term BDNF secretion (48h-3,162.9pg/mL, 72h-5,106.7pg/mL; both p<0.05 vs. 24h-720pg/mL). For splenic B cells, the percentage of transfected mCherry+ B cells was highest at 24h after transfection (12.6% of CD45+CD19+ cells) and reduced by 48h (8.77%; p<0.01 vs. 24h) and 72h (6.03%; p<0.01 vs. 24h). This trend was also reflected in absolute mCherry+ B cell numbers. Despite this reduction in mCherry+ B cells, BDNF secretion was consistently detected over 72h (24h-303.3pg/mL, 48h-453pg/mL, 72h-317.6pg/mL). Conclusions Our studies show successful overexpression of BDNF in primary B cells. We are currently assessing the magnitude of B cell-derived neurotrophic support on neuroplasticity under homeostatic conditions and in vitro stroke injury models.

Seizure-Suppressant and Neuroprotective Effects of Encapsulated BDNF-Producing Cells in a Rat Model of Temporal Lobe Epilepsy

Brain-derived neurotrophic factor (BDNF) may represent a therapeutic for chronic epilepsy, but evaluating its potential is complicated by difficulties in its delivery to the brain. Here, we describe the effects on epileptic seizures of encapsulated cell biodelivery (ECB) devices filled with genetically modified human cells engineered to release BDNF. These devices, implanted into the hippocampus of pilocarpine-treated rats, highly decreased the frequency of spontaneous seizures by more than 80%. These benefits were associated with improved cognitive performance, as epileptic rats treated with BDNF performed significantly better on a novel object recognition test. Importantly, long-term BDNF delivery did not alter normal behaviors such as general activity or sleep/wake patterns. Detailed immunohistochemical analyses revealed that the neurological benefits of BDNF were associated with several anatomical changes, including reduction in degenerating cells and normalization of hippocampal volume, neuronal counts (including parvalbumin-positive interneurons), and neurogenesis. In conclusion, the present data suggest that BDNF, when continuously released in the epileptic hippocampus, reduces the frequency of generalized seizures, improves cognitive performance, and reverts many histological alterations associated with chronic epilepsy. Thus, ECB device-mediated long-term supplementation of BDNF in the epileptic tissue may represent a valid therapeutic strategy against epilepsy and some of its co-morbidities.

BDNF contributes to both rapid and homeostatic alterations in AMPA receptor surface expression in nucleus accumbens medium spiny neurons

Brain-derived neurotrophic factor (BDNF) plays a critical role in plasticity at glutamate synapses and in the effects of repeated cocaine exposure. We recently showed that intracranial injection of BDNF into the rat nucleus accumbens (NAc), a key region for cocaine addiction, rapidly increases α-amino-3-hyroxy-5-methyl-4-isoxazole-propionic acid receptor (AMPAR) surface expression. To further characterize BDNF's role in both rapid AMPAR trafficking and slower, homeostatic changes in AMPAR surface expression, we investigated the effects of acute (30min) and long-term (24h) treatment with BDNF on AMPAR distribution in NAc medium spiny neurons from postnatal rats co-cultured with mouse prefrontal cortex neurons to restore excitatory inputs. Immunocytochemical studies showed that acute BDNF treatment increased cell surface GluA1 and GluA2 levels, as well as their co-localization, on NAc neurons. This effect of BDNF, confirmed using a protein crosslinking assay, was dependent on ERK but not AKT signaling. In contrast, long-term BDNF treatment decreased AMPAR surface expression on NAc neurons. Based on this latter result, we tested the hypothesis that BDNF plays a role in AMPAR 'scaling down' in response to a prolonged increase in neuronal activity produced by bicuculline (24h). Supporting this hypothesis, decreasing BDNF signaling with the extracellular BDNF scavenger TrkB-Fc prevented the scaling down of GluA1 and GluA2 surface levels in NAc neurons normally produced by bicuculline. In conclusion, BDNF exerts bidirectional effects on NAc AMPAR surface expression, depending on duration of exposure. Furthermore, BDNF's involvement in synaptic scaling in the NAc differs from its previously described role in the visual cortex.

Recovery and aging of serotonergic fibers after single and intermittent MDMA treatment in dark agouti rat

3,4-Methylenedioxymethamphetamine (MDMA; ecstasy) is a popular party drug known to cause selective serotonergic damage. Here we examined the long-term recovery and aging of serotonergic fibers and levels of brain-derived neurotrophic factor (BDNF) after intermittent MDMA administration (15 mg kg(-1) i.p. every 7th day for 4 weeks, MDMA ×4) and a single-dose treatment (15 mg kg(-1) i.p., MDMA ×1) in adolescent/young adult male Dark Agouti rats. After MDMA treatment, tryptophan hydroxylase-immunoreactive fiber density decreased and then recovered in all brain regions. Recovery was more pronounced in the MDMA ×4 group compared with the MDMA ×1 group, but similar long-term BDNF responses were found after both treatments. Twenty-two months after treatment, there were fewer clusters of aberrant serotonergic fibers in the parietal cortex in the MDMA ×4 group compared with the MDMA ×1 group. There was no difference in the density of microglial cells or astrocytes in treated groups versus the control 22 months after the treatments. These results indicate that recovery of serotonergic fibers is faster after intermittent MDMA treatment than after single-dose administration, and differences in BDNF levels per se are unlikely to account for this difference. Moreover, it seems that intermittent MDMA treatment attenuates the morphological signs of aging in serotonergic fibers. In addition, neither intermittent nor single-dose MDMA exposition of young animals induces accelerated aging processes or neurodegeneration in senescence, as indicated by the unaltered densities of microglial cells and astrocytes in the treated groups compared with the control.

Transcriptional profiling of brain‐derived‐neurotrophic factor‐induced neuronal plasticity: A novel role for nociceptin in hippocampal neurite outgrowth

Brain derived neurotrophic factor (BDNF) exhibits a sequence of actions on neurons ranging from acute enhancement of transmission to long-term promotion of neurite outgrowth and synaptogenesis associated with learning and memory. The manifold effects of BDNF on neuronal modifications may be mediated by genomic alterations. We previously found that BDNF treatment acutely increases transcription of the synaptic vesicle protein Rab3A, required for trophin-induced synaptic plasticity, as well as the peptide VGF, which increases during learning. To elucidate comprehensive transcriptional programs associated with short- and long-term BDNF exposure, we now examine mRNA abundance and complexity using Affymetrix GeneChips in cultured hippocampal neurons. Consistent with the modulation of synaptic plasticity, BDNF treatment (3-6 h) induced mRNAs encoding the synapse-associated proteins synaptojanin 2, neuronal pentraxin 1, septin 9, and ryanodine receptor 2. BDNF also induced expression of mRNAs encoding neuropeptides (6-12 h), including prepronociceptin, neuropeptide Y, and secretogranin. To determine whether these neuropeptides induced by BDNF mediate neuronal development, we examined their effects on hippocampal neurons. The four mature peptides derived from post-translational processing of the ppNociceptin propeptide induced the expression of several immediate early genes in hippocampal cultures, indicating neuronal activation. To examine the significance of activation, the effects of nociceptin (orphanin FQ) and nocistatin on neurite outgrowth were examined. Quantitative morphometric analysis revealed that nociceptin significantly increased both average neurite length and average number of neurites per neuron, while nocistatin had no effect on these parameters. These results reveal a novel role for nociceptin and suggest that these neuropeptide systems may contribute to the regulation of neuronal function by BDNF.

Brain-Derived Neurotrophic Factor Is Required for the Establishment of the Proper Number of Dopaminergic Neurons in the Substantia Nigra Pars Compacta

Brain-derived neurotrophic factor (BDNF) has been implicated in regulating neuronal survival, differentiation, and synaptic plasticity. Reduced expression of BDNF within the substantia nigra accompanies the deterioration of dopaminergic neurons in Parkinson's disease (PD) patients. Analysis of the effects of long-term BDNF absence from the CNS has been difficult because of the early postnatal lethality of BDNF-/- mice. Mice with a floxed BDNF allele were bred with Wnt1-Cre mice to generate Wnt-BDNF(KO) mice that lack BDNF from the midbrain-hindbrain (MHB). These mice are viable but exhibit hindlimb clutching and poor rotarod performance. Tyrosine hydroxylase (TH)-positive neuron numbers in the substantia nigra pars compacta (SNC) were estimated using stereological methods, revealing a persistent approximately 23% reduction of these cells at postnatal day 21 (P21) in Wnt-BDNF(KO) mice compared with controls. The diminishment of TH-expressing neurons was present at birth and continued through P120. This deficit appears selective for the dopaminergic population, because at P21, total neuron number within the SNC, defined as neuronal nuclei protein-positive cells, was not significantly reduced. Interestingly, and similar to observations in PD patients, SNC neuron subpopulations are not equally affected. Calbindin- and calretinin-expressing SNC populations show no significant difference between Wnt-BDNF(KO) mice and controls. Thus, BDNF depletion from the MHB selectively leads to reduced TH expression in a subpopulation of neurons, but it remains unclear whether these cells are lost.