Both Brain-derived Neurotrophic Factor Research Articles

LncRNA NPTN-IT1-201 Ameliorates Depressive-like Behavior by Targeting miR-142-5p and Regulating Inflammation and Apoptosis via BDNF.

Long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) are widely expressed in the brain and are associated with the development of neurological and neurodegenerative diseases. However, their roles and molecular mechanisms in major depressive disorder (MDD) remain largely unknown. This study aimed to identify lncRNAs and miRNAs involved in the development of MDD and elucidate their molecular mechanisms. Transcriptome and bioinformatic analyses were performed to identify miRNAs and lncRNAs related to MDD. C57 mice were subjected to chronic unpredictable mild stress (CUMS) to establish a depression model. Lentiviruses containing either lncRNA NPTN-IT1-201 or miR-142-5p were microinjected into the hippocampal region of these mice. Behavioral tests including the sucrose preference test (SPT), tail suspension test (TST), and forced swim test (FST) were conducted to evaluate depressive-like behaviors. The results revealed that overexpression of lncRNA NPTN-IT1-201 or inhibition of miR-142-5p significantly ameliorated depressive-like behaviors in CUMS-treated mice. Dual-luciferase reporter assays confirmed interactions between miR-142-5p with both brain-derived neurotrophic factor (BDNF) and NPTN-IT1-201. ELISA analysis revealed significant alterations in relevant biomarkers in the blood samples of MDD patients compared to healthy controls. Histological analyses, including HE and Nissl staining, showed marked structural changes in brain tissues following CUMS treatment, which were partially reversed by lncRNA NPTN-IT1-201 overexpression or miR-142-5p inhibition. Immunofluorescence imaging demonstrated significant differences in the levels of BAX, Bcl2, p65, Iba1 among different treatment groups. TUNEL assays confirmed reduced apoptosis in brain tissues following these interventions. Western blotting showed the significant differences in BDNF, BAX, and Bcl2 protein levels among different treatment groups. NPTN-IT1-201 regulates inflammation and apoptosis in MDD by targeting BDNF via miR-142-5p, making it a potential therapeutic target for MDD.

Serum brain-derived neurotrophic factor and vitamin D: Two concordant players controlling depression among alopecia areata and vitiligo patients: A case-control study.

Depression is a common psychiatric comorbidity among chronic dermatology patients. There is extreme lacking in the research studying biomarkers responsible for it. Both brain-derived neurotrophic factor (BDNF) and vitamin D have a significant role in the development of depression. To assess BDNF and vitamin D serum levels in different clinical verities of alopecia areata (AA) and vitiligo patients, correlating them with depression prevalence and quality of life. In all, 30 AA patients, 30 vitiligo patients, and 30 healthy volunteers were included. Both alopecia and vitiligo severity and activity were evaluated using the suitable clinical scores. Depression was assessed using Beck depression inventory (BDI) scale and quality of life was recorded using Dermatology Life Quality Index (DLQI). Both serum BDNF and vitamin D levels were investigated using ELISA. In both alopecia and vitiligo patients, serum BDNF and serum vitamin D were significantly lower compared to controls (p= 0.001 for both). Both were associated and negatively correlated with BDI and DLQI. Regarding alopecia, they showed a significant decline in more sever disease and with longer disease duration. However, in vitiligo, BDNF (p= 0.001) and vitamin D (p= 0.03) correlated negatively with disease activity, but not with disease severity. Serum BDNF and vitamin D correlated positively with each other (p= 0.001) in both AA and vitiligo cases. The inverse association of both serum BDNF and vitamin D with depression, and the positive correlation noted between their serum levels, may indicate a potential combined effect of these two players on development of depression and its negative health-related outcomes.

Chronic Corticosterone Elevation Suppresses Adult Hippocampal Neurogenesis by Hyperphosphorylating Huntingtin

Chronic exposure to stress is a major risk factor for neuropsychiatric disease, and elevated plasma corticosterone (CORT) correlates with reduced levels of both brain-derived neurotrophic factor (BDNF) and hippocampal neurogenesis. Precisely how these phenomena are linked, however, remains unclear. Using a cortico-hippocampal network-on-a-chip, we find that the glucocorticoid receptor agonist dexamethasone (DXM) stimulates the cyclin-dependent kinase 5 (CDK5) to phosphorylate huntingtin (HTT) at serines 1181 and 1201 (S1181/1201), which retards BDNF vesicular transport in cortical axons. Parallel studies in mice show that CORT induces phosphorylation of these same residues, reduces BDNF levels, and suppresses neurogenesis. The adverse effects of CORT are reduced in mice bearing an unphosphorylatable mutant HTT (HdhS1181A/S1201A). The protective effect of unphosphorylatable HTT, however, disappears if neurogenesis is blocked. The CDK5-HTT pathway, which regulates BDNF transport in the cortico-hippocampal network, thus provides a missing link between elevated CORT levels and suppressed neurogenesis.

Calycosin Preserves BDNF/TrkB Signaling and Reduces Post-Stroke Neurological Injury after Cerebral Ischemia by Reducing Accumulation of Hypertrophic and TNF-α-Containing Microglia in Rats.

Both brain-derived neurotrophic factor (BDNF) and microglia activation are involved in the pathogenesis of ischemic stroke. Herein, we attempt to ascertain whether Calycosin, an isoflavonoid, protects against ischemic stroke by modulating the endogenous production of BDNF and/or the microglia activation. This study was a prospective, randomized, blinded and placebo-controlled preclinical experiment. Sprague-Dawley adult rats, subjected to transient focal cerebral ischemia by middle cerebral artery occlusion (MCAO), were treated randomly with 0 (corn oil and/or saline as placebo), 30mg/kg of Calycosin and/or 1mg/kg of a tropomyosin-related kinase B (TrkB) receptor antagonist (ANA12) at 1h after reperfusion and once daily for a total of 7 consecutive days. BDNF and its functional receptor, full-length TrkB (TrkB-FL) levels, the percentage of hypertrophic microglia, tumor necrosis factor-α (TNF-α)-containing microglia, and degenerative and apoptotic neurons in ischemic brain regions were determined 7days after cerebral ischemia. A battery of functional sensorimotor test was performed over 7days. Post-stroke Calycosin therapy increased the cerebral expression of BDNF/TrkB, ameliorated the neurological injury and switched the microglia from the activated amoeboid state to the resting ramified state in ischemic stroke rats. However, the beneficial effects of BDNF/ TrkB-mediated Calycosin could be reversed by ANA12. Our data indicate that BDNF/TrkB-mediated Calycosin ameliorates rat ischemic stroke injury by switching the microglia from the activated amoeboid state to the resting ramified state. Graphical abstract.

Sitagliptin rescues memory deficits in Parkinsonian rats via upregulating BDNF to prevent neuron and dendritic spine loss

ABSTRACTObjectives: Parkinson’s disease (PD) is a neurodegenerative disease with high morbidity among adults worldwide that causes tremendous trouble to people’s lives. The purpose of this study was to investigate the impact of sitagliptin on PD and its potential mechanism.Methods: First, the memory of rats in each group was evaluated with the Morris water maze (MWM) test and the passive avoidance test. Then, both brain-derived neurotrophic factor (BDNF) protein and mRNA levels were detected by ELISA and qPCR assays, respectively. Then, rapid Golgi impregnation was used to observe the density of dendritic spines in the hippocampal CA1 area. Finally, k252a, an antagonist of Trk receptors, was used to block the binding of BDNF with its receptors, and the effects of sitagliptin on PD improvement were detected.Results: Our study showed that sitagliptin improved memory deficits in PD rats. Meanwhile, the expression level of BDNF and tyrosine hydroxylase (TH) was upregulated, and the density of dendritic spine was increased by sitagliptin administration. Moreover, K252a administration blocked the positive effects of sitagliptin on memory in PD rats.Discussion: Sitagliptin rescued the memory deficits, which was achieved by upregulating BDNF to prevent neuronal death and dendritic spine loss. Our findings indicate that sitagliptin might be a promising potential drug for PD treatment in the future.

Brain-derived neurotrophic factor haploinsufficiency impairs high-frequency cortical oscillations in mice.

Schizophrenia is a complex psychiatric disorder with a heterogeneous aetiology involving genetic and environmental factors. Deficiencies in both brain-derived neurotrophic factor (BDNF) and NMDA receptor function have been implicated in the disorder and may play causal and synergistic roles. Perturbations in the regulation of electrophysiological signals, including high-frequency (γ: 30-80Hz and β: 20-30Hz) neuronal oscillations, are also associated with the disorder. This study investigated the influence of BDNF deficiency and NMDA receptor hypofunction on electrophysiological responses to brief acoustic stimuli. Adult BDNF heterozygote (BDNF+/- ) and wild-type littermate C57Bl/6J mice were surgically implanted with EEG recording electrodes. All mice underwent EEG recording sessions to measure ongoing and auditory-evoked electrophysiological responses following treatment with MK-801 (0.3mg/kg ip) or vehicle. Western blotting on post-mortem cortical tissue assessed parvalbumin and GAD67 expression - markers of interneurons which are involved in the generation of gamma oscillations. Compared with wild-type controls, BDNF+/- mice exhibited markedly dampened electrophysiological responses to auditory stimuli, including reductions in the amplitude of multiple components of the event-related potential and auditory-evoked oscillations, as well as reduced ongoing cortical gamma oscillations. MK-801 elevated ongoing gamma power but suppressed evoked gamma power, and this was observed equally across genotypes. BDNF+/- mice also displayed reductions in parvalbumin, but not GAD67 expression. We conclude that reduced BDNF expression leads to impairments in the generation of high-frequency neural oscillations, but this is not synergistic with NMDA receptor hypofunction. Reduced parvalbumin expression associated with BDNF haploinsufficiency may provide a molecular explanation for these electrophysiological deficits.

Glucose concentrations modulate brain-derived neurotrophic factor responsiveness of neurones in the paraventricular nucleus of the hypothalamus.

The hypothalamic paraventricular nucleus (PVN) is critical for normal energy balance and has been shown to contain high levels of both brain-derived neurotrophic factor (BDNF) and tropomyosin-receptor kinase B mRNA. Microinjections of BDNF into the PVN increase energy expenditure, suggesting that BDNF plays an important role in energy homeostasis through direct actions in this nucleus. The present study aimed to examine the postsynaptic effects of BDNF on the membrane potential of PVN neurones, and also to determine whether extracellular glucose concentrations modulated these effects. We used hypothalamic PVN slices from male Sprague-Dawley rats to perform whole cell current-clamp recordings from PVN neurones. BDNF was bath applied at a concentration of 2nmol L-1 and the effects on membrane potential determined. BDNF caused depolarisations in 54% of neurones (n=25; mean±SEM, 8.9±1.2 mV) and hyperpolarisations in 23% (n=11; -6.7±1.4 mV), whereas the remaining cells were unaffected. These effects were maintained in the presence of tetrodotoxin (n=9; 56% depolarised, 22% hyperpolarised, 22% nonresponders), or the GABAa antagonist bicuculline (n=12; 42% depolarised, 17% hyperpolarised, 41% nonresponders), supporting the conclusion that these effects on membrane potential were postsynaptic. Current-clamp recordings from PVN neurones next examined the effects of BDNF on these neurones at varying extracellular glucose concentrations. Larger proportions of PVN neurones hyperpolarised in response to BDNF as the glucose concentrations decreased [10mmol L-1 glucose 23% (n=11) of neurones hyperpolarised, whereas, at 0.2mmol L-1 glucose, 71% showed hyperpolarising effects (n=12)]. Our findings reveal that BDNF has direct GABAA independent effects on PVN neurones, which are modulated by local glucose concentrations. The latter observation further emphasises the critical importance of using physiologically relevant conditions in an investigation of the central pathways involved in the regulation of energy homeostasis.

Control of Retinal Ganglion Cell Positioning and Neurite Growth: Combining 3D Printing with Radial Electrospun Scaffolds.

Retinal ganglion cells (RGCs) are responsible for the transfer of signals from the retina to the brain. As part of the central nervous system, RGCs are unable to regenerate following injury, and implanted cells have limited capacity to orient and integrate in vivo. During development, secreted guidance molecules along with signals from extracellular matrix and the vasculature guide cell positioning, for example, around the fovea, and axon outgrowth; however, these changes are temporally regulated and are not the same in the adult. Here, we combine electrospun cell transplantation scaffolds capable of RGC neurite guidance with thermal inkjet 3D cell printing techniques capable of precise positioning of RGCs on the scaffold surface. Optimal printing parameters are developed for viability, electrophysiological function and, neurite pathfinding. Different media, commonly used to promote RGC survival and growth, were tested under varying conditions. When printed in growth media containing both brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF), RGCs maintained survival and normal electrophysiological function, and displayed radial axon outgrowth when printed onto electrospun scaffolds. These results demonstrate that 3D printing technology may be combined with complex electrospun surfaces in the design of future retinal models or therapies.

Alterations in Brain-Derived Neurotrophic Factor in the Mouse Hippocampus Following Acute but Not Repeated Benzodiazepine Treatment

Benzodiazepines (BZs) are safe drugs for treating anxiety, sleep, and seizure disorders, but their use also results in unwanted effects including memory impairment, abuse, and dependence. The present study aimed to reveal the molecular mechanisms that may contribute to the effects of BZs in the hippocampus (HIP), an area involved in drug-related plasticity, by investigating the regulation of immediate early genes following BZ administration. Previous studies have demonstrated that both brain derived neurotrophic factor (BDNF) and c-Fos contribute to memory- and abuse-related processes that occur within the HIP, and their expression is altered in response to BZ exposure. In the current study, mice received acute or repeated administration of BZs and HIP tissue was analyzed for alterations in BDNF and c-Fos expression. Although no significant changes in BDNF or c-Fos were observed in response to twice-daily intraperitoneal (i.p.) injections of diazepam (10 mg/kg + 5 mg/kg) or zolpidem (ZP; 2.5 mg/kg + 2.5 mg/kg), acute i.p. administration of both triazolam (0.03 mg/kg) and ZP (1.0 mg/kg) decreased BDNF protein levels within the HIP relative to vehicle, without any effect on c-Fos. ZP specifically reduced exon IV-containing BDNF transcripts with a concomitant increase in the association of methyl-CpG binding protein 2 (MeCP2) with BDNF promoter IV, suggesting that MeCP2 activity at this promoter may represent a ZP-specific mechanism for reducing BDNF expression. ZP also increased the association of phosphorylated cAMP response element binding protein (pCREB) with BDNF promoter I. Future work should examine the interaction between ZP and DNA as the cause for altered gene expression in the HIP, given that BZs can enter the nucleus and intercalate into DNA directly.

NMDA receptor dysfunction contributes to impaired brain‐derived neurotrophic factor‐induced facilitation of hippocampal synaptic transmission in a Tau transgenic model

While the spatiotemporal development of Tau pathology has been correlated with occurrence of cognitive deficits in Alzheimer's patients, mechanisms underlying these deficits remain unclear. Both brain-derived neurotrophic factor (BDNF) and its tyrosine kinase receptor TrkB play a critical role in hippocampus-dependent synaptic plasticity and memory. When applied on hippocampal slices, BDNF is able to enhance AMPA receptor-dependent hippocampal basal synaptic transmission through a mechanism involving TrkB and N-methyl-d-Aspartate receptors (NMDAR). Using THY-Tau22 transgenic mice, we demonstrated that hippocampal Tau pathology is associated with loss of synaptic enhancement normally induced by exogenous BDNF. This defective response was concomitant to significant memory impairments. We show here that loss of BDNF response was due to impaired NMDAR function. Indeed, we observed a significant reduction of NMDA-induced field excitatory postsynaptic potential depression in the hippocampus of Tau mice together with a reduced phosphorylation of NR2B at the Y1472, known to be critical for NMDAR function. Interestingly, we found that both NR2B and Src, one of the NR2B main kinases, interact with Tau and are mislocalized to the insoluble protein fraction rich in pathological Tau species. Defective response to BDNF was thus likely related to abnormal interaction of Src and NR2B with Tau in THY-Tau22 animals. These are the first data demonstrating a relationship between Tau pathology and synaptic effects of BDNF and supporting a contribution of defective BDNF response and impaired NMDAR function to the cognitive deficits associated with Tauopathies.

P.1.014 Spatial memory and expression levels of BDNF and steroid hormone receptors in the hippocampus of socially isolated offspring

Purpose: Rats deprived of social contact with other rats at a young age experience a form of prolonged stress that leads to long-lasting alteration in their behaviour profile. This chronic stress paradigm results in changes of emotional state, hormonal secretion, abnormal reactivity to environmental and pharmacological stimuli and changes in GABAA receptor plasticity and function [1,2]. Moreover, isolated rats, although showed a down-regulation of both brain-derived neurotrophic factor (BDNF) and activityregulated cytoskeletal associated protein (Arc) in the hippocampus, demonstrated an improvement in memory performances in the Morris water maze (MWM) together with an increase in the expression of BDNF and Arc in the hippocampus on both days 1 and 5 and increased plasma level of corticosterone on the 5th day of MWM training [3]. To examine possible trans-generational effects on social isolated offspring we have investigated (1) basal plasma levels of corticosterone, (2) spatial memory performance in the MWM, (3) expression levels of BDNF and Arc in the hippocampus during the 1th and 5th days of MWM. Moreover, in the hippocampus of both isolated and isolated offspring we measured the expression levels of glucocorticoid (GR) and mineralcorticoid (MR) receptors. Methods:Male Sprague-Dawley rats were used. Steroid levels were quantified in plasma by RIA. The levels of BDNF, Arc, GR and MR proteins were determined by Western Blot analysis. The measurement of spatial memory was performed trough the MWM. Data were analyzed by one or two-way ANOVA followed by Newman-Keuls post-hoc test. Results: In social isolated offspring the plasma levels of corticosterone were significantly increased by 31% (p< 0.05) vs group-housed offspring (controls). In the MWM, social isolated offspring showed a decrease in latency to reach the platform during the days of training, and a decrease of the proximity measure to the target zone during the probe trial. Moreover, although the basal levels of hippocampal BDNF and Arc did not differ significantly between the two groups of animals, we found a significant increase of BDNF expression at the 5th day of MWM in isolated offspring vs the control animals (p< 0.05). Finally, the expression of hippocampal GR was significantly augmented in both isolated and isolated offspring (+41%, p< 0.05; +42%, p< 0.05, respectively), while the expression of MR was significantly increased only in the isolated rats (+35%, p< 0.05). Conclusions: Our results suggest that a stressful condition that have been experienced by the parents in early life time influence hormonal secretion, neuronal plasticity and cognitive performances in the offspring. Thus, isolated offspring showed an improvement in learning and spatial memory in MWM vs the control animals. Likewise, high circulating levels of corticosterone with high levels of GR expression in the hippocampus may play an important role in improving the cognitive performance of these animals. These data are in agreement with the increased expression of BDNF since it is involved in various forms of hippocampal learning.

Down-regulation of hippocampal BDNF and Arc associated with improvement in aversive spatial memory performance in socially isolated rats

Rats deprived of social contact with other rats at a young age experience a form of prolonged stress that leads to long-lasting changes in behavioral profile. Such isolation is thought to be anxiogenic for these normally gregarious animals, and the abnormal reactivity of isolated rats to environmental stimuli is thought to be a product of prolonged stress. We now show that isolation of rats at weaning reduced immobility time in the forced swim test, decreased sucrose intake and preference, and down-regulated both brain-derived neurotrophic factor (BDNF) and activity-regulated cytoskeletal associated protein (Arc) in the hippocampus. In the Morris water maze, isolated rats showed a reduced latency to reach the hidden platform during training, indicative of an improved learning performance, compared with group-housed rats. The cumulative search error during place training trials indicated a reliable difference between isolated and group-housed rats on days 4 and 5. The probe trial revealed a significant decrease of the average proximity to the target location in the isolated rats suggesting an improvement in spatial memory.Isolated rats also showed an increase in the plasma level of corticosterone on the 5th day of training and increased expression of BDNF and Arc in the hippocampus on both days 1 and 5. These results show that social isolation from weaning in rats results in development of depressive-like behavior but has a positive effect on spatial learning, supporting the existence of a facilitating effect of stress on cognitive function.

P02-209 - BDNF and DISC1 are associated with cognitive dysfunction but not with schizophrenia in a hungarian sample

IntroductionPrevious studies have found association between several schizophrenia candidate genes and neurocognition in schizophrenia patients and healthy individuals. Both brain-derived neurotrophic factor (BDNF) and disrupted in schizophrenia 1 (DISC1) are important for neurodevelopmental processes and have been implicated as schizophrenia candidate genes, as well as genes influencing neurocognition.Objectives and aimsTo test for the previously described association of these genes with schizophrenia and neurocognition.MethodsDNA samples from a homogeneous sample of 280 schizophrenia patients and 230 healthy controls were genotyped for polymorphisms in schizophrenia candidate genes DISC1 (rs821597 and rs821616) and BDNF (rs6265). Clinical assessment was performed using the Schedule for Deficit Syndrome and the Positive and Negative Symptom Scale. Neurocognitive functioning was assessed in a subsample of 263 patients and 135 healthy controls by a comprehensive neuropsychological test-battery. Based on the raw neuropsychological measures we calculated a global index of cognitive impairment and domain-specific composite z-scores. Association between the above composite scores and the SNPs was examined using GLM and GENMOD analysis.ResultsThe investigated SNPs were not associated with schizophrenia, nor with the deficit or non-deficit subgroups. However we found significant association between global cognitive impairment and rs821616 in DISC1 (F = 3.02, p = 0.05) and rs6265 in BDNF (F = 4.47, p = 0.01); moreover rs6265 was associated with working memory (F = 6.22, p = 0.002) and attention (F = 7.27, p = 0.0074)ConclusionUsing neurocognition as an endophenotype for psychotic disorders in genetic studies has the potential to determine common and separate genetic factors influencing disease risk and neurocognition.

Brain-Derived Neurotrophic Factor and Epidermal Growth Factor Activate Neuronal m-Calpain via Mitogen-Activated Protein Kinase-Dependent Phosphorylation

Calpain is a calcium-dependent protease that plays a significant role in synaptic plasticity, cell motility, and neurodegeneration. Two major calpain isoforms are present in brain, with mu-calpain (calpain1) requiring micromolar calcium concentrations for activation and m-calpain (calpain2) needing millimolar concentrations. Recent studies in fibroblasts indicate that epidermal growth factor (EGF) can activate m-calpain independently of calcium via mitogen-activated protein kinase (MAPK)-mediated phosphorylation. In neurons, MAPK is activated by both brain-derived neurotrophic factor (BDNF) and EGF. We therefore examined whether these growth factors could activate m-calpain by MAPK-dependent phosphorylation using cultured primary neurons and HEK-TrkB cells, both of which express BDNF and EGF receptors. Calpain activation was monitored by quantitative analysis of spectrin degradation and by a fluorescence resonance energy transfer (FRET)-based assay, which assessed the truncation of a calpain-specific peptide flanked by the FRET fluorophore pair DABCYL and EDANS. In both cell types, BDNF and EGF rapidly elicited calpain activation, which was completely blocked by MAPK and calpain inhibitors. BDNF stimulated m-calpain but not mu-calpain serine phosphorylation, an effect also blocked by MAPK inhibitors. Remarkably, BDNF- and EGF-induced calpain activation was preferentially localized in dendrites and dendritic spines of hippocampal neurons and was associated with actin polymerization, which was prevented by calpain inhibition. Our results indicate that, in cultured neurons, both BDNF and EGF activate m-calpain by MAPK-mediated phosphorylation. These results strongly support a role for calpain in synaptic plasticity and may explain why m-calpain, although widely expressed in CNS, requires nonphysiological calcium levels for activation.

Gustatory papillae and taste bud development and maintenance in the absence of TrkB ligands BDNF and NT-4

Taste buds and the peripheral nerves innervating them are two important components of the peripheral gustatory system. They require appropriate connections for the taste system to function. Neurotrophic factors play crucial roles in the innervation of peripheral sensory organs and tissues. Both brain-derived neurotrophic factor (BDNF) null-mutated and neurotrophin-4 (NT-4) null-mutated mice exhibit peripheral gustatory deficits. BDNF and NT-4 bind to a common high affinity tyrosine kinase receptor, TrkB (NTRK-2), and a common p75 neurotrophin receptor (NGFR). We are currently using a transgenic mouse model to study peripheral taste system development and innervation in the absence of both TrkB ligands. We show that taste cell progenitors express taste cell markers during early stages of taste bud development in both BDNF(-/-)xNT-4(-/-) and wild-type mice. At early embryonic stages, taste bud progenitors express Troma-1, Shh, and Sox2 in all mice. At later stages, lack of innervation becomes a prominent feature in BDNF(-/-)xNT-4(-/-) mice leading to a decreasing number of fungiform papillae and morphologically degenerating taste cells. A total loss of vallate taste cells also occurs in postnatal transgenic mice. Our data indicate an initial independence but a later permissive and essential role for innervation in taste bud development and maintenance.

BDNF downregulates 5-HT 2A receptor protein levels in hippocampal cultures

Both brain-derived neurotrophic factor (BDNF) and the serotonin receptor 2A (5-HT 2A) have been related to depression pathology. Specific 5-HT 2A receptor changes seen in BDNF conditional mutant mice suggest that BDNF regulates the 5-HT 2A receptor level. Here we show a direct effect of BDNF on 5-HT 2A receptor protein levels in primary hippocampal neuronal and mature hippocampal organotypic cultures exposed to different BDNF concentrations for either 1, 3, 5 or 7 days. In vivo effects of BDNF on hippocampal 5-HT 2A receptor levels were further corroborated in (BDNF +/−) mice with reduced BDNF levels. In primary neuronal cultures, 7 days exposure to 25 and 50 ng/mL BDNF resulted in downregulation of 5-HT 2A, but not of 5-HT 1A, receptor protein levels. The BDNF-associated downregulation of 5-HT 2A receptor levels was also observed in mature hippocampal organotypic cultures, excluding confounding effects of BDNF on immature tissue. BDNF +/− mice showed significant increased 5-HT 2A receptor levels in hippocampus confirming the association between 5-HT 2A receptor and BDNF levels in vivo. In conclusion, our results point to a regulatory role of BDNF on 5-HT2A receptor levels. This interaction may be an important mechanism in the role of BDNF in affective disorders emphasizing the need for further elucidating the specificity and the mechanism behind this regulation.

Acute and chronic effects of neurotrophic factors BDNF and GDNF on responses mediated by thermo-sensitive TRP channels in cultured rat dorsal root ganglion neurons

Neurotrophic factors (NTFs), beside regulating neuronal survival in the central and peripheral nervous system, are also involved in the modulation of neuronal function in the adult animal. Both brain-derived neurotrophic factor (BDNF) and glial cell-derived neurotrophic factor (GDNF) levels are altered in pathological pain states, and exogenous BDNF and GDNF have multiple effects on pain behavior, depending on the animal model (i.e. inflammatory vs. neuropathic). Thermally gated TRP channels TRPM8, TRPA1 and TRPV1 play a significant role in pain signaling and their pattern and level of expression as well as their biophysical properties are altered in chronic pain states. Our aim was to investigate the effect of long-term and acute exposure to BDNF and GDNF on the functional expression of these thermoTRP channels in cultured rat dorsal root ganglion (DRG) neurons. We found that while BDNF treatment primarily increased the fraction of capsaicin-sensitive (TRPV1-expressing) neurons, GDNF exposure led to an increase in the allyl isothiocyanate (AITC)-responding (TRPA1-expressing) population. Moreover, BDNF treatment increased the amplitude of the response to both AITC and capsaicin. Acute treatment with both NTFs leads to a reduction in the magnitude of tachyphylaxis to noxious stimuli (heat and AITC). Overall, our data provides evidence for a role of BDNF and GDNF in regulating the pattern of expression and level of activity of the transducer channels TRPA1 and TRPV1, leading to enhanced neuronal sensitivity to painful stimuli and increased co-expression of thermoTRP channels.

Pre-Differentiated Embryonic Stem Cells Promote Neuronal Regeneration by Cross-Coupling of BDNF and IL-6 Signaling Pathways in the Host Tissue

The mechanism of embryonic stem (ES) cell therapeutic action remains far from being elucidated. Our recent report has shown that transplantation of ES cells, predifferentiated into neuronal progenitors, prevented appearance of chronic pain behaviors in mice after experimentally induced spinal cord injury. In the current study, we tested the hypothesis that this beneficial effect is mediated by antiapoptotic and regenerative signaling pathways activated in the host tissue by transplanted ES cells. Spinal cord injury was induced by unilateral microinjections of quisqualic acid at spinal levels T12-L2. At 1 week after injury, the pre-differentiated towards neuronal phenotype ES cells were transplanted into the site of injury. Here we show that transplantation of pre-differentiated ES cells activate both brain-derived neurotrophic factor (BDNF) and interleukin-6 (IL-6) signaling pathways in the host tissue, leading to activation of cAMP/PKA, phosporylation of cofilin and synapsin I, and promoting regenerative growth and neuronal survival.

Different postischemic protein expression of the GABA_{A} receptor α2 subunit and the plasticity-associated protein MAP1B after treatment with BDNF versus G-CSF in the rat brain

Recent data indicate that both brain-derived neurotrophic factor (BDNF) and granulocyte-colony stimulating factor (G-CSF) exert substantial neuroregenerative effects and improve functional outcome after ischemic stroke. In the present study, we checked for potential differences in the postischemic modulation of various excitatory and inhibitory neurotransmitter receptors as well as various marker molecules for structural plasticity by BDNF versus G-CSF. Adult male Wistar rats were subjected to photothrombotic ischemia and subsequently treated with NaCl, BDNF or G-CSF, respectively. After 6 weeks, postischemic protein expression of the NR1, GluR1 and alpha2 subunit of the NMDA, AMPA and GABA(A) receptor, respectively, was semiquantitatively determined ipsi- and contralateral to the ischemic lesion. Structural plasticity was further analyzed immunohistochemically using antibodies against MAP1B, MAP2 and synaptophysin. Only BNDF caused a significantly reduced postischemic protein expression of the GABA(A) receptor alpha2 subunit and the NR1 subunit of the NMDA receptor in the hippocampus. Furthermore, BDNF compared to G-CSF increased MAP1B protein expression in the periischemic regenerative region. Although both BDNF and G-CSF have been shown to improve postischemic functional outcome to a similar extent, exogenous administration results in different underlying structural reorganization processes suggesting specific modulations of plasticity-associated events by these trophic factors.

Forkhead Box, Class O Transcription Factors in Brain: Regulation and Behavioral Manifestation

The mammalian forkhead box, class O (FoxO) transcription factors function to regulate diverse physiological processes. Emerging evidence that both brain-derived neurotrophic factor (BDNF) and lithium suppress FoxO activity suggests a potential role of FoxOs in regulating mood-relevant behavior. Here, we investigated whether brain FoxO1 and FoxO3a can be regulated by serotonin and antidepressant treatment and whether their genetic deletion affects behaviors. C57BL/6 mice were treated with D-fenfluramine to increase brain serotonergic activity or with the antidepressant imipramine. The functional status of brain FoxO1 and FoxO3a was audited by immunoblot analysis for phosphorylation and subcellular localization. The behavioral manifestations in FoxO1- and FoxO3a-deficient mice were assessed via the Elevated Plus Maze Test, Forced Swim Test, Tail Suspension Test, and Open Field Test. Increasing serotonergic activity by d-fenfluramine strongly increased phosphorylation of FoxO1 and FoxO3a in several brain regions and reduced nuclear FoxO1 and FoxO3a. The effect of D-fenfluramine was mediated by the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. Chronic, but not acute, treatment with the antidepressant imipramine also increased the phosphorylation of brain FoxO1 and FoxO3a. When FoxO1 was selectively deleted from brain, mice displayed reduced anxiety. In contrast, FoxO3a-deficient mice presented with a significant antidepressant-like behavior. FoxOs may be a transcriptional target for anxiety and mood disorder treatment. Despite their physical and functional relatedness, FoxO1 and FoxO3a influence distinct behavioral processes linked to anxiety and depression. Findings in this study reveal important new roles of FoxOs in brain and provide a molecular framework for further investigation of how FoxOs may govern mood and anxiety disorders.