Brain-derived neurotrophic factor (BDNF) and polysialylated-neural cell adhesion molecule (PSA-NCAM): codistribution in the human brainstem precerebellar nuclei from prenatal to adult age

BDNF and Cerebellar Ataxia

Brain-derived neurotrophic factor (BDNF) has been proposed as a treatment for neurodegeneration, including diseases of the cerebellum, where BDNF levels or those of its main receptor, TrkB, are often diminished relative to controls, thereby serving as replacement therapy. Experimental evidence indicates that BDNF signaling countered cerebellar degeneration, sensorimotor deficits, or both, in transgenic ATXN1 mice mutated for ataxin-1, Cacna1a knock-in mice mutated for ataxin-6, mice injected with lentivectors encoding RNA sequences against human FXN into the cerebellar cortex, Kcnj6Wv (Weaver) mutant mice with granule cell degeneration, and rats with olivocerebellar transaction, similar to a BDNF-overexpressing transgenic line interbred with Cacng2stg mutant mice. In this regard, this study discusses whether BDNF is effective in cerebellar pathologies where BDNF levels are normal and whether it is effective in cases with combined cerebellar and basal ganglia damage.

PSA-NCAM Regulatory Gene Expression Changes in the Alzheimer's Disease Entorhinal Cortex Revealed with Multiplexed in situ Hybridization

BACKGROUND

Alzheimer's disease (AD) is the most common form of dementia and is characterized by a substantial reduction of neuroplasticity. Our previous work demonstrated that neurons involved in memory function may lose plasticity because of decreased protein levels of polysialylated neural cell adhesion molecule (PSA-NCAM) in the entorhinal cortex (EC) of the human AD brain, but the cause of this decrease is unclear.

OBJECTIVE

To investigate genes involved in PSA-NCAM regulation which may underlie its decrease in the AD EC.

METHODS

We subjected neurologically normal and AD human EC sections to multiplexed fluorescent in situ hybridization and immunohistochemistry to investigate genes involved in PSA-NCAM regulation. Gene expression changes were sought to be validated in both human tissue and a mouse model of AD.

RESULTS

In the AD EC, a cell population expressing a high level of CALB2 mRNA and a cell population expressing a high level of PST mRNA were both decreased. CALB2 mRNA and protein were not decreased globally, indicating that the decrease in CALB2 was specific to a sub-population of cells. A significant decrease in PST mRNA expression was observed with single-plex in situ hybridization in middle temporal gyrus tissue microarray cores from AD patients, which negatively correlated with tau pathology, hinting at global loss in PST expression across the AD brain. No significant differences in PSA-NCAM or PST protein expression were observed in the MAPT P301S mouse brain at 9 months of age.

CONCLUSION

We conclude that PSA-NCAM dysregulation may cause subsequent loss of structural plasticity in AD, and this may result from a loss of PST mRNA expression. Due PSTs involvement in structural plasticity, intervention for AD may be possible by targeting this disrupted plasticity pathway.

BDNF and its signaling in cancer

PURPOSE

Brain-derived neurotrophic factor (BDNF) belongs to the family of neurotrophic factors that can potentially increase cancer cell growth, survival, proliferation, anoikis, and migration by tyrosine kinase receptors TrkB and the p75NTR death receptor. The activation of BDNF/TrkB pathways leads to several downstream signaling pathways, including PI3K/Akt, Jak/STAT, PLCγ, Ras-Raf-MEK-ERK, NF-kB, and transactivation of EGFR. The current review aimed to provide an overview of the role of BDNF and its signaling in cancer.

METHODS

We searched a major medical database, PubMed, to identify eligible studies for a narrative synthesis.

RESULTS

Pathological examinations demonstrate BDNF overexpression in human cancer, notably involving the prostate, lung, breast, and underlying tissues, associated with a higher death rate and poor prognosis. Therefore, measurement of BDNF, either for identifying the disease or predicting response to therapy, can be helpful in cancer patients. Expression profiling studies have recognized the role of microRNAs (miR) in modulating BDNF/TrkB pathways, such as miR-101, miR-107, miR-134, miR-147, miR-191, miR-200a/c, miR-204, miR-206, miR-210, miR-214, miR-382, miR-496, miR-497, miR-744, and miR-10a-5p, providing a potential biological mechanism by which targeted therapies may correlate with decreased BDNF expression in cancers. Clinical studies investigating the use of agents targeting BDNF receptors and related signaling pathways and interfering with the related oncogenic effect, including Entrectinib, Larotrectinib, Cabozantinib, Repotrectinib, Lestaurtinib, and Selitrectinib, are in progress.

CONCLUSION

The aberrant signaling of BDNF is implicated in various cancers. Well-designed clinical trials are needed to clarify the BDNF role in cancer progression and target it as a therapeutic method.

Neuroplastic changes in c-Fos, ΔFosB, BDNF, trkB, and Arc expression in the hippocampus of male Roman rats: differential effects of sexual activity

Sexual activity causes differential changes in the expression of markers of neural activation (c-Fos and ΔFosB) and neural plasticity (Arc and BDNF/trkB), as determined either by Western Blot (BDNF, trkB, Arc, and ΔFosB) or immunohistochemistry (BDNF, trkB, Arc, and c-Fos), in the hippocampus of male Roman high (RHA) and low avoidance (RLA) rats, two psychogenetically selected rat lines that display marked differences in sexual behavior (RHA rats exhibit higher sexual motivation and better copulatory performance than RLA rats). Both methods showed (with some differences) that sexual activity modifies the expression levels of these markers in the hippocampus of Roman rats depending on: (i) the level of sexual experience, that is, changes were usually more evident in sexually naïve than in experienced rats; (ii) the hippocampal partition, that is, BDNF and Arc increased in the dorsal but tended to decrease in the ventral hippocampus; (iii) the marker considered, that is, in sexually experienced animals BDNF, c-Fos, and Arc levels were similar to those of controls, while ΔFosB levels increased; and (iv) the rat line, that is, changes were usually larger in RHA than RLA rats. These findings resemble those of early studies in RHA and RLA rats showing that sexual activity influences the expression of these markers in the nucleus accumbens, medial prefrontal cortex, and ventral tegmental area, and show for the first time that also in the hippocampus sexual activity induces neural activation and plasticity, events that occur mainly during the first phase of the acquisition of sexual experience and depend on the genotypic/phenotypic characteristics of the animals.

Development of the human perihypoglossal nuclei from mid-gestation to the perinatal period: A morphological study

INTRODUCTION

Morphological data on the development of the human perihypoglossal nuclei (PHN) are scarce. This study describes the morphology of the human PHN from mid-gestation to the perinatal period.

MATERIALS AND METHODS

Ten brains were collected from infants aged 21-43 postmenstrual weeks (PW). Serial sections were cut and stained using the Klüver-Barrera method. Morphometric parameters [volume, neuronal numerical density (Nv) and total number (Nt), and neuronal profile area (PA)] were analyzed from microscopic observations.

RESULTS

Four PHN [nucleus of Roller (RO), interfascicular nucleus (IF), intercalated nucleus (IC), and prepositus nucleus (PR)] were identified at 21 PW. Medium-sized to large, oval, or polygonal neurons were concentrated in the ventral nuclei (RO and IF) and localized regions near the IC-PR transition of the dorsal nuclei (IC and PR). Small to large neurons of various shapes were scattered across the dorsal nuclei. The PR showed rostrocaudal differences in the neuronal cytoarchitecture. The volume of each nucleus increased between 21 and 43 PW, with a typical exponential increase for the dorsal nuclei. The Nv in each nucleus exponentially decreased, whereas the Nt was almost stable. The median PA linearly increased for every nucleus, and the increasing rates were greater for the ventral nuclei than those for the dorsal nuclei.

CONCLUSIONS

The dorsal and ventral PHN are identifiable at mid-gestation. The topographic relationships of the four nuclei are conserved until the perinatal period. The characteristic neuronal cytoarchitecture of each group is rapidly formed by 28-30 PW.

Overview of sialylation status in human nervous and skeletal muscle tissues during aging

Sialic acids (Sias) are a large and heterogeneous family of electronegatively charged nine-carbon monosaccharides containing a carboxylic acid and are mostly found as terminal residues in glycans of glycoproteins and glycolipids such as gangliosides. They are linked to galactose or N-acetylgalactosamine via α2,3 or α2,6 linkage, or to other Sias via α2,8 or more rarely α2,9 linkage, resulting in mono, oligo and polymeric forms. Given their characteristics, Sias play a crucial role in a multitude of human tissue biological processes in physiological and pathological conditions, ranging from development and growth to adult life until aging. Here, we review the sialylation status in human adult life focusing on the nervous and skeletal muscle tissues, which both display significant structural and functional changes during aging, strongly impacting on the whole human body and, therefore, on the quality of life. In particular, this review highlights the fundamental roles played by different types of glycoconjugates Sias in several cellular biological processes in the nervous and skeletal muscle tissues during adult life, also discussing how changes in Sia content during aging may contribute to the physiological decline of physical and nervous functions and to the development of age-related degenerative pathologies. Based on our current knowledge, further in-depth investigations could help to develop novel prophylactic strategies and therapeutic approaches that, by maintaining and/or restoring the correct sialylation status in the nervous and skeletal muscle tissues, could contribute to aging slowing and the prevention of age-related pathologies.

Red nucleus structure and function: from anatomy to clinical neurosciences

The red nucleus (RN) is a large subcortical structure located in the ventral midbrain. Although it originated as a primitive relay between the cerebellum and the spinal cord, during its phylogenesis the RN shows a progressive segregation between a magnocellular part, involved in the rubrospinal system, and a parvocellular part, involved in the olivocerebellar system. Despite exhibiting distinct evolutionary trajectories, these two regions are strictly tied together and play a prominent role in motor and non-motor behavior in different animal species. However, little is known about their function in the human brain. This lack of knowledge may have been conditioned both by the notable differences between human and non-human RN and by inherent difficulties in studying this structure directly in the human brain, leading to a general decrease of interest in the last decades. In the present review, we identify the crucial issues in the current knowledge and summarize the results of several decades of research about the RN, ranging from animal models to human diseases. Connecting the dots between morphology, experimental physiology and neuroimaging, we try to draw a comprehensive overview on RN functional anatomy and bridge the gap between basic and translational research.

Polysialic acid in the rat brainstem and thoracolumbar spinal cord: Distribution, cellular location, and comparison with mouse

Polysialic acid (polySia), a homopolymer of α2,8-linked glycans, is a posttranslational modification on a few glycoproteins, most commonly in the brain, on the neural cell adhesion molecule. Most research in the adult central nervous system has focused on its expression in higher brain regions, where its distribution coincides with regions known to exhibit high levels of synaptic plasticity. In contrast, scant attention has been paid to the expression of polySia in the hindbrain. The main aims of the study were to examine the distribution of polySia immunoreactivity in the brainstem and thoracolumbar spinal cord, to compare the distribution of polySia revealed by two commercial antibodies commonly used for its investigation, and to compare labeling in the rat and mouse. We present a comprehensive atlas of polySia immunoreactivity: we report that polySia labeling is particularly dense in the dorsal tegmentum, medial vestibular nuclei and lateral parabrachial nucleus, and in brainstem regions associated with autonomic function, including the dorsal vagal complex, A5, rostral ventral medulla, A1, and midline raphe, as well as sympathetic preganglionic neurons in the spinal cord and central targets of primary sensory afferents (nucleus of the solitary tract, spinal trigeminal nucleus, and dorsal horn [DH]). Ultrastructural examination showed labeling was present predominantly on the plasma membrane/within the extracellular space/in or on astrocytes. Labeling throughout the brainstem and spinal cord were very similar for the two antibodies and was eliminated by the polySia-specific sialidase, Endo-NF. Similar patterns of distribution were found in rat and mouse brainstem with differences evident in DH.

Location of the Cell Adhesion Molecule "Coxsackievirus and Adenovirus Receptor" in the Adult Mouse Brain

The coxsackievirus and adenovirus receptor (CAR) is a single-pass transmembrane cell adhesion molecule (CAM). CAR is expressed in numerous mammalian tissues including the brain, heart, lung, and testes. In epithelial cells, CAR functions are typical of the quintessential roles of numerous CAMs. However, in the brain the multiple roles of CAR are poorly understood. To better understand the physiological role of CAR in the adult brain, characterizing its location is a primordial step to advance our knowledge of its functions. In addition, CAR is responsible for the attachment, internalization, and retrograde transport of canine adenovirus type 2 (CAV-2) vectors, which have found a niche in the mapping of neuronal circuits and gene transfer to treat and model neurodegenerative diseases. In this study, we used immunohistochemistry and immunofluorescence to document the global location of CAR in the healthy, young adult mouse brain. Globally, we found that CAR is expressed by maturing and mature neurons in the brain parenchyma and located on the soma and on projections. While CAR occasionally colocalizes with glial fibrillary acidic protein, this overlap was restricted to areas that are associated with adult neurogenesis.

The Role of Forced and Voluntary Training on Accumulation of Neural Cell Adhesion Molecule and Polysialic Acid in Muscle of Mice with Experimental Autoimmune Encephalomyelitis

It has been suggested that depletion of adhesion molecules is one of the factors associated with or possibly responsible for multiple sclerosis (MS) progression. The aim of this study was to investigate the effect of forced and voluntary training before and after induction of experimental autoimmune encephalomyelitis (EAE) on accumulation of neural cell adhesion molecule (NCAM) and polysialic acid (PSA) in neuromuscular junction denervation in plantaris and soleus muscles in C57BL/6 female mice. A total of 40 female C57BL/6 mice, 10-week-old, were randomly divided into four groups, including induced control groups without EAE induction, induced EAE without training, and forced and voluntary training groups. Myelin oligodendrocyte glycoprotein peptide 35–55 (300 μg in saline; MOG 35–55; KJ Ross-Petersen ApS, Denmark) was injected subcutaneously at the base of the tail of each mouse. Clinical assessment of EAE was performed daily using a 15-point scoring system following immunization. Training groups performed the swimming program for 30 min/day, 5 times/week, for 4 weeks. Mice had access to a treadmill for one hour per day, 5times/week, for 4 weeks in individual cage. The mice were scarified, and the plantaris and soleus muscles were then isolated for investigation of proteins expression using IHC. An analysis of the preventive exercise (before) and recovery exercise (after) of the EAE was performed. Images of the stained sections were taken using a fluorescent microscope. Quantitative image analysis was performed using ImageJ software package. The obtained data from the mean percentage expression of PSA and NCAM in pre- and post-soleus and plantaris muscles showed that the highest and lowest expression levels of PSA and NCAM belonged to control and swim EAE (SE) groups, respectively. The low expression levels of PSA and NCAM were detected in rat with MS without intervention. In conclusion, the relationship between increasing levels of NCAM and PSA protein expression and voluntary and compulsory activity were detectable both in pre and post-soleus and plantaris. However, voluntary activity resulted in more expression levels of NCAM and PSA than that of compulsory. In conclusion, since it has been suggested that depletion of NCAM is one of the factors associated with or possibly responsible for MS progression, these findings show exercise MS progression may be reduced by increasing expression of exercise-related adhesion molecule such as NCAM and PSA (a glycan modification of the NCAM).

Neuroanatomical distribution and functions of brain-derived neurotrophic factor in zebrafish (Danio rerio) brain

Brain-derived neurotrophic factor (BDNF) is an extensively studied protein that is evolutionarily conserved and widely distributed in the brain of vertebrates. It acts via its cognate receptors TrkB and p75^NTR and plays a central role in the developmental neurogenesis, neuronal survival, proliferation, differentiation, synaptic plasticity, learning and memory, adult hippocampal neurogenesis, and brain regeneration. BDNF has also been implicated in a plethora of neurological disorders. Hence, understanding the processes that are controlled by BDNF and their regulating mechanisms is important. Although, BDNF has been thoroughly studied in the mammalian models, contradictory effects of its functions have been reported on several occasions. These contradictory effects may be attributed to the sheer complexity of the mammalian brain. The study of BDNF and its associated functions in a simpler vertebrate model may provide some clarity about the effects of BDNF on the neurophysiology of the brain. Keeping that in mind, this review aims at summarizing the current knowledge about the distribution of BDNF and its associated functions in the zebrafish brain. The main focus of the review is to give a comparative overview of BDNF distribution and function in zebrafish and mammals with respect to distinct life stages. We have also reviewed the regulation of bdnf gene in zebrafish and discussed its role in developmental and adult neurogenesis.

Resveratrol Regulates BDNF, trkB, PSA-NCAM, and Arc Expression in the Rat Cerebral Cortex after Bilateral Common Carotid Artery Occlusion and Reperfusion

The polyphenol resveratrol (RVT) may drive protective mechanisms of cerebral homeostasis during the hypoperfusion/reperfusion triggered by the transient bilateral common carotid artery occlusion followed by reperfusion (BCCAO/R). This immunochemical study investigates if a single dose of RVT modulates the plasticity-related markers brain-derived neurotrophic factor (BDNF), the tyrosine kinase trkB receptor, Polysialylated-Neural Cell Adhesion Molecule (PSA-NCAM), and Activity-regulated cytoskeleton-associated (Arc) protein in the brain cortex after BCCAO/R. Frontal and temporal-occipital cortical regions were examined in male Wistar rats randomly subdivided in two groups, sham-operated and submitted to BCCAO/R. Six hours prior to surgery, half the rats were gavage fed a dose of RVT (180 mg·kg⁻¹ in 300 µL of sunflower oil as the vehicle), while the second half was given the vehicle alone. In the frontal cortex of BCCAO/R vehicle-treated rats, BDNF and PSA-NCAM decreased, while trkB increased. RVT pre-treatment elicited an increment of all examined markers in both sham- and BCCAO/R rats. No variations occurred in the temporal-occipital cortex. The results highlight a role for RVT in modulating neuronal plasticity through the BDNF-trkB system and upregulation of PSA-NCAM and Arc, which may provide both trophic and structural local support in the dynamic changes occurring during the BCCAO/R, and further suggest that dietary supplements such as RVT are effective in preserving the tissue potential to engage plasticity-related events and control the functional response to the hypoperfusion/reperfusion challenge.

Effect of Acute Stress on the Expression of BDNF, trkB, and PSA-NCAM in the Hippocampus of the Roman Rats: A Genetic Model of Vulnerability/Resistance to Stress-Induced Depression

The Roman High-Avoidance (RHA) and the Roman Low-Avoidance (RLA) rats, represent two psychogenetically-selected lines that are, respectively, resistant and prone to displaying depression-like behavior, induced by stressors. In the view of the key role played by the neurotrophic factors and neuronal plasticity, in the pathophysiology of depression, we aimed at assessing the effects of acute stress, i.e., forced swimming (FS), on the expression of brain-derived neurotrophic factor (BDNF), its trkB receptor, and the Polysialilated-Neural Cell Adhesion Molecule (PSA-NCAM), in the dorsal (dHC) and ventral (vHC) hippocampus of the RHA and the RLA rats, by means of western blot and immunohistochemical assays. A 15 min session of FS elicited different changes in the expression of BDNF in the dHC and the vHC. In RLA rats, an increment in the CA2 and CA3 subfields of the dHC, and a decrease in the CA1 and CA3 subfields and the dentate gyrus (DG) of the vHC, was observed. On the other hand, in the RHA rats, no significant changes in the BDNF levels was seen in the dHC and there was a decrease in the CA1, CA3, and DG of the vHC. Line-related changes were also observed in the expression of trkB and PSA-NCAM. The results are consistent with the hypothesis that the differences in the BDNF/trkB signaling and neuroplastic mechanisms are involved in the susceptibility of RLA rats and resistance of RHA rats to stress-induced depression.

BDNF, Brain, and Regeneration: Insights from Zebrafish

Zebrafish (Danio rerio) is a teleost fish widely accepted as a model organism for neuroscientific studies. The adults show common basic vertebrate brain structures, together with similar key neuroanatomical and neurochemical pathways of relevance to human diseases. However, the brain of adult zebrafish possesses, differently from mammals, intense neurogenic activity, which can be correlated with high regenerative properties. Brain derived neurotrophic factor (BDNF), a member of the neurotrophin family, has multiple roles in the brain, due also to the existence of several biologically active isoforms, that interact with different types of receptors. BDNF is well conserved in the vertebrate evolution, with the primary amino acid sequences of zebrafish and human BDNF being 91% identical. Here, we review the available literature regarding BDNF in the vertebrate brain and the potential involvement of BDNF in telencephalic regeneration after injury, with particular emphasis to the zebrafish. Finally, we highlight the potential of the zebrafish brain as a valuable model to add new insights on future BDNF studies.

Neuronal expression of brain derived neurotrophic factor in the injured telencephalon of adult zebrafish

The reparative ability of the central nervous system varies widely in the animal kingdom. In the mammalian brain, the regenerative mechanisms are very limited and newly formed neurons do not survive longer, probably due to a non-suitable local environment. On the opposite, fish can repair the brain after injury, with fast and complete recovery of damaged area. The brain of zebrafish, a teleost fish widely used as vertebrate model, also possesses high regenerative properties after injury. Taking advantage of this relevant model, the aim of the present study was to investigate the role of brain-derived neurotrophic factor (BDNF) in the regenerative ability of adult brain, after stab wound telencephalic injury. BDNF is involved in many brain functions and plays key roles in the repair process after traumatic brain lesions. It has been reported that BDNF strengthens the proliferative activity of neuronal precursor cells, facilitates the neuronal migration toward injured areas, and shows survival properties due to its anti-apoptotic effects. BDNF mRNA levels, assessed by quantitative PCR and in situ hybridization at 1, 4, 7, and 15 days after the lesion, were increased in the damaged telencephalon, mostly suddenly after the lesion. Double staining using in situ hybridization and immunocytochemistry revealed that BDNF mRNA was restricted to cells identified as mature neurons. BDNF mRNA expressing neurons mostly increased in the area around the lesion, showing a peak 1 day after the lesion. Taken together, these results highlight the role of BDNF in brain repair processes and reinforce the value of zebrafish for the study of regenerative neurogenesis.

Expression of BDNF and trkB in the hippocampus of a rat genetic model of vulnerability (Roman low-avoidance) and resistance (Roman high-avoidance) to stress-induced depression

INTRODUCTION

The selective breeding of Roman High- (RHA) and Low-Avoidance (RLA) rats for, respectively, rapid versus poor acquisition of the active avoidance response has generated two distinct phenotypes differing in many behavioral traits, including coping strategies to aversive conditions. Thus, RLA rats are considered as a genetic model of vulnerability to stress-induced depression whereas RHA rats are a model of resilience to that trait. Besides the monoamine hypothesis of depression, there is evidence that alterations in neuronal plasticity in the hippocampus and other brain areas are critically involved in the pathophysiology of mood disorders.

MATERIALS AND METHODS

Western blot (WB) and immunohistochemistry were used to investigate the basal immunochemical occurrence of brain-derived neurotrophic factor (BDNF) and its high-affinity tyrosine-kinase receptor trkB in the dorsal and ventral hippocampus of adult RHA and RLA rats.

RESULTS

WB analysis indicated that the optical density of BDNF- and trkB-positive bands in the dorsal hippocampus is, respectively, 48% and 25% lower in RLA versus RHA rats. Densitometric analysis of BDNF- and trkB-like immunoreactivity (LI) in brain sections showed that BDNF-LI is 24% to 34% lower in the different sectors of the Ammon's horn of RLA versus RHA rats, whereas line-related differences are observed in the dentate gyrus (DG) only in the ventral hippocampus. As for trkB-LI, significant differences are observed only in the dorsal hippocampus, where density is 23% lower in the DG of RLA versus RHA rats, while no differences across lines occur in the Ammon's horn.

CONCLUSION

These findings support the hypothesis that a reduced BDNF/trkB signaling in the hippocampus of RLA versus RHA rats may contribute to their more pronounced vulnerability to stress-induced depression.

Integrative analysis of methylation and transcriptional profiles to predict aging and construct aging specific cross-tissue networks

BACKGROUND

Aging is a complex process relating multi-scale omics data. Finding key age markers in normal tissues could help to provide reliable aging predictions in human. However, predicting age based on multi-omics data with both accuracy and informative biological function has not been performed systematically, thus relative cross-tissue analysis has not been investigated entirely, either.

RESULTS

Here we have developed an improved prediction pipeline, the Integrating and Stepwise Age-Prediction (ISAP) method, to regress age and find key aging markers effectively. Furthermore, we have performed a serious of network analyses, such as the PPI network, cross-tissue networks and pathway interaction networks.

CONCLUSION

Our results find important coordinated aging patterns between different tissues. Both co-profiling and cross-pathway analyses identify more thorough functions of aging, and could help to find aging markers, pathways and relative aging disease researches.

BDNF Expression in Larval and Adult Zebrafish Brain: Distribution and Cell Identification

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, has emerged as an active mediator in many essential functions in the central nervous system of mammals. BDNF plays significant roles in neurogenesis, neuronal maturation and/or synaptic plasticity and is involved in cognitive functions such as learning and memory. Despite the vast literature present in mammals, studies devoted to BDNF in the brain of other animal models are scarse. Zebrafish is a teleost fish widely known for developmental genetic studies and is emerging as model for translational neuroscience research. In addition, its brain shows many sites of adult neurogenesis allowing higher regenerative properties after traumatic injuries. To add further knowledge on neurotrophic factors in vertebrate brain models, we decided to determine the distribution of bdnf mRNAs in the larval and adult zebrafish brain and to characterize the phenotype of cells expressing bdnf mRNAs by means of double staining studies. Our results showed that bdnf mRNAs were widely expressed in the brain of 7 days old larvae and throughout the whole brain of mature female and male zebrafish. In adults, bdnf mRNAs were mainly observed in the dorsal telencephalon, preoptic area, dorsal thalamus, posterior tuberculum, hypothalamus, synencephalon, optic tectum and medulla oblongata. By combining immunohistochemistry with in situ hybridization, we showed that bdnf mRNAs were never expressed by radial glial cells or proliferating cells. By contrast, bdnf transcripts were expressed in cells with neuronal phenotype in all brain regions investigated. Our results provide the first demonstration that the brain of zebrafish expresses bdnf mRNAs in neurons and open new fields of research on the role of the BDNF factor in brain mechanisms in normal and brain repairs situations.

Brain-derived neurotrophic factor: mRNA expression and protein distribution in the brain of the teleost Nothobranchius furzeri

BDNF (brain-derived neurotrophic factor) is a member of the neurotrophin family and it is implicated in regulating brain development and function. The BDNF gene organization and coding sequence are conserved in all vertebrates. The present survey was conducted in a teleost fish, Nothobranchius furzeri, because it is an emerging model of aging studies due to its short lifespan and shows the high rate of adult neurogenesis typical of anamniotes. The present survey reports: 1) the identification and characterization of the cDNA fragment encoding BDNF protein, and 2) the localization of BDNF in the whole brain. BDNF mRNA expression was assessed by in situ hybridization, by employing an antisense RNA probe; BDNF protein was detected by employing a sensitive immunohistochemical technique, along with highly specific affinity-purified antibodies to BDNF. Both BDNF mRNA and protein were detected in neurons and glial cells of all regions of the brain of N. furzeri. Interestingly, BDNF was localized also in brain areas involved in adult neurogenic activities, suggesting a specific role for this neurotrophic factor in controlling cell proliferation. These results provide baseline information for future studies concerning BDNF involvement in the aging processes of the teleost brain.

Structural plasticity of climbing fibers and the growth-associated protein GAP-43

Structural plasticity occurs physiologically or after brain damage to adapt or re-establish proper synaptic connections. This capacity depends on several intrinsic and extrinsic determinants that differ between neuron types. We reviewed the significant endogenous regenerative potential of the neurons of the inferior olive (IO) in the adult rodent brain and the structural remodeling of the terminal arbor of their axons, the climbing fiber (CF), under various experimental conditions, focusing on the growth-associated protein GAP-43. CFs undergo remarkable collateral sprouting in the presence of denervated Purkinje cells (PCs) that are available for new innervation. In addition, severed olivo-cerebellar axons regenerate across the white matter through a graft of embryonic Schwann cells. In contrast, CFs undergo a regressive modification when their target is deleted. In vivo knockdown of GAP-43 in olivary neurons, leads to the atrophy of their CFs and a reduction in the ability to sprout toward surrounding denervated PCs. These findings demonstrate that GAP-43 is essential for promoting denervation-induced sprouting and maintaining normal CF architecture.

The effect of PTZ-induced epileptic seizures on hippocampal expression of PSA-NCAM in offspring born to kindled rats

BACKGROUND

Maternal epileptic seizures during pregnancy can affect the hippocampal neurons in the offspring. The polysialylated neural cell adhesion molecule (PSA-NCAM), which is expressed in the developing central nervous system, may play important roles in neuronal migration, synaptogenesis, and axonal outgrowth. This study was designed to assess the effects of kindling either with or without maternal seizures on hippocampal PSA-NCAM expression in rat offspring.

METHODS

Forty timed-pregnant Wistar rats were divided into four groups: A) Kind+/Seiz+, pregnant kindled (induced two weeks prior to pregnancy) rats that received repeated intraperitoneal (i.p.) pentylenetetrazol, PTZ injections on gestational days (GD) 14-19; B) Kind-/Seiz+, pregnant non-kindled rats that received PTZ injections on GD14-GD19; C) Kind+/Seiz-, pregnant kindled rats that did not receive any PTZ injections; and D) Kind-/Seiz-, the sham controls. Following birth, the pups were sacrificed on PD1 and PD14, and PSA-NCAM expression and localization in neonates' hippocampi were analyzed by Western blots and immunohistochemistry.

RESULTS

Our data show a significant down regulation of hippocampal PSA-NCAM expression in the offspring of Kind+/Seiz+ (p = 0.001) and Kind-/Seiz+ (p = 0.001) groups compared to the sham control group. The PSA-NCAM immunoreactivity was markedly decreased in all parts of the hippocampus, especially in the CA3 region, in Kind+/Seiz+ (p = 0.007) and Kind-/Seiz+ (p = 0.007) group's newborns on both PD1 and 14.

CONCLUSION

Our findings demonstrate that maternal seizures but not kindling influence the expression of PSA-NCAM in the offspring's hippocampi, which may be considered as a factor for learning/memory and cognitive impairments reported in children born to epileptic mothers.

Insulin-like growth factor I signaling for brain recovery and exercise ability in brain ischemic rats

PURPOSE

Exercise increases neuron survival and plasticity in the adult brain by enhancing the uptake of insulin-like growth factor I (IGF-I). Exercise also reduces the infarct volume in the ischemic brain and improves motor function after such a brain insult. However, the underlying mechanisms are not fully known. The purpose of this study was to investigate the involvement of IGF-I signaling in neuroprotection after exercise.

METHOD

Rats were assigned to one of four groups: middle cerebral artery occlusion (MCAO) without exercise training (MC), MCAO with exercise training (ME), MCAO with IGF-I receptor inhibitor and without exercise training (MAg), and MCAO with IGF-I receptor inhibitor and exercise training (MEAg). Rats in the ME and MEAg groups underwent treadmill training for 14 d, and rats in the MC and MAg groups served as controls. After the final intervention, rats were sacrificed under anesthesia, and samples were collected from the affected motor cortex, striatum, and plasma.

RESULTS

IGF-I and p-Akt levels in the affected motor cortex and the striatum of the ME group were significantly higher than those in the MC group, with significant decreases in infarct volume and improvements in motor function. However, IGF-I receptor inhibitor eliminated these effects and decreased the exercise ability. The brain IGF-I signaling strongly correlated with exercise ability.

CONCLUSIONS

Exercise-enhanced IGF-I entrance into ischemic brain and IGF-I signaling was related to exercise-mediated neuroprotection. IGF-1 signaling also affected the ability to exercise after brain ischemia.