Acute stress alters transcript expression pattern and reduces processing of proBDNF to mature BDNF in Dicentrarchus labrax

GM1 and GD3 Gangliosides Attenuate NGF-TrkA and BDNF-TrkB Signaling Dysfunction Associated with Acute Diisopropylfluorophosphate Exposure in Mouse Brain

The prevalence of neurodegenerative diseases and mental health disorders has been increasing over the past few decades. While genetic and lifestyle factors are important to the etiology of these illnesses, the pathogenic role of environmental factors, especially toxicants such as pesticides encountered over the life span, is receiving increased attention. As an environmental factor, organophosphates pose a constant threat to human health due to their widespread use as pesticides, their deployment by rogue militaries, and their use in terrorist attacks. The standard organophosphate-antidotal regimen provides modest efficacy against lethality, although morbidity remains high, and there is little evidence that it attenuates long-term neurobehavioral sequelae. Here we show that a novel intranasally administered treatment strategy with specific gangliosides can prevent the organophosphate-related alterations in important neurotrophin pathways that are involved in cognition and depression. We found that a single toxic dose of the organophosphate diisopropylfluorophosphate (DFP) in mice leads to persistent decreases in the neurotrophins NGF and BDNF and their receptors, TrkA and TrkB. Moreover, seven days of repeated intranasal administration of gangliosides GM1 or GD3 24 hours after the DFP injection prevented the neurotrophin receptor alterations. As NGF and BDNF signaling are involved in cognitive function and depression symptoms, respectively, intranasal administration of GM1 or GD3 can prevent the organophosphate-related alterations in those brain functions. Our study thus supports the potential of a novel therapeutic strategy for neurological deficits associated with a class of poisons that endangers millions of people worldwide.

Highlights

A single exposure to DFP, which causes cognitive deficits, dysregulates NGF and BDNF signalingGM1 or GD3 24 hours after DFP injection prevents the alteration of the neurotrophin signalingIntranasal ganglioside treatment provides neuroprotective effects against persistent organophosphate toxicity.

Maternal Hyperhomocysteinemia Disturbs the Mechanisms of Embryonic Brain Development and Its Maturation in Early Postnatal Ontogenesis

Maternal hyperhomocysteinemia causes the disruption of placental blood flow and can lead to serious disturbances in the formation of the offspring's brain. In the present study, the effects of prenatal hyperhomocysteinemia (PHHC) on the neuronal migration, neural tissue maturation, and the expression of signaling molecules in the rat fetal brain were described. Maternal hyperhomocysteinemia was induced in female rats by per os administration of 0.15% aqueous methionine solution in the period of days 4-21 of pregnancy. Behavioral tests revealed a delay in PHHC male pups maturing. Ultrastructure of both cortical and hippocampus tissue demonstrated the features of the developmental delay. PHHC was shown to disturb both generation and radial migration of neuroblasts into the cortical plate. Elevated Bdnf expression, together with changes in proBDNF/mBDNF balance, might affect neuronal cell viability, positioning, and maturation in PHHC pups. Reduced Kdr gene expression and the content of SEMA3E might lead to impaired brain development. In the brain tissue of E20 PHHC fetuses, the content of the procaspase-8 was decreased, and the activity level of the caspase-3 was increased; this may indicate the development of apoptosis. PHHC disturbs the mechanisms of early brain development leading to a delay in brain tissue maturation and formation of the motor reaction of pups.

Ulexite modulates the neurotoxicological outcomes of acetylferrocene-exposed rainbow trout

In this study, the neuroprotective action potential by ulexite (UX) (18.75 mg/L) against acetylferrocene (AFC) (3.82 mg/L) induced neurotoxicity was aimed to investigate in brain tissues of Oncorhynchus mykiss. For this purpose, the effects on neurotoxicity markers, proinflammatory cytokines, antioxidant immune system, DNA, and apoptosis mechanisms were assessed on brain tissues in the 48-96  h of the 96- trial period. In this research, it was determined that brain-derived nerve cell growth factor (BDNF) level and acetylcholinesterase (AChE) activity were inhibited in the brain tissue compared to the control group by AFC. In addition, inhibition in glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH) values (which are antioxidant system biomarkers), and inductions in malondialdehyde (MDA) and myeloperoxidase (MPO) amounts (which are indicators of lipid peroxidation) were determined (p < 0.05) after exposure to AFC. And, while tumor necrosis factor-α (TNF-α) and IL-6 levels were increased in the AFC-exposed group, Nrf-2 levels were found to be remarkably decreased. Upregulation was also detected in 8-hydroxydeoxyguanosine (8-OHdG) and caspase-3 levels, which are related to DNA damage and apoptosis mechanism. On the contrary, UX (single/with AFC) suppressed the AChE and BDNF inhibition by AFC. Moreover, UX mitigated AFC-induced oxidative, inflammatory, and DNA damage and attenuated AFC-mediated neurotoxicity via activating Nrf2 signaling in fish. Collectively, our findings revealed that UX supplementation might exert beneficial effects and may be considered as a natural and promising neuroprotective agent against AFC-induced toxicity.

Can Neuropeptide S Be an Indicator for Assessing Anxiety in Psychiatric Disorders?

Neuropeptide S (NPS) is a neuropeptide primarily produced within three brainstem regions including locus coeruleus, trigeminal nerve nucleus, and lateral parabrachial nucleus. NPS is involved in the central regulation of stress, fear, and cognitive integration. NPS is a mediator of behavior, seeking food, and the proliferation of new adipocytes in the setting of obesity. So far, current research of NPS is only limited to animal models; data regarding its functions in humans is still scarce. Animal studies showed that anxiety and appetite might be suppressed by the action of NPS. The discovery of this neuromodulator peptide is effective considering its strong anxiolytic action, which has the potential to be an interesting therapeutic option in treating neuropsychiatric disorders. In this article, we aimed to analyze the pharmaceutical properties of NPS as well as its influence on several neurophysiological aspects-modulation of behavior, association with obesity, as well as its potential application in rehabilitation and treatment of psychiatric disorders.

Aspirin ameliorates the cognition impairment in mice following benzo[a]pyrene treatment via down-regulating BDNF IV methylation

Benzo[a]pyrene (B[a]P) is neurotoxic, however, the mechanisms remain unclear and there is no effective prevention. Available evidence suggests a role of DNA methylation in B[a]P-induced neurotoxicity. This study investigated the brain-derived neurotrophic factor (BDNF) IV methylation in the development of and aspirin intervention against B[a]P's neurotoxicity in mice and HT22 cells. Mice were intraperitoneally treated with solvent or B[a]P (0.5, 2, and 10 mg/kg b.w.) for 60 days. An intervention group was treated simultaneously with B[a]P (10 mg/kg, i.p.) and aspirin (10 mg/kg, daily water-drinking). The treated mice showed a dose-dependent cognitive and behavioral impairment, and cerebral cell apoptosis, which were alleviated by aspirin co-treatment. Following B[a]P treatment, DNA methyltransferase (DNMTs) and BDNF IV hypermethylation were increased in the cerebral cortex of mice compared to controls, while significant decreases were found in BDNF IV and BDNF mRNA, and BDNF protein levels. Aspirin co-treatment rescued DNMTs activation and BDNF IV hypermethylation, and mitigated the recession in BDNF mRNA and protein induced by B[a]P treatment. Similar results were shown in HT22 cells. These findings reveal a critical role of BDNF IV methylation in the neurotoxicity of B[a]P, and demonstrate a promising prevention of aspirin against B[a]P-induced cognitive impairment via inhibiting BDNF IV hypermethylation.

Intermediation of perceived stress between early trauma and plasma M/P ratio levels in obsessive-compulsive disorder patients

OBJECTIVES

This study is to find the correlation among BDNF metabolism, early trauma, and current stress status of OCD patients. As well as to study the BDNF metabolism-stress related pathological mechanism in OCD development.

METHODS

A total of 140 participants were recruited in this study, including 64 drug-naïve OCD patients (OCDs) and 76 healthy controls (HCs). The clinical data of the subjects were measured using YBOCS, CTQ, and PSS. The plasma mBDNF and proBDNF values were measured by ELISA while the M/P ratio was calculated.

RESULTS

The mBDNF, proBDNF plasma levels, and M/P ratio of unmedicated OCD individuals decreased evidently comparing with HCs. Also, positive associations were found between PSS and CTQ and between CTQ and M/P ratio. The negative correlation included proBDNF and PSS as well as proBDNF and CTQ. Intermediary analysis generated by SPSS has showed that the perceived stress played a complete mediating role between early trauma and plasma M/P ratio levels, and the mediating effect was 0.043 in non-medication OCD patients.

CONCLUSIONS

Findings from this study suggested that early trauma experience and stress state work together in regulating BDNF metabolism level in OCD patients. The nucleus accumbens and reward loop are also pivotal in the pathogenesis of OCD.

The impact of antipsoriatic treatment on serum pro-BDNF, BDNF levels, depression, anxiety scores, and quality of life

Depression is a comorbidity of psoriasis. Suppression of neurotrophins has been proposed to cause depression. Peripheral brain-derived neurotrophic factor (BDNF) and its precursor, pro-BDNF have been shown to be altered in depression. To compare serum pro-BDNF and BDNF levels, depression, anxiety, and quality of life (QoL) in psoriasis patients, diseased, and healthy controls, to assess impact of 12-week antipsoriatic treatment on abovementioned markers. At baseline, all groups completed Beck Depression Inventory (BDI), Spielberger State-Trait Anxiety Inventory-II (STAI-II) and DLQI; serum BDNF, proBDNF levels were measured. These were repeated after 3-months of treatment in psoriasis patients. Depression and anxiety were significantly higher, QoL was poorer in psoriasis. ProBDNF and proBDNF/BDNF ratios were not different among groups at baseline but significantly decreased after treatment in psoriasis. Depression and QoL improved significantly, BDNF and anxiety scores did not change. Altered pro-BDNF and proBDNF/BDNF ratios may have a role in depression pathogenesis in psoriasis. Antipsoriatic treatment causes improvement in depression, QoL, and reduction of proBDNF and proBDNF/BDNF ratios. Effective disease control may reverse dysregulated neurotrophin pathways and its consequences like depression.

Family-effects in the epigenomic response of red blood cells to a challenge test in the European sea bass (Dicentrarchus labrax, L.)

Abstract

Background

In fish, minimally invasive blood sampling is widely used to monitor physiological stress with blood plasma biomarkers. As fish blood cells are nucleated, they might be a source a potential new markers derived from ‘omics technologies. We modified the epiGBS (epiGenotyping By Sequencing) technique to explore changes in genome-wide cytosine methylation in the red blood cells (RBCs) of challenged European sea bass (Dicentrarchus labrax), a species widely studied in both natural and farmed environments.

Results

We retrieved 501,108,033 sequencing reads after trimming, with a mean mapping efficiency of 73.0% (unique best hits). Minor changes in RBC methylome appeared to manifest after the challenge test and a family-effect was detected. Only fifty-seven differentially methylated cytosines (DMCs) close to 51 distinct genes distributed on 17 of 24 linkage groups (LGs) were detected between RBCs of pre- and post-challenge individuals. Thirty-seven of these genes were previously reported as differentially expressed in the brain of zebrafish, most of them involved in stress coping differences. While further investigation remains necessary, few DMC-related genes associated to the Brain Derived Neurotrophic Factor, a protein that favors stress adaptation and fear memory, appear relevant to integrate a centrally produced stress response in RBCs.

Conclusion

Our modified epiGBS protocol was powerful to analyze patterns of cytosine methylation in RBCs of D. labrax and to evaluate the impact of a challenge using minimally invasive blood samples. This study is the first approximation to identify epigenetic biomarkers of exposure to stress in fish.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07420-9.

Comparative Genomics of the BDNF Gene, Non-Canonical Modes of Transcriptional Regulation, and Neurological Disease

Alternative splicing of genes in the central nervous system is ubiquitous and utilizes many different mechanisms. Splicing generates unique transcript or protein isoforms of the primary gene that result in shortened, lengthened, or reorganized products that may have distinct functions from the parent gene. Learning and memory genes respond selectively to a variety of environmental stimuli and have evolved a number of complex mechanisms for transcriptional regulation to act rapidly and flexibly to environmental demands. Their patterns of expression, however, are incompletely understood. Many activity-inducible genes generate transcripts by alternative splicing that have an unknown physiological or behavioral function. One such gene codes for the protein brain-derived neurotrophic factor (BDNF). BDNF is a neurotrophin whose expression is essential for cellular growth, synaptogenesis, and synaptic plasticity. It is an important model gene because of its complex structure and the variety of transcriptional mechanisms it displays for expression in response to external stimuli. Some of these are unexpected, or non-canonical, transcriptional control mechanisms that require further exploration in an activity-dependent context. In this review, a comparative genomics approach is taken to highlight the different forms of BDNF gene transcription including potential autoregulatory mechanisms. Modes of BDNF control have general implications for understanding the origins of several neurological disorders that are associated with reduced BDNF function.

Oral quetiapine treatment results in time-dependent alterations of recognition memory and brain-derived neurotrophic factor-related signaling molecules in the hippocampus of rats

Antipsychotic drugs (APDs) have a variety of important therapeutic applications for neuropsychiatric disorders. However, they are routinely prescribed off-label across all age categories, a controversial practice given their potential for producing metabolic and extrapyramidal side effects. Evidence also suggests that chronic treatment with some APDs may lead to impairments in cognition and decreases in brain volume, although these findings are controversial. The purpose of the studies described here was to evaluate one of the most commonly prescribed APDs, quetiapine, for chronic effects on recognition memory, brain-derived neurotrophic factor (BDNF), its precursor proBDNF, as well as relevant downstream signaling molecules that are known to influence neuronal plasticity and cognition. Multiple cohorts of adult rats were treated with quetiapine (25.0 mg/kg/day) for 30 or 90 days in their drinking water then evaluated for drug effects on motor function in a catalepsy assessment, recognition memory in a spontaneous novel object recognition (NOR) task, and BDNF-related signaling molecules in the post mortem hippocampus via Western Blot. The results indicated that oral quetiapine at a dose that did not induce catalepsy, led to time-dependent impairments in NOR performance, increases in the proBDNF/BDNF ratio, and decreases in Akt and CREB phosphorylation in the hippocampus. These results indicate that chronic treatment with quetiapine has the potential to adversely affect recognition memory and neurotrophin-related signaling molecules that support synaptic plasticity and cognitive function. Given the widespread use this APD across multiple conditions and patient populations, such long-term effects observed in animals should be considered.

Increased ratio of mature BDNF to precursor-BDNF in patients with major depressive disorder with severe anhedonia

BACKGROUND

Although studies have shown that severe anhedonia in patients with major depressive disorder (MDD) is associated with poor treatment outcomes, the biological mechanism of this feature is unclear. The aim of this study was to investigate the dysfunction of brain-derived neurotrophic factor (BDNF) metabolism, measured by the ratio of mature BDNF to precursor-BDNF, in MDD patients with severe anhedonia.

METHODS

We measured plasma levels of mature BDNF (mBDNF), precursor-BDNF (proBDNF), tissue plasminogen activator (tPA) and tropomyosin-related kinase B (trkB) in outpatients with MDD with anhedonia (n = 26), outpatients with MDD without anhedonia (n = 29) and age- and sex-matched healthy controls (HCs, n = 38) by enzyme-linked immunosorbent assay kits, and we calculated the ratio of mBDNF to proBDNF (M/P). We compared these biological determinants among the three groups and explored the interrelationships between anhedonia severity and BDNF metabolism.

RESULTS

The levels of mBDNF, proBDNF, and tPA and the ratio of M/P were identified with highly significant differences among the three groups. Compared with MDD patients without anhedonia and healthy controls, MDD patients with anhedonia showed higher level of the ratio of M/P, and it was positively associated with the SHAPS scores in MDD patients. Compared to healthy controls, the plasma tPA concentrations were higher in MDD patients with anhedonia but were not different from those in MDD patients without anhedonia.

CONCLUSION

These results provide novel evidence regarding the relationship between anhedonia and plasma BDNF metabolism. The hypermetabolism of BDNF may be a function of anhedonia rather than other characteristics in MDD.

Chronic oral treatment with risperidone impairs recognition memory and alters brain-derived neurotrophic factor and related signaling molecules in rats

Antipsychotic drugs (APDs) are essential for the treatment of schizophrenia and other neuropsychiatric illnesses such as bipolar disease. However, they are also extensively prescribed off-label for many other conditions, a practice that is controversial given their potential for long-term side effects. There is clinical and preclinical evidence that chronic treatment with some APDs may lead to impairments in cognition and decreases in brain volume, although the molecular mechanisms of these effects are unknown. The purpose of the rodent studies described here was to evaluate a commonly prescribed APD, risperidone, for chronic effects on recognition memory, brain-derived neurotrophic factor (BDNF), its precursor proBDNF, as well as relevant downstream signaling molecules that are known to influence neuronal plasticity and cognition. Multiple cohorts of adult rats were treated with risperidone (2.5 mg/kg/day) or vehicle (dilute acetic acid solution) in their drinking water for 30 or 90 days. Subjects were then evaluated for drug effects on recognition memory in a spontaneous novel object recognition task and protein levels of BDNF-related signaling molecules in the hippocampus and prefrontal cortex. The results indicated that depending on the treatment period, a therapeutically relevant daily dose of risperidone impaired recognition memory and increased the proBDNF/BDNF ratio in the hippocampus and prefrontal cortex. Risperidone treatment also led to a decrease in Akt and CREB phosphorylation in the prefrontal cortex. These results indicate that chronic treatment with a commonly prescribed APD, risperidone, has the potential to adversely affect recognition memory and neurotrophin-related signaling molecules that support synaptic plasticity and cognitive function.

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.

Repeated fluoxetine treatment induces long-lasting neurotrophic changes in the medial prefrontal cortex of adult rats

Fluoxetine (Flx), a selective serotonin reuptake inhibitor, is extensively used to treat mood and anxiety disorders. Previous animal studies have shown that early-life exposure to Flx results in long-lasting behavioral alterations and neuroplasticity in the hippocampus and cortex, which may persist into adulthood. It remains unclear whether repeated Flx treatment in normal adult animals can induce lasting neuroplasticity and behavioral alterations persisting long beyond the treatment period. In this study, young adult rats (about 9 weeks old) were treated with Flx (10 mg/kg body weight, twice daily) for 15 consecutive days, and the effects of Flx on medial prefrontal cortex (mPFC) neuroplasticity and mPFC-related behaviors were assessed 20 days after the last injection. It was observed that the mPFC of Flx-treated rats had significant increases in the number of 5-bromodeoxyuridine-positive (BrdU⁺) cells, dendritic complexity/spine density in layer II/III pyramidal neurons, and brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB) expression levels, as well as a significant decrease in the number of parvalbumin-positive (PV⁺) interneurons. The Flx-treated rats exhibited higher motivation to explore new environments, evidenced by a significantly increased number of entries into the novel arm in the Y-maze test. However, they did not show any significant changes in the anhedonia and anxiety levels measured by sucrose preference and elevated plus maze tests respectively. In conclusion, repeated Flx treatment, with the paradigm used, induces long-lasting neuroplastic changes in the mPFC of normal adult rats; such changes and related behavioral manifestations may persist up to 20 days after the last dose.

Neurobiology of Wild and Hatchery-Reared Atlantic Salmon: How Nurture Drives Neuroplasticity

Life experiences in the rearing environment shape the neural and behavioral plasticity of animals. In fish stocking practices, the hatchery environment is relatively stimulus-deprived and does not optimally prepare fish for release into the wild. While the behavioral differences between wild and hatchery-reared fish have been examined to some extent, few studies have compared neurobiological characteristics between wild and hatchery-reared individuals. Here, we compare the expression of immediate early gene cfos and neuroplasticity marker brain-derived neurotrophic factor (bdnf) in telencephalic subregions associated with processing of stimuli in wild and hatchery-reared Atlantic salmon at basal and 30 min post (acute) stress conditions. Using in situ hybridization, we found that the expression level of these markers is highly specific per neuronal region and affected by both the origin of the fish, and exposure to acute stress. Expression of cfos was increased by stress in all brain regions and cfos was more highly expressed in the Dlv (functional equivalent to the mammalian hippocampus) of hatchery-reared compared to wild fish. Expression of bdnf was higher overall in hatchery fish, while acute stress upregulated bdnf in the Dm (functional equivalent to the mammalian amygdala) of wild, but not hatchery individuals. Our findings demonstrate that the hatchery environment affects neuroplasticity and neural activation in brain regions that are important for learning processes and stress reactivity, providing a neuronal foundation for the behavioral differences observed between wild and hatchery-reared fish.

Visual Experience Facilitates BDNF-Dependent Adaptive Recruitment of New Neurons in the Postembryonic Optic Tectum

Postembryonic brain development is sensitive to environmental input and sensory experience, but the mechanisms underlying healthy adaptive brain growth are poorly understood. Here, we tested the importance of visual experience on larval zebrafish (Danio rerio) postembryonic development of the optic tectum (OT), a midbrain structure involved in visually guided behavior. We first characterized postembryonic neurogenic growth in OT, in which new neurons are generated along the caudal tectal surface and contribute appositionally to anatomical growth. Restricting visual experience during development by rearing larvae in dim light impaired OT anatomical and neurogenic growth, specifically by reducing the survival of new neurons in the medial periventricular gray zone. Neuronal survival in the OT was reduced only when visual experience was restricted for the first 5 d following new neuron generation, suggesting that tectal neurons exhibit an early sensitive period in which visual experience protects these cells from subsequent neuronal loss. The effect of dim rearing on neuronal survival was mimicked by treatment with an NMDA receptor antagonist early, but not later, in a new neuron's life. Both dim rearing and antagonist treatment reduced BDNF production in the OT, and supplementing larvae with exogenous BDNF during dim rearing prevented neuronal loss, suggesting that visual experience protects new tectal neurons through neural activity-dependent BDNF expression. Collectively, we present evidence for a sensitive period of neurogenic adaptive growth in the larval zebrafish OT that relies on visual experience-dependent mechanisms.SIGNIFICANCE STATEMENT Early brain development is shaped by environmental factors via sensory input; however, this form of experience-dependent neuroplasticity is traditionally studied as structural and functional changes within preexisting neurons. Here, we found that restricting visual experience affects development of the larval zebrafish optic tectum, a midbrain structure involved in visually guided behavior, by limiting the survival of newly generated neurons. We found that new tectal neurons exhibit a sensitive period soon after cell birth in which adequate visual experience, likely mediated by neuronal activity driving BDNF production within the tectum, would protect them from subsequent neuronal loss over the following week. Collectively, we present evidence for neurogenic adaptive tectal growth under different environmental lighting conditions.

Morpho-Functional Features of the Gonads of Danio rerio: the Role of Brain-Derived Neurotrophic Factor

Zebrafish, a suitable and widely used teleost fish model in basic biomedical research, displays morphophysiological features of adult gonads that share some commonalities with those of mammalian species. In mammals, gametogenesis is regulated, among several factors, by brain-derived neurotrophic factor (BDNF). This neurotrophin has a well-established role in the developing and adult nervous system, as well as gonads development and functions in vertebrate species. We hypothesize that BDNF has a role also in the gonadal functions of zebrafish. At this purpose, we investigated BDNF and its receptors p75 and TrkB in the ovary and testis of adult zebrafish, kept under laboratory conditions. Our results display (1) the expression of BDNF mRNA and pro-BDNF protein outside of the nervous system, specifically in the ovary and testis; (2) the presence of pro-BDNF in primary oocytes and follicular layer, and p75 in follicular cells; (3) the localization of pro-BDNF in type B spermatogonia, and Sertoli cells in testis. Altogether, these data lead us to consider that BDNF is involved in the gonadal function of adult zebrafish, and mainly in the adult ovary. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 301:140-147, 2018. © 2017 Wiley Periodicals, Inc.

Epigenetic Regulation of BDNF Gene during Development and Diseases

Brain-derived neurotrophic factor (BDNF) is required for the development of the nervous system, proper cognitive function and memory formation. While aberrant expression of BDNF has been implicated in neurological disorders, the transcriptional regulation of BDNF remains to be elucidated. In response to different stimuli, BDNF expression can be initiated from different promoters. Several studies have suggested that the expression of BDNF is regulated by promoter methylation. An emerging theme points to the possibility that histone modifications at the BDNF promoters may link to the neurological pathology. Thus, understanding the epigenetic regulation at the BDNF promoters will shed light on future therapies for neurological disorders. The present review summarizes the current knowledge of histone modifications of the BDNF gene in neuronal diseases, as well as the developmental regulation of the BDNF gene based on data from the Encyclopedia of DNA Elements (ENCODE).

Ratio of mBDNF to proBDNF for Differential Diagnosis of Major Depressive Disorder and Bipolar Depression

There is a high rate of misdiagnosis between major depressive disorder (MDD) and bipolar disorder (BD) in clinical practice. Our previous work provided suggestive evidence for brain-derived neurotrophic factor (BDNF) in differentiating BD from MDD. In this study, we aimed to investigate the role of mature BDNF (mBDNF) and its precursor (proBDNF) in distinguishing bipolar depression (BP) from MDD during acute depressive episode. A total of 105 participants, including 44 healthy controls, 37 MDD patients and 24 BP patients, were recruited. Enzyme-linked immunosorbent assay kits were applied to measure plasma mBDNF levels and proBDNF levels of all participants. Plasma mBDNF levels were significantly decreased in BP group than those in MDD group (P = 0.001) and healthy controls (P = 0.002). Significantly higher ratio of mBDNF to proBDNF (M/P) at baseline was showed in MDD group than those in BP group as well as in healthy controls (P = 0.000 and P = 0.000, respectively). The optimal model for discriminating BP was the M/P ratio (area under the ROC curve = 0.858, 95 % CI 0.753-0.963). Furthermore, the M/P ratio was restored to normal levels after antidepressants treatment in MDD group. In summary, our data demonstrated that both plasma mBDNF levels and M/P ratio were lower in BP compared with MDD. These findings further support M/P ratio as a potential differential diagnostic biomarker for BP among patients in depressive episodes.

Decreased Plasma BDNF Levels of Patients with Somatization Disorder

OBJECTIVE

Brain-derived neurotrophic factor (BDNF), one of the most abundant and important neurotrophins, is known to be involved in the development, survival, maintenance, and plasticity of neurons in the nervous system. Some studies have suggested that BDNF may play a role in the pathophysiology of several psychiatric illnesses such as depression and schizophrenia. Similarly, it is likely that the alteration of BDNF may be associated with the neuro-modulation that contributes to the development of somatization disorder.

METHODS

The purpose of this study was to determine whether there is an abnormality of plasma BDNF levels in patients with somatization disorder, and to analyze the nature of the alteration after pharmacotherapy using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

The plasma BDNF levels of the patients with a somatization disorder were significantly lower compared with those of the control volunteers (83.61±89.97 pg/mL vs. 771.36±562.14 pg/mL); moreover, the plasma BDNF levels of those patients who received an antidepressant were significantly increased after the treatment (118.13±91.45 pg/mL vs. 72.92±88.21 pg/mL).

CONCLUSION

These results suggest that BDNF may play a role in the pathophysiology of somatization disorder.

Effects of titanium dioxide nanoparticle exposure in Mytilus galloprovincialis gills and digestive gland

Despite the wide use of nanoscale materials in several fields, some aspects of the nanoparticle behavior have to be still investigated. In this work, we faced the aspect of environmental effects of increasing concentrations of TiO2NPs using the Mytilus galloprovincialis as an animal model and carrying out a multidisciplinary approach to better explain the results. Bioaccumulation suggested that the gills and digestive gland are the most sensitive organs to TiO2NP exposure. Histological observations have evidenced an altered tissue organization and a consistent infiltration of hemocytes, as a consequence of the immune system activation, even though an increase in lipid peroxidation is uncertain and DNA damage became relevant only at high exposure dose (10 mg/L) or for longer exposure time (96 h). However, the over expression of SOD1 mRNA strengthen the concept that the toxicity of TiO2NPs could occur indirectly by ROS production. TEM analysis showed the presence of multilamellar bodies, RER fragmentation, and cytoplasmic vacuolization within relevant presence of dense granules, residual bodies, and lipid inclusions. These findings support the evidence of an initial inflammatory response by the cells of the target organs leading to apoptosis. In conclusion, we can state that certainly the exposure to TiO2NPs has affected our animal model from cellular to molecular levels. Interestingly, the same responses are caused by lower TiO2NP concentration and longer exposure time as well as higher doses and shorter exposure. We do not know if some of the conditions detected are reversible, then further studies are required to clarify this aspect.

Zerovalent Fe, Co and Ni nanoparticle toxicity evaluated on SKOV-3 and U87 cell lines

We have considered nanoparticles (NPs) of Fe, Co and Ni, three transition metals sharing similar chemical properties. NP dissolution, conducted by radioactive tracer method and inductively coupled plasma mass spectrometry, indicated that NiNPs and FeNPs released in the medium a much smaller amount of ions than that released by Co NPs. The two considered methodological approaches, however, gave comparable but not identical results. All NPs are readily internalized by the cells, but their quantity inside the cells is less than 5%. Cytotoxicity and gene expression experiments were performed on SKOV‐3 and U87 cells. In both cell lines, CoNPs and NiNPs were definitely more toxic than FeNPs. Real‐time polymerase chain reaction experiments aimed to evaluate modifications of the expression of genes involved in the cellular stress response (HSP70, MT2A), or susceptible to metal exposure (SDHB1 and MLL), or involved in specific cellular processes (caspase3, IQSEC1 and VMP1), gave different response patterns in the two cell lines. HSP70, for example, was highly upregulated by CoNPs and NiNPs, but only in SKOV‐3 cell lines. Overall, this work underlines the difficulties in predicting NP toxicological properties based only on their chemical characteristics. We, consequently, think that, at this stage of our knowledge, biological effects induced by metal‐based NPs should be examined on a case‐by‐case basis following studies on different in vitro models. Moreover, with the only exception of U87 exposed to Ni, our results suggest that metallic NPs have caused, on gene expression, similar effects to those caused by their corresponding ions. Copyright © 2015 The Authors. Journal of Applied Toxicology published by John Wiley & Sons, Ltd.

We have considered Fe, Co and Ni nanoparticles and studied their dissolution by radioactive tracer method and ICP‐MS. We have also performed cytotoxicity and gene expression experiments on two different cell lines. The obtained results convinced us that, at this stage of our knowledge, metal‐based nanoparticles should be examined on a case‐by‐case basis on different in vitro models. Moreover, our results suggest that metal‐based nanoparticles have caused similar effects to those caused by their corresponding ions.

Explore the Features of Brain-Derived Neurotrophic Factor in Mood Disorders

Objectives

Brain-derived neurotrophic factor (BDNF) plays important roles in neuronal survival and differentiation; however, the effects of BDNF on mood disorders remain unclear. We investigated BDNF from the perspective of various aspects of systems biology, including its molecular evolution, genomic studies, protein functions, and pathway analysis.

Methods

We conducted analyses examining sequences, multiple alignments, phylogenetic trees and positive selection across 12 species and several human populations. We summarized the results of previous genomic and functional studies of pro-BDNF and mature-BDNF (m-BDNF) found in a literature review. We identified proteins that interact with BDNF and performed pathway-based analysis using large genome-wide association (GWA) datasets obtained for mood disorders.

Results

BDNF is encoded by a highly conserved gene. The chordate BDNF genes exhibit an average of 75% identity with the human gene, while vertebrate orthologues are 85.9%-100% identical to human BDNF. No signs of recent positive selection were found. Associations between BDNF and mood disorders were not significant in most of the genomic studies (e.g., linkage, association, gene expression, GWA), while relationships between serum/plasma BDNF level and mood disorders were consistently reported. Pro-BDNF is important in the response to stress; the literature review suggests the necessity of studying both pro- and m-BDNF with regard to mood disorders. In addition to conventional pathway analysis, we further considered proteins that interact with BDNF (I-Genes) and identified several biological pathways involved with BDNF or I-Genes to be significantly associated with mood disorders.

Conclusions

Systematically examining the features and biological pathways of BDNF may provide opportunities to deepen our understanding of the mechanisms underlying mood disorders.

Identifying rare variants for genetic risk through a combined pedigree and phenotype approach: application to suicide and asthma

Suicidal behavior is a complex disorder, with evidence for genetic risk independent of other genetic risk factors including psychiatric disorders. Since 1996, over 3000 DNA samples from Utah suicide decedents have been collected and banked for research use through the Utah Medical Examiner. In addition, over 12,000 Utah suicides were identified through examination of death certificates back to 1904. By linking this data with the Utah Population Database, we have identified multiple extended pedigrees with increased risk for suicide completion. A number of medical conditions co-occur with suicide, including asthma, and this study was undertaken to identify genetic risk common to asthma and suicide. This study tests the hypothesis that a particular comorbid condition may identify a more homogeneous genetic subgroup, facilitating the identification of specific genetic risk factors in that group. From pedigrees at increased risk for suicide, we identified three pedigrees also at significantly increased familial risk for asthma. Five suicide decedents from each of these pedigrees, plus an additional three decedents not from these pedigrees with diagnosed asthma, and 10 decedents with close relatives with asthma were genotyped. Results were compared with 183 publicly available unaffected control exomes from 1000 Genomes and CEPH (Centre d'etude du polymorphisme humain) samples genotyped on the same platform. A further 432 suicide decedents were also genotyped as non-asthma suicide controls. Genotyping was done using the Infinium HumanExome BeadChip. For analysis, we used the pedigree extension of Variant Annotation, Analysis and Search Tool (pVAAST) to calculate the disease burden of each gene. The Phenotype Driven Variant Ontological Re-ranking tool (Phevor) then re-ranked our pVAAST results in context of the phenotype. Using asthma as a seed phenotype, Phevor traversed biomedical ontologies and identified genes with similar biological properties to those known to result in asthma. Our top associated genes included those related to neurodevelopment or neural signaling (brain-derived neurotrophic factor (BDNF), neutral sphingomyelinase 2 (SMPD2), homeobox b2 (HOXB2), neural cell adhesion molecule (NCAM2), heterogeneous nuclear ribonucleoprotein A0 (HNRNPA0)), inflammation (free fatty acid receptor 2 (FFAR2)) and inflammation with additional evidence of neuronal involvement (oxidized low density lipoprotein receptor 1 (OLR1), toll-like receptor 3 (TLR3)). Of particular interest, BDNF has been previously implicated in both psychiatric disorders and asthma. Our results demonstrate the utility of combining pedigree and co-occurring phenotypes to identify rare variants associated with suicide risk in conjunction with specific co-occurring conditions.

BDNF contributes to the facilitation of hippocampal synaptic plasticity and learning enabled by environmental enrichment

Sensory, motor, and cognitive stimuli, resulting from interactions with the environment, play a key role in optimizing and modifying the neuronal circuitry required for normal brain function. An experimental animal model for this phenomenon comprises environmental enrichment (EE) in rodents. EE causes profound changes in neuronal and signaling levels of excitation and plasticity throughout the entire central nervous system and the hippocampus is particularly affected. The mechanisms underlying these changes are not yet fully understood. As brain-derived neurotrophic factor (BDNF) supports hippocampal long-term potentiation (LTP), we explored whether it participates in the facilitation of synaptic plasticity and hippocampus-dependent learning that occurs following EE. In the absence of EE, LTP elicited by high-frequency stimulation was equivalent in wildtype mice and heterozygous BDNF(+/-) siblings. LTP elicited by theta-burst stimulation in BDNF(+/-) mice was less than in wildtypes. Long-term depression (LTD) was also impaired. EE for three weeks, beginning after weaning, improved hippocampal LTP in both wildtype and transgenic animals, with LTP in transgenics achieving levels seen in wildtypes in the absence of EE. Object recognition memory was evident in wildtypes 24 h and 7 days after initial object exposure. EE improved memory performance in wildtypes 24 h but not 7 days after initial exposure. BDNF(+/-) mice in the absence of EE showed impaired memory 7 days after initial object exposure that was restored by EE. Western blotting revealed increased levels of BDNF, but not proBDNF, among both EE cohorts. These data support that BDNF plays an intrinsic role in improvements of synaptic plasticity and cognition that occur in EE.

Genetic and epigenetic regulation of the brain-derived neurotrophic factor in the central nervous system

The BDNF is required for the development and proper function of the central nervous system, where it is involved in a variety of neural and molecular events relevant to cognition, learning, and memory processes. Although only a functional mature protein is synthesized, the human BDNF gene possesses an extensive structural complexity, including the presence of multiple promoters, splicing events, and 3´UTR poly-adenylation sites, resulting in an intricate transcriptional regulation and numerous messengers RNA. Recent data support specific cellular roles of these transcripts. Moreover, a central role of epigenetic modifications on the regulation of BDNF gene transcription is also emerging. The present essay aims to summarize the published information on the matter, emphasizing their possible implications in health and disease or in the treatment of different neurologic and psychiatric disorders.

Ectoparasitic sea lice (Lepeophtheirus salmonis) affect behavior and brain serotonergic activity in Atlantic salmon (Salmo salar L.): Perspectives on animal welfare

Scientific research and public debate on the welfare of animals in human custody is increasing at present. Fish are in this context mentioned with particular attention to the high numbers of individuals reared in aquaculture. Research on fish has also contributed to the understanding of individual variation in the ability to cope with stress and disease. One mediator of such variation is the brain serotonergic (5-hydroxytryptamine, 5-HT) system, which conveys physiological and behavioral responses to stress and sub-optimal rearing conditions. Here we study links between the 5-HT response, melanin-based skin pigmentation, and behavior in laboratory-reared Atlantic salmon (Salmo salar) experimentally infested with ectoparasitic sea lice (Lepeophtheirus salmonis). Lice numbers were more variable in less pigmented fish, while the neurochemical response to ectoparastic lice-increased levels of the main 5-HT catabolite 5-HIAA in the brain stem-did not differ between pigmentation groups. A strong depression of growth and locomotor activity was seen in all infested fish but less pigmented fish grew better than fish with more skin melanization regardless of infestation status. The observed combination of neurochemical and behavioral effects clearly suggest that animal welfare concerns can be added to the list of negative effects of ectoparasitic sea lice.

Neural plasticity and stress coping in teleost fishes

Physiological and behavioural responses to environmental change are individually variable traits, which manifest phenotypically and are subject to natural selection as correlated trait-clusters (coping styles, behavioural syndromes, or personality traits). Comparative research has revealed a range of neuroendocrine-behavioural associations which are conserved throughout the vertebrate subphylum. Regulatory mechanisms universally mediate a switch between proactive (e.g. active/aggressive) and reactive (e.g. conservation/withdrawal) behaviour in response to unpredictable and uncontrollable events. Thresholds for switching from active coping to behavioural inhibition are individually variable, and depend on experience and genetic factors. Such factors affect physiological stress responses as well as perception, learning, and memory. Here we review the role of an important contributor to neural processing, the set of biochemical, molecular, and structural processes collectively referred to as neural plasticity. We will concentrate on work in teleost fishes, while also elucidating conserved aspects. In fishes, environmental and physiological control of brain cell proliferation and neurogenesis has received recent attention. This work has revealed that the expression of genes involved in CNS plasticity is affected by heritable variation in stress coping style, and is also differentially affected by short- and long-term stress. Chronic stress experienced by subordinate fish in social hierarchies leads to a marked suppression of brain cell proliferation. Interestingly, typically routine dependent and inflexible behaviour in proactive individuals is also associated with low transcription of neurogenesis related genes. The potential for these findings to illuminate stress-related neurobiological disorders in other vertebrates is also discussed.

Fish welfare and genomics

There is a considerable public and scientific debate concerning welfare of fish in aquaculture. In this review, we will consider fish welfare as an integration of physiological, behavioral, and cognitive/emotional responses, all of which are essentially adaptative responses to stressful situations. An overview of fish welfare in this context suggests that understanding will rely on knowledge of all components of allostatic responses to stress and environmental perturbations. The development of genomic technologies provides new approaches to this task, exemplified by how genome-wide analysis of genetic structures and corresponding expression patterns can lead to the discovery of new aspects of adaptative responses. We will illustrate how the genomic approach may give rise to new biomarkers for fish welfare and also increase our understanding of the interaction between physiological, behavioral, and emotional responses. In a first part, we present data on expression of candidate genes selected a priori. This is a common avenue to develop molecular biomarkers capable of diagnosing a stress condition at its earliest onset, in order to allow quick corrective intervention in an aquaculture setting. However, most of these studies address isolated physiological functions and stress responses that may not be truly indicative of animal welfare, and there is only rudimentary understanding of genes related to possible cognitive and emotional responses in fish. We also present an overview on transcriptomic analysis related to the effect of aquaculture stressors, environmental changes (temperature, salinity, hypoxia), or concerning specific behavioral patterns. These studies illustrate the potential of genomic approaches to characterize the complexity of the molecular mechanisms which underlies not only physiological but also behavioral responses in relation to fish welfare. Thirdly, we address proteomic studies on biological responses to stressors such as salinity change and hypoxia. We will also consider proteomic studies developed in mammals in relation to anxiety and depressive status which may lead to new potential candidates in fish. Finally, in the conclusion, we will suggest new developments to facilitate an integrated view of fish welfare. This includes use of laser microdissection in the transcriptomic/proteomic studies, development of meta-analysis methods for extracting information from genomic data sets, and implementation of technological advances for high-throughput proteomic studies. Development of these new approaches should be as productive for our understanding of the biological processes underlying fish welfare as it has been for the progress of pathophysiological research.

BDNF Val66Met and cognition: all, none, or some? A meta-analysis of the genetic association

The Val66Met, G196A (rs6265) polymorphism in the brain-derived neurotrophic factor gene, BDNF, located at 11p13, has been associated with a wide range of cognitive functions. Yet, the pattern of results is complex and conflicting. In this study, we conducted a meta-analysis that included 23 publications containing 31 independent samples comprised of 7095 individuals. The phenotypes that were examined in this analysis covered a wide variety of cognitive functions and included indicators of general cognitive ability, memory, executive function, visual processing skills and cognitive fluency. The meta-analysis did not establish significant genetic associations between the Val66Met polymorphism and any of the phenotypes that were included.

The lighter side of BDNF

Brain-derived neurotrophic factor (BDNF) mediates energy metabolism and feeding behavior. As a neurotrophin, BDNF promotes neuronal differentiation, survival during early development, adult neurogenesis, and neural plasticity; thus, there is the potential that BDNF could modify circuits important to eating behavior and energy expenditure. The possibility that "faulty" circuits could be remodeled by BDNF is an exciting concept for new therapies for obesity and eating disorders. In the hypothalamus, BDNF and its receptor, tropomyosin-related kinase B (TrkB), are extensively expressed in areas associated with feeding and metabolism. Hypothalamic BDNF and TrkB appear to inhibit food intake and increase energy expenditure, leading to negative energy balance. In the hippocampus, the involvement of BDNF in neural plasticity and neurogenesis is important to learning and memory, but less is known about how BDNF participates in energy homeostasis. We review current research about BDNF in specific brain locations related to energy balance, environmental, and behavioral influences on BDNF expression and the possibility that BDNF may influence energy homeostasis via its role in neurogenesis and neural plasticity.