Phase advance of the light-dark cycle perturbs diurnal rhythms of brain-derived neurotrophic factor and neurotrophin-3 protein levels, which reduces synaptophysin-positive presynaptic terminals in the cortex of juvenile rats

Circadian rhythm of brain-derived neurotrophic factor in serum and plasma

The neurotrophic growth factor brain-derived neurotrophic factor (BDNF) plays a crucial role in various neurodegenerative and psychiatric diseases, such as Alzheimer's disease, schizophrenia and depression. BDNF has been proposed as a potential biomarker for diagnosis, prognosis and monitoring therapy. Understanding the factors influencing BDNF levels and whether they follow a circadian rhythm is essential for interpreting fluctuations in BDNF measurements. We aimed to investigate the circadian rhythm of BDNF by collecting multiple peripheral venous blood samples from young, healthy male participants at 12 different time points over 24 h. In addition, vital parameters, cortisol and insulin like growth factor 1 (IGF1) were measured to explore potential regulatory mechanisms, interfering variables and their correlations with BDNF concentration. The findings revealed that plasma BDNF did not exhibit any significant fluctuations over 24 h, suggesting the absence of a circadian rhythm. However, serum BDNF levels decreased during sleep. Furthermore, serum BDNF showed a positive correlation with heart rate but a negative correlation with IGF1. No significant correlation was observed between cortisol and BDNF or IGF1. Although plasma BDNF suggests steady-state conditions, the decline of serum BDNF during the nocturnal period could be attributed to physical inactivity and associated with reduced haemodynamic blood flow (heart rate reduction during sleep). The type of sample collection (peripheral venous cannula vs. blood sampling using a butterfly system) does not significantly affect the measured BDNF levels. The sample collection during the day did not significantly affect BDNF analysis, emphasizing the importance of considering activity levels rather than timing when designing standardized protocols for BDNF assessments.

Interactions between neurotrophins, mood, and physical activity under the conditions of sleep deprivation

Sleep deprivation (DS) is the forced elimination of sleep. While brain-derived neurotrophic factor (BDNF) has been extensively studied in the context of in mood changes following DS, the role of other neurotrophins remains elusive. This study explores the impact of DS on BDNF, glial cell line-derived neurotrophic factor (GDNF), neurotrophin-3 (NT3), and neurotrophin-4 (NT4) at mRNA and protein level, considering their potential links to mood disturbances. The study involved 81 participants subjected to polysomnography (PSG) and DS. Blood samples, mood assessments, and actigraphy data were collected twice, after PSG and DS. NT mRNA expression and serum protein concentrations of BDNF, GDNF, NT3, and NT4 were measured. Participants were divided into Responders and Non-Responders based on mood improvement after DS. DS reduced BDNF mRNA expression in all participants, with no change in serum BDNF protein. GDNF protein decreased in Non-Responders, while Responders exhibited reduced GDNF mRNA. NT3 protein increased in both groups, while NT3 mRNA decreased in Respondents. NT4 protein rose universally post-DS, but NT4 mRNA remained unchanged. Physical activity (PA) negatively correlated with mRNA expression of BDNF, GDNF, and NT3 post-DS. The study's short DS duration and exclusion of immature NT forms limit comprehensive insights. GDNF, together with NT3, might play an important role in mood response to DS. PA during DS seems to impair the mRNA expression of NTs in leukocytes. Future studies on the subject of sleep deprivation might consider investigating the relationship between BDNF and NT4 in the context of their apparent redundancy.

Knockdown of astrocytic Grin2a exacerbated sleep deprivation-induced cognitive impairments and elevation of amyloid-beta

Sleep disorders are associated with cognitive impairments, greater amyloid-β (Aβ) burden and increased risk of developing Alzheimer's disease, while the underlying mechanism is unclear. N-methyl-d-aspartate receptors (NMDARs), as vital modulators of cognition, are sensitive to sleep disturbance. Sleep deprivation (SD) could induce the alterations of neuronal NMDAR subunits expression, however the alterations of astrocytic NMDARs in SD have not been reported. Our previous study has demonstrated knockdown of astrocytic Grin2a (gene encoding NMDAR subunit GluN2A) could aggravate Aβ-induced cognitive impairments, but what role astrocytic GluN2A may play in SD is unknown. Here we focused on the changes and roles of hippocampal astrocytic GluN2A in SD. Our results showed SD increased the expression of astrocytic GluN2A. Specific knockdown of hippocampal astrocytic Grin2a aggravated SD-induced cognitive decline, elevated Aβ, and attenuated the SD-induced increase in autophagy flux. Our finding, for the first time, revealed a novel neuroprotective role for astrocytic GluN2A in SD, which may be helpful for developing new preventive and therapeutic targets to sleep disorders.

Influence of excessive daily sleeping and sleep quality on BDNF and NGF serum levels in adolescents

INTRODUCTION

The brain-derived neurotrophic factor (BDNF) and neural growth factor (NGF) are widely expressed in the brain and play an important role in neuroplasticity, neurogenesis, and increased neuronal connections. Previous studies have shown that reduced serum levels of these proteins are associated with disorders in human sleep.

OBJECTIVE

Current study evaluates the prevalence in adolescents of excessive daytime sleepiness (EDS) and sleep quality, and analyzes the influence of these factors on BDNF and NGF serum levels.

METHODS

A cross-section population-based study was conducted with data from a Brazilian birth cohort, with a sample of five hundred and thirteen 18-19-year-old adolescents. Sleep quality was assessed by the Pittsburgh Sleep Quality Index and EDS by Epworth Sleepiness Scale. Neurotrophins serum levels were measured by Luminex™ technology kits. Analysis consisted of marginal structural models which compared people who were exposed and not exposed to sleep quality and EDS.

RESULTS

Poor sleep quality and EDS were detected in 62.57% and 36.35% of the sample. Adolescents with poor sleep quality and EDS had -0.39 (p-value = 0.049) and -0.51 pg/ml in NGF (p-value = 0.009). Individuals with self-reported sleep disorder had lower serum levels of NGF (Coef. -0.41, p-value = 0.045).

CONCLUSION

High prevalence of EDS and low sleep quality in a population of adolescents were evidenced. Poor sleep quality and EDS were associated with lower NGF levels, whilst adolescents with self-reported sleep disorder had lower serum levels of NGF.

Concussive head injury exacerbates neuropathology of sleep deprivation: Superior neuroprotection by co-administration of TiO2-nanowired cerebrolysin, alpha-melanocyte-stimulating hormone, and mesenchymal stem cells

Sleep deprivation (SD) is common in military personnel engaged in combat operations leading to brain dysfunction. Military personnel during acute or chronic SD often prone to traumatic brain injury (TBI) indicating the possibility of further exacerbating brain pathology. Several lines of evidence suggest that in both TBI and SD alpha-melanocyte-stimulating hormone (α-MSH) and brain-derived neurotrophic factor (BDNF) levels decreases in plasma and brain. Thus, a possibility exists that exogenous supplement of α-MSH and/or BDNF induces neuroprotection in SD compounded with TBI. In addition, mesenchymal stem cells (MSCs) are very portent in inducing neuroprotection in TBI. We examined the effects of concussive head injury (CHI) in SD on brain pathology. Furthermore, possible neuroprotective effects of α-MSH, MSCs and neurotrophic factors treatment were explored in a rat model of SD and CHI. Rats subjected to 48h SD with CHI exhibited higher leakage of BBB to Evans blue and radioiodine compared to identical SD or CHI alone. Brain pathology was also exacerbated in SD with CHI group as compared to SD or CHI alone together with a significant reduction in α-MSH and BDNF levels in plasma and brain and enhanced level of tumor necrosis factor-alpha (TNF-α). Exogenous administration of α-MSH (250μg/kg) together with MSCs (1×10⁶) and cerebrolysin (a balanced composition of several neurotrophic factors and active peptide fragments) (5mL/kg) significantly induced neuroprotection in SD with CHI. Interestingly, TiO₂ nanowired delivery of α-MSH (100μg), MSCs, and cerebrolysin (2.5mL/kg) induced enhanced neuroprotection with higher levels of α-MSH and BDNF and decreased the TNF-α in SD with CHI. These observations are the first to show that TiO₂ nanowired administration of α-MSH, MSCs and cerebrolysin induces superior neuroprotection following SD in CHI, not reported earlier. The clinical significance of our findings in light of the current literature is discussed.

Journey of brain-derived neurotrophic factor: from intracellular trafficking to secretion

Brain-derived neurotrophic factor (BDNF) is known to control a wide variety of brain functions, ranging from memory formation to food intake. However, since the BDNF levels are extremely low in the nervous system, the dynamics in neurons from intracellular trafficking to secretion is absolutely complicated; the understanding is not fully promoted. We here review the findings of those critical mechanisms from intracellular trafficking to the secretion of BDNF. Furthermore, to solve this issue, technological advances for the detection, measurement, and imaging of this growth factor are essential. We believe that this review helps the study of these complex but critical mechanisms of BDNF.

Memory and the circadian system: Identifying candidate mechanisms by which local clocks in the brain may regulate synaptic plasticity

The circadian system is an endogenous biological network responsible for coordinating near-24-h cycles in behavior and physiology with daily timing cues from the external environment. In this review, we explore how the circadian system regulates memory formation, retention, and recall. Circadian rhythms in these memory processes may arise through several endogenous pathways, and recent work highlights the importance of genetic timekeepers found locally within tissues, called local clocks. We evaluate the circadian memory literature for evidence of local clock involvement in memory, identifying potential nodes for direct interactions between local clock components and mechanisms of synaptic plasticity. Our discussion illustrates how local clocks may pervasively modulate neuronal plastic capacity, a phenomenon that we designate here as circadian metaplasticity. We suggest that this function of local clocks supports the temporal optimization of memory processes, illuminating the potential for circadian therapeutic strategies in the prevention and treatment of memory impairment.

NTF3 Is a Novel Target Gene of the Transcription Factor POU3F2 and Is Required for Neuronal Differentiation

POU-homeodomain transcription factor POU3F2 is a critical transcription factor that participates in neuronal differentiation. However, little is known about its downstream mediators. Here genome-wide analyses of a human neuronal differentiation cell model, NT2D1, suggested neurotrophin-3 (NTF3), a key mediator of neuronal development during the early neurogenic period, as a putative regulatory target of POU3F2. Western blot, cDNA microarray, and real-time quantitative PCR analyses showed that POU3F2 and NTF3 were upregulated during neuronal differentiation. Next-generation-sequence-based POU3F2 chromatin immunoprecipitation-sequencing and genome-wide in silico prediction demonstrated that POU3F2 binds to the NTF3 promoter during neuronal differentiation. Furthermore, unidirectional deletion or mutation of the binding site of POU3F2 in the NTF3 promoter decreased promoter-driven luciferase activity, indicating that POU3F2 is a positive regulator of NTF3 promoter activity. While NTF3 knockdown resulted in decreased viability and differentiation of NT2D1 cells, and POU3F2 knockdown downregulated NTF3 expression, recombinant NTF3 significantly rescued viable neuronal cells from NTF3- or POU3F2-knockdown cell cultures. Moreover, immunostaining showed colocalization of POU3F2 and NTF3 in developing mouse neurons. Thus, our data suggest that NTF3 is a novel target gene of POU3F2 and that the POU3F2/NTF3 pathway plays a role in the process of neuronal differentiation.

Chronic Light Exposure in the Middle of the Night Disturbs the Circadian System and Emotional Regulation

In mammals, the circadian system is composed of a principal circadian oscillator located in the suprachiasmatic nucleus (SCN) and a number of subordinate oscillators in extra-SCN brain regions and peripheral tissues/organs. However, how the time-keeping functions of this multiple oscillator circuit are affected by aberrant lighting environments remains largely unknown. In the present study, we investigated the effects of chronic light exposure in the middle of the night on the circadian system by comparing the mice housed in a 12:4:4:4-h L:DLD condition with the controls in 12:12-h L:D condition. Daily rhythms in locomotor activity were analyzed and the expression patterns of protein products of clock genes Period1 and Period2 (PER1 and PER2) were examined in the SCN and extra-SCN brain regions, including the dorsal striatum, hippocampus, paraventricular nucleus (PVN), and basolateral amygdala (BLA). Following 2 weeks of housing in the L:DLD condition, animals showed disturbed daily rhythms in locomotor activity and lacked daily rhythms of PER1 and PER2 in the SCN. In the extra-SCN brain regions, the PER1 and PER2 rhythms were affected in a region-specific pattern, such that they were relatively undisturbed in the striatum and hippocampus, phase-shifted in the BLA, and abolished in the PVN. In addition, mice in the L:DLD condition showed increased anxiety-like behaviors and reduced brain-derived neurotropic factor messenger RNA expression in the hippocampus, amygdala, and medial prefrontal cortex, which are brain regions that are involved in emotional regulation. These results indicate that nighttime light exposure leads to circadian disturbances not only by abolishing the circadian rhythms in the SCN but also by inducing misalignment among brain oscillators and negatively affects emotional processing. These observations serve to identify risks associated with decisions regarding lifestyle in our modern society.

Sleep deprivation and gene expression

Sleep occurs in a wide range of animal species as a vital process for the maintenance of homeostasis, metabolic restoration, physiological regulation, and adaptive cognitive functions in the central nervous system. Long-term perturbations induced by the lack of sleep are mostly mediated by changes at the level of transcription and translation. This chapter reviews studies in humans, rodents, and flies to address the various ways by which sleep deprivation affects gene expression in the nervous system, with a focus on genes related to neuronal plasticity, brain function, and cognition. However, the effects of sleep deprivation on gene expression and the functional consequences of sleep loss are clearly not restricted to the cognitive domain but may include increased inflammation, expression of stress-related genes, general impairment of protein translation, metabolic imbalance, and thermal deregulation.

Circadian modulation of memory and plasticity gene products in a diurnal species

Cognition is modulated by circadian rhythms, in both nocturnal and diurnal species. Rhythms of clock gene expression occur in brain regions that are outside the master circadian oscillator of the suprachiasmatic nucleus and that control cognitive functions, perhaps by regulating the expression neural-plasticity genes such as brain derived neurotrophic factor (BDNF) and its high affinity receptor, tyrosine kinase B (TrkB). In the diurnal grass rat (Arvicanthis niloticus), the hippocampus shows rhythms of clock genes that are 180° out of phase with those of nocturnal rodents. Here, we examined the hypothesis that this reversal extends to the optimal phase for learning a hippocampal-dependent task and to the phase of hippocampal rhythms in BDNF/TrkB expression. We used the Morris water maze (MWM) to test for time of day differences in reference memory and monitored daily patterns of hippocampal BDNF/TrkB expression in grass rats. Grass rats showed superior long-term retention of the MWM, when the training and testing occurred during the day as compared to the night, at a time when nocturnal laboratory rats show superior retention; acquisition of the MWM was not affected by time of day. BDNF/TrkB expression was rhythmic in the hippocampus of grass rats, and the phase of the rhythms was reversed compared to that of nocturnal rodents. Our findings provide correlational evidence for the claim that the circadian regulation of cognition may involve rhythms of BDNF/TrkB expression in the hippocampus and that their phase may contribute to species differences in the optimal phase for learning.

Mouse models of mutations and variations in autism spectrum disorder-associated genes: mice expressing Caps2/Cadps2 copy number and alternative splicing variants

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by disturbances in interpersonal relationships and behavior. Although the prevalence of autism is high, effective treatments have not yet been identified. Recently, genome-wide association studies have identified many mutations or variations associated with ASD risk on many chromosome loci and genes. Identification of the biological roles of these mutations or variations is necessary to identify the mechanisms underlying ASD pathogenesis and to develop clinical treatments. At present, mice harboring genetic modifications of ASD-associated gene candidates are the best animal models to analyze hereditary factors involved in autism. In this report, the biological significance of ASD-associated genes is discussed by examining the phenotypes of mouse models with ASD-associated mutations or variations in mouse homologs, with a focus on mice harboring genetic modifications of the Caps2/Cadps2 (Ca²⁺-dependent activator protein for secretion 2) gene.

Developmental traumatic brain injury decreased brain derived neurotrophic factor expression late after injury

Pediatric traumatic brain injury (TBI) is a major cause of acquired cognitive dysfunction in children. Hippocampal Brain Derived Neurotrophic Factor (BDNF) is important for normal cognition. Little is known about the effects of TBI on BDNF levels in the developing hippocampus. We used controlled cortical impact (CCI) in the 17 day old rat pup to test the hypothesis that CCI would first increase rat hippocampal BDNF mRNA/protein levels relative to SHAM and Naïve rats by post injury day (PID) 2 and then decrease BDNF mRNA/protein by PID14. Relative to SHAM, CCI did not change BDNF mRNA/protein levels in the injured hippocampus in the first 2 days after injury but did decrease BDNF protein at PID14. Surprisingly, BDNF mRNA decreased at PID 1, 3, 7 and 14, and BDNF protein decreased at PID 2, in SHAM and CCI hippocampi relative to Naïve. In conclusion, TBI decreased BDNF protein in the injured rat pup hippocampus 14 days after injury. BDNF mRNA levels decreased in both CCI and SHAM hippocampi relative to Naïve, suggesting that certain aspects of the experimental paradigm (such as craniotomy, anesthesia, and/or maternal separation) may decrease the expression of BDNF in the developing hippocampus. While BDNF is important for normal cognition, no inferences can be made regarding the cognitive impact of any of these factors. Such findings, however, suggest that meticulous attention to the experimental paradigm, and possible inclusion of a Naïve group, is warranted in studies of BDNF expression in the developing brain after TBI.