Involvement of brain-derived neurotrophic factor in late-life depression

Potentiation of antidepressant effects: NPY1R agonist and ketamine synergy enhances TrkB signaling and neurogenesis in the ventral hippocampus

BACKGROUND

Major Depressive Disorder (MDD) poses a significant challenge to global health, with current treatments often limited by efficacy and onset delays. This study explores the synergistic antidepressant-like effects of an NPY1R agonist and Ketamine, targeting their neurobiological interactions within the ventral hippocampus.

RESEARCH DESIGN AND METHODS

Utilizing a preclinical model, this study administered Neuropeptide Y receptor 1 (NPY1R) agonist and Ketamine, both separately and in combination, through intracerebroventricular (icv) and intranasal (i.n.) routes. The Forced Swimming Test (FST) was employed to assess antidepressant-like activity, while in situ Proximity Ligation Assay and immunohistochemistry were used to examine NPY1R/TrkB heteroreceptor complexes and BDNF expression in the ventral dentate gyrus (DG), along with neurogenesis markers.

RESULTS

The combined treatment significantly reduced immobility in the FST, indicative of enhanced antidepressant-like effects, correlated with increased formation of NPY1R/TrkB complex and brain-derived neurotrophic factor (BDNF) expression in the ventral DG. These molecular alterations were associated with increased neurogenesis.

CONCLUSIONS

The coadministration of an NPY1R agonist and Ketamine in a rodent model demonstrated potentiated antidepressant responses through synergistic neurobiological pathways, including TrkB signaling and hippocampal neurogenesis. This indicates a novel therapeutic strategy for MDD, warranting further clinical investigation to fully understand its implications.

Targeting BDNF with acupuncture: A novel integrated strategy for diabetes and depression comorbidity

Diabetes and depression are common comorbid conditions that impose a substantial health burden. Acupuncture may effectively improve symptoms in patients with diabetes and depression, but the underlying mechanism remains unclear. Brain-derived neurotrophic factor (BDNF) may play a vital role in the effects of acupuncture on diabetes and depression comorbidity. This review summarizes the potential role of BDNF in acupuncture for diabetes and depression comorbidity. BDNF appears to exert its effects via the BDNF-TrkB-ERK-CREB signaling pathway. BDNF levels are reduced in diabetes and depression, and acupuncture may increase BDNF expression, improving symptoms and glycemic control. High-quality research is needed to validate the efficacy of acupuncture for diabetes and depression comorbidity. Randomized controlled trials and mechanistic studies should investigate the BDNF pathway and other potential mechanisms. Improved understanding of the links between diabetes, depression and acupuncture may enable targeted and individualized patient care. Earlier diagnosis and management of diabetes and depression comorbidity should also be a priority.

Antidepressant effects of 70% ethanolic extract of Lonicerae japonicae flos and it contained chlorogenic acid via upregulation of BDNF-TrkB pathway in the hippocampus of mice

Lonicera japonica flos (LJF) is a common clinical herb with outstanding medicinal and nutritional value. This study aimed to evaluate the antidepressant effects of LJF's active extract and compound chlorogenic acid (CGA) around brain-derived neurotrophic factor(BDNF)-tropomyosin receptor kinase B (TrkB) pathway. The results showed that LJF's extracts and CGA had significant antidepressant effects, and the antidepressant effects of different extracts of LJF were highly positively correlated with the content of CGA (forced swimming test, r = 0.998; tail suspension test, r = 0.934). Moreover, LJF-70% ethanolic extract and CGA improved chronic unpredictable mild stress-induced depressive behavior, upregulated protein expression levels of BDNF and p-TrkB in the hippocampus, restored the damage of hippocampal neurons, and protected liver from damage. In summary, this study demonstrated for the first time that LJF-70% ethanolic extract was the active extract of LJF in antidepressant and CGA was its active compound, and the antidepressant mechanisms mainly involved the upregulation of BDNF-TrkB signaling pathway in the hippocampus of mice.

Cannabidiol Modulates Emotional Function and Brain-Derived Neurotrophic Factor Expression in Middle-Aged Female Rats Exposed to Social Isolation

Aging is associated with changes in cognitive and emotional function. Cannabidiol (CBD) has been reported to attenuate stress and anxiety in human and animal studies. In this study, we aimed to assess the therapeutic potential of CBD among middle-aged female rats exposed to social isolation (SI) and the potential involvement of brain-derived neurotrophic factor (BDNF) in these effects. Thirteen-month-old female rats were group-housed (GH) or exposed to social isolation (SI) and treated with vehicle or CBD (10 mg/kg). CBD restored the SI-induced immobility in the forced swim test and the SI-induced decrease in the expression of BDNF protein levels in the nucleus accumbens (NAc). CBD also increased the time that rats spent in the center in an open field, improved spatial training, and increased BDNF expression in the medial prefrontal cortex (mPFC) and basolateral amygdala (BLA). BDNF expression was found to be correlated with an antidepressant (in the NAc) and an anxiolytic (in the mPFC, BLA, NAc) phenotype, and with learning improvement in the PFC. Together, our results suggest that CBD may serve as a beneficial agent for wellbeing in old age and may help with age-related cognitive decline.

Oxidative Stress in Depression: The Link with the Stress Response, Neuroinflammation, Serotonin, Neurogenesis and Synaptic Plasticity

Depression is a prevalent, complex, and highly debilitating disease. The full comprehension of this disease is still a global challenge. Indeed, relapse, recurrency, and therapeutic resistance are serious challenges in the fight against depression. Nevertheless, abnormal functioning of the stress response, inflammatory processes, neurotransmission, neurogenesis, and synaptic plasticity are known to underlie the pathophysiology of this mental disorder. The role of oxidative stress in disease and, particularly, in depression is widely recognized, being important for both its onset and development. Indeed, excessive generation of reactive oxygen species and lack of efficient antioxidant response trigger processes such as inflammation, neurodegeneration, and neuronal death. Keeping in mind the importance of a detailed study about cellular and molecular mechanisms that are present in depression, this review focuses on the link between oxidative stress and the stress response, neuroinflammation, serotonergic pathways, neurogenesis, and synaptic plasticity's imbalances present in depression. The study of these mechanisms is important to lead to a new era of treatment and knowledge about this highly complex disease.

Nanowired Delivery of Cerebrolysin Together with Antibodies to Amyloid Beta Peptide, Phosphorylated Tau, and Tumor Necrosis Factor Alpha Induces Superior Neuroprotection in Alzheimer's Disease Brain Pathology Exacerbated by Sleep Deprivation

Sleep deprivation induces amyloid beta peptide and phosphorylated tau deposits in the brain and cerebrospinal fluid together with altered serotonin metabolism. Thus, it is likely that sleep deprivation is one of the predisposing factors in precipitating Alzheimer's disease (AD) brain pathology. Our previous studies indicate significant brain pathology following sleep deprivation or AD. Keeping these views in consideration in this review, nanodelivery of monoclonal antibodies to amyloid beta peptide (AβP), phosphorylated tau (p-tau), and tumor necrosis factor alpha (TNF-α) in sleep deprivation-induced AD is discussed based on our own investigations. Our results suggest that nanowired delivery of monoclonal antibodies to AβP with p-tau and TNF-α induces superior neuroprotection in AD caused by sleep deprivation, not reported earlier.

Dissecting early life stress-induced adolescent depression through epigenomic approach

Early life stress (ELS), such as abuse and neglect during childhood, can lead to psychiatric disorders in later life. Previous studies have suggested that ELS can cause profound changes in gene expression through epigenetic mechanisms, which can lead to psychiatric disorders in adulthood; however, studies on epigenetic modifications associated with ELS and psychiatric disorders in adolescents are limited. Moreover, how these epigenetic modifications can lead to psychiatric disorders in adolescents is not fully understood. Commonly, DNA methylation, histone modification, and the regulation of noncoding RNAs have been attributed to the reprogramming of epigenetic profiling associated with ELS. Although only a few studies have attempted to examine epigenetic modifications in adolescents with ELS, existing evidence suggests that there are commonalities and differences in epigenetic profiling between adolescents and adults. In addition, epigenetic modifications are sex-dependent and are influenced by the type of ELS. In this review, we have critically evaluated the current evidence on epigenetic modifications in adolescents with ELS, particularly DNA methylation and the expression of microRNAs in both preclinical models and humans. We have also clarified the impact of ELS on psychiatric disorders in adolescents to predict the development of neuropsychiatric disorders and to prevent and recover these disorders through personalized medicine.

BDNF receptor TrkB as the mediator of the antidepressant drug action

Brain-derived neurotrophic factor (BDNF) signaling through its receptor TrkB has for a long time been recognized as a critical mediator of the antidepressant drug action, but BDNF signaling has been considered to be activated indirectly through the action of typical and rapid-acting antidepressants through monoamine transporters and glutamate NMDA receptors, respectively. However, recent findings demonstrate that both typical and the fast-acting antidepressants directly bind to TrkB and thereby allosterically potentiate BDNF signaling, suggesting that TrkB is the direct target for antidepressant drugs. Increased TrkB signaling particularly in the parvalbumin-expressing interneurons orchestrates iPlasticity, a state of juvenile-like enhanced plasticity in the adult brain. iPlasticity sensitizes neuronal networks to environmental influences, enabling rewiring of networks miswired by adverse experiences. These findings have dramatically changed the position of TrkB in the antidepressant effects and they propose a new end-to-end model of the antidepressant drug action. This model emphasizes the enabling role of antidepressant treatment and the active participation of the patient in the process of recovery from mood disorders.

Neurotrophin-targeted therapeutics: A gateway to cognition and more?

Neurotrophins, such as brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), are small proteins expressed in the brain and peripheral tissues, which regulate several key aspects of neuronal function, including neurogenesis, synaptic plasticity and neuroprotection, but also programmed cell death. This broad range of effects is a result of a complex downstream signaling pathway, with differential spatial and temporal activation patterns further diversifying their physiological effects. Alterations in neurotrophin levels, or known polymorphisms in neurotrophin genes, have been linked to a variety of disorders, including depression and Alzheimer's disease (AD). Historically, their therapeutic potential in these disorders has been hampered by the lack of suitable tool molecules for clinical studies. However, recent advancements have led to the development of new therapeutic candidates, which are now in clinical testing.

Participation of the Serotonergic System and Brain-Derived Neurotrophic Factor in the Antidepressant-like Effect of Flavonoids

Depressive disorders are among the most disabling diseases experienced around the world, and their incidence has significantly increased over the last few decades due to multiple environmental, social, and biological factors. The search for new pharmacological alternatives to treat depression is a global priority. In preclinical research, molecules obtained from plants, such as flavonoids, have shown promising antidepressant-like properties through several mechanisms of action that have not been fully elucidated, including crossing of the blood brain barrier (BBB). This review will focus on discussing the main findings related to the participation of the serotonergic system and brain-derived neurotrophic factor (BDNF) on the antidepressant-like effect of some flavonoids reported by behavioral, neurochemical, and molecular studies. In this sense, evidence shows that depressive individuals have low levels of serotonin and BDNF, while flavonoids can reverse it. Finally, the elucidation of the mechanism used by flavonoids to modulate serotonin and BDNF will contribute to our understanding of the neurobiological bases underlying the antidepressant-like effects produced by these natural compounds.

Coadministration of tianeptine alters behavioral parameters and levels of neurotrophins in a chronic model of Maple Syrup Urine disease

Maple Syrup Urine Disease (MSUD) is caused by the deficiency in the activity of the branched-chain α-ketoacid dehydrogenase complex (BCKDC), resulting in the accumulation of the branched-chain amino acids (BCAA) leucine, isoleucine, and valine, and their respective branched-chain α-keto acids. Patients with MSUD are at high risk of developing chronic neuropsychiatric disorders; however, the pathophysiology of brain damage in these patients remains unclear. We hypothesize that MSUD can cause depressive symptoms in patients. To test our hypothesis, Wistar rats were submitted to the BCAA and tianeptine (antidepressant) administration for 21 days, starting seven days postnatal. Depression-like symptoms were assessed by testing for anhedonia and forced swimming after treatments. After the last test, the brain structures were dissected for the evaluation of neutrophins. We demonstrate that chronic BCAA administration induced depressive-like behavior, increased BDNF levels, and decreased NGF levels, suggesting a relationship between BCAA toxicity and brain damage, as observed in patients with MSUD. However, the administration of tianeptine was effective in preventing behavioral changes and restoring neurotrophins levels.

Aluminium oxide nanoparticles compromise spatial memory performance and proBDNF-mediated neuronal function in the hippocampus of rats

Background

Alumina nanoparticles (aluminaNPs), which are widely used in a range of daily and medical fields, have been shown to penetrate blood-brain barrier, and distribute and accumulate in different brain areas. Although oral treatment of aluminaNPs induces hippocampus-dependent learning and memory impairments, characteristic effects and exact mechanisms have not been fully elucidated. Here, male adult rats received a single bilateral infusion of aluminaNPs (10 or 20 µg/kg of body weight) into the hippocampal region, and their behavioral performance and neural function were assessed.

Results

The results indicated that the intra-hippocampus infusions at both doses of aluminaNPs did not cause spatial learning inability but memory deficit in the water maze task. This impairment was attributed to the effects of aluminaNP on memory consolidation phase through activation of proBDNF/RhoA pathway. Inhibition of the increased proBDNF by hippocampal infusions of p75^NTR antagonist could effectively rescue the memory impairment. Incubation of aluminaNPs exaggerated GluN2B-dependent LTD induction with no effects on LTD expression in hippocampal slices. AluminaNP could also depress the amplitude of NMDA-GluN2B EPSCs. Meanwhile, increased reactive oxygen specie production was reduced by blocking proBDNF-p75^NTR pathway in the hippocampal homogenates. Furthermore, the neuronal correlate of memory behavior was drastically weakened in the aluminaNP-infused groups. The dysfunction of synaptic and neuronal could be obviously mitigated by blocking proBDNF receptor p75^NTR, implying the involvement of proBDNF signaling in aluminaNP-impaired memory process.

Conclusions

Taken together, our findings provide the first evidence that the accumulation of aluminaNPs in the hippocampus exaggeratedly activates proBDNF signaling, which leads to neural and memory impairments.

Pathomechanisms of Vascular Depression in Older Adults

Depression in older individuals is a common complex mood disorder with high comorbidity of both psychiatric and physical diseases, associated with high disability, cognitive decline, and increased mortality The factors predicting the risk of late-life depression (LLD) are incompletely understood. The reciprocal relationship of depressive disorder and age- and disease-related processes has generated pathogenic hypotheses and provided various treatment options. The heterogeneity of depression complicates research into the underlying pathogenic cascade, and factors involved in LLD considerably differ from those involved in early life depression. Evidence suggests that a variety of vascular mechanisms, in particular cerebral small vessel disease, generalized microvascular, and endothelial dysfunction, as well as metabolic risk factors, including diabetes, and inflammation that may induce subcortical white and gray matter lesions by compromising fronto-limbic and other important neuronal networks, may contribute to the development of LLD. The "vascular depression" hypothesis postulates that cerebrovascular disease or vascular risk factors can predispose, precipitate, and perpetuate geriatric depression syndromes, based on their comorbidity with cerebrovascular lesions and the frequent development of depression after stroke. Vascular burden is associated with cognitive deficits and a specific form of LLD, vascular depression, which is marked by decreased white matter integrity, executive dysfunction, functional disability, and poorer response to antidepressive therapy than major depressive disorder without vascular risk factors. Other pathogenic factors of LLD, such as neurodegeneration or neuroimmune regulatory dysmechanisms, are briefly discussed. Treatment planning should consider a modest response of LLD to antidepressants, while vascular and metabolic factors may provide promising targets for its successful prevention and treatment. However, their effectiveness needs further investigation, and intervention studies are needed to assess which interventions are appropriate and effective in clinical practice.

Brain-Derived Neurotrophic Factor Signaling in Depression and Antidepressant Action

Neurotrophic factors, particularly BDNF (brain-derived neurotrophic factor), have been associated with depression and antidepressant drug action. A variety of preclinical and clinical studies have implicated impaired BDNF signaling through its receptor TrkB (neurotrophic receptor tyrosine kinase 2) in the pathophysiology of mood disorders, but many of the initial findings have not been fully supported by more recent meta-analyses, and more both basic and clinical research is needed. In contrast, increased expression and signaling of BDNF has been repeatedly implicated in the mechanisms of both typical and rapid-acting antidepressant drugs, and recent findings have started to elucidate the mechanisms through which antidepressants regulate BDNF signaling. BDNF is a critical regulator of various types of neuronal plasticities in the brain, and plasticity has increasingly been connected with antidepressant action. Although some equivocal data exist, the hypothesis of a connection between neurotrophic factors and neuronal plasticity with mood disorders and antidepressant action has recently been further strengthened by converging evidence from a variety of more recent data reviewed here.

Neural substrates for late-life depression: A selective review of structural neuroimaging studies

Recent neuroimaging studies have characterized the pathophysiology of late-life depression (LLD) as a dysfunction of the brain networks involved in the regulation of emotion, motivational behavior, cognitive control, executive function, and self-referential thinking. In this article, we reviewed LLD-associated structural neuroimaging markers such as white matter hyperintensity (WMH), white matter integrity measured by diffusion tensor imaging, cortical and subcortical volumes, and cortical thickness, which may provide a structural basis for brain network dysfunction in LLD. LLD was associated with greater severity or volumes of deep, periventricular, or overall WMH and with decreased white matter integrity in the brain regions belonging to the fronto-striatal-limbic circuits and reduced white matter tract integrity which connects these circuits, such as the cingulum, corpus callosum, or uncinate fasciculus. Decreased volumes or cortical thickness in the prefrontal cortex, orbitofrontal cortex, anterior and posterior cingulate cortex, several temporal and parietal regions, hippocampus, amygdala, striatum, thalamus, and the insula were associated with LLD. These structural neuroimaging findings were also associated with cognitive dysfunction, which is a prominent clinical feature in LLD. Several structural neuroimaging markers including the WMH burden, white matter integrity, and cortical and subcortical volumes predicted antidepressant response in LLD. These structural neuroimaging findings support the hypothesis that disruption of the brain networks involved in emotion regulation and cognitive processing by impaired structural connectivity is strongly associated with the pathophysiology of LLD.

Influence of BDNF Genetic Polymorphisms in the Pathophysiology of Aging-related Diseases

For the first time in history, most of the population has a life expectancy equal or greater than 60 years. By the year 2050, it is expected that the world population in that age range will reach 2000 million, an increase of 900 million with respect to 2015, which poses new challenges for health systems. In this way, it is relevant to analyze the most common diseases associated with the aging process, namely Alzheimer´s disease, Parkinson Disease and Type II Diabetes, some of which may have a common genetic component that can be detected before manifesting, in order to delay their progress. Genetic inheritance and epigenetics are factors that could be linked in the development of these pathologies. Some researchers indicate that the BDNF gene is a common factor of these diseases, and apparently some of its polymorphisms favor the progression of them. In this regard, alterations in the level of BDNF expression and secretion, due to polymorphisms, could be linked to the development and/or progression of neurodegenerative and metabolic disorders. In this review we will deepen on the different polymorphisms in the BDNF gene and their possible association with age-related pathologies, to open the possibilities of potential therapeutic targets.

Long-term effects of stress early in life on microRNA-30a and its network: Preventive effects of lurasidone and potential implications for depression vulnerability

Exposure to early life stress can interfere with neurodevelopmental trajectories to increase the vulnerability for psychiatric disorders later in life. With this respect, epigenetic mechanisms play a key role for the long-lasting changes in brain functions that may elicit and sustain psychopathologic outcomes.

Here, we investigated DNA methylation changes as possible epigenetic mechanism mediating the effect of prenatal stress (PNS), an experimental paradigm associated with behavioral and molecular alterations relevant for psychiatric disorders. We identified 138 genes as being differentially methylated in the prefrontal cortex (PFC) and in the hippocampus (HIP) of male and female adult rats exposed to PNS. Among these genes, miR-30a and Neurod1 emerged as potential players for the negative outcomes associated with PNS exposure. Indeed, in addition to showing consistent methylation differences in both brain regions and in both sexes, and interacting with each other, they are both involved in Axon guidance and Neurotrophin signaling, which are important to neurodevelopmental disorders. We also found a significant reduction in the expression of a panel of genes (CAMK2A, c-JUN, LIMK1, MAP2K1, MAP2K2, PIK3CA and PLCG1) that belong to these two biological pathways and are also validated targets of miR-30a, pointing to a down-regulation of these pathways as a consequence of PNS exposure. Interestingly, we also found that miR-30a levels were significantly upregulated in depressed patients exposed to childhood trauma, as compared to control individuals. Importantly, we also found that a sub-chronic treatment with the atypical antipsychotic drug, lurasidone, during adolescence was able to prevent the up-regulation of miR-30a and normalized the expression of its target genes in response to PNS exposure.

Our results demonstrate that miR-30a undergoes epigenetic changes following early life stress exposure and suggest that this miRNA could play a key role in producing broad and long-lasting alterations in neuroplasticity-related pathways, contributing to the etiology of psychiatric disorders.

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MiR-30a and Neurod1 undergo epigenetic changes following PNS exposure.

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MiR-30 and Neurod1 are involved in Axon guidance and Neurotrophin signaling, two important pathways for neurodevelopment.

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We found lower expression levels of a panel of genes targeted by miR-30a.

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MiR-30a was significantly up-regulated in depressed patients exposed to childhood trauma.

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A chronic treatment with lurasidone during adolescence prevented the up-regulation of miR-30a following PNS exposure.

Low-molecular mimetics of nerve growth factor and brain-derived neurotrophic factor: Design and pharmacological properties

To overcome the limitations of the clinical use of neurotrophins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), scientists have been trying to create their low-molecular-weight mimetics having improved pharmacokinetic properties and lacking side effects of full-sized proteins since the 90s of the last century. The efforts of various research groups have led to the production of peptide and nonpeptide mimetics, being agonists or modulators of the corresponding Trk or p75 receptors that reproduced the therapeutic effects of full-sized proteins. This review discusses different strategies and approaches to the design of such compounds. The relationship between the structure of the mimetics obtained and their action mechanisms and pharmacological properties are analyzed. Special attention is paid to the dipeptide mimetics of individual NGF and BDNF loops having different patterns of activation of Trk receptors signal transduction pathways, phosphoinositide 3-kinase/protein kinase B and mitogen-activated protein kinase/extracellular signal-regulated kinase, which allowed to evaluate the contribution of each pathway to different pharmacological effects. In conclusion, data on therapeutically promising compounds being at different stages of preclinical and clinical studies are summarized.

Therapeutic Effects of Spirulina platensis Against Adolescent Stress-Induced Oxidative Stress, Brain-Derived Neurotrophic Factor Alterations and Morphological Remodeling in the Amygdala of Adult Female Rats

Objective

The amygdala structural and functional abnormalities have been implicated in numerous neuropsychiatric and neurodevelopmental disorders. Given the important role of the amygdala in stress responses and the susceptibility of the females to adolescent stress, the present study investigated the beneficial effects of Spirulina platensis microalgae (SP) as a neuroprotective supplement against adolescent stress-induced oxidative stress, brain-derived neurotrophic factor (BDNF) alterations, molecular and morphological remodeling in the basolateral amygdala (BLA) of adult female rats.

Methods

During the adolescent period (PNDs 30–40) rats were subjected to restraint stress (2 h/day for 10 days). Then, the animals were subjected to 15 days treatment (PNDs 41–55) with SP (200 mg/kg/day) followed by biochemical (BDNF and stress oxidative markers), molecular (BDNF and its receptor tropomyosin receptor kinase B [TrkB] mRNA expression), and morphological (dendritic length and spines) assessments in the BLA.

Results

The study revealed that adolescent stress decreased BDNF levels and reduced apical dendritic length and branch points of pyramidal neurons in the BLA. In addition, chronic stress significantly increased oxidative stress parameters and decreased BDNF and TrkB mRNA expression in the BLA. Treatment with SP alleviated both biochemical, molecular, and neuroanatomical deficits that induced by adolescent stress.

Conclusion

Our findings provide important evidence that SP as a non-pharmacological intervention during adolescent period can protect against chronic stress-induced neuroanatomical biochemical, and molecular deficits in adulthood, and thus, reduce stress-related disorders.

Depressive disorders in the elderly and dementia: An update

The relationship between depressive disorders in the elderly and dementia, particularly Alzheimer’s disease (AD), is highly complex. While the nature of this relationship is still a matter of debate, differential diagnosis and treatment remain a great clinical challenge. We review recent findings on the conundrum of depressive disorders in the elderly and AD. There is a biological continuum between depressive disorders in the elderly – or at least a subgroup of them – and AD. While elderly subjects with depression and patients with AD exhibit higher circulating levels of pro-inflammatory molecules and lower BDNF than matched controls, CSF levels of Aβ42 can discriminate AD from depressive disorders in the elderly. The role of antidepressant treatment as a strategy to minimize the risk of AD remains to be established.

The Low Molecular Weight Brain-derived Neurotrophic Factor Mimetics with Antidepressant-like Activity

The search for new highly-effective, fast-acting antidepressant drugs is extremely relevant. Brain derived neurotrophic factor (BDNF) and signaling through its tropomyosin-related tyrosine kinase B (TrkB) receptor, represents one of the most promising therapeutic targets for treating depression. BDNF is a key regulator of neuroplasticity in the hippocampus and the prefrontal cortex, the dysfunction of which is considered to be the main pathophysiological hallmark of this disorder. BDNF itself has no favorable drug-like properties due to poor pharmacokinetics and possible adverse effects. The design of small, proteolytically stable BDNF mimetics might provide a useful approach for the development of therapeutic agents. Two small molecule BDNF mimetics with antidepressant-like activity have been reported, 7,8-dihydroxyflavone and the dimeric dipeptide mimetic of BDNF loop 4, GSB-106. The article reflects on the current literature on the role of BDNF as a promising therapeutic target in the treatment of depression and on the current advances in the development of small molecules on the base of this neurotrophin as potential antidepressants.

Brain-Derived Neurotrophic Factor and Its Potential Therapeutic Role in Stroke Comorbidities

With the rise in the aging global population, stroke comorbidities have become a serious health threat and a tremendous economic burden on human society. Current therapeutic strategies mainly focus on protecting neurons from cytotoxic damage at the acute phase upon stroke onset, which not only is a difficult way to ameliorate stroke symptoms but also presents a challenge for the patients to receive effective treatment in time. The brain-derived neurotrophic factor (BDNF) is the most abundant neurotrophin in the adult brain, which possesses a remarkable capability to repair brain damage. Recent promising preclinical outcomes have made BDNF a popular late-stage target in the development of novel stroke treatments. In this review, we aim to summarize the latest progress in the understanding of the cellular/molecular mechanisms underlying stroke pathogenesis, current strategies and difficulties in drug development, the mechanism of BDNF action in poststroke neurorehabilitation and neuroplasticity, and recent updates in novel therapeutic methods.

Association of brain-derived neurotrophic factor levels and depressive symptoms in young adults with acne vulgaris

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is one of the proteins that contributes to the survival, growth, maintenance of neurons, and plays important roles in the pathophysiology of depression. It has been reported that depression is closely associated with the pathogenesis of acne vulgaris disease. But, there is no report of serum BDNF levels in patients with acne vulgaris. The study aimed to determine the potential association between BDNF and depressive symptoms in young adults with acne vulgaris.

METHODS

In this analytical cross-sectional study, the serum BDNF levels were measured in peripheral blood samples of 20 consecutive acne vulgaris patients with depression and 98 consecutive acne vulgaris patients without depression and also compared it with a 59 healthy control group by using a ELISA. The potential correlation between the BDNF levels, interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-α), and depressive symptoms such as nine-item patient health questionnaire (PHQ-9) and Athens insomnia scale (AIS) were evaluated with multivariate logistic regression analysis.

RESULTS

Our results showed that levels of BDNF expression were lower in consecutive acne vulgaris patients when compared with healthy control (P < 0.05). There was a negative correlation between levels of BDNF and the PHQ-9 scores (r = - 0.486, P < 0.001). Furthermore, acne vulgaris patients with depression showed lower serum BDNF levels (10.96 ± 2.12 ng/ml) compared with acne vulgaris patients without depression (13.85 ± 2.47 ng/ml), as well as with healthy control (14.35 ± 2.70 ng/mg; both P < 0.05). No difference was found in serum BDNF levels between healthy control and acne vulgaris patients without depressive symptoms (z = 0.964, P > 0.05). Similarly, the overall area under the curve of receiver operating characteristic was 0.82, indicating the highly conserving of serum BDNF levels as an biomarker for screening of depression in young adults with acne vulgaris (72% sensitivity and 85% specificity).

CONCLUSION

Serum BDNF levels were decreased and negatively associated with depressive symptoms in young Chinese adults with acne vulgaris.

Dysregulation of the SNARE-binding protein Munc18-1 impairs BDNF secretion and synaptic neurotransmission: a novel interventional target to protect the aging brain

Brain-derived neurotrophic factor (BDNF) has a central role in maintaining and strengthening neuronal connections and to stimulate neurogenesis in the adult brain. Decreased levels of BDNF in the aging brain are thought to usher cognitive impairment. BDNF is stored in dense core vesicles and released through exocytosis from the neurites. The exact mechanism for the regulation of BDNF secretion is not well understood. Munc18-1 (STXBP1) was found to be essential for the exocytosis of synaptic vesicles, but its involvement in BDNF secretion is not known. Interestingly, neurons lacking munc18-1 undergo severe degeneration in knock-out mice. Here, we report the effects of BDNF treatment on the presynaptic terminal using munc18-1-deficient neurons. Reduced expression of munc18-1 in heterozygous (+/-) neurons diminishes synaptic transmitter release, as tested here on individual synaptic connections with FM1-43 fluorescence imaging. Transduction of cultured neurons with BDNF markedly increased BDNF secretion in wild-type but was less effective in munc18-1 +/- cells. In turn, BDNF enhanced synaptic functions and restored the severe synaptic dysfunction induced by munc18-1 deficiency. The role of munc18-1 in the synaptic effect of BDNF is highlighted by the finding that BDNF upregulated the expression of munc18-1 in neurons, consistent with enhanced synaptic functions. Accordingly, this is the first evidence showing the functional effect of BDNF in munc18-1 deficient synapses and about the direct role of munc18-1 in the regulation of BDNF secretion. We propose a molecular model of BDNF secretion and discuss its potential as therapeutic target to prevent cognitive decline in the elderly.

Psychobiological factors of resilience and depression in late life

In contrast to traditional perspectives of resilience as a stable, trait-like characteristic, resilience is now recognized as a multidimentional, dynamic capacity influenced by life-long interactions between internal and environmental resources. We review psychosocial and neurobiological factors associated with resilience to late-life depression (LLD). Recent research has identified both psychosocial characteristics associated with elevated LLD risk (e.g., insecure attachment, neuroticism) and psychosocial processes that may be useful intervention targets (e.g., self-efficacy, sense of purpose, coping behaviors, social support). Psychobiological factors include a variety of endocrine, genetic, inflammatory, metabolic, neural, and cardiovascular processes that bidirectionally interact to affect risk for LLD onset and course of illness. Several resilience-enhancing intervention modalities show promise for the prevention and treatment of LLD, including cognitive/psychological or mind-body (positive psychology; psychotherapy; heart rate variability biofeedback; meditation), movement-based (aerobic exercise; yoga; tai chi), and biological approaches (pharmacotherapy, electroconvulsive therapy). Additional research is needed to further elucidate psychosocial and biological factors that affect risk and course of LLD. In addition, research to identify psychobiological factors predicting differential treatment response to various interventions will be essential to the development of more individualized and effective approaches to the prevention and treatment of LLD.

Glycyrrhizic Acid Alleviates 6-Hydroxydopamine and Corticosterone-Induced Neurotoxicity in SH-SY5Y Cells Through Modulating Autophagy

Recent researches have shown that autophagy is associated with the pathogenesis of neurodegenerative disorders, but there is no paper to investigate the effects of autophagy modulation on Parkinson's disease depression (PDD). In addition, glycyrrhizic acid (GA), the major bioactive ingredient of Radix glycyrrhizae, can induce autophagy and ease rotenone-induced Parkinson's disease (PD). However, there is also no paper to study the action and molecular mechanisms of GA on PDD. In this research, we built the injury model of SH-SY5Y cells through 6-hydroxydopamine (6-OHDA) and corticosterone (CORT). Then, our results showed that GA markedly increased the viability and decreased the apoptosis in SH-SY5Y cells after pre-treating with 6-OHDA and CORT. Moreover, GA notably decreased the expressions of α-Syn and p-S1292-LRRK2 proteins, and significantly increased the levels of CREB and BDNF proteins. Previous papers have suggested that CORT contributed to dopaminergic neurodegeneration via the glucocorticoid (GC)/glucocorticoid receptor (GR) interaction, and our results showed that GA reduced GC level and hypothalamic-pituitary-adrenal (HPA) activity in SH-SY5Y cells by regulating GR signaling pathway. Furthermore, mechanism investigations also showed that GA had the ability to up-regulate the conversion of LC3B II/I and the expression of Beclin-1, and induce autophagy in SH-SY5Y cells, which were reversed by the autophagy inhibitor 3-methyladenine (3-MA). Collectively, these findings proved that GA exerted efficient activity against neurotoxicity in SH-SY5Y cells induced by 6-OHDA and CORT via activation of autophagy, which should be developed as an efficient candidate for treating PDD in the future.

Resveratrol and Depression in Animal Models: A Systematic Review of the Biological Mechanisms

Depression is currently treated by pharmacotherapies that can elicit debilitating side effects for patients. Novel treatment options with limited side effects are currently being researched. Resveratrol is a polyphenol and phytoalexin found in the skins of grapes, red wine, Japanese knotweed, and peanuts. It has been studied extensively for its antioxidant and anti-inflammatory properties. Resveratrol has also gained attention for its neuroprotective properties. The aim of the review was to examine the mechanisms by which resveratrol reduces depressive behaviors in animal models. In total, 22 studies met the established criteria for final review. Behavioral aspects of depression were investigated using validated measures such as the forced swimming test, tail suspension test, sucrose preference test, and open field test. While many physical measures were taken, three main biological mechanisms were explored: Regulation of the hypothalamic⁻pituitary⁻adrenal axis; decreased inflammation; and increased Brain-Derived Neurotrophic Factor and neurogenesis. Based on these findings, resveratrol may be deemed an effective treatment for depression in animal models at doses between 10⁻80 mg/kg/day, although higher doses had the most significant effects. Future studies should examine the effects of resveratrol on depression in humans to determine the eligibility of resveratrol as a natural antidepressant with less severe side effects.

The Serum BDNF Level Offers Minimum Predictive Value for Motor Function Recovery After Stroke

Brain-derived neurotrophic factor (BDNF) plays an important role in neuroplasticity and neurogenesis following ischemic and non-ischemic brain injury. The predictive value of BDNF for short-term outcome after stroke is controversial. The objective of this study was to investigate the relationship among serum BDNF level, fractional anisotropy (FA), and functional outcome during post-acute stroke rehabilitation. Serum BDNF levels were measured on admission to an acute inpatient rehabilitation hospital. The primary functional outcome was functional independence measure (FIM) motor subscore at discharge. The secondary outcome measures were FIM total score at discharge, FIM motor subscore on admission, length of stay in the hospital, and discharge destination. We investigated the relationship among the level of serum BDNF and FA as well as functional outcome measures. Three hundred forty-eight consecutive stroke subjects were included in the analysis. Serum BDNF levels on admission were statistically but not clinically correlated with FIM motor subscore at discharge (r = 0.173, P = 0.001) and FIM total score at discharge (r = 0.155, P = 0.004). Receiver operating characteristic (ROC) analysis of BDNF as a predictor for FIM motor subscore improvement showed low accuracy of prediction with an area under the curve (AUC) of 0.581 (P = 0.026). Serum BDNF significantly correlated with FA in the high FIM motor group (n = 10, r = 0.609, P = 0.031) but not in the low FIM motor group (n = 11, r = - 0.132, P = 0.349). The serum BDNF level alone offers minimum predictive value for recovery of motor function during post-acute rehabilitation. Our findings suggest that serum BDNF level may be correlated with FA.

Peripheral Blood Brain-Derived Neurotrophic Factor as a Biomarker of Alzheimer's Disease: Are There Methodological Biases?

Mounting evidence that alterations in brain-derived neurotrophic factor (BDNF) levels and signaling may be involved in the etiopathogenesis of Alzheimer's disease (AD) has suggested that its blood levels could be used as a biomarker of the disease. However, higher, lower, or unchanged circulating BDNF levels have all been described in AD patients compared to healthy controls. Although the reasons for such different findings are unclear, methodological issues are likely to be involved. The heterogeneity of participant recruitment criteria and the lack of control of variables that influence circulating BDNF levels regardless of dementia (depressive symptoms, medications, lifestyle, lack of overlap between serum and plasma, and experimental aspects) are likely to bias result and prevent study comparability. The present work reviews a broad panel of factors, whose close control could help reduce the inconsistency of study findings, and offers practical advice on their management. Research directed at elucidating the weight of each of these variables and at standardizing analytical methodologies is urgently needed.

Antidepressant effects of magnolol in a mouse model of depression induced by chronic corticosterone injection

Evidence showed that the stress hormone corticosterone (CORT) injection resulted in dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis implicated in major depressive disorder. Magnolol, main constituent identified in the barks of Magnolia officinalis, exerted antidepressant effects in a rat model of depression induced by chronic unpredictable mild stress in previous studies. However, its antidepressant-like effects and mechanisms have never been studied in depression model induced by CORT administration in rodents. This study aimed to investigate the antidepressant-like effects and possible mechanisms of magnolol in CORT-treated mice by utilizing a combination of behavioral and biochemical analysis. The depressive model was developed by subcutaneous injection of CORT for 21 days at a dose of 20 mg/kg. CORT administration formed depressive-like behaviors in mice, as indicated by increased immobility time in the forced swim test (FST) and tail suspension test (TST), as well as decreased sucrose intake in sucrose preference test (SPT). Moreover, we also found that CORT levels in serum were significantly increased, along with the decrease of brain-derived neurotrophic factor (BDNF) mRNA, BDNF protein, 5-hydroxytryptamine (5-HT) and norepinephrine (NE) levels in the hippocampus. Treatment with magnolol alleviated depressive-like behaviors, reduced the levels of CORT, and improved the levels of BDNF protein, 5-HT, and NE compared with those in CORT-treated mice. These findings indicated that magnolol possessed antidepressant effects in mice exposed to CORT, which might be partially related to modulate HPA axis, up-regulate BDNF expression and increase neurotransmitters levels in the hippocampus.

Brain derived neurotrophic factor (BDNF) and suicidal behavior: A review of studies from Asian countries

The biological basis of suicide and suicidal behavior is actively researched. Recently, the role of Brain Derived Neurotropic Factor (BDNF) in suicidal behavior has gained attention and significant results are observed. In this review, we aimed to focus on the studies from Asian countries that have explored the role of BDNF and suicidal behavior. The review highlights the findings from these studies and discusses the possible avenues that should be explored in future studies from Asian countries to understand more on suicidal behavior and possible prevention.

Interplay of Brain-Derived Neurotrophic Factor and Cytokines in Schizophrenia

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family and plays an important role in neuroplasticity, differentiation and survival of neurons, as well as their function. Neuroinflammation has been explored in the pathophysiology of many mental disorders, such as schizophrenia. Cytokines representing different types of immune responses have an impact on neurogenesis and BDNF expression. Cross-regulation of BDNF and cytokines is accomplished through several signalling pathways. Also, typical and atypical antipsychotic drugs variously modulate the expression of BDNF and serum levels of cytokines, which can possibly be used in evaluation of therapy effectiveness. Comorbidity of metabolic syndrome and atopic diseases has been considered in the context of BDNF and cytokines interplay in schizophrenia.

Antidepressant-Like Effects of Acupuncture-Insights From DNA Methylation and Histone Modifications of Brain-Derived Neurotrophic Factor

Sensitive and stable biomarkers that facilitate depression detection and monitor the antidepressant efficiency are currently unavailable. Thus, the objective is to investigate the potential of DNA methylation and histone modifications of brain-derived neurotrophic factor (BDNF) in monitoring severity and antidepressive effects of acupuncture. The depression rat model was imitated by social isolation and chronic unpredicted mild stress (CUMS). The expression of serum BDNF was detected by enzyme-linked immunosorbent assay (ELISA), the hippocampal BDNF, acetylation levels in histone H3 lysine 9 (acH3K9), and HDAC2 by Western blot, the hippocampal mRNA of BDNF by RT-polymerase chain reaction (PCR). The DNA methylation patterns of the promoter I of BDNF was detected by MS-PCR. We investigated that the expression of BDNF in serum and hippocampus were significantly downregulated compared with controls. The same trend was found in mRNA of BDNF. Notably, acupuncture reversed the downregulation of BDNF in serum and hippocampus and mRNA of BDNF compared with model group. Acupuncture reversed the CUMS-induced downregulation of hippocampal acH3K9. On the contrary, the CUMS-induced upregulation of hippocampal HDAC2 in model group was significantly reversed by acupuncture. Collectively, the antidepressant effect of acupuncture might be mediated by regulating the DNA methylation and histone modifications of BDNF, which may represent novel biomaker for detection of depression and monitoring severity and antidepressive effects.

Dihydromyricetin exerts a rapid antidepressant-like effect in association with enhancement of BDNF expression and inhibition of neuroinflammation

RATIONALE

Major depressive disorder (MDD) is a highly prevalent illness that affects large populations across the world, and increasing evidence suggests that neuroinflammation and levels of brain-derived neurotrophic factor (BDNF) are closely related to depression. Dihydromyricetin (DHM) is a kind of flavonoid natural product that has been reported to display multiple pharmacological effects, including anti-inflammatory and anti-oxidative properties, and these may contribute to ameliorate MDD.

OBJECTIVE

This study investigated the effect of DHM on depression-related phenotypes in various experimental animal models.

METHODS

The antidepressant-like effect of DHM was validated via depression-related behavioral tests in naïve male C57BL/6 mice, as well as in the acute lipopolysaccharide-induced mouse model of depression. The chronic unpredicted mild stress (CUMS) mouse model of depression was also used to assess the rapid antidepressant-like effect of DHM by tail suspension test (TST), forced swimming test (FST), locomotor activity, and sucrose preference test (SPT). The expression of BDNF and inflammatory factors were determined through Western blotting and enzyme-linked immunosorbent assay, respectively.

RESULTS

DHM reduced immobility time in the TST and FST both in mice and the acute LPS-induced mouse model of depression. Seven days of DHM treatment ameliorated depression-related behaviors induced by CUMS, whereas similar treatment with the typical antidepressant venlafaxine did not. DHM activated the ERK1/2-CREB pathway and increased glycogen synthase kinase-3 beta (GSK-3β) phosphorylation at ser-9, with upregulation of BDNF expression, in both hippocampal tissues and cultured hippocampal cells.

CONCLUSION

The present data indicate that DHM exerts a more rapid antidepressant-like effect than does a typical antidepressant, in association with enhancement of BDNF expression and inhibition of neuroinflammation.

Cortical Atrophy is Associated with Accelerated Cognitive Decline in Mild Cognitive Impairment with Subsyndromal Depression

OBJECTIVES

To investigate the association between cognitive decline and cortical atrophy in individuals with mild cognitive impairment (MCI) and chronic subsyndromal symptoms of depression (SSD) over a 4-year period.

DESIGN

Prospective cohort study.

SETTING

Multicenter, clinic-based.

PARTICIPANTS

Within the Alzheimer's Disease Neuroimaging Initiative repository, the Neuropsychiatric Inventory was used to identify individuals with MCI and stable endorsement (SSD group N = 32) or no endorsement (non-SSD group N = 69) of depressive symptoms across time points.

MEASUREMENTS

Repeated measures of cognitive outcomes, cortical atrophy, and their associations were evaluated with mixed effects models adjusting for age, education, sex, and APOE genotype.

RESULTS

The SSD group demonstrated accelerated decline on measures of global cognition (Alzheimer Disease Assessment Scale; df = 421, t = 2.242, p = 0.025), memory (Wechsler Memory Scale-Revised Logical Memory II; df = 244, t = -2.525, p = 0.011), information processing speed (Trail Making Test Parts A [df = 421, t = 2.376, p = 0.018] and B [df = 421, t = 2.533, p = 0.012]), and semantic fluency (Category Fluency; df = 424, t = -2.418, p = 0.016), as well as accelerated frontal lobe (df = 341, t = -2.648, p = 0.008) and anterior cingulate (df = 341, t = -3.786, p < 0.001) atrophy. No group differences were observed for rate of decline on measures of attention, learning, and confrontation naming or for rate of atrophy in any other regions. Accelerated frontal lobe and anterior cingulate atrophy was associated with cognitive decline on measures of global cognition, information processing speed, and semantic fluency (all p < 0.05), but not memory.

CONCLUSIONS

Individuals with chronic SSD may represent an MCI subgroup that is highly vulnerable to accelerated cognitive decline, an effect that may be governed by frontal lobe and anterior cingulate atrophy.

Brain-derived neurotrophic factor plasma levels are increased in older women after an acute episode of low back pain

BACKGROUND

Low back pain (LBP) is a growing public health problem in old age, and it is associated with disabling pain and depressive disorders. We compared brain-derived neurotrophic factor (BDNF) plasma levels, a key neurotrophin in pain modulation, between older women after an acute episode of LBP and age-matched pain-free controls, and investigated potential differences in BDNF levels between controls and LBP subgroups based on pain severity, presence of depressive symptoms and use of analgesic and antidepressant drugs.

METHODS

A total of 221 participants (154 with LBP and 67 pain-free) were studied. A comprehensive assessment of sociodemographic and clinical variables was conducted including pain severity (11-point NRS), depressive symptoms (GDS-15), age, body mass index, physical activity and total number of comorbidities and medications in use.

RESULTS

BDNF levels in LBP group were significantly higher than controls (7515.9±3021.2; Md=7116.0 vs 6331.8±3364.0; Md=5897.5pg/mL, P=0.005). LBP subgroups exhibited higher BDNF levels than controls, regardless of pain severity, presence of depressive symptoms and use of analgesic drugs. BDNF levels were significantly higher in LBP subgroup without use of antidepressant drugs compared to both controls and LBP subgroup with use of antidepressant drugs.

DISCUSSION

This study provides evidence that older women with acute low back pain exhibit higher BDNF plasma levels compared to pain-free controls. Subgroup comparisons suggest that use of pain-relief drugs may influence BDNF levels. The study results offer a novel target for research on mechanisms of back pain in older adults.

Ocular Nerve Growth Factor Administration Modulates Brain-derived Neurotrophic Factor Signaling in Prefrontal Cortex of Healthy and Diabetic Rats

AIMS

Nerve growth factor (NGF) eyedrops (ed-NGF) activate brain neurons, stimulate growth factors, including brain-derived neurotrophic factor (BDNF), and exert neuroprotection in the forebrain of streptozotocin-induced diabetic rats (STZ rats). In this study, the effects of ed-NGF on BDNF signaling in the prefrontal cortex (PFC) were explored in healthy and STZ-diabetic rats, in which cortical neuronal and axonal loss, and altered circulating BDNF associated with depressive phenotype are also described.

METHODS

STZ and healthy (CTR) adult rats received ed-NGF twice a day for 2 weeks. Depressive phenotype was identified by force swimming test (FST). Proteins extracted from PFC were processed for ELISA and Western blot analyses to measure the expression of BDNF, proBDNF, and their receptors and intracellular signals.

RESULTS

ed-NGF treatment modulates BDNF pathway in PFC and normalizes the STZ-induced BDNF alterations by stimulating TRK-mediated survival mechanism. A decreased latency in FST was also found in STZ rats, while no change was observed comparing CTR + NGF and STZ + NGF with CTR.

CONCLUSION

The present data confirm the capacity of ed-NGF treatment to affect brain neurons and lead to brain damage recovery by activating protective and remodeling pathways triggered by BDNF. We suggest that the ed-NGF-induced changes in BDNF signaling might influence the manifestation of depressive phenotype in diabetic rats.

Decreased Brain-Derived Neurotrophic Factor in Older Adults with Bipolar Disorder

OBJECTIVES

Decreased levels of brain derived neurotrophic factor (BDNF) have been found in adult patients with bipolar disorder (BD) compared with a comparison group, yet there are no data specifically examining this in geriatric patients. The objective of this study was to examine whether euthymic late-life BD patients have lower BDNF levels than healthy comparators.

DESIGN

Cross-sectional study.

SETTING

Clinics at the University of Pittsburgh and the Centre for Addiction and Mental Health (Toronto).

PARTICIPANTS

Older patients with BD (age ≥50 years, N = 118) and similarly aged healthy comparators (N = 76). There were both BD type I (N = 91) and type II (N = 27) patients.

MEASUREMENTS

Serum BDNF levels were assessed in BD patients and healthy comparators.

RESULTS

We found lower levels of BDNF in patients with BD than in healthy comparators (9.0 ± 6.2 versus 12.3 ± 8.9 pg/µg, t(192) = -3.01, p = 0.002), which remained even after controlling for age, sex, lithium use, and site (F(1,176) = 4.32, p = 0.039). This decrease was found specifically in patients with BD type I (8.0 ± 5.5 versus 12.3 ± 8.9 pg/µg, t(165) = 3.7, Bonferroni p < 0.001), but not type II (12.0 ± 7.5 versus 12.3 ± 8.9 pg/µg, t(101) = 0.14, Bonferroni p = 1.0).

CONCLUSIONS

Older patients with BD have lower serum levels of BDNF compared with similarly aged comparators. These effects appear to be specific to patients with BD type I. Future studies are needed to investigate the impact of reduced BDNF levels on cognition, mood, and other aspects of BD throughout the life course.

Microglial dysfunction connects depression and Alzheimer's disease

Alzheimer's disease (AD) and major depressive disorder (MDD) are highly prevalent neuropsychiatric conditions with intriguing epidemiological overlaps. Depressed patients are at increased risk of developing late-onset AD, and around one in four AD patients are co-diagnosed with MDD. Microglia are the main cellular effectors of innate immunity in the brain, and their activation is central to neuroinflammation - a ubiquitous process in brain pathology, thought to be a causal factor of both AD and MDD. Microglia serve several physiological functions, including roles in synaptic plasticity and neurogenesis, which may be disrupted in neuroinflammation. Following early work on the 'sickness behavior' of humans and other animals, microglia-derived inflammatory cytokines have been shown to produce depressive-like symptoms when administered exogenously or released in response to infection. MDD patients consistently show increased circulating levels of pro-inflammatory cytokines, and anti-inflammatory drugs show promise for treating depression. Activated microglia are abundant in the AD brain, and concentrate around senile plaques, hallmark lesions composed of aggregated amyloid-β peptide (Aβ). The Aβ burden in affected brains is regulated largely by microglial clearance, and the complex activation state of microglia may be crucial for AD progression. Intriguingly, recent reports have linked soluble Aβ oligomers, toxins that accumulate in AD brains and are thought to cause memory impairment, to increased brain cytokine production and depressive-like behavior in mice. Here, we review recent findings supporting the inflammatory hypotheses of AD and MDD, focusing on microglia as a common player and therapeutic target linking these devastating disorders.

Maternal separation prior to neonatal hypoxia-ischemia: Impact on emotional aspects of behavior and markers of synaptic plasticity in hippocampus

Exposure to early-life stress is associated with long-term alterations in brain and behavior, and may aggravate the outcome of neurological insults. This study aimed at investigating the possible interaction between maternal separation, a model of early stress, and subsequent neonatal hypoxia-ischemia on emotional behavior and markers of synaptic plasticity in hippocampus. Therefore, rat pups (N=60) were maternally separated for a prolonged (MS 180min) or a brief (MS 15min) period during the first six postnatal days, while a control group was left undisturbed. Hypoxia-ischemia was applied to a subgroup of each rearing condition on postnatal day 7. Emotional behavior was examined at three months of age and included assessments of anxiety (elevated plus maze), depression-like behavior (forced swimming) and spontaneous exploration (open field). Synaptic plasticity was evaluated based on BDNF and synaptophysin expression in CA3 and dentate gyrus hippocampal regions. We found that neonatal hypoxia-ischemia caused increased levels of anxiety, depression-like behavior and locomotor activity (ambulation). Higher anxiety levels were also seen in maternally separated rats (MS180min) compared to non-maternally separated rats, but prolonged maternal separation prior to HI did not potentiate the HI-associated effect. No differences among the three rearing conditions were found regarding depression-like behavior or ambulation. Immunohistochemical evaluation of synaptophysin revealed that both prolonged maternal separation (MS180min) and neonatal hypoxia-ischemia significantly reduced its expression in the CA3 and dentate gyrus. Decreases in synaptophysin expression in these areas were not exacerbated in rats that were maternally separated for a prolonged period prior to HI. Regarding BDNF expression, we found a significant decrease in immunoreactivity only in the hypoxic-ischemic rats that were subjected to the prolonged maternal separation paradigm. The above findings suggest that early-life stress prior to neonatal hypoxia-ischemia leads to significant alterations in synaptic plasticity of the dorsal hippocampus during adulthood, but does not exacerbate HI-related changes in emotional behavior.

Anti-apoptotic and anti-glycative effects of asiatic acid in the brain of D-galactose treated mice

Protection of asiatic acid (AA) in mice brain against D-galactose (DG) induced aging was examined. AA at 5, 10 or 20 mg kg(-1) per day was supplied to DG treated mice for 8 weeks. AA intake at 10 or 20 mg kg(-1) per day increased its deposit in brain. DG treatment increased Bax, cleaved caspase-3 protein expression and decreased Bcl-2 expression. AA intake at 10 and 20 mg kg(-1) per day declined Bax, cleaved caspase-3 expression, and retained Bcl-2 expression. DG treatment decreased brain glutathione content and glutathione peroxidase activity; increased brain reactive oxygen species and protein carbonyl levels, and enhanced NAPDH oxidase expression. AA intake at test doses reversed these changes. DG treatment up-regulated the expression of advanced glycation end product (AGE), carboxymethyllysine, receptor of AGE (RAGE), mitogen-activated protein kinases and CD11b as well as increasing the interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha release in the brain. AA intake at 5, 10 and 20 mg kg(-1) per day lowered AGE and carboxymethyllysine expression, and at 10 and 20 mg kg(-1) per day reduced RAGE production. AA intake dose-dependently suppressed p-p38 expression and lowered IL-6 and TNF-alpha levels, and at 10 and 20 mg kg(-1) per day down-regulated p-JNK and CD11b expression. DG treatment declined brain-derived neurotropic factor (BDNF) expression and raised glial fibrillary acidic protein (GFAP) expression. AA intake at 20 mg kg(-1) per day retained BDNF expression and at 10 and 20 mg kg(-1) per day reduced GFAP expression. These findings indicated that the supplement of asiatic acid might be beneficial to the prevention or alleviation of brain aging.

Gestational stress induces depressive-like and anxiety-like phenotypes through epigenetic regulation of BDNF expression in offspring hippocampus

Exposure to stressful life events during pregnancy exerts profound effects on neurodevelopment and increases the risk for several neurodevelopmental disorders including major depression. The mechanisms underlying the consequences of gestational stress are complex and remain to be elucidated. This study investigated the effects of gestational stress on depressive-like behavior and epigenetic modifications in young adult offspring. Gestational stress was induced by a combination of restraint and 24-hour light disturbance to pregnant dams throughout gestation. Depressive-like and anxiety-like behaviors of young adult offspring were examined. The expression and promoter methylation of brain derived neurotrophic factor (BDNF) were measured using RT-qPCR, Western blot, methylated DNA immunoprecipitation (MeDIP) and chromatin immunoprecipitation (ChIP). In addition, the expressions of histone deacetylases (HDACs) and acetylated histone H3 lysine 14 (AcH3K14) were also analyzed. Our results show that offspring from gestational stress dams exhibited depressive-like and anxiety-like behaviors. Biochemically, stress-offspring showed decreased expression of BDNF, increased expression of DNMT1, HDAC1, and HDAC2, and decreased expression of AcH3K14 in the hippocampus as compared to non-stress offspring. Data from MeDIP and ChIP assays revealed an increased methylation as well as decreased binding of AcH3K14 on specific BDNF promoters. Pearson analyses indicated that epigenetic changes induced by gestational stress were correlated with depressive-like and anxiety-like behaviors. These data suggest that gestational stress may be a suitable model for understanding the behavioral and molecular epigenetic changes observed in patients with depression.

Depressive symptoms and cognitive decline: A longitudinal analysis of potentially modifiable risk factors in community dwelling older adults

BACKGROUND

Depressive symptoms have been associated with increased risk of cognitive decline in later life. There are no interventions proven to reduce risk of cognitive decline in older adults with depression, and it is unclear how these effects are mediated. We aim to determine what mediates the relationship between depressive symptoms and cognitive decline in later life.

METHODS

Seven thousand six hundred and sixty six community dwelling older adults (age ≥ 50) from the English Longitudinal study of Ageing (ELSA) underwent clinical assessment. Inflammation was assessed with C Reactive Protein and depressive symptoms were assessed with the 8-item version of the Center for Epidemiologic Studies (CESD) scale.

RESULTS

Five thousand, five hundred and ninety (73.5%) had a follow-up cognitive assessment after a median of 47 months. Depressive symptoms were independently associated with cognitive decline (B=0.09, p<0.001). Low physical activity, inflammation, metabolic syndrome and vascular risk factors were associated with elevated depressive symptoms. Low physical activity (z=2.16, p=0.03) and inflammation (z=2.3, p=0.02) mediated the relationship between depressive symptoms and cognitive decline while hypertension, diabetes and smoking also contributed.

LIMITATIONS

This is an observational study with a limited duration of follow up. Not all variables related to cognitive decline were accounted for in this analysis.

CONCLUSIONS

The relationship between depressive symptoms and cognitive decline in later life appears to be mediated by low physical activity, increased inflammation and vascular risk factors that may be amenable to modification.

Relevance of Post-Stroke Circulating BDNF Levels as a Prognostic Biomarker of Stroke Outcome. Impact of rt-PA Treatment

The recombinant form of tissue plasminogen activator (rt-PA) is the only curative treatment for ischemic stroke. Recently, t-PA has been linked to the metabolism of brain-derived neurotrophic factor (BDNF), a major neurotrophin involved in post-stroke neuroplasticity. Thus, the objective of our study was to investigate the impact of rt-PA treatment on post-stroke circulating BDNF levels in humans and in animals. Serum BDNF levels and t-PA/plasmin activity were measured at hospital admission and at up to 90 days in stroke patients receiving (n = 24) or not (n = 14) rt-PA perfusion. We investigated the relationships between serum BDNF with concurrent t-PA/plasmin activity, neurological outcomes and cardiovascular scores at admission. In parallel, serum BDNF levels and t-PA/plasmin activity were assessed before and after (1, 4 and 24h) the induction of ischemic stroke in rats. Our study revealed higher serum BDNF levels and better neurological outcome in rt-PA-treated than non-treated patients. However, serum BDNF levels did not predict stroke outcome when the whole cohort of stroke patients was analyzed. By contrast, serum BDNF levels when measured at admission and at day 90 correlated with cardiovascular scores, and those at day 1 correlated with serum t-PA/plasmin activity in the whole cohort of patients whereas no association could be found in the rt-PA-treated group. In rats devoid of cardiovascular risk, no difference in post-stroke serum BDNF levels was detected between rt-PA- and vehicle-treated animals and no correlation was found between serum BDNF levels and t-PA/plasmin activity. Overall, the data suggest that serum BDNF levels may not be useful as a prognostic biomarker of stroke outcome and that endothelial dysfunction could be a confounding factor when serum BDNF levels after stroke are used to reflect of brain BDNF levels.

Sleep deprivation induces differential morphological changes in the hippocampus and prefrontal cortex in young and old rats

Sleep is a fundamental state necessary for maintenance of physical and neurological homeostasis throughout life. Several studies regarding the functions of sleep have been focused on effects of sleep deprivation on synaptic plasticity at a molecular and electrophysiological level, and only a few studies have studied sleep function from a structural perspective. Moreover, during normal aging, sleep architecture displays some changes that could affect normal development in the elderly. In this study, using a Golgi-Cox staining followed by Sholl analysis, we evaluate the effects of 24 h of total sleep deprivation on neuronal morphology of pyramidal neurons from Layer III of the prefrontal cortex (PFC) and the dorsal hippocampal CA1 region from male Wistar rats at two different ages (3 and 22 months). We found no differences in total dendritic length and branching length in both analyzed regions after sleep deprivation. Spine density was reduced in the CA1 of young-adults, and interestingly, sleep deprivation increased spine density in PFC of aged animals. Taken together, our results show that 24 h of total sleep deprivation have different effects on synaptic plasticity and could play a beneficial role in cognition during aging.