Psychosocial stress on neuroinflammation and cognitive dysfunctions in Alzheimer's disease: the emerging role for microglia?

Interplay between microglia and environmental risk factors in Alzheimer's disease

Alzheimer's disease, among the most common neurodegenerative disorders, is characterized by progressive cognitive impairment. At present, the Alzheimer's disease main risk remains genetic risks, but major environmental factors are increasingly shown to impact Alzheimer's disease development and progression. Microglia, the most important brain immune cells, play a central role in Alzheimer's disease pathogenesis and are considered environmental and lifestyle "sensors." Factors like environmental pollution and modern lifestyles (e.g., chronic stress, poor dietary habits, sleep, and circadian rhythm disorders) can cause neuroinflammatory responses that lead to cognitive impairment via microglial functioning and phenotypic regulation. However, the specific mechanisms underlying interactions among these factors and microglia in Alzheimer's disease are unclear. Herein, we: discuss the biological effects of air pollution, chronic stress, gut microbiota, sleep patterns, physical exercise, cigarette smoking, and caffeine consumption on microglia; consider how unhealthy lifestyle factors influence individual susceptibility to Alzheimer's disease; and present the neuroprotective effects of a healthy lifestyle. Toward intervening and controlling these environmental risk factors at an early Alzheimer's disease stage, understanding the role of microglia in Alzheimer's disease development, and targeting strategies to target microglia, could be essential to future Alzheimer's disease treatments.

Association between hippocampal microglia, AD and LATE-NC, and cognitive decline in older adults

INTRODUCTION

This study investigates the relationship between microglia inflammation in the hippocampus, brain pathologies, and cognitive decline.

METHODS

Participants underwent annual clinical evaluations and agreed to brain donation. Neuropathologic evaluations quantified microglial burden in the hippocampus, amyloid beta (Aβ), tau tangles, and limbic age-related transactive response DNA-binding protein 43 (TDP-43) encephalopathy neuropathologic changes (LATE-NC), and other common brain pathologies. Mixed-effect and linear regression models examined the association of microglia with a decline in global and domain-specific cognitive measures, and separately with brain pathologies. Path analyses estimated direct and indirect effects of microglia on global cognition.

RESULT

Hippocampal microglia were associated with a faster decline in global cognition, specifically in episodic memory, semantic memory, and perceptual speed. Tau tangles and LATE-NC were independently associated with microglia. Other pathologies, including Aβ, were not related. Regional hippocampal burden of tau tangles and TDP-43 accounted for half of the association of microglia with cognitive decline.

DISCUSSION

Microglia inflammation in the hippocampus contributes to cognitive decline. Tau tangles and LATE-NC partially mediate this association.

Neuroinflammation of Microglial Regulation in Alzheimer's Disease: Therapeutic Approaches

Alzheimer's disease (AD) is a complex degenerative disease of the central nervous system that is clinically characterized by a progressive decline in memory and cognitive function. The pathogenesis of AD is intricate and not yet fully understood. Neuroinflammation, particularly microglial activation-mediated neuroinflammation, is believed to play a crucial role in increasing the risk, triggering the onset, and hastening the progression of AD. Modulating microglial activation and regulating microglial energy metabolic disorder are seen as promising strategies to intervene in AD. The application of anti-inflammatory drugs and the targeting of microglia for the prevention and treatment of AD has emerged as a new area of research interest. This article provides a comprehensive review of the role of neuroinflammation of microglial regulation in the development of AD, exploring the connection between microglial energy metabolic disorder, neuroinflammation, and AD development. Additionally, the advancements in anti-inflammatory and microglia-regulating therapies for AD are discussed.

The regulatory role of BDNF in neuroimmune axis function and neuroinflammation induced by chronic stress: A new therapeutic strategies for neurodegenerative disorders

Neurodegenerative disorders account for a high proportion of neurological diseases that significantly threaten public health worldwide. Various factors are involved in the pathophysiology of such diseases which can lead to neurodegeneration and neural damage. Furthermore, neuroinflammation is a well-known factor in predisposing factors of neurological and especially neurodegenerative disorders which can be strongly suppressed by "anti-inflammatory" actions of brain-derived neurotrophic factor (BDNF). Stress has has also been identified as a risk factor in developing neurodegenerative disorders potentially leading to increased neuroinflammation in the brain and progressive loss in neuronal structures and impaired functions in the CNS. Recently, more studies have increasingly been focused on the role of neuroimmune system in regulating the neurobiology of stress. Emerging evidence indicate that exposure to chronic stress might alter the susceptibility to neurodegeneration via influencing the microglia function. Microglia is considered as the first responding group of cells in suppressing neuroinflammation, leading to an increased inflammatory cytokine signaling that promote the synaptic plasticity deficiencies, impairment in neurogenesis, and development of neurodegenerative disorders. In this review we discuss how exposure to chronic stress might alter the neuroimmune response potentially leading to progress of neurodegenerative disorders. We also emphasize on the role of BDNF in regulating the neuroimmune axis function and microglia modulation in neurodegenerative disorders.

Essential oil from Ligusticum chuanxiong Hort. Alleviates lipopolysaccharide-induced neuroinflammation: Integrating network pharmacology and molecular mechanism evaluation

ETHNOPHARMACOLOGICAL RELEVANCE

Chuanxiong, the rhizome of Ligusticum chuanxiong Hort., is an ancient herbal medicine that has gained extensive popularity in alleviating migraines with satisfying therapeutic effects in China. As the major bioactive component of Chuanxiong, the essential oil also exerts a marked impact on the treatment of migraine. It is widely recognized that neuroinflammation contributes to migraine. However, it remains unknown whether Chuanxiong essential oil has anti-neuroinflammatory activity.

AIM OF THE STUDY

To explore the anti-neuroinflammatory properties of Chuanxiong essential oil and its molecular mechanisms by network pharmacology analysis and in vitro experiments.

MATERIALS AND METHODS

Gas chromatography-mass spectrometry (GC-MS) was used to identify the chemical components of Chuanxiong essential oil. Public databases were used to predict possible targets, build the protein-protein interaction network (PPI), and perform Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. Moreover, cytological experiments, nitric oxide assay, enzyme-link immunosorbent assay, western blotting, and immunofluorescence assay were adopted to prove the critical signaling pathway in lipopolysaccharide (LPS)-induced BV2 cells.

RESULTS

Thirty-six compounds were identified from Chuanxiong essential oil by GC-MS, and their corresponding putative targets were predicted. The network pharmacology study identified 232 candidate targets of Chuanxiong essential oil in anti-neuroinflammation. Furthermore, Chuanxiong essential oil was found to potentially affect the C-type lectin receptor, FoxO, and NF-κB signaling pathways according to the KEGG analysis. Experimentally, we verified that Chuanxiong essential oil could significantly reduce the overproduction of inflammatory mediators and pro-inflammatory factors via the NF-κB signaling pathway.

CONCLUSION

Chuanxiong essential oil alleviates neuroinflammation through the NF-κB signaling pathway, which provides a theoretical foundation for a better understanding of the clinical application of Chuanxiong essential oil in migraine treatment.

Long-term results on the suppression of secondary brain injury by early administered low-dose baclofen in a traumatic brain injury mouse model

Secondary injury from traumatic brain injury (TBI) perpetuates cerebral damages through varied ways. Attenuating neuroinflammation, which is a key feature of TBI, is important for long-term prognosis of its patients. Baclofen, a muscle relaxant, has shown promise in reducing excessive inflammation in other neurologic disorders. However, its effectiveness in TBI remains ambiguous. Thus, our study aimed to investigate whether early administration of baclofen could elicit potential therapeutic effects by diminishing exaggerated neuroinflammation in TBI mice. In this study, 80 C57BL/6 mice were used, of which 69 mice received controlled cortical impact. The mice were divided into six groups (11-16 mice each). Baclofen, administered at dose of 0.05, 0.2 and 1 mg/kg, was injected intraperitoneally a day after TBI for 3 consecutive weeks. 3 weeks after completing the treatments, the mice were assessed histologically. The results showed that mice treated with baclofen exhibited a significantly lower volume of lesion tissue than TBI mice with normal saline. Baclofen also reduced activated glial cells with neurotoxic immune molecules and inhibited apoptotic cells. Significant recovery was observed and sustained for 6 weeks at the 0.2 mg/kg dose in the modified neurological severity score. Furthermore, memory impairment was recovered with low-doses of baclofen in the Y-maze. Our findings demonstrate that early administration of low dose baclofen can regulate neuroinflammation, prevent cell death, and improve TBI motor and cognitive abnormalities.

The effects of social environment on AD-related pathology in hAPP-J20 mice and tau-P301L mice

In humans, social factors (e.g., loneliness) have been linked to the risk of developing Alzheimer's Disease (AD). To date, AD pathology is primarily characterized by amyloid-β plaques and tau tangles. We aimed to assess the effect of single- and group-housing on AD-related pathology in a mouse model for amyloid pathology (J20, and WT controls) and a mouse model for tau pathology (P301L) with and without seeding of synthetic human tau fragments (K18). Female mice were either single housed (SH) or group housed (GH) from the age of 6-7 weeks onwards. In 12-week-old P301L mice, tau pathology was induced through seeding by injecting K18 into the dorsal hippocampus (P301LK18), while control mice received a PBS injection (P301LPBS). P301L mice were sacrificed at 4 months of age and J20 mice at 10 months of age. In all mice brain pathology was histologically assessed by examining microglia, the CA1 pyramidal cell layer and specific AD pathology: analysis of plaques in J20 mice and tau hyperphosphorylation in P301L mice. Contrary to our expectation, SH-J20 mice interestingly displayed fewer plaques in the hippocampus compared to GH-J20 mice. However, housing did not affect tau hyperphosphorylation at Ser202/Thr205 of P301L mice, nor neuronal cell death in the CA1 region in any of the mice. The number of microglia was increased by the J20 genotype, and their activation (based on cell body to cell size ratio) in the CA1 was affected by genotype and housing condition (interaction effect). Single housing of P301L mice was linked to the development of stereotypic behavior (i.e. somersaulting and circling behavior). In P301LK18 mice, an increased number of microglia were observed, among which were rod microglia. Taken together, our findings point to a significant effect of social housing conditions on amyloid plaques and microglia in J20 mice and on the development of stereotypic behavior in P301L mice, indicating that the social environment can modulate AD-related pathology.

The effects of tea polyphenols on emotional homeostasis: Understanding dementia risk through stress, mood, attention & sleep

Decades of research provide evidence that certain phytochemicals in tea (Camellia sinensis) and other herbal beverages are protective against the development of sporadic types of dementia in later life. Since tea drinking is an economical and widely adopted social-cultural practice across all age groups, it is an ideal product to target in designing low-cost dietary interventions for Alzheimer's Disease (AD), the most prevalent form of dementia. In this review, we focus on the protective roles of tea-derived polyphenols and other phytochemicals on mood, the stress response, attention, and sleep, in keeping with the perspective that many early neuropathological events in AD may stem, in part, from allostatic overload. This approach aligns with the perspective that many forms of dementia, including AD, begin to take root in the brain decades prior to symptom onset, underscoring the need for early uptake of accessible and viable lifestyle interventions. The findings reviewed here suggest that consuming green and oolong tea can improve mood and reduce overall stress. However, given the caffeine content in tea and its association with stress reactivity, the effects of daily whole tea consumption on the emotional state are likely dose-dependent with an inverted-U relationship to wellbeing. Plant-based beverages that are to be consumed in high daily quantities for health purposes and which are naturally free of caffeine, such as Rooibos, may be more appropriate as a dietary supplement for managing emotional regulation over the lifetime.

Social isolation produces a sex- and brain region-specific alteration of microglia state

Social isolation is a profound form of psychological stress that impacts the mental health of a large proportion of society. Other experimental models of stress have demonstrated a microglia response that serves either a protective or pathological function. However, the effect of adult social isolation on microglia has not been thoroughly investigated. We measured microglia territory, branching, end points and phagocytic-lysosomal activity in group housed C57Bl/6 mice and mice that were socially isolated for 2 weeks. Our results show that the dorsomedial hypothalamus and hippocampal CA2 region of adult male mice undergo increased microglia volume, territory and endpoints following social isolation, whereas females exhibit this increase in the hypothalamus only. Males exhibited decreases in the phagocytic-lysosomal marker CD68 in microglia in these regions, whereas females showed an increase in CD68 in the hypothalamus suggesting sexually dimorphic and brain region-specific change in microglia state in response to social isolation. The prefrontal cortex, central amygdala, nucleus accumbens shell and visual cortex did not exhibit changes in microglia structure in either male or female mice. These data show that microglia in different brain regions undergo a distinct response to social isolation which may account for changes in cognition and behaviour associated with this prevalent form of psychological stress.

Early Chronic Stress Induced Changes within the Locus Coeruleus in Sporadic Alzheimer's Disease

Chronic exposure to stress throughout the lifespan has been the focus of many studies on Alzheimer's disease (AD) because of the similarities between the biological mechanisms involved in chronic stress and the pathophysiology of AD. In fact, the earliest abnormality associated with the disease is the presence of phosphorylated tau protein in locus coeruleus neurons, a brain structure highly responsive to stress and perceived threat. Here, we introduce allostatic load as a useful concept for understanding many of the complex, interacting neuropathological changes involved in the AD degenerative process. In response to chronic stress, aberrant tau proteins that begin to accumulate within the locus coeruleus decades prior to symptom onset appear to represent a primary pathological event in the AD cascade, triggering a wide range of interacting brain changes involving neuronal excitotoxicity, endocrine alterations, inflammation, oxidative stress, and amyloid plaque exacerbation. While it is acknowledged that stress will not necessarily be the major precipitating factor in all cases, early tau-induced changes within the locus coeruleus-norepinephrine pathway suggests that a therapeutic window might exist for preventative measures aimed at managing stress and restoring balance within the HPA axis.

The Adverse Outcome Pathway Framework Applied to Neurological Symptoms of COVID-19

Several reports have shown that the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has the potential to also be neurotropic. However, the mechanisms by which SARS-CoV-2 induces neurologic injury, including neurological and/or psychological symptoms, remain unclear. In this review, the available knowledge on the neurobiological mechanisms underlying COVID-19 was organized using the AOP framework. Four AOPs leading to neurological adverse outcomes (AO), anosmia, encephalitis, stroke, and seizure, were developed. Biological key events (KEs) identified to induce these AOs included binding to ACE2, blood–brain barrier (BBB) disruption, hypoxia, neuroinflammation, and oxidative stress. The modularity of AOPs allows the construction of AOP networks to visualize core pathways and recognize neuroinflammation and BBB disruption as shared mechanisms. Furthermore, the impact on the neurological AOPs of COVID-19 by modulating and multiscale factors such as age, psychological stress, nutrition, poverty, and food insecurity was discussed. Organizing the existing knowledge along an AOP framework can represent a valuable tool to understand disease mechanisms and identify data gaps and potentially contribute to treatment, and prevention. This AOP-aligned approach also facilitates synergy between experts from different backgrounds, while the fast-evolving and disruptive nature of COVID-19 emphasizes the need for interdisciplinarity and cross-community research.

Chronic social instability stress down-regulates IL-10 and up-regulates CX3CR1 in tumor-bearing and non-tumor-bearing female mice

Extensive literature has reported a link between stress and tumor progression, and between both of these factors and mental health. Despite the higher incidence of affective disorders in females and the neurochemical differences according to sex, female populations have been understudied. The aim of this study was therefore to analyze the effect of stress on tumor development in female OF1 mice. For this purpose, subjects were inoculated with B16F10 melanoma cells and exposed to the Chronic Social Instability Stress (CSIS) model. Behavioral, neurochemical and neuroendocrine parameters were analyzed. Female mice exposed to CSIS exhibited reduced body weight and increased arousal, but there was no evidence of depressive behavior or anxiety. Exposure to CSIS did not affect either corticosterone levels or tumor development, although it did provoke an imbalance in cerebral inflammatory cytokines, decreasing IL-10 expression (IL-6/IL-10 and TNF-α/IL-10); chemokines, increasing CX3CR1 expression (CX3CL1/CX3CR1); and glucocorticoid receptors, decreasing GR expression (MR/GR). In contrast, tumor development did not alter body weight and, although it did alter behavior, it did so to a much lesser extent. Tumor inoculation did not affect corticosterone levels, but increased the MR/GR ratio in the hippocampus and provoked an imbalance in cerebral inflammatory cytokines and chemokines, although differently from stress. These results underscore the need for experimental approaches that allow us to take sex differences into account when exploring this issue, since these results appear to indicate that the female response to stress is mediated by mechanisms different from those often proposed in relation to male mice.

Transdiagnostic In Vivo Magnetic Resonance Imaging Markers of Neuroinflammation

Accumulating evidence suggests that inflammation is not limited to archetypal inflammatory diseases such as multiple sclerosis, but instead represents an intrinsic feature of many psychiatric and neurological disorders not typically classified as neuroinflammatory. A growing body of research suggests that neuroinflammation can be observed in early and prodromal stages of these disorders and, under certain circumstances, may lead to tissue damage. Traditional methods to assess neuroinflammation include serum or cerebrospinal fluid markers and positron emission tomography. These methods require invasive procedures or radiation exposure and lack the exquisite spatial resolution of magnetic resonance imaging (MRI). There is, therefore, an increasing interest in noninvasive neuroimaging tools to evaluate neuroinflammation reliably and with high specificity. While MRI does not provide information at a cellular level, it facilitates the characterization of several biophysical tissue properties that are closely linked to neuroinflammatory processes. The purpose of this review is to evaluate the potential of MRI as a noninvasive, accessible, and cost-effective technology to image neuroinflammation across neurological and psychiatric disorders. We provide an overview of current and developing MRI methods used to study different aspects of neuroinflammation and weigh their strengths and shortcomings. Novel MRI contrast agents are increasingly able to target inflammatory processes directly, therefore offering a high degree of specificity, particularly if used in conjunction with multitissue, biophysical diffusion MRI compartment models. The capability of these methods to characterize several aspects of the neuroinflammatory milieu will likely push MRI to the forefront of neuroimaging modalities used to characterize neuroinflammation transdiagnostically.

The Role of Exosomes as Mediators of Neuroinflammation in the Pathogenesis and Treatment of Alzheimer’s Disease

Alzheimer’s disease (AD) is a common neurodegenerative disease characterized by progressive dementia. Accumulation of β–amyloid peptide 1–42 and phosphorylation of tau protein in the brain are the two main pathological features of AD. However, comprehensive studies have shown that neuroinflammation also plays a crucial role in the pathogenesis of AD. Neuroinflammation is associated with neuronal death and abnormal protein aggregation and promotes the pathological process of β-amyloid peptide 1–42 and tau protein. The inflammatory components associated with AD include glial cells, complement system, cytokines and chemokines. In recent years, some researchers have focused on exosomes, a type of membrane nano vesicles. Exosomes can transport proteins, lipids, microRNAs and other signaling molecules to participate in a variety of signaling pathways for signal transmission or immune response, affecting the activity of target cells and participating in important pathophysiological processes. Therefore, exosomes play an essential role in intercellular communication and may mediate neuroinflammation to promote the development of AD. This paper reviews the occurrence and development of neuroinflammation and exosomes in AD, providing a deeper understanding of the pathogenesis of AD. Furthermore, the role of exosomes in the pathogenesis and treatment of AD is further described, demonstrating their potential as therapeutic targets for neuroinflammation and AD in the future.

Ferulic acid produces neuroprotection against radiation-induced neuroinflammation by affecting NLRP3 inflammasome activation

PURPOSE

After radiation therapy of brain tumors, radiation-induced cognitive impairment is a common and severe complication. Neuroinflammation mediated by microglia is a critical event that accelerates cognitive or functional decline. Ferulic acid (FA), a phenolic plant component, possesses multiple pharmacological effects, such as anti-inflammatory and anti-radiation. The current research attempts to ascertain the protection of FA on radiation-induced neuroinflammation and the mechanism of this effect.

MATERIALS AND METHODS

C57BL/6 mice were irradiated with ⁶⁰Co γ-ray to establish a brain injury model. The Morris water maze experiment was used to observe the effects of FA on the spatial learning and memory impairment of irradiated mice. The pathological changes of hippocampal tissue were observed by HE staining. Besides, microglia BV-2 cell lines were used to study the anti-neuroinflammatory impacts of FA on radiation-induced microglial activation and further elucidate the potential mechanisms influencing FA-mediated neuroprotective properties. The cell morphological changes were observed using an optical microscope. The cytotoxicity of FA and radiation to BV-2 cells was determined using the CCK-8 assay. Additionally, Western blot and quantitative real-time PCR detected the expression and transcription of NLRP3 inflammasome and pro-inflammatory cytokines in hippocampus and BV-2 cells.

RESULTS

FA could enhance learning and memory capacity and ameliorate pathological changes in the hippocampal tissues of irradiated mice. The cell radiation injury model was established by 8 Gy ⁶⁰Co γ-ray, and the concentration of subsequent administration was determined to be 2.5, 5, and 10 μmol/L. Furthermore, FA could suppress the transcription and expression of NLRP3 in hippocampal tissue and microglia, and also the increased secretion of pro-inflammatory factors.

CONCLUSION

This study established that FA targeting the NLRP3 inflammasome has a neuroprotective effect against radiation-induced nerve damage, implying that FA might have some potential in the treatment of radiation-induced cognitive impairment.

The Role of Cyclooxygenase 2 in the Cognitive Impairment Induced by Alcohol or Stress in Rats

Background:

Cognitive impairment is an unpleasant and progressive mental disorder characterized by learning and memory disabilities. Stress and alcohol are two known environmental factors that increase cognitive impairment. This study was designed to evaluate the relative role of cyclooxygenase 2 in alcohol or stress-induced cognitive impairment.

Materials and Methods:

Male Wistar rats were randomly divided into groups with six rats in each. The groups included sham, control, alcohol (15% ethanol in drinking water), and restraint stress (restraint 6 h per day). Three separated groups received celecoxib at a dose of 20 mg/kg in addition to those listed above. The treatments continued daily for 28 days. The object recognition task (ORT) and Morris water maze (MWM) are used to evaluate the learning and memory.

Results:

Alcohol or restrain stress significantly increased the time and distance needed to find the hidden platform in MWM. Furthermore, they decreased the recognition index in ORT compared to the control group. Administration of celecoxib significantly decreased the required time and traveled distance to reach the platform in alcohol-treated animals but not in the stress-exposed rats. Celecoxib also significantly increased the recognition index both in alcohol- or restraint stress-exposed animals.

Conclusion:

We found that either alcohol or restraint stress impairs memory in rats. In MWM, celecoxib improved the alcohol-induced memory impairment but could not show a reduction in memory deterioration due to restraint stress. In ORT, celecoxib reversed memory impairment due to both alcohol and restraint stress.

Lipopolysaccharide, Identified Using an Antibody and by PAS Staining, Is Associated With Corpora amylacea and White Matter Injury in Alzheimer's Disease and Aging Brain

Corpora amylacea (CA) increase in number and size with aging. Their origins and functions remain unknown. Previously, we found that Alzheimer's disease (AD) brains have more CA in the periventricular white matter (PVWM) compared to aging controls. In addition, CA is associated with neurodegeneration as indicated by colocalization of degraded myelin basic protein (dMBP) with periodic acid-Schiff (PAS), a CA marker. We also found that bacterial lipopolysaccharide is present in aging brains, with more LPS in AD compared with controls. Periodic acid-Schiff staining is used to identify CA by virtue of their high polysaccharide content. Despite the growing knowledge of CA as a contributor to AD pathology, the molecules that contribute to the polysaccharides in CA are not known. Notably, lipopolysaccharides (LPS) are important cell-surface polysaccharides found in all Gram-negative bacteria. However, it is unknown whether PAS could detect LPS, whether the LPS found in aging brains contribute to the polysaccharide found in CA, and whether LPS associate with myelin injury. In this study, we found that aging brains had a myelin deficit zone (MDZ) adjacent to the ventricles in PVWM. The MDZ contained vesicles, most of which were CA. LPS and dMBP levels were higher in AD than in control brains. LPS was colocalized with dMBP in the vesicles/CA, linking white matter injury with a bacterial pro-inflammatory molecule. The vesicles also contained oxidized fibers, C-reactive protein, NG2, and GALC, markers of oligodendrocyte precursor cells (OPCs) and oligodendrocyte cells (OLs), respectively. The vesicles/CA were surrounded by dense astrocyte processes in control and AD brains. LPS was co-localized with CA by double staining of PAS with LPS in aging brains. The relationship of LPS with PAS staining was confirmed by PAS staining of purified LPS on nitrocellulose membranes. These findings reveal that LPS is one of the polysaccharides found in CA which can be stained with PAS. In addition, vesicles/CA are associated with oxidized and damaged myelin. The LPS in these vesicles/CA may have contributed to this oxidative myelin damage and may have contributed to oxidative stress to OPCs and OLs which could impair the ability to repair damaged myelin in AD and control brains.

Cortical complexity in world trade center responders with chronic posttraumatic stress disorder

Approximately 23% of World Trade Center (WTC) responders are experiencing chronic posttraumatic stress disorder (PTSD) associated with their exposures at the WTC following the terrorist attacks of 9/11/2001, which has been demonstrated to be a risk factor for cognitive impairment raising concerns regarding their brain health. Cortical complexity, as measured by analyzing Fractal Dimension (FD) from T1 MRI brain images, has been reported to be reduced in a variety of psychiatric and neurological conditions. In this report, we hypothesized that FD would be also reduced in a case-control sample of 99 WTC responders as a result of WTC-related PTSD. The results of our surface-based morphometry cluster analysis found alterations in vertex clusters of complexity in WTC responders with PTSD, with marked reductions in regions within the frontal, parietal, and temporal cortices, in addition to whole-brain absolute bilateral and unilateral complexity. Furthermore, region of interest analysis identified that the magnitude of changes in regional FD severity was associated with increased PTSD symptoms (reexperiencing, avoidance, hyperarousal, negative affect) severity. This study confirms prior findings on FD and psychiatric disorders and extends our understanding of FD associations with posttraumatic symptom severity. The complex and traumatic experiences that led to WTC-related PTSD were associated with reductions in cortical complexity. Future work is needed to determine whether reduced cortical complexity arose prior to, or concurrently with, onset of PTSD.

Thioperamide attenuates neuroinflammation and cognitive impairments in Alzheimer's disease via inhibiting gliosis

Alzheimer's disease (AD) is an age-related neurodegenerative disease, which characterized by deposition of amyloid-β (Aβ) plaques, neurofibrillary tangles, neuronal loss, and accompanied by neuroinflammation. Neuroinflammatory processes are well acknowledged to contribute to the progression of AD pathology. Histamine H3 receptor (H3R) is a presynaptic autoreceptor regulating histamine release via negative feedback way. Recently, studies show that H3R are highly expressed not only in neurons but also in microglia and astrocytes. H3R antagonist has been reported to have anti-inflammatory efficacy. However, whether inhibition of H3R is responsible for the anti-neuroinflammation in glial cells and neuroprotection on APPswe, PSEN1dE9 (APP/PS1 Tg) mice remain unclear. In this study, we found that inhibition of H3R by thioperamide reduced the gliosis and induced a phenotypical switch from A1 to A2 in astrocytes, and ultimately attenuated neuroinflammation in APP/PS1 Tg mice. Additionally, thioperamide rescued the decrease of cyclic AMP response element-binding protein (CREB) phosphorylation and suppressed the phosphorylated P65 nuclear factor kappa B (p-P65 NF-κB) in APP/PS1 Tg mice. H89, an inhibitor of CREB signaling, abolished these effects of thioperamide to suppress gliosis and proinflammatory cytokine release. Lastly, thioperamide alleviated the deposition of amyloid-β (Aβ) and cognitive dysfunction in APP/PS1 mice, which were both reversed by administration of H89. Taken together, these results suggested the H3R antagonist thioperamide improved cognitive impairment in APP/PS1 Tg mice via modulation of the CREB-mediated gliosis and inflammation inhibiting, which contributed to Aβ clearance. This study uncovered a novel mechanism involving inflammatory regulating behind the therapeutic effect of thioperamide in AD.

Microglia and BDNF at the crossroads of stressor related disorders: Towards a unique trophic phenotype

Stressors ranging from psychogenic/social to neurogenic/injury to systemic/microbial can impact microglial inflammatory processes, but less is known regarding their effects on trophic properties of microglia. Recent studies do suggest that microglia can modulate neuronal plasticity, possibly through brain derived neurotrophic factor (BDNF). This is particularly important given the link between BDNF and neuropsychiatric and neurodegenerative pathology. We posit that certain activated states of microglia play a role in maintaining the delicate balance of BDNF release onto neuronal synapses. This focused review will address how different "activators" influence the expression and release of microglial BDNF and address the question of tropomyosin receptor kinase B (TrkB) expression on microglia. We will then assess sex-based differences in microglial function and BDNF expression, and how microglia are involved in the stress response and related disorders such as depression. Drawing on research from a variety of other disorders, we will highlight challenges and opportunities for modulators that can shift microglia to a "trophic" phenotype with a view to potential therapeutics relevant for stressor-related disorders.

N-salicyloyl tryptamine derivatives as potential therapeutic agents for Alzheimer's disease with neuroprotective effects

Alzheimer's disease (AD) has become a serious threat to the developed nations with burgeoning patients and annual costs on health care system in modern society. Neuroinflammation, as one of the specific biochemical factors in the progress of neurodegeneration diseases, performs a crucial role in the pathogenesis and development of AD. Therefore, it is of great significance to develop effective anti-neuroinflammatory strategies for the treatment of AD. N-salicyloyl tryptamine derivatives were previously reported and demonstrated that possessed great potential anti-neuroinflammatory effects and favorable blood-brain barrier (BBB) permeation. Herein, a series of novel N-salicyloyl tryptamine derivatives were synthesized and their anti-AD potential was evaluated both in vitro and in vivo. Among them, L7 performed well anti-neuroinflammatory effects and excellent neuroprotective effects, as well as little toxicity. To lucubrate its potential for the treatment of AD, behavior tests including morris water maze (MWM), eight-arm radial maze, open field test and novel object recognition (NOR) test were carried out and the results showed that L7 could remarkably improve Aβ-induced cognitive impairment. Moreover, the mechanism of action of L7 on improving Aβ-induced AD was preliminarily investigated, and the results uncovered that the neuroprotective effects of L7 was might exerte via intervening Aβ-induced pyroptosis through NLRP3-caspase-1-GSDMD axis and ameliorating neuronal apoptosis by mitochondrial apoptosis pathway. Besides, the distribution of Aβ plaques in brain tissues were detected by immunohistochemical (IHC) assay and the results indicated that L7 could significantly attenuate the deposition of Aβ plaques in the brain.

Mitochondrial Disorders in Alzheimer's Disease

Alzheimer's disease is the most common age-related neurodegenerative disease. Understanding of its etiology and pathogenesis is constantly expanding. Thus, the increasing attention of researchers is directed to the study of the role of mitochondrial disorders. In addition, in recent years, the concept of Alzheimer's disease as a stress-induced disease has begun to form more and more actively. The stress-induced damage to the neuronal system can trigger a vicious circle of pathological processes, among which mitochondrial dysfunctions have a significant place, since mitochondria represent a substantial component in the anti-stress activity of the cell. The study of mitochondrial disorders in Alzheimer's disease is relevant for at least two reasons: first, as important pathogenetic component in this disease; second, due to vital role of mitochondria in formation of the body resistance to various conditions, including stressful ones, throughout the life. This literature review analyzes the results of a number of recent studies assessing potential significance of the mitochondrial disorders in Alzheimer's disease. The probable mechanisms of mitochondrial disorders associated with the development of this disease are considered: bioenergetic dysfunctions, changes in mitochondrial DNA (including assessment of the significance of its haplogroup features), disorders in the dynamics of these organelles, oxidative damage to calcium channels, damage to MAM complexes (membranes associated with mitochondria; mitochondria-associated membranes), disruptions of the mitochondrial quality control system, mitochondrial permeability, etc. The issues of the "primary" or "secondary" mitochondrial damage in Alzheimer's disease are discussed. Potentials for the development of new methods for diagnosis and therapy of mitochondrial disorders in Alzheimer's disease are considered.

Current Views on the Role of Stress in the Pathogenesis of Chronic Neurodegenerative Diseases

The review summarizes the results of studies on the cellular and molecular mechanisms mediating the impact of stress on the pathogenesis of neurodegenerative brain pathologies (Alzheimer's disease, Parkinson's disease, etc.) and presents current information on the role of stress in the hyperphosphorylation of tau protein, aggregation of beta-amyloid, and hyperactivation of the hypothalamic-pituitary-adrenal axis involved in the hyperproduction of factors that contribute to the pathogenetic role of stress in neurodegeneration. The data on the participation of microglia in the effects of stress on the pathogenesis of neurodegenerative diseases are presented.

Effect of pyrrolo[3,4-d]pyridazinone derivatives in neuroinflammation induced by preincubation with lipopolysaccharide or coculturing with microglia-like cells

Alzheimer's disease is one of the most serious disorders of the 21st century. There is still no effective therapy for this condition. The study investigated the potential regenerative effect of four pyrrolo[3,4-d]pyridazinone derivatives in cultures of SH-SY5Y neuron-like cells preincubated with lipopolysaccharide (LPS) or cocultured with microglia-like cells. In addition to the traditional investigation of the effect on viability, the level of free radicals and nitric oxide, the average length of neurites was also measured. Via in silico studies, the possibility of penetration of the blood-brain barrier (BBB) by the tested compounds was assessed. The administration of LPS to the culture of SH-SY5Y cells as well as coculturing with microglia-like cells had a significant negative effect on the results of all the assays performed. The treatment with the tested derivatives in most cases significantly reduced this negative effect. The obtained results suggest that the compound L2 may have a beneficial impact on neuronal damage caused by LPS or proinflammatory cytokines secreted by microglia-like cells. Importantly, tested compounds can pass through the BBB, which allows them to enter the brain.

Construction of a risk prediction model for Alzheimer's disease in the elderly population

BACKGROUND

Dementia is one of the greatest global health and social care challenges of the twenty-first century. The etiology and pathogenesis of Alzheimer's disease (AD) as the most common type of dementia remain unknown. In this study, a simple nomogram was drawn to predict the risk of AD in the elderly population.

METHODS

Nine variables affecting the risk of AD were obtained from 1099 elderly people through clinical data and questionnaires. Least Absolute Shrinkage Selection Operator (LASSO) regression analysis was used to select the best predictor variables, and multivariate logistic regression analysis was used to construct the prediction model. In this study, a graphic tool including 9 predictor variables (nomogram-see precise definition in the text) was drawn to predict the risk of AD in the elderly population. In addition, calibration diagram, receiver operating characteristic (ROC) curve and decision curve analysis (DCA) were used to verify the model.

RESULTS

Six predictors namely sex, age, economic status, health status, lifestyle and genetic risk were identified by LASSO regression analysis of nine variables (body mass index, marital status and education level were excluded). The area under the ROC curve in the training set was 0.822, while that in the validation set was 0.801, suggesting that the model built with these 6 predictors showed moderate predictive ability. The DCA curve indicated that a nomogram could be applied clinically if the risk threshold was between 30 and 40% (30 to 42% in the validation set).

CONCLUSION

The inclusion of sex, age, economic status, health status, lifestyle and genetic risk into the risk prediction nomogram could improve the ability of the prediction model to predict AD risk in the elderly patients.

Stress diagnoses in midlife and risk of dementia: a register-based follow-up study

OBJECTIVES

Previous studies indicated that stress diagnoses increase the risk of dementia. However, previous results may be biased by confounding, reverse causation and misclassification. Therefore, the main aim of this study was to investigate the association between clinically diagnosed stress in midlife and later dementia risk, while addressing limitations of previous studies.

METHODS

The study population was selected from all individuals in Denmark born 1935-1956. Individuals diagnosed with stress in midlife (aged 37-58 years) were matched (1:5) with individuals without stress diagnoses based on sex and birthdate (N = 103,484). Data were retrieved from national registers. Cox regression models were adjusted for socio-demographic factors and different morbidities.

RESULTS

We found a 2.20 (95% CI: 1.93-2.50) times higher rate of dementia among individuals with any stress diagnosis registered in midlife compared with no stress diagnosis. Hazard rate ratios of dementia were 1.73 (95% CI: 1.13-2.65) among individuals with acute stress reactions, 2.37 (95% CI: 2.05-2.74) among individuals with adjustment disorders, and 2.20 (95% CI: 1.73-2.80) among individuals with unspecified stress reactions. Individuals with PTSD and other stress reactions had non-significantly elevated rates of dementia. Adjustment for confounding only slightly attenuated the association, and reverse causation did not appear to bias the results substantially.

CONCLUSION

Our results support the hypothesis that severe stress in midlife is an important risk factor for dementia. This finding emphasizes the importance of identifying and treating severe stress in midlife to reduce potential detrimental consequences for brain health in later life.

Narciclasine inhibits LPS-induced neuroinflammation by modulating the Akt/IKK/NF-κB and JNK signaling pathways

BACKGROUND

Neuroinflammation is defined as innate immune system activation in the central nervous system, and is a complex response involved in removing pathogens, toxic components, and dead cells by activating microglial cells. However, over-activated microglia have been implicated in the pathogenesis of neurodegenerative diseases, because they release large amounts of neurotoxic factors. Thus, inhibiting microglial activation may represent an attractive approach for preventing neuroinflammatory disorders. The objective of this study was to investigate the effect of narciclasine (NA) on lipopolysaccharide (LPS)-induced neuroinflammation by evaluating related markers and neurotoxic factors.

METHODS

BV-2 cells were pre-incubated with NA at 0.1, 0.2, and 0.3 µM for 1h, and then co-treated with LPS for 12 h. Cellular medium and lysates were measured using a nitric oxide assay, enzyme-link immunosorbent assay (ELISA), western blotting, kinase activity assay, luciferase assay, and immunofluorescence assay. C57BL/6N mice were orally administered NA and intraperitoneally injected with LPS, and the cerebral cortex was examined using western blotting and immunofluorescence assays.

RESULTS

NA showed novel pharmacological activity, inhibiting pro-inflammatory factors, including TNF-α, IL-6, IL-18, NO, and PGE₂, but increasing the anti-inflammatory cytokines IL-10 and TGF-β1 in LPS-induced microglial cells. Moreover, NA also attenuated the LPS-induced mRNA and proteins of iNOS and COX-2. The mechanistic study indicated that NA attenuates the secretion of pro-inflammatory factor by down-regulating the Akt/IKK/NF-κB and JNK signaling pathways, and directly inhibits the catalytic activity of IKKα/β. Furthermore, we found that NA also reduced the expression of the microglial markers Iba-1, COX-2, and TNF-α in the mouse brain.

CONCLUSION

NA inhibits the over-expression of pro-inflammatory factors but it promotes anti-inflammatory cytokines by down-regulating the Akt/IKK/NF-κB and JNK signaling pathways in experimental models. Thus, NA may be a potential candidate for relieving neuroinflammation.

Ganoderic Acid A Attenuates LPS-Induced Neuroinflammation in BV2 Microglia by Activating Farnesoid X Receptor

Neuroinflammation plays an important role in the onset and progression of neurodegenerative diseases. Microglia-mediated neuroinflammation have been proved to be the main reason for causing the neurodegenerative diseases. Ganoderic acid A (GAA), isolated from Ganoderma lucidum, showed anti-inflammatory effect in metabolism diseases. However, little research has been focused on the effect of GAA in neuroinflammation and the related mechanism. In the present study, lipopolysaccharide(LPS)-stimulated BV2 microglial cells were used to evaluate the anti-inflammatory capacity of GAA. Our data showed that GAA significantly suppressed LPS-induced BV2 microglial cells proliferation and activation in vitro. More strikingly, GAA promoted the conversion of BV2 microglial cells from M1 status induced by LPS to M2 status. Furthermore, GAA inhibited the pro-inflammatory cytokines release and promoted neurotrophic factor BDNF expression in LPS-induced BV2 microglial cells. Finally, we found that the expression of farnesoid-X-receptor (FXR) was prominently downregulated in LPS-stimulated BV2 microglial cells, antagonism of FXR with z-gugglesterone and FXR siRNA can reverse the effect of GAA in LPS-induced BV2 microglial cells. Taking together, our findings demonstrate that GAA can significantly inhibit LPS-induced neuroinflammation in BV2 microglial cells via activating FXR receptor.

Plasma d-glutamate levels for detecting mild cognitive impairment and Alzheimer's disease: Machine learning approaches

BACKGROUND

d-glutamate, which is involved in N-methyl-d-aspartate receptor modulation, may be associated with cognitive ageing.

AIMS

This study aimed to use peripheral plasma d-glutamate levels to differentiate patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD) from healthy individuals and to evaluate its prediction ability using machine learning.

METHODS

Overall, 31 healthy controls, 21 patients with MCI and 133 patients with AD were recruited. Serum d-glutamate levels were measured using high-performance liquid chromatography (HPLC). Cognitive deficit severity was assessed using the Clinical Dementia Rating scale and the Mini-Mental Status Examination (MMSE). We employed four machine learning algorithms (support vector machine, logistic regression, random forest and naïve Bayes) to build an optimal predictive model to distinguish patients with MCI or AD from healthy controls.

RESULTS

The MCI and AD groups had lower plasma d-glutamate levels (1097.79 ± 283.99 and 785.10 ± 720.06 ng/mL, respectively) compared to healthy controls (1620.08 ± 548.80 ng/mL). The naïve Bayes model and random forest model appeared to be the best models for determining MCI and AD susceptibility, respectively (area under the receiver operating characteristic curve: 0.8207 and 0.7900; sensitivity: 0.8438 and 0.6997; and specificity: 0.8158 and 0.9188, respectively). The total MMSE score was positively correlated with d-glutamate levels (r = 0.368, p < 0.001). Multivariate regression analysis indicated that d-glutamate levels were significantly associated with the total MMSE score (B = 0.003, 95% confidence interval 0.002-0.005, p < 0.001).

CONCLUSIONS

Peripheral plasma d-glutamate levels were associated with cognitive impairment and may therefore be a suitable peripheral biomarker for detecting MCI and AD. Rapid and cost-effective HPLC for biomarkers and machine learning algorithms may assist physicians in diagnosing MCI and AD in outpatient clinics.

Neuroinflammation in Alzheimer's disease and beneficial action of luteolin

Alzheimer's disease (AD), already the world's most common form of dementia, is projected to continue increasing in prevalence over the next several decades. The current lack of understanding of the pathogenesis of AD has hampered the development of effective treatments. Historically, AD research has been predicated on the amyloid cascade hypothesis (ACH), which attributes disease progression to the build-up of amyloid protein. However, multiple clinical studies of drugs interfering with ACH have failed to show any benefit demonstrating that AD etiology is more complex than previously thought. Here we review the current literature on the emerging key role of neuroinflammation, especially activation of microglia, in AD pathogenesis. Moreover, we provide compelling evidence that certain flavonoids, especially luteolin formulated in olive pomace oil together with hydroxytyrosol, offers a reasonable prophylactic treatment approach due to its many beneficial actions.

Antiallergic drug desloratadine as a selective antagonist of 5HT2A receptor ameliorates pathology of Alzheimer's disease model mice by improving microglial dysfunction

Alzheimer's disease (AD) is a progressively neurodegenerative disease characterized by cognitive deficits and alteration of personality and behavior. As yet, there is no efficient treatment for AD. 5HT_2A receptor (5HT_2A R) is a subtype of 5HT₂ receptor belonging to the serotonin receptor family, and its antagonists have been clinically used as antipsychotics to relieve psychopathy. Here, we discovered that clinically first-line antiallergic drug desloratadine (DLT) functioned as a selective antagonist of 5HT_2A R and efficiently ameliorated pathology of APP/PS1 mice. The underlying mechanism has been intensively investigated by assay against APP/PS1 mice with selective 5HT_2A R knockdown in the brain treated by adeno-associated virus (AAV)-ePHP-si-5HT_2A R. DLT reduced amyloid plaque deposition by promoting microglial Aβ phagocytosis and degradation, and ameliorated innate immune response by polarizing microglia to an anti-inflammatory phenotype. It stimulated autophagy process and repressed neuroinflammation through 5HT_2A R/cAMP/PKA/CREB/Sirt1 pathway, and activated glucocorticoid receptor (GR) nuclear translocation to upregulate the transcriptions of phagocytic receptors TLR2 and TLR4 in response to microglial phagocytosis stimulation. Together, our work has highly supported that 5HT_2A R antagonism might be a promising therapeutic strategy for AD and highlighted the potential of DLT in the treatment of this disease.

Associations between malnutrition and cognitive impairment in an elderly Chinese population: an analysis based on a 7-year database

AIM

This study aimed to elucidate whether malnutrition is associated with cognitive impairment in an older Chinese population.

METHODS

A cross-sectional study was conducted in 2365 participants aged 60 years or older from January 2013 to September 2019. Nutritional status was measured by using the Mini Nutritional Assessment Short Form (MNA-SF). Cognitive function was assessed with the Mini-Mental State Examination (MMSE). The relationship between malnutrition or each Mini Nutritional Assessment Short Form domain and cognitive impairment was examined with univariate and multivariate logistic regression analysis.

RESULTS

The prevalence of malnutrition, risk of malnutrition, and cognitive impairment was 5.54%, 33.45%, and 36.74%, respectively. The prevalence was higher in those 80 years and older: 7.88%, 40.75%, and 53.65%, respectively. The Mini-Mental State Examination score was positively correlated with the Mini Nutritional Assessment Short Form score (r = 0.364, P < 0.001). After adjustment for age, gender, education, marital status, and living alone, malnutrition (odds ratio (OR) = 3.927, 95% confidence interval (CI): 2.650-5.819), anorexia (OR = 1.454, 95%CI: 1.192-1.774), weight loss (OR = 1.697, 95%CI: 1.406-2.047), impaired mobility (OR = 4.156, 95%CI: 3.311-5.218), and psychological stress (OR = 1.414, 95%CI: 1.070-1.869) were significantly associated with an increased risk of cognitive impairment.

CONCLUSIONS

Our results suggest that the prevalence of malnutrition and cognitive impairment is relatively high and increases with age. Malnutrition, anorexia, weight loss, impaired mobility, and psychological stress are significantly associated with an increased risk of cognitive impairment. Therefore, clinicians should assess the nutritional and cognitive status of the elderly regularly to improve early detection and timely intervention.

Discovery of Soluble Epoxide Hydrolase Inhibitors from Chemical Synthesis and Natural Products

Soluble epoxide hydrolase (sEH) is an α/β hydrolase fold protein and widely distributed in numerous organs including the liver, kidney, and brain. The inhibition of sEH can effectively maintain endogenous epoxyeicosatrienoic acids (EETs) levels and reduce dihydroxyeicosatrienoic acids (DHETs) levels, resulting in therapeutic potentials for cardiovascular, central nervous system, and metabolic diseases. Therefore, since the beginning of this century, the development of sEH inhibitors is a hot research topic. A variety of potent sEH inhibitors have been developed by chemical synthesis or isolated from natural sources. In this review, we mainly summarized the interconnected aspects of sEH with cardiovascular, central nervous system, and metabolic diseases and then focus on representative inhibitors, which would provide some useful guidance for the future development of potential sEH inhibitors.

Protective Activity of Aβ on Cell Cultures (PC12 and THP-1 after Differentiation) Preincubated with Lipopolysaccharide (LPS)

Amyloid-β (Aβ), the influence of which is considered the pathomechanism of Alzheimer’s disease, is also present in healthy people. The microbiome’s impact is also taken into account, where bacterial lipopolysaccharide (LPS) activates inflammatory processes and stimulates microglia via TLRs. Molecules of bacterial origin can co-create senile plaques with Aβ. This study evaluated the activity of physiological Aβ concentrations on neuronal and microglial cells after preincubation with LPS. Two cell lines were used in the study: PC12 cells differentiated with NGF and THP-1 cells differentiated with phorbol 12-myristate 13-acetate (PMA). Cells were incubated with LPS at concentrations of 1–100 μM for 24 h and then with Aβ_25–35 at a concentration of 0.001 μM or 1.0 μM for another 24 h. The viability of the culture and free oxygen radicals and the number of DNA strand breaks in both cell lines were evaluated. Additionally, for PC12 cells, neural features were assessed. Stimulation of repair processes in the presence of Aβ was observed for both studied cell lines. There was a decrease in free radical level and DNA damage number compared to control cultures (cells treated with LPS and without Aβ). The neurotrophic activity of Aβ was observed—the effect on neurites’ growth even after the preincubation of PC12 cells with LPS. At the lowest concentration of LPS used, the increase in neurite length was about 50% greater than in the negative control. At low concentrations, Aβ has a protective effect on neuron-like PC12 cells pretreated with LPS.

Perceived stress and dementia: Results from the Copenhagen city heart study

Objectives: We investigated if perceived stress in midlife increased the risk of dementia. Furthermore, we explored differences between subgroups related to sex, age and employment status when reporting stress.Methods: In this longitudinal study, we used information on perceived stress from 10,814 participants (mean age 56.7 years). Participants were followed through Danish national registers for development of dementia. Participants were considered at risk of dementia from the date they turned 60 years. Perceived stress was assessed as a combination of self-reported intensity and frequency of stress, and categorized into low (score 0-1), medium (score 2-4), and high stress (score 5-6). We used Poisson regression to estimate incidence rate ratios (IRR) and their 95% confidence intervals (CI) and adjusted for sociodemographic factors and psychiatric morbidity at baseline (main model) as well as cardio/cerebrovascular diseases and health behaviors at baseline (additional model).Results: The mean follow-up time was 13.8 years, and 1,519 participants were registered with dementia. Dementia risk was higher in participants reporting medium stress (IRR = 1.11, 95% CI: 0.99-1.24) and high stress (IRR = 1.36, 95% CI: 1.13-1.65). Adjustment for cardio/cerebrovascular diseases and health behaviors did not alter the results. We did not find strong support for differences between subgroups, although the association between stress and dementia was stronger for those who were employed at the time of reporting high stress.Conclusion: Our results provide empirical support for an effect of perceived stress on the risk of dementia in old age.

COVID-19, Mast Cells, Cytokine Storm, Psychological Stress, and Neuroinflammation

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a new pandemic infectious disease that originated in China. COVID-19 is a global public health emergency of international concern. COVID-19 causes mild to severe illness with high morbidity and mortality, especially in preexisting risk groups. Therapeutic options are now limited to COVID-19. The hallmark of COVID-19 pathogenesis is the cytokine storm with elevated levels of interleukin-6 (IL-6), IL-1β, tumor necrosis factor-alpha (TNF-α), chemokine (C-C-motif) ligand 2 (CCL2), and granulocyte-macrophage colony-stimulating factor (GM-CSF). COVID-19 can cause severe pneumonia, and neurological disorders, including stroke, the damage to the neurovascular unit, blood-brain barrier disruption, high intracranial proinflammatory cytokines, and endothelial cell damage in the brain. Mast cells are innate immune cells and also implicated in adaptive immune response, systemic inflammatory diseases, neuroinflammatory diseases, traumatic brain injury and stroke, and stress disorders. SARS-CoV-2 can activate monocytes/macrophages, dendritic cells, T cells, mast cells, neutrophils, and induce cytokine storm in the lung. COVID-19 can activate mast cells, neurons, glial cells, and endothelial cells. SARS-CoV-2 infection can cause psychological stress and neuroinflammation. In conclusion, COVID-19 can induce mast cell activation, psychological stress, cytokine storm, and neuroinflammation.

An Epigenetics-Based, Lifestyle Medicine-Driven Approach to Stress Management for Primary Patient Care: Implications for Medical Education

Over 75% of patients in the primary care setting present with stress-related complaints. Curiously, patients and health care providers all too often see stress as a relatively benign sequela of many common illnesses such as heart disease, cancer, lung disease, dementia, diabetes, and mental illness. Unfortunately, various day-to-day lifestyle choices and environmental factors, unrelated to the presence of any disease, can cause stress sufficient to contribute to the development of various diseases/disorders and suboptimal health. There is evidence suggesting that counseling in stress management-oriented therapeutic interventions (as offered by lifestyle medicine-oriented practitioners) may prevent or reduce the onset, severity, duration, and/or overall burden of stress-related illnesses. Such counseling often involves considerations such as the patient's nutrition, physical activity, interest in/capacity to meditate, drug abuse/cessation, and so on. Unfortunately, lifestyle medicine-oriented approaches to stress management are rarely offered in primary care-the patient care arena wherein such counseling would likely be best received by patients. Would health care outcomes improve if primary care providers offered counseling in both stress management and positive lifestyle choices? The purpose of this article is to provide both primary care practitioners and educators in health care training programs with an introductory overview of epigenetics. An emerging field of science offering insights into how factors such as stress and lifestyle choices interact with our genes in ways that can both positively and negatively impact the various micro (eg, cellular) through macro (eg, physiologic, pathophysiologic) processes that determine our tendencies toward illness or wellness. A deeper understanding of epigenetics, as provided herein, should enable primary care providers and medical educators to more confidently advocate for the primary benefits associated with counseling in both stress reduction and the pursuit of healthy lifestyle choices.

Design, synthesis and bioactivity study of N-salicyloyl tryptamine derivatives as multifunctional agents for the treatment of neuroinflammation

Because of the complex etiology in neuroinflammatory process, the design of multifunctional agents is a potent strategy to cure neuroinflammatory diseases including AD and PD. Herein, based on the combination principles, 23 of N-salicyloyl tryptamine derivatives as multifunctional agents were designed and their new application for anti-neuroinflammation was disclosed. In cyclooxygenase assay, two compounds 3 and 16 displayed extremely preferable COX-2 inhibition than N-salicyloyl tryptamine. In LPS-induced C6 and BV2 cell models, some compounds decreased the production of proinflammatory mediators NO, PGE₂, TNF-α, iNOS, COX-2 and ROS, while increased the production of IL-10. Among them, compound 3 and 16 showed approximately six-fold better inhibition on nitric oxide production than N-salicyloyl tryptamine in C6. Besides, compounds 3, 13 and 16 attenuated the activation of BV2 and C6 cells. More importantly, in vivo, compounds 3 and 16 reduced GFAP and Iba-1 levels in the hippocampus, and displayed neuroprotection in Nissl staining. Besides, both compounds 3 and 16 had high safety (LD₅₀ > 1000 mg/kg). Longer plasma half-life of compounds 3 and 16 than melatonin supported combination strategy. All these results demonstrated that N-salicyloyl tryptamine derivatives are potential anti-neuroinflammation agents for the treatment of neurodegenerative disorder.

Transcardial perfusion is not required to accurately measure cytokines within the brain

BACKGROUND

Cytokines are key signaling molecules within the immune system that regulate a host's response to pathogens and neuronal damage. Aberrant cytokine signaling has been implicated in many neurological diseases. Therefore, accurately measuring cytokine concentrations within the brain is crucial.

NEW METHOD

This study demonstrates that removing blood within brain vasculature via saline perfusion does not alter brain parenchymal cytokine protein concentrations or mRNA expression.

RESULTS

Hippocampal protein and mRNA data demonstrate that brain parenchymal cytokine concentrations do not significantly differ based on the method of euthanasia (i.e., perfusion or no perfusion). These results are consistent within naive and immune challenged mice.

COMPARISON WITH EXISTING METHOD

Due to the potential of cytokine contamination from circulating blood, it is believed that transcardial perfusion is required for accurate measurement of cytokine concentrations and gene expression within the brain. However, our data indicate that cytokine concentrations are unaffected by not perfusing mice with saline prior to tissue collection.

CONCLUSIONS

Brain cytokine concentrations are unaffected by perfusing with saline prior to tissue collection; this holds true regardless of immune status (homeostatic or immune challenged), suggesting that this time-consuming step may be unnecessary.

Neuroinflammation and Neurogenesis in Alzheimer's Disease and Potential Therapeutic Approaches

In adult brain, new neurons are generated throughout adulthood in the subventricular zone and the dentate gyrus; this process is commonly known as adult neurogenesis. The regulation or modulation of adult neurogenesis includes various intrinsic pathways (signal transduction pathway and epigenetic or genetic modulation pathways) or extrinsic pathways (metabolic growth factor modulation, vascular, and immune system pathways). Altered neurogenesis has been identified in Alzheimer's disease (AD), in both human AD brains and AD rodent models. The exact mechanism of the dysregulation of adult neurogenesis in AD has not been completely elucidated. However, neuroinflammation has been demonstrated to alter adult neurogenesis. The presence of various inflammatory components, such as immune cells, cytokines, or chemokines, plays a role in regulating the survival, proliferation, and maturation of neural stem cells. Neuroinflammation has also been considered as a hallmark neuropathological feature of AD. In this review, we summarize current, state-of-the art perspectives on adult neurogenesis, neuroinflammation, and the relationship between these two phenomena in AD. Furthermore, we discuss the potential therapeutic approaches, focusing on the anti-inflammatory and proneurogenic interventions that have been reported in this field.

The role of anxiety in the integrative memory model

We suggest that the inclusion of anxiety, as one relevant mood factor, could enhance the implementation of the integrative memory model in research and the clinic. The role of anxiety in Alzheimer's disease neuroanatomy, symptomology, and progression is used as an example. Customization of the integrative memory model can establish strong foundations for pathology-specific models of memory deficits, enhancing the development of precision medicine applications.

Association of anxiety with subcortical amyloidosis in cognitively normal older adults

Late-life anxiety has been associated with increased progression from normal cognition to amnestic MCI, suggesting that anxiety may be a neuropsychiatric symptom of Alzheimer's disease (AD) pathological changes and a possible marker of anatomical progression in preclinical AD. This study examined whether cortical or subcortical amyloidosis, indicating earlier or later stages of preclinical AD, was associated with greater self-reported anxiety among 118 cognitively normal volunteers, aged 65-90 years, and whether this association was stronger in APOEε4 carriers. Participants underwent Pittsburgh Compound B Positron Emission Tomography (PiB-PET) to assess fibrillar amyloid-β burden in cortical and subcortical regions, and measurement of anxiety using the Hospital Anxiety and Depression Scale-anxiety subscale. Higher PiB-PET measures in the subcortex (striatum, amygdala, and thalamus), but not in the cortex, were associated with greater anxiety, adjusting for demographics, cognition, and depression. Findings were similar using a cortico-striatal staging system and continuous PET measurements. Anxiety was highest in APOEε4 carriers with subcortical amyloidosis. This work supports in vivo staging of amyloid-β deposition in both cortical and subcortical regions as a promising approach to the study of neuropsychiatric symptoms such as anxiety in cognitively normal older individuals. Elevated anxiety symptoms in combination with high-risk biological factors such as APOEε4 and subcortical amyloid-β may identify participants closest to MCI for secondary prevention trials.

Alleviation of symptoms of Alzheimer's disease by diminishing Aβ neurotoxicity and neuroinflammation

Alzheimer's disease (AD) is one of the most prevailing neurodegenerative illnesses in the elderly. Accumulation of amyloid-β peptide (Aβ) and inflammation play critical roles in the pathogenesis and development of AD. Multi-target drugs may interdict the progress of AD through a synergistic mechanism. A neuromodulator, 2-((1H-benzo[d]imidazole-2-yl)methoxy)benzoic acid (BIBA), consisting of an Aβ-targeting group and a derivative of anti-inflammatory aspirin was designed as a potential anti-AD agent. BIBA exhibits a remarkable inhibitory effect on the self- and metal-induced Aβ aggregations and shows outstanding anti-inflammatory activity simultaneously. The neurotoxicity of Aβ aggregates is attenuated, and the production of pro-inflammatory cytokines (PICs), such as IL-6, IL-1β and TNF-α, in microglia stimulated by lipopolysaccharide (LPS) or Aβ is reduced. Owing to the synergy between the inhibition of Aβ oligomerization and downregulation of PICs, BIBA markedly prolongs the lifespan and relieves the Aβ-induced paralysis of Aβ-transgenic Caenorhabditis elegans, thus showing the potential to ameliorate the symptoms of AD through inhibiting Aβ neurotoxicity and deactivating microglia. These findings demonstrate that both Aβ aggregation and neuroinflammation are therapeutic targets for anti-AD drugs, and dual-functional agents that integrate anti-Aβ and anti-inflammatory capabilities have great advantages over the traditional single-target agents for AD treatment.

A Microglia Sublineage Protects from Sex-Linked Anxiety Symptoms and Obsessive Compulsion

Aberrant microglia activity is associated with many neurological and psychiatric disorders, yet our knowledge about the pathological mechanisms is incomplete. Here, we describe a genetically defined microglia sublineage in mice which has the ability to suppress obsessive compulsion and anxiety symptoms. These microglia derive from precursors expressing the transcription factor Hoxb8. Selective ablation of Hoxb8-lineage microglia or the Hoxb8 gene revealed that dysfunction in this cell type causes severe over-grooming and anxiety-like behavior and stress responses. Moreover, we show that the severity of the pathology is set by female sex hormones. Together, our findings reveal that different microglia lineages have distinct functions. In addition, our data suggest a mechanistic link between biological sex and genetics, two major risk factors for developing anxiety and related disorders in humans.

Corticotropin releasing factor-binding protein (CRF-BP) as a potential new therapeutic target in Alzheimer's disease and stress disorders

Alzheimer's disease is the most common cause of dementia and one of the most complex human neurodegenerative diseases. Numerous studies have demonstrated a critical role of the environment in the pathogenesis and pathophysiology of the disease, where daily life stress plays an important role. A lot of epigenetic studies have led to the conclusion that chronic stress and stress-related disorders play an important part in the onset of neurodegenerative disorders, and an enormous amount of research yielded valuable discoveries but has so far not led to the development of effective treatment strategies for Alzheimer's disease. Corticotropin-releasing factor (CRF) is one of the major hormones and at the same time a neuropeptide acting in stress response. Deregulation of protein levels of CRF is involved in the pathogenesis of Alzheimer's disease, but little is known about the precise roles of CRF and its binding protein, CRF-BP, in neurodegenerative diseases. In this review, we summarize the key evidence for and against the involvement of stress-associated modulation of the CRF system in the pathogenesis of Alzheimer's disease and discuss how recent findings could lead to new potential treatment possibilities in Alzheimer's disease by using CRF-BP as a therapeutic target.

The formative role of microglia in stress-induced synaptic deficits and associated behavioral consequences

Psychological stress can precipitate depression, and emerging preclinical data suggest a link between stress-induced alterations in microglia function and development of depressive-like behaviors. Microglia are highly dynamic, and play an integral role in maintaining neuronal homeostasis and synaptic plasticity. In this capacity, microglial dysfunction represents a compelling avenue through which stress might disrupt neuronal integrity and induce psychopathology. This review examines preclinical and clinical postmortem findings that indicate microglia-neuron interactions contribute to stress-induced synaptic deficits and associated behavioral and cognitive consequences. We focus on pathways that are implicated in microglia-mediated neuronal remodeling, including CSF1-CSF1R, CX3CL1-CX3CR1, and CD11b (CR3)-C3, as well as purinergic signaling via P2RX7 and P2RY12. We also highlight sex differences in stress effects on microglia, and the potential for microglia in the development of sex-specific treatments for depressive disorders.

Calcineurin signaling as a target for the treatment of alcohol abuse and neuroinflammatory disorders

Converging lines of evidence point to a significant role of neuroinflammation in a host of psychiatric conditions, including alcohol use disorder, TBI, and PTSD. A complex interaction of both peripheral and central signaling underlies processes involved in neuroinflammation. Calcineurin is a molecule that sits at the nexus of these processes and has been clearly linked to a number of psychiatric disorders including alcohol use disorder (AUD). Like its role in regulating peripheral immune cells, calcineurin (CN) plays an integral role in processes regulating neuroimmune function and neuroinflammatory processes. Targeting CN or elements of its signaling pathways at critical points may aid in the functional recovery from neuroinflammatory related disorders. In this review we will highlight the role of neuroinflammation and calcineurin signaling in AUD, TBI and stress-induced disorders and discuss recent findings demonstrating a therapeutic effect of immunosuppressant-induced calcineurin inhibition in a pre-clinical model of binge alcohol drinking.