Neuronal driven pre-plaque inflammation in a transgenic rat model of Alzheimer's disease

Inflammatory Cytokines and Cognition in Alzheimer's Disease and Its Prodrome

OBJECTIVE

The aim of this study was to investigate the association between blood levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) and cognitive impairments among elderly individuals.

METHODS

Peripheral concentration of TNF-α and IL-6 were measured in all subjects. To assess individual cognitive function, the Consortium to Establish a Registry for Alzheimer's Disease Neuropsychological Assessment Battery (CERAD-NP) was used, and standardized scores (z-scores) were calculated for each test. Cytokine levels were compared between the diagnostic groups, and correlations between blood inflammatory factor levels and z-scores were analyzed.

RESULTS

The 37 participants included 8 patients with Alzheimer's disease (AD), 15 subjects with mild cognitive impairment (MCI), and 14 cognitively healthy controls. TNF-α and IL-6 levels were higher in patients with AD than in healthy controls. TNF-α levels were higher in the AD group than in the MCI group. However, after adjusting for age, the associations between diagnosis and TNF-α and IL-6 were not significant. The higher the plasma IL-6 level, the lower the z-scores on the Boston Naming Test, Word List Learning, Word List Recognition, and Constructional Recall. The higher the serum TNF-α level, the lower the z-scores on the Word List Learning and Constructional Recall. Negative correlation between serum TNF-α level and the z-score on Word List Learning remained significant when age was adjusted.

CONCLUSION

The difference in the blood levels of TNF-α and IL-6 between the diagnostic groups may be associated with aging. However, elevated TNF-α levels were associated with worse immediate memory performance, even after adjusting for age.

Brain Microvascular Pericyte Pathology Linking Alzheimer's Disease to Diabetes

The brain microvasculature, which delivers oxygen and nutrients and forms a critical barrier protecting the central nervous system via capillaries, is deleteriously affected by both Alzheimer's disease (AD) and type 2 diabetes (T2D). T2D patients have an increased risk of developing AD, suggesting potentially related microvascular pathological mechanisms. Pericytes are an ideal cell type to study for functional links between AD and T2D. These specialized capillary-enwrapping cells regulate capillary density, lumen diameter, and blood flow. Pericytes also maintain endothelial tight junctions to ensure blood-brain barrier integrity, modulation of immune cell extravasation, and clearance of toxins. Changes in these phenomena have been observed in both AD and T2D, implicating "pericyte pathology" as a common feature of AD and T2D. This review examines the mechanisms of AD and T2D from the perspective of the brain microvasculature, highlighting how pericyte pathology contributes to both diseases. Our review identifies voids in understanding how AD and T2D negatively impact the brain microvasculature and suggests future studies to examine the intersections of these diseases.

Neuroinflammation, cerebrovascular dysfunction and diurnal cortisol biomarkers in a memory clinic cohort: Findings from the Co-STAR study

Cortisol dysregulation, neuroinflammation, and cerebrovascular dysfunction are biological processes that have been separately shown to be affected in Alzheimer's disease (AD). Here, we aimed to identify biomarker signatures reflecting these pathways in 108 memory clinic patients with subjective cognitive decline (SCD, N = 40), mild cognitive impairment (MCI, N = 39), and AD (N = 29). Participants were from the well-characterized Cortisol and Stress in Alzheimer's Disease (Co-STAR) cohort, recruited at Karolinska University Hospital. Salivary diurnal cortisol measures and 41 CSF proteins were analyzed. Principal component analysis was applied to identify combined biosignatures related to AD pathology, synaptic loss, and neuropsychological assessments, in linear regressions adjusted for confounders, such as age, sex, education and diagnosis. We found increased CSF levels of C-reactive protein (CRP), interferon γ-inducible protein (IP-10), thymus and activation-regulated chemokine (TARC), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) in MCI patients. Further, markers of cortisol dysregulation (flattened salivary cortisol awakening response and flattened cortisol slope) correlated with increased levels of placental growth factor (PlGF), IP-10, and chitinase 3-like 1 (YKL-40) in the total cohort. A biosignature composed of cortisol awakening response, cortisol slope, and CSF IL-6 was downregulated in AD patients. Moreover, biomarker signatures reflecting overlapping pathophysiological processes of neuroinflammation and vascular injury were associated with AD pathology, synaptic loss, and worsened processing speed. Our findings suggest an early dysregulation of immune and cerebrovascular processes during the MCI stage and provide insights into the interrelationship of chronic stress and neuroinflammation in AD.

Metabolic and Immune System Dysregulation: Unraveling the Connections between Alzheimer's Disease, Diabetes, Inflammatory Bowel Diseases, and Rheumatoid Arthritis

Alzheimer's disease (AD), diabetes mellitus (DM), inflammatory bowel diseases (IBD), and rheumatoid arthritis (RA) are chronic conditions affecting millions globally. Despite differing clinical symptoms, these diseases share pathophysiological mechanisms involving metabolic and immune system dysregulation. This paper examines the intricate connections between these disorders, focusing on shared pathways such as insulin resistance, lipid metabolism dysregulation, oxidative stress, and chronic inflammation. An important aspect is the role of amyloid-beta plaques and tau protein tangles, which are hallmark features of AD. These protein aggregates are influenced by metabolic dysfunction and inflammatory processes similar to those seen in DM, RA, and IBD. This manuscript explores how amyloid and tau pathologies may be exacerbated by shared metabolic and immune dysfunction. Additionally, this work discusses the gut-brain axis and the influence of gut microbiota in mediating disease interactions. Understanding these commonalities opens new avenues for multi-targeted therapeutic approaches that address the root causes rather than merely the symptoms of these conditions. This integrative perspective could lead to more effective interventions and improved patient outcomes, emphasizing the importance of a unified approach in managing these interconnected diseases.

Modeling Alzheimer's disease using human cell derived brain organoids and 3D models

Age-related neurodegenerative diseases, like Alzheimer's disease (AD), are challenging diseases for those affected with no cure and limited treatment options. Functional, human derived brain tissues that represent the diverse genetic background and cellular subtypes contributing to sporadic AD (sAD) are limited. Human stem cell derived brain organoids recapitulate some features of human brain cytoarchitecture and AD-like pathology, providing a tool for illuminating the relationship between AD pathology and neural cell dysregulation leading to cognitive decline. In this review, we explore current strategies for implementing brain organoids in the study of AD as well as the challenges associated with investigating age-related brain diseases using organoid models.

Differential effect of an evolving amyloid and tau pathology on brain phospholipids and bioactive lipid mediators in rat models of Alzheimer-like pathology

BACKGROUND

Brain inflammation contributes significantly to the pathophysiology of Alzheimer's disease, and it is manifested by glial cell activation, increased production of cytokines/chemokines, and a shift in lipid mediators from a pro-homeostatic to a pro-inflammatory profile. However, whether the production of bioactive lipid mediators is affected at earlier stages, prior to the deposition of Aβ plaques and tau hyperphosphorylation, is unknown. The differential contribution of an evolving amyloid and tau pathology on the composition and abundance of membrane phospholipids and bioactive lipid mediators also remains unresolved.

METHODS

In this study, we examined the cortical levels of DHA- and AA-derived bioactive lipid mediators and of membrane phospholipids by liquid chromatography with tandem mass spectrometry in transgenic rat models of the Alzheimer's-like amyloid and tau pathologies at early and advanced pathological stages.

RESULTS

Our findings revealed a complex balance between pro-inflammatory and pro-resolving processes in which tau pathology has a more pronounced effect compared to amyloid pathology. At stages preceding tau misfolding and aggregation, there was an increase in pro-resolving lipid mediators (RVD6 and NPD1), DHA-containing phospholipids and IFN-γ levels. However, in advanced tau pathology displaying NFT-like inclusions, neuronal death, glial activation and cognitive deficits, there was an increase in cytokine and PGD2, PGE2, and PGF2α generation accompanied by a drop in IFN-γ levels. This pathology also resulted in a marked increase in AA-containing phospholipids. In comparison, pre-plaque amyloid pathology already presented high levels of cytokines and AA-containing phospholipids together with elevated RVD6 and NPD1 levels. Finally, Aβ plaque deposition was accompanied by a modest increase in prostaglandins, increased AA-containing phospholipids and reduced DHA-containing phospholipids.

CONCLUSIONS

Our findings suggest a dynamic trajectory of inflammatory and lipid mediators in the evolving amyloid and tau pathologies and support their differing roles on membrane properties and, consequentially, on signal transduction.

Early oxidative stress and DNA damage in Aβ-burdened hippocampal neurons in an Alzheimer's-like transgenic rat model

Oxidative stress is a key contributor to AD pathology. However, the earliest role of pre-plaque neuronal oxidative stress, remains elusive. Using laser microdissected hippocampal neurons extracted from McGill-R-Thy1-APP transgenic rats we found that intraneuronal amyloid beta (iAβ)-burdened neurons had increased expression of genes related to oxidative stress and DNA damage responses including Ercc2, Fancc, Sod2, Gsr, and Idh1. DNA damage was further evidenced by increased neuronal levels of XPD (Ercc2) and γH2AX foci, indicative of DNA double stranded breaks (DSBs), and by increased expression of Ercc6, Rad51, and Fen1, and decreased Sirt6 in hippocampal homogenates. We also found increased expression of synaptic plasticity genes (Grin2b (NR2B), CamkIIα, Bdnf, c-fos, and Homer1A) and increased protein levels of TOP2β. Our findings indicate that early accumulation of iAβ, prior to Aβ plaques, is accompanied by incipient oxidative stress and DSBs that may arise directly from oxidative stress or from maladaptive synaptic plasticity.

Effects of Intravenously Administered Plasma from Exercise-Trained Donors on Microglia and Cytokines in a Transgenic Rat Model of Alzheimer's Disease

Background

Microglia and inflammation play a significant role in Alzheimer's disease (AD). Physical exercise and peripheral signals can influence microglial activity in the brain. Modulating the inflammatory response in the brain may provide therapeutic approaches for AD.

Objective

To assess the effects of intravenously administered blood plasma from exercise-trained donor rats on cognitive function, microglia, and cytokine levels in an AD rat model at two different pathological stages; an early pre-plaque stage and a later stage closer to the emergence of extracellular plaques.

Methods

Male transgenic McGill-R-Thy1-APP rats aged 2 and 5 months received 14 injections over 6 weeks: 1) plasma from exercise-trained rats (ExPlas), 2) plasma from sedentary rats (SedPlas), or 3) saline. Cognitive function was evaluated in a novel object recognition task. Microglia count and morphology were analyzed in cornu ammonis, dentate gyrus, entorhinal cortex, and subiculum. Amyloid plaque number and size were assessed in the rats with the later treatment start. A multiplex assay was used to measure 23 cytokines in cornu ammonis.

Results

In rats treated from 2 months of age, ExPlas and SedPlas increased number and length of microglial branches in cornu ammonis and dentate gyrus compared to saline. Only ExPlas-treated rats exhibited similar changes in subiculum, while entorhinal cortex showed no differences across treatments. Microglia count remained unaffected. In rats treated from 5 months of age, there were no significant differences in microglia count or morphology or the number or size of amyloid plaques in any brain region. Compared to both other treatments in early pre-plaque stage rats, SedPlas increased TNF-α levels. ExPlas upregulated GM-CSF, IL-18, and VEGF, while SedPlas increased IL-10 compared to saline. In later-stage rats, ExPlas upregulated IL-17, and SedPlas upregulated TNF-α compared to saline. There were no effects of treatments on recognition memory.

Conclusions

Intravenous injections of blood plasma from exercise-trained and sedentary donors differentially modulated microglial morphology and cytokine levels in the AD rat model at an early pre-plaque stage of pathology. Exercised plasma may reduce proinflammatory TNF-α signaling and promote microglial responses to early Aβ accumulation but the lack of treatment effects in the later-stage rats emphasizes the potential importance of treatment timing.

Important roles of linoleic acid and α-linolenic acid in regulating cognitive impairment and neuropsychiatric issues in metabolic-related dementia

Metabolic syndrome (MetS), which is characterized by insulin resistance, high blood glucose, obesity, and dyslipidemia, is known to increase the risk of dementia accompanied by memory loss and depression. The direct pathways and specific mechanisms in the central nervous system (CNS) for addressing fatty acid imbalances in MetS have not yet been fully elucidated. Among polyunsaturated acids, linoleic acid (LA, n6-PUFA) and α-linolenic acid (ALA, n3-PUFA), which are two essential fatty acids that should be provided by food sources (e.g., vegetable oils and seeds), have been reported to regulate various cellular mechanisms including apoptosis, inflammatory responses, mitochondrial biogenesis, and insulin signaling. Furthermore, inadequate intake of LA and ALA is reported to be involved in neuropathology and neuropsychiatric diseases as well as imbalanced metabolic conditions. Herein, we review the roles of LA and ALA on metabolic-related dementia focusing on insulin resistance, dyslipidemia, synaptic plasticity, cognitive function, and neuropsychiatric issues. This review suggests that LA and ALA are important fatty acids for concurrent treatment of both MetS and neurological problems.

Early treatment with an M1 and sigma-1 receptor agonist prevents cognitive decline in a transgenic rat model displaying Alzheimer-like amyloid pathology

The application of the selective allosteric M1 muscarinic and sigma-1 receptor agonist, AF710B (aka ANAVEX3-71), has shown to attenuate Alzheimer's disease-like hallmarks in McGill-R-Thy1-APP transgenic rats when administered at advanced pathological stages. It remains unknown whether preventive treatment strategies applying this compound may be equally effective. We tested whether daily oral administration of AF710B (10 µg/kg) in 7-month-old, preplaque, McGill-R-Thy1-APP rats for 7 months, followed by a 4-week washout period, could prevent Alzheimer's disease-like pathological hallmarks. Long-term AF710B treatment prevented the cognitive impairment of McGill-R-Thy1-APP rats. The effect was accompanied by a reduction in the number of amyloid plaques in the hippocampus and the levels of Aβ42 and Aβ40 peptides in the cerebral cortex. AF710B treatment also reduced microglia and astrocyte recruitment toward CA1 hippocampal Aβ-burdened neurons compared to vehicle-treated McGill-R-Thy1-APP rats, also altering the inflammatory cytokines profile. Lastly, AF710B treatment rescued the conversion of brain-derived neurotrophic factor precursor to its mature and biologically active form. Overall, these results suggest preventive and disease-modifying properties of the compound.

The Effect of Fat Intake with Increased Omega-6-to-Omega-3 Polyunsaturated Fatty Acid Ratio in Animal Models of Early and Late Alzheimer's Disease-like Pathogenesis

This work aims to clarify the effect of dietary polyunsaturated fatty acid (PUFA) intake on the adult brain affected by amyloid pathology. McGill-R-Thy1-APP transgenic (Tg) rat and 5xFAD Tg mouse models that represent earlier or later disease stages were employed. The animals were exposed to a control diet (CD) or an HFD based on corn oil, from young (rats) or adult (mice) ages for 24 or 10 weeks, respectively. In rats and mice, the HFD impaired reference memory in wild-type (WT) animals but did not worsen it in Tg, did not cause obesity, and did not increase triglycerides or glucose levels. Conversely, the HFD promoted stronger microglial activation in Tg vs. WT rats but had no effect on cerebral amyloid deposition. IFN-γ, IL-1β, and IL-6 plasma levels were increased in Tg rats, regardless of diet, while CXCL1 chemokine levels were increased in HFD-fed mice, regardless of genotype. Hippocampal 3-nitrotyrosine levels tended to increase in HFD-fed Tg rats but not in mice. Overall, an HFD with an elevated omega-6-to-omega-3 ratio as compared to the CD (25:1 vs. 8.4:1) did not aggravate the outcome of AD regardless of the stage of amyloid pathology, suggesting that many neurobiological processes relevant to AD are not directly dependent on PUFA intake.

Prevention of Alzheimer Pathology by Blocking Neuregulin Signaling on Microglia

Plaque formation, microglial activation, and synaptic loss are pathologic hallmarks of Alzheimer's disease; however, removing plaques has had little clinical benefit. Here, we show that neuregulin-1, a glial growth factor, induces inflammatory cytokines and promotes phagocytic activity in vitro and augments microglial activation and plaque formation in 5XFAD Alzheimer's mice. Brain-specific targeting of neuregulin-1 by intraventricular delivery of a novel neuregulin-1 fusion protein antagonist, GlyB4, significantly alters microglial morphology and function to a nonpathogenic morphology in early-stage 5XFAD mice and prevents plaques from forming. Once plaques have already formed, GlyB4 reduces new plaque formation and prevents synaptic loss. Selective, targeted disruption of neuregulin-1 signaling on brain microglia with GlyB4 could be a novel "upstream" approach to slow or stop disease progression in Alzheimer's disease.

Alzheimer's Disease-like Pathological Features in the Dorsal Hippocampus of Wild-Type Rats Subjected to Methionine-Diet-Evoked Mild Hyperhomocysteinaemia

Multifactorial interactions, including nutritional state, likely participate in neurodegeneration's pathogenesis and evolution. Dysregulation in methionine (Met) metabolism could lead to the development of hyperhomocysteinaemia (hHcy), playing an important role in neuronal dysfunction, which could potentially lead to the development of Alzheimer's disease (AD)-like pathological features. This study combines proton magnetic resonance spectroscopy (1H MRS) with immunohistochemical analysis to examine changes in the metabolic ratio and histomorphological alterations in the dorsal rat hippocampus (dentate gyrus-DG) subjected to a high Met diet. Male Wistar rats (420-480 g) underwent hHcy evoked by a Met-enriched diet (2 g/kg of weight/day) lasting four weeks. Changes in the metabolic ratio profile and significant histomorphological alterations have been found in the DG of hHcy rats. We have detected increased morphologically changed neurons and glial cells with increased neurogenic markers and apolipoprotein E positivity parallel with a diminished immunosignal for the N-Methyl-D-Aspartate receptor 1 in hHcy animals. A Met diet induced hHcy, likely via direct Hcy neurotoxicity, an interference with one carbon unit metabolism, and/or epigenetic regulation. These conditions lead to the progression of neurodegeneration and the promotion of AD-like pathological features in the less vulnerable hippocampal DG, which presents a plausible therapeutic target.

Emerging Roles of Cells and Molecules of Innate Immunity in Alzheimer's Disease

The inflammatory response that marks Alzheimer's disease (neuroinflammation) is considered a double-edged sword. Microglia have been shown to play a protective role at the beginning of the disease. Still, persistent harmful stimuli further activate microglia, inducing an exacerbating inflammatory process which impairs β-amyloid peptide clearance capability and leads to neurotoxicity and neurodegeneration. Moreover, microglia also appear to be closely involved in the spread of tau pathology. Soluble TREM2 also represents a crucial player in the neuroinflammatory processes. Elevated levels of TREM2 in cerebrospinal fluid have been associated with increased amyloid plaque burden, neurodegeneration, and cognitive decline in individuals with Alzheimer's disease. Understanding the intricate relationship between innate immunity and Alzheimer's disease will be a promising strategy for future advancements in diagnosis and new therapeutic interventions targeting innate immunity, by modulating its activity. Still, additional and more robust studies are needed to translate these findings into effective treatments. In this review, we focus on the role of cells (microglia, astrocytes, and oligodendrocytes) and molecules (TREM2, tau, and β-amyloid) of the innate immune system in the pathogenesis of Alzheimer's disease and their possible exploitation as disease biomarkers and targets of therapeutical approaches.

Do Sleep Disturbances have a Dual Effect on Alzheimer's Disease?

Sleep disturbances and Alzheimer's disease have deleterious effects on various physiological and cognitive functions including synaptic plasticity, oxidative stress, neuroinflammation, and memory. In addition, clock genes expression is significantly altered following sleep disturbances, which may be involved in the pathogenesis of Alzheimer's disease. In this review article, we aimed to discuss the role of sleep disturbances and Alzheimer's disease in the regulation of synaptic plasticity, oxidative stress, neuroinflammation, and clock genes expression. Also, we aimed to find significant relationships between sleep disturbances and Alzheimer's disease in the modulation of these mechanisms. We referred to the controversial effects of sleep disturbances (particularly those related to the duration of sleep deprivation) on the modulation of synaptic function and neuroinflammation. We aimed to know that, do sleep disturbances have a dual effect on the progression of Alzheimer's disease? Although numerous studies have discussed the association between sleep disturbances and Alzheimer's disease, the new point of this study was to focus on the controversial effects of sleep disturbances on different biological functions, and to evaluate the potential dualistic role of sleep disturbances in the pathogenesis of Alzheimer's disease.

The Fuzzy Border between the Functional and Dysfunctional Effects of Beta-Amyloid: A Synaptocentric View of Neuron-Glia Entanglement

Recent observations from clinical trials using monoclonal antibodies against Aβ seem to suggest that Aβ-targeting is modestly effective and not sufficiently based on an effective challenge of the role of Aβ from physiological to pathological. After an accelerated approval procedure for aducanumab, and more recently lecanemab, their efficacy and safety remain to be fully defined despite previous attempts with various monoclonal antibodies, and both academic institutions and pharmaceutical companies are actively searching for novel treatments. Aβ needs to be clarified further in a more complicated context, taking into account both its accumulation and its biological functions during the course of the disease. In this review, we discuss the border between activities affecting early, potentially reversible dysfunctions of the synapse and events trespassing the threshold of inflammatory, self-sustaining glial activation, leading to irreversible damage. We detail a clear understanding of the biological mechanisms underlying the derangement from function to dysfunction and the switch of the of Aβ role from physiological to pathological. A picture is emerging where the optimal therapeutic strategy against AD should involve a number of allied molecular processes, displaying efficacy not only in reducing the well-known AD pathogenesis players, such as Aβ or neuroinflammation, but also in preventing their adverse effects.

Type 2 Diabetes and Alzheimer's Disease: The Emerging Role of Cellular Lipotoxicity

Type 2 diabetes (T2D) and Alzheimer's diseases (AD) represent major health issues that have reached alarming levels in the last decades. Although growing evidence demonstrates that AD is a significant comorbidity of T2D, and there is a ~1.4-2-fold increase in the risk of developing AD among T2D patients, the involvement of possible common triggers in the pathogenesis of these two diseases remains largely unknown. Of note, recent mechanistic insights suggest that lipotoxicity could represent the missing ring in the pathogenetic mechanisms linking T2D to AD. Indeed, obesity, which represents the main cause of lipotoxicity, has been recognized as a major risk factor for both pathological conditions. Lipotoxicity can lead to inflammation, insulin resistance, oxidative stress, ceramide and amyloid accumulation, endoplasmic reticulum stress, ferroptosis, and autophagy, which are shared biological events in the pathogenesis of T2D and AD. In the current review, we try to provide a critical and comprehensive view of the common molecular pathways activated by lipotoxicity in T2D and AD, attempting to summarize how these mechanisms can drive future research and open the way to new therapeutic perspectives.

Molecular Imaging of Neuroinflammation in Alzheimer's Disease and Mild Cognitive Impairment

Alzheimer's disease (AD) is the most prevalent neurocognitive disorder. Due to the ineffectiveness of treatments targeting the amyloid cascade, molecular biomarkers for neuroinflammation are attracting attention with increasing knowledge about the role of neuroinflammation in the pathogenesis of AD. This chapter will explore the results of studies using molecular imaging for diagnosing AD and mild cognitive impairment (MCI). Because it is critical to interpreting the data to understand which substances are targeted in molecular imaging, this chapter will discuss the two most significant targets, microglia and astrocytes, as well as the best-known radioligands for each. Then, neuroimaging results with PET neuroinflammation imaging will be reviewed for AD and MCI. Although a growing body of evidence has suggested that these molecular imaging biomarkers for neuroinflammation may have a role in the diagnosis of AD and MCI, the findings are inconsistent or cross-sectional, which indicates that it is difficult to apply the contents in practice due to the need for additional study. In particular, because the results of multiple interventions targeting neuroinflammation were inconclusive, molecular imaging markers for neuroinflammation can be used in combination with conventional markers to select appropriate patients for early intervention for neuroinflammation rather than as a single marker.

PET Imaging of Fructose Metabolism in a Rodent Model of Neuroinflammation with 6-[18F]fluoro-6-deoxy-D-fructose

Fluorine-18 labeled 6-fluoro-6-deoxy-D-fructose (6-[¹⁸F]FDF) targets the fructose-preferred facilitative hexose transporter GLUT5, which is expressed predominantly in brain microglia and activated in response to inflammatory stimuli. We hypothesize that 6-[¹⁸F]FDF will specifically image microglia following neuroinflammatory insult. 6-[¹⁸F]FDF and, for comparison, [¹⁸F]FDG were evaluated in unilateral intra-striatal lipopolysaccharide (LPS)-injected male and female rats (50 µg/animal) by longitudinal dynamic PET imaging in vivo. In LPS-injected rats, increased accumulation of 6-[¹⁸F]FDF was observed at 48 h post-LPS injection, with plateaued uptake (60-120 min) that was significantly higher in the ipsilateral vs. contralateral striatum (0.985 ± 0.047 and 0.819 ± 0.033 SUV, respectively; p = 0.002, n = 4M/3F). The ipsilateral-contralateral difference in striatal 6-[¹⁸F]FDF uptake expressed as binding potential (BP_SRTM) peaked at 48 h (0.19 ± 0.11) and was significantly decreased at one and two weeks. In contrast, increased [¹⁸F]FDG uptake in the ipsilateral striatum was highest at one week post-LPS injection (BP_SRTM = 0.25 ± 0.06, n = 4M). Iba-1 and GFAP immunohistochemistry confirmed LPS-induced activation of microglia and astrocytes, respectively, in ipsilateral striatum. This proof-of-concept study revealed an early response of 6-[¹⁸F]FDF to neuroinflammatory stimuli in rat brain. 6-[¹⁸F]FDF represents a potential PET radiotracer for imaging microglial GLUT5 density in brain with applications in neuroinflammatory and neurodegenerative diseases.

Inflammation-Related microRNAs-146a and -155 Are Upregulated in Mild Cognitive Impairment Subjects Among Older Age Population in Montenegro

Background: Pathological and clinical features of Alzheimer’s disease (AD) are in temporal discrepancy and currently accepted clinical tests provide the diagnosis decades after the initial pathophysiological events. In order to enable a more timely detection of AD, research efforts are directed to identification of biomarkers of the early symptomatic stage. Neuroinflammatory signaling pathways and inflammation-related microRNAs (miRNAs) could possibly have a crucial role in AD, making them promising potential biomarkers. Objective: We examined the expression of circulatory miRNAs with a documented role in AD pathophysiology: miR-29a/b, miR-101, miR-125b, miR-146a, and miR-155 in the plasma of AD patients (AD, n = 12), people with mild cognitive impairment (MCI, n = 9), and normocognitive group (CTRL, n = 18). We hypothesized that these miRNA expression levels could correlate with the level of participants’ cognitive decline. Methods: The study participants completed the standardized interview, neurological examination, neuropsychological assessment, and biochemical analyses. miRNA expression levels were assessed by RT-PCR. Results: Neurological and laboratory findings could not account for MCI, but miR-146a and -155 were upregulated in the MCI group compared to the control. miR-146a, known to mediate early neuroinflammatory AD events, was also upregulated in the MCI compared to AD group. ROC curve analysis for miRNA-146a showed 77.8% sensitivity and 94.4% specificity and 66.7% sensitivity and 88.9% specificity for miR-155. Conclusion: Determination of circulatory inflamma-miRs-146a and -155 expression, together with neuropsychological screening, could become a non-invasive tool for detecting individuals with an increased risk for AD, but research on a larger cohort is warranted.

p38 MAPK Is a Major Regulator of Amyloid Beta-Induced IL-6 Expression in Human Microglia

The accumulation of amyloid beta (Aβ) plaques in the brain is a hallmark of Alzheimer's disease (AD) pathology. Microglial activation-mediated neuroinflammation has been implicated in the pathogenesis of AD and the expression levels of interleukin-6 (IL-6) were increased in the brains of AD patients. However, the mechanisms by which IL-6 expression is regulated in human microglia are incompletely understood. Here, we show that Aβ1-40 oligomers (Aβ40) dose-dependently stimulate IL-6 expression in HMC3 human microglial cells. Treatment with Aβ40 promotes the transcription of IL-6 and tumor necrosis factor α (TNFα) mRNAs in both HMC3 and THP-1 cells. Mechanistic studies reveal that Aβ40-induced increase of IL-6 secretion is associated with the activation of p38 mitogen-activated protein kinase (p38 MAPK). Inhibition of p38 MAPK by BIRB 796 or SB202190 abrogates Aβ40-induced increase of IL-6 production. Through analyzing brain specimens, we found that the immunoreactivity for IL-6 and phosphorylated (the activated form) p38 MAPK was markedly higher in microglia of AD patients than in age-matched control subjects. Moreover, our studies identified the co-localization of IL-6 with phosphorylated p38 MAPK in microglia in the cortices of AD patients. Taken together, these results indicate that p38 MAPK is a major regulator of Aβ-induced IL-6 production in human microglia, which suggests that targeting p38 MAPK may represent a new approach to ameliorate Aβ accumulation-induced neuroinflammation in AD.

Pharmacological targeting of microglia dynamics in Alzheimer's disease: Preclinical and clinical evidence

Numerous clinical trials of anti-amyloid agents for Alzheimer's disease (AD) were so far unsuccessful thereby challenging the validity of the amyloid hypothesis. This lack of progress has encouraged researchers to investigate alternative mechanisms in non-neuronal cells, among which microglia represent nowadays an attractive target. Microglia play a key role in the developing brain and contribute to synaptic remodeling in the mature brain. On the other hand, the intimate relationship between microglia and synapses led to the so-called synaptic stripping hypothesis, a process in which microglia selectively remove synapses from injured neurons. Synaptic stripping, along with the induction of a microglia-mediated chronic neuroinflammatory environment, promote the progressive synaptic degeneration in AD. Therefore, targeting microglia may pave the way for a new disease modifying approach. This review provides an overview of the pathophysiological roles of the microglia cells in AD and describes putative targets for pharmacological intervention. It also provides evidence for microglia-targeted strategies in preclinical AD studies and in early clinical trials.

Early loss of locus coeruleus innervation promotes cognitive and neuropathological changes before amyloid plaque deposition in a transgenic rat model of Alzheimer's disease

AIMS

The locus coeruleus (LC) is the main source of noradrenaline (NA) in the mammalian brain and has been found to degenerate during the initial stages of Alzheimer's disease (AD). Recent studies indicate that at late stages of the amyloid pathology, LC-pathological alterations accelerate AD-like pathology progression by interfering with the neuromodulatory and anti-inflammatory properties of NA. However, the impact of LC degeneration at the earliest stages of amyloidosis on the AD-like pathology is not well understood.

METHODS

The LC was lesioned in wild-type (wt) and McGill-R-Thy1-APP transgenic rats (APP tg) by administering N-(2-chloroethyl)-N-ethyl-bromo-benzylamine (DSP4) before amyloid plaque deposition. Cognitive deficits and AD-like neuropathological changes were measured after the LC lesion.

RESULTS

Four months post-treatment, rats displayed a decrease in brain noradrenergic innervation. The LC lesion in APP tg-treated rats enhanced cognitive deficits and decreased hippocampal cholinergic innervation and neurotrophin expression. In addition, the APP tg-treated rats displayed an increased microglial and astroglial cell number in close vicinity to hippocampal amyloid-beta burdened neurons. The recruited microglia showed cellular alterations indicative of an intermediate activation state.

CONCLUSIONS

Our results indicate that early LC demise aggravates the early neuroinflammatory process, cognitive impairments, cholinergic deficits and neurotrophin deregulation at the earliest stages of the human-like brain amyloidosis.

Microglial Endocannabinoid Signalling in AD

Chronic inflammation in Alzheimer's disease (AD) has been recently identified as a major contributor to disease pathogenesis. Once activated, microglial cells, which are brain-resident immune cells, exert several key actions, including phagocytosis, chemotaxis, and the release of pro- or anti-inflammatory mediators, which could have opposite effects on brain homeostasis, depending on the stage of disease and the particular phenotype of microglial cells. The endocannabinoids (eCBs) are pleiotropic bioactive lipids increasingly recognized for their essential roles in regulating microglial activity both under normal and AD-driven pathological conditions. Here, we review the current literature regarding the involvement of this signalling system in modulating microglial phenotypes and activity in the context of homeostasis and AD-related neurodegeneration.

Positive feedback regulation of microglial glucose metabolism by histone H4 lysine 12 lactylation in Alzheimer's disease

The pro-inflammatory activation of microglia is a hallmark of Alzheimer's disease (AD), and this process involves a switch from oxidative phosphorylation (OXPHOS) toward glycolysis. Here, we show how a positive feedback loop in microglia drives AD pathogenesis, and we demonstrate that inhibiting this cycle in microglia can ameliorate Aβ burden and cognitive deficits in an AD mouse model (5XFAD). After first detecting elevated histone lactylation in brain samples from both 5XFAD mice and individuals with AD, we observed that H4K12la levels are elevated in Aβ plaque-adjacent microglia. This lactate-dependent histone modification is enriched at the promoters of glycolytic genes and activates transcription, thereby increasing glycolytic activity. Ultimately, the glycolysis/H4K12la/PKM2 positive feedback loop exacerbates microglial dysfunction in AD. Pharmacologic inhibition of PKM2 attenuated microglial activation, and microglia-specific ablation of Pkm2 improved spatial learning and memory in AD mice. Thus, our study illustrates that disruption of the positive feedback loop may be a potential therapeutic approach for the treatment of AD.

An App knock-in rat model for Alzheimer's disease exhibiting Aβ and tau pathologies, neuronal death and cognitive impairments

A major obstacle in Alzheimer's disease (AD) research is the lack of predictive and translatable animal models that reflect disease progression and drug efficacy. Transgenic mice overexpressing amyloid precursor protein (App) gene manifest non-physiological and ectopic expression of APP and its fragments in the brain, which is not observed in AD patients. The App knock-in mice circumvented some of these problems, but they do not exhibit tau pathology and neuronal death. We have generated a rat model, with three familiar App mutations and humanized Aβ sequence knocked into the rat App gene. Without altering the levels of full-length APP and other APP fragments, this model exhibits pathologies and disease progression resembling those in human patients: deposit of Aβ plaques in relevant brain regions, microglia activation and gliosis, progressive synaptic degeneration and AD-relevant cognitive deficits. Interestingly, we have observed tau pathology, neuronal apoptosis and necroptosis and brain atrophy, phenotypes rarely seen in other APP models. This App knock-in rat model may serve as a useful tool for AD research, identifying new drug targets and biomarkers, and testing therapeutics.

Mitochondrial Deficits With Neural and Social Damage in Early-Stage Alzheimer's Disease Model Mice

Alzheimer’s disease (AD) is the most common neurodegenerative disorder worldwide. Mitochondrial dysfunction is thought to be an early event in the onset and progression of AD; however, the precise underlying mechanisms remain unclear. In this study, we investigated mitochondrial proteins involved in organelle dynamics, morphology and energy production in the medial prefrontal cortex (mPFC) and hippocampus (HIPP) of young (1∼2 months), adult (4∼5 months) and aged (9∼10, 12∼18 months) APP/PS1 mice. We observed increased levels of mitochondrial fission protein, Drp1, and decreased levels of ATP synthase subunit, ATP5A, leading to abnormal mitochondrial morphology, increased oxidative stress, glial activation, apoptosis, and altered neuronal morphology as early as 4∼5 months of age in APP/PS1 mice. Electrophysiological recordings revealed abnormal miniature excitatory postsynaptic current in the mPFC together with a minor connectivity change between the mPFC and HIPP, correlating with social deficits. These results suggest that abnormal mitochondrial dynamics, which worsen with disease progression, could be a biomarker of early-stage AD. Therapeutic interventions that improve mitochondrial function thus represent a promising approach for slowing the progression or delaying the onset of AD.

The Correlation Between Olfactory Test and Hippocampal Volume in Alzheimer's Disease and Mild Cognitive Impairment Patients: A Meta-Analysis

Background: Previous studies have reported that olfactory identification deficits may be the earliest clinical features of Alzheimer's disease (AD). However, the association between odor identification and hippocampal atrophy remains unclear.

Objective: This meta-analysis quantified the correlation between odor identification test scores and hippocampal volume in AD.

Method: A search of the PUBMED, EMBASE, and WEB OF SCIENCE databases was conducted from January 2003 to June 2020 on studies with reported correlation coefficients between olfactory identification score and hippocampal volume in patients with amnestic AD or mild cognitive impairment (MCI). The quality of the studies was assessed using the Newcastle-Ottawa quality assessment scale (NOS). Pooled r-values were combined and computed in R studio.

Results: Seven of 627 original studies on AD/MCI using an olfactory identification test (n = 902) were included. A positive correlation was found between hippocampal volume and olfactory test scores (r = 0.3392, 95% CI: 0.2335–0.4370). Moderator analysis showed that AD and MCI patients were more profoundly correlated than normal controls (AD: r = 0.3959, 95% CI: 0.2605–0.5160; MCI: r = 0.3691, 95% CI: 0.1841–0.5288; NC: r = 0.1305, 95% CI: −0.0447–0.2980). Age difference and patient type were the main sources of heterogeneity in this analysis.

Conclusion: The correlation appears to be more predominant in the cognitive disorder group (including MCI and AD) than in the non-cognitive disorder group. Age is an independent factor that affects the severity of the correlation during disease progression. The mildness of the correlation suggests that olfactory tests may be more accurate when combined with other non-invasive examinations for early detection.

Systematic Review Registration:https://inplasy.com/, identifier INPLASY202140088.

Photobiomodulation Improves the Inflammatory Response and Intracellular Signaling Proteins Linked to Vascular Function and Cell Survival in the Brain of Aged Rats

Photobiomodulation is a non-pharmacological tool widely used to reduce inflammation in many tissues. However, little is known about its effects on the inflammatory response in the aged brain. We conducted the study to examine anti-inflammatory effects of photobiomodulation in aging brains. We used aged rats (20 months old) with control (handled, laser off) or transcranial laser (660 nm wavelength, 100 mW power) treatments for 10 consecutive days and evaluated the level of inflammatory cytokines and chemokines, and the expression and activation of intracellular signaling proteins in the cerebral cortex and the hippocampus. Inflammatory analysis showed that aged rats submitted to transcranial laser treatment had increased levels of IL-1alpha and decreased levels of IL-5 in the cerebral cortex. In the hippocampus, the laser treatment increased the levels of IL-1alpha and decreased levels of IL-5, IL-18, and fractalkine. Regarding the intracellular signaling proteins, a reduction in the ERK and p38 expression and an increase in the STAT3 and ERK activation were observed in the cerebral cortex of aged rats from the laser group. In addition, the laser treatment increased the hippocampal expression of p70S6K, STAT3, and p38 of aged rats. Taken together, our data indicate that transcranial photobiomodulation can improve the inflammatory response and the activation of intracellular signaling proteins linked to vascular function and cell survival in the aged brain.

cGAS- Stimulator of Interferon Genes Signaling in Central Nervous System Disorders

Cytosolic nucleic acid sensors contribute to the initiation of innate immune responses by playing a critical role in the detection of pathogens and endogenous nucleic acids. The cytosolic DNA sensor cyclic-GMP-AMP synthase (cGAS) and its downstream effector, stimulator of interferon genes (STING), mediate innate immune signaling by promoting the release of type I interferons (IFNs) and other inflammatory cytokines. These biomolecules are suggested to play critical roles in host defense, senescence, and tumor immunity. Recent studies have demonstrated that cGAS-STING signaling is strongly implicated in the pathogenesis of central nervous system (CNS) diseases which are underscored by neuroinflammatory-driven disease progression. Understanding and regulating the interactions between cGAS-STING signaling and the nervous system may thus provide an effective approach to prevent or delay late-onset CNS disorders. Here, we present a review of recent advances in the literature on cGAS-STING signaling and provide a comprehensive overview of the modulatory patterns of the cGAS-STING pathway in CNS disorders.

Cognitive and brain cytokine profile of non-demented individuals with cerebral amyloid-beta deposition

BACKGROUND

Brain inflammation has been increasingly associated with early amyloid accumulation in Alzheimer's disease models; however, evidence of its occurrence in humans remains scarce. To elucidate whether amyloid deposition is associated with neuroinflammation and cognitive deficits, we studied brain inflammatory cytokine expression and cognitive decline in non-demented elderly individuals with and without cerebral amyloid-beta deposition.

METHODS

Global cognition, episodic, working, and semantic memory, perceptual speed, visuospatial ability, and longitudinal decline (5.7 ± 3.6 years) in each cognitive domain were compared between elderly individuals (66-79 years) with and without cerebral amyloid-beta deposition. The expression of 20 inflammatory cytokines was analyzed in frozen temporal, parietal, and frontal cortices and compared between older individuals with and without amyloid-beta deposition in each brain region. Correlation analyses were performed to analyze associations between amyloid-beta load, cytokine expression, and cognitive decline.

RESULTS

Individuals with cortical amyloid-beta deposition displayed deficits and a faster rate of cognitive decline in perceptual speed as compared with those individuals without amyloid-beta. This decline was positively associated with cortical amyloid-beta levels. Elderly individuals with amyloid-beta deposition had higher levels of IL-1β, IL-6, and eotaxin-3 in the temporal cortex accompanied by an increase in MCP-1 and IL-1β in the parietal cortex and a trend towards higher levels of IL-1β and MCP-1 in the frontal cortex as compared with age-matched amyloid-free individuals. Brain IL-1β levels displayed a positive association with cortical amyloid burden in each brain region. Finally, differential cytokine expression in each cortical region was associated with cognitive decline.

CONCLUSIONS

Elderly individuals with amyloid-beta neuropathology but no symptomatic manifestation of dementia, exhibit cognitive decline and increased brain cytokine expression. Such observations suggest that increased cytokine expression might be an early event in the Alzheimer's continuum.

Microglia Biomarkers in Alzheimer's Disease

Early detection and clinical diagnosis of Alzheimer's disease (AD) have become an extremely important link in the prevention and treatment of AD. Because of the occult onset, the diagnosis and treatment of AD based on clinical symptoms are increasingly challenged by current severe situations. Therefore, molecular diagnosis models based on early AD pathological markers have received more attention. Among the possible pathological mechanisms, microglia which are necessary for normal brain function are highly expected and have been continuously studied in various models. Several AD biomarkers already exist, but currently there is a paucity of specific and sensitive microglia biomarkers which can accurately measure preclinical AD. Bringing microglia biomarkers into the molecular diagnostic system which is based on fluid and neuroimaging will play an important role in future scientific research and clinical practice. Furthermore, developing novel, more specific, and sensitive microglia biomarkers will make it possible to pharmaceutically target chemical pathways that preserve beneficial microglial functions in response to AD pathology. This review discusses microglia biomarkers in the context of AD.

Vitamin K2 Holds Promise for Alzheimer's Prevention and Treatment

Recent studies have highlighted the importance of vitamin K2 (VK2) in human health. However, there have been no clinical studies investigating the role of VK2 in the prevention or treatment of Alzheimer's disease (AD), a debilitating disease for which currently there is no cure. In reviewing basic science research and clinical studies that have connected VK2 to factors involved in AD pathogenesis, we have found a growing body of evidence demonstrating that VK2 has the potential to slow the progression of AD and contribute to its prevention. In our review, we consider the antiapoptotic and antioxidant effects of VK2 and its impact on neuroinflammation, mitochondrial dysfunction, cognition, cardiovascular health, and comorbidities in AD. We also examine the link between dysbiosis and VK2 in the context of the microbiome's role in AD pathogenesis. Our review is the first to consider the physiological roles of VK2 in the context of AD, and, given the recent shift in AD research toward nonpharmacological interventions, our findings emphasize the timeliness and need for clinical studies involving VK2.

Peripheral and central nervous system alterations in a rat model of inflammatory arthritis

It is consistently reported that in inflammatory arthritis (IA), pain may continue despite well-controlled inflammation, most likely due to interactions between joint pathology and pain pathway alterations. Nervous system alterations have been described, but much remains to be understood about neuronal and central non-neuronal changes in IA. Using a rat model of IA induced by intra-articular complete Freund's adjuvant injection, this study includes a thorough characterization of joint pathology and objectives to identify peripheral innervation changes and alterations in the spinal dorsal horn (DH) that could alter DH excitatory balancing. Male and female rats displayed long-lasting pain-related behavior, but, in agreement with our previous studies, other pathological alterations emerged only at later times. Cartilage vascularization, thinning, and decreased proteoglycan content were not detectable in the ipsilateral cartilage until 4 weeks after complete Freund's adjuvant. Sympathetic and peptidergic nociceptive fibers invaded the ipsilateral cartilage alongside blood vessels, complex innervation changes were observed in the surrounding skin, and ipsilateral nerve growth factor protein expression was increased. In the DH, we examined innervation by peptidergic and nonpeptidergic nociceptors, inhibitory terminal density, the KCl cotransporter KCC2, microgliosis, and astrocytosis. Here, we detected the presence of microgliosis and, interestingly, an apparent loss of inhibitory terminals and decreased expression of KCC2. In conclusion, we found evidence of anatomical, inflammatory, and neuronal alterations in the peripheral and central nervous systems in a model of IA. Together, these suggest that there may be a shift in the balance between incoming and outgoing excitation, and modulatory inhibitory tone in the DH.

Precision Nutrition for Alzheimer's Prevention in ApoE4 Carriers

The ApoE4 allele is the most well-studied genetic risk factor for Alzheimer’s disease, a condition that is increasing in prevalence and remains without a cure. Precision nutrition targeting metabolic pathways altered by ApoE4 provides a tool for the potential prevention of disease. However, no long-term human studies have been conducted to determine effective nutritional protocols for the prevention of Alzheimer’s disease in ApoE4 carriers. This may be because relatively little is yet known about the precise mechanisms by which the genetic variant confers an increased risk of dementia. Fortunately, recent research is beginning to shine a spotlight on these mechanisms. These new data open up the opportunity for speculation as to how carriers might ameliorate risk through lifestyle and nutrition. Herein, we review recent discoveries about how ApoE4 differentially impacts microglia and inflammatory pathways, astrocytes and lipid metabolism, pericytes and blood–brain barrier integrity, and insulin resistance and glucose metabolism. We use these data as a basis to speculate a precision nutrition approach for ApoE4 carriers, including a low-glycemic index diet with a ketogenic option, specific Mediterranean-style food choices, and a panel of seven nutritional supplements. Where possible, we integrate basic scientific mechanisms with human observational studies to create a more complete and convincing rationale for this precision nutrition approach. Until recent research discoveries can be translated into long-term human studies, a mechanism-informed practical clinical approach may be useful for clinicians and patients with ApoE4 to adopt a lifestyle and nutrition plan geared towards Alzheimer’s risk reduction.

Preclinical Marmoset Model for Targeting Chronic Inflammation as a Strategy to Prevent Alzheimer's Disease

Due to the aging population, modern society is facing an increasing prevalence of neurological diseases such as Alzheimer’s disease (AD). AD is an age-related chronic neurodegenerative disorder for which no satisfying therapy exists. Understanding the mechanisms underlying the onset of AD is necessary to find targets for protective treatment. There is growing awareness of the essential role of the immune system in the early AD pathology. Amyloidopathy, the main feature of early-stage AD, has a deregulating effect on the immune function. This is reciprocal as the immune system also affects amyloidopathy. It seems that the inflammatory reaction shows a heterogeneous pattern depending on the stage of the disease and the variation between individuals, making not only the target but also the timing of treatment important. The lack of relevant translational animal models that faithfully reproduce clinical and pathogenic features of AD is a major cause of the delay in developing new disease-modifying therapies and their optimal timing of administration. This review describes the communication between amyloidopathy and inflammation and the possibility of using nonhuman primates as a relevant animal model for preclinical AD research.

From Metabolic Syndrome to Neurological Diseases: Role of Autophagy

Metabolic syndrome is not a single pathology, but a constellation of cardiovascular disease risk factors including: central and abdominal obesity, systemic hypertension, insulin resistance (or type 2 diabetes mellitus), and atherogenic dyslipidemia. The global incidence of Metabolic syndrome is estimated to be about one quarter of the world population; for this reason, it would be desirable to better understand the underlying mechanisms involved in order to develop treatments that can reduce or eliminate the damage caused. The effects of Metabolic syndrome are multiple and wide ranging; some of which have an impact on the central nervous system and cause neurological and neurodegenerative diseases. Autophagy is a catabolic intracellular process, essential for the recycling of cytoplasmic materials and for the degradation of damaged cellular organelle. Therefore, autophagy is primarily a cytoprotective mechanism; even if excessive cellular degradation can be detrimental. To date, it is known that systemic autophagic insufficiency is able to cause metabolic balance deterioration and facilitate the onset of metabolic syndrome. This review aims to highlight the current state of knowledge regarding the connection between metabolic syndrome and the onset of several neurological diseases related to it. Furthermore, since autophagy has been found to be of particular importance in metabolic disorders, the probable involvement of this degradative process is assumed to be responsible for the attenuation of neurological disorders resulting from metabolic syndrome.

Improved Spatial Memory And Neuroinflammatory Profile Changes in Aged Rats Submitted to Photobiomodulation Therapy

Recent evidences have shown the therapeutic potential of transcranial photobiomodulation on traumatic brain injury and Alzheimer's disease. Despite the promising benefits in the brain, little is known about the laser's effects in the absence of pathological conditions. We submitted young (4 months old) and aged (20 months old) rats to transcranial low-level laser and evaluated their exploratory activity and habituation in open field, anxiety in elevated plus maze, spatial memory in Barnes maze, and aversive memory in a step-down inhibitory avoidance task. Additionally, the levels of a panel of inflammatory cytokines and chemokines were quantified in two different brain regions: the cerebral cortex and the hippocampus. Young and aged rats submitted to transcranial laser exhibited better cognitive performance in Barnes maze than did control rats. Transcranial laser therapy decreased cortical levels of GM-CSF, IL-10, MCP-1, LIX, and TNFα in young rats and IL-5 in aged rats. High levels of IL-6, IL-10, and TNF-alpha were found in the cerebral cortex of aged rats submitted to transcranial laser. In the hippocampus, a decrease in IP-10 and fractalkine levels was observed in the aged rats from the laser group when compared to the aged rats from the control group. Our data indicate that transcranial photobiomodulation improves spatial learning and memory and alters the neuroinflammatory profile of young and aged rats' brains.

Evolution of neuroinflammation across the lifespan of individuals with Down syndrome

Epidemiological and experimental studies suggest that a disease-aggravating neuroinflammatory process is present at preclinical stages of Alzheimer's disease. Given that individuals with Down syndrome are at increased genetic risk of Alzheimer's disease and therefore develop the spectrum of Alzheimer's neuropathology in a uniform manner, they constitute an important population to study the evolution of neuroinflammation across the Alzheimer's continuum. Therefore, in this cross-sectional study, we characterized the brain inflammatory profile across the lifespan of individuals with Down syndrome. Microglial morphology and inflammatory cytokine expression were analysed by immunohistochemistry and electrochemiluminescent-based immunoassays in the frontal cortex from foetuses to adults with Down syndrome and control subjects (16 gestational weeks to 64 years), totalling 127 cases. Cytokine expression in mixed foetal primary cultures and hippocampus of adults with Down syndrome, as well as the effects of sex on cytokine expression were also analysed. A higher microglial soma size-to-process length ratio was observed in the frontal cortex of children and young adults with Down syndrome before the development of full-blown Alzheimer's pathology. Moreover, young adults with Down syndrome also displayed increased numbers of rod-like microglia. Increased levels of interleukin-8 and interleukin-10 were observed in children with Down syndrome (1-10 years; Down syndrome n = 5, controls n = 10) and higher levels of interleukin-1β, interleukin-1α, interleukin-6, interleukin-8, interleukin-10, interleukin-15, eotaxin-3, interferon gamma-induced protein 10, macrophage-derived chemokine, and macrophage inflammatory protein-beta, were found in young adults with Down syndrome compared to euploid cases (13-25 years, Down syndrome n = 6, controls n = 24). Increased cytokine expression was also found in the conditioned media of mixed cortical primary cultures from second trimester foetuses with Down syndrome (Down syndrome n = 7, controls n = 7). Older adults with Down syndrome (39-68 years, Down syndrome n = 22, controls n = 16) displayed reduced levels of interleukin-10, interleukin-12p40, interferon-gamma and tumour necrosis factor-alpha. Microglia displayed larger somas and shorter processes. Moreover, an increase in dystrophic microglia and rod-like microglia aligning to neurons harbouring tau pathology were also observed. Sex stratification analyses revealed that females with Down syndrome had increased interleukin-6 and interleukin-8 levels compared to males with Down syndrome. Finally, multivariate projection methods identified specific cytokine patterns among individuals with Down syndrome. Our findings indicate the presence of an early and evolving neuroinflammatory phenotype across the lifespan in Down syndrome, a knowledge that is relevant for the discovery of stage-specific targets and for the design of possible anti-inflammatory trials against Alzheimer's disease in this population.

Neuroinflammation and microglial activation in Alzheimer disease: where do we go from here?

Alzheimer disease (AD) is the most common form of neurodegenerative disease, estimated to contribute 60-70% of all cases of dementia worldwide. According to the prevailing amyloid cascade hypothesis, amyloid-β (Aβ) deposition in the brain is the initiating event in AD, although evidence is accumulating that this hypothesis is insufficient to explain many aspects of AD pathogenesis. The discovery of increased levels of inflammatory markers in patients with AD and the identification of AD risk genes associated with innate immune functions suggest that neuroinflammation has a prominent role in the pathogenesis of AD. In this Review, we discuss the interrelationships between neuroinflammation and amyloid and tau pathologies as well as the effect of neuroinflammation on the disease trajectory in AD. We specifically focus on microglia as major players in neuroinflammation and discuss the spatial and temporal variations in microglial phenotypes that are observed under different conditions. We also consider how these cells could be modulated as a therapeutic strategy for AD.

Milrinone Ameliorates the Neuroinflammation and Memory Function of Alzheimer's Disease in an APP/PS1 Mouse Model

PURPOSE

Alzheimer's disease (AD) is a complex neurodegenerative disorder, which is characterized by memory loss and cognitive deficits. The neuroprotective role of milrinone on the injury of spinal cord or cerebral ischemia-reperfusion has been confirmed. However, the accurate function of milrinone on AD pathogeny is still unclear.

METHODS

APP/PS1 transgenic mouse was used to explore the role of milrinone in behaviour tests, and the effects on histopathologic features of AD such as the formation of neuronal amyloid-β (Aβ) plaque, microglial activation, tau protein hyperphosphorylation, oxidative stress, and neuroinflammation. Lipopolysaccharide (LPS)/Aβ-treated BV-2 cells were used to understand the anti-inflammation mechanism of milrinone on AD in vitro.

RESULTS

Our in vivo results showed that milrinone ameliorates the memory functions of AD mice. Meanwhile, milrinone reduced Aβ deposits, repressed microglial activation and tau protein hyperphosphorylation, attenuated the oxidative stress, and decreased the levels of inflammatory cytokines. The in vitro results demonstrated that milrinone could inhibit the secretion of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α via regulation of NLRP3 inflammasomes and TLR4/MyD88/NF-κB signalling pathway.

CONCLUSION

Overall, milrinone could ameliorate the memory loss and cognitive deficits through repressing the multiple pathological processes of AD, suggesting that milrinone may be an underlying and effective drug for treating AD clinically.

Cerebrospinal Fluid and Blood CX3CL1 as a Potential Biomarker in Early Diagnosis and Prognosis of Dementia

BACKGROUND

A growing body of evidence highlights the crucial role of neuroinflammation and chemokine involvement in cognitive impairment pathophysiology. Fractalkine (CX3CL1) appears to be a relevant causative factor in the development of dementia, particularly at the early stages of the disease. However, limited data are available on the levels of CX3CL1 in the cerebrospinal fluid (CSF) and blood. Additionally, to date, its utility as a biomarker for MCI or AD has not been studied.

OBJECTIVE

The aim of the present study was to evaluate the clinical utility of CX3CL1 in the early diagnosis of cognitive impairment. We also compared the diagnostic usefulness of CX3CL1 with other biomarkers associated with neuroinflammation.

METHODS

A total of 60 patients with cognitive impairment, including 42 patients with AD and 18 subjects with MCI, as well as 20 cognitively healthy controls were enrolled in the study. CSF and blood concentrations of CX3CL1, CCL-2, and YKL-40 were measured by ELISA.

RESULTS

Significantly higher CSF and blood concentrations of CX3CL1 were observed in MCI and AD patients compared to older individuals without cognitive impairment. The increase in the levels of CX3CL1 and YKL-40 in non-demented subjects was associated with MCI. The area under the ROC curve for CX3CL1 in MCI subjects was larger in comparison to classical AD markers.

CONCLUSION

Presented results indicate a crucial role of CX3CL1 in the pathology of cognitive impairment and the potential usefulness of this protein in the early diagnosis of MCI and AD.

Distinct effects of beta-amyloid and tau on cortical thickness in cognitively healthy older adults

INTRODUCTION

Published reports of associations between β-amyloid (Aβ) and cortical integrity conflict. Tau biomarkers may help elucidate the complex relationship between pathology and neurodegeneration in aging.

METHODS

We measured cortical thickness using magnetic resonance imaging, Aβ using Pittsburgh compound B positron emission tomography (PiB-PET), and tau using flortaucipir (FTP)-PET in 125 cognitively normal older adults. We examined relationships among PET measures, cortical thickness, and cognition.

RESULTS

Cortical thickness was reduced in PiB+/FTP+ participants compared to the PiB+/FTP- and PiB-/FTP- groups. Continuous PiB associations with cortical thickness were weak but positive in FTP- participants and negative in FTP+. FTP strongly negatively predicted thickness regardless of PiB status. FTP was associated with memory and cortical thickness, and mediated the association of PiB with memory.

DISCUSSION

Past findings linking Aβ and cortical thickness are likely weak due to opposing effects of Aβ on cortical thickness relative to tau burden. Tau, in contrast to Aβ, is strongly related to cortical thickness and memory.

Connecting the "Dots": From Free Radical Lipid Autoxidation to Cell Pathology and Disease

Our understanding of lipid peroxidation in biology and medicine is rapidly evolving, as it is increasingly implicated in various diseases but also recognized as a key part of normal cell function, signaling, and death (ferroptosis). Not surprisingly, the root and consequences of lipid peroxidation have garnered increasing attention from multiple disciplines in recent years. Here we "connect the dots" between the fundamental chemistry underpinning the cascade reactions of lipid peroxidation (enzymatic or free radical), the reactive nature of the products formed (lipid-derived electrophiles), and the biological targets and mechanisms associated with these products that culminate in cellular responses. We additionally bring light to the use of highly sensitive, fluorescence-based methodologies. Stemming from the foundational concepts in chemistry and biology, these methodologies enable visualizing and quantifying each reaction in the cascade in a cellular and ultimately tissue context, toward deciphering the connections between the chemistry and physiology of lipid peroxidation. The review offers a platform in which the chemistry and biomedical research communities can access a comprehensive summary of fundamental concepts regarding lipid peroxidation, experimental tools for the study of such processes, as well as the recent discoveries by leading investigators with an emphasis on significant open questions.

Selective autophagy as a therapeutic target for neurological diseases

The neurological diseases primarily include acute injuries, chronic neurodegeneration, and others (e.g., infectious diseases of the central nervous system). Autophagy is a housekeeping process responsible for the bulk degradation of misfolded protein aggregates and damaged organelles through the lysosomal machinery. Recent studies have suggested that autophagy, particularly selective autophagy, such as mitophagy, pexophagy, ER-phagy, ribophagy, lipophagy, etc., is closely implicated in neurological diseases. These forms of selective autophagy are controlled by a group of important proteins, including PTEN-induced kinase 1 (PINK1), Parkin, p62, optineurin (OPTN), neighbor of BRCA1 gene 1 (NBR1), and nuclear fragile X mental retardation-interacting protein 1 (NUFIP1). This review highlights the characteristics and underlying mechanisms of different types of selective autophagy, and their implications in various forms of neurological diseases.

Rodent Models of Amyloid-Beta Feature of Alzheimer's Disease: Development and Potential Treatment Implications

Alzheimer's disease (AD) is the most common neurodegenerative disorder worldwide and causes severe financial and social burdens. Despite much research on the pathogenesis of AD, the neuropathological mechanisms remain obscure and current treatments have proven ineffective. In the past decades, transgenic rodent models have been used to try to unravel this disease, which is crucial for early diagnosis and the assessment of disease-modifying compounds. In this review, we focus on transgenic rodent models used to study amyloid-beta pathology in AD. We also discuss their possible use as promising tools for AD research. There is still no effective treatment for AD and the development of potent therapeutics are urgently needed. Many molecular pathways are susceptible to AD, ranging from neuroinflammation, immune response, and neuroplasticity to neurotrophic factors. Studying these pathways may shed light on AD pathophysiology as well as provide potential targets for the development of more effective treatments. This review discusses the advantages and limitations of these models and their potential therapeutic implications for AD.

Therapeutic Strategies Targeting Amyloid-β in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder linked to protein misfolding and aggregation. AD is pathologically characterized by senile plaques formed by extracellular Amyloid-β (Aβ) peptide and Intracellular Neurofibrillary Tangles (NFT) formed by hyperphosphorylated tau protein. Extensive synaptic loss and neuronal degeneration are responsible for memory impairment, cognitive decline and behavioral dysfunctions typical of AD. Amyloidosis has been implicated in the depression of acetylcholine synthesis and release, overactivation of N-methyl-D-aspartate (NMDA) receptors and increased intracellular calcium levels that result in excitotoxic neuronal degeneration. Current drugs used in AD treatment are either cholinesterase inhibitors or NMDA receptor antagonists; however, they provide only symptomatic relief and do not alter the progression of the disease. Aβ is the product of Amyloid Precursor Protein (APP) processing after successive cleavage by β- and γ-secretases while APP proteolysis by α-secretase results in non-amyloidogenic products. According to the amyloid cascade hypothesis, Aβ dyshomeostasis results in the accumulation and aggregation of Aβ into soluble oligomers and insoluble fibrils. The former are synaptotoxic and can induce tau hyperphosphorylation while the latter deposit in senile plaques and elicit proinflammatory responses, contributing to oxidative stress, neuronal degeneration and neuroinflammation. Aβ-protein-targeted therapeutic strategies are thus a promising disease-modifying approach for the treatment and prevention of AD. This review summarizes recent findings on Aβ-protein targeted AD drugs, including β-secretase inhibitors, γ-secretase inhibitors and modulators, α-secretase activators, direct inhibitors of Aβ aggregation and immunotherapy targeting Aβ, focusing mainly on those currently under clinical trials.

Pain-related behavior is associated with increased joint innervation, ipsilateral dorsal horn gliosis, and dorsal root ganglia activating transcription factor 3 expression in a rat ankle joint model of osteoarthritis

Supplemental Digital Content is Available in the Text.

In a rat model of osteoarthritis, we found increased joint sensory and sympathetic innervation and glia changes in dorsal horn, accompanying pain-related behavior onset.

Introduction:

Osteoarthritis (OA)-associated pain is often poorly managed, as our understanding of the underlying pain mechanisms remains limited. The known variability from patient to patient in pain control could be a consequence of a neuropathic component in OA.

Methods:

We used a rat monoiodoacetate model of the ankle joint to study the time-course of the development of pain-related behavior and pathological changes in the joint, dorsal root ganglia (DRG), and spinal cord, and to investigate drug treatments effects.

Results:

Mechanical hypersensitivity and loss of mobility (as assessed by treadmill) were detected from 4 weeks after monoiodoacetate. Cold allodynia was detected from 5 weeks. Using histology and x-ray microtomography, we confirmed significant cartilage and bone degeneration at 5 and 10 weeks. We detected increased nociceptive peptidergic and sympathetic fiber innervation in the subchondral bone and synovium at 5 and 10 weeks. Sympathetic blockade at 5 weeks reduced pain-related behavior. At 5 weeks, we observed, ipsilaterally only, DRG neurons expressing anti-activating transcription factor 3, a neuronal stress marker. In the spinal cord, there was microgliosis at 5 and 10 weeks, and astrocytosis at 10 weeks only. Inhibition of glia at 5 weeks with minocycline and fluorocitrate alleviated mechanical allodynia.

Conclusion:

Besides a detailed time-course of pathology in this OA model, we show evidence of contributions of the sympathetic nervous system and dorsal horn glia to pain mechanisms. In addition, late activating transcription factor 3 expression in the DRG that coincides with these changes provides evidence in support of a neuropathic component in OA pain.

Neurovascular Inflammaging in Health and Disease

Aging is characterized by a chronic low-grade sterile inflammation dubbed as inflammaging, which in part originates from accumulating cellular debris. These, acting as danger signals with many intrinsic factors such as cytokines, are sensed by a network of pattern recognition receptors and other cognate receptors, leading to the activation of inflammasomes. Due to the inflammasome activity-dependent increase in the levels of pro-inflammatory interleukins (IL-1β, IL-18), inflammation is initiated, resulting in tissue injury in various organs, the brain and the spinal cord included. Similarly, in age-related diseases of the central nervous system (CNS), inflammasome activation is a prominent moment, in which cells of the neurovascular unit occupy a significant position. In this review, we discuss the inflammatory changes in normal aging and summarize the current knowledge on the role of inflammasomes and contributing mechanisms in common CNS diseases, namely Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis and stroke, all of which occur more frequently with aging.