Inflammatory process in Alzheimer's Disease

"Cerebral Small Vessel Disease in subclinical and clinical stages, role of inflammation for risk prediction and potential treatment targets, and management strategies"

Stroke and dementia are the most common neurological disorders worldwide. Cerebrovascular disease, particularly cerebral small vessel disease (CSVD) is implicated in both, and the two main types of CSVD (hypertensive vasculopathy and cerebral amyloid angiopathy) account for the majority of cerebrovascular contributions to stroke and dementia. Current knowledge of CSVD may influence treatment decisions and preventive efforts. Although the causes of CSVD are not entirely elucidated, ongoing research of the pathophysiology of CSVD, such as the role of inflammation, is helping identify potential treatment targets, evaluate prediction models and develop preventive strategies. Given the detectability of CSVD in preclinical stages using brain MRI, a long window of opportunity is presented to implement existent preventive measures. This review considers CSVD including its subclinical manifestations detected using brain MRI, clinical manifestations, use of markers of CSVD as predictors of clinical outcomes such as dementia and stroke, and presents potential management strategies when seeing patients with cerebral small vessel disease to reduce its disease burden and clinical consequences. Clinical trials have evaluated some aspects of CSVD treatment and are beginning to recognize CSVD as endpoint in subclinical stages. Future studies will clarify if this approach is able to delay onset of dementia and prevent stroke occurrence, meanwhile implementation of existent recommendations for the prevention and treatment of stroke and dementia may reduce disability and clinical outcomes related to CSVD.

Viscoelastic and ultrastructural characteristics of whole blood and plasma in Alzheimer-type dementia, and the possible role of bacterial lipopolysaccharides (LPS)

Alzheimer-type dementia (AD) is a neurodegenerative disorder and the most common form of dementia. Patients typically present with neuro- and systemic inflammation and iron dysregulation, associated with oxidative damage that reflects in hypercoagulability. Hypercoagulability is closely associated with increased fibrin(ogen) and in AD patients fibrin(ogen) has been implicated in the development of neuroinflammation and memory deficits. There is still no clear reason precisely why (a) this hypercoagulable state, (b) iron dysregulation and (c) increased fibrin(ogen) could together lead to the loss of neuronal structure and cognitive function. Here we suggest an alternative hypothesis based on previous ultrastructural evidence of the presence of a (dormant) blood microbiome in AD. Furthermore, we argue that bacterial cell wall components, such as the endotoxin lipopolysaccharide (LPS) of Gram-negative strains, might be the cause of the continuing and low-grade inflammation, characteristic of AD. Here, we follow an integrated approach, by studying the viscoelastic and ultrastructural properties of AD plasma and whole blood by using scanning electron microscopy, Thromboelastography (TEG^®) and the Global Thrombosis Test (GTT^®). Ultrastructural analysis confirmed the presence and close proximity of microbes to erythrocytes. TEG^® analysis showed a hypercoagulable state in AD. TEG^® results where LPS was added to naive blood showed the same trends as were found with the AD patients, while the GTT^® results (where only platelet activity is measured), were not affected by the added LPS, suggesting that LPS does not directly impact platelet function. Our findings reinforce the importance of further investigating the role of LPS in AD.

L-3-n-butylphthalide Rescues Hippocampal Synaptic Failure and Attenuates Neuropathology in Aged APP/PS1 Mouse Model of Alzheimer's Disease

AIMS

Our previous studies showed that L-3-n-butylphthalide (L-NBP), an extract from seeds of Apium graveolens Linn (Chinese celery), improved cognitive ability in animal models of cerebral ischemia, vascular dementia, and Alzheimer's disease (AD). It is well known that cognitive deficit of AD is caused by synaptic dysfunction. In this study, we investigated the effect of L-NBP on hippocampal synaptic function in APP/PS1 AD transgenic mice and related mechanisms.

METHODS

Eighteen-month-old APP/PS1 transgenic (Tg) mice were administrated 15 mg/kg L-NBP by oral gavage for 3 months. Synaptic morphology and the thickness of postsynaptic density (PSD) in hippocampal neurons were investigated by electron microscope. The dendritic spines, Aβ plaques, and glial activation were detected by staining. The expressions of synapse-related proteins were observed by Western blotting.

RESULTS

L-NBP treatment significantly increased the number of synapses and apical dendritic thorns and the thickness of PSD, increased the expression levels of synapse-associated proteins including PSD95, synaptophysin (SYN), β-catenin, and GSK-3β, and attenuated Aβ plaques and neuroinflammatory responses in aged APP/PS1 Tg mice.

CONCLUSION

L-NBP may restore synaptic and spine function in aged APP Tg mice through inhibiting Aβ plaques deposition and neuroinflammatory response. Wnt/β-catenin signaling pathway may be involved in L-NBP-related restoration of synaptic function.

Arabidopsis thaliana extracts optimized for polyphenols production as potential therapeutics for the APOE-modulated neuroinflammation characteristic of Alzheimer's disease in vitro

Although the cause of Alzheimer's disease (AD) is unknown, glial-induced neuroinflammation is an early symptom. Familial AD is caused by increases in amyloid-beta (Aβ) peptide, particularly soluble oligomeric (oAβ), considered a proximal neurotoxin and neuroinflammatory stimuli. APOE4, a naturally occurring genotype of APOE, is the greatest genetic risk factor for AD; increasing risk up to 12-fold compared to APOE3 and APOE2. oAβ-induced neuroinflammation is greater with APOE4 compared to APOE3 and APOE2. As sinapates and flavonoids have anti-inflammatory properties, a protocol was developed for optimizing polyphenol production in seedlings of Arabidopsis thaliana (A. thaliana). Three mutants (cop1, prn1, xpf3) were identified, and the extracts treated with liver microsomes to mimic physiological metabolism, with HPLC and MS performed on the resulting metabolites for peak identification. These extracts were used to treat primary glial cells isolated from human APOE-targeted-replacement (APOE-TR) and APOE-knock-out (KO) mice, with neuroinflammation induced by lipopolysaccharide (LPS) or oAβ. The dose-response data for TNFα secretion demonstrate the followed the order: APOE-KO > APOE4 > APOE3 > APOE2, with xpf3 the most effective anti-neuroinflammatory across APOE genotypes. Thus, the plant-based approach described herein may be particularly valuable in treating the APOE4-induced neuroinflammatory component of AD risk.

Selective Brain-Targeted Antagonism of p38 MAPKα Reduces Hippocampal IL-1β Levels and Improves Morris Water Maze Performance in Aged Rats

Background: P38 mitogen activated protein kinase (MAPK) α modulates microglia-mediated inflammatory responses and a number of neuronal physiological processes.

Objective: To evaluate pre-clinically the pharmacological effects in the brain of p38 MAPKα inhibition with a brain-penetrant specific chemical antagonist.

Methods: VX-745, a blood-brain barrier penetrant, highly selective p38 MAPKα inhibitor, and clinical stage investigational drug, was utilized. Initially, a pilot study in 26-month-old Tg2576 mice was conducted. Subsequently, a definitive dose-response study was conducted in aged (20–22 months) rats with identified cognitive deficits; n = 15 per group: vehicle, 0.5, 1.5, and 4.5 mg/kg VX-745 by oral gavage twice daily for 3 weeks. Assessments in aged rats included IL-1β, PSD-95, TNFα protein levels in hippocampus; and Morris water maze (MWM) test for cognitive performance.

Results: Drug effect could not be assessed in Tg2576 mice, as little inflammation was evident. In cognitively-impaired aged rats, VX-745 led to significantly improved performance in the MWM and significant reduction in hippocampal IL-1β protein levels, though the effects were dissociated as the MWM effect was evident at a lower dose level than that required to lower IL-1β. Drug concentration-effect relationships and predicted human doses were determined.

Conclusions: Selective inhibition of p38 MAPKα with VX-745 in aged rats reduces hippocampal IL-1β levels and improves performance in the MWM. As the two effects occur at different dose levels, the behavioral effect appears to be via a mechanism that is independent of reducing cytokine production. The predicted human doses should minimize risks of systemic toxicity.

Serum-based protein profiles of Alzheimer's disease and mild cognitive impairment in elderly Hispanics

AIM

To describe the biomarker profiles in elderly Panamanians diagnosed with Alzheimer's disease (AD), mild cognitive impairment (MCI) or no impairment using serum-based biomarkers.

METHODS

Twenty-four proteins were analyzed using an electrochemiluminescence-based multiplex biomarker assay platform. A biomarker profile was generated using random forest analyses.

RESULTS

Two proteins differed among groups: IL-18 and T-lymphocyte-secreted protein I-309. The AD profile was highly accurate and independent of age, gender, education and Apolipoprotein E ε4 status. AD and MCI profiles had substantial overlap among the top markers, suggesting common functions in AD and MCI but differences in their relative importance.

CONCLUSION

Our results underscore the potential influence of genetic and environmental differences within Hispanic populations on the proteomic profile of AD.

Autologous transplantation of intestine-isolated glia cells improves neuropathology and restores cognitive deficits in β amyloid-induced neurodegeneration

Alzheimer's disease (AD) is characterized by chronic deposition of β-amyloid (Aβ) in the brain, progressive neurodegeneration and consequent cognitive and behavioral deficits that typify the disease. Astrocytes are pivotal in this process because they are activated in the attempt to digest Aβ which starts a neuroinflammatory response that further contributes to neurodegeneration. The intestine is a good source of astrocytes-like cells-referred to as enteric glial cells (EGCs). Here we show that the autologous transplantation of EGCs into the brain of Aβ-injected rats arrested the development of the disease after their engraftment. Transplanted EGCs showed anti-amyloidogenic activity, embanked Aβ-induced neuroinflammation and neurodegeneration, and released neutrophic factors. The overall result was the amelioration of the pathological hallmarks and the cognitive and behavioral deficits typical of Aβ-associated disease. Our data indicate that autologous EGCs transplantation may provide an efficient alternative for applications in cell-replacement therapies to treat neurodegeneration in AD.

GDF15/MIC1 and MMP9 Cerebrospinal Fluid Levels in Parkinson's Disease and Lewy Body Dementia

Based on animal and ex-vivo experiments, Growth/Differentiation Factor-15 (GDF15, also called Macrophage Inhibitory Cytokine-1, MIC1), a member of the transforming growth factor-beta family, and Matrix Metalloproteinase-9 (MMP9), a member of the matrix metalloprotease family may be potential markers for Lewy body disorders, i.e. Parkinson’s disease with (PDD) and without dementia (PDND) and Lewy body dementia (DLB). GDF15 has a prominent role in development, cell proliferation, differentiation, and repair, whereas MMP9 degrades, as a proteolytic enzyme, components of the extracellular matrix. In this study, cerebrospinal fluid GDF15 and MMP9 levels of 59 PDND, 17 PDD and 23 DLB patients, as well as of 95 controls were determined, and associated with demographic, clinical and biochemical parameters. Our analysis confirmed the already described association of GDF15 levels with age and gender. Corrected GDF15 levels were significantly higher in PDD than in PDND patients, and intermediate in DLB patients. Within Lewy body disorders, GDF15 levels correlated positively with age at onset of Parkinsonism and dementia, Hoehn & Yahr stage and cerebrospinal fluid t-Tau and p-Tau levels, and negatively with the Mini Mental State Examination. Remarkably, it does not relevantly correlate with disease duration. MMP9 was not relevantly associated with any of these parameters. Cerebrospinal GDF15, but not MMP9, may be a potential marker of and in Lewy body disorders.

An overview on therapeutics attenuating amyloid β level in Alzheimer's disease: targeting neurotransmission, inflammation, oxidative stress and enhanced cholesterol levels

Alzheimer's disease (AD) is the most common underlying cause of dementia, and novel drugs for its treatment are needed. Of the different theories explaining the development and progression of AD, "amyloid hypothesis" is the most supported by experimental data. This hypothesis states that the cleavage of amyloid precursor protein (APP) leads to the formation of amyloid beta (Aβ) peptides that congregate with formation and deposition of Aβ plaques in the frontal cortex and hippocampus. Risk factors including neurotransmitter modulation, chronic inflammation, metal-induced oxidative stress and elevated cholesterol levels are key contributors to the disease progress. Current therapeutic strategies abating AD progression are primarily based on anti-acetylcholinesterase (AChE) inhibitors as cognitive enhancers. The AChE inhibitor, donepezil, is proven to strengthen cognitive functions and appears effective in treating moderate to severe AD patients. N-Methyl-D-aspartate receptor antagonist, memantine, is also useful, and its combination with donepezil demonstrated a strong stabilizing effect in clinical studies on AD. Nonsteroidal anti-inflammatory drugs delayed the onset and progression of AD and attenuated cognitive dysfunction. Based upon epidemiological evidence and animal studies, antioxidants emerged as potential AD preventive agents; however, clinical trials revealed inconsistencies. Pharmacokinetic and pharmacodynamic profiling demonstrated pleiotropic functions of the hypolipidemic class of drugs, statins, potentially contributing towards the prevention of AD. In addition, targeting the APP processing pathways, stimulating neuroprotective signaling mechanisms, using the amyloid anti-aggregants and Aβ immunotherapy surfaced as well-tested strategies in reducing the AD-like pathology. Overall, this review covers mechanism of inducing the Aβ formation, key risk factors and major therapeutics prevalent in the AD treatment nowadays. It also delineates the need for novel screening approaches towards identifying drugs that may prevent or at least limit the progression of this devastating disease.

Suppression of LPS-induced tau hyperphosphorylation by serum amyloid A

BACKGROUND

Accumulation of hyperphosphorylated tau is a major neuropathological feature of tauopathies including Alzheimer's disease (AD). Serum amyloid A (SAA), an acute-phase protein with cytokine-like property, has been implicated in amyloid deposition. It remains unclear whether SAA affects tau hyperphosphorylation.

METHODS

Potential involvement of SAA in tau hyperphosphorylation was examined using intracerebral injection of SAA, and in Saa3 (-/-) mice receiving systemic administration of lipopolysaccharide (LPS). Induced SAA expression and microglial activation were evaluated in these mice using real-time PCR and/or immunofluorescence staining. Cultured primary neuronal cells were treated with condition media (CM) from SAA-stimulated primary microglial cells. The alteration in tau hyperphosphorylation was determined using Western blotting.

RESULTS

Saa3 is the predominant form of SAA proteins induced by LPS in the mouse brain that co-localizes with neurons. Overexpression of SAA by intracerebral injection attenuated tau hyperphosphorylation in the brain. Conversely, Saa3 deficiency enhanced tau phosphorylation induced by systemic LPS administration. Intracerebral injection of SAA also induced the activation of microglia in the brains. IL-10 released to CM from SAA-stimulated microglia attenuated tau hyperphosphorylation in cultured primary neurons. IL-10 neutralizing antibody reversed the effect of SAA in the attenuation of tau phosphorylation.

CONCLUSIONS

LPS-induced expression of SAA proteins in the brain leads to the activation of microglia and release of IL-10, which in turn suppresses tau hyperphosphorylation in a mouse model of systemic inflammation.

The Ever-Changing Morphology of Hippocampal Granule Neurons in Physiology and Pathology

Newborn neurons are continuously added to the hippocampal dentate gyrus throughout adulthood. In this review, we analyze the maturational stages that newborn granule neurons go through, with a focus on their unique morphological features during each stage under both physiological and pathological circumstances. In addition, the influence of deleterious (such as schizophrenia, stress, Alzheimer's disease, seizures, stroke, inflammation, dietary deficiencies, or the consumption of drugs of abuse or toxic substances) and neuroprotective (physical exercise and environmental enrichment) stimuli on the maturation of these cells will be examined. Finally, the regulation of this process by proteins involved in neurodegenerative and neurological disorders such as Glycogen synthase kinase 3β, Disrupted in Schizophrenia 1 (DISC-1), Glucocorticoid receptor, pro-inflammatory mediators, Presenilin-1, Amyloid precursor protein, Cyclin-dependent kinase 5 (CDK5), among others, will be evaluated. Given the recently acquired relevance of the dendritic branch as a functional synaptic unit required for memory storage, a full understanding of the morphological alterations observed in newborn neurons may have important consequences for the prevention and treatment of the cognitive and affective alterations that evolve in conjunction with impaired adult hippocampal neurogenesis.

The neuropathology and cerebrovascular mechanisms of dementia

The prevalence of dementia is increasing in our aging population at an alarming rate. Because of the heterogeneity of clinical presentation and complexity of disease neuropathology, dementia classifications remain controversial. Recently, the National Plan to address Alzheimer’s Disease prioritized Alzheimer’s disease-related dementias to include: Alzheimer’s disease, dementia with Lewy bodies, frontotemporal dementia, vascular dementia, and mixed dementias. While each of these dementing conditions has their unique pathologic signature, one common etiology shared among all these conditions is cerebrovascular dysfunction at some point during the disease process. The goal of this comprehensive review is to summarize the current findings in the field and address the important contributions of cerebrovascular, physiologic, and cellular alterations to cognitive impairment in these human dementias. Specifically, evidence will be presented in support of small-vessel disease as an underlying neuropathologic hallmark of various dementias, while controversial findings will also be highlighted. Finally, the molecular mechanisms shared among all dementia types including hypoxia, oxidative stress, mitochondrial bioenergetics, neuroinflammation, neurodegeneration, and blood–brain barrier permeability responsible for disease etiology and progression will be discussed.

Targeting New Candidate Genes by Small Molecules Approaching Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are among the most feared of the disorders that afflict humankind for the lack of specific diagnostic tests and effective treatments. Understanding the molecular, cellular, biochemical changes of NDs may hold therapeutic promise against debilitating central nerve system (CNS) disorders. In the present review, we summarized the clinical presentations and biology backgrounds of NDs, including Parkinson's disease (PD), Huntington's disease (HD), and Alzheimer's disease (AD) and explored the role of molecular mechanisms, including dys-regulation of epigenetic control mechanisms, Ataxia-telangiectasia-mutated protein kinase (ATM), and neuroinflammation in the pathogenesis of NDs. Targeting these mechanisms may hold therapeutic promise against these devastating diseases.

Interlukin-18 Is a Pivot Regulatory Factor on Matrix Metalloproteinase-13 Expression and Brain Astrocytic Migration

The expression of matrix metalloproteinase-13 (MMP-13) has been shown to be elevated in some pathophysiological conditions and is involved in the degradation of extracellular matrix in astrocytes. In current study, the function of MMP-13 was further investigated. The conditioned medium (CM) collected from activated microglia increased interleukin (IL)-18 production and enhanced MMP-13 expression in astrocytes. Furthermore, treatment with recombinant IL-18 increased MMP-13 protein and mRNA levels in astrocytes. Recombinant IL-18 stimulation also increased the enzymatic activity of MMP-13 and the migratory activity of astrocytes, while administration of MMP-13 or pan-MMP inhibitors antagonized IL-18-induced migratory activity of astrocytes. In addition, administration of recombinant IL-18 to astrocytes led to the phosphorylation of JNK, Akt, or PKCδ, and treatment of astrocytes with JNK, PI3 kinase/Akt, or PKCδ inhibitors significantly decreased the IL-18-induced migratory activity. Taken together, the results suggest that IL-18-induced MMP-13 expression in astrocytes is regulated by JNK, PI3 kinase/Akt, and PKCδ signaling pathways. These findings also indicate that IL-18 is an important regulator leading to MMP-13 expression and cell migration in astrocytes.

Preclinical Evaluation of miR-15/107 Family Members as Multifactorial Drug Targets for Alzheimer's Disease

Alzheimer's disease (AD) is a multifactorial, fatal neurodegenerative disorder characterized by the abnormal accumulation of Aβ and Tau deposits in the brain. There is no cure for AD, and failure at different clinical trials emphasizes the need for new treatments. In recent years, significant progress has been made toward the development of miRNA-based therapeutics for human disorders. This study was designed to evaluate the efficiency and potential safety of miRNA replacement therapy in AD, using miR-15/107 paralogues as candidate drug targets. We identified miR-16 as a potent inhibitor of amyloid precursor protein (APP) and BACE1 expression, Aβ peptide production, and Tau phosphorylation in cells. Brain delivery of miR-16 mimics in mice resulted in a reduction of AD-related genes APP, BACE1, and Tau in a region-dependent manner. We further identified Nicastrin, a γ-secretase component involved in Aβ generation, as a target of miR-16. Proteomics analysis identified a number of additional putative miR-16 targets in vivo, including α-Synuclein and Transferrin receptor 1. Top-ranking biological networks associated with miR-16 delivery included AD and oxidative stress. Collectively, our data suggest that miR-16 is a good candidate for future drug development by targeting simultaneously endogenous regulators of AD biomarkers (i.e., Aβ and Tau), inflammation, and oxidative stress.

The triggering receptor expressed on myeloid cells 2 (TREM2) is associated with enhanced inflammation, neuropathological lesions and increased risk for Alzheimer's dementia

INTRODUCTION

The objective of this study was to elucidate the relationship between the triggering receptor expressed on myeloid cells 2 (TREM2) risk variant, neuropathological lesions, alterations in gene and protein expression, and the severity of neuroinflammation.

METHODS

The genetic association study of the R47 H TREM2 variant with Alzheimer's disease (AD), neuropathology, and changes in TREM2 and TYRO protein tyrosine kinase-binding protein (TYROBP) gene and protein expression, and neuroinflammatory markers.

RESULTS

The TREM2 variant is associated with: (i) AD (odds ratio: 4.76; P = .014); (ii) increased density of amyloid plaques and neurofibrillary tangles in multiple brain regions; (iii) increased TREM2 (P = .041) and TYROBP (P = .006) gene expression; (iv) decreased TREM2 protein levels (P = .016); and (v) upregulation of proinflammatory cytokines (regulated on activation, normal T cell expressed and secreted [RANTES] and interferon [IFN] gamma) (P = .003) and nominal downregulation of protective markers (α2-macroglobulin, interleukin 4 or IL-4, and ApoA1) (P = .018).

DISCUSSION

These findings link the TREM2 missense mutation with specific molecular abnormalities and increases in neuropathological lesions in the human brain.

Deficiency of macrophage migration inhibitory factor attenuates tau hyperphosphorylation in mouse models of Alzheimer's disease

BACKGROUND

Pathological features of Alzheimer's disease (AD) include aggregation of amyloid beta (Aβ) and tau protein. Macrophage migration inhibitory factor (MIF), a proinflammatory cytokine, has been implicated in the toxicity of aggregated Aβ. It remains unclear whether MIF affects hyperphosphorylation and aggregation of tau.

METHODS

The effects of MIF deficiency in tau hyperphosphorylation were examined in Mif (-/-) mice receiving intracerebroventricular (ICV) injection of streptozotocin (STZ) and in APP/PS1 transgenic mice mated with Mif (-/-) mice. MIF expression and astrocyte activation were evaluated in ICV-STZ mice using immunofluorescence staining. Cultured primary astrocytes were treated with high glucose to mimic STZ function in vitro, and the condition medium (CM) was collected. The level of tau hyperphosphorylation in neurons treated with the astrocyte CM was determined using Western blotting.

RESULTS

MIF deficiency attenuated tau hyperphosphorylation in mice. ICV injection of STZ increased astrocyte activation and MIF expression in the hippocampus. MIF deficiency attenuated astrocyte activation in ICV-STZ mice. CM from high glucose-treated WT astrocytes increased tau hyperphosphorylation in cultured primary neurons, an effect absent from Mif (-/-) astrocytes and WT astrocytes treated with the MIF inhibitor ISO-1. ISO-1 had no direct effect on tau phosphorylation in cultured primary neurons.

CONCLUSIONS

These results suggest that MIF deficiency is associated with reduced astrocyte activation and tau hyperphosphorylation in the mouse AD models tested. Inhibition of MIF and MIF-induced astrocyte activation may be useful in AD prevention and therapy.

The Incremental Induction of Neuroprotective Properties by Multiple Therapeutic Strategies for Primary and Secondary Neural Injury

Neural diseases including injury by endogenous factors, traumatic brain injury, and degenerative neural injury are eventually due to reactive oxygen species (ROS). Thus ROS generation in neural tissues is a hallmark feature of numerous forms of neural diseases. Neural degeneration and the neural damage process is complex, involving a vast array of tissue structure, transcriptional/translational, electrochemical, metabolic, and functional events within the intact neighbors surrounding injured neural tissues. During aging, multiple changes involving physical, chemical, and biochemical processes occur from the molecular to the morphological levels in neural tissues. Among many recommended therapeutic candidates, melatonin also plays a role in protecting the nervous system from anti-inflammation and efficiently safeguards neuronal cells via antioxidants and other endogenous/exogenous beneficial factors. Therefore, given the wide range of mechanisms responsible for neuronal damage, multi-action drugs or therapies for the treatment of neural injury that make use of two or more agents and target several pathways may have greater efficacy in promoting functional recovery than a single therapy alone.

Plant alkaloids as drug leads for Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative illness associated with dementia and is most prevalent among the elderly population. Current medications can only treat symptoms. Alkaloids are structurally diverse and have been an important source of therapeutics for various brain disorders. Two US Food and Drug Administration (FDA)-approved acetylcholinesterase inhibitors for AD, galantamine and rivastigmine, are in fact alkaloids. In addition, clinical trials of four other extensively studied alkaloids-huperzine A, caffeine, nicotine, and indomethacin-have been conducted but do not convincingly demonstrate their clinical efficacy for AD. Interestingly, rhynchophylline, a known neuroprotective alkaloid, was recently discovered by in silico screening as an inhibitor of EphA4, a novel target for AD. Here, we review the pathophysiological mechanisms underlying AD, current treatment strategies, and therapeutic potential of several selected plant alkaloids in AD, highlighting their various drug targets and the key supportive preclinical and clinical studies. Future research should include more rigorous clinical studies of the most promising alkaloids, the further development of recently discovered candidate alkaloids, and the continual search for new alkaloids for relevant drug targets. It remains promising that an alkaloid drug candidate could significantly affect the progression of AD in addition to providing symptomatic relief.

Role of pro-inflammatory cytokines released from microglia in Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder of the brain, which is characterized by the formation of extracellular amyloid plaques (or senile plaques) and intracellular neurofibrillary tangles. However, increasing evidences demonstrated that neuroinflammatory changes, including chronic microgliosis are key pathological components of AD. Microglia, the resident immune cells of the brain, is constantly survey the microenvironment under physiological conditions. In AD, deposition of β-amyliod (Aβ) peptide initiates a spectrum of cerebral neuroinflammation mediated by activating microglia. Activated microglia may play a potentially detrimental role by eliciting the expression of pro-inflammatory cytokines such as interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) influencing the surrounding brain tissue. Emerging studies have demonstrated that up-regulation of pro-inflammatory cytokines play multiple roles in both neurodegeneration and neuroprotection. Understanding the pro-inflammatory cytokines signaling pathways involved in the regulation of AD is crucial to the development of strategies for therapy. This review will discuss the mechanisms and important role of pro-inflammatory cytokines in the pathogenesis of AD, and the ongoing drug targeting pro-inflammatory cytokine for therapeutic modulation.

Oligodendrocytes and Alzheimer's disease

Extensive evidence has indicated that the breakdown of myelin is associated with Alzheimer's disease (AD) since the vulnerability of oligodendrocytes under Alzheimer's pathology easily induces the myelin breakdown and the loss of the myelin sheath which might be the initiating step in the changes of the earliest stage of AD prior to appearance of amyloid and tau pathology. Considerable research implicated that beta-amyloid (Aβ)-mediated oligodendrocyte dysfunction and myelin breakdown may be via neuroinflammation, oxidative stress and/or apoptosis. It also seems that the oligodendrocyte dysfunction is triggered by the formation of neurofibrillary tangles (NFTs) through inflammation and oxidative stress as the common pathophysiological base. Impaired repair of oligodendrocyte precursor cells (OPCs) might possibly enhance the disease progress under decreased self-healing ability from aging process and pathological factors including Aβ pathology and/or NFTs. Thus, these results have suggested that targeting oligodendrocytes may be a novel therapeutic intervention for the prevention and treatment of AD.

Cinnamamide Derivatives for Central and Peripheral Nervous System Disorders--A Review of Structure-Activity Relationships

The cinnamamide scaffold has been incorporated in to the structure of numerous organic compounds with therapeutic potential. The scaffold enables multiple interactions, such as hydrophobic, dipolar, and hydrogen bonding, with important molecular targets. Additionally, the scaffold has multiple substitution options providing the opportunity to optimize and modify the pharmacological activity of the derivatives. In particular, cinnamamide derivatives have exhibited therapeutic potential in animal models of both central and peripheral nervous system disorders. Some have undergone clinical trials and were introduced on to the pharmaceutical market. The diverse activities observed in the nervous system included anticonvulsant, antidepressant, neuroprotective, analgesic, anti-inflammatory, muscle relaxant, and sedative properties. Over the last decade, research has focused on the molecular mechanisms of action of these derivatives, and the data reported in the literature include targeting the γ-aminobutyric acid type A (GABAA ) receptors, N-methyl-D-aspartate (NMDA) receptors, transient receptor potential (TRP) cation channels, voltage-gated potassium channels, histone deacetylases (HDACs), prostanoid receptors, opioid receptors, and histamine H3 receptors. Here, the literature data from reports evaluating cinnamic acid amide derivatives for activity in target-based or phenotypic assays, both in vivo and in vitro, relevant to disorders of the central and peripheral nervous systems are analyzed and structure-activity relationships discussed.

Evaluation of inflammation-related genes polymorphisms in Mexican with Alzheimer's disease: a pilot study

Amyloid peptide is able to promote the activation of microglia and astrocytes in Alzheimer’s disease (AD), and this stimulates the production of pro-inflammatory cytokines. Inflammation contributes to the process of neurodegeneration and therefore is a key factor in the development of AD. Some of the most important proteins involved in AD inflammation are: clusterin (CLU), complement receptor 1 (CR1), C reactive protein (CRP), tumor necrosis factor α (TNF-α), the interleukins 1α (IL-1α), 6 (IL-6), 10 (IL-10) and cyclooxygenase 2 (COX-2). In particular, COX-2 is encoded by the prostaglandin-endoperoxide synthase 2 gene (PTGS2). Since variations in the genes that encode these proteins may modify gene expression or function, it is important to investigate whether these variations may change the developing AD. The aim of this study was to determine whether the presence of polymorphisms in the genes encoding the aforementioned proteins is associated in Mexican patients with AD. Fourteen polymorphisms were genotyped in 96 subjects with AD and 100 controls; the differences in allele, genotype and haplotype frequencies were analyzed. Additionally, an ancestry analysis was conducted to exclude differences in genetic ancestry among groups as a confounding factor in the study. Significant differences in frequencies between AD and controls were found for the single-nucleotide polymorphism (SNP) rs20417 within the PTGS2 gene. Ancestry analysis revealed no significant differences in the ancestry of the compared groups, and the association was significant even after adjustment for ancestry and correction for multiple testing, which strengthens the validity of the results. We conclude that this polymorphism plays an important role in the development of the AD pathology and further studies are required, including their proteins.

APOE-modulated Aβ-induced neuroinflammation in Alzheimer's disease: current landscape, novel data, and future perspective

Chronic glial activation and neuroinflammation induced by the amyloid-β peptide (Aβ) contribute to Alzheimer's disease (AD) pathology. APOE4 is the greatest AD-genetic risk factor; increasing risk up to 12-fold compared to APOE3, with APOE4-specific neuroinflammation an important component of this risk. This editorial review discusses the role of APOE in inflammation and AD, via a literature review, presentation of novel data on Aβ-induced neuroinflammation, and discussion of future research directions. The complexity of chronic neuroinflammation, including multiple detrimental and beneficial effects occurring in a temporal and cell-specific manner, has resulted in conflicting functional data for virtually every inflammatory mediator. Defining a neuroinflammatory phenotype (NIP) is one way to address this issue, focusing on profiling the changes in inflammatory mediator expression during disease progression. Although many studies have shown that APOE4 induces a detrimental NIP in peripheral inflammation and Aβ-independent neuroinflammation, data for APOE-modulated Aβ-induced neuroinflammation are surprisingly limited. We present data supporting the hypothesis that impaired apoE4 function modulates Aβ-induced effects on inflammatory receptor signaling, including amplification of detrimental (toll-like receptor 4-p38α) and suppression of beneficial (IL-4R-nuclear receptor) pathways. To ultimately develop APOE genotype-specific therapeutics, it is critical that future studies define the dynamic NIP profile and pathways that underlie APOE-modulated chronic neuroinflammation. In this editorial review, we present data supporting the hypothesis that impaired apoE4 function modulates Aβ-induced effects on inflammatory receptor signaling, including amplification of detrimental (TLR4-p38α) and suppression of beneficial (IL-4R-nuclear receptor) pathways, resulting in an adverse NIP that causes neuronal dysfunction. NIP, Neuroinflammatory phenotype; P.I., pro-inflammatory; A.I., anti-inflammatory.

3,5,6,7,8,3',4'-heptamethoxyflavone, a citrus polymethoxylated flavone, attenuates inflammation in the mouse hippocampus

Citrus polymethoxylated flavones (PMFs) have recently been shown to suppress inflammation in peripheral tissues. In the present study, we investigated the effects of 3,5,6,7,8,3',4'-heptamethoxyflavone (HMF), one of the PMFs, on inflammation in the brain in vivo using mice injected intrahippocampally with lipopolysaccharide (LPS). We demonstrated that subcutaneously injected HMF suppressed: (1) LPS-induced losses in body weight; (2) LPS-induced microglial activation in the hippocampus; and (3) LPS-induced interleukin-1β mRNA expression in the hippocampus. These results suggest that HMF has the ability to reduce neuroinflammation in the brain.

The relationship of serum macrophage inhibitory cytokine-1 levels with gray matter volumes in community-dwelling older individuals

Using circulating inflammatory markers and magnetic resonance imaging (MRI), recent studies have associated inflammation with brain volumetric measures. Macrophage Inhibitory Cytokine-1 (MIC-1/GDF15) is a divergent transforming growth factor - beta (TGF-β) superfamily cytokine. To uncover the underlying mechanisms of the previous finding of a negative association between MIC-1/GDF15 serum levels and cognition, the present study aimed to examine the relationship of circulating MIC-1/GDF15 levels with human brain gray matter (GM) volumes, in a community-dwelling sample aged 70-90 years over two years (Wave 1: n = 506, Wave 2: n = 327), of which the age-related brain atrophy had been previously well defined. T1-weighted MRI scans were obtained at both waves and analyzed using the FMRIB Software Library and FreeSurfer. The results showed significantly negative associations between MIC-1/GDF15 serum levels and both subcortical and cortical GM volumes. GM volumes of the whole brain, cortex, temporal lobe, thalamus and accumbens showed significant mediating effects on the associations between MIC-1/GDF15 serum levels and global cognition scores. Increases in MIC-1/GDF15 serum levels were associated with decreases in cortical and subcortical GM volume over two years. In conclusion, MIC-1/GDF15 serum levels were inversely associated with GM volumes both cross-sectionally and longitudinally.

Heart failure and Alzheimer's disease

It has recently been proposed that heart failure is a risk factor for Alzheimer's disease. Decreased cerebral blood flow and neurohormonal activation due to heart failure may contribute to the dysfunction of the neurovascular unit and cause an energy crisis in neurons. This leads to the impaired clearance of amyloid beta and hyperphosphorylation of tau protein, resulting in the formation of amyloid beta plaques and neurofibrillary tangles. In this article, we will summarize the current understanding of the relationship between heart failure and Alzheimer's disease based on epidemiological studies, brain imaging research, pathological findings and the use of animal models. The importance of atherosclerosis, myocardial infarction, atrial fibrillation, blood pressure and valve disease as well as the effect of relevant medications will be discussed.

α7 Nicotinic acetylcholine receptor-specific antibody induces inflammation and amyloid β42 accumulation in the mouse brain to impair memory

Nicotinic acetylcholine receptors (nAChRs) expressed in the brain are involved in regulating cognitive functions, as well as inflammatory reactions. Their density is decreased upon Alzheimer disease accompanied by accumulation of β-amyloid (Aβ42), memory deficit and neuroinflammation. Previously we found that α7 nAChR-specific antibody induced pro-inflammatory interleukin-6 production in U373 glioblastoma cells and that such antibodies were present in the blood of humans. We raised a hypothesis that α7 nAChR-specific antibody can cause neuroinflammation when penetrating the brain. To test this, C57Bl/6 mice were either immunized with extracellular domain of α7 nAChR subunit α7(1-208) or injected with bacterial lipopolysaccharide (LPS) for 5 months. We studied their behavior and the presence of α3, α4, α7, β2 and β4 nAChR subunits, Aβ40 and Aβ42 and activated astrocytes in the brain by sandwich ELISA and confocal microscopy. It was found that either LPS injections or immunizations with α7(1-208) resulted in region-specific decrease of α7 and α4β2 and increase of α3β4 nAChRs, accumulation of Aβ42 and activated astrocytes in the brain of mice and worsening of their episodic memory. Intravenously transferred α7 nAChR-specific-antibodies penetrated the brain parenchyma of mice pre-injected with LPS. Our data demonstrate that (1) neuroinflammation is sufficient to provoke the decrease of α7 and α4β2 nAChRs, Aβ42 accumulation and memory impairment in mice and (2) α7(1-208) nAChR-specific antibodies can cause inflammation within the brain resulting in the symptoms typical for Alzheimer disease.

Insulin resistance as a key link for the increased risk of cognitive impairment in the metabolic syndrome

Metabolic syndrome (MetS) is a cluster of cardiovascular risk factors that includes obesity, diabetes, and dyslipidemia. Accumulating evidence implies that MetS contributes to the development and progression of Alzheimer's disease (AD); however, the factors connecting this association have not been determined. Insulin resistance (IR) is at the core of MetS and likely represent the key link between MetS and AD. In the central nervous system, insulin plays key roles in learning and memory, and AD patients exhibit impaired insulin signaling that is similar to that observed in MetS. As we face an alarming increase in obesity and T2D in all age groups, understanding the relationship between MetS and AD is vital for the identification of potential therapeutic targets. Recently, several diabetes therapies that enhance insulin signaling are being tested for a potential therapeutic benefit in AD and dementia. In this review, we will discuss MetS as a risk factor for AD, focusing on IR and the recent progress and future directions of insulin-based therapies.

GFAP and vimentin deficiency alters gene expression in astrocytes and microglia in wild-type mice and changes the transcriptional response of reactive glia in mouse model for Alzheimer's disease

Reactive astrocytes with an increased expression of intermediate filament (IF) proteins Glial Fibrillary Acidic Protein (GFAP) and Vimentin (VIM) surround amyloid plaques in Alzheimer's disease (AD). The functional consequences of this upregulation are unclear. To identify molecular pathways coupled to IF regulation in reactive astrocytes, and to study the interaction with microglia, we examined WT and APPswe/PS1dE9 (AD) mice lacking either GFAP, or both VIM and GFAP, and determined the transcriptome of cortical astrocytes and microglia from 15- to 18-month-old mice. Genes involved in lysosomal degradation (including several cathepsins) and in inflammatory response (including Cxcl5, Tlr6, Tnf, Il1b) exhibited a higher AD-induced increase when GFAP, or VIM and GFAP, were absent. The expression of Aqp4 and Gja1 displayed the same pattern. The downregulation of neuronal support genes in astrocytes from AD mice was absent in GFAP/VIM null mice. In contrast, the absence of IFs did not affect the transcriptional alterations induced by AD in microglia, nor was the cortical plaque load altered. Visualizing astrocyte morphology in GFAP-eGFP mice showed no clear structural differences in GFAP/VIM null mice, but did show diminished interaction of astrocyte processes with plaques. Microglial proliferation increased similarly in all AD groups. In conclusion, absence of GFAP, or both GFAP and VIM, alters AD-induced changes in gene expression profile of astrocytes, showing a compensation of the decrease of neuronal support genes and a trend for a slightly higher inflammatory expression profile. However, this has no consequences for the development of plaque load, microglial proliferation, or microglial activation.

Inflammation and neurodegenerative disorders: is there still hope for therapeutic intervention?

PURPOSE OF REVIEW

This review aims to describe the current understanding of neuroinflammation in neurodegeneration and evaluate the value of various anti-inflammatory treatments.

RECENT FINDINGS

Inflammation plays important roles in common disease such as dementia and depression. Underlying mechanisms including the role of inflammasomes in these diseases have been recently described. Interventions using Ω-3 polyunsaturated fatty acids, NSAIDs and targeted antagonists (e.g., etanercept) show no convincing clinical efficacy in inflammation-associated depression, cognitive decline and dementia.

SUMMARY

Therapeutic targeting of inflammation appears to be relevant in brain conditions characterized by neuroinflammation and neurodegeneration, although published anti-inflammatory interventions have shown no relevant clinical efficacy. Newly described pharmacological targets in the neuroinflammation pathways may not only offer a more profound understanding of the underlying pathophysiology but also raise hope for the development of novel pharmacological agents.

The flavonoid quercetin ameliorates Alzheimer's disease pathology and protects cognitive and emotional function in aged triple transgenic Alzheimer's disease model mice

Alzheimer's disease (AD) is the most common senile dementia in the world. Although important progress has been made in understanding the pathogenesis of AD, current therapeutic approaches provide only modest symptomatic relief. In this study, we evaluated the neuroprotective effect of quercetin (25 mg/kg) administration via i.p. injection every 48 h for 3 months on aged (21-24 months old) triple transgenic AD model (3xTg-AD) mice. Our data show that quercetin decreases extracellular β-amyloidosis, tauopathy, astrogliosis and microgliosis in the hippocampus and the amygdala. These results were supported by a significant reduction in the paired helical filament (PHF), β-amyloid (βA) 1-40 and βA 1-42 levels and a decrease in BACE1-mediated cleavage of APP (into CTFβ). Additionally, quercetin induced improved performance on learning and spatial memory tasks and greater risk assessment behavior based on the elevated plus maze test. Together, these findings suggest that quercetin reverses histological hallmarks of AD and protects cognitive and emotional function in aged 3xTg-AD mice.

Protection of TGF-β1 against neuroinflammation and neurodegeneration in Aβ1-42-induced Alzheimer's disease model rats

Neuroinflammation has been reported to be associated with Alzheimer’s disease (AD) pathogenesis. Neuroinflammation is generally considered as an outcome of glial activation; however, we recently demonstrated that T helper (Th)17 cells, a subpopulation of proinflammatory CD4+ T cells, are also involved in AD pathogenesis. Transforming growth factor (TGF)-β1, a cytokine that can be expressed in the brain, can be immunosuppressive, but its effects on lymphocyte-mediated neuroinflammation in AD pathogenesis have not been well addressed. In the current study we administered TGF-β1 via intracerebroventricle (ICV) and intranasal (IN) routes in AD model rats to investigate its antiinflammatory and neuroprotective effects. The AD rat model was prepared by bilateral hippocampal injection of amyloid-β (Aβ)_1–42. TGF-β1 was administered via ICV one hour prior to Aβ_1–42 injection or via both nares seven days after Aβ_1–42 injection. ICV administration of TGF-β1 before Aβ_1–42 injection remarkably ameliorated Aβ_1–42-induced neurodegeneration and prevented Aβ_1–42-induced increases in glia-derived proinflammatory mediators (TNF-α, IL-1β and iNOS), as well as T cell-derived proinflammatory cytokines (IFN-γ, IL-2, IL-17 and IL-22), in the hypothalamus, serum or cerebrospinal fluid (CSF) in a concentration-dependent manner. TGF-β1 pretreatment also prevented Aβ_1–42-induced decreases in the neurotrophic factors, IGF-1, GDNF and BDNF, and in the antiinflammatory cytokine, IL-10. Similarly, IN administration of TGF-β1 after Aβ_1–42 injection reduced neurodegeneration, elevation of proinflammatory mediators and cytokines, and reduction of neurotrophic and antiinflammatory factors, in the hypothalamus, serum or CSF. These findings suggest that TGF-β1 suppresses glial and T cell-mediated neuroinflammation and thereby alleviates AD-related neurodegeneration. The effectiveness of IN administered TGF-β1 in reducing Aβ_1–42 neurotoxicity suggests a possible therapeutic approach in patients with AD.

Silver nanoparticles affect on gene expression of inflammatory and neurodegenerative responses in mouse brain neural cells

Silver nanoparticles (AgNPs) have antibacterial characteristics, and currently are applied in Ag-containing products. This study found neural cells can uptake 3-5 nm AgNPs, and investigated the potential effects of AgNPs on gene expression of inflammation and neurodegenerative disorder in murine brain ALT astrocytes, microglial BV-2 cells and neuron N2a cells. After AgNPs (5, 10, 12.5 μg/ml) exposure, these neural cells had obviously increased IL-1β secretion, and induced gene expression of C-X-C motif chemokine 13 (CXCL13), macrophage receptor with collagenous structure (MARCO) and glutathione synthetase (GSS) for inflammatory response and oxidative stress neutralization. Additionally, this study found amyloid-β (Aβ) plaques for pathological feature of Alzheimer's disease (AD) deposited in neural cells after AgNPs treatment. After AgNPs exposure, the gene expression of amyloid precursor protein (APP) was induced, and otherwise, neprilysin (NEP) and low-density lipoprotein receptor (LDLR) were reduced in neural cells as well as protein level. These results suggested AgNPs could alter gene and protein expressions of Aβ deposition potentially to induce AD progress in neural cells. It's necessary to take notice of AgNPs distribution in the environment.

Olive Oil Phenols as Promising Multi-targeting Agents Against Alzheimer's Disease

Amyloid diseases are characterized by the deposition of typically aggregated proteins/peptides in tissues, associated with degeneration and progressive functional impairment. Alzheimer's disease is one of the most studied neurodegenerative amyloid diseases and, in Western countries, a significant cause of dementia in the elderly. The so-called "Mediterranean diet" has been considered for long as the healthier dietary regimen, characterised by a great abundance in vegetables and fruits, extra virgin olive oil as the main source of fat, a moderate consumption of red wine and a reduced intake of proteins from red meat. Recent epidemiological studies support the efficacy of the Mediterranean diet not only against cardiovascular and cancer diseases (as previously demonstrated) but also against the cognitive decline associated with ageing, and several data are highlighting the role played by natural phenols, of which red wine and extra virgin olive oil are rich, in such context. In the meantime, studies conducted both in vivo and in vitro have started to reveal the great potential of the phenolic component of extra virgin olive oil (mainly oleuropein aglycone and oleocanthal) in counteracting amyloid aggregation and toxicity, with a particular emphasis on the pathways involved in the onset and progression of Alzheimer's disease: amyloid precursor protein processing, amyloid-beta (Aβ) peptide and tau aggregation, autophagy impairment, neuroinflammation. The aim of this review is to summarize the results of such research efforts, showing how the action of these phenols goes far beyond their renowned antioxidant activity and revealing their potential as multi-targeting agents against Alzheimer's disease.

Brain intracellular metabolites are freely diffusing along cell fibers in grey and white matter, as measured by diffusion-weighted MR spectroscopy in the human brain at 7 T

Due to the specific compartmentation of brain metabolites, diffusion-weighted magnetic resonance spectroscopy opens unique insight into neuronal and astrocytic microstructures. The apparent diffusion coefficient (ADC) of brain metabolites depends on various intracellular parameters including cytosol viscosity and molecular crowding. When diffusion time (t d) is long enough, the size and geometry of the compartment in which the metabolites diffuse strongly influence metabolites ADC. In a previous study, performed in the macaque brain, we measured neuronal and astrocytic metabolites ADC at long t d (from 86 to 1,011 ms) in a large voxel enclosing an equal proportion of white and grey matter. We showed that metabolites apparently diffuse freely along the axis of dendrites, axons and astrocytic processes. To assess potential differences between these two tissue types, here we measured for the first time in the Human brain the t d-dependency of metabolites trace/3 ADC at 7 teslas using a localized diffusion-weighted STEAM sequence, in parietal and occipital voxels, respectively, containing mainly white and grey matter. We show that, in both tissues and over the observed timescale (t d varying from 92 to 712 ms) metabolite ADC reaches a non-zero plateau, suggesting that metabolites are not confined inside subcellular regions such as cell bodies, or inside subcellular compartments such as organelles, but are rather free to diffuse in the whole fiber-like structure of neurons and astrocytes. Beyond the fundamental insights into intracellular compartmentation of metabolites, this work also provides a new framework for interpreting results of neuroimaging techniques based on molecular diffusion, such as diffusion-weighted magnetic resonance spectroscopy and imaging.

Versatility of the complement system in neuroinflammation, neurodegeneration and brain homeostasis

The immune response after brain injury is highly complex and involves both local and systemic events at the cellular and molecular level. It is associated to a dramatic over-activation of enzyme systems, the expression of proinflammatory genes and the activation/recruitment of immune cells. The complement system represents a powerful component of the innate immunity and is highly involved in the inflammatory response. Complement components are synthesized predominantly by the liver and circulate in the bloodstream primed for activation. Moreover, brain cells can produce complement proteins and receptors. After acute brain injury, the rapid and uncontrolled activation of the complement leads to massive release of inflammatory anaphylatoxins, recruitment of cells to the injury site, phagocytosis and induction of blood brain barrier (BBB) damage. Brain endothelial cells are particularly susceptible to complement-mediated effects, since they are exposed to both circulating and locally synthesized complement proteins. Conversely, during neurodegenerative disorders, complement factors play distinct roles depending on the stage and degree of neuropathology. In addition to the deleterious role of the complement, increasing evidence suggest that it may also play a role in normal nervous system development (wiring the brain) and adulthood (either maintaining brain homeostasis or supporting regeneration after brain injury). This article represents a compendium of the current knowledge on the complement role in the brain, prompting a novel view that complement activation can result in either protective or detrimental effects in brain conditions that depend exquisitely on the nature, the timing and the degree of the stimuli that induce its activation. A deeper understanding of the acute, subacute and chronic consequences of complement activation is needed and may lead to new therapeutic strategies, including the ability of targeting selective step in the complement cascade.

Toll-like receptors 2, -3 and -4 prime microglia but not astrocytes across central nervous system regions for ATP-dependent interleukin-1β release

Interleukin-1β (IL-1β) is a crucial mediator in the pathogenesis of inflammatory diseases at the periphery and in the central nervous system (CNS). Produced as an unprocessed and inactive pro-form which accumulates intracellularly, release of the processed cytokine is strongly promoted by ATP acting at the purinergic P2X₇ receptor (P2X₇R) in cells primed with lipopolysaccharide (LPS), a Toll-like receptor (TLR) 4 ligand. Microglia are central to the inflammatory process and a major source of IL-1β when activated. Here we show that purified (>99%) microglia cultured from rat cortex, spinal cord and cerebellum respond robustly to ATP-dependent IL-1β release, upon priming with a number of TLR isoform ligands (zymosan and Pam3CSK4 for TLR2, poly(I:C) for TLR3). Cytokine release was prevented by a P2X₇R antagonist and inhibitors of stress-activated protein kinases. Enriched astrocytes (≤5% microglia) from these CNS regions displayed responses qualitatively similar to microglia but became unresponsive upon eradication of residual microglia with the lysosomotropic agent Leu-Leu-OMe. Activation of multiple TLR isoforms in nervous system pathology, coupled with elevated extracellular ATP levels and subsequent P2X₇R activation may represent an important route for microglia-derived IL-1β. This phenomenon may have important consequences for neuroinflammation and its position to the common pathology of CNS diseases.

Stem cell treatment for Alzheimer's disease

Alzheimer’s disease (AD) is a progressive and neurodegenerative disorder that induces dementia in older people. It was first reported in 1907 by Alois Alzheimer, who characterized the disease as causing memory loss and cognitive impairment. Pathologic characteristics of AD are β-amyloid plaques, neurofibrillary tangles and neurodegeneration. Current therapies only target the relief of symptoms using various drugs, and do not cure the disease. Recently, stem cell therapy has been shown to be a potential approach to various diseases, including neurodegenerative disorders, and in this review, we focus on stem cell therapies for AD.

Inflammasomes in neuroinflammation and changes in brain function: a focused review

Recent literature has pointed to the existence of inflammasome-mediated inflammatory pathways in central nervous system (CNS) disorders and associated changes in behavior. Neuroinflammation, which is an innate immune response in the CNS against harmful and irritable stimuli such as pathogens and metabolic toxic waste, as well as to chronic mild stress, is mediated by protein complexes known as inflammasomes. Inflammasomes activate pro-inflammatory caspases 1 and 5, which then cleave the precursor forms of pro-inflammatory cytokines IL-1β, IL-18, and IL-33 into their active forms. These pro-inflammatory cytokines have been shown to promote a variety of innate immune processes associated with infection, inflammation, and autoimmunity, and thereby play an instrumental role in the instigation of neuroinflammation during old age and subsequent occurrence of neurodegenerative diseases, cognitive impairment, and dementia. In particular, NLRP inflammasomes may also have a role in the etiologies of depression, Alzheimer's disease (AD) and in metabolic disorders, such as Type II diabetes, obesity and cardiovascular diseases that have been shown to be co-morbid with psychiatric illnesses. It has been reported that while these inflammasomes may be activated through TNF-α dependent pathways, other cytokines, like IFN-γ, may assist in inhibiting their activation and thus delay disease progression. Furthermore, some other cytokines, including IL-6, may not have a direct role in inflammasome-mediated diseases. An array of recent research suggests that NLRP inflammasomes targeted therapies could be used for alleviating neuroinflammation and for treatment of associated psychiatric illnesses, although this still remains a challenge and necessitates further extensive research. This review examines the complex inflammatory signaling pathways involved in the activation of NLRP inflammasomes and the role they play in promoting neuroinflammation and subsequent behavioral changes.

Peripherally triggered and GSK-3β-driven brain inflammation differentially skew adult hippocampal neurogenesis, behavioral pattern separation and microglial activation in response to ibuprofen

Both familial and sporadic forms of Alzheimer disease (AD) present memory impairments. It has been proposed that these impairments are related to inflammation in relevant brain areas such as the hippocampus. Whether peripherally triggered and neuron-driven brain inflammation produce similar and equally reversible alterations is a matter of discussion. Here we studied the effects of ibuprofen administration on a familial AD mouse model overexpressing GSK-3β that presents severe brain inflammation. We compared these effects with those observed in a peripherally triggered brain inflammation model based on chronic lipopolysaccharide (LPS) administration. Both proinflammatory stimuli produced equivalent reversible morphological alterations in granule neurons; however, GSK-3β had a much more prominent role in newborn neuron connectivity, causing alterations that were not reversed by ibuprofen. Although both insults triggered similar behavioral impairments, ibuprofen rescued this defect in LPS-treated mice but did not produce any improvement in GSK-3β-overexpressing animals. This observation could be attributable to the different microglial phenotype induced by ibuprofen treatment. These data may be clinically relevant for AD therapies, as GSK-3β appears to determine the efficacy of ibuprofen treatment.

Eryptosis as a marker of Parkinson's disease

A major trend in recent Parkinson's disease (PD) research is the investigation of biological markers that could help in identifying at-risk individuals or to track disease progression and response to therapies. Central to this is the knowledge that inflammation is a known hallmark of PD and of many other degenerative diseases. In the current work, we focus on inflammatory signalling in PD, using a systems approach that allows us to look at the disease in a more holistic way. We discuss cyclooxygenases, prostaglandins, thromboxanes and also iron in PD. These particular signalling molecules are involved in PD pathophysiology, but are also very important in an aberrant coagulation/hematology system. We present and discuss a hypothesis regarding the possible interaction of these aberrant signalling molecules implicated in PD, and suggest that these molecules may affect the erythrocytes of PD patients. This would be observable as changes in the morphology of the RBCs and of PD patients relative to healthy controls. We then show that the RBCs of PD patients are indeed rather dramatically deranged in their morphology, exhibiting eryptosis (a kind of programmed cell death). This morphological indicator may have useful diagnostic and prognostic significance.

Amyloid-β pathology is attenuated by tauroursodeoxycholic acid treatment in APP/PS1 mice after disease onset

Alzheimer's disease (AD) is a neurodegenerative disorder hallmarked by the accumulation of extracellular amyloid-β (Aβ) peptide and intraneuronal hyperphosphorylated tau, as well as chronic neuroinflammation. Tauroursodeoxycholic acid (TUDCA) is an endogenous anti-apoptotic bile acid with potent neuroprotective properties in several experimental models of AD. We have previously reported the therapeutic efficacy of TUDCA treatment before amyloid plaque deposition in APP/PS1 double-transgenic mice. In the present study, we evaluated the protective effects of TUDCA when administrated after the onset of amyloid pathology. APP/PS1 transgenic mice with 7 months of age were injected intraperitoneally with TUDCA (500 mg/kg) every 3 days for 3 months. TUDCA treatment significantly attenuated Aβ deposition in the brain, with a concomitant decrease in Aβ₁₋₄₀ and Aβ₁₋₄₂ levels. The amyloidogenic processing of amyloid precursor protein was also reduced, indicating that TUDCA interferes with Aβ production. In addition, TUDCA abrogated GSK3β hyperactivity, which is highly implicated in tau hyperphosphorylation and glial activation. This effect was likely dependent on the specific activation of the upstream kinase, Akt. Finally, TUDCA treatment decreased glial activation and reduced proinflammatory cytokine messenger RNA expression, while partially rescuing synaptic loss. Overall, our results suggest that TUDCA is a promising therapeutic strategy not only for prevention but also for treatment of AD after disease onset.

Brilliant Blue G improves cognition in an animal model of Alzheimer's disease and inhibits amyloid-β-induced loss of filopodia and dendrite spines in hippocampal neurons

Deposits of amyloid-β (Aβ) protein are one of the hallmarks of Alzheimer's disease (AD). Numerous studies report that the Aβ peptide, especially in the oligomeric form, causes memory decline and other cognitive deficits. However, there have been very few effective interventions for termination or even delay of AD progression. Brilliant Blue G (BBG), a safe triphenylmethane dye and P2X7 antagonist, has been reported to have protective effects on neuroinflammation, ischemia, spinal injury and neurodegenerative disorders. Here we report that systematic administration of BBG diminishes spatial memory impairment and cognitive deficits in a mouse AD model produced by injecting soluble Aβ peptide into the hippocampal CA1 region. In addition, we show that Aβ-induced loss of filopodia and spine density in cultured hippocampal neurons was prevented by administration of BBG. We conclude that BBG prevents the learning and memory impairment and cognitive deficits induced by the toxicity of soluble Aβ, and improves the development of dendritic spines in hippocampal neurons in an AD model mouse. Considering the safety and blood-brain-barrier (BBB)-permeability of BBG, our data suggest a potential for BBG as a new therapy for AD.

Targeting Hsp90 and its co-chaperones to treat Alzheimer's disease

INTRODUCTION

Alzheimer's disease, characterized by the accumulation of hyperphosphorylated tau and β amyloid (Aβ), currently lacks effective treatment. Chaperone proteins, such as the heat shock protein (Hsp) 90, form macromolecular complexes with co-chaperones, which can regulate tau metabolism and Aβ processing. Although small molecule inhibitors of Hsp90 have been successful at ameliorating tau and Aβ burden, their development into drugs to treat disease has been slow due to the off- and on-target effects of this approach as well as challenges with the pharmacology of current scaffolds. Thus, other approaches are being developed to improve these compounds and to target co-chaperones of Hsp90 in an effort to limit these liabilities.

AREAS COVERED

This article discusses the most current developments in Hsp90 inhibitors including advances in blood-brain barrier permeability, decreased toxicity and homolog-specific small-molecule inhibitors. In addition, we discuss current strategies targeting Hsp90 co-chaperones rather than Hsp90 itself to reduce off-target effects.

EXPERT OPINION

Although Hsp90 inhibitors have proven their efficacy at reducing tau pathology, they have yet to meet with success in the clinic. The development of Hsp90/tau complex-specific inhibitors and further development of Hsp90 co-chaperone-specific drugs should yield more potent, less toxic therapeutics.

Physical activity, inflammation, and volume of the aging brain

Physical activity influences inflammation, and both affect brain structure and Alzheimer's disease (AD) risk. We hypothesized that older adults with greater reported physical activity intensity and lower serum levels of the inflammatory marker tumor necrosis factor α (TNFα) would have larger regional brain volumes on subsequent magnetic resonance imaging (MRI) scans. In 43 cognitively intact older adults (79.3±4.8 years) and 39 patients with AD (81.9±5.1 years at the time of MRI) participating in the Cardiovascular Health Study, we examined year-1 reported physical activity intensity, year-5 blood serum TNFα measures, and year-9 volumetric brain MRI scans. We examined how prior physical activity intensity and TNFα related to subsequent total and regional brain volumes. Physical activity intensity was measured using the modified Minnesota Leisure Time Physical Activities questionnaire at year 1 of the study, when all subjects included here were cognitively intact. Stability of measures was established for exercise intensity over 9 years and TNFα over 3 years in a subset of subjects who had these measurements at multiple time points. When considered together, more intense physical activity intensity and lower serum TNFα were both associated with greater total brain volume on follow-up MRI scans. TNFα, but not physical activity, was associated with regional volumes of the inferior parietal lobule, a region previously associated with inflammation in AD patients. Physical activity and TNFα may independently influence brain structure in older adults.

Risk of dementia among patients with asthma: a nationwide longitudinal study

BACKGROUND

Previous studies have suggested an association between asthma and dementia, but the results are still inconsistent.

METHODS

Using the Taiwan National Health Insurance Database, we enrolled 11,030 participants aged more than 45 years with asthma and 44,120 (1:4) age-/sex-matched controls between 1998 and 2008, and followed them to the end of 2011. Cases of any dementia or Alzheimer's disease that developed during the follow-up period were identified.

RESULTS

Asthma was associated with an increased risk of developing any dementia [hazard ratio (HR): 2.17, 95% confidence interval (CI): 1.87-2.52] and Alzheimer's disease (HR: 2.62, 95% CI: 1.71-4.02). Stratified by age, both asthma in midlife (>45 years and <65 years) and in late life (≥65 years) was associated with a greater likelihood of any dementia (HR: 2.48, 95% CI: 1.80-3.41; HR: 2.06, 95% CI: 1.74-2.44).

DISCUSSION

Asthma in midlife and in late life increased the risk of developing any dementia and Alzheimer's disease. The underlying mechanisms between asthma and dementia require further investigation.

A role for human brain pericytes in neuroinflammation

BACKGROUND

Brain inflammation plays a key role in neurological disease. Although much research has been conducted investigating inflammatory events in animal models, potential differences in human brain versus rodent models makes it imperative that we also study these phenomena in human cells and tissue.

METHODS

Primary human brain cell cultures were generated from biopsy tissue of patients undergoing surgery for drug-resistant epilepsy. Cells were treated with pro-inflammatory compounds IFNγ, TNFα, IL-1β, and LPS, and chemokines IP-10 and MCP-1 were measured by immunocytochemistry, western blot, and qRT-PCR. Microarray analysis was also performed on late passage cultures treated with vehicle or IFNγ and IL-1β.

RESULTS

Early passage human brain cell cultures were a mixture of microglia, astrocytes, fibroblasts and pericytes. Later passage cultures contained proliferating fibroblasts and pericytes only. Under basal culture conditions all cell types showed cytoplasmic NFκB indicating that they were in a non-activated state. Expression of IP-10 and MCP-1 were significantly increased in response to pro-inflammatory stimuli. The two chemokines were expressed in mixed cultures as well as cultures of fibroblasts and pericytes only. The expression of IP-10 and MCP-1 were regulated at the mRNA and protein level, and both were secreted into cell culture media. NFκB nuclear translocation was also detected in response to pro-inflammatory cues (except IFNγ) in all cell types. Microarray analysis of brain pericytes also revealed widespread changes in gene expression in response to the combination of IFNγ and IL-1β treatment including interleukins, chemokines, cellular adhesion molecules and much more.

CONCLUSIONS

Adult human brain cells are sensitive to cytokine challenge. As expected 'classical' brain immune cells, such as microglia and astrocytes, responded to cytokine challenge but of even more interest, brain pericytes also responded to such challenge with a rich repertoire of gene expression. Immune activation of brain pericytes may play an important role in communicating inflammatory signals to and within the brain interior and may also be involved in blood brain barrier (BBB) disruption . Targeting brain pericytes, as well as microglia and astrocytes, may provide novel opportunities for reducing brain inflammation and maintaining BBB function and brain homeostasis in human brain disease.

ABCA7 in Alzheimer's Disease

ATP-binding cassette A7 (ABCA7) gene has recently been identified as a strong genetic locus associated with late-onset Alzheimer's disease (LOAD) through genome-wide association studies (GWASs). ABCA7 is a member of the ATP-binding cassette (ABC) transporter gene superfamily, which codes for 49 ABC proteins, divided into 7 subfamilies (coded A-G). As a multispan transmembrane protein, ABCA7 is most abundantly expressed in the microglial cells in the brain. The levels of ABCA7 have been detected to be increased in the Alzheimer's disease (AD) brain, which positively correlated with amyloid plaque burden and disease severity. Emerging data suggests that ABCA7 could be associated with AD via various pathways, possibly including amyloid-β (Aβ) accumulation, lipid metabolism, and phagocytosis. In this review, we summarize the known functions of ABCA7 and discuss the single-nucleotide polymorphisms (SNPs) related to LOAD, as well as their potential physiological effects. Finally, given the contributions of ABCA7 to AD pathogenesis, targeting ABCA7 might provide novel opportunities for AD therapy.