Presenilin-1 familial Alzheimer's disease mutation alters hippocampal neurogenesis and memory function in CCL2 null mice

Role of Chemokines in the Development and Progression of Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive neurogenerative disorder manifested by gradual memory loss and cognitive decline due to profound damage of cholinergic neurons. The neuropathological hallmarks of AD are intracellular deposits of neurofibrillary tangles (NFTs) and extracellular aggregates of amyloid β (Aβ). Mounting evidence indicates that intensified neuroinflammatory processes play a pivotal role in the pathogenesis of AD. Chemokines serve as signaling molecules in immune cells but also in nerve cells. Under normal conditions, neuroinflammation plays a neuroprotective role against various harmful factors. However, overexpression of chemokines initiates disruption of the integrity of the blood–brain barrier, facilitating immune cells infiltration into the brain. Then activated adjacent glial cells–astrocytes and microglia, release massive amounts of chemokines. Prolonged inflammation loses its protective role and drives an increase in Aβ production and aggregation, impairment of its clearance, or enhancement of tau hyperphosphorylation, contributing to neuronal loss and exacerbation of AD. Moreover, chemokines can be further released in response to growing deposits of toxic forms of Aβ. On the other hand, chemokines seem to exert multidimensional effects on brain functioning, including regulation of neurogenesis and synaptic plasticity in regions responsible for memory and cognitive abilities. Therefore, underexpression or complete genetic ablation of some chemokines can worsen the course of AD. This review covers the current state of knowledge on the role of particular chemokines and their receptors in the development and progression of AD. Special emphasis is given to their impact on forming Aβ and NFTs in humans and in transgenic murine models of AD.

CD4+ effector T cells accelerate Alzheimer's disease in mice

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by pathological deposition of misfolded self-protein amyloid beta (Aβ) which in kind facilitates tau aggregation and neurodegeneration. Neuroinflammation is accepted as a key disease driver caused by innate microglia activation. Recently, adaptive immune alterations have been uncovered that begin early and persist throughout the disease. How these occur and whether they can be harnessed to halt disease progress is unclear. We propose that self-antigens would induct autoreactive effector T cells (Teffs) that drive pro-inflammatory and neurodestructive immunity leading to cognitive impairments. Here, we investigated the role of effector immunity and how it could affect cellular-level disease pathobiology in an AD animal model.

METHODS

In this report, we developed and characterized cloned lines of amyloid beta (Aβ) reactive type 1 T helper (Th1) and type 17 Th (Th17) cells to study their role in AD pathogenesis. The cellular phenotype and antigen-specificity of Aβ-specific Th1 and Th17 clones were confirmed using flow cytometry, immunoblot staining and Aβ T cell epitope loaded haplotype-matched major histocompatibility complex II IAb (MHCII-IAb-KLVFFAEDVGSNKGA) tetramer binding. Aβ-Th1 and Aβ-Th17 clones were adoptively transferred into APP/PS1 double-transgenic mice expressing chimeric mouse/human amyloid precursor protein and mutant human presenilin 1, and the mice were assessed for memory impairments. Finally, blood, spleen, lymph nodes and brain were harvested for immunological, biochemical, and histological analyses.

RESULTS

The propagated Aβ-Th1 and Aβ-Th17 clones were confirmed stable and long-lived. Treatment of APP/PS1 mice with Aβ reactive Teffs accelerated memory impairment and systemic inflammation, increased amyloid burden, elevated microglia activation, and exacerbated neuroinflammation. Both Th1 and Th17 Aβ-reactive Teffs progressed AD pathology by downregulating anti-inflammatory and immunosuppressive regulatory T cells (Tregs) as recorded in the periphery and within the central nervous system.

CONCLUSIONS

These results underscore an important pathological role for CD4+ Teffs in AD progression. We posit that aberrant disease-associated effector T cell immune responses can be controlled. One solution is by Aβ reactive Tregs.

Alzheimer's Disease and Its Potential Alternative Therapeutics

Alzheimer’s Disease (AD) is a chronic neurodegenerative disease that affects over 5 million individuals in the United States alone. Currently, there are only two kinds of pharmacological interventions available for symptomatic relief of AD; Acetyl Cholinesterase Inhibitors (AChEI) and N-methyl-D-aspartic Acid (NMDA) receptor antagonists and these drugs do not slow down or stop the progression of the disease. Several molecular targets have been implicated in the pathophysiology of AD, such as the tau (τ) protein, Amyloid-beta (Aβ), the Amyloid Precursor Protein (APP) and more and several responses have also been observed in the advancement of the disease, such as reduced neurogenesis, neuroinflammation, oxidative stress and iron overload. In this review, we discuss general features of AD and several small molecules across different experimental AD drug classes that have been studied for their effects in the context of the molecular targets and responses associated with the AD progression. These drugs include: Paroxetine, Desferrioxamine (DFO), N-acetylcysteine (NAC), Posiphen/-(−)Phenserine, JTR-009, Carvedilol, LY450139, Intravenous immunoglobulin G 10%, Indomethacin and Lithium Carbonate (Li₂CO₃).

Reboxetine Treatment Reduces Neuroinflammation and Neurodegeneration in the 5xFAD Mouse Model of Alzheimer's Disease: Role of CCL2

The reduction of brain noradrenaline levels is associated to the initiation of Alzheimer's disease and contributes to its progression. This seems to be due mainly to the anti-neuroinflammatory actions of noradrenaline. The analysis of noradrenaline effects on brain cells demonstrates that it also regulates the production of the chemokine CCL2. In the present study, we analyzed the effect of the selective noradrenaline reuptake inhibitor, reboxetine, on the inflammatory and neurodegenerative alterations present in 5xFAD mice, and how the genetic removal of CCL2 affects reboxetine actions. We observed that the removal of CCL2 reduced the memory impairments in 5xFAD mice as well as the neuroinflammatory response, the accumulation of amyloid beta plaques, and the degeneration of neurons in the brain cortex. The administration of reboxetine with osmotic pumps for 28 days also resulted in anti-inflammatory and neuroprotective changes in 5xFAD mice, even in the absence of CCL2. Yet, 6-month-old CCL2KO mice presented a significant degree of neuroinflammation and neuronal damage. These findings indicate that reboxetine treatment prevents the brain alterations caused by prolonged overproduction of amyloid beta, being these effects independent of CCL2, which is a mediator of the damage caused by amyloid beta in the brain cortex, but necessary for the prevention of the development of neurodegeneration in normal healthy conditions.

Induction of a Na+/K+-ATPase-dependent form of autophagy triggers preferential cell death of human immunodeficiency virus type-1-infected macrophages

Although antiretroviral therapy is highly effective in suppressing human immunodeficiency virus type-1 (HIV) replication, treatment has failed to eliminate viral reservoirs and discontinuation of treatment results in viral reactivation. Here, we demonstrate that peptides Tat-vFLIP-α2 and Tat-Beclin 1/BECN1 which have been shown to induce a Na⁺/K⁺-ATPase- and a macroautophagy/autophagy-dependent form of cell death, autosis, can preferentially kill HIV-infected macrophages while preventing virological rebound. To improve bioavailability and drug delivery, Tat-vFLIP-α2 was encapsulated into biodegradable PLGA (poly lactic-co-glycolic acid)-lipid-PEG (polyethylene glycol) nanoparticles for long-lasting intracellular delivery. After a single dose of NP-vFLIP-α2, HIV-infected macrophages were preferentially killed in a dose-dependent manner compared to uninfected or untreated HIV-infected cells with complete inhibition of HIV infection at 10 μM of peptide. HIV-infected macrophages treated with NP-vFLIP-α2 exhibited increased markers of autophagy including LC3B lipidation, SQSTM1/p62 degradation and Na⁺/K⁺-ATPase expression compared to untreated uninfected or infected cells. Moreover, the increased cell death observed in HIV-infected cells was not altered by treatment with bafilomycin A₁ (BAF) or the caspase inhibitor Z-VAD-FMK, but could be reversed following treatment with the Na⁺/K⁺-ATPase inhibitor, digoxin, or knockdown of ATG5 or ATG7. NP-vFLIP-α2 induced preferential killing was also detected in HIV-infected macrophages under antiretroviral suppression without inducing viral reactivation. Additionally, we found that Na⁺/K⁺-ATPase was upregulated in HIV-infected cells, which enhanced NP-vFLIP-α2 induced cell death. These findings provide a novel strategy to eradicate HIV-infected macrophages by selectively killing infected cells through the induction of Na⁺/K⁺-ATPase dependent autophagy, while preventing reactivation of virus and new infection of uninfected bystander cells.

Granulocyte-macrophage colony-stimulating factor neuroprotective activities in Alzheimer's disease mice

We investigated the effects of granulocyte-macrophage colony stimulating factor (GM-CSF) on behavioral and pathological outcomes in Alzheimer's disease (AD) and non-transgenic mice. GM-CSF treatment in AD mice reduced brain amyloidosis, increased plasma Aβ, and rescued cognitive impairment with increased hippocampal expression of calbindin and synaptophysin and increased levels of doublecortin-positive cells in the dentate gyrus. These data extend GM-CSF pleiotropic neuroprotection mechanisms in AD and include regulatory T cell-mediated immunomodulation of microglial function, Aβ clearance, maintenance of synaptic integrity, and induction of neurogenesis. Together these data support further development of GM-CSF as a neuroprotective agent for AD.

URMC-099 facilitates amyloid-β clearance in a murine model of Alzheimer's disease

Background

The mixed lineage kinase type 3 inhibitor URMC-099 facilitates amyloid-beta (Aβ) clearance and degradation in cultured murine microglia. One putative mechanism is an effect of URMC-099 on Aβ uptake and degradation. As URMC-099 promotes endolysosomal protein trafficking and reduces Aβ microglial pro-inflammatory activities, we assessed whether these responses affect Aβ pathobiogenesis. To this end, URMC-099’s therapeutic potential, in Aβ precursor protein/presenilin-1 (APP/PS1) double-transgenic mice, was investigated in this model of Alzheimer’s disease (AD).

Methods

Four-month-old APP/PS1 mice were administered intraperitoneal URMC-099 injections at 10 mg/kg daily for 3 weeks. Brain tissues were examined by biochemical, molecular and immunohistochemical tests.

Results

URMC-099 inhibited mitogen-activated protein kinase 3/4-mediated activation and attenuated β-amyloidosis. Microglial nitric oxide synthase-2 and arginase-1 were co-localized with lysosomal-associated membrane protein 1 (Lamp1) and Aβ. Importatly, URMC-099 restored synaptic integrity and hippocampal neurogenesis in APP/PS1 mice.

Conclusions

URMC-099 facilitates Aβ clearance in the brain of APP/PS1 mice. The multifaceted immune modulatory and neuroprotective roles of URMC-099 make it an attractive candidate for ameliorating the course of AD. This is buttressed by removal of pathologic Aβ species and restoration of the brain’s microenvironment during disease.

Anti-retroviral drugs: current state and development in the next decade

The pace of discovery of new antiretroviral (ARV) drugs has slowed, although the efficacy and safety of once-daily fixed dose combinations have been extensively investigated. Several traditional ARV drugs remain in phase III clinical trials. This review summarizes current information on ARV drugs in phase III clinical trials and focuses on the development of ARV drugs in the next decade.

Cytoprotective effect of kaempferol against palmitic acid-induced pancreatic β-cell death through modulation of autophagy via AMPK/mTOR signaling pathway

Lipotoxicity of pancreatic β-cells is the pathological manifestation of obesity-linked type II diabetes. We intended to determine the cytoprotective effect of kaempferol on pancreatic β-cells undergoing apoptosis in palmitic acid (PA)-stressed condition. The data showed that kaempferol treatment increased cell viability and anti-apoptotic activity in PA-stressed RIN-5F cells and murine pancreatic islets. Furthermore, kaempferol's ability to instigate autophagy was illustrated by MDC-LysoTracker red staining and TEM analysis which corroborated well with the observed increase in LC3 puncta and LC3-II protein expressions along with the concomitant decline in p62 expression. Apart from this, the data showed that kaempferol up/down-regulates AMPK/mTOR phosphorylation respectively. Subsequently, upon inhibition of AMPK phosphorylation by AMPK inhibitors, kaempferol-mediated autophagy was abolished which further led to the decline in β-cell survival. Such observations collectively lead to the conclusion that, kaempferol exerts its cytoprotective role against lipotoxicity by activation of autophagy via AMPK/mTOR pathway.

Magnesium Elevation Promotes Neuronal Differentiation While Suppressing Glial Differentiation of Primary Cultured Adult Mouse Neural Progenitor Cells through ERK/CREB Activation

This study aimed to explore the influence of magnesium elevation on fate determination of adult neural progenitor cells (aNPCs) and the underlying mechanism in vitro. Adult neurogenesis, which is the generation of functional neurons from neural precursors, occurs throughout life in restricted anatomical regions in mammals. Magnesium is the fourth most abundant ion in mammals, and its elevation in the brain has been shown to enhance memory and synaptic plasticity in vivo. However, the effects of magnesium on fate determination of aNPCs, which are vital processes in neurogenesis, remain unknown. NPCs isolated from the dentate gyrus of adult C57/BL6 mice were induced to differentiate in a medium with varying magnesium concentrations (0.6, 0.8, and 1.0 mM) and extracellular signal-regulated kinase (ERK) inhibitor PD0325901. The proportion of cells that differentiated into neurons and glial cells was evaluated using immunofluorescence. Quantitative real-time polymerase chain reaction and Western blot methods were used to determine the expression of β-III tubulin (Tuj1) and glial fibrillary acidic protein (GFAP). The activation of ERK and cAMP response element-binding protein (CREB) was examined by Western blot to reveal the underlying mechanism. Magnesium elevation increased the proportion of Tju1-positive cells and decreased the proportion of GFAP-positive cells. Also, the expression of Tuj1 was upregulated, whereas the expression of GFAP was downregulated. Moreover, magnesium elevation enhanced the activation of both ERK and CREB. Treatment with PD0325901 reversed these effects in a dose-dependent manner. Magnesium elevation promoted neural differentiation while suppressing glial cell differentiation, possibly via ERK-induced CREB activation.

Cathepsin B Improves ß-Amyloidosis and Learning and Memory in Models of Alzheimer's Disease

Amyloid-ß (Aß) precursor protein (APP) metabolism engages neuronal endolysosomal pathways for Aß processing and secretion. In Alzheimer's disease (AD), dysregulation of APP leads to excess Aß and neuronal dysfunction; suggesting that neuronal APP/Aß trafficking can be targeted for therapeutic gain. Cathepsin B (CatB) is a lysosomal cysteine protease that can lower Aß levels. However, whether CatB-modulation of Aß improves learning and memory function deficits in AD is not known. To this end, progenitor neurons were infected with recombinant adenovirus expressing CatB and recovered cell lysates subjected to proteomic analyses. The results demonstrated Lamp1 deregulation and linkages between CatB and the neuronal phagosome network. Hippocampal injections of adeno-associated virus expressing CatB reduced Aß levels, increased Lamp1 and improved learning and memory. The findings were associated with the emergence of c-fos + cells. The results support the idea that CatB can speed Aß metabolism through lysosomal pathways and as such reduce AD-associated memory deficits.

Dynamic expression of the mouse orthologue of the human amyotropic lateral sclerosis associated gene C9orf72 during central nervous system development and neuronal differentiation

The hexanucleotide repeat in the first intron of the C9orf72 gene is the most significant cause of amyotropic lateral sclerosis as well as some forms of fronto-temporal dementia. The C9orf72 protein has been previously reported to be expressed in post-mortem human brain as well as in late embryonic and some postnatal stages in mice. Herein, we present a detailed study of the distribution of C9orf72 protein in the embryonic, postnatal and adult mouse brain, spinal cord as well as during the differentiation of P19 embryonal carcinoma cells to neurons including motor neurons. We show that the expression levels of the C9orf72 transcripts in the developing and adult mouse brain as well as in differentiating neurons, are dynamic. Besides the strong expression in the cerebellum and motor cortex reported previously, we show for the first time that C9orf72 is expressed strongly in the olfactory bulb and also in the hippocampus. Our immunostaining data also reveal a hitherto unreported switch in the cellular distribution of C9orf72 from a predominantly cytoplasmic to a nucleo-cytoplasmic distribution during corticogenesis. This switch in distribution was also observed during differentiation of the pluripotent embryonal carcinoma P19 cell line to mature neurons. Our findings have implications for interpreting the pathophysiology caused by the repeat expansions in C9orf72 in mouse models.