Effects of methylphenidate on the behavior of male 5xFAD mice

Expansion of the neocortex and protection from neurodegeneration by in vivo transient reprogramming

Yamanaka factors (YFs) can reverse some aging features in mammalian tissues, but their effects on the brain remain largely unexplored. Here, we induced YFs in the mouse brain in a controlled spatiotemporal manner in two different scenarios: brain development and adult stages in the context of neurodegeneration. Embryonic induction of YFs perturbed cell identity of both progenitors and neurons, but transient and low-level expression is tolerated by these cells. Under these conditions, YF induction led to progenitor expansion, an increased number of upper cortical neurons and glia, and enhanced motor and social behavior in adult mice. Additionally, controlled YF induction is tolerated by principal neurons in the adult dorsal hippocampus and prevented the development of several hallmarks of Alzheimer's disease, including cognitive decline and altered molecular signatures, in the 5xFAD mouse model. These results highlight the powerful impact of YFs on neural proliferation and their potential use in brain disorders.

Vulnerability of Spatial Pattern Separation in 5xFAD Alzheimer's Disease Mouse Model

Background

Alzheimer's disease (AD) is the most common cause of dementia and remains incurable. This age-related neurodegenerative disease is characterized by an early decline in episodic and spatial memory associated with progressive disruption of the hippocampal functioning. Recent clinical evidence suggests that impairment of the spatial pattern separation (SPS) function, which enables the encoding and storage of episodic spatial information, may be an indicator of the early stages of AD.

Objective

The aim of our study was to characterize SPS performance at a prodromal stage in 5xFAD transgenic mouse model of AD.

Methods

Behavioral performance of male wild-type (WT) and 5xFAD mice (n = 14 per group) was assessed from the age of 4 months in two validated paradigms of SPS function either based on spontaneous exploration of objects or on the use of a touchscreen system.

Results

Compared with age-matched WT littermates, a mild deficit in SPS function was observed in the object recognition task in 5xFAD mice, whereas both groups showed similar performance in the touchscreen-based task. These results were observed in the absence of changes in locomotor activity or anxiety-like behavior that could have interfered with the tasks assessing SPS function.

Conclusions

Our results indicate an early vulnerability of the SPS function in 5xFAD mice in the paradigm based on spontaneous exploration of objects. Our work opens up the possibility of examining the early neurobiological processes involved in the decline of episodic memory and may help to propose new therapeutic strategies in the context of AD.

Promising candidates from drug clinical trials: Implications for clinical treatment of Alzheimer's disease in China

Alzheimer's disease is the most common neurodegenerative disease. Prior to 2017, National Medical Products Administration approved only four drugs to treat Alzheimer's disease, including three cholinesterase inhibitors and one N-methyl-D-aspartate receptor antagonist. We queried ClinicalTrials.gov to better understand Alzheimer's drug development over the past 5 years and found 16 promising candidates that have entered late-stage trials and analyzed their impact on clinical treatment of Alzheimer's disease in China. The 16 compounds selected include disease-modifying therapies and symptomatic therapies. The research and development pipeline now focuses on disease-modifying therapies such as gantenerumab, aducanumab, ALZ-801, ALZT-OP1, donanemab, lecanemab, simufilam, NE3107, semaglutide, and GV-971, which could put an end to the situation where Alzheimer's patients in China have no effective treatment alternatives. The reuse of drugs or combinations currently under investigation for the psychiatric treatment of Alzheimer's disease, including AXS-05, AVP-786, nabilone, brexpiprazole, methylphenidate, and pimavanserin, could provide physicians with additional treatment options. Although most of these drugs have not been explored in China yet, due to the current development trend in this field in China, it is expected that China will be involved in research on these drugs in the future.

Visuo-spatial learning and memory impairments in the 5xFAD mouse model of Alzheimer's disease: Effects of age, sex, albinism, and motor impairments

The 5xFAD mouse model of Alzheimer's disease (AD) rapidly develops AD-related neuro-behavioral pathology. Learning and memory impairments in 5xFAD mice, however, are not always replicated and the size of impairments varies considerably across studies. To examine possible sources of this variability, we analyzed the effects of age, sex, albinism due to background genes (Tyrc , Oca2p ) and motor impairment on learning and memory performance of wild type and 5xFAD mice on the Morris water maze, from 3 to 15 months of age. The 5xFAD mice showed impaired learning at 6-9 months of age, but memory impairments were not detected with the test procedure used in this study. Performance of 5xFAD mice was profoundly impaired at 12-15 months of age, but was accompanied by slower swim speeds than wild-type mice and a frequent failure to locate the escape platform. Overall female mice performed worse than males, and reversal learning impairments in 5xFAD mice were more pronounced in females than males. Albino mice performed worse than pigmented mice, confirming that albinism can impair performance of 5xFAD mice independently of AD-related transgenes. Overall, these results show that 5xFAD mice have impaired learning performance at 6-9 months of age, but learning and memory performance at 12-15 months is confounded with motor impairments. Furthermore, sex and albinism should be controlled to provide an accurate assessment of AD-related transgenes on learning and memory. These results will help reduce variability across pre-clinical experiments with 5xFAD mice, and thus enhance the reliability of studies developing new therapeutics for AD.

The Dynamics of β-Amyloid Proteoforms Accumulation in the Brain of a 5xFAD Mouse Model of Alzheimer’s Disease

Alzheimer’s disease (AD) is the leading cause of dementia among the elderly. Neuropathologically, AD is characterized by the deposition of a 39- to 42-amino acid long β-amyloid (Aβ) peptide in the form of senile plaques. Several post-translational modifications (PTMs) in the N-terminal domain have been shown to increase the aggregation and cytotoxicity of Aβ, and specific Aβ proteoforms (e.g., Aβ with isomerized D7 (isoD7-Aβ)) are abundant in the senile plaques of AD patients. Animal models are indispensable tools for the study of disease pathogenesis, as well as preclinical testing. In the presented work, the accumulation dynamics of Aβ proteoforms in the brain of one of the most widely used amyloid-based mouse models (the 5xFAD line) was monitored. Mass spectrometry (MS) approaches, based on ion mobility separation and the characteristic fragment ion formation, were applied. The results indicated a gradual increase in the Aβ fraction of isoD7-Aβ, starting from approximately 8% at 7 months to approximately 30% by 23 months of age. Other specific PTMs, in particular, pyroglutamylation, deamidation, and oxidation, as well as phosphorylation, were also monitored. The results for mice of different ages demonstrated that the accumulation of Aβ proteoforms correlate with the formation of Aβ deposits. Although the mouse model cannot be a complete analogue of the processes occurring in the human brain in AD, and several of the observed parameters differ significantly from human values supposedly due to the limited lifespan of the model animals, this dynamic study provides evidence on at least one of the possible mechanisms that can trigger amyloidosis in AD, i.e., the hypothesis on the relationship between the accumulation of isoD7-Aβ and the progression of AD-like pathology.

Vortioxetine administration attenuates cognitive and synaptic deficits in 5×FAD mice

RATIONALE AND OBJECTIVE

Vortioxetine has been reported to exhibit a variety of neurobiological functions and neuroprotective effects. In the present study, we aimed to investigate the effects of vortioxetine on cognitive performance in a transgenic mouse model of Alzheimer's disease (AD).

METHODS

We administered vortioxetine (10 mg/kg, i.p., every day, for approximately 6 weeks), which acts on multiple 5-serotonin (5-HT) receptors, to 3.5-month-old 5×FAD mice. Subsequently, we used the open field (OF) test to detect anxiety-like behavior in the mice. The novel object recognition (NOR) test and Morris water maze (MWM) were used to assess the cognitive states of the 5×FAD mice. We also measured the levels of insoluble amyloid plaques and soluble β-amyloid (Aβ) plaques. Finally, we explored the expression levels of postsynaptic density protein 95 (PSD95), synaptophysin (SYP), and synaptotagmin-1 (SYT1) in the hippocampus of the mice.

RESULTS

The administration of vortioxetine effectively reversed the reduction in anxiety-type behaviors in 5×FAD mice and improved the impairment in recognition memory and spatial reference memory. However, we did not find that vortioxetine decreased or delayed the formation of amyloid plaques or Aβ. Interestingly, we found a significant increase in the expression levels of PSD95, SYP, and SYT1 in the 5×FAD mice after vortioxetine treatment compared with the control group.

CONCLUSION

These results demonstrate that vortioxetine may improve cognitive impairment in 5×FAD mice. The role in cognitive improvement may be related to the beneficial effects of vortioxetine on synaptic function.

Myeloperoxidase Deficiency Inhibits Cognitive Decline in the 5XFAD Mouse Model of Alzheimer's Disease

Myeloperoxidase (MPO) is an enzyme expressed mostly by neutrophils and is a primary mediator of neutrophils oxidative stress response. While a profound body of evidence associates neutrophil-derived MPO in the pathogenesis of Alzheimer’s disease (AD), this role has not been assessed in an animal model of AD. Here, we produced hematologic chimerism in the 5XFAD mouse model of AD, with MPO deficient mice, resulting in 5XFAD with hematologic MPO deficiency (5XFAD-MPO KO). Behavioral examinations of 5XFAD-MPO KO showed significant superior performance in spatial learning and memory, associative learning, and anxiety/risk assessment behavior, as compared to 5XFAD mice transplanted with WT cells (5XFAD-WT). Hippocampal immunohistochemical and mRNA expression analyses showed significantly reduced levels of inflammatory mediators in 5XFAD-MPO KO mice with no apparent differences in the numbers of amyloid-β plaques. In addition, immunoblotting and mRNA analyses showed significantly reduced levels of APOE in 5XFAD-MPO KO. Together, these results indicate a substantial involvement of neutrophil-derived MPO in the pathology of 5XFAD model of AD and suggest MPO as a potential therapeutic target in AD.

Repeated Use of the Psychoactive Substance Ethylphenidate Impacts Neurochemistry and Reward Learning in Adolescent Male and Female Mice

Schedule II prescription psychostimulants, such as methylphenidate (MPH), can be misused as nootropic drugs, i.e., drugs that enhance focus and cognition. When users are unable to obtain these prescribed medications, they may seek out novel psychoactive substances (NPSs) that are not yet scheduled. An example of a NPS reportedly being abused is ethylphenidate (EPH), a close analog of MPH but with a higher preference for the dopamine transporter compared with the norepinephrine transporter. Therefore, based upon this pharmacological profile and user self-reports, we hypothesized that repeated EPH exposure in adolescent mice may be rewarding and alter cognition. Here, we report that repeated exposure to 15 mg/kg EPH decreased spatial cognitive performance as assessed by the Barnes maze spatial learning task in adolescent male C57Bl/6 mice; however, male mice did not show alterations in the expression of mature BDNF - a protein associated with increased cognitive function - in key brain regions. Acute EPH exposure induced hyperlocomotion at a high dose (15 mg/kg, i.p.), but not a low dose (5 mg/kg, i.p.). Interestingly, mice exhibited significant conditioned place preference at the low EPH dose, suggesting that even non-stimulating doses of EPH are rewarding. In both males and females, repeated EPH exposure increased expression of deltaFosB - a marker associated with increased risk of drug abuse - in the dorsal striatum, nucleus accumbens, and prefrontal cortex. Overall, our results suggest that repeated EPH use in adolescence is psychostimulatory, rewarding, increases crucial brain markers of reward-related behaviors, and may negatively impact spatial performance.

Conditional BDNF Delivery from Astrocytes Rescues Memory Deficits, Spine Density, and Synaptic Properties in the 5xFAD Mouse Model of Alzheimer Disease

It has been well documented that neurotrophins, including brain-derived neurotrophic factor (BDNF), are severely affected in Alzheimer's disease (AD), but their administration faces a myriad of technical challenges. Here we took advantage of the early astrogliosis observed in an amyloid mouse model of AD (5xFAD) and used it as an internal sensor to administer BDNF conditionally and locally. We first demonstrate the relevance of BDNF release from astrocytes by evaluating the effects of coculturing WT neurons and BDNF-deficient astrocytes. Next, we crossed 5xFAD mice with pGFAP:BDNF mice (only males were used) to create 5xFAD mice that overexpress BDNF when and where astrogliosis is initiated (5xF:pGB mice). We evaluated the behavioral phenotype of these mice. We first found that BDNF from astrocytes is crucial for dendrite outgrowth and spine number in cultured WT neurons. Double-mutant 5xF:pGB mice displayed improvements in cognitive tasks compared with 5xFAD littermates. In these mice, there was a rescue of BDNF/TrkB downstream signaling activity associated with an improvement of dendritic spine density and morphology. Clusters of synaptic markers, PSD-95 and synaptophysin, were also recovered in 5xF:pGB compared with 5xFAD mice as well as the number of presynaptic vesicles at excitatory synapses. Additionally, experimentally evoked LTP in vivo was increased in 5xF:pGB mice. The beneficial effects of conditional BDNF production and local delivery at the location of active neuropathology highlight the potential to use endogenous biomarkers with early onset, such as astrogliosis, as regulators of neurotrophic therapy in AD.SIGNIFICANCE STATEMENT Recent evidence places astrocytes as pivotal players during synaptic plasticity and memory processes. In the present work, we first provide evidence that astrocytes are essential for neuronal morphology via BDNF release. We then crossed transgenic mice (5xFAD mice) with the transgenic pGFAP-BDNF mice, which express BDNF under the GFAP promoter. The resultant double-mutant mice 5xF:pGB mice displayed a full rescue of hippocampal BDNF loss and related signaling compared with 5xFAD mice and a significant and specific improvement in all the evaluated cognitive tasks. These improvements did not correlate with amelioration of β amyloid load or hippocampal adult neurogenesis rate but were accompanied by a dramatic recovery of structural and functional synaptic plasticity.

Neonatal 6-OHDA lesion model in mouse induces Attention-Deficit/ Hyperactivity Disorder (ADHD)-like behaviour

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder characterized by impaired attention, impulsivity and hyperactivity. The "neonatal 6-hydroxydopamine" (6-OHDA) lesion is a commonly used model of ADHD in rat. However, a comprehensive assessment of ADHD-like symptoms is still missing, and data in mouse remain largely unavailable. Our aim was to analyse symptoms of ADHD in the mouse neonatal 6-OHDA model. 6-OHDA mice exhibited the major ADHD-like symptoms, i.e. hyperactivity (open field), attention deficit and impulsivity (five-choice serial reaction time task). Further, the model revealed discrete co-existing symptoms, i.e. anxiety-like (elevated plus maze test) and antisocial (social interaction) behaviours and decreased cognitive functioning (novel object recognition). The efficacy of methylphenidate, a classical psychostimulant used in the treatment of ADHD, was also evaluated. A histological analysis further supports the model validity by indicating dopamine depletion, changes in cortical thickness and abnormalities in anterior cingulate cortex neurons. A principal component analysis of the behaviour profile confirms that the 6-OHDA mouse model displayed good face and predictive validity. We conclude that neonatal dopamine depletion results in behavioural and morphological changes similar to those seen in patients and therefore could be used as a model for studying ADHD pathophysiological mechanisms and identifying therapeutic targets.

The small molecule CA140 inhibits the neuroinflammatory response in wild-type mice and a mouse model of AD

Background

Neuroinflammation is associated with neurodegenerative diseases, including Alzheimer’s disease (AD). Thus, modulating the neuroinflammatory response represents a potential therapeutic strategy for treating neurodegenerative diseases. Several recent studies have shown that dopamine (DA) and its receptors are expressed in immune cells and are involved in the neuroinflammatory response. Thus, we recently developed and synthesized a non-self-polymerizing analog of DA (CA140) and examined the effect of CA140 on neuroinflammation.

Methods

To determine the effects of CA140 on the neuroinflammatory response, BV2 microglial cells were pretreated with lipopolysaccharide (LPS, 1 μg/mL), followed by treatment with CA140 (10 μM) and analysis by reverse transcription-polymerase chain reaction (RT-PCR). To examine whether CA140 alters the neuroinflammatory response in vivo, wild-type mice were injected with both LPS (10 mg/kg, intraperitoneally (i.p.)) and CA140 (30 mg/kg, i.p.), and immunohistochemistry was performed. In addition, familial AD (5xFAD) mice were injected with CA140 or vehicle daily for 2 weeks and examined for microglial and astrocyte activation.

Results

Pre- or post-treatment with CA140 differentially regulated proinflammatory responses in LPS-stimulated microglia and astrocytes. Interestingly, CA140 regulated D1R levels to alter LPS-induced proinflammatory responses. CA140 significantly downregulated LPS-induced phosphorylation of ERK and STAT3 in BV2 microglia cells. In addition, CA140-injected wild-type mice exhibited significantly decreased LPS-induced microglial and astrocyte activation. Moreover, CA140-injected 5xFAD mice exhibited significantly reduced microglial and astrocyte activation.

Conclusions

CA140 may be beneficial for preventing and treating neuroinflammatory-related diseases, including AD.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1321-3) contains supplementary material, which is available to authorized users.

Aβ pathology downregulates brain mGluR5 density in a mouse model of Alzheimer

The aim of the present study was to evaluate functional changes of mGluR5 expression in advanced Alzheimer's disease (AD) using positron emission tomography (PET) with an mGluR5 specific radiotracer ([¹⁸F]FPEB) in 5xFAD AD model. Subsequently, in the same animal, mGluR5 expression was quantified by immunoassay techniques. The non-displaceable binding potential values for mGluR5 was estimated by the Logan's graphical analysis. Brain PET imaging revealed that radioactivities in the hippocampus and the striatum were significantly lower in 5xFAD mice compared to control animals. Binding values were also significantly lowered in 5xFAD mice. This decline was validated by immunoblotting of protein isolates from brain tissues, as the mean band density for 5xFAD mice had a lower mGluR5 intensity than for wild type mice. These results indicated that mGluR5 levels in 5xFAD mice were down regulated in the limbic system.

The locus coeruleus neuroprotective drug vindeburnol normalizes behavior in the 5xFAD transgenic mouse model of Alzheimer's disease

Damage to noradrenergic neurons in the Locus coeruleus (LC) occurs contributes to neuropathology and behavioral deficits in Alzheimer's disease (AD); methods to reduce LC damage may therefore be of benefit. We previously showed that vindeburnol, a derivative of the plant alkaloid vincamine, reduced neuroinflammation, amyloid burden, and LC damage in a mouse model of AD; however, effects on behavior were not tested. We now tested the effects of vindeburnol on anxiety-like behavior in 5xFAD mice which develop robust amyloid burden at early ages. During novel object recognition testing, we observed that 5xFAD mice spent more time exploring than wildtype littermates, and that time was reduced by vindeburnol. Vindeburnol also reduced hyperlocomotion in the 5xFAD mice which may have contributed to their increased exploration times. In an open field test, vindeburnol normalized the increase of time spent in the center, and the decrease of time spent near the walls in 5xFAD mice. Vindeburnol reduced amyloid burden in the hippocampus and cortex, areas that contribute to regulation of anxiety-like behavior. In vitro, vindeburnol increased neuronal BDNF expression in a cAMP-dependent manner; and inhibited phosphodiesterase activity with an EC₅₀ near 50 μM. These findings suggest that cAMP-mediated increases in neurotrophic factors contribute to beneficial effects of vindeburnol within the context of LC damage, which may be of value for treatment of some neuropsychiatric symptoms of AD.

Motor function deficits in the 12 month-old female 5xFAD mouse model of Alzheimer's disease

Motor problems occur early in some patients with Alzheimer's disease (AD) and as the disease progresses many patients develop motor dysfunction. Motor dysfunction has been reported in some mouse models of AD, including the 5xFAD mouse, thus this model may be particularly useful for studying motor dysfunction in AD. In order to determine the extent of motor dysfunction in these mice, we tested 11-13 month old female 5xFAD and wildtype (WT) control mice in a battery of motor behaviour tasks. The 5xFAD mice showed hind limb clasping, weighed less and had slower righting reflexes than WT mice. In the open field, the 5xFAD mice travelled a shorter distance than the WT mice, spent less time moving and had a slower movement speed. The 5xFAD mice fell faster than the WT mice from the balance beam, wire suspension, grid suspension and rotarod tasks, indicating dysfunctions in balance, grip strength, motor co-ordination and motor learning. The 5xFAD mice had a short, shuffling gait with a shorter stride length than WT mice and had a slower swim speed. The 5xFAD mice also failed to show an acoustic startle response, likely due to motor dysfunction and previously reported hearing impairment. The 5xFAD mice did not show deficits in the ability of peripheral motor nerves to drive muscle output, suggesting that motor impairments are not due to dysfunction in peripheral motor nerves. These results indicate that the aged 5xFAD mice are deficient in numerous motor behaviours, and suggest that these mice may prove to be a good model for studying the mechanisms of motor dysfunction in AD, and motor behaviour might prove useful for assessing the efficacy of AD therapeutics. Motor dysfunction in 5xFAD mice must also be considered in behavioural tests of sensory and cognitive function so that performance is not confounded by impaired locomotor or swimming behaviour.

Modulation of neuroinflammation and pathology in the 5XFAD mouse model of Alzheimer's disease using a biased and selective beta-1 adrenergic receptor partial agonist

Degeneration of noradrenergic neurons occurs at an early stage of Alzheimer's Disease (AD). The noradrenergic system regulates arousal and learning and memory, and has been implicated in regulating neuroinflammation. Loss of noradrenergic tone may underlie AD progression at many levels. We have previously shown that acute administration of a partial agonist of the beta-1 adrenergic receptor (ADRB1), xamoterol, restores behavioral deficits in a mouse model of AD. The current studies examined the effects of chronic low dose xamoterol on neuroinflammation, pathology, and behavior in the pathologically aggressive 5XFAD transgenic mouse model of AD. In vitro experiments in cells expressing human beta adrenergic receptors demonstrate that xamoterol is highly selective for ADRB1 and functionally biased for the cAMP over the β-arrestin pathway. Data demonstrate ADRB1-mediated attenuation of TNF-α production with xamoterol in primary rat microglia culture following LPS challenge. Finally, two independent cohorts of 5XFAD and control mice were administered xamoterol from approximately 4.0-6.5 or 7.0-9.5 months, were tested in an array of behavioral tasks, and brains were examined for evidence of neuroinflammation, and amyloid beta and tau pathology. Xamoterol reduced mRNA expression of neuroinflammatory markers (Iba1, CD74, CD14 and TGFβ) and immunohistochemical evidence for microgliosis and astrogliosis. Xamoterol reduced amyloid beta and tau pathology as measured by regional immunohistochemistry. Behavioral deficits were not observed for 5XFAD mice. In conclusion, chronic administration of a selective, functionally biased, partial agonist of ADRB1 is effective in reducing neuroinflammation and amyloid beta and tau pathology in the 5XFAD model of AD.

Apathy associated with neurocognitive disorders: Recent progress and future directions

INTRODUCTION

Apathy is common in neurocognitive disorders (NCDs) such as Alzheimer's disease and mild cognitive impairment. Although the definition of apathy is inconsistent in the literature, apathy is primarily defined as a loss of motivation and decreased interest in daily activities.

METHODS

The Alzheimer's Association International Society to Advance Alzheimer's Research and Treatment (ISTAART) Neuropsychiatric Syndromes Professional Interest Area (NPS-PIA) Apathy workgroup reviewed the latest research regarding apathy in NCDs.

RESULTS

Progress has recently been made in three areas relevant to apathy: (1) phenomenology, including the use of diagnostic criteria and novel instruments for measurement, (2) neurobiology, including neuroimaging, neuropathological and biomarker correlates, and (3) interventions, including pharmacologic, nonpharmacologic, and noninvasive neuromodulatory approaches.

DISCUSSION

Recent progress confirms that apathy has a significant impact on those with major NCD and those with mild NCDs. As such, it is an important target for research and intervention.