Validation of a 2-day water maze protocol in mice

"Sigma-1 receptor modulation by clemastine highlights its repurposing as neuroprotective agent against seizures and cognitive deficits in PTZ-kindled rats"

Epilepsy is a neurological disorder characterized by recurrent spontaneous seizures alongside other neurological comorbidities. Cognitive impairment is the most frequent comorbidity secondary to progressive neurologic changes in epilepsy. Sigma 1 receptors (σ1 receptors) are involved in the neuroprotection and pathophysiology of both conditions and targeting these receptors may have the potential to modulate both seizures and comorbidities. The current research demonstrated the effect of clemastine (10 mg/kg, P.O.), a non-selective σ1 receptor agonist, on pentylenetetrazol (PTZ) (35 mg/kg, i.p., every 48 h for 14 doses)-kindling rats by acting on σ1 receptors through its anti-inflammatory/antioxidant capacity. Clemastine and phenytoin (30 mg/kg, P.O.) or their combination were given once daily. Clemastine treatment showed a significant effect on neurochemical, behavioural, and histopathological analyses through modulation of σ1 receptors. It protected the kindling animals from seizures and attenuated their cognitive impairment in the Morris water maze test by reversing the PTZ hippocampal neuroinflammation/oxidative stress state through a significant increase in inositol-requiring enzyme 1 (IRE1), x-box binding protein 1 (XBP1), along with a reduction of total reactive oxygen species (TROS) and amyloid beta protein (Aβ). The involvement of σ1 receptors in the protective effects of clemastine was confirmed by their abrogation when utilizing NE-100, a selective σ1 receptor antagonist. In light of our findings, modulating σ1 receptors emerges as a compelling therapeutic strategy for epilepsy and its associated cognitive impairments. The significant neuroprotective effects observed with clemastine underscore the potential of σ1 receptor-targeted treatments to address both the primary symptoms and comorbidities of neurological disorders.

L-carnitine Modulates Cognitive Impairment Induced by Doxorubicin and Cyclophosphamide in Rats; Insights to Oxidative Stress, Inflammation, Synaptic Plasticity, Liver/brain, and Kidney/brain Axes

Chemotherapy-induced cognitive impairment in cancer patients is known as "chemobrain". Doxorubicin and Cyclophosphamide are two chemotherapeutic agents used in combination to treat solid tumors. L-carnitine was reported for its anti-oxidant and anti-inflammatory activities. The goal of the present study was to elucidate the neuroprotective effect of L-carnitine against chemobrain induced by Doxorubicin and Cyclophosphamide in rats. Rats were divided into five groups: Control group; Doxorubicin (4mg/kg, IV) and Cyclophosphamide (40mg/kg, IV)-treated group; two L-carnitine-treated groups (150 and 300mg/kg, ip) with Doxorubicin and Cyclophosphamide; and L-carnitine alone-treated group (300mg/kg). Doxorubicin and Cyclophosphamide induced histopathological changes in rats' hippocampi and prefrontal cortices, as well as reduced memory as evidenced by behavioural testing. L-carnitine treatment showed opposite effects. In addition, chemotherapy treatment enhanced oxidative stress via reducing catalase and glutathione levels, and inducing lipid peroxidation. By contrast, L-carnitine treatment showed powerful antioxidant effects reversing chemotherapy-induced oxidative damage. Moreover, chemotherapy combination induced inflammation via their effect on nuclear factor kappa B (p65), interleukin-1β, and tumor necrosis factor-α. However, L-carnitine treatment corrected such inflammatory responses. Furthermore, Doxorubicin and Cyclophosphamide reduced synaptic plasticity via hindering expression of brain-derived neurotrophic factor, phosphorylated cyclase response element binding protein, synaptophysin, and postsynaptic density protein 95 whereas protein expression of such synaptic plasticity biomarkers was enhanced by L-carnitine treatment. Finally, acetylcholinesterase activity was found to be enhanced by chemotherapy treatment affecting rats' memory while L-carnitine treatment reduced acetylcholinesterase activity. L-carnitine also showed hepatoprotective and renal protective effects suggesting liver/brain and kidney/brain axes as possible mechanisms for its neuroprotective effects.

Engineered macrophage-biomimetic versatile nanoantidotes for inflammation-targeted therapy against Alzheimer's disease by neurotoxin neutralization and immune recognition suppression

Immune recognition of excessive neurotoxins by microglia is a trigger for the onset of neuroinflammation in the brain, leading to neurodegeneration in Alzheimer's disease (AD). Blocking active recognition of microglia while removing neurotoxins holds promise for fundamentally alleviating neurotoxin-induced immune responses, but is very challenging. Herein, an engineered macrophage-biomimetic versatile nanoantidote (OT-Lipo@M) is developed for inflammation-targeted therapy against AD by neurotoxin neutralization and immune recognition suppression. Coating macrophage membranes can not only endow OT-Lipo@M with anti-phagocytic and inflammation-tropism capabilities to target inflammatory lesions in AD brain, but also efficiently reduce neurotoxin levels to prevent them from activating microglia. The loaded oxytocin (OT) can be slowly released to downregulate the expression of immune recognition site Toll-like receptor 4 (TLR4) on microglia, inhibiting TLR4-mediated pro-inflammatory signalling cascade. Benefiting from this two-pronged immunosuppressive strategy, OT-Lipo@M exhibits outstanding therapeutic effects on ameliorating cognitive deficits, inhibiting neuronal apoptosis, and enhancing synaptic plasticity in AD mice, accompanied by the delayed hippocampal atrophy and brain microstructural disruption by in vivo 9.4T MR imaging. This work provides new insights into potential AD therapeutics targeting microglia-mediated neuroinflammation at the source.

Rosmarinic Acid Improves Cognitive Abilities and Glucose Metabolism in Aged C57Bl/6N Mice While Disrupting Lipid Profile in Young Adults in a Sex-Dependent Fashion

A growing body of evidence suggests that regular consumption of natural products might promote healthy aging; however, their mechanisms of action are still unclear. Rosmarinic acid (RA) is a polyphenol holding anti-inflammatory, antioxidant and neuroprotective properties. The aim of this study was to characterise the efficacy of an oral administration of RA in promoting healthspan in a mouse model of physiological aging. Aged C57Bl/6 male and female (24-month-old) mice were either administered with RA (500 mg/Kg) or a vehicle in drinking bottles for 52 days while 3-month-old mice receiving the same treatment were used as controls. All subjects were assessed for cognitive abilities in the Morris water maze (MWM) and for emotionality in the elevated-plus maze test (EPM). Brain-derived Neurotrophic Factor (BDNF) protein levels were evaluated in the hippocampus. Since the interaction between metabolic signals and cerebral functions plays a pivotal role in the etiopathogenesis of cognitive decline, the glycaemic and lipid profiles of the mice were also assessed. RA enhanced learning and memory in 24-month-old mice, an effect that was associated to improved glucose homeostasis. By contrast, the lipid profile was disrupted in young adults. This effect was associated with worse glycaemic control in males and with reduced BDNF levels in females, suggesting powerful sex-dependent effects and raising a note of caution for RA administration in young healthy adult subjects.

Differential effects of exposure to toxic or nontoxic mold spores on brain inflammation and Morris water maze performance

People who live or work in moldy buildings often complain of "brain fog" that interferes with cognitive performance. Until recently, there was no published research on the effects of controlled exposure to mold stimuli on cognitive function or an obvious mechanism of action, fueling controversy over these claims. The constellation of health problems reported by mold-exposed individuals (respiratory issues, fatigue, pain, anxiety, depression, and cognitive deficits) correspond to those caused by innate immune activation following exposure to bacterial or viral stimuli. To determine if mold-induced innate immune activation might cause cognitive issues, we quantified the effects of both toxic and nontoxic mold on brain immune activation and spatial memory in the Morris water maze. We intranasally administered either 1) intact, toxic Stachybotrys chartarum spores; 2) ethanol-extracted, nontoxic Stachybotrys chartarum spores; or 3) control saline vehicle to mice. Inhalation of nontoxic spores caused significant deficits in the test of long-term memory of platform location, while not affecting short-term memory. Inhalation of toxic spores increased motivation to reach the platform. Interestingly, in both groups of mold-exposed males, numbers of interleukin-1β-immunoreactive cells in many areas of the hippocampus significantly correlated with latency to find the platform, path length, and swimming speed during training, but not during testing for long-term memory. These data add to our prior evidence that mold inhalation can interfere with cognitive processing in different ways depending on the task, and that brain inflammation is significantly correlated with changes in behavior.

High-fat diet exacerbates cognitive decline in mouse models of Alzheimer's disease and mixed dementia in a sex-dependent manner

BACKGROUND

Approximately 70% of Alzheimer's disease (AD) patients have co-morbid vascular contributions to cognitive impairment and dementia (VCID); this highly prevalent overlap of dementia subtypes is known as mixed dementia (MxD). AD is more prevalent in women, while VCID is slightly more prevalent in men. Sex differences in risk factors may contribute to sex differences in dementia subtypes. Unlike metabolically healthy women, diabetic women are more likely to develop VCID than diabetic men. Prediabetes is 3× more prevalent than diabetes and is linked to earlier onset of dementia in women, but not men. How prediabetes influences underlying pathology and cognitive outcomes across different dementia subtypes is unknown. To fill this gap in knowledge, we investigated the impact of diet-induced prediabetes and biological sex on cognitive function and neuropathology in mouse models of AD and MxD.

METHODS

Male and female 3xTg-AD mice received a sham (AD model) or unilateral common carotid artery occlusion surgery to induce chronic cerebral hypoperfusion (MxD model). Mice were fed a control or high fat (HF; 60% fat) diet from 3 to 7 months of age. In both sexes, HF diet elicited a prediabetic phenotype (impaired glucose tolerance) and weight gain.

RESULTS

In females, but not males, metabolic consequences of a HF diet were more severe in AD or MxD mice compared to WT. In both sexes, HF-fed AD or MxD mice displayed deficits in spatial memory in the Morris water maze (MWM). In females, but not males, HF-fed AD and MxD mice also displayed impaired spatial learning in the MWM. In females, but not males, AD or MxD caused deficits in activities of daily living, regardless of diet. Astrogliosis was more severe in AD and MxD females compared to males. Further, AD/MxD females had more amyloid beta plaques and hippocampal levels of insoluble amyloid beta 40 and 42 than AD/MxD males. In females, but not males, more severe glucose intolerance (prediabetes) was correlated with increased hippocampal microgliosis.

CONCLUSIONS

High-fat diet had a wider array of metabolic, cognitive, and neuropathological consequences in AD and MxD females compared to males. These findings shed light on potential underlying mechanisms by which prediabetes may lead to earlier dementia onset in women.

A review of behavioral methods for the evaluation of cognitive performance in animal models: Current techniques and links to human cognition

INTRODUCTION

Memory is defined as the ability to store, maintain and retrieve information. Learning is the acquisition of information that changes behavior and memory. Stress, dementia, head trauma, amnesia, Alzheimer's, Huntington, Parkinson's, Wernicke-Korsakoff syndrome (WKS) may be mentioned among the diseases in which memory and learning are affected. The task of understanding deficits in memory and learning in humans is daunting due to the complexity of neural and cognitive mechanisms in the nervous system. This job is made more difficult for clinicians and researchers by the fact that many techniques used to research memory are not ethically acceptable or technically feasible for use in humans. Thus, animal models have been necessary alternative for studying normal and disordered learning and memory. This review attempts to bridge these domains to allow biomedical researchers to have a firm grasp of "memory" and "learning" as constructs in humans whereby they may then select the proper animal cognitive test.

RESULTS AND CONCLUSION

Various tests (open field habituation test, Y-maze test, passive avoidance test, step-down inhibitory avoidance test, active avoidance test, 8-arms radial maze test, Morris water maze test, radial arm water maze, novel object recognition test and gait function test) have been designed to evaluate different kinds of memory. Each of these tests has their strengths and limits. Abnormal results obtained using these tasks in non-human animals indicate malfunctions in memory which may be due to several physiological and psychological diseases of nervous system. Further studies by using the discussed tests can be very beneficial for achieving a therapeutic answer to these diseases.

The effect of exercise on early sensorimotor performance alterations in the 3xTg-AD model of Alzheimer's disease

Alzheimer's disease (AD) is characterized by a progressive decline in cognitive function; however, recent evidence suggests that non-cognitive sensorimotor and psychomotor symptoms accompany early stages of the disease in humans and AD models. Although exercise is emerging as an important therapeutic to combat AD progression, little is known about the effect of exercise on sensorimotor domain functions. The purpose of this study was to determine if early sensorimotor symptoms accompany deficits in Morris water maze (MWM) performance in the 3xTg-AD model, and investigate if exercise could protect against early behavioral decline. 3xTg-AD and wild-type (WT) control mice were subjected to 12 weeks of moderate intensity wheel running or remained sedentary. At 6 months of age, animals underwent a series of sensorimotor and MWM testing. 3xTg-AD mice displayed deficits in sensorimotor function (beam traversal, spontaneous activity, and adhesive removal) and MWM performance. Interestingly, 3xTg-AD animals exhibited increased freezing and unusual shaking/tremoring behaviors not displayed by WT controls. Exercise improved beam traversal, adhesive removal, and reduced the unusual motor-related behaviors in 3xTg-AD mice. Our study shows that sensorimotor symptoms coincide with deficits in MWM performance, and suggest that exercise may mitigate deficits associated with early disease in 3xTg-AD mice.

Genotype Load Modulates Amyloid Burden and Anxiety-Like Patterns in Male 3xTg-AD Survivors despite Similar Neuro-Immunoendocrine, Synaptic and Cognitive Impairments

The wide heterogeneity and complexity of Alzheimer’s disease (AD) patients’ clinical profiles and increased mortality highlight the relevance of personalized-based interventions and the need for end-of-life/survival predictors. At the translational level, studying genetic and age interactions in a context of different levels of expression of AD-genetic-load can help to understand this heterogeneity better. In the present report, a singular cohort of long-lived (19-month-old survivors) heterozygous and homozygous male 3xTg-AD mice were studied to determine whether their AD-genotype load can modulate the brain and peripheral pathological burden, behavioral phenotypes, and neuro-immunoendocrine status, compared to age-matched non-transgenic controls. The results indicated increased amyloid precursor protein (APP) levels in a genetic-load-dependent manner but convergent synaptophysin and choline acetyltransferase brain levels. Cognitive impairment and HPA-axis hyperactivation were salient traits in both 3xTg-AD survivor groups. In contrast, genetic load elicited different anxiety-like profiles, with hypoactive homozygous, while heterozygous resembled controls in some traits and risk assessment. Complex neuro-immunoendocrine crosstalk was also observed. Bodyweight loss and splenic, renal, and hepatic histopathological injury scores provided evidence of the systemic features of AD, despite similar peripheral organs’ oxidative stress. The present study provides an interesting translational scenario to study further genetic-load and age-dependent vulnerability/compensatory mechanisms in Alzheimer’s disease.

Oroxylum Indicum ameliorates chemotherapy induced cognitive impairment

While chemotherapy is the most effective therapeutic approach for treating a variety of cancer patients, commonly used chemotherapeutic agents, often induce several adverse effects. Escalating evidence indicates that chemotherapeutics, particularly doxorubicin (DOX) and cyclophosphamide (CPS), induce cognitive impairment associated with central nervous system toxicity. This study was performed to determine neuroprotective effects of Oroxylum indicum extract (OIE) in regard to preventing chemotherapy induced cognitive impairment (CICI) occurring after 4 cycles of DOX (2mg/kg) and CPS (50mg/kg) combination chemotherapy in male C57BL/6J mice. OIE significantly prevented the chemotherapy impaired short-term cognitive performance, exploratory behavior associated with cognitive performance, cognitive performance, and spatial learning and memory in the Y-maze, Open-Field, Novel Object Recognition, and Morris Water Maze tests, respectively. These data suggest that OIE protects from the CICI. OIE decreased the reactive oxygen species and lipid peroxide generated by the chemotherapy treatment in the brain, while also blocking the chemotherapy-induced glutathione depletion. These results establish that OIE exhibits potent antioxidant activity in chemotherapy treated mice. Notably, OIE significantly increased the Complex-I and Complex-IV activities in the brain, indicating that OIE enhances mitochondrial function in the brain. In silico analysis of the major active chemical constituents (Oroxylin A, Baicalein and Chrysin) of OIE indicated that OIE has a favorable absorption, distribution, metabolism and excretion (ADME) profile. Taken together, our results are consistent with the conclusion that OIE prevents CICI by counteracting oxidative stress and perhaps by improving mitochondrial function.

Sex-Dependent End-of-Life Mental and Vascular Scenarios for Compensatory Mechanisms in Mice with Normal and AD-Neurodegenerative Aging

Life expectancy decreases with aging, with cardiovascular, mental health, and neurodegenerative disorders strongly contributing to the total disability-adjusted life years. Interestingly, the morbidity/mortality paradox points to females having a worse healthy life expectancy. Since bidirectional interactions between cardiovascular and Alzheimer’s diseases (AD) have been reported, the study of this emerging field is promising. In the present work, we further explored the cardiovascular–brain interactions in mice survivors of two cohorts of non-transgenic and 3xTg-AD mice, including both sexes, to investigate the frailty/survival through their life span. Survival, monitored from birth, showed exceptionally worse mortality rates in females than males, independently of the genotype. This mortality selection provided a “survivors” cohort that could unveil brain–cardiovascular interaction mechanisms relevant for normal and neurodegenerative aging processes restricted to long-lived animals. The results show sex-dependent distinct physical (worse in 3xTg-AD males), neuropsychiatric-like and cognitive phenotypes (worse in 3xTg-AD females), and hypothalamic–pituitary–adrenal (HPA) axis activation (higher in females), with higher cerebral blood flow and improved cardiovascular phenotype in 3xTg-AD female mice survivors. The present study provides an experimental scenario to study the suggested potential compensatory hemodynamic mechanisms in end-of-life dementia, which is sex-dependent and can be a target for pharmacological and non-pharmacological interventions.

Maternal L-thyroxine treatment during lactation affects learning and anxiety-like behaviors but not spatial memory in adult rat progeny

BACKGROUND

The present study compared behavioral and molecular indicators of hippocampal function in L-thyroxine treated rats to determine whether thyroid hormone excessiveness produces relatively stable lifelong changes.

METHODS

Hyperthyroidism was induced in rats by daily injections of L-thyroxine (0.2 mg/kg) to their dams for lactation period (MOH: maternal-onset hyperthyroidism) or to the rats itself during the young adult period (AOH: adult-onset hyperthyroidism; between the day 39-60). Spatial learning was assessed in the Morris Water Maze (MWM). Levels of type 2 and type 3 deiodinases, Erk1/2, JNK and P38^MAPK were assessed via western blotting in the hippocampus of trained rats. Measurements were all done in rats aged 60-66 days.

RESULTS

In MWM, maternally treated rats with L-thyroxine swam more away from the hidden platform, with showing more anxiety-like behavior, as compared to the rats treated or no treated with L-thyroxine in young adulthood. In spite of impaired acquisition, MOH group was not significantly different from the other groups in probe trial. In Western blot of the hippocampus, a decreased the expression of P38MAPK was found in rats treated with L-thyroxine in young adulthood period. However, maternal treatment with L-thyroxine resulted in an increased expression of Type 2 deiodinase and a tendency toward decreased expression of total and phosphorylated ERK1/2. No detectable band for type 3 deiodinase, p-JNK and p-P38^MAPK was observed in all three groups.

CONCLUSION

These results suggest that perinatal excessiveness of thyroid hormone has longstanding effects on hippocampal function and may account for memory problems experienced by adolescents with lactational hyperthyroidism.

Detection and Prediction of Mild Cognitive Impairment in Alzheimer's Disease Mice

Background:

The recent failure of clinical trials to treat Alzheimer’s disease (AD) indicates that the current approach of modifying disease is either wrong or is too late to be efficient. Mild cognitive impairment (MCI) denotes the phase between the preclinical phase and clinical overt dementia. AD mouse models that overexpress human amyloid-β (Aβ) are used to study disease pathogenesis and to conduct drug development/testing. However, there is no direct correlation between the Aβ deposition, the age of onset, and the severity of cognitive dysfunction.

Objective:

To detect and predict MCI when Aβ plaques start to appear in the hippocampus of an AD mouse.

Methods:

We trained wild-type and AD mice in a Morris water maze (WM) task with different inter-trial intervals (ITI) at 3 months of age and assessed their WM performance. Additionally, we used a classification algorithm to predict the genotype (APPtg versus wild-type) of an individual mouse from their respective WM data.

Results:

MCI can be empirically detected using a short-ITI protocol. We show that the ITI modulates the spatial learning of AD mice without affecting the formation of spatial memory. Finally, a simple classification algorithm such as logistic regression on WM data can give an accurate prediction of the cognitive dysfunction of a specific mouse.

Conclusion:

MCI can be detected as well as predicted simultaneously with the onset of Aβ deposition in the hippocampus in AD mouse model. The mild cognitive impairment prediction can be used for assessing the efficacy of a treatment.

Sex-specific effects of high-fat diet on cognitive impairment in a mouse model of VCID

Mid-life metabolic disease (ie, obesity, diabetes, and prediabetes) causes vascular dysfunction and is a risk factor for vascular contributions to cognitive impairment and dementia (VCID), particularly in women. Using middle-aged mice, we modeled metabolic disease (obesity/prediabetes) via chronic high-fat (HF) diet and modeled VCID via unilateral common carotid artery occlusion. VCID impaired spatial memory in both sexes, but episodic-like memory in females only. HF diet caused greater weight gain and glucose intolerance in middle-aged females than males. HF diet alone impaired episodic-like memory in both sexes, but spatial memory in females only. Finally, the combination of HF diet and VCID elicited cognitive impairments in all tests, in both sexes. Sex-specific correlations were found between metabolic outcomes and memory. Notably, both visceral fat and the pro-inflammatory cytokine tumor necrosis factor alpha correlated with spatial memory deficits in middle-aged females, but not males. Overall, our data show that HF diet causes greater metabolic impairment and a wider array of cognitive deficits in middle-aged females than males. The combination of HF diet with VCID elicits deficits across multiple cognitive domains in both sexes. Our data are in line with clinical data, which shows that mid-life metabolic disease increases VCID risk, particularly in females.

Rigor and reproducibility in rodent behavioral research

Behavioral neuroscience research incorporates the identical high level of meticulous methodologies and exacting attention to detail as all other scientific disciplines. To achieve maximal rigor and reproducibility of findings, well-trained investigators employ a variety of established best practices. Here we explicate some of the requirements for rigorous experimental design and accurate data analysis in conducting mouse and rat behavioral tests. Novel object recognition is used as an example of a cognitive assay which has been conducted successfully with a range of methods, all based on common principles of appropriate procedures, controls, and statistics. Directors of Rodent Core facilities within Intellectual and Developmental Disabilities Research Centers contribute key aspects of their own novel object recognition protocols, offering insights into essential similarities and less-critical differences. Literature cited in this review article will lead the interested reader to source papers that provide step-by-step protocols which illustrate optimized methods for many standard rodent behavioral assays. Adhering to best practices in behavioral neuroscience will enhance the value of animal models for the multiple goals of understanding biological mechanisms, evaluating consequences of genetic mutations, and discovering efficacious therapeutics.

Alcohol drinking exacerbates neural and behavioral pathology in the 3xTg-AD mouse model of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that represents the most common cause of dementia in the United States. Although the link between alcohol use and AD has been studied, preclinical research has potential to elucidate neurobiological mechanisms that underlie this interaction. This study was designed to test the hypothesis that nondependent alcohol drinking exacerbates the onset and magnitude of AD-like neural and behavioral pathology. We first evaluated the impact of voluntary 24-h, two-bottle choice home-cage alcohol drinking on the prefrontal cortex and amygdala neuroproteome in C57BL/6J mice and found a striking association between alcohol drinking and AD-like pathology. Bioinformatics identified the AD-associated proteins MAPT (Tau), amyloid beta precursor protein (APP), and presenilin-1 (PSEN-1) as the main modulators of alcohol-sensitive protein networks that included AD-related proteins that regulate energy metabolism (ATP5D, HK1, AK1, PGAM1, CKB), cytoskeletal development (BASP1, CAP1, DPYSL2 [CRMP2], ALDOA, TUBA1A, CFL2, ACTG1), cellular/oxidative stress (HSPA5, HSPA8, ENO1, ENO2), and DNA regulation (PURA, YWHAZ). To address the impact of alcohol drinking on AD, studies were conducted using 3xTg-AD mice that express human MAPT, APP, and PSEN-1 transgenes and develop AD-like brain and behavioral pathology. 3xTg-AD and wild-type mice consumed alcohol or saccharin for 4 months. Behavioral tests were administered during a 1-month alcohol-free period. Alcohol intake induced AD-like behavioral pathologies in 3xTg-AD mice including impaired spatial memory in the Morris Water Maze, diminished sensorimotor gating as measured by prepulse inhibition, and exacerbated conditioned fear. Multiplex immunoassay conducted on brain lysates showed that alcohol drinking upregulated primary markers of AD pathology in 3xTg-AD mice: Aβ 42/40 ratio in the lateral entorhinal and prefrontal cortex and total Tau expression in the lateral entorhinal cortex, medial prefrontal cortex, and amygdala at 1-month post alcohol exposure. Immunocytochemistry showed that alcohol use upregulated expression of pTau (Ser199/Ser202) in the hippocampus, which is consistent with late-stage AD. According to the NIA-AA Research Framework, these results suggest that alcohol use is associated with Alzheimer's pathology. Results also showed that alcohol use was associated with a general reduction in Akt/mTOR signaling via several phosphoproteins (IR, IRS1, IGF1R, PTEN, ERK, mTOR, p70S6K, RPS6) in multiple brain regions including hippocampus and entorhinal cortex. Dysregulation of Akt/mTOR phosphoproteins suggests alcohol may target this pathway in AD progression. These results suggest that nondependent alcohol drinking increases the onset and magnitude of AD-like neural and behavioral pathology in 3xTg-AD mice.

Analysis of Motor Function in the Tg4-42 Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder and the most common form of dementia. Hallmarks of AD are memory impairments and cognitive deficits, but non-cognitive impairments, especially motor dysfunctions are also associated with the disease and may even precede classic clinical symptoms. With an aging society and increasing hospitalization of the elderly, motor deficits are of major interest to improve independent activities in daily living. Consistent with clinical findings, a variety of AD mouse models develop motor deficits as well. We investigated the motor function of 3- and 7-month-old Tg4-42 mice in comparison to wild-type controls and 5XFAD mice and discuss the results in context with several other AD mouse model. Our study shows impaired balance and motor coordination in aged Tg4-42 mice in the balance beam and rotarod test, while general locomotor activity and muscle strength is not impaired at 7 months. The cerebellum is a major player in the regulation and coordination of balance and locomotion through practice. Particularly, the rotarod test is able to detect cerebellar deficits. Furthermore, supposed cerebellar impairment was verified by 18F-FDG PET/MRI. Aged Tg4-42 mice showed reduced cerebellar glucose metabolism in the 18F-FDG PET. Suggesting that, deficits in coordination and balance are most likely due to cerebellar impairment. In conclusion, Tg4-42 mice develop motor deficits before memory deficits, without confounding memory test. Thus, making the Tg4-42 mouse model a good model to study the effects on cognitive decline of therapies targeting motor impairments.

Tolfenamic Acid: A Modifier of the Tau Protein and its Role in Cognition and Tauopathy

BACKGROUND

Tangles are deposits of hyperphosphorylated tau, which are found in multiple neurodegenerative disorders that are referred to as tauopathies, of which Alzheimer's disease (AD) is the most common. Tauopathies are clinically characterized by dementia and share common cortical lesions composed of aggregates of the protein tau.

OBJECTIVE

In this study, we explored the therapeutic potential of tolfenamic acid (TA), in modifying disease processes in a transgenic animal model that carries the human tau gene (hTau).

METHODS

Behavioral tests, Western blotting and Immunohistochemical analysis were used to demonstrate the efficacy of TA.

RESULTS

Treatment of TA improved improving spatial learning deficits and memory impairments in young and aged hTau mice. Western blot analysis of the hTau protein revealed reductions in total tau as well as in sitespecific hyperphosphorylation of tau in response to TA administration. Immunohistochemical analysis for phosphorylated tau protein revealed reduced staining in the frontal cortex, hippocampus, and striatum in animals treated with TA.

CONCLUSION

TA holds the potential as a disease-modifying agent for the treatment of tauopathies including AD.

SIRT3 mediates hippocampal synaptic adaptations to intermittent fasting and ameliorates deficits in APP mutant mice

Intermittent food deprivation (fasting, IF) improves mood and cognition and protects neurons against excitotoxic degeneration in animal models of epilepsy and Alzheimer’s disease (AD). The mechanisms by which neuronal networks adapt to IF and how such adaptations impact neuropathological processes are unknown. We show that hippocampal neuronal networks adapt to IF by enhancing GABAergic tone, which is associated with reduced anxiety-like behaviors and improved hippocampus-dependent memory. These neuronal network and behavioral adaptations require the mitochondrial protein deacetylase SIRT3 as they are abolished in SIRT3-deficient mice and wild type mice in which SIRT3 is selectively depleted from hippocampal neurons. In the App^NL-G-F mouse model of AD, IF reduces neuronal network hyperexcitability and ameliorates deficits in hippocampal synaptic plasticity in a SIRT3-dependent manner. These findings demonstrate a role for a mitochondrial protein deacetylase in hippocampal neurons in behavioral and GABAergic synaptic adaptations to IF.

Intermittent fasting has been shown to have beneficial effects on hippocampal function in rodents, but the underlying mechanism is not fully understood. Here the authors show that the mitochondrial protein SIRT3 contributes to the beneficial cognitive and synaptic effects of intermittent fasting in mice.

Dissociable cognitive impairments in two strains of transgenic Alzheimer's disease mice revealed by a battery of object-based tests

Object recognition tasks detect cognitive deficits in transgenic Alzheimer's disease (AD) mouse models. Object recognition, however, is not a unitary process, and there are many uncharacterized facets of object processing with relevance to AD. We therefore systematically evaluated object processing in 5xFAD and 3xTG AD mice to clarify the nature of object recognition-related deficits. Twelve-month-old male and female 5xFAD and 3xTG mice were assessed on tasks for object identity recognition, spatial recognition, and multisensory object perception. Memory and multisensory perceptual impairments were observed, with interesting dissociations between transgenic AD strains and sex that paralleled neuropathological changes. Overreliance on the widespread "object recognition" task threatens to slow discovery of potentially significant and clinically relevant behavioural effects related to this multifaceted cognitive function. The current results support the use of carefully designed object-based test batteries to clarify the relationship between "object recognition" impairments and specific aspects of AD pathology in rodent models.

Diet-induced insulin resistance elevates hippocampal glutamate as well as VGLUT1 and GFAP expression in AβPP/PS1 mice

The symptomologies of Alzheimer's disease (AD) develop over decades suggesting modifiable lifestyle factors may contribute to disease pathogenesis. In humans, hyperinsulinemia associated with type 2 diabetes mellitus increases the risk for developing AD and both diseases share similar age-related etiologies including amyloidogenesis. Since we have demonstrated that soluble Aβ₄₂ elicits glutamate release, we wanted to understand how diet-induced insulin resistance alters hippocampal glutamate dynamics, which are important for memory formation and consolidation. Eight to twelve-week-old C57BL/6J and AβPP/PS1 mice were placed on either a low-fat diet or high-fat diet (HFD) for 8 months. A HFD led to significant weight increases as well as impaired insulin sensitivity, glucose tolerance, and learning in both C57BL/6J and AβPP/PS1 mice. AβPP/PS1 low-fat diet mice had elevated hippocampal basal as well as stimulus-evoked glutamate release that was further increased with consumption of a HFD. Immunohistochemistry indicated an increase in vesicular glutamate transporter 1 and glial fibrillary acidic protein density in hippocampal subregions corresponding with this elevated extracellular glutamate. While no differences in hippocampal plaque load were observed, the elevated astrogliotic response surrounding the plaques in AβPP/PS1 HFD mice may have been a compensatory mechanism to control plaque accumulation. These data support that AβPP/PS1 mice have chronically elevated extracellular glutamate that is exacerbated by a HFD and that modifiable lifestyle factors such as obesity-induced insulin resistance can contribute to AD pathogenesis. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* and for *Open Data* because it made the data publicly available. The data can be accessed at https://osf.io/5whvu (figures for data) and https://osf.io/gd5vf (materials and methods). The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/. Cover Image for this issue: doi: 10.1111/jnc.14490.

A standardised Andrographis paniculata Burm. Nees aqueous extract prevents Lipopolysaccharide-induced cognitive deficits through suppression of inflammatory cytokines and oxidative stress mediators

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Lipopolysaccharide (LPS)-induced impairment of cognitive function.

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Andrographis paniculata aqueous extract (APAE) averted LPS-induced cognitive deficit.

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APAE pretreatment prevented LPS-induced hippocampal proinflammatory cytokine release.

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APAE pretreatment prevented LPS-induced hippocampal oxidative stress mediator release.

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Pretreatment with APAE inhibited LPS-induced hippocampal cholinesterase activity.

Substantial evidence has shown that most cases of memory impairment are associated with increased neuroinflammation and oxidative stress. In this study, the potential of a standardised Andrographis paniculata aqueous extract (APAE) to reverse neuroinflammation and cognitive impairment induced by lipopolysaccharide (LPS) was examined in vivo. Rats were treated with APAE (50, 100, 200, and 400 mg·kg⁻¹, p.o.) for 7 consecutive days prior to LPS (1 mg·kg⁻¹, i.p.)-induced neuroinflammation and cognitive impairment. Spatial learning and memory were evaluated using the Morris water maze (MWM) test, while neuroinflammation and oxidative stress were assessed through the measurement of specific mediators, namely, tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-1β, superoxide dismutase (SOD), catalase (CAT), antioxidant glutathione (GSH), reactive oxygen species (ROS), and thiobarbituric acid reactive substance (TBARS). Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) were also evaluated. LPS caused significant memory deficits in the 2-day MWM protocol, whereas pretreatment with standardised APAE dose-dependently improved performance in the MWM test. APAE treatment also blocked the LPS-induced hippocampal increase in the concentration and expression of proinflammatory cytokines (TNF-α, IL-1β, and IL-6) and production of ROS and TBARS and enhanced the activities of AChE and BChE. Furthermore, APAE enhanced the decrease in the levels and expression of hippocampal antioxidant enzymes (SOD and CAT) following LPS-induced neuroinflammation and cognitive deficit. The findings from these studies suggested that standardised APAE improved memory and had potent neuroprotective effects against LPS-induced neurotoxicity.

Effect of Edible Bird's Nest Extract on Lipopolysaccharide-Induced Impairment of Learning and Memory in Wistar Rats

Cognitive disability is a common feature associated with a variety of neurological conditions including Alzheimer's Disease (AD), Parkinson's Disease (PD), brain injury, and stroke. Emerging evidence has demonstrated that neuroinflammation plays an important role in the development of cognitive impairment. Current available therapies are relatively ineffective in treating or preventing cognitive disabilities, thus representing an important, unfulfilled medical need. Hence, developing potential treatment is one of the major areas of research interest. Edible bird's nests (EBN) are nests formed by swiftlet's saliva containing sialic acid, which is believed to improve brain function. This present study was embarked upon to evaluate the learning and memory enhancing potential effect of EBN by using Morris water maze test in a Wistar rat model of LPS-induced neuroinflammation. LPS elicited cognitive impairment in the rats by significantly increasing the escape latency while decreasing the number of entries in the probe trial, which are coupled with increased production of proinflammatory cytokines (TNF-α, IL-1β, and IL-6) and oxidative markers (ROS and TBARS) in the hippocampus. Treatment with EBN (125 mg/kg, 250 mg/kg, and 500 mg/kg; p.o.) effectively reversed the effect of LPS on escape latency and probe trial and, in addition, inhibited the LPS-induced upregulation of proinflammatory cytokines and oxidative markers. These findings are suggestive that there is existence of neuroprotective effect contained inside the edible bird's nest.

Genetic reduction of Nrf2 exacerbates cognitive deficits in a mouse model of Alzheimer's disease

Aging is the major risk factor for several neurodegenerative diseases, including Alzheimer's disease (AD). However, the mechanisms by which aging contributes to neurodegeneration remain elusive. The nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a transcription factor that regulates expression of a vast number of genes by binding to the antioxidant response element. Nrf2 levels decrease as a function of age, and reduced Nrf2 levels have been reported in postmortem human brains and animal models of AD. Nevertheless, it is still unknown whether Nrf2 plays a role in the cognitive deficits associated with AD. To address this question, we used a genetic approach to remove the Nrf2 gene from APP/PS1 mice, a widely used animal model of AD. We found that the lack of Nrf2 significantly exacerbates cognitive deficits in APP/PS1, without altering gross motor function. Specifically, we found an exacerbation of deficits in spatial learning and memory, as well as in working and associative memory. Different brain regions control these behavioral tests, indicating that the lack of Nrf2 has a global effect on brain function. The changes in cognition were linked to an increase in Aβ and interferon-gamma (IFNγ) levels, and microgliosis. The changes in IFNγ levels are noteworthy as previously published evidence indicates that IFNγ can increase microglia activation and induce Aβ production. Our data suggest a clear link between Nrf2 and AD-mediated cognitive decline and further strengthen the connection between Nrf2 and AD.

Cognitive benefits of lithium chloride in APP/PS1 mice are associated with enhanced brain clearance of β-amyloid

Epidemiological evidence suggests that people with bipolar disorder prescribed lithium exhibit a lower risk of Alzheimer's disease (AD) relative to those prescribed other mood-stabilizing medicines. Lithium chloride (LiCl) reduces brain β-amyloid (Aβ) levels, and the brain clearance of Aβ is reduced in AD. Therefore, the purpose of this study was to assess whether the cognitive benefits of LiCl are associated with enhanced brain clearance of exogenously-administered Aβ. The brain clearance of intracerebroventricularly (icv) administered ¹²⁵I-Aβ₄₂ was assessed in male Swiss outbred mice administered daily oral NaCl or LiCl (300 mg/kg for 21 days). LiCl exhibited a 31% increase in the brain clearance of ¹²⁵I-Aβ₄₂ over 10 min, which was associated with a 1.6-fold increase in brain microvascular expression of the blood-brain barrier efflux transporter low density lipoprotein receptor-related protein 1 (LRP1) and increased cerebrospinal fluid (CSF) bulk-flow. 8-month-old female wild type (WT) and APP/PS1 mice were also administered daily NaCl or LiCl for 21 days, which was followed by cognitive assessment by novel object recognition and water maze, and measurement of soluble Aβ₄₂, plaque-associated Aβ₄₂, and brain efflux of ¹²⁵I-Aβ₄₂. LiCl treatment restored the long-term spatial memory deficit observed in APP/PS1 mice as assessed by the water maze (back to similar levels of escape latency as WT mice), but the short-term memory deficit remained unaffected by LiCl treatment. While LiCl did not affect plaque-associated Aβ₄₂, soluble Aβ₄₂ levels were reduced by 49.9% in APP/PS1 mice receiving LiCl. The brain clearance of ¹²⁵I-Aβ₄₂ decreased by 27.8% in APP/PS1 mice, relative to WT mice, however, LiCl treatment restored brain ¹²⁵I-Aβ₄₂ clearance in APP/PS1 mice to a rate similar to that observed in WT mice. These findings suggest that the cognitive benefits and brain Aβ₄₂ lowering effects of LiCl are associated with enhanced brain clearance of Aβ₄₂, possibly via brain microvascular LRP1 upregulation and increased CSF bulk-flow, identifying a novel mechanism of protection by LiCl for the treatment of AD.

Fatty Acid-Binding Protein 5 at the Blood-Brain Barrier Regulates Endogenous Brain Docosahexaenoic Acid Levels and Cognitive Function

Fatty acid-binding protein 5 (FABP5) at the blood-brain barrier contributes to the brain uptake of docosahexaenoic acid (DHA), a blood-derived polyunsaturated fatty acid essential for maintenance of cognitive function. Given the importance of DHA in cognition, the aim of this study was to investigate whether deletion of FABP5 results in cognitive dysfunction and whether this is associated with reduced brain endothelial cell uptake of exogenous DHA and subsequent attenuation in the brain levels of endogenous DHA. Cognitive function was assessed in male and female FABP5^+/+ and FABP5^-/- mice using a battery of memory paradigms. FABP5^-/- mice exhibited impaired working memory and short-term memory, and these cognitive deficits were associated with a 14.7 ± 5.7% reduction in endogenous brain DHA levels. The role of FABP5 in the blood-brain barrier transport of DHA was assessed by measuring ¹⁴C-DHA uptake into brain endothelial cells and capillaries isolated from FABP5^+/+ and FABP5^-/- mice. In line with a crucial role of FABP5 in the brain uptake of DHA, ¹⁴C-DHA uptake into brain endothelial cells and brain capillaries of FABP5^-/- mice was reduced by 48.4 ± 14.5% and 14.0 ± 4.2%, respectively, relative to those of FABP5^+/+ mice. These results strongly support the hypothesis that FABP5 is essential for maintaining brain endothelial cell uptake of DHA, and that cognitive deficits observed in FABP5^-/- mice are associated with reduced CNS access of DHA.

SIGNIFICANCE STATEMENT

Genetic deletion of fatty acid-binding protein 5 (FABP5) in mice reduces uptake of exogenous docosahexaenoic acid (DHA) into brain endothelial cells and brain capillaries and reduces brain parenchymal levels of endogenous DHA. Therefore, FABP5 in the brain endothelial cell is a crucial contributor to the brain levels of DHA. Critically, lowered brain DHA levels in FABP5^-/- mice occurred in tandem with cognitive deficits in a battery of memory paradigms. This study provides evidence of a critical role for FABP5 in the maintenance of cognitive function via regulating the brain uptake of DHA, and suggests that upregulation of FABP5 in neurodegenerative diseases, where brain DHA levels are possibly diminished (e.g., Alzheimer's disease), may provide a novel therapeutic approach for restoring cognitive function.

A novel Alzheimer's disease drug candidate targeting inflammation and fatty acid metabolism

Background

CAD-31 is an Alzheimer’s disease (AD) drug candidate that was selected on the basis of its ability to stimulate the replication of human embryonic stem cell-derived neural precursor cells as well as in APPswe/PS1ΔE9 AD mice. To move CAD-31 toward the clinic, experiments were undertaken to determine its neuroprotective and pharmacological properties, as well as to assay its therapeutic efficacy in a rigorous mouse model of AD.

Results

CAD-31 has potent neuroprotective properties in six distinct nerve cell assays that mimic toxicities observed in the old brain. Pharmacological and preliminary toxicological studies show that CAD-31 is brain-penetrant and likely safe. When fed to old, symptomatic APPswe/PS1ΔE9 AD mice starting at 10 months of age for 3 additional months in a therapeutic model of the disease, there was a reduction in the memory deficit and brain inflammation, as well as an increase in the expression of synaptic proteins. Small-molecule metabolic data from the brain and plasma showed that the major effect of CAD-31 is centered on fatty acid metabolism and inflammation. Pathway analysis of gene expression data showed that CAD-31 had major effects on synapse formation and AD energy metabolic pathways.

Conclusions

All of the multiple physiological effects of CAD-31 were favorable in the context of preventing some of the toxic events in old age-associated neurodegenerative diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-017-0277-3) contains supplementary material, which is available to authorized users.

Lasting Retinal Injury in a Mouse Model of Blast-Induced Trauma

Traumatic brain injury due to blast exposure is currently the most prevalent of war injuries. Although secondary ocular blast injuries due to flying debris are more common, primary ocular blast exposure resulting from blast wave pressure has been reported among survivors of explosions, but with limited understanding of the resulting retinal pathologies. Using a compressed air-driven shock tube system, adult male and female C57BL/6 mice were exposed to blast wave pressure of 300 kPa (43.5 psi) per day for 3 successive days, and euthanized 30 days after injury. We assessed retinal tissues using immunofluorescence for glial fibrillary acidic protein, microglia-specific proteins Iba1 and CD68, and phosphorylated tau (AT-270 pThr181 and AT-180 pThr231). Primary blast wave pressure resulted in activation of Müller glia, loss of photoreceptor cells, and an increase in phosphorylated tau in retinal neurons and glia. We found that 300-kPa blasts yielded no detectable cognitive or motor deficits, and no neurochemical or biochemical evidence of injury in the striatum or prefrontal cortex, respectively. These changes were detected 30 days after blast exposure, suggesting the possibility of long-lasting retinal injury and neuronal inflammation after primary blast exposure.

Postnatal and adult consequences of loss of huntingtin during development: Implications for Huntington's disease

The mutation in huntingtin (mHtt) leads to a spectrum of impairments in the developing forebrain of Huntington's disease (HD) mouse models. Whether these developmental alterations are due to loss- or gain-of-function mechanisms and contribute to HD pathogenesis is unknown. We examined the role of selective loss of huntingtin (Htt) function during development on postnatal vulnerability to cell death. We employed mice expressing very low levels of Htt throughout embryonic life to postnatal day 21 (Hdh^d•hyp). We demonstrated that Hdh^d•hyp mice exhibit: (1) late-life striatal and cortical neuronal degeneration; (2) neurological and skeletal muscle alterations; and (3) white matter tract impairments and axonal degeneration. Hdh^d•hyp embryos also exhibited subpallial heterotopias, aberrant striatal maturation and deregulation of gliogenesis. These results indicate that developmental deficits associated with Htt functions render cells present at discrete neural foci increasingly susceptible to cell death, thus implying the potential existence of a loss-of-function developmental component to HD pathogenesis.

Hippocampal changes in STZ-model of Alzheimer's disease are dependent on sex

The majority of Alzheimer's disease (AD) cases are sporadic and aging is the major risk factor for developing the disease, affecting more women than men. In spite of different gender prevalence, most experimental studies in animal models have been performed in male. This study investigates the streptozotocin (STZ)-induced AD model at three different times (2, 4 and 8 weeks afterwards) and in male and female rats, evaluating cognitive deficit, cholinergic neurotransmission, glucose uptake, glutathione content and specific glial markers (GFAP and S100B protein) in the hippocampus of the rat. Our data reinforce the relevance of alterations in STZ model of dementia, reported in the genesis and/or progression of AD such as cholinergic deficit and glucose uptake decrease. All alterations in these parameters (except GFAP) were dependent on sex. It is unclear, at this moment, which alterations are due to sex steroid modulation. In spite of limitations of this experimental model, these data may contribute to understand AD susceptibility and progression dependent on sex.

Neuropsychiatric systemic lupus erythematosus persists despite attenuation of systemic disease in MRL/lpr mice

Background

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease marked by both B and T cell hyperactivity which commonly affects the joints, skin, kidneys, and brain. Neuropsychiatric disease affects about 40 % of SLE patients, most frequently manifesting as depression, memory deficits, and general cognitive decline. One important and yet unresolved question is whether neuropsychiatric SLE (NPSLE) is a complication of systemic autoimmunity or whether it is primarily driven by brain-intrinsic factors.

Methods

To dissect the relative contributions of the central nervous system from those of the hematopoietic compartment, we generated bone marrow chimeras between healthy control (MRL/+) and lupus-prone MRL/Tnfrsf6^lpr/lpr mice (MRL/+ → MRL/lpr), as well as control chimeras. After bone marrow reconstitution, mice underwent extensive behavioral testing, analysis of brain tissue, and histological assessment.

Results

Despite transfer of healthy MRL/+ bone marrow and marked attenuation of systemic disease, we found that MRL/+ → MRL/lpr mice had a behavioral phenotype consisting of depressive-like behavior and visuospatial memory deficits, comparable to MRL/lpr → MRL/lpr control transplanted mice and the behavioral profile previously established in MRL/lpr mice. Moreover, MRL/+ → MRL/lpr chimeric mice displayed increased brain RANTES expression, neurodegeneration, and cellular infiltration in the choroid plexus, as well as blood brain barrier disruption, all in the absence of significant systemic autoimmunity.

Conclusions

Chimeric MRL/+ → MRL/lpr mice displayed no attenuation of the behavioral phenotype found in MRL/lpr mice, despite normalized serum autoantibodies and conserved renal function. Therefore, neuropsychiatric disease in the MRL/lpr lupus-prone strain of mice can occur absent any major contributions from systemic autoimmunity.

A mouse model replicating hippocampal sparing cranial irradiation in humans: A tool for identifying new strategies to limit neurocognitive decline

Cancer patients undergoing cranial irradiation are at risk of developing neurocognitive impairments. Recent evidence suggests that radiation-induced injury to the hippocampi could play an important role in this cognitive decline. As a tool for studying the mechanisms of hippocampal-dependent cognitive decline, we developed a mouse model replicating the results of the recent clinical RTOG 0933 study of hippocampal sparing whole-brain irradiation. We irradiated 16-week-old female C57BL/6J mice to a single dose of 10 Gy using either whole-brain irradiation (WBRT) or hippocampal sparing irradiation (HSI). These animals, as well as sham-irradiated controls, were subjected to behavioral/cognitive assessments distinguishing between hippocampal-dependent and hippocampal-independent functions. Irradiation was well tolerated by all animals and only limited cell death of proliferating cells was found within the generative zones. Animals exposed to WBRT showed significant deficits compared to sham-irradiated controls in the hippocampal-dependent behavioral task. In contrast, HSI mice did not perform significantly different from sham-irradiated mice (control group) and performed significantly better when compared to WBRT mice. This is consistent with the results from the RTOG 0933 clinical trial, and as such this animal model could prove a helpful tool for exploring new strategies for mitigating cognitive decline in cancer patients receiving cranial irradiation.

Learning impairments identified early in life are predictive of future impairments associated with aging

The Morris water maze (MWM) behavioral paradigm is commonly used to measure spatial learning and memory in rodents. It is widely accepted that performance in the MWM declines with age. However, young rats ubiquitously perform very well on established versions of the water maze, suggesting that more challenging tasks may be required to reveal subtle differences in young animals. Therefore, we have used a one-day water maze and novel object recognition to test whether more sensitive paradigms of memory in young animals could identify subtle cognitive impairments early in life that might become accentuated later with senescence. We have found that these two tasks reliably separate young rats into inferior and superior learners, are highly correlated, and that performance on these tasks early in life is predictive of performance at 12 months of age. Furthermore, we have found that repeated training in this task selectively improves the performance of inferior learners, suggesting that behavioral training from an early age may provide a buffer against age-related cognitive decline.

Learning ability is a key outcome determinant of GSK-3 inhibition on visuospatial memory in rats

Learning aptitude has never been a focus of visuospatial performance studies, particularly on memory consolidation and reconsolidation. The aim of this study was to determine the consequences of learning ability on memory consolidation/reconsolidation following inhibition of glucose synthase kinase-3 (GSK-3) by 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8). The anxiety-like nature of rats was characterized in the elevated plus maze. The rats were then trained for four days in the Morris water maze (MWM) and classified as 'superior', 'intermediate' or 'inferior' learners. There were no major differences between superior, intermediate or inferior learners with respect to anxiety which might have influenced learning. After training (day-5), TDZD-8 (2.0 mg/kg) was administered and half of the cohort were exposed to a MWM retrieval trial. Ten days later, animals were subjected to repeated MWM learning. TDZD-8 without a retrieval trial impaired subsequent reconsolidation in inferior learners, but enhanced it in superior learners. There was no modification of performance in intermediate learners. In TDZD-8-treated subjects exposed to retrieval, the pattern of outcomes was identical whereby impairment of reconsolidation occurred in inferior learners, enhancement occurred in superior learners but there was no modification of performance in intermediate learners. Thus, learning ability was a key determinant of the qualitative outcome from GSK-3 inhibition on visuospatial memory.

How fisetin reduces the impact of age and disease on CNS function

It is becoming increasingly clear that neurological diseases are multi-factorial involving disruptions in multiple cellular systems. Thus, while each disease has its own initiating mechanisms and pathologies, certain common pathways appear to be involved in most, if not all, neurological diseases. Thus, it is unlikely that modulating only a single factor will be effective at either preventing disease development or slowing disease progression. A better approach is to identify small (< 900 daltons) molecules that have multiple biological activities relevant to the maintenance of brain function. We have identified an orally active, novel neuroprotective and cognition-enhancing molecule, the flavonoid fisetin. Fisetin not only has direct antioxidant activity but it can also increase the intracellular levels of glutathione, the major intracellular antioxidant. Fisetin can also activate key neurotrophic factor signaling pathways. In addition, it has anti-inflammatory activity and inhibits the activity of lipoxygenases, thereby reducing the production of pro-inflammatory eicosanoids and their by-products. This wide range of actions suggests that fisetin has the ability to reduce the impact of age-related neurological diseases on brain function.

Deficits in memory-guided limb movements impair obstacle avoidance locomotion in Alzheimer's disease mouse model

Memory function deficits induced by Alzheimer's disease (AD) are believed to be one of the causes of an increased risk of tripping in patients. Working memory contributes to accurate stepping over obstacles during locomotion, and AD-induced deficits of this memory function may lead to an increased risk of contact with obstacles. We used the triple transgenic (3xTg) mice to examine the effects of memory deficits in terms of tripping and contact with obstacles. We found that the frequency of contact of the hindlimbs during an obstacle avoidance task increased significantly in 10–13 month-old 3xTg (Old-3xTg) mice compared with control mice. However, no changes in limb kinematics during unobstructed locomotion or successful obstacle avoidance locomotion were observed in the Old-3xTg mice. Furthermore, we found that memory-based movements in stepping over an obstacle were impaired in these mice. Our findings suggest that working memory deficits as a result of AD are associated with an increased risk of tripping during locomotion.

Cognitive and emotional alterations in young Alzheimer's disease (3xTgAD) mice: effects of neonatal handling stimulation and sexual dimorphism

Alzheimer disease is the most common neurodegenerative disorder and cause of senile dementia. It is characterized by an accelerated memory loss, and alterations of mood, reason, judgment and language. The main neuropathological hallmarks of the disorder are β-amyloid (βA) plaques and neurofibrillary Tau tangles. The triple transgenic 3xTgAD mouse model develops βA and Tau pathologies in a progressive manner which mimicks the pattern that takes place in the human brain with AD, and showing cognitive alterations characteristic of the disease. The present study intended to examine whether 3xTgAD mice of both sexes present cognitive, emotional and other behavioral alterations at the early age of 4 months, an age in which only some intraneuronal amyloid accumulation is found. Neonatal handling (H) is an early-life treatment known to produce profound and long-lasting behavioral and neurobiological effects in rodents, as well as improvements in cognitive functions. Therefore, we also aimed at evaluating the effects of H on the behavioral/cognitive profile of 4-month-old male and female 3xTgAD mice. The results indicate that, (1) 3xTgAD mice present spatial learning/memory deficits and emotional alterations already at the early age of 4 months, (2) there exists sexual dimorphism effects on several behavioral variables at this age, (3) neonatal handling exerts a preventive effect on some cognitive (spatial learning) and emotional alterations appearing in 3xTgAD mice already at early ages, and 4) H treatment appears to produce stronger positive effects in females than in males in several spatial learning measures and in the open field test.

Long- and short-term CDK5 knockdown prevents spatial memory dysfunction and tau pathology of triple transgenic Alzheimer's mice

CDK5 is a member of the cyclin-dependent kinase family with diverse functions in both the developing and mature nervous system. The inappropriate activation of CDK5 due to the proteolytic release of the activator fragment p25 from the membrane contributes to the formation of neurofibrillary tangles and chronic neurodegeneration. At 18 months of age 3xTg-AD mice were sacrificed after 1 year (long term) or 3 weeks (short term) of CDK5 knockdown. In long-term animals CDK5 knockdown prevented insoluble Tau formation in the hippocampi and prevented spatial memory impairment. In short-term animals, CDK5 knockdown showed reduction of CDK5, reversed Tau aggregation, and improved spatial memory compared to scrambled treated old 3xTg-AD mice. Neither long-term nor short-term CDK5 knock-down had an effect on old littermates. These findings further validate CDK5 as a target for Alzheimer’s disease both as a preventive measure and after the onset of symptoms.

Erythropoietin protects newborn rat against sevoflurane-induced neurotoxicity

INTRODUCTION

Recent data on newborn animals exposed to anesthetics have raised safety concerns regarding anesthesia practices in young children. Indeed, studies on rodents have demonstrated a widespread increase in brain apoptosis shortly after exposure to sevoflurane, followed by long-term neurologic impairment. In this context, we aimed to evaluate the protective effect of rh-EPO, a potent neuroprotective agent, in rat pups exposed to sevoflurane.

MATERIAL AND METHODS

At postnatal day 7, 75 rat pups were allocated into three groups: SEVO + EPO (n = 27) exposed to sevoflurane 2 vol% (0.5 MAC) for 6 h in an air/O2 mixture (60/40) + 5000 UI.kg(-1) rh-EPO IP; SEVO (n = 27) exposed to sevoflurane + vehicle IP; and CONTROL (n = 21) exposed to the mixture without sevoflurane + vehicle IP. Three days after anesthesia (D10), apoptosis was quantified on brain extract with TUNEL method and caspase 3. NGF and BDNF expression was determined by Western blotting. Rats reaching adulthood were evaluated in terms of exploration capacities (object exploration duration) together with spatial and object learning (water maze and novel object test).

RESULTS

Sevoflurane exposure impaired normal behavior in adult rats by reducing the exploratory capacities during the novel object test and impaired both spatial and object learning capacities in adult rats (water maze, ratio time to find platform 3rd trial/1st trial: 1.1 ± 0.2 vs 0.4 ± 0.1; n = 9, SEVO vs CONTROL; P = 0.01). Rh-EPO reduced sevoflurane-induced behavior and learning abnormalities in adult rats (water maze, ratio time to find platform 3rd trial/1st trial: 0.3 ± 0.1 vs 1.1 ± 0.2; n = 9, SEVO + EPO vs SEVO; P = 0.01). Three days after anesthesia, rh-EPO prevented sevoflurane-induced brain apoptosis (5 ± 3 vs 35 ± 6 apoptotic cells·mm(-2) ; n = 6, SEVO + EPO vs SEVO; P = 0.01) and elevation of caspase three level and significantly increased the brain expression of BDNF and NGF (n = 6, SEVO + EPO vs SEVO; P = 0.01).

CONCLUSION

Six hours of sevoflurane anesthesia in newborn rats induces significant long-term cognitive impairment. A single administration of rh-EPO immediately after postnatal exposure to sevoflurane reduces both early activation of apoptotic phenomenon and late onset of neurologic disorders.

Long-term hydrocephalus alters the cytoarchitecture of the adult subventricular zone

Hydrocephalus can develop secondarily to a disturbance in production, flow and/or absorption of cerebrospinal fluid. Experimental models of hydrocephalus, especially subacute and chronic hydrocephalus, are few and limited, and the effects of hydrocephalus on the subventricular zone are unclear. The aim of this study was to analyze the effects of long-term obstructive hydrocephalus on the subventricular zone, which is the neurogenic niche lining the lateral ventricles. We developed a new method to induce hydrocephalus by obstructing the aqueduct of Sylvius in the mouse brain, thus simulating aqueductal stenosis in humans. In 120-day-old rodents (n=18 per group), the degree of ventricular dilatation and cellular composition of the subventricular zone were studied by immunofluorescence and transmission electron microscopy. In adult patients (age>18years), the sizes of the subventricular zone, corpus callosum, and internal capsule were analyzed by magnetic resonance images obtained from patients with and without aqueductal stenosis (n=25 per group). Mice with 60-day hydrocephalus had a reduced number of Ki67+ and doublecortin+cells on immunofluorescence, as well as decreased number of neural progenitors and neuroblasts in the subventricular zone on electron microscopy analysis as compared to non-hydrocephalic mice. Remarkably, a number of extracellular matrix structures (fractones) contacting the ventricular lumen and blood vessels were also observed around the subventricular zone in mice with hydrocephalus. In humans, the widths of the subventricular zone, corpus callosum, and internal capsule in patients with aqueductal stenosis were significantly smaller than age and gender-matched patients without aqueductal stenosis. In summary, supratentorial hydrocephalus reduces the proliferation rate of neural progenitors and modifies the cytoarchitecture and extracellular matrix compounds of the subventricular zone. In humans, this similar process reduces the subventricular niche as well as the width of corpus callosum and internal capsule.

Cognitive and emotional profiles of aged Alzheimer's disease (3×TgAD) mice: effects of environmental enrichment and sexual dimorphism

Alzheimer's disease is a neurodegenerative disorder associated with age which represents the most common cause of dementia. It is characterized by an accelerated memory loss compared to normal aging, and deterioration of other cognitive abilities that interfere with mood, reason, judgment and language. The main neuropathological hallmarks of the disorder are β-amyloid (βA) plaques and neurofibrillary Tau tangles. Triple transgenic 3×TgAD mouse model develops βA and Tau pathologies in a progressive manner, with a specific temporal and anatomic profile mimicking the pattern that takes place in the human brain with AD, and showing cognitive alterations characteristic of the disease. Environmental enrichment treatment in mice induces behavioral and emotional reactivity changes, including cognitive improvements in some AD-related transgenic mice. The present work intended to characterize the behavioral profile of 3×TgAD mice at advanced stages of neuropathological development (12 and 15 months of age) and to investigate whether environmental enrichment administered during adulthood was able to modify some of their behavioral and cognitive alterations. Results show that, at advanced stages of the disease 3×TgAD mice show deficits of spatial learning acquisition, as well as short-term and working memory deficits, while displaying increased levels of anxiety/fearfulness and normal sensorimotor functions. 3×TgAD mice also show sexual dimorphism, as reflected by increased cognitive deficits in females and increased levels of novelty-induced behavioral inhibition in males. Environmental enrichment exerts some slight positive effects, by mainly improving the initial acquisition of the spatial learning and working memory in 12-month-old 3×TgAD mice. Such effects vary depending on the gender.

Modulation of p25 and inflammatory pathways by fisetin maintains cognitive function in Alzheimer's disease transgenic mice

Alzheimer's disease (AD) is the most common type of dementia. It is the only one of the top ten causes of death in the USA for which prevention strategies have not been developed. Although AD has traditionally been associated with the deposition of amyloid β plaques and tau tangles, it is becoming increasingly clear that it involves disruptions in multiple cellular systems. Therefore, it is unlikely that hitting a single target will result in significant benefits to patients with AD. An alternative approach is to identify molecules that have multiple biological activities that are relevant to the disease. Fisetin is a small, orally active molecule which can act on many of the target pathways implicated in AD. We show here that oral administration of fisetin to APPswe/PS1dE9 double transgenic AD mice from 3 to 12 months of age prevents the development of learning and memory deficits. This correlates with an increase in ERK phosphorylation along with a decrease in protein carbonylation, a marker of oxidative stress. Importantly, fisetin also reduces the levels of the cyclin-dependent kinase 5 (Cdk5) activator p35 cleavage product, p25, in both control and AD brains. Elevated levels of p25 relative to p35 cause dysregulation of Cdk5 activity leading to neuroinflammation and neurodegeneration. These fisetin-dependent changes correlate with additional anti-inflammatory effects, including alterations in global eicosanoid synthesis, and the maintenance of markers of synaptic function in the AD mice. Together, these results suggest that fisetin may provide a new approach to the treatment of AD.