Effect of rotation preference on spontaneous alternation behavior on Y maze and introduction of a new analytical method, entropy of spontaneous alternation

Canagliflozin Mitigated Cognitive Impairment in Streptozotocin-Induced Sporadic Alzheimer's Disease in Mice: Role of AMPK/SIRT-1 Signaling Pathway in Modulating Neuroinflammation

Sporadic Alzheimer's disease (SAD) represents a major health concern especially among elderly. Noteworthy, neuroinflammation and oxidative stress are highly implicated in AD pathogenesis resulting in enhanced disease progression. Moreover, most of the available anti-Alzheimer drugs have several adverse effects with variable efficacy, therefore new strategies, including agents with anti-inflammatory and antioxidant effects, are encouraged. Along these lines, canagliflozin (CAN), with its anti-inflammatory and anti-apoptotic activities, presents a promising candidate for AD treatment. Therefore, this study aimed to evaluate the therapeutic potential of CAN via regulation of AMPK/SIRT-1/BDNF/GSK-3β signaling pathway in SAD. SAD model was induced by intracerebroventricular streptozotocin injection (ICV-STZ;3 mg/kg, once), while CAN was administered (10 mg/kg/day, orally) to STZ-treated mice for 21 days. Behavioral tests, novel object recognition (NOR), Y-Maze, and Morris Water Maze (MWM) tests, histopathological examination, total adenosine monophosphate-activated protein kinase (T-AMPK) expression, p-AMPK, and silent information regulator-1 (SIRT-1) were evaluated. Furthermore, brain-derived neurotrophic factor (BDNF), glycogen synthase kinase-3β (GSK-3β), acetylcholinesterase (AChE), Tau protein, insulin-degrading enzyme (IDE), nuclear factor erythroid-2 (Nrf-2), interleukin-6 (IL-6), nuclear factor kappa-B-p65 (NFκB-p65), beta-site APP cleaving enzyme 1 (BACE-1), and amyloid beta (Aβ) plaque were assessed. CAN restored STZ-induced cognitive deficits, confirmed by improved behavioral tests and histopathological examination. Besides, CAN halted STZ-induced neurotoxicity through activation of p-AMPK/SIRT-1/BDNF pathway, subsequently reduction of GSK-3β, Tau protein, AChE, NFκB-p65, IL-6, BACE-1, and Aβ plaque associated with increased IDE and Nrf-2. Consequentially, our findings assumed that CAN, via targeting p-AMPK/SIRT-1 pathway, combated neuroinflammation and oxidative stress in STZ-induced AD. Thus, this study highlighted the promising effect of CAN for treating AD.

Acupuncture Alleviates Chronic Ischemic White Matter Injury in SHR Rats via JNK-NMDAR Circuit

To study the protective mechanism of acupuncture at "Jiangya Recipe" on chronic ischemic white matter injury in spontaneously hypertensive rats (SHR) and the regulation of Jun N-terminal kinase-N-methyl-D-aspartate receptor (JNK-NMDAR) loop. A hypertensive white matter injury model was established in 46 male SHR rats aged 11 weeks by bilateral common carotid artery tapering (SHR-2VGO). In the SHR sham operation group, only bilateral common carotid arteries were isolated and in the SHR-2VGO modeling group, 36 rats were used for microcoil spring clip implantation to narrow the common carotid arteries and then, after 2 weeks of modeling, rats with impaired motor function were removed, and SHR-2VGO rats with successful final models were randomly divided into the model group, JNK blocking group, and acupuncture group. The sham operation group, model group, and JNK blocking group underwent the same grasping fixation, and the acupuncture group received acupuncture at acupoints "Jiangya Fang" once daily. In the JNK blocker group, an injection cannula was implanted into the lateral ventricle and sp600125 was injected into the lateral ventricle at 4.5 ul/day for 4 weeks. One week after the end of the intervention, white matter lesions were detected by MRI DWI and T2 imaging, and the learning and memory ability of rats was tested by Y-Maze and Passive Avoidance. Myelin density was detected by luxol fast blue (LFB) staining, also axon arrangement, myelin integrity, and thickness of neurons were detected by electron microscopy; neuronal morphology and the number of Nissl bodies in the hippocampus were detected by Nissl staining, dendritic spine density changes were detected by Golgi staining, and JNK, NMDAR1, and N-methyl-D-receptor 2B (NMDAR2B) in DG, CA3 region of hippocampus were detected by immunohistochemistry, protein expression of p-JNK/JNK, p-NMDAR1/NMDAR1, NMDAR2B, GSK3β protein expression in the fimbria of hippocampus was detected by Western blot. The Y maze test of SHR-2VGO+Acu and SHR-2VGO+ sp600125 group showed that the spontaneous alternating reaction rate increased significantly. At the same time, the incubation period increased significantly and the number of errors decreased significantly in Passive Avoidance. MRI T2WI showed that the white matter high signal of the corpus callosum, internal capsule and hippocampal fimbria in the SHR-2VGO+ sp600125 and SHR-2VGO+Acu groups was significantly lower than that in the SHR-2VGO model group, and the striatum and anterior commissure were not obvious. DWI showed that the SHR-2VGO model group had scattered high signal and limited diffusion movement in both the internal capsule and striatum, but the difference between groups was not obvious. Compared with SHR-2VGO rats, LFB staining of SHR-2VGO + sp600125 and SHR-2VGO +Acu groups showed significant relaxation of myelin porosity in corpus callosum, striatum, inner capsule, anterior commissure and hippocampal fimbria, and electron microscopy showed improved axonal myelin integrity and thickness in corpus callosum region. Also, the number of blue patchy Nissl bodies increased, and the number and complexity of dendritic spines increased significantly in Golgi staining. Immunohistochemical detection showed that JNK levels in DG and CA3 region were increased and NMDAR1 and NMDAR2B levels were decreased in SHR-2VGO+Acu and SHR-2VGO+ sp600125 groups. Meanwhile, protein expressions of GSK3β, NMDAR1/p-NMDAR1 and NMDAR2B in fimbria of hippocampus were increased, and JNK/P-JNK protein expression decreased. Acupuncture can increase the density and thickness of myelin sheath in white matter areas of corpus callosum, anterior commissure and hippocampal fimbria, increase the number and length of hippocampal neuronal dendrites, and improve hypertensive white matter injury and cognitive decline through JNK-NMDAR pathway.

Aquaporin-4 inhibition attenuates Pentylenetetrazole-induced behavioral seizures and cognitive impairments in kindled rats

Epilepsy is a neurological condition distinguished by recurrent and unexpected seizures. Astrocytic channels and transporters are essential for maintaining normal neuronal functionality. The astrocytic water channel, aquaporin-4 (AQP4), which plays a pivotal role in regulating water homeostasis, is a potential target for epileptogenesis. In present study, we examined the effect of different doses (10, 50, 100 μM and 5 mM) of AQP4 inhibitor, 2-nicotinamide-1, 3, 4-thiadiazole (TGN-020), during kindling acquisition, on seizure parameters and seizure-induced cognitive impairments. Animals were kindled by injection of pentylenetetrazole (PTZ: 37.5 mg/kg, i.p.). TGN-020 was administered into the right lateral cerebral ventricle 30 min before PTZ every alternate day. Seizure parameters were assessed 20 min after PTZ administration. One day following the last PTZ injection, memory performance was investigated using spontaneous alternation in Y-maze and novel object recognition (NOR) tests. The inhibition of AQP4 during the kindling process significantly decreased the maximal seizure stage and seizure duration (two-way ANOVA, P = 0.0001) and increased the latency of seizure onset and the number of PTZ injections required to induce different seizure stages (one-way ANOVA, P = 0.0001). Compared to kindled rats, the results of the NOR tests showed that AQP4 inhibition during PTZ-kindling prevented recognition memory impairment. Based on these results, AQP4 could be involved in seizure development and seizure-induced cognitive impairment. More investigation is required to fully understand the complex interactions between seizure activity, water homeostasis, and cognitive dysfunction, which may help identify potential therapeutic targets for these conditions.

Roseburia intestinalis Supplementation Could Reverse the Learning and Memory Impairment and m6A Methylation Modification Decrease Caused by 27-Hydroxycholesterol in Mice

The abnormality in N6-methyladenosine (m6A) methylation is involved in the course of Alzheimer's disease (AD), while the intervention of 27-Hydroxycholesterol (27-OHC) can affect the m6A methylation modification in the brain cortex. Disordered gut microbiota is a key link in 27-OHC leading to cognitive impairment, and further studies have found that the abundance of Roseburia intestinalis in the gut is significantly reduced under the intervention of 27-OHC. This study aims to investigate the association of 27-OHC, Roseburia intestinalis in the gut, and brain m6A modification in the learning and memory ability injury. In this study, 9-month-old male C57BL/6J mice were treated with antibiotic cocktails for 6 weeks to sweep the intestinal flora, followed by 27-OHC or normal saline subcutaneous injection, and then Roseburia intestinalis or normal saline gavage were applied to the mouse. The 27-OHC level in the brain, the gut barrier function, the m6A modification in the brain, and the memory ability were measured. From the results, we observed that 27-OHC impairs the gut barrier function, causing a disturbance in the expression of m6A methylation-related enzymes and reducing the m6A methylation modification level in the brain cortex, and finally leads to learning and memory impairment. However, Roseburia intestinalis supplementation could reverse the negative effects mentioned above. This study suggests that 27-OHC-induced learning and memory impairment might be linked to brain m6A methylation modification disturbance, while Roseburia intestinalis, as a probiotic with great potential, could reverse the damage caused by 27-OHC. This research could help reveal the mechanism of 27-OHC-induced neural damage and provide important scientific evidence for the future use of Roseburia intestinalis in neuroprotection.

Hemerocallis citrina Baroni ameliorates chronic sleep deprivation-induced cognitive deficits and depressive-like behaviours in mice

Sleep deprivation (SD) is common during spaceflight. SD is known to cause cognitive deficits and depression, requiring treatment and prevention. Hemerocallis citrina Baroni (Liliaceae) is a perennial herb with antidepressant, antioxidant, antitumor, anti-inflammatory, and neuroprotective effects.The aim of our study was to investigate the effects of H. citrina extract (HCE) on SD-induced cognitive decline and depression-like behavior and possible neuroinflammation-related mechanisms. HCE (2 g/kg/day, i.g.) or vortioxetine (10 mg/kg/day, i.g.) were given to mice by oral gavage for a total of 28 days during the SD process. HCE treatment was found to ameliorate SD-induced impairment of short- and long-term spatial and nonspatial memory, measured using Y-maze, object recognition, and Morris water maze tests, as well as mitigating SD-induced depression-like behaviors, measured by tail suspension and forced swimming tests. HCE also reduced the levels of inflammatory cytokines (IL-1β, IL-18, and IL-6) in the serum and hippocampus. Furthermore, HCE suppressed SD-induced microglial activation in the prefrontal cortex (PFC) and the CA1 and dentate gyrus (DG) regions of the hippocampus. HCE also inhibited the expression of phosphorylated NF-κB and activation of the NLRP3 inflammasome. In summary, our findings indicated that HCE attenuated SD-induced cognitive impairment and depression-like behavior and that this effect may be mediated by the inhibition of inflammatory progression and microglial activation in the hippocampus, as well as the down-regulation of NF-κB and NLRP3 signaling. The findings of these studies showingTthese results indicate that HCE exerts neuroprotective effects and are consistent with the findings of previous studies, suggesting that HCE is beneficial for the prevention and treatment of cognitive decline and depression in SD.

The GluN2C/D-specific positive allosteric modulator CIQ rescues delay-induced working memory deficits in mice

Working memory is of short duration and is, therefore, particularly sensitive to time delays. Moreover, NMDA receptors are significantly involved in working memory. In the present study, we tested whether a commonly used measure of working memory, spontaneous alternation in the Y-maze, is sensitive to time delays and, if so, whether impairments due to time-delay can be rescued by treatment with CIQ, a positive allosteric modulator of the GluN2C/D subunits of NMDA receptor. Our results indicate that the effects of time delay do depend on the performance of the individual mice under basal condition. Those mice that performed well under basal conditions showed impaired spontaneous alternations when tested with a 45-s delay. Treatment with CIQ resulted in an improvement of spontaneous alternations, regardless of delay, sex, or basal performance. On the one hand, our study shows that repeated measures of individual behavior can better control the effects of confounding factors such as time delays. On the other hand, our study also highlights the potential of GluN2C/D-specific positive allosteric modulators in the treatment of human disorders associated with working memory deficits, such as schizophrenia.

Direct Evidence for Using Coriandrum sativum var. microcarpum Essential Oil to Ameliorate Scopolamine-Induced Memory Impairment and Brain Oxidative Stress in the Zebrafish Model

Essential oil from Coriandrum sativum has been demonstrated to provide various pharmacological properties, such as antioxidant, antimicrobial, antibacterial, antifungal, antidiabetic, anticonvulsive, anxiolytic-antidepressant, and anti-aging properties. This study investigated the mechanism of Coriandrum sativum var. microcarpum essential oil (CSEO, 25, 150, and 300 μL/L) and cognitive impairment and brain oxidative stress in a scopolamine (SCOP, 100 μM) zebrafish model (Danio rerio) of cognitive impairment. Spatial memory, response to novelty, and recognition memory were assessed using the Y-maze test and the novel object recognition test (NOR), while anxiety-like behavior was investigated using the novel tank diving test (NTT). The cholinergic system activity and brain oxidative stress were also evaluated. CSEO was administered to zebrafish once a day for 21 days, while SCOP and galantamine (GAL, 1 mg/L) were delivered 30 min before behavioral testing and euthanasia. Our data revealed that SCOP induced memory dysfunction and anxiety-like behavior, while CSEO improved memory performance, as evidenced by behavioral tasks. Moreover, CSEO attenuated SCOP-induced brain oxidative stress and decreased acetylcholinesterase (AChE) activity. The results demonstrated the potential use of the CSEO in providing beneficial effects by reducing memory deficits and brain oxidative stress involved in the genesis of a dementia state.

Salidroside alleviates cognitive impairment by inhibiting ferroptosis via activation of the Nrf2/GPX4 axis in SAMP8 mice

BACKGROUND

Alzheimer's disease (AD) is a neurogenerative disease and remains no effective method for stopping its progress. Ferroptosis and adaptive immunity have been proven to contribute to AD pathogenesis. Salidroside exhibits neuroprotective and immunomodulatory effects. However, the underlying mechanisms linking salidroside, ferroptosis, and adaptive immunity in AD remain uncertain.

PURPOSE

The objective of this study is to explore the neuroprotective effects and the potential molecular mechanisms of salidroside against neuronal ferroptosis and CD8⁺ T cell infiltration in senescence-accelerated mouse prone 8 (SAMP8) mice.

STUDY DESIGN AND METHODS

SAMP8 mice were employed as an AD model and were treated with salidroside for 12 weeks. Behavioral tests, immunohistochemistry, HE and Nissl staining, immunofluorescence, transmission electron microscopy, quantitative proteomics, bioinformatic analysis, flow cytometry, iron staining, western blotting, and molecular docking were performed.

RESULTS

Treatment with salidroside dose-dependently attenuated cognitive impairment, reduced the accumulation of Aβ plaques and restored neuronal damage. Salidroside also suppressed the infiltration of CD8⁺T cells, oxidative stress, and inflammatory cytokines, and improved mitochondrial metabolism, iron metabolism, lipid metabolism, and redox in the SAMP8 mice brain. The administration of salidroside decreased iron deposition, reduced TFR1, and ACSL4 protein expression, upregulated SLC7A11, and GPX4 protein expression, and promoted the Nrf2/GPX4 axis activation.

CONCLUSION

In conclusion, neuronal ferroptosis and CD8⁺T cells are involved in the process of cognitive impairment in SAMP8 mice. Salidroside alleviates cognitive impairment and inhibits neuronal ferroptosis. The underlying mechanisms may involve the Nrf2/GPX4 axis activation and reduction in CD8⁺T cells infiltration. This study provides some evidence for the roles of salidroside in adaptive immunity and neuronal ferroptosis in SAMP8 mice.

Methods to Identify Cognitive Alterations from Animals to Humans: A Translational Approach

The increasing prevalence of cognitive dysfunction and dementia in developed countries, associated with population aging, has generated great interest in characterizing and quantifying cognitive deficits in these patients. An essential tool for accurate diagnosis is cognitive assessment, a lengthy process that depends on the cognitive domains analyzed. Cognitive tests, functional capacity scales, and advanced neuroimaging studies explore the different mental functions in clinical practice. On the other hand, animal models of human diseases with cognitive impairment are essential for understanding disease pathophysiology. The study of cognitive function using animal models encompasses multiple dimensions, and deciding which ones to investigate is necessary to select the most appropriate and specific tests. Therefore, this review studies the main cognitive tests for assessing cognitive deficits in patients with neurodegenerative diseases. Cognitive tests, the most commonly used functional capacity scales, and those resulting from previous evidence are considered. In addition, the leading behavioral tests that assess cognitive functions in animal models of disorders with cognitive impairment are highlighted.

Augmented impulsive behavior in febrile seizure-induced mice

Febrile seizure (FS) is one of the most prevalent etiological events in childhood affecting 2-5% of children from 3 months to 5 years old. Debates on whether neurodevelopmental consequences rise in later life following a febrile seizure or not are still ongoing however there is limited evidence of its effect, especially in a laboratory setting. Moreover, the comparative study using both male and female animal models is sparse. To examine the effect of FS on the behavioral features of mice, both sexes of ICR mice were induced with hyperthermic seizures through exposure to an infrared heat lamp. The mice were divided into two groups, one receiving a single febrile seizure at postnatal day 11 (P11) and one receiving three FS at P11, P13, and P15. Starting at P30 the FS-induced mice were subjected to a series of behavioral tests. Mice with seizures showed no locomotor and motor coordination deficits, repetitive, and depressive-like behavior. However, the FS-induced mice showed impulsive-like behavior in both elevated plus maze and cliff avoidance tests, which is more prominent in male mice. A greater number of mice displayed impaired CAT in both males and females in the three-time FS-induced group compared to the single induction group. These results demonstrate that after induction of FS, male mice have a higher susceptibility to consequences of febrile seizure than female mice and recurrent febrile seizure has a higher chance of subsequent disorders associated with decreased anxiety and increased impulsivity. We confirmed the dysregulated expression of impulsivity-related genes such as 5-HT1A and tryptophan hydroxylase 2 from the prefrontal cortices of FS-induced mice implying that the 5-HT system would be one of the mechanisms underlying the increased impulsivity after FS. Taken together, these findings are useful in unveiling future discoveries about the effect of childhood febrile seizure and the mechanism behind it.

Phosphodiesterase-5 Inhibitor Attenuates Anxious Phenotypes and Movement Disorder Induced by Mild Ischemic Stroke in Rats

Objective

Patients with mild ischemic stroke experience various sequela and residual symptoms, such as anxious behavior and deficits in movement. Few approaches have been proved to be effective and safe therapeutic approaches for patients with mild ischemic stroke by acute stroke. Sildenafil (SIL), a phosphodiesterase-5 inhibitor (PDE5i), is a known remedy for neurodegenerative disorders and vascular dementia through its angiogenesis and neurogenesis effects. In this study, we investigated the efficacy of PDE5i in the emotional and behavioral abnormalities in rats with mild ischemic stroke.

Methods

We divided the rats into four groups as follows (n=20, respectively) : group 1, naïve; group 2, middle cerebral artery occlusion (MCAo30); group 3, MCAo30+SIL-pre; and group 4, MCAo30+SIL-post. In the case of drug administration groups, single dose of PDE5i (sildenafil citrate, 20 mg/kg) was given at 30-minute before and after reperfusion of MCAo in rats. After surgery, we investigated and confirmed the therapeutic effect of sildenafil on histology, immunofluorescence, behavioral assays and neural oscillations.

Results

Sildenafil alleviated a neuronal loss and reduced the infarction volume. And results of behavior task and immunofluorescence shown possibility that anti-inflammation process and improve motor deficits sildenafil treatment after mild ischemic stroke. Furthermore, sildenafil treatment attenuated the alteration of theta-frequency rhythm in the CA1 region of the hippocampus, a known neural oscillatory marker for anxiety disorder in rodents, induced by mild ischemic stroke.

Conclusion

PDE5i as effective therapeutic agents for anxiety and movement disorders and provide robust preclinical evidence to support the development and use of PDE5i for the treatment of mild ischemic stroke residual disorders.

Butyric Acid Precursor Tributyrin Modulates Hippocampal Synaptic Plasticity and Prevents Spatial Memory Deficits: Role of PPARγ and AMPK

BACKGROUND

Short chain fatty acids (SCFA), such as butyric acid (BA), derived from the intestinal fermentation of dietary fiber and contained in dairy products, are gaining interest in relation to their possible beneficial effects on neuropsychological disorders.

METHODS

C57BL/6J male mice were used to investigate the effect of tributyrin (TB), a prodrug of BA, on hippocampus (HIP)-dependent spatial memory, HIP synaptic transmission and plasticity mechanisms, and the expression of genes and proteins relevant to HIP glutamatergic transmission.

RESULTS

Ex vivo studies, carried out in HIP slices, revealed that TB can transform early-LTP into late-LTP (l-LTP) and to rescue LTP-inhibition induced by scopolamine. The facilitation of l-LTP induced by TB was blocked both by GW9662 (a PPARγ antagonist) and C-Compound (an AMPK inhibitor), suggesting the involvement of both PPARγ and AMPK on TB effects. Moreover, 48-hour intake of a diet containing 1% TB prevented, in adolescent but not in adult mice, scopolamine-induced impairment of HIP-dependent spatial memory. In the adolescent HIP, TB upregulated gene expression levels of Pparg, leptin, and adiponectin receptors, and that of the glutamate receptor subunits AMPA-2, NMDA-1, NMDA-2A, and NMDA-2B.

CONCLUSIONS

Our study shows that TB has a positive influence on LTP and HIP-dependent spatial memory, which suggests that BA may have beneficial effects on memory.

Spatial working memory is disparately interrelated with social status through different developmental stages in rats

Social life necessitates cognitive competence to meet the dynamic demands of social development. The formation of dominance hierarchy is a general phenomenon in social groups. As an essential element of executive and cognitive function, working memory could influence and be influenced by social status in a dominance hierarchy. However, the direction and degree of the association between them through different developmental stages remain unclear. To address this issue and clarify the "cause or consequence" problem, we investigated the spatial working memory performance in a Y-maze and Morris water maze in home-caged sibling Wistar rats (N = 26 cages, three rats/cage) through three stages of their life: before (week 7), during (week 10), and after (week 20) assumed timings of the social dominance hierarchy formation (SDHF). We used the social dominance tube test during the assumed time of hierarchy formation (weeks 9-11) to measure the relative dominance status in each cage. Here, we found that higher working memory index before SDHF could be predictive of later acquisition of higher social status. Working memory performance declined for all animals during SDHF, in which agonistic conflicts are increased. However, living within an established hierarchical social network for several weeks deteriorated the working memory performance of dominant and middle-ranked animals, while the performance of subordinates improved and got significantly better than higher-ranked animals. In conclusion, while working memory and social status were correlated positively before dominance hierarchy formation, there was a trade-off between them after the formation of it. In contrast to the common view, these results highlight the adverse effect of higher social status on cognitive behavior.

Exploring Refinement Strategies for Single Housing of Male C57BL/6JRj Mice: Effect of Cage Divider on Stress-Related Behavior and Hypothalamic-Pituitary-Adrenal-Axis Activity

Introduction: Single housing of laboratory mice is a common practice to meet experimental needs, or to avoid intermale aggression. However, single housing is considered to negatively affect animal welfare and may compromise the scientific validity of experiments. The aim of this study was to investigate whether the use of a cage with a cage divider, which avoids physical contact between mice while maintaining sensory contact, may be a potential refinement strategy for experiments in which group housing of mice is not possible.

Methods: Eight-week-old male C57BL/6JRj mice were single housed, pair housed or pair housed with a cage divider for four (experiment 1) or ten (experiment 2) weeks, after which we performed an open field test, Y-maze spontaneous alternation test, elevated plus maze test, an auditory fear conditioning task, and assessed responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis.

Results: Housing conditions did not affect body weight, exploratory activity, anxiety, working memory, fear memory processing or markers for HPA-axis functioning in either experiment 1 or experiment 2. There was an increased distance traveled in mice housed with a cage divider compared to pair housed mice after 4 weeks, and after 10 weeks mice housed with a cage divider made significantly more arm entries in the Y-maze spontaneous alternation test.

Conclusion: Taken together, our study did not provide evidence for robust differences in exploratory activity, anxiety, working memory and fear memory processing in male C57BL/6JRj mice that were single housed, pair housed or pair housed with a cage divider.

A GLP-1/GIP Dual Receptor Agonist DA4-JC Effectively Attenuates Cognitive Impairment and Pathology in the APP/PS1/Tau Model of Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is a degenerative disorder, accompanied by progressive cognitive decline, for which there is no cure. Recently, the close correlation between AD and type 2 diabetes mellitus (T2DM) has been noted, and a promising anti-AD strategy is the use of anti-T2DM drugs.

OBJECTIVE

To investigate if the novel glucagon-like peptide-1 (GLP-1)/glucose-dependent insulinotropic polypeptide (GIP) receptor agonist DA4-JC shows protective effects in the triple APP/PS1/tau mouse model of AD.

METHODS

A battery of behavioral tests were followed by in vivo recording of long-term potentiation (LTP) in the hippocampus, quantified synapses using the Golgi method, and biochemical analysis of biomarkers.

RESULTS

DA4-JC improved cognitive impairment in a range of tests and relieved pathological features of APP/PS1/tau mice, enhanced LTP in the hippocampus, increased numbers of synapses and dendritic spines, upregulating levels of post-synaptic density protein 95 (PSD95) and synaptophysin (SYP), normalized volume and numbers of mitochondria and improving the phosphatase and tensin homologue induced putative kinase 1 (PINK1) - Parkin mitophagy signaling pathway, while downregulating amyloid, p-tau, and autophagy marker P62 levels.

CONCLUSION

DA4-JC is a promising drug for the treatment of AD.

Increasing cerebral blood flow improves cognition into late stages in Alzheimer's disease mice

Alzheimer's disease is associated with a 20-30% reduction in cerebral blood flow. In the APP/PS1 mouse model of Alzheimer's disease, inhibiting neutrophil adhesion using an antibody against the neutrophil specific protein Ly6G was recently shown to drive rapid improvements in cerebral blood flow that was accompanied by an improvement in performance on short-term memory tasks. Here, in a longitudinal aging study, we assessed how far into disease development a single injection of anti-Ly6G treatment can acutely improve short-term memory function. We found that APP/PS1 mice as old as 15-16 months had improved performance on the object replacement and Y-maze tests of spatial and working short-term memory, measured at one day after anti-Ly6G treatment. APP/PS1 mice at 17-18 months of age or older did not show acute improvements in cognitive performance, although we did find that capillary stalls were still reduced and cerebral blood flow was still increased by 17% in 21-22-months-old APP/PS1 mice given anti-Ly6G antibody. These data add to the growing body of evidence suggesting that cerebral blood flow reductions are an important contributing factor to the cognitive dysfunction associated with neurodegenerative disease. Thus, interfering with neutrophil adhesion could be a new therapeutic approach for Alzheimer's disease.

Assessing behavior and cognition in rodents, nonhuman primates, and humans: where are the limits of translation?

New psychopharmacological treatments are needed for affective and nonaffective psychoses, especially for the associated negative and cognitive symptoms. Earlier developments mostly failed, probably partly because of limitations in behavioral models used for validation. Now, deeper understanding of the genetics underlying disease pathogenesis and progress in genetic engineering will generate many rodent models with increased construct validity. To improve these models’ translational value, we need complementary data from nonhuman primates. We also have to improve and streamline behavioral test systems to cope with increased demand. Here, we propose a comprehensive neurocognitive test battery that should overcome the disadvantages of single tests and yield cognitive/behavioral profiles for modeling subsets of patient symptoms. Further, we delineate a concept for classifying disease-relevant cognitive endophenotypes to balance between face and construct validity and clinical diagnostics. In summary, this review discusses new concepts and the limitations and future potential of translational research on cognition in psychiatry.


Dendrobium nobile Lindl alkaloid and metformin ameliorate cognitive dysfunction in senescence-accelerated mice via suppression of endoplasmic reticulum stress

The senescence-accelerated mouse prone 8 (SAMP8) mice have many pathological features of Alzheimer's disease (AD) with aging. We previously reported that Dendrobium nobile Lindl alkaloid (DNLA) effectively improved cognitive deficits in multiple Alzheimer's disease (AD) models. This study further used SAMP8 mice to study the anti-aging effects of DNLA, focusing on endoplasmic reticulum (ER) stress. DNLA and metformin were orally administered to SAMP8 mice starting at 4-month of age for 6 months. Behavioral tests were performed in 10-month-old SAMP8 mice and age-matched SAMR1 control mice. At the end of experiment, neuron damage was evaluated by histology and transmission electron microscopy. ER stress-related proteins were analyzed with Western-blot. DNLA improved learning and memory impairments, reduced the loss of neurons and Nissl bodies in the hippocampus and cortex. DNLA ameliorated ER dilation and swelling in the hippocampal neurons. DNLA down-regulated the protein kinase RNA-like endoplasmic reticulum kinase (PERK) signaling pathway, decreased calpain 1, GSK-3β and Cdk5 activities and the Tau hyper-phosphorylation. The effects of DNLA were comparable to metformin. In summary, DNLA was effective in improving cognitive deficits in aged SAMP8 mice, possibly via suppression of ER stress-related PERK signaling pathway, sequential inhibition of calpain 1, GSK-3β and Cdk5 activities, and eventually reducing the hyper-phosphorylation of Tau.

Photobiomodulation therapy for repeated closed head injury in rats

Repeated traumatic brain injury, leads to cumulative neuronal injury and neurological impairments. There are currently no effective treatments to prevent these consequences. Growing interest is building in the use of transcranial photobiomodulation (PBM) therapy to treat traumatic brain injury. Here, we examined PBM in a repeated closed head injury (rCHI) rat model. Rats were administered a total of three closed head injuries, with each injury separated by 5 days. PBM treatment was initiated 2 hours after the first injury and administered daily for a total of 15 days. We found that PBM-treated rCHI rats had a significant reduction in motor ability, anxiety and cognitive deficits compared to CHI group. PBM group showed an increase of synaptic proteins and surviving neurons, along with a reduction in reactive gliosis and neuronal injury. These findings highlight the complexity of gliosis and neuronal injury following rCHI and suggest that PBM may be a viable treatment option to mitigate these effects and their detrimental consequences.

A dual GLP-1 and Gcg receptor agonist rescues spatial memory and synaptic plasticity in APP/PS1 transgenic mice

Alzheimer's disease (AD) is a neurodegenerative disease that severely affects the health and lifespan of the elderly worldwide. Recently, the correlation between AD and type 2 diabetes mellitus (T2DM) has received intensive attention, and a promising new anti-AD strategy is the use of anti-diabetic drugs. Oxyntomodulin (Oxm) is a peptide hormone and growth factor that acts on neurons in the hypothalamus. OXM activates glucagon-like peptide 1 (GLP-1) and glucagon (Gcg) receptors, facilitates insulin signaling and has neuroprotective effects against Aβ_1-42-induced cytotoxicity in primary hippocampal neurons. Here, we tested the effects of the protease-resistant analogue (D-Ser2)Oxm on spatial memory and synaptic plasticity and the underlying molecular mechanisms in the APP/PS1 transgenic mouse model of AD. The results showed that (D-Ser2)Oxm not only alleviated the impairments of working memory and long-term spatial memory, but also reduced the number of Aβ plaques in the hippocampus, and reversed the suppression of hippocampal synaptic long-term potentiation (LTP). Moreover, (D-Ser2)Oxm administration significantly increased p-PI3K/p-AKT1 expression and decreased p-GSK3β levels in the hippocampus. These results are the first to show an in vivo neuroprotective role of (D-Ser2)Oxm in APP/PS1 mice, and this role involves the improvement of synaptic plasticity, clearance of Aβ and normalization of PI3K/AKT/GSK3β cell signaling in the hippocampus. This study suggests that (D-Ser2)Oxm holds promise for the prevention and treatment of AD.

Plant sphingolipids promote extracellular vesicle release and alleviate amyloid-β pathologies in a mouse model of Alzheimer's disease

The accumulation of amyloid-β protein (Aβ) in brain is linked to the early pathogenesis of Alzheimer’s disease (AD). We previously reported that neuron-derived exosomes promote Aβ clearance in the brains of amyloid precursor protein transgenic mice and that exosome production is modulated by ceramide metabolism. Here, we demonstrate that plant ceramides derived from Amorphophallus konjac, as well as animal-derived ceramides, enhanced production of extracellular vesicles (EVs) in neuronal cultures. Oral administration of plant glucosylceramide (GlcCer) to APP overexpressing mice markedly reduced Aβ levels and plaque burdens and improved cognition in a Y-maze learning task. Moreover, there were substantial increases in the neuronal marker NCAM-1, L1CAM, and Aβ in EVs isolated from serum and brain tissues of the GlcCer-treated AD model mice. Our data showing that plant ceramides prevent Aβ accumulation by promoting EVs-dependent Aβ clearance in vitro and in vivo provide evidence for a protective role of plant ceramides in AD. Plant ceramides might thus be used as functional food materials to ameliorate AD pathology.

Neurobehavioral effects of chronic low-dose risperidone administration in juvenile male rats

Despite substantial increases in the use of antipsychotics to treat various psychiatric conditions in children, there is a lack of literature regarding long-term effects of early treatment. Some studies have indicated that early administration results in differential alterations to neurotransmission systems, but few studies have investigated whether there are long-term behavioral modifications. Therefore, the aim of the current study was to investigate the neurobehavioral effects of low dose risperidone (a commonly prescribed antipsychotic) treatment using juvenile rats. Twenty-four male Sprague-Dawley rats were either subcutaneously implanted with a continuous release risperidone pellet (.04 mg/day) or a placebo pellet. To encompass the peri-adolescent to adolescent timeframe (postnatal day 40-70) thought to be important for brain development, male rats began risperidone treatment at post-natal day 35. Six weeks following commencement of risperidone treatment, all rats were tested on a battery of behavioral assessments including open field, object recognition, Morris Water Maze, and Y-Maze tasks. Risperidone treatment did not affect performance on the open field, object recognition, or Morris Water maze. A significant effect was found on the Y-maze. Although all rats exhibited normal spontaneous alternation, risperidone treated rats demonstrated significantly higher same arm returns, indicative of a working memory deficit. Continued research is needed to determine whether early exposure to risperidone may lead to differences in working memory at longer time-points. These results seem to indicate that early low dose risperidone treatment during the peri-adolescent and adolescent period does not severely impair behavior.

Resveratrol ameliorates estrogen deficiency-induced depression- and anxiety-like behaviors and hippocampal inflammation in mice

RATIONALE

Resveratrol (RSV) has been indicated to exhibit beneficial effects on depression and anxiety treatment by suppression of inflammatory processes. Depression triggered by deficiency of estrogen and anxiety-like behaviors are associated with inflammation. The role of RSV in ovariectomized mice is unclear.

OBJECTIVES

We examine whether the RSV, a Sirt1 activator, alleviates ovariectomy-induced anxiety- and depression-like behaviors through the inhibition of inflammatory processes.

METHODS

Female C57BL/6J mice (6-8 weeks of age, 17-20 g) were ovariectomized and treated with RSV at a dose of 20 mg/kg for 2 weeks. Depression- and anxiety-like behaviors were compared with vehicle-injected control animals. Immunohistochemistry and qPCR were used to detect inflammation in the hippocampal region.

RESULTS

Ovariectomized mice were observed to suffer from anxiety- and depression-like behaviors. These effects were attenuated by treatment with RSV. Immunohistochemical staining results showed that RSV could reverse the increase of microglial activation in the hippocampal dentate gyrus. At a molecular level, RSV inhibited the activation of NLRP3 and NF-κB in the hippocampal region caused by deficiency of estrogen.

CONCLUSIONS

RSV suppressed the production of inflammatory cytokines by enhancing Sirt1 levels. Our findings indicated that RSV-induced Sirt1 activation counteracted estrogen deficiency-induced psychobehavioral changes via inhibition of inflammatory processes in the hippocampus. In anxiety and depression disorders, RSV is supposed to be an effective treatment for postmenopausal changes.

Inonotus obliquus polysaccharides protect against Alzheimer's disease by regulating Nrf2 signaling and exerting antioxidative and antiapoptotic effects

Inonotus obliquus polysaccharide (IOPS) was initially separated and purified via precipitation from an aqueous extract with 80% alcohol, a DEAE-52 cellulose anion exchange column, and a Sephadex G-100 gel permeation chromatography system. IOPS was found to have a molecular weight of 111.9 kDa. In L-glutamic acid (L-Glu)-damaged HT22 cells, a 3-h pre-incubation with IOPS enhanced cell viability, inhibited apoptosis and caspase-3 activity, reduced the release of lactate dehydrogenase, restored the dissipated mitochondrial membrane potential, and suppressed the excess accumulation of intracellular reactive oxygen species. Compared with L-Glu-exposed cells, IOPS pre-treated cells exhibited reduced levels of Bcl-2 associated X protein (Bax) and Kelch-like ECH-associated protein 1 (Keap1) and enhanced levels of B-cell lymphoma-2 (Bcl-2), NF-E2p45-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), superoxide dismutase-1 (SOD-1), and cysteine ligase catalytic subunit. In amyloid precursor protein/presenilin 1 (APP/PS1) transgenic mice, an 8-week course of IOPS improved the pathological behaviors related to memory and cognition, reduced the deposition of β-amyloid peptides and neuronal fiber tangles induced by enhanced phosphor-Tau in the brain, and modulated the levels of anti- and pro-oxidative stress enzymes. Additionally, IOPS enhanced the expression levels of Nrf2 and its downstream proteins, including HO-1 and SOD-1, in the brains of APP/PS1 mice. The present study successfully demonstrated the protective effect of IOPS against AD and revealed the possible mechanism underlying the ability of IOPS to modulate oxidative stress, especially Nrf2 signaling, and mediate mitochondrial apoptosis.

Analysis of Metabolic Alterations Related to Pathogenic Process of Diabetic Encephalopathy Rats

Diabetic encephalopathy (DE) is a diabetic complication characterized by alterations in cognitive function and nervous system structure. The pathogenic transition from hyperglycemia to DE is a long-term process accompanied by multiple metabolic disorders. Exploring time-dependent metabolic changes in hippocampus will facilitate our understanding of the pathogenesis of DE. In the present study, we first performed behavioral and histopathological experiments to confirm the appearance of DE in rats with streptozotocin-induced diabetes. We then utilized nuclear magnetic resonance-based metabonomics to analyze metabolic disorders in the hippocampus at different stages of DE. After 1 week, we observed no cognitive or structural impairments in diabetic rats, although some metabolic changes were observed in local hippocampal extracts. At 5 weeks, while cognitive function was still normal, we then examined initial levels of neuronal apoptosis. The characteristic metabolic changes of this stage included elevated levels of energy metabolites (i.e., ATP, ADP, AMP, and creatine phosphate/creatine). At 9 weeks, significant cognitive decline and histopathological brain damage were observed, in conjunction with reduced levels of some amino acids. Thus, this stage was classified as the DE period. Our findings indicated that the pathogenesis of DE is associated with time-dependent alterations in metabolic features in hippocampal regions, such as glycolysis, osmoregulation, energy metabolism, choline metabolism, branched-chain amino acid metabolism, and the glutamate-glutamine cycle. Furthermore, we observed alterations in levels of lactate and its receptor in hippocampal cells, which may be involved in the pathogenesis of DE.

Okadaic acid attenuates short-term and long-term synaptic plasticity of hippocampal dentate gyrus neurons in rats

Protein phosphorylation states have a pivotal role in regulation of synaptic plasticity and long-term modulation of synaptic transmission. Serine/threonine protein phosphatase 1 (PP1) and 2A (PP2A) have a critical effect on various regulatory mechanisms involved in synaptic plasticity, learning and memory. Okadaic acid (OKA), a potent inhibitor of PP1 and PP2A, reportedly leads to cognitive decline and Alzheimer's disease (AD)-like pathology. The aim of this study was to examine the effect of OKA on electrophysiological characteristics of hippocampal dentate gyrus (DG) neurons in vivo. Male Wistar rats were divided into two control and OKA groups. OKA was injected intracerebroventricularly (i.c.v.) into lateral ventricles and after two weeks the long-term potentiation (LTP) and paired-pulse responses recorded from hippocampal perforant path-DG synapses in order to assess short-term and long-term synaptic plasticity. Results of this study revealed that OKA-induced inhibition of PP1 and PP2A activity drastically attenuates the field excitatory postsynaptic potential (fEPSP) slope and population spike (PS) amplitude following paired pulse and high frequency stimulation (HFS) of hippocampal DG neurons indicating pre- and post-synaptic involvement in electrical activity of these neurons. Administration of OKA impaired the short-term and long-term spatial memories conducted by Y-maze and passive avoidance tests, respectively. OKA-induced attenuation in electrophysiological activity and consequent memory deficits also provide a beneficial tool for studying neurodegenerative disorders such as AD.

Brain Amide Proton Transfer Imaging of Rat With Alzheimer's Disease Using Saturation With Frequency Alternating RF Irradiation Method

Amyloid-β (Aβ) deposits and some proteins play essential roles in the pathogenesis of Alzheimer's disease (AD). Amide proton transfer (APT) imaging, as an imaging modality to detect tissue protein, has shown promising features for the diagnosis of AD disease. In this study, we chose 10 AD model rats as the experimental group and 10 sham-operated rats as the control group. All the rats underwent a Y-maze test before APT image acquisition, using saturation with frequency alternating RF irradiation (APT_SAFARI) method on a 7.0 T animal MRI scanner. Compared with the control group, APT (3.5 ppm) values of brain were significantly reduced in AD models (p < 0.002). The APT_SAFARI imaging is more significant than APT imaging (p < 0.0001). AD model mice showed spatial learning and memory loss in the Y-maze experiment. In addition, there was significant neuronal loss in the hippocampal CA1 region and cortex compared with sham-operated rats. In conclusion, we demonstrated that APT imaging could potentially provide molecular biomarkers for the non-invasive diagnosis of AD. APT_SAFARI MRI could be used as an effective tool to improve the accuracy of diagnosis of AD compared with conventional APT imaging.

Neuroprotective effects of Bergenia ciliata on NMDA induced injury in SH-SY5Y cells and attenuation of cognitive deficits in scopolamine induced amnesia in rats

Bergenia ciliata (Haw) Sternb. possess immunomodulatory, anti-inflammatory, antioxidant, anti-urolithiatic, wound healing, anti-malarial, anti-diabetic and anti-cancer properties. Moreover, the methanolic extracts of the rhizomes of the plant were found to demonstrate beneficial neuroprotective effects in the intracerebroventricular streptozotocin-induced model in rats. Thus, the present study was undertaken to further explore the neuroprotective potential of the aqueous (BA) and methanolic extracts (BM) of B. ciliata through various in-vitro and in-vivo studies. Both the extracts at all tested concentrations i.e. 50-50,000 ng/mL did not cause any significant reduction of cell viability of SH-SY5Y cells when tested for 48 h when assessed through MTT and resazurin metabolism- based cell viability assays. The pre-treatment with the extracts could confer significant (p < 0.001) and dose-dependent protective effects against NMDA induced injury in SH-SY5Y cells. BM [IC₅₀: 5.7 and 5.19 μg/mL for acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) respectively] led to more potent inhibition of both the enzymes as compared to BA (IC₅₀: 227.12 and 23.25 μg/mL for AChE and BuChE respectively). BM also proved to be a 1.85-fold better scavenger of the DPPH free radicals as compared to BA. Thus, BM was taken further for the evaluation of the beneficial effects of 14-day pre-treatment in rats in the scopolamine (2 mg/kg, i.p.) induced amnesia model at 125, 250 and 500 mg/kg, p.o. BM pre-treatment at 250 and 500 mg/kg could significantly ameliorate the cognitive impairment (p < 0.001), inhibit AChE (p < 0.001) and BuChE (p < 0.05) activity, restore GSH levels (p < 0.05) in serum and brain homogenates and recover the morphology of hippocampal neurons back to normal. Moreover, the BM administration at 500 mg/kg also showed beneficial effects through the significant (p < 0.05) reduction of Aβ_1-42, phosphorylated tau (p-tau) and GSK-3β immunoreactivity in the brain homogenates of the intracerebroventricularly streptozotocin (ICV STZ) injected rats as observed from the results of the ELISA assays. The outcomes of the study unveiled that BM exerts its beneficial effects through prevention of NMDA induced excitotoxic cell death, dual cholinesterase inhibition, antioxidant activity coupled with the reduction of the immunoreactivity for the Aβ_1-42, p-tau and GSK-3β indicating its potential to be screened further for various other models to determine the exact mechanism of action.

Sensorimotor and Neurocognitive Dysfunctions Parallel Early Telencephalic Neuropathology in Fucosidosis Mice

Fucosidosis is a lysosomal storage disorder (LSD) caused by lysosomal α-L-fucosidase deficiency. Insufficient α-L-fucosidase activity triggers accumulation of undegraded, fucosylated glycoproteins and glycolipids in various tissues. The human phenotype is heterogeneous, but progressive motor and cognitive impairments represent the most characteristic symptoms. Recently, Fuca1-deficient mice were generated by gene targeting techniques, constituting a novel animal model for human fucosidosis. These mice display widespread LSD pathology, accumulation of secondary storage material and neuroinflammation throughout the brain, as well as progressive loss of Purkinje cells. Fuca1-deficient mice and control littermates were subjected to a battery of tests detailing different aspects of motor, emotional and cognitive function. At an early stage of disease, we observed reduced exploratory activity, sensorimotor disintegration as well as impaired spatial learning and fear memory. These early markers of neurological deterioration were related to the respective stage of neuropathology using molecular genetic and immunochemical procedures. Increased expression of the lysosomal marker Lamp1 and neuroinflammation markers was observed throughout the brain, but appeared more prominent in cerebral areas in comparison to cerebellum of Fuca1-deficient mice. This is consistent with impaired behaviors putatively related to early disruptions of motor and cognitive circuits particularly involving cerebral cortex, basal ganglia, and hippocampus. Thus, Fuca1-deficient mice represent a practical and promising fucosidosis model, which can be utilized for pathogenetic and therapeutic studies.

Downregulation of 5-hydroxytryptamine7 receptor in the medial prefrontal cortex ameliorates impulsive actions in animal models of schizophrenia

R mRNA in the mPFC was significantly decreased to 5-Hydroxytryptamine₇ (5-HT₇) receptors in the medial prefrontal cortex (mPFC) play a critical role in complex cognitive impairment in schizophrenia. The mouse model of schizophrenia was established through the neonatal administration of phencyclidine (nPCP). Recombinant adeno-associated virus-mediated gene knockdown was used to investigate the role of mPFC 5-HT₇ receptor in the schizophrenia-like symptoms in mice. Under baseline conditions in the 5-choice serial reaction time task (5-CSRTT), nPCP produced a significant attentional impairment that was exacerbated when mice were tested under LITI. Premature and perseverative responding in nPCP mice were both increased, thus suggesting deficits in inhibitory response control. The deficits in attentional performance and premature responding of nPCP mice were improved or fully rescued by 5-HT₇ receptor downregulation under heavy perceptual load. Downregulation of the 5-HT₇ receptor in the mPFC ameliorated spatial working memory and had no effects on nPCP-induced impairments in recognition memory and MA-induced hyperlocomotion. These results suggest that 5-HT₇ receptor is involved in the cognitive outcomes of schizophrenia-like symptoms similar to humans. Downregulation of the 5-HT₇ receptor in the mPFC exert complex effects in a mouse model of schizophrenia and may be of benefit in treating schizophrenia-related impulsive actions.