Location Recognition Tasks Research Articles

Exercise mitigates a gut microbiota-mediated reduction in adult hippocampal neurogenesis and associated behaviours in rats

Lifestyle factors, especially exercise, impact the manifestation and progression of psychiatric and neurodegenerative disorders such as depression and Alzheimer’s disease, mediated by changes in hippocampal neuroplasticity. The beneficial effects of exercise may be due to its promotion of adult hippocampal neurogenesis (AHN). Gut microbiota has also been showed to be altered in a variety of brain disorders, and disturbances of the microbiota have resulted in alterations in brain and behaviour. However, whether exercise can counteract the negative effects of altered gut microbiota on brain function remains under explored. To this end, chronic disruption of the gut microbiota was achieved using an antibiotic cocktail in rats that were sedentary or allowed voluntary access to running wheels. Sedentary rats with disrupted microbiota displayed impaired performance in hippocampal neurogenesis-dependent tasks: the modified spontaneous location recognition task and the novelty suppressed feeding test. Performance in the elevated plus maze was also impaired due to antibiotics treatment. These behaviours, and an antibiotics-induced reduction in AHN were attenuated by voluntary exercise. The effects were independent of changes in the hippocampal metabolome but were paralleled by caecal metabolomic changes. Taken together these data highlight the importance of the gut microbiota in AHN-dependent behaviours and demonstrate the power of lifestyle factors such as voluntary exercise to attenuate these changes.

Muscarinic receptor activation promotes destabilization and updating of object location memories in mice

The storage of long-term memories is a dynamic process. Reminder cues can destabilize previously consolidated memories, rendering them labile and modifiable. However, memories that are strongly encoded or relatively remote at the time of reactivation can resist destabilization only being rendered labile under conditions that favour memory updating. Using the object location recognition task, here we show in male C57BL/6 mice that novelty-induced destabilization of strongly-encoded memories requires muscarinic acetylcholine receptor (mAChR) activation. Furthermore, we use the objects-in-updated locations task to show that updating of object location memories is mAChR-dependent. Thus, mAChR stimulation appears to be critical for spatial memory destabilization and related memory updating. Enhancing our understanding of the role of ACh in memory updating should inform future research into the underlying causes of behavioural disorders that are characterized by persistent maladaptive memories, such as age-related cognitive inflexibility and post-traumatic stress disorder.

Adolescent food insecurity in female rodents and susceptibility to diet-induced obesity

Food insecurity is defined as having limited or uncertain access to nutritious foods, and adolescent food insecurity is associated with obesity and disordered eating behaviors in humans. We developed a rodent model of adolescent food insecurity to determine whether adolescent food insecurity per se promotes increased susceptibility to diet-induced obesity and altered eating behaviors during adulthood. Female juvenile Wistar rats were singly housed and assigned to three experimental diets: food-secure with standard chow (CHOW), food-secure with a high-fat/sugar Western diet (WD), and food-insecure with WD (WD-FI). Food-secure rats (CHOW and WD) received meals at fixed feeding times (9:00, 13:00, and 16:00). WD-FI rats received meals at unpredictable intervals of the above-mentioned feeding times but had isocaloric amounts of food to WD. We investigated the impact of adolescent food insecurity on motivation for sucrose (Progressive Ratio), approach-avoidance behavior for palatable high-fat food (Approach-Avoidance task), and susceptibility to weight gain and hyperphagia when given an obesogenic choice diet. Secondary outcomes were the effects of food insecurity during development on anxiety-like behaviors (Open Field and Elevated Plus Maze) and learning and memory function (Novel Location Recognition task). Rodents with adolescent food insecurity showed a greater trend of weight gain and significantly increased fat mass and liver fat accumulation on an obesogenic diet in adulthood, despite no increases in motivation for sucrose or high-fat food. These data suggest that adolescent unpredictable food access increases susceptibility to diet-induced fat gain without impacting food motivation or food intake in female rodents. These findings are among a small group of recent studies modeling food insecurity in rodents and suggest that adolescent food insecurity in females may have long-term implications for metabolic physiology later in life.

Chronotate: An open-source tool for manual timestamping and quantification of animal behavior

A core necessity to behavioral neuroscience research is the ability to accurately measure performance on behavioral assays, such as the novel object location and novel object recognition tasks. These tasks are widely used in neuroscience research and measure a rodent’s instinct for investigating novel features as a proxy to test their memory of a previous experience. Automated tools for scoring behavioral videos can be cost prohibitive and often have difficulty distinguishing between active investigation of an object and simply being in close proximity to an object. As such, many experimenters continue to rely on hand scoring interactions using stopwatches, which makes it difficult to review scoring after-the-fact and results in the loss of temporal information. Here, we introduce Chronotate, a free, open-source tool to aid in manually scoring novel object behavior videos. The software consists of an interactive video player with keyboard integration for marking timestamps of behavioral events during video playback, making it simple to quickly score and review bouts of rodent-object interaction. In addition, Chronotate outputs detailed interaction bout data, allowing for nuanced behavioral performance analyses. Using this detailed temporal information, we demonstrate that novel object location performance peaks within the first 3 s of interaction time and preference for the novel location becomes reduced across the test session. Thus, Chronotate can be used to determine the temporal structure of interactions on this task and can provide new insight into the memory processes that drive this behavior. Chronotate is available for download at: https://github.com/ShumanLab/Chronotate.

Effects of repeated developmental GLP-1R agonist exposure on young adult behavior and hippocampal structure in mice

Glucagon-like peptide-1 receptor (GLP-1R) agonists are common type 2 diabetes medications that have been repurposed for adult chronic weight management. Clinical trials suggest this class may also be beneficial for obesity in pediatric populations. Since several GLP-1R agonists cross the blood–brain barrier, it is important to understand how postnatal developmental exposure to GLP-1R agonists might affect brain structure and function later in life. Toward that end, we systemically treated male and female C57BL/6 mice with the GLP-1R agonist exendin-4 (0.5 mg/kg, twice daily) or saline from postnatal day 14 to 21, then allowed uninterrupted development to young adulthood. Beginning at 7 weeks of age, we performed open field and marble burying tests to assess motor behavior and the spontaneous location recognition (SLR) task to assess hippocampal-dependent pattern separation and memory. Mice were sacrificed, and we counted ventral hippocampal mossy cells, as we have recently shown that most murine hippocampal neuronal GLP-1R is expressed in this cell population. We found that GLP-1R agonist treatment did not alter P14-P21 weight gain, but modestly reduced young adult open field distance traveled and marble burying. Despite these motor changes, there was no effect on SLR memory performance or time spent investigating objects. Finally, we did not detect any changes in ventral mossy cell number using two different markers. These data suggest developmental exposure to GLP-1R agonists might have specific rather than global effects on behavior later in life and that extensive additional study is necessary to clarify how drug timing and dose affect distinct constellations of behavior in young adulthood.

Impairment in novelty-promoted memory via behavioral tagging and capture before apparent memory loss in a knock-in model of Alzheimer’s disease

Alzheimer’s disease (AD) is associated with cognitive impairments and age-dependent memory deficits which have been studied using genetic models of AD. Whether the processes for modulating memory persistence are more vulnerable to the influence of amyloid pathology than the encoding and consolidation of the memory remains unclear. Here, we investigated whether early amyloid pathology would affect peri-learning novelty in promoting memory, through a process called behavioral tagging and capture (BTC). AppNL-G-F/NL-G-F mice and wild-type littermates were trained in an appetitive delayed matching-to-place (ADMP) task which allows for the assessment of peri-learning novelty in facilitating memory. The results show that novelty enabled intermediate-term memory in wild-type mice, but not in AppNL-G-F/NL-G-F mice in adulthood. This effect preceded spatial memory impairment in the ADMP task seen in middle age. Other memory tests in the Barnes maze, Y-maze, novel object or location recognition tasks remained intact. Together, memory modulation through BTC is impaired before apparent deficits in learning and memory. Relevant biological mechanisms underlying BTC and the implication in AD are discussed.

Age-related loss of recognition memory and its correlation with hippocampal and perirhinal cortex changes in female Sprague Dawley rats

Ageing is associated with impaired performance in recognition memory, a process that consists of the discrimination of familiar and novel stimuli. Previous studies have shown the impact of ageing on object recognition memories. However, the early stages of memory impairment remain unknown. To fill this gap, we aimed at evaluating the ability of young (Y), middle-aged (MA), and senile (S) female Sprague-Dawley rats to retain 24 h long-term recognition memory. The MA cohort was included to characterise early memory deficits under two behavioural paradigms based on spontaneous location recognition (SLR) and spontaneous object recognition (SOR) tasks. In the SLR task, there was a markedly diminished novel discrimination capacity in the MA and S rats compared with the Y ones. In the SOR task, S rats evidenced a deterioration in novelty discrimination, while MA rats partially preserved the capacity to distinguish the new stimulus as compared with Y rats. Regarding early changes from MA to S rats, immunohistochemistry showed a marked decrease in the number and diameter of adult-born immature neurons in the Dentate Gyrus (DG) with a positive correlation with behavioural performance in the SLR task. Furthermore, we found a slight reduction in CA3 mature neurons and a decrease in the number of total microglia in the perirhinal cortex (Prh) in MA and S rats as compared with Y rats. As regards changes that were only observed in S rats, we found an increase in the number of total and reactive microglia in CA3 and a reduction in the number of total microglia in the DG. We conclude that spatial discrimination capacity could be affected earlier than feature discrimination capacity. We suggest that early depletion of neurogenesis in MA rats is involved in object location recognition deficits, whereas the disruption of microglial homeostasis in the Prh could be associated with object feature discrimination capacity.

Aging-Associated Changes in Cognition, Expression and Epigenetic Regulation of Chondroitin 6-Sulfotransferase Chst3.

Understanding changes in the expression of genes involved in regulating various components of the neural extracellular matrix (ECM) during aging can provide an insight into aging-associated decline in synaptic and cognitive functions. Hence, in this study, we compared the expression levels of ECM-related genes in the hippocampus of young, aged and very aged mice. ECM gene expression was downregulated, despite the accumulation of ECM proteoglycans during aging. The most robustly downregulated gene was carbohydrate sulfotransferase 3 (Chst3), the enzyme responsible for the chondroitin 6-sulfation (C6S) of proteoglycans. Further analysis of epigenetic mechanisms revealed a decrease in H3K4me3, three methyl groups at the lysine 4 on the histone H3 proteins, associated with the promoter region of the Chst3 gene, resulting in the downregulation of Chst3 expression in non-neuronal cells. Cluster analysis revealed that the expression of lecticans—substrates of CHST3—is tightly co-regulated with this enzyme. These changes in ECM-related genes were accompanied by an age-confounded decline in cognitive performance. Despite the co-directional impairment in cognitive function and average Chst3 expression in the studied age groups, at the individual level we found a negative correlation between mRNA levels of Chst3 and cognitive performance within the very aged group. An analysis of correlations between the expression of ECM-related genes and cognitive performance in novel object versus novel location recognition tasks revealed an apparent trade-off in the positive gene effects in one task at the expense of another. Further analysis revealed that, despite the reduction in the Chst3 mRNA, the expression of CHST3 protein is increased in glial cells but not in neurons, which, however, does not lead to changes in the absolute level of C6S and even results in the decrease in C6S in perineuronal, perisynaptic and periaxonal ECM relative to the elevated expression of its protein carrier versican.

Trans-urocanic acid facilitates spatial memory, implications for Alzheimer's disease

Trans-urocanic acid (trans-UCA) is an isomer of cis-UCA and is widely distributed in the brain, predominantly in the hippocampus and prefrontal cortex. Previous studies have investigated the role of trans-UCA in non-spatial memory; however, its influence on spatial memory remains unclear. In the present study, network pharmacology strategy and behavioral testing were used to evaluate the role of trans-UCA in spatial memory and predict its possible mechanism. The results showed that there are 40 intersecting targets between trans-UCA and spatial memory identified by several databases and Venn diagram, indicating that trans-UCA may be involved in spatial memory. Behavioral results show that trans-UCA facilitates spatial working memory in the Y-maze test as well as spatial recognition memory acquisition, consolidation and retrieval in an object location recognition (OLR) task. Furthermore, PPI (protein-protein interaction) network analysis, GO (gene ontology) and KEGG (Kyoto encyclopedia of genes and genomes) pathway enrichment analyses show that the molecular mechanisms underlying the enhancing effect of trans-UCA on spatial memory are mainly associated with the regulation of insulin, mitogen-activated protein kinase (MAPK) and nuclear factor Kappa B (NF-κB) signaling pathways, serotonergic synapse and arginine and proline metabolism. The results of this study suggest that trans-UCA facilitates spatial memory in the Y-maze test and OLR task and may offer therapeutic potential for Alzheimer's disease (AD). The underlying mechanisms predicted by network pharmacology should be further verified.

Recovery of Post-Stroke Spatial Memory and Thalamocortical Connectivity Following Novel Glycomimetic and rhBDNF Treatment.

Stroke-induced cognitive impairments remain of significant concern, with very few treatment options available. The involvement of glycosaminoglycans in neuroregenerative processes is becoming better understood and recent advancements in technology have allowed for cost-effective synthesis of novel glycomimetics. The current study evaluated the therapeutic potential of two novel glycomimetics, compound A and G, when administered systemically five-days post-photothrombotic stroke to the PFC. As glycosaminoglycans are thought to facilitate growth factor function, we also investigated the combination of our glycomimetics with intracerebral, recombinant human brain-derived neurotrophic factor (rhBDNF). C56BL/6J mice received sham or stroke surgery and experimental treatment (day-5), before undergoing the object location recognition task (OLRT). Four-weeks post-surgery, animals received prelimbic injections of the retrograde tracer cholera toxin B (CTB), before tissue was collected for quantification of thalamo-PFC connectivity and reactive astrogliosis. Compound A or G treatment alone modulated a degree of reactive astrogliosis yet did not influence spatial memory performance. Contrastingly, compound G+rhBDNF treatment significantly improved spatial memory, dampened reactive astrogliosis and limited stroke-induced loss of connectivity between the PFC and midline thalamus. As rhBDNF treatment had negligible effects, these findings support compound A acted synergistically to enhance rhBDNF to restrict secondary degeneration and facilitate functional recovery after PFC stroke.

The Cognitive-Enhancing Effects of Dendrobium nobile Lindl Extract in Sleep Deprivation-Induced Amnesic Mice.

Chronic sleep deprivation (SD) causes neurological and neurodegenerative dysfunction including learning and memory deficit. The orchid Dendrobium nobile Lindl (DNL), is widely used as a Yin tonic and medicinal food throughout Asia, and has many reported pharmacological effects. This study focused on the cognitive-enhancing effects of DNL in sleep deprivation-induced amnesia in mice and its biochemical mechanisms. Our results showed that the mice displayed significant cognitive deficits after 2-week SD while treatment with the extract of DNL prevented these impairments. In the novel object recognition and object location recognition tasks, a significant increase in the discrimination index was observed in DNL-treated (200 and 400 mg/kg) mice. In the MWM test, DNL (200 and 400 mg/kg) treatment shorten the prolongation of latency and increased the crossing numbers compared with SD mice. The biochemical analysis of brain tissue showed a decrease in NE, dismutase (T-SOD) and catalase (CAT) activity and an increase in 5-HT and malondialdehyde (MDA) concentration after the treatment with DNL in mice. Our findings indicated that DNL exerted a positive effect in preventing and improving cognitive impairment induced by SD, which may be mediated via the regulation of neurotransmitters and alleviation of oxidative stress.

Taurine and N‐acetylcysteine supplementation prevents memory impairment in high‐fat diet‐fed female mice

AbstractBackgroundThe risk to develop memory impairment in has been widely investigated in type 2 diabetes (T2D). There are several mechanisms proposed for T2D‐associated cognitive impairment, such as brain insulin resistance, synaptic dysfunction, inflammation, gliosis, or disruption of neuron‐astrocyte interactions (Garcia‐Serrano & Duarte, 2020). On the other hand, supplementation with the antioxidants taurine and N‐acetylcysteine (NAC) have been suggested to have benefits on reducing T2D phenotype and enhancing memory performance in diabetic mice models (Inam‐U‐Ilah et al, 2018). We aimed at studying mechanisms by which taurine and NAC improve memory in obesity‐associated T2D.MethodTen‐week‐old female C57Bl/6J mice were divided in 6 groups (n=10): control diet (CD 10%‐fat diet), high‐fat diet (HFD; 60% fat diet), CD/HFD supplemented with 3% taurine in drinking water (CD+T or HFD+T) or 3% N‐acetylcysteine (CD+NAC or HFD+NAC). After 2 months, hippocampal metabolic profiles were analysed by magnetic resonance spectroscopy (MRS) under isoflurane anaesthesia, memory performance was evaluated by behavioural testing with the novel location recognition (NLR) and novel object recognition (NOR) tasks, and diabetes phenotype was measured by monitoring weight, glucose tolerance test and HOMA insulin resistance.ResultHFD group was overweight compared to CD group (p<0.01), with no effects of taurine or NAC. HFD‐fed mice showed glucose intolerance compared to CD mice (p<0.001). Although HFD+T and HFD+NAC groups were glucose intolerant but to a lesser degree than untreated HFD mice (p< 0.05 and p<0.01, respectively). None of the experimental groups displayed insulin resistance, neither memory impairment in the NOR test. The NLR test showed memory impairment in the HFD‐fed mice compared to controls (p<0.037), which was prevented by taurine and NAC treatments. The metabolic profile showed decreased concentration of the neuronal marker N‐acetylaspartate and lactate in the hippocampus of HFD‐fed mice compared to controls (p<0.01). While N‐acetylaspartate concentrations were recovered to control levels in both HFD+T and HFD+NAC mice, only HFD+NAC group recovered lactate concentration in the hippocampus.ConclusionMemory impairment in HFD‐fed mice was restored by taurine and NAC treatments, through mechanisms that involve metabolism in mitochondria, which is the organelle responsible for producing N‐acetylaspartate in neurons.Garcia‐Serrano & Duarte, 2020. https://doi.org/10.1177/0271678X20942397 Inam‐U‐Ilah et al, 2018. https://doi.org/10.1007/s00726‐018‐2544‐4

Upregulation of TRPC5 in hippocampal excitatory synapses improves memory impairment associated with neuroinflammation in microglia knockout IL-10 mice

BackgroundMembers of the transient receptor potential canonical (TRPC) protein family are widely distributed in the hippocampus of mammals and exert respective and cooperative influences on the functions of neurons. The relationship between specific TRPC subtypes and neuroinflammation is receiving increasing attention.MethodsUsing Cx3cr1CreERIL-10−/− transgenic mice and their littermates to study the relationship between TRPC channels and memory impairment.ResultsWe demonstrated that Cx3cr1CreERIL-10−/− mice displayed spatial memory deficits in object location recognition (OLR) and Morris water maze (MWM) tasks. The decreased levels of TRPC4 and TRPC5 in the hippocampal regions were verified via reverse transcription polymerase chain reaction, western blotting, and immunofluorescence tests. The expression of postsynaptic density protein 95 (PSD95) and synaptophysin in the hippocampus decreased with an imbalance in the local inflammatory environment in the hippocampus. The number of cells positive for ionized calcium-binding adaptor molecule 1 (Iba1), a glial fibrillary acidic protein (GFAP), increased with the high expression of interleukin 6 (IL-6) in Cx3cr1CreERIL-10−/− mice. The nod-like receptor protein 3 (NLRP3) inflammasome was also involved in this process, and the cytokines IL-1β and IL-18 activated by NLRP3 were also elevated by western blotting. The co-localization of TRPC5 and calmodulin-dependent protein kinase IIα (CaMKIIα) significantly decreased TRPC5 expression in excitatory neurons. AAV9-CaMKIIα-TRPC5 was used to upregulate TRPC5 in excitatory neurons in the hippocampus.ConclusionsThe results showed that the upregulation of TRPC5 improved the memory performance of Cx3cr1CreERIL-10−/− mice related to inhibiting NLRP3 inflammasome-associated neuroinflammation.Graphical

The spontaneous location recognition task for assessing spatial pattern separation and memory across a delay in rats and mice.

Keeping similar memories distinct from one another is a critical cognitive process without which we would have difficulty functioning in everyday life. Memories are thought to be kept distinct through the computational mechanism of pattern separation, which reduces overlap between similar input patterns to amplify differences among stored representations. At the behavioral level, impaired pattern separation has been shown to contribute to memory deficits seen in neuropsychiatric and neurodegenerative diseases, including Alzheimer's disease, and in normal aging. This protocol describes the use of the spontaneous location recognition (SLR) task in mice and rats to behaviorally assess spatial pattern separation ability. This two-phase spontaneous memory task assesses the extent to which animals can discriminate and remember object locations presented during the encoding phase. Using three configurations of the task, the similarity of the to-be-remembered locations can be parametrically manipulated by altering the spatial positions of objects-dissimilar, similar or extra similar-to vary the load on pattern separation. Unlike other pattern separation tasks, SLR varies the load on pattern separation during encoding, when pattern separation is thought to occur. Furthermore, SLR can be used in standard rodent behavioral facilities with basic expertise in rodent handling. The entire protocol takes ~20 d from habituation to testing of the animals on all three task configurations. By incorporating breaks between testing, and varying the objects used as landmarks, animals can be tested repeatedly, increasing experimental power by allowing for within-subjects manipulations.

Memantine improves memory and hippocampal proliferation in adult male rats.

Neurogenesis occurs during the embryological development of the brain. However, it is universally accepted that in all adult mammalian brains, there are two sites of high-density cell division: the subventricular zone of the lateral ventricles (SVZ) and the subgranular zone (SGZ) of the dentate gyrus of the hippocampal formation. Doxorubicin (DOX) is an anthracycline agent which results in cognitive deterioration and memory impairment, whereas memantine (MEM) is an NMDA receptor antagonist which is approved for the treatment of Alzheimer's dementia. Many studies have revealed MEM's positive impact on memory and demonstrated that it stimulates neuronal division in the hippocampus. This study aimed to assess the effect of MEM on spatial memory and neural proliferation in the hippocampus in adult male rats treated with DOX. For this purpose, forty male Sprague-Dawley rats were divided into four groups of ten rats each according to the agent: control, MEM (2.5 mg/kg), DOX (2 mg/kg), and DOX with MEM. The rats were given seven intraperitoneal injections every other day. We tracked the rat's weights to assess the weight-reducing effects of the drugs. In order to test spatial memory, the rats were subjected to the novel location recognition (NLR) task 30 minutes after the last injection. Additionally, Ki67 immunohistochemistry was performed to examine hippocampal proliferation. The results showed a significant reduction in discrimination index (DI) in the DOX-treated group compared to MEM- (p < 0.001) and MEM with DOX-treated groups (p < 0.001). There was a significant increase in Ki67-positive cells in the MEM-treated group compared to the saline-treated group. Treatment with DOX impaired hippocampal proliferation compared to treatment with MEM or saline. The co-administration of MEM with DOX ameliorated the decline in hippocampal proliferation compared to treatment with DOX alone. There was a significant weight reduction in the DOX group in comparison to the control group, but MEM attenuated DOX-induced weight loss. Rats treated with DOX displayed a drop in memory, hippocampal proliferation, and weight compared to the MEM-treated group, whereas the co-administration of MEM with DOX protected memory, hippocampal proliferation, and doxorubicin-induced weight loss.

(m)RVD-hemopressin (α) and (m)VD-hemopressin (α) improve the memory-impairing effect of scopolamine in novel object and object location recognition tasks in mice

Dysfunction of cholinergic system plays an important role in disease associated with cognitive blockage, such as Alzheimer's disease (AD). Central administration of scopolamine, an antagonist of acetylcholine receptor, could induce memory impairment in mice. Endocannabinoid system was also implicated in AD, as two peptides agonists of cannabinoid 1 receptor (CB1R), (m)RVD-hemopressin (α) (RVD) and (m)VD-hemopressin (α) (VD) have been reported to inhibit the AD-relating impairment in animal and cell models. More than one-third of the cholinergic cells expressed CB1R, so we speculated that RVD and VD might have ability to inhibit the memory-impairing effect of scopolamine. Our results showed RVD and VD ameliorated the memory toxicity of scopolamine, and the effects of the two peptides could be blocked by CB1R antagonists hemopressin (Hp) and AM251 in novel object and object location recognition tasks in mice. This study suggested that RVD and VD might be potential compounds for the treatment of the disease associated with impairment of cholinergic system.

Protective effects of Genistein on the cognitive deficits induced by chronic sleep deprivation

Sleep deprivation has been widely reported to cause cognitive dysfunction, and elevation in oxidative stress and inflammation in the body, including the brain, have been suggested as the main factors. Genistein (GE) is an isoflavone widely present in leguminous plants, and it was found to exert a wide spectrum of biological activities, including antioxidant, anti-inflammatory, hepatoprotective, neuroprotective, and antimetastatic effects. In this study, the protective effect of GE on chronic sleep deprivation (CSD)-induced cognitive dysfunction was investigated. The mice were subjected to the sleep interruption apparatus and continuously sleep deprived for 25 days. GE was orally administrated (10, 20, and 40 mg/kg) during the sleep deprivation process totally for 25 days. Cognitive behavioral tests were conducted to study the learning and memory using the object location recognition (OLR) task, novel object recognition (NOR) test, and the Morris water maze (MWM) task. Additionally, the cortex and hippocampus were dissected to measure the oxidative stress markers and the antioxidant element nuclear erythroid-2-related factor 2 (Nrf2) and its downstream targets, including glutamate cysteine ligase catalytic, glutamate cysteine ligase modifier, heme oxygenase 1, and quinone oxidoreductase 1, as well as nuclear factor kappa B (NF-κB) p65, nitric oxide synthase (iNOS), and cyclooxygenase 2 (COX-2) protein expression. Moreover, the pro-inflammatory cytokines (TNF-α, interleukin [IL]-6, and IL-1β) level was examined in the serum. The current results showed that GE could dose-dependently ameliorate the cognitive deficits of CSD-treated mice in the OLR, NOR, and MWM tasks. In addition, GE treatment significantly elevated the activities of total antioxidant capacity and superoxide dismutase and the level of glutathione and lowered the content of malondialdehyde in the cortex and hippocampus of CSD-treated mice. Furthermore, GE administration effectively activated the antioxidant element Nrf2 and its downstream targets in the cortex and hippocampus of CSD-treated mice. Moreover, GE treatment significantly suppressed CSD-induced NF-κB p65, iNOS, and COX-2 activation in the cortex and hippocampus, as well as inhibited CSD-induced pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) release in the serum. Taken together, all these results suggested that GE has substantial potential as a therapeutic intervention for the alleviation of CSD-induced deleterious effects.

Chemerin-9 Peptide Enhances Memory and Ameliorates Aβ1-42-Induced Object Memory Impairment in Mice.

Accumulating evidence suggests that the inhibition of neuroinflammation is a potential target for therapeutic or preventive strategies for Alzheimer's disease (AD). Chemerin has attracted particular attention for its role in the regulation of inflammation. In addition, amyloid β1-42 (Aβ1-42) can interact with chemokine-like receptor 1 (CMKLR1), the receptor for chemerin, and induce microglial chemotaxis. Meanwhile, CMKLR1 is expressed in the brain, and both chemerin and Aβ1-42 share the same receptor. Thus, we hypothesized that chemerin (C9), a chemerin-derived nonapeptide, may have the potential to ameliorate Aβ1-42 mediated AD disease progression. The results showed that an intracerebroventricular (i.c.v.) injection of C9 (8 µg/kg) facilitated memory formation and improved memory retention, as evidenced by the results of both the novel object recognition test (NOR) and object location recognition (OLR) tasks. These memory-enhancing effects of C9 were also observed after C9 (2 µg/kg) was infused into the hippocampus. Moreover, we found that treatment with C9 reversed the deficits in memory and learning ability induced by oligomeric Aβ1-42. Meanwhile, C9 also significantly inhibited Aβ1-42-induced increases in the levels of pro-inflammatory cytokines such as interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the hippocampus. The same results were obtained for Western blotting and enzyme-linked immunosorbent assay (ELISA) experiments. Finally, we observed that C9 did not affect locomotor activity, suggesting that its improvement of memory is not a false positive induced by hypolocomotion. In conclusion, C9 may facilitate memory formation, prolong memory retention, and ameliorate Aβ1-42-induced memory impairment, suggesting that C9 may potentially represent a novel strategy for the treatment of AD.

TGF\u03b2RI antagonist inhibits HIV-1 Nef-induced CC chemokine family ligand 2 (CCL2) in the brain and prevents spatial learning impairment

BackgroundHIV-1–associated neurocognitive disorders (HAND) progression is related to continued inflammation despite undetectable viral loads and may be caused by early viral proteins expressed by latently infected cells. Astrocytes represent an HIV reservoir in the brain where the early viral neurotoxin negative factor (Nef) is produced. We previously demonstrated that astrocytic expression of Nef in the hippocampus of rats causes inflammation, macrophage infiltration, and memory impairment. Since these processes are affected by TGFβ signaling pathways, and TGFβ-1 is found at higher levels in the central nervous system of HIV-1+ individuals and is released by astrocytes, we hypothesized a role for TGFβ-1 in our model of Nef neurotoxicity.MethodsTo test this hypothesis, we compared cytokine gene expression by cultured astrocytes expressing Nef or green fluorescent protein. To determine the role of Nef and a TGFβRI inhibitor on memory and learning, we infused astrocytes expressing Nef into the hippocampus of rats and then treated them daily with an oral dose of SD208 (10 mg/kg) or placebo for 7 days. During this time, locomotor activity was recorded in an open field and spatial learning tested in the novel location recognition paradigm. Postmortem tissue analyses of inflammatory and signaling molecules were conducted using immunohistochemistry and immunofluorescence.ResultsTGFβ-1 was induced in cultures expressing Nef at 24 h followed by CCL2 induction which was prevented by blocking TGFβRI with SD208 (competitive inhibitor). Interestingly, Nef seems to change the TGFβRI localization as suggested by the distribution of the immunoreactivity. Nef caused a deficit in spatial learning that was recovered upon co-administration of SD208. Brain tissue from Nef-treated rats given SD208 showed reduced CCL2, phospho-SMAD2, cluster of differentiation 163 (CD163), and GFAP immunoreactivity compared to the placebo group.ConclusionsConsistent with our previous findings, rats treated with Nef showed deficits in spatial learning and memory in the novel location recognition task. In contrast, rats treated with Nef + SD208 showed better spatial learning suggesting that Nef disrupts memory formation in a TGFβ-1-dependent manner. The TGFβRI inhibitor further reduced the induction of inflammation by Nef which was concomitant with decreased TGFβ signaling. Our findings suggest that TGFβ-1 signaling is an intriguing target to reduce neuroHIV.

Intranasal MMI-0100 Attenuates Aβ1-42- and LPS-Induced Neuroinflammation and Memory Impairments via the MK2 Signaling Pathway.

Background: Accumulating evidence suggests inhibiting neuroinflammation as a potential target in therapeutic or preventive strategies for Alzheimer's disease (AD). MAPK-activated protein kinase II (MK2), downstream kinase of p38 mitogen activated protein kinase (MAPK) p38 MAPK, was unveiled as a promising option for the treatment of AD. Increasing evidence points at MK2 as involved in neuroinflammatory responses. MMI-0100, a cell-penetrating peptide inhibitor of MK2, exhibits anti-inflammatory effects and is in current clinical trials for the treatment of pulmonary fibrosis. Therefore, it is important to understand the actions of MMI-0100 in neuroinflammation.Methods: The mouse memory function was evaluated using novel object recognition (NOR) and object location recognition (OLR) tasks. Brain hippocampus tissue samples were analyzed by quantitative PCR, Western blotting, and immunostaining. Near-infrared fluorescent and confocal microscopy experiments were used to detect the brain uptake and distribution after intranasal MMI-0100 application.Results: Central MMI-0100 was able to ameliorate the memory deficit induced by Aβ1−42 or LPS in novel object and location memory tasks. MMI-0100 suppressed LPS-induced activation of astrocytes and microglia, and dramatically decreased a series of pro-inflammatory cytokines such as TNF-α, IL-6, IL-1β, COX-2, and iNOS via inhibiting phosphorylation of MK2, but not ERK, JNK, and p38 in vivo and in vitro. Importantly, one of the reasons for the failure of macromolecular protein or peptide drugs in the treatment of AD is that they cannot cross the blood–brain barrier. Our data showed that intranasal administration of MMI-0100 significantly ameliorates the memory deficit induced by Aβ1−42 or LPS. Near-infrared fluorescent and confocal microscopy experiment results showed that a strong fluorescent signal, coming from mouse brains, was observed at 2 h after nasal applications of Cy7.5-MMI-0100. However, brains from control mice treated with saline or Cy7.5 alone displayed no significant signal.Conclusions: MMI-0100 attenuates Aβ1−42- and LPS-induced neuroinflammation and memory impairments via the MK2 signaling pathway. Meanwhile, these data suggest that the MMI-0100/MK2 system may provide a new potential target for treatment of AD.