Novel Object Recognition Test for the Investigation of Learning and Memory in Mice

Vortioxetine Prevents Lipopolysaccharide-Induced Memory Impairment Without Inhibiting the Initial Inflammatory Cascade

Vortioxetine is a novel multimodal antidepressant that modulates a wide range of neurotransmitters throughout the brain. Preclinical and clinical studies have shown that vortioxetine exerts positive effects on different cognitive domains and neuroprotective effects. Considering the key role of microglial cells in brain plasticity and cognition, we aimed at investigating the effects of pretreatment with vortioxetine in modulating behavioral and molecular effects induced by an immune challenge: peripheral injection of lipopolysaccharide (LPS). To this purpose, C57BL/6J male mice were first exposed to a 28-day standard diet or vortioxetine-enriched diet, which was followed by an acute immune challenge with LPS. Sickness symptoms and depressive-like behaviors (anhedonia and memory impairment) were tested 6 and 24 h after exposure to LPS, respectively. Moreover, the expressions of markers of immune activation and M1/M2 markers of microglia polarization were measured in the dorsal and ventral parts of the hippocampus. The pretreatment with vortioxetine did not affect both LPS-induced sickness behavior and anhedonia but prevented the deficit in the recognition memory induced by the immune challenge. At the transcriptional level, chronic exposure to vortioxetine did not prevent LPS-induced upregulation of proinflammatory cytokines 6 h after the immune challenge but rather seemed to potentiate the immune response to the challenge also by affecting the levels of expression of markers of microglia M1 phenotype, like cluster of differentiation (CD)14 and CD86, in an area-dependent manner. However, at the same time point, LPS injection significantly increased the expression of the M2 polarization inducer, interleukin 4, only in the hippocampus of animals chronically exposed to vortioxetine. These results demonstrate that a chronic administration of vortioxetine specifically prevents LPS-induced memory impairment, without affecting acute sickness behavior and anhedonia, and suggest that hippocampal microglia may represent a cellular target of this novel antidepressant medication. Moreover, we provide a useful model to further explore the molecular mechanisms specifically underlying cognitive impairments following an immune challenge.

Cognitive decline prevention in offspring of Pb+2 exposed mice by maternal aerobic training and Cur/CaCO3@Cur supplementations: In vitro and in vivo studies

Heavy metals are considered contaminants that hazardously influence the healthy life of humans and animals as they are widely used in industry. Contact of youngsters and women at ages of parturition with lead (Pb⁺²) is a main related concern, which passes through the placental barricade and its better absorption in the intestine leads to flaws in the fetal developfment. However, the metals threaten animal and human life, in particular throughout developmental stages. Products existing in the nature have a major contribution to innovating chemo-preventives. As a naturally available polyphenol and necessary curcuminoid, curcumin (Cur) is a derivative of the herb Curcuma longa (L.) rhizome, which globally recognized as "wonder drug of life"; however, Cur has a limited clinical use as it is poorly dissolved in water. Therefore, to enhance its clinically relevant parameters, curcumin-loaded calcium carbonate (CaCO₃@Cur) was synthesized by one step coprecipitation method as a newly introduced in this research. Initially, its structure was physio chemically characterized using FT-IR, FESEM and DLS equipment and then the cytotoxicity of lead when it was pretreated with Cur/CaCO₃@Cur were assessed by MTT assay. Both Cur and CaCO₃@Cur diminished the toxic effects of Pb⁺² while the most protective effect on the Pb⁺² cytotoxicity was achieved by pre-incubation of cells with CaCO₃@Cur. Besides, the morphological changes of Pb⁺²-treated cells that were pre-incubated with or without Cur/CaCO₃@Cur were observed by normal and florescent microscopes. A non-pharmacologic method that lowers the hazard of brain damage is exercise training that is capable of both improving and alleviating memory. In the current study, the role of regular aerobic training and CaCO₃@Cur was assessed in reducing the risk of brain damage induced by lead nitrate contact. To achieve the mentioned goal, pregnant Balb/C mice were assigned to five groups (six mice/group) at random: negative and positive controls, aerobic training group and Cur and CaCO₃@Cur treated (50 mg/kg/b.wt) trained groups that exposed to Pb⁺² (2 mg/kg) by drinking water during breeding and pregnancy. With the completion of study, offspring were subjected to the behavioral tasks that was tested by step-through ORT, DLB, MWM and YM tests. As a result, having regular aerobic training and CaCO₃@Cur co-administration with lead nitrate could reverse the most defected behavioral indicators; yet, this was not visible for both sexes and it seems that gender can also be a source of different effects in the animal's body. In fact, having regular aerobic training along with CaCO₃@Cur supplementation during pregnancy may be encouraging protecting potential agents towards the toxicity of Pb⁺² that could be recommended in the areas with high pollution of heavy metals.

3D-Printed Capacitive Sensor Objects for Object Recognition Assays

Object recognition tasks are widely used assays for studying learning and memory in rodents. Object recognition typically involves familiarizing mice with a set of objects and then presenting a novel object or displacing an object to a novel location or context. Learning and memory are inferred by a relative increase in time investigating the novel/displaced object. These tasks are in widespread use, but there are many inconsistencies in the way they are conducted across labs. Two major contributors to this are the lack of consistency in the method of measuring object investigation and the lack of standardization of the objects that are used. Current video-based automated algorithms can often be unreliable whereas manual scoring of object investigation is time consuming, tedious, and more subjective. To resolve these issues, we sought to design and implement 3D-printed objects that can be standardized across labs and use capacitive sensing to measure object investigation. Using a 3D printer, conductive filament, and low-cost off-the-shelf components, we demonstrate that employing 3D-printed capacitive touch objects is a reliable and precise way to perform object recognition tasks. Ultimately, this approach will lead to increased standardization and consistency across labs, which will greatly improve basic and translational research into learning and memory mechanisms.

Amentoflavone Ameliorates Memory Deficits and Abnormal Autophagy in Aβ25-35-Induced Mice by mTOR Signaling

Alzheimer's disease (AD) is a neurodegenerative disease in which autophagy plays a crucial role. Amentoflavone is a flavonoid obtained from various plants and has been shown to have AD-resistant neuroprotective effects. This study investigated the role of amentoflavone on memory impairment and abnormal autophagy in amyloid-β25-35 (Aβ_25-35)-induced mice to elucidate the mechanisms by which it exerts neuroprotective effects. In this experiment, the AD mouse model was established by intracerebroventricular (ICV) injection of Aβ_25-35 peptides, and amentoflavone was administered orally for 4 weeks. Behavioral changes in mice and pathological changes in the hippocampus were observed, and levels of inflammation, oxidative stress, and autophagy in the brain were detected and analyzed. PC-12 and APPswe-N2a cells were used in vitro to further investigate the effect of amentoflavone on the level of intracellular autophagy. Molecular docking was used to determine the action sites of amentoflavone. The results showed that amentoflavone improved memory function, eased anxiety symptoms in Aβ_25-35-induced mice, and reduced atrophic degeneration of neurons in the hippocampus. Moreover, amentoflavone lessened the oxidative stress and inflammation in the brains of mice. Through in vivo and in vitro experiments, we found that amentoflavone may enhance autophagy, by way of binding to the ATP site of the mTOR protein kinase domain. Amentoflavone not only interacted with mTOR, but also improved Aβ_25-35-induced cognitive dysfunction in mice by enhancing autophagy, attenuating levels of inflammation and oxidative stress, and reducing apoptosis in brain cells.

Alpinia oxyphylla Miq. and Its Active Compound P-Coumaric Acid Promote Brain-Derived Neurotrophic Factor Signaling for Inducing Hippocampal Neurogenesis and Improving Post-cerebral Ischemic Spatial Cognitive Functions

Alpinia oxyphylla Miq. (AOM) is a medicinal herb for improving cognitive functions in traditional Chinese medicine for poststroke treatment, but its efficacies and underlying mechanisms remain unknown. In the present study, we tested the hypothesis that AOM could induce adult hippocampal neurogenesis and improve poststroke cognitive impairment via inducing brain-derived neurotrophic factor (BDNF) signaling pathway. In order to test the hypothesis, we performed both in vivo rat experiments using transient middle cerebral artery occlusion (MCAO) model and in vitro neural stem cell (NSC) experiments using oxygen–glucose deprivation plus reoxygenation. First, AOM treatment significantly up-regulated the expression of BDNF, tropomycin receptor kinase B (TrkB), and phosphorylated AKT (p-AKT) in the hippocampus, enhanced adult hippocampal neurogenesis, and improved the spatial learning/memory and cognitive functions in the post-MCAO ischemic rats in vivo. Next, in vitro studies confirmed p-coumaric acid (P-CA) to be the most effective compound identified from AOM extract with the properties of activating BDNF/TrkB/AKT signaling pathway and promoting NSC proliferation. Cotreatment of BDNF/TrkB-specific inhibitor ANA12 abolished the effects of P-CA on inducing BDNF/TrkB/AKT activation and the NSC proliferation. Finally, animal experiments showed that P-CA treatment enhanced the neuronal proliferation and differentiation in the hippocampus, improved spatial learning and memory functions, and reduced anxiety in the transient MCAO ischemic rats. In conclusion, P-CA is a representative compound from AOM for its bioactivities of activating BDNF/TrkB/AKT signaling pathway, promoting hippocampal neurogenesis, improving cognitive functions, and reducing anxiety in post–ischemic stroke rats.

Effects of Melatonin on Neurobehavior and Cognition in a Cerebral Palsy Model of plppr5-/- Mice

Cerebral palsy (CP), a group of clinical syndromes caused by non-progressive brain damage in the developing fetus or infant, is one of the most common causes of lifelong physical disability in children in most countries. At present, many researchers believe that perinatal cerebral hypoxic ischemic injury or inflammatory injury are the main causes of cerebral palsy. Previous studies including our works confirmed that melatonin has a protective effect against convulsive brain damage during development and that it affects the expression of various molecules involved in processes such as metabolism, plasticity and signaling in the brain. Integral membrane protein plppr5 is a new member of the plasticity-related protein family, which is specifically expressed in brain and spinal cord, and induces filopodia formation as well as neurite growth. It is highly expressed in the brain, especially in areas of high plasticity, such as the hippocampus. The signals are slightly lower in the cortex, the cerebellum, and in striatum. Noteworthy, during development plppr5 mRNA is expressed in the spinal cord, i.e., in neuron rich regions such as in medial motor nuclei, suggesting that plppr5 plays an important role in the regulation of neurons. However, the existing literature only states that plppr5 is involved in the occurrence and stability of dendritic spines, and research on its possible involvement in neonatal ischemic hypoxic encephalopathy has not been previously reported. We used plppr5 knockout (plppr5-/-) mice and their wild-type littermates to establish a model of hypoxicischemic brain injury (HI) to further explore the effects of melatonin on brain injury and the role of plppr5 in this treatment in an HI model, which mainly focuses on cognition, exercise, learning, and memory. All the tests were performed at 3-4 weeks after HI. As for melatonin treatment, which was performed 5 min after HI injury and followed by every 24h. In these experiments, we found that there was a significant interaction between genotype and treatment in novel object recognition tests, surface righting reflex tests and forelimb suspension reflex tests, which represent learning and memory, motor function and coordination, and the forelimb grip of the mice, respectively. However, a significant main effect of genotype and treatment on performance in all behavioral tests were observed. Specifically, wild-type mice with HI injury performed better than plppr5-/- mice, regardless of treatment with melatonin or vehicle. Moreover, treatment with melatonin could improve behavior in the tests for wild-type mice with HI injury, but not for plppr5-/- mice. This study showed that plppr5 knockout aggravated HI damage and partially weakened the neuroprotection of melatonin in some aspects (such as novel object recognition test and partial nerve reflexes), which deserves further study.

Dammarane Sapogenins Improving Simulated Weightlessness-Induced Depressive-Like Behaviors and Cognitive Dysfunction in Rats

Background: Our studies demonstrated that the space environment has an impact on the brain function of astronauts. Numerous ground-based microgravity and social isolation showed that the space environment can induce brain function damages in humans and animals. Dammarane sapogenins (DS), an active fraction from oriental ginseng, possesses neuropsychic protective effects and has been shown to improve depression and memory. This study aimed to explore the effects and mechanisms of DS in attenuating depressive-like behaviors and cognitive deficiency induced by simulated weightlessness and isolation [hindlimb suspension and isolation (HLSI)] in rats. Methods: Male rats were orally administered with two different doses of DS (37.5, 75 mg/kg) for 14 days, and huperzine-A (1 mg/kg) served as positive control. Rats were subjected to HLSI for 14 days except the control group during drug administration. The depressive-like behaviors were then evaluated by the open-field test, the novel object recognition test, and the forced swimming test. The spatial memory and working memory were evaluated by the Morris water maze (MWM) test, and the related mechanism was further explored by analyzing the activity of choline acetyltransferase (ChAT), acetylcholinesterase (AChE), and superoxide dismutase (SOD) in the hippocampus of rats. Results: The results showed that DS treatment significantly reversed the HLSI-induced depressive-like behaviors in the open-field test, the novel object recognition test, and the forced swimming test and improved the HLSI-induced cognitive impairment in the MWM test. Furthermore, after DS treatment, the ChAT and SOD activities of HLSI rats were increased while AChE activity was significantly suppressed. Conclusions: These findings clearly demonstrated that DS might exert a significant neuropsychic protective effect induced by spaceflight environment, driven in part by the modulation of cholinergic system and anti-oxidation in the hippocampus.

Early-Life Stress Alters Synaptic Plasticity and mTOR Signaling: Correlation With Anxiety-Like and Cognition-Related Behavior

Early-life stress (ELS) predisposes individuals to psychiatric disorders, including anxiety and depression, and cognitive impairments later in life. However, the underlying molecular mechanisms are not completely understood. Developmental deficits in hippocampal synaptic plasticity are among the primary detrimental alterations in brain function induced by ELS. Impaired synaptic plasticity is usually accompanied by decreased synaptic proteins, such as postsynaptic density 95 (PSD95) and synaptophysin, which are important for synaptic function. The mTOR signaling pathway plays a vital role in regulating protein translation, and mTOR activation is functionally associated with synaptic protein synthesis. In the present study, we observed whether ELS impacts synaptic protein synthesis and mTOR signaling, which is involved in synaptic plasticity. Herein, we established a maternal separation (MS) and chronic restraint stress (CRS) model and evaluated anxiety-like behavior and cognitive function (e.g., learning and memory) in adulthood through behavioral examination and analyzed hippocampal expression levels of PSD95 and synaptophysin. To explore whether the mTOR signaling pathway was associated with ELS, we also examined the activity of mTOR and s6. The behavior tests indicated that maternally separated mice showed increased anxiety-like behavior and cognitive impairments. PSD95 and synaptophysin mRNA and protein expression levels were decreased in the hippocampus, and phosphorylated mTOR and phosphorylated s6 were significantly decreased in maternally separated mice vs. those not exposed to MS. Our data demonstrate that MS impairs synaptic plasticity and inhibits mTOR signaling, specifically via s6. Therefore, we speculate that ELS decreased synaptic plasticity via the inhibition of the mTOR pathway in the hippocampus, which may underlie vulnerability to stress and mental disorders in adulthood.

Transcranial Ultrasound Stimulation of Hypothalamus in Aging Mice

The hypothalamus plays an important role in the control of aging. Transcranial ultrasound stimulation (TUS) has been reported as a noninvasive method of neuromodulation. However, the effect of TUS of the hypothalamus on aging remains unclear. Therefore, the aim of this study is to verify whether TUS of the hypothalamus could affect the behaviors of aging mice and the expression level of apoptosis factors and inflammatory cytokines. TUS was delivered to the hypothalamus of mice ( n = 44 ) for 14 days (15 min/day) at a fundamental frequency of 1 MHz, pulse repetition frequency of 1 kHz (US1) or 10 Hz (US2), duty cycle of 10%, and acoustic pressure of 0.13 MPa. The effect of TUS on aging was evaluated by the behavioral tests or Western blotting in different stages. The behavioral results showed that mice in the US2 group improved their movement and learning. In addition, there was a significant improvement in the grip strength after TUS in the second behavioral tests (Sham: 0.0351 ± 0.0020 N/g; US1: 0.0340 ± 0.0023 N/g; US2: 0.0425 ± 0.0029 N/g, p = 0.034 ). Furthermore, the level of inflammation (TNF- α : Sham: 0.69 ± 0.084; US1: 0.39 ± 0.054; US2: 0.49 ± 0.1, p = 0.021 ) and apoptosis (Bax: Sham: 0.47 ± 0.049; US1: 0.42 ± 0.054; US2: 0.18 ± 0.055, p = 0.001 ) was significantly reduced after TUS in this stage. We did not see a long-lasting effect of TUS in the third behavioral tests. In addition, we found that TUS is safe according to hematoxylin and eosin (HE) staining. In conclusion, TUS could effectively modulate the hypothalamus, which may provide a new method for controlling aging.

Neuroprotective potential of imatinib in global ischemia-reperfusion-induced cerebral injury: possible role of Janus-activated kinase 2/signal transducer and activator of transcription 3 and connexin 43

The present study was aimed to explore the neuroprotective role of imatinib in global ischemia-reperfusion-induced cerebral injury along with possible mechanisms. Global ischemia was induced in mice by bilateral carotid artery occlusion for 20 min, which was followed by reperfusion for 24 h by restoring the blood flow to the brain. The extent of cerebral injury was assessed after 24 h of global ischemia by measuring the locomotor activity (actophotometer test), motor coordination (inclined beam walking test), neurological severity score, learning and memory (object recognition test) and cerebral infarction (triphenyl tetrazolium chloride stain). Ischemia-reperfusion injury produced significant cerebral infarction, impaired the behavioral parameters and decreased the expression of connexin 43 and phosphorylated signal transducer and activator of transcription 3 (p-STAT3) in the brain. A single dose administration of imatinib (20 and 40 mg/kg) attenuated ischemia-reperfusion-induced behavioral deficits and the extent of cerebral infarction along with the restoration of connexin 43 and p-STAT3 levels. However, administration of AG490, a selective Janus-activated kinase 2 (JAK2)/STAT3 inhibitor, abolished the neuroprotective actions of imatinib and decreased the expression of connexin 43 and p-STAT3. It is concluded that imatinib has the potential of attenuating global ischemia-reperfusion-induced cerebral injury, which may be possibly attributed to activation of JAK2/STAT3 signaling pathway along with the increase in the expression of connexin 43.

Melatonin Reduces NLRP3 Inflammasome Activation by Increasing α7 nAChR-Mediated Autophagic Flux

Microglia controls the immune system response in the brain. Specifically, the activation and dysregulation of the NLRP3 inflammasome is responsible for the initiation of the inflammatory process through IL-1β and IL-18 release. In this work, we have focused on studying the effect of melatonin on the regulation of the NLRP3 inflammasome through α7 nicotinic receptor (nAChR) and its relationship with autophagy. For this purpose, we have used pharmacological and genetic approaches in lipopolysaccharide (LPS)-induced inflammation models in both in vitro and in vivo models. In the BV2 cell line, LPS inhibited autophagy, which increased NLRP3 protein levels. However, melatonin promoted an increase in the autophagic flux. Treatment of glial cultures from wild-type (WT) mice with LPS followed by extracellular adenosine triphosphate (ATP) produced the release of IL-1β, which was reversed by melatonin pretreatment. In cultures from α7 nAChR knock-out (KO) mice, melatonin did not reduce IL-1β release. Furthermore, melatonin decreased the expression of inflammasome components and reactive oxygen species (ROS) induced by LPS; co-incubation of melatonin with α-bungarotoxin (α-bgt) or luzindole abolished the anti-inflammatory and antioxidant effects. In vivo, melatonin reverted LPS-induced cognitive decline, reduced NLRP3 levels and promoted autophagic flux in the hippocampi of WT mice, whereas in α7 nAChR KO mice melatonin effect was not observed. These results suggest that melatonin may modulate the complex interplay between α7 nAChR and autophagy signaling.

Effects of Hippeastrum reticulatum on memory, spatial learning and object recognition in a scopolamine-induced animal model of Alzheimer's disease

CONTEXT

The methanol extracts from Hippeastrum reticulatum (L'Hér.) Herb. (Amaryllidaceae) (HR) display acetylcholinesterase inhibitory (AChEI) activity.

OBJECTIVE

AChEI of alkaloids isolated from HR bulbs and the ameliorating effects of the alkaloid fraction (AHR) on memory and cognitive dysfunction in scopolamine-treated mice were investigated.

MATERIALS AND METHODS

Alkaloids were isolated by column chromatography and identified by spectroscopy. AChEI was evaluated using the modified Ellman's method. Sixty Swiss male mice were randomly divided into six groups, received samples for 15 days. Normal group received saline, scopolamine-treated group scopolamine (1.5 mg/kg, intraperitoneal injection). Test groups received AHR (5, 10 and 15 mg/kg, per os) and positive control group donepezil (5 mg/kg, per os), administered 1 h before the test, scopolamine was injected 30 min prior to testing. The cognitive-enhancing activity of AHR against scopolamine-induced memory impairments was investigated using Y-maze, the novel object recognition test (NORT) and the Morris water maze (MWM) test.

RESULTS

Seven alkaloids were isolated for the first time from the genus Hippeastrum: trans-dihydronarciclasine (1), N-chloromethylnarcissidinium (2), narciprimin (3), narciclasine-4-O-β-d-xylopyranoside (4), N-methyltyramine (5), 3β,11α-dihydroxy-1,2-dehydrocrinane (6) and brunsvigine (7); three are new compounds (2, 5, 6). Among them, 2-3 and 5-6 showed AChEI in vitro with IC₅₀ values of 29.1, 46.4, 70.1 and 104.5 µg/mL, respectively. The anti-AChEI of 2, 5 and 6 are reported for the first time. In in vivo test, AHR (15 mg/kg) significantly increased in spontaneous alternation performance in the Y-maze test (p < 0.01), it significantly increased the time spent exploring the novel object (p < 0.05) comparison with scopolamine-treated group. The administration of AHR at doses 10 and 15 mg/kg significantly decreased escapes latency and swimming distance to the platform on day 6 compared to these in day 1 (p < 0.01 and p < 0.05, respectively).

CONCLUSIONS

AHR could be a potential candidate of future trials for treatment of memory and cognitive dysfunction in Alzheimer's disease.

Methyl jasmonate reverses chronic stress-induced memory dysfunctions through modulation of monoaminergic neurotransmission, antioxidant defense system, and Nrf2 expressions

Unpredictable chronic mild stress (UCMS) has been shown to cause memory loss via increased oxidative stress and deregulation of monoaminergic and cholinergic neurotransmissions. Although the benefits of methyl jasmonate (MJ), a well-known anti-stress plant hormone against chronic stress-induced psychopathologies, have been earlier reported, its effects on antioxidant defense molecules, monoaminergic transmitters, and nuclear factor erythroid 2-related factor 2 (Nrf2) immunopositive cells have not been extensively studied. The present study was designed to examine its effect on memory functions, antioxidant biomarkers, monoaminergic transmitters, and Nrf2 immunopositive cell expression in rats exposed to UCMS. Rats received an intraperitoneal injection of MJ (10, 25, and 50 mg/kg) 30 min before exposure to UCMS daily for 28 days. Memory function was assessed on day 29 using a modified elevated plus maze and novel object recognition tests. The antioxidant biomarkers, level of monoamines (serotonin, noradrenaline, and dopamine), and Nrf2 immunopositive cell expression were determined in the rat brain tissues. The activity of cholinesterase and monoamine oxidase enzymes was also determined. MJ attenuated memory deficits and elevated the brain levels of monoamines in UCMS rats. UCMS-induced increase of brain cholinesterase and monoamine oxidase activities was inhibited by MJ. Also, MJ attenuated UCMS-induced decrease in antioxidant enzymes (CAT, GPx, GST, and SOD) and thiol contents in the brains of rats. UCMS-induced increase in NO level and Nrf2 immunopositive cell expression in the rat's brain was attenuated by MJ. Taken together, these findings suggest that increasing antioxidant defense molecules and monoaminergic/cholinergic neurotransmitters and decreasing the Nrf2 immunopositive cell expressions may contribute to the memory-promoting effects of MJ in rats exposed to UCMS.

A novel mouse model for vulnerability to alcohol dependence induced by early-life adversity

Childhood adversity increases vulnerability to alcohol use disorders and preclinical models are needed to investigate the underlying neurobiological mechanisms. The present study modeled early-life adversity by rearing male and female C57BL/6J mouse pups in a limited bedding and nesting (LBN) environment, which induces erratic maternal care. As adults, mice were given limited access to two-bottle choice (2BC) alcohol drinking, combined or not with chronic intermittent ethanol (CIE) vapor inhalation to induce alcohol dependence. We tested the hypothesis that LBN rearing might exacerbate or facilitate the emergence of the motivational and affective effects of CIE. Consistent with our hypothesis, although LBN-reared males consumed the same baseline levels of alcohol as controls, they escalated their ethanol intake at an earlier stage of CIE exposure, i.e., after 4 rounds vs. 5 rounds for controls. In contrast, females were insensitive to both LBN rearing and CIE exposure. Males were further subjected to a behavioral test battery. Withdrawal from CIE-2BC increased digging activity and lowered mechanical nociceptive thresholds regardless of early-life conditions. On the other hand, LBN-reared CIE-2BC males showed reduced open arm exploration in the elevated plus maze and increased immobility in the tail suspension test compared to alcohol-naïve counterparts, while no group differences were detected among control-reared males. Finally, LBN rearing and alcohol exposure did not affect grooming in response to a sucrose spray (splash test), novel object recognition, or corticosterone levels. In summary, the LBN experience accelerates the transition from moderate to excessive alcohol drinking and produces additional indices of affective dysfunction during alcohol withdrawal in C57BL/6J male mice.

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Early-life adversity was generated by rearing C57BL/6J mouse pups in a limited bedding and nesting (LBN) environment.

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Alcohol dependence was induced in adulthood via chronic intermittent ethanol (CIE) inhalation.

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The LBN experience accelerated alcohol intake escalation in males.

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LBN exacerbated affective disturbances upon CIE withdrawal in males.

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Alcohol intake in females was insensitive to both LBN and CIE.

Plasma dilution improves cognition and attenuates neuroinflammation in old mice

Our recent study has established that young blood factors are not causal, nor necessary, for the systemic rejuvenation of mammalian tissues. Instead, a procedure referred to as neutral blood exchange (NBE) that resets signaling milieu to a pro-regenerative state through dilution of old plasma, enhanced the health and repair of the muscle and liver, and promoted better hippocampal neurogenesis in 2-year-old mice (Mehdipour et al., Aging 12:8790–8819, 2020). Here we expand the rejuvenative phenotypes of NBE, focusing on the brain. Namely, our results demonstrate that old mice perform much better in novel object and novel texture (whisker discrimination) tests after a single NBE, which is accompanied by reduced neuroinflammation (less-activated CD68⁺ microglia). Evidence against attenuation/dilution of peripheral senescence-associated secretory phenotype (SASP) as the main mechanism behind NBE was that the senolytic ABT 263 had limited effects on neuroinflammation and did not enhance hippocampal neurogenesis in the old mice. Interestingly, peripherally acting ABT 263 and NBE both diminished SA-βGal signal in the old brain, demonstrating that peripheral senescence propagates to the brain, but NBE was more robustly rejuvenative than ABT 263, suggesting that rejuvenation was not simply by reducing senescence. Explaining the mechanism of the positive effects of NBE on the brain, our comparative proteomics analysis demonstrated that dilution of old blood plasma yields an increase in the determinants of brain maintenance and repair in mice and in people. These findings confirm the paradigm of rejuvenation through dilution of age-elevated systemic factors and extrapolate it to brain health and function.

Graphene Oxide Ameliorates the Cognitive Impairment Through Inhibiting PI3K/Akt/mTOR Pathway to Induce Autophagy in AD Mouse Model

Alzheimer's disease (AD) is a neurodegenerative disease of the central nervous system characterised by cognitive impairment. Its major pathological feature is the deposition of β-amyloid (Aβ) peptide, which triggers a series of pathological cascades. Autophagy is a main pathway to eliminate abnormal aggregated proteins, and increasing autophagy represents a plausible treatment strategy against relative overproduction of neurotoxic Aβ. Graphene oxide (GO) is an emerging carbon-based nanomaterial. As a derivative of graphene with neuroprotective effects, it can effectively increase the clearance of abnormally aggregated protein. In this article, we investigated the protective function of GO in an AD mouse model. GO (30 mg/kg, intraperitoneal) was administered for 2 weeks. The results of the Morris water maze test and the novel object recognition test suggested that GO ameliorated learning and memory impairments in 5xFAD mice. The long-term potentiation and depotentiation from the perforant path to the dentate gyrus in the hippocampus were increased with GO treatment in 5xFAD mice. Furthermore, GO upregulated the expression of synapse-related proteins and increased the cell density in the hippocampus. Our results showed that GO up-regulated LC3II/LC3I and Beclin-1 and decreased p62 protein levels in 5xFAD mice. In addition, GO downregulated the PI3K/Akt/mTOR signalling pathway to induce autophagy. These results have revealed the protective potential of GO in AD.

Alternative splicing of neurexins 1-3 is modulated by neuroinflammation in the prefrontal cortex of a murine model of multiple sclerosis

Mounting evidence points to immune-mediated synaptopathy and impaired plasticity as early pathogenic events underlying cognitive decline (CD) in Multiple sclerosis (MS) and in the experimental autoimmune encephalomyelitis (EAE) mouse model of the disease. However, knowledge of the neurobiology of synaptic dysfunction is still incomplete. Splicing regulation represents a flexible and powerful mechanism involved in dynamic remodeling of the synapse, which allows the expression of synaptic protein variants that dynamically control the specificity of contacts between neurons. The pre-synaptic adhesion molecules neurexins (NRXNs) 1-3 play a relevant role in cognition and are alternatively spliced to yield variants that differentially cluster specific ligands in the postsynaptic compartment and modulate functional properties of the synaptic contact. Notably, mutations in these genes or disruption of their splicing program are associated with neuropsychiatric disorders. Herein, we have investigated how inflammatory changes imposed by EAE impact on alternative splicing of the Nrxn 1-3 mouse genes in the acute phase of disease. Due to its relevance in cognition, we focused on the prefrontal cortex (PFC) of SJL/J mice, in which EAE-induced inflammatory lesions extend to the rostral forebrain. We found that inclusion of the Nrxn 1-3 AS4 exon is significantly increased in the PFC of EAE mice and that splicing changes are correlated with local Il1β-expression levels. This correlation is sustained by the concomitant downregulation of SLM2, the main splicing factor involved in skipping of the AS4 exon, in EAE mice displaying high levels of Il1β- expression. We also observed that Il1β-expression levels correlate with changes in parvalbumin (PV)-positive interneuron connectivity. Moreover, exposure to environmental enrichment (EE), a condition known to stimulate neuronal connectivity and to improve cognitive functions in mice and humans, modified PFC phenotypes of EAE mice with respect to Il1β-, Slm2-expression, Nrxn AS4 splicing and PV-expression, by limiting changes associated with high levels of inflammation. Our results reveal that local inflammation results in early splicing modulation of key synaptic proteins and in remodeling of GABAergic circuitry in the PFC of SJL/J mice. We also suggest EE as a tool to counteract these inflammation-associated events, thus highlighting potential therapeutic targets for limiting the progressive CD occurring in MS.

Inhibition of the prostaglandin EP2 receptor prevents long-term cognitive impairment in a model of systemic inflammation

Long-term cognitive and affective impairments are common problems in the survivors of sepsis, which weakens their vocational and daily life ability. Neuroinflammation has been reported to exert a key role in the development of cognitive deficit in different disorders including epilepsy, Alzheimer's disease (AD) and stroke. Mice treated with lipopolysaccharide (LPS), an endotoxin produced by gram-negative bacteria, show a robust but short-lived neuroinflammation and develop long-term memory and affective problems. In this study, we test the hypothesis that pharmacological blockade of the EP2 receptor for prostaglandin E2 reduces neuroinflammation and prevents long-term affective and memory deficits in a mouse model of LPS-induced, sepsis-associated encephalopathy (SAE). Our results show that an EP2 antagonist, TG6-10-1, promotes the recovery of body weight, mitigates neuroinflammation as judged by inflammatory cytokines and microgliosis, prevents the loss of synaptic proteins, and ameliorates depression-like behavior in the sucrose preference test as well as memory loss in the novel object recognition test. Our results point to a new avenue to ameliorate neuroinflammation and long-term affective and cognition problems of sepsis survivors.

Reducing Glut2 throughout the body does not result in cognitive behaviour differences in aged male mice

Objectives

GLUT2 is a major facilitative glucose transporter, expressed from the SLC2A2 gene, with essential roles in the liver. Recent work in mice has shown that preventing Glut2 production in specific neuronal populations increases sugar-seeking behaviour, highlighting the importance of Slc2a2 gene expression in the brain. It implies that reduced GLUT2 in the brain, due to genetic polymorphisms or disease, impacts health through behaviour change. Defects in glucose transport in the brain are observed in conditions including type-2 diabetes and dementia. Few studies have directly examined the effect of modulating neuronal glucose transporter expression on cognitive function. The aim of this study was to investigate whether inactivating one Slc2a2 allele throughout the body had major effects on cognition. Cognitive tests to assess recognition memory, spatial working memory and anxiety were performed in Slc2a2 whole-body heterozygous mice (i.e. reduced Glut2 mRNA and protein), alongside littermates expressing normal levels of the transporter.

Results

No significant effects on neurological functions and cognitive capabilities were observed in mice lacking one Slc2a2 allele when fed a chow diet. This suggests that the minor variations in GLUT2 levels that occur in the human population are unlikely to influence behaviour and basic cognition.

Dim Light at Night Induced Neurodegeneration and Ameliorative Effect of Curcumin

It is a well-known fact that following a proper routine light/dark or diurnal rhythm controls almost all biological processes. With the introduction of modern lighting and artificial illumination systems, continuous exposure to light at night may lead to the disruption of diurnal rhythm. However, the effect of light during the night on brain anatomy, physiology, and human body functions is less explored and poorly understood. In this study, we have evaluated the effect of exposure to dim light (5 lux) at night (dLAN) on Swiss Albino mice over a duration of three consecutive weeks. Results have revealed that exposure to dLAN led to an impairment of cognitive and non-cognitive behaviour, oxidative stress–mediated elevation of lipid peroxidation, and reduction of superoxide dismutase and catalase activity. It also led to the downregulation of hippocampal proteins (BDNF, Synapsin II and DCX) at both protein and mRNA level. Additionally, there was downregulation of CREB and SIRT1 mRNAs and neurodegeneration-associated miRNA21a-5p and miRNA34a-5p. The pyramidal and cortical neurons started showing pyknotic and chromatolysis characteristics. However, a dose of curcumin administered to the mice positively modulated these parameters in our experimental animals. We proposed the modulatory role of curcumin in addressing the deleterious effects of dLAN.

Ameliorative Properties of Boronic Compounds in In Vitro and In Vivo Models of Alzheimer's Disease

Alzheimer's disease (AD) is characterized by amyloid (Aβ) aggregation, hyperphosphorylated tau, neuroinflammation, and severe memory deficits. Reports that certain boronic compounds can reduce amyloid accumulation and neuroinflammation prompted us to compare trans-2-phenyl-vinyl-boronic-acid-MIDA-ester (TPVA) and trans-beta-styryl-boronic-acid (TBSA) as treatments of deficits in in vitro and in vivo models of AD. We hypothesized that these compounds would reduce neuropathological deficits in cell-culture and animal models of AD. Using a dot-blot assay and cultured N₂a cells, we observed that TBSA inhibited Aβ42 aggregation and increased cell survival more effectively than did TPVA. These TBSA-induced benefits were extended to C. elegans expressing Aβ42 and to the 5xFAD mouse model of AD. Oral administration of 0.5 mg/kg dose of TBSA or an equivalent amount of methylcellulose vehicle to groups of six- and 12-month-old 5xFAD or wild-type mice over a two-month period prevented recognition- and spatial-memory deficits in the novel-object recognition and Morris-water-maze memory tasks, respectively, and reduced the number of pyknotic and degenerated cells, Aβ plaques, and GFAP and Iba-1 immunoreactivity in the hippocampus and cortex of these mice. These findings indicate that TBSA exerts neuroprotective properties by decreasing amyloid plaque burden and neuroinflammation, thereby preventing neuronal death and preserving memory function in the 5xFAD mice.

Differentially Expressed Genes in the Brain of Aging Mice With Cognitive Alteration and Depression- and Anxiety-Like Behaviors

Despite the great increase in human lifespan with improved medical care, the physiological and pathological changes such as memory and cognitive disorders and associated anxiety and depression are major concern with aging. Molecular mechanisms underlying these changes are little known. The present study examined the differentially expressed genes (DEGs) and the genes with differentially expressed isoforms in three brain regions, anterior cingulate cortex (ACC), amygdala and hippocampus, throughout the lifespan of mice. Compared to 2-month old mice, both 12- and 24-month old mice displayed memory and cognitive impairments in the Morris water maze, Y-maze, and novel object recognition tests and depression- and anxiety-like behaviors in the tail suspension, forced swimming, open field, and elevated plus maze tests. RNA sequencing analysis identified 634 and 1078 DEGs in ACC, 453 and 1015 DEGs in the amygdala and 884 and 1054 DEGs in hippocampus in the 12- and 24-month old mice, respectively. Similarly, many genes with differentially expressed isoforms were also identified in these three brain regions in the 12- and 24-month old mice. Further functional analysis revealed that many DEGs and the genes with differentially expressed isoforms in the ACC and amygdala were mapped to depression- and anxiety-related genes, respectively and that a lot of DEGs and the genes with differentially expressed isoforms in hippocampus were mapped to cognitive dysfunction-related genes from both 12- and 24-month old mice. All of these mapped DEGs and the genes with differentially expressed isoforms were closely related to neuroinflammation. Our findings indicate that these neuroinflammation-related DEGs and the genes with differentially expressed isoforms are likely new targets in the management of memory/cognitive impairment and emotional disorders during the aging.

Ellagic Acid Inhibits Neuroinflammation and Cognitive Impairment Induced by Lipopolysaccharides

Neuroinflammation is a predisposing factor for the development of cognitive impairment and dementia. Among the new molecules that are currently being studied, ellagic acid (EA) has stood out for its neuroprotective properties. The present study investigated the effects of ellagic acid in the object recognition test, oxidative stress, cholinergic neurotransmission, glial cell expression, and phosphorylated Tau protein expression. For this, 32 male Wistar rats received an intraperitoneal (IP) application of lipopolysaccharides (LPS) at a dose of 250 µg/kg or 0.9% saline solution (SAL) for 8 days. Two hours after the IP injections, the animals received 100 mg/kg of EA or SAL via intragastric gavage. Behavioral parameters (open field test and object recognition) were performed on days 5, 6, and 7 of the experimental periods. The results showed that the treatment with EA in the LPS group was able to inhibit cognitive impairment, modulate the immune system response by significantly reducing glial cell expression, attenuating phosphorylated Tau and oxidative damage with consequent improvement in the antioxidant system, as well as preventing the increase of acetylcholinesterase activity. Thus, the neuroprotective effects of EA and its therapeutic potential in cognitive disorders secondary to neuroinflammation were demonstrated.

Social Isolation Stress in Adolescence, but not Adulthood, Produces Hypersocial Behavior in Adult Male and Female C57BL/6J Mice

Chronic stress during the developmental period of adolescence increases susceptibility to many neuropsychiatric diseases in adulthood, including anxiety, affective, and alcohol/substance use disorders. Preclinical rodent models of adolescent stress have produced varying results that are species, strain, sex, and laboratory-dependent. However, adolescent social isolation is a potent stressor in humans that has been reliably modeled in male rats, increasing adult anxiety-like and alcohol drinking behaviors, among others. In this study, we examined the generalizability and sex-dependence of this model in C57BL/6J mice, the most commonly used rodent strain in neuroscience research. We also performed a parallel study using social isolation in adulthood to understand the impact of adult social isolation on basal behavioral phenotypes. We found that 6 weeks of social isolation with minimal handling in adolescence through early adulthood [postnatal day (PD) 28-70] produced a hypersocial phenotype in both male and female mice and an anxiolytic phenotype in the elevated plus-maze in female mice. However, it had no effects in other assays for avoidance behavior or on fear conditioning, alcohol drinking, reward or aversion sensitivity, or novel object exploration in either sex. In contrast, 6 weeks of social isolation in adulthood beginning at PD77 produced an anxiogenic phenotype in the light/dark box but had no effects on any other assays. Altogether, our results suggest that: (1) adolescence is a critical period for social stress in C57BL/6J mice, producing aberrant social behavior in a sex-independent manner; and (2) chronic individual housing in adulthood does not alter basal behavioral phenotypes that may confound interpretation of behavior following other laboratory manipulations.

The potential role of pomegranate and its nano-formulations on cerebral neurons in aluminum chloride induced Alzheimer rat model

The oxidative stress leading to degenerative changes in the brain of Alzheimer's disease (AD) is evident. Our aim was to evaluate the therapeutic and protective effects of pomegranate extract (PE) and pomegranate extract-loaded nanoparticles (PE nano) in an AlCl 3-induced AD rat model. Nanoparticles were synthesized with a PE load of 0.68% w/w, and 70 male Wistar rats were divided into 7 groups: Group I was the control, Group II received PE., Group III received PE nano for 2 weeks, Group IV received AlCl 3 (50 mg/kg) daily orally for 4 weeks, Group V received PE for 2 weeks, Group VI received PE nano for 2 weeks, and Groups V and VI were started after AlCl 3 administration was stopped. Group VII received PE for 2 weeks and was stopped before AlCl 3 was administered. The Results revealed that the discrimination index in the novel object recognition test was the least in AD rat model but increased in cases protected with PE treated with PE nano. Similar results were shown based on calculating the brain weight/body weight percent. The biomarkers of antioxidant activity (catalase, glutathione and total antioxidant activity) in brain homogenate were significantly increased in groups treated with either PE or PE nano. The thiobarbituric acid reactive substance measured to estimate lipid peroxidation was significantly increased in AD rat model and decreased in groups protected with PE or treated with PE nano. Histopathological studies using hematoxylin and eosin, cresyl violet, and silver stains revealed hyaline degeneration, chromatolysis, and hallmarks of AD; neurofibrillary tangles and the senile plaques in brains of AD rat model. Restoration of the histological architecture, Nissl granules, and minimal appearance of hallmarks of AD characterized brains treated with PE or PE nano. In conclusion, PE was more effective as a protectant than a therapeutic measure in alleviating the antioxidant, lipid peroxidative effects and histopathological hallmarks in AD brains. But, the therapeutic PE-loaded nanoparticles increased the efficacy of active components and produced similar results as the protective PE.

Ketamine contributes to the alteration of Ca2+ transient evoked by behavioral tests in the prelimbic area of mPFC: A study on chronic CORT-induced depressive mice

Recent studies have showed that ketamine is a rapid and efficient antidepressant, but the mechanism of its antidepressant effect is not fully clear. It is still lack of the research investigating the relation between depressive-like behaviors and neuronal activities in specific brain area after administration of ketamine in vivo. Medial prefrontal cortex (mPFC) involved in the pathogenesis of depression. As a result of effective assessments after behavioral test, most studies lack of direct evidence of the relation between efficacy and the activity of specific brain area. Therefore, we used fiber photometry to explore the alteration of Ca²⁺ transient in the prelimbic (PrL) area of mPFC during behavioral tests in freely moving mice. Our results showed that the chronic corticosterone (CORT) protocol induced depressive-like behaviors. Administration of ketamine reversed these effects. The activation of Ca²⁺ transients was associated with some behaviors during behavioral tests. Struggling, rearing and exploring evoked strong Ca²⁺ transients, but moving and grooming did not. The Ca²⁺ transients amplitude reductions of struggling, rearing and exploring induced by CORT were reversed by ketamine. The results indicated that ketamine ameliorated depressive-like behaviors via mediating neural activation in PrL.

Efficacy of THN201, a Combination of Donepezil and Mefloquine, to Reverse Neurocognitive Deficits in Alzheimer's Disease

Donepezil (DPZ) is an acetylcholinesterase inhibitor used in Alzheimer’s disease to restore cognitive functions but is endowed with limited efficacy. Recent studies pointed out the implication of astroglial networks in cognitive processes, notably via astrocyte connexins (Cxs), proteins involved in gap junction intercellular communications. Hence, we investigated the impact on cognition of pharmacological or genetic modulations of those astrocyte Cxs during DPZ challenge in two rodent models of Alzheimer’s disease–like memory deficits. We demonstrated that the Cx modulator mefloquine (MEF) significantly enhanced the procognitive effect of DPZ in both models. In parallel, we determined that MEF potentiated DPZ-induced release of acetylcholine in hippocampus. Finally, local genetic silencing of astrocyte Cxs in the hippocampus was also found to enhance the procognitive effect of DPZ, pointing out the importance of Cx-dependent astrocyte networks in memory processes.

A Proline Derivative-Enriched Fraction from Sideroxylon obtusifolium Protects the Hippocampus from Intracerebroventricular Pilocarpine-Induced Injury Associated with Status Epilepticus in Mice

The N-methyl-(2S,4R)-trans-4-hydroxy-l-proline-enriched fraction (NMP) from Sideroxylon obtusifolium was evaluated as a neuroprotective agent in the intracerebroventricular (icv) pilocarpine (Pilo) model. To this aim, male mice were subdivided into sham (SO, vehicle), Pilo (300 µg/1 µL icv, followed by the vehicle per os, po) and NMP-treated groups (Pilo 300 µg/1 µL icv, followed by 100 or 200 mg/kg po). The treatments started one day after the Pilo injection and continued for 15 days. The effects of NMP were assessed by characterizing the preservation of cognitive function in both the Y-maze and object recognition tests. The hippocampal cell viability was evaluated by Nissl staining. Additional markers of damage were studied-the glial fibrillary acidic protein (GFAP) and the ionized calcium-binding adaptor molecule 1 (Iba-1) expression using, respectively, immunofluorescence and western blot analyses. We also performed molecular docking experiments revealing that NMP binds to the γ-aminobutyric acid (GABA) transporter 1 (GAT1). GAT1 expression in the hippocampus was also characterized. Pilo induced cognitive deficits, cell damage, increased GFAP, Iba-1, and GAT1 expression in the hippocampus. These alterations were prevented, especially by the higher NMP dose. These data highlight NMP as a promising candidate for the protection of the hippocampus, as shown by the icv Pilo model.

Aging with Toxoplasma gondii results in pathogen clearance, resolution of inflammation, and minimal consequences to learning and memory

Persistent inflammation has been identified as a contributor to aging-related neurodegenerative disorders such as Alzheimer's disease. Normal aging, in the absence of dementia, also results in gradual cognitive decline and is thought to arise, in part, because of a chronic pro-inflammatory state in the brain. Toxoplasma gondii is an obligate intracellular parasite that establishes a persistent, asymptomatic infection of the central nervous system (CNS) accompanied by a pro-inflammatory immune response in many of its hosts, including humans and rodents. Several studies have suggested that the inflammation generated by certain strains of T. gondii infection can be neuroprotective in the context of a secondary insult like beta-amyloid accumulation or stroke. Given these neuroprotective studies, we hypothesized that a prolonged infection with T. gondii may protect against age-associated decline in cognition. To test this hypothesis, we infected young adult mice with either of two genetically distinct, persistent T. gondii strains (Prugniaud/type II/haplogroup 2 and CEP/type III/haplogroup 3) and monitored mouse weight, survival, and learning and memory over the ensuing 20 months. At the end of the study, we evaluated CNS inflammation and parasite burden in the surviving mice. We found that parasite infection had no impact on age-associated decline in learning and memory and that by 20 months post infection, in the surviving mice, we found no evidence of parasite DNA, cysts, or inflammation in the CNS. In addition, we found that mice infected with type III parasites, which are supposed to be less virulent than the type II parasites, had a lower rate of long-term survival. Collectively, these data indicate that T. gondii may not cause a life-long CNS infection. Rather, parasites are likely slowly cleared from the CNS and infection and parasite clearance neither positively nor negatively impacts learning and memory in aging.

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.

Binge-Like, Naloxone-Sensitive, Voluntary Ethanol Intake at Adolescence Is Greater Than at Adulthood, but Does Not Exacerbate Subsequent Two-Bottle Choice Drinking

The present study assessed the effects of ethanol exposure during adolescence or adulthood. We exposed Wistar rats, males or females, to self-administered 8–10% (v/v) ethanol (BINGE group) during the first 2 h of the dark cycle, three times a week (Monday, Wednesday, and Friday) during postnatal days (PDs) 32–54 or 72–94 (adolescent and adults, respectively). During this period, controls were only handled, and a third (IP) condition was given ethanol intraperitoneal administrations, three times a week (Monday, Wednesday, and Friday), at doses that matched those self-administered by the BINGE group. The rats were tested for ethanol intake and preference in a two-bottle (24 h long) choice test, shortly before (PD 30 or 70) and shortly after (PD 56 or 96) exposure to the binge or intraperitoneal protocol; and then tested for free-choice drinking during late adulthood (PDs 120–139) in intermittent two-bottle intake tests. Binge drinking was significantly greater in adolescents vs. adults, and was blocked by naloxone (5.0 mg/kg) administered immediately before the binge session. Mean blood ethanol levels (mg/dl) at termination of binge session 3 were 60.82 ± 22.39. Ethanol exposure at adolescence, but not at adulthood, significantly reduced exploration of an open field-like chamber and significantly increased shelter-seeking behavior in the multivariate concentric square field. The rats that had been initially exposed to ethanol at adolescence drank, during the intake tests conducted at adulthood, significantly more than those that had their first experience with ethanol at adulthood, an effect that was similar among BINGE, IP and control groups. The study indicates that binge ethanol drinking is greater in adolescent that in adults and is associated with heightened ethanol intake at adulthood. Preventing alcohol access to adolescents should reduce the likelihood of problematic alcohol use or alcohol-related consequences.

Neuroinflammatory and Behavioral Outcomes Measured in Adult Offspring of Mice Exposed Prenatally to E-Cigarette Aerosols

BACKGROUND

In an effort to decrease the rates of smoking conventional tobacco cigarettes, electronic cigarettes (e-cigarettes) have been proposed as an effective smoking cessation tool. However, little is known about their toxicological impacts. This is concerning given that e-cigarette use is perceived as less harmful than conventional tobacco cigarettes during pregnancy for both the mother and fetus.

OBJECTIVE

The goal of this study was to test the neurodevelopmental consequences of maternal e-cigarette use on adult offspring behavior and neuroimmune outcomes.

METHODS

Pregnant female CD-1 mice were randomly assigned to one of three treatment groups (n=8-10 per group) and exposed daily to either filtered air, propylene glycol and vegetable glycerol (50:50 PG/VG vehicle), or to PG/VG with 16mg/mL nicotine (+Nic). Whole-body exposures were carried out for 3 h/d, 7 d/week, from gestational day (GD)0.5 until GD17.5. Adult male and female offspring (8 weeks old) were assessed across a battery of behavioral assessments followed by region-specific quantification of brain cytokines using multiplex immunoassays.

RESULTS

Adult offspring of both sexes exposed to +Nic exhibited elevated locomotor activity in the elevated plus maze and altered stress-coping strategies in the forced swim task. Moreover, male and female offspring exposed to PG/VG with and without nicotine had a 5.2% lower object discrimination score in the novel object recognition task. In addition to differences in offspring behavior, maternal e-cigarette exposure with nicotine led to a reduction in interleukin (IL)-4 and interferon-gamma (IFNγ) in the diencephalon, as well as lower levels of hippocampal IFNγ (females only). E-cigarette exposure without nicotine resulted in a 2-fold increase of IL-6 in the cerebellum.

DISCUSSION

These findings support previous adverse findings of e-cigarette exposure on neurodevelopment in a mouse model and provide substantial evidence of persistent adverse behavioral and neuroimmunological consequences to adult offspring following maternal e-cigarette exposure during pregnancy. https://doi.org/10.1289/EHP6067.

Maternal alcoholism and neonatal hypoxia-ischemia: Neuroprotection by stilbenoid polyphenols

The impact of maternal nutrition on neurodevelopment and neonatal neuroprotection is a research topic with increasing interest. Maternal diet can also have deleterious effects on fetal brain development. Fetal exposure to alcohol is responsible for poor neonatal global development, and may increase brain vulnerability to hypoxic-ischemic encephalopathy, one of the major causes of acute mortality and chronic neurological disability in newborns. Despite frequent prevention campaigns, about 10% of women in the general population drinks alcohol during pregnancy and breastfeeding. This study was inspired by this alarming fact. Its aim was to evaluate the beneficial effects of maternal supplementation with two polyphenols during pregnancy and breastfeeding, on hypoxic-ischemic neonate rat brain damages, sensorimotor and cognitive impairments, in a context of moderate maternal alcoholism. Both stilbenoid polyphenols, trans-resveratrol (RSV - 0.15 mg/kg/day), and its hydroxylated analog, trans-piceatannol (PIC - 0.15 mg/kg/day), were administered in the drinking water, containing or not alcohol (0.5 g/kg/day). In a 7-day post-natal rat model of hypoxia-ischemia (HI), our data showed that moderate maternal alcoholism does not increase brain lesion volumes measured by MRI but leads to higher motor impairments. RSV supplementation could not reverse the deleterious effects of HI coupled with maternal alcoholism. However, PIC supplementation led to a recovery of all sensorimotor and cognitive functions. This neuroprotection was obtained with a dose of PIC corresponding to the consumption of a single passion fruit per day for a pregnant woman.

Vaccines targeting the primary amino acid sequence and conformational epitope of amyloid-β had distinct effects on neuropathology and cognitive deficits in EAE/AD mice

BACKGROUND AND PURPOSE

Immunotherapeutic intervention is one of the most promising strategies for the prevention and treatment of Alzheimer's disease (AD). Although they showed great success in AD mouse models, the clinical trials of many immune approaches failed due to low efficacy and safety. Thus, an animal model which can show the potential side effects of vaccines or antibodies is urgently needed. In this study, we generated EAE/AD mice by crossing APP/PS1 mice with experimental autoimmune encephalomyelitis (EAE) mice. We then investigated the efficacy and safety of two vaccines: the immunogens of which were Aβ1-42 aggregates (Aβ42 vaccine) and an oligomer-specific conformational epitope (AOE1 vaccine), respectively.

EXPERIMENTAL APPROACH

EAE/AD mice were immunized with the Aβ42 vaccine or AOE1 vaccine five times at biweekly intervals. After the final immunization, cognitive function was evaluated by the Morris water maze, Y maze, and object recognition tests. Neuropathological changes in the mouse brains were analysed by immunohistochemistry and ELISA.

KEY RESULTS

In contrast to previous findings in conventional AD animal models, Aβ42 immunization promoted neuroinflammation, enhanced Aβ levels and plaque burden, and failed to restore cognitive deficits in EAE/AD mice. By contrast, AOE1 immunization dramatically attenuated neuroinflammation, reduced Aβ levels, and improved cognitive performance in EAE/AD mice.

CONCLUSION AND IMPLICATIONS

These results suggest that the EAE/AD mouse model can exhibit the potential side effects of AD immune approaches that conventional AD animal models fail to display. Furthermore, strategies specifically targeting Aβ oligomers may be safe and show clinical benefit for AD treatment.

Effect of Metformin on Doxorubicin-Induced Memory Dysfunction

Doxorubicin (DOX) is widely used to treat many types of cancer; however, it is associated with chemotherapy-related complications such as cognitive dysfunction, known as chemobrain. Chemobrain affects up to 75% of cancer survivors, and there are currently no available therapeutic options. This study aims to examine whether metformin (MET) can protect against the neurotoxicity caused by DOX treatment. Forty male rats were divided into four groups (10 rats/group): control, DOX, DOX + MET, and MET. Rats treated with DOX received five doses of 4 mg/kg DOX weekly (cumulative dose: 20 mg/kg). For the DOX-MET and MET groups, MET (3 mg/mL) was dissolved in drinking water. Behavioral and glucose tests were performed one day after treatment was completed. We found DOX (4 mg/kg/week, 5 weeks) caused learning and memory impairment in the Y-maze, novel object recognition, and elevated plus maze behavioral tests. MET did not rescue these DOX-induced memory impairments. Neither DOX nor MET nor MET + DOX altered glucose levels following the treatment. In summary, DOX treatment is associated with memory impairment in rats, but MET does not rescue this cognitive dysfunction.

Direct activation of G-protein-gated inward rectifying K+ channels promotes nonrapid eye movement sleep

STUDY OBJECTIVES

A major challenge in treating insomnia is to find effective medicines with fewer side effects. Activation of G-protein-gated inward rectifying K+ channels (GIRKs) by GABAB agonists baclofen or γ-hydroxybutyric acid (GHB) promotes nonrapid eye movement (NREM) sleep and consolidates sleep. However, baclofen has poor brain penetration, GHB possesses abuse liability, and in rodents both drugs cause spike-wave discharges (SWDs), an absence seizure activity. We tested the hypothesis that direct GIRK activation promotes sleep without inducing SWD using ML297, a potent and selective GIRK activator.

METHODS

Whole-cell patch-clamp recordings from hypocretin/orexin or hippocampal neurons in mouse brain slices were made to study neuronal excitability and synaptic activity; spontaneous activity, locomotion, contextual and tone-conditioned memory, and novel object recognition were assessed. Electroencephalogram/electromyogram (EEG/EMG) recordings were used to study GIRK modulation of sleep.

RESULTS

ML297, like baclofen, caused membrane hyperpolarization, decreased input resistance, and blockade of spontaneous action potentials. Unlike baclofen, ML297 (5-10 µM) did not cause significant depression of postsynaptic excitatory and inhibitory currents (EPSCs-IPSCs), indicating preferential postsynaptic inhibition. ML297 (30 mg/kg, i.p.) inhibited wake activity and locomotion, and preferentially increased NREM sleep without altering EEG delta power, REM sleep, inducing SWDs, or impairing conditioned memory and novel object recognition.

CONCLUSIONS

This study finds that direct activation of neuronal GIRK channels modulates postsynaptic membrane excitability and prolongs NREM sleep without changing sleep intensity, inducing SWDs, or impairing memory in rodents. These results suggest that direct GIRK activation with a selective compound may present an innovative approach for the treatment of chronic insomnia.

Huperzine A ameliorates obesity-related cognitive performance impairments involving neuronal insulin signaling pathway in mice

Type 2 diabetes (T2D) and Alzheimer's disease (AD) share several common pathophysiological features. Huperzine A (Hup A), a Lycopodium alkaloid extracted from the Chinese herb moss Huperzia serrata, is a specific and reversible inhibitor of acetylcholinesterase, which is clinically used for the treatment of AD. In this study, we investigated whether Hup A improved the metabolic and cognitive functions in the high fat-induced (HFD) obese mice and genetic ob/ob mice. HFD and ob/ob mice were treated with Hup A (0.1, 0.3 mg · kg-1 · d-1, ig) for 3 months. Body weight was monitored and glucose tolerance tests were performed. Novel object recognition test and Morris water maze assay were conducted to evaluate the cognitive functions. We found that the Hup A treatment had no significant effect on peripheral metabolism of obese mice, whereas Hup A (0.1, mg · kg-1 · d-1) improved both the abilities of object recognition and spatial memory in HFD-fed mice, but not in ob/ob mice. Furthermore, Hup A treatment significantly upregulated the insulin and phosphorylated Akt levels in the cortex of HFD-fed mice, but not ob/ob mice. In addition, Hup A (0.3, mg · kg-1 · d-1) significantly decreased cortical β-secretase (BACE1) expression. In conclusion, these results demonstrate that treatment with Hup A (0.1, mg · kg-1 · d-1) can effectively improve the cognitive functions, at least in diet-induced obese mice.

Bile duct ligation of C57BL/6 mice as a model of hepatic encephalopathy

Background

Bile duct ligation (BDL) has been used for experimental research on hepatic encephalopathy (HE) caused by chronic liver disease. However, little research has been done on a BDL model in C57BL/6 mouse. Therefore, we evaluated the suitability of a BDL model in C57BL/6 mouse for the study of HE and determined which behavioral tests are appropriate for the identification of HE in this model.

Methods

Twelve to fourteen-week-old male C57BL/6 mice were randomly assigned to either sham group or BDL group. Histological changes in liver were confirmed by hematoxylin/eosin and Masson’s trichrome staining. Liver function alterations were detected by alanine aminotransferase (ALT) and ammonia levels. To identify behavioral changes, open field, elevated plus maze, novel object recognition, and passive avoidance tests were performed.

Results

Inflammatory liver injury and fibrosis were observed 14 days after BDL. ALT and ammonia levels were significantly higher in BDL group than in sham group. There were no differences in general locomotor activity or anxiety between the groups. No difference was observed between these two groups in the novel object recognition test, but BDL group showed significant learning/memory impairment in the passive avoidance test compared to sham group.

Conclusions

Fourteen days of BDL in 12–14-week-old male C57BL/6 mice is a clinically relevant model for HE, as these mice have liver fibrosis with impaired liver function, hyperammonemia, and learning/memory impairment. Passive avoidance can be used as the major behavioral test in this model of HE.

Effect of morphine exposure on novel object memory of the offspring: The role of histone H3 and ΔFosB

It has been demonstrated that alteration in histone acetylation in the regions of the brain involved in the reward which may have an important role in morphine addiction. It is well established that epigenetic changes prior to birth influence the function and development of the brain. The current study was designed to evaluate changes in novel object memory, histone acetylation and ΔFosB in the brain of the offspring of morphine-withdrawn parents. Male and female Wistar rats received morphine orally for 21 following days. After ten days of abstinent, they were prepared for mating. The male offspring of the first parturition were euthanized on postnatal days 5, 21, 30 and 60. The novel object recognition (NOR) test was performed on adult male offspring. The amount of acetylated histone H3 and ΔFosB were evaluated in the prefrontal cortex (PFC) and hippocampus using western blotting. Obtained results indicated that the discrimination index in the NOR test was decreased in the offspring of morphine-withdrawn parents as compared with morphine-naïve offspring. In addition, the level of acetylated histone H3 was decreased in the PFC and hippocampus in the offspring of morphine-withdrawn parents during lifetime (postnatal days 5, 21, 30 and 60). In the case of ΔFosB, it also decreased in these regions in the morphine-withdrawn offspring. These results demonstrated that parental morphine exposure affects NOR memory, and decreased the level of histone H3 acetylation and ΔFosB in the PFC and hippocampus. Taken together, the effect of morphine might be transmitted to the next generation even after stop consuming morphine.

(−)-Epicatechin mitigates high fat diet-induced neuroinflammation and altered behavior in mice

(−)-Epicatechin improves memory in high fat diet-induced obese mice in association with prevention of endotoxemia and mitigation of neuroinflammation.

Tau inhibits PKA by nuclear proteasome-dependent PKAR2α elevation with suppressed CREB/GluA1 phosphorylation

Intraneuronal accumulation of wild-type tau plays a key role in Alzheimer's disease, while the mechanisms underlying tauopathy and memory impairment remain unclear. Here, we report that overexpressing full-length wild-type human tau (hTau) in mouse hippocampus induces learning and memory deficits with remarkably reduced levels of multiple synapse- and memory-associated proteins. Overexpressing hTau inhibits the activity of protein kinase A (PKA) and decreases the phosphorylation level of cAMP-response element binding protein (CREB), GluA1, and TrkB with reduced BDNF mRNA and protein levels both in vitro and in vivo. Simultaneously, overexpressing hTau increased PKAR2α (an inhibitory subunit of PKA) in nuclear fraction and inactivated proteasome activity. With an increased association of PKAR2α with PA28γ (a nuclear proteasome activator), the formation of PA28γ-20S proteasome complex remarkably decreased in the nuclear fraction, followed by a reduced interaction of PKAR2α with 20S proteasome. Both downregulating PKAR2α by shRNA and upregulating proteasome by expressing PA28γ rescued hTau-induced PKA inhibition and CREB dephosphorylation, and upregulating PKA improved hTau-induced cognitive deficits in mice. Together, these data reveal that intracellular tau accumulation induces synapse and memory impairments by inhibiting PKA/CREB/BDNF/TrkB and PKA/GluA1 signaling, and deficit of PA28γ-20S proteasome complex formation contributes to PKAR2α elevation and PKA inhibition.

Inhibition of acetylcholinesterase activity and β-amyloid oligomer formation by 6-bromotryptamine A, a multi-target anti-Alzheimer's molecule

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by learning and memory impairments. Recent studies have suggested that AD can be induced by multiple factors, such as cholinergic system dysfunction and β-amyloid (Aβ) neurotoxicity. It was reported that 6-bromo-N-propionyltryptamine could treat neurological diseases, including AD. In the present study, 6-bromotryptamine A, a derivative of 6-bromo-N-propionyltryptamine, was synthesized by the condensation of 2-(6-bromo-1H-indol-3-yl)ethan-1-amine and 2-(4-bromophenyl)acetic acid, and was used as a potential anti-AD molecule. Furthermore, scopolamine can induce impairments of learning and memory, and was widely used to establish AD animal models. The results demonstrated that 6-bromotryptamine A significantly prevented scopolamine-induced short-term cognitive impairments, as revealed by various behavioral tests in mice. Furthermore, an acetylcholinesterase (AChE) activity assay revealed that 6-bromotryptamine A directly inhibited AChE activity. Notably, it was observed that 6-bromotryptamine A blocked the formation of Aβ oligomer, as evaluated by the dot blot assay. All these results suggested that 6-bromotryptamine A may be used to prevent impairments in short-term learning and memory ability possibly via the inhibition of AChE and the blockade of Aβ oligomer formation.

Tetramethylpyrazine Reduces Epileptogenesis Progression in Electrical Kindling Models by Modulating Hippocampal Excitatory Neurotransmission

Antiepileptic drugs (AEDs) are the primary agents prescribed for clinical management of limbic epilepsy. However, high incidence of pharmacoresistance and a limited armory of drugs for inhibiting the pathological progression of epilepsy pose major obstacles to managing epilepsy. Here, we investigated the effect of tetramethylpyrazine (TMP), the main bioactive alkaloid isolated from the oriental medicine Ligusticum chuanxiong Hort., against the epileptogenesis progression of acute hippocampal and corneal (6 Hz) electrical kindling models of TLE. TMP dose-dependently limited the progression of seizures and reduced the after-discharge duration (ADDs) in a hippocampal mouse kindling model. Mice treated with TMP (20, 50 mg/kg, i.p.) remained in stage 1 of epileptic progression for a protracted period, requiring additional stimulation to induce stages 2-5 epileptic phenotypes. TMP (50 mg/kg) also inhibited 6 Hz corneal kindling progression. In contrast, TMP did not reverse the phenotypes induced in a generalized seizures (GS) model, or the maximal electroshock (MES) or pentylenetetrazole (PTZ)-induced models of epilepsy. Furthermore, patch clamp recordings revealed no effect of TMP (10 μM) on CA1 hippocampal neurons' intrinsic properties but suppressed the (i) frequency of spontaneous excitatory post synaptic currents (sEPSCs), (ii) paired pulse ratio (PPR), and (iii) long-term potentiation (LTP) induction in the Schaffer collateral-CA1 pathway. TMP suppressed the activity of calcium, but not sodium, channels. Taken together, these results suggest that TMP has an antiepileptogenic effect, likely through suppression of excitatory synaptic transmission by its effects on inhibition of calcium channels; these traits distinguish TMP from currently available AEDs. As mice administered TMP did not show any neurologic impairment in the object recognition and open field tests, the data support further development of TMP as a promising treatment for epilepsy.

CFTR Therapeutics Normalize Cerebral Perfusion Deficits in Mouse Models of Heart Failure and Subarachnoid Hemorrhage

Heart failure (HF) and subarachnoid hemorrhage (SAH) chronically reduce cerebral perfusion, which negatively affects clinical outcome. This work demonstrates a strong relationship between cerebral artery cystic fibrosis transmembrane conductance regulator (CFTR) expression and altered cerebrovascular reactivity in HF and SAH. In HF and SAH, CFTR corrector compounds (C18 or lumacaftor) normalize pathological alterations in cerebral artery CFTR expression, vascular reactivity, and cerebral perfusion, without affecting systemic hemodynamic parameters. This normalization correlates with reduced neuronal injury. Therefore, CFTR therapeutics have emerged as valuable clinical tools to manage cerebrovascular dysfunction, impaired cerebral perfusion, and neuronal injury.

Myelin Deficits Caused by Olig2 Deficiency Lead to Cognitive Dysfunction and Increase Vulnerability to Social Withdrawal in Adult Mice

Oligodendrocyte (OL) and myelin development are crucial for network integration and are associated with higher brain functions. Accumulating evidence has demonstrated structural and functional impairment of OLs and myelin in serious mental illnesses. However, whether these deficits contribute to the brain dysfunction or pathogenesis of such diseases still lacks direct evidence. In this study, we conditionally deleted Olig2 in oligodendroglial lineage cells (Olig2 cKO) and screened the behavioral changes in adult mice. We found that Olig2 ablation impaired myelin development, which further resulted in severe hypomyelination in the anterior cingulate cortex. Strikingly, Olig2 cKO mice exhibited an anxious phenotype, aberrant responses to stress, and cognitive deficits. Moreover, Olig2 cKO mice showed increased vulnerability to social avoidance under the mild stress of social isolation. Together, these results indicate that developmental deficits in OL and myelin lead to cognitive impairment and increase the risk of phenotypes reminiscent of mental illnesses.

Early Celastrol Administration Prevents Ketamine-Induced Psychotic-Like Behavioral Dysfunctions, Oxidative Stress and IL-10 Reduction in The Cerebellum of Adult Mice

Administration of subanesthetic doses of ketamine during brain maturation represents a tool to mimic an early insult to the central nervous system (CNS). The cerebellum is a key player in psychosis pathogenesis, to which oxidative stress also contributes. Here, we investigated the impact of early celastrol administration on behavioral dysfunctions in adult mice that had received ketamine (30 mg/kg i.p.) at postnatal days (PNDs) 7, 9, and 11. Cerebellar levels of 8-hydroxydeoxyguanosine (8-OHdG), NADPH oxidase (NOX) 1 and NOX2, as well as of the calcium-binding protein parvalbumin (PV), were also assessed. Furthermore, celastrol effects on ketamine-induced alterations of proinflammatory (TNF-α, IL-6 and IL-1β) and anti-inflammatory (IL-10) cytokines in this brain region were evaluated. Early celastrol administration prevented ketamine-induced discrimination index decrease at adulthood. The same was found for locomotor activity elevations and increased close following and allogrooming, whereas no beneficial effects on sniffing impairment were detected. Ketamine increased 8-OHdG in the cerebellum of adult mice, which was also prevented by early celastrol injection. Cerebellar NOX1 levels were enhanced at adulthood following postnatal ketamine exposure. Celastrol per se induced NOX1 decrease in the cerebellum. This effect was more significant in animals that were early administered with ketamine. NOX2 levels did not change. Ketamine administration did not affect PV amount in the cerebellum. TNF-α levels were enhanced in ketamine-treated animals; however, this was not prevented by early celastrol administration. While no changes were observed for IL-6 and IL-1β levels, ketamine determined a reduction of cerebellar IL-10 expression, which was prevented by early celastrol treatment. Our results suggest that NOX inhibition during brain maturation prevents the development of psychotic-like behavioral dysfunctions, as well as the increased cerebellar oxidative stress and the reduction of IL-10 in the same brain region following ketamine exposure in postnatal life. This opens novel neuroprotective opportunities against early detrimental insults occurring during brain development.