Investigating navigation strategies in the Morris Water Maze through deep reinforcement learning

Navigation is a complex skill with a long history of research in animals and humans. In this work, we simulate the Morris Water Maze in 2D to train deep reinforcement learning agents. We perform automatic classification of navigation strategies, analyze the distribution of strategies used by artificial agents, and compare them with experimental data to show similar learning dynamics as those seen in humans and rodents. We develop environment-specific auxiliary tasks and examine factors affecting their usefulness. We suggest that the most beneficial tasks are potentially more biologically feasible for real agents to use. Lastly, we explore the development of internal representations in the activations of artificial agent neural networks. These representations resemble place cells and head-direction cells found in mouse brains, and their presence has correlation to the navigation strategies that artificial agents employ.

Investigating the effects of age and prior military service on fluid and crystallized cognitive functions using virtual morris water maze (vMWM) and NIH Toolbox tasks

Much of current knowledge of aging involves war veterans and research about age-related cognitive changes in veterans involves generalized or single function tests or health or neurological disorders. The current study examined military service within the context of comparisons of young and old humans involving generally healthy individuals to address normal age-associated cognitive changes. Adult participants included 11 young females (8 non-veterans; 3 veterans; 21-31 years), 5 young males (non-veterans, 21-24 years), 9 older females (non-veterans, 62-80 years), and 21 older males (11 non-veterans; 10 veterans; 60-86 years). They were tested in virtual Morris water maze (vMWM) tasks, which were designed to test spatial learning, cognitive flexibility and working memory, similar to rodent studies, and were validated by correlations with specific NIH Toolbox (NIH-TB) Cognitive Battery or Wechsler Memory Scale (WMS) Logical Memory I and II tests. Significant age-related deficits were seen on multiple vMWM tasks and NIH-TB fluid cognition tasks. Among older males, vMWM tasks appeared to be more sensitive, based on finding statistical differences, to prior military service than NIH Toolbox tasks. Compared with male non-veterans of comparable age and younger, older male veterans exhibited significant deficits in spatial learning, cognitive flexibility, and working memory on vMWM tasks. Our findings support continued development and characterization of vMWM tasks that are comparable between rodents and humans for translating aging interventions between species, and provide impetus for larger investigations examining the extent to which prior military service can serve as a "hidden" variable in normal biological declines of cognitive functions.

Refinement of the Barnes and Morris water maze protocols improves characterization of spatial cognitive deficits in the lithium-pilocarpine rat model of epilepsy

Temporal lobe epilepsy (TLE) often causes cognitive impairment, especially a decline in spatial memory. Reductions in spatial memory and learning are also common in rodent models of TLE. The Morris water maze and the Barnes maze are the standard methods for evaluating spatial learning and memory in rodents. However, animals with TLE may exhibit agitation, distress, and fail to follow the paradigmatic context of these tests, making the interpretation of experimental data difficult. This study optimized the procedure of the Morris water maze and the Barnes maze to evaluate spatial learning and memory in rats with the lithium-pilocarpine TLE model (LPM rats). It was demonstrated that LPM rats required a mandatory and prolonged habituation stage for both tests. Therefore, the experimental rats performed relatively well on these tests. Nevertheless, LPM rats exhibited a slower learning process compared to the control rats. LPM rats also showed a reduction in spatial memory formation. This was more pronounced in the Barnes maze. Also, LPM rats utilized a sequential strategy for searching in the Barnes maze and were incapable of developing a more efficient spatial search strategy that is common in control animals. The Barnes maze may be a better choice for assessing search strategies, learning deficits, and spatial memory in rats with TLE when choosing between the two tests. This is because of the risk of unexpected seizure occurrence during the Morris water maze tests, and the potential risks for animal welfare.

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

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

In vitro and in vivo evaluations of antioxidative, anti-Alzheimer, antidiabetic and anticancer potentials of hydroponically and soil grown Lactuca sativa

BACKGROUND

Lactuca sativa is an edible plant commonly used by local communities to manage diabetes and stomach problems.

METHODS

This work aimed to investigate the anti-oxidant, anticancer, antidiabetic and Anti-Alzheimer effects of hydroponically (HyL) and soil-grown (SoL) Lactuca sativa. Streptozotocin-induced diabetes and AlCl3-induced Alzheimer's disease model was used to evaluate the medicinal effects of Lactuca sativa.

RESULTS

HyL showed significant activity in lipid peroxidation assay, DPPH and DNA protection assay, while SoL extract showed moderated activity, respectively. A similar activity response was quantified for α-glucosidase, α-amylase, acetylcholinesterase and butyrylcholinesterase inhibition assays. The cytotoxic potential of HyL and SoL extracts against MCF7, and HePG2 cancer cell lines exhibited significant activity. HyL and SoL showed a substantial decrease in blood glucose levels in streptozotocin-induced diabetic rats. Diabetes-related liver/kidney biomarkers and anti-oxidant enzyme trends moved toward normal after HyL and SoL treatment. In Anti-Alzheimer's based Morris water and elevated plus maze tests, HyL and SoL displayed memory-enhancing response and anti-anxiety behaviour, respectively. HPLC quantification of dopamine and serotonin revealed a moderate but significant (p<0.05) increase in the level of these neurotransmitters in HyL and SoL groups.

CONCLUSION

Overall, the study revealed that hydroponic Lactuca sativa possesses the therapeutic potential to treat diseases like Alzheimer's and diabetes.

Effects of perampanel on cognitive behavior and GluR1 expression in immature mice of temporal lobe epilepsy

Temporal lobe epilepsy (TLE) has a low antiepileptic drug (AED) treatment response rate, and about 70% of patients eventually progress to refractory epilepsy. Perampanel (PER) is a noncompetitive α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor antagonist, which is used clinically for the treatment of partially refractory epilepsy, but its mechanism of action is not completely clear. In this study, kainic acid (KA) was successfully used to induce TLE in 3-week-old C57BL/6 immature mice, and the effects of PER on the cognitive behavior of the epileptic mice were characterized using the Morris water maze paradigm. To determine the mechanism underlying the therapeutic effects of PER, the morphological evolution of the hippocampus and the expression of AP-1 and GluR1 were systematically evaluated. Compared to control TLE mice, escape latency was reduced and the number of target platform crossings was increased in the Morris water maze by treatment with PER. The therapeutic effects of PER were mediated mainly via inhibition of the expression of AP-1 and GluR1, as the TLE mice showed significantly improved learning and memory and decreased seizure frequency after treatment with PER.

Influence of diurnal phase on behavioral tests of sensorimotor performance, anxiety, learning and memory in mice

Behavioral measurements in mice are critical tools used to evaluate the effects of interventions. Whilst mice are nocturnal animals, many studies conduct behavioral tests during the day. To better understand the effects of diurnal rhythm on mouse behaviors, we compared the results from behavioral tests conducted in the active and inactive phases. C57BL/6 mice were used in this study; we focus on sensorimotor performance, anxiety, learning and memory. Overall, our results show mice exhibit slightly higher cutaneous sensitivity, better long-term contextual memory, and a greater active avoidance escape response during the active phase. We did not observe significant differences in motor coordination, anxiety, or spatial learning and memory. Furthermore, apart from the elevated-O-maze, there was no remarkable sex effect among these tests. This study provides information on the effects of different diurnal phases on types of behavior and demonstrates the importance of the circadian cycle on learning and memory. Although we did not detect differences in anxiety and spatial learning/memory, diurnal rhythm may interact with other factors to influence these behaviors.

Role of RGS2 in sevoflurane-induced cognitive dysfunction in aged rats

After undergoing inhalation anesthesia, some patients, especially elderly patients, experience postoperative cognitive dysfunction, such as personality changes and memory impairment. In the present study, 20-month-old rats were randomly allocated to sevoflurane (Sevo group) and control groups (Con group), and they inhaled 3% sevoflurane or 40% oxygen for 8 hours, respectively. The Morris water maze test found that the cognitive function of rats in the Sevo group were significantly different on 1d and 3d after anesthesia than that of rats in the Con group. The expression of RGS2 mRNA and protein in hippocampus of Sevo group was lower compared to the Con group, while Ca^{2 +} was higher than con group. The expression of CaM and CaMK II in Sevo group was higher compared to the Con group. We found that Bcl-2 reduced, but the expression of Bax and Caspase-3 increased, indicating that apoptosis of hippocampal neurons was increased after sevoflurane inhalation. Both the expression of NGF and BDNF was depressed in the Sevo group. After continuous inhalation of 3% sevoflurane for 8h, the expression of RGS2 in the hippocampi of aged rats is down regulated. RGS2 may be an important factor that leads to cognitive dysfunction in rats.

Excess Folic Acid Supplementation before and during Pregnancy and Lactation Alters Behaviors and Brain Gene Expression in Female Mouse Offspring

Use of folic acid (FA) during early pregnancy protects against birth defects. However, excess FA has shown gender-specific neurodevelopmental toxicity. Previously, we fed the mice with 2.5 times the recommended amount of FA one week prior to mating and during the pregnancy and lactation periods, and detected the activated expression of Fos and related genes in the brains of weaning male offspring, as well as behavioral abnormalities in the adults. Here, we studied whether female offspring were affected by the same dosage of FA. An open field test, three-chamber social approach and social novelty test, an elevated plus-maze, rotarod test and the Morris water maze task were used to evaluate their behaviors. RNA sequencing was performed to identify differentially expressed genes in the brains. Quantitative real time-PCR (qRT-PCR) and Western blots were applied to verify the changes in gene expression. We found increased anxiety and impaired exploratory behavior, motor coordination and spatial memory in FA-exposed females. The brain transcriptome revealed 36 up-regulated and 79 down-regulated genes in their brains at weaning. The increase of Tlr1; Sult1a1; Tph2; Acacb; Etnppl; Angptl4 and Apold1, as well as a decrease of Ppara mRNA were confirmed by qRT-PCR. Among these genes; the mRNA levels of Etnppl; Angptl4andApold1 were increased in the both FA-exposed female and male brains. The elevation of Sult1a1 protein was confirmed by Western blots. Our data suggest that excess FA alteres brain gene expression and behaviors in female offspring, of which certain genes show apparent gender specificity.

Danggui-Shaoyao-San improves cognitive impairment through inhibiting O-GlcNAc-modification of estrogen α receptor in female db/db mice

ETHNOPHARMACOLOGICAL RELEVANCE

The traditional Chinese medicine formula Danggui-Shaoyao-San (DSS) has been reported to show therapeutic effect on dementia.

AIM OF THE STUDY

The present study aims to investigate whether DSS treatment could alleviate diabetes-induced cognitive dysfunction, and explores its neuroprotective mechanism on db/db mice.

MATERIALS AND METHODS

The female db/db mice were randomly divided into model group, DSS low-dose group and DSS high-dose group. Homologous female db/m mice were used as the control group. DSS was intragastric administrated for 15 weeks. Glucose tolerance, insulin tolerance, blood glucose and blood lipid levels were measured. Morris water maze was used to measure spatial learning and memory ability in mice. Nissl staining and Tunel staining were used to measure the changes of brain neurons, and ELISA kits were used to measure levels of inflammatory mediators (PGE2, TXB2 and LTB4). The kits detected oxidative stress (MDA, SOD, CAT, GSH-PX), nitrosative stress (NO, iNOS, TNOS) and glucose metabolism (LDH, PK, HK) levels. Western blot and immunofluorescence detected neurotrophic factors (PSD95, BDNF, NGF and SYN), apoptosis (Bcl-2, Bax, Bcl-xl, Caspase-3) and changes of ERα, O-GlcNAc, OGT, OGA levels.

RESULTS

Morris water maze results showed that DSS could improve the learning and memory abilities of female db/db mice. Nissl staining showed that DSS could relieve hippocampal neurons damage of db/db mice. In addition, the serological tests showed that DSS could improve the impaired glucose tolerance and insulin resistance, while reduce hyperlipemia in db/db mice. Besides, DSS treatment increased the activities of SOD, GSH-PX, and CAT, and reduced MDA, NO, iNOs, tNOS, PGE2, TXB2 and LTB4 levels. Western blot and immunofluorescence results of PSD95, BDNF, NGF, and SYN showed that DSS could improve the expressions of neurotrophic factors. Meanwhile, Tunel staning and Western blot (Bcl-2, Bax, Bcl-xl, Caspase-3) results indicated that DSS could reduce neuronal apoptosis. Finally, Western blot (ERα, O-GlcNAc, OGA, and OGT) and immunofluorescence (ERα and O-GlcNAc) results indicated that DSS could increase the levels of ERα and OGA, decrease the levels of O-GlcNAc and OGT.

CONCLUSION

DSS alleviate DE might be related to improve the abnormal O-GlcNAc-modification of ERα.

The molecular mechanisms of signal pathway activating effect of E2F-1/NF-κB/GSK-3β on cognitive dysfunction of Alzheimer rats

Alzheimer disease (AD) seriously harms human health and its onset is insidious. Therefore, it is of great significance to find out the pathogenesis of AD disease for improving the prevention and treatment effect of the disease. The study drew attention to the influence of E2F-1/NF-κB/GSK-3β signaling pathway on cognitive dysfunction of Alzheimer rats. 60 specific pathogen-free (SPF) SD rats were selected as research subjects. The, the AD model was created by injecting Aβ1-42 into hippocampus CA1 region of AD rats using a microscopic syringe. Besides, Morris water maze test and Western blot were performed to detect the cognitive function, the levels of destination protein and active oxidation products in the brain of rats. Compared to the Sham group, the escape latency and the distance of the model group significantly increased (P < 0.05), and the number of times to pass the target quadrant was significantly reduced (P < 0.05); the expression levels of E2F-1 and NF-κB protein in the hippocampus and the phosphorylation levels of Tau231, Tau262, Tau396, Tau404 and T216-GSK-3β protein of the model group were significantly increased (P < 0.05); the ROS/RNS value in the hippocampus of the model group significantly increased (P < 0.05). AD model rats exhibit obvious cognitive dysfunction, which is associated with the activation of E2F-1/NF-κB/GSK-3β signaling pathway and the heightened Tau protein phosphorylation level.

Melatonin rescues the mice brain against cisplatin-induced neurodegeneration, an insight into antioxidant and anti-inflammatory effects

Herein, we evaluated the neuroprotective effect of melatonin against cisplatin-induced oxidative damage, neuroinflammation, and synaptic dysfunction in mice. Cisplatin was administered at a dose of 2 mg/kg for eleven consecutive days to induce symptoms of cognitive impairment and neurodegeneration, while melatonin was administered at a 20 mg/kg dose for thirty consecutive days. We used various experimental techniques such as western blotting, immunofluorescence analysis, and oxidative stress marker assays to support our notion. Moreover, for cognitive impairment, we conducted behavioral analyses such as Morris Water Maze (MWM) and Y-Maze tests. The results indicated that melatonin attenuated oxidative stress by upregulating the expression of NF-E2-related factor-2 (Nrf2) dependent anti-oxidative protein levels. Similarly, melatonin positively modulated the expression of Sirt1 (a member of the sirtuin family), Phospho-AMPKα (Thr172), peroxisome proliferator-activated receptor (PPARγ), PPAR gamma coactivator 1 alpha (PGC-1α) coupled to downregulation of neuroinflammatory mediators and markers such as nuclear factor kappa-B (NF-κB), tumor necrosis factor-alpha (TNF-α), and interleukin-1 beta (IL-1β). Moreover, melatonin significantly upregulated the expression of synaptic markers such as postsynaptic density protein -95 (PSD-95), synaptosomal-associated protein 23 (SNAP-23), and synaptophysin compared to the cisplatin alone group. Furthermore, the results of behavior tests suggested that melatonin significantly improved the cognitive functions of the cisplatin injected mice.

Structure-activity relationship, in vitro and in vivo evaluation of novel dienyl sulphonyl fluorides as selective BuChE inhibitors for the treatment of Alzheimer's disease

To discover novel scaffolds as leads against dementia, a series of δ-aryl-1,3-dienesulfonyl fluorides with α-halo, α-aryl and α-alkynyl were assayed for ChE inhibitory activity, in which compound A10 was identified as a selective BuChE inhibitor (IC50 = 0.021 μM for eqBChE, 3.62 μM for hBuChE). SAR of BuChE inhibition showed: (i) o- > m- > p-; -OCH3 > -CH3 > -Cl (-Br) for δ-aryl; (ii) α-Br > α-Cl, α-I. Compound A10 exhibited neuroprotective, BBB penetration, mixed competitive inhibitory effect on BuChE (Ki = 29 nM), and benign neural and hepatic safety. Treatment with A10 could almost entirely recover the Aβ1-42-induced cognitive dysfunction to the normal level, and the assessment of total amount of Aβ1-42 confirmed its anti-amyloidogenic profile. Therefore, the potential BuChE inhibitor A10 is a promising effective lead for the treatment of AD.

MicroRNA-155 influences cell damage in ischemic stroke via TLR4/MYD88 signaling pathway

Cerebral ischemic stroke (CIS) is extremely harmful, and its treatment should be underpinned by understanding its pathogenic mechanism. This study was designed to determine the involvement of miR-155 in CIS development via the TLR4/MyD88 signaling pathway. First, we quantified serum miR-155 in patients with CIS and healthy individuals, and found high expression of miR-155 in such patients and a decrease in it in the patients after therapy (P < 0.05). Serum miR-155 demonstrated a favorable function in predicting the development and prognosis of CIS (P < 0.001). We also conducted a mouse assay, and found that knocking out miR-155 can improve the neurological function of mice and suppress protein TLR4 and MyD88 (all P < 0.05). Finally, we carried out a cell assay, and found enhancement in the activity of SH-SY5Y cells, decrease in their apoptosis, and protein TLR4 and MyD88 in them after suppression of miR-155 (all P < 0.05). Furthermore, we also found complete reverse by TLR4/MyD88 pathway inhibitor on the influence of increasing miR-155 on cells (P > 0.05). Therefore, with an increase in cases with CIS, miR-155 takes a part in the development of cell damage by activating TLR4/MyD88, and it is probably the key to diagnosing and treating CIS.

Agomelatine attenuates alcohol craving and withdrawal symptoms by modulating the Notch1 signaling pathway in rats

AIM

Alcohol abuse is a significant causative factor of death worldwide. The Notch1 signaling pathway is involved in alcohol tolerance, withdrawal and dependence. Agomelatine is a known antidepressant acting as a melatonin receptor (MT1/2) agonist and a 5-hydroxytryptamine receptor-2C antagonist. However, its effects on alcohol cravings and alcohol withdrawal symptoms have not been investigated. In this study, we assessed the possibility of using agomelatine for the treatment of these symptoms in a rat model of alcoholism and the possible role of Notch1 signaling.

MAIN METHODS

We induced alcoholism in rats using a free-choice drinking model for 60 days. From day 61, free-choice was continued until day 82 for the craving model, whereas only water was offered in the withdrawal model. Meanwhile, the treated groups for both models received agomelatine (50 mg/kg/day) orally from day 61 to 82, followed by behavioral, histopathological and biochemical assessment.

KEY FINDINGS

Agomelatine treatment caused significant decrease in alcohol consumption with a positive effect on anxiety-like behavior in the open field, memory in the Morris water maze and immobility in the forced swim test. Moreover, agomelatine induced the expression of Notch1 pathway markers, including Notch1, NICD, CREB, CCNE-2, Hes-1, both total and phosphorylated ERK1/2, MMP9, Per2and RGS-2 in the hippocampal formation. By contrast, NMDAR expression was reduced. Furthermore, agomelatine normalized the serum levels of BDNF, cortisol, dopamine and glutamate which were disrupted by alcohol consumption.

SIGNIFICANCE

Based on these findings, agomelatine reversed alcohol cravings and withdrawal symptoms associated with alcohol dependence by modulating the Notch1 signaling pathway.

Folic acid alleviates age-related cognitive decline and inhibits apoptosis of neurocytes in senescence-accelerated mouse prone 8: deoxythymidine triphosphate biosynthesis as a potential mechanism

Disturbed deoxythymidine triphosphate biosynthesis due to the inhibition of thymidylate synthase (TS) can lead to uracil accumulation in DNA, eventually, lead to neurocytes apoptosis and cognitive decline. Folic acid supplementation delayed cognitive decline and neurodegeneration in senescence-accelerated mouse prone 8 (SAMP8). Whether folic acid, one of nutrition factor, the effect on the expression of TS is unknown. The study aimed to determine if folic acid supplementation could alleviate age-related cognitive decline and apoptosis of neurocytes by increasing TS expression in SAMP8 mice. According to folic acid concentration in diet, four-month-old male SAMP8 mice were randomly divided into three different diet groups by baseline body weight in equal numbers. Moreover, to evaluate the role of TS, a TS inhibitor was injected intraperitoneal. Cognitive test, apoptosis rates of neurocytes, expression of TS, relative uracil level in telomere, and telomere length in brain tissue were detected. The results showed that folic acid supplementation decreased deoxyuridine monophosphate accumulation, uracil misincorporation in telomere, alleviated telomere length shorting, increased expression of TS, then decreased apoptosis rates of neurocytes, and alleviated cognitive performance in SAMP8 mice. Moreover, at the same concentration of folic acid, TS inhibitor raltitrexed increased deoxyuridine monophosphate accumulation, uracil misincorporation in telomere, and exacerbated telomere length shorting, decreased expression of TS, then increased apoptosis rates of neurocytes, and decreased cognitive performance in SAMP8 mice. In conclusion, folic acid supplementation alleviated age-related cognitive decline and inhibited apoptosis of neurocytes by increasing TS expression in SAMP8 mice.

Active constituent of Polygala tenuifolia attenuates cognitive deficits by rescuing hippocampal neurogenesis in APP/PS1 transgenic mice

BACKGROUND

Alzheimer's disease (AD) is the most common dementia worldwide, and there is still no satisfactory drug or therapeutic strategy. Polygala tenuifolia is a traditional Chinese medicine with multiple neuroprotective effects. In present study, we investigated the effects of three active constituents [3,6'-disinapoyl sucrose (DISS), onjisaponin B (OB) and tenuifolin (TEN)] of Polygala tenuifolia (PT) on the proliferation and differentiation of neural stem cells (NSCs) to identify the potential active constituent of PT promoting hippocampal neurogenesis.

METHODS

NSCs were isolated from hippocampi of newborn C57BL/6 mice, and transfected with mutant amyloid precursor protein (APP) gene to establish an AD cell model (APP-NSCs). 3-(4,5- Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays were performed, and the proliferation and differentiation of NSCs were assessed by neurosphere formation assay, 5-bromo-2'-deoxyuridine (BrdU) incorporation assay and immunofluorescence (IF) staining analysis. APP/PS1 transgenic mice were administrated with the potential active constituent DISS for 4 weeks. Morris water maze (MWM), Nissl staining assay and IF staining assays were carried out to evaluate the cognitive function, neural damages and hippocampal neurogenesis, respectively.

RESULTS

DISS exerted the optimal ability to strengthen APP-NSCs proliferation and neuronal differentiation, followed by OB and TEN. Furthermore, DISS treatment for 4 weeks strikingly rescued the cognitive deficits, neuronal injures, and neurogenesis disorder in adult APP/PS1 transgenic mice.

CONCLUSIONS

Our findings demonstrated that DISS is the constituent of PT that triggers the most potent increase of hippocampal neurogenesis in our mouse model of AD.

Behavioral and brain morphological analysis of non-inflammatory and inflammatory rat models of preterm brain injury

Investigations using preclinical models of preterm birth have much contributed, together with human neuropathological studies, for advances in our understanding of preterm brain injury. Here, we evaluated whether the neurodevelopmental and behavioral consequences of preterm birth induced by a non-inflammatory model of preterm birth using mifepristone would differ from those after inflammatory prenatal transient hypoxia-ischemia (TSHI) model. Pregnant Wistar rats were either injected with mifepristone, and pups were delivered on embryonic day 21 (ED21 group), or laparotomized on the 18th day of gestation for 60 min of uterine arteries occlusion. Rat pups were tested postnatally for characterization of developmental milestones and, after weaning, they were behaviorally tested for anxiety and for spatial learning and memory. One month later, brains were processed for quantification of doublecortin (DCX)- and neuropeptide Y (NPY)-immunoreactive cells, and cholinergic varicosities in the hippocampus. ED21 rats did not differ from controls with respect to neonatal developmental milestones, anxiety, learning and memory functions, and neurochemical parameters. Conversely, in TSHI rats the development of neonatal reflexes was delayed, the levels of anxiety were reduced, and spatial learning and memory was impaired; in the hippocampus, the total number of DCX and NPY cells was increased, and the density of cholinergic varicosities was reduced. With these results we suggest that a preterm birth, in a non-inflammatory prenatal environment, does not significantly change neonatal development and adult neurologic outcome. On other hand, prenatal hypoxia and ischemia (inflammation) modifies developmental trajectory, learning and memory, neurogenesis, and NPY GABAergic and cholinergic brain systems.

Cannabinoid Receptor 2 Alters Social Memory and Microglial Activity in an Age-Dependent Manner

Physiological brain aging is characterized by gradual, substantial changes in cognitive ability, accompanied by chronic activation of the neural immune system. This form of inflammation, termed inflammaging, in the central nervous system is primarily enacted through microglia, the resident immune cells. The endocannabinoid system, and particularly the cannabinoid receptor 2 (CB2R), is a major regulator of the activity of microglia and is upregulated under inflammatory conditions. Here, we elucidated the role of the CB2R in physiological brain aging. We used CB2R-/- mice of progressive ages in a behavioral test battery to assess social and spatial learning and memory. This was followed by detailed immunohistochemical analysis of microglial activity and morphology, and of the expression of pro-inflammatory cytokines in the hippocampus. CB2R deletion decreased social memory in young mice, but did not affect spatial memory. In fact, old CB2R-/- mice had a slightly improved social memory, whereas in WT mice we detected an age-related cognitive decline. On a cellular level, CB2R deletion increased lipofuscin accumulation in microglia, but not in neurons. CB2R-/- microglia showed an increase of activity markers Iba1 and CD68, and minor upregulation in tnfa and il6 expression and downregulation of ccl2 with age. This was accompanied by a change in morphology as CB2R-/- microglia had smaller somas and lower polarity, with increased branching, cell volume, and tree length. We present that CB2Rs are involved in cognition and age-induced microglial activity, but may also be important for microglial activation itself.

Mizagliflozin, a selective SGLT1 inhibitor, improves vascular cognitive impairment in a mouse model of small vessel disease

Previously, we showed that sodium/glucose cotransporter 1 (SGLT1) participates in vascular cognitive impairment in small vessel disease. We hypothesized that SGLT1 inhibitors can improve the small vessel disease induced-vascular cognitive impairment. We examined the effects of mizagliflozin, a selective SGLT1 inhibitor, and phlorizin, a non-selective SGLT inhibitor, on vascular cognitive impairment in a mouse model of small vessel disease. Small vessel disease was created using a mouse model of asymmetric common carotid artery surgery (ACAS). Two and/or 4 weeks after ACAS, all experiments were performed. Cerebral blood flow (CBF) was decreased in ACAS compared with sham-operated mice. Phlorizin but not mizagliflozin reversed the decreased CBF of ACAS mice. Both mizagliflozin and phlorizin reversed the ACAS-induced decrease in the latency to fall in a wire hang test of ACAS mice. Moreover, they reversed the ACAS-induced longer escape latencies in the Morris water maze test of ACAS mice. ACAS increased SGLT1 and proinflammatory cytokine gene expressions in mouse brains and phlorizin but not mizagliflozin normalized all gene expressions in ACAS mice. Hematoxylin/eosin staining demonstrated that they inhibited pyknotic cell death in the ACAS mouse hippocampus. In PC12HS cells, IL-1β increased SGLT1 expression and decreased survival rates of cells. Both mizagliflozin and phlorizin increased the survival rates of IL-1β-treated PC12HS cells. These results suggest that mizagliflozin and phlorizin can improve vascular cognitive impairment through the inhibition of neural SGLT1 and phlorizin also does so through the improvement of CBF in a mouse model of small vessel disease.

Resveratrol Attenuates Learning, Memory, and Social Interaction Impairments in Rats Exposed to Arsenic

Arsenic (As) toxicity has deleterious effects on human health causing disorder in the brain. The aim of this study was to investigate the possible neuroprotective effect of resveratrol (RSV) on arsenic-induced neurotoxicity in rats. Neurotoxicity in rats was developed by treating As 10 mg/kg/day for 21 days orally. Animals were put into seven groups: control, vehicle, As, As+RSV10, As+RSV20 mg/kg, RSV10, and RSV20 mg/kg. Behavioral assessments such as the social interaction test, novel object recognition test, elevated plus maze, open field, the Morris water maze, in addition to assessment of biomarkers such as ferric reducing ability of plasma assay, glutathione assay, and malondialdehyde assay, were used to evaluate the effects of RSV on cognitive impairment and molecular changes induced by As. The results showed that cognitive performance impaired in As rats. RSV20 mg/kg significantly could ameliorate behavioral changes like spatial learning in days 3 and 4 (p < 0.05), recognition learning and memory (p < 0.01), disabilities in motor coordination and stress (p < 0.05), increased anxiety (p < 0.05), and social interaction deficit (sociability (p < 0.001) and social memory (p < 0.05)). RSV20 mg/kg also attenuated molecular modifications like decreased antioxidant power (p < 0.001), reduced glutathione content (p < 0.05), and increased malondialdehyde level (p < 0.05) induced by As. In addition to oxidative stress assessments, RSV10 mg/kg could significantly increase FRAP (p < 0.01) and GSH (p < 0.05); however, MDA was not significantly increased. Our current behavioral findings suggest that RSV has neuroprotective effects against AS toxicity.

Dihydroergotamine affects spatial behavior and neurotransmission in the central nervous system of Wistar rats

INTRODUCTION

Dihydroergotamine (DHE) is a derivative of an ergot alkaloid used as an antimigraine medication. Nowadays, ergot alkaloids may still endanger the safety of humans and animals as food or medicine pollutants, but the outcomes of long-term DHE administration on the behaviour and neurotransmission remain undescribed.

MATERIAL AND METHODS

Adult male Wistar Albino Glaxo rats pre-treated orally with DHE for six weeks were investigated to assess the relationship between concentration of neurotransmitters and behavioural response. The behavioural effects of the drug administered at doses of either 30 µg/kg b.w. (group DHE30, n = 11) or 100 µg/kg b.w. per day (group DHE100, n = 10) were evaluated in the Morris Water Maze. It is known that monoaminergic neurotransmitters (serotonin, noradrenaline and dopamine) in some brain structures (prefrontal cortex, hippocampus, striatum, cerebellum, spinal cord) play a role in the control of cognitive and motor functions. The concentration of neurotransmitters was determined by High Performance Liquid Chromatography (HPLC).

RESULTS

Administration of DHE influenced neither the learning processes nor memory in rats. Nevertheless, an increased motor activity of the DHE-administered animals was observed in both the cued and non-cued behavioural tasks. In HPLC examination, changes in the concentration of monoaminergic neurotransmitters and their metabolites were noted in all tested structures, except for the hippocampus.

CONCLUSIONS

DHE is able to modulate noradrenergic, serotonergic and dopaminergic neurotransmission that may support the increase in locomotion.

The Golgi-Associated PDZ Domain Protein Gopc/PIST Is Required for Synaptic Targeting of mGluR5

In neuronal cells, many membrane receptors interact via their intracellular, C-terminal tails with PSD-95/discs large/ZO-1 (PDZ) domain proteins. Some PDZ proteins act as scaffold proteins. In addition, there are a few PDZ proteins such as Gopc which bind to receptors during intracellular transport. Gopc is localized at the trans-Golgi network (TGN) and binds to a variety of receptors, many of which are eventually targeted to postsynaptic sites. We have analyzed the role of Gopc by knockdown in primary cultured neurons and by generating a conditional Gopc knockout (KO) mouse line. In neurons, targeting of neuroligin 1 (Nlgn1) and metabotropic glutamate receptor 5 (mGlu5) to the plasma membrane was impaired upon depletion of Gopc, whereas NMDA receptors were not affected. In the hippocampus and cortex of Gopc KO animals, expression levels of Gopc-associated receptors were not altered, while their subcellular localization was disturbed. The targeting of mGlu5 to the postsynaptic density was reduced, coinciding with alterations in mGluR-dependent synaptic plasticity and deficiencies in a contextual fear conditioning paradigm. Our data imply Gopc in the correct subcellular sorting of its associated mGlu5 receptor in vivo.

Endogenous ω-3 fatty acids in Fat-1 mice attenuated depression-like behaviors, spatial memory impairment and relevant changes induced by olfactory bulbectomy

OBJECTIVES

Olfactory bulbectomy (OB) induced behaviors, hypercortisolism, inflammation and neurotrophin dysfunctions are similar to those observed in depressed patients. Omega (n)-3 polyunsaturated fatty acids (PUFAs) can effectively treat depression via anti-inflammatory and neuroprotective effects. However, n-3 PUFA purities, caloric contents, and ratios in different diets often cause contradictive results. This study used Fat-1 mice, which can convert n-6 to n-3 PUFAs in the brain, to study the effect of n-3 PUFAs on OB-induced behaviors and related changes.

METHODS

Fat-1 and wild-type littermates were fed safflower oil for 3 months. Behaviors were tested on day 21 after surgery. Monoamine neurotransmitters were measured by HPLC. Macrophage activity was measured by MTT assay. Astrocyte phenotypes A1 S100β, A2 BDNF and cholesterol level were measured by ELISA and total cholesterol assay kits respectively. PUFA profile and membrane fluidity were detected by GC and DPH fluorescence probe respectively.

RESULTS

OB significantly induced animal hyperactivity and spatial memory impairment, while decreased sucrose consumption and social contact with decreased 5-HT turnover, increased the macrophage activity and S100β/BDNF ratio. Meanwhile, n-3/n-6 PUFAs ratio and total cholesterol level were reduced in OB mice. Whereas, OB-induced behavioral changes were attenuated, which were associated with increasing 5-HT turnover, decrease macrophage activity, restored S100β/BDNF and n-3/n-6 PUFAs ratios, and total cholesterol concentrations in Fat-1 mice.

CONCLUSION

The present study for the first time demonstrated that endogenous n-3 PUFAs attenuated OB-induced depression-like behaviors and spatial memory impairment through modulating serotonergic and immune function, balancing the astrocyte A1/A2 phenotypes, and normalizing PUFAs profile and membrane function.

Gut microbiota mediates cognitive impairment in young mice after multiple neonatal exposures to sevoflurane

Multiple exposures to anesthesia may increase the risk of cognitive impairment in young children. However, the mechanisms underlying this neurodevelopmental disorder remain elusive. In this study, we investigated alteration of the gut microbiota after multiple neonatal exposures to the anesthetic sevoflurane and the potential role of microbiota alteration on cognitive impairment using a young mice model. Multiple neonatal sevoflurane exposures resulted in obvious cognitive impairment symptoms and altered gut microbiota composition. Fecal transplantation experiments confirmed that alteration of the microbiota was responsible for the cognitive disorders in young mice. Microbiota profiling analysis identified microbial taxa that showed consistent differential abundance before and after fecal microbiota transplantation. Several of the differentially abundant taxa are associated with memory and/or health of the host, such as species of Streptococcus, Lachnospiraceae, and Pseudoflavonifractor. The results reveal that abnormal composition of the gut microbiota is a risk factor for cognitive impairment in young mice after multiple neonatal exposures to sevoflurane and provide insight into a potential therapeutic strategy for sevoflurane-related neurotoxicity.

Adult neurogenesis mediates forgetting of multiple types of memory in the rat

The formation and retention of hippocampus-dependent memories is impacted by neurogenesis, a process that involves the production of new neurons in the dentate gyrus of the hippocampus. Recent studies demonstrate that increasing neurogenesis after memory formation induces forgetting of previously acquired memories. Neurogenesis-induced forgetting was originally demonstrated in mice, but a recent report suggests that the same effect may be absent in rats. Although a general species difference is possible, other potential explanations for these incongruent findings are that memories which are more strongly reinforced become resilient to forgetting or that perhaps only certain types of memories are affected. Here, we investigated whether neurogenesis-induced forgetting occurs in rats using several hippocampus-dependent tasks including contextual fear conditioning (CFC), the Morris Water Task (MWT), and touchscreen paired associates learning (PAL). Neurogenesis was increased following training using voluntary exercise for 4 weeks before recall of the previous memory was assessed. We show that voluntary running causes forgetting of context fear memories in a neurogenesis-dependent manner, and that neurogenesis-induced forgetting is present in rats across behavioral tasks despite differences in complexity or reliance on spatial, context, or object memories. In addition, we asked whether stronger memories are less susceptible to forgetting by varying the strength of training. Even with a very strong training protocol in the CFC task, we still observed enhanced forgetting related to increased neurogenesis. These results suggest that forgetting due to neurogenesis is a conserved mechanism that aids in the clearance of memories.

Neutrophil-specific deletion of Syk results in recruitment-independent stabilization of the barrier and a long-term improvement in cognitive function after traumatic injury to the developing brain

While traumatic brain injury (TBI) is the leading cause of death and disability in children, we have yet to identify those pathogenic events that determine the extent of recovery. Neutrophils are best known as "first responders" to sites of infection and trauma where they become fully activated, killing pathogens via proteases that are released during degranulation. However, this activational state may generate substantial toxicity in the young brain after TBI that is partially due to developmentally regulated inadequate antioxidant reserves. Neutrophil degranulation is triggered via a downstream signaling pathway that is dependent on spleen tyrosine kinase (Syk). To test the hypothesis that the activational state of neutrophils is a determinant of early pathogenesis and long-term recovery, we compared young, brain-injured conditional knockouts of Syk (syk^f/fMRP8-cre⁺) to congenic littermates (syk^f/f). Based upon flow cytometry, there was an extended recruitment of distinct leukocyte subsets, including Ly6G⁺/Ly6C^- and Ly6G⁺/Ly6C^int, over the first several weeks post-injury which was similar between genotypes. Subsequent assessment of the acutely injured brain revealed a reduction in blood-brain barrier disruption to both high and low molecular weight dextrans and reactive oxygen species in syk^f/fMRP8-cre⁺ mice compared to congenic littermates, and this was associated with greater preservation of claudin 5 and neuronal integrity, as determined by Western blot analyses. At adulthood, motor learning was less affected in brain-injured syk^f/fMRP8-cre⁺ mice as compared to syk^f/f mice. Performance in the Morris Water Maze revealed a robust improvement in hippocampal-dependent acquisition and short and long-term spatial memory retention in syk^f/fMRP8-cre⁺ mice. Subsequent analyses of swim path lengths during hidden platform training and probe trials showed greater thigmotaxis in brain-injured syk^f/f mice than sham syk^f/f mice and injured syk^f/fMRP8-cre⁺ mice. Our results establish the first mechanistic link between the activation state of neutrophils and long-term functional recovery after traumatic injury to the developing brain. These results also highlight Syk kinase as a novel therapeutic target that could be further developed for the brain-injured child.

Apelin-13 attenuates spatial memory impairment by anti-oxidative, anti-apoptosis, and anti-inflammatory mechanism against ethanol neurotoxicity in the neonatal rat hippocampus

It has been shown that alcohol consumption by pregnant women can have detrimental effects on the developing fetus and lead to fetal alcohol spectrum disorders (FASD). Exposure to alcohol in rat pups during this period causes long-term changes in the structure of the animal's hippocampus, leading to impaired hippocampal-related brain functions such as navigation tasks and spatial memory. Apelin-13, a principal neuropeptide with inhibitory effects on neuroinflammation and brain oxidative stress production, has beneficial properties on memory impairment and neuronal injury. The protective effects of apelin-13 have been evaluated on ethanol-related neurotoxicity in the hippocampus of rat pups. Rat pups from 2 until 10 postnatal day, similar to the third trimester of pregnancy in humans, were intubated total daily dose of ethanol (5/27 g/kg/day). Immediately after intubation, 25 and 50 μg/ kg of apelin-13 was injected subcutaneously. By using Morris water maze task, the hippocampus- dependent memory and spatial learning were evaluated 36 days after birth. Then, Immunohistochemical staining was done to determine the levels of GFAP and caspase-3. ELISA assay was also performed to measure both TNF-α and antioxidant enzymes levels. The current study demonstrates that administration of apelin-13 attenuates spatial memory impairment significantly (P < 0.001). After ethanol neurotoxicity, apelin-13 could also increase the catalase level (P < 0.001), activity of total superoxide dismutase as well as glutathione concentration noticeably (P < 0.05). Other impacts of it could be mentioned as attenuating TNF-α production and also preventing lipid peroxidation (P < 0.001). In addition, the results showed that the level of GFAP as a neuroinflammation factor and the number of active caspase-3 positive cells can be decreased by apelin-13 (P < 0.01). Regarding the protective effects of apelin-13 against ethanol-induced neurotoxicity, it is a promising therapeutic choice for FASD; but more studies are needed.

Neuroprotective Effect and Antioxidant Potency of Fermented Cultured Wild Ginseng Root Extracts of Panax ginseng C.A. Meyer in Mice

Wild ginseng has better pharmacological effects than cultivated ginseng. However, its industrialization is limited by the inability to grow wild ginseng on a large scale. Herein, we demonstrate how to optimize ginseng production through cultivation, and how to enhance the concentrations of specific ginsenosides through fermentation. In the study, we also evaluated the ability of fermented cultured wild ginseng root extract (HLJG0701-β) to inhibit acetylcholinesterase (AChE), as well as its neuroprotective effects and antioxidant activity. In invitro tests, HLJG0701-β inhibited AChE activity and exerted neuroprotective and antioxidant effects (showing increased catalyst activity but decreased reactive oxygen species concentration). In invivo tests, after HLJG0701-β was orally administered at doses of 0, 125, 250, and 500 mg/kg in an animal model of memory impairment, behavioral evaluation (Morris water maze test and Y-maze task test) was performed. The levels of AChE, acetylcholine (ACh), blood catalase (CAT), and malondialdehyde (MDA) in brain tissues were measured. The results showed that HLJG0701-β produced the best results at a dose of 250 mg/kg or more. The neuroprotective mechanism of HLJG0701-β was determined to involve the inhibition of AChE activity and a decrease in oxidative stress. In summary, both invitro and invivo tests confirmed that HJG0701-β administration can lead to memory improvement.

Determination of anxiolytic and antidepressant like activity of hydro alcoholic fruit extract of Pyrus communis (L.) and its impact on the memory after chronic dosing in animal models

The purpose of this study was to evaluate the anxiolytic and antidepressant activity of ethanolic fruit extract of Pyrus communis (pear), in comparison with escitalopram in rodents (rats and mice). Thirty Wistar rats of about 200-250gm and albino mice of 25-30gm, male gender were divided into three groups each comprising of (n=10) animal respectively. Control group received distilled water, positive control received 10mg escitalopram & treated group received 200mg/kg/day of Pyrus communis ethanolic fruit extract orally for 30 days. They were evaluated by using the open field test, forced swim test (FST), plus maze test, light and dark test, hole poking test, stationary rod test, water maze test & cage crossing activity. Results were expressed as mean ± SD. Data was analyzed by using SPSS software (VERSION 21) one way ANOVA followed by Tukey test was used for post hoc analysis. Our result showed that fruit extract had significant antidepressant-like behavior in FST (p<0.001), open field (p<0.05), cage crossing (p<0.001) , significant anxiolytic activity in light and dark box test, plus-maze activity and significantly enhanced learning in water maze and stationary rod test when compared with control. The Pyrus communis fruit extract showed the anxiolytic and antidepressant-like profile in rats and mice. However, further studies need to be carried out in clinical trials for its use in different neuropsychological disorders.

Ginkgolide B promotes oligodendrocyte precursor cell differentiation and survival via Akt/CREB/bcl-2 signaling pathway after white matter lesion

White matter lesion (WML) is caused by chronic cerebral hypoperfusion, which are usually associated with cognitive impairment. Evidence from recent studies has shown that ginkgolide B has a neuroprotective effect that could be beneficial for the treatment of ischemia; however, it is not clear whether ginkgolide B has a protective effect on WML. Our data show that ginkgolide B can promote the differentiation of oligodendrocyte precursor cell (OPC) into oligodendrocytes and promote oligodendrocyte survival following a WML. Ginkgolide B (5, 10, 20 mg/kg) or saline is administered intraperitoneally every day after WML. After 4 weeks, the data of Morris water maze suggested that rats' memory and learning abilities were impaired, and the administration of ginkgolide B enhanced behavioral achievement. Also, treatment with ginkgolide B significantly attenuated this loss of myelin. Our result suggests that ginkgolide B promotes the differentiation of OPC into oligodendrocytes. We also found that ginkgolide B ameliorates oligodendrocytes apoptosis. Furthermore, ginkgolide B enhanced the expression of phosphorylated Akt and CREB. In conclusion, our data firstly show that ginkgolide B promotes oligodendrocyte genesis and oligodendrocyte myelin following a WML, possibly involving the Akt and CREB pathways.

Intracerebral hemorrhage influences hippocampal neurogenesis and neurological function recovery via Notch1 signaling

Intracerebral hemorrhage (ICH) is associated with high rate of mortality and morbidity, but lacks effective therapies. Accumulating studies indicated that the hippocampal neurogenesis plays an essential role in the recovery of neurological function after ICH. The Notch1 signaling pathway shows important roles in neurogenesis. However, the effects of Notch1 on the recovery of neurological function after ICH remain unclear. Here, we used ICH mice model to investigate whether Notch1 signaling was involved in the hippocampal neurogenesis and the recovery of neurological function post-ICH. Our results showed that the rate of symmetric division pattern of hippocampal neural stem cells (NSCs) decreased significantly at 3 days after ICH. Meanwhile, the expression of Notch1 in the hippocampus also was reduced significantly. However, Notch1 activator treatment enhanced the expression of Notch1 and increased the number of Sox2+GFAP+ cells. Further, the rate of symmetric division pattern of NSCs also increased after Notch1 activator treatment in mice with ICH. Importantly, the number of DCX+ cells and BrdU+NeuN+ in hippocampus were increased on 28 days post-ICH as the Notch1 expression was upregulated. The motor function and spatial memory ability in post-ICH mice following Notch1 activator treatment also were improved. Taken together, our results suggested that Notch1 signaling could influence the recovery of long-term neurological function by regulating the proliferation and differentiation of the hippocampal NSCs in mice after ICH. Our study may provide ideas for the improvement of neurological function and spatial memory defects after ICH.

Dissociable effects of dietary sodium in early life upon somatic growth, fluid homeostasis, and spatial memory in mice of both sexes

Postnatal growth failure is a common morbidity for preterm infants and is associated with adverse neurodevelopmental outcomes. Although sodium (Na) deficiency early in life impairs somatic growth, its impact on neurocognitive functions has not been extensively studied. We hypothesized that Na deficiency during early life is sufficient to cause growth failure and program neurobehavioral impairments in later life. C57BL/6J mice were placed on low- (0.4), normal- (1.5), or high- (3 g/kg) Na chow at weaning (PD22) and continued on the diet for 3 wk (to PD40). Body composition and fluid distribution were determined serially by time-domain NMR and bioimpedance spectroscopy, and anxiety, learning, and memory were assessed using the elevated plus maze and Morris water maze paradigms in later adulthood (PD63-PD69). During the diet intervention, body mass gains were suppressed in the low- compared with normal- and high-Na groups despite similar caloric uptake rates across groups. Fat mass was reduced in males but not in females fed low-Na diet. Fat-free mass and hydration were significantly reduced in both males and females fed the low-Na diet, although rapidly corrected after return to normal diet. Measures of anxiety-like behavior and learning in adulthood were not affected by diet in either sex, yet memory performance was modified by a complex interaction between sex and early life Na intake. These data support the concepts that Na deficiency impairs growth and that the amount of Na intake which supports optimal somatic growth during early life may be insufficient to fully support neurocognitive development.

GR/NF-κB signaling pathway regulates hippocampal inflammatory responses in diabetic rats with chronic unpredictable mild stress

Clinical studies have shown that diabetes can present with underlying depression, and a combination of the two can lead to emotional, memory and cognitive disorders, closely associated with hippocampal neuroinflammation. However, the mechanism underlying the development of hippocampal neuroinflammation under the above condition remains elusive. The aims of this study were to explore the pathogenesis of diabetes combined with depression, and the effect of dexamethasone (Dex), a glucocorticoid receptor (GR) agonist, on hippocampal neuroinflammation in diabetic rats with chronic unpredictable mild stress (CUMS). Therefore, rats were intragastrically fed on a high-fat diet (10% cholesterol 10 ml/kg) for 14 days and thereafter injected with 38 mg/kg of streptozotocin on the 15th day to induce diabetes. Dex treatment of the diabetic and CUMS rats ameliorated the depression-associated behavior in the respective rats. Apart from enhanced depressive behavior, diabetes-depressed condition also up-regulated the expression of hippocampus microglia chemokine Ⅰ receptor (CX3CR1) and secretion of several pro-inflammatory factors, in particular, interleukin 1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor - α (TNF-α). Hematoxylin-eosin staining revealed inflammatory damages in the hippocampus. Western blot analysis further revealed repression of GR proteins converse to the nuclear factor kappa-B (NF-κB) proteins, which were up-regulated. Intriguingly, Dex reversed the above events by inhibiting inflammatory reactions in the hippocampus. Consequently, played an antidepressant effect in diabetic and CUMS model rats. Overall, findings of this research suggest that the physiopathology of diabetes with stress cormobity are mediated by inflammatory reactions in the hippocampus. In particular, the responses are associated with regulation of GR/NF-κB signaling pathway.

Downregulation of lncRNA GAS5 Alleviates Hippocampal Neuronal Damage in Mice with Depression-Like Behaviors Via Modulation of MicroRNA-26a/EGR1 Axis

BACKGROUND

Accumulating evidences have demonstrated the roles of several long non-coding RNAs (lncRNAs) in depression. We aim to examine the capabilities of lncRNA growth arrest-specific transcript 5 (GAS5) on mice with depression-like behaviors and the mechanism of action.

METHODS

Fifty-six healthy mice were selected for model establishment. Morris water maze test and trapeze test were performed for evaluating learning and memory ability. The binding relationship between lncRNA GAS5 and microRNA-26a (miR-26a) and the target relationship between miR-26a and EGR1 were verified by dual-luciferase reporter gene assay. The apoptosis of neurons in the hippocampal CA1 region of mice was detected by TUNEL staining. The expression of inflammatory factors, lncRNA GAS5, miR-26a, early growth response gene 1 (EGR1), phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway- and apoptosis-related factors in hippocampal tissues was tested by RT-qPCR and western blot analysis.

RESULTS

miR-26a expression was down-regulated while EGR1 and lncRNA GAS5 expression were up-regulated in hippocampal tissues of mice with depression-like behaviors. LncRNA GAS5 specifically bound to miR-26a and miR-26a targeted EGR1. Silencing of lncRNA GAS5 curtailed the release of inflammatory factors and the apoptosis of hippocampal neuron of mice with depression-like behaviors. EGR1 suppressed PI3K/AKT pathway activation to promote the release of inflammatory factors and the apoptosis of hippocampal neurons in mice with depression-like behaviors.

CONCLUSION

Our study provides evidence that silencing of lncRNA GAS5 could activate PI3K/AKT pathway to protect hippocampal neurons against damage in mice with depression-like behaviors by regulating the miR-26a/EGR1 axis.

Hashimoto's Thyroiditis Induces Hippocampus-Dependent Cognitive Alterations by Impairing Astrocytes in Euthyroid Mice

Background: Although studies have reported an increased risk for cognitive disorders in Hashimoto's thyroiditis (HT) patients, even in the euthyroid state, the mechanisms involved remain unclear. The hippocampus is a classic brain region associated with cognitive function, among which the formation of long-term potentiation (LTP) in the Schaffer collateral-CA1 pathway plays an important role in the process of learning and memory. Therefore, this study established a euthyroid HT model in mice and investigated whether and how HT itself has the ability to trigger LTP alterations accompanied by learning and memory abnormality. Methods: An experimental euthyroid HT model was established in NOD mice through immunization with porcine thyroglobulin (Tg). Morris water maze was measured to determine mice spatial learning and memory. We investigated the effect of HT on synaptic transmission and high-frequency stimulation-induced LTP in the Schaffer collateral-CA1 synapse of mice hippocampus in vivo. Then, animals were sacrificed for thyroid-related parameter measure as well as detection of cellular and molecular events associated with the induction of LTP. Results: HT mice showed intrathyroidal lymphocyte infiltration and rising serum thyroid autoantibody levels accompanied by normal thyroid function. The HT mice had poorer performance in Morris water maze than controls. These alterations were mirrored by abnormalities in synaptic plasticity in the Schaffer collateral-CA1 synapses of the hippocampus in vivo. The integrity of the synaptic structure is the premise for the production of LTP. As detected by transmission electron microscopy, the ultrastructure of synapse and astrocyte in the hippocampus were impaired in euthyroid HT mice. Additionally, Western blot and real-time polymerase chain reaction analyses confirmed that in HT mice, GS, GLAST, and GLT-1, key elements in glutamate-glutamine circulation located in astrocyte, were downregulated, accompanied by elevated levels of glutamate in the hippocampus, which impaired the material basis for LTP induction. NMDR2B expression in the hippocampus was also downregulated. Conclusion: HT can induce damage of LTP in the hippocampal Schaffer collateral-CA1 pathway in the euthyroid state, and this can be attributed, at least partly, to astrocytes impairment, which may underlie the deleterious effects of HT itself on hippocampal-dependent learning and memory function.

Harmony of T cell profile in brain, nasal, spleen, and cervical lymph nodes tissues in Alzheimer's: A systemic disease with local manifestations

The brain has special importance and is known as immune privileged site to and from which trafficking of immune cells is tightly regulated. However, in Alzheimer's disease (AD) the balance of the immune system is disturbed and damages the brain. Given the anatomical and immunological barriers in the brain, we attempted to evaluate if the neuroinflammation occurred in AD is limited to the brain or is expanded to the periphery. Hence, rat model of AD was induced by intra-hippocampal injection of beta-amyloid1-42. Then, nasal, brain, cervical lymph nodes, and spleen were isolated. Then, profile of T-helper (Th)1, Th2, and Th17, represented by IFN-γ, IL-4, and IL-17, respectively, was determined. The results were compared between the organs and with the corresponding tissue in normal animals. IFN-γ and IL-17 levels in the brain, nasal tissue, and cervical lymph nodes of AD model were higher than IL-4, comparing with normal animals. Similar profile was observed in the spleen. The results suggest Alzheimer's as a systemic disease whose complication are observed locally. The possibility of epitope spreading and autoimmune nature of AD is raised again. Interestingly, although AD model was induced by injection of beta-amyloid in the brain, the cellular responses in the brain and nasal tissue were similar indicating that the nasal-brain axis is two-sided. In addition, both of IFN-γ/IL-17 and IL-4/IL-17 ratios, just in nasal tissue were markedly decreased in AD model comparing with normal animals. This suggests development of future nasal-based diagnostic approaches.

Sesamol alleviates chronic intermittent hypoxia-induced cognitive deficits via inhibiting oxidative stress and inflammation in rats

Chronic intermittent hypoxia (CIH) is a major pathophysiological feature of obstructive sleep apnea (OSA), which can cause oxidative stress and inflammation which can further impair the nervous system. Cognitive impairment is a common complication of the nervous system in OSA. Sesamol, a natural extract from Sesamum plants, is believed to have strong antioxidant and anti-inflammation capacity, which has a powerful neuroprotective function. But whether sesamol can improve CIH-induced cognitive impairment is unclear. This study aimed to explore whether sesamol can improve CIH-induced cognitive impairment and its relative mechanism in the model rats with OSA. Rats were exposed to CIH for 8 h a day for 2, 4, 6, and 8 weeks separately and concurrently were treated with sesamol (20 mg/kg/day, intraperitoneal). The Morris water maze (MWM) test was used to evaluate their learning and memory function. The activity of the superoxide dismutase (SOD) and the level of malondialdehyde were measured to evaluate the oxidative stress in the hippocampus of the rats. The levels of tumour necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) in the hippocampus were quantified to analyse neuroinflammation by ELISA. The MWM test showed that sesamol improved learning and memory impairment in CIH-exposed rats. We also found that the sesamol-treated CIH-exposed rats had significantly increased the activity of SOD, as well as reduced the level of malondialdehyde in the hippocampus. In addition, sesamol also reduced the levels of TNF-α and IL-1β in the hippocampus. These data show that sesamol is able to alleviate cognitive impairments in CIH-exposed rats, with its neuroprotective effects likely inhibiting oxidative stress and inflammation.

Dysfunction in nonsense-mediated decay, protein homeostasis, mitochondrial function, and brain connectivity in ALS-FUS mice with cognitive deficits

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) represent two ends of the same disease spectrum of adult-onset neurodegenerative diseases that affect the motor and cognitive functions, respectively. Multiple common genetic loci such as fused in sarcoma (FUS) have been identified to play a role in ALS and FTD etiology. Current studies indicate that FUS mutations incur gain-of-toxic functions to drive ALS pathogenesis. However, how the disease-linked mutations of FUS affect cognition remains elusive. Using a mouse model expressing an ALS-linked human FUS mutation (R514G-FUS) that mimics endogenous expression patterns, we found that FUS proteins showed an age-dependent accumulation of FUS proteins despite the downregulation of mouse FUS mRNA by the R514G-FUS protein during aging. Furthermore, these mice developed cognitive deficits accompanied by a reduction in spine density and long-term potentiation (LTP) within the hippocampus. At the physiological expression level, mutant FUS is distributed in the nucleus and cytosol without apparent FUS aggregates or nuclear envelope defects. Unbiased transcriptomic analysis revealed a deregulation of genes that cluster in pathways involved in nonsense-mediated decay, protein homeostasis, and mitochondrial functions. Furthermore, the use of in vivo functional imaging demonstrated widespread reduction in cortical volumes but enhanced functional connectivity between hippocampus, basal ganglia and neocortex in R514G-FUS mice. Hence, our findings suggest that disease-linked mutation in FUS may lead to changes in proteostasis and mitochondrial dysfunction that in turn affect brain structure and connectivity resulting in cognitive deficits.

Wip1 phosphatase deficiency impairs spatial learning and memory

Spatial learning and memory are typically assessed to evaluate hippocampus-dependent cognitive and memory functions in vivo. Protein phosphorylation and dephosphorylation by kinases and phosphatases play critical roles in spatial learning and memory. Here we report that the Wip1 phosphatase is essential for spatial learning, with knockout mice lacking Wip1 phosphatase exhibiting dysfunctional spatial cognition. Aberrant phosphorylation of the Wip1 substrates p38, ATM, and p53 were observed in the hippocampi of Wip1^-/- mice, but only p38 inhibition reversed impairments in long-term potentiation in Wip1-knockout mice. p38 inhibition consistently ameliorated the spatial learning dysfunction caused by Wip1 deficiency. Our results demonstrate that deletion of Wip1 phosphatase impairs hippocampus-dependent spatial learning and memory, with aberrant downstream p38 phosphorylation involved in this process and providing a potential therapeutic target.

Norepinephrine in the dentate gyrus is involved in spatial learning and memory alteration induced by chronic restraint stress in aged rats

The role of norepinephrine of the hippocampal dentate gyrus in spatial learning and memory alteration induced by chronic restraint stress (CRS, 3 h/day, 6 weeks) was investigated in aged rats. Spatial learning and memory were assessed by the Morris water maze (MWM), and the extracellular concentration of norepinephrine and amplitude of field excitatory postsynaptic potential (fEPSP) were measured in the dentate gyrus during MWM test in freely-moving rats. Next, the involvement of β-adrenoceptors in spatial learning and memory of CRS rats was examined by microinjection of its antagonist (propranolol) into the dentate gyrus. In addition, we observed the expression of brain-derived neurotrophic factor (BDNF) protein and activation of cAMP-response element binding protein (CREB) in the dentate gyrus. Compared with the control group, the basal level of norepinephrine, BDNF expression and CREB activation in the dentate gyrus were increased, and the spatial learning and memory abilities were enhanced in CRS rats. In the control group, the norepinephrine concentration and fEPSP amplitude in the dentate gyrus were increased on the second to fourth days of MWM test, and these responses were significantly enhanced in CRS rats. Furthermore, in CRS rats, propranolol significantly decreased the spatial learning and memory abilities, and attenuated the fEPSP response during MWM test, and the BDNF expression and CREB activation in the dentate gyrus. Our results suggest that norepinephrine activation of β-adrenoceptors in the hippocampal dentate gyrus is involved in spatial learning and memory enhancement induced by CRS in aged rats, in part via modulations of synaptic efficiency and CREB-BDNF signaling pathway.

Serine Racemase Deletion Affects the Excitatory/Inhibitory Balance of the Hippocampal CA1 Network

d-serine is the major co-agonist of N-methyl-D-aspartate receptors (NMDAR) at CA3/CA1 hippocampal synapses, the activation of which drives long-term potentiation (LTP). The use of mice with targeted deletion of the serine racemase (SR) enzyme has been an important tool to uncover the physiological and pathological roles of D-serine. To date, some uncertainties remain regarding the direction of LTP changes in SR-knockout (SR-KO) mice, possibly reflecting differences in inhibitory GABAergic tone in the experimental paradigms used in the different studies. On the one hand, our extracellular recordings in hippocampal slices show that neither isolated NMDAR synaptic potentials nor LTP were altered in SR-KO mice. This was associated with a compensatory increase in hippocampal levels of glycine, another physiologic NMDAR co-agonist. SR-KO mice displayed no deficits in spatial learning, reference memory and cognitive flexibility. On the other hand, SR-KO mice showed a weaker LTP and a lower increase in NMDAR potentials compared to controls when GABAA receptors were pharmacologically blocked. Our results indicate that depletion of endogenous D-serine caused a reduced inhibitory activity in CA1 hippocampal networks, altering the excitatory/inhibitory balance, which contributes to preserve functional plasticity at synapses and to maintain related cognitive abilities.

Marinoid J, a phenylglycoside from Avicennia marina fruit, ameliorates cognitive impairment in rat vascular dementia: a quantitative iTRAQ proteomic study

CONTEXT

Fruit of Avicennia marina (Forsk.) Vierh. (Acanthaceae) is used as a Chinese herb. Studies have found that it contains marinoid J, a novel phenylethanoid glycoside (PG) compound, but its neuroprotective functions are largely unknown.

OBJECTIVE

This study evaluated the effects of marinoid J on vascular dementia (VD) and determined its potential mechanisms of action.

MATERIALS AND METHODS

The VD model was established by the ligation of the bilateral common carotid artery in Sprague-Dawley rats, who received daily intragastrically administration of saline, marinoid J (125 or 500 mg/kg body weight/d), or oxiracetam (250 mg/kg body weight/d) for 14 days (20 rats in each group). The Morris water maze (MWM) was used to evaluate cognitive performance. The hippocampus was subjected to histological and proteomic analyses.

RESULTS

Marinoid J shortened the escape latency of VD rats (31.07 ± 3.74 s, p < 0.05). It also decreased malondialdehyde (MDA) (27.53%) and nitric oxide (NO) (20.41%) while increasing superoxide dismutase (SOD) (11.26%) and glutathione peroxidase (GSH-Px) (20.38%) content in hippocampus tissues. Proteomic analysis revealed 45 differentially expressed proteins (DEPs) in marinoid J-treated VD rats, which included angiotensin-converting enzyme (ACE), keratin 18 (KRT18), cluster of differentiation 34 (CD34), and synaptotagmin II (SYT2).

CONCLUSIONS

Marinoid J played a role in protecting hippocampal neurons by regulating a set of proteins that influence oxidative stress and apoptosis, this effect may thereby alleviate the symptoms of VD rats. Thus, pharmacological manipulation of marinoid J may offer a novel opportunity for VD treatment.

Stroke promotes the development of brain atrophy and delayed cell death in hypertensive rats

Post-stroke cognitive impairment (PSCI) is a major source of disability, affecting up to two thirds of stroke survivors with no available therapeutic options. The condition remains understudied in preclinical models due to its delayed presentation. Although hypertension is a leading risk factor for dementia, how ischemic stroke contributes to this neurodegenerative condition is unknown. In this study, we used a model of hypertension to study the development of PSCI and its mechanisms. Spontaneously hypertensive rats (SHR) were compared to normotensive rats and were subjected to 1-h middle cerebral artery occlusion or sham surgery. Novel object recognition, passive avoidance test and Morris water maze were used to assess cognition. In addition, brain magnetic resonance images were obtained 12-weeks post-stroke and tissue was collected for immunohistochemistry and protein quantification. Stroked animals developed impairment in long-term memory at 4-weeks post-stroke despite recovery from motor deficits, with hypertensive animals showing some symptoms of anhedonia. Stroked SHRs displayed grey matter atrophy and had a two-fold increase in apoptosis in the ischemic borderzone and increased markers of inflammatory cell death and DNA damage at 12 weeks post-stroke. This indicates that preexisting hypertension exacerbates the development of secondary neurodegeneration after stroke beyond its acute effects on neurovascular injury.

Astaxanthin protects cognitive function of vascular dementia

OBJECTIVE

The purpose of this study was to evaluate the effect of astaxanthin (AST) on cognition function, inflammatory response and oxidative stress in vascular dementia (VD) mice.

METHOD

VD mice model was established by left unilateral common carotid arteries occlusion (LUCCAO). Following LUCCAO, AST was intragastrically administered for 30 days. Object recognition test and morris water maze test were used to evaluate cognitive function. Hematoxylin and eosin staining was performed to observe the hippocampal neuron structure. Enzyme-linked immunosorbent assay kit and bicinchoninic acid kit were respectively adopted to measure IL-1β and IL-4 protein expression and superoxide dismutase (SOD) activity and malondialdehyde (MDA) content in hippocampus and prefrontal cortex.

RESULTS

AST improved the discrimination ability of VD mice. The escape latency and path length of VD mice treated with AST were dramatically reduced. Besides, AST 200 mg/kg enhanced crossing platform time and the number of times crossing the platform quadrant, and alleviated the morphological impairment in VD mice. Moreover, we found that AST inhibited IL-1β expression and MDA content, whereas promoted IL-4 expression and SOD activity in a dose-dependent manner.

CONCLUSION

AST could improve cognitive impairment and hippocampal neurons in VD mice, which may be related to suppression of inflammatory response and oxidative stress.

Cognitive dysfunction associated with activation of the mTOR signaling pathway after TSH suppression therapy in rats

Thyroid stimulating hormone (TSH) suppression therapy after thyroid carcinoma surgery could lead to cognitive impairment. But, the possible mechanism of TSH suppression therapy impairs cognitive function is yet unknown. In this study, forty Wistar rats were randomized into the sham operation control (OC), total thyroidectomy (TD), thyroxine replacement therapy (TR), and TSH suppression therapy (TS) groups. We observed that compared to the OC group, escape latency on 1-4 days was significantly prolonged in the TD and TS groups, and the number of rats crossing the virtual platform was significantly reduced in the TD and TS groups. In the TD, TR, and TS groups, the residence time in the target quadrant was significantly decreased, while the activity distance in the target quadrant in the TD group was significantly decreased compared with OC group. In the TD and TS groups, the pyramidal cells in the hippocampal CA1 region showed a disordered arrangement. The cytoplasm was lightly stained, the cells were swollen and round, and spotty liquefaction necrosis could be observed. Compared to the OC group, hippocampal p-mTOR and p-p70s6k levels were significantly decreased in the TD group, while no significant changes were detected in the TR group. Hippocampal p-mTOR and p-p70s6k amounts in the TS group were significantly increased compared with OC group. These results indicated that TSH suppression therapy after total thyroidectomy in rats could impair cognitive function, which might be related to the activation of the mTOR signaling pathway and the damage and necrosis of hippocampal neurons.

Molecular mechanisms underlying altered neurobehavioural development of female offspring of mothers with polycystic ovary syndrome: FOS-mediated regulation of neurotrophins in placenta

BACKGROUND

This study explored the mechanisms underlying altered neurobehavioural development of female offspring born to mothers with polycystic ovary syndrome (PCOS).

METHODS

In total, 20 women with PCOS and 32 healthy women who underwent caesarean deliveries with a single female foetus were recruited. Infants were assessed with Dubowitz scoring. Swan71 cell line with stable FOS overexpression was used to verify the regulatory effects of FOS on brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) expression. Learning and memory in female first-generation (F1) and second-generation (F2) offspring in a rat model of PCOS was tested using the Morris water maze at puberty and adulthood. Transcriptome analysis of pubertal hippocampi and hypothalami of female F1 offspring was conducted.

FINDINGS

Total score and behaviour subscales of Dubowitz scoring were significantly lower in female infants of women with PCOS. FOS and NGF protein levels were downregulated in placental villi of the PCOS group. FOS played a key role in BDNF inhibition and enhancing NGF in Swan71 cells. PCOS female F1 rats exhibited lower target crossing times during puberty when compared to controls. Transcriptome analysis revealed significant changes in hippocampal and hypothalamic neuronal pathways in female F1 rats at puberty.

INTERPRETATION

FOS regulation of neurotrophins in the placenta negatively affects neurobehavioural development of female offspring of PCOS mothers.

FUNDING

This study was funded by the National Key R&D Program of China (2018YFC1004900 to F.Q. and F.W.) and the National Natural Science Foundation of China (81874480 to F.Q.; 81873837 to F.W.).

Longitudinal neuroanatomical and behavioral analyses show phenotypic drift and variability in the Ts65Dn mouse model of Down syndrome

Mouse models of Down syndrome (DS) have been invaluable tools for advancing knowledge of the underlying mechanisms of intellectual disability in people with DS. The Ts(1716)65Dn (Ts65Dn) mouse is one of the most commonly used models as it recapitulates many of the phenotypes seen in individuals with DS, including neuroanatomical changes and impaired learning and memory. In this study, we use rigorous metrics to evaluate multiple cohorts of Ts65Dn ranging from 2014 to the present, including a stock of animals recovered from embryos frozen within ten generations after the colony was first created in 2010. Through quantification of prenatal and postnatal brain development and several behavioral tasks, our results provide a comprehensive comparison of Ts65Dn across time and show a significant amount of variability both across cohorts as well as within cohorts. The inconsistent phenotypes in Ts65Dn mice highlight specific cautions and caveats for use of this model. We outline important steps for ensuring responsible use of Ts65Dn in future research.This article has an associated First Person interview with the first author of the paper.