Modulation of learning and memory by cytokines: signaling mechanisms and long term consequences

Neuroprotective effects of Levisticum officinale on LPS-induced spatial learning and memory impairments through neurotrophic, anti-inflammatory, and antioxidant properties

Levisticum officinale (Apiaceae) has been identified as a medicinal plant in traditional medicine, with the anti-inflammatory, antioxidant, and anticholinesterase activities. The present study aims to evaluate the effects of Levisticum officinale extract (LOE) on lipopolysaccharide (LPS)-induced learning and memory deficits and to examine its potential mechanisms. LOE was administered to adult male Wistar rats at doses of 100, 200, and 400 mg kg-1 for a week. Later, LPS was intraperitoneally injected at a dose of 1 mg kg-1 to induce neuroinflammation, and treatment with LOE continued for 3 more weeks. Behavioral, biochemical, and molecular analyses were performed at the end of the experiment. Moreover, quantitative immunohistochemical assessments of the expression of Ki-67 (intracellular proliferation marker) in the hippocampus were performed. The results revealed that LPS injection caused spatial memory impairment in the rats. Daily LOE treatment at applied doses for 4 weeks attenuated spatial learning and memory deficits in LPS-injected rats. Furthermore, LPS significantly increased the mRNA expression level of interleukin-6 in the hippocampus, which was accompanied by decreased brain-derived neurotrophic factor (BDNF) mRNA expression levels. Moreover, LPS increased the levels of malondialdehyde, reduced the antioxidant enzyme activities of catalase and superoxide dismutase in the hippocampus, and impaired neurogenesis. However, pre-treatment with LOE at a dose of 100 mg kg-1 significantly reversed the LPS-induced changes, and improved neurogenesis. In conclusion, the beneficial effect of LOE on the improvement of learning and memory could be attributed to its anti-inflammatory and antioxidant activities, along with its ability to increase BDNF expression and neurogenesis in the hippocampus.

An emerging role for microglia in stress‐effects on memory

Stressful experiences evoke, among others, a rapid increase in brain (nor)epinephrine (NE) levels and a slower increase in glucocorticoid hormones (GCs) in the brain. Microglia are key regulators of neuronal function and contain receptors for NE and GCs. These brain cells may therefore potentially be involved in modulating stress effects on neuronal function and learning and memory. In this review, we discuss that stress induces (1) an increase in microglial numbers as well as (2) a shift toward a pro‐inflammatory profile. These microglia have (3) impaired crosstalk with neurons and (4) disrupted glutamate signaling. Moreover, microglial immune responses after stress (5) alter the kynurenine pathway through metabolites that impair glutamatergic transmission. All these effects could be involved in the impairments in memory and in synaptic plasticity caused by (prolonged) stress, implicating microglia as a potential novel target in stress‐related memory impairments.

Neuroimmune reactivity marker expression in rodent models of chemotherapy-induced cognitive impairment: A systematic scoping review

BACKGROUND

Chemotherapy-induced cognitive impairment (CICI) is a debilitating side effect arising from chemotherapy treatments. The condition is characterised by a range of cognitive deficits including impairment to memory, attention, and concentration. Whilst the underlying mechanisms that contribute to CICI remain unclear, neuroinflammation has been suggested as one key contributor.

METHOD

A comprehensive systematic search of EMBASE and Medline via PubMed was conducted to identify studies on neuroimmune reactivity marker expression changes and resulting cognitive changes in preclinical rodent models of CICI.

RESULTS

A total of twenty studies met the eligibility criteria and were included in the scoping review. There was significant heterogeneity in the methodology employed in the included studies. Our findings demonstrate that widespread changes in cytokines, chemokines, microglia reactivity, and astrocyte reactivity are observed in CICI in the brain regions expected to be affected, given the nature of the cognitive impairment observed in CICI.

CONCLUSIONS

Although there was considerable heterogeneity in study design that made comparisons between studies difficult, our findings suggest that neuroinflammation commonly occurs in CICI preclinical rodent models and shows an association with cognitive impairment.

Neuro-Immune Cross-Talk in the Striatum: From Basal Ganglia Physiology to Circuit Dysfunction

The basal ganglia network is represented by an interconnected group of subcortical nuclei traditionally thought to play a crucial role in motor learning and movement execution. During the last decades, knowledge about basal ganglia physiology significantly evolved and this network is now considered as a key regulator of important cognitive and emotional processes. Accordingly, the disruption of basal ganglia network dynamics represents a crucial pathogenic factor in many neurological and psychiatric disorders. The striatum is the input station of the circuit. Thanks to the synaptic properties of striatal medium spiny neurons (MSNs) and their ability to express synaptic plasticity, the striatum exerts a fundamental integrative and filtering role in the basal ganglia network, influencing the functional output of the whole circuit. Although it is currently established that the immune system is able to regulate neuronal transmission and plasticity in specific cortical areas, the role played by immune molecules and immune/glial cells in the modulation of intra-striatal connections and basal ganglia activity still needs to be clarified. In this manuscript, we review the available evidence of immune-based regulation of synaptic activity in the striatum, also discussing how an abnormal immune activation in this region could be involved in the pathogenesis of inflammatory and degenerative central nervous system (CNS) diseases.

Short- and Long-Term Social Recognition Memory Are Differentially Modulated by Neuronal Histamine

The ability of recognizing familiar conspecifics is essential for many forms of social interaction including reproduction, establishment of dominance hierarchies, and pair bond formation in monogamous species. Many hormones and neurotransmitters have been suggested to play key roles in social discrimination. Here we demonstrate that disruption or potentiation of histaminergic neurotransmission differentially affects short (STM) and long-term (LTM) social recognition memory. Impairments of LTM, but not STM, were observed in histamine-deprived animals, either chronically (Hdc^−/− mice lacking the histamine-synthesizing enzyme histidine decarboxylase) or acutely (mice treated with the HDC irreversible inhibitor α-fluoromethylhistidine). On the contrary, restriction of histamine release induced by stimulation of the H₃R agonist (VUF16839) impaired both STM and LTM. H₃R agonism-induced amnesic effect was prevented by pre-treatment with donepezil, an acetylcholinesterase inhibitor. The blockade of the H₃R with ciproxifan, which in turn augmented histamine release, resulted in a procognitive effect. In keeping with this hypothesis, the procognitive effect of ciproxifan was absent in both Hdc^−/− and αFMH-treated mice. Our results suggest that brain histamine is essential for the consolidation of LTM but not STM in the social recognition test. STM impairments observed after H₃R stimulation are probably related to their function as heteroreceptors on cholinergic neurons.

[The role of cytokines in the processes of adaptive integration of immune and neuroendocrine reactions of the human body]

Иммунная, эндокринная и нервная системы интегрированы благодаря существованию взаимных путей передачи информации об изменениях их фактического функционального состояния. Главными задачами мозга являются прием, интеграция и хранение информации, и есть убедительные доказательства, что это относится и к информации, полученной с помощью иммунных реакций организма. Доказано, что выработка цитокинов в головном мозге может быть вызвана не только периферической иммунной стимуляцией, но и собственно нервными клетками, стимулированными определенными нейросенсорными сигналами. Эволюционно сохраненные антигомеостатические механизмы, характерные для конкретных заболеваний, — предмет дальнейших исследований, результаты которых могут быть очень важны для разработки терапевтических стратегий, которые препятствовали бы нежелательным комбинированным эффектам иммунных и нейроэндокринных медиаторов.

Contribution of Pro-Inflammatory Molecules Induced by Respiratory Virus Infections to Neurological Disorders

Neurobehavioral alterations and cognitive impairment are common phenomena that represent neuropsychiatric disorders and can be triggered by an exacerbated immune response against pathogens, brain injury, or autoimmune diseases. Pro-inflammatory molecules, such as cytokines and chemokines, are produced in the brain by resident cells, mainly by microglia and astrocytes. Brain infiltrating immune cells constitutes another source of these molecules, contributing to an impaired neurological synapse function, affecting typical neurobehavioral and cognitive performance. Currently, there is increasing evidence supporting the notion that behavioral alterations and cognitive impairment can be associated with respiratory viral infections, such as human respiratory syncytial virus, influenza, and SARS-COV-2, which are responsible for endemic, epidemic, or pandemic outbreak mainly in the winter season. This article will review the brain′s pro-inflammatory response due to infection by three highly contagious respiratory viruses that are the leading cause of acute respiratory illness, morbidity, and mobility in infants, immunocompromised and elderly population. How these respiratory viral pathogens induce increased secretion of pro-inflammatory molecules and their relationship with the alterations at a behavioral and cognitive level will be discussed.

Inflammatory cytokines derived from peripheral blood contribute to the modified electroconvulsive therapy-induced cognitive deficits in major depressive disorder

Little is known about the pathophysiology of memory deficits in patients with major depressive disorder (MDD) treated with modified electroconvulsive therapy (MECT). This study examined the profiles of cytokines, the memory function, and their association in MECT-treated MDD patients. Forty first-episode, drug-free MDD patients and 40 healthy controls were recruited. MECT was started with antidepressant treatment at a stable initial dose. The Wechsler Memory Scale (WMS) and Hamilton Rating Scale for Depression 17 (HRSD-17) were used to assess the cognitive function. MDD patients were divided into the memory impairment group (WMS < 50) and the non-memory impairment group (WMS ≥ 50) based on the total WMS scores after MECT. The levels of NOD-like receptor 3 (NLRP3) inflammasome, interleukin-18 (IL-18) and nuclear factor kappa-B (NF-κB) in the serum were measured. MDD patients showed significantly higher levels of NLRP3 inflammasome, IL-18 and NF-κB than that in the controls prior to MECT, and the levels also significantly increased after MECT. In MDD patients, the serum levels of these inflammatory cytokines were negatively associated with the total WMS scores and likely contributed to the scores independently. The receiver operating characteristic curve showed that the serum levels of these inflammatory cytokines may predict the cognitive impairment risk in MDD patients receiving MECT. Abnormal levels of NLRP3 inflammasome, IL-18 and NF-κB reflecting the disturbed balance of pro-inflammatory and anti-inflammatory mechanisms likely contribute to the MECT-induced cognitive deficits in MDD patients.

Gut dysbiosis-influence on amygdala-based functional activity in patients with end stage renal disease: a preliminary study

Patients with end-stage renal disease (ESRD) are notably accompanied by cognitive disorder and anxiety or depressive symptom. We aimed to explore the linkages of the amygdala-based MR parameters, cognitive and mood performance, systematic inflammation and gut microbiota in ESRD. This prospective study enrolled 28 ESRD patients (13 males and 15 females, mean age of 43.9 ± 13.8 years) and 19 age- and sex-matched healthy control (HC) (12 males and 7 females, mean age of 44.1 ± 10.0 years). All subjects underwent cognitive assessment, inflammatory factor and stool microbiota analysis, and brain MRI analysis [amygdala-based functional connectivity and voxel-based morphometry (VBM)]. ERSD was separated by different microbiota strains. All factors were compared between ESRD and HC, as well as between ESRD subgroups. Pearson correlation analysis and causal mediation analysis were conducted to further investigate the relationship among the factors derived from the gut microbiota, brain and systemic inflammation. ESRD displayed gut dysbiosis and increased systemic inflammation when compared to HC (all P < 0.05). Meanwhile, ESRD showed smaller VBM in amygdala, decreased functional connectivity in left amygdala - right inferior parietal lobe [P < 0.05, Gaussian Random Field (GRF) corrected] and worse cognitive or mood performance. Moreover, ESRD-B (Prevutella mainly), when compared to ESRD-A (Bacteroides mainly), displayed increased interleukin-6, self-rating anxiety scale and functional connectivity in left amygdala - bilateral anterior cingulate cortex / medial superior frontal cortex (P < 0.05, GRF corrected). Furthermore, the correlation network of ESRD showed that both gut dysbiosis and amygdala-based alteration were correlated with cognitive performance and systemic inflammation. Causal mediation analysis validated that the disrupted distribution of Roseburia indirectly regulated the amygdala-based functional connectivity through tumor necrosis factor-alpha. The gut dysbiosis induced by ESRD was closely related to pro-inflammatory cytokines, amygdala-based phenotype, and mood performance. The lower abundance in Roseburia indirectly modulated amygdala-based functional connectivity pattern by tumor necrosis factor-alpha, which might provide a new way in diagnosis and treatment in patients of ESRD with depressive/anxious mood.

Microglial Pruning: Relevance for Synaptic Dysfunction in Multiple Sclerosis and Related Experimental Models

Microglia, besides being able to react rapidly to a wide range of environmental changes, are also involved in shaping neuronal wiring. Indeed, they actively participate in the modulation of neuronal function by regulating the elimination (or “pruning”) of weaker synapses in both physiologic and pathologic processes. Mounting evidence supports their crucial role in early synaptic loss, which is emerging as a hallmark of several neurodegenerative diseases, including multiple sclerosis (MS) and its preclinical models. MS is an inflammatory, immune-mediated pathology of the white matter in which demyelinating lesions may cause secondary neuronal death. Nevertheless, primitive grey matter (GM) damage is emerging as an important contributor to patients’ long-term disability, since it has been associated with early and progressive cognitive decline (CD), which seriously worsens the quality of life of MS patients. Widespread synapse loss even in the absence of demyelination, axon degeneration and neuronal death has been demonstrated in different GM structures, thus raising the possibility that synaptic dysfunction could be an early and possibly independent event in the neurodegenerative process associated with MS. This review provides an overview of microglial-dependent synapse elimination in the neuroinflammatory process that underlies MS and its experimental models.

Tumor Necrosis Factor (TNF) Is Required for Spatial Learning and Memory in Male Mice under Physiological, but Not Immune-Challenged Conditions

Increasing evidence demonstrates that inflammatory cytokines-such as tumor necrosis factor (TNF)-are produced at low levels in the brain under physiological conditions and may be crucial for synaptic plasticity, neurogenesis, learning and memory. Here, we examined the effects of developmental TNF deletion on spatial learning and memory using 11-13-month-old TNF knockout (KO) and C57BL6/J wild-type (WT) mice. The animals were tested in the Barnes maze (BM) arena under baseline conditions and 48 h following an injection of the endotoxin lipopolysaccharide (LPS), which was administered at a dose of 0.5 mg/kg. Vehicle-treated KO mice were impaired compared to WT mice during the acquisition and memory-probing phases of the BM test. No behavioral differences were observed between WT and TNF-KO mice after LPS treatment. Moreover, there were no differences in the hippocampal content of glutamate and noradrenaline between groups. The effects of TNF deletion on spatial learning and memory were observed in male, but not female mice, which were not different compared to WT mice under baseline conditions. These results indicate that TNF is required for spatial learning and memory in male mice under physiological, non-inflammatory conditions, however not following the administration of LPS. Inflammatory signalling can thereby modulate spatial cognition in male subjects, highlighting the importance of sex- and probably age-stratified analysis when examining the role of TNF in the brain.

The Interaction of Inflammatory Markers and Alcohol-Use on Cognitive Function in Korean Male Firefighters

OBJECTIVE

Cognitive functions have been shown to become impaired due to alcoholism. Recently, neuroinflammation gained attention for playing a role in the neurotoxic effect of alcohol. However, there is limited data on the relationship between alcohol and cognitive function, based on the mechanism of inflammation. This study examined whether the interaction between alcohol use and pro-inflammatory biomarkers is related to cognitive function in Korean male firefighters.

METHODS

A total of 474 firefighters were assessed for alcohol-related problems using CAGE, cognitive functions, and pro-inflammatory biomarkers (CRP, IL-6, TNF-α). Sequential multiple regression analyses were conducted to determine if inflammatory markers moderate the relationship between alcohol use and cognitive function.

RESULTS

Only a decreased attentional function was associated with the interaction of alcohol use and inflammatory markers, after controlling for age, sex, body mass index, lipid profiles, smoking, depression, fatigue, self-reported hypertension, diabetes, and musculoskeletal problems.

CONCLUSION

This study revealed that the interaction between alcohol use and inflammation is related to attentional function in Korean male firefighters. Additionally, this cross-sectional study suggests that diminishing attention, related to alcohol use, may be based on the mechanism of inflammation.

Delayed voluntary physical exercise restores "when" and "where" object recognition memory after traumatic brain injury

Physical exercise has been associated with improved cognition and may even reduce memory deficits after brain injuries. The aims of this work were to: 1) assess whether voluntary physical exercise can reduce the deficits associated with traumatic brain injury (TBI) in two different components of episodic-like memory based on object recognition, temporal order memory ("when"), and object location memory ("where"); and 2) determine whether changes in levels of brain-derived neurotrophic factor (BDNF) in the hippocampus and prefrontal cortex, as well as alterations in hippocampal cytokines, insulin-like growth factor-1 (IGF-1) and vascular endothelial growth factor (VEGF), may influence the effects exercise has on either or both tasks. The rats were distributed into a sham group, a TBI group that remained sedentary (TBI-sed), and a TBI group that had access to a running wheel for a 25-day period from post-injury day 11 (TBI-exe). The rats were sacrificed after the "where" memory task, at post-injury day 37. Physical exercise restored the "when" and "where" memories, which had been impaired by the TBI, and increased the concentration of BDNF in the hippocampus, but not the prefrontal cortex. Neither TBI nor exercise were found to significantly affect hippocampal cytokines, IGF-1 or VEGF at this time post-injury. BDNF levels showed significant positive correlations with exercise, and with "when" (but not "where") memory. These results indicate that post-injury physical exercise restores "when" and "where" object recognition memory tasks after TBI, and that increased BDNF seems to be involved in this effect, particularly with regard to "when" memory.

Peripheral inflammation exacerbates α-synuclein toxicity and neuropathology in Parkinson's models

AIMS

Parkinson's disease and related disorders are devastating neurodegenerative pathologies. Since α-synuclein was identified as a main component of Lewy bodies and neurites, efforts have been made to clarify the pathogenic mechanisms of α-synuclein's detrimental effects. α-synuclein oligomers are the most harmful species and may recruit and activate glial cells. Inflammation is emerging as a bridge between genetic susceptibility and environmental factors co-fostering Parkinson's disease. However, direct evidence linking inflammation to the harmful activities of α-synuclein oligomers or to the Parkinson's disease behavioural phenotype is lacking.

METHODS

To clarify whether neuroinflammation influences Parkinson's disease pathogenesis, we developed: (i) a 'double-hit' approach in C57BL/6 naive mice where peripherally administered lipopolysaccharides were followed by intracerebroventricular injection of an inactive oligomer dose; (ii) a transgenic 'double-hit' model where lipopolysaccharides were given to A53T α-synuclein transgenic Parkinson's disease mice.

RESULTS

Lipopolysaccharides induced a long-lasting neuroinflammatory response which facilitated the detrimental cognitive activities of oligomers. LPS-activated microglia and astrocytes responded differently to the oligomers with microglia activating further and acquiring a pro-inflammatory M1 phenotype, while astrocytes atrophied. In the transgenic 'double-hit' A53T mouse model, lipopolysaccharides aggravated cognitive deficits and increased microgliosis. Again, astrocytes responded differently to the double challenge. These findings indicate that peripherally induced neuroinflammation potentiates the α-synuclein oligomer's actions and aggravates cognitive deficits in A53T mice.

CONCLUSIONS

The fine management of both peripheral and central inflammation may offer a promising therapeutic approach to prevent or slow down some behavioural aspects in α-synucleinopathies.

Co-administration of berberine/gypenosides/bifendate ameliorates metabolic disturbance but not memory impairment in type 2 diabetic mice

Cognitive impairment is a well-known complication of Type 2 diabetes mellitus (T2DM) characterized by cellular insulin resistance, chronic inflammation, and metabolic disturbances. Berberine, gypenosides and bifendate are traditional Chinese herbal medicines with multiple pharmacological activities including anti-inflammation, anti-oxidant, metabolism improvement and memory improvement. To investigate whether they have synergistic effect on T2DM metabolic syndrome and associated memory impairment, we measured in this study the effect of a low dose of berberine/gypenosides/bifendate (BGB) co-administration on metabolism and memory performance of T2DM model mice. We found that BGB co-administration ameliorated metabolic abnormalities of both high-fat diet/streptozotocin (STZ)-induced T2DM mice and db/db mice. However, it did not alleviate memory impairment in either type of T2DM model mice. Since neither berberine, gypenosides nor bifendate alone at the low dose is effective, we presume that BGB co-administration has synergistic action on T2DM metabolic syndrome. In addition, our findings suggest that higher doses of BGB might be required to ameliorate memory impairment than metabolic disturbance associated with T2DM.

Blocking the Mineralocorticoid Receptor Improves Cognitive Impairment after Anesthesia/Splenectomy in Rats

Recent mounting studies showed that neuroinflammation caused by surgery or anesthesia is closely related to postoperative cognitive dysfunction (POCD). This study investigated the effect of mineralocorticoid receptor (MR) on neuroinflammation and POCD. To detect the MR effect in an animal model, we randomly divided rats into control, anesthesia, and surgery groups. To determine whether the MR-specific blocker eplerenone (EPL) could improve cognitive dysfunction, we assigned other animals into the control, surgery and EPL treatment, and surgery groups. Cognitive function was detected using the Morris water maze. Serum cytokine levels were measured by ELISA, and the histopathological changes of hippocampal neurons were identified by hematoxylin/eosin and Nissl staining. Our research confirmed that anesthesia and surgical stimulation could lead to IL-1β, IL-6, and TNF-α activation and hippocampal neuronal degeneration and pathological damage. MR was upregulated in the hippocampus under cognitive impairment condition. Additionally, EPL could alleviate inflammatory activation and neuronal damage by exerting neuroprotective effects. The preclinical model of sevoflurane anesthesia/splenectomy implied that MR expression is upregulated by regulating the neuroinflammation in the brain under POCD condition. Manipulating the MR expression by EPL could improve the inflammation activation and neuronal damage.

Lung pathology due to hRSV infection impairs blood-brain barrier permeability enabling astrocyte infection and a long-lasting inflammation in the CNS

The human respiratory syncytial virus (hRSV) is the most common infectious agent that affects children before two years of age. hRSV outbreaks cause a significant increase in hospitalizations during the winter season associated with bronchiolitis and pneumonia. Recently, neurologic alterations have been associated with hRSV infection in children, which include seizures, central apnea, and encephalopathy. Also, hRSV RNA has been detected in cerebrospinal fluids (CSF) from patients with neurological symptoms after hRSV infection. Additionally, previous studies have shown that hRSV can be detected in the lungs and brains of mice exposed to the virus, yet the potential effects of hRSV infection within the central nervous system (CNS) remain unknown. Here, using a murine model for hRSV infection, we show a significant behavior alteration in these animals, up to two months after the virus exposure, as shown in marble-burying tests. hRSV infection also produced the expression of cytokines within the brain, such as IL-4, IL-10, and CCL2. We found that hRSV infection alters the permeability of the blood-brain barrier (BBB) in mice, allowing the trespassing of macromolecules and leading to increased infiltration of immune cells into the CNS together with an increased expression of pro-inflammatory cytokines in the brain. Finally, we show that hRSV infects murine astrocytes both, in vitro and in vivo. We identified the presence of hRSV in the brain cortex where it colocalizes with vWF, MAP-2, Iba-1, and GFAP, which are considered markers for endothelial cells, neurons, microglia, and astrocyte, respectively. hRSV-infected murine astrocytes displayed increased production of nitric oxide (NO) and TNF-α. Our results suggest that hRSV infection alters the BBB permeability to macromolecules and immune cells and induces CNS inflammation, which can contribute to the behavioral alterations shown by infected mice. A better understanding of the neuropathy caused by hRSV could help to reduce the potential detrimental effects on the CNS in hRSV-infected patients.

Exercise alters LPS-induced glial activation in the mouse brain

Experimental and epidemiological evidence suggest that modifiable lifestyle factors, including physical exercise, can build structural and cognitive reserve in the brain, increasing resilience to injury and insult. Accordingly, exercise can reduce the increased expression of proinflammatory cytokines in the brain associated with ageing or experimentally induced neuroinflammation. However, the cellular mechanisms by which exercise exerts this effect are unknown, including the effects of exercise on classic or alternative activation of astrocytes and microglia. In the present study, we assess the effects of nine consecutive days of treadmill running on the glial cell response to a single systemic injection of lipopolysaccharide (LPS) and, in parallel, the effects on spatial learning and memory. We show that prior exercise protects against LPS-induced impairment of performance in the object displacement task concomitant with attenuation of IL-1β, TNFα and IL-10 mRNA expression in the hippocampus. Assessment of isolated astrocytes and microglia revealed that LPS induced a proinflammatory response in these cells that was not observed in cells prepared from the brains of mice who had undergone prior exercise. The results suggest that exercise modulates neuroinflammation by reducing the proinflammatory microglial response, suggesting a mechanism by which exercise may be neuroprotective.

Anti-Inflammatory Treatment with FTY720 Starting after Onset of Symptoms Reverses Synaptic Deficits in an AD Mouse Model

Therapeutic approaches providing effective medication for Alzheimer's disease (AD) patients after disease onset are urgently needed. Previous studies in AD mouse models suggested that physical exercise or changed lifestyle can delay AD-related synaptic and memory dysfunctions when treatment started in juvenile animals long before onset of disease symptoms, while a pharmacological treatment that can reverse synaptic and memory deficits in AD mice was thus far not identified. Repurposing food and drug administration (FDA)-approved drugs for treatment of AD is a promising way to reduce the time to bring such medication into clinical practice. The sphingosine-1 phosphate analog fingolimod (FTY720) was approved recently for treatment of multiple sclerosis patients. Here, we addressed whether fingolimod rescues AD-related synaptic deficits and memory dysfunction in an amyloid precursor protein/presenilin-1 (APP/PS1) AD mouse model when medication starts after onset of symptoms (at five months). Male mice received intraperitoneal injections of fingolimod for one to two months starting at five to six months. This treatment rescued spine density as well as long-term potentiation in hippocampal cornu ammonis-1 (CA1) pyramidal neurons, that were both impaired in untreated APP/PS1 animals at six to seven months of age. Immunohistochemical analysis with markers of microgliosis (ionized calcium-binding adapter molecule 1; Iba1) and astrogliosis (glial fibrillary acid protein; GFAP) revealed that our fingolimod treatment regime strongly down regulated neuroinflammation in the hippocampus and neocortex of this AD model. These effects were accompanied by a moderate reduction of Aβ accumulation in hippocampus and neocortex. Our results suggest that fingolimod, when applied after onset of disease symptoms in an APP/PS1 mouse model, rescues synaptic pathology that is believed to underlie memory deficits in AD mice, and that this beneficial effect is mediated via anti-neuroinflammatory actions of the drug on microglia and astrocytes.

Serum Tumor Necrosis Factor-Alpha Levels Correlate with Cognitive Function Scales Scores in Multiple Sclerosis Patients

BACKGROUND

Cognitive dysfunction is an important feature and source of disability for patients with multiple sclerosis (MS). The correlation of cognitive function scales' scores and serum levels of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-α) in MS is not well established. We aim to investigate the correlation of TNF-α serum levels with cognitive function as measured by multiple cognitive scales in patients with MS.

METHODS

Eligible sequential MS patients attending neurology clinics between October 2018 and June 2019 at King Abdulla University Hospital (KAUH) in Jordan were included. Demographic data were collected from all participants. Motor disability was measured using the Expanded Disability Status Score (EDSS), the Functional System Score (FSS), as well as the Patient Determined Disease Steps (PDDS). The Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS) and the Montreal Cognitive Assessment (MOCA) were used to evaluate the cognitive status. TNF-α serum levels were measured for each patient. Correlations of TNF-α levels with cognitive function scales' scores and motor disability scores were statistically analyzed.

RESULTS

A total of 88 MS patients were included in the study. The mean age (± SD) was 35.78 (± 10.30) years, and 72.7% were females. The majority of patients (82) had relapsing multiple sclerosis (RMS). Serum TNF-α levels were significantly correlated with scores of motor disability scales in the whole patient cohort (EDSS: Pearson correlation coefficient r = 0.230, p=0.031; FSS: r = 0.260, p=0.022; and PDDS: r = 0.261, p=0.014) and in females, but not in males. In the whole cohort, the correlation between TNF-α and EDSS score was also statistically significant (r = 0.216, p=0.047) after adjustment for confounding factors including age, disease duration, and type of MS. Likewise, Serum TNF-α levels were correlated with the scores of cognitive function scales in the whole patient cohort (BICAMS: r = -0.328, p=0.002; and MOCA: r = -0.256, p=0.016). After adjusting for age, gender, education, type of MS, and EDSS score, cognitive performance was still negatively correlated with TNF-α levels (p<0.05).

CONCLUSION

Our findings confirm the presence of a significant correlation between TNF-α levels and different cognitive scales' scores in MS patients.

Modeling alcohol-induced neurotoxicity using human induced pluripotent stem cell-derived three-dimensional cerebral organoids

Maternal alcohol exposure during pregnancy can substantially impact the development of the fetus, causing a range of symptoms, known as fetal alcohol spectrum disorders (FASDs), such as cognitive dysfunction and psychiatric disorders, with the pathophysiology and mechanisms largely unknown. Recently developed human cerebral organoids from induced pluripotent stem cells are similar to fetal brains in the aspects of development and structure. These models allow more relevant in vitro systems to be developed for studying FASDs than animal models. Modeling binge drinking using human cerebral organoids, we sought to quantify the downstream toxic effects of alcohol (ethanol) on neural pathology phenotypes and signaling pathways within the organoids. The results revealed that alcohol exposure resulted in unhealthy organoids at cellular, subcellular, bioenergetic metabolism, and gene expression levels. Alcohol induced apoptosis on organoids. The apoptotic effects of alcohol on the organoids depended on the alcohol concentration and varied between cell types. Specifically, neurons were more vulnerable to alcohol-induced apoptosis than astrocytes. The alcohol-treated organoids exhibit ultrastructural changes such as disruption of mitochondria cristae, decreased intensity of mitochondrial matrix, and disorganized cytoskeleton. Alcohol exposure also resulted in mitochondrial dysfunction and metabolic stress in the organoids as evidenced by (1) decreased mitochondrial oxygen consumption rates being linked to basal respiration, ATP production, proton leak, maximal respiration and spare respiratory capacity, and (2) increase of non-mitochondrial respiration in alcohol-treated organoids compared with control groups. Furthermore, we found that alcohol treatment affected the expression of 199 genes out of 17,195 genes analyzed. Bioinformatic analyses showed the association of these dysregulated genes with 37 pathways related to clinically relevant pathologies such as psychiatric disorders, behavior, nervous system development and function, organismal injury and abnormalities, and cellular development. Notably, 187 of these genes are critically involved in neurodevelopment, and/or implicated in nervous system physiology and neurodegeneration. Furthermore, the identified genes are key regulators of multiple pathways linked in networks. This study extends for the first time animal models of binge drinking-related FASDs to a human model, allowing in-depth analyses of neurotoxicity at tissue, cellular, subcellular, metabolism, and gene levels. Hereby, we provide novel insights into alcohol-induced pathologic phenotypes, cell type-specific vulnerability, and affected signaling pathways and molecular networks, that can contribute to a better understanding of the developmental neurotoxic effects of binge drinking during pregnancy.

Relationships of Stresses on Alveolar Bone and Abutment of Dental Implant from Various Bite Forces by Three-Dimensional Finite Element Analysis

Occlusal trauma caused by improper bite forces owing to the lack of periodontal membrane may lead to bone resorption, which is still a problem for the success of dental implant. In our study, to avoid occlusal trauma, we put forward a hypothesis that a microelectromechanical system (MEMS) pressure sensor is settled on an implant abutment to track stress on the abutment and predict the stress on alveolar bone for controlling bite forces in real time. Loading forces of different magnitudes (0 N–100 N) and angles (0–90°) were applied to the crown of the dental implant of the left central incisor in a maxillary model. The stress distribution on the abutment and alveolar bone were analyzed using a three-dimensional finite element analysis (3D FEA). Then, the quantitative relation between them was derived using Origin 2017 software. The results show that the relation between the loading forces and the stresses on the alveolar bone and abutment could be described as 3D surface equations associated with the sine function. The appropriate range of stress on the implant abutment is 1.5 MPa–8.66 MPa, and the acceptable loading force range on the dental implant of the left maxillary central incisor is approximately 6 N–86 N. These results could be used as a reference for the layout of MEMS pressure sensors to maintain alveolar bone dynamic remodeling balance.

Deconstructing the effects of concentration meditation practice on interference control: The roles of controlled attention and inflammatory activity

Prior work has linked meditation practice to improvements in interference control. However, the mechanisms underlying these improvements are relatively unknown. In the context of meditation training, improvements in interference control could result eitherfrom increases in controlled attention to goal-relevant stimuli, or from reductions in automatic capture by goal-irrelevant stimuli. Moreover, few studies have linked training-related changes in attention to physiological processes, such as inflammatory activity, that are thought to influence cognitive function. This study addresses these gaps by examining associations between cognitive performance and cytokines in the context of an intensive meditation retreat. Participants were randomly assigned to complete 3 months of meditation training first, or to serve as waitlist controls. The waitlist-control participants then later completed a separate 3-month training intervention. We assessed participants' interference control with a flanker task and used computational modeling to derive component processes of controlled and automatic attention. We also collected blood samples at the beginning, middle, and end of training to quantify changes in cytokine activity. Participants who completed training evidenced better controlled attention than waitlist controls during the first retreat intervention, and controls showed significant improvements in controlled attention when they completed their own, second retreat. Importantly, inflammatory activity was inversely associated with controlled attention during both interventions. Our results suggest that practice of concentration meditation influences interference control by enhancing controlled attention to goal-relevant task elements, and that inflammatory activity relates to individual differences in controlled attention.

Langat virus infection affects hippocampal neuron morphology and function in mice without disease signs

Background

Tick-borne encephalitis virus (TBEV) is an important human pathogen that can cause the serious illness tick-borne encephalitis (TBE). Patients with clinical symptoms can suffer from severe meningoencephalitis with sequelae that include cognitive disorders and paralysis. While less than 30% of patients with clinical symptoms develop meningoencephalitis, the number of seropositive individuals in some regions indicates a much higher prevalence of TBEV infections, either with no or subclinical symptoms. The functional relevance of these subclinical TBEV infections and their influence on brain functions, such as learning and memory, has not been investigated so far.

Methods

To compare the effect of low and high viral replication in the brain, wildtype and Irf-7^−/− mice were infected with Langat virus (LGTV), which belongs to the TBEV-serogroup. The viral burden was analyzed in the olfactory bulb and the hippocampus. Open field, elevated plus maze, and Morris water maze experiments were performed to determine the impact on anxiety-like behavior, learning, and memory formation. Spine density of hippocampal neurons and activation of microglia and astrocytes were analyzed.

Results

In contrast to susceptible Irf-7^−/− mice, wildtype mice showed no disease signs upon LGTV infection. Detection of viral RNA in the olfactory bulb revealed CNS infections in wildtype and Irf-7^−/− mice. Very low levels of viral replication were detectable in the hippocampus of wildtype mice. Although wildtype mice develop no disease signs, they showed reduced anxiety-like behavior and impaired memory formation, whereas Irf-7^−/− mice were not affected. This impairment was associated with a significant decrease in spine density of neurons in the hippocampal CA1 region of wildtype mice. Microglia activation and astrogliosis were detected in the hippocampus.

Conclusion

In this study, we demonstrate that subclinical infections by viruses from the TBEV-serogroup affected anxiety-like behavior. Virus replication in the olfactory bulb induced far-reaching effects on hippocampal neuron morphology and impaired hippocampus-dependent learning and memory formation.

Paraquat increases Interleukin-1β in hippocampal dentate gyrus to impair hippocampal neurogenesis in adult mice

Paraquat (1,1'-dimethyl-4,4'-bipyridium dichloride, PQ), a non-selective and efficient herbicide, causes neuroinflammation, neurodegeneration and memory dysfunction. However, adverse effects of PQ on the neuroimmune interactions have rarely been investigated. Female adult C57/BL6 mice were divided into 3 groups and treated with PQ (intraperitoneal injection, 1 mg/kg or 5 mg/kg) or the vehicle (an equivalent volume of 0.9% saline) every two days, at day 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, for a total of 14 doses. We evaluated blood-brain barrier (BBB) integrity and PQ concentrations during the course of PQ exposure and tested interleukin-1β (IL-1β) concentrations in dentate gyrus (DG) after 28 days PQ exposure. In addition, memory function, neural stem cells (NSCs) proliferation, neurogenesis and microglia polarization were analyzed after PQ exposure. Furthermore, mice were intraperitoneal injections of anti-IL-1β during 5 mg/kg PQ exposure to test the rule of IL-1β. Blood-brain barrier (BBB) permeability and PQ concentrations increased gradually during PQ exposure (n = 6). Moreover, memory function, NSCs proliferation and neurogenesis were impaired after 5 mg/kg PQ exposure (n = 6). Further analyses revealed that 'classically' activated (M1) microglia and IL-1β concentrations in DG were increased after 5 mg/kg PQ treatment (n = 6). Moreover, we found that neutralization of IL-1β partly restored PQ-induced NSCs impairments and memory dysfunction (n = 6). In conclusion, our results revealed that PQ induced NSCs impairments and memory dysfunction in adult mice, which was related to the release of IL-1β by M1-polarized microglia in DG. These findings may help understand the neurotoxic effect of PQ.

Effect of age at menarche on the mother's weight status two and four years after delivery: a cohort study

We aimed to estimate the effect of age at menarche on the risk of excess body weight in Brazilian women two and four years after delivery. This was a cohort study that used data from adult women of the Predictors of Maternal and Child Excess Body Weight (PREDI) Study obtained at baseline (2012) and at 1^st(2014) and 2^nd(2016) follow-up. A total of 435 women attending a public maternity hospital in Joinville-Brazil were initially included in the study (baseline) and 215 of them continued to participate in the 2^nd follow-up carried out in the homes of the participants. Regression analysis was used to estimate the association between age at menarche (<12; ≥12 years) and excess body weight (≥25 kg/m²) trajectory during the follow-ups. Unadjusted analysis showed that mothers with age at menarche <12 years were 1.29 times (p = .018) more likely to be overweight/obese than those with age at menarche ≥12 years. After adjustment, age at menarche continued to exert an independent effect on the mother's body mass index (RR = 1.23; p = .037) four years after delivery. Strategies designed to attenuate the rising prevalence of maternal overweight and obesity, especially after pregnancy, could help improve the mother's health status in the future.

Interferon-gamma Facilitates Neurogenesis by Activating Wnt/β-catenin Cell Signaling Pathway via Promotion of STAT1 Regulation of the β-Catenin Promoter

Interferon-gamma (IFN-γ) is critical for central nervous system (CNS) functions and it may be a promising treatment to stimulate CNS regeneration. However, previous studies reported inconsistent results, and the molecular mechanisms remain controversial. Here we show that IFN-γ-treated mice via intraperitoneal injection have elevated IFN-γ level in central hippocampus and superior cognitive behaviors IFN-γ could activates the level of protein expression of Wnt7a, β-catenin, and CyclinD1 in Wnt/β-catenin signaling pathway of mice hippocampus. Functional and mechanism analysis in vitro revealed that IFN-γ promoted the proliferation and differentiation in primary cultured neural stem cells (NSCs). STAT1 was accountable for IFN-γ-induced activation of the β-catenin promoter, and IFN-γ increased the binding affinity of STAT1 to β-catenin promoter based on luciferase activity and chromatin immunoprecipitation. Our results suggest that IFN-γ exerts many effects ranging from cognitive function in vivo to NSC proliferation, self-renewal, and differentiation in vitro. It does so by recruiting STAT1 to the β-catenin promoter, enhancing cis-regulation by STAT1, and ultimately activating Wnt/β-catenin signaling. In this study, we first found that STAT1 was recruited into the promoter of β-catenin to activate β-catenin expression, and this effect was regulated by IFN-γ. It is also discovered firstly that Wnt/β-catenin and JAK/STAT pathways form cross-links through STAT1. Promoting neurogenesis through immune stimulation might be a promising strategy for repairing the diseased/injured CNS. This study provides a scientific basis for immunomodulation to promote nerve regeneration and offer a new therapeutic direction for central nervous system regeneration.

Tumor Necrosis Factor α Influences Phenotypic Plasticity and Promotes Epigenetic Changes in Human Basal Forebrain Cholinergic Neuroblasts

TNFα is the main proinflammatory cytokine implicated in the pathogenesis of neurodegenerative disorders, but it also modulates physiological functions in both the developing and adult brain. In this study, we investigated a potential direct role of TNFα in determining phenotypic changes of a recently established cellular model of human basal forebrain cholinergic neuroblasts isolated from the nucleus basalis of Meynert (hfNBMs). Exposing hfNBMs to TNFα reduced the expression of immature markers, such as nestin and β-tubulin III, and inhibited primary cilium formation. On the contrary, TNFα increased the expression of TNFα receptor TNFR2 and the mature neuron marker MAP2, also promoting neurite elongation. Moreover, TNFα affected nerve growth factor receptor expression. We also found that TNFα induced the expression of DNA-methylation enzymes and, accordingly, downregulated genes involved in neuronal development through epigenetic mechanisms, as demonstrated by methylome analysis. In summary, TNFα showed a dual role on hfNBMs phenotypic plasticity, exerting a negative influence on neurogenesis despite a positive effect on differentiation, through mechanisms that remain to be elucidated. Our results help to clarify the complexity of TNFα effects in human neurons and suggest that manipulation of TNFα signaling could provide a potential therapeutic approach against neurodegenerative disorders.

Impact of acute inflammation on the extinction of aversive gut memories

Impaired extinction of pain-related fear memories can lead to persistent or resurging fear of pain, contributing to the development and maintenance of chronic pain conditions. The mechanisms underlying maladaptive pain-related learning and memory processes remain incompletely understood, particularly in the context of interoceptive, visceral pain. Inflammation is known to interfere with learning and memory, but its effects on the extinction of pain-related fear memories have never been tested. In a randomized, double-blind, placebo-controlled study, we assessed the impact of experimental acute inflammation on the extinction and reinstatement of conditioned visceral pain-related fear. Forty healthy male volunteers underwent differential fear conditioning with visceral pain as clinically relevant unconditioned stimulus (US). Participants then received an intravenous injection of either 0.8 ng/kg lipopolysaccharide (LPS) as inflammatory stimulus or physiological saline as placebo, and extinction training was conducted at the peak of the inflammatory response. Extinction recall and reinstatement test were performed after overnight consolidation. Results showed that visceral pain represents an effective US, eliciting pronounced conditioned pain-related fear responses. Repeated unreinforced presentation of the pain-predictive cue during extinction training resulted in full extinction of the conditioned behavioral response. However, unexpected re-exposure to the US during reinstatement test resulted in return of fear. Despite pronounced LPS-induced effects on inflammatory markers, cortisol, and negative affect, we did not find evidence that acute inflammation resulted in altered fear extinction. The findings support the notion that visceral pain-related fear learning establishes a robust aversive memory trace that remains preserved during inhibitory learning, leaving a latent vulnerability for the return of fear. Inflammation during inhibitory learning did neither weaken nor further amplify this aversive memory trace, suggesting that it is rather resistant to acute inflammation-induced effects, at least in healthy individuals with no additional vulnerability factors.

Behavioral and neurobiological alterations induced by chronic use of crack cocaine

Crack cocaine is the crystal form of cocaine and can be smoked, and rapidly absorbed, and, in part for this reason, is potently addictive. It is hypothesized that crack cocaine is able to induce important changes in different tissues and organs, and thus dramatically alter behavior. Nevertheless, which alterations in the central nervous system are related to its frequent use is still a matter of discussion. The present study is a literature review of articles published between the years 2008 and 2018 on the theme 'crack cocaine and brain' available in PUBMED, MEDLINE, EMBASE, and Google scholar databases. The results show that the use of crack cocaine induces important behavioral, neuroanatomical, and biochemical alterations. The main behavioral sequelae include cognitive and emotional changes, such as increased anxiety and depressive symptoms, attention and memory deficits, and hyperactivity. Among the neurobiological alterations are reductions in the activity of the prefrontal, anterior cingulate cortex, and nucleus accumbens. Molecular changes include decreases in neurotrophic factors and increases in oxidative stress and inflammatory cytokines, which may be responsible for the morphological alterations observed. It is also hypothesized that these neurobiological changes might explain the emotional and cognitive dysfunctions experienced by crack cocaine addicts.

Molecular changes in glaucomatous trabecular meshwork. Correlations with retinal ganglion cell death and novel strategies for neuroprotection

Glaucoma is a chronic neurodegenerative disease characterized by retinal ganglion cell loss. Although significant advances in ophthalmologic knowledge and practice have been made, some glaucoma mechanisms are not yet understood, therefore, up to now there is no effective treatment able to ensure healing. Indeed, either pharmacological or surgical approaches to this disease aim in lowering intraocular pressure, which is considered the only modifiable risk factor. However, it is well known that several factors and metabolites are equally (if not more) involved in glaucoma. Oxidative stress, for instance, plays a pivotal role in both glaucoma onset and progression because it is responsible for the trabecular meshwork cell damage and, consequently, for intraocular pressure increase as well as for glaucomatous damage cascade. This review at first shows accurately the molecular-derived dysfunctions in antioxidant system and in mitochondria homeostasis which due to both oxidative stress and aging, lead to a chronic inflammation state, the trabecular meshwork damage as well as the glaucoma neurodegeneration. Therefore, the main molecular events triggered by oxidative stress up to the proapoptotic signals that promote the ganglion cell death have been highlighted. The second part of this review, instead, describes some of neuroprotective agents such as polyphenols or polyunsaturated fatty acids as possible therapeutic source against the propagation of glaucomatous damage.

[Mental disorders and cognitive impairment in patients with antiphospholipid syndrome]

Mental disorders (mainly anxiety and depressive disorders) and cognitive impairment are often found in patients with antiphospholipid syndrome (APS), but their prevalence, structure, and mechanisms of occurrence are not well researched. The review provides literature data on the frequency, spectrum and possible causes of mental disorders and cognitive impairment in patients with APS, the pathogenetic mechanisms of these disorders (in particular, the important role of antiphospholipid antibodies, stress factors, chronic inflammation), the relationship between APS, mental disorders and as well as cognitive impairment is examined. Special attention is paid to the influence of mental disorders and cognitive impairment on patients adherence to treatment, their quality of life, as well as the particularities of psychopharmacotherapy of mental disorders in patients with APS. The aim of the review is to actualize the interdisciplinary problem of mental disorders and cognitive impairment in patients with APS and the need to introduce a partnership model of care.

Effect of mobile phone radiation on oxidative stress, inflammatory response, and contextual fear memory in Wistar rat

In the present lifestyle, we are continuously exposed to radiofrequency electromagnetic field (RF-EMF) radiation generated mainly by mobile phones (MP). Among other organs, our brain and hippocampus in specific, is the region where effect of any environmental perturbation is most pronounced. So, this study was aimed to examine changes in major parameters (oxidative stress, level of pro-inflammatory cytokines (PICs), hypothalamic-pituitary-adrenal (HPA) axis hormones, and contextual fear conditioning) which are linked to hippocampus directly or indirectly, upon exposure to mobile phone radiofrequency electromagnetic field (MP-RF-EMF) radiation. Exposure was performed on young adult male Wistar rats for 16 weeks continuously (2 h/day) with MP-RF-EMF radiation having frequency, power density, and specific absorption rate (SAR) of 1966.1 MHz, 4.0 mW/cm², and 0.36 W/kg, respectively. Another set of animals kept in similar conditions without any radiation exposure serves as control. Towards the end of exposure period, animals were tested for fear memory and then euthanized to measure hippocampal oxidative stress, level of circulatory PICs, and stress hormones. We observed significant increase in hippocampal oxidative stress (p < 0.05) and elevated level of circulatory PICs viz. IL-1beta (p < 0.01), IL-6 (p < 0.05), and TNF-alpha (p < 0.001) in experimental animals upon exposure to MP-RF-EMF radiation. Adrenal gland weight (p < 0.001) and level of stress hormones viz. adrenocorticotropic hormone (ACTH) (p < 0.01) and corticosterone (CORT) (p < 0.05) were also found to increase significantly in MP-RF-EMF radiation-exposed animals as compared with control. However, alteration in contextual fear memory was not significant enough. In conclusion, current study shows that chronic exposure to MP-RF-EMF radiation emitted from mobile phones may induce oxidative stress, inflammatory response, and HPA axis deregulation. However, changes in hippocampal functionality depend on the complex interplay of several opposing factors that got affected upon MP-RF-EMF exposure.

Dysregulation of inflammation, neurobiology, and cognitive function in PTSD: an integrative review

Compelling evidence from animal and human research suggest a strong link between inflammation and posttraumatic stress disorder (PTSD). Furthermore, recent findings support compromised neurocognitive function as a key feature of PTSD, particularly with deficits in attention and processing speed, executive function, and memory. These cognitive domains are supported by brain structures and neural pathways that are disrupted in PTSD and which are implicated in fear learning and extinction processes. The disruption of these supporting structures potentially results from their interaction with inflammation. Thus, the converging evidence supports a model of inflammatory dysregulation and cognitive dysfunction as combined mechanisms underpinning PTSD symptomatology. In this review, we summarize evidence of dysregulated inflammation in PTSD and further explore how the neurobiological underpinnings of PTSD, in the context of fear learning and extinction acquisition and recall, may interact with inflammation. We then present evidence for cognitive dysfunction in PTSD, highlighting findings from human work. Potential therapeutic approaches utilizing novel pharmacological and behavioral interventions that target inflammation and cognition also are discussed.

Role of Glia in the Regulation of Sleep in Health and Disease

Sleep is a naturally occurring physiological state that is required to sustain physical and mental health. Traditionally viewed as strictly regulated by top-down control mechanisms, sleep is now known to also originate locally. Glial cells are emerging as important contributors to the regulation of sleep-wake cycles, locally and among dedicated neural circuits. A few pioneering studies revealed that astrocytes and microglia may influence sleep pressure, duration as well as intensity, but the precise involvement of these two glial cells in the regulation of sleep remains to be fully addressed, across contexts of health and disease. In this overview article, we will first summarize the literature pertaining to the role of astrocytes and microglia in the regulation of sleep under normal physiological conditions. Afterward, we will discuss the beneficial and deleterious consequences of glia-mediated neuroinflammation, whether it is acute, or chronic and associated with brain diseases, on the regulation of sleep. Sleep disturbances are a main comorbidity in neurodegenerative diseases, and in several brain diseases that include pain, epilepsy, and cancer. Identifying the relationships between glia-mediated neuroinflammation, sleep-wake rhythm disruption and brain diseases may have important implications for the treatment of several disorders. © 2020 American Physiological Society. Compr Physiol 10:687-712, 2020.

Chronic alcohol-induced liver injury correlates with memory deficits: Role for neuroinflammation

Alcohol use disorder (AUD) affects over 15 million adults over age 18 in the United States, with estimated costs of 220 billion dollars annually - mainly due to poor quality of life and lost productivity, which in turn is intricately linked to cognitive dysfunction. AUD-induced neuroinflammation in the brain, notably the hippocampus, is likely to contribute to cognitive impairments. The neuroinflammatory mechanisms mediating the impact of chronic alcohol on the central nervous system, specifically cognition, require further study. We hypothesized that chronic alcohol consumption impairs memory and increases the inflammatory cytokines TNFα, IL6, MCP1, and IL1β in the hippocampus and prefrontal cortex regions in the brain. Using the chronic-binge Gao-NIAAA alcohol mouse model of liver disease, representative of the drinking pattern common to human alcoholics, we investigated behavioral and neuroinflammatory parameters. Our data show that chronic alcohol intake elevated peripheral and brain alcohol levels, induced serum alanine aminotransferase (ALT, a marker of liver injury), impaired memory and sensorimotor coordination, and increased inflammatory gene expression in the hippocampus and prefrontal cortex. Interestingly, serum ALT and hippocampal IL6 correlated with memory impairment, suggesting an intrinsic relationship between neuroinflammation, cognitive decline, and liver disease. Overall, our results point to a likely liver-brain functional partnership and suggest that future strategies to alleviate hepatic and/or neuroinflammatory impacts of chronic AUD may result in improved cognitive outcomes.

Stress and cognition: A user's guide to designing and interpreting studies

Fueling the rapid growth in our understanding of how stress influences cognition, the number of studies examining the effects of stress on various cognitive processes has grown substantially over the last two decades. Despite this growth, few published guidelines exist for designing these studies, and divergent paradigm designs can diminish typical effects of stress or even reverse them. The goal of this review, therefore, is to survey necessary considerations (e.g., validating a stress induction), important considerations (e.g., specifying the timing of the stressor and cognitive task), and best practices (e.g., using Bayesian analyses) when designing a study that aims at least in part to examine the effects of acute stress on some cognitive process or function. These guidelines will also serve to help readers of these studies interpret what may otherwise be very confusing, anomalous results. Designing and interpreting studies with these considerations and practices in mind will help to move the field of stress and cognition forward by clarifying how, exactly, stress influences performance on a given cognitive task in a population of interest.

NADPH oxidase 2 as a potential therapeutic target for protection against cognitive deficits following systemic inflammation in mice

BACKGROUND

Research indicates that sepsis increases the risk of developing cognitive impairment. After systemic inflammation, a corresponding activation of microglia is rapidly induced in the brain, and multiple neurotoxic factors, including inflammatory mediators (e.g., cytokines) and reactive oxygen species (e.g., superoxide), are also released that contribute to neuronal injury. NADPH oxidase (NOX) enzymes play a vital role in microglial activation through the generation of superoxide anions. We hypothesized that NOX isoforms, particularly NOX2, could exhibit remarkable abilities in developing cognitive deficits induced by systemic inflammation.

METHODS

Mice with deficits of NOX2 organizer p47phox (p47^phox-/-) and wild-type (WT) mice treated with the NOX inhibitor diphenyleneiodonium (DPI) were used in this study. Intraperitoneal lipopolysaccharide (LPS) injection was used to induce systemic inflammation. Spatial learning and memory were compared among treatment groups using the radial arm maze task. Brain tissues were collected for evaluating the transcript levels of proinflammatory cytokines, whereas immunofluorescence staining and immunoblotting were conducted to determine the percentage of activated glia (microglia and astroglia) and damaged neurons and the expression of synaptic proteins and BDNF.

RESULTS

Cognitive impairment induced by systemic inflammation was significantly attenuated in the p47^phox-/- mice compared to that in the WT mice. The p47^phox-/- mice exhibited reduced microglial and astroglial activation and neuronal damage and attenuated the induction of multiple proinflammatory cytokines, including tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and CCL2. Similar to that observed in the p47^phox-/- mice, the administration of DPI significantly attenuated the cognitive impairment, reduced the glial activation and brain cytokine concentrations, and restored the expression of postsynaptic proteins (PSD-95) and BDNF in neurons and astrocytes, compared to those in the vehicle-treated controls within 10 days after LPS injection.

CONCLUSIONS

This study clearly demonstrates that NOX2 contributes to glial activation with subsequent reduction in the expression of BDNF, synaptic dysfunction, and cognitive deficits after systemic inflammation in an LPS-injected mouse model. Our results provide evidence that NOX2 might be a promising pharmacological target that could be used to protect against synaptic dysregulation and cognitive impairment following systemic inflammation.

The role of cytokines in modulating learning and memory and brain plasticity

Cytokines are proteins secreted in the central nervous system by neurons, microglia, astrocytes and infiltrating peripheral immune cells under physiological and pathological conditions. Over the last 20 years, a growing number of reports have investigated the effects of these molecules on brain plasticity. In this review, we describe how the key cytokines interleukin 1β, interleukin 6 and tumour necrosis factor α were found to support long-term plasticity and learning and memory processes in physiological conditions. In contrast, during inflammation where cytokines levels are elevated such as in models of brain injury or infection, depression or neurodegeneration, the effects of cytokines are mostly detrimental to memory mechanisms, associated behaviours and homeostatic plasticity.

Enduring and Sex-specific Changes in Hippocampal Gene Expression after a Subchronic Immune Challenge

Major illnesses, including heart attack and sepsis, can cause cognitive impairments, depression, and progressive memory decline that persist long after recovery from the original illness. In rodent models of sepsis or subchronic immune challenge, memory deficits also persist for weeks or months, even in the absence of ongoing neuroimmune activation. This raises the question of what mechanisms in the brain mediate such persistent changes in neural function. Here, we used RNA-sequencing as a large-scale, unbiased approach to identify changes in hippocampal gene expression long after a subchronic immune challenge previously established to cause persistent memory impairments in both males and females. We observed enduring dysregulation of gene expression three months after the end of a subchronic immune challenge. Surprisingly, there were striking sex differences in both the magnitude of changes and the specific genes and pathways altered, where males showed persistent changes in both immune- and plasticity-related genes three months after immune challenge, whereas females showed few such changes. In contrast, females showed striking differential gene expression in response to a subsequent immune challenge. Thus, immune activation has enduring and sex-specific consequences for hippocampal gene expression and the transcriptional response to subsequent stimuli. Together with findings of long-lasting memory impairments after immune challenge, these data suggest that illnesses can cause enduring vulnerability to, cognitive decline, affective disorders, and memory impairments via dysregulation of transcriptional processes in the brain.

Nightmares and the Cannabinoids

The cannabinoids, Δ9 tetrahydrocannabinol and its analogue, nabilone, have been found to reliably attenuate the intensity and frequency of post-traumatic nightmares. This essay examines how a traumatic event is captured in the mind, after just a single exposure, and repeatedly replicated during the nights that follow. The adaptive neurophysiological, endocrine and inflammatory changes that are triggered by the trauma and that alter personality and behavior are surveyed. These adaptive changes, once established, can be difficult to reverse. But cannabinoids, uniquely, have been shown to interfere with all of these post-traumatic somatic adaptations. While cannabinoids can suppress nightmares and other symptoms of post-traumatic stress disorder, they are not a cure. There may be no cure. The cannabinoids may best be employed, alone, but more likely in conjunction with other agents, in the immediate aftermath of a trauma to mitigate or even abort the metabolic changes which are set in motion by the trauma and which may permanently alter the reactivity of the nervous system. Steps in this direction have already been taken.

Interferon-γ potentiates GABAA receptor-mediated inhibitory currents in rat hippocampal CA1 pyramidal neurons

The neural transmission and plasticity can be differentially modulated by various elements of the immune system. Interferon-γ (IFN-γ) is a "pro-inflammatory" cytokine mainly produced by T lymphocytes, activates its corresponding receptor and plays important roles under both homeostatic and inflammatory conditions. However, the impact of IFN-γ on the γ-aminobutyric acid (GABA)-mediated currents in the hippocampus, a major brain region involved in the cognitive function, has not been investigated. Here we detected abundant expression of both IFN-γ receptor subunit gene transcripts (Ifngr1 and Ifngr2) in the rat hippocampus by quantitative PCR. In addition, we pre-incubated rat hippocampal slices with IFN-γ (100 ng/ml) and recorded GABA-activated spontaneous and miniature postsynaptic inhibitory currents (sIPSCs and mIPSCs) and tonic currents in hippocampal CA1 pyramidal neurons by the whole-cell patch-clamp method. The pre-incubation with IFN-γ increased the frequency but not the mean amplitude, rise time or decay time of both sIPSCs and mIPSCs in hippocampal CA1 pyramidal neurons, suggesting a presynaptic effect of IFN-γ. Moreover, the GABA-activated tonic currents were enhanced by IFN-γ. In conclusion, the potentiation of GABAergic currents in hippocampal neurons by IFN-γ may contribute to the disturbed neuronal excitability and cognitive dysfunction during neuroinflammation.

Adipocyte cannabinoid CB1 receptor deficiency alleviates high fat diet-induced memory deficit, depressive-like behavior, neuroinflammation and impairment in adult neurogenesis

BACKGROUND

Obesity is a low-grade inflammation condition that facilitates the development of numerous comorbidities and the dysregulation of brain homeostasis. Additionally, obesity also causes distinct behavioral alterations both in humans and rodents. Here, we investigated the effect of inducible genetic deletion of the cannabinoid type 1 receptor (CB1) in adipocytes (Ati-CB1-KO mice) on obesity-induced memory deficits, depressive-like behavior, neuroinflammation and adult neurogenesis.

METHODS

Behavioral, mRNA expression and immunohistochemical studies were performed in Ati-CB1-KO mice and corresponding wild-type controls under standard and high-fat diet.

RESULTS

Adipocyte-specific CB1 deletion reversed metabolic disturbances associated with an obese condition confirming previous studies. As compared to obese mice, the metabolic amelioration in Ati-CB1-KO mice was associated with an improvement of mood-related behavior and recognition memory, concomitantly with an increase in cell proliferation in metabolic relevant neurogenic niches in hippocampus and hypothalamus. In mutant mice, these changes were related to an increased neuronal maturation/survival in the hippocampus. Furthermore, CB1 deletion in adipocytes was sufficient to reduce obesity-induced inflammation, gliosis and apoptosis in a brain region-specific manner.

CONCLUSIONS

Overall our data provide compelling evidence of the physiological relevance of the adipocyte-brain crosstalk where adipocyte-specific CB1 influences obesity-related cognitive deficits and depression-like behavior, concomitantly with brain remodeling, such as adult neurogenesis and neuroinflammation in the hippocampus and hypothalamus.

Obesity-related cognitive impairment: The role of endothelial dysfunction

Obesity is a global pandemic associated with macro- and microvascular endothelial dysfunction. Microvascular endothelial dysfunction has recently emerged as a significant risk factor for the development of cognitive impairment. In this review, we present evidence from clinical and preclinical studies supporting a role for obesity in cognitive impairment. Next, we discuss how obesity-related hyperinsulinemia/insulin resistance, systemic inflammation, and gut dysbiosis lead to cognitive impairment through induction of endothelial dysfunction and disruption of the blood brain barrier. Finally, we outline the potential clinical utility of dietary interventions, exercise, and bariatric surgery in circumventing the impacts of obesity on cognitive function.

CCL2/CCR2 Chemokine System in Embryonic Hypothalamus: Involvement in Sexually Dimorphic Stimulatory Effects of Prenatal Ethanol Exposure on Peptide-Expressing Neurons

Maternal consumption of ethanol during pregnancy is known to increase the offspring's risk for developing alcohol use disorders and associated behavioral disturbances. Studies in adolescent and adult animals suggest the involvement of neuroimmune and neurochemical systems in the brain that control these behaviors. To understand the origin of these effects during early developmental stages, we examined in the embryo and neonate the effects of maternal intraoral administration of ethanol (2 g/kg/day) from embryonic day 10 (E10) to E15 on the inflammatory chemokine C-C motif ligand 2 (CCL2) and its receptor CCR2 in a specific, dense population of neurons in the lateral hypothalamus (LH), where they are closely related to an orexigenic neuropeptide, melanin-concentrating hormone (MCH), known to promote ethanol consumption and related behaviors. We found that prenatal ethanol exposure increases the expression and density of CCL2 and CCR2 cells along with MCH neurons in the LH and the colocalization of CCL2 with MCH. We also discovered that these effects are sexually dimorphic, consistently stronger in female embryos, and are blocked by maternal administration of a CCL2 antibody (1 and 5 µg/day, i.p., E10-E15) that neutralizes endogenous CCL2 and of a CCR2 antagonist INCB3344 (1 mg/day, i.p., E10-E15) that blocks CCL2's main receptor. These results, which in the embryo anatomically and functionally link the CCL2/CCR2 system to MCH neurons in the LH, suggest an important role for this neuroimmune system in mediating ethanol's sexually dimorphic, stimulatory effect on MCH neurons that may promote higher level of alcohol consumption described in females.