Molecular mechanisms involved in interleukin 1-beta (IL-1β)-induced memory impairment. Modulation by alpha-melanocyte-stimulating hormone (α-MSH)

IL-1β, the first piece to the puzzle of sepsis-related cognitive impairment?

Sepsis is a leading cause of death resulting from an uncontrolled inflammatory response to an infectious agent. Multiple organ injuries, including brain injuries, are common in sepsis. The underlying mechanism of sepsis-associated encephalopathy (SAE), which is associated with neuroinflammation, is not yet fully understood. Recent studies suggest that the release of interleukin-1β (IL-1β) following activation of microglial cells plays a crucial role in the development of long-lasting neuroinflammation after the initial sepsis episode. This review provides a comprehensive analysis of the recent literature on the molecular signaling pathways involved in microglial cell activation and interleukin-1β release. It also explores the physiological and pathophysiological role of IL-1β in cognitive function, with a particular focus on its contribution to long-lasting neuroinflammation after sepsis. The findings from this review may assist healthcare providers in developing novel interventions against SAE.

The Influence of Microglia on Neuroplasticity and Long-Term Cognitive Sequelae in Long COVID: Impacts on Brain Development and Beyond

Microglial cells, the immune cells of the central nervous system, are key elements regulating brain development and brain health. These cells are fully responsive to stressors, microenvironmental alterations and are actively involved in the construction of neural circuits in children and the ability to undergo full experience-dependent plasticity in adults. Since neuroinflammation is a known key element in the pathogenesis of COVID-19, one might expect the dysregulation of microglial function to severely impact both functional and structural plasticity, leading to the cognitive sequelae that appear in the pathogenesis of Long COVID. Therefore, understanding this complex scenario is mandatory for establishing the possible molecular mechanisms related to these symptoms. In the present review, we will discuss Long COVID and its association with reduced levels of BDNF, altered crosstalk between circulating immune cells and microglia, increased levels of inflammasomes, cytokines and chemokines, as well as the alterations in signaling pathways that impact neural synaptic remodeling and plasticity, such as fractalkines, the complement system, the expression of SIRPα and CD47 molecules and altered matrix remodeling. Together, these complex mechanisms may help us understand consequences of Long COVID for brain development and its association with altered brain plasticity, impacting learning disabilities, neurodevelopmental disorders, as well as cognitive decline in adults.

Heart-brain interaction in cardiogenic dementia: pathophysiology and therapeutic potential

Diagnosis and treatment of patients with cardiovascular and neurologic diseases primarily focus on the heart and brain, respectively. An increasing number of preclinical and clinical studies have confirmed a causal relationship between heart and brain diseases. Cardiogenic dementia is a cognitive impairment caused by heart dysfunction and has received increasing research attention. The prevention and treatment of cardiogenic dementia are essential to improve the quality of life, particularly in the elderly and aging population. This study describes the changes in cognitive function associated with coronary artery disease, myocardial infarction, heart failure, atrial fibrillation and heart valve disease. An updated understanding of the two known pathogenic mechanisms of cardiogenic dementia is presented and discussed. One is a cascade of events caused by cerebral hypoperfusion due to long-term reduction of cardiac output after heart disease, and the other is cognitive impairment regardless of the changes in cerebral blood flow after cardiac injury. Furthermore, potential medications for the prevention and treatment of cardiogenic dementia are reviewed, with particular attention to multicomponent herbal medicines.

Heterogeneity and synaptic plasticity analysis of hippocampus based on db-/- mice induced diabetic encephalopathy

Chronic hyperglycemia can cause changes in synaptic plasticity of hippocampal cells, which has accelerated the pathological process of cognitive dysfunction. However, the heterogeneity of the hippocampal cell populations under long term high glucose statement remains largely unknown. To mimic chronic hyperglycemia induced cognitive function deficit in vivo, db-/- diabetic mice was selected and Novel Object Recognition(NOR) behavior tests were performed. Based on diabetic induced cognitive impairment(CI) animal model, single-cell RNA sequencing was performed in the hippocampus of CI group (21,379 cells) or control group (20,045 cells), and single cell RNA sequencing was applied, and then the single cell atlas of gene expression was profiled. The comprehensive analysis explicated 18 nerve cell clusters, including 9 distinct sub-clusters, More in-depth analysis of oligodendrocyte precursor cells(OPCs) showed five distinct OPCs sub-clusters including expressing marker gene Lingo2-OPCs, Kcnc1-OPCs, Sst-OPCs, Slc6a1-OPCs and Lhfpl3-OPCs, which seems to be able to proliferate, migrate, and finally differentiate into mature oligodendrocytes and produce myelin. To be noted, differentially expressed genes(DEGs) of the Sst-OPCs sub-cluster indicated that the genes participating in neuroactive ligand-receptor interaction, nervous system development and inflammatory process were up-regulated in diabetic induced cognitive impairment(DCI) groups compared to normal control groups. Integrating the data of neuroplasticity regulation, the 20th top-enriched biological process was associated with neuroplasticity regulation in CI groups compared to control groups. Among these neuroplasticity-related genes, the intersectional gene Sstr2 may play an important role in neuroplasticity regulation. Focused on neuroplasticity regulation and its related specific genes may provide potential new clues for the treatment of diabetes mellitus complicated with cognitive impairment. In summary, we showed the comprehensively transcriptional landscape of hippocampal cells in the db-/- diabetic mice with cognitive dysfunction, distinctive cell sub-clusters and the gene expression characteristics were identified, and also their special functions were proposed, which may give new clues and potential targets for diagnosis and treatment of diabetic encephalopathy.

Modulatory role of α-MSH in hippocampal-dependent memory impairment, synaptic plasticity changes, oxidative stress, and astrocyte reactivity induced by short-term high-fat diet intake

High-fat diet (HFD) consumption is associated with cognitive deficits and neurodegenerative diseases. Since the hippocampus is extremely sensitive to pathophysiological changes, neuroinflammation and the concomitant oxidative stress induced by HFD can significantly interfere with hippocampal-dependent functions related to learning and memory. The neuropeptide alpha-melanocyte stimulating hormone (α-MSH) mediates neuroprotective actions in the central nervous system and can reverse the effects of neuroinflammation in cognitive functions that depend on the hippocampus. In this study, we used male Wistar rats to evaluate the effect of short-term HFD intake (5 days) plus a mild immune challenge, Lipopolysaccharide (LPS 10 μg/kg) on contextual fear, changes in structural plasticity, oxidative stress, and astrocyte reactivation in the hippocampus. We also determined the possible modulatory role of α-MSH. HFD consumption was associated with an increase in markers of oxidative stress (Advanced oxidation protein products and Malondialdehyde) in the dorsal hippocampus (DH). We also found changes in hippocampal structural synaptic plasticity, observing a decrease in total spine in the DH after HFD plus LPS. We observed astrocyte proliferation and a significant increase in the percentage of the area occupied by GFAP. Treatment with α-MSH (0.1 μg/0.25 μl) in the DH reversed the effect of short-term HFD plus LPS on contextual fear memory, oxidative stress, and spine density. α-MSH also reduced astrocyte proliferation. Our present results indicate that HFD consumption for a short period sensitizes the central nervous system (CNS) to a subsequent immune challenge and impairs contextual fear memory and that α-MSH could have a modulatory protective effect.

Simultaneous Pericytes and M2 Microglia Transplantation Improve Cognitive Function in Mice Model of mPFC Ischemia

Cerebral ischemia is one of the major problems threatening global health. Many of the cerebral ischemia survivors would suffer from the physical and cognitive disabilities for their whole lifetime. Cell based-therapies have been introduced as a therapeutic approach for alleviating ischemia-enforced limitations. Photothrombotic stroke model was applied on the left medial prefrontal cortex (mPFC) of adult male BALB/c mice. Then, pericytes isolated from brain microvessels of adult male BALB/c mice, microglia isolated from brain cortices of the neonatal male BALB/c mice, and M2 phenotype shifted microglia by IL-4 treatment were used for transplantation into the injured area after 24 h of ischemia induction. The behavioural outcomes evaluated by social interaction and Barnes tests and the levels of growth associated protein (GAP)-43 and inflammatory cytokine interleukin (IL)-1 protein were assessed by western blotting 7 days after cell transplantation. Animals in both of the microglia + pericytes and microglia M2 + pericytes transplanted groups showed better performance in social memory as well as enhanced spatial learning and memory compared to ischemic controls. Also, improved escape latency was only observed in microglia M2 + pericytes (p < 0.01) group compared to ischemic controls. GAP-43 showed significant protein expression in microglia + pericytes and microglia M2 + pericytes groups compared to the control group. Conversely, IL-1 levels diminished in all of the pericytes microglia + pericytes, and microglia M2 + pericytes groups compared to the ischemic controls. Current study highlights efficiency of M2 microglia and pericytes combinatory transplantation therapeutic role on relieving ischemic stroke outcomes.

Ouabain Reverts CUS-Induced Disruption of the HPA Axis and Avoids Long-Term Spatial Memory Deficits

Ouabain (OUA) is a cardiotonic steroid that modulates Na+, K+ -ATPase activity. OUA has been identified as an endogenous substance that is present in human plasma, and it has been shown to be associated with the response to acute stress in both animals and humans. Chronic stress is a major aggravating factor in psychiatric disorders, including depression and anxiety. The present work investigates the effects of the intermittent administration of OUA (1.8 μg/kg) during the chronic unpredictable stress (CUS) protocol in a rat's central nervous system (CNS). The results suggest that the intermittent OUA treatment reversed CUS-induced HPA axis hyperactivity through a reduction in (i) glucocorticoids levels, (ii) CRH-CRHR1 expression, and by decreasing neuroinflammation with a reduction in iNOS activity, without interfering with the expression of antioxidant enzymes. These changes in both the hypothalamus and hippocampus may reflect in the rapid extinction of aversive memory. The present data demonstrate the ability of OUA to modulate the HPA axis, as well as to revert CUS-induced long-term spatial memory deficits.

Vitamin D3 exerts immunomodulatory and memory improving properties in rats with lipopolysaccharide-induced inflammation

INTRODUCTION

Vitamin D is a fat-soluble secosteroid, its primary function being regulation of calcium-phosphate homeostasis and maintenance of bone integrity and mineralization. Recently, pleotropic effects of this vitamin have been recognized, including an immunomodulatory role and involvement in normal brain development and functioning.

Long Covid brain fog: a neuroinflammation phenomenon?

Neuroinflammation is a process triggered by an attack on the immune system. Activation of microglia in response to an immune system challenge can lead to a significant impact on cognitive processes, such as learning, memory and emotional regulation. Long Covid is an ongoing problem, affecting an estimated 1.3 million people within the UK alone, and one of its more significant, and as yet unexplained, symptoms is brain fog. Here, we discuss the potential role of neuroinflammation in Long Covid cognitive difficulties. Inflammatory cytokines have been found to play a significant role in reductions in LTP and LTD, a reduction in neurogenesis, and in dendritic sprouting. The potential behavioural consequences of such impacts are discussed. It is hoped that this article will allow for greater examination of the effects of inflammatory factors on brain function, most particularly in terms of their role in chronic conditions.

IL-37 expression reduces acute and chronic neuroinflammation and rescues cognitive impairment in an Alzheimer's disease mouse model

The anti-inflammatory cytokine interleukin-37 (IL-37) belongs to the IL-1 family but is not expressed in mice. We used a human IL-37 (hIL-37tg) expressing mouse, which has been subjected to various models of local and systemic inflammation as well as immunological challenges. Previous studies reveal an immunomodulatory role of IL-37, which can be characterized as an important suppressor of innate immunity. Here, we examined the functions of IL-37 in the central nervous system and explored the effects of IL-37 on neuronal architecture and function, microglial phenotype, cytokine production and behavior after inflammatory challenge by intraperitoneal LPS-injection. In wild-type mice, decreased spine density, activated microglial phenotype and impaired long-term potentiation (LTP) were observed after LPS injection, whereas hIL-37tg mice showed no impairment. In addition, we crossed the hIL-37tg mouse with an animal model of Alzheimer’s disease (APP/PS1) to investigate the anti-inflammatory properties of IL-37 under chronic neuroinflammatory conditions. Our results show that expression of IL-37 is able to limit inflammation in the brain after acute inflammatory events and prevent loss of cognitive abilities in a mouse model of AD.

Chrysin alleviates lipopolysaccharide-induced neuron damage and behavioral deficits in mice through inhibition of Fyn

Fyn, a non-receptor tyrosine kinase, plays an important role in microglial-mediated neuroinflammation and may serve as a candidate therapeutic target for neuropsychiatric diseases. In this study, we discovered that chrysin, a natural flavonoid compound, suppressed the activation of Fyn kinase and further alleviated neuroinflammation-induced neuron damage and behavior deficits. Functionally, chrysin improved lipopolysaccharide (LPS)-induced memory impairment and depressive behaviors in mice, it also protected against LPS-induced neuronal degeneration and loss and synaptic defects in mice. Our study demonstrated that chrysin inhibited the activation of microglia and reduced the expression of NLRP3 and IL-1β. Furthermore, our data indicated that chrysin blocked phosphorylation of Fyn and activation of NF-κB. Transfection with siRNA-Fyn validated that knockdown of Fyn partly abolished the inhibitory effect of chrysin on the expression of the NLRP3 inflammasome and NF-κB activation. Taken together, our findings revealed that chrysin alleviated LPS-induced neuron damage and behavioral deficits by inhibiting the expression of the NLRP3 inflammasome and NF-κB pathway, which might be mediated by inhibition of Fyn.

Learning Deficits Induced by High-Calorie Feeding in the Rat are Associated With Impaired Brain Kynurenine Pathway Metabolism

In addition to be a primary risk factor for type 2 diabetes and cardiovascular disease, obesity is associated with learning disabilities. Here we examined whether a dysregulation of the kynurenine pathway (KP) of tryptophan (Trp) metabolism might underlie the learning deficits exhibited by obese individuals. The KP is initiated by the enzymatic conversion of Trp into kynurenine (KYN) by indoleamine 2,3-dioxygenase (IDO). KYN is further converted to several signaling molecules including quinolinic acid (QA) which has a negative impact on learning. Wistar rats were fed either standard chow or made obese by exposure to a free choice high-fat high-sugar (fcHFHS) diet. Their learning capacities were evaluated using a combination of the novel object recognition and the novel object location tasks, and the concentrations of Trp and KYN-derived metabolites in several brain regions determined by ultra-performance liquid chromatography-tandem mass spectrometry. Male, but not female, obese rats exhibited reduced learning capacity characterized by impaired encoding along with increased hippocampal concentrations of QA, Xanthurenic acid (XA), Nicotinamide (Nam), and oxidized Nicotinamide Adenine Dinucleotide (NAD+). In contrast, no differences were detected in the serum levels of Trp or KP metabolites. Moreover, obesity enhanced the expression in the hippocampus and frontal cortex of kynurenine monooxygenase (KMO), an enzyme involved in the production of QA from kynurenine. QA stimulates the glutamatergic system and its increased production leads to cognitive impairment. These results suggest that the deleterious effects of obesity on cognition are sex dependent and that altered KP metabolism might contribute to obesity-associated learning disabilities.

Exercise to spot the differences: a framework for the effect of exercise on hippocampal pattern separation in humans

Exercise has a beneficial effect on mental health and cognitive functioning, but the exact underlying mechanisms remain largely unknown. In this review, we focus on the effect of exercise on hippocampal pattern separation, which is a key component of episodic memory. Research has associated exercise with improvements in pattern separation. We propose an integrated framework mechanistically explaining this relationship. The framework is divided into three pathways, describing the pro-neuroplastic, anti-inflammatory and hormonal effects of exercise. The pathways are heavily intertwined and may result in functional and structural changes in the hippocampus. These changes can ultimately affect pattern separation through direct and indirect connections. The proposed framework might guide future research on the effect of exercise on pattern separation in the hippocampus.

Cognitive Impairment in Heart Failure: Landscape, Challenges, and Future Directions

Heart failure (HF) is a major global healthcare problem accounting for substantial deterioration of prognosis. As a complex clinical syndrome, HF often coexists with multi-comorbidities of which cognitive impairment (CI) is particularly important. CI is increasing in prevalence among patients with HF and is present in around 40%, even up to 60%, of elderly patients with HF. As a potent and independent prognostic factor, CI significantly increases the hospitalization and mortality and decreases quality of life in patients with HF. There has been a growing awareness of the complex bidirectional interaction between HF and CI as it shares a number of common pathophysiological pathways including reduced cerebral blood flow, inflammation, and neurohumoral activations. Research that focus on the precise mechanism for CI in HF is still ever insufficient. As the tremendous adverse consequences of CI in HF, effective early diagnosis of CI in HF and interventions for these patients may halt disease progression and improve prognosis. The current clinical guidelines in HF have begun to emphasize the importance of CI. However, nearly half of CI in HF is underdiagnosed, and few recommendations are available to guide clinicians about how to approach CI in patients with HF. This review aims to synthesize knowledge about the link between HF and cognitive dysfunction, issues pertaining to screening, diagnosis and management of CI in patients with HF, and emerging therapies for prevention. Based on data from current studies, critical gaps in knowledge of CI in HF are identified, and future research directions to guide the field forward are proposed.

The mTOR/NF-κB Pathway Mediates Neuroinflammation and Synaptic Plasticity in Diabetic Encephalopathy

Diabetic encephalopathy, a severe complication of diabetes mellitus, is characterized by neuroinflammation and aberrant synaptogenesis in the hippocampus leading to cognitive decline. Mammalian target of rapamycin (mTOR) is associated with cognition impairment. Nuclear factor-κB (NF-κB) is a transcription factor of proinflammatory cytokines. Although mTOR has been ever implicated in processes occurring in neuroinflammation, the role of this enzyme on NF-κB signaling pathway remains unclear in diabetic encephalopathy. In the present study, we investigated whether mTOR regulates the NF-κB signaling pathway to modulate inflammatory cytokines and synaptic plasticity in hippocampal neurons. In vitro model was constructed in mouse HT-22 hippocampal neuronal cells exposed to high glucose. With the inhibition of mTOR or NF-κB by either chemical inhibitor or short-hairpin RNA (shRNA)-expressing lentivirus-vector, we examined the effects of mTOR/NF-κB signaling on proinflammatory cytokines and synaptic proteins. The diabetic mouse model induced by a high-fat diet combined with streptozotocin injection was administrated with rapamycin (mTOR inhibitor) and PDTC (NF-κB inhibitor), respectively. High glucose significantly increased mTOR phosphorylation in HT-22 cells. While inhibiting mTOR by rapamycin or shmTOR significantly suppressed high glucose-induced activation of NF-κB and its regulators IKKβ and IκBα, suggesting mTOR is the upstream regulator of NF-κB. Furthermore, inhibiting NF-κB by PDTC and shNF-κB decreased proinflammatory cytokines expression (IL-6, IL-1β, and TNF-α) and increased brain-derived neurotrophic factor (BDNF) and synaptic proteins (synaptophysin and PSD-95) in HT-22 cells under high glucose conditions. Besides, the mTOR and NF-κB inhibitors improved cognitive decline in diabetic mice. The inhibition of mTOR and NF-κB suppressed mTOR/NF-κB signaling pathway, increased synaptic proteins, and improved ultrastructural synaptic plasticity in the hippocampus of diabetic mice. Activating mTOR/NF-κB signaling pathway regulates the pathogenesis of diabetic encephalopathy, such as neuroinflammation, synaptic proteins loss, and synaptic ultrastructure impairment. The findings provide the implication that mTOR/NF-κB is potential new drug targets to treat diabetic encephalopathy.

Translocator protein 18 kDa: a potential therapeutic biomarker for post traumatic stress disorder

Post traumatic stress disorder (PTSD) is widely regarded as a stress-related and trauma disorder. The symptoms of PTSD are characterized as a spectrum of vulnerabilities after the exposure to an extremely traumatic stressor. Considering as one of complex mental disorders, little progress has been made toward its diagnostic biomarkers, despite the involvement of PTSD has been studied. Many studies into the underlying neurobiology of PTSD implicated the dysfunction of neurosteroids biosynthesis and neuorinflammatory processes. Translocator protein 18 kDa (TSPO) has been considered as one of the promising therapeutic biomarkers for neurological stress disorders (like PTSD, depression, anxiety, et al) without the benzodiazepine-like side effects. This protein participates in the formation of neurosteroids and modulation of neuroinflammation. The review outlines current knowledge involving the role of TSPO in the neuropathology of PTSD and the anti-PTSD-like effects of TSPO ligands.

Effect of NMDAR-NMNAT1/2 pathway on neuronal cell damage and cognitive impairment of sevoflurane-induced aged rats

Objective: The possible effect of NMDAR (N-methyl-D-aspartate receptor)-NMNAT1/2 (nicotinamide/nicotinic acid mono-nucleotide adenylyltransferase) signaling pathway on the neuronal cell damage and cognitive impairment of aged rats anesthetized by sevoflurane was explored.Methods: Adult male Wistar rats were selected and divided into Control, Sevo (Sevoflurane), Sevo+DCS (NMDAR agonist D-cycloserine) 30 mg/kg, Sevo+DCS 100 mg/kg, and Sevo+DCS 200 mg/kg groups. Morris water maze and fear conditioning text were used to observe cognitive function changes of rats. The inflammatory cytokines were determined by quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) assay, neuronal apoptosis by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labelling (TUNEL) staining and MDAR-NMNAT1/2 pathway-related proteins by Western blotting.Results: The longer escape latency, decreased platform crossing times and reduced staying time spent in platform quadrant were found in rats from Sevo group, with decreased percentage of freezing time in contextual test and tone cued test; and meanwhile, these rats had increased inflammatory cytokines (interleukin (IL)-1β, tumor necrosis factor (TNF-α), IL-6, and IL-8) and neuronal apoptosis, but declined expressions of MDAR-NMNAT1/2 pathway-related proteins. However, the above changes were exhibited an opposite tendency in those Sevo rats treated with different concentrations of DCS (including 30, 100, and 200 mg/kg, respectively). Particularly, the improving effect of low-dose DCS on each aspect in aged rats was better than high-dose ones.Conclusion: Activation of NMDAR-NMNAT1/2 signaling pathway could not only reduce neuronal apoptosis, but also alleviate sevoflurane-induced neuronal inflammation and cognitive impairment in aged rats.

Memory consolidation impairment induced by Interleukin-1β is associated with changes in hippocampal structural plasticity

Pro-inflammatory cytokines, particularly Interleukin-1β (IL-1β), can affect cognitive processes such as learning and memory. The aim of this study was to establish whether the effect of IL-1β on contextual fear memory is associated with changes in hippocampal structural plasticity. We also studied the effect of α-melanocyte-stimulating hormone (α-MSH), a potent anti-inflammatory and neuro-protective peptide. Different groups of animals were implanted bilaterally in dorsal hippocampus (DH). After recovery they were conditioned for contextual fear memory and received the different treatments (vehicle, IL-1β, α-MSH or IL-1β + α-MSH). Memory was assessed 24 hs after conditioning and immediately after rats were perfused for dendritic spine analysis. Our results show that local hippocampal administration of IL-1β just after memory encoding induced impairment in contextual memory and a reduction in the total density of CA1 hippocampal dendritic spines, particularly the mature ones. α-MSH administration reversed the IL-1β induced changes. The results suggest that neuro-inflammation induced by IL-1β interferes with experience-dependent structural plasticity in DH whereas α-MSH has a beneficial modulatory role in preventing this effect.

Neuroinflammation and cognition across psychiatric conditions

Cognitive impairments reported across psychiatric conditions (ie, major depressive disorder, bipolar disorder, schizophrenia, and posttraumatic stress disorder) strongly impair the quality of life of patients and the recovery of those conditions. There is therefore a great need for consideration for cognitive dysfunction in the management of psychiatric disorders. The redundant pattern of cognitive impairments across such conditions suggests possible shared mechanisms potentially leading to their development. Here, we review for the first time the possible role of inflammation in cognitive dysfunctions across psychiatric disorders. Raised inflammatory processes (microglia activation and elevated cytokine levels) across diagnoses could therefore disrupt neurobiological mechanisms regulating cognition, including Hebbian and homeostatic plasticity, neurogenesis, neurotrophic factor, the HPA axis, and the kynurenine pathway. This redundant association between elevated inflammation and cognitive alterations across psychiatric disorders hence suggests that a cross-disorder approach using pharmacological and nonpharmacological (ie, physical activity and nutrition) anti-inflammatory/immunomodulatory strategies should be considered in the management of cognition in psychiatry.

Characterization of the Hippocampal Neuroimmune Response to Binge-Like Ethanol Consumption in the Drinking in the Dark Model

OBJECTIVES

Alcohol dependence leads to dysregulation of the neuroimmune system, but the effects of excessive alcohol consumption on key players of the neuroimmune response after episodic binge drinking in nondependence has not been readily assessed. These studies seek to determine how the neuroimmune system within the hippocampus responds to binge-like consumption prior to dependence or evidence of brain damage.

METHODS

C57BL/6J mice underwent the drinking in the dark (DID) paradigm to recapitulate binge consumption. Immunohistochemical techniques were employed to determine the effects of ethanol on cytokine and astrocyte responses within the hippocampus. Astrocyte activation was also assessed using qRT-PCR.

RESULTS

Our results indicated that binge-like ethanol consumption resulted in a 3.6-fold increase in the proinflammatory cytokine interleukin (IL)-1β immunoreactivity in various regions of the hippocampus. The opposite effect was seen in the anti-inflammatory cytokine IL-10. Binge-like consumption resulted in a 67% decrease in IL-10 immunoreactivity but had no effect on IL-4 or IL-6 compared with the water-drinking control group. Moreover, astrocyte activation occurred following ethanol exposure as GFAP immunoreactivity was increased over 120% in mice that experienced 3 cycles of ethanol binges. PCR analyses indicated that the mRNA increased by almost 4-fold after one cycle of DID, but this effect did not persist in abstinence.

CONCLUSIONS

Altogether, these findings suggest that binge-like ethanol drinking prior to dependence causes dysregulation to the neuroimmune system. This altered neuroimmune state may have an impact on behavior but could also result in a heightened neuroimmune response that is exacerbated from further ethanol exposure or other immune-modulating events.

Investigating the role of interleukin-1 beta and glutamate in inflammatory bowel disease and epilepsy using discovery browsing

BACKGROUND

Structured electronic health records are a rich resource for identifying novel correlations, such as co-morbidities and adverse drug reactions. For drug development and better understanding of biomedical phenomena, such correlations need to be supported by viable hypotheses about the mechanisms involved, which can then form the basis of experimental investigations.

METHODS

In this study, we demonstrate the use of discovery browsing, a literature-based discovery method, to generate plausible hypotheses elucidating correlations identified from structured clinical data. The method is supported by Semantic MEDLINE web application, which pinpoints interesting concepts and relevant MEDLINE citations, which are used to build a coherent hypothesis.

RESULTS

Discovery browsing revealed a plausible explanation for the correlation between epilepsy and inflammatory bowel disease that was found in an earlier population study. The generated hypothesis involves interleukin-1 beta (IL-1 beta) and glutamate, and suggests that IL-1 beta influence on glutamate levels is involved in the etiology of both epilepsy and inflammatory bowel disease.

CONCLUSIONS

The approach presented in this paper can supplement population-based correlation studies by enabling the scientist to identify literature that may justify the novel patterns identified in such studies and can underpin basic biomedical research that can lead to improved treatments and better healthcare outcomes.

Melanocortin 4 receptor activation protects striatal neurons and glial cells from 3-nitropropionic acid toxicity

α-Melanocyte stimulating hormone (α-MSH) is a melanocortin which exerts potent anti-inflammatory and anti-apoptotic effects. Melanocortin 4 receptors (MC4R) are abundantly expressed in the brain and we previously demonstrated that [Nle(4), D-Phe(7)]melanocyte-stimulating hormone (NDP-MSH), an α-MSH analogue, increased expression of brain derived-neurotrophic factor (BDNF), and peroxisome proliferator-activated receptor-γ (PPAR-γ). We hypothesized that melanocortins could affect striatal cell survival through BDNF and PPAR-γ. First, we determined the expression of these factors in the striatum. Acute intraperitoneal administration (0.5 mg/kg) of α-MSH increased the levels of BDNF mRNA in rat striatum but not in rat cerebral cortex. Also, protein expression of PPAR-γ and MC4R was increased by acute treatment with α-MSH in striatum but not in cortex. No changes were observed by 48 h treatment. Next, we evaluated melanocortins effect on neuron and glial survival. 3-nitropropionic acid (3-NP), which is known to induce striatal degeneration, was used to induce cell death in the rat striatal cell line ST14A expressing mutant human huntingtin (Q120) or in ST14A cells expressing normal human huntingtin (Q15), in primary cultured astrocytes, and in BV2 cells. NDP-MSH protected Q15 cells, astrocytes and BV2 cells from death by 3-NP whereas it did not fully protect Q120 cells. Protection of Q15 cells and astrocytes was blocked by a MC4R specific inhibitor (JKC-363) and a PPAR-γ antagonist (GW9662). The BDNF receptor antagonist (ANA-12) abolished NDP-MSH protective effect in astrocytes but not in Q15 cells. We demonstrate for the first time that melanocortins, acting through PPAR-γ and BDNF, protect neurons and glial cells from 3-NP toxicity.

Ameliorative effects of hydrogen sulfide (NaHS) on chronic kidney disease-induced brain dysfunction in rats: implication on role of nitric oxide (NO) signaling

Chronic kidney disease (CKD) is a major public health problem worldwide and is associated with spatial learning deficits. The aim of the present study was to evaluate the protective effects of hydrogen sulfide (H2S) on CKD-mediated behavioral deficits with emphasis to the role of nitric oxide (NO) in these effects. Fifty rats were randomly allocated to five experimental groups including: sham, Five-sixth (5/6) nephrectomy (Nx), 5/6Nx + NaHS, 5/6Nx + NaHS+L-nitroarginine methyl ester (L-NAME), and 5/6Nx + NaHS+aminoguanidine (AMG). Twelve weeks after 5/6Nx, we evaluated proteinuria, creatinine clearance (CrCl), oxidative/antioxidant status, and hippocampus neuro-inflammation and NO synthase genes in all groups. Furthermore, training trials of all animals were conducted in the Morris water maze (MWM) task one day before animal euthanizing. As predicted, 5/6Nx induced several injuries, including enhancement of proteinuria and reduction of CCr, oxidant/antioxidant imbalance and up-regulation of TNF-α and IL-1β gene expressions in the hippocampus tissues. As predicted, 5/6Nx resulted in learning and memory impairments, and increased escape latency during acquisition trials in the MWM task. Interestingly, NaHS (H2S donor) improved behavioral deficits, renal dysfunction, accelerated anti-oxidant/anti-inflammatory responses and increased eNOS and decreased iNOS. Moreover, these effects of NaHS were prevented by L-NAME but not AMG co-administration. In conclusion, H2S ameliorates CKD-mediated brain dysfunctions, through interaction with NO signaling in the hippocampus.

Central intracrine DHEA synthesis in ageing-related neuroinflammation and neurodegeneration: therapeutic potential?

It is a well-known fact that DHEA declines on ageing and that it is linked to ageing-related neurodegeneration, which is characterised by gradual cognitive decline. Although DHEA is also associated with inflammation in the periphery, the link between DHEA and neuroinflammation in this context is less clear. This review drew from different bodies of literature to provide a more comprehensive picture of peripheral vs central endocrine shifts with advanced age—specifically in terms of DHEA. From this, we have formulated the hypothesis that DHEA decline is also linked to neuroinflammation and that increased localised availability of DHEA may have both therapeutic and preventative benefit to limit neurodegeneration. We provide a comprehensive discussion of literature on the potential for extragonadal DHEA synthesis by neuroglial cells and reflect on the feasibility of therapeutic manipulation of localised, central DHEA synthesis.

Neuroimmune Activation Drives Multiple Brain States

Neuroimmune signaling is increasingly identified as a critical component of neuronal processes underlying memory, emotion and cognition. The interactions of microglia and astrocytes with neurons and synapses, and the individual cytokines and immune signaling molecules that mediate these interactions are a current focus of much research. Here, we discuss neuroimmune activation as a mechanism triggering different states that modulate cognitive and affective processes to allow for appropriate behavior during and after illness or injury. We propose that these states lie on a continuum from a naïve homeostatic baseline state in the absence of stimulation, to acute neuroimmune activity and chronic activation. Importantly, consequences of illness or injury including cognitive deficits and mood impairments can persist long after resolution of immune signaling. This suggests that neuroimmune activation also results in an enduring shift in the homeostatic baseline state with long lasting consequences for neural function and behavior. Such different states can be identified in a multidimensional way, using patterns of cytokine and glial activation, behavioral and cognitive changes, and epigenetic signatures. Identifying distinct neuroimmune states and their consequences for neural function will provide a framework for predicting vulnerability to disorders of memory, cognition and emotion both during and long after recovery from illness.

Aluminum trichloride-induced hippocampal inflammatory lesions are associated with IL-1β-activated IL-1 signaling pathway in developing rats

Aluminum (Al) is a recognized environmental pollutant that causes neuroinflammatory lesions, leading to neurodegenerative diseases. Interleukin-1 (IL-1) signaling pathway is responsible for regulating inflammatory lesions. However, it remains unclear whether IL-1 signaling pathway is involved in neuroinflammatory lesions induced by Al exposure. In the present study, one hundred and twenty Wistar rats were orally exposed to 0, 50, 150 and 450 mg/kg BW/d aluminum trichloride (AlCl₃) for 90 days, respectively. We found that AlCl₃ exposure increased hippocampal Al concentration, reduced hippocampus coefficient, impaired cognitive ability, deteriorated microstructure of hippocampal CA1 and CA3 regions, increased reactive oxygen species (ROS) level, activated astrocytes and microglia, increased pro-inflammatory cytokines contents and mRNA expressions, and decreased anti-inflammatory cytokines contents and mRNA expressions in the hippocampus. These results indicated that AlCl₃ induced the hippocampal inflammatory lesion (HIL). Moreover, AlCl₃ exposure increased the mRNA and protein expression of IL-1 signaling pathway core components in the hippocampus, demonstrating that AlCl₃ activated IL-1 signaling pathway. Furthermore, the correlation between interleukin-1β (IL-1β) content and HIL and activation of the IL-1 signaling pathway was analyzed. Results showed that IL-1β content was positively correlated with pro-inflammatory cytokines contents and mRNA expressions and activation of IL-1 signaling pathway, and was negatively correlated with hippocampus coefficient, anti-inflammatory cytokines contents and mRNA expressions, and the number of hippocampal neurons. The above results demonstrate that AlCl₃-induced HIL is associated with IL-1 signaling pathway, in which IL-1β is a link.

Dietary supplementation with Allium hirtifolium and/or Astragalus hamosus improved memory and reduced neuro-inflammation in the rat model of Alzheimer’s disease

Allium hirtifolium Boiss and Astragalus hamosus L. are mentioned in Iranian traditional medicine documentation as therapy for a kind of dementia with the features and symptoms similar to those of Alzheimer’s disease (AD). In the present study, the effects of these herbs on neuro-inflammation and memory have been evaluated as new therapies in amyloid beta (Aβ)-induced memory impairment model. Separate groups of rats were fed with A. hirtifolium or A. hamosus extract (both 100 mg/(kg·day)−1) started 1 week before stereotaxic surgery to 24 h before behavioral testing (totally, for 16 successive days). The effects of oral administration of mentioned extracts on the memory and neuro-inflammation were assessed in the Aβ-injected rats. The results of this study showed that oral administration of both A. hirtifolium and A. hamosus improved the memory, examined by using Y-maze test and shuttle box apparatus. Also, Western blotting analysis of cyclooxygenase-2, interleukin-1β, and tumor necrosis factor-α showed that these herbs have ameliorating effects against the neuro-inflammation caused by Aβ. These findings suggest that the use of A. hirtifolium and A. hamosus as herbal therapy may be suitable for decreasing AD-related symptoms and treatment of other neurodegenerative disorders.

Nuclear deterrents: Intrinsic regulators of IL-1β-induced effects on hippocampal neurogenesis

Hippocampal neurogenesis, the process by which new neurons are born and develop into the host circuitry, begins during embryonic development and persists throughout adulthood. Over the last decade considerable insights have been made into the role of hippocampal neurogenesis in cognitive function and the cellular mechanisms behind this process. Additionally, an increasing amount of evidence exists on the impact of environmental factors, such as stress and neuroinflammation on hippocampal neurogenesis and subsequent impairments in cognition. Elevated expression of the pro-inflammatory cytokine interleukin-1β (IL-1β) in the hippocampus is established as a significant contributor to the neuronal demise evident in many neurological and psychiatric disorders and is now known to negatively regulate hippocampal neurogenesis. In order to prevent the deleterious effects of IL-1β on neurogenesis it is necessary to identify signalling pathways and regulators of neurogenesis within neural progenitor cells that can interact with IL-1β. Nuclear receptors are ligand regulated transcription factors that are involved in modulating a large number of cellular processes including neurogenesis. In this review we focus on the signalling mechanisms of specific nuclear receptors involved in regulating neurogenesis (glucocorticoid receptors, peroxisome proliferator activated receptors, estrogen receptors, and nuclear receptor subfamily 2 group E member 1 (NR2E1 or TLX)). We propose that these nuclear receptors could be targeted to inhibit neuroinflammatory signalling pathways associated with IL-1β. We discuss their potential to be therapeutic targets for neuroinflammatory disorders affecting hippocampal neurogenesis and associated cognitive function.

IL-1β reduces GluA1 phosphorylation and its surface expression during memory reconsolidation and α-melanocyte-stimulating hormone can modulate these effects

Pro-inflammatory cytokines can affect cognitive processes such as learning and memory. Particularly, interleukin-1β (IL-1β) influences hippocampus-dependent memories. We previously reported that administration of IL-1β in dorsal hippocampus impaired contextual fear memory reconsolidation. This effect was reversed by the melanocortin alpha-melanocyte-stimulating hormone (α-MSH). Our results also demonstrated that IL-1β produced a significant decrease in glutamate release from dorsal hippocampus synaptosomes after reactivation of the fear memory. Therefore, we investigated whether IL-1β administration can affect GluA1 AMPA subunit phosphorylation, surface expression, and total expression during reconsolidation of a contextual fear memory. Also, we studied the modulatory effect of α-MSH. We found that IL-1β reduced phosphorylation of this subunit at Serine 831 and Serine 845 60 min after contextual fear memory reactivation. The intrahippocampal administration of IL-1β after memory reactivation also induced a decrease in surface expression and total expression of GluA1. α-MSH prevented the effect of IL-1β on GluA1 phosphorylation in Serine 845, but not in Serine 831. Moreover, treatment with α-MSH also prevented the effect of the cytokine on GluA1 surface and total expression after memory reactivation. Our results demonstrated that IL-1β regulates phosphorylation of GluA1 and may thus play an important role in modulation of AMPAR function and synaptic plasticity in the brain. These findings further illustrate the importance of IL-1β in cognition processes dependent on the hippocampus, and also reinforced the fact that α-MSH can reverse IL-1β effects on memory reconsolidation.

Posttraumatic stress disorder: A metabolic disorder in disguise?

Posttraumatic stress disorder (PTSD) is a heterogeneous psychiatric disorder that affects individuals exposed to trauma and is highly co-morbid with other adverse health outcomes, including cardiovascular disease and obesity. The unique pathophysiological feature of PTSD is the inability to inhibit fear responses, such that individuals suffering from PTSD re-experience traumatic memories and are unable to control psychophysiological responses to trauma-associated stimuli. However, underlying alterations in sympathetic nervous system activity, neuroendocrine systems, and metabolism associated with PTSD are similar to those present in traditional metabolic disorders, such as obesity and diabetes. The current review highlights existing clinical, translational, and preclinical data that support the notion that underneath the primary indication of impaired fear inhibition, PTSD is itself also a metabolic disorder and proposes altered function of inflammatory responses as a common underlying mechanism. The therapeutic implications of treating PTSD as a whole-body condition are significant, as targeting any underlying biological system whose activity is altered in both PTSD and metabolic disorders, (i.e. HPA axis, sympathetic nervous systems, inflammation) may elicit symptomatic relief in individuals suffering from these whole-body adverse outcomes.

[Nle4, D-Phe7]-α-MSH Inhibits Toll-Like Receptor (TLR)2- and TLR4-Induced Microglial Activation and Promotes a M2-Like Phenotype

α-melanocyte stimulating hormone (α-MSH) is an anti-inflammatory peptide, proved to be beneficial in many neuroinflammatory disorders acting through melanocortin receptor 4 (MC4R). We previously determined that rat microglial cells express MC4R and that NDP-MSH, an analog of α-MSH, induces PPAR-γ expression and IL-10 release in these cells. Given the great importance of modulation of glial activation in neuroinflammatory disorders, we tested the ability of NDP-MSH to shape microglial phenotype and to modulate Toll-like receptor (TLR)-mediated inflammatory responses. Primary rat cultured microglia were stimulated with NDP-MSH followed by the TLR2 agonist Pam₃CSK₄ or the TLR4 agonist LPS. NDP-MSH alone induced expression of the M2a/M2c marker Ag1 and reduced expression of the M2b marker Il-4rα and of the LPS receptor Tlr4. Nuclear translocation of NF-κB subunits p65 and c-Rel was induced by LPS and these effects were partially prevented by NDP-MSH. NDP-MSH reduced LPS- and Pam₃CSK₄-induced TNF-α release but did not affect TLR-induced IL-10 release. Also, NDP-MSH inhibited TLR2-induced HMGB1 translocation from nucleus to cytoplasm and TLR2-induced phagocytic activity. Our data show that NDP-MSH inhibits TLR2- and TLR4-mediated proinflammatory mechanisms and promotes microglial M2-like polarization, supporting melanocortins as useful tools for shaping microglial activation towards an alternative immunomodulatory phenotype.

The role of inflammatory cytokines and ERK1/2 signaling in chronic prostatitis/chronic pelvic pain syndrome with related mental health disorders

Mental health disorders(MHD) in chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) have been widely studied. However, the underlying role of inflammatory cytokines and their associated signaling pathways have not been investigated. Here, we report the potential role of cytokines and associated signaling pathways in CP/CPPS patients with MHD and in a CP/CPPS animal model. CP/CPPS patients (n = 810) and control subjects (n = 992) were enrolled in this case-control multicenter study, and serum cytokine levels were measured. Male Sprague-Dawley rats received multiple intracutaneous injections of an immuno-agent along with a pertussis-diphtheria-tetanus triple vaccine for autoimmune CP/CPPS development. The results revealed that, in CP/CPPS patients with significant MHD, elevated IL-1α, IL-1β, IL-4, IL-13, and TNF-α serum levels were observed. The above five cytokines in CP/CPPS rats were significantly elevated in prostate tissue (p < 0.05), and IL-1β levels were elevated in serum and cerebrospinal fluid. In behavioral tests, CP/CPPS rats showed anxiety- and depression-like symptoms, and impaired spatial and associative memory performance (p < 0.05). In the CP/CPPS group, ERK1/2 phosphorylation levels were increased in the amygdala and nucleus accumbens, and decreased in the hippocampus, but not caudate nucleus. Thus, prostate-derived cytokines, especially IL-1β, cross the blood brain barrier and may lead to enhanced ERK1/2 signaling in several brain areas, possibly underlying induction of CP/CPPS-related MHD.

Candesartan ameliorates impaired fear extinction induced by innate immune activation

Patients with post-traumatic stress disorder (PTSD) tend to show signs of a relatively increased inflammatory state suggesting that activation of the immune system may contribute to the development of PTSD. In the present study, we tested whether activation of the innate immune system can disrupt acquisition or recall of auditory fear extinction using an animal model of PTSD. Male adolescent rats received auditory fear conditioning in context A. The next day, an intraperitoneal injection of lipopolysaccharide (LPS; 100 μg/kg) prior to auditory fear extinction in context B impaired acquisition and recall of extinction. LPS (100 μg/kg) given after extinction training did not impair extinction recall suggesting that LPS did not affect consolidation of extinction. In contrast to cued fear extinction, contextual fear extinction was not affected by prior injection of LPS (100 μg/kg). Although LPS also reduced locomotion, we could dissociate the effects of LPS on extinction and locomotion by using a lower dose of LPS (50 μg/kg) which impaired locomotion without affecting extinction. In addition, 15 h after an injection of 250 μg/kg LPS in adult rats, extinction learning and recall were impaired without affecting locomotion. A sub-chronic treatment with candesartan, an angiotensin II type 1 receptor blocker, prevented the LPS-induced impairment of extinction in adult rats. Our results demonstrate that activation of the innate immune system can disrupt auditory fear extinction in adolescent and adult animals. These findings also provide direction for clinical studies of novel treatments that modulate the innate immune system for stress-related disorders like PTSD.

Hazelnut and neuroprotection: Improved memory and hindered anxiety in response to intra-hippocampal Aβ injection

OBJECTIVES

Corylus avellana L. (hazelnut) is known to be a delicious and nutritious food. This study was carried out to evaluate the use of hazelnut as a therapy for memory impairment because in Iranian traditional medicine, it is recommended for those suffering from a particular type of dementia, with symptoms of Alzheimer's disease.

METHODS

In this study, rats were fed with hazelnut kernel [(without skin) 800 mg/kg/day] during 1 week before stereotaxic surgery to 24 hours before behavioral testing (in general, for 16 consecutive days) and the effect of hazelnut eating on memory, anxiety, neuroinflammation and apoptosis was assessed in the amyloid beta-injected rat.

RESULTS

The results of this study showed that feeding with hazelnut improved memory, (which was examined by using Y-maze test and shuttle box apparatus), and reduced anxiety-related behavior, that was evaluated using elevated plus maze. Also, western blotting analysis of cyclooxygenase-2, interleukin-1β, tumor necrosis factor-α, B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein, and caspase-3 showed that hazelnut has an ameliorating effect on the neuroinflammation and apoptosis caused by Aβ.

DISCUSSION

These findings suggest that hazelnut, as a dietary supplement, improves healthy aging and could be a beneficial diet for the treatment of AD.

Synapse-specific IL-1 receptor subunit reconfiguration augments vulnerability to IL-1β in the aged hippocampus

In the aged brain, synaptic plasticity and memory show increased vulnerability to impairment by the inflammatory cytokine interleukin 1β (IL-1β). In this study, we evaluated the possibility that synapses may directly undergo maladaptive changes with age that augment sensitivity to IL-1β impairment. In hippocampal neuronal cultures, IL-1β increased the expression of the IL-1 receptor type 1 and the accessory coreceptor AcP (proinflammatory), but not of the AcPb (prosurvival) subunit, a reconfiguration that potentiates the responsiveness of neurons to IL-1β. To evaluate whether synapses develop a similar heightened sensitivity to IL-1β with age, we used an assay to track long-term potentiation (LTP) in synaptosomes. We found that IL-1β impairs LTP directly at the synapse and that sensitivity to IL-1β is augmented in aged hippocampal synapses. The increased synaptic sensitivity to IL-1β was due to IL-1 receptor subunit reconfiguration, characterized by a shift in the AcP/AcPb ratio, paralleling our culture data. We suggest that the age-related increase in brain IL-1β levels drives a shift in IL-1 receptor configuration, thus heightening the sensitivity to IL-1β. Accordingly, selective blocking of AcP-dependent signaling with Toll-IL-1 receptor domain peptidomimetics prevented IL-1β-mediated LTP suppression and blocked the memory impairment induced in aged mice by peripheral immune challenge (bacterial lipopolysaccharide). Overall, this study demonstrates that increased AcP signaling, specifically at the synapse, underlies the augmented vulnerability to cognitive impairment by IL-1β that occurs with age.

Melanocortin 4 receptor activates ERK-cFos pathway to increase brain-derived neurotrophic factor expression in rat astrocytes and hypothalamus

Melanocortins are neuropeptides with well recognized anti-inflammatory and anti-apoptotic effects in the brain. Of the five melanocortin receptors (MCR), MC4R is abundantly expressed in the brain and is the only MCR present in astrocytes. We have previously shown that MC4R activation by the α-melanocyte stimulating hormone (α-MSH) analog, NDP-MSH, increased brain-derived neurotrophic factor (BDNF) expression through the classic cAMP-Protein kinase A-cAMP responsive element binding protein pathway in rat astrocytes. Now, we examined the participation of the mitogen activated protein kinases pathway in MC4R signaling. Rat cultured astrocytes treated with NDP-MSH 1 µM for 1 h showed increased BDNF expression. Inhibition of extracellular signal-regulated kinase (ERK) and ribosomal p90 S6 kinase (RSK), an ERK substrate, but not of p38 or JNK, prevented the increase in BDNF expression induced by NDP-MSH. Activation of MC4R increased cFos expression, a target of both ERK and RSK. ERK activation by MC4R involves cAMP, phosphoinositide-3 kinase (PI3K) and the non receptor tyrosine kinase, Src. Both PI3K and Src inhibition abolished NDP-MSH-induced BDNF expression. Moreover, we found that intraperitoneal injection of α-MSH induces BDNF and MC4R expression and activates ERK and cFos in male rat hypothalamus. Our results show for the first time that MC4R-induced BDNF expression in astrocytes involves ERK-RSK-cFos pathway which is dependent on PI3K and Src, and that melanocortins induce BDNF expression and ERK-cFos activation in rat hypothalamus.

Interleukin-1β-induced memory reconsolidation impairment is mediated by a reduction in glutamate release and zif268 expression and α-melanocyte-stimulating hormone prevented these effects

The immune system is an important modulator of learning, memory and neural plasticity. Interleukin 1β (IL-1β), a pro-inflammatory cytokine, significantly affects several cognitive processes. Previous studies by our group have demonstrated that intrahippocampal administration of IL-1β impairs reconsolidation of contextual fear memory. This effect was reversed by the melanocortin alpha-melanocyte-stimulating hormone (α-MSH). The mechanisms underlying the effect of IL-1β on memory reconsolidation have not yet been established. Therefore, we examined the effect of IL-1β on glutamate release, ERK phosphorylation and the activation of the transcription factor zinc finger- 268 (zif268) during reconsolidation. Our results demonstrated that IL-1β induced a significant decrease of glutamate release after reactivation of the fear memory and this effect was related to calcium concentration in hippocampal synaptosomes. IL-1β also reduced ERK phosphorylation and zif268 expression in the hippocampus. Central administration of α-MSH prevented the decrease in glutamate release, ERK phosphorylation and zif268 expression induced by IL-1β. Our results establish possible mechanisms involved in the detrimental effect of IL-1β on memory reconsolidation and also indicate that α-MSH may exert a beneficial modulatory role in preventing IL-1β effects.

Anti-interleukin-1β antibody prevents the occurrence of repeated restraint stress-induced alterations in synaptic transmission and long-term potentiation in the rat frontal cortex

BACKGROUND

The mechanisms of the influence of prolonged stress on glutamatergic transmission and synaptic plasticity in the cerebral cortex remain poorly understood. The purpose of this study was to determine an involvement of interleukin-1β (IL-1β) in the effects of repeated restraint stress on excitatory synaptic transmission and long-term potentiation (LTP) in the rat frontal cortex.

METHODS

The effects of restraint stress lasting for 10 min, repeated twice daily for 3 consecutive days were studied ex vivo in the rat frontal cortex slices prepared 24h after the last stress session. Rats received intraperitoneal injections of interleukin-1β antibody. In a separate experimental group, rats received injections of IL-1β. Field potentials were recorded in the cortical layer II/III.

RESULTS

In slices originating from stressed animals, the amplitude of field potentials was increased. Consistent with the previous studies, restraint stress resulted in a reduced magnitude of LTP. Similar effects were evident after administration of IL-1β. Stress-induced modifications of the glutamatergic transmission and synaptic plasticity were prevented by interleukin-1β antibody, which was administered 15 min before each restraint session.

CONCLUSIONS

These data point to an involvement of peripherally produced IL-1β in mediating the influence of repeated restraint stress on the functions of the frontal cortex.

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

This review describes the role of cytokines and their downstream signaling cascades on the modulation of learning and memory. Immune proteins are required for many key neural processes and dysregulation of these functions by systemic inflammation can result in impairments of memory that persist long after the resolution of inflammation. Recent research has demonstrated that manipulations of individual cytokines can modulate learning, memory, and synaptic plasticity. The many conflicting findings, however, have prevented a clear understanding of the precise role of cytokines in memory. Given the complexity of inflammatory signaling, understanding its modulatory role requires a shift in focus from single cytokines to a network of cytokine interactions and elucidation of the cytokine-dependent intracellular signaling cascades. Finally, we propose that whereas signal transduction and transcription may mediate short-term modulation of memory, long-lasting cellular and molecular mechanisms such as epigenetic modifications and altered neurogenesis may be required for the long lasting impact of inflammation on memory and cognition.

Critical role of inflammatory cytokines in impairing biochemical processes for learning and memory after surgery in rats

Background

Patients with postoperative cognitive dysfunction have poor outcomes. Neuroinflammation may be the underlying pathophysiology for this dysfunction. We determined whether proinflammatory cytokines affect the trafficking of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors to the plasma membrane, a fundamental biochemical process for learning and memory.

Methods

Four-month-old male Fischer 344 rats were subjected to right carotid exposure under isoflurane anesthesia. Some rats received intravenous lidocaine infusion during anesthesia. Rats were tested two weeks later by Barnes maze. The hippocampus was harvested six hours after the surgery for western blotting of interleukin (IL)-1β or IL-6. Hippocampal slices were prepared from control rats or rats subjected to surgery two weeks previously. They were incubated with tetraethylammonium, an agent that can induce long term potentiation, for determining the trafficking of GluR1, an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit.

Results

Surgery or anesthesia increased the time to identify the target box during the Barnes maze test training sessions and one day after the training sessions. Surgery also prolonged the time to identify the target box eight days after the training sessions. Surgery increased IL-1β and IL-6 in the hippocampus. The tetraethylammonium–induced GluR1 phosphorylation and trafficking were abolished in the hippocampal slices of rats after surgery. These surgical effects were partly inhibited by lidocaine. The incubation of control hippocampal slices with IL-1β and IL-6 abolished tetraethylammonium–induced GluR1 trafficking and phosphorylation. Lidocaine minimally affected the effects of IL-1β on GluR1 trafficking.

Conclusions

Our results suggest that surgery increases proinflammatory cytokines that then inhibit GluR1 trafficking, leading to learning and memory impairment.

Pyrrolidine dithiocarbamate attenuates surgery-induced neuroinflammation and cognitive dysfunction possibly via inhibition of nuclear factor κB

Surgery induces learning and memory impairment. Neuroinflammation may contribute to this impairment. Nuclear factor κB (NF-κB) is an important transcription factor to regulate the expression of inflammatory cytokines. We hypothesize that inhibition of NF-κB by pyrrolidine dithiocarbamate (PDTC) reduces neuroinflammation and the impairment of learning and memory. To test this hypothesis, four-month-old male Fischer 344 rats were subjected to right carotid exploration under propofol and buprenorphine anesthesia. Some rats received two doses of 50mg/kg PDTC given intraperitoneally 30min before and 6h after the surgery. Rats were tested in the Barnes maze and fear conditioning paradigm begun 6days after the surgery. Expression of various proteins related to inflammation was examined in the hippocampus at 24h or 21days after the surgery. Here, surgery, but not anesthesia alone, had a significant effect on prolonging the time needed to identify the target hole during the training sessions of the Barnes maze. Surgery also increased the time for identifying the target hole in the long-term memory test and decreased context-related learning and memory in fear conditioning test. Also, surgery increased nuclear expression of p65, a NF-κB component, decreased cytoplasmic amount of inhibitor of NF-κB, and increased the expression of interleukin-1β, interleukin-6, ionized calcium binding adaptor molecule 1 and active matrix metalloproteinase 9 (MMP-9). Finally, surgery enhanced IgG extravasation in the hippocampus. These surgical effects were attenuated by PDTC. These results suggest that surgery, but not propofol-based anesthesia, induces neuroinflammation and impairment of learning and memory. PDTC attenuates these effects possibly by inhibiting NF-κB activation and the downstream MMP-9 activity.