Hippocampal Cytokine Levels Research Articles

Interleukin‐6 induces cognitive impairment via toll‐like receptor 4 (TLR4)‐mediated neuroinflammation and neurodegeneration in mice with chronic kidney disease

AbstractBackgroundsPast epidemiological and experimental studies in rodents have demonstrated that chronic kidney disease (CKD) leads to cognitive impairment. However, the underlying mechanism requires further investigation. Herein, a mouse model of CKD was established using conventional 5/6 nephrectomy. We aimed to examine the relationship between CKD and cognitive impairment and elucidate the underlying mechanisms.MethodsCognitive behavior was assessed using the Morris water maze, novel object recognition test, and fear conditioning test. Further experiments were also conducted to investigate the underlying molecular mechanisms.ResultsOur clinical data revealed a decrease in cognitive function among patients with CKD, accompanied by elevated plasma levels of pro‐inflammatory cytokines. A positive correlation between cytokine concentrations and serum creatinine levels, as well as a significant positive correlation with cognitive dysfunction, were observed. Correlation analyzes demonstrated that hippocampal cytokine levels were positively correlated with serum creatinine levels and cognitive dysfunction in CKD model mice. Furthermore, 20 mg/mL interleukin‐6 (IL‐6) significantly decreased HT22 cell activity in vitro. Further, HT22 cells treated with IL‐6 showed increased expression levels of toll‐like receptor 4 (TLR4) and myeloid differentiation primary response gene 88 (MyD88), thereby inducing the nuclear factor kappa‐B p65 inflammatory pathway and mitochondria‐dependent apoptosis. The CKD mouse model showed increased expression of TLR4 and cytokines in the hippocampus. TLR4 knockdown antagonized the IL‐6‐mediated pro‐inflammatory and pro‐apoptotic effects in HT22 cells. TLR4 knockdown in the CKD model mice decreased hippocampal inflammation and increased the number of neuron dendrites, thus ameliorated cognitive impairment.ConclusionThese results suggest that IL‐6 triggers TLR4 activation to induce neuroinflammation and neurodegeneration in CKD, ultimately culminate in cognitive impairment.

CD8+ T cells contribute to diet-induced memory deficits in aged male rats

We have previously shown that short-term (3-day) high fat diet (HFD) consumption induces a neuroinflammatory response and subsequent impairment of long-term memory in aged, but not young adult, male rats. However, the immune cell phenotypes driving this proinflammatory response are not well understood. Previously, we showed that microglia isolated from young and aged rats fed a HFD express similar levels of priming and proinflammatory transcripts, suggesting that additional factors may drive the exaggerated neuroinflammatory response selectively observed in aged HFD-fed rats. It is established that T cells infiltrate both the young and especially the aged central nervous system (CNS) and contribute to immune surveillance of the parenchyma. Thus, we investigated the modulating role of short-term HFD on T cell presence in the CNS in aged rats using bulk RNA sequencing and flow cytometry. RNA sequencing results indicate that aging and HFD altered the expression of genes and signaling pathways associated with T cell signaling, immune cell trafficking, and neuroinflammation. Moreover, flow cytometry data showed that aging alone increased CD4+ and CD8+ T cell presence in the brain and that CD8+, but not CD4+, T cells were further increased in aged rats fed a HFD. Based on these data, we selectively depleted circulating CD8+ T cells via an intravenous injection of an anti-CD8 antibody in aged rats prior to 3 days of HFD to infer the functional role these cells may be playing in long-term memory and neuroinflammation. Results indicate that peripheral depletion of CD8+ T cells lowered hippocampal cytokine levels and prevented the HFD-induced i) increase in brain CD8+ T cells, ii) memory impairment, and iii) alterations in pre- and post-synaptic structures in the hippocampus and amygdala. Together, these data indicate a substantial role for CD8+ T cells in mediating diet-induced memory impairments in aged male rats.

Choline Supplementation Alters Hippocampal Cytokine Levels in Adolescence and Adulthood in an Animal Model of Fetal Alcohol Spectrum Disorders.

Alcohol (ethanol) exposure during pregnancy can adversely affect development, with long-lasting consequences that include neuroimmune, cognitive, and behavioral dysfunction. Alcohol-induced alterations in cytokine levels in the hippocampus may contribute to abnormal cognitive and behavioral outcomes in individuals with fetal alcohol spectrum disorders (FASD). Nutritional intervention with the essential nutrient choline can improve hippocampal-dependent behavioral impairments and may also influence neuroimmune function. Thus, we examined the effects of choline supplementation on hippocampal cytokine levels in adolescent and adult rats exposed to alcohol early in development. From postnatal day (PD) 4-9 (third trimester-equivalent), Sprague-Dawley rat pups received ethanol (5.25 g/kg/day) or sham intubations and were treated with choline chloride (100 mg/kg/day) or saline from PD 10-30; hippocampi were collected at PD 35 or PD 60. Age-specific ethanol-induced increases in interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), and keratinocyte chemoattractant/human growth-regulated oncogene (KC/GRO) were identified in adulthood, but not adolescence, whereas persistent ethanol-induced increases of interleukin-6 (IL-6) levels were present at both ages. Interestingly, choline supplementation reduced age-related changes in interleukin-1 beta (IL-1β) and interleukin-5 (IL-5) as well as mitigating the long-lasting increase in IFN-γ in ethanol-exposed adults. Moreover, choline influenced inflammatory tone by modulating ratios of pro- to -anti-inflammatory cytokines. These results suggest that ethanol-induced changes in hippocampal cytokine levels are more evident during adulthood than adolescence, and that choline can mitigate some effects of ethanol exposure on long-lasting inflammatory tone.

Predictive link between systemic metabolism and cytokine signatures in the brain of apolipoprotein E ε4 mice

The ε4 variant of apolipoprotein E (APOE) is the strongest and most common genetic risk factor for Alzheimer's disease (AD). While the mechanism of conveyed risk is incompletely understood, promotion of inflammation, dysregulated metabolism, and protein misfolding and aggregation are contributors to accelerating disease. Here we determined the concurrent effects of systemic metabolic changes and brain inflammation in young (3-month-old) and aged (18-month-old) male and female mice carrying the APOE4 gene. Using functional metabolic assays alongside multivariate modeling of hippocampal cytokine levels, we found that brain cytokine signatures are predictive of systemic metabolic outcomes, independent of AD proteinopathies. Male and female mice each produce different cytokine signatures as they age and as their systemic metabolic phenotype declines, and these signatures are APOE genotype dependent. Ours is the first study to identify a quantitative and predictive link between systemic metabolism and specific pathological cytokine signatures in the brain. Our results highlight the effects of APOE4 beyond the brain and suggest the potential for bi-directional influence of risk factors in the brain and periphery.

Luteolin-7-O-Glucuronide Improves Depression-like and Stress Coping Behaviors in Sleep Deprivation Stress Model by Activation of the BDNF Signaling.

Stress exposure is a major risk factor for mental disorders such as depression. Because of the limitations of classical antidepressants such as side effects, low efficacy, and difficulty in long-term use, new natural medicines and bioactive molecules from plants with greater safety and efficacy have recently attracted attention. Luteolin-7-O-glucuronide (L7Gn), a bioactive molecule present in Perilla frutescens, is known to alleviate severe inflammatory responses and oxidative stress in macrophages. However, its antistress and antidepressant effects have not been elucidated. The present study aims to explore the antidepressant the effect of L7Gn on stress-induced behaviors and the underlying mechanism in a mouse sleep deprivation (SD) model. L7Gn treatment improved depression-like and stress coping behaviors induced by SD stress, as confirmed by the tail suspension test and forced swimming test. Furthermore, L7Gn treatment reduced the blood corticosterone and hippocampal proinflammatory cytokine levels which were increased by SD stress, and L7Gn also increased the mRNA and protein levels of hippocampal brain-derived neurotrophic factor (BDNF) which were reduced by SD stress. Additionally, treatment with L7Gn resulted in increases in the phosphorylation of tropomyosin-related kinase B (TrkB), extracellular signal-regulated kinase (ERK), and cAMP response element-binding protein (CREB), which are downstream molecules of BDNF signaling. These findings suggest that L7Gn have therapeutic potential for SD-induced stress, via activating the BDNF signaling.

Short-term exposure to an obesogenic diet during adolescence elicits anxiety-related behavior and neuroinflammation: modulatory effects of exogenous neuregulin-1

Childhood obesity leads to hippocampal atrophy and altered cognition. However, the molecular mechanisms underlying these impairments are poorly understood. The neurotrophic factor neuregulin-1 (NRG1) and its cognate ErbB4 receptor play critical roles in hippocampal maturation and function. This study aimed to determine whether exogenous NRG1 administration reduces hippocampal abnormalities and neuroinflammation in rats exposed to an obesogenic Western-like diet (WD). Lewis rats were randomly divided into four groups (12 rats/group): (1) control diet+vehicle (CDV); (2) CD + NRG1 (CDN) (daily intraperitoneal injections: 5 μg/kg/day; between postnatal day, PND 21-PND 41); (3) WD + VEH (WDV); (4) WD + NRG1 (WDN). Neurobehavioral assessments were performed at PND 43–49. Brains were harvested for MRI and molecular analyses at PND 49. We found that NRG1 administration reduced hippocampal volume (7%) and attenuated hippocampal-dependent cued fear conditioning in CD rats (56%). NRG1 administration reduced PSD-95 protein expression (30%) and selectively reduced hippocampal cytokine levels (IL-33, GM-CSF, CCL-2, IFN-γ) while significantly impacting microglia morphology (increased span ratio and reduced circularity). WD rats exhibited reduced right hippocampal volume (7%), altered microglia morphology (reduced density and increased lacunarity), and increased levels of cytokines implicated in neuroinflammation (IL-1α, TNF-α, IL-6). Notably, NRG1 synergized with the WD to increase hippocampal ErbB4 phosphorylation and the tumor necrosis alpha converting enzyme (TACE/ADAM17) protein levels. Although the results did not provide sufficient evidence to conclude that exogenous NRG1 administration is beneficial to alleviate obesity-related outcomes in adolescent rats, we identified a potential novel interaction between obesogenic diet exposure and TACE/ADAM17-NRG1-ErbB4 signaling during hippocampal maturation. Our results indicate that supraoptimal ErbB4 activities may contribute to the abnormal hippocampal structure and cognitive vulnerabilities observed in obese individuals.

MESENCHYMAL STROMAL CELLS PROTECT THE BLOOD-BRAIN BARRIER, REDUCE ASTROGLIOSIS, AND PREVENT COGNITIVE AND BEHAVIORAL IMPAIRMENTS IN EXPERIMENTAL SEPSIS

<h3>Background</h3> Sepsis is a systemic inflammatory host-response against a pathogen; it is the largest cause of admission to intensive care units (ICUs) in the United States. Sepsis-associated encephalopathies (SAEs) are neurological complications that occur during or after sepsis events. SAE causes long-term neurological consequences affecting memory, cognition and mood. Currently, there is no prevention or treatment for neurological damage resulting from SAEs. Thus, investigating new therapies is necessary. Both clinical and experimental studies have been show the effects of cell therapy in neurodegenerative diseases. Indeed, the immunomodulatory capacity of mesenchymal stromal cells (MSCs) is well established. Considering that, the aim of the present study was to evaluate the effects of MSC therapy on blood-brain barrier (BBB) maintenance, astrocyte activation, cognitive and behavioral damage in an experimental model of sepsis. <h3>Methods</h3> Male adult Swiss mice underwent cecal ligation and puncture (CLP) surgery for sepsis induction and sham-operated animals were used as control. Six hours after surgery, mice were treated with MSC intravenously (1 × 10⁵ cells in 0.05 mL of saline/mouse) or saline. For in vitro, analysis cultured astrocytes were stimulated with lipopolysaccharide (LPS) (1μg/ ml). After 24 hours, cells were washed to eliminated residual LPS and then treated with conditioned media from MSCs (CM-MSCs). <h3>Results</h3> MSC therapy led to a reduction in systemic levels of IL-1β, IL-6, and MCP-1, a decrease in cortical and hippocampal cytokine levels, a reduction in astrogliosis (evaluated by immunofluorescence) and BBB protection (evaluated by Evans Blue Dye Assay). In cultured astrocytes stimulated with LPS, CM-MSCs reduced astrogliosis at 24h, suggesting a paracrine mechanism of action. These results might be associated with an improvement in spatial memory (Morris Water Maze test), aversive memory (fear-conditioned test) and anxiety-like behavior (Elevated plus maze test). <h3>Conclusion</h3> A single dose- therapy with MSC led to an improvement in cognitive damage, behavioral impairments, protection of the BBB, reduction in local levels of cytokines and astrogliosis and these effects might be associated with a decrease in systemic levels of inflammatory mediators.

Altered hippocampal function and cytokine levels in a rat model of Gulf War illness

AimsGulf War illness (GWI) is a disorder affecting military personnel deployed in the Gulf War (GW) from 1990 to 1991. Here, we will use a rat model of GWI to evaluate hippocampal function and cytokine levels. Materials and methodsRats were exposed to diethyltoluamide and permethrin via dermal absorption and pyridostigmine bromide via gavage with or without a 5-min restraint for 28 days. Immediate and delayed effects of GW chemical exposure were evaluated using electrophysiology to quantitate hippocampal function, behavioral tests to assess cognitive effects and biochemical assays to measure neurotransmitter and cytokine levels. Key findingsBehavioral data revealed a statistically significant increase in motor activity at 3 months following completion of exposures, potentially indicating increased excitability, and/or restlessness. Electrophysiology data revealed statistically significant changes in paired pulse facilitation and input-output function of CA1 hippocampal neurons within 24 h and 3 months following completion of exposures. There was also a statistically significant reduction in the frequency of spontaneous firing activity of hippocampal neurons within 24 h following exposures. Naïve hippocampal slices directly incubated in GW chemicals also resulted in similar changes in electrophysiological parameters. Biochemical measurements revealed reduced hippocampal glutamate level at 3 months post-exposure. Furthermore, there was a statistically significant increase in plasma and hippocampal levels of IL-13, as well as decrease in plasma level of IL-1β. SignificanceOur data support an effect on glutamate signaling within the hippocampus as indicated by changes in PPF and hippocampal level of glutamate, with some activation of T helper type 2 immune response.

A model of negative emotional contagion between male-female rat dyads: Effects of voluntary exercise on stress-induced behavior and BDNF-TrkB signaling

Emotional contagion refers to the sharing of emotional states between individuals and can cause depressive behaviors in healthy persons who live with depressed individuals. Negative emotional contagion has been observed in animal models, but the vast majority of studies are short-term and bear little resemblance to long-term human relationships. Thus, the first aim of this study was to establish an animal model of stress-induced negative emotional contagion that develops across time and between pairs. To accomplish this, we tested the hypothesis that sedentary male rats that cohabitate for five weeks with a stress-exposed female will exhibit a depression-like phenotype that is observable on behavioral and physiological measures. In addition, drawing from a comprehensive literature that describes the beneficial effects of prior exercise on stress-related behavior, we tested our second hypothesis that in males that were paired with a stressed female, prior voluntary exercise will diminish the impact of negative emotional contagion. We found that pair housing a healthy male with a stressed female led to emotional contagion; males gained less body weight, were anhedonic, demonstrated heightened anxiety-like behavior, had lower serum brain-derived neurotrophic factor (BDNF) levels, had decreased hippocampal BDNF-stimulated tyrosine receptor kinase B (TrkB) signaling and had increased pro-inflammatory cytokine expression in the hippocampus. For the most part, the five-week exercise window that occurred prior to pair housing had few effects in non-stress paired rats, but had partial, yet substantial protective effects in rats that were pair-housed with a stressed female. Specifically, stress-paired, exercised rats showed less depressive-like behavior, had partially preserved hippocampal BDNF-stimulated TrkB signaling, had normalized serum BDNF concentration, and had hippocampal cytokine and immediate early gene levels that were equivalent to controls. These preclinical findings introduce a new model of negative emotional contagion between dyads of male-female rats and support the view that inclusion of exercise programs would be beneficial for persons that may, in the future, be susceptible to negative emotional contagion.

The spleen mediates chronic sleep restriction-mediated enhancement of LPS-induced neuroinflammation, cognitive deficits, and anxiety-like behavior.

Chronic sleep restriction promotes neuroinflammation and cognitive deficits in neurodegenerative and neurobehavioral diseases. The spleens of mice exposed to chronic and repeated psychological stress serve as a reservoir of inflammatory myeloid cells that are released into the blood and brain following secondary acute stress. Here, we tested whether chronic and repeated short-term sleep restriction (CRSR) would exacerbate lipopolysaccharide (LPS)-induced neuroinflammation, cognitive deficits, and anxiety-like behavior in a spleen-dependent manner. LPS was administered to aged mice 14 days after exposure to CRSR consisting of three cycles of 7 days of sleep restriction with 7-day intervals in between. CRSR increased plasma proinflammatory cytokine levels, blood-brain barrier permeability, hippocampal proinflammatory cytokine levels, and transition of microglia to the M1 phenotype 24 h after LPS treatment. This in turn led to cognitive deficits and anxiety-like behavior. Interestingly, removal of the spleen 14 days prior to CRSR abrogated the enhancement of LPS-induced increases in systemic inflammation, neuroinflammation, cognitive deficits, and anxiety-like behavior. These data indicate that the spleen was essential for CRSR-induced exacerbation of LPS-induced brain damage.

Enriched environment effect on lipopolysaccharide-induced spatial learning, memory impairment and hippocampal inflammatory cytokine levels in male rats

Neuro-inflammation is responsible for cognitive impairments and neurodegenerative diseases such as Alzheimer’s disease. In this study, we aimed to investigate the enriched environment (EE) effect on learning and memory impairment as well as on pro-inflammatory cytokines changes induced by lipopolysaccharide (LPS). LPS injection (1 mg/kg/i.p, days 1, 3, 5, and 7) was used to develop the animal model of neuro-inflammation. Twenty-eight male Wistar rats were used in the experiment and randomly divided into 4 groups: 1) sham (S), 2) sham + enriched environment (SE), 3) LPS (L), and 4) LPS + EE (LE). Two different housing conditions, including standard environment (SE) and enriched environment, were used. The Morris Water Maze (MWM) test was used to examine animals learning and memory. IL-1β, IL-10, and TNF-α levels were measured in the brain using ELISA. We found that LPS significantly impaired learning and memory (p < 0.05) in the MWM task, but EE could significantly improve learning and memory impairment (p < 0.05). IL-1 and IL-10 levels dramatically increased in the LPS group (P < 0.05), whereas EE could decrease and increase IL-1β and IL-10 values in the LPS + EE group (P < 0.05), respectively. TNF-α levels were traced but had not detectable values in the hippocampus. Thus, we can conclude that EE has healing effects on LPS induced neuro-inflammation and can improve learning and memory deficit; however, further studies are needed to support the findings of our study.

The influence of sex, genotype, and dose on serum and hippocampal cytokine levels in juvenile mice developmentally exposed to a human-relevant mixture of polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) are pervasive environmental contaminants implicated as risk factors for neurodevelopmental disorders (NDDs). Immune dysregulation is another NDD risk factor, and developmental PCB exposures are associated with early life immune dysregulation. Studies of the immunomodulatory effects of PCBs have focused on the higher-chlorinated congeners found in legacy commercial mixtures. Comparatively little is known about the immune effects of contemporary, lower-chlorinated PCBs. This is a critical data gap given recent reports that lower-chlorinated congeners comprise >70% of the total PCB burden in serum of pregnant women enrolled in the MARBLES study who are at increased risk for having a child with an NDD. To examine the influence of PCBs, sex, and genotype on cytokine levels, mice were exposed throughout gestation and lactation to a PCB mixture in the maternal diet, which was based on the 12 most abundant PCBs in sera from MARBLES subjects. Using multiplex array, cytokines were quantified in the serum and hippocampus of weanling mice expressing either a human gain-of-function mutation in ryanodine receptor 1 (T4826I mice), a human CGG premutation repeat expansion in the fragile X mental retardation gene 1 (CGG mice), or both mutations (DM mice). Congenic wildtype (WT) mice were used as controls. There were dose-dependent effects of PCB exposure on cytokine concentrations in the serum but not hippocampus. Differential effects of genotype were observed in the serum and hippocampus. Hippocampal cytokines were consistently elevated in T4826I mice and also in WT animals for some cytokines compared to CGG and DM mice, while serum cytokines were usually elevated in the mutant genotypes compared to the WT group. Males had elevated levels of 19 cytokines in the serum and 4 in the hippocampus compared to females, but there were also interactions between sex and genotype for 7 hippocampal cytokines. Only the chemokine CCL5 in the serum showed an interaction between PCB dose, genotype, and sex. Collectively, these findings indicate differential influences of PCB exposure and genotype on cytokine levels in serum and hippocampal tissue of weanling mice. These results suggest that developmental PCB exposure has chronic effects on baseline serum, but not hippocampal, cytokine levels in juvenile mice.

Gestational poly(I:C) attenuates, not exacerbates, the behavioral, cytokine and mTOR changes caused by isolation rearing in a rat ‘dual-hit’ model for neurodevelopmental disorders

Many psychiatric illnesses have a multifactorial etiology involving genetic and environmental risk factors that trigger persistent neurodevelopmental impairments. Several risk factors have been individually replicated in rodents, to understand disease mechanisms and evaluate novel treatments, particularly for poorly-managed negative and cognitive symptoms. However, the complex interplay between various factors remains unclear. Rodent dual-hit neurodevelopmental models offer vital opportunities to examine this and explore new strategies for early therapeutic intervention. This study combined gestational administration of polyinosinic:polycytidylic acid (poly(I:C); PIC, to mimic viral infection during pregnancy) with post-weaning isolation of resulting offspring (to mirror adolescent social adversity). After in vitro and in vivo studies required for laboratory-specific PIC characterization and optimization, we administered 10 mg/kg i.p. PIC potassium salt to time-mated Lister hooded dams on gestational day 15. This induced transient hypothermia, sickness behavior and weight loss in the dams, and led to locomotor hyperactivity, elevated striatal cytokine levels, and increased frontal cortical JNK phosphorylation in the offspring at adulthood. Remarkably, instead of exacerbating the well-characterized isolation syndrome, gestational PIC exposure actually protected against a spectrum of isolation-induced behavioral and brain regional changes. Thus isolation reared rats exhibited locomotor hyperactivity, impaired associative memory and reversal learning, elevated hippocampal and frontal cortical cytokine levels, and increased mammalian target of rapamycin (mTOR) activation in the frontal cortex – which were not evident in isolates previously exposed to gestational PIC. Brains from adolescent littermates suggest little contribution of cytokines, mTOR or JNK to early development of the isolation syndrome, or resilience conferred by PIC. But notably hippocampal oxytocin, which can protect against stress, was higher in adolescent PIC-exposed isolates so might contribute to a more favorable outcome. These findings have implications for identifying individuals at risk for disorders like schizophrenia who may benefit from early therapeutic intervention, and justify preclinical assessment of whether adolescent oxytocin manipulations can modulate disease onset or progression.

Inflammatory mechanism of hippocampal tissue injury induced by PM2.5 in nasal drip in mice

Objective: To investigate the inflammatory mechanism of nasal instillation of fine particulate matter (PM2.5)on hippocampal tissue injury in mice.Methods: Thirty C57BL/6J mice were randomly divided into 3 groups(n=10):control group, low-dose group, high-dose group. The nasal instillation doses of PM2.5 in the low-dose group and the high-dose group were 1.5 mg/kg BW and 7.5 mg/kg BW, respectively, and the control group was given saline with an equal volume. Saline was sprayed once every other time for 12 times. The serum levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) were determined by ELISA method. HE staining and electron microscopy were used to observe the pathological changes and ultrastructure of lung tissue and hippocampus. The inflammatory cytokine levels in hippocampus were detected by antibody chip technique. Results: There was no significant effect of PM2.5 nasal instillation on serum TNF-α, IL-1β and IL-6 levels (P＞0.05), and there was no obvious pathological changes in lung tissue structure. In hippocampus, low-dose and high-dose PM2.5 exposure could lead to disordered neuronal arrangement in the hippocampal CA3 region, and there were neurological changes around the neuron cells and ultrastructural changes such as edema around small blood vessels. Compared with the control group, the levels of inflammatory cytokines such as CX3CL1, CSF2 and TECK in the low-dose group were increased significantly (P ＜0.05), while sTNFR1 was decreased significantly (P＜0.05); the inflammatory factors CX3CL1, CSF2, and TCA-3 were significantly increased in the high-dose group (P＜0.05), while leptin, MIG, and FASLG were significantly decreased (P＜0.05). Conclusion: Nasal instillation of PM2.5 can induce tissue damage in the hippocampus of mice, and its mechanism of action may be the olfactory brain pathway. The increasing of TNF-α and IL-6 and the decreasing of sTNFR1 and FASLG may be involved in inflammatory mechanisms.

The effects of moderate exercise and overtraining on learning and memory, hippocampal inflammatory cytokine levels, and brain oxidative stress markers in rats

To investigate the exercise intensity effects on rats' memory and learning, animals were divided into control, moderate training (MT), and overtraining (OT) groups. At training last week, learning andmemory was assessed using Morris water maze (MWM) and passive avoidance (PA) tests. Finally, the rat's brains were removed for evaluating oxidative stress and inflammatory cytokines. Overtraining impaired animal's performance in MWM and PA tests. In MT group, hippocampal levels of interleukin 1 beta (IL-1β) and malondialdehyde (MDA) increased, and thiol contents in hippocampal and cortical tissues decreased compared to control. In OT group, tumor necrosis factor α, IL-1β, and C-reactive protein hippocampal levels increased, MDA and nitric oxide metabolite in hippocampal and cortical tissues increased, thiol contents, catalase and superoxide dismutase activity in hippocampal and cortical tissues decreased compared to control and MT groups. Overtraining might lead to learning and memory impairment by increasing the inflammatory cytokine and oxidative stress markers.

Postpartum Changes in Microglia Density and Activation in a Rat Model of Superimposed Preeclampsia

Microglia are the primary immune cells of the central nervous system, surveying the microenvironment and responding to cell injury or tissue damage. The Dahl Salt Sensitive (Dahl‐S) rat model of superimposed preeclampsia (PE) has preexisting hypertension and chronic kidney disease and exhibits characteristic symptoms of PE during pregnancy. Preexisting cardiovascular and renal disease increase the risk of superimposed PE, which further increases risk of maternal complications. Recently, we showed that the rat model of placental ischemia (induced preeclampsia) has increased posterior cortical microglia activation 2 months postpartum. However, whether superimposed PE exacerbates postpartum microglia activation is not known. Because the Dahl‐S rat has increased peripheral inflammation (increased circulating TNFα) during pregnancy and exacerbated hypertension and proteinuria with subsequent pregnancies, we hypothesized that the Dahl‐S model has increased microglia activation after two pregnancies. Dahl‐S rats were randomly assigned to virgin (DSV) or postpartum (DSP) groups (n=3 per group). Postpartum rats were mated twice (3 and 5 months of age) and brains were collected at 8 months of age. Posterior cerebrum was cryo‐sectioned and immuno‐stained using ionized calcium binding adapter molecule (Iba1). Microglia density and morphology were analyzed using ImageJ in 3 images per region and averaged per rat. There was no difference in microglia density (number of Iba1+ microglia per image) in the hippocampus (10±2 in DSV vs. 9±1 in DSP) or cortex (7±1 in DSV vs. 7±2 in DSP). DSP rats had higher proportion of hippocampal Type 3 (78% vs. 62% in DSV) and fewer Type 4 (5% vs. 22% in DSV) microglia (p&lt;0.05). DSP had fewer hippocampal amoeboid (activated) microglia and higher cortical ramified (surveying) microglia compared to DSV (Figure). Taken together, history of superimposed preeclampsia symptoms in DSP rats does not induce exacerbated microglia activation suggesting that pregnancy is either protective to the brain or that following damage, microglia fail to activate, contributing to incomplete repair processes. These hypotheses will be tested in future studies. Future studies will also determine cortical and hippocampal cytokine levels and astrocyte activation in the postpartum Dahl‐S rats.Support or Funding InformationNIH R00HL129192, R25HL121042, 5T32HL105324‐09, R01HL134711This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The effects of exercise on hippocampal inflammatory cytokine levels, brain oxidative stress markers and memory impairments induced by lipopolysaccharide in rats.

The exercise effects on behavioral tests, hippocampal and cortical oxidative stress, and hippocampal inflammatory cytokines of lipopolysaccharide (LPS) administered rats were investigated. The rats were divided into four groups (N= 8): (1) control; (2) moderate training (MT, 15m/min, 30min/day, 9weeks); (3) LPS (1mg/kg LPS) and (4) LPS + MT (1mg/kg LPS; 15m/min, 30min/day, 9weeks). LPS was injected 2h before the behavioral experiments during the last week of training. Finally, the rats' brain were removed for biochemical assessments. LPS increased escape latency and traveled distance to reach the platform in Morris water maze (MWM) test (P < 0.05-P < 0.001). In the passive avoidance (PA) test, LPS decreased the latency to enter the dark compartment and the time spent in the light compartment and increased the time spent in the dark compartment (P < 0.01-P < 0.001), while MT improved the rats performances in MWM and PA tests (P < 0.01-P < 0.001). Additionally, LPS increased tumor necrosis factor α (TNF-α), interleukin 1 beta (IL-1β) and C-reactive protein levels in the hippocampal tissues, malondialdehyde (MDA) and nitric oxide metabolite in hippocampal and cortical tissues, and decreased thiol contents and catalase (CAT) and superoxide dismutase (SOD) activity in hippocampal and cortical tissues compared to the control group (P < 0.01-P < 0.001); while moderate training decreased the levels of TNF-α, IL-1β and MDA; increased thiol contents, and SOD and CAT activity in the LPS + MT compared to the LPS group (P < 0.001). These results indicated that moderate training improved LPS-induced learning and memory impairments by attenuating the hippocampal cytokine levels and brain oxidative damage.

Effect of moxibustion on inflammatory cytokine levels in hippocampus and hypothalamus in rats with fatigue

To investigate the effect of moxibustion of "Zusanli "(ST36) on levels of inflammatory cytokines in the hippocampus and hypothalamus regions of rats with fatigue, so as to reveal its anti-fatigue mechanism. Twenty-four male Sprague-Dawley rats were randomly divided into normal control, fatigue model, and moxibustion groups, with 8 rats in each group. The fatigue model was established by chronic weight-loaded exhaustive swimming. During modeling, the rats in the moxibustion group were given moxibustion (3 moxa cones, about 8 min in duration) at bilateral ST36, once every other day for 11 times in total. The duration of exhausted swimming was observed, and ELISA was used to measure the contents of interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and interferon gamma (IFN-γ) in the hippocampus and hypothalamus tissues. The duration of exhausted swimming was obviously prolonged on day 14 and 21 after moxibustion intervention relevant to the model group (P<0.05, P<0.01). The contents of IL-1β， IL-6 and TNF-α in the hippocampus were significantly increased in the model group than in the normal group (P<0.01), and that of hippocampal IL-6 was considerably decreased in the moxibustion group than in the model group (P<0.05). The content of hippocampal IFN-γ was significantly lower in the model group than in the normal group (P<0.05) and was increased mildly after moxibustion (P>0.05). No significantly changes were found in the levels of hypothalamic IL-1β， IL-6, TNF-α and IFN-γ after modeling and moxibustion (P>0.05), and in the levels of hippocampal IL-1β， TNF-α and IFN-γ after moxibustion (P>0.05)．. Moxibustion can significantly down-regulate hippocampal IL-6 content in fatigue rats, which maybe contribute to its effect in alleviating fatigue. Further studies need being conducted to identify this conclusion.

Heavy Alcohol Exposure Activates Astroglial Hemichannels and Pannexons in the Hippocampus of Adolescent Rats: Effects on Neuroinflammation and Astrocyte Arborization.

A mounting body of evidence indicates that adolescents are specially more susceptible to alcohol influence than adults. However, the mechanisms underlying this phenomenon remain poorly understood. Astrocyte-mediated gliotransmission is crucial for hippocampal plasticity and recently, the opening of hemichannels and pannexons has been found to participate in both processes. Here, we evaluated whether adolescent rats exposed to ethanol exhibit changes in the activity of astrocyte hemichannels and pannexons in the hippocampus, as well as alterations in astrocyte arborization and cytokine levels. Adolescent rats were subjected to ethanol (3.0 g/kg) for two successive days at 48-h periods over 14 days. The opening of hemichannels and pannexons was examined in hippocampal slices by dye uptake, whereas hippocampal cytokine levels and astroglial arborization were determined by ELISA and Sholl analysis, respectively. We found that adolescent ethanol exposure increased the opening of connexin 43 (Cx43) hemichannels and pannexin-1 (Panx1) channels in astrocytes. Blockade of p38 mitogen-activated protein kinase (MAPK), inducible nitric oxide synthase (iNOS) and cyclooxygenases (COXs), as well as chelation of intracellular Ca2+, drastically reduced the ethanol-induced channel opening in astrocytes. Importantly, ethanol-induced Cx43 hemichannel and Panx1 channel activity was correlated with increased levels of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), IL-6 in the hippocampus, as well as with profound alterations in astrocyte arbor complexity. Thus, we propose that uncontrolled opening of astrocyte hemichannels and pannexons may contribute not only to the glial dysfunction and neurotoxicity caused by adolescent alcohol consumption, but also to the pathogenesis of alcohol use disorders in the adulthood.

Resveratrol-loaded nanoemulsion prevents cognitive decline after abdominal surgery in aged rats

The maladaptive response of aged microglia to surgery and consequent neuroinflammation plays a key pathogenic role in postoperative cognitive dysfunction (POCD). Here, we assessed the preventive effect of resveratrol (RESV) for POCD in aged rats. The emulsified form of RESV (e-RESV) was selected to improve its oral and brain bioavailability. Animals were assigned to one of four groups: e-RESV (80 mg/kg) versus vehicle treatment by abdominal surgery versus isoflurane anesthesia alone (n = 8 in each group). The dose-dependent effects of e-RESV were also assessed in dose range of 0–60 mg/kg. Either vehicle or e-RESV was administered intragastrically 24 h before surgery. Seven days after procedure, cognitive function was evaluated using a novel object recognition test, followed by measurement of hippocampal pro-inflammatory cytokine levels. Our results showed that pre-treatment with e-RESV attenuated the surgery-induced cognitive impairment and related hippocampal neuroinflammation at 40 mg/kg or higher doses. Additionally, the ex-vivo experiments revealed that the preemptive e-RESV regimen reduced the hippocampal microglial immune reactivity to lipopolysaccharide. Furthermore, e-RESV induced neuroprotective benefits were inhibited by the concomitant administration of sirtinol, a specific SIRT1 inhibitor. Our findings imply the preventive potential of e-RESV for POCD via the SIRT1 signaling pathway.