Systemic inflammation in early neonatal mice induces transient and lasting neurodegenerative effects

Phyllanthus amarus protects against spatial memory impairment induced by lipopolysaccharide in mice

Phyllanthus amarus Schumach. and Thonn. is a wide spread medicinal herb with various traditional uses. It is well documented for its antioxidant, anti-inflammatory, and hepatoprotective activities. Therefore, it is of interest to evaluate the 80% ethanol extract of Phyllanthus amarus (PA) on spatial memory using the 8-radial arm maze (8-RAM) in mice after induction of neuro inflammation by lipopolysaccharide (LPS) in a 14- and 28-days treatment study. LC-MS/MS was performed to profile the chemical composition in PA extract. Mice were treated orally with 5% v/v tween 20, PA extract (100, 200 and 400 mg/kg), or ibuprofen (IBF 40 mg/kg) for 14 and 28 days. All groups were challenged with LPS (1 mg/kg) via intraperitoneal (i.p.) injection a day prior to the 8-RAM task except for the negative control group which received an i.p. injection of saline. Data obtained were analyzed with one-way ANOVA followed by post hoc Dunnett's test (comparison of all groups against vehicle control). Analysis of LC-MS/MS data revealed the presence of 16 compounds in the PA extract. Administration of PA extract at 200 and 400 mg/kg for 14 and 28 days significantly (*P<0.05) decreased the working and reference memory errors against LPS-induced spatial memory impairment. The observed protective action is possibly due to the putative antineuroinflammatory effects of PA. In conclusion, PA extract possess neuroprotective effects against spatial memory impairment mediated by LPS.

Systemic inflammation impairs microglial Aβ clearance through NLRP3 inflammasome

Alzheimer's disease is the most prevalent type of dementia and is caused by the deposition of extracellular amyloid-beta and abnormal tau phosphorylation. Neuroinflammation has emerged as an additional pathological component. Microglia, representing the brain's major innate immune cells, play an important role during Alzheimer's. Once activated, microglia show changes in their morphology, characterized by a retraction of cell processes. Systemic inflammation is known to increase the risk for cognitive decline in human neurogenerative diseases including Alzheimer's. Here, we assess for the first time microglial changes upon a peripheral immune challenge in the context of aging and Alzheimer's in vivo, using 2-photon laser scanning microscopy. Microglia were monitored at 2 and 10 days post-challenge by lipopolysaccharide. Microglia exhibited a reduction in the number of branches and the area covered at 2 days, a phenomenon that resolved at 10 days. Systemic inflammation reduced microglial clearance of amyloid-beta in APP/PS1 mice. NLRP3 inflammasome knockout blocked many of the observed microglial changes upon lipopolysaccharide, including alterations in microglial morphology and amyloid pathology. NLRP3 inhibition may thus represent a novel therapeutic target that may protect the brain from toxic peripheral inflammation during systemic infection.

Late Brain Involvement after Neonatal Immune Activation

The neonatal immune system is still immature, which makes it more susceptible to the infectious agents. Neonatal immune activation is associated with increased permeability of the blood-brain barrier, causing an inflammatory cascade in the CNS and altering behavioral and neurochemical parameters. One of the hypotheses that has been studied is that neuroinflammation may be involved in neurodegenerative processes, such as Alzheimer's disease (AD). We evaluate visuospatial memory, cytokines levels, and the expression of tau and GSK-3β proteins in hippocampus and cortex of animals exposed to neonatal endotoxemia. C57BL/6 mice aging two days received a single injection of subcutaneous lipopolysaccharide (LPS). At 60,120, and 180 days of age, visual-spatial memory was evaluated and the hippocampus and cortex were dissected to evaluate the cytokines levels and expression of tau and GSK-3β proteins. The animals exposed to LPS in the neonatal period present with visuospatial memory impairment at 120 and 180 days of age. Here there was an increase of TNF-α and IL-1β levels in the hippocampus and cortex only at 60 days of age. Here there was an increase in the expression of GSK-3β in hippocampus of the animals at 60, 120, and 180 days of age. In the cortex, this increase occurred in the 120 and 180 days of age. Tau protein expression was high in hippocampus and cortex at 120 days of age and in hippocampus at 180 days of age. The data observed show that neonatal immune activation may be associated with visuospatial memory impairment, neuroinflammation, and increased expression of GSK-3β and Tau proteins in the long term.

High-Mobility Group Box 1 Neutralization Prevents Chronic Cerebral Hypoperfusion-Induced Optic Tract Injuries in the White Matter Associated with Down-regulation of Inflammatory Responses

Chronic cerebral hypoperfusion (CCH)-induced white matter lesions (WMLs) are region-specific with the optic tract (OT) displaying the most severe damages and leading to visual-based behavioral impairment. Previously we have demonstrated that anti-high-mobility group box 1 (HMGB1) neutralizing antibody (Ab) prevents CCH-induced hippocampal damages via inhibition of neuroinflammation. Here we tested the protective role of the Ab on CCH-induced OT injuries. Rats were treated with permanent occlusion of common carotid arteries (2-VO) or a sham surgery, and then administered with PBS, anti-HMGB1 Ab, or paired control Ab. Pupillary light reflex examination, visual water maze, and tapered beam-walking were performed 28 days post-surgery to investigate the behavioral deficits. Meanwhile, WMLs were measured by Klüver-Barrera (KB) and H&E staining, and glial activation was further assessed to evaluate inflammatory responses in OT. Results revealed that anti-HMGB1 Ab ameliorated the morphological damages (grade scores, vacuoles, and thickness) in OT area and preserved visual abilities. Additionally, the increased levels of inflammatory responses and expressions of TLR4 and NF-κB p65 and phosphorylated NF-κB p65 (p-p65) in OT area were partly down-regulated after anti-HMGB1 treatment. Taken together, these findings suggested that HMGB1 neutralization could ease OT injuries and visual-guided behavioral deficits via suppressing inflammatory responses.

A severe mouse model of spinal muscular atrophy develops early systemic inflammation

Spinal muscular atrophy (SMA) is a fatal genetic disease, mainly affecting children. A number of recent studies show, aside from lower motor neuron degeneration and atrophy of skeletal muscles, widespread defects present in the central nervous system (CNS) and peripheral non-neuronal cell types of SMA patients and mouse models, particularly of severe forms. However, molecular mechanisms underlying the multi-organ manifestations of SMA were hardly understood. Here, using histology, flow cytometry and gene expression analysis in both messenger RNA and protein levels in various tissues, we found that a severe SMA mouse model develops systemic inflammation in early symptomatic stages. SMA mice had an enhanced intestinal permeability, resulting in microbial invasion into the circulatory system. Expression of proinflammatory cytokines was increased in all tissues and the acute phase response in the liver was activated. Systemic inflammation further mobilized glucocorticoid signaling and in turn led to dysregulation of a large set of genes, including robust upregulation of FAM107A in the spinal cord, increased expression of which has been implicated in neurodegeneration. Moreover, we show that lipopolysaccharide challenge markedly suppressed survival of motor neuron 2 exon 7 splicing in all examined peripheral and CNS tissues, resulting in global survival of motor neuron level reduction. Therefore, we identified a novel pathological mechanism in a severe SMA mouse model, which affects phenotypic severity through multiple paths and should contribute to progression of broad neuronal and non-neuronal defects.

Experimental necrotizing enterocolitis induces neuroinflammation in the neonatal brain

Background

Necrotizing enterocolitis (NEC) is an inflammatory gastrointestinal disease primarily affecting preterm neonates. Neonates with NEC suffer from a degree of neurodevelopmental delay that is not explained by prematurity alone. There is a need to understand the pathogenesis of neurodevelopmental delay in NEC. In this study, we assessed the macroscopic and microscopic changes that occur to brain cell populations in specific brain regions in a neonatal mouse model of NEC. Moreover, we investigated the role of intestinal inflammation as part of the mechanism responsible for the changes observed in the brain of pups with NEC.

Methods

Brains of mice were assessed for gross morphology and cerebral cortex thickness (using histology). Markers for mature neurons, oligodendrocytes, neural progenitor cells, microglia, and astrocytes were used to quantify their cell populations in different regions of the brain. Levels of cell apoptosis in the brain were measured by Western blotting and immunohistochemistry. Endoplasmic reticulum (ER) stress markers and levels of pro-inflammatory cytokines (in the ileum and brain) were measured by RT-qPCR and Western blotting. A Pearson test was used to correlate the levels of cytokines (ELISA) in the brain and ileum and to correlate activated microglia and astrocyte populations to the severity of NEC.

Results

NEC pups had smaller brain weights, higher brain-to-body weight ratios, and thinner cortices compared to control pups. NEC pups had increased levels of apoptosis and ER stress. In addition, NEC was associated with a reduction in the number of neurons, oligodendrocytes, and neural progenitors in specific regions of the brain. Levels of pro-inflammatory cytokines and the density of activated microglia and astrocytes were increased in the brain and positively correlated with the increase in the levels pro-inflammatory cytokines in the gut and the severity of NEC damage respectively.

Conclusions

NEC is associated with severe changes in brain morphology, a pro-inflammatory response in the brain that alters cell homeostasis and density of brain cell populations in specific cerebral regions. We show that the severity of neuroinflammation is associated with the severity of NEC. Our findings suggest that early intervention during NEC may reduce the chance of acute neuroinflammation and cerebral damage.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1481-9) contains supplementary material, which is available to authorized users.

Targeting the Blood-Brain Barrier to Prevent Sepsis-Associated Cognitive Impairment

Sepsis is a systemic inflammatory disease resulting from an infection. This disorder affects 750 000 people annually in the United States and has a 62% rehospitalization rate. Septic symptoms range from typical flu-like symptoms (eg, headache, fever) to a multifactorial syndrome known as sepsis-associated encephalopathy (SAE). Patients with SAE exhibit an acute altered mental status and often have higher mortality and morbidity. In addition, many sepsis survivors are also burdened with long-term cognitive impairment. The mechanisms through which sepsis initiates SAE and promotes long-term cognitive impairment in septic survivors are poorly understood. Due to its unique role as an interface between the brain and the periphery, numerous studies support a regulatory role for the blood-brain barrier (BBB) in the progression of acute and chronic brain dysfunction. In this review, we discuss the current body of literature which supports the BBB as a nexus which integrates signals from the brain and the periphery in sepsis. We highlight key insights on the mechanisms that contribute to the BBB's role in sepsis which include neuroinflammation, increased barrier permeability, immune cell infiltration, mitochondrial dysfunction, and a potential barrier role for tissue non-specific alkaline phosphatase (TNAP). Finally, we address current drug treatments (eg, antimicrobials and intravenous immunoglobulins) for sepsis and their potential outcomes on brain function. A comprehensive understanding of these mechanisms may enable clinicians to target specific aspects of BBB function as a therapeutic tool to limit long-term cognitive impairment in sepsis survivors.

Astroglia in Sepsis Associated Encephalopathy

Cellular pathophysiology of sepsis associated encephalopathy (SAE) remains poorly characterised. Brain pathology in SAE, which is manifested by impaired perception, consciousness and cognition, results from multifactorial events, including high levels of systemic cytokines, microbial components and endotoxins, which all damage the brain barriers, instigate neuroinflammation and cause homeostatic failure. Astrocytes, being the principal homeostatic cells of the central nervous system contribute to the brain defence against infection. Forming multifunctional anatomical barriers, astroglial cells maintain brain-systemic interfaces and restrict the damage to the nervous tissue. Astrocytes detect, produce and integrate inflammatory signals between immune cells and cells of brain parenchyma, thus regulating brain immune response. In SAE astrocytes are present in both reactive and astrogliopathic states; balance between these states define evolution of pathology and neurological outcomes. In humans pathophysiology of SAE is complicated by frequent presence of comorbidities, as well as age-related remodelling of the brain tissue with senescence of astroglia; these confounding factors further impact upon SAE progression and neurological deficits.

Consequences of early postnatal lipopolysaccharide exposure on developing lungs in mice

Bronchopulmonary dysplasia (BPD) is a chronic lung disease of infants that is characterized by interrupted lung development. Postnatal sepsis causes BPD, yet the contributory mechanisms are unclear. To address this gap, studies have used lipopolysaccharide (LPS) during the alveolar phase of lung development. However, the lungs of infants who develop BPD are still in the saccular phase of development, and the effects of LPS during this phase are poorly characterized. We hypothesized that chronic LPS exposure during the saccular phase disrupts lung development by mechanisms that promote inflammation and prevent optimal lung development and repair. Wild-type C57BL6J mice were intraperitoneally administered 3, 6, or 10 mg/kg of LPS or a vehicle once daily on postnatal days (PNDs) 3-5. The lungs were collected for proteomic and genomic analyses and flow cytometric detection on PND6. The impact of LPS on lung development, cell proliferation, and apoptosis was determined on PND7. Finally, we determined differences in the LPS effects between the saccular and alveolar lungs. LPS decreased the survival and growth rate and lung development in a dose-dependent manner. These effects were associated with a decreased expression of proteins regulating cell proliferation and differentiation and increased expression of those mediating inflammation. While the lung macrophage population of LPS-treated mice increased, the T-regulatory cell population decreased. Furthermore, LPS-induced inflammatory and apoptotic response and interruption of cell proliferation and alveolarization was greater in alveolar than in saccular lungs. Collectively, the data support our hypothesis and reveal several potential therapeutic targets for sepsis-mediated BPD in infants.

Leaky brain in neurological and psychiatric disorders: Drivers and consequences

BACKGROUND

The blood-brain barrier acts as a highly regulated interface; its dysfunction may exacerbate, and perhaps initiate, neurological and neuropsychiatric disorders.

METHODS

In this narrative review, focussing on redox, inflammatory and mitochondrial pathways and their effects on the blood-brain barrier, a model is proposed detailing mechanisms which might explain how increases in blood-brain barrier permeability occur and can be maintained with increasing inflammatory and oxidative and nitrosative stress being the initial drivers.

RESULTS

Peripheral inflammation, which is causatively implicated in the pathogenesis of major psychiatric disorders, is associated with elevated peripheral pro-inflammatory cytokines, which in turn cause increased blood-brain barrier permeability. Reactive oxygen species, such as superoxide radicals and hydrogen peroxide, and reactive nitrogen species, such as nitric oxide and peroxynitrite, play essential roles in normal brain capillary endothelial cell functioning; however, chronically elevated oxidative and nitrosative stress can lead to mitochondrial dysfunction and damage to the blood-brain barrier. Activated microglia, redox control of which is mediated by nitric oxide synthases and nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, secrete neurotoxic molecules such as reactive oxygen species, nitric oxide, prostaglandin, cyclooxygenase-2, quinolinic acid, several chemokines (including monocyte chemoattractant protein-1 [MCP-1], C-X-C motif chemokine ligand 1 [CXCL-1] and macrophage inflammatory protein 1α [MIP-1α]) and the pro-inflammatory cytokines interleukin-6, tumour necrosis factor-α and interleukin-1β, which can exert a detrimental effect on blood-brain barrier integrity and function. Similarly, reactive astrocytes produce neurotoxic molecules such as prostaglandin E2 and pro-inflammatory cytokines, which can cause a 'leaky brain'.

CONCLUSION

Chronic inflammatory and oxidative and nitrosative stress is associated with the development of a 'leaky gut'. The following evidence-based approaches, which address the leaky gut and blood-brain barrier dysfunction, are suggested as potential therapeutic interventions for neurological and neuropsychiatric disorders: melatonin, statins, probiotics containing Bifidobacteria and Lactobacilli, N-acetylcysteine, and prebiotics containing fructo-oligosaccharides and galacto-oligosaccharides.

Preconditioned neurons with NaB and nicorandil, a favorable source for stroke cell therapy

Poor survival of stem cells in the harsh microenvironment at the site of stroke, especially during acute phase of injury, remains a serious obstacle to achieve the desired prognosis. We hypothesized that combined treatment of neural stem cells (NSCs) with small molecules would precondition them to become robust and survive better as compared with the native nonpreconditioned cells. Mouse ganglionic NSCs were isolated, cultured, and characterized. The cells were preconditioned by treatment with sodium butyrate (NaB) and nicorandil (Nico) and transplanted in an experimentally induced stroke model. Sham-operated animals without treatment or animals with experimental stroke treated with basal medium, native NSCs, NSCs preconditioned with NaB or Nico alone were used as controls. The tissue samples and cells with different treatments were used to measure brain-tissue-derived neurotrophic factor (BDNF) level and the activity of phosphatidylinositol-3 kinase (PI3K), apurinic/apyrimidinic endonuclease 1 (APE1), and nuclear factor-κB (NF-κB) p50 both in vitro and in vivo, respectively. Additionally, survival of the cells and recovery indices for stroke were studied. The combined treatment with NaB + Nico resulted in increased BDNF level and higher PI3K, APE1, and the downstream NF-κB activation, which were blocked by pretreatment with their respective inhibitors. Donor cell survival increased postengraftment as assessed by 5-bromo-2'-deoxyuridine immunostaining and reduced Terminal deoxynucleotide transferase dUTP Nick End Labeling positivity at the site of engraftment. There was reduction in proinflammatory cytokines and infiltration of both GFAP ⁺ and CD68 ⁺ at the injury site. There was reduction in the infarct size and neurological function was preserved in the preconditioned cell treatment group. Our preconditioning approach with small molecules effectively improved the survival as well as functionality of NSCs.

Impact of Neuroinflammation on Hippocampal Neurogenesis: Relevance to Aging and Alzheimer's Disease

The cognitive reserve is associated with the capacity of the brain to maintain cognitive performance in spite of being challenged by stressful degenerative insults related to aging. Hippocampal neurogenesis is a life-long process of continuous addition of functional new neurons in the memory processing circuits. Accordingly, adult hippocampal neurogenesis is increasingly seen as a key determinant of cognitive reserve robustness. On the other side, neuroinflammation, by releasing a plethora of proinflammatory cytokines and other inflammatory molecules, is increasingly shown to be one of the key determinant pathophysiological factors that negatively impact on neurogenesis and on the cognitive reserve, playing a detrimental role in hippocampal neurogenic niche dynamics and in the progression of neurodegenerative diseases, such as Alzheimer's disease. In the present manuscript, we highlight the functional interplay between neuroinflammation, dynamics of the neurogenic niche, and spatial memory performance in healthy and age-related pathological processes, including progression of Alzheimer's disease.

Gray matter structural networks are associated with cardiovascular risk factors in healthy older adults

While recent 'big data' analyses discovered structural brain networks that alter with age and relate to cognitive decline, identifying modifiable factors that prevent these changes remains a major challenge. We therefore aimed to determine the effects of common cardiovascular risk factors on vulnerable gray matter (GM) networks in a large and well-characterized population-based cohort. In 616 healthy elderly (258 women, 60-80 years) of the LIFE-Adult-Study, we assessed the effects of obesity, smoking, blood pressure, markers of glucose and lipid metabolism as well as physical activity on major GM-networks derived using linked independent component analysis. Age, sex, hypertension, diabetes, white matter hyperintensities, education and depression were considered as confounders. Results showed that smoking, higher blood pressure, and higher glycated hemoglobin (HbA1c) were independently associated with lower GM volume and thickness in GM-networks that covered most areas of the neocortex. Higher waist-to-hip ratio was independently associated with lower GM volume in a network of multimodal regions that correlated negatively with age and memory performance. In this large cross-sectional study, we found selective negative associations of smoking, higher blood pressure, higher glucose, and visceral obesity with structural covariance networks, suggesting that reducing these factors could help to delay late-life trajectories of GM aging.

Impact of developmental exposure to methylphenidate on rat brain's immune privilege and behavior: Control versus ADHD model

Attention deficit hyperactivity disorder (ADHD) is the most prevalent childhood mental disorders that often persists into adulthood. Moreover, methylphenidate (MPH) is the mainstay of medical treatment for this disorder. Yet, not much is known about the neurobiological impact of MPH on control versus ADHD conditions, which is crucial to simultaneously clarify the misuse/abuse versus therapeutic use of this psychostimulant. In the present study, we applied biochemical and behavioral approaches to broadly explore the early-life chronic exposure of two different doses of MPH (1.5 and 5 mg/kg/day) on control and ADHD rats (Wistar Kyoto and Spontaneously Hypertensive rats, respectively). We concluded that the higher dose of MPH promoted blood-brain barrier (BBB) permeability and elicited anxiety-like behavior in both control and ADHD animals. BBB dysfunction triggered by MPH was particularly prominent in control rats, which was characterized by a marked disruption of intercellular junctions, an increase of endothelial vesicles, and an upregulation of adhesion molecules concomitantly with the infiltration of peripheral immune cells into the prefrontal cortex. Moreover, both doses of MPH induced a robust neuroinflammatory and oxidative response in control rats. Curiously, in the ADHD model, the lower dose of MPH (1.5 mg/kg/day) had a beneficial effect since it balanced both immunity and behavior relative to vehicle animals. Overall, the contrasting effects of MPH observed between control and ADHD models support the importance of an appropriate MPH dose regimen for ADHD, and also suggest that MPH misuse negatively affects brain and behavior.

Cerebellar microglia are dynamically unique and survey Purkinje neurons in vivo

Microglia are the innate immune cells of the central nervous system and are also important participants in normal development and synaptic plasticity. Here, we demonstrate that the microglia of the mouse cerebellum represent a unique population compared to cortical microglia. Microglia are more sparsely distributed within the cerebellum and have a markedly less ramified morphology compared to their cortical counterparts. Using time-lapse in vivo imaging, we found that these differences in distribution and morphology ultimately lead to decreased parenchymal surveillance by cerebellar microglia. We also observed a novel form of somal motility in cerebellar microglia in vivo, which has not been described in cortical populations. We captured microglial interactions with Purkinje neurons in vivo. Cerebellar microglia interact dynamically with both the dendritic arbors and somas of Purkinje neurons. These findings suggest that cerebellar microglia are physiologically distinct from cortical populations and that these differences may ultimately alter how they could contribute to plasticity and disease processes in the cerebellum. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 78: 627-644, 2018.

Glial cell responses in a murine multifactorial perinatal brain injury model

The impact of traumatic brain injury during the perinatal period, which coincides with glial cell (astrocyte and oligodendrocyte) maturation was assessed to determine whether a second insult, e.g., increased inflammation due to remote bacterial exposure, exacerbates the initial injury's effects, possibly eliciting longer-term brain damage. Thus, a murine multifactorial injury model incorporating both mechanisms consisting of perinatal penetrating traumatic brain injury, with or without intraperitoneal injection of lipopolysaccharide (LPS), an analog of remote pathogen exposure has been developed. Four days after injury, gene expression changes for different cell markers were assessed using mRNA in situ hybridization (ISH) and qPCR. Astrocytic marker mRNA levels increased in the stab-alone and stab-plus-LPS treated animals indicating reactive gliosis. Activated microglial/macrophage marker levels, increased in the ipsilateral sides of stab and stab-plus LPS animals by P10, but the differences resolved by P15. Ectopic expression of glial precursor and neural stem cell markers within the cortical injury site was observed by ISH, suggesting that existing precursors and neural stem cells migrate into the injured areas to replace the cells lost in the injury process. Furthermore, single exposure to LPS concomitant with acute stab injury affected the oligodendrocyte population in both the injured and contralateral uninjured side, indicating that after compromise of the blood-brain barrier integrity, oligodendrocytes become even more susceptible to inflammatory injury. This multifactorial approach should lead to a better understanding of the pathogenic sequelae observed as a consequence of perinatal brain insult/injury, caused by combinations of trauma, intrauterine infection, hypoxia and/or ischemia in humans.

γδT cells but not αβT cells contribute to sepsis-induced white matter injury and motor abnormalities in mice

BACKGROUND

Infection and sepsis are associated with brain white matter injury in preterm infants and the subsequent development of cerebral palsy.

METHODS

In the present study, we used a neonatal mouse sepsis-induced white matter injury model to determine the contribution of different T cell subsets (αβT cells and γδT cells) to white matter injury and consequent behavioral changes. C57BL/6J wild-type (WT), T cell receptor (TCR) δ-deficient (Tcrd ^-/-, lacking γδT cells), and TCRα-deficient (Tcra ^-/-, lacking αβT cells) mice were administered with lipopolysaccharide (LPS) at postnatal day (PND) 2. Brain myelination was examined at PNDs 12, 26, and 60. Motor function and anxiety-like behavior were evaluated at PND 26 or 30 using DigiGait analysis and an elevated plus maze.

RESULTS

White matter development was normal in Tcrd ^-/- and Tcrα ^-/- compared to WT mice. LPS exposure induced reductions in white matter tissue volume in WT and Tcrα ^-/- mice, but not in the Tcrd ^-/- mice, compared with the saline-treated groups. Neither LPS administration nor the T cell deficiency affected anxiety behavior in these mice as determined with the elevated plus maze. DigiGait analysis revealed motor function deficiency after LPS-induced sepsis in both WT and Tcrα ^-/- mice, but no such effect was observed in Tcrd ^-/- mice.

CONCLUSIONS

Our results suggest that γδT cells but not αβT cells contribute to sepsis-induced white matter injury and subsequent motor function abnormalities in early life. Modulating the activity of γδT cells in the early stages of preterm white matter injury might represent a novel therapeutic strategy for the treatment of perinatal brain injury.

Contributions of polygenic risk for obesity to PTSD-related metabolic syndrome and cortical thickness

BACKGROUND

Research suggests that posttraumatic stress disorder (PTSD) is associated with metabolic syndrome (MetS) and that PTSD-associated MetS is related to decreased cortical thickness. However, the role of genetic factors in these associations is unclear. This study evaluated contributions of polygenic obesity risk and PTSD to MetS and of MetS and polygenic obesity risk to cortical thickness.

METHODS

196 white, non-Hispanic veterans of the wars in Iraq and Afghanistan underwent clinical diagnostic interviews, physiological assessments, and genome-wide genotyping; 168 also completed magnetic resonance imaging scans. Polygenic risk scores (PRSs) for obesity were calculated from results of a prior genome-wide association study (Speliotes et al., 2010) and PTSD and MetS severity factor scores were obtained.

RESULTS

Obesity PRS (β=0.15, p=0.009) and PTSD (β=0.17, p=0.005) predicted MetS and interacted such that the association between PTSD and MetS was stronger in individuals with greater polygenic obesity risk (β=0.13, p=0.02). Whole-brain vertex-wise analyses suggested that obesity PRS interacted with MetS to predict decreased cortical thickness in left rostral middle frontal gyrus (β=-0.40, p<0.001).

CONCLUSIONS

Results suggest that PTSD, genetic variability, and MetS are related in a transactional fashion wherein obesity genetic risk increases stress-related metabolic pathology, and compounds the ill health effects of MetS on the brain. Genetic proclivity towards MetS should be considered in PTSD patients when prescribing psychotropic medications with adverse metabolic profiles. Results are consistent with a growing literature suggestive of PTSD-related accelerated aging.

Developmental psychoneuroendocrine and psychoneuroimmune pathways from childhood adversity to disease

Childhood adversity has been repeatedly and robustly linked to physical and mental illness across the lifespan. Yet, the biological pathways through which this occurs remain unclear. Functioning of the inflammatory arm of the immune system and the hypothalamic-pituitary-adrenal (HPA)-axis are both hypothesized pathways through which childhood adversity leads to disease. This review provides a novel developmental framework for examining the role of adversity type and timing in inflammatory and HPA-axis functioning. In particular, we identify elements of childhood adversity that are salient to the developing organism: physical threat, disrupted caregiving, and unpredictable environmental conditions. We propose that existing, well-characterized animal models may be useful in differentiating the effects of these adversity elements and review both the animal and human literature that supports these ideas. To support these hypotheses, we also provide a detailed description of the development and structure of both the HPA-axis and the inflammatory arm of the immune system, as well as recent methodological advances in their measurement. Recommendations for future basic, developmental, translational, and clinical research are discussed.

Neonatal Lipopolysaccharide Infection Causes Demyelination and Behavioral Deficits in Adult and Senile Rat Brain

BACKGROUND

Neonatal bacterial infections have been reported to cause white matter loss, although studies concerning the influence of infection on the expression of myelin and aging are still in their emerging state.

PURPOSE

The present study aimed to investigate the effects of perinatal lipopolysaccharide (LPS) exposure on the myelination at different age points using histochemical and immunocytochemical techniques and the relative motor coordination.

METHODS

A rat bacterial infection model was established by exposing the neonatal rats with LPS (0.3 mg/kg body weight, i.p., on postnatal day (PND) 3 followed by a booster at PND 5) and its impact was studied on the myelination and motor coordination in young, adult, and senile rats.

RESULTS

The results obtained suggest that the administration of LPS induces demyelination, predominantly in cortex and corpus callosum. Low expression level of myelin oligodendrocyte glycoprotein (MOG) was observed at all time points, with prominence at 12, 18, and 24 months of age. In addition, reduced staining with luxol fast blue stain was also recorded in the experimentals. With the increasing demyelination and declining motor ability, LPS exposure also seemed to accelerate normal aging symptoms.

CONCLUSION

There is a direct correlation of myelin damage and poor motor coordination with age. This would provide a better incite to understand inflammation-associated demyelinating changes in age-associated neurodegenerative disorders. Since, no long-term studies on behavioral impairments caused by LPS-induced demyelination in the central nervous system has been reported so far, this work would help in the better understanding of the long-term pathological effects of bacterial-induced demyelination.

Downregulated Glia Interplay and Increased miRNA-155 as Promising Markers to Track ALS at an Early Stage

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of unknown cause. Absence of specific targets and biomarkers compromise the development of new therapeutic strategies and of innovative tools to stratify patients and assess their responses to treatment. Here, we investigate changes in neuroprotective-neuroinflammatory actions in the spinal cord of SOD1 ^G93A mice, at presymptomatic and symptomatic stages to identify stage-specific biomarkers and potential targets. Results showed that in the presymptomatic stage, there are alterations in both astrocytes and microglia, which comprise decreased expression of GFAP and S100B and upregulation of GLT-1, as well as reduced expression of CD11b, M2-phenotype markers, and a set of inflammatory mediators. Reduced levels of Connexin-43, Pannexin-1, CCL21, and CX3CL1 further indicate the existence of a compromised intercellular communication. In contrast, in the symptomatic stage, increased markers of inflammation became evident, such as NF-κB/Nlrp3-inflammasome, Iba1, pro-inflammatory cytokines, and M1-polarizion markers, together with a decreased expression of M2-phenotypic markers. We also observed upregulation of the CX3CL1-CX3CR1 axis, Connexin-43, Pannexin-1, and of microRNAs (miR)-124, miR-125b, miR-146a and miR-21. Reduced motor neuron number and presence of reactive astrocytes with decreased GFAP, GLT-1, and GLAST further characterized this inflammatory stage. Interestingly, upregulation of miR-155 and downregulation of MFG-E8 appear as consistent biomarkers of both presymptomatic and symptomatic stages. We hypothesize that downregulated cellular interplay at the early stages may represent neuroprotective mechanisms against inflammation, SOD1 aggregation, and ALS onset. The present study identified a set of inflamma-miRNAs, NLRP3-inflammasome, HMGB1, CX3CL1-CX3CR1, Connexin-43, and Pannexin-1 as emerging candidates and promising pharmacological targets that may represent potential neuroprotective strategies in ALS therapy.

Neuroanatomy and Physiology of Brain Dysfunction in Sepsis

Sepsis-associated encephalopathy (SAE), a complication of sepsis, is often complicated by acute and long-term brain dysfunction. SAE is associated with electroencephalogram pattern changes and abnormal neuroimaging findings. The major processes involved are neuroinflammation, circulatory dysfunction, and excitotoxicity. Neuroinflammation and microcirculatory alterations are diffuse, whereas excitotoxicity might occur in more specific structures involved in the response to stress and the control of vital functions. A dysfunction of the brainstem, amygdala, and hippocampus might account for the increased mortality, psychological disorders, and cognitive impairment. This review summarizes clinical and paraclinical features of SAE and describes its mechanisms at cellular and structural levels.

The blood-brain barrier in systemic inflammation

The blood-brain barrier (BBB) plays a key role in maintaining the specialized microenvironment of the central nervous system (CNS), and enabling communication with the systemic compartment. BBB changes occur in several CNS pathologies. Here, we review disruptive and non-disruptive BBB changes in systemic infections and other forms of systemic inflammation, and how these changes may affect CNS function in health and disease. We first describe the structure and function of the BBB, and outline the techniques used to study the BBB in vitro, and in animal and human settings. We then summarise the evidence from a range of models linking BBB changes with systemic inflammation, and the underlying mechanisms. The clinical relevance of these BBB changes during systemic inflammation are discussed in the context of clinically-apparent syndromes such as sickness behaviour, delirium, and septic encephalopathy, as well as neurological conditions such as Alzheimer's disease and multiple sclerosis. We review emerging evidence for two novel concepts: (1) a heightened sensitivity of the diseased, versus healthy, BBB to systemic inflammation, and (2) the contribution of BBB changes induced by systemic inflammation to progression of the primary disease process.

Enteric glial reactivity to systemic LPS administration: Changes in GFAP and S100B protein

Lipopolysaccharide (LPS) is used to induce inflammation and promotes nervous system activation. Different regions of the brain present heterogeneous glial responses; thus, in order to verify whether systemic LPS-induced inflammation affects the enteric glia differently across the intestinal segments, we evaluated the expressions of two glial activity markers, GFAP and S100B protein, in different intestine segments, at 1h, 24h and 7days after acute systemic LPS administration (0.25 or 2.5mgkg^-1) in rats. Histological inflammatory analysis indicated that the cecum was most affected when compared to the duodenum and proximal colon at the highest doses of LPS. LPS induced an increased S100B content after 24h in all three regions, which decreased at 7days after the highest dose in all regions. Moreover, at 24h, this dose of LPS increased ex-vivo S100B secretion only in the cecum. The highest dose of LPS also increased GFAP in all regions at 24h, but earlier in the cecum, where LPS-induced enteric S100B and GFAP alterations were dependent on dose, time and intestine region. No associated changes in serum S100B were observed. Our results indicate heterogeneous enteric glial responses to inflammatory insult, as observed in distinct brain areas.

Disrupting the blood-brain barrier by focused ultrasound induces sterile inflammation

MRI-guided pulsed focused ultrasound (pFUS) combined with systemic infusion of ultrasound contrast agent microbubbles (MB) causes localized blood-brain barrier (BBB) disruption that is currently being advocated for increasing drug or gene delivery in neurological diseases. The mechanical acoustic cavitation effects of opening the BBB by low-intensity pFUS+MB, as evidenced by contrast-enhanced MRI, resulted in an immediate damage-associated molecular pattern (DAMP) response including elevations in heat-shock protein 70, IL-1, IL-18, and TNFα indicative of a sterile inflammatory response (SIR) in the parenchyma. Concurrent with DAMP presentation, significant elevations in proinflammatory, antiinflammatory, and trophic factors along with neurotrophic and neurogenesis factors were detected; these elevations lasted 24 h. Transcriptomic analysis of sonicated brain supported the proteomic findings and indicated that the SIR was facilitated through the induction of the NFκB pathway. Histological evaluation demonstrated increased albumin in the parenchyma that cleared by 24 h along with TUNEL+ neurons, activated astrocytes, microglia, and increased cell adhesion molecules in the vasculature. Infusion of fluorescent beads 3 d before pFUS+MB revealed the infiltration of CD68+ macrophages at 6 d postsonication, as is consistent with an innate immune response. pFUS+MB is being considered as part of a noninvasive adjuvant treatment for malignancy or neurodegenerative diseases. These results demonstrate that pFUS+MB induces an SIR compatible with ischemia or mild traumatic brain injury. Further investigation will be required before this approach can be widely implemented in clinical trials.

Selective induction of IL-1β after a brief isoflurane anesthetic in children undergoing MRI examination

PURPOSE

To determine if isoflurane anesthesia without surgery causes systemic inflammation in children. Inflammation is targeted as responsible for the development of many neurologic pathologies. The effect will be evaluated by measuring serum cytokine levels before and after isoflurane anesthesia. The possible neurotoxic effect of anesthetic agents is a concern in pediatric anesthesia. Questions remain as to the true effects of anesthesia alone on systemic inflammation. The current study assesses systemic inflammatory response to general anesthesia in children not exposed to surgical stress.

METHODS

Twenty-five patients, aged 6 months to 11 years undergoing MRI scanning were recruited. Patients with ASA Physical Status Classification >II, known neurologic disease, prematurity, recent infection, or current treatment with anti-inflammatory medications were excluded. Each patient received a sevoflurane induction, peripheral intravenous catheterization, and laryngeal mask airway placement. Isoflurane was titrated to ensure adequate depth of anesthesia. Two peripheral blood samples were obtained: one immediately after placement of the PIV and one upon arrival to the post-anesthesia care unit. Serum cytokine levels were compared between pre- and post-isoflurane time points using paired t tests.

RESULTS

For all patients, interleukin-1β increased after isoflurane when compared to pre-isoflurane samples (pre = 25.97 ± 9.01, post = 38.53 ± 16.56, p = 0.0002). Serum levels of IL-6 (pre = 2.28 ± 2.27, post = 2.04 ± 2.15, p = 0.146) and tumor necrosis factor-α (pre = 94.26 ± 18.07, post = 85.84 ± 12.12, p = 0.057) were not significantly changed. Interleukin-10 and vascular endothelial growth factor were undetectable in pre- and post-isoflurane samples at a minimum detection threshold of 6.6 and 10 pg/ml, respectively.

CONCLUSIONS

A brief (approximately 60 min) exposure to isoflurane general anesthesia, without induced surgical stress, significantly increased serum IL-1β, a selective activation marker of systemic inflammation (IL-1β pathway).

The impact of inflammation on respiratory plasticity

Breathing is a vital homeostatic behavior and must be precisely regulated throughout life. Clinical conditions commonly associated with inflammation, undermine respiratory function may involve plasticity in respiratory control circuits to compensate and maintain adequate ventilation. Alternatively, other clinical conditions may evoke maladaptive plasticity. Yet, we have only recently begun to understand the effects of inflammation on respiratory plasticity. Here, we review some of common models used to investigate the effects of inflammation and discuss the impact of inflammation on nociception, chemosensory plasticity, medullary respiratory centers, motor plasticity in motor neurons and respiratory frequency, and adaptation to high altitude. We provide new data suggesting glial cells contribute to CNS inflammatory gene expression after 24h of sustained hypoxia and inflammation induced by 8h of intermittent hypoxia inhibits long-term facilitation of respiratory frequency. We also discuss how inflammation can have opposite effects on the capacity for plasticity, whereby it is necessary for increases in the hypoxic ventilatory response with sustained hypoxia, but inhibits phrenic long term facilitation after intermittent hypoxia. This review highlights gaps in our knowledge about the effects of inflammation on respiratory control (development, age, and sex differences). In summary, data to date suggest plasticity can be either adaptive or maladaptive and understanding how inflammation alters the respiratory system is crucial for development of better therapeutic interventions to promote breathing and for utilization of plasticity as a clinical treatment.

Activation of the Akt/mTOR signaling pathway: A potential response to long-term neuronal loss in the hippocampus after sepsis

Survivors of sepsis may suffer chronic cognitive impairment as a long-term sequela. However, the precise mechanisms of cognitive dysfunction after sepsis are not well understood. We employed the cecal ligation-and-puncture-induced septic mouse model. We observed elevated phosphorylation of Akt, mammalian target of rapamycin (mTOR) and p70S6K on days 14 and 60, progressive neuronal loss in the cornu ammonis 1 region, and abnormal neuronal morphology in the hippocampus in the sepsis mouse model. These findings indicate that changes in neuronal morphology and number in the hippocampus after sepsis were associated with strong activation of the Akt/mTOR signaling pathway, and may reflect a "self-rescuing" feedback response to neuronal loss after sepsis.

High Mobility Group Box-1: A Missing Link between Diabetes and Its Complications

High mobility group box-1 (HMGB-1), a damage-associated molecular pattern, can be actively or passively released from various cells under different conditions and plays a pivotal role in the pathogenesis of inflammation and angiogenesis-dependent diseases. More and more evidence suggests that inflammation, in addition to its role in progression of diabetes, also promotes initiation and development of diabetic complications. In this review, we focus on the role of HMGB-1 in diabetes-related complications and the therapeutic strategies targeting HMGB-1 in diabetic complications.

Critical Illness Brain Injury

A growing body of literature has shown that survivors of critical illness often struggle with cognitive impairment that persists months to years after hospital discharge. We describe the epidemiology of this form of cognitive impairment-which we refer to as critical illness brain injury-and review the history and maturation of the investigation of this previously unrecognized, yet common problem. We then review the characteristics of critical illness brain injury, which can vary in severity and typically affects multiple domains of cognition. Finally, we examine known risk factors for critical illness brain injury and, based on these data, suggest approaches to patient management.

Ethanol-Induced Neurodegeneration and Glial Activation in the Developing Brain

Ethanol induces neurodegeneration in the developing brain, which may partially explain the long-lasting adverse effects of prenatal ethanol exposure in fetal alcohol spectrum disorders (FASD). While animal models of FASD show that ethanol-induced neurodegeneration is associated with glial activation, the relationship between glial activation and neurodegeneration has not been clarified. This review focuses on the roles of activated microglia and astrocytes in neurodegeneration triggered by ethanol in rodents during the early postnatal period (equivalent to the third trimester of human pregnancy). Previous literature indicates that acute binge-like ethanol exposure in postnatal day 7 (P7) mice induces apoptotic neurodegeneration, transient activation of microglia resulting in phagocytosis of degenerating neurons, and a prolonged increase in glial fibrillary acidic protein-positive astrocytes. In our present study, systemic administration of a moderate dose of lipopolysaccharides, which causes glial activation, attenuates ethanol-induced neurodegeneration. These studies suggest that activation of microglia and astrocytes by acute ethanol in the neonatal brain may provide neuroprotection. However, repeated or chronic ethanol can induce significant proinflammatory glial reaction and neurotoxicity. Further studies are necessary to elucidate whether acute or sustained glial activation caused by ethanol exposure in the developing brain can affect long-lasting cellular and behavioral abnormalities observed in the adult brain.

Macrophage depletion reduced brain injury following middle cerebral artery occlusion in mice

Background

Macrophages are involved in demyelination in many brain diseases. However, the role of macrophages in the recovery phase of the ischemic brain is unknown. The present study aims to explore the role of macrophages in the ischemic brain injury and tissue repair following a 90-min transient middle cerebral artery occlusion in mice.

Methods

Clodronate liposomes were injected into mice to deplete periphery macrophages. These mice subsequently underwent middle cerebral artery occlusion. F4/80⁺ and CD68⁺ cells were examined in the mouse spleen and brain to confirm macrophage depletion at 14 days after middle cerebral artery occlusion. Modified neurological severity scores were used to evaluate the behavioral function between 1 and 14 days after middle cerebral artery occlusion. MBP, Iba1, and CD31 immunostaining were performed to determine myelin lesion, microglia activation, and microvessel density.

Results

Clodronate liposomes depleted 80 % of the macrophages in the mouse spleen and reduced macrophage infiltration in the mouse brain. Macrophage depletion reduced the myelin damage in the ipsilateral striatum and microglia activation in both the ipsilateral cortex and striatum, enhanced the microvessel density in the peri-infarct region, attenuated brain atrophy, and promoted neurological recovery following middle cerebral artery occlusion.

Conclusions

Our results suggested that macrophage depletion is a potential intervention that can promote tissue repair and remodeling after brain ischemia, reduce demyelination and microglia activation, and enhance focal microvessel density.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0504-z) contains supplementary material, which is available to authorized users.

Nanoparticle-Based and Bioengineered Probes and Sensors to Detect Physiological and Pathological Biomarkers in Neural Cells

Nanotechnology, a rapidly evolving field, provides simple and practical tools to investigate the nervous system in health and disease. Among these tools are nanoparticle-based probes and sensors that detect biochemical and physiological properties of neurons and glia, and generate signals proportionate to physical, chemical, and/or electrical changes in these cells. In this context, quantum dots (QDs), carbon-based structures (C-dots, grapheme, and nanodiamonds) and gold nanoparticles are the most commonly used nanostructures. They can detect and measure enzymatic activities of proteases (metalloproteinases, caspases), ions, metabolites, and other biomolecules under physiological or pathological conditions in neural cells. Here, we provide some examples of nanoparticle-based and genetically engineered probes and sensors that are used to reveal changes in protease activities and calcium ion concentrations. Although significant progress in developing these tools has been made for probing neural cells, several challenges remain. We review many common hurdles in sensor development, while highlighting certain advances. In the end, we propose some future directions and ideas for developing practical tools for neural cell investigations, based on the maxim "Measure what is measurable, and make measurable what is not so" (Galileo Galilei).