Inflammation mediates varying effects in neurogenesis: relevance to the pathogenesis of brain injury and neurodegenerative disorders

Suppression of methylmercury-induced MIP-2 expression by N-acetyl-L-cysteine in murine RAW264.7 macrophage cell line

Background

The aim of this study is to examine the inflammatory-cytokine expressions in the presence of non-cytotoxic dose of methylmercury (MeHg) in murine macrophages, which is suspected to play an important role in brain damage caused by MeHg exposure. We focused on murine macrophage inflammatory protein-2 (MIP-2), keratinocyte chemoattractant (KC), and monocyte chemoattractant protein-5 (MCP-5). MIP-2 and KC are murine functional homologues of human IL-8 and MCP-5 for human MCP-1. Furthermore, we examined the suppressive effect of N-acetyl-l-cysteine (NAC) on the MeHg-induced inflammatory cytokines.

Methods

In a murine RAW264.7 macrophage cell line, MeHg-induced cytokine expressions were measured using real-time PCR. The suppressive effect of NAC was examined by putting it into the culture medium together with MeHg (co-treatment). In addition, pre- and post-treatment experiments were conducted, in which the cells were treated with NAC before and after MeHg exposure, respectively.

Results

Exposure to a non-cytotoxic dose of MeHg up-regulated the mRNA expression of MIP-2 and MCP-5. On the other hand, KC expression was not induced in the presence of MeHg. Effect of MeHg on MIP-2 expressions was suppressed by pre-, co-, and post-treatment with NAC. However, the suppressive effect of pre-treatment was less than the post-treatment, which was as effective as co-treatment.

Conclusion

In functional homologues of human IL-8, only MIP-2 expression, not KC, was activated in the presence of non-cytotoxic dose of MeHg in murine RAW264.7 macrophage cell line. The more evident inhibitory effect of NAC observed in post-treatment experiments suggests a possible involvement of intracellular activities such as antioxidant effects.

Functional connectivity structure of cortical calcium dynamics in anesthetized and awake mice

The interplay between hemodynamic-based markers of cortical activity (e.g. fMRI and optical intrinsic signal imaging), which are an indirect and relatively slow report of neural activity, and underlying synaptic electrical and metabolic activity through neurovascular coupling is a topic of ongoing research and debate. As application of resting state functional connectivity measures is extended further into topics such as brain development, aging and disease, the importance of understanding the fundamental physiological basis for functional connectivity will grow. Here we extend functional connectivity analysis from hemodynamic- to calcium-based imaging. Transgenic mice (n = 7) expressing a fluorescent calcium indicator (GCaMP6) driven by the Thy1 promoter in glutamatergic neurons were imaged transcranially in both anesthetized (using ketamine/xylazine) and awake states. Sequential LED illumination (λ = 454, 523, 595, 640nm) enabled concurrent imaging of both GCaMP6 fluorescence emission (corrected for hemoglobin absorption) and hemodynamics. Functional connectivity network maps were constructed for infraslow (0.009–0.08Hz), intermediate (0.08–0.4Hz), and high (0.4–4.0Hz) frequency bands. At infraslow and intermediate frequencies, commonly used in BOLD fMRI and fcOIS studies of functional connectivity and implicated in neurovascular coupling mechanisms, GCaMP6 and HbO₂ functional connectivity structures were in high agreement, both qualitatively and also quantitatively through a measure of spatial similarity. The spontaneous dynamics of both contrasts had the highest correlation when the GCaMP6 signal was delayed with a ~0.6–1.5s temporal offset. Within the higher-frequency delta band, sensitive to slow wave sleep oscillations in non-REM sleep and anesthesia, we evaluate the speed with which the connectivity analysis stabilized and found that the functional connectivity maps captured putative network structure within time window lengths as short as 30 seconds. Homotopic GCaMP6 functional connectivity maps at 0.4–4.0Hz in the anesthetized states show a striking correlated and anti-correlated structure along the anterior to posterior axis. This structure is potentially explained in part by observed propagation of delta-band activity from frontal somatomotor regions to visuoparietal areas. During awake imaging, this spatio-temporal quality is altered, and a more complex and detailed functional connectivity structure is observed. The combined calcium/hemoglobin imaging technique described here will enable the dissociation of changes in ionic and hemodynamic functional structure and neurovascular coupling and provide a framework for subsequent studies of neurological disease such as stroke.

Astrocytes mediated the nootropic and neurotrophic effects of Sarsasapogenin-AA13 via upregulating brain-derived neurotrophic factor

Rhizoma Anemarrhena, a widely used traditional Chinese medicine, has previously been shown to have neuroprotective effect. Sarsasapogenin-AA13 (AA13) is a novel synthetic derivative of Sarsasapogenin, which is extracted from Rhizoma Anemarrhena. The aim of this study is to investigate the nootropic and neurotrophic effects of AA13 and underlying mechanisms. In vitro, cell viability of rat primary astrocytes treated with AA13 and neurons cultured with conditioned medium of AA13-treated rat primary astrocytes was tested by MTT assays. In vivo, a pharmacological model of cognitive impairment induced by scopolamine was employed and spatial memory of the mice was assessed by Morris water maze. This study found that AA13 increased cell viability of primary astrocytes and AA13-treated astrocyte-conditioned medium enhanced the survival rate of primary neurons. Interestingly, AA13 markedly enhanced the level of BDNF in astrocytes. Furthermore, AA13 (6 mg/kg) improved the cognitive deficits in animal models (p<0.05) and BDNF and PSD95 levels were increased in brain. Therefore, we hypothesize that AA13 exerts nootropic and neurotrophic activities through astrocytes mediated upregulation of BDNF secretion. The results suggest that AA13 could be a potential compound for cognitive impairment after further research.

Beneficial effect of aspirin against interferon-α-2b-induced depressive behavior in Sprague Dawley rats

Accumulating data advocates that inflammatory mediators may contribute to depression in experimental models as well as in humans. Nonetheless, whether anti-inflammatory treatments can prevent depression still remains controversial. To substantiate our hypothesis, we used an interferon-α-2b model of depression using Sprague Dawley rats. Interferon-α-2b is a cytokine which activates immune response and also produces depression. The animals were treated for 21 days with aspirin (10 mg/kg, per oral (p.o.)) dexamethasone (1 mg/kg p.o.) and amitriptyline (10 mg/kg p.o.). Amitriptyline was used as reference standard, and given concurrently with aspirin and dexamethasone to examine any synergy. Interferon-α-2b (6000 IU/kg, intraperitoneal (i.p.)) was administered in all the above groups daily, except normal control. Tests performed included sucrose preference test, behavioural tests like forced swim test, elevated plus maze, light dark box and locomotor activity along with biochemical estimations like serum cortisol and brain neurotransmitters. The rats in the group treated with Interferon-α-2b produced depressive behaviour in rats. We found that animals treated with aspirin decreased immobility time in forced swim test, increased sucrose preference, decreased serum cortisol and increased brain serotonin levels signifying antidepressant action. In contrast, there was no effect in groups treated with dexamethasone. Our results suggest that aspirin can serve as a potential antidepressant both individually and as adjuvant agent in the treatment of depression. Inhibition of the cyclo-oxygenase-2 levels and prostaglandins concentration or any other potential physiological and biochemical mechanisms may be involved in antidepressant effect.

High dose tetrabromobisphenol A impairs hippocampal neurogenesis and memory retention

Tetrabromobisphenol A (TBBPA) is a brominated flame retardant that is commonly used in commercial and household products, such as, computers, televisions, mobile phones, and electronic boards. TBBPA can accumulate in human body fluids, and it has been reported that TBBPA possesses endocrine disruptive activity. However, the neurotoxic effect of TBBPA on hippocampal neurogenesis has not yet been investigated. Accordingly, the present study was undertaken to evaluate the effect of TBBPA on adult hippocampal neurogenesis and cognitive function. Male C57BL/6 mice were orally administrated vehicle or TBBPA (20 mg/kg, 100 mg/kg, or 500 mg/kg daily) for two weeks. TBBPA was observed to significantly and dose-dependently reduce the survival of newly generated cells in the hippocampus but not to affect the proliferation of newly generated cells. Numbers of hippocampal BrdU and NeuN positive cells were dose-dependently reduced by TBBPA, indicating impaired neurogenesis in the hippocampus. Interestingly, glial activation without neuronal death was observed in hippocampi exposed to TBBPA. Furthermore, memory retention was found to be adversely affected by TBBPA exposure by a mechanism involving suppression of the BDNF-CREB signaling pathway. The study suggests high dose TBBPA disrupts hippocampal neurogenesis and induces associated memory deficits.

HIV Tat Impairs Neurogenesis through Functioning As a Notch Ligand and Activation of Notch Signaling Pathway

Alterations in adult neurogenesis have been noted in the brain of HIV-infected individuals and are likely linked to HIV-associated neurocognitive deficits, including those in learning and memory. But the underlying molecular mechanisms are not fully understood. In the study, we took advantage of doxycycline-inducible and astrocyte-specific HIV-1 Tat transgenic mice (iTat) and determined the relationship between Tat expression and neurogenesis. Tat expression in astrocytes was associated with fewer neuron progenitor cells (NPCs), fewer immature neurons, and fewer mature neurons in the dentate gyrus of the hippocampus of the mouse brain. In vitro NPC-derived neurosphere assays showed that Tat-containing conditioned media from astrocytes or recombinant Tat protein inhibited NPC proliferation and migration and altered NPC differentiation, while immunodepletion of Tat from Tat-containing conditioned media or heat inactivation of recombinant Tat abrogated those effects. Notch signaling downstream gene Hes1 promoter-driven luciferase reporter gene assay and Western blotting showed that recombinant Tat or Tat-containing conditioned media activated Hes1 transcription and protein expression, which were abrogated by Tat heat inactivation, immunodepletion, and cysteine mutation at position 30. Last, Notch signaling inhibitor N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT) significantly rescued Tat-impaired NPC differentiation in vitro and neurogenesis in vivo Together, these results show that Tat adversely affects NPCs and neurogenesis through Notch signaling and point to the potential of developing Notch signaling inhibitors as HIV/neuroAIDS therapeutics.

SIGNIFICANCE STATEMENT

HIV infection of the CNS causes cognitive and memory deficits, which have become more prevalent in the era of combination antiretroviral therapy (cART). Neurogenesis is impaired in HIV-infected individuals. But the underlying molecular mechanisms remain largely unknown. In this study, we have discovered that HIV Tat impairs neurogenesis through the Notch signaling pathway. These findings are particularly important because Tat protein has recently been detected in the brain of HIV-infected individuals with HIV replication in the periphery being effectively controlled by cART. The current study not only further highlights the importance of HIV Tat protein in HIV/neuroAIDS, but also presents a new strategy to develop novel HIV/neuroAIDS therapeutics, particularly in the era of cART.

A 2-oxa-spiro[5.4]decane scaffold displays neurotrophic, neurogenic and anti-neuroinflammatory activities with high potential for development as a versatile CNS therapeutic

Following our recent discovery of a new scaffold exhibiting significant neurotrophic and neurogenic activities, a structurally tweaked analogue, embodying a 2-oxa-spiro [5.4]decane framework, has been conceptualised and found to be more potent and versatile. It exhibits enhanced neurotrophic and neurogenic action in in vitro, ex vivo and in vivo models and also shows robust neuroprotection in mouse acute cerebral stroke model. The observed attributes are traceable to the predominant activation of the TrkB-PI3K-AKT-CREB pathway. In addition, it also exhibits remarkable anti-neuroinflammatory activity by concurrently down-regulating pro-inflammatory cytokines IL-1α and IL-6, thereby providing a unique molecule with a trinity of neuroactivities, i.e. neurotrophic, neurogenic and anti-inflammatory. The new chemical entity disclosed here has the potential to be advanced as a versatile therapeutic molecule to treat stroke, depression, and possibly other neuropsychiatric disorders associated with attenuated neurotrophic/ neurogenic activity, together with heightened neuroinflammation.

Acute effects of focused ultrasound-induced increases in blood-brain barrier permeability on rat microvascular transcriptome

Therapeutic treatment options for central nervous system diseases are greatly limited by the blood-brain barrier (BBB). Focused ultrasound (FUS), in conjunction with circulating microbubbles, can be used to induce a targeted and transient increase in BBB permeability, providing a unique approach for the delivery of drugs from the systemic circulation into the brain. While preclinical research has demonstrated the utility of FUS, there remains a large gap in our knowledge regarding the impact of sonication on BBB gene expression. This work is focused on investigating the transcriptional changes in dorsal hippocampal rat microvessels in the acute stages following sonication. Microarray analysis of microvessels was performed at 6 and 24 hrs post-FUS. Expression changes in individual genes and bioinformatic analysis suggests that FUS may induce a transient inflammatory response in microvessels. Increased transcription of proinflammatory cytokine genes appears to be short-lived, largely returning to baseline by 24 hrs. This observation may help to explain some previously observed bioeffects of FUS and may also be a driving force for the angiogenic processes and reduced drug efflux suggested by this work. While further studies are necessary, these results open up intriguing possibilities for novel FUS applications and suggest possible routes for pharmacologically modifying the technique.

The far-reaching scope of neuroinflammation after traumatic brain injury

The 'silent epidemic' of traumatic brain injury (TBI) has been placed in the spotlight as a result of clinical investigations and popular press coverage of athletes and veterans with single or repetitive head injuries. Neuroinflammation can cause acute secondary injury after TBI, and has been linked to chronic neurodegenerative diseases; however, anti-inflammatory agents have failed to improve TBI outcomes in clinical trials. In this Review, we therefore propose a new framework of targeted immunomodulation after TBI for future exploration. Our framework incorporates factors such as the time from injury, mechanism of injury, and secondary insults in considering potential treatment options. Structuring our discussion around the dynamics of the immune response to TBI - from initial triggers to chronic neuroinflammation - we consider the ability of soluble and cellular inflammatory mediators to promote repair and regeneration versus secondary injury and neurodegeneration. We summarize both animal model and human studies, with clinical data explicitly defined throughout this Review. Recent advances in neuroimmunology and TBI-responsive neuroinflammation are incorporated, including concepts of inflammasomes, mechanisms of microglial polarization, and glymphatic clearance. Moreover, we highlight findings that could offer novel therapeutic targets for translational and clinical research, assimilate evidence from other brain injury models, and identify outstanding questions in the field.

Association between obesity-related biomarkers and cognitive and motor development in infants

BACKGROUND

This study aimed to verify the association between obesity-related biomarkers and cognitive and motor development in infants between 6 and 24 months of age.

METHODS

A cross-sectional study was conducted with 50 infants and plasma levels of leptin, adiponectin, resistin, soluble tumor necrosis factor receptors 1 and 2 (sTNFR1 and sTNFR2), chemokines, brain-derived neurotrophic factor (BDNF), serum cortisol and redox status were measured. The Bayley-III test was utilized to evaluate cognitive and motor development, and multiple linear stepwise regression models were performed to verify the association between selected biomarkers and cognitive and motor development.

RESULTS

A significant association was found among plasma leptin and sTNFR1 levels with cognitive composite scores, and these two independents variables together explained 37% of the variability of cognitive composite scores (p=0.001). Only plasma sTNFR1 levels were associated and explained 24% of the variability of motor composite scores (p=0.003).

CONCLUSIONS

Plasma levels of sTNFR1 were associated with the increase in cognitive and motor development scores in infants between 6 and 24 months of age through a mechanism not directly related to excess body weight. Moreover, increase in plasma levels of leptin reduced the cognitive development in this age range.

The Function of the Mitochondrial Calcium Uniporter in Neurodegenerative Disorders

The mitochondrial calcium uniporter (MCU)-a calcium uniporter on the inner membrane of mitochondria-controls the mitochondrial calcium uptake in normal and abnormal situations. Mitochondrial calcium is essential for the production of adenosine triphosphate (ATP); however, excessive calcium will induce mitochondrial dysfunction. Calcium homeostasis disruption and mitochondrial dysfunction is observed in many neurodegenerative disorders. However, the role and regulatory mechanism of the MCU in the development of these diseases are obscure. In this review, we summarize the role of the MCU in controlling oxidative stress-elevated mitochondrial calcium and its function in neurodegenerative disorders. Inhibition of the MCU signaling pathway might be a new target for the treatment of neurodegenerative disorders.

The Therapeutic Potential of Targeting Substance P/NK-1R Interactions in Inflammatory CNS Disorders

The inflammatory responses of resident central nervous system (CNS) cells are now known to play a critical role in the initiation and progression of an array of infectious and sterile neuroinflammatory disorders such as meningitis, encephalitis, Parkinson's disease, Alzheimer's disease and multiple sclerosis (MS). Regulating glial inflammatory responses in a timely manner is therefore critical in preserving normal CNS functions. The neuropeptide substance P is produced at high levels within the CNS and its selective receptor, the neurokinin 1 receptor (NK-1R), is abundantly expressed by neurons and is present on glial cell types including microglia and astrocytes. In addition to its functions as a neurotransmitter in the perception of pain and its essential role in gut motility, this tachykinin is widely recognized to exacerbate inflammation at peripheral sites including the skin, gastrointestinal tract and the lungs. Recently, a number of studies have identified a role for substance P and NK-1R interactions in neuroinflammation and described the ability of this neuropeptide to alter the immune functions of activated microglia and astrocytes. In this review article, we describe the expression of substance P and its receptor by resident CNS cells, and we discuss the ability of this neuropeptide to exacerbate the inflammatory responses of glia and immune cells that are recruited to the brain during neurodegenerative diseases. In addition, we discuss the available data indicating that the NK-1R-mediated augmentation of such responses appears to be detrimental during microbial infection and some sterile neurodegenerative disorders, and propose the repurposed use of NK-1R antagonists, of a type that are currently approved as anti-emetic and anti-anxiolytic agents, as an adjunct therapy to ameliorate the inflammatory CNS damage in these conditions.

Hyperglycemia and high nitric oxide level induced oxidative stress in the brain and molecular alteration in the neurons and glial cells of laboratory mouse, Mus musculus

Chronic hyperglycemia (glucotoxicity) is reported to have detrimental effects on various brain functions leading to neurodegenerative changes. However, the effect of hyperglycemia in combination with high nitric oxide (NO) level (reported to be increased during glucotoxicity), on brain functions is not clear yet. The present study was designed to investigate the effects of hyperglycemic drug Streptozotocin (STZ) and NO donor Sodium nitroprusside (SNP) on the brain of laboratory mouse, Mus musculus. Effects of these conditions were studied on the markers of oxidative stress, NF-κB signalling and the markers of neuronal and glial cell activation/inflammation. Results indicate increased level of MDA and altered antioxidant enzymes activity in both the treated groups compared to control but high levels of AGEs, AOPP and AR activity (markers of diabetic complications) were observed in STZ group only. On the other hand, while STZ group showed decreased IL-6 level, it was increased in SNP group but IFN-ϒ level increased in both the treated groups compared to control. Further, in addition to alterations in the expressions of iNOS, IKKβ, IKBα and NF-κB subunits (RelA-p65/RelB-p50) observed in the neurons and glial cells of different brain regions (hypothalamus, basolateral amygdala and cerebral cortex), enhanced expression of microglial CD11b and astrocytic GFAP was also found in both the treated groups compared to control. Present findings led us to conclude that both hyperglycemia and high NO level causes oxidative stress in addition to molecular alteration in the neurons and glial cells. It is suggested that high blood glucose and NO level induced oxidative stress may lead to neuroinflammation possibly via NF-κB signalling.

Anti-Inflammatory Effect of Ethanolic Extract of Sargassum serratifolium in Lipopolysaccharide-Stimulated BV2 Microglial Cells

Sargassum serratifolium was found to contain high concentrations of meroterpenoids, having strong antioxidant, anti-inflammatory, and neuroprotective activities. This study aims to investigate the anti-inflammatory mechanisms of an ethanolic extract of S. serratifolium (ESS) using lipopolysaccharide (LPS)-stimulated BV2 microglial cells and to identify the anti-inflammatory components in ESS. The level of proinflammatory cytokines was measured by enzyme-linked immunosorbent assay. The expression of inflammation-related proteins and mRNA was evaluated by Western blot and reverse transcription-polymerase chain reaction analysis, respectively. Anti-inflammatory activities of isolated components from ESS were analyzed in LPS-stimulated BV2 cells. ESS inhibited LPS-induced nitric oxide (NO) and prostaglandin E2 and the expression of inducible NO synthase and cyclooxygenase-2. ESS also decreased the release of proinflammatory cytokines in a dose-dependent manner. LPS-induced nuclear factor-kappa B (κB) transcriptional activity and translocation into the nucleus were remarkably suppressed by ESS through the prevention of inhibitor κB-α degradation. The main anti-inflammatory components in ESS were identified as sargahydroquinoic acid, sargachromenol, and sargaquinoic acid based on the inhibition of NO production using LPS-stimulated BV2 cells. Furthermore, treatment with ESS significantly reduced levels of tumor necrosis factor-α and interleukin-1β stimulated with LPS in mouse hippocampus. Our results indicate that ESS can be used as a functional food or therapeutic agent for the treatment of neuroinflammatory diseases.

Neuron-microglia interaction induced bi-directional cytotoxicity associated with calpain activation

Activated microglia release pro-inflammatory factors and calpain into the extracellular milieu, damaging surrounding neurons. However, mechanistic links to progressive neurodegeneration in disease such as multiple sclerosis (MS) remain obscure. We hypothesize that persistent damaged/dying neurons may also release cytotoxic factors and calpain into the media, which then activate microglia again. Thus, inflammation, neuronal damage, and microglia activation, i.e., bi-directional interaction between neurons and microglia, may be involved in the progressive neurodegeneration. We tested this hypothesis using two in vitro models: (i) the effects of soluble factors from damaged primary cortical neurons upon primary rat neurons and microglia and (ii) soluble factors released from CD3/CD28 activated peripheral blood mononuclear cells of MS patients on primary human neurons and microglia. The first model indicated that neurons due to injury with pro-inflammatory agents (IFN-γ) release soluble neurotoxic factors, including COX-2, reactive oxygen species, and calpain, thus activating microglia, which in turn released neurotoxic factors as well. This repeated microglial activation leads to persistent inflammation and neurodegeneration. The released calpain from neurons and microglia was confirmed by the use of calpain inhibitor calpeptin or SNJ-1945 as well as μ- and m-calpain knock down using the small interfering RNA (siRNA) technology. Our second model using activated peripheral blood mononuclear cells, a source of pro-inflammatory Th1/Th17 cytokines and calpain released from auto-reactive T cells, corroborated similar results in human primary cell cultures and confirmed calpain to be involved in progressive MS. These insights into reciprocal paracrine regulation of cell injury and calpain activation in the progressive phase of MS, Parkinson's disease, and other neurodegenerative diseases suggest potentially beneficial preventive and therapeutic strategies, including calpain inhibition.

Demyelination-Induced Inflammation Attracts Newly Born Neurons to the White Matter

There is compelling evidence that microglial activation negatively impacts neurogenesis. However, microglia have also been shown to promote recruitment of newly born neurons to injured areas of the gray matter. In the present study, we explored whether demyelination-triggered inflammation alters the process of neurogenesis in the white matter. A 2-μl solution of 0.04 % ethidium bromide was stereotaxically injected into the corpus callosum of adult male rats. Brain inflammation was dampened by daily injections of progesterone (5 mg/kg, s.c.) for 14 days. Control rats received oil (s.c.). Newly born neurons (DCX and Tbr2), microglia (Iba-1), astrocytes (vimentin or GFAP), oligodendrocyte progenitor cells (OPCs; NG2), and mature oligodendrocytes (CC-1) were monitored in the vicinity of demyelination site using immunofluorescent staining. Western blot was used to explore microglial polarization using M1 (iNOS) and M2 (arginase-1) markers. Focal demyelination elicited strong microglial and astroglial activation and reduced the number of OPCs at the site of demyelination. This inflammatory response was associated with enhanced number of newly born neurons in the white matter and the subventricular zone (SVZ). A proportion of newly born neurons within the white matter showed features of OPCs. Interestingly, blunting brain inflammation led to reduced neurogenesis around the demyelination area and in the SVZ. These data suggest that the white matter inflammation creates a conducive environment for the recruitment of newly born neurons. The fact that a sizable fraction of these newly born neurons adopt OPC features suggests that they could contribute to the remyelination process.

Plasma cytokines IL-6, IL-8, and IL-10 are associated with the development of acute respiratory distress syndrome in patients with severe traumatic brain injury

Background

Patients with severe traumatic brain injury (TBI) are at risk of the development of acute respiratory distress syndrome (ARDS). TBI and ARDS pathophysiologic mechanisms are known to independently involve significant inflammatory responses. The literature on the association between plasma inflammatory cytokines and ARDS in patients with TBI is sparse.

Methods

The study was a secondary analysis of the safety of a randomized trial of erythropoietin and transfusion threshold in patients with severe TBI. Inflammatory markers within the first 24 hours after injury were compared in patients who developed ARDS and patients without ARDS, using Cox proportional hazards models.

Results

There were 200 patients enrolled in the study. The majority of plasma and cerebrospinal fluid (CSF) cytokine levels were obtained within 6 hours. Plasma proinflammatory markers IL-6 and IL-8 and anti-inflammatory marker IL-10 were associated with the development of ARDS (adjusted hazard ratio (HR) = 1.55, confidence interval (CI) = 1.14, 2.11, P = 0.005 for IL-6; adjusted HR = 1.32, CI = 1.10, 1.59, P = 0.003 for IL-8).

Conclusion

Plasma markers of IL-6, IL-8, and IL-10 are associated with ARDS in patients with severe TBI.

Trial registration

NCT00313716 registered 4/2006

Lupus brain fog: a biologic perspective on cognitive impairment, depression, and fatigue in systemic lupus erythematosus

Cognitive disturbances, mood disorders and fatigue are common in SLE patients with substantial adverse effects on function and quality of life. Attribution of these clinical findings to immune-mediated disturbances associated with SLE remains difficult and has compromised research efforts in these areas. Improved understanding of the role of the immune system in neurologic processes essential for cognition including synaptic plasticity, long term potentiation and adult neurogenesis suggests multiple potential mechanisms for altered central nervous system function associated with a chronic inflammatory illness such as SLE. This review will focus on the biology of cognition and neuroinflammation in normal circumstances and potential biologic mechanisms for cognitive impairment, depression and fatigue attributable to SLE.

Computational modeling of cytokine signaling in microglia

Neuroinflammation due to glial activation has been linked to many CNS diseases. We developed a computational model of a microglial cytokine interaction network to study the regulatory mechanisms of microglia-mediated neuroinflammation. We established a literature-based cytokine network, including TNFα, TGFβ, and IL-10, and fitted a mathematical model to published data from LPS-treated microglia. The addition of a previously unreported TGFβ autoregulation loop to our model was required to account for experimental data. Global sensitivity analysis revealed that TGFβ- and IL-10-mediated inhibition of TNFα was critical for regulating network behavior. We assessed the sensitivity of the LPS-induced TNFα response profile to the initial TGFβ and IL-10 levels. The analysis showed two relatively shifted TNFα response profiles within separate domains of initial condition space. Further analysis revealed that TNFα exhibited adaptation to sustained LPS stimulation. We simulated the effects of functionally inhibiting TGFβ and IL-10 on TNFα adaptation. Our analysis showed that TGFβ and IL-10 knockouts (TGFβ KO and IL-10 KO) exert divergent effects on adaptation. TFGβ KO attenuated TNFα adaptation whereas IL-10 KO enhanced TNFα adaptation. We experimentally tested the hypothesis that IL-10 KO enhances TNFα adaptation in murine macrophages and found supporting evidence. These opposing effects could be explained by differential kinetics of negative feedback. Inhibition of IL-10 reduced early negative feedback that results in enhanced TNFα-mediated TGFβ expression. We propose that differential kinetics in parallel negative feedback loops constitute a novel mechanism underlying the complex and non-intuitive pro- versus anti-inflammatory effects of individual cytokine perturbations.

Relationship between trauma-induced coagulopathy and progressive hemorrhagic injury in patients with traumatic brain injury

Progressive hemorrhagic injury (PHI) can be divided into coagulopathy-related PHI and normal coagu- lation PHI. Coagulation disorders after traumatic brain injuries can be included in trauma-induced coagulopathy (TIC). Some studies showed that TIC is associated with PHI and increases the rates of disability and mortality. In this review, we discussed some mechanisms in TIC, which is of great importance in the development of PHI, including tissue factor (TF) hypothesis, protein C pathway and thrombocytopenia. The main mechanism in the relation of TIC to PHI is hypocoagulability. We also reviewed some coagulopathy parameters and proposed some possible risk factors, predictors and therapies.

Functions and mechanisms of microglia/macrophages in neuroinflammation and neurogenesis after stroke

Microglia/macrophages are the major immune cells involved in the defence against brain damage. Their morphology and functional changes are correlated with the release of danger signals induced by stroke. These cells are normally responsible for clearing away dead neural cells and restoring neuronal functions. However, when excessively activated by the damage-associated molecular patterns following stroke, they can produce a large number of proinflammatory cytokines that can disrupt neural cells and the blood-brain barrier and influence neurogenesis. These effects indicate the important roles of microglia/macrophages in the pathophysiological processes of stroke. However, the modifiable and adaptable nature of microglia/macrophages may also be beneficial for brain repair and not just result in damage. These distinct roles may be attributed to the different microglia/macrophage phenotypes because the M1 population is mainly destructive, while the M2 population is neuroprotective. Additionally, different gene expression signature changes in microglia/macrophages have been found in diverse inflammatory milieus. These biofunctional features enable dual roles for microglia/macrophages in brain damage and repair. Currently, it is thought that the proper inflammatory milieu may provide a suitable microenvironment for neurogenesis; however, detailed mechanisms underlying the inflammatory responses that initiate or inhibit neurogenesis remain unknown. This review summarizes recent progress concerning the mechanisms involved in brain damage, repair and regeneration related to microglia/macrophage activation and phenotype transition after stroke. We also argue that future translational studies should be targeting multiple key regulating molecules to improve brain repair, which should be accompanied by the concept of a "therapeutic time window" for sequential therapies.

Glial Modulation by N-acylethanolamides in Brain Injury and Neurodegeneration

Neuroinflammation involves the activation of glial cells and represents a key element in normal aging and pathophysiology of brain damage. N-acylethanolamides (NAEs), naturally occurring amides, are known for their pro-homeostatic effects. An increase in NAEs has been reported in vivo and in vitro in the aging brain and in brain injury. Treatment with NAEs may promote neuroprotection and exert anti-inflammatory actions via PPARα activation and/or by counteracting gliosis. This review aims to provide an overview of endogenous and exogenous properties of NAEs in neuroinflammation and to discuss their interaction with glial cells.

Adult neurogenesis and reproductive functions in mammals

During adulthood, the mammalian brain retains the capacity to generate new cells and new neurons in particular. It is now well established that the birth of these new neurons occurs in well-described sites: the hippocampus and the subventricular zone of the lateral ventricle, as well as in other brain regions including the hypothalamus. In this review, we describe the canonical neurogenic niches and illustrate the functional relevance of adult-born neurons of each neurogenic niche in the reproductive physiology. More specifically, we highlight the effect of reproductive social stimuli on the neurogenic processes and conversely, the contributions of adult-born neurons to the reproductive physiology and behavior. We next review the recent discovery of a novel neurogenic niche located in the hypothalamus and the median eminence and the compelling evidence of the link existing between the new-born hypothalamic neurons and the regulation of metabolism. In addition, new perspectives on the possible involvement of hypothalamic neurogenesis in the control of photoperiodic reproductive physiology in seasonal mammals are discussed. Altogether, the studies highlighted in this review demonstrate the potential role of neurogenesis in reproductive function and emphasize the importance of increasing our knowledge on the regulation processes and the physiological relevance of these adult-born neurons. This constitutes a necessary step toward a potential manipulation of these plasticity mechanisms.

Mesencephalic astrocyte-derived neurotrophic factor attenuates inflammatory responses in lipopolysaccharide-induced neural stem cells by regulating NF-κB and phosphorylation of p38-MAPKs pathways

Mesencephalic astrocyte-derived neurotrophic factor (MANF), a new evolutionary conserved neurotrophic factor (NTF), has been reported to protect midbrain dopaminergic neurons of neurodegenerative diseases such as Parkinson's disease (PD) model. Neural stem cells (NSCs) can play a role as the therapeutic tool in neurodegenerative diseases, but the inflammatory responses of central nervous system (CNS) appear to harm this function. Although studies have previously demonstrated the protective effect of MANF on neurons of CNS, it is lacking in making great efforts on the function of MANF on NSCs. The aim of this study was to investigate the antiinflammatory responses and signaling mechanisms of MANF on lipopolysaccharide (LPS)-induced NSCs. In the results, MANF decreased the proinflammatory cytokines of IL-1β, TNF-α, and IFN-γ induced by LPS by regulating NF-κB and phosphorylation of p38-mitogen-activated protein kinases (MAPKs) pathways, neither p-JNK nor p-ERK signaling. These findings suggest that MANF can facilitate to protect the inflammatory responses of NSCs, and provide beneficial function for the application of NSCs in the therapy.

Retinal ganglion cell death in glaucoma: Exploring the role of neuroinflammation

In clinical glaucoma, as well as in experimental models, the loss of retinal ganglion cells occurs by apoptosis. This final event is preceded by inflammatory responses involving the activation of innate and adaptive immunity, with retinal and optic nerve resident glial cells acting as major players. Here we review the current literature on the role of neuroinflammation in neurodegeneration, focusing on the inflammatory molecular mechanisms involved in the pathogenesis and progression of the optic neuropathy.

Effects of Ranolazine on Astrocytes and Neurons in Primary Culture

Ranolazine (Rn) is an antianginal agent used for the treatment of chronic angina pectoris when angina is not adequately controlled by other drugs. Rn also acts in the central nervous system and it has been proposed for the treatment of pain and epileptic disorders. Under the hypothesis that ranolazine could act as a neuroprotective drug, we studied its effects on astrocytes and neurons in primary culture. We incubated rat astrocytes and neurons in primary cultures for 24 hours with Rn (10-7, 10-6 and 10-5 M). Cell viability and proliferation were measured using trypan blue exclusion assay, MTT conversion assay and LDH release assay. Apoptosis was determined by Caspase 3 activity assay. The effects of Rn on pro-inflammatory mediators IL-β and TNF-α was determined by ELISA technique, and protein expression levels of Smac/Diablo, PPAR-γ, Mn-SOD and Cu/Zn-SOD by western blot technique. In cultured astrocytes, Rn significantly increased cell viability and proliferation at any concentration tested, and decreased LDH leakage, Smac/Diablo expression and Caspase 3 activity indicating less cell death. Rn also increased anti-inflammatory PPAR-γ protein expression and reduced pro-inflammatory proteins IL-1 β and TNFα levels. Furthermore, antioxidant proteins Cu/Zn-SOD and Mn-SOD significantly increased after Rn addition in cultured astrocytes. Conversely, Rn did not exert any effect on cultured neurons. In conclusion, Rn could act as a neuroprotective drug in the central nervous system by promoting astrocyte viability, preventing necrosis and apoptosis, inhibiting inflammatory phenomena and inducing anti-inflammatory and antioxidant agents.

Immunomodulation in stem cell differentiation into neurons and brain repair

Immunomodulators regulate stem cell activity at all stages of development as well as during adulthood. Embryonic stem cell (ESC) proliferation as well as neurogenic processes during embryonic development are controlled by factors of the immune system. We review here immunophenotypic expression patterns of  different stem cell types, including ESC, neural (NSC) and tissue-specific mesenchymal stem cells (MSC), and focus on immunodulatory properties of these cells. Immune and inflammatory responses, involving actions of cytokines as well as toll-like receptor (TLR) signaling are known to affect the differentiation capacity of NSC and MSC. Secretion of pro- and anti-inflammatory messengers by MSC have been observed as the consequence of TLR and cytokine activation and promotion of differentiation into specified phenotypes. As result of augmented differentiation capacity, stem cells secrete angiogenic factors including vascular endothelial growth factor, resulting in multifactorial actions in tissue repair. Immunoregulatory properties of tissue specific adult stem cells are put into the context of possible clinical applications.

Neuroepidemiology of traumatic brain injury

Traumatic brain injury (TBI) is a significant public-health concern. TBI is defined as an acute brain injury resulting from mechanical energy to the head from external physical forces. Some of the leading causes of TBI include falls, assaults, motor vehicle or traffic accidents, and sport-related concussion. Two of the most common identified risk factors are sex (males are nearly three times more likely to suffer a TBI than females); and a bimodal age pattern (persons 65 years and older, and children under 14 years old). It is estimated that approximately 1.5-2 million Americans suffer from TBI annually. TBIs account for around 1.4 million emergency room visits, 275 000 hospital admissions, and 52 000 deaths in the USA each year. TBI contributes to approximately 30% of all deaths in the USA annually. In Australia, it is estimated that approximately 338 700 individuals (1.9% of the population) suffer from a disability related to TBI. Of these, 160 200 were severely or profoundly affected by acquired brain injury, requiring daily support. In the UK, TBI accounted for 3.4% of all emergency department attendances annually. An overall rate of 453 per 100 000 was found for all TBI severities, of which 40 per 100 000 (10.9%) were moderate to severe. TBI often results in residual symptoms that affect an individual's cognition, movement, sensation, and/or emotional functioning. Recovery and rehabilitation from TBI may require considerable resources and may take years. Some individuals never fully recover, and some require lifetime ongoing care and support. TBI has an enormous social and financial cost, with estimates of the annual financial burden associated with TBI ranging between 9 and 10 billion US dollars.

Propranolol and Mesenchymal Stromal Cells Combine to Treat Traumatic Brain Injury

More than 6.5 million patients are burdened by the physical, cognitive, and psychosocial deficits associated with traumatic brain injury (TBI) in the U.S. Despite extensive efforts to develop neuroprotective therapies for this devastating disorder, there have been no successful outcomes in human clinical trials to date. Retrospective studies have shown that β-adrenergic receptor blockers, specifically propranolol, significantly decrease mortality of TBI through mechanisms not yet fully elucidated but are thought to counterbalance a hyperadrenergic state resulting from a TBI. Conversely, cellular therapies have been shown to improve long-term behavior following TBI, likely by reducing inflammation. Given the nonredundancy in their therapeutic mechanisms, we hypothesized that a combination of acute propranolol followed by mesenchymal stem cells (MSCs) isolated from human bone marrow would have additive effects in treating a rodent model of TBI. We have found that the treatments are well-tolerated individually and in combination with no adverse events. MSCs decrease BBB permeability at 96 hours after injury, inhibit a significant accumulation of activated microglia/macrophage in the thalamic region of the brain both short and long term, and enhance neurogenesis short term. Propranolol decreases edema and reduces the number of fully activated microglia at 7 days and the number of semiactivated microglia at 120 days. Combinatory treatment improved cognitive and memory functions 120 days following TBI. Therefore, the results here suggest a new, efficacious sequential treatment for TBI may be achieved using the β-blocker propranolol followed by MSC treatment.

SIGNIFICANCE

Despite continuous efforts, traumatic brain injury (TBI) remains the leading cause of death and disability worldwide in patients under the age of 44. In this study, an animal model of moderate-severe TBI was treated with an acute dose of propranolol followed by a delayed dose of human mesenchymal stem cells (MSCs), resulting in improved short- and long-term measurements. These results have direct translational application. They reinforce the inevitable clinical trial of MSCs to treat TBI by demonstrating, among other benefits, a notable decrease in chronic neuroinflammation. More importantly, these results demonstrate that MSCs and propranolol, which is increasingly being used clinically for TBI, are compatible treatments that improve overall outcome.

Glutaminase-containing microvesicles from HIV-1-infected macrophages and immune-activated microglia induce neurotoxicity

BACKGROUND

HIV-1-infected and/or immune-activated microglia and macrophages are pivotal in the pathogenesis of HIV-1-associated neurocognitive disorders (HAND). Glutaminase, a metabolic enzyme that facilitates glutamate generation, is upregulated and may play a pathogenic role in HAND. Our previous studies have demonstrated that glutaminase is released to the extracellular fluid during HIV-1 infection and neuroinflammation. However, key molecular mechanisms that regulate glutaminase release remain unknown. Recent advances in understanding intercellular trafficking have identified microvesicles (MVs) as a novel means of shedding cellular contents. We posit that during HIV-1 infection and immune activation, microvesicles may mediate glutaminase release, generating excessive and neurotoxic levels of glutamate.

RESULTS

MVs isolated through differential centrifugation from cell-free supernatants of monocyte-derived macrophages (MDM) and BV2 microglia cell lines were first confirmed in electron microscopy and immunoblotting. As expected, we found elevated number of MVs, glutaminase immunoreactivities, as well as glutaminase enzyme activity in the supernatants of HIV-1 infected MDM and lipopolysaccharide (LPS)-activated microglia when compared with controls. The elevated glutaminase was blocked by GW4869, a neutral sphingomyelinase inhibitor known to inhibit MVs release, suggesting a critical role of MVs in mediating glutaminase release. More importantly, MVs from HIV-1-infected MDM and LPS-activated microglia induced significant neuronal injury in rat cortical neuron cultures. The MV neurotoxicity was blocked by a glutaminase inhibitor or GW4869, suggesting that the neurotoxic potential of HIV-1-infected MDM and LPS-activated microglia is dependent on the glutaminase-containing MVs.

CONCLUSIONS

These findings support MVs as a potential pathway/mechanism of excessive glutamate generation and neurotoxicity in HAND and therefore MVs may serve as a novel therapeutic target.

Nitric Oxide Regulates Neurogenesis in the Hippocampus following Seizures

Hippocampal neurogenesis is changed by brain injury. When neuroinflammation accompanies injury, activation of resident microglial cells promotes the release of inflammatory cytokines and reactive oxygen/nitrogen species like nitric oxide (NO). In these conditions, NO promotes proliferation of neural stem cells (NSC) in the hippocampus. However, little is known about the role of NO in the survival and differentiation of newborn cells in the injured dentate gyrus. Here we investigated the role of NO following seizures in the regulation of proliferation, migration, differentiation, and survival of NSC in the hippocampus using the kainic acid (KA) induced seizure mouse model. We show that NO increased the proliferation of NSC and the number of neuroblasts following seizures but was detrimental to the survival of newborn neurons. NO was also required for the maintenance of long-term neuroinflammation. Taken together, our data show that NO positively contributes to the initial stages of neurogenesis following seizures but compromises survival of newborn neurons.

Differentiation of stem cells derived from carious teeth into dopaminergic-like cells

AIM

To investigate whether dental pulp stem cells from carious teeth (DPSCs-CT) can differentiate into functional dopaminergic-like (DAergic) cells and provide an alternative cell source in regenerative medicine.

METHODOLOGY

Dental pulp stem cells from healthy (DPSCs) and carious teeth (DPSCs-CT) were isolated from young donors. Both cell lines were expanded in identical culture conditions and subsequently differentiated towards DAergic-like cells using pre-defined dopaminergic cocktails. The dopaminergic efficiencies were evaluated both at gene and protein as well as at secretome levels.

RESULTS

The efficiency of DPSCs-CT to differentiate into DAergic-like cells was not equivalent to that of DPSCs. This was further reflected in both gene and protein generation whereby key neuronal markers such as nestin, NURR1 and beta-III-tubulin were expressed significantly lower as compared to differentiated DPSCs (P < 0.05). In addition, expressions of transcriptomes related to neurogenesis revealed downregulation of more than 50% of the genes as compared to differentiated DPSC (P < 0.05). Amongst the notable genes were those from the transcription factors family (FLNA, MEF2C, NEUROG2), signalling pathway family (DLL1, Notch1, TGF-β1), neuro-inducer family (BDNF) and cell communication family (APBB1).

CONCLUSIONS

DPSCs-CT were able to differentiate into DAergic-like cells but not as efficiently as DPSCs. As such, prior to use in regenerative medicine, stem cells from any source should be thoroughly investigated beyond conventional benchmarks such as that proposed by the International Society for Cellular Therapy (ISCT).

Alginate micro-encapsulation of mesenchymal stromal cells enhances modulation of the neuro-inflammatory response

BACKGROUND AIMS

Modulation of inflammation after brain trauma is a key therapeutic goal aimed at limiting the consequences of the subsequent injury cascade. Mesenchymal stromal cells (MSCs) have been demonstrated to dynamically regulate the inflammatory environment in several tissue systems, including the central nervous system. There has been limited success, however, with the use of direct implantation of cells in the brain caused by low viability and engraftment at the injury site. To circumvent this, we encapsulated MSCs in alginate microspheres and evaluated the ability of these encapsulated MSCs to attenuate inflammation in rat organotypic hippocampal slice cultures (OHSC).

METHODS

OHSC were administered lipopolysaccharide to induce inflammation and immediately co-cultured with encapsulated or monolayer human MSCs. After 24 h, culture media was assayed for the pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-α) produced by OHSC, as well as MSC-produced trophic mediators.

RESULTS

Encapsulated MSCs reduced TNF-α more effectively than did monolayer MSCs. Additionally, there was a strong correlation between increased prostaglandin E2 (PGE2) and reduction of TNF-α. In contrast to monolayer MSCs, inflammatory signals were not required to stimulate PGE2 production by encapsulated MSCs. Further encapsulation-stimulated changes were revealed in a multiplex panel analyzing 27 MSC-produced cytokines and growth factors, from which additional mediators with strong correlations to TNF-α levels were identified.

CONCLUSIONS

These results suggest that alginate encapsulation of MSCs may not only provide an improved delivery vehicle for transplantation but may also enhance MSC therapeutic benefit for treating neuro-inflammation.

Neuroimaging assessment of early and late neurobiological sequelae of traumatic brain injury: implications for CTE

Traumatic brain injury (TBI) has been increasingly accepted as a major external risk factor for neurodegenerative morbidity and mortality. Recent evidence indicates that the resultant chronic neurobiological sequelae following head trauma may, at least in part, contribute to a pathologically distinct disease known as Chronic Traumatic Encephalopathy (CTE). The clinical manifestation of CTE is variable, but the symptoms of this progressive disease include impaired memory and cognition, affective disorders (i.e., impulsivity, aggression, depression, suicidality, etc.), and diminished motor control. Notably, mounting evidence suggests that the pathology contributing to CTE may be caused by repetitive exposure to subconcussive hits to the head, even in those with no history of a clinically evident head injury. Given the millions of athletes and military personnel with potential exposure to repetitive subconcussive insults and TBI, CTE represents an important public health issue. However, the incidence rates and pathological mechanisms are still largely unknown, primarily due to the fact that there is no in vivo diagnostic tool. The primary objective of this manuscript is to address this limitation and discuss potential neuroimaging modalities that may be capable of diagnosing CTE in vivo through the detection of tau and other known pathological features. Additionally, we will discuss the challenges of TBI research, outline the known pathology of CTE (with an emphasis on Tau), review current neuroimaging modalities to assess the potential routes for in vivo diagnosis, and discuss the future directions of CTE research.

Neurorestorative Therapy of Stroke in Type 2 Diabetes Mellitus Rats Treated With Human Umbilical Cord Blood Cells

BACKGROUND AND PURPOSE

Diabetes mellitus is a high-risk factor for ischemic stroke. Diabetic stroke patients suffer worse outcomes, poor long-term recovery, risk of recurrent strokes, and extensive vascular damage. We investigated the neurorestorative effects and the underlying mechanisms of stroke treatment with human umbilical cord blood cells (HUCBCs) in type 2 diabetes mellitus (T2DM) rats.

METHODS

Adult male T2DM rats were subjected to 2 hours of middle cerebral artery occlusion (MCAo). Three days after MCAo, rats were treated via tail-vein injection with (1) PBS and (2) HUCBCs (5×10(6)), n=10 per group.

RESULTS

HUCBC stroke treatment initiated 3 days after MCAo in T2DM rats did not significantly decrease blood-brain barrier leakage (P=0.1) and lesion volume (P=0.078), but significantly improved long-term functional outcome and decreased brain hemorrhage (P<0.05) when compared with the PBS-treated T2DM MCAo control group. HUCBC treatment significantly promoted white matter remodeling as indicated by increased expression of Bielschowsky silver (axons marker), Luxol fast blue (myelin marker), SMI-31 (neurofilament), and Synaptophysin in the ischemic border zone. HUCBC promoted vascular remodeling and significantly increased arterial and vascular density. HUCBC treatment of stroke in T2DM rats significantly increased M2 macrophage polarization (increased M2 macrophage, CD163and CD 206; decreased M1 macrophage, ED1 and inducible nitric oxide synthase expression) in the ischemic brain compared with PBS-treated T2DM MCAo controls (P<0.05). HUCBC also significantly decreased proinflammatory factors, that is, matrix metalloproteinase 9, receptor for advanced glycation end products and toll-like receptor 4 expression in the ischemic brain.

CONCLUSIONS

HUCBC treatment initiated 3 days after stroke significantly increased white matter and vascular remodeling in the ischemic brain as well as decreased neuroinflammatory factor expression in the ischemic brain in T2DM rats and promoted M2 macrophage polarization. HUCBC reduction of neuroinflammation and increased vascular and white matter axonal remodeling may contribute to the HUCBC-induced beneficial effects in T2DM stroke rats.

Temporal profile of M1 and M2 responses in the hippocampus following early 24h of neurotrauma

Traumatic brain injury (TBI) elicits complex inflammatory assets (M1 and M2 responses) in the brain that include the expression of various cytokines/chemokines and the recruitment of blood cells, contributing secondary injury cascades (SIC), and also recovery processes. The modulation of such inflammatory assets might be a therapeutic option following TBI. The present study assesses a temporal profile of various molecular markers of M1 and M2 response in the hippocampus after TBI. Following a unilateral controlled cortical impact (CCI) on young rats, hippocampal tissues of each brain were harvested at 2, 4, 6, 10, and 24h post trauma. Including shams (craniotomy only), half of the rats were assessed for gene expression and half for the protein of various markers for M1 [interferon-gamma (IFNγ), tumor necrosis factor-α (TNFα), interleukin (IL)-1-β (IL-1β), and IL-6] and M2 [IL-4, IL-10, IL-13, arginase 1 (Arg1), YM1, FIZZ1, and mannose receptor C-1 (MRC1)] responses. Analysis revealed that molecular markers of M1 and M2 responses have heterogeneous injury effects in the hippocampus and that "time-post-injury" is an important factor in determining inflammation status. With the heterogeneous gene expression of pro-inflammatory cytokines, M1 response was significantly elevated at 2h and declined at 24h after TBI, however, their levels remained higher than the sham rats. Except IFNγ, proteins of M1 cytokines were significantly elevated in the first 24h, and peaked between 2-6h [TNFα (2h), IL-1β (6h), and IL-6 (4-6h)]. With the heterogeneous relative gene expression of Arg1, YM1, FIZZ1, and MRC1, levels of M2 cytokines were peaked at 24h post TBI. IL-10 and IL-13 expression appeared biphasic in the first 24h. Protein values of IL-4 and IL-13 peaked at 24h and IL-10 at 6h post injury. Results suggest that the M1 response rises rapidly after injury and overpowers the initial, comparatively smaller, or transient M2 response. A treatment that can modulate inflammation, reduce SIC, and improve recovery should be initiated early (within 10h) after TBI.

Microglia-derived IL-1β triggers p53-mediated cell cycle arrest and apoptosis in neural precursor cells

Neurogenesis persists in the adult brain and can contribute to learning and memory processes and potentially to regeneration and repair of the affected nervous system. Deregulated neurogenesis has been observed in neuropathological conditions including neurodegenerative diseases, trauma and stroke. However, the survival of neural precursor cells (NPCs) and newly born neurons is adversely affected by the inflammatory environment that arises as a result of microglial activation associated with injury or disease processes. In the present study, we have investigated the mechanisms by which microglia affect NPC proliferation and survival. Importantly, we demonstrate that interleukin-1β (IL-1β) produced by lipopolysaccharide/interferon-γ-activated microglia is necessary to induce cell cycle arrest and apoptosis in NPCs in vitro. Mechanistically, we show that IL-1β activates the tumor suppressor p53 through an oxidative stress-dependent mechanism resulting in p53-mediated induction of the cyclin-dependent kinase inhibitor p21 and the proapoptotic Bcl-2 (B-cell lymphoma-2) family members Puma (p53-upregulated modulator of apoptosis) and Noxa. Furthermore, we demonstrate that cell cycle arrest and apoptosis induced by recombinant IL-1β or activated microglia is attenuated in p53-deficient NPCs. Finally, we have determined that IL-1β induces NPC death via the p53-dependent induction of Puma leading to the activation of a Bax (Bcl-2-associated X protein)-mediated mitochondrial apoptotic pathway. In summary, we have elucidated a novel role for p53 in the regulation of NPC proliferation and survival during neuroinflammatory conditions that could be targeted to promote neurogenesis and repair in a number of neurological conditions.

Suppression of methylmercury-induced IL-6 and MCP-1 expressions by N-acetylcysteine in U-87MG human astrocytoma cells

AIMS

The aim of this study was to clarify the involvement of oxidative stress in methylmercury (MeHg)-induced pro-inflammatory cytokine expressions and the suppressive effects of N-acetylcysteine (NAC) in MeHg-induced cytokine expression.

MATERIALS AND METHODS

Using U-87-MG human astrocytoma cell line, interleukin (IL)-6 and monocyte chemoattractant protein (MCP)-1 expressions induced by 4 μM MeHg were measured at mRNA and protein levels. Hydrogen peroxide (H2O2) and superoxide anion (O2(-)) were quantified by flow-cytometry analysis. To examine the suppressive effects of NAC on the cytokine expressions among different timing of NAC treatment, cells were treated with 0.5 or 5mM NAC before, simultaneously, or after MeHg administration.

KEY FINDINGS

MeHg exposure at 4 μM, a non-cytotoxic concentration, significantly induced MCP-1 and IL-6 expressions at both mRNA and protein levels. A significant increase of H2O2 production but not O2(-) was observed. MeHg-induced expression of MCP-1 and IL-6 mRNA was reduced by 10-20% in the presence of 5mM NAC (co-treatment experiment) compared to cells treated with MeHg only. Pre-treatment of cells with 0.5 or 5mM NAC at 0.5 or 1h and its subsequent washout before MeHg addition suppressed MCP-1 and IL-6 cytokine expressions. Post-treatment of cells with NAC after MeHg addition also suppressed the cytokine induction, but the magnitude of suppression was evidently lower than in co-treated cells even though the H2O2 generation was almost completely suppressed by NAC.

SIGNIFICANCE

NAC may effectively suppress the MeHg-induced cytokine production through both, inhibition of reactive oxygen species as well as extracellular chelation of MeHg in astrocytes.

Neuroimmune basis of methamphetamine toxicity

Although it is not known which antigen-specific immune responses (or if antigen-specific immune responses) are relevant or required for methamphetamine's neurotoxic effects, it is apparent that methamphetamine exposure is associated with significant effects on adaptive and innate immunity. Alterations in lymphocyte activity and number, changes in cytokine signaling, impairments in phagocytic functions, and glial activation and gliosis have all been reported. These drug-induced changes in immune response, particularly within the CNS, are now thought to play a critical role in the addiction process for methamphetamine dependence as well as for other substance use disorders. In Section 2, methamphetamine's effects on glial cell (e.g., microglia and astrocytes) activity and inflammatory signaling cascades are summarized, including how alterations in immune cell function can induce the neurotoxic and addictive effects of methamphetamine. Section 2 also describes neurotransmitter involvement in the modulation of methamphetamine's inflammatory effects. Section 3 discusses the very recent use of pharmacological and genetic animal models which have helped elucidate the behavioral effects of methamphetamine's neurotoxic effects and the role of the immune system. Section 4 is focused on the effects of methamphetamine on blood-brain barrier integrity and associated immune consequences. Clinical considerations such as the combined effects of methamphetamine and HIV and/or HCV on brain structure and function are included in Section 4. Finally, in Section 5, immune-based treatment strategies are reviewed, with a focus on vaccine development, neuroimmune therapies, and other anti-inflammatory approaches.

Anti-Inflammatory Effects of 3-(4'-Hydroxyl-3',5'-Dimethoxyphenyl)Propionic Acid, an Active Component of Korean Cabbage Kimchi, in Lipopolysaccharide-Stimulated BV2 Microglia

We investigated the protective ability of 3-(4'-hydroxyl-3',5'-dimethoxyphenyl)propionic acid (HDMPPA), an active principle in Korean cabbage kimchi, against the production of proinflammatory mediators and cytokines, and the mechanisms involved in lipopolysaccharide (LPS)-stimulated BV2 microglial cells. HDMPPA significantly suppressed the production of nitric oxide (NO) and prostaglandin E2, along with the expression of inducible NO synthase and cyclooxygenase-2 in LPS-stimulated BV2 cells, at concentrations with no cytotoxicity. HDMPPA also attenuated the LPS-induced expression and secretion of proinflammatory cytokines, such as tumor necrosis factor-α and interleukin-1β. Furthermore, HDMPPA inhibited LPS-induced nuclear factor-κB (NF-κB) activation, which was associated with the abrogation of IκB-α degradation and phosphorylation, and subsequent decreases in NF-κB p65 levels. Moreover, the phosphorylation of mitogen-activated protein kinases (MAPKs) and Akt, a downstream molecule of phosphatidylinositol-3-kinase (PI3K), in LPS-stimulated BV2 cells was suppressed markedly by HDMPPA. This effect was associated with a significant reduction in the formation of intracellular reactive oxygen species. The findings in this study suggest that HDMPPA may exert anti-inflammatory responses by suppressing LPS-induced expression of proinflammatory mediators and cytokines through blockage of NF-κB, MAPKs, and PI3K/Akt signaling pathways and oxidative stress in microglia.