The role of monocyte chemoattractant protein MCP1/CCL2 in neuroinflammatory diseases

Inflammatory serum cytokines and chemokines increase associated with the disease extent in pediatric Langerhans cell histiocytosis

OBJECTIVE

Langerhans cell histiocytosis (LCH) is characterized by immature dendritic cell proliferation, infiltration of LCH lesions by various inflammatory cells, and a lesional cytokine storm. It is classified into three groups on the basis of disease extent, namely, multisystem with risk-organ involvement (MS+), multisystem without risk-organ involvement (MS-), and single-system (SS) disease. We comprehensively analyzed whether serum levels of cytokines/chemokines reflect the disease extent.

METHODS

Serum samples from 52 children with LCH (eight, 25, and 19 with MS+, MS-, and SS, respectively) and 34 control children were analyzed quantitatively for 48 humoral factors. DNA samples extracted from biopsied LCH lesions from 12 patients were tested for BRAF V600E status.

RESULTS

The LCH patients had significantly higher serum levels of IL-1Ra, IL-3, IL-6, IL-8, IL-9, IL-10, IL12, IL-13, IL-15, IL-17, IL-18, TNF-α, G-CSF, M-CSF, MIF, HGF, VEGF, CCL2, CCL3, CCL7, CXCL1, and CXCL9 than the controls by univariate analysis. Of these IL-9, IL-15 and MIF were significant by multivariate analysis; but not differed between MS and SS diseases. MS disease associated with significantly higher IL-2R, IL-3, IL-8, IL-18, M-CSF, HGF, CCL2, CXCL1, and CXCL9 levels than SS disease by univariate analysis. Of these, CCL2 and M-CSF were significant by multivariate analysis. IL-18 levels were significantly higher in MS+ disease than MS- disease. The LCH patients with BRAF V600E mutation had higher serum levels of CCL7.

CONCLUSION

Numerous inflammatory cytokines and chemokines play a role in LCH. Of those, more specific ones reflect the disease extent (MS vs. SS and MS+ vs. MS-) or the BRAF V600E mutation status. It is thought that the most responsible cytokines and chemokines involved in the poor outcome may become future candidate therapeutic targets in LCH.

Interleukin 17A Promotes Lymphocytes Adhesion and Induces CCL2 and CXCL1 Release from Brain Endothelial Cells

The nature of the interaction between Th17 cells and the blood-brain barrier (BBB) is critical for the development of autoimmune inflammation in the central nervous system (CNS). Tumor necrosis factor alpha (TNF-α) or interleukin 17 (IL-17) stimulation is known to enhance the adherence of Th17 cells to the brain endothelium. The brain endothelial cells (bEnd.3) express Vascular cell adhesion molecule 1 (VCAM-1), the receptor responsible for inflammatory cell adhesion, which binds very late antigen 4 (VLA-4) on migrating effector lymphocytes at the early stage of brain inflammation. The present study examines the effect of the pro-inflammatory cytokines TNF-α and IL-17 on the adherence of Th17 cells to bEnd.3. The bEnd.3 cells were found to increase production of CCL2 and CXCL1 after stimulation by pro-inflammatory cytokines, while CCL2, CCL5, CCL20 and IL17 induced Th17 cell migration through a bEnd.3 monolayer. This observation may suggest potential therapeutic targets for the prevention of autoimmune neuroinflammation development in the CNS.

Interleukin 17A Promotes Lymphocytes Adhesion and Induces CCL2 and CXCL1 Release from Brain Endothelial Cells

The nature of the interaction between Th17 cells and the blood-brain barrier (BBB) is critical for the development of autoimmune inflammation in the central nervous system (CNS). Tumor necrosis factor alpha (TNF-α) or interleukin 17 (IL-17) stimulation is known to enhance the adherence of Th17 cells to the brain endothelium. The brain endothelial cells (bEnd.3) express Vascular cell adhesion molecule 1 (VCAM-1), the receptor responsible for inflammatory cell adhesion, which binds very late antigen 4 (VLA-4) on migrating effector lymphocytes at the early stage of brain inflammation. The present study examines the effect of the pro-inflammatory cytokines TNF-α and IL-17 on the adherence of Th17 cells to bEnd.3. The bEnd.3 cells were found to increase production of CCL2 and CXCL1 after stimulation by pro-inflammatory cytokines, while CCL2, CCL5, CCL20 and IL17 induced Th17 cell migration through a bEnd.3 monolayer. This observation may suggest potential therapeutic targets for the prevention of autoimmune neuroinflammation development in the CNS.

Microglia amplify inflammatory activation of astrocytes in manganese neurotoxicity

BACKGROUND

As the primary immune response cell in the central nervous system, microglia constantly monitor the microenvironment and respond rapidly to stress, infection, and injury, making them important modulators of neuroinflammatory responses. In diseases such as Parkinson's disease, Alzheimer's disease, multiple sclerosis, and human immunodeficiency virus-induced dementia, activation of microglia precedes astrogliosis and overt neuronal loss. Although microgliosis is implicated in manganese (Mn) neurotoxicity, the role of microglia and glial crosstalk in Mn-induced neurodegeneration is poorly understood.

METHODS

Experiments utilized immunopurified murine microglia and astrocytes using column-free magnetic separation. The effect of Mn on microglia was investigated using gene expression analysis, Mn uptake measurements, protein production, and changes in morphology. Additionally, gene expression analysis was used to determine the effect Mn-treated microglia had on inflammatory responses in Mn-exposed astrocytes.

RESULTS

Immunofluorescence and flow cytometric analysis of immunopurified microglia and astrocytes indicated cultures were 97 and 90% pure, respectively. Mn treatment in microglia resulted in a dose-dependent increase in pro-inflammatory gene expression, transition to a mixed M1/M2 phenotype, and a de-ramified morphology. Conditioned media from Mn-exposed microglia (MCM) dramatically enhanced expression of mRNA for Tnf, Il-1β, Il-6, Ccl2, and Ccl5 in astrocytes, as did exposure to Mn in the presence of co-cultured microglia. MCM had increased levels of cytokines and chemokines including IL-6, TNF, CCL2, and CCL5. Pharmacological inhibition of NF-κB in microglia using Bay 11-7082 completely blocked microglial-induced astrocyte activation, whereas siRNA knockdown of Tnf in primary microglia only partially inhibited neuroinflammatory responses in astrocytes.

CONCLUSIONS

These results provide evidence that NF-κB signaling in microglia plays an essential role in inflammatory responses in Mn toxicity by regulating cytokines and chemokines that amplify the activation of astrocytes.

Selective inhibition of EZH2 by a small molecule inhibitor regulates microglial gene expression essential for inflammation

Multiple studies have documented that Enhancer of zeste homolog 2 (EZH2) could play a role in inflammation and a wide range of malignancies; however, the underlying mechanisms remain largely unaddressed. Microglial activation is a key process in the production and release of numerous pro-inflammatory mediators that play important roles in inflammation and neurodegeneration in the central nervous system (CNS). Therefore, our aim was to investigate whether inhibition of EZH2 with the selective small molecule inhibitor EPZ-6438 protects against neonatal microglial activation. First, in mouse primary microglial cells and a microglial cell line, we found that LPS can rapidly increase EZH2 mRNA level and we subsequently performed gene expression profiling and constructed networks in resting, EPZ-6438-treated, LPS-treated and LPS+EPZ-6438-treated primary microglial cells and a microglial cell line using transcriptome RNA sequencing and bioinformatics analyses. By examining the RNA sequencing, we identified EPZ-6438 target genes and co-regulated modules that were critical for inflammation. We also identified unexpected relationships between the inducible transcription factors (TFs), motif strength, and the transcription of key inflammatory mediators. Furthermore, we showed that EPZ-6438 controls important inflammatory gene targets by modulating interferon regulatory factor (IRF) 1, IRF8, and signal transducer and activator of transcription (STAT) 1 levels at their promoter sites. Our unprecedented findings demonstrate that pharmacological interventions built upon EZH2 inhibition by EPZ-6438 could be a useful therapeutic approach for the treatment of neuroinflammatory diseases associated with microglial activation.

Transgenic mice with increased astrocyte expression of CCL2 show altered behavioral effects of alcohol

Emerging research provides strong evidence that activation of CNS glial cells occurs in neurological diseases and brain injury and results in elevated production of neuroimmune factors. These factors can contribute to pathophysiological processes that lead to altered CNS function. Recently, studies have also shown that both acute and chronic alcohol consumption can produce activation of CNS glial cells and the production of neuroimmune factors, particularly the chemokine ligand 2 (CCL2). The consequences of alcohol-induced increases in CCL2 levels in the CNS have yet to be fully elucidated. Our studies focus on the hypothesis that increased levels of CCL2 in the CNS produce neuroadaptive changes that modify the actions of alcohol on the CNS. We utilized behavioral testing in transgenic mice that express elevated levels of CCL2 to test this hypothesis. The increased level of CCL2 in the transgenic mice involves increased astrocyte expression. Transgenic mice and their non-transgenic littermate controls were subjected to one of two alcohol exposure paradigms, a two-bottle choice alcohol drinking procedure that does not produce alcohol dependence or a chronic intermittent alcohol procedure that produces alcohol dependence. Several behavioral tests were carried out including the Barnes maze, Y-maze, cued and contextual conditioned fear test, light-dark transfer, and forced swim test. Comparisons between alcohol naïve, non-dependent, and alcohol-dependent CCL2 transgenic and non-transgenic mice show that elevated levels of CCL2 in the CNS interact with alcohol in tests for alcohol drinking, spatial learning, and associative learning.

Differential subnetwork of chemokines/cytokines in human, mouse, and rat brain cells after oxygen-glucose deprivation

Mice and rats are the most commonly used animals for preclinical stroke studies, but it is unclear whether targets and mechanisms are always the same across different species. Here, we mapped the baseline expression of a chemokine/cytokine subnetwork and compared responses after oxygen-glucose deprivation in primary neurons, astrocytes, and microglia from mouse, rat, and human. Baseline profiles of chemokines (CX3CL1, CXCL12, CCL2, CCL3, and CXCL10) and cytokines (IL-1α, IL-1β, IL-6, IL-10, and TNFα) showed significant differences between human and rodents. The response of chemokines/cytokines to oxygen-glucose deprivation was also significantly different between species. After 4 h oxygen-glucose deprivation and 4 h reoxygenation, human and rat neurons showed similar changes with a downregulation in many chemokines, whereas mouse neurons showed a mixed response with up- and down-regulated genes. For astrocytes, subnetwork response patterns were more similar in rats and mice compared to humans. For microglia, rat cells showed an upregulation in all chemokines/cytokines, mouse cells had many down-regulated genes, and human cells showed a mixed response with up- and down-regulated genes. This study provides proof-of-concept that species differences exist in chemokine/cytokine subnetworks in brain cells that may be relevant to stroke pathophysiology. Further investigation of differential gene pathways across species is warranted.

FTY720 (fingolimod) regulates key target genes essential for inflammation in microglial cells as defined by high-resolution mRNA sequencing

Although microglial cells have an essential role in the host defense of the brain, the abnormal activation of microglia can lead to devastating outcomes, such as neuroinflammation and neurodegeneration. Emerging evidence indicates that FTY720 (fingolimod), an FDA-approved drug, has beneficial effects on brain cells in the central nervous system (CNS) and, more recently, immunosuppressive activities in microglia via modulation of the sphingosine 1 phosphate (S1P) 1 receptor. However, the exact molecular aspects of FTY720 contribution in microglia remain largely unaddressed. To understand the molecular mechanisms underlying the roles of FTY720 in microglia, we performed gene expression profiling in resting, FTY720, LPS and LPS + FTY720 challenged primary microglial (PM) cells isolated from 3-day-old ICR mice, and we identified FTY720 target genes and co-regulated modules that were critical in inflammation. By examining RNA sequencing and binding motif datasets from FTY720 suppressed LPS-induced inflammatory mediators, we also identified unexpected relationships between the inducible transcription factors (TFs), motif strength, and the transcription of key inflammatory mediators. Furthermore, we showed that FTY720 controls important inflammatory genes targets by modulating STAT1 and IRF8 levels at their promoter site. Our unprecedented findings demonstrate that FTY720 could be a useful therapeutic application for neuroinflammatory diseases associated with microglia activation, as well as provide a rich resource and framework for future analyses of FTY720 effects on microglia interaction.

[Hypothalamic inflammation and energy balance deregulations: focus on chemokines.]

The hypothalamus is a key brain region in the regulation of energy balance. It especially controls food intake and both energy storage and expenditure through integration of humoral, neural and nutrient-related signals and cues. Hypothalamic neurons and glial cells act jointly to orchestrate, both spatially and temporally, regulated metabolic functions of the hypothalamus. Thus, the existence of a causal link between hypothalamic inflammation and deregulations of feeding behavior, such as involuntary weight-loss or obesity, has been suggested. Among the inflammatory mediators that could induce deregulations of hypothalamic control of the energy balance, chemokines represent interesting candidates. Indeed, chemokines, primarily known for their chemoattractant role of immune cells to the inflamed site, have also been suggested capable of neuromodulation. Thus, chemokines could disrupt cellular activity together with synthesis and/or secretion of multiple neurotransmitters/mediators that are involved in the maintenance of energy balance. Here, we relate, on one hand, recent results showing the primary role of the central chemokinergic signaling CCL2/CCR2 for metabolic and behavioral adaptation to high-grade inflammation, especially loss of appetite and weight, through its activity on hypothalamic neurons producing the orexigenic peptide Melanin-Concentrating Hormone (MCH) and, on the other hand, results that suggest that chemokines could also deregulate hypothalamic neuropeptidergic circuits to induce an opposite phenotype and eventually participate in the onset/development of obesity. In more details, we will emphasize a study recently showing, in a model of high-grade acute inflammation of LPS injection in mice, that central CCL2/CCR2 signaling is of primary importance for several aspects explaining weight loss associated with inflammation: after LPS injection, animals lose weight, reduce their food intake, increase their fat oxidation (thus energy consumption from fat storage)...These inflammation-induced metabolic and behavioral changes are reduced when central CCR2 signaling is disrupted either pharmacologically (by a specific inhibitor of CCR2) or genetically (in mice deficient for CCR2). This underlines the importance of this signaling in inflammation-related weight loss. We further determined that the LPS-induced and CCR2-mediated weight loss depends on the direct effect of CCR2 activation on MCH neurons activity. Indeed, the MCH neurons express CCR2, and the application of CCL2 on brain slices revealed that activation of CCR2 actually depolarizes MCH neurons and induces delays and/or failures of action potential emission. Furthermore, CCL2 is able to reduce KCl-evoked MCH secretion from hypothalamic explants. Taken together, these results demonstrate the role of the central CCL2/CCR2 signaling in metabolic and behavioral adaptation to inflammation. On the other hand, this first description of how the chemokinergic system can actually modulate the activity of the hypothalamic regulation of energy balance, but also some less advanced studies and some unpublished data, suggest that some other chemokines, such as CCL5, could participate in the development of the opposite phenotype, that is to say obesity.

Teriflunomide and monomethylfumarate target HIV-induced neuroinflammation and neurotoxicity

HIV-associated neurocognitive disorders (HAND) affect about 50% of infected patients despite combined antiretroviral therapy (cART). Ongoing compartmentalized inflammation mediated by microglia which are activated by HIV-infected monocytes has been postulated to contribute to neurotoxicity independent from viral replication. Here, we investigated effects of teriflunomide and monomethylfumarate on monocyte/microglial activation and neurotoxicity. Human monocytoid cells (U937) transduced with a minimal HIV-Vector were co-cultured with human microglial cells (HMC3). Secretion of pro-inflammatory/neurotoxic cytokines (CXCL10, CCL5, and CCL2: p < 0.001; IL-6: p < 0.01) by co-cultures was strongly increased compared to microglia in contact with HIV-particles alone. Upon treatment with teriflunomide, cytokine secretion was decreased (CXCL10, 3-fold; CCL2, 2.5-fold; IL-6, 2.2-fold; p < 0.001) and monomethylfumarate treatment led to 2.9-fold lower CXCL10 secretion (p < 0.001). Reduced toxicity of co-culture conditioned media on human fetal neurons by teriflunomide (29%, p < 0.01) and monomethylfumarate (27%, p < 0.05) indicated functional relevance. Modulation of innate immune functions by teriflunomide and monomethylfumarate may target neurotoxic inflammation in the context of HAND.

Enhancement of macrophage inflammatory responses by CCL2 is correlated with increased miR-9 expression and downregulation of the ERK1/2 phosphatase Dusp6

Macrophage polarization plays a central role in both protective immunity and immunopathology. While the role of cytokines in driving macrophage polarization is well characterized, less is understood about the role of chemokines. The purpose of this study was to determine if CC chemokine 2 (CCL2/MCP1) could influence macrophage polarization in response to subsequent activation with cytokines and microbial products. Treatment of bone marrow-derived macrophages with CCL2 alone did not result in increased expression of either classical or alternatively-activated macrophage genes as compared to standard skewing cytokines or Toll-like receptor agonists. However, subsequent stimulation of CCL2 pre-treated macrophages with classical activation stimuli resulted in enhanced expression of genes associated with classical activation. This enhancement correlated with increased phosphorylation of ERK1/2 kinases, a decrease in expression of the ERK phosphatase Dusp6 and enhanced expression of miR-9. These results indicate that CCL2 supports the classical activation of macrophages, with miR-9 mediated down-regulation of Dusp6 and enhanced ERK-mediated signal transduction possibly mediating this enhanced pro-inflammatory gene expression.

Dexmedetomidine Attenuates Lipopolysaccharide Induced MCP-1 Expression in Primary Astrocyte

Background. Neuroinflammation which presents as a possible mechanism of delirium is associated with MCP-1, an important proinflammatory factor which is expressed on astrocytes. It is known that dexmedetomidine (DEX) possesses potent anti-inflammatory properties. This study aimed to investigate the potential effects of DEX on the production of MCP-1 in lipopolysaccharide-stimulated astrocytes. Materials and Methods. Astrocytes were treated with LPS (10 ng/ml, 50 ng/ml, 100 ng/ml, and 1000 ng/ml), DEX (500 ng/mL), LPS (100 ng/ml), and DEX (10, 100, and 500 ng/mL) for a duration of three hours; expression levels of MCP-1 were measured by real-time PCR. The double immunofluorescence staining protocol was utilized to determine the expression of α2-adrenoceptors (α2AR) and glial fibrillary acidic protein (GFAP) on astrocytes. Results. Expressions of MCP-1 mRNA in astrocytes were induced dose-dependently by LPS. Administration of DEX significantly inhibited the expression of MCP-1 mRNA (P < 0.001). Double immunofluorescence assay showed that α2AR colocalize with GFAP, which indicates the expression of α2-adrenoceptors in astrocytes. Conclusions. DEX is a potent suppressor of MCP-1 in astrocytes induced with lipopolysaccharide through α₂A-adrenergic receptors, which potentially explains its beneficial effects in the treatment of delirium by attenuating neuroinflammation.

Clearance of cerebral Aβ in Alzheimer's disease: reassessing the role of microglia and monocytes

Deficiency in cerebral amyloid β-protein (Aβ) clearance is implicated in the pathogenesis of the common late-onset forms of Alzheimer’s disease (AD). Accumulation of misfolded Aβ in the brain is believed to be a net result of imbalance between its production and removal. This in turn may trigger neuroinflammation, progressive synaptic loss, and ultimately cognitive decline. Clearance of cerebral Aβ is a complex process mediated by various systems and cell types, including vascular transport across the blood–brain barrier, glymphatic drainage, and engulfment and degradation by resident microglia and infiltrating innate immune cells. Recent studies have highlighted a new, unexpected role for peripheral monocytes and macrophages in restricting cerebral Aβ fibrils, and possibly soluble oligomers. In AD transgenic (ADtg) mice, monocyte ablation or inhibition of their migration into the brain exacerbated Aβ pathology, while blood enrichment with monocytes and their increased recruitment to plaque lesion sites greatly diminished Aβ burden. Profound neuroprotective effects in ADtg mice were further achieved through increased cerebral recruitment of myelomonocytes overexpressing Aβ-degrading enzymes. This review summarizes the literature on cellular and molecular mechanisms of cerebral Aβ clearance with an emphasis on the role of peripheral monocytes and macrophages in Aβ removal.

Osteoarthritis: toward a comprehensive understanding of pathological mechanism

Osteoarthritis (OA) is the most common degenerative joint disease and a major cause of pain and disability in adult individuals. The etiology of OA includes joint injury, obesity, aging, and heredity. However, the detailed molecular mechanisms of OA initiation and progression remain poorly understood and, currently, there are no interventions available to restore degraded cartilage or decelerate disease progression. The diathrodial joint is a complicated organ and its function is to bear weight, perform physical activity and exhibit a joint-specific range of motion during movement. During OA development, the entire joint organ is affected, including articular cartilage, subchondral bone, synovial tissue and meniscus. A full understanding of the pathological mechanism of OA development relies on the discovery of the interplaying mechanisms among different OA symptoms, including articular cartilage degradation, osteophyte formation, subchondral sclerosis and synovial hyperplasia, and the signaling pathway(s) controlling these pathological processes.

Cognitive impairment in heart failure: A protective role for angiotensin-(1-7)

Patients with congestive heart failure (CHF) have increased hospital readmission rates and mortality if they are concomitantly diagnosed with cognitive decline and memory loss. Accordingly, we developed a preclinical model of CHF-induced cognitive impairment with the goal of developing novel protective therapies against CHF related cognitive decline. CHF was induced by ligation of the left coronary artery to instigate a myocardial infarction (MI). By 4- and 8-weeks post-MI, CHF mice had approximately a 50% and 70% decline in ejection fraction as measured by echocardiography. At both 4- and 8-weeks post-MI, spatial memory performance in CHF mice as tested using the Morris water task was significantly impaired as compared with sham. In addition, CHF mice had significantly worse performance on object recognition when compared with shams as measured by discrimination ratios during the novel object recognition NOR task. At 8-weeks post-MI, a subgroup of CHF mice were given Angiotensin (Ang)-(1-7) (50mcg/kg/hr) subcutaneously for 4 weeks. Following 3 weeks treatment with systemic Ang-(1-7), the CHF mice NOR discrimination ratios were similar to shams and significantly better than the performance of CHF mice treated with saline. Ang-(1-7) also improved spatial memory in CHF mice as compared with shams. Ang-(1-7) had no effect on cardiac function. Inflammatory biomarker studies from plasma revealed a pattern of neuroprotection that may underlie the observed improvements in cognition. These results demonstrate a preclinical mouse model of CHF that exhibits both spatial memory and object recognition dysfunction. Furthermore, this CHF-induced cognitive impairment is attenuated by treatment with systemic Ang-(1-7). (PsycINFO Database Record

Hypothalamic Inflammation and Energy Balance Disruptions: Spotlight on Chemokines

The hypothalamus is a key brain region in the regulation of energy balance as it controls food intake and both energy storage and expenditure through integration of humoral, neural, and nutrient-related signals and cues. Many years of research have focused on the regulation of energy balance by hypothalamic neurons, but the most recent findings suggest that neurons and glial cells, such as microglia and astrocytes, in the hypothalamus actually orchestrate together several metabolic functions. Because glial cells have been described as mediators of inflammatory processes in the brain, the existence of a causal link between hypothalamic inflammation and the deregulations of feeding behavior, leading to involuntary weight loss or obesity for example, has been suggested. Several inflammatory pathways that could impair the hypothalamic control of energy balance have been studied over the years such as, among others, toll-like receptors and canonical cytokines. Yet, less studied so far, chemokines also represent interesting candidates that could link the aforementioned pathways and the activity of hypothalamic neurons. Indeed, chemokines, in addition to their role in attracting immune cells to the inflamed site, have been suggested to be capable of neuromodulation. Thus, they could disrupt cellular activity together with synthesis and/or secretion of multiple neurotransmitters/mediators involved in the maintenance of energy balance. This review discusses the different inflammatory pathways that have been identified so far in the hypothalamus in the context of feeding behavior and body weight control impairments, with a particular focus on chemokines signaling that opens a new avenue in the understanding of the major role played by inflammation in obesity.

Central CCL2 signaling onto MCH neurons mediates metabolic and behavioral adaptation to inflammation

Sickness behavior defines the endocrine, autonomic, behavioral, and metabolic responses associated with infection. While inflammatory responses were suggested to be instrumental in the loss of appetite and body weight, the molecular underpinning remains unknown. Here, we show that systemic or central lipopolysaccharide (LPS) injection results in specific hypothalamic changes characterized by a precocious increase in the chemokine ligand 2 (CCL2) followed by an increase in pro-inflammatory cytokines and a decrease in the orexigenic neuropeptide melanin-concentrating hormone (MCH). We therefore hypothesized that CCL2 could be the central relay for the loss in body weight induced by the inflammatory signal LPS. We find that central delivery of CCL2 promotes neuroinflammation and the decrease in MCH and body weight. MCH neurons express CCL2 receptor and respond to CCL2 by decreasing both electrical activity and MCH release. Pharmacological or genetic inhibition of CCL2 signaling opposes the response to LPS at both molecular and physiologic levels. We conclude that CCL2 signaling onto MCH neurons represents a core mechanism that relays peripheral inflammation to sickness behavior.

The chemokine CXCL16 modulates neurotransmitter release in hippocampal CA1 area

Chemokines have several physio-pathological roles in the brain. Among them, the modulation of synaptic contacts and neurotransmission recently emerged as crucial activities during brain development, in adulthood, upon neuroinflammation and neurodegenerative diseases. CXCL16 is a chemokine normally expressed in the brain, where it exerts neuroprotective activity against glutamate-induced damages through cross communication with astrocytes and the involvement of the adenosine receptor type 3 (A3R) and the chemokine CCL2. Here we demonstrated for the first time that CXCL16 exerts a modulatory activity on inhibitory and excitatory synaptic transmission in CA1 area. We found that CXCL16 increases the frequency of the miniature inhibitory synaptic currents (mIPSCs) and the paired-pulse ratio (PPR) of evoked IPSCs (eIPSCs), suggesting a presynaptic modulation of the probability of GABA release. In addition, CXCL16 increases the frequency of the miniature excitatory synaptic currents (mEPSCs) and reduces the PPR of evoked excitatory transmission, indicating that the chemokine also modulates and enhances the release of glutamate. These effects were not present in the A3RKO mice and in WT slices treated with minocycline, confirming the involvement of A3 receptors and introducing microglial cells as key mediators of the modulatory activity of CXCL16 on neurons.

Cerebrospinal Fluid Chemokine (C-C Motif) Ligand 2 Is an Early-Response Biomarker for Blast-Overpressure-Wave-Induced Neurotrauma in Rats

Chemokines and their receptors are of great interest within the milieu of immune responses elicited in the central nervous system in response to trauma. Chemokine (C-C motif)) ligand 2 (CCL2), which is also known as monocyte chemotactic protein-1, has been implicated in the pathogenesis of traumatic brain injury (TBI), brain ischemia, Alzheimer's disease, and other neurodegenerative diseases. In this study, we investigated the time course of CCL2 accumulation in cerebrospinal fluid (CSF) after exposures to single and repeated blast overpressures of varied intensities along with the neuropathological changes and motor deficits resulting from these blast conditions. Significantly increased concentrations of CCL2 in CSF were evident by 1 h of blast exposure and persisted over 24 h with peak levels measured at 6 h post-injury. The increased levels of CCL2 in CSF corresponded with both the number and intensities of blast overpressure and were also commensurate with the extent of neuromotor impairment and neuropathological abnormalities resulting from these exposures. CCL2 levels in CSF and plasma were tightly correlated with levels of CCL2 messenger RNA in cerebellum, the brain region most consistently neuropathologically disrupted by blast. In view of the roles of CCL2 that have been implicated in multiple neurodegenerative disorders, it is likely that the sustained high levels of CCL2 and the increased expression of its main receptor, CCR2, in the brain after blast may similarly contribute to neurodegenerative processes after blast exposure. In addition, the markedly elevated concentration of CCL2 in CSF might be a candidate early-response biomarker for diagnosis and prognosis of blast-induced TBI.

Micronutrient Antioxidants and Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is one of the most important chronic liver diseases worldwide and has garnered increasing attention in recent decades. NAFLD is characterized by a wide range of liver changes, from simple steatosis to nonalcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma. The blurred pathogenesis of NAFLD is very complicated and involves lipid accumulation, insulin resistance, inflammation, and fibrogenesis. NAFLD is closely associated with complications such as obesity, diabetes, steatohepatitis, and liver fibrosis. During the progression of NAFLD, reactive oxygen species (ROS) are activated and induce oxidative stress. Recent attempts at establishing effective NAFLD therapy have identified potential micronutrient antioxidants that may reduce the accumulation of ROS and finally ameliorate the disease. In this review, we present the molecular mechanisms involved in the pathogenesis of NAFLD and introduce some dietary antioxidants that may be used to prevent or cure NAFLD, such as vitamin D, E, and astaxanthin.

Characterization of Eicosanoids Produced by Adipocyte Lipolysis: IMPLICATION OF CYCLOOXYGENASE-2 IN ADIPOSE INFLAMMATION

Excessive adipocyte lipolysis generates lipid mediators and triggers inflammation in adipose tissue. However, the specific roles of lipolysis-generated mediators in adipose inflammation remain to be elucidated. In the present study, cultured 3T3-L1 adipocytes were treated with isoproterenol to activate lipolysis and the fatty acyl lipidome of released lipids was determined by using LC-MS/MS. We observed that β-adrenergic activation elevated levels of approximately fifty lipid species, including metabolites of cyclooxygenases, lipoxygenases, epoxygenases, and other sources. Moreover, we found that β-adrenergic activation induced cyclooxygenase 2 (COX-2), not COX-1, expression in a manner that depended on activation of hormone-sensitive lipase (HSL) in cultured adipocytes and in the epididymal white adipose tissue (EWAT) of C57BL/6 mice. We found that lipolysis activates the JNK/NFκB signaling pathway and inhibition of the JNK/NFκB axis abrogated the lipolysis-stimulated COX-2 expression. In addition, pharmacological inhibition of COX-2 activity diminished levels of COX-2 metabolites during lipolytic activation. Inhibition of COX-2 abrogated the induction of CCL2/MCP-1 expression by β-adrenergic activation and prevented recruitment of macrophage/monocyte to adipose tissue. Collectively, our data indicate that excessive adipocyte lipolysis activates the JNK/NFκB pathway leading to the up-regulation of COX-2 expression and recruitment of inflammatory macrophages.

Cerebrospinal fluid biomarkers of inflammation and degeneration as measures of fingolimod efficacy in multiple sclerosis

BACKGROUND

The disease-modifying therapies (DMTs) in relapsing-remitting multiple sclerosis (RRMS) vary in their mode of action and when therapies are changed, the consequences on inflammatory and degenerative processes are largely unknown.

OBJECTIVE

We investigated the effect of switching from other DMTs to fingolimod on cerebrospinal fluid (CSF) biomarkers.

METHODS

43 RRMS patients were followed up after 4-12 months of fingolimod treatment. Concentrations of C-X-C motif chemokine 13 (CXCL13), chemokine (C-C motif) ligand 2 (CCL2), chitinase-3-like protein 1 (CHI3L1), glial fibrillary acidic protein (GFAP), neurofilament light protein (NFL), and neurogranin (NGRN) were analyzed by enzyme-linked immunosorbent assay (ELISA), while chitotriosidase (CHIT1) was analyzed by spectrofluorometry.

RESULTS

The levels of NFL, CXCL13, and CHI3L1 decreased ( p < 0.05) after fingolimod treatment. Subgroup analysis revealed a reduction in NFL ( p < 0.001), CXCL13 ( p = 0.001), CHI3L1 ( p < 0.001), and CHIT1 ( p = 0.002) in patients previously treated with first-line therapies. In contrast, the levels of all analyzed biomarkers were essentially unchanged in patients switching from natalizumab.

CONCLUSION

We found reduced inflammatory activity (CXCL13, CHI3L1, and CHIT1) and reduced axonal damage (NFL) in patients switching from first-line DMTs to fingolimod. Biomarker levels in patients switching from natalizumab indicate similar effects on inflammatory and degenerative processes. The CSF biomarkers provide an additional measure of treatment efficacy.

Effect of Cocaine on HIV Infection and Inflammasome Gene Expression Profile in HIV Infected Macrophages

We have observed significantly increased HIV infection in HIV infected macrophages in the presence of cocaine that could be due to the downregulation of BST2 restriction factor in these cells. In human inflammasome PCR array, among different involved in inflammasome formation, in HIV infected macrophages in the presence of cocaine, we have observed significant upregulation of NLRP3, AIM2 genes and downstream genes IL-1β and PTGS2. Whereas negative regulatory gene MEFV was upregulated, CD40LG and PYDC1 were significantly downregulated. Among various NOD like receptors, NOD2 was significantly upregulated in both HIV alone and HIV plus cocaine treated cells. In the downstream genes, chemokine (C-C motif) ligand 2 (CCL2), CCL7 and IL-6 were significantly up regulated in HIV plus cocaine treated macrophages. We have also observed significant ROS production (in HIV and/or cocaine treated cells) which is one of the indirect-activators of inflammasomes formation. Further, we have observed early apoptosis in HIV alone and HIV plus cocaine treated macrophages which may be resultant of inflammasome formation and cspase-1 activation. These results indicate that in case of HIV infected macrophages exposed to cocaine, increased ROS production and IL-1β transcription serve as an activators for the formation of NLRP3 and AIM2 mediated inflammasomes that leads to caspase 1 mediated apoptosis.

Western Zika Virus in Human Fetal Neural Progenitors Persists Long Term with Partial Cytopathic and Limited Immunogenic Effects

The recent Zika virus (ZIKV) outbreak in the Western hemisphere is associated with severe pathology in newborns, including microcephaly and brain damage. The mechanisms underlying these outcomes are under intense investigation. Here, we show that a 2015 ZIKV isolate replicates in multiple cell types, including primary human fetal neural progenitors (hNPs). In immortalized cells, ZIKV is cytopathic and grossly rearranges endoplasmic reticulum membranes similar to other flaviviruses. In hNPs, ZIKV infection has a partial cytopathic phase characterized by cell rounding, pyknosis, and activation of caspase 3. Despite notable cell death, ZIKV did not activate a cytokine response in hNPs. This lack of cell intrinsic immunity to ZIKV is consistent with our observation that virus replication persists in hNPs for at least 28 days. These findings, supported by published fetal neuropathology, establish a proof-of-concept that neural progenitors in the developing human fetus can be direct targets of detrimental ZIKV-induced pathology.

CCL2 mediates the circadian response to low dose endotoxin

The mammalian circadian system is mainly originated in a master oscillator located in the suprachiasmatic nuclei (SCN) in the hypothalamus. Previous reports from our and other groups have shown that the SCN are sensitive to systemic immune activation during the early night, through a mechanism that relies on the action of proinflammatory factors within this structure. Chemokine (C-C motif) ligand 2 (CCL2) is induced in the brain upon peripheral immune activation, and it has been shown to modulate neuronal physiology. In the present work we tested whether CCL2 might be involved in the response of the circadian clock to peripheral endotoxin administration. The CCL2 receptor, C-C chemokine receptor type 2 (CCR2), was detected in the SCN of mice, with higher levels of expression during the early night, when the clock is sensitive to immune activation. Ccl2 was induced in the SCN upon intraperitoneal lipopolysaccharide (LPS) administration. Furthermore, mice receiving an intracerebroventricular (Icv) administration of a CCL2 synthesis inhibitor (Bindarit), showed a reduction LPS-induced circadian phase changes and Icv delivery of CCL2 led to phase delays in the circadian clock. In addition, we tested the possibility that CCL2 might also be involved in the photic regulation of the clock. Icv administration of Bindarit did not modify the effects of light pulses on the circadian clock. In summary, we found that CCL2, acting at the SCN level is important for the circadian effects of immune activation.

Alpha-linolenic acid given as enteral or parenteral nutritional intervention against sensorimotor and cognitive deficits in a mouse model of ischemic stroke

Stroke is a leading cause of disability and death worldwide. Numerous therapeutics applied acutely after stroke have failed to improve long-term clinical outcomes. An emerging direction is nutritional intervention with omega-3 polyunsaturated fatty acids acting as disease-modifying factors and targeting post-stroke disabilities. Our previous studies demonstrated that the omega-3 precursor, alpha-linolenic acid (ALA) administrated by injections or dietary supplementation reduces stroke damage by direct neuroprotection, and triggering brain artery vasodilatation and neuroplasticity. Successful translation of putative therapies will depend on demonstration of robust efficacy on common deficits resulting from stroke like loss of motor control and memory/learning. This study evaluated the value of ALA as adjunctive therapy for stroke recovery by comparing whether oral or intravenous supplementation of ALA best support recovery from ischemia. Motor and cognitive deficits were assessed using rotarod, pole and Morris water maze tests. ALA supplementation in diet was better than intravenous treatment in improving motor coordination, but this improvement was not due to a neuroprotective effect since infarct size was not reduced. Both types of ALA supplementation improved spatial learning and memory after stroke. This cognitive improvement correlated with higher survival of hippocampal neurons. These results support clinical investigation establishing therapeutic plans using ALA supplementation.

Help-me signaling: Non-cell autonomous mechanisms of neuroprotection and neurorecovery

Self-preservation is required for life. At the cellular level, this fundamental principle is expressed in the form of molecular mechanisms for preconditioning and tolerance. When the cell is threatened, internal cascades of survival signaling become triggered to protect against cell death and defend against future insults. Recently, however, emerging findings suggest that this principle of self-preservation may involve not only intracellular signals; the release of extracellular signals may provide a way to recruit adjacent cells into an amplified protective program. In the central nervous system where multiple cell types co-exist, this mechanism would allow threatened neurons to "ask for help" from glial and vascular compartments. In this review, we describe this new concept of help-me signaling, wherein damaged or diseased neurons release signals that may shift glial and vascular cells into potentially beneficial phenotypes, and help remodel the neurovascular unit. Understanding and dissecting these non-cell autonomous mechanisms of self-preservation in the CNS may lead to novel opportunities for neuroprotection and neurorecovery.

Brain radiation injury leads to a dose- and time-dependent recruitment of peripheral myeloid cells that depends on CCR2 signaling

BACKGROUND

Cranial radiotherapy is used to treat tumors of the central nervous system (CNS), as well as non-neoplastic conditions such as arterio-venous malformations; however, its use is limited by the tolerance of adjacent normal CNS tissue, which can lead to devastating long-term sequelae for patients. Despite decades of research, the underlying mechanisms by which radiation induces CNS tissue injury remain unclear. Neuroinflammation and immune cell infiltration are a recognized component of the CNS radiation response; however, the extent and mechanisms by which bone marrow-derived (BMD) immune cells participate in late radiation injury is unknown. Thus, we set out to better characterize the response and tested the hypothesis that C-C chemokine receptor type 2 (CCR2) signaling was required for myeloid cell recruitment following brain irradiation.

METHODS

We used young adult C57BL/6 male bone marrow chimeric mice created with donor mice that constitutively express enhanced green fluorescent protein (eGFP). The head was shielded to avoid brain radiation exposure during chimera construction. Radiation dose and time response studies were conducted in wild-type chimeras, and additional experiments were performed with chimeras created using donor marrow from CCR2 deficient, eGFP-expressing mice. Infiltrating eGFP+ cells were identified and quantified using immunofluorescent microscopy.

RESULTS

Brain irradiation resulted in a dose- and time-dependent infiltration of BMD immune cells (predominately myeloid) that began at 1 month and persisted until 6 months following ≥15 Gy brain irradiation. Infiltration was limited to areas that were directly exposed to radiation. CCR2 signaling loss resulted in decreased numbers of infiltrating cells at 6 months that appeared to be restricted to cells also expressing major histocompatibility complex class II molecules.

CONCLUSIONS

The potential roles played by infiltrating immune cells are of current importance due to increasing interest in immunotherapeutic approaches for cancer treatment and a growing clinical interest in survivorship and quality of life issues. Our findings demonstrate that injury from brain radiation facilitates a dose- and time-dependent recruitment of BMD cells that persists for at least 6 months and, in the case of myeloid cells, is dependent on CCR2 signaling.

Plasma Biomarkers of Brain Injury as Diagnostic Tools and Outcome Predictors After Extracorporeal Membrane Oxygenation

OBJECTIVE

To determine if elevations in plasma brain injury biomarkers are associated with outcome at hospital discharge in children who require extracorporeal membrane oxygenation.

DESIGN

Prospective observational study.

SETTING

Single tertiary-care academic center.

PARTICIPANTS

Eighty children who underwent extracorporeal membrane oxygenation between June 2010 and December 2013.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We measured six brain injury biomarkers (glial fibrillary acidic protein, monocyte chemoattractant protein 1/chemokine (C-C motif) ligand 2, neuron-specific enolase, S100b, intercellular adhesion molecule-5, and brain-derived neurotrophic factor) daily during extracorporeal membrane oxygenation, using an electrochemiluminescent multiplex assay. We recorded clinical, neuroimaging, and extracorporeal membrane oxygenation course data. We analyzed the association of biomarker concentrations with favorable versus unfavorable outcome at hospital discharge. Favorable outcome was defined as Pediatric Cerebral Performance Category 1, 2, or no change from baseline. Patients had a median age of 3 days (interquartile range, 1 d-10 mo), and 56% were male. Thirty-three of 80 (41%) had unfavorable outcome, and 22 of 70 (31%) had abnormal neuroimaging findings during or after extracorporeal membrane oxygenation. Peak concentrations were significantly higher in patients with unfavorable outcome than in those with favorable outcome for glial fibrillary acidic protein (p = 0.002), monocyte chemoattractant protein 1/chemokine (C-C motif) ligand 2 (p = 0.030), neuron-specific enolase (p = 0.006), and S100b (p = 0.015) and in patients with versus without abnormal neuroimaging findings for glial fibrillary acidic protein (p = 0.001) and intercellular adhesion molecule-5 (p = 0.001). The area under the receiver operator characteristic curve for unfavorable outcome was 0.73 for a noncollinear biomarker combination. After removing collinear biomarkers, the adjusted odds ratios for unfavorable outcome were 2.89 (95% CI, 1.09-7.73) for neuron-specific enolase, using a cutoff of 62.0 ng/mL, and 2.15 (95% CI, 1.06-4.38) for glial fibrillary acidic protein, using a cutoff of 0.46 ng/mL.

CONCLUSIONS

Elevated plasma brain injury biomarker concentrations during the extracorporeal membrane oxygenation course are associated with unfavorable outcome and/or the presence of neuroimaging abnormalities. Combinations of brain-specific proteins increase the sensitivity and specificity for outcome prediction.

Transcriptional Profiling of a Selective CREB Binding Protein Bromodomain Inhibitor Highlights Therapeutic Opportunities

Bromodomains are involved in transcriptional regulation through the recognition of acetyl lysine modifications on diverse proteins. Selective pharmacological modulators of bromodomains are lacking, although the largely hydrophobic nature of the pocket makes these modules attractive targets for small-molecule inhibitors. This work describes the structure-based design of a highly selective inhibitor of the CREB binding protein (CBP) bromodomain and its use in cell-based transcriptional profiling experiments. The inhibitor downregulated a number of inflammatory genes in macrophages that were not affected by a selective BET bromodomain inhibitor. In addition, the CBP bromodomain inhibitor modulated the mRNA level of the regulator of G-protein signaling 4 (RGS4) gene in neurons, suggesting a potential therapeutic opportunity for CBP inhibitors in the treatment of neurological disorders.

Evidence of IL-17, IP-10, and IL-10 involvement in multiple-organ dysfunction and IL-17 pathway in acute renal failure associated to Plasmodium falciparum malaria

Background

Plasmodium falciparum malaria in India is characterized by high rates of severe disease, with multiple organ dysfunction (MOD)—mainly associated with acute renal failure (ARF)—and increased mortality. The objective of this study is to identify cytokine signatures differentiating severe malaria patients with MOD, cerebral malaria (CM), and cerebral malaria with MOD (CM-MOD) in India. We have previously shown that two cytokines clusters differentiated CM from mild malaria in Maharashtra. Hence, we also aimed to determine if these cytokines could discriminate malaria subphenotypes in Odisha.

Methods

P. falciparum malaria patients from the SCB Medical College Cuttack in the Odisha state in India were enrolled along with three sets of controls: healthy individuals, patients with sepsis and encephalitis (n = 222). We determined plasma concentrations of pro- and anti-inflammatory cytokines and chemokines for all individuals using a multiplex assay. We then used an ensemble of statistical analytical methods to ascertain whether particular sets of cytokines/chemokines were predictors of severity or signatures of a disease category.

Results

Of the 26 cytokines/chemokines tested, 19 increased significantly during malaria and clearly distinguished malaria patients from controls, as well as sepsis and encephalitis patients. High amounts of IL-17, IP-10, and IL-10 predicted MOD, decreased IL-17 and MIP-1α segregated CM-MOD from MOD, and increased IL-12p40 differentiated CM from CM-MOD. Most severe malaria patients with ARF exhibited high levels of IL-17.

Conclusion

We report distinct differences in cytokine production correlating with malarial disease severity in Odisha and Maharashtra populations in India. We show that CM, CM-MOD and MOD are clearly distinct malaria-associated pathologies. High amounts of IL-17, IP-10, and IL-10 were predictors of MOD; decreased IL-17 and MIP-1α separated CM-MOD from MOD; and increased IL-12p40 differentiated CM from CM-MOD. Data also suggest that the IL-17 pathway may contribute to malaria pathogenesis via different regulatory mechanisms and may represent an interesting target to mitigate the pathological processes in malaria-associated ARF.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0731-6) contains supplementary material, which is available to authorized users.

Whole-genome sequencing suggests a chemokine gene cluster that modifies age at onset in familial Alzheimer's disease

We have sequenced the complete genomes of 72 individuals affected with early-onset familial Alzheimer's disease caused by an autosomal dominant, highly penetrant mutation in the presenilin-1 (PSEN1) gene, and performed genome-wide association testing to identify variants that modify age at onset (AAO) of Alzheimer's disease. Our analysis identified a haplotype of single-nucleotide polymorphisms (SNPs) on chromosome 17 within a chemokine gene cluster associated with delayed onset of mild-cognitive impairment and dementia. Individuals carrying this haplotype had a mean AAO of mild-cognitive impairment at 51.0 ± 5.2 years compared with 41.1 ± 7.4 years for those without these SNPs. This haplotype thus appears to modify Alzheimer's AAO, conferring a large (~10 years) protective effect. The associated locus harbors several chemokines including eotaxin-1 encoded by CCL11, and the haplotype includes a missense polymorphism in this gene. Validating this association, we found plasma eotaxin-1 levels were correlated with disease AAO in an independent cohort from the University of California San Francisco Memory and Aging Center. In this second cohort, the associated haplotype disrupted the typical age-associated increase of eotaxin-1 levels, suggesting a complex regulatory role for this haplotype in the general population. Altogether, these results suggest eotaxin-1 as a novel modifier of Alzheimer's disease AAO and open potential avenues for therapy.

Aging diminishes the resistance of AO rats to EAE: putative role of enhanced generation of GM-CSF Expressing CD4+ T cells in aged rats

BACKGROUND

Aging influences immune response and susceptibility to EAE in a strain specific manner. The study was designed to examine influence of aging on EAE induction in Albino Oxford (AO) rats.

RESULTS

Differently from 3-month-old (young) rats, which were resistant to EAE induction, the majority of aged (24-26-month-old) rats developed mild chronic form of EAE. On 16(th) day post-immunization, when in aged rats the neurological deficit reached plateau, more mononuclear cells, including CD4+ T lymphocytes was retrieved from spinal cord of aged than young rats. The frequencies of IL-17+ and GM-CSF+ cells within spinal cord infiltrating CD4+ lymphocytes were greater in aged rats. To their increased frequency contributed the expansion of GM-CSF + IL-17 + IFN-γ+ cells, which are highly pathogenic in mice. The expression of the cytokines (IL-1β and IL-23/p19) driving GM-CSF + IL-17 + IFN-γ + cell differentiation in mice was also augmented in aged rat spinal cord mononuclear cells. Additionally, in aged rat spinal cord the expansion of GM-CSF + IL-17-IFN-γ- CD4+ T lymphocytes was found. Consistently, the expression of mRNAs for IL-3, the cytokine exhibiting the same expression pattern as GM-CSF, and IL-7, the cytokine driving differentiation of GM-CSF + IL-17-IFN-γ- CD4 + lymphocytes in mice, was upregulated in aged rat spinal cord mononuclear cells, and the tissue, respectively. This was in accordance with the enhanced generation of the brain antigen-specific GM-CSF+ CD4+ lymphocytes in aged rat draining lymph nodes, as suggested by (i) the higher frequency of GM-CSF+ cells (reflecting the expansion of IL-17-IFN-γ- cells) within their CD4+ lymphocytes and (ii) the upregulated GM-CSF and IL-3 mRNA expression in fresh CD4+ lymphocytes and MBP-stimulated draining lymph node cells and IL-7 mRNA in lymph node tissue from aged rats. In agreement with the upregulated GM-CSF expression in aged rats, strikingly more CD11b + CD45(int) (activated microglia) and CD45(hi) (mainly proinflammatory dendritic cells and macrophages) cells was retrieved from aged than young rat spinal cord. Besides, expression of mRNA for SOCS1, a negative regulator of proinflammatory cytokine expression in innate immunity cells, was downregulated in aged rat spinal cord mononuclear cells.

CONCLUSIONS

The study revealed that aging may overcome genetic resistance to EAE, and indicated the cellular and molecular mechanisms contributing to this phenomenon in AO rats.

Inflammation in Alzheimer's Disease and Molecular Genetics: Recent Update

Alzheimer's disease (AD) is a complex age-related neurodegenerative disorder of the central nervous system. Since the first description of AD in 1907, many hypotheses have been established to explain its causes. The inflammation theory is one of them. Pathological and biochemical studies of brains from AD individuals have provided solid evidence of the activation of inflammatory pathways. Furthermore, people with long-term medication of anti-inflammatory drugs have shown a reduced risk to develop the disease. After three decades of genetic study in AD, dozens of loci harboring genetic variants influencing inflammatory pathways in AD patients has been identified through genome-wide association studies (GWAS). The most well-known GWAS risk factor that is responsible for immune response and inflammation in AD development should be APOE ε4 allele. However, a growing number of other GWAS risk AD candidate genes in inflammation have recently been discovered. In the present study, we try to review the inflammation in AD and immunity-associated GWAS risk genes like HLA-DRB5/DRB1, INPP5D, MEF2C, CR1, CLU and TREM2.

The role of chemokine C-C motif ligand 2 genotype and cerebrospinal fluid chemokine C-C motif ligand 2 in neurocognition among HIV-infected patients

OBJECTIVES

We examined interrelationships between chemokine C-C motif ligand 2 (CCL2) genotype and expression of inflammatory markers in the cerebrospinal fluid (CSF), plasma viral load, CD4 cell count and neurocognitive functioning among HIV-infected adults. We hypothesized that HIV-positive carriers of the 'risk' CCL2 -2578G allele, caused by a single nucleotide polymorphism (SNP) at rs1024611, would have a higher concentration of CCL2 in CSF, and that CSF CCL2 would be associated with both higher concentrations of other proinflammatory markers in CSF and worse neurocognitive functioning.

DESIGN

A cross-sectional study of 145 HIV-infected individuals enrolled in the National NeuroAIDS Tissue Consortium cohort for whom genotyping, CSF and neurocognitive data were available.

METHODS

Genomic DNA was extracted from peripheral blood mononuclear cells and/or frozen tissue specimens. CSF levels of CCL2, interleukin (IL)-2, IL-6, tumour necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), soluble tumor necrosis factor receptor 2, sIL-6Rα, sIL-2, sCD14 and B-cell activating factor were quantified. Neurocognitive functioning was measured using a comprehensive battery of neuropsychological tests.

RESULTS

Carriers of the CCL2 -2578G allele had a significantly higher concentration of CCL2 in CSF. CSF CCL2 level was positively and significantly associated with other CSF neuroinflammatory markers and worse cognitive functioning. There was a significant association between genotype and plasma viral load, such that carriers of the CCL2 -2578G allele with high viral load expressed greater levels of CCL2 and had higher neurocognitive deficit scores than other genotype/viral load groups.

CONCLUSION

Individuals with the CCL2 -2578G allele had higher levels of CCL2 in CSF, which was associated with increased pro-inflammatory markers in CSF and worse neurocognitive functioning. The results highlight the potential role of intermediate phenotypes in studies of genotype and cognition.

Upregulation of P2RX7 in Cx3cr1-Deficient Mononuclear Phagocytes Leads to Increased Interleukin-1β Secretion and Photoreceptor Neurodegeneration

Photoreceptor degeneration in age-related macular degeneration (AMD) is associated with an infiltration and chronic accumulation of mononuclear phagocytes (MPs). We have previously shown that Cx3cr1-deficient mice develop age- and stress- related subretinal accumulation of MPs, which is associated with photoreceptor degeneration. Cx3cr1-deficient MPs have been shown to increase neuronal apoptosis through IL-1β in neuroinflammation of the brain. The reason for increased IL-1β secretion from Cx3cr1-deficient MPs, and whether IL-1β is responsible for increased photoreceptor apoptosis in Cx3cr1-deficient mice, has not been elucidated. Here we show that Cx3cr1-deficient MPs express increased surface P2X7 receptor (P2RX7), which stimulates IL-1β maturation and secretion. P2RX7 and IL-1β inhibition efficiently blunted Cx3cr1-MP-dependent photoreceptor apoptosis in a monocyte/retina coculture system and in light-induced subretinal inflammation of Cx3cr1-deficient mice in vivo. Our results provide an explanation for increased CX3CR1-dependent IL-1β secretion and suggest that IL-1β or P2RX7 inhibition can help inhibit the inflammation-associated photoreceptor cell loss in late AMD, including geographic atrophy, for which no efficient treatment currently exists.

Transcriptome sequencing of microglial cells stimulated with TLR3 and TLR4 ligands

Background

Resident macrophages in the CNS microglia become activated and produce proinflammatory molecules upon encountering bacteria or viruses. TLRs are a phylogenetically conserved diverse family of sensors that drive innate immune responses following interactions with PAMPs. TLR3 and TLR4 recognize viral dsRNA Poly (I:C) and bacterial endotoxin LPS, respectively. Importantly, these receptors differ in their downstream adaptor molecules. Thus far, only a few studies have investigated the effects of TLR3 and TLR4 in macrophages. However, a genome-wide search for the effects of these TLRs has not been performed in microglia using RNA-seq. Gene expression patterns were determined for the BV-2 microglial cell line when stimulated with viral dsRNA Poly (I:C) or bacterial endotoxin LPS to identify novel transcribed genes, as well as investigate how differences in downstream signaling could influence gene expression in innate immunity.

Results

Sequencing assessment and quality evaluation revealed that common and unique patterns of proinflammatory genes were significantly up-regulated in response to TLR3 and TLR4 stimulation. However, the IFN/viral response gene showed a stronger response to TLR3 stimulation than to TLR4 stimulation. Unexpectedly, TLR3 and TLR4 stimulation did not activate IFN-ß and IRF3 in BV-2 microglia. Most importantly, we observed that previously unidentified transcription factors (TFs) (i.e., IRF1, IRF7, and IRF9) and the epigenetic regulators KDM4A and DNMT3L were significantly up-regulated in both TLR3- and TLR4-stimulated microglia. We also identified 29 previously unidentified genes that are important in immune regulation. In addition, we confirmed the expressions of key inflammatory genes as well as pro-inflammatory mediators in the supernatants were significantly induced in TLR3-and TLR4-stimulated primary microglial cells. Moreover, transcriptional start sites (TSSs) and isoforms, as well as differential promoter usage, revealed a complex pattern of transcriptional and post-transcriptional gene regulation upon infection with TLR3 and TLR4. Furthermore, TF motif analysis (-950 to +50 bp of the 5′ upstream promoters) revealed that the DNA sequences for NF-κB, IRF1, and STAT1 were significantly enriched in TLR3- and TLR4-stimulated microglia.

Conclusions

These unprecedented findings not only permit a comparison of TLR3-and TLR4-stimulated genes but also identify new genes that have not been previously implicated in innate immunity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1728-5) contains supplementary material, which is available to authorized users.

Monocyte Count and 30-Day Case Fatality in Intracerebral Hemorrhage

BACKGROUND AND PURPOSE

Monocytes may contribute to secondary injury after intracerebral hemorrhage (ICH). We tested the association of absolute monocyte count with 30-day ICH case fatality in a multiethnic cohort.

METHODS

Ethnic/Racial Variations of Intracerebral Hemorrhage (ERICH) study is a prospective, multicenter, case-control study of ICH among white, black, and Hispanic patients. In 240 adults with nontraumatic ICH within 24 hours of symptom onset, we evaluated the influence of ICH score and complete blood count components on 30-day case fatality using generalized linear models.

RESULTS

Mean age was 62.8 years (SD, 14 years); 61.7% were men, 33.3% black, and 29.6% Hispanic. Median ICH volume was 9.9 mL (interquartile range, 4.4-26.7). After adjusting for patient age and initial hemoglobin, higher total white blood cell count (P=0.0011), driven by higher absolute neutrophil count (P=0.002), was associated with larger ICH volume, whereas absolute monocyte count was not (P=0.15). After adjusting for age, Glasgow Coma Scale, ICH volume, location, and the presence or absence of intraventricular hemorrhage, baseline absolute monocyte count was independently associated with higher 30-day case-fatality (odds ratio, 5.39; 95% confidence interval, 1.87-15.49; P=0.0018), whereas absolute neutrophil count (odds ratio, 1.04; 0.46-2.32; P=0.93) and white blood cell count (odds ratio, 1.62; 0.58-4.54; P=0.36) were not.

CONCLUSIONS

These data support an independent association between higher admission absolute monocyte count and 30-day case-fatality in ICH. Inquiry into monocyte-mediated pathways of inflammation and apoptosis may elucidate the basis for the observed association and may be targets for ICH neuroprotection.

Bacterial meningitis: insights into pathogenesis and evaluation of new treatment options: a perspective from experimental studies

Bacterial meningitis is associated with high mortality and morbidity rates. Bacterial components induce an overshooting inflammatory reaction, eventually leading to brain damage. Pathological correlates of neurofunctional deficits include cortical necrosis, damage of the inner ear and hippocampal apoptosis. The hippocampal dentate gyrus is important for memory acquisition and harbors a neuronal stem cell niche, thus being potentially well equipped for regeneration. Adjuvant therapies aimed at decreasing the inflammatory reaction, for example, dexamethasone, and those protecting the brain from injury have been evaluated in animal models of the disease. They include nonbacteriolytic antibiotics (e.g., daptomycin), metalloproteinase inhibitors and modulators of the immunological response, for example, granulocyte colony-stimulating factor. Increasing research interest has recently been focused on interventions aimed at supporting regenerative processes.

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.

Is there a role for monocyte chemoattractant protein-1 in delirium? Novel observations in elderly hip fracture patients

Background

Delirium is common, associated with poor outcome, but its pathophysiology remains obscure. The aim of the present study was to study a possible role of monocyte chemoattractant protein-1 (MCP-1) in the development of delirium.

Findings

A prospective cohort of 19 hip fracture patients (median age 83 years) were screened for delirium daily by validated methods. MCP-1 was measured on arrival and postoperatively. The number of patients with a raise in MCP-1 was statistically significantly higher in the group with delirium in the postoperative phase compared to the no-delirium group (5/6 vs. 1/7, p = .03).

Conclusions

MCP-1 might play a role in the development of delirium.

Multivariate analysis of traumatic brain injury: development of an assessment score

Important challenges for the diagnosis and monitoring of mild traumatic brain injury (mTBI) include the development of plasma biomarkers for assessing neurologic injury, monitoring pathogenesis, and predicting vulnerability for the development of untoward neurologic outcomes. While several biomarker proteins have shown promise in this regard, used individually, these candidates lack adequate sensitivity and/or specificity for making a definitive diagnosis or identifying those at risk of subsequent pathology. The objective for this study was to evaluate a panel of six recognized and novel biomarker candidates for the assessment of TBI in adult patients. The biomarkers studied were selected on the basis of their relative brain-specificities and potentials to reflect distinct features of TBI mechanisms including (1) neuronal damage assessed by neuron-specific enolase (NSE) and brain derived neurotrophic factor (BDNF); (2) oxidative stress assessed by peroxiredoxin 6 (PRDX6); (3) glial damage and gliosis assessed by glial fibrillary acidic protein and S100 calcium binding protein beta (S100b); (4) immune activation assessed by monocyte chemoattractant protein 1/chemokine (C–C motif) ligand 2 (MCP1/CCL2); and (5) disruption of the intercellular adhesion apparatus assessed by intercellular adhesion protein-5 (ICAM-5). The combined fold-changes in plasma levels of PRDX6, S100b, MCP1, NSE, and BDNF resulted in the formulation of a TBI assessment score that identified mTBI with a receiver operating characteristic (ROC) area under the curve of 0.97, when compared to healthy controls. This research demonstrates that a profile of biomarker responses can be used to formulate a diagnostic score that is sensitive for the detection of mTBI. Ideally, this multivariate assessment strategy will be refined with additional biomarkers that can effectively assess the spectrum of TBI and identify those at particular risk for developing neuropathologies as consequence of a mTBI event.

Dual RNA sequencing reveals the expression of unique transcriptomic signatures in lipopolysaccharide-induced BV-2 microglial cells

Microglial cells become rapidly activated through interactions with pathogens, and the persistent activation of these cells is associated with various neurodegenerative diseases. Previous studies have investigated the transcriptomic signatures in microglia or macrophages using microarray technologies. However, this method has numerous restrictions, such as spatial biases, uneven probe properties, low sensitivity, and dependency on the probes spotted. To overcome this limitation and identify novel transcribed genes in response to LPS, we used RNA Sequencing (RNA-Seq) to determine the novel transcriptomic signatures in BV-2 microglial cells. Sequencing assessment and quality evaluation showed that approximately 263 and 319 genes (≥ 1.5 log₂-fold), such as cytokines and chemokines, were strongly induced after 2 and 4 h, respectively, and the induction of several genes with unknown immunological functions was also observed. Importantly, we observed that previously unidentified transcription factors (TFs) (irf1, irf7, and irf9), histone demethylases (kdm4a) and DNA methyltransferases (dnmt3l) were significantly and selectively expressed in BV-2 microglial cells. The gene expression levels, transcription start sites (TSS), isoforms, and differential promoter usage revealed a complex pattern of transcriptional and post-transcriptional gene regulation upon infection with LPS. In addition, gene ontology, molecular networks and pathway analyses identified the top significantly regulated functional classification, canonical pathways and network functions at each activation status. Moreover, we further analyzed differentially expressed genes to identify transcription factor (TF) motifs (−950 to +50 bp of the 5’ upstream promoters) and epigenetic mechanisms. Furthermore, we confirmed that the expressions of key inflammatory genes as well as pro-inflammatory mediators in the supernatants were significantly induced in LPS treated primary microglial cells. This transcriptomic analysis is the first to show a comparison of the family-wide differential expression of most known immune genes and also reveal transcription evidence of multiple gene families in BV-2 microglial cells. Collectively, these findings reveal unique transcriptomic signatures in BV-2 microglial cells required for homeostasis and effective immune responses.

CCL2 induces neural stem cell proliferation and neuronal differentiation in Niemann-Pick type C mice

Niemann-Pick type C disease (NP-C) is a rare and ultimately fatal lysosomal storage disorder with variable neurologic symptoms. Loss of neuronal function and neuronal cell death occur in the NP-C brain, similar to the findings for other neurodegenerative diseases. Targeting of neuronal cells in the brain therefore represents a potential clinical intervention strategy to reduce the rate of disease progression and improve the quality of life. We previously reported that bone marrow stem cells show a neurogenic effect through CCL2 (also known as monocyte chemoattractant protein-1, MCP-1) secretion in the brains of NP-C mice. However, the direct effect of CCL2 on neurogenesis has not been ascertained. Here, to define neurogenic effects of CCL2 in NP-C, we applied human recombinant CCL2 to neural stem cells (NSCs) derived from NP-C mice. CCL2-treated NSCs showed significantly increased capacity for self-renewal, proliferation and neuronal differentiation. Similar results were observed in the subventricular zone of NP-C mice after CCL2 treatment. Furthermore, infusion of CCL2 into the NP-C mouse brain resulted in reduction of neuroinflammation. Taken together, our results demonstrate that CCL2 is a potential new therapeutic agent for NP-C.