Analysis of glial secretome: The long pentraxin PTX3 modulates phagocytic activity of microglia

Glial polarization in neurological diseases: Molecular mechanisms and therapeutic opportunities

Glial cell polarization plays a pivotal role in various neurological disorders. In response to distinct stimuli, glial cells undergo polarization to either mitigate neurotoxicity or facilitate neural repair following injury, underscoring the importance of glial phenotypic polarization in modulating central nervous system function. This review presents an overview of glial cell polarization, focusing on astrocytes and microglia. It explores the involvement of glial polarization in neurological diseases such as Alzheimer's disease, Parkinson's disease, stroke, epilepsy, traumatic brain injury, amyotrophic lateral sclerosis, multiple sclerosis and meningoencephalitis. Specifically, it emphasizes the role of glial cell polarization in disease pathogenesis through mechanisms including neuroinflammation, neurodegeneration, calcium signaling dysregulation, synaptic dysfunction and immune response. Additionally, it summarizes various therapeutic strategies including pharmacological treatments, dietary supplements and cell-based therapies, aimed at modulating glial cell polarization to ameliorate brain dysfunction. Future research focused on the spatio-temporal manipulation of glial polarization holds promise for advancing precision diagnosis and treatment of neurological diseases.

Proteomic analysis of APOEε4 carriers implicates lipid metabolism, complement and lymphocyte signaling in cognitive resilience

BACKGROUND

Apolipoprotein E (APOE) ε4 allele is the strongest genetic risk factor for late onset Alzheimer's disease (AD). This case-cohort study used targeted plasma biomarkers and large-scale proteomics to examine the biological mechanisms that allow some APOEε4 carriers to maintain normal cognitive functioning in older adulthood.

METHODS

APOEε4 carriers and APOEε3 homozygotes enrolled in the Women's Health Initiative Memory Study (WHIMS) from 1996 to 1999 were classified as resilient if they remained cognitively unimpaired beyond age 80, and as non-resilient if they developed cognitive impairment before or at age 80. AD pathology (Aß42/40) and neurodegeneration (NfL, tau) biomarkers, as well as 1007 proteins (Olink) were quantified in blood collected at study enrollment (on average 14 years prior) when participants were cognitively normal. We identified plasma proteins that distinguished between resilient and non-resilient APOEε4 carriers, examined whether these associations generalized to APOEε3 homozygotes, and replicated these findings in the UK Biobank.

RESULTS

A total of 1610 participants were included (baseline age: 71.3 [3.8 SD] years; all White; 42% APOEε4 carriers). Compared to resilient APOEε4 carriers, non-resilient APOEε4 carriers had lower Aß42/40/tau ratio and greater NfL at baseline. Proteomic analyses identified four proteins differentially expressed between resilient and non-resilient APOEε4 carriers at an FDR-corrected P < 0.05. While one of the candidate proteins, a marker of neuronal injury (NfL), also distinguished resilient from non-resilient APOEε3 homozygotes, the other three proteins, known to be involved in lipid metabolism (ANGPTL4) and immune signaling (PTX3, NCR1), only predicted resilient vs. non-resilient status among APOEε4 carriers (protein*genotype interaction-P < 0.05). Three of these four proteins also predicted 14-year dementia risk among APOEε4 carriers in the UK Biobank validation sample (N = 9420). While the candidate proteins showed little to no association with targeted biomarkers of AD pathology, protein network and enrichment analyses suggested that natural killer (NK) cell and T lymphocyte signaling (via PKC-θ) distinguished resilient from non-resilient APOEε4 carriers.

CONCLUSIONS

We identified and replicated a plasma proteomic signature associated with cognitive resilience among APOEε4 carriers. These proteins implicate specific immune processes in the preservation of cognitive status despite elevated genetic risk for AD. Future studies in diverse cohorts will be needed to assess the generalizability of these results.

Proteomic insights into breast cancer response to brain cell-secreted factors

The most devastating feature of cancer cells is their ability to metastasize to distant sites in the body. HER2 + and TN breast cancers frequently metastasize to the brain and stay potentially dormant for years until favorable conditions support their proliferation. The sheltered and delicate nature of the brain prevents, however, early disease detection and effective delivery of therapeutic drugs. Moreover, the challenges associated with the acquisition of brain biopsies add compounding difficulties to exploring the mechanistic aspects of tumor development. To provide insights into the determinants of cancer cell behavior at the brain metastatic site, this study was aimed at exploring the early response of HER2 + breast cancer cells (SKBR3) to factors present in the brain perivascular niche. The neural microenvironment was simulated by using the secretome of a set of brain cells that come first in contact with the cancer cells upon crossing the blood brain barrier, i.e., endothelial cells, astrocytes, and microglia. Cytokine microarrays were used to investigate the secretome mediators of intercellular communication, and proteomic technologies for assessing the changes in the behavior of cancer cells upon exposure to the brain cell-secreted factors. The cytokines detected in the brain secretomes were supportive of inflammatory conditions, while the SKBR3 cells secreted numerous cancer-promoting growth factors that were either absent or present in lower abundance in the brain cell cultures, indicating that upon exposure the SKBR3 cells may have been deprived of favorable conditions for optimal growth. Altogether, the results suggest that the exposure of SKBR3 cells to the brain cell-secreted factors altered their growth potential and drove them toward a state of quiescence, with broader overall outcomes that affected cellular metabolism, adhesion and immune response processes. The findings of this study underscore the key role played by the neural niche in shaping the behavior of metastasized cancer cells, provide insights into the cellular cross-talk that may lead cancer cells into dormancy, and highlight novel opportunities for the development of metastatic breast cancer therapeutic strategies.

Long-chain pentraxin 3 possesses agglutination activity and plays a role in host defense against bacterial infection in Oreochromis niloticus

Pentraxin 3 (PTX3) is a soluble pattern recognition molecule in the innate immune system that has multiple functions. It is involved in resisting pathogen infection. However, the functions of PTX3 in teleost fish are not well understood. In this study, we identified and characterized PTX3 in Nile tilapia (Oreochromis niloticus) (OnPTX3). The open reading frame of OnPTX3 was found to be 1305 bp, encoding 434 aa. We conducted spatial mRNA expression analysis and found that the expression of OnPTX3 was significantly increased after infection with Streptococcus agalactiae and Aeromonas hydrophila, both in vivo and in vitro. We also observed that recombinant OnPTX3 protein could bind and agglutinate bacterial pathogen. Furthermore, OnPTX3 enhanced the phagocytosis of bacteria (S. agalactiae and A. hydrophila) by head kidney macrophages. Additionally, OnPTX3 was found to influence the expression of inflammatory cytokines, suggesting its involvement in the regulation of the inflammatory response. Moreover, OnPTX3 was shown to promote complement-mediated hemolysis and possess antibacterial activity. In conclusion, our research demonstrates that OnPTX3 has bacterial binding and agglutination activities, enhances phagocytosis, and regulates inflammation. It plays a crucial role in the defense of Nile tilapia against pathogenic bacteria, providing valuable insights for the prevention and control of aquatic diseases in the future.

Proteomic Insights into Metastatic Breast Cancer Response to Brain Cell-Secreted Factors

The most devastating feature of cancer cells is their ability to metastasize to distant sites in the body. HER2+ and triple negative breast cancers frequently metastasize to the brain and stay potentially dormant for years, clinging to the microvasculature, until favorable environmental conditions support their proliferation. The sheltered and delicate nature of the brain prevents, however, early disease detection, diagnosis, and effective delivery of therapeutic drugs. Moreover, the challenges associated with the acquisition of brain tissues and biopsies add compounding difficulties to exploring the mechanistic aspects of tumor development, leading to slow progress in understanding the drivers of disease progression and response to therapy. To provide insights into the determinants of cancer cell behavior at the brain metastatic site, this study was aimed at exploring the growth and initial response of HER2+ breast cancer cells (SKBR3) to factors present in the brain perivascular niche. The neural microenvironment conditions were simulated by using the secretome of a set of brain cells that come first in contact with the cancer cells upon crossing the blood brain barrier, i.e., human endothelial cells (HBEC5i), human astrocytes (NHA) and human microglia (HMC3) cells. Cytokine microarrays were used to investigate the cell secretomes and explore the mediators responsible for cell-cell communication, and proteomic technologies for assessing the changes in the behavior of cancer cells upon exposure to the brain cell-secreted factors. The results of the study suggest that the exposure of SKBR3 cells to the brain secretomes altered their growth potential and drove them towards a state of quiescence. The cytokines, growth factors and enzymes detected in the brain cell-conditioned medium were supportive of mostly inflammatory conditions, indicating a collective functional contribution to cell activation, defense, inflammatory responses, chemotaxis, adhesion, angiogenesis, and ECM organization. The SKBR3 cells, on the other hand, secreted numerous cancer-promoting growth factors that were either absent or present in lower abundance in the brain cell culture media, suggesting that upon exposure the SKBR3 cells were deprived of favorable environmental conditions required for optimal growth. The findings of this study underscore the key role played by the neural niche in shaping the behavior of metastasized cancer cells, providing insights into the cancer-host cell cross-talk that contributes to driving metastasized cancer cells into dormancy and into the opportunities that exist for developing novel therapeutic strategies that target the brain metastases of breast cancer.

Extracellular histones as damage-associated molecular patterns in neuroinflammatory responses

The four core histones H2A, H2B, H3, H4, and the linker histone H1 primarily bind DNA and regulate gene expression within the nucleus. Evidence collected mainly from the peripheral tissues illustrates that histones can be released into the extracellular space by activated or damaged cells. In this article, we first summarize the innate immune-modulatory properties of extracellular histones and histone-containing complexes, such as nucleosomes, and neutrophil extracellular traps (NETs), described in peripheral tissues. There, histones act as damage-associated molecular patterns (DAMPs), which are a class of endogenous molecules that trigger immune responses by interacting directly with the cellular membranes and activating pattern recognition receptors (PRRs), such as toll-like receptors (TLR) 2, 4, 9 and the receptor for advanced glycation end-products (RAGE). We then focus on the available evidence implicating extracellular histones as DAMPs of the central nervous system (CNS). It is becoming evident that histones are present in the brain parenchyma after crossing the blood-brain barrier (BBB) or being released by several types of brain cells, including neurons, microglia, and astrocytes. However, studies on the DAMP-like effects of histones on CNS cells are limited. For example, TLR4 is the only known molecular target of CNS extracellular histones and their interactions with other PRRs expressed by brain cells have not been observed. Nevertheless, extracellular histones are implicated in the pathogenesis of a variety of neurological disorders characterized by sterile neuroinflammation; therefore, detailed studies on the role these proteins and their complexes play in these pathologies could identify novel therapeutic targets.

Host PTX3 Protein and Bacterial Capsule Coordinately Regulate the Inflammatory Response during Streptococcus suis Infection

Streptococcus suis serotype 2 (SS2) is a noteworthy zoonotic pathogen that has been responsible for large economic losses in pig production and a great threat to human health. Pentraxin 3 (PTX3) is an essential regulator of the innate immune response to bacterial pathogens; however, its role during SS2 infection is not fully understood. In this study, we found that the SS2 strain HA9801 induced a significant inflammatory response in the mouse air pouch model; this response was amplified by the treatment of exogenous PTX3 simultaneously in terms of the results of inflammatory cell recruitment and proinflammatory cytokine IL-6 production. In addition, PTX3 facilitated the phagocytosis of macrophage Ana-1 against SS2 strain HA9801. The supplementation of exogenous PTX3 significantly reduced the bacterial loads in a dose-dependent manner in lungs, livers and bloods of SS2-infected mice compared to the samples with HA9801 infection alone; this finding indicated that PTX3 may facilitate the bacterial clearance through enhancing the host inflammatory response during SS2 infection. Both PTX3 and SS2 capsular polysaccharide (CPS2) were required for the robust inflammatory response, implying that the host PTX3 protein and SS2 surface CPS2 modulate the host innate immune response in concert. All of these results suggested that PTX3 is a potential novel biological agent for the SS2 infection; however, the recommended dose of PTX3 must be evaluated strictly to avoid inducing an excessive inflammatory response that can cause serious tissue injury and animal death.

MicroRNA-mediated regulation of reactive astrocytes in central nervous system diseases

Astrocytes (AST) are abundant glial cells in the human brain, accounting for approximately 20-50% percent of mammalian central nervous system (CNS) cells. They display essential functions necessary to sustain the physiological processes of the CNS, including maintaining neuronal structure, forming the blood-brain barrier, coordinating neuronal metabolism, maintaining the extracellular environment, regulating cerebral blood flow, stabilizing intercellular communication, participating in neurotransmitter synthesis, and defending against oxidative stress et al. During the pathological development of brain tumors, stroke, spinal cord injury (SCI), neurodegenerative diseases, and other neurological disorders, astrocytes undergo a series of highly heterogeneous changes, which are called reactive astrocytes, and mediate the corresponding pathophysiological process. However, the pathophysiological mechanisms of reactive astrocytes and their therapeutic relevance remain unclear. The microRNAs (miRNAs) are essential for cell differentiation, proliferation, and survival, which play a crucial role in the pathophysiological development of CNS diseases. In this review, we summarize the regulatory mechanism of miRNAs on reactive astrocytes in CNS diseases, which might provide a theoretical basis for the diagnosis and treatment of CNS diseases.

Microglial phagocytosis and regulatory mechanisms after stroke

Stroke, including ischemic stroke and hemorrhagic stroke can cause massive neuronal death and disruption of brain structure, which is followed by secondary inflammatory injury initiated by pro-inflammatory molecules and cellular debris. Phagocytic clearance of cellular debris by microglia, the brain's scavenger cells, is pivotal for neuroinflammation resolution and neurorestoration. However, microglia can also exacerbate neuronal loss by phagocytosing stressed-but-viable neurons in the penumbra, thereby expanding the injury area and hindering neurofunctional recovery. Microglia constantly patrol the central nervous system using their processes to scour the cellular environment and start or cease the phagocytosis progress depending on the "eat me" or "don't eat me'' signals on cellular surface. An optimal immune response requires a delicate balance between different phenotypic states to regulate neuro-inflammation and facilitate reconstruction after stroke. Here, we examine the literature and discuss the molecular mechanisms and cellular pathways regulating microglial phagocytosis, their resulting effects in brain injury and neural regeneration, as well as the potential therapeutic targets that might modulate microglial phagocytic activity to improve neurological function after stroke.

β-Galactosylceramidase Deficiency Causes Upregulation of Long Pentraxin-3 in the Central Nervous System of Krabbe Patients and Twitcher Mice

Globoid cell leukodystrophy (GLD), or Krabbe disease, is a neurodegenerative sphingolipidosis caused by genetic deficiency of lysosomal β-galactosylceramidase (GALC), characterized by neuroinflammation and demyelination of the central (CNS) and peripheral nervous system. The acute phase protein long pentraxin-3 (PTX3) is a soluble pattern recognition receptor and a regulator of innate immunity. Growing evidence points to the involvement of PTX3 in neurodegeneration. However, the expression and role of PTX3 in the neurodegenerative/neuroinflammatory processes that characterize GLD remain unexplored. Here, immunohistochemical analysis of brain samples from Krabbe patients showed that macrophages and globoid cells are intensely immunoreactive for PTX3. Accordingly, Ptx3 expression increases throughout the course of the disease in the cerebrum, cerebellum, and spinal cord of GALC-deficient twitcher (Galc^twi/twi) mice, an authentic animal model of GLD. This was paralleled by the upregulation of proinflammatory genes and M1-polarized macrophage/microglia markers and of the levels of PTX3 protein in CNS and plasma of twitcher animals. Crossing of Galc^twi/twi mice with transgenic PTX3 overexpressing animals (hPTX3 mice) demonstrated that constitutive PTX3 overexpression reduced the severity of clinical signs and the upregulation of proinflammatory genes in the spinal cord of P35 hPTX3/Galc^twi/twi mice when compared to Galc^twi/twi littermates, leading to a limited increase of their life span. However, this occurred in the absence of a significant impact on the histopathological findings and on the accumulation of the neurotoxic metabolite psychosine when evaluated at this late time point of the disease. In conclusion, our results provide the first evidence that PTX3 is produced in the CNS of GALC-deficient Krabbe patients and twitcher mice. PTX3 may exert a protective role by reducing the neuroinflammatory response that occurs in the spinal cord of GALC-deficient animals.

All roads lead to heterogeneity: The complex involvement of astrocytes and microglia in the pathogenesis of Alzheimer’s disease

In recent years, glial cells have been acknowledged as key players in the pathogenesis of Alzheimer’s disease (AD), a neurodegenerative condition in which an accumulation of intracellular neurofibrillary tangles and extracellular fibrillar amyloid beta is notably observed in the central nervous system. Genome-wide association studies have shown, both in microglia and astrocytes, an increase in gene variants associated with a higher risk of developing late-onset AD. Microglia, the resident innate immune cells of the brain, and astrocytes, glial cells crucial for vascular integrity and neuronal support, both agglomerate near amyloid beta plaques and dystrophic neurites where they participate in the elimination of these harmful parenchymal elements. However, their role in AD pathogenesis has been challenging to resolve due to the highly heterogeneous nature of these cell populations, i.e., their molecular, morphological, and ultrastructural diversity, together with their ever-changing responsiveness and functions throughout the pathological course of AD. With the recent expansions in the field of glial heterogeneity through innovative advances in state-of-the-art microscopy and -omics techniques, novel concepts and questions arose, notably pertaining to how the diverse microglial and astrocytic states interact with each other and with the AD hallmarks, and how their concerted efforts/actions impact the progression of the disease. In this review, we discuss the recent advances and findings on the topic of glial heterogeneity, particularly focusing on the relationships of these cells with AD hallmarks (e.g., amyloid beta plaques, neurofibrillary tangles, synaptic loss, and dystrophic neurites) in murine models of AD pathology and post-mortem brain samples of patients with AD.

Microglial Priming in Infections and Its Risk to Neurodegenerative Diseases

Infectious diseases of different etiologies have been associated with acute and long-term neurological consequences. The primary cause of these consequences appears to be an inflammatory process characterized primarily by a pro-inflammatory microglial state. Microglial cells, the local effectors' cells of innate immunity, once faced by a stimulus, alter their morphology, and become a primary source of inflammatory cytokines that increase the inflammatory process of the brain. This inflammatory scenario exerts a critical role in the pathogenesis of neurodegenerative diseases. In recent years, several studies have shown the involvement of the microglial inflammatory response caused by infections in the development of neurodegenerative diseases. This has been associated with a transitory microglial state subsequent to an inflammatory response, known as microglial priming, in which these cells are more responsive to stimuli. Thus, systemic inflammation and infections induce a transitory state in microglia that may lead to changes in their state and function, making priming them for subsequent immune challenges. However, considering that microglia are long-lived cells and are repeatedly exposed to infections during a lifetime, microglial priming may not be beneficial. In this review, we discuss the relationship between infections and neurodegenerative diseases and how this may rely on microglial priming.

Signatures of glial activity can be detected in the CSF proteome

SignificanceSingle-cell transcriptomics has revealed specific glial activation states associated with the pathogenesis of neurodegenerative diseases, such as Alzheimer's and Parkinson's disease (AD and PD). What is still needed are clinically relevant biomarkers for deciphering such glial states in AD and PD patients. To this end, we applied proteome analysis in cerebrospinal fluid (CSF) of mouse models of AD and PD pathology. This allowed us to identify a panel of glial CSF proteins that largely match the transcriptomic changes. The identified proteins can also be quantified in human CSF and show changes in AD patients, supporting their relevance as biomarker candidates to stage glial activation in patients with neurodegenerative diseases.

Neuroimmune mechanisms of cognitive impairment in a mouse model of Gulf War illness

Gulf War Illness (GWI) is a chronic, multi-symptom disorder affecting approximately 30 percent of the nearly 700,000 Veterans of the 1991 Persian Gulf War. GWI-related chemical (GWIC) exposure promotes immune activation that correlates with cognitive impairment and other symptoms of GWI. However, the molecular mechanisms and signaling pathways linking GWIC to inflammation and neurological symptoms remain unclear. Here we show that acute exposure of murine macrophages to GWIC potentiates innate immune signaling and inflammatory cytokine production. Using an established mouse model of GWI, we report that neurobehavioral changes and neuroinflammation are attenuated in mice lacking the cyclic GMP-AMP synthase (cGAS)-Stimulator of Interferon Genes (STING) and NOD-, LRR- or pyrin domain-containing protein 3 (NLRP3) innate immune pathways. In addition, we report sex differences in response to GWIC, with female mice showing more pronounced cognitive impairment and hippocampal astrocyte hypertrophy. In contrast, male mice display a GWIC-dependent upregulation of proinflammatory cytokines in the plasma that is not present in female mice. Our results indicate that STING and NLRP3 are key mediators of the cognitive impairment and inflammation observed in GWI and provide important new information on sex differences in this model.

Potential neurotoxic activity of diverse molecules released by microglia

Microglia are the professional immune cells of the brain, which support numerous physiological processes. One of the defensive functions provided by microglia involves secretion of cytotoxins aimed at destroying invading pathogens. It is also recognized that the adverse activation of microglia in diseased brains may lead to secretion of cytotoxic molecules, which could be damaging to the surrounding cells, including neurons. Several of these toxins, such as reactive oxygen and nitrogen species, L-glutamate, and quinolinic acid, are widely recognized and well-studied. This review is focused on a structurally diverse group of less-established microglia neurotoxins, which were selected by applying the two criteria that these molecules 1) can be released by microglia, and 2) have the potential to be directly harmful to neurons. The following 11 molecules are discussed in detail: amyloid beta peptides (Aβ); cathepsin (Cat)B and CatD; C-X-C motif chemokine ligand (CXCL)10 and CXCL12 (5-67); high mobility group box (HMGB)1; lymphotoxin (LT)-α; matrix metalloproteinase (MMP)-2 and MMP-9; platelet-activating factor (PAF); and prolyl endopeptidase (PEP). Molecular mechanisms of their release by microglia and neurotoxicity, as well as available evidence implicating their involvement in human neuropathologies are summarized. Further studies on several of the above molecules are warranted to confirm either their microglial origin in the brain or direct neurotoxic effects. In addition, investigations into the differential secretion patterns of neurotoxins by microglia in response to diverse stimuli are required. This research could identify novel therapeutic targets for neurological disorders involving adverse microglial activation.

The Phagocytic Code Regulating Phagocytosis of Mammalian Cells

Mammalian phagocytes can phagocytose (i.e. eat) other mammalian cells in the body if they display certain signals, and this phagocytosis plays fundamental roles in development, cell turnover, tissue homeostasis and disease prevention. To phagocytose the correct cells, phagocytes must discriminate which cells to eat using a 'phagocytic code' - a set of over 50 known phagocytic signals determining whether a cell is eaten or not - comprising find-me signals, eat-me signals, don't-eat-me signals and opsonins. Most opsonins require binding to eat-me signals - for example, the opsonins galectin-3, calreticulin and C1q bind asialoglycan eat-me signals on target cells - to induce phagocytosis. Some proteins act as 'self-opsonins', while others are 'negative opsonins' or 'phagocyte suppressants', inhibiting phagocytosis. We review known phagocytic signals here, both established and novel, and how they integrate to regulate phagocytosis of several mammalian targets - including excess cells in development, senescent and aged cells, infected cells, cancer cells, dead or dying cells, cell debris and neuronal synapses. Understanding the phagocytic code, and how it goes wrong, may enable novel therapies for multiple pathologies with too much or too little phagocytosis, such as: infectious disease, cancer, neurodegeneration, psychiatric disease, cardiovascular disease, ageing and auto-immune disease.

A1/A2 astrocytes in central nervous system injuries and diseases: Angels or devils?

Astrocytes play a pivotal role in maintaining the central nervous system (CNS) homeostasis and function. In response to CNS injuries and diseases, reactive astrocytes are triggered. By purifying and genetically profiling reactive astrocytes, it has been now found that astrocytes can be activated into two polarization states: the neurotoxic or pro-inflammatory phenotype (A1) and the neuroprotective or anti-inflammatory phenotype (A2). Although the simple dichotomy of the A1/A2 phenotypes does not reflect the wide range of astrocytic phenotypes, it facilitates our understanding of the reactive state of astrocytes in various CNS disorders. This article reviews the recent evidences regarding A1/A2 astrocytes, including (a) the specific markers and morphological characteristics, (b) the effects of A1/A2 astrocytes on the neurovascular unit, and (c) the molecular mechanisms involved in the phenotypic switch of astrocytes. Although many questions remain, a deeper understanding of different phenotypic astrocytes will eventually help us to explore effective strategies for neurological disorders by targeting astrocytes.

Gamma subunit of complement component 8 is a neuroinflammation inhibitor

The complement system is part of the innate immune system that comprises several small proteins activated by sequential cleavages. The majority of these complement components, such as components 3a (C3a) and C5a, are chemotactic and pro-inflammatory. However, in this study, we revealed an inhibitory role of complement component 8 gamma (C8G) in neuroinflammation. In patients with Alzheimer's disease, who exhibit strong neuroinflammation, we found higher C8G levels in brain tissue, CSF, and plasma. Our novel findings also showed that the expression level of C8G increases in the inflamed mouse brain, and that C8G is mainly localized to brain astrocytes. Experiments using recombinant C8G protein and shRNA-mediated knockdown showed that C8G inhibits glial hyperactivation, neuroinflammation, and cognitive decline in acute and chronic animal models of Alzheimer's disease. Additionally, we identified sphingosine-1-phosphate receptor 2 (S1PR2) as a novel interaction protein of C8G and demonstrated that astrocyte-derived C8G interacts with S1PR2 to antagonize the pro-inflammatory action of S1P in microglia. Taken together, our results reveal the previously unrecognized role of C8G as a neuroinflammation inhibitor. Our findings pave the way towards therapeutic containment of neuroinflammation in Alzheimer's disease and related neurological diseases.

Expression Profiling of Primary and Recurrent Glioblastomas Reveals a Reduced Level of Pentraxin 3 in Recurrent Glioblastomas

Glioblastomas (GBM) are highly infiltrative tumors and despite intensive treatment tumor recurrence is inevitable. The immune microenvironment in recurrent GBM is poorly characterized, but it is potentially influenced by therapeutic interventions with surgery, radiotherapy, and chemotherapy. The aim of this study was to obtain a deeper insight in the immune microenvironment in primary and recurrent GBM. Primary and recurrent glioblastoma samples from 18 patients were identified and expression profiling of 770 myeloid innate immune-related markers was performed. Leukemia inhibitory factor and pentraxin 3 were expressed at lower levels in recurrent tumors. Using in silico data and immunohistochemical staining, this was validated for pentraxin 3. Both high leukemia inhibitory factor and pentraxin 3 expression appeared to be associated with shorter survival in primary and recurrent GBM using in silico data. In primary GBM, gene set analysis also showed higher expression of genes involved in metabolism, extracellular matrix remodeling and complement activation, whereas genes involved in T cell activation and checkpoint signaling were expressed at higher levels in recurrent GBM. The reduced level of pentraxin 3 in recurrent glioblastomas and the gene set analysis results suggest an altered microenvironment in recurrent GBM that might be more active.

Increased plasma levels of chitinase 3-like 1 (CHI3L1) protein in patients with idiopathic normal-pressure hydrocephalus

Idiopathic normal-pressure hydrocephalus (iNPH) is an uncommon neurological disorder with no known pathological hallmarks. INPH may share common degenerative pathways with other neurological diseases, such as Alzheimer's disease (AD). However, the reversible properties of iNPH may share differing pathophysiological mechanisms with other diseases. This study aimed at assessing the diagnostic value of plasma chitinase 3-like 1 (CHI3L1) protein levels as a disease-specific biomarker for iNPH. We selected both iNPH and AD patients as well as normal and disease control subjects from an enrolled dementia registry. A total of 121 AD, 80 iNPH, 13 idiopathic Parkinson's disease, and 23 mild cognitive impairment patients with 83 healthy controls were included in the final analysis. The Aβ42, total tau, and phosphorylated tau levels within the cerebrospinal fluid, as well as plasma levels of CHI3L1, were measured using commercially available enzyme-linked immunosorbent assay kits. CHI3L1 levels for iNPH patients were higher than those of the other groups. Analysis of covariance adjusting for age showed significantly increased plasma CHI3L1 levels in iNPH patients than in the controls (p < 0.001). CHI3L1 plasma levels may be useful in differentiating iNPH patients from healthy individuals.

Function and Dysfunction of Complement Factor H During Formation of Lipid-Rich Deposits

Complement-mediated inflammation or dysregulation in lipid metabolism are associated with the pathogenesis of several diseases. These include age-related macular degeneration (AMD), C3 glomerulonephritis (C3GN), dense deposit disease (DDD), atherosclerosis, and Alzheimer's disease (AD). In all these diseases, formation of characteristic lipid-rich deposits is evident. Here, we will discuss molecular mechanisms whereby dysfunction of complement, and especially of its key regulator factor H, could be involved in lipid accumulation and related inflammation. The genetic associations to factor H polymorphisms, the role of factor H in the resolution of inflammation in lipid-rich deposits, modification of macrophage functions, and complement-mediated clearance of apoptotic and damaged cells indicate that the function of factor H is crucial in limiting inflammation in these diseases.

Glial cells in Parkinson´s disease: protective or deleterious?

Glial cells have been identified more than 100 years ago, and are known to play a key role in the central nervous system (CNS) function. A recent piece of evidence is emerging showing that in addition to the capacity of CNS modulation and homeostasis, glial cells are also being looked like as a promising cell source not only to study CNS pathologies initiation and progression but also to the establishment and development of new therapeutic strategies. Thus, in the present review, we will discuss the current evidence regarding glial cells' contribution to neurodegenerative diseases as Parkinson's disease, providing cellular, molecular, functional, and behavioral data supporting its active role in disease initiation, progression, and treatment. As so, considering their functional relevance, glial cells may be important to the understanding of the underlying mechanisms regarding neuronal-glial networks in neurodegeneration/regeneration processes, which may open new research opportunities for their future use as a target or treatment in human clinical trials.

12-months prospective Pentraxin-3 and metabolomic evaluation in multiple sclerosis patients treated with glatiramer acetate

BACKGROUND

Pentraxin-3 (PTX-3) is involved in acute immunological responses and it is a pro-inflammatory protein and a novel biomarker of inflammatory diseases. It is demonstrated that PTX-3 is higher in cerebrospinal fluid (CSF) of aggressive Multiple Sclerosis (MS). Metabolomics, the identification of small endogenous molecules, offers a molecular profile of MS. Glatiramer acetate (GA) is a widely used treatment for (MS) but its mechanism of action is not completely defined. The aim of our study is to analyze PTX-3 and metabolomic profile in MS patients compared to controls and to investigate the effect of GA on PXT-3 and metabolic molecules during treatment in responder and not responder MS patients.

METHODS

28 unrelated MS patients and 27 age-and sex-matched controls were recruited. In serum, PTX-3 levels were measured by ELISA and Metabolomic panel was evaluated trough Nuclear Magnetic Resonance (NMR). According to clinical practice patients started GA treatment; PTX-3 and metabolomic identification were performed before and during treatment. Responders to treatment were identified if no evidence of instrumental, clinical relapses and disability progression (NEDA) occurred during follow up.

RESULTS

Serum PTX-3 levels were higher in MS patients compared to matched controls (7,85 ± 2,19 vs 6,20 ± 1,63 ng/ml) (p = 0,03); metabolomic evaluation shows higher levels of lactate and lower levels of valine, tyrosine and tryptophan in MS patients compared to controls. During therapy, PTX-3 levels have been reduced statistically significant (p = 0,001) at six months and one year of treatment. After one year, of the twenty patients that completed the study, 55% were considered fully responders to treatment; in these patients the mean reduction of PTX-3 at one year was higher respect to not responders (-3,82 ± 1,24 ng/ml vs -2,32 ± 1,03 ng/ml p = 0,02) and we observed a higher reduction of lactate, tyrosine and hypoxanthine and an increase of hydroxyproline and ADP as well as of three oxidative phosphorylation markers, citrulline, ornithine and tryptophan approaching the metabolic profile of healthy subjects.

DISCUSSION AND CONCLUSIONS

We demonstrated a metabolomic imbalance with mitochondrial dysfunction detected by higher levels of lactate and lower levels of tryptophan, tyrosine and valine in MS patients compared to healthy controls. The reduction of PTX-3 levels and the restoring of mitochondrial function, reducing oxidative stress by GA, allows to identify responder patients. Further and larger studies are needed to understand the predictive role of PTX-3 and metabolomic pattern in the identification of responder patients to GA.

Affective Immunology: The Crosstalk Between Microglia and Astrocytes Plays Key Role?

Emerging evidence demonstrates the critical role of the immune response in the mechanisms relating to mood disorders, such as major depression (MDD) and bipolar disorder (BD). This has cast a spotlight on a specialized branch committed to the research of dynamics of the fine interaction between emotion (or affection) and immune response, which has been termed as “affective immunology.” Inflammatory cytokines and gut microbiota are actively involved in affective immunology. Furthermore, abnormalities of the astrocytes and microglia have been observed in mood disorders from both postmortem and molecular imaging studies; however, the underlying mechanisms remain elusive. Notably, the crosstalk between astrocyte and microglia acts as a mutual and pivotal intermediary factor modulating the immune response posed by inflammatory cytokines and gut microbiota. In this study, we propose the “altered astrocyte-microglia crosstalk (AAMC)” hypothesis which suggests that the astrocyte-microglia crosstalk regulates emotional alteration through mediating immune response, and thus, contributing to the development of mood disorders.

Microglia: Agents of the CNS Pro-Inflammatory Response

The pro-inflammatory immune response driven by microglia is a key contributor to the pathogenesis of several neurodegenerative diseases. Though the research of microglia spans over a century, the last two decades have increased our understanding exponentially. Here, we discuss the phenotypic transformation from homeostatic microglia towards reactive microglia, initiated by specific ligand binding to pattern recognition receptors including toll-like receptor-4 (TLR4) or triggering receptors expressed on myeloid cells-2 (TREM2), as well as pro-inflammatory signaling pathways triggered such as the caspase-mediated immune response. Additionally, new research disciplines such as epigenetics and immunometabolism have provided us with a more holistic view of how changes in DNA methylation, microRNAs, and the metabolome may influence the pro-inflammatory response. This review aimed to discuss our current knowledge of pro-inflammatory microglia from different angles, including recent research highlights such as the role of exosomes in spreading neuroinflammation and emerging techniques in microglia research including positron emission tomography (PET) scanning and the use of human microglia generated from induced pluripotent stem cells (iPSCs). Finally, we also discuss current thoughts on the impact of pro-inflammatory microglia in neurodegenerative diseases.

Proteomic examination of the neuroglial secretome: lessons for the clinic

Introduction: Glial cells are closely associated with neurons located throughout the nervous system and regulate neuronal activity and function through various mechanisms including the secretion of proteins and other signaling molecules. Glia-secreted proteins play crucial roles in modulating neuronal function in physiological and pathological conditions. Aberrant activation of glial cells leading to neuroinflammation is a common phenomenon observed in various neurological disorders. Aberrantly activated glial cells secrete proteins in disease-specific manner and can be exploited as a repository for novel biomarker discovery.Areas covered: In this review, we describe the recent advances in proteomic techniques, highlighting the need for their application to the secretomic field. Studies regarding the secretome profile of glial cells published within the last 5 years are discussed in detail. The use of glia-based biomarkers in various neuroinflammatory and neurodegenerative diseases is also discussed.Expert opinion: Precise diagnosis and timely treatment of neurological disorders remains a challenge and glia-focused research to identify specific biomarkers appears to be a promising approach to combat these disorders. Recent technological advancement in proteomic research would open new frontiers for more rigorous analysis of glial secretome variations over time and the discovery/development of novel biomarkers for neurological disorders.

The Role of Pentraxin 3 in Aspergillosis: Reality and Prospects

Pentraxin 3 (PTX3) is a soluble pattern recognition receptor (PRR), which is produced by several kinds of cells, such as neutrophils, dendritic cells, macrophages, and epithelial cells. PTX3 is known to play an important protective effect against Aspergillus. Genetic linkage in gene-targeted mice and human PTX3 plays a non-redundant role in the immune protection against specific pathogens, especially Aspergillus. Recent studies have shown that the polymorphism of PTX3 is associated with increased susceptibility to invasive aspergillosis (IA). In this review, we provide an overview of these studies that underline the potential of PTX3 in diagnosis and therapy of IA.

Characterization of Mesenchymal Stem Cells Derived from Patients with Cerebellar Ataxia: Downregulation of the Anti-Inflammatory Secretome Profile

Mesenchymal stem cell (MSC) therapy is a promising alternative approach for the treatment of neurodegenerative diseases, according to its neuroprotective and immunomodulatory potential. Despite numerous clinical trials involving autologous MSCs, their outcomes have often been unsuccessful. Several reports have indicated that MSCs from patients have low capacities in terms of the secretion of neurotrophic or anti-inflammatory factors, which might be associated with cell senescence or disease severity. Therefore, a new strategy to improve their capacities is required for optimal efficacy of autologous MSC therapy. In this study, we compared the secretory potential of MSCs among cerebellar ataxia patients (CA-MSCs) and healthy individuals (H-MSCs). Our results, including secretome analysis findings, revealed that CA-MSCs have lower capacities in terms of proliferation, oxidative stress response, motility, and immunomodulatory functions when compared with H-MSCs. The functional differences were validated in a scratch wound healing assay and neuron-glia co-cultures. In addition, the neuroprotective and immunoregulatory protein follistatin-like 1 (FSTL1) was identified as one of the downregulated proteins in the CA-MSC secretome, with suppressive effects on proinflammatory microglial activation. Our study findings suggest that targeting aspects of the downregulated anti-inflammatory secretome, such as FSTL1, might improve the efficacy of autologous MSC therapy for CA.

Pentraxin 3 contributes to neurogenesis after traumatic brain injury in mice

Emerging evidence indicates that pentraxin 3 is an acute-phase protein that is linked with the immune response to inflammation. It is also a newly discovered marker of anti-inflammatory A2 reactive astrocytes, and potentially has multiple protective effects in stroke; however, its role in the adult brain after traumatic brain injury is unknown. In the present study, a moderate model of traumatic brain injury in mice was established using controlled cortical impact. The models were intraventricularly injected with recombinant pentraxin 3 (the recombinant pentraxin 3 group) or an equal volume of vehicle (the control group). The sham-operated mice underwent craniotomy, but did not undergo the controlled cortical impact. The potential neuroprotective and neuroregenerative roles of pentraxin 3 were investigated on days 14 and 21 after traumatic brain injury. Western blot assay showed that the expression of endogenous pentraxin 3 was increased after traumatic brain injury in mice. Furthermore, the neurological severity test and wire grip test revealed that recombinant pentraxin 3 treatment reduced the neurological severity score and increased the wire grip score, suggesting an improved recovery of sensory-motor functions. The Morris water maze results demonstrated that recombinant pentraxin 3 treatment reduced the latency to the platform, increased the time spent in the correct quadrant, and increased the number of times traveled across the platform, thus suggesting an improved recovery of cognitive function. In addition, to investigate the effects of pentraxin 3 on astrocytes, specific markers of A2 astrocytes were detected in primary astrocyte cultures in vitro using western blot assay. The results demonstrated that pentraxin 3 administration activates A2 astrocytes. To explore the protective mechanisms of pentraxin 3, immunofluorescence staining was used. Intraventricular injection of recombinant pentraxin 3 increased neuronal maintenance in the peri-injured cortex and ipsilateral hippocampus, increased the number of doublecortin-positive neural progenitor cells in the subventricular and subgranular zones, and increased the number of bromodeoxyuridine (proliferation) and neuronal nuclear antigen (mature neuron) double-labeled cells in the hippocampus and peri-injured cortex. Pentraxin 3 administration also increased the number of neurospheres and the number of bromodeoxyuridine and doublecortin double-labeled cells in neurospheres, and enhanced the proliferation of neural progenitor cells in primary neural progenitor cell cultures in vitro. In conclusion, recombinant pentraxin 3 administration activated A2 astrocytes, and consequently improved the recovery of neural function by increasing neuronal survival and enhancing neurogenesis. All experiments were approved by the Animal Ethics Committee of the First Affiliated Hospital of Chongqing Medical University, China on March 1, 2016.

Role of the Immune System in the Development of the Central Nervous System

The central nervous system (CNS) and the immune system are both intricate and highly organized systems that regulate the entire body, with both sharing certain common features in developmental mechanisms and operational modes. It is known that innate immunity-related molecules, such as cytokines, toll-like receptors, the complement family, and acquired immunity-related molecules, such as the major histocompatibility complex and antibody receptors, are also expressed in the brain and play important roles in brain development. Moreover, although the brain has previously been regarded as an immune-privileged site, it is known to contain lymphatic vessels. Not only microglia but also lymphocytes regulate cognition and play a vital role in the formation of neuronal circuits. This review provides an overview of the function of immune cells and immune molecules in the CNS, with particular emphasis on their effect on neural developmental processes.

Tissue Dependent Role of PTX3 During Ischemia-Reperfusion Injury

Reperfusion of an ischemic tissue is the treatment of choice for several diseases, including myocardial infarction and stroke. However, reperfusion of an ischemic tissue causes injury, known as Ischemia and Reperfusion Injury (IRI), that limits the benefit of blood flow restoration. IRI also occurs during solid organ transplantation. During IRI, there is activation of the innate immune system, especially neutrophils, which contributes to the degree of injury. It has been shown that PTX3 can regulate multiple aspects of innate immunity and tissue inflammation during sterile injury, as observed during IRI. In humans, levels of PTX3 increase in blood and elevated levels associate with extent of IRI. In mice, there is also enhanced expression of PTX3 in tissues and plasma after IRI. In general, absence of PTX3, as seen in PTX3-deficient mice, results in worse outcome after IRI. On the contrary, increased expression of PTX3, as seen in PTX3 transgenic mice and after PTX3 administration, is associated with better outcome after IRI. The exception is the gut where PTX3 seems to have a clear deleterious role. Here, we discuss mechanisms by which PTX3 contributes to IRI and the potential of taming this system for the treatment of injuries associated with reperfusion of solid organs.

PTX3, a Humoral Pattern Recognition Molecule, in Innate Immunity, Tissue Repair, and Cancer

Innate immunity includes a cellular and a humoral arm. PTX3 is a fluid-phase pattern recognition molecule conserved in evolution which acts as a key component of humoral innate immunity in infections of fungal, bacterial, and viral origin. PTX3 binds conserved microbial structures and self-components under conditions of inflammation and activates effector functions (complement, phagocytosis). Moreover, it has a complex regulatory role in inflammation, such as ischemia/reperfusion injury and cancer-related inflammation, as well as in extracellular matrix organization and remodeling, with profound implications in physiology and pathology. Finally, PTX3 acts as an extrinsic oncosuppressor gene by taming tumor-promoting inflammation in murine and selected human tumors. Thus evidence suggests that PTX3 is a key homeostatic component at the crossroad of innate immunity, inflammation, tissue repair, and cancer. Dissecting the complexity of PTX3 pathophysiology and human genetics paves the way to diagnostic and therapeutic exploitation.

Microglia-Astrocyte Crosstalk: An Intimate Molecular Conversation

Microglia-astrocyte crosstalk has recently been at the forefront of glial research. Emerging evidence illustrates that microglia- and astrocyte-derived signals are the functional determinants for the fates of astrocytes and microglia, respectively. By releasing diverse signaling molecules, both microglia and astrocytes establish autocrine feedback and their bidirectional conversation for a tight reciprocal modulation during central nervous system (CNS) insult or injury. Microglia, the constant sensors of changes in the CNS microenvironment and restorers of tissue homeostasis, not only serve as the primary immune cells of the CNS but also regulate the innate immune functions of astrocytes. Similarly, microglia determine the functions of reactive astrocytes, ranging from neuroprotective to neurotoxic. Conversely, astrocytes through their secreted molecules regulate microglial phenotypes and functions ranging from motility to phagocytosis. Altogether, the microglia-astrocyte crosstalk is fundamental to neuronal functions and dysfunctions. This review discusses the current understanding of the intimate molecular conversation between microglia and astrocytes and outlines its potential implications in CNS health and disease.

Deconvolution of Human Brain Cell Type Transcriptomes Unraveled Microglia-Specific Potential Biomarkers

Microglial cells form a context-dependent network of brain immunoeffector cells. Despite their indispensable roles, unresolved questions exist around biomarker discovery relevant to their cellular localization, self-renewing potential, and brain developmental dynamics. To resolve the existent gap in the annotation of candidate biomarkers, we conducted a meta-analysis of brain cells using available high-throughput data sets for deciphering microglia-specific expression profiles. We have identified 3,290 significant genes specific to microglia and further selected the top 20 dysregulated genes on the basis of p-value and log₂FC. To this list, we added 7 known microglia-specific markers making the candidate list comprising 27 genes for further downstream analyses. Next, we established a connectome of these potential markers with their putative protein partners, which demonstrated strong associations of upregulated genes like Dedicator of cytokinesis 2 (DOCK2) with early/mature microglial markers such as Sphingosine kinase 1 (SPHK1), CD68, and CD45. To elucidate their respective brain anatomical location, we deconvoluted the BrainSpan Atlas expression data. This analysis showed high expression of the majority of candidate genes in microglia-dense regions (Amygdala, Hippocampus, Striatum) in the postnatal brain. Furthermore, to decipher their localized expression across brain ages, we constructed a developmental dynamics map (DDM) comprising extensive gene expression profiles throughout prenatal to postnatal stages, which resulted in the discovery of novel microglia-specific gene signatures. One of the interesting readout from DDM is that all the microglia-dense regions exhibit dynamic regulation of few genes at 37 post conception week (pcw), the transition period between pre- and postnatal stages. To validate these findings and correlate them as potential biomarkers, we analyzed the expression of corresponding proteins in hESC-derived human microglia precursors. The cultured microglial precursors showed expression of Pentraxin 3 (PTX3) and SPHK1 as well as several known markers like CD68, Allograft inflammatory factor 1 (AIF1/IBA1). In summary, this study has furnished critical insights into microglia dynamics across human brain ages and cataloged potential transcriptomic fingerprints that can be further exploited for designing novel neurotherapeutics.

Cell adhesion and matricellular support by astrocytes of the tripartite synapse

Astrocytes contribute to the formation, function, and plasticity of synapses. Their processes enwrap the neuronal components of the tripartite synapse, and due to this close interaction they are perfectly positioned to modulate neuronal communication. The interaction between astrocytes and synapses is facilitated by cell adhesion molecules and matricellular proteins, which have been implicated in the formation and functioning of tripartite synapses. The importance of such neuron-astrocyte integration at the synapse is underscored by the emerging role of astrocyte dysfunction in synaptic pathologies such as autism and schizophrenia. Here we review astrocyte-expressed cell adhesion molecules and matricellular molecules that play a role in integration of neurons and astrocytes within the tripartite synapse.

Functional dissection of astrocyte-secreted proteins: Implications in brain health and diseases

Astrocytes, which are homeostatic cells of the central nervous system (CNS), display remarkable heterogeneity in their morphology and function. Besides their physical and metabolic support to neurons, astrocytes modulate the blood-brain barrier, regulate CNS synaptogenesis, guide axon pathfinding, maintain brain homeostasis, affect neuronal development and plasticity, and contribute to diverse neuropathologies via secreted proteins. The identification of astrocytic proteome and secretome profiles has provided new insights into the maintenance of neuronal health and survival, the pathogenesis of brain injury, and neurodegeneration. Recent advances in proteomics research have provided an excellent catalog of astrocyte-secreted proteins. This review categorizes astrocyte-secreted proteins and discusses evidence that astrocytes play a crucial role in neuronal activity and brain function. An in-depth understanding of astrocyte-secreted proteins and their pathways is pivotal for the development of novel strategies for restoring brain homeostasis, limiting brain injury/inflammation, counteracting neurodegeneration, and obtaining functional recovery.

Update on the role of Pentraxin 3 in atherosclerosis and cardiovascular diseases

Pentraxin 3 (PTX3) is an acute-phase protein that was recently demonstrated to play pleiotropic activities in cardiovascular (CV) diseases. Tumor necrosis factor and interleukins up-regulates PTX3 transcription in different cell types (i.e. endothelial cells, phagocytes, smooth muscle cells, fibroblasts and glial cells) involved in atherogenesis. By interacting with numerous ligands, PTX3 acts as a modulatory molecule of complement system, inflammatory response, angiogenesis, and vascular/tissue remodeling. Experimental data point to a beneficial role of PTX3 in atherosclerotic plaque development and vulnerability. Animal studies indicated a protective role of PTX3 signaling in ischemic/reperfusion injury and failing heart. Clinical studies have so far provided contrasting results, highlighting a debated role of PTX3 as an active mediator of endothelial dysfunction, atherosclerotic plaque vulnerability and worse outcome after ischemic events. Therefore, substantial evidence suggests a dual role of PTX3 as modulator or amplifiers of the innate immune response. The final result of PTX3 activation might be determined by a fine tuning of time, space and environmental signals. The aim of this review is to provide an overview of biological properties of PTX3 in CV diseases and to discuss the ability of PTX3 to act as a crossroad between pro- and anti-inflammatory pathways.

Particulate matter-mediated release of long pentraxin 3 (PTX3) and vascular endothelial growth factor (VEGF) in vitro: Limited importance of endotoxin and organic content

Exposure to particulate matter (PM) is associated with adverse health effects, but it is still relatively unknown which role PM sources and physicochemical properties play in the observed effects. It was postulated that PM in vitro induces release of long pentraxin 3 (PTX3) and vascular endothelial growth factor (VEGF) and that endotoxin and organic compounds present in the PM regulate this release. A contact coculture of THP-1 human leukemia monocytes and A549 human adenocarcinoma alveolar pneumocytes was exposed to PM from Traffic, Wood, Diesel, and Quartz (10-40 µg/cm²) for 12-64 h to determine release of PTX3 and VEGF. The role of endotoxin and the organic fraction in the mediator release was assessed using polymyxin B sulfate and organic extracts, respectively. Finally, antagonists were used to investigate whether the early proinflammatory cytokines interleukin (IL)-1 and tumor necrosis factor (TNF)-α affected the PTX3 and VEGF release. All PM samples induced a time-dependent release of both PTX3 and VEGF. Traffic mediated the greatest release of PTX3, whereas Wood and Diesel were more potent inducers of VEGF. The endotoxin content did not markedly affect release of either mediator, while the organic fraction exerted no significant effect on VEGF release and limited influence on PTX3 release. In addition, the IL-1 and TNF-α agonists affected PTX3 release more strongly than VEGF release. In conclusion, the current data show a limited impact of endotoxin and organic compounds on PTX3 and VEGF release. Further, the observed differences in response patterns may point toward differential regulation of PM-mediated release of PTX3 and VEGF.

Circulating Inflammatory Mediators as Potential Prognostic Markers of Human Colorectal Cancer

Background

Cytokines and chemokines in the tumor microenvironment drive metastatic development and their serum levels might mirror the ongoing inflammatory reaction at the tumor site. Novel highly sensitive tools are needed to identify colorectal cancer patients at high risk of recurrence that should be more closely monitored during post-surgical follow up. Here we study whether circulating inflammatory markers might be used to predict recurrence in CRC patients.

Methods

Circulating levels of the inflammatory cytokines IL-1, IL-6, IL-10, TNFalpha, CCL2, CXCL8, VEGF and the acute phase protein Pentraxin-3 were measured by ELISA in preoperative serum samples prospectively collected from a cohort of sixty-nine patients undergoing surgical resection for stage 0–IV CRC and associated with post-operative disease recurrence.

Results

Cox multivariate analysis showed that combined high levels (≥ROC cut off-value) of CXCL8, VEGF and Pentraxin3 were associated with increased risk of disease recurrence [HR: 14.28; 95%CI: (3.13–65.1)] independently of TNM staging. Kaplan-Meier analysis showed that CXCL8, VEGF and Pentraxin3 levels were significantly associated with worse survival (P<0.001).

Conclusions

Circulating inflammatory mediators efficiently predicted postoperative recurrence after CRC surgery. Therefore, this study suggest that their validation in large-scale clinical trials may help in tailoring CRC post-surgical management.

Emerging roles of the acute phase protein pentraxin-3 during central nervous system disorders

Pentraxin-3 (PTX3) is an acute phase protein (APP) and a member of the long pentraxin family that is recognised for its role in peripheral immunity and vascular inflammation in response to injury, infection and diseases such as atherosclerosis, cancer and respiratory disease. Systemic levels of PTX3 are highly elevated in these conditions, and PTX3 is now recognised as a new biomarker of disease risk and progression. There is extensive evidence demonstrating that central nervous system (CNS) disorders are primarily characterised by central activation of innate immunity, as well as activation of a potent peripheral acute phase response (APR) that influences central inflammation and contributes to poor outcome. PTX3 has been recently recognised to play important roles in CNS disorders, having both detrimental and neuroprotective effects. The present review aims to give an up-to-date account of the emerging roles of PTX3 in CNS disorders, and to provide a critical comparison between peripheral and central actions of PTX3 in inflammatory diseases.

Pentraxin-3 is upregulated in the central nervous system during MS and EAE, but does not modulate experimental neurological disease

Pentraxin-3 (PTX3), an acute-phase protein released during inflammation, aids phagocytic clearance of pathogens and apoptotic cells, and plays diverse immunoregulatory roles in tissue injury. In neuroinflammatory diseases, like MS, resident microglia could become activated by endogenous agonists for Toll like receptors (TLRs). Previously we showed a strong TLR2-mediated induction of PTX3 in cultured human microglia and macrophages by HspB5, which accumulates in glia during MS. Given the anti-inflammatory effects of HspB5, we examined the contribution of PTX3 to these effects in MS and its animal model EAE. Our data indicate that TLR engagement effectively induces PTX3 expression in human microglia, and that such expression is readily detectable in MS lesions. Enhanced PTX3 expression is prominently expressed in microglia in preactive MS lesions, and in microglia/macrophages engaged in myelin phagocytosis in actively demyelinating lesions. Yet, we did not detect PTX3 in cerebrospinal fluid of MS patients. PTX3 expression is also elevated in spinal cords during chronic relapsing EAE in Biozzi ABH mice, but the EAE severity and time course in PTX3-deficient mice did not differ from WT mice. Moreover, systemic PTX3 administration did not alter the disease onset or severity. Our findings reveal local functions of PTX3 during neuroinflammation in facilitating myelin phagocytosis, but do not point to a role for PTX3 in controlling the development of autoimmune neuroinflammation.

In-depth characterization of the secretome of mouse CNS cell lines by LC-MS/MS without prefractionation

Microglia, astrocytes, and neurons, which have important functions in the central nervous system (CNS), communicate mutually to generate a signal through secreted proteins or small molecules, but many of which have not been identified. Because establishing a reference for the secreted proteins from CNS cells could be invaluable in examining cell-to-cell communication in the brain, we analyzed the secretome of three murine CNS cell lines without prefractionation by high-resolution mass spectrometry. In this study, 2795 proteins were identified from conditioned media of the three cell lines, and 2125 proteins were annotated as secreted proteins by bioinformatics analysis. Further, approximately 500 secreted proteins were quantifiable as differentially expressed proteins by label-free quantitation. As a result, our secretome references are useful datasets for the future study of neuronal diseases. All MS data have been deposited in the ProteomeXchange with identifier PXD001597 (http://proteomecentral.proteomexchange.org/dataset/PXD001597).

Involvement of Immune Responses in the Efficacy of Cord Blood Cell Therapy for Cerebral Palsy

This study evaluated the efficacy of umbilical cord blood (UCB) cell for patients with cerebral palsy (CP) in a randomized, placebo-controlled, double-blind trial and also assessed factors and mechanisms related to the efficacy. Thirty-six children (ages 6 months to 20 years old) with CP were enrolled and treated with UCB or a placebo. Muscle strength and gross motor function were evaluated at baseline and 1, 3, and 6 months after treatment. Along with function measurements, each subject underwent (18)F-fluorodeoxyglucose positron emission tomography at baseline and 2 weeks after treatment. Cytokine and receptor levels were quantitated in serial blood samples. The UCB group showed greater improvements in muscle strength than the controls at 1 (0.94 vs. -0.35, respectively) and 3 months (2.71 vs. 0.65) after treatment (Ps<0.05). The UCB group also showed greater improvements in gross motor performance than the control group at 6 months (8.54 vs. 2.60) after treatment (P<0.01). Additionally, positron emission tomography scans revealed decreased periventricular inflammation in patients administered UCB, compared with those treated with a placebo. Correlating with enhanced gross motor function, elevations in plasma pentraxin 3 and interleukin-8 levels were observed for up to 12 days after treatment in the UCB group. Meanwhile, increases in blood cells expressing Toll-like receptor 4 were noted at 1 day after treatment in the UCB group, and they were correlated with increased muscle strength at 3 months post-treatment. In this trial, treatment with UCB alone improved motor outcomes and induced systemic immune reactions and anti-inflammatory changes in the brain. Generally, motor outcomes were positively correlated with the number of UCB cells administered: a higher number of cells resulted in better outcomes. Nevertheless, future trials are needed to confirm the long-term efficacy of UCB therapy, as the follow-up duration of the present trial was short.

Characterization of the membrane proteome and N-glycoproteome in BV-2 mouse microglia by liquid chromatography-tandem mass spectrometry

BACKGROUND

Microglial cells are resident macrophages of the central nervous system and important cellular mediators of the immune response and neuroinflammatory processes. In particular, microglial activation and communication between microglia, astrocytes, and neurons are hallmarks of the pathogenesis of several neurodegenerative diseases. Membrane proteins and their N-linked glycosylation mediate this microglial activation and regulate many biological process including signal transduction, cell-cell communication, and the immune response. Although membrane proteins and N-glycosylation represent a valuable source of drug target and biomarker discovery, the knowledge of their expressed proteome in microglia is very limited.

RESULTS

To generate a large-scale repository, we constructed a membrane proteome and N-glycoproteome from BV-2 mouse microglia using a novel integrated approach, comprising of crude membrane fractionation, multienzyme-digestion FASP, N-glyco-FASP, and various mass spectrometry. We identified 6928 proteins including 2850 membrane proteins and 1450 distinct N-glycosylation sites on 760 N-glycoproteins, of which 556 were considered novel N-glycosylation sites. Especially, a total of 114 CD antigens are identified via MS-based analysis in normal conditions of microglia for the first time. Our bioinformatics analysis provides a rich proteomic resource for examining microglial function in, for example, cell-to-cell communication and immune responses.

CONCLUSIONS

Herein, we introduce a novel integrated proteomic approach for improved identification of membrane protein and N-glycosylation sites. To our knowledge, this workflow helped us to obtain the first and the largest membrane proteomic and N-glycoproteomic datesets for mouse microglia. Collectively, our proteomics and bioinformatics analysis significantly expands the knowledge of the membrane proteome and N-glycoproteome expressed in microglia within the brain and constitutes a foundation for ongoing proteomic studies and drug development for various neurological diseases.

Proteome of brain glia: the molecular basis of diverse glial phenotypes

Several different types of nonneuronal glial cells with diverse phenotypes are present in the CNS, and all have distinct indispensible functions. Although glial cells primarily provide neurons with metabolic and structural support in the healthy brain, they may switch phenotype from a "resting" to a "reactive" state in response to pathological insults. Furthermore, this reactive gliosis is an invariant feature of the pathogeneses of CNS maladies. The glial proteome serves as a signature of glial phenotype, and not only executes physiological functions, but also acts as a molecular mediator of the reactive glial phenotype. The glial proteome is also involved in intra- and intercellular communications as exemplified by glia-glia and neuron-glia interactions. The utilization of authoritative proteomic tools and the bioinformatic analyses have helped to profile the brain glial proteome and explore the molecular mechanisms of diverse glial phenotypes. Furthermore, technologic innovations have equipped the field of "glioproteomics" with refined tools for studies of the expression, interaction, and function of glial proteins in the healthy and in the diseased CNS. Glioproteomics is expected to contribute to the elucidation of the molecular mechanisms of CNS pathophysiology and to the discovery of biomarkers and theragnostic targets in CNS disorders.