CNS inflammation and neurodegeneration

Autophagy and Immune-Related Diseases

Autophagy is an intracellular degradation and recycling machinery by which cellular materials are delivered to the lysosome for disposal. Beyond lysosomal degradation, autophagy genes play additional roles in secretion and membrane-trafficking pathways. Ranging from cell-intrinsic and cell-type-specific regulation of innate inflammatory signaling pathways to intercellular cross talk through secretion of soluble factors (e.g., shaping the MHC immunopeptidome for T cell response, etc.), autophagy exerts multiple functions in driving inflammation and modulating the pathological progression of immune-related disorders such as neurodegenerative diseases, inflammatory bowel diseases, autoimmunity, and metabolic diseases. Notably, owing to the complexity of autophagy process involving multiple proteins and stepwise assembly of protein complexes, noncanonical forms of autophagy or autophagic proteins, which function beyond autophagy, are equally important in the maintenance of cellular homeostasis and pathogenesis. This chapter summarizes the most up-to-date findings of autophagy proteins in the regulation of immune-related diseases. Understanding of the autophagy machinery offers therapeutic strategies for treating inflammatory diseases.

Emerging Immunotherapies for Parkinson Disease

Symptomatic treatment options for Parkinson disease have steadily improved, and individualized therapeutic approaches are becoming established for every stage of the disease. However, disease-modifying therapy with a causal approach is still unavailable. The central causative role of alpha-synuclein pathology, including its progressive spread to most areas of the CNS, has been widely recognized, and a strong involvement of immune responses has recently been discovered. New immunologic technologies have been shown to effectively prevent the progression of alpha-synuclein pathology in animal models. These approaches have recently been translated into the first human clinical trials, representing a novel starting point for the causal therapy of Parkinson disease. In this review, the pathomechanistic role of alpha-synuclein and its influence on the surrounding cellular environment are analyzed with a strong focus on immune responses and neuroinflammation. The potential of novel immunotherapeutic approaches that reduce the burden of alpha-synuclein pathology in the CNS is critically evaluated, and currently ongoing human clinical trials are presented. The clinical development of these new immunotherapies is progressing rapidly and gives reason to hope that a causal therapy of Parkinson disease could be possible in the foreseeable future.

Mesenchymal Stem Cells (MSCs) Coculture Protects [Ca2+]i Orchestrated Oxidant Mediated Damage in Differentiated Neurons In Vitro

Cell-therapy modalities using mesenchymal stem (MSCs) in experimental strokes are being investigated due to the role of MSCs in neuroprotection and regeneration. It is necessary to know the sequence of events that occur during stress and how MSCs complement the rescue of neuronal cell death mediated by [Ca²⁺]_i and reactive oxygen species (ROS). In the current study, SH-SY5Y-differentiated neuronal cells were subjected to in vitro cerebral ischemia-like stress and were experimentally rescued from cell death using an MSCs/neuronal cell coculture model. Neuronal cell death was characterized by the induction of proinflammatory tumor necrosis factor (TNF)-α, interleukin (IL)-1β and -12, up to 35-fold with corresponding downregulation of anti-inflammatory cytokine transforming growth factor (TGF)-β, IL-6 and -10 by approximately 1 to 7 fold. Increased intracellular calcium [Ca²⁺]_i and ROS clearly reaffirmed oxidative stress-mediated apoptosis, while upregulation of nuclear factor NF-κB and cyclo-oxygenase (COX)-2 expressions, along with ~41% accumulation of early and late phase apoptotic cells, confirmed ischemic stress-mediated cell death. Stressed neuronal cells were rescued from death when cocultured with MSCs via increased expression of anti-inflammatory cytokines (TGF-β, 17%; IL-6, 4%; and IL-10, 13%), significantly downregulated NF-κB and proinflammatory COX-2 expression. Further accumulation of early and late apoptotic cells was diminished to 23%, while corresponding cell death decreased from 40% to 17%. Low superoxide dismutase 1 (SOD1) expression at the mRNA level was rescued by MSCs coculture, while no significant changes were observed with catalase (CAT) and glutathione peroxidase (GPx). Interestingly, increased serotonin release into the culture supernatant was proportionate to the elevated [Ca²⁺]_i and corresponding ROS, which were later rescued by the MSCs coculture to near normalcy. Taken together, all of these results primarily support MSCs-mediated modulation of stressed neuronal cell survival in vitro.

Microglial distribution, branching, and clearance activity in aged rat hippocampus are affected by astrocyte meshwork integrity: evidence of a novel cell-cell interglial interaction

Aging and neurodegenerative diseases share a condition of neuroinflammation entailing the production of endogenous cell debris in the CNS that must be removed by microglia ( i.e., resident macrophages), to restore tissue homeostasis. In this context, extension of microglial cell branches toward cell debris underlies the mechanisms of microglial migration and phagocytosis. Amoeboid morphology and the consequent loss of microglial branch functionality characterizes dysregulated microglia. Microglial migration is assisted by another glial population, the astroglia, which forms a dense meshwork of cytoplasmic projections. Amoeboid microglia and disrupted astrocyte meshwork are consistent traits in aged CNS. In this study, we assessed a possible correlation between microglia and astroglia morphology in rat models of chronic neuroinflammation and aging, by 3-dimensional confocal analysis implemented with particle analysis. Our findings suggest that a microglia-astroglia interaction occurs in rat hippocampus via cell-cell contacts, mediating microglial cell branching in the presence of inflammation. In aged rats, the impairment of such an interaction correlates with altered distribution, morphology, and inefficient clearance by microglia. These data support the idea that generally accepted functional boundaries between microglia and astrocytes should be re-evaluated to better understand how their functions overlap and interact.-Lana, D., Ugolini, F., Wenk, G. L., Giovannini, M. G., Zecchi-Orlandini, S., Nosi, D. Microglial distribution, branching, and clearance activity in aged rat hippocampus are affected by astrocyte meshwork integrity: evidence of a novel cell-cell interglial interaction.

Effect of exposure to low doses of ozone on interleukin 17A expression during progressive neurodegeneration in the rat hippocampus

INTRODUCTION

Chronic exposure to low doses of ozone causes oxidative stress and loss of regulation of the inflammatory response, leading to progressive neurodegeneration.

OBJECTIVE

We studied the effect of chronic exposure to low doses of ozone on IL-17A concentration and expression in neurons, microglia, astrocytes, and T cells in the rat hippocampus.

METHODS

We used 72 Wistar rats, divided into 6 groups (n=12): a control group (no ozone exposure) and 5 groups exposed to ozone (0.25ppm, 4h daily) for 7, 15, 30, 60, and 90 days. We processed 6 rats from each group to quantify IL-17A by ELISA; the remaining 6 were processed for immunohistochemistry (against IL-17A and GFAP, Iba1, NeuN, and CD3).

RESULTS

The ELISA study data showed a significant increase in IL-17A concentrations in the 7-, 15-, 30-, and 60-day exposure groups, with regard to the control group (P<.05). Furthermore, they indicate that hippocampal neurons were the cells showing greatest immunoreactivity against IL-17A between 60 and 90 days of exposure to ozone; we also observed an increase in activated astrocytes in the 30- and 60-day exposure groups.

CONCLUSION

Exposure to ozone in rats induces an increase in IL-17A expression, mainly in hippocampal neurons, accompanied by hippocampal astrocyte activation during chronic neurodegeneration, similar to that observed in Alzheimer disease in humans.

Fibrin-targeting immunotherapy protects against neuroinflammation and neurodegeneration

Activation of innate immunity and deposition of blood-derived fibrin in the central nervous system (CNS) occur in autoimmune and neurodegenerative diseases, including multiple sclerosis (MS) and Alzheimer's disease (AD). However, the mechanisms that link disruption of the blood-brain barrier (BBB) to neurodegeneration are poorly understood, and exploration of fibrin as a therapeutic target has been limited by its beneficial clotting functions. Here we report the generation of monoclonal antibody 5B8, targeted against the cryptic fibrin epitope γ377-395, to selectively inhibit fibrin-induced inflammation and oxidative stress without interfering with clotting. 5B8 suppressed fibrin-induced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation and the expression of proinflammatory genes. In animal models of MS and AD, 5B8 entered the CNS and bound to parenchymal fibrin, and its therapeutic administration reduced the activation of innate immunity and neurodegeneration. Thus, fibrin-targeting immunotherapy inhibited autoimmunity- and amyloid-driven neurotoxicity and might have clinical benefit without globally suppressing innate immunity or interfering with coagulation in diverse neurological diseases.

18F-PBR06 Versus 11C-PBR28 PET for Assessing White Matter Translocator Protein Binding in Multiple Sclerosis

BACKGROUND AND PURPOSE

F-PBR06 and C-PBR28 are second-generation PET radioligands targeting the 18-kd translocator protein to assess microglial activation. We directly compared F-PBR06 and C-PBR28 for detecting brain translocator protein binding in multiple sclerosis (MS).

METHODS

Six patients with MS (4 women; mean age ± SD, 32.1 ± 4.9 [range, 23.5-37.4 years]; Expanded Disability Status Scale score 2.3 ± 1.2 [range, 1.0-4.0]) underwent brain PET with both ligands, along with 3-T MRI. MRI was coregistered to the summed 60- to 90-minute PET images. SUV ratios (SUVRs), derived by normalization to global brain radioactivity, were obtained for whole-brain white matter (WM), supratentorial WM, normal-appearing WM (NAWM), and T2 (fluid-attenuated inversion recovery) hyperintense and T1 hypointense MS WM lesions. The highest mean SUVR for the fluid-attenuated inversion-recovery lesional slices was defined as SUVRmax.

RESULTS

F-PBR06 and C-PBR28 were moderately intercorrelated for whole-brain WM SUVR (r = 0.83, P = 0.04) and supratentorial WM SUVR (r = 0.81, P = 0.05) but not for SUVRs of NAWM, T1 lesions, T2 lesions, or SUVRmax. Both tracers demonstrated that SUVR was higher in NAWM than in T1 and T2 lesions (all P < 0.05). F-PBR06 (but not C-PBR28) demonstrated a higher SUVR in T1 versus T2 lesions (0.85 ± 0.07 vs 0.78 ± 0.03, P = 0.03). F-PBR06-derived (but not C-PBR28) SUVRmax correlated with both Expanded Disability Status Scale score (r = 0.82, P = 0.04) and timed 25-ft walking speed (r = 0.89, P = 0.01).

CONCLUSIONS

Our preliminary results suggest an association between microglial activation and physical disability in MS. Microglial detection in lesions was not interchangeable between the tracers, with a higher clinical relevance suggested for F-PBR06.

Emerging Roles of Sonic Hedgehog in Adult Neurological Diseases: Neurogenesis and Beyond

Sonic hedgehog (Shh), a member of the hedgehog (Hh) family, was originally recognized as a morphogen possessing critical characters for neural development during embryogenesis. Recently, however, Shh has emerged as an important modulator in adult neural tissues through different mechanisms such as neurogenesis, anti-oxidation, anti-inflammation, and autophagy. Therefore, Shh may potentially have clinical application in neurodegenerative diseases and brain injuries. In this article, we present some examples, including ours, to show different aspects of Shh signaling and how Shh agonists or mimetics are used to alter the neuronal fates in various disease models, both in vitro and in vivo. Other potential mechanisms that are discussed include alteration of mitochondrial function and anti-aging effect; both are critical for age-related neurodegenerative diseases. A thorough understanding of the protective mechanisms elicited by Shh may provide a rationale to design innovative therapeutic regimens for various neurodegenerative diseases.

In Vitro Model of Neuroinflammation: Efficacy of Cannabigerol, a Non-Psychoactive Cannabinoid

Inflammation and oxidative stress play main roles in neurodegeneration. Interestingly, different natural compounds may be able to exert neuroprotective actions against inflammation and oxidative stress, protecting from neuronal cell loss. Among these natural sources, Cannabis sativa represents a reservoir of compounds exerting beneficial properties, including cannabigerol (CBG), whose antioxidant properties have already been demonstrated in macrophages. Here, we aimed to evaluate the ability of CBG to protect NSC-34 motor neurons against the toxicity induced from the medium of LPS-stimulated RAW 264.7 macrophages. Using MTT assay, we observed that CBG pre-treatment was able to reduce the loss of cell viability induced by the medium of LPS-stimulated macrophages in NSC-34 cells. Indeed, CBG pre-treatment inhibited apoptosis, as shown by the reduction of caspase 3 activation and Bax expression, while Bcl-2 levels increased. Furthermore, CBG pre-treatment counteracted not only inflammation, as demonstrated by the reduction of IL-1β, TNF-α, IFN-γ and PPARγ protein levels assessed by immunocytochemistry, but also oxidative stress in NSC-34 cells treated with the medium of LPS-stimulated RAW 264.7. Indeed, immunocytochemistry showed that CBG pre-treatment reduced nitrotyrosine, SOD1 and iNOS protein levels and restored Nrf-2 levels. All together, these results indicated the neuroprotective effects of CBG, that may be a potential treatment against neuroinflammation and oxidative stress.

Intranasally Administered S100A9 Amyloids Induced Cellular Stress, Amyloid Seeding, and Behavioral Impairment in Aged Mice

Amyloid formation and neuroinflammation are major features of Alzheimer's disease pathology. Proinflammatory mediator S100A9 was shown to act as a link between the amyloid and neuroinflammatory cascades in Alzheimer's disease, leading together with Aβ to plaque formation, neuronal loss and memory impairment. In order to examine if S100A9 alone in its native and amyloid states can induce neuronal stress and memory impairment, we have administered S100A9 species intranasally to aged mice. Single and sequential immunohistochemistry and passive avoidance behavioral test were conducted to evaluate the consequences. Administered S100A9 species induced widespread cellular stress responses in cerebral structures, including frontal lobe, hippocampus and cerebellum. These were manifested by increased levels of S100A9, Bax, and to a lesser extent activated caspase-3 immunopositive cells. Upon administration of S100A9 fibrils, the amyloid oligomerization was observed in the brain tissues, which can further exacerbate cellular stress. The cellular stress responses correlated with significantly increased training and decreased retention latencies measured in the passive avoidance test for the S100A9 treated animal groups. Remarkably, the effect size in the behavioral tests was moderate already in the group treated with native S100A9, while the effect sizes were large in the groups administered S100A9 amyloid oligomers or fibrils. The findings demonstrate the brain susceptibility to neurotoxic damage of S100A9 species leading to behavioral and memory impairments. Intranasal administration of S100A9 species proved to be an effective method to study amyloid induced brain dysfunctions, and S100A9 itself may be postulated as a target to allay early stage neurodegenerative and neuroinflammatory processes.

Profiling of Canonical and Non-Traditional Cytokine Levels in Interferon-β-Treated Relapsing-Remitting-Multiple Sclerosis Patients

Background

Multiple sclerosis (MS) is a chronic, progressive autoimmune disease of the central nervous system in which inflammation plays a key role in the induction, development, and progression. Most of the MS patients present with relapsing–remitting (RR) form, characterized by flare-ups followed by periods of recovery. Many inflammatory and anti-inflammatory cytokines have been proposed as backers in MS pathogenesis, and the balance between these differing cytokines can regulate MS severity. Interferon (IFN)-β, a current disease-modifying therapy for MS, has demonstrated beneficial effects in reducing disease severity in MS patients. However, its immunoregulatory and anti-inflammatory actions in MS are not wholly understood. The aim of the study was to define, in clinically stable patients with RR-MS, the serum concentration of several cytokines, canonical or not, and their modulation by IFN-β therapy.

Methods

Relapsing–remitting-MS patients were enrolled and diagnosed according to revised Mc Donald Diagnostic Criteria. A set of cytokines [including non-canonical neurotransmitter acetylcholine (ACh) and adipokines] and B-cell differentiation molecules, as potential biomarkers, were evaluated in 30 non-treated RR-MS patients compared to 30 IFN-β-treated MS patients and 30 age, gender, and body mass index-matched healthy controls (HC).

Results

Naïve MS patients showed significantly higher levels of interleukin (IL)-1β, IL-12/IL-23p40, IL-18, high-mobility group box protein-1, and IL-18 binding protein (IL-18BP) than MS-treated patients (p < 0.001 for all) and HC (p < 0.01). IFN-β therapy has significantly downmodulated IL-1β, IL-12/IL-23p40, IL-18 to normal levels (p < 0.001), whereas it has decreased IL-18BP (p < 0.001). ACh was significantly higher in the IFN-β-treated than HC and non-treated MS patients (p < 0.001). No significant differences were observed either in adipokines concentration or in B-cell-associated molecules among the three study groups.

Conclusion

Although more experimental evidence are required, we speculate that the efficacy of treatment of MS with IFN-β is mediated, at least in part, by its ability to work on several levels to slow down the disease progression. Proposed actions include the modulation of IL-1–inflammasome axis and modulation of ACh, B-cell activating factor/a proliferation-inducing ligand system, and several adipokines.

Deletion of plasma Phospholipid Transfer Protein (PLTP) increases microglial phagocytosis and reduces cerebral amyloid-β deposition in the J20 mouse model of Alzheimer's disease

Plasma phospholipid transfer protein (PLTP) binds and transfers a number of amphipathic compounds, including phospholipids, cholesterol, diacylglycerides, tocopherols and lipopolysaccharides. PLTP functions are relevant for many pathophysiological alterations involved in neurodegenerative disorders (especially lipid metabolism, redox status, and immune reactions), and a significant increase in brain PLTP levels was observed in patients with Alzheimer's disease (AD) compared to controls. To date, it has not been reported whether PLTP can modulate the formation of amyloid plaques, i.e. one of the major histopathological hallmarks of AD.

We thus assessed the role of PLTP in the AD context by breeding PLTP-deficient mice with an established model of AD, the J20 mice. A phenotypic characterization of the amyloid pathology was conducted in J20 mice expressing or not PLTP. We showed that PLTP deletion is associated with a significant reduction of cerebral Aβ deposits and astrogliosis, which can be explained at least in part by a rise of Aβ clearance through an increase in the microglial phagocytic activity and the expression of the Aβ-degrading enzyme neprilysin.

PLTP arises as a negative determinant of plaque clearance and over the lifespan, elevated PLTP activity could lead to a higher Aβ load in the brain.

Excitotoxicity in the pathogenesis of neurological and psychiatric disorders: Therapeutic implications

Neurological and psychiatric disorders are leading contributors to the global disease burden, having a serious impact on the quality of life of both patients and their relatives. Although the molecular events underlying these heterogeneous diseases remain poorly understood, some studies have raised the idea of common mechanisms involved. In excitotoxicity, there is an excessive activation of glutamate receptors by excitatory amino acids, leading to neuronal damage. Thus, the excessive release of glutamate can lead to a dysregulation of Ca²⁺ homeostasis, triggering the production of free radicals and oxidative stress, mitochondrial dysfunction and eventually cell death. Although there is a consensus in considering excitotoxicity as a hallmark in most neurodegenerative diseases, increasing evidence points to the relevant role of this pathological mechanism in other illnesses affecting the central nervous system. Consequently, antagonists of glutamate receptors are used in current treatments or in clinical trials in both neurological and psychiatric disorders. However, drugs modulating other aspects of the excitotoxic mechanism could be more beneficial. This review discusses how excitotoxicity is involved in the pathogenesis of different neurological and psychiatric disorders and the promising strategies targeting the excitotoxic insult.

Disruption of ER-mitochondria signalling in fronto-temporal dementia and related amyotrophic lateral sclerosis

Fronto-temporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are two related and incurable neurodegenerative diseases. Features of these diseases include pathological protein inclusions in affected neurons with TAR DNA-binding protein 43 (TDP-43), dipeptide repeat proteins derived from the C9ORF72 gene, and fused in sarcoma (FUS) representing major constituent proteins in these inclusions. Mutations in C9ORF72 and the genes encoding TDP-43 and FUS cause familial forms of FTD/ALS which provides evidence to link the pathology and genetics of these diseases. A large number of seemingly disparate physiological functions are damaged in FTD/ALS. However, many of these damaged functions are regulated by signalling between the endoplasmic reticulum and mitochondria, and this has stimulated investigations into the role of endoplasmic reticulum-mitochondria signalling in FTD/ALS disease processes. Here, we review progress on this topic.

Nanoparticle-Based Strategies to Treat Neuro-Inflammation

Neuro-inflammation is a pivotal physio-pathological feature of brain disorders, including neurodegenerative diseases. As such, it is a relevant therapeutic target against which drugs have to be proposed. Targeting neuro-inflammation implies crossing the Blood-Brain Barrier (BBB) to reach the Central Nervous System (CNS). Engineered nanoparticles (ENPs) are promising candidates to carry and deliver drugs to the CNS by crossing the BBB. There are several strategies to design ENPs intended for crossing through the BBB. Herein, we first put nanotechnologies back in their historical context and introduce neuro-inflammation and its consequences in terms of public health. In a second part, we explain how ENPs can get access to the brain and review this area by highlighting recent papers in the field. Finally, after pointing out potential guidelines for preclinical studies involving ENPs, we conclude by opening the debate on the questions of nanosafety and toxicity of these ENPs and in particular on ecotoxicity related to regulatory issues and public concerns.

Three-Dimensional in Vitro Cell Culture Models in Drug Discovery and Drug Repositioning

Drug development is a lengthy and costly process that proceeds through several stages from target identification to lead discovery and optimization, preclinical validation and clinical trials culminating in approval for clinical use. An important step in this process is high-throughput screening (HTS) of small compound libraries for lead identification. Currently, the majority of cell-based HTS is being carried out on cultured cells propagated in two-dimensions (2D) on plastic surfaces optimized for tissue culture. At the same time, compelling evidence suggests that cells cultured in these non-physiological conditions are not representative of cells residing in the complex microenvironment of a tissue. This discrepancy is thought to be a significant contributor to the high failure rate in drug discovery, where only a low percentage of drugs investigated ever make it through the gamut of testing and approval to the market. Thus, three-dimensional (3D) cell culture technologies that more closely resemble in vivo cell environments are now being pursued with intensity as they are expected to accommodate better precision in drug discovery. Here we will review common approaches to 3D culture, discuss the significance of 3D cultures in drug resistance and drug repositioning and address some of the challenges of applying 3D cell cultures to high-throughput drug discovery.

Role of nuclear factor κB in multiple sclerosis and experimental autoimmune encephalomyelitis

The transcription factor nuclear factor κB (NF-κB) plays major roles in inflammatory diseases through regulation of inflammation and cell viability. Multiple sclerosis (MS) is a chronic inflammatory demyelinating and neurodegenerative disease of the central nervous system (CNS). It has been shown that NF-κB is activated in multiple cell types in the CNS of MS patients, including T cells, microglia/macrophages, astrocytes, oligodendrocytes, and neurons. Interestingly, data from animal model studies, particularly studies of experimental autoimmune encephalomyelitis, have suggested that NF-κB activation in these individual cell types has distinct effects on the development of MS. In this review, we will cover the current literature on NF-κB and the evidence for its role in the development of MS and its animal model experimental autoimmune encephalomyelitis.

Synucleinopathies in neurodegenerative diseases: Accomplices, an inside job and selective vulnerability

Pathogenesis of degenerative diseases is complex and multifaceted. The disease phenotypes depend on the location of injury/damage in the brain networks and pathologically are characterized by loss of brain cells. The reason for this loss appears to be an accumulation of misfolded and dysfunctional proteins that trigger apoptotic cell death. The role of alpha-synuclein mutations, its interaction with other proteins and the cellular environment is discussed in the context of selective neuron loss.