Influence of Peripheral inflammation on the progression of multiple sclerosis: Evidence from the clinic and experimental animal models

Macrophage polarization: an important role in inflammatory diseases

Macrophages are crucial cells in the human body's innate immunity and are engaged in a variety of non-inflammatory reactions. Macrophages can develop into two kinds when stimulated by distinct internal environments: pro-inflammatory M1-like macrophages and anti-inflammatory M2-type macrophages. During inflammation, the two kinds of macrophages are activated alternatively, and maintaining a reasonably steady ratio is critical for maintaining homeostasis in vivo. M1 macrophages can induce inflammation, but M2 macrophages suppress it. The imbalance between the two kinds of macrophages will have a significant impact on the illness process. As a result, there are an increasing number of research being conducted on relieving or curing illnesses by altering the amount of macrophages. This review summarizes the role of macrophage polarization in various inflammatory diseases, including autoimmune diseases (RA, EAE, MS, AIH, IBD, CD), allergic diseases (allergic rhinitis, allergic dermatitis, allergic asthma), atherosclerosis, obesity and type 2 diabetes, metabolic homeostasis, and the compounds or drugs that have been discovered or applied to the treatment of these diseases by targeting macrophage polarization.

Peripheral inflammation is a potential etiological factor in Alzheimer's disease

Peripheral inflammation could constitute a risk factor for AD. This review summarizes the research related to peripheral inflammation that appears to have a relationship with Alzheimer's disease. We find there are significant associations between AD and peripheral infection induced by various pathogens, including herpes simplex virus type 1, cytomegalovirus, Epstein-Barr virus, human immunodeficiency virus, severe acute respiratory syndrome coronavirus 2, Porphyromonas gingivalis, Helicobacter pylori, and Toxoplasma gondii. Chronic inflammatory diseases are also reported to contribute to the pathophysiology of AD. The mechanisms by which peripheral inflammation affects the pathophysiology of AD are complex. Pathogen-derived neurotoxic molecule composition, disrupted BBB, and dysfunctional neurogenesis may all play a role in peripheral inflammation, promoting the development of AD. Anti-pathogenic medications and anti-inflammatory treatments are reported to decrease the risk of AD. Studies that could improve understanding the associations between AD and peripheral inflammation are needed. If our assumption is correct, early intervention against inflammation may be a potential method of preventing and treating AD.

¿ Can COVID-19 exacerbate multiple sclerosis symptoms? A case series analysis

INTRODUCTION

Peripheral inflammation can exacerbate pre-existing lesions in the Central Nervous System (CNS) in the context of neurodegenerative diseases, including Multiple Sclerosis (MS).

OBJECTIVE

To analyze the clinical effect of COVID-19 infection, as a generator of peripheral inflammation, in a MS patients group.

METHODS

A retrospective analysis of 400 medical records of MS patients from a referral center was carried out. MS patients who presented COVID-19 were surveyed about symptoms exacerbation: type, duration and onset of exacerbation, previous vaccination against COVID-19 and MS severity. Clinical and demographic information from the medical records were included. Descriptive and inferential analysis were performed using the GraphPad Prism V6.

RESULTS

41 patients were included, 61% (n = 25) reported neurological worsening, 9.7% (n = 4) as relapses, and 7.3% (n = 3) required corticosteroids. We found significant differences in the EDSS between patients who exacerbated their MS symptoms and those who did not (p = 0.03). When performing a multivariate regression analysis, we found that EDSS was independently associated with the presence of exacerbations of MS in the context of SARS-CoV2 infection (OR = 2.44, p = 0.022).

CONCLUSIONS

This preliminary study suggests that COVID-19 infection could trigger exacerbations of MS symptoms. New studies are needed to elucidate the relationship between COVID-19 and MS.

Assessment of Cerebrovascular Dynamics and Cognitive Function with Acute Aerobic Exercise in Persons with Multiple Sclerosis

Background

Cognitive dysfunction in multiple sclerosis (MS) may partially stem from inadequate cerebral blood flow. Cerebral blood flow and cognitive function improve with aerobic exercise in healthy adults. The effect of aerobic exercise on cerebrovascular hemodynamics and cognitive performance in persons with MS is unclear. The acute effect of aerobic exercise versus quiet rest on cerebrovascular hemodynamics and cognitive performance in relapsing-remitting MS was examined.

Methods

Sixteen adults with relapsing-remitting MS underwent cerebrovascular hemodynamics and cognitive performance testing before, 2 minutes after, and 30 minutes after aerobic exercise (20-minute treadmill walking, 60% peak oxygen consumption) and a time-matched seated control. Brachial blood pressure was obtained via an oscillometric cuff. Right middle cerebral artery (MCA) blood velocity was measured via transcranial Doppler and used to calculate mean velocity, pulsatility index (PI), and conductance. Carotid artery stiffness was measured via ultrasonography and tonometry. Cognitive performance (accuracy, reaction time) was assessed using a modified flanker task.

Results

Exercise elicited significant increases in mean pressure and carotid artery stiffness and decreases in MCA conductance at 2 minutes after exercise, which subsided by 30 minutes (P < .05). Exercise did not significantly alter MCA PI. Flanker reaction time decreased during posttesting in both conditions (P < .05). There were no condition × time interactions for cognitive performance.

Conclusions

Persons with MS seem resilient to exercise-induced acute changes in MCA PI despite transient carotid stiffening, potentially via reductions in MCA conductance. These data suggest that changes in cognitive performance after acute aerobic exercise are not directly related to transient cerebrovascular responses in persons with MS.

Temporal lobe epilepsy: Evaluation of central and systemic immune-inflammatory features associated with drug resistance

Neuroinflammation is probably one of the factors involved in drug resistance in people with epilepsy. Finding peripheral markers reflecting the intensity of neuroinflammation could be of great help to decide for which patients anti-inflammatory treatment might be an option. In this context, peripheral cytokines levels and lymphocyte phenotypes were assessed by ELISA and flow cytometry in 3 groups of subjects: drug resistant patients with temporal lobe epilepsy (DR-TLE), non DR-TLE patients and healthy controls. The same parameters were assessed in brain tissue in the DR-TLE group. Differences in the peripheral immune-inflammatory status between the 3 groups of subjects, and correlations between the central and peripheral immune-inflammatory status in DR-TLE patients were evaluated. Forty-one patients with DR-TLE, ten with non-DR-TLE and twenty controls were included. In the periphery, decrease in regulatory cells were observed in DR-TLE patients compared to controls. In addition, significant increase of IL-6 and IL-5 was observed in patients with epilepsy (particularly DR-TLE patients). Two groups of DR-TLE patients with significant differences in several central inflammatory parameters were identified in a cluster analysis. The inflammatory cluster was associated with a peripheral increase of CD4+CD38+ cells and different significant correlations between central and systemic inflammatory parameters were observed. Although their interpretation is not immediate, they demonstrate a clear dialogue between central and peripheral inflammatory reactions. In conclusion, our results add new elements to better understand the interactions between the central and peripheral compartments in patients with DR-TLE, and to help better define treatment options in this group of patients.

Effect of Cannabinoid 2 Receptor Modulation on the Peripheral Immune Response in Central Nervous System Injury-Induced Immunodeficiency Syndrome

Introduction: Acute central nervous system (CNS) injury, such as stroke, spinal cord injury, or traumatic brain injury can result in dysregulated immune response, and the condition is known as CNS injury-induced immunodeficiency syndrome (CIDS). The endocannabinoid system is an important homeostatic regulator in the CNS and immune system. Activation of cannabinoid 2 receptors (CB2R) on immune cells has been reported to dampen inflammation, suggesting a potential role of CB2R in the peripheral immune response following CNS injury. In this study, we have investigated the effect of CB2R modulation on the peripheral immune response during CIDS. Materials and Methods: Experimental CNS injury was induced in C57BL/6 mice through intracerebral injection of the vasopressor peptide, endothelin-1. A selective CB2R agonist (HU308) was used as an early treatment before the onset of CIDS and AM630, a selective CB2R antagonist, was administered as a later-phase therapy to combat the systemic immunodeficiency following the CNS injury. The peripheral immune response to endotoxin was studied 24 h after the CNS injury using intravital microscopy to examine leukocyte activation within the intestinal microcirculation in mice. Brain infarct size, and plasma levels of cytokines and soluble adhesion molecules were measured as additional parameters for the assessment of treatment outcomes. Results: Our results showed that early CB2R activation with HU308 reduced brain injury size and restored leukocyte response to endotoxin in the peripheral microcirculation. Late CB2R inhibition with AM630 also improved the peripheral leukocyte response to endotoxin and did not exacerbate the extent of brain injury. Discussion: CB2R activation has the potential to mitigate CNS injury as an early treatment by limiting neuroinflammation and preventing the development of CIDS. At the later stage with already-established CIDS, treatment may require dampening CB2R activation to improve the patient's outcome.

Coagulation/Complement Activation and Cerebral Hypoperfusion in Relapsing-Remitting Multiple Sclerosis

Introduction

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system with an underlying immune-mediated and inflammatory pathogenesis. Innate immunity, in addition to the adaptive immune system, plays a relevant role in MS pathogenesis. It represents the immediate non-specific defense against infections through the intrinsic effector mechanism “immunothrombosis” linking inflammation and coagulation. Moreover, decreased cerebral blood volume (CBV), cerebral blood flow (CBF), and prolonged mean transit time (MTT) have been widely demonstrated by MRI in MS patients. We hypothesized that coagulation/complement and platelet activation during MS relapse, likely during viral infections, could be related to CBF decrease. Our specific aims are to evaluate whether there are differences in serum/plasma levels of coagulation/complement factors between relapsing-remitting (RR) MS patients (RRMS) in relapse and those in remission and healthy controls as well as to assess whether brain hemodynamic changes detected by MRI occur in relapse compared with remission. This will allow us to correlate coagulation status with perfusion and demographic/clinical features in MS patients.

Materials and Methods

This is a multi-center, prospective, controlled study. RRMS patients (1° group: 30 patients in relapse; 2° group: 30 patients in remission) and age/sex-matched controls (3° group: 30 subjects) will be enrolled in the study. Patients and controls will be tested for either coagulation/complement (C3, C4, C4a, C9, PT, aPTT, fibrinogen, factor II, VIII, and X, D-dimer, antithrombin, protein C, protein S, von-Willebrand factor), soluble markers of endothelial damage (thrombomodulin, Endothelial Protein C Receptor), antiphospholipid antibodies, lupus anticoagulant, complete blood count, viral serological assays, or microRNA microarray. Patients will undergo dynamic susceptibility contrast-enhanced MRI using a 3.0-T scanner to evaluate CBF, CBV, MTT, lesion number, and volume.

Statistical Analysis

ANOVA and unpaired t-tests will be used. The level of significance was set at p ≤ 0.05.

Discussion

Identifying a link between activation of coagulation/complement system and cerebral hypoperfusion could improve the identification of novel molecular and/or imaging biomarkers and targets, leading to the development of new effective therapeutic strategies in MS.

Clinical Trial Registration

Clinicaltrials.gov, identifier NCT04380220.

Nicotinic Mitigation of Neuroinflammation and Oxidative Stress After Chronic Sleep Deprivation

Sleep deprivation negatively influences all aspects of health. Oxidative stress and inflammatory responses induced by sleep deprivation participate in its adverse effects but the regulatory mechanisms to counteract them remain poorly understood. In mice subjected to sleep deprivation for 7 days, we found activation of microglia and astrocyte accompanied by down-regulation of α7 nicotinic acetylcholine receptor (α7-nAChR) and reduced activation of downstream PI3K/AKT/GSK-3β. These changes occurred with an increase of pro-inflammatory factors, together with reduced levels of anti-inflammatory factors, transcriptor Nrf-2, and anti-oxidant enzyme HO-1. Administration of an α7-nAChR agonist PHA-543613 induced activation of PI3K/AKT/GSK-3β, and reversed changes in pro-inflammatory and anti-inflammatory factors, Nrf-2 and HO-1. These results suggest that stimulation of α7-nAChR reduce neuroinflammation and oxidative stress after chronic sleep deprivation.

Tocopherol Emulsions as Functional Autoantigen Delivery Vehicles Evoke Therapeutic Efficacy in Experimental Autoimmune Encephalomyelitis

Contemporary approaches to treating autoimmune diseases like multiple sclerosis broadly modulate the immune system and leave patients susceptible to severe adverse effects. Antigen-specific immunotherapies (ASIT) offer a unique opportunity to selectively suppress autoreactive cell populations but have suffered from marginal efficacy even when employing traditional adjuvants to improve delivery. The development of immunologically active antigen delivery vehicles could potentially increase the clinical success of antigen-specific immunotherapies. An emulsion of the antioxidant tocopherol delivering an epitope of proteolipid protein autoantigen (PLP139-151) yielded significant efficacy in mice with experimental autoimmune encephalomyelitis (EAE). In vitro studies indicated tocopherol emulsions reduced oxidative stress in antigen-presenting cells. Ex vivo analysis revealed that tocopherol emulsions shifted cytokine responses in EAE splenocytes. In addition, IgG responses against PLP139-151 were increased in mice treated with tocopherol emulsions delivering the antigen, suggesting a possible skew in immunity. Overall, tocopherol emulsions provide a functional delivery vehicle for ASIT capable of ameliorating autoimmunity in a murine model.

Peripheral Inflammation and Demyelinating Diseases

In recent decades, several neurodegenerative diseases have been shown to be exacerbated by systemic inflammatory processes. There is a wide range of literature that demonstrates a clear but complex relationship between the central nervous system (CNS) and the immunological system, both under naïve or pathological conditions. In diseased brains, peripheral inflammation can transform "primed" microglia into an "active" state, which can trigger stronger pathological responses. Demyelinating diseases are a group of neurodegenerative diseases characterized by inflammatory lesions associated with demyelination, which in turn induces axonal damage, neurodegeneration, and progressive loss of function. Among them, the most important are multiple sclerosis (MS) and neuromyelitis optica (NMO). In this review, we will analyze the effect of specific peripheral inflammatory stimuli in the progression of demyelinating diseases and discuss their animal models. In most cases, peripheral immune stimuli are exacerbating.

Infections Up to 76 Days After Stroke Increase Disability and Death

Early infection after stroke is associated with a poor outcome. We aimed to determine whether delayed infections (up to 76 days post-stroke) are associated with poor outcome at 90 days. Data came from the international Efficacy of Nitric Oxide Stroke (ENOS, ISRCTN99414122) trial. Post hoc data on infections were obtained from serious adverse events reports between 1 and 76 days following stroke in this large cohort of patients. Regression models accounting for baseline covariates were used to analyse fatalities and functional outcomes (modified Rankin Scale (mRS), Barthel Index, Euro-Qol-5D) at 90 days, in patients with infection compared to those without infection. Of 4011 patients, 242 (6.0%) developed one or more serious infections. Infections were associated with an increased risk of death (p < 0.001) and an increased likelihood of dependency (measured by mRS) compared to those of all other patients (p < 0.001). This remained when only surviving patients were analysed, indicating that the worsening of functional outcome is not due to mortality (p < 0.001). In addition, the timing of the infection after stroke did not alter its detrimental association with fatality (p = 0.14) or functional outcome (p = 0.47). In conclusion, severe post-stroke infections, whether occurring early or late after stroke, are associated with an increased risk of death and poorer functional outcome, independent of differences in baseline characteristics or treatment. Not only are strategies needed for reducing the risk of infection immediately after stroke, but also during the first 3 months following a stroke. This study is registered: ISRCTN registry, number ISRCTN99414122, ClinicalTrials.gov Identifier, NCT00989716.

Brain inflammation is accompanied by peripheral inflammation in Cstb -/- mice, a model for progressive myoclonus epilepsy

Progressive myoclonus epilepsy of Unverricht-Lundborg type (EPM1) is an autosomal recessively inherited childhood-onset neurodegenerative disorder, characterized by myoclonus, seizures, and ataxia. Mutations in the cystatin B gene (CSTB) underlie EPM1. The CSTB-deficient (Cstb -/- ) mouse model recapitulates key features of EPM1, including myoclonic seizures. The mice show early microglial activation that precedes seizure onset and neuronal loss and leads to neuroinflammation. We here characterized the inflammatory phenotype of Cstb -/- mice in more detail. We found higher concentrations of chemokines and pro-inflammatory cytokines in the serum of Cstb -/- mice and higher CXCL13 expression in activated microglia in Cstb -/- compared to control mouse brains. The elevated chemokine levels were not accompanied by blood-brain barrier disruption, despite increased brain vascularization. Macrophages in the spleen and brain of Cstb -/- mice were predominantly pro-inflammatory. Taken together, these data show that CXCL13 expression is a hallmark of microglial activation in Cstb -/- mice and that the brain inflammation is linked to peripheral inflammatory changes, which might contribute to the disease pathology of EPM1.

LPS-induced Murine Neuroinflammation Model: Main Features and Suitability for Pre-clinical Assessment of Nutraceuticals

Neuroinflammation is an important feature in the pathogenesis and progression of neurodegenerative diseases such as Alzheimer´s disease (AD), Parkinson´s disease (PD), frontotemporal dementia and amyotrophic lateral sclerosis. Based on current knowledge in the field, suggesting that targeting peripheral inflammation could be a promising additional treatment/prevention approach for neurodegenerative diseases, drugs and natural products with anti-inflammatory properties have been evaluated in animal models of neuroinflammation and neurodegeneration. In this review, we provide an extensive analysis of one of the most important and widely-used animal models of peripherally induced neuroinflammation and neurodegeneration - lipopolysaccharide (LPS)-treated mice, and address the data reproducibility in published research. We also summarize briefly basic features of various natural products, nutraceuticals, with known anti-inflammatory effects and present an overview of data on their therapeutic potential for reducing neuroinflammation in LPS-treated mice.

Ethynylphenyl carbonates and carbamates as dual-action acetylcholinesterase inhibitors and anti-inflammatory agents

Novel ethynylphenyl carbonates and carbamates containing carbon- and silicon-based choline mimics were synthesized from their respective phenol and aniline precursors and screened for anticholinesterase and anti-inflammatory activities. All molecules were micromolar inhibitors of acetylcholinesterase (AChE), with IC50s of 28-86 μM; the carbamates were two-fold more potent than the carbonates. Two of the most potent AChE inhibitors suppressed 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation by 40%. Furthermore, these molecules have physicochemical properties in the range of other CNS drugs. These molecules have the potential to treat inflammation; they could also dually target Alzheimer's disease through restoration of cholinergic balance and inflammation suppression.

Thyroid Hormone Potentially Benefits Multiple Sclerosis via Facilitating Remyelination

Myelin destruction due to inflammatory damage of oligodendrocytes (OLs) in conjunction with axonal degeneration is one of the major histopathological hallmarks of multiple sclerosis (MS), a common autoimmune disorder affecting the central nervous system (CNS). Therapies over the last 20 years mainly focus on the immune system and, more specifically, on the modulation of immune cell behavior. It seems to be effective in MS with relapse, while it is of little benefit to progressive MS in which neurodegeneration following demyelination outweighs inflammation. Otherwise, remyelination, as a result of oligodendrocyte production from oligodendrocyte precursor cells (OPCs), is considered to be a potential target for the treatment of progressive MS. In this review, positive effects of remyelination on MS will be discussed in view of the critical role played by thyroid hormone (TH), focusing on the following points: (1) promising treatment of TH on MS that potentially targets to remyelination; (2) the active role of TH that is able to promote remyelination; (3) the regulative role of TH that works on endogenous stem and precursor cells; (4) the effect of TH on gene transcription; and (5) a working hypothesis which is developed that TH can alleviate MS by promoting remyelination, and the mechanism of which is its regulative role in gene transcription of OPCs.

Infection risk in patients on multiple sclerosis therapeutics

The interface of multiple sclerosis (MS) and infection occurs on several levels. First, infectious disease has been postulated as a potential trigger, if not cause, of MS. Second, exacerbation of MS has been well-documented as a consequence of infection, and, lastly, infectious diseases have been recognized as a complication of the therapies currently employed in the treatment of MS. MS is a disease in which immune dysregulation is a key component. Examination of central nervous system (CNS) tissue of people affected by MS demonstrates immune cell infiltration, activation and inflammation. Therapies that alter the immune response have demonstrated efficacy in reducing relapse rates and evidence of brain inflammation on magnetic resonance imaging (MRI). Despite the altered immune response in MS, there is a lack of evidence that these patients are at increased risk of infectious disease in the absence of treatment or debility. Links between infections and disease-modifying therapies (DMTs) used in MS will be discussed in this review, as well as estimates of occurrence and ways to potentially minimize these risks. We address infection in MS in a comprehensive fashion, including (1) the impact of infections on relapse rates in patients with MS; (2) a review of available infection data from pivotal trials and postmarketing studies for the approved and experimental DMTs, including frequency, types and severity of infections; and (3) relevant risk minimization strategies, particularly as they pertain to progressive multifocal leukoencephalopathy (PML).

Multiple sclerosis: the role of melatonin and N-acetylserotonin

Multiple sclerosis (MS) is an immune mediated disorder that is under intensive investigation in an attempt to improve on available treatments. Many of the changes occurring in MS, including increased mitochondrial dysfunction, pain reporting and depression may be partly mediated by increased indoleamine 2,3-dioxygenase, which drives tryptophan to the production of neuroregulatory tryptophan catabolites and away from serotonin, N-acetylserotonin and melatonin production. The consequences of decreased melatonin have classically been attributed to circadian changes following its release from the pineal gland. However, recent data shows that melatonin may be produced by all mitochondria containing cells to some degree, including astrocytes and immune cells, thereby providing another important MS treatment target. As well as being a powerful antioxidant, anti-inflammatory and antinociceptive, melatonin improves mitochondrial functioning, partly via increased oxidative phosphorylation. Melatonin also inhibits demyelination and increases remyelination, suggesting that its local regulation in white matter astrocytes by serotonin availability and apolipoprotein E4, among other potential factors, will be important in the etiology, course and treatment of MS. Here we review the role of local melatonin and its precursors, N-acetylserotonin and serotonin, in MS.

Chronic systemic IL-1β exacerbates central neuroinflammation independently of the blood-brain barrier integrity

Peripheral circulating cytokines are involved in immune to brain communication and systemic inflammation is considered a risk factor for flaring up the symptoms in most neurodegenerative diseases. We induced both central inflammatory demyelinating lesion, and systemic inflammation with an interleukin-1β expressing adenovector. The peripheral pro-inflammatory stimulus aggravated the ongoing central lesion independently of the blood-brain barrier (BBB) integrity. This model allows studying the role of specific molecules and cells (neutrophils) from the innate immune system, in the relationship between central and peripheral communication, and on relapsing episodes of demyelinating lesions, along with the role of BBB integrity.

Time matters - acute stress response and glucocorticoid sensitivity in early multiple sclerosis

OBJECTIVE

Psychosocial stress has frequently been associated with disease activity and acute exacerbations in multiple sclerosis (MS). Despite this well established finding, strikingly little is known about the acute hypothalamic-pituitary-adrenal (HPA) and sympathetic-adrenal-medullary (SAM) stress response in MS.

METHODS

Twenty-six early relapsing-remitting MS (RRMS) patients and seventeen age- and sex-matched healthy control subjects (CS) took part in the Trier Social Stress Test (TSST), a well validated psycho-social laboratory stress protocol. Repeated blood samples were analyzed for stress-related cortisol and catecholamine levels as well as for glucocorticoid sensitivity (GCS) of target immune cells. Chronic and acute stress appraisals were assessed by self-report measures.

RESULTS

RRMS patients and CS did not differ in stress-related cortisol/catecholamine levels, GCS or stress appraisal in response to the TSST. However, cortisol release as well as GCS was strongly correlated with time since diagnosis but not with neurological disability. Patients with shorter disease duration (2-12 months) expressed a significantly higher cortisol stress response while MS patients with longer disease duration (14-36 months) showed a significantly diminished HPA response as well as lower post-stress GCS.

DISCUSSION

There is evidence for a time-dependent variability in the HPA stress system with an increased cortisol stress response in the first year after diagnosis along with a more blunted HPA stress response and a diminished GCS in subsequent disease stages. Data underscore the highly dynamic nature of HPA axis regulation in the MS disease process, which could possibly relate to compensatory mechanisms within a cytokine-HPA axis feedback circuit model.

Systemic inflammation regulates microglial responses to tissue damage in vivo

Microglia, the resident immune cells of the central nervous system, exist in either a "resting" state associated with physiological tissue surveillance or an "activated" state in neuroinflammation. We recently showed that ATP is the primary chemoattractor to tissue damage in vivo and elicits opposite effects on the motility of activated microglia in vitro through activation of adenosine A2A receptors. However, whether systemic inflammation affects microglial responses to tissue damage in vivo remains largely unknown. Using in vivo two-photon imaging of mice, we show that injection of lipopolysaccharide (LPS) at levels that can produce both clear neuroinflammation and some features of sepsis significantly reduced the rate of microglial response to laser-induced ablation injury in vivo. Under proinflammatory conditions, microglial processes initially retracted from the ablation site, but subsequently moved toward and engulfed the damaged area. Analyzing the process dynamics in 3D cultures of primary microglia indicated that only A2A , but not A1 or A3 receptors, mediate process retraction in LPS-activated microglia. The A2A receptor antagonists caffeine and preladenant reduced adenosine-mediated process retraction in activated microglia in vitro. Finally, administration of preladenant before induction of laser ablation in vivo accelerated the microglial response to injury following systemic inflammation. The regulation of rapid microglial responses to sites of injury by A2A receptors could have implications for their ability to respond to the neuronal death occurring under conditions of neuroinflammation in neurodegenerative disorders.

Immunomodulatory effects of licochalcone A on experimental autoimmune encephalomyelitis

OBJECTIVES

Experimental autoimmune encephalomyelitis (EAE) is a murine autoimmune disease used to study multiple sclerosis. Herein, we have investigated the immunomodulatory effect of licochalcone A (LicoA) on NO, H2 O2 , tumour necrosis factor-alpha (TNF-α), interferon gamma (IFN-γ) and IL-17 production in cultured cells from EAE mice.

METHODS

EAE was induced in C57Bl/6 mice with myelin oligodendrocyte glycoprotein peptide (MOG35-55 ). LicoA was isolated from the roots of Glycyrrhiza inflata. Splenocytes were obtained from EAE mice and incubated with LicoA (4, 20 and 40 μm). Peritoneal cells were obtained from EAE mice treated with LicoA (15 and 30 mg/kg/day. p.o.). H2 O2 , NO, IFN-γ, TNF-α and IL-17 production was determined in the presence or absence of concanavalin (ConA) or MOG35-55 stimulation.

KEY FINDINGS

LicoA (40 μm) inhibited H2 O2 , NO, IFN-γ, TNF-α and IL-17 production in splenocytes spontaneously or after both ConA and MOG35-55 stimulation. LicoA (30 mg/kg/day) reduced clinical score and severity of EAE mice, and inhibited TNF-α, IFN-γ and IL-17 production in peritoneal cells.

CONCLUSIONS

LicoA possesses immunomodulatory effects on H2 O2 , NO, IFN-γ, TNF-α and IL-17 production in cells from EAE mice. It is suggested that LicoA acts on the mechanism of development of EAE by IFN-γ, IL-17 and TNF-α inhibition, modulating the immune response on both Th1 and Th17 cells.

Role of pathogens in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating autoimmune disease of the central nervous system (CNS). Although the etiology of MS is unknown, genetic and environmental factors play a role. Infectious pathogens are the likely environmental factors involved in the development of MS. Pathogens associated with the development or exacerbation of MS include bacteria, such as Mycoplasma pneumoniae and Chlamydia pneumoniae, the Staphylococcus aureus-produced enterotoxins that function as superantigens, viruses of the herpes virus (Epstein-Barr virus and human herpesvirus 6) and human endogenous retrovirus (HERV) families and the protozoa Acanthamoeba castellanii. Evidence, from studies with humans and animal models, supporting the association of these various pathogens with the development and/or exacerbation of MS will be discussed along with the potential mechanisms including molecular mimicry, epitope spreading and bystander activation. In contrast, infection with certain parasites such as helminthes (Schistosoma mansoni, Fasciola hepatica, Hymenolepis nana, Trichuris trichiura, Ascaris lumbricoides, Strongyloides stercolaris, Enterobius vermicularis) appears to protect against the development or exacerbation of MS. Evidence supporting the ability of parasitic infections to protect against disease will be discussed along with a brief summary of a recent Phase I clinical trial testing the ability of Trichuris suis ova treatment to improve the clinical course of MS. A complex interaction between the CNS (including the blood-brain barrier), multiple infections with various infectious agents (occurring in the periphery or within the CNS), and the immune response to those various infections may have to be deciphered before the etiology of MS can be fully understood.

Neuroprotection in multiple sclerosis: a therapeutic approach

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system that is pathologically characterized by inflammatory demyelination and neurodegeneration. Axonal damage, along with neuronal loss, occurs from disease onset and may lead to progressive and permanent disability. In contrast with the inflammatory pathways, the molecular mechanisms leading to MS neurodegeneration remain largely elusive. With improved understanding of these mechanisms, new potential therapeutic targets for neuroprotection have emerged. We review the current understanding of neurodegenerative processes at play in MS and discuss potential outcome measures and targets for neuroprotection trials.