Complement component C3 and butyrylcholinesterase activity are associated with neurodegeneration and clinical disability in multiple sclerosis

Association of Complement Factors With Disability Progression in Primary Progressive Multiple Sclerosis

BACKGROUND AND OBJECTIVES

The complement system is known to play a role in multiple sclerosis (MS) pathogenesis. However, its contribution to disease progression remains elusive. The study investigated the role of the complement system in disability progression of patients with primary progressive MS (PPMS).

METHODS

Sixty-eight patients with PPMS from 12 European MS centers were included in the study. Serum and CSF levels of a panel of complement components (CCs) were measured by multiplex enzyme-linked immunosorbent assay at a baseline time point (i.e., sampling). Mean (SD) follow-up time from baseline was 9.6 (4.8) years. Only one patient (1.5%) was treated during follow-up. Univariable and multivariable logistic regressions adjusted for age, sex, and albumin quotient were performed to assess the association between baseline CC levels and disability progression in short term (2 years), medium term (6 years), and long term (at the time of the last follow-up).

RESULTS

In short term, CC played little or no role in disability progression. In medium term, an elevated serum C3a/C3 ratio was associated with a higher risk of disability progression (adjusted OR 2.30; 95% CI 1.17-6.03; p = 0.040). By contrast, increased CSF C1q levels were associated with a trend toward reduced risk of disability progression (adjusted OR 0.43; 95% CI 0.17-0.98; p = 0.054). Similarly, in long term, an elevated serum C3a/C3 ratio was associated with higher risk of disability progression (adjusted OR 1.81; 95% CI 1.09-3.40; p = 0.037), and increased CSF C1q levels predicted lower disability progression (adjusted OR 0.41; 95% CI 0.17-0.86; p = 0.025).

DISCUSSION

Proteins involved in the activation of early complement cascades play a role in disability progression as risk (elevated serum C3a/C3 ratio) or protective (elevated CSF C1q) factors after 6 or more years of follow-up in patients with PPMS. The protective effects associated with C1q levels in CSF may be related to its neuroprotective and anti-inflammatory properties.

The complement system in neurodegenerative diseases

Complement is an important component of innate immune defence against pathogens and crucial for efficient immune complex disposal. These core protective activities are dependent in large part on properly regulated complement-mediated inflammation. Dysregulated complement activation, often driven by persistence of activating triggers, is a cause of pathological inflammation in numerous diseases, including neurological diseases. Increasingly, this has become apparent not only in well-recognized neuroinflammatory diseases like multiple sclerosis but also in neurodegenerative and neuropsychiatric diseases where inflammation was previously either ignored or dismissed as a secondary event. There is now a large and rapidly growing body of evidence implicating complement in neurological diseases that cannot be comprehensively addressed in a brief review. Here, we will focus on neurodegenerative diseases, including not only the 'classical' neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease, but also two other neurological diseases where neurodegeneration is a neglected feature and complement is implicated, namely, schizophrenia, a neurodevelopmental disorder with many mechanistic features of neurodegeneration, and multiple sclerosis, a demyelinating disorder where neurodegeneration is a major cause of progressive decline. We will discuss the evidence implicating complement as a driver of pathology in these diverse diseases and address briefly the potential and pitfalls of anti-complement drug therapy for neurodegenerative diseases.

Combination protein biomarkers predict multiple sclerosis diagnosis and outcomes

Establishing biomarkers to predict multiple sclerosis diagnosis and prognosis has been challenging using a single biomarker approach. We hypothesised that a combination of biomarkers would increase the accuracy of prediction models to differentiate multiple sclerosis from other neurological disorders and enhance prognostication for people with multiple sclerosis. We measured 24 fluid biomarkers in the blood and cerebrospinal fluid of 77 people with multiple sclerosis and 80 people with other neurological disorders, using ELISA or Single Molecule Array assays. Primary outcomes were multiple sclerosis versus any other diagnosis, time to first relapse, and time to disability milestone (Expanded Disability Status Scale 6), adjusted for age and sex. Multivariate prediction models were calculated using the area under the curve value for diagnostic prediction, and concordance statistics (the percentage of each pair of events that are correctly ordered in time for each of the Cox regression models) for prognostic predictions. Predictions using combinations of biomarkers were considerably better than single biomarker predictions. The combination of cerebrospinal fluid [chitinase-3-like-1 + TNF-receptor-1 + CD27] and serum [osteopontin + MCP-1] had an area under the curve of 0.97 for diagnosis of multiple sclerosis, compared to the best discriminative single marker in blood (osteopontin: area under the curve 0.84) and in cerebrospinal fluid (chitinase-3-like-1 area under the curve 0.84). Prediction for time to next relapse was optimal with a combination of cerebrospinal fluid[vitamin D binding protein + Factor I + C1inhibitor] + serum[Factor B + Interleukin-4 + C1inhibitor] (concordance 0.80), and time to Expanded Disability Status Scale 6 with cerebrospinal fluid [C9 + Neurofilament-light] + serum[chitinase-3-like-1 + CCL27 + vitamin D binding protein + C1inhibitor] (concordance 0.98). A combination of fluid biomarkers has a higher accuracy to differentiate multiple sclerosis from other neurological disorders and significantly improved the prediction of the development of sustained disability in multiple sclerosis. Serum models rivalled those of cerebrospinal fluid, holding promise for a non-invasive approach. The utility of our biomarker models can only be established by robust validation in different and varied cohorts.

Dysregulation of butyrylcholinesterase, BCHE gene SNP rs1803274, and pro-inflammatory cytokines in occupational workers

BACKGROUND

People in different occupations are exposed to a variety of xenobiotics which affect the health and physiological processes of the body. Butyrylcholinesterase (BChE), has been reported to play neuronal and non-neuronal roles, though its exact function is yet to be established. This study aimed to find the status and role of BChE in seven different occupational groups; gasoline fillers, auto-mechanics, carpenters, textile shop workers, furniture shop workers, electricians, and office workers.

METHODS

A total of 400 samples were screened. BChE activity was determined by Worek et al. method based on Ellman's principle. Pro-inflammatory cytokines were determined by ELISA. Genotypic analysis of the K-variant of BCHE gene SNP was carried out by standard molecular methods. Among seven groups, office workers were taken as a control to compare the results with all other occupational groups.

RESULTS

The results revealed a significant decrease in BChE activity in gasoline fillers (79.52%) followed by carpenters (73.49%), auto mechanics (39.76%), textile shop workers (18.07%), electricians (10.84%), and furniture shop workers (7.23%). TNF-α, IL-6, and IL1-β were elevated in all groups. IL-6 and IL1-β in gasoline fillers, and electricians were not statistically significantly increased. Binomial regression to determine the odd ratio was found to be significant (p < 0.05) in all groups. However, correlation (Pearson) did not reveal significance between different biochemical parameters. Genotypic analysis of the K-variant SNP of the BCHE gene showed a significant association with occupational groups when compared with control which indicates a possible association with xenobiotics exposure and the physiological role of K-variant in understudied occupational groups.

CONCLUSION

The study concluded that BChE and its gene SNP rs 1803274 and proinflammatory cytokines significantly dysregulates under the exposure to cumulative multiple xenobiotics in different occupational groups which may lead to pathophysiological conditions.

Multiple Sclerosis: Inflammatory and Neuroglial Aspects

Multiple sclerosis (MS) represents the most common acquired demyelinating disorder of the central nervous system (CNS). Its pathogenesis, in parallel with the well-established role of mechanisms pertaining to autoimmunity, involves several key functions of immune, glial and nerve cells. The disease's natural history is complex, heterogeneous and may evolve over a relapsing-remitting (RRMS) or progressive (PPMS/SPMS) course. Acute inflammation, driven by infiltration of peripheral cells in the CNS, is thought to be the most relevant process during the earliest phases and in RRMS, while disruption in glial and neural cells of pathways pertaining to energy metabolism, survival cascades, synaptic and ionic homeostasis are thought to be mostly relevant in long-standing disease, such as in progressive forms. In this complex scenario, many mechanisms originally thought to be distinctive of neurodegenerative disorders are being increasingly recognized as crucial from the beginning of the disease. The present review aims at highlighting mechanisms in common between MS, autoimmune diseases and biology of neurodegenerative disorders. In fact, there is an unmet need to explore new targets that might be involved as master regulators of autoimmunity, inflammation and survival of nerve cells.

Free complement and complement containing extracellular vesicles as potential biomarkers for neuroinflammatory and neurodegenerative disorders

The complement system is implicated in a broad range of neuroinflammatory disorders such as Alzheimer's disease (AD) and multiple sclerosis (MS). Consequently, measuring complement levels in biofluids could serve as a potential biomarker for these diseases. Indeed, complement levels are shown to be altered in patients compared to controls, and some studies reported a correlation between the level of free complement in biofluids and disease progression, severity or the response to therapeutics. Overall, they are not (yet) suitable as a diagnostic tool due to heterogeneity of reported results. Moreover, measurement of free complement proteins has the disadvantage that information on their origin is lost, which might be of value in a multi-parameter approach for disease prediction and stratification. In light of this, extracellular vesicles (EVs) could provide a platform to improve the diagnostic power of complement proteins. EVs are nanosized double membrane particles that are secreted by essentially every cell type and resemble the (status of the) cell of origin. Interestingly, EVs can contain complement proteins, while the cellular origin can still be determined by the presence of EV surface markers. In this review, we summarize the current knowledge and future opportunities on the use of free and EV-associated complement proteins as biomarkers for neuroinflammatory and neurodegenerative disorders.

Complement activation and increased anaphylatoxin receptor expression are associated with cortical grey matter lesions and the compartmentalised inflammatory response of multiple sclerosis

Background

The extent of cortical pathology is an important determinant of multiple sclerosis (MS) severity. Cortical demyelination and neurodegeneration are related to inflammation of the overlying leptomeninges, a more inflammatory CSF milieu and with parenchymal microglia and astroglia activation. These are all components of the compartmentalised inflammatory response. Compartmentalised inflammation is a feature of progressive MS, which is not targeted by disease modifying therapies. Complement is differentially expressed in the MS CSF and complement, and complement receptors, are associated with demyelination and neurodegeneration.

Methods

To better understand if complement activation in the leptomeninges is associated with underlying cortical demyelination, inflammation, and microglial activation, we performed a neuropathological study of progressive MS (n = 22, 14 females), neuroinflammatory (n = 8), and non-neurological disease controls (n = 10). We then quantified the relative extent of demyelination, connective tissue inflammation, complement, and complement receptor positive microglia/macrophages.

Results

Complement was elevated at the leptomeninges, subpial, and within and around vessels of the cortical grey matter. The extent of complement C1q immunoreactivity correlated with connective tissue infiltrates, whilst activation products C4d, Bb, and C3b associated with grey matter demyelination, and C3a receptor 1+ and C5a receptor 1+ microglia/macrophages closely apposed C3b labelled cells. The density of C3a receptor 1+ and C5a receptor 1+ cells was increased at the expanding edge of subpial and leukocortical lesions. C5a receptor 1+ cells expressed TNFα, iNOS and contained puncta immunoreactive for proteolipid protein, neurofilament and synaptophysin, suggesting their involvement in grey matter lesion expansion.

Interpretation

The presence of products of complement activation at the brain surfaces, their association with the extent of underlying pathology and increased complement anaphylatoxin receptor positive microglia/macrophages at expanding cortical grey matter lesions, could represent a target to modify compartmentalised inflammation and cortical demyelination.

The validity of animal models to explore the pathogenic role of the complement system in multiple sclerosis: A review

Animal models of multiple sclerosis (MS) have been extensively used to characterize the disease mechanisms in MS, as well as to identify potential pharmacologic targets for this condition. In recent years, the immune complement system has gained increased attention as an important effector in the pathogenesis of MS. Evidence from histological, serum, and CSF studies of patients supports an involvement of complement in both relapsing-remitting and progressive MS. In this review, we discuss the history and advances made on the use of MS animal models to profile the effects of the complement system in this condition. The first studies that explored the complement system in the context of MS used cobra venom factor (CVF) as a complement depleting agent in experimental autoimmune encephalomyelitis (EAE) Lewis rats. Since then, multiple mice and rat models of MS have revealed a role of C3 and the alternative complement cascade in the opsonization and phagocytosis of myelin by microglia and myeloid cells. Studies using viral vectors, genetic knockouts and pharmacologic complement inhibitors have also shown an effect of complement in synaptic loss. Antibody-mediated EAE models have revealed an involvement of the C1 complex and the classical complement as an effector of the humoral response in this disease. C1q itself may also be involved in modulating microglia activation and oligodendrocyte differentiation in these animals. In addition, animal and in vitro models have revealed that multiple complement factors may act as modulators of both the innate and adaptive immune responses. Finally, evidence gathered from mice models suggests that the membrane attack complex (MAC) may even exert protective roles in the chronic stages of EAE. Overall, this review summarizes the importance of MS animal models to better characterize the role of the complement system and guide future therapeutic approaches in this condition.

A Scoping Review on Body Fluid Biomarkers for Prognosis and Disease Activity in Patients with Multiple Sclerosis

Multiple sclerosis (MS) is a complex demyelinating disease of the central nervous system, presenting with different clinical forms, including clinically isolated syndrome (CIS), which is a first clinical episode suggestive of demyelination. Several molecules have been proposed as prognostic biomarkers in MS. We aimed to perform a scoping review of the potential use of prognostic biomarkers in MS clinical practice. We searched MEDLINE up to 25 November 2021 for review articles assessing body fluid biomarkers for prognostic purposes, including any type of biomarkers, cell types and tissues. Original articles were obtained to confirm and detail the data reported by the review authors. We evaluated the reliability of the biomarkers based on the sample size used by various studies. Fifty-two review articles were included. We identified 110 molecules proposed as prognostic biomarkers. Only six studies had an adequate sample size to explore the risk of conversion from CIS to MS. These confirm the role of oligoclonal bands, immunoglobulin free light chain and chitinase CHI3L1 in CSF and of serum vitamin D in the prediction of conversion from CIS to clinically definite MS. Other prognostic markers are not yet explored in adequately powered samples. Serum and CSF levels of neurofilaments represent a promising biomarker.

The role of the complement system in Multiple Sclerosis: A review

The complement system has been involved in the pathogenesis of multiple neuroinflammatory and neurodegenerative conditions. In this review, we evaluated the possible role of complement activation in multiple sclerosis (MS) with a focus in progressive MS, where the disease pathogenesis remains to be fully elucidated and treatment options are limited. The evidence for the involvement of the complement system in the white matter plaques and gray matter lesions of MS stems from immunohistochemical analysis of post-mortem MS brains, in vivo serum and cerebrospinal fluid biomarker studies, and animal models of Experimental Autoimmune Encephalomyelitis (EAE). Complement knock-out studies in these animal models have revealed that this system may have a “double-edge sword” effect in MS. On the one hand, complement proteins may aid in promoting the clearance of myelin degradation products and other debris through myeloid cell-mediated phagocytosis. On the other, its aberrant activation may lead to demyelination at the rim of progressive MS white matter lesions as well as synapse loss in the gray matter. The complement system may also interact with known risk factors of MS, including as Epstein Barr Virus (EBV) infection, and perpetuate the activation of CNS self-reactive B cell populations. With the mounting evidence for the involvement of complement in MS, the development of complement modulating therapies for this condition is appealing. Herein, we also reviewed the pharmacological complement inhibitors that have been tested in MS animal models as well as in clinical trials for other neurologic diseases. The potential use of these agents, such as the C5-binding antibody eculizumab in MS will require a detailed understanding of the role of the different complement effectors in this disease and the development of better CNS delivery strategies for these compounds.

Phenotypic Displays of Cholinergic Enzymes Associate With Markers of Inflammation, Neurofibrillary Tangles, and Neurodegeneration in Pre- and Early Symptomatic Dementia Subjects

Background

Cholinergic drugs are the most commonly used drugs for the treatment of Alzheimer’s disease (AD). Therefore, a better understanding of the cholinergic system and its relation to both AD-related biomarkers and cognitive functions is of high importance.

Objectives

To evaluate the relationships of cerebrospinal fluid (CSF) cholinergic enzymes with markers of amyloidosis, neurodegeneration, neurofibrillary tangles, inflammation and performance on verbal episodic memory in a memory clinic cohort.

Methods

In this cross-sectional study, 46 cholinergic drug-free subjects (median age = 71, 54% female, median MMSE = 28) were recruited from an Icelandic memory clinic cohort targeting early stages of cognitive impairment. Enzyme activity of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) was measured in CSF as well as levels of amyloid-β_1–42 (Aβ₄₂), phosphorylated tau (P-tau), total-tau (T-tau), neurofilament light (NFL), YKL-40, S100 calcium-binding protein B (S100B), and glial fibrillary acidic protein (GFAP). Verbal episodic memory was assessed with the Rey Auditory Verbal Learning (RAVLT) and Story tests.

Results

No significant relationships were found between CSF Aβ₄₂ levels and AChE or BuChE activity (p > 0.05). In contrast, T-tau (r = 0.46, p = 0.001) and P-tau (r = 0.45, p = 0.002) levels correlated significantly with AChE activity. Although neurodegeneration markers T-tau and NFL did correlate with each other (r = 0.59, p < 0.001), NFL did not correlate with AChE (r = 0.25, p = 0.09) or BuChE (r = 0.27, p = 0.06). Inflammation markers S100B and YKL-40 both correlated significantly with AChE (S100B: r = 0.43, p = 0.003; YKL-40: r = 0.32, p = 0.03) and BuChE (S100B: r = 0.47, p < 0.001; YKL-40: r = 0.38, p = 0.009) activity. A weak correlation was detected between AChE activity and the composite score reflecting verbal episodic memory (r = −0.34, p = 0.02). LASSO regression analyses with a stability approach were performed for the selection of a set of measures best predicting cholinergic activity and verbal episodic memory score. S100B was the predictor with the highest model selection frequency for both AChE (68%) and BuChE (73%) activity. Age (91%) was the most reliable predictor for verbal episodic memory, with selection frequency of both cholinergic enzymes below 10%.

Conclusions

Results indicate a relationship between higher activity of the ACh-degrading cholinergic enzymes with increased neurodegeneration, neurofibrillary tangles and inflammation in the stages of pre- and early symptomatic dementia, independent of CSF Aβ₄₂ levels.

Long Non-coding RNA and mRNA Expression Change in Spinal Dorsal Horn After Exercise in Neuropathic Pain Rats

Exercise can help inhibition of neuropathic pain (NP), but the related mechanism remains being explored. In this research, we performed the effect of swimming exercise on the chronic constriction injury (CCI) rats. Compared with CCI group, the mechanical withdrawal threshold of rats in the CCI-Swim group significantly increased on the 21st and 28th day after CCI surgery. Second-generation RNA-sequencing technology was employed to investigate the transcriptomes of spinal dorsal horns in the Sham, CCI, and CCI-Swim groups. On the 28th day post-operation, 306 intersecting long non-coding RNAs (lncRNAs) and 173 intersecting mRNAs were observed between the CCI vs Sham group and CCI-Swim vs CCI groups. Then, the biological functions of lncRNAs and mRNAs in the spinal dorsal horn of CCI rats were then analyzed. Taking the results together, this study could provide a novel perspective for the treatment for NP.

The association between neurodegeneration and local complement activation in the thalamus to progressive multiple sclerosis outcome

The extent of grey matter demyelination and neurodegeneration in the progressive multiple sclerosis (PMS) brains at post‐mortem associates with more severe disease. Regional tissue atrophy, especially affecting the cortical and deep grey matter, including the thalamus, is prognostic for poor outcomes. Microglial and complement activation are important in the pathogenesis and contribute to damaging processes that underlie tissue atrophy in PMS. We investigated the extent of pathology and innate immune activation in the thalamus in comparison to cortical grey and white matter in blocks from 21 cases of PMS and 10 matched controls. Using a digital pathology workflow, we show that the thalamus is invariably affected by demyelination and had a far higher proportion of active inflammatory lesions than forebrain cortical tissue blocks from the same cases. Lesions were larger and more frequent in the medial nuclei near the ventricular margin, whilst neuronal loss was greatest in the lateral thalamic nuclei. The extent of thalamic neuron loss was not associated with thalamic demyelination but correlated with the burden of white matter pathology in other forebrain areas (Spearman r = 0.79, p < 0.0001). Only thalamic neuronal loss, and not that seen in other forebrain cortical areas, correlated with disease duration (Spearman r = −0.58, p = 0.009) and age of death (Spearman r = −0.47, p = 0.045). Immunoreactivity for the complement pattern recognition molecule C1q, and products of complement activation (C4d, Bb and C3b) were elevated in thalamic lesions with an active inflammatory pathology. Complement regulatory protein, C1 inhibitor, was unchanged in expression. We conclude that active inflammatory demyelination, neuronal loss and local complement synthesis and activation in the thalamus, are important to the pathological and clinical disease outcomes of PMS.

The Role of Complement in Synaptic Pruning and Neurodegeneration

The complement system, an essential part of the innate immune system, is composed of a group of secreted and membrane proteins that collectively participate in maintaining the function of the healthy and diseased brain. However, an inappropriate activation of the complement system has been related to an inflammatory response in multiple diseases, such as stroke, traumatic brain injury, multiple sclerosis, and Alzheimer's disease, as well as Zika infection and radiotherapy. In addition, C1q and C3 (initial activation components of the complement cascade) have been shown to play a key beneficial role in the refinement of synaptic circuits during developmental stages and adult plasticity. Nevertheless, excessive synaptic pruning in the adult brain can be detrimental and has been associated with synaptic loss in several pathological conditions. In this brief review, we will discuss the role of the complement system in synaptic pruning as well as its contribution to neurodegeneration and cognitive deficits. We also mention potential therapeutic approaches to target the complement system to treat several neuroinflammatory diseases and unintended consequences of radiotherapy.

Possible Role of Butyrylcholinesterase in Fat Loss and Decreases in Inflammatory Levels in Patients with Multiple Sclerosis after Treatment with Epigallocatechin Gallate and Coconut Oil: A Pilot Study

(1) Background. Multiple sclerosis (MS) is characterised by the loss of muscle throughout the course of the disease, which in many cases is accompanied by obesity and related to inflammation. Nonetheless, consuming epigallocatechin gallate (EGCG) and ketone bodies (especially β-hydroxybutyrate (βHB)) produced after metabolising coconut oil, have exhibited anti-inflammatory effects and a decrease in body fat. In addition, butyrylcholinesterase (BuChE), seems to be related to the pathogenesis of the disease associated with inflammation, and serum concentrations have been related to lipid metabolism. Objective. The aim of the study was to determine the role of BuChE in the changes caused after treatment with EGCG and ketone bodies on the levels of body fat and inflammation state in MS patients. (2) Methods. A pilot study was conducted for 4 months with 51 MS patients who were randomly divided into an intervention group and a control group. The intervention group received 800 mg of EGCG and 60 mL of coconut oil, and the control group was prescribed a placebo. Fat percentage and concentrations of the butyrylcholinesterase enzyme (BuChE), paraoxonase 1 (PON1) activity, triglycerides, interleukin 6 (IL-6), albumin and βHB in serum were measured. (3) Results. The intervention group exhibited significant decreases in IL-6 and fat percentage and significant increases in BuChE, βHB, PON1, albumin and functional capacity (determined by the Expanded Disability Status Scale (EDSS)). On the other hand, the control group only exhibited a decrease in IL-6. After the intervention, BuChE was positively correlated with the activity of PON1, fat percentage and triglycerides in the intervention group, whereas these correlations were not observed in the control group (4). Conclusions. BuChE seems to have an important role in lipolytic activity and the inflammation state in MS patients, evidenced after administering EGCG and coconut oil as a βHB source.

Neurofilaments in progressive multiple sclerosis: a systematic review

BACKGROUND

Neurofilament proteins have been extensively studied in relapsing-remitting multiple sclerosis, where they are promising biomarkers of disease activity and treatment response. Their role in progressive multiple sclerosis, where there is a particularly urgent need for improved biomarkers, is less clear. The objectives of this systematic review are to summarise the literature on neurofilament light and heavy in progressive multiple sclerosis, addressing key questions.

METHODS

A systematic search of PubMed, Embase, Web of Science and Scopus identified 355 potential sources. 76 relevant sources were qualitatively reviewed using QUADAS-2 criteria, and 17 were identified as at low risk of bias. We summarise the findings from all relevant sources, and separately from the 17 high-quality studies.

RESULTS

Differences in neurofilament light between relapsing-remitting and progressive multiple sclerosis appear to be explained by differences in covariates. Neurofilament light is consistently associated with current inflammatory activity and future brain atrophy in progressive multiple sclerosis, and is consistently shown to be a marker of treatment response with immunosuppressive disease-modifying therapies. Associations with current or future disability are inconsistent, and there is no evidence of NFL being a responsive marker of purportedly neuroprotective treatments. Evidence on neurofilament heavy is more limited and inconsistent.

CONCLUSIONS

Neurofilament light has shown consistent utility as a biomarker of neuroinflammation, future brain atrophy and immunosuppressive treatment response at a group level. Neither neurofilament light or heavy has shown a consistent treatment response to neuroprotective disease-modifying therapies, which will require further data from successful randomised controlled trials.

Genetic Association of Butyrylcholinesterase with Major Depressive Disorder

Major depressive disorder (MDD) is characterized as clinical depression, which primarily affects the mood and behaviour of an individual. In the present study butyrylcholinesterase (BChE), a co-regulatory cholinergic neurotransmitter enzyme implicated in several putative neuronal and non-neuronal physiological roles was investigated for its role in MDD. Eighty MDD patients and sixty-one healthy controls were recruited for the study. BChE activity was measured by Ellman's method using serum while DNA samples of the patients were genotyped for BCHE polymorphisms rs3495 (c.*189G > A) and rs1803274 (c.1699G > A) by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and tetra-primer Amplification Refractory Mutation System- polymerase chain reaction (ARMS-PCR). The genotyping was further validated by Sanger Sequencing. Biochemical estimation of serum BChE levels revealed a statistically significant decrease of enzyme activity in MDD patients (69.96) as compared to healthy controls (90.97), which was independent of age and gender. BCHE single nucleotide polymorphism rs1803274 genotype GA was found to be associated with the disease under a dominant model (OR 2.32; 95% CI 1.09-4.96; p value = 0.025). Furthermore, risk allele-A frequency was higher in cases (p value = 0.013) than control. Carriers of rs1803274 GA genotype showed reduced mean BChE activity than wild-type allele GG homozygotes (p value = 0.040). Gender-based analysis revealed a protective role of rs3495 in females (χ² = 6.87, p value = 0.032, RM: OR 0.173, CI = 0.043-0.699 (p value = 0.017). In addition, rs1803274 risk allele-A was observed to be significantly higher in males (χ² = 4.258, p value = 0.039). In conclusion, the present study is indicative of a role of BChE in the pathophysiology of MDD where genetic polymorphisms were observed to effect BChE activity. Further replication studies in different ethnicities are recommended to validate the current observations.

Anti-inflammatory Therapy by Cholinergic and Purinergic Modulation in Multiple Sclerosis Associated with SARS-CoV-2 Infection

The virus "acute respiratory syndrome coronavirus 2" (SARS-CoV-2) is the etiologic agent of coronavirus disease 2019 (COVID-19), initially responsible for an outbreak of pneumonia in Wuhan, China, which, due to the high level of contagion and dissemination, has become a pandemic. The clinical picture varies from mild to critical cases; however, all of these signs already show neurological problems, from sensory loss to neurological diseases. Thus, patients with multiple sclerosis (MS) infected with the new coronavirus are more likely to develop severe conditions; in addition to worsening the disease, this is due to the high level of pro-inflammatory cytokines, which is closely associated with increased mortality both in COVID-19 and MS. This increase is uncontrolled and exaggerated, characterizing the cytokine storm, so a possible therapy for this neuronal inflammation is the modulation of the cholinergic anti-inflammatory pathway, since acetylcholine (ACh) acts to reduce pro-inflammatory cytokines and acts directly on the brain for being released by cholinergic neurons, as well as acting on other cells such as immune and blood cells. In addition, due to tissue damage, there is an exacerbated release of adenosine triphosphate (ATP), potentiating the inflammatory process and activating purinergic receptors which act directly on neuroinflammation and positively modulate the inflammatory cycle. Associated with this, in neurological pathologies, there is greater expression of P2X7 in the cells of the microglia, which positively activates the immune inflammatory response. Thus, the administration of blockers of this receptor can act in conjunction with the action of ACh in the anticholinergic inflammatory pathway. Finally, there will be a reduction in the cytokine storm and triggered hyperinflammation, as well as the level of mortality in patients with multiple sclerosis infected with SARS-CoV-2 and the development of possible neurological damage.

Evidence of upregulation of the cholinergic anti-inflammatory pathway in late-life depression

BACKGROUND

Decreased cholinergic tone associated with increased proinflammatory cytokines has been observed in several human diseases associated with low-grade inflammation. We examined if this attenuated cholinergic anti-inflammatory pathway (CAP) mechanism contributed to increased neuroinflammation observed in depression.

METHODS

We measured cerebrospinal fluid (CSF) cholinergic markers (AChE and BChE activities) in 28 individuals with longstanding late-life major depression (LLMD) and 19 controls and their relationship to central and peripheral levels of pro-inflammatory cytokines (IL-6 and IL-8). Additionally, we examined if these cholinergic indices were related to CSF markers of microglial activation and neuroinflammation (sTREM2 and complement C3).

RESULTS

Compared with controls, LLMD patients had a significant reduction in CSF BChE levels. Lower CSF BChE and AChE activities were associated with lower CSF markers of microglial and neuroinflammation (sTREM2 and C3). In addition, in LLMD patients we found an inverse relationship between peripheral marker of inflammation (plasma IL-6) and CSF BChE and AChE levels.

CONCLUSIONS

Our results suggest an upregulation of the CAP mechanism in LLMD with an elevation in peripheral markers of inflammation and concomitant reduction in markers of glial activation associated with a higher cholinergic tone. Future studies should confirm these findings in a larger sample including individuals with acute and more severe depressive episodes and across all ages.

Aberrant Complement System Activation in Neurological Disorders

The complement system is an assembly of proteins that collectively participate in the functions of the healthy and diseased brain. The complement system plays an important role in the maintenance of uninjured (healthy) brain homeostasis, contributing to the clearance of invading pathogens and apoptotic cells, and limiting the inflammatory immune response. However, overactivation or underregulation of the entire complement cascade within the brain may lead to neuronal damage and disturbances in brain function. During the last decade, there has been a growing interest in the role that this cascading pathway plays in the neuropathology of a diverse array of brain disorders (e.g., acute neurotraumatic insult, chronic neurodegenerative diseases, and psychiatric disturbances) in which interruption of neuronal homeostasis triggers complement activation. Dysfunction of the complement promotes a disease-specific response that may have either beneficial or detrimental effects. Despite recent advances, the explicit link between complement component regulation and brain disorders remains unclear. Therefore, a comprehensible understanding of such relationships at different stages of diseases could provide new insight into potential therapeutic targets to ameliorate or slow progression of currently intractable disorders in the nervous system. Hence, the aim of this review is to provide a summary of the literature on the emerging role of the complement system in certain brain disorders.

Microglial Pruning: Relevance for Synaptic Dysfunction in Multiple Sclerosis and Related Experimental Models

Microglia, besides being able to react rapidly to a wide range of environmental changes, are also involved in shaping neuronal wiring. Indeed, they actively participate in the modulation of neuronal function by regulating the elimination (or “pruning”) of weaker synapses in both physiologic and pathologic processes. Mounting evidence supports their crucial role in early synaptic loss, which is emerging as a hallmark of several neurodegenerative diseases, including multiple sclerosis (MS) and its preclinical models. MS is an inflammatory, immune-mediated pathology of the white matter in which demyelinating lesions may cause secondary neuronal death. Nevertheless, primitive grey matter (GM) damage is emerging as an important contributor to patients’ long-term disability, since it has been associated with early and progressive cognitive decline (CD), which seriously worsens the quality of life of MS patients. Widespread synapse loss even in the absence of demyelination, axon degeneration and neuronal death has been demonstrated in different GM structures, thus raising the possibility that synaptic dysfunction could be an early and possibly independent event in the neurodegenerative process associated with MS. This review provides an overview of microglial-dependent synapse elimination in the neuroinflammatory process that underlies MS and its experimental models.

Dimethyl Fumarate Suppresses Demyelination and Axonal Loss through Reduction in Pro-Inflammatory Macrophage-Induced Reactive Astrocytes and Complement C3 Deposition

Dimethyl fumarate (DMF) is an oral agent for relapsing-remitting multiple sclerosis (RRMS). In this study, we investigated the therapeutic mechanism of DMF using experimental autoimmune encephalomyelitis (EAE). DMF treatment decreased the proliferation of T cells and the production of IL-17A and GM-CSF. DMF treatment also decreased the development and/or infiltration of macrophages in the central nervous system (CNS), and reduced the ratio of iNOS⁺ pro-inflammatory macrophage versus Ym1⁺ immunomodulatory macrophages. Furthermore, DMF treatment suppressed the deposition of complement C3 (C3) and development of reactive C3⁺ astrocytes. The decrease in iNOS⁺ macrophages, C3⁺astrocytes, and C3 deposition in the CNS resulted in the reduction in demyelination and axonal loss. This study suggests that the beneficial effects of DMF involve the suppression of iNOS⁺ pro-inflammatory macrophages, C3⁺ astrocytes, and deposition of C3 in the CNS.

Neuronal and glial CSF biomarkers in multiple sclerosis: a systematic review and meta-analysis

Multiple sclerosis (MS) is a neurodegenerative disease associated with inflammatory demyelination and astroglial activation, with neuronal and axonal damage as the leading factors of disability. We aimed to perform a meta-analysis to determine changes in CSF levels of neuronal and glial biomarkers, including neurofilament light chain (NFL), total tau (t-tau), chitinase-3-like protein 1 (CHI3L1), glial fibrillary acidic protein (GFAP), and S100B in various groups of MS (MS versus controls, clinically isolated syndrome (CIS) versus controls, CIS versus MS, relapsing-remitting MS (RRMS) versus progressive MS (PMS), and MS in relapse versus remission. According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, we included 64 articles in the meta-analysis, including 4071 subjects. For investigation of sources of heterogeneity, subgroup analysis, meta-regression, and sensitivity analysis were conducted. Meta-analyses were performed for comparisons including at least three individual datasets. NFL, GFAP, t-tau, CHI3L1, and S100B were higher in MS and NFL, t-tau, and CHI3L1 were also elevated in CIS patients than controls. CHI3L1 was the only marker with higher levels in MS than CIS. GFAP levels were higher in PMS versus RRMS, and NFL, t-tau, and CHI3L1 did not differ between different subtypes. Only levels of NFL were higher in patients in relapse than remission. Meta-regression showed influence of sex and disease severity on NFL and t-tau levels, respectively and disease duration on both. Added to the role of these biomarkers in determining prognosis and treatment response, to conclude, they may serve in diagnosis of MS and distinguishing different subtypes.

Neuroprotective versus Neuroinflammatory Roles of Complement: From Development to Disease

Complement proteins are ancient components of innate immunity that have emerged as crucial regulators of neural networks. We discuss these roles in the context of the CNS development, acute CNS viral infections, and post-infectious and noninfectious CNS disorders, with an emphasis on microglia-mediated loss of synapses. Despite extensive examples that implicate classical complement proteins and their receptors in CNS dysfunction, recent data suggest that they exert neuroprotective roles in CNS homeostasis through continued refinement of synaptic connections. Thorough understanding of the mechanisms involved in these processes may lead to novel targets for the treatment of CNS diseases involving aberrant complement-mediated synapse loss.

Targeted Complement Inhibition at Synapses Prevents Microglial Synaptic Engulfment and Synapse Loss in Demyelinating Disease

Multiple sclerosis (MS) is a demyelinating, autoimmune disease of the central nervous system. While work has focused on myelin and axon loss in MS, less is known about mechanisms underlying synaptic changes. Using postmortem human MS tissue, a preclinical nonhuman primate model of MS, and two rodent models of demyelinating disease, we investigated synapse changes in the visual system. Similar to other neurodegenerative diseases, microglial synaptic engulfment and profound synapse loss were observed. In mice, synapse loss occurred independently of local demyelination and neuronal degeneration but coincided with gliosis and increased complement component C3, but not C1q, at synapses. Viral overexpression of the complement inhibitor Crry at C3-bound synapses decreased microglial engulfment of synapses and protected visual function. These results indicate that microglia eliminate synapses through the alternative complement cascade in demyelinating disease and identify a strategy to prevent synapse loss that may be broadly applicable to other neurodegenerative diseases. VIDEO ABSTRACT.

Complement activation in cerebrospinal fluid in clinically isolated syndrome and early stages of relapsing remitting multiple sclerosis

To assess if markers of complement activation are associated with disease activity, C1q, C3, C3a and sC5b-9 levels in plasma and cerebrospinal fluid (CSF) were determined in 41 patients with clinically isolated syndrome (CIS) or remitting multiple sclerosis (RRMS), in a prospective longitudinal four-year cohort study. C1q in CSF (CSF-C1q) was significantly higher in patients than in controls. Baseline CSF-C1q and CSF-C3a correlated with several neuroinflammatory markers and neurofilament light chain levels. Baseline CSF-C3a correlated with the number of T2 lesions at baseline and new T2 lesions during follow-up. Baseline CSF-C3a was also significantly higher in patients with (n = 21) than in patients without (n = 20) signs of disease activity according to the NEDA-3 concept during one year of follow-up (p ≤ .01) Study results support that complement activation is involved in MS pathophysiology and that CSF-C3a carries prognostic information.

Cerebrospinal fluid complement system biomarkers in demyelinating disease

BACKGROUND

Multiple sclerosis (MS) can be difficult to differentiate from other demyelinating diseases, notably neuromyelitis optica spectrum disorder (NMOSD). We previously showed that NMOSD is distinguished from MS by plasma complement biomarkers.

OBJECTIVE

Here, we measure cerebrospinal fluid (CSF) complement proteins in MS, NMOSD and clinically isolated syndrome (CIS), a neurological episode that may presage MS, to test whether these distinguish NMOSD from MS and CIS.

MATERIALS AND METHODS

CSF (53 MS, 17 CIS, 11 NMOSD, 35 controls) was obtained; complement proteins (C4, C3, C5, C9, C1, C1q, Factor B (FB)), regulators (Factor I (FI), Factor H (FH), FH-Related Proteins 1, 2 and 5 (FHR125), C1 Inhibitor (C1INH), Properdin) and activation products (terminal complement complex (TCC), iC3b) were quantified by ELISA and results expressed relative to CSF total protein (μg/mg).

RESULTS

Compared to control CSF, (1) levels of C4, C1INH and Properdin were elevated in MS; (2) TCC, iC3b, FI and FHR125 were increased in CIS; and (3) all complement biomarkers except TCC, FHR125, Properdin and C5 were higher in NMOSD CSF. A statistical model comprising six analytes (C3, C9, FB, C1q, FI, Properdin) plus age/gender optimally differentiated MS from NMOSD.

Cerebrospinal fluid neurofilament light chain in multiple sclerosis and its subtypes: a meta-analysis of case-control studies

OBJECTIVE

Neurofilament is a biomarker of axonal injury proposed as a useful adjunct in the monitoring of patients with multiple sclerosis (MS). We conducted a systematic review and meta-analysis of case-control studies that have measured neurofilament light chain (NfL) levels in cerebrospinal fluid (CSF) of people with MS (pwMS), in order to determine whether, and to what degree, CSF NfL levels differentiate MS from controls, or the subtypes or stages of MS from each other.

METHODS

Guidelines on Preferred Reporting Items for Systematic Reviews and Meta-Analyses were followed. Electronic databases were searched for published and 'grey' literature, with 151 hits. Of 51 full articles screened, 20 were included in qualitative analysis, and 14 in meta-analysis.

RESULTS

CSF NfL was higher in 746 pwMS than 435 (healthy and disease) controls, with a moderate effect size of 0.61 (p < 0.00001). Mean CSF NfL levels were significantly higher in 176 pwMS with relapsing disease than 92 with progressive disease (2124.8 ng/L, SD 3348.9 vs 1121.4 ng/L, SD 947.7, p = 0.0108). CSF NfL in 138 pwMS in relapse (irrespective of MS subtype) was double that seen in 268 pwMS in remission (3080.6 ng/L, SD 4715.9 vs 1541.7 ng/L, SD 2406.5, p < 0.0001).

CONCLUSIONS

CSF NfL correlates with MS activity throughout the course of MS, reflecting the axonal damage in pwMS. Relapse is more strongly associated with elevated CSF NfL levels than the development of progression, and NfL may be most useful as a marker of disease 'activity' rather than as a marker of disability or disease stage.

Diagnostic Value of Cerebrospinal Fluid Neurofilament Light Protein in Neurology: A Systematic Review and Meta-analysis

IMPORTANCE

Neurofilament light protein (NfL) is elevated in cerebrospinal fluid (CSF) of a number of neurological conditions compared with healthy controls (HC) and is a candidate biomarker for neuroaxonal damage. The influence of age and sex is largely unknown, and levels across neurological disorders have not been compared systematically to date.

OBJECTIVES

To assess the associations of age, sex, and diagnosis with NfL in CSF (cNfL) and to evaluate its potential in discriminating clinically similar conditions.

DATA SOURCES

PubMed was searched for studies published between January 1, 2006, and January 1, 2016, reporting cNfL levels (using the search terms neurofilament light and cerebrospinal fluid) in neurological or psychiatric conditions and/or in HC.

STUDY SELECTION

Studies reporting NfL levels measured in lumbar CSF using a commercially available immunoassay, as well as age and sex.

DATA EXTRACTION AND SYNTHESIS

Individual-level data were requested from study authors. Generalized linear mixed-effects models were used to estimate the fixed effects of age, sex, and diagnosis on log-transformed NfL levels, with cohort of origin modeled as a random intercept.

MAIN OUTCOME AND MEASURE

The cNfL levels adjusted for age and sex across diagnoses.

RESULTS

Data were collected for 10 059 individuals (mean [SD] age, 59.7 [18.8] years; 54.1% female). Thirty-five diagnoses were identified, including inflammatory diseases of the central nervous system (n = 2795), dementias and predementia stages (n = 4284), parkinsonian disorders (n = 984), and HC (n = 1332). The cNfL was elevated compared with HC in a majority of neurological conditions studied. Highest levels were observed in cognitively impaired HIV-positive individuals (iHIV), amyotrophic lateral sclerosis, frontotemporal dementia (FTD), and Huntington disease. In 33.3% of diagnoses, including HC, multiple sclerosis, Alzheimer disease (AD), and Parkinson disease (PD), cNfL was higher in men than women. The cNfL increased with age in HC and a majority of neurological conditions, although the association was strongest in HC. The cNfL overlapped in most clinically similar diagnoses except for FTD and iHIV, which segregated from other dementias, and PD, which segregated from atypical parkinsonian syndromes.

CONCLUSIONS AND RELEVANCE

These data support the use of cNfL as a biomarker of neuroaxonal damage and indicate that age-specific and sex-specific (and in some cases disease-specific) reference values may be needed. The cNfL has potential to assist the differentiation of FTD from AD and PD from atypical parkinsonian syndromes.

Glial pathology and retinal neurotoxicity in the anterior visual pathway in experimental autoimmune encephalomyelitis

The animal model experimental autoimmune encephalomyelitis (EAE) has been used extensively in the past to test mechanisms that target peripheral immune cells for treatment of multiple sclerosis (MS). While there have been some notable successes in relapsing MS, the development of therapies for progressive multiple sclerosis (MS) has been hampered by lack of an appropriate animal model. Further, the mechanisms underlying CNS inflammation and neuronal injury remain incompletely elucidated. It is known that the MOG _35-55 EAE mouse model does not have insidious behavioral progression as occurs in people with MS, but there is significant neuronal and axonal injury in EAE, as a result of the inflammation. In the present study, we describe the time course of glial activation and retinal neurodegeneration in the EAE model, and highlight the utility of studying the anterior visual pathway for modeling mechanisms of neuronal injury that may recapitulate critical aspects of the pathology described in people with MS following optic neuritis and subclinical optic neuropathy. We show that A1 neurotoxic astrocytes are prevalent in optic nerve tissue and retina, and are associated with subsequent RGC loss in the most commonly used form of the EAE model induced by MOG _35-55 peptide in C57/B6 mice. We developed a semi-automatic method to quantify retinal ganglion cells (RGC) and show that RGCs remain intact at peak EAE (PID 16) but are significantly reduced in late EAE (PID 42). Postsynaptic proteins and neurites were also compromised in the retina of late EAE mice. The retinal pathology manifests weeks after the microglial and astrocyte activation, which were prominent in optic nerve tissues at PID 16. Microglia expressed iNOS and had increased gene expression of C1q, TNF-α, and IL-1α. Astrocytes expressed high levels of complement component 3 and other genes associated with A1 neurotoxic astrocytes. Our data suggest that EAE can be used to study the pathobiology of optic neuropathy and to examine the preclinical neuroprotective effects of drugs that target activation of neurotoxic A1 astrocytes.

Exome sequencing in multiple sclerosis families identifies 12 candidate genes and nominates biological pathways for the genesis of disease

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system characterized by myelin loss and neuronal dysfunction. Although the majority of patients do not present familial aggregation, Mendelian forms have been described. We performed whole-exome sequencing analysis in 132 patients from 34 multi-incident families, which nominated likely pathogenic variants for MS in 12 genes of the innate immune system that regulate the transcription and activation of inflammatory mediators. Rare missense or nonsense variants were identified in genes of the fibrinolysis and complement pathways (PLAU, MASP1, C2), inflammasome assembly (NLRP12), Wnt signaling (UBR2, CTNNA3, NFATC2, RNF213), nuclear receptor complexes (NCOA3), and cation channels and exchangers (KCNG4, SLC24A6, SLC8B1). These genes suggest a disruption of interconnected immunological and pro-inflammatory pathways as the initial event in the pathophysiology of familial MS, and provide the molecular and biological rationale for the chronic inflammation, demyelination and neurodegeneration observed in MS patients.

Biochemical Analysis and Association of Butyrylcholinesterase SNPs rs3495 and rs1803274 with Substance Abuse Disorder

Addiction is a complex mental and behavioral disorder that changes the neurochemistry and physiology of the brain. Genetics also plays a significant role in the pathophysiology of addiction. Butyrylcholinesterase (BChE), a cholinergic enzyme, has been implicated in the metabolism of various drugs, including cocaine, and an association between single-nucleotide polymorphisms (SNPs) of the butyrylcholinesterase gene (BCHE) and neuronal disorders has been reported. We report here the first investigation to be conducted on the status of BChE activity and the potential association of two BCHE gene SNPs, rs3495 (c.*189G > A) and rs1803274 (c.1699G>A, p.Ala567Thr, K-variant), with addiction vulnerability in heroin, hashish and polydrug users. Seventy-five individuals with an addiction to heroin, hashish and/or polydrug use were recruited to this study. BChE levels in the plasma were determined by Ellman's principle. SNPs were genotyped by standard procedures, followed by Sanger sequencing. Plasma BChE levels were found to be significantly higher (p ≤ 0.05) in addicts (mean ± standard error of the mean 0.031 ± 0.004 μmol/L/min; 95% confidence interval [CI] 0.024-0.038) than in non-addicts (controls) (0.014 ± 0.001 μmol/L/min; 95% CI 0.012-0.017). Statistical significant differences were also observed between the addicted cohorts. A statistically significant association for both SNPs (rs3495 and rs1803274) was not observed in addicted subjects tested in the dominant, recessive and allele genetic models, but trends of variations of the rs3495 risk G allele were noted. The authors conclude that BChE plays significant roles in addiction pathophysiology as increased BChE activity in blood samples obtained from the cohorts with addiction was evident. Further studies in this direction may provide novel approaches for the treatment of addiction, but studies with a larger sample size and different ethnic groups are warranted for broader conclusions to be drawn.

Increased Active OMI/HTRA2 Serine Protease Displays a Positive Correlation with Cholinergic Alterations in the Alzheimer's Disease Brain

OMI/HTRA2 (high-temperature requirement serine protease A2) is a mitochondrial serine protease involved in several cellular processes, including autophagy, chaperone activity, and apoptosis. Few studies on the role of OMI/HTRA2 in Alzheimer's disease (AD) are available, but none on its relationship with the cholinergic system and neurotrophic factors as well as other AD-related proteins. In this study, immunohistochemical analyses revealed that AD patients had a higher cytosolic distribution of OMI/HTRA2 protein compared to controls. Quantitative analyses on brain extracts indicated a significant increase in the active form of OMI/HTRA2 in the AD brain. Activated OMI/HTRA2 protein positively correlated with stress-associated read-through acetylcholinesterase activity. In addition, α7 nicotinic acetylcholine receptor gene expression, a receptor also known to be localized on the outer membrane of mitochondria, showed a strong correlation with OMI/HTRA2 gene expression in three different brain regions. Interestingly, the activated OMI/HTRA2 levels also correlated with the activity of the acetylcholine-biosynthesizing enzyme, choline acetyltransferase (ChAT); with levels of the neurotrophic factors, NGF and BDNF; with levels of the soluble fragments of amyloid precursor protein (APP); and with gene expression of the microtubule-associated protein tau in the examined brain regions. Overall, the results demonstrate increased levels of the mitochondrial serine protease OMI/HTRA2, and a coherent pattern of association between the activated form of OMI/HTRA2 and several key proteins involved in AD pathology. In this paper, we propose a new hypothetical model to highlight the importance and needs of further investigation on the role of OMI/HTRA2 in the mitochondrial function and AD.

The complement system as a biomarker of disease activity and response to treatment in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory, demyelinating, and neurodegenerative disease of the central nervous system. The complement system has an established role in the pathogenesis of MS, and evidence suggests that its components can be used as biomarkers of disease-state activity and response to treatment in MS. Plasma C4a levels have been found to be significantly elevated in patients with active relapsing-remitting MS (RRMS), as compared to both controls and patients with stable RRMS. C3 levels are also significantly elevated in the cerebrospinal fluid (CSF) of patients with RRMS, and C3 levels are correlated with clinical disability. Furthermore, increased levels of factor H can predict the transition from relapsing to progressive disease, since factor H levels have been found to increase progressively with disease progression over a 2-year period in patients transitioning from RRMS to secondary progressive (SP) MS. In addition, elevations in C3 are seen in primary progressive (PP) MS. Complement components can also differentiate RRMS from neuromyelitis optica. Response gene to complement (RGC)-32, a novel molecule induced by complement activation, is a possible biomarker of relapse and response to glatiramer acetate (GA) therapy, since RGC-32 mRNA expression is significantly decreased during relapse and increased in responders to GA treatment. The predictive accuracy of RGC-32 as a potential biomarker (by ROC analysis) is 90% for detecting relapses and 85% for detecting a response to GA treatment. Thus, complement components can serve as biomarkers of disease activity to differentiate MS subtypes and to measure response to therapy.

Convergent effects of a functional C3 variant on brain atrophy, demyelination, and cognitive impairment in multiple sclerosis

BACKGROUND

Complement system activation products are present in areas of neuroinflammation, demyelination, and neurodegeneration in brains of patients with multiple sclerosis (MS). C3 is a central element in the activation of complement cascades. A common coding variant in the C3 gene (rs2230199, C3R102G) affects C3 activity.

OBJECTIVES

To assess the effects of rs2230199 on MS severity using clinical, cognitive, and imaging measures.

METHODS

In total, 161 relapse-onset MS patients (Expanded Disability Status Scale (EDSS) ≤ 6) underwent physical assessments, cognitive tests (Paced Auditory Serial Addition Test (PASAT), Symbol Digit Modalities Test (SDMT), and California Verbal Learning Test (CVLT)), and magnetic resonance imaging (MRI). Lesion volumes were quantified semi-automatically. Voxel-wise analyses were performed to assess the effects of rs2230199 genotype on gray matter (GM) atrophy ( n = 155), white matter (WM) fractional anisotropy (FA; n = 105), and WM magnetization transfer ratio (MTR; n = 90).

RESULTS

While rs2230199 minor-allele dosage (C3-102G) showed no significant effect on EDSS and Multiple Sclerosis Functional Composite (MSFC), it was associated with worse cognitive performance ( p = 0.02), lower brain parenchymal fraction ( p = 0.003), and higher lesion burden ( p = 0.02). Moreover, voxel-wise analyses showed lower GM volume in subcortical structures and insula, and lower FA and MTR in several WM areas with higher copies of rs2230199 minor allele.

CONCLUSION

C3-rs2230199 affects white and GM damage as well as cognitive impairment in MS patients. Our findings support a causal role for complement system activity in the pathophysiology of MS.

Gut dysbiosis breaks immunological tolerance toward the central nervous system during young adulthood

Multiple sclerosis (MS) is an autoimmune disease targeting the central nervous system (CNS) mainly in young adults, and a breakage of immune tolerance to CNS self-antigens has been suggested to initiate CNS autoimmunity. Age and microbial infection are well-known factors involved in the development of autoimmune diseases, including MS. Recent studies have suggested that alterations in the gut microbiota, referred to as dysbiosis, are associated with MS. However, it is still largely unknown how gut dysbiosis affects the onset and progression of CNS autoimmunity. In this study, we investigated the effects of age and gut dysbiosis on the development of CNS autoimmunity in humanized transgenic mice expressing the MS-associated MHC class II (MHC-II) gene, HLA-DR2a, and T-cell receptor (TCR) genes specific for MBP87-99/DR2a that were derived from an MS patient. We show here that the induction of gut dysbiosis triggers the development of spontaneous experimental autoimmune encephalomyelitis (EAE) during adolescence and early young adulthood, while an increase in immunological tolerance with aging suppresses disease onset after late young adulthood in mice. Furthermore, gut dysbiosis induces the expression of complement C3 and production of the anaphylatoxin C3a, and down-regulates the expression of the Foxp3 gene and anergy-related E3 ubiquitin ligase genes. Consequently, gut dysbiosis was able to trigger the development of encephalitogenic T cells and promote the induction of EAE during the age window of young adulthood.

Complement is activated in progressive multiple sclerosis cortical grey matter lesions

BACKGROUND

The symptoms of multiple sclerosis (MS) are caused by damage to myelin and nerve cells in the brain and spinal cord. Inflammation is tightly linked with neurodegeneration, and it is the accumulation of neurodegeneration that underlies increasing neurological disability in progressive MS. Determining pathological mechanisms at play in MS grey matter is therefore a key to our understanding of disease progression.

METHODS

We analysed complement expression and activation by immunocytochemistry and in situ hybridisation in frozen or formalin-fixed paraffin-embedded post-mortem tissue blocks from 22 progressive MS cases and made comparisons to inflammatory central nervous system disease and non-neurological disease controls.

RESULTS

Expression of the transcript for C1qA was noted in neurons and the activation fragment and opsonin C3b-labelled neurons and glia in the MS cortical and deep grey matter. The density of immunostained cells positive for the classical complement pathway protein C1q and the alternative complement pathway activation fragment Bb was significantly increased in cortical grey matter lesions in comparison to control grey matter. The number of cells immunostained for the membrane attack complex was elevated in cortical lesions, indicating complement activation to completion. The numbers of classical (C1-inhibitor) and alternative (factor H) pathway regulator-positive cells were unchanged between MS and controls, whilst complement anaphylatoxin receptor-bearing microglia in the MS cortex were found closely apposed to cortical neurons. Complement immunopositive neurons displayed an altered nuclear morphology, indicative of cell stress/damage, supporting our finding of significant neurodegeneration in cortical grey matter lesions.

CONCLUSIONS

Complement is activated in the MS cortical grey matter lesions in areas of elevated numbers of complement receptor-positive microglia and suggests that complement over-activation may contribute to the worsening pathology that underlies the irreversible progression of MS.

Low activity of complement in the cerebrospinal fluid of the patients with various prion diseases

Background

The aim of this study was to analyze the state of activity and levels of complement in the cerebrospinal fluid (CSF) of patients with various prion diseases (PrDs).

Findings

The proteomic data emphasized the levels of 20 known complement components found in the CSF of the sCJD panel that were lower than those found in the non-PrD panel. 50 % of the complement hemolytic activity (CH50) assays revealed significantly lower activity of complement in the CSF of the sCJD panel. The decreased levels of three key complement subunits, C3a/α, C4β, and C9 in the CSF of the sCJD panel were verified by Western blots. Furthermore, the CH50 values in the CSF of 136 sCJD, 39 gCJD, 22 FFI and 145 non-CJD patients were individually tested. Compared with the control of non-PrD, the CH50 value in the CSF specimens of various PrDs, especially in three subtypes of inherited PrDs, were significantly lower. Relationship analysis identified that the CH50 activity in the CSF was negatively associated with the protein 14–3–3 positive in the CSF.

Conclusion

These results indicate a silent complement system in the CSF of PrD patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-016-0128-7) contains supplementary material, which is available to authorized users.

Complement Receptor 2 is increased in cerebrospinal fluid of multiple sclerosis patients and regulates C3 function

Besides its vital role in immunity, the complement system also contributes to the shaping of the synaptic circuitry of the brain. We recently described that soluble Complement Receptor 2 (sCR2) is part of the nerve injury response in rodents. We here study CR2 in context of multiple sclerosis (MS) and explore the molecular effects of CR2 on C3 activation. Significant increases in sCR2 levels were evident in cerebrospinal fluid (CSF) from both patients with relapsing-remitting MS (n=33; 6.2ng/mL) and secondary-progressive MS (n=9; 7.0ng/mL) as compared to controls (n=18; 4.1ng/mL). Furthermore, CSF sCR2 levels correlated significantly both with CSF C3 and C1q as well as to a disease severity measure. In vitro, sCR2 inhibited the cleavage and down regulation of C3b to iC3b, suggesting that it exerts a modulatory role in complement activation downstream of C3. These results propose a novel function for CR2/sCR2 in human neuroinflammatory conditions.

Ischemic, traumatic and neurodegenerative brain inflammatory changes

This review serves to link the role of the immune system in the neuropathology of acute ischemic stroke, traumatic brain injury and neurodegenerative disease. The blood–brain barrier delineates the CNS from the peripheral immune system. However, the blood–cerebrospinal fluid barrier acts as a gate between the periphery and the brain, permitting immune activity crosstalk and modulation. In acute ischemic stroke, traumatic brain injury and other neurodegenerative diseases, the blood–brain barrier is compromised and an influx of inflammatory cells and plasma proteins occurs, resulting in edema, demyelination, cell dysfunction and death, and neurobehavioral changes. The role of the complement system, key cytokines, microglia and other neuroglia in brain degenerative pathology will be discussed.

Adipsin Is Associated with Multiple Sclerosis: A Follow-Up Study of Adipokines

Background and Objective. The role of adipokines in regulation of immune responses has been recognized, but very little is known about their impact on multiple sclerosis (MS). In this study, we analysed whether the major adipokines are differentially expressed in plasma of patients with different MS subtypes and clinically isolated syndrome (CIS) and explored their association with major disease characteristics. Methods. The levels of adiponectin, adipsin, leptin, and resistin in the plasma of 80 patients with different subtypes of MS and CIS were followed up annually over the two years. The data obtained were correlated with disease activity, EDSS and volumes of T1-weighted lesions (T1-LV), and fluid attenuation inversion recovery lesions (FLAIR-LV) on MRI. Results. In MS group, a correlation was found between the level of adipsin and EDSS score at baseline (r = 0.506, p < 0.001). In RRMS, the levels of adipsin correlated with EDSS scores (r = 0.542, p = 0.002), T1-LV (r = 0.410, p = 0.034), and FLAIR-LV (r = 0.601, p = 0.0001) at baseline and an increase in the T1-LV over the follow-up (r = 0.582, p = 0.003). Associations with other adipokines were not detected. Conclusion. Our exploratory study provides novel insights on the impact of adipokines in MS and suggests that adipsin exerts predictive potential as a biomarker of neurodegeneration.