Sera from patients with multifocal motor neuropathy disrupt the blood-nerve barrier

Therapeutic potentials of adoptive cell therapy in immune-mediated neuropathy

Immune-mediated neuropathy (IMN) is a group of heterogenous neuropathies caused by intricate autoimmune responses. For now, known mechanisms of different IMN subtypes involve the production of autoantibodies, complement activation, enhanced inflammation and subsequent axonal/demyelinating nerve damages. Recent therapeutic studies mainly focus on specific antibodies and small molecule inhibitors previously approved in rheumatoid diseases. Initial strategies based on the pathophysiologic features of IMN should be explored. Adoptive cell therapy (ACT) refers to the emerging immunotherapies in which circulating immunocytes are collected from peripheral blood and modified with killing and immunomodulatory capacities. It consists of chimeric antigen receptor-T cell therapy, T cell receptor-engineered T cell, CAR-Natural killer cell therapy, and others. In the last decade, ACT has demonstrated extraordinary potentials in treating cancers, infectious diseases and autoimmune diseases. Versatile combinations of targets, chimeric domains and effector cells greatly empower ACT to treat complicated immune disorders. In this review, we summarized the advances of ACT and envisioned suitable strategies for different IMN subtypes.

Novel Insight Into the Role of Immune Dysregulation in Amyotrophic Lateral Sclerosis Based on Bioinformatic Analysis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the progressive degeneration of motor neurons. The causative pathogenic mechanisms in ALS remain unclear, limiting the development of treatment strategies. Neuroinflammation and immune dysregulation were involved in the disease onset and progression of several neurodegenerative disorders, including ALS. In this study, we carried out a bioinformatic analysis using publicly available datasets from Gene Expression Omnibus (GEO) to investigate the role of immune cells and genes alterations in ALS. Single-sample gene set enrichment analysis revealed that the infiltration of multiple types of immune cells, including macrophages, type-1/17 T helper cells, and activated CD4 + /CD8 + T cells, was higher in ALS patients than in controls. Weighted gene correlation network analysis identified immune genes associated with ALS. The Gene Ontology analysis revealed that receptor and cytokine activities were the most highly enriched terms. Pathway analysis showed that these genes were enriched not only in immune-related pathways, such as cytokine-cytokine receptor interaction, but also in PI3K-AKT and MAPK signaling pathways. Nineteen immune-related genes (C3AR1, CCR1, CCR5, CD86, CYBB, FCGR2B, FCGR3A, HCK, ITGB2, PTPRC, TLR1, TLR2, TLR7, TLR8, TYROBP, VCAM1, CD14, CTSS, and FCER1G) were identified as hub genes based on least absolute shrinkage and selection operator analysis. This gene signature could differentiate ALS patients from non-neurological controls (p < 0.001) and predict disease occurrence (AUC = 0.829 in training set; AUC = 0.862 in test set). In conclusion, our study provides potential biomarkers of ALS for disease diagnosis and therapeutic monitoring.

Multifocal motor neuropathy: controversies and priorities

Despite 30 years of research there are still significant unknowns and controversies associated with multifocal motor neuropathy (MMN) including disease pathophysiology, diagnostic criteria and treatment. Foremost relates to the underlying pathophysiology, specifically whether MMN represents an axonal or demyelinating neuropathy and whether the underlying pathophysiology is focused at the node of Ranvier. In turn, this discussion promotes consideration of therapeutic approaches, an issue that becomes more directed in this evolving era of precision medicine. It is generally accepted that MMN represents a chronic progressive immune-mediated motor neuropathy clinically characterised by progressive asymmetric weakness and electrophysiologically by partial motor conduction block. Anti-GM1 IgM antibodies are identified in at least 40% of patients. There have been recent developments in the use of neuromuscular ultrasound and MRI to aid in diagnosing MMN and in further elucidation of its pathophysiological mechanisms. The present Review will critically analyse the knowledge accumulated about MMN over the past 30 years, culminating in a state-of-the-art approach to therapy.

Different distribution of demyelination in chronic inflammatory demyelinating polyneuropathy subtypes

In demyelinating polyneuropathies, distribution patterns of demyelination reflect underlying pathogenesis. Median and ulnar nerve conduction studies were reviewed in 85 typical chronic inflammatory demyelinating polyneuropathy (CIDP) patients and 29 multifocal acquired demyelinating sensory and motor neuropathy (MADSAM). Distal latencies were prolonged in typical CIDP and near normal in MADSAM. Abnormal amplitude reductions in the nerve trunks were more frequent in MADSAM than typical CIDP. Presumably because the blood-nerve barrier is anatomically deficient at the distal nerve terminals, antibody-mediated demyelination is a major pathophysiology in typical CIDP. In contrast, blood-nerve barrier breakdown is likely to be predominant in MADSAM.

Increased IP-10 production by blood-nerve barrier in multifocal acquired demyelinating sensory and motor neuropathy and multifocal motor neuropathy

OBJECTIVE

Dysfunction of the blood-nerve barrier (BNB) plays important roles in chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN). The aim of the present study was to identify the candidate cytokines/chemokines that cause the breakdown of the BNB using sera from patients with CIDP and MMN.

METHODS

We determined the levels of 27 cytokines and chemokines in human peripheral nerve microvascular endothelial cells (PnMECs) after exposure to sera obtained from patients with CIDP variants (typical CIDP and multifocal acquired demyelinating sensory and motor neuropathy [MADSAM]), MMN and amyotrophic lateral sclerosis (ALS), and healthy controls (HC), using a multiplexed fluorescent bead-based immunoassay system.

RESULTS

The induced protein (IP)10 level in the cells in both the MADSAM and MMN groups was markedly increased in comparison with the typical CIDP, ALS and HC groups. The other cytokines, including granulocyte colony-stimulating factor,vascular endothelial growth factor (VEGF) and interleukin-7, were also significantly upregulated in the MADSAM group. The increase of IP-10 produced by PnMECs was correlated with the presence of conduction block in both the MADSAM and MMN groups.

CONCLUSION

The autocrine secretion of IP-10 induced by patient sera in PnMECs was markedly upregulated in both the MADSAM and MMN groups. The overproduction of IP-10 by PnMECs leads to the focal breakdown of the BNB and may help to mediate the transfer of pathogenic T cells across the BNB, thereby resulting in the appearance of conduction block in electrophysiological studies of patients with MADSAM and MMN.

Immune-mediated neuropathies

Since the discovery of an acute monophasic paralysis, later coined Guillain-Barré syndrome, almost 100 years ago, and the discovery of chronic, steroid-responsive polyneuropathy 50 years ago, the spectrum of immune-mediated polyneuropathies has broadened, with various subtypes continuing to be identified, including chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and multifocal motor neuropathy (MMN). In general, these disorders are speculated to be caused by autoimmunity to proteins located at the node of Ranvier or components of myelin of peripheral nerves, although disease-associated autoantibodies have not been identified for all disorders. Owing to the numerous subtypes of the immune-mediated neuropathies, making the right diagnosis in daily clinical practice is complicated. Moreover, treating these disorders, particularly their chronic variants, such as CIDP and MMN, poses a challenge. In general, management of these disorders includes immunotherapies, such as corticosteroids, intravenous immunoglobulin or plasma exchange. Improvements in clinical criteria and the emergence of more disease-specific immunotherapies should broaden the therapeutic options for these disabling diseases.

Pathophysiological Changes of Physical Barriers of Peripheral Nerves After Injury

Peripheral nerves are composed of complex layered anatomical structures, including epineurium, perineurium, and endoneurium. Perineurium and endoneurium contain many physical barriers, including the blood-nerve barrier at endoneurial vessels and the perineurial barrier. These physical barriers help to eliminate flux penetration and thus contribute to the establishment of a stable microenvironment. In the current review, we introduce the anatomical compartments and physical barriers of peripheral nerves and then describe the cellular and molecular basis of peripheral physical barriers. We also specifically explore peripheral nerve injury-induced changes of peripheral physical barriers, including elevated endoneurial fluid pressure, increased leakage of tracer, decreased barrier-type endothelial cell ratio, and altered distributions and expressions of cellular junctional proteins. The understanding of the pathophysiological changes of physical barriers following peripheral nerve injury may provide a clue for the treatment of peripheral nerve injury.

General Approach to Peripheral Nerve Disorders

PURPOSE OF REVIEW

This article provides a conceptual framework for the evaluation of patients with suspected polyneuropathy to enhance the clinician's ability to localize and confirm peripheral nervous system pathology and, when possible, identify an etiologic diagnosis through use of rational clinical and judicious testing strategies.

RECENT FINDINGS

Although these strategies are largely time-honored, recent insights pertaining to the pathophysiology of certain immune-mediated neuropathies and to evolving genetic testing strategies may modify the way that select causes of neuropathy are conceptualized, evaluated, and managed.

SUMMARY

The strategies suggested in this article are intended to facilitate accurate bedside diagnosis in patients with suspected polyneuropathy and allow efficient and judicious use of supplementary testing and application of rational treatment when indicated.

Fingolimod promotes blood-nerve barrier properties in vitro

OBJECTIVE

The main effect of fingolimod is thought to be functional antagonism of lymphocytic S1P1 receptors and the prevention of lymphocyte egress from lymphoid tissues, thereby reducing lymphocyte infiltration into the nervous system. However, a growing number of reports suggest that fingolimod also has a direct effect on several cell types in the nervous system. Although we previously reported that fingolimod enhances blood-brain barrier (BBB) functions, there have been no investigations regarding the blood-nerve barrier (BNB). In this study, we examine how fingolimod affects the BNB.

METHODS

An immortalized human peripheral nerve microvascular endothelial cell line (HPnMEC) was used to evaluate BNB barrier properties. We examined tight junction proteins and barrier functions of HPnMECs in conditioned medium with or without fingolimod-phosphate and blood sera from patients with typical chronic inflammatory demyelinating polyneuropathy (CIDP).

RESULTS

Incubation with fingolimod-phosphate increased levels of claudin-5 mRNA and protein as well as TEER values in HPnMECs. Conversely, typical CIDP sera decreased claudin-5 mRNA/protein levels and TEER values in HPnMECs; however, pretreatment with fingolimod-phosphate inhibited the effects of the typical CIDP sera.

CONCLUSIONS

Fingolimod-phosphate directly modifies the BNB and enhances barrier properties. This mechanism may be a viable therapeutic target for CIDP, and fingolimod may be useful in patients with typical CIDP who have severe barrier disruption.

Hello from the Other Side: How Autoantibodies Circumvent the Blood-Brain Barrier in Autoimmune Encephalitis

Antibodies against neuronal receptors and synaptic proteins are associated with autoimmune encephalitides (AE) that produce movement and psychiatric disorders. In order to exert their pathological effects on neural circuits, autoantibodies against central nervous system (CNS) targets must gain access to the brain and spinal cord by crossing the blood–brain barrier (BBB), a tightly regulated gateway formed by endothelial cells lining CNS blood vessels. To date, the pathogenic mechanisms that underlie autoantibody-triggered encephalitic syndromes are poorly understood, and how autoantibodies breach the barrier remains obscure for almost all AE syndromes. The relative importance of cellular versus humoral immune mechanisms for disease pathogenesis also remains largely unexplored. Here, we review the proposed triggers for various autoimmune encephalopathies and their animal models, as well as basic structural features of the BBB and how they differ among various CNS regions, a feature that likely underlies some regional aspects of autoimmune encephalitis pathogenesis. We then discuss the routes that antibodies and immune cells employ to enter the CNS and their implications for AE. Finally, we explore future therapeutic strategies that may either preserve or restore barrier function and thereby limit immune cell and autoantibody infiltration into the CNS. Recent mechanistic insights into CNS autoantibody entry indicate promising future directions for therapeutic intervention beyond current, short-lived therapies that eliminate circulating autoantibodies.

Different electrophysiological profiles and treatment response in 'typical' and 'atypical' chronic inflammatory demyelinating polyneuropathy

BACKGROUND

Chronic inflammatory demyelinating polyneuropathy (CIDP) is currently classified into 'typical' CIDP and 'atypical' subtypes such as multifocal acquired demyelinating sensory and motor neuropathy (MADSAM).

OBJECTIVES

To assess the frequency of CIDP subtypes, and to elucidate clinical and electrophysiological features, and treatment response in each subtype.

METHODS

We reviewed data from 100 consecutive patients fulfilling criteria for CIDP proposed by the European Federation of Neurological Societies and the Peripheral Nerve Society. The Kaplan-Meier curve was used to estimate long-term outcome.

RESULTS

Patients were classified as having typical CIDP (60%), MADSAM (34%), demyelinating acquired distal symmetric neuropathy (8%) or pure sensory CIDP (1%). Compared with patients with MADSAM, patients with typical CIDP showed more rapid progression and severe disability, and demyelination predominant in the distal nerve segments. MADSAM was characterised by multifocal demyelination in the nerve trunks. Abnormal median-normal sural sensory responses were more frequently found for typical CIDP (53% vs 13%). Patients with typical CIDP invariably responded to corticosteroids, immunoglobulin or plasmapheresis, whereas patients with MADSAM were more refractory to these treatments. The Kaplan-Meier analyses showed that 64% of patients with typical CIDP and 41% of patients with MADSAM had a clinical remission 5 years later (p=0.02).

CONCLUSIONS

Among the CIDP spectrum, typical CIDP and MADSAM are the major subtypes, and their pathophysiology appears to be distinct. In typical CIDP, the distal nerve terminals and possibly the nerve roots, where the blood-nerve barrier is anatomically deficient, are preferentially affected, raising the possibility of antibody-mediated demyelination, whereas cellular immunity with breakdown of the barrier may be important in MADSAM neuropathy.

Relation between symptoms and pathophysiology in inflammatory neuropathies: Controversies and hypotheses

This review attempts to explain the symptoms experienced by patients with inflammatory neuropathies by pathophysiological events. The emphasis is not on the primary events that may cause a particular illness but on downstream events taking place in peripheral nerves or muscles. Symptoms that will be discussed include sensory predominance, motor predominance, activity-induced weakness, heat paresis, and cold paresis. Each symptom is associated with, but not limited to, particular neuropathies.

The pathogenesis of multifocal motor neuropathy and an update on current management options

Multifocal motor neuropathy (MMN) is a rare and disabling disease. Several experimental studies and clinical data are strongly suggestive of an immune-mediated pathogenesis, although underlying mechanisms in MMN seem to be very specific, mainly because of the presence of IgM anti-GM1 serum antibodies and the dramatic response to intravenous immunoglobulins (IVIg). The origin of antiganglioside antibodies and the way in which they act at the molecular level remain unclear. Several studies have demonstrated the key role of complement activation in the underlying mechanisms of MMN, as well as in animal models of acute motor axonal neuropathy (AMAN). Deposition of the membrane attack complex may disrupt the architecture of the nodes of Ranvier and paranodal areas, causing local disruption of nodal sodium-channel clusters. In patients with MMN, muscle weakness is the consequence of conduction blocks (CB), which leads to secondary axonal degeneration, consequently the aim of the treatment is to reverse CB at early stages of the disease. High-dose immunoglobulin is to date the only therapy which has proven efficacy in MMN patients in providing transient improvement of muscle strength, but long-term follow-up studies show a progressive motor decline. Therefore, other therapies are needed to improve the conduction nerve properties in long-term design. The reduction of complement activation and more generally the gain in paranodal stabilization could be directions for future therapeutic strategies.

[2013: what's new in inflammatory neuropathies]

Several high-quality publications were published in 2013 and some major trials studies were started. In Guillain-Barré syndrome, events included the launch of IGOS and a better understanding of diagnostic limits, the effect of influenza vaccination, and better care, but uncertainty remains about analgesics. A new mouse model was also described. In chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), diagnostic pitfalls can be recalled. Our knowledge of underlying pathophysiological processes has improved, and the value of monitoring with function and deficit scores has been demonstrated. IVIG can sometimes be effective longer than expected, but CIDP remains sensitive to corticosteroids, particularly with the long-term beneficial effects of megadose dexamethasone. The impact of fingolimod remains to be demonstrated in an ongoing trial. Advances concerning multifocal motor neuropathy, inflammatory plexopathy, and neuropathy with anti -MAG activity are discussed but treatments already recognized as effective should not be changed. Imaging of peripheral nerve progresses.

Severity and patterns of blood-nerve barrier breakdown in patients with chronic inflammatory demyelinating polyradiculoneuropathy: correlations with clinical subtypes

Objective

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is currently classified into clinical subtypes, including typical and atypical forms (multifocal acquired demyelinating sensory and motor neuropathy (MADSAM) and distal acquired demyelinating symmetric neuropathy (DADS)). The aim of this study was to elucidate the patterns and severity of breakdown of the blood-nerve barrier (BNB) in each CIDP subtype.

Methods

We evaluated the effects of sera obtained from patients with typical CIDP, MADSAM and DADS and control subjects on the expression levels of tight junction proteins and transendothelial electrical resistance (TEER) value in human peripheral nerve microvascular endothelial cells (PnMECs).

Results

The sera obtained from the patients with the three clinical phenotypes of CIDP decreased the amount of claudin-5 protein levels and TEER values in the PnMECs. In addition, the sera obtained from typical CIDP patients more prominently reduced claudin-5 protein levels and TEER values in the PnMECs than did that obtained from the MADSAM and DADS patients. Furthermore, the severity of BNB disruption after exposure to the sera was associated with higher Hughes grade, lower MRC score, more pronounced slowing of motor nerve conduction in the median nerve and higher frequency of abnormal temporal dispersion.

Conclusions

Sera derived from typical CIDP patients destroy the BNB more severely than those from MADSAM or DADS patients. The extent of BNB disruption in the setting of CIDP is associated with clinical disability and demyelination in the nerve trunk. These observations may explain the phenotypical differences between CIDP subtypes.

MMN: from immunological cross-talk to conduction block

Multifocal motor neuropathy (MMN) is a rare inflammatory neuropathy characterized by progressive, asymmetric distal limb weakness and conduction block (CB). Clinically MMN is a pure motor neuropathy, which as such can mimic motor neuron disease. GM1-specific IgM antibodies are present in the serum of approximately half of all MMN patients, and are thought to play a key role in the immune pathophysiology. Intravenous immunoglobulin (IVIg) treatment has been shown to be effective in MMN in five randomized placebo-controlled trials. Despite long-term treatment with intravenous immunoglobulin (IVIg), which is efficient in the majority of patients, slowly progressive axonal degeneration and subsequent muscle weakness cannot be fully prevented. In this review, we will discuss the current understanding of the immune pathogenesis underlying MMN and how this may cause CB, available treatment strategies and future therapeutic targets.