Neurofilament a biomarker of neurodegeneration in autoimmune encephalomyelitis

Profiling Blood-Based Neural Biomarkers and Cytokines in Experimental Autoimmune Encephalomyelitis Model of Multiple Sclerosis Using Single-Molecule Array Technology

Experimental autoimmune encephalomyelitis (EAE) is a preclinical animal model widely used to study multiple sclerosis (MS). Blood-based analytes, including cytokines and neural biomarkers are the predictors of neurodegeneration, disease activity, and disability in patients with MS. However, understudied confounding factors cause variation in reports on EAE across animal strains/studies, limiting the utility of these biomarkers for predicting disease activity. In this study, we investigated blood-based analyte profiles, including neural markers (NFL and GFAP) and cytokines (IL-6, IL-17, IL-12p70, IL-10, and TNF-α), in two clinically distinct EAE models: relapsing-remitting (RR)-EAE and chronic-EAE. Ultrasensitive single-molecule array technology (SIMOA, Quanterix) was used to profile the analytes in the blood plasma of mice at the acute, chronic, and progressive phases of disease. In both models, NFL was substantially increased during post-disease onset across all phases, with a pronounced increase observed in chronic-EAE. The leakage of GFAP into peripheral blood was also greater after disease onset in both EAE models, especially in the acute phase of chronic-EAE. Among all cytokines, only IL-10 had consistently lower levels in both EAE models throughout the course of disease. This study suggests NFL, GFAP, and IL-10 as potential translational predictors of disease activity in EAE, making them potential candidates as surrogate markers for the preclinical testing of therapeutic interventions in animal models of MS.

Profiling blood-based neural biomarkers and cytokines in experimental autoimmune encephalomyelitis model of multiple sclerosis using single-molecule array technology

Experimental autoimmune encephalomyelitis (EAE) is a preclinical animal model widely used to study multiple sclerosis (MS). Blood-based cytokines and neural biomarkers are predictors of neurodegeneration, disease activity, and disability in patients with MS. However, understudied confounding factors cause variation in reports on EAE across animal strains/studies, limiting the utility of these biomarkers for predicting disease activity. In this study, we investigated blood-based analyte profiles, including neural markers (NFL and GFAP) and cytokines (IL-6, IL-17, IL-12p70, IL-10, and TNF-α), in two clinically distinct EAE models: relapsing-remitting (RR)-EAE and chronic-EAE. Ultrasensitive single-molecule array technology (SIMOA, Quanterix) was used to profile the analytes in blood plasma of mice at the acute, chronic, and progressive phases of disease. In both models, NFL was substantially increased during post-disease onset at the peak, chronic, and progressive phases, with pronounced increase in chronic-EAE. Leakage of GFAP into peripheral blood was also greater after disease onset in both EAE models, especially in the acute phase of chronic-EAE. Among all cytokines, only IL-10 had consistently lower levels in both EAE models throughout the course of disease. This study suggests NFL, GFAP, and IL-10 as potential translational predictors of disease activity in EAE, making them potential candidates for surrogate markers for preclinical testing of therapeutic interventions in animal models of MS.

Developing Biomarkers for MS

Existing clinical outcomes of disease activity, including relapse rates, are inherently insensitive to the underlying pathological process in MS. Moreover, it is extremely difficult to measure clinical disability in patients, which is often a retrospective assessment, and definitely not within the time frame of a clinical trial. Biomarkers , conversely are more specific for a pathologic process and if used correctly can prove invaluable in the diagnosis, stratification and monitoring of disease activity, including any subclinical activity which is not visible to the naked eye. In this chapter, we discuss the development of neurofilaments as surrogate outcomes of disability in MS. The validation and qualification are vital steps in biomarker development and to gaining acceptance in scientific community, and the pitfalls leading up to this are also discussed.

Antiphospholipid autoantibodies as blood biomarkers for detection of early stage Alzheimer's disease

A robust blood biomarker is urgently needed to facilitate early prognosis for those at risk for Alzheimer's disease (AD). Redox reactive autoantibodies (R-RAAs) represent a novel family of antibodies detectable only after exposure of cerebrospinal fluid (CSF), serum, plasma or immunoglobulin fractions to oxidizing agents. We have previously reported that R-RAA antiphospholipid antibodies (aPLs) are significantly decreased in the CSF and serum of AD patients compared to healthy controls (HCs). These studies were extended to measure R-RAA aPL in serum samples obtained from Alzheimer's Disease Neuroimaging Initiative (ADNI). Serum samples from the ADNI-1 diagnostic groups from participants with mild cognitive impairment (MCI), AD and HCs were blinded for diagnosis and analyzed for R-RAA aPL by ELISA. Demographics, cognitive data at baseline and yearly follow-up were subsequently provided by ADNI after posting assay data. As observed in CSF, R-RAA aPL in sera from the AD diagnostic group were significantly reduced compared to HC. However, the sera from the MCI population contained significantly elevated R-RAA aPL activity relative to AD patient and/or HC sera. The data presented in this study indicate that R-RAA aPL show promise as a blood biomarker for detection of early AD, and warrant replication in a larger sample. Longitudinal testing of an individual for increases in R-RAA aPL over a previously established baseline may serve as a useful early sero-epidemiologic blood biomarker for individuals at risk for developing dementia of the Alzheimer's type.

Autoimmunity in 2012

The initiation and perpetuation of autoimmunity recognize numerous checkpoints, from the genomic susceptibility to the breakdown of tolerance. This latter phenomenon includes the loss of B cell anergy and T regulatory cell failure, as well as the production of autoantibodies and autoreactive T cells. These mechanisms ultimately lead to tissue injury via different mechanisms that span from the production of proinflammatory cytokines to the chemotaxis of immune cells to the target sites. The pathways to autoimmunity have been widely investigated over the past year and resulted in a number of articles in peer-reviewed journals that has increased by nearly 10 % compared to 2011. We herein follow on the attempt to provide a brief discussion of the majority of articles on autoimmune diseases that were published in the major immunology journals in the previous solar year. The selection is necessarily arbitrary and may thus not be seen as comprehensive but reflects current research trends. Indeed, 2012 articles were mostly dedicated to define new and old mechanisms with potential therapeutic implications in autoimmunity in general, though based on specific clinical conditions or animal models. As paradigmatic examples, the environmental influence on autoimmunity, Th17 changes modulating the autoimmune response, serum autoantibodies and B cell changes as biomarkers and therapeutic targets were major issues addressed by experimental articles in 2012. Further, a growing number of studies investigated the sex bias of autoimmunity and supported different working hypotheses to explain the female predominance, including sex chromosome changes and reproductive life factors. In conclusion, the resulting scenario illustrates that common factors may underlie different autoimmune diseases and this is well represented by the observed alterations in interferon-α and TGFβ or by the shared signaling pathways.

Immune reactivity to neurofilament proteins in the clinical staging of amyotrophic lateral sclerosis

BACKGROUND

Neurofilament (NF) proteins detection in biological fluids as a by-product of axonal loss is technically challenging and to date relies mostly on cerebrospinal fluid (CSF) measurements. Plasma antibodies against NF proteins and particularly to their soluble light chain (NF-L) could be a more practical surrogate marker for disease staging in amyotrophic lateral sclerosis (ALS), an invariably fatal and clinically heterogeneous neuromuscular disorder.

METHODOLOGY

We have used a recombinant neurofilament light chain (NF-L) protein for the ELISA detection of antibodies against NF proteins in plasma samples from a well-characterised cohort of ALS individuals (n:73). The use of an established functional rating scale and of a recently proposed staging of disease progression allowed stratification of the ALS cohort based on disease stage, site of onset, survival and speed of disease progression.

RESULTS

Antibody levels to NF proteins in plasma were significantly higher in ALS individuals compared to healthy controls (p<0.001). Higher NF plasma immunoreactivity was seen in advanced ALS cases (stage IVA-B) compared to earlier phases of the disease (p<0.05). There was no difference in anti-NF plasma antibodies between ALS individuals treated with riluzole and untreated patients; although riluzole-treated ALS cases with an earlier age of onset and with a shorter diagnostic delay displayed higher anti-NFL antibody levels compared to untreated ALS patients with similar features.

CONCLUSIONS

Immunoreactivity to plasma NF-L and homologous NF proteins is informative of the stage of disease progression in ALS. The determination of NF antibody levels in plasma could be added to the growing panel of disease-monitoring biomarkers in ALS targeting cytoskeletal antigens.

Lesional-targeting of neuroprotection to the inflammatory penumbra in experimental multiple sclerosis

Progressive multiple sclerosis is associated with metabolic failure of the axon and excitotoxicity that leads to chronic neurodegeneration. Global sodium-channel blockade causes side effects that can limit its use for neuroprotection in multiple sclerosis. Through selective targeting of drugs to lesions we aimed to improve the potential therapeutic window for treatment. This was assessed in the relapsing-progressive experimental autoimmune encephalomyelitis ABH mouse model of multiple sclerosis using conventional sodium channel blockers and a novel central nervous system-excluded sodium channel blocker (CFM6104) that was synthesized with properties that selectively target the inflammatory penumbra in experimental autoimmune encephalomyelitis lesions. Carbamazepine and oxcarbazepine were not immunosuppressive in lymphocyte-driven autoimmunity, but slowed the accumulation of disability in experimental autoimmune encephalomyelitis when administered during periods of the inflammatory penumbra after active lesion formation, and was shown to limit the development of neurodegeneration during optic neuritis in myelin-specific T cell receptor transgenic mice. CFM6104 was shown to be a state-selective, sodium channel blocker and a fluorescent p-glycoprotein substrate that was traceable. This compound was >90% excluded from the central nervous system in normal mice, but entered the central nervous system during the inflammatory phase in experimental autoimmune encephalomyelitis mice. This occurs after the focal and selective downregulation of endothelial p-glycoprotein at the blood-brain barrier that occurs in both experimental autoimmune encephalomyelitis and multiple sclerosis lesions. CFM6104 significantly slowed down the accumulation of disability and nerve loss in experimental autoimmune encephalomyelitis. Therapeutic-targeting of drugs to lesions may reduce the potential side effect profile of neuroprotective agents that can influence neurotransmission. This class of agents inhibit microglial activity and neural sodium loading, which are both thought to contribute to progressive neurodegeneration in multiple sclerosis and possibly other neurodegenerative diseases.

Noninvasive assessments of optic nerve neurodegeneration in transgenic mice with isolated optic neuritis

PURPOSE

To determine if phosphorylated neurofilament heavy chain (pNF-H) released into the bloodstream and the pattern ERG are noninvasive indicators of neurodegeneration in experimental optic neuritis.

METHODS

Serum from Myelin oligodendrocyte glycoprotein (MOG)-specific T cell receptor-positive (TCR+) transgenic mice that develop isolated optic neuritis usually without any other characteristic lesions of inflammation or demyelination in the spinal cord and littermates negative for the transgene were assayed for the presence of serum phosphorylated neurofilament H (pNF-H). In vivo measurements of optic nerve and retinal ganglion cell injury were assessed by magnetic resonance imaging (MRI), optical coherence tomography (OCT), and pattern electroretinogram (PERG). Automated two dimensional fluorescence differential in-gel electrophoresis (2D-DIGE) of pooled optic nerve samples, light, and transmission electron micrographs were used to evaluate optic atrophy postmortem.

RESULTS

We found an almost 3-fold elevation in serum pNF-H levels in MOG+ mice relative to MOG-littermates (P = 0.02). 2D-DIGE revealed a 3-fold reduction in optic nerve neurofilaments. Visual function assessed by the PERG was reduced by one-quarter (P = 0.033) and latencies increased by 38% (P = 0.036). MOG+ mice with the lowest PERG amplitudes had optic nerve atrophy visualized by MRI. Optic nerve diameters were reduced by one-third (P = 0.0001) and axon counts reduced by more than two-thirds. Histopathology of the spinal cords was normal.

CONCLUSIONS

Elevated serum pNF-H levels and the PERG are useful markers of neurodegeneration of the optic nerve in isolated experimental optic neuritis. Our findings suggest that elevations of this axonal protein in patients with optic neuritis who had a poor visual outcome are likely also due to demise of optic nerve axons.

Safinamide and flecainide protect axons and reduce microglial activation in models of multiple sclerosis

Axonal degeneration is a major cause of permanent disability in the inflammatory demyelinating disease multiple sclerosis, but no therapies are known to be effective in axonal protection. Sodium channel blocking agents can provide effective protection of axons in the white matter in experimental models of multiple sclerosis, but the mechanism of action (directly on axons or indirectly via immune modulation) remains uncertain. Here we have examined the efficacy of two sodium channel blocking agents to protect white matter axons in two forms of experimental autoimmune encephalomyelitis, a common model of multiple sclerosis. Safinamide is currently in phase III development for use in Parkinson's disease based on its inhibition of monoamine oxidase B, but the drug is also a potent state-dependent inhibitor of sodium channels. Safinamide provided significant protection against neurological deficit and axonal degeneration in experimental autoimmune encephalomyelitis, even when administration was delayed until after the onset of neurological deficit. Protection of axons was associated with a significant reduction in the activation of microglia/macrophages within the central nervous system. To clarify which property of safinamide was likely to be involved in the suppression of the innate immune cells, the action of safinamide on microglia/macrophages was compared with that of the classical sodium channel blocking agent, flecainide, which has no recognized monoamine oxidase B activity, and which has previously been shown to protect the white matter in experimental autoimmune encephalomyelitis. Flecainide was also potent in suppressing microglial activation in experimental autoimmune encephalomyelitis. To distinguish whether the suppression of microglia was an indirect consequence of the reduction in axonal damage, or possibly instrumental in the axonal protection, the action of safinamide was examined in separate experiments in vitro. In cultured primary rat microglial cells activated by lipopolysaccharide, safinamide potently suppressed microglial superoxide production and enhanced the production of the anti-oxidant glutathione. The findings show that safinamide is effective in protecting axons from degeneration in experimental autoimmune encephalomyelitis, and that this effect is likely to involve a direct effect on microglia that can result in a less activated phenotype. Together, this work highlights the potential of safinamide as an effective neuroprotective agent in multiple sclerosis, and implicates microglia in the protective mechanism.

Plasma neurofilament heavy chain levels correlate to markers of late stage disease progression and treatment response in SOD1(G93A) mice that model ALS

Background

Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disorder characterised by progressive degeneration of motor neurons leading to death, typically within 3–5 years of symptom onset. The diagnosis of ALS is largely reliant on clinical assessment and electrophysiological findings. Neither specific investigative tools nor reliable biomarkers are currently available to enable an early diagnosis or monitoring of disease progression, hindering the design of treatment trials.

Methodology/Principal Findings

In this study, using the well-established SOD1^G93A mouse model of ALS and a new in-house ELISA method, we have validated that plasma neurofilament heavy chain protein (NfH) levels correlate with both functional markers of late stage disease progression and treatment response. We detected a significant increase in plasma levels of phosphorylated NfH during disease progression in SOD1^G93A mice from 105 days onwards. Moreover, increased plasma NfH levels correlated with the decline in muscle force, motor unit survival and, more significantly, with the loss of spinal motor neurons in SOD1 mice during this critical period of decline. Importantly, mice treated with the disease modifying compound arimoclomol had lower plasma NfH levels, suggesting plasma NfH levels could be validated as an outcome measure for treatment trials.

Conclusions/Significance

These results show that plasma NfH levels closely reflect later stages of disease progression and therapeutic response in the SOD1^G93A mouse model of ALS and may potentially be a valuable biomarker of later disease progression in ALS.