Elevated neurofilament levels in neurological diseases

Phosphatidylinositol phosphates directly bind to neurofilament light chain (NF-L) for the regulation of NF-L self assembly

Phosphatidylinositol phosphates (PtdInsPs) are ubiquitous membrane phospholipids that play diverse roles in cell growth and differentiation. To clarify the regulation mechanism acting on neurofilament light chain (NF-L) self assembly, we examined the effects of various PtdInsPs on this process. We found that PtdInsPs, including PI(4,5)P((2)), directly bind to the positively charged Arg(54) of murine NF-L, and this binding promotes NF-L self assembly in vitro. Mutant NF-L (R53A/R54A) proteins lacking binding affinity to PtdInsPs did not have the same effect, but the mutant NF-L proteins showed greater self assembly than the wild-type in the absence of any PtdInsP. These results collectively suggest that Arg(54) plays a pivotal role in NF-L self assembly by binding with PtdInsPs.

Mortalin inhibition in experimental Parkinson's disease

Among heat shock proteins, mortalin has been linked to the pathogenesis of Parkinson's disease. In the present work a rat model of Parkinson's disease was used to analyze the expression of striatal proteins and, more specifically, mortalin expression. The possible involvement of mortalin in Parkinson's disease pathogenesis was further investigated by utilizing an electrophysiological approach and pharmacological inhibition of mortalin in both the physiological and the parkinsonian states. Proteomic analysis was used to investigate changes in striatal protein expression in the 6-hydroxydopamine rat model of Parkinson's disease. The electrophysiological effects of MKT-077, a rhodamine-123 analogue acting as an inhibitor of mortalin, were measured by field potential recordings from corticostriatal brain slices obtained from control, sham-operated, and 6-hydroxydopamine-denervated animals. Slices in the presence of rotenone, an inhibitor of mitochondrial complex I, were also analyzed. Proteomic analysis revealed downregulation of mortalin in the striata of 6-hydroxydopamine-treated rats in comparison with sham-operated animals. MKT-077 reduced corticostriatal field potential amplitude in physiological conditions, inducing membrane depolarization and inward current in striatal medium spiny neurons. In addition, we observed that concentrations of MKT-077 not inducing any electrophysiological effect in physiological conditions caused significant changes in striatal slices from parkinsonian animals as well as in slices treated with a submaximal concentration of rotenone. These findings suggest a critical link between mortalin function and mitochondrial activity in both physiological and pathological conditions mimicking Parkinson's disease.

Cerebrospinal fluid and blood biomarkers of neuroaxonal damage in multiple sclerosis

Following emerging evidence that neurodegenerative processes in multiple sclerosis (MS) are present from its early stages, an intensive scientific interest has been directed to biomarkers of neuro-axonal damage in body fluids of MS patients. Recent research has introduced new candidate biomarkers but also elucidated pathogenetic and clinical relevance of the well-known ones. This paper reviews the existing data on blood and cerebrospinal fluid biomarkers of neuroaxonal damage in MS and highlights their relation to clinical parameters, as well as their potential predictive value to estimate future disease course, disability, and treatment response. Strategies for future research in this field are suggested.

Biomarker-based dissection of neurodegenerative diseases

The diagnosis of neurodegenerative diseases within neurology and psychiatry are hampered by the difficulty in getting biopsies and thereby validating the diagnosis by pathological findings. Biomarkers for other types of disease have been readily adopted into the clinical practice where for instance troponins are standard tests when myocardial infarction is suspected. However, the use of biomarkers for neurodegeneration has not been fully incorporated into the clinical routine. With the development of cerebrospinal fluid (CSF) biomarkers that reflect pathological events within the central nervous system (CNS), important clinical diagnostic tools are becoming available. This review summarizes the most promising biomarker candidates that may be used to monitor different types of neurodegeneration and protein inclusions, as well as different types of metabolic changes, in living patients in relation to the clinical phenotype and disease progression over time. Our aim is to provide the reader with an updated lexicon on currently available biomarker candidates, how far they have come in development and how well they reflect pathogenic processes in different neurodegenerative diseases. Biomarkers for specific pathogenetic processes would also be valuable tools both to study disease pathogenesis directly in patients and to identify and monitor the effect of novel treatment strategies.

Problems associated with fluid biomarkers for Parkinson's disease

This article focuses on biochemical markers that may be used in the diagnostics of Parkinson's disease and associated disorders, and to identify early cases and stratify patients into subgroups. We present an updated account of some currently available candidate fluid biomarkers, and discuss their diagnostic performance and limitations. We also discuss some of the general problems with Parkinson's disease biomarkers and possible ways of moving forward. It may be concluded that a diagnostically useful fluid biomarker for Parkinson's disease is yet to be identified. However, some interesting candidates exist and may prove useful in the future, alone or when analyzed together in patterns.

Neurofilament proteins as body fluid biomarkers of neurodegeneration in multiple sclerosis

Biomarkers of axonal degeneration have the potential to improve our capacity to predict and monitor neurological outcome in multiple sclerosis (MS) patients. Neurofilament proteins, one of the major proteins expressed within neurons and axons, have been detected in cerebrospinal fluid and blood samples from MS patients and are now being actively investigated for their utility as prognostic indicators of disease progression in MS. In this paper, we summarize the current literature on neurofilament structure, assembly, and degeneration and discuss their potential utility as biomarkers for monitoring neurological decline in MS. We also discuss the need to further develop sensitive methods for assaying neurofilaments in blood to improve clinical applicability.

Neurofilament heavy subunit in cerebrospinal fluid: a biomarker of amyotrophic lateral sclerosis?

The objectives of this study were to investigate the presence of the three neurofilament subunits, ubiquitin, proteasome and 3-nitrotyrosine, in CSF samples of ALS patients. CSF samples were obtained by lumbar puncture from 10 ALS patients and six controls. All samples were analysed by Western blotting. Results revealed that neurofilament heavy subunit was identified in 70% of ALS cases and we conclude that this subunit may be a promising biomarker for clinical diagnosis of ALS.

Cerebrospinal fluid CXCL13 in multiple sclerosis: a suggestive prognostic marker for the disease course

Background: Levels of CXCL13, a potent B-cell chemoattractant, are elevated in the cerebrospinal fluid (CSF) during multiple sclerosis (MS) and are associated with markers of MS activity. Levels decrease upon effective treatments.

Objective: Here we validate the potential role of CSF CXCL13 as a biomarker for aspects of MS in a large amount of clinical material, the majority collected at early diagnostic work-up.

Methods: CXCL13 was measured by ELISA in 837 subjects: relapsing–remitting MS (RRMS; n = 323), secondary progressive MS (SPMS; n = 40), primary progressive MS (PPMS; n = 24), clinically isolated syndrome (CIS; n = 79), other neurological diseases (ONDs; n = 181), ONDs with signs of inflammation or viral/bacterial infections (iONDs; n = 176) and healthy controls ( n = 14).

Results: Subjects with viral/bacterial infections had extremely high CXCL13 levels compared to all included groups ( p < 0.0001). CXCL13 was otherwise significantly higher in MS compared to the remaining controls ( p < 0.0001), and CIS ( p < 0.01). A significant and positive correlation between CXCL13 and relapse rate, the results obtained for the Expanded Disability Status Scale (EDSS) and the number of lesions detected by MRI was demonstrated. CXCL13 was increased in CIS conversion to clinically definite MS ( p < 0.001). Oligoclonal immunoglobulin band (OCB)-positive CIS or MS had significantly increased CXCL13 levels compared to OCB-negative CIS or MS ( p < 0.001 and p < 0.0001, respectively).

Conclusion: CXCL13 was associated with disease exacerbations and unfavourable prognosis in RRMS. Increased CXCL13 was not specific for MS since subjects with viral/bacterial infections exhibited even higher levels. High levels predicted CIS conversion to MS. We suggest that measurement of CSF CXCL13 can be part of the armamentarium in the diagnostic and prognostic work-up in MS and be of help in future treatment decisions.

Is there a CSF biomarker profile related to depression in elderly women?

In light of our previous observation of higher levels of cerebrospinal fluid (CSF) amyloid beta-42 (Abeta42) and CSF/serum albumin ratio in major depressive disorder (MDD), we analyzed two additional CSF biomarkers reflecting neurodegeneration-neurofilament protein light (NFL) and glial fibrillary acidic protein (GFAp)-in relationship to prevalent geriatric depression. Neuropsychiatric, physical, and lumbar puncture examinations, with DSM-III-R-based depression diagnoses and measurement of CSF levels of NFL and GFAp, were evaluated among a population-based sample of 78 elderly women (mean age, 73.9+/-3.2 years) without dementia for at least 10 years after CSF collection. Eleven (13.1%) women had MDD, and higher levels of NFL compared with women without depression. A multivariate model including age, NFL, Abeta42 and the CSF/serum albumin ratio showed that each biomarker was independently and positively associated with MDD, and that this biomarker profile explained more variation in the model compared with single or combined biomarkers. A CSF profile with higher levels of NFL, Abeta42, and CSF/serum albumin ratio may indicate neuropathological and vascular events in depression etiology. This contrasts with the well-characterized pattern of low Abeta42, higher CSF/serum albumin ratio, and higher NFL in Alzheimer's disease.

Neurofilament light as a prognostic marker in multiple sclerosis

Relapsing-remitting multiple sclerosis has a variable prognosis and lacks a reliable laboratory prognostic marker. Our aim in this study was to investigate the association between neurofilament light levels in cerebrospinal fluid in early multiple sclerosis and disease severity at long-term follow-up. Neurofilament light levels in cerebrospinal fluid collected at diagnostic lumbar puncture were measured in 99 multiple sclerosis cases. Clinical data were obtained from 95 out of those at follow-up visits made 14 years (range 8-20 years) after disease onset. Significant correlations between neurofilament light levels and the multiple sclerosis severity score were found for all cases (r = 0.30, p = 0.005), for relapsing-remitting multiple sclerosis cases (r = 0.47, p < 0.001) and for cases with a recent relapse (r = 0.60, p < 0.001). In the multivariate logistic regression analysis, neurofilament light levels >386 ng/L (median value of cases with detectable levels) increased the risk for severe multiple sclerosis fivefold (odds ratio 5.2, 95% confidence interval 1.8-15). Kaplan-Meier analysis showed that conversion to secondary-progressive multiple sclerosis was more likely in cases with neurofilament light levels >386 ng/L than in those with neurofilament light levels <60 ng/L (p = 0.01) or 60-386 ng/L (p = 0.03). We conclude that elevated levels of neurofilament light in cerebrospinal fluid collected at diagnostic lumbar puncture were associated with unfavourable prognosis. These data suggest that the neurofilament light level could be used as a prognostic marker in early relapsing-remitting multiple sclerosis.

Neurofilament ELISA validation

BACKGROUND

Neurofilament proteins (Nf) are highly specific biomarkers for neuronal death and axonal degeneration. As these markers become more widely used, an inter-laboratory validation study is required to identify assay criteria for high quality performance.

METHODS

The UmanDiagnostics NF-light (R)enzyme-linked immunoabsorbent assays (ELISA) for the neurofilament light chain (NfL, 68kDa) was used to test the intra-assay and inter-laboratory coefficient of variation (CV) between 35 laboratories worldwide on 15 cerebrospinal fluid (CSF) samples. Critical factors, such as sample transport and storage, analytical delays, reaction temperature and time, the laboratories' accuracy and preparation of standards were documented and used for the statistical analyses.

RESULTS

The intra-laboratory CV averaged 3.3% and the inter-laboratory CV 59%. The results from the test laboratories correlated with those from the reference laboratory (R=0.60, p<0.0001). Correcting for critical factors improved the strength of the correlation. Differences in the accuracy of standard preparation were identified as the most critical factor. Correcting for the error introduced by variation in the protein standards improved the correlation to R=0.98, p<0.0001 with an averaged inter-laboratory CV of 14%. The corrected overall inter-rater agreement was subtantial (0.6) according to Fleiss' multi-rater kappa and Gwet's AC1 statistics.

CONCLUSION

This multi-center validation study identified the lack of preparation of accurate and consistent protein standards as the main reason for a poor inter-laboratory CV. This issue is also relevant to other protein biomarkers based on this type of assay and will need to be solved in order to achieve an acceptable level of analytical accuracy. The raw data of this study is available online.

Immunoreactivity of the phosphorylated axonal neurofilament H subunit (pNF-H) in blood of ALS model rodents and ALS patients: evaluation of blood pNF-H as a potential ALS biomarker

Levels of neurofilament subunits, potential biomarkers of motor axon breakdown, are increased in amyotrophic lateral sclerosis (ALS) patient's CSF but data on blood are not available. We measured blood levels of the phosphorylated axonal form of neurofilament H (pNF-H) by ELISA in transgenic rodent models of superoxide dismutase 1 (SOD1) ALS, and in 20 ALS patients and 20 similar aged controls monthly for 4 months. All symptomatic rodent ALS models showed robust levels of blood pNF-H, while control rodents or mice transgenic for unmutated SOD1 showed no detectable blood pNF-H. Average pNF-H levels in the G93A SOD1 mouse progressively increased from day 74 through death (day approximately 130). Median blood pNF-H level in ALS patients was 2.8-fold higher than controls (p < 0.001). Median ALSFRS-R declined a median of 0.8 pt/month (p < 0.001); higher baseline pNF-H level appeared to be associated with faster ALSFRS-R decline over 4 months (p = 0.087). The median rate of decline in ALSFRS-R was 1.9 pt/month in patients with baseline pNF-H levels above the median pNF-H value of 0.53 ng/mL; ALSFRS-R declined at a median of 0.6 pt/month in patients below this level. The pNF-H levels were relatively stable month to month in individual patients, raising questions regarding the molecular pathogenesis of ALS. Baseline control human pNF-H levels were higher in men than women and increased minimally over time. These data suggest that blood pNF-H can be used to monitor axonal degeneration in ALS model rodents and support further study of this protein as a potential biomarker of disease prognosis in ALS patients.

Comparative study of CSF neurofilaments in HTLV-1-associated myelopathy/tropical spastic paraparesis and other neurological disorders

HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a progressive CNS disease leading to corticospinal tract degeneration. Various degenerative diseases have increased neurofilament subunit concentration in cerebrospinal fluid (CSF), frequently showing hyperphosphorylation in neurofilaments. The aim of this study was to determine if there were elevated concentrations of neurofilament light subunit (NFL) and phosphorylated forms of neurofilament heavy subunit (PNFH) in HAM/TSP CSF. NF concentrations were compared with those of controls and patients with neurodegenerative diseases associated with other retroviruses (HIV-associated dementia, HAD) and a form of prion disease (familiar Creutzfeldt-Jakob, FCJD). Western blotting of CSF with antibodies against NFL showed two immunoreactive bands of 66 and 59 kDa, the latter probably corresponding to a partially degraded NFL form. The concentration of the 59-kDa form was not different in HAM/TSP compared with controls, but it was significantly increased in HAD and FCJD groups. ELISA assay for PNFH did not show differences among HAM/TSP, HAD, and control groups, while PNFH concentration was significantly elevated in FCJD. Our results show that CSF NFL and PNFH are not molecular markers of axonal damage for HAM/TSP probably due to the slow progression of this disease. NFL phosphorylation studies required previous immunoprecipitation from CSF for mass spectrometric analysis. This preliminary analysis indicated phosphorylation at S472 and at some other residues.

Elevated cerebrospinal fluid levels of prostaglandin E2 and 15-(S)-hydroxyeicosatetraenoic acid in multiple sclerosis

OBJECTIVE

To test the hypothesis that the arachodinic acid metabolites prostaglandin E2 (PGE2) and 15-(S)-hydroxyeicosatetraenoic acid (15(S)-HETE) in cerebrospinal fluid (CSF) are elevated and reflect neuroinflammation and degenerative changes in multiple sclerosis (MS).

PATIENTS AND METHODS

We measured PGE2 and 15(S)-HETE concentrations, as well as markers of axonal and astroglial injury in CSF from 46 MS patients, 46 healthy siblings and 50 controls.

RESULTS

We found elevated levels of both PGE2 and 15(S)-HETE in MS compared with the control and sibling groups. Siblings had lower PGE2 levels and higher 15(S)-HETE levels than controls. There were no correlations between either PGE2 or 15(S)-HETE and clinical scores of MS severity or biochemical markers of axonal or astroglial injury.

CONCLUSION

These data suggest no direct involvement of PGE2 and 15(S)-HETE in the MS disease process. Rather, the elevated levels reflect a general up-regulation of arachidonic acid metabolism and neuroinflammation.

CSF neurofilament protein analysis in the differential diagnosis of ALS

BACKGROUND

Cerebrospinal fluid (CSF) biomarkers have been studied to differentiate between patients with ALS and neurological controls, but not in comparison to clinically more relevant disorders mimicking ALS.

METHODS

In this retrospective study, CSF concentrations of various brain-specific proteins were analyzed in patients with ALS (n = 32) and ALS-mimic disorders (n = 26).

RESULTS

CSF concentrations of neurofilament light (NFL) and heavy chain (NFHp35), but not other brain-specific proteins, were significantly higher in patients with ALS than in patients with an ALS-mimic disorder, however with maximum sensitivity or specificity of 80%. The mean CSF level of NFHp35 was 781 ng/L in the ALS group vs. 338 ng/L in the ALS-mimic disorders group and for NFL the mean CSF levels were 62 ng/L vs. 24 ng/L.

CONCLUSION

Although CSF concentrations of NFL and NFHp35 are higher in patients with ALS, the diagnostic accuracy for differentiating ALS from ALS-mimic disorders seems insufficient. Our results suggest that, in the clinical work-up of patients suspected of ALS, application of CSF analysis alone is limited but may have potential in combination with other clinical and electrophysiological markers.

T-cell responses to neurofilament light protein are part of the normal immune repertoire

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system in which axonal damage and degeneration contribute significantly to the progressive irreversible neurological disability. Similar to pathogenic myelin autoimmunity, autoimmune responses to neuronal antigens may contribute to axonal damage and irreversible disability in MS. Auto-antibodies to the axonal cytoskeletal protein neurofilament light (NF-L) are associated with cerebral atrophy in MS and we have recently reported that NF-L autoimmunity is pathogenic in mice. However, the T-cell response to NF-L in MS patients has not been examined. Here, we identify and characterize T-cell proliferative responses to NF-L as compared with myelin oligodendrocyte glycoprotein (MOG) in MS patients and healthy controls. Using a carboxyfluorescein succinimidyl ester dilution assay, we show that while responses to MOG are dominated by CD3(+)CD4(+) T cells, responses to NF-L were observed in both CD3(+)CD4(+) and CD3(+)CD8(+) T-cell populations. Both MOG- and NF-L-reactive cells expressed CD45RO(+), indicative of a memory phenotype. Moreover, in contrast to MOG stimulation which predominantly induced IFN-gamma, both T(h)1- and T(h)2-type T-cell responses to NF-L were observed as indicated by the induction of IFN-gamma, tumor necrosis factor-alpha as well as IL-4. The finding of T-cell responses to NF-L in MS patients may reflect transient activation of pathogenic potential but their presence also in healthy controls indicates that these cells are part of the normal immune repertoire.

Preventing brain damage in HIV infection

HIV-1 is a virus with neurotropic features causing major morbidity and also mortality if untreated. Mild symptoms of neurocognitive impairment are common and precede more severe forms of dementia, termed AIDS dementia complex (ADC). The pathogenesis of neurodegeneration in HIV-1 infection is not fully understood, and we lack specific markers to verify the diagnosis. Fortunately, antiretroviral treatment is effective in treating both systemic and CNS infection, and neurocognitive symptoms and ADC will, in most cases, improve on treatment. This review focuses on current research regarding cerebral spinal fluid biomarkers and effects of highly active antiretroviral treatment on HIV-1 CNS disease.

Cerebrospinal fluid biomarkers of neurodegeneration in chronic neurological diseases

Chronic neurological diseases (CND) like amyotrophic lateral sclerosis (ALS), dementia or multiple sclerosis (MS) share a chronic progressive course of disease that frequently leads to the common pathological pathway of neurodegeneration, including neuroaxonal damage, apoptosis and gliosis. There is an ongoing search for biomarkers that could support early diagnosis of CND and help to identify responders to interventions in therapeutic treatment trials. Cerebrospinal fluid (CSF) is a promising source of biomarkers in CND, since the CSF compartment is in close anatomical contact with the brain interstitial fluid, where biochemical changes related to CND are reflected. We review recent advances in CSF biomarkers research in CND and thereby focus on markers associated with neurodegeneration.

Protein biomarkers for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive motor neuron disease with largely unknown pathogenesis that typically results in death within a few years from diagnosis. There are currently no effective therapies for ALS. Clinical diagnosis usually takes several months to complete and the long delay between symptom onset and diagnosis limits the possibilities for effective intervention and clinical trials. The establishment of protein biomarkers for ALS may aid an earlier diagnosis, facilitating the search for effective therapeutic interventions and monitoring drug efficacy during clinical trials. Biomarkers could also be used to discriminate between subtypes of ALS, to measure disease progression and to detect susceptibility for developing ALS or monitor adverse effects of drug treatment. The present review will discuss the opportunities and proteomic platforms used for biomarker discovery efforts in ALS, summarizing putative ALS protein biomarkers identified in different biofluids.

Reduced SMN protein impairs maturation of the neuromuscular junctions in mouse models of spinal muscular atrophy

Spinal muscular atrophy (SMA) is a common pediatric neuromuscular disorder caused by insufficient levels of the survival of motor neuron (SMN) protein. Studies involving SMA patients and animal models expressing the human SMN2 gene have yielded relatively little information about the earliest cellular consequences of reduced SMN protein. In this study, we have used severe- and mild-SMN2 expressing mouse models of SMA as well as material from human patients to understand the initial stages of neurodegeneration in the human disease. We show that the earliest structural defects appear distally and involve the neuromuscular synapse. Insufficient SMN protein arrests the post-natal development of the neuromuscular junction (NMJ), impairing the maturation of acetylcholine receptor (AChR) clusters into 'pretzels'. Pre-synaptic defects include poor terminal arborization and intermediate filament aggregates which may serve as a useful biomarker of the disease. These defects are reflected in functional deficits at the NMJ characterized by intermittent neurotransmission failures. We suggest that SMA might best be described as a NMJ synaptopathy and that one promising means of treating it could involve maintaining function at the NMJ.

Biomarkers of HIV related central nervous system disease

In this review we critically assess biomarkers of the direct effects of HIV related brain disease. This area is becoming increasingly complex because of the presence of confounds and varying degrees of activity of HIV brain disease. Sensitive and specific biomarkers are urgently needed although existing biomarkers do have some utility. The review will focus on the practical implications of the more established biomarkers. We discuss blood, cerebrospinal fluid and neurophysiological biomarkers but not neuroimaging techniques as they are beyond the scope of this review.

CSF biomarkers in the evaluation of idiopathic normal pressure hydrocephalus

BACKGROUND - To evaluate cerebrospinal fluid (CSF) markers for neuronal degeneration and demyelination in idiopathic normal pressure hydrocephalus (INPH), subcortical arteriosclerotic encephalopathy (SAE), and neurologically healthy subjects. METHODS - Lumbar CSF concentrations of sulfatide, neurofilament protein light (NFL), total-tau (T-tau), hyperphosphorylated tau (P-tau), and beta-amyloid(1-42) (Abeta42) were analyzed in 62 INPH patients, 26 SAE patients, and 23 neurologically healthy controls. In INPH patients, samples before and after shunt surgery were analysed. RESULTS - The CSF concentration of NFL was elevated in INPH and SAE compared with the controls, and levels of T-tau, P-tau, and Abeta42 were lower in INPH compared with SAE and controls. No difference was seen for sulfatide. All markers except Abeta42 were significantly elevated after shunt surgery. CONCLUSIONS - The most striking finding was the power of the combined pattern of NFL, P-tau, and Abeta42 in distinguishing between the clinical diagnoses of INPH, SAE, and neurologically healthy elderly.

Cerebrospinal fluid neurofilament light levels in amyotrophic lateral sclerosis: impact ofSOD1genotype

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative syndrome with familial and sporadic forms. Most ALS-associated mutations are found in the superoxide dismutase 1 (SOD1) gene. We conducted a study including 60 sporadic and 19 familial ALS patients, 206 reference patients with other neurological disorders and 40 age- and sex-matched healthy controls to test the hypothesis that cerebrospinal fluid (CSF) levels of neurofilament light (NF-L) protein, a marker of axonal degeneration, might provide diagnostic and prognostic information on the disease. All ALS patients were screened for SOD1 mutations. Ten of the familial and five of the sporadic cases carried SOD1 mutations. NF-L concentration [median (range)] was strongly elevated in ALS [2110 (255-10 800) ng/l] compared with reference patients and healthy controls [277 (<125-15 506) and 175 (<125-710) ng/l, respectively, P < 0.001] and correlated inversely with disease duration (Spearman R = -0.518, P = 0.001). NF-L levels were lower in SOD1 mutation-associated ALS compared with SOD1 wild-type (wt) ALS (P = 0.03). In conclusion, CSF NF-L levels may provide both diagnostic and prognostic information, particularly in SOD1 wt ALS.

CSF neurofilament proteins in the differential diagnosis of dementia

BACKGROUND

Neurofilament (NF) proteins are major cytoskeletal constituents of neurons. Increased CSF NF levels may reflect neuronal degeneration.

OBJECTIVE

To investigate the diagnostic value of CSF NF analysis to discriminate in relatively young dementia patients between frontotemporal lobe degeneration (FTLD) and early onset Alzheimer's disease (EAD; onset < or = 65 years of age), and in elderly dementia patients between dementia with Lewy bodies (DLB) and late onset AD (LAD; onset > 65 years of age).

METHODS

In CSF of 28 FTLD, 37 EAD, 18 DLB and 33 LAD patients, and 26 control subjects, we analysed NF light chain (NFL), phosphorylated NF heavy chain (pNFH), amyloid beta42 protein (Abeta42), total tau and tau phosphorylated at threonine 181 (p-tau181).

RESULTS

CSF NFL levels were higher in FTLD patients compared with EAD patients (p<0.001), and diagnostic accuracy of p-tau181 and Abeta42 analysis improved with addition of NFL analysis (sensitivity 86%, specificity 100%). CSF pNFH levels were elevated in DLB, LAD and FTLD compared with controls (p<0.05) but no significant differences were found between the dementia groups.

CONCLUSIONS

In the diagnostic workup of relatively young dementia patients, CSF NFL levels may play a role in the discrimination between FTLD and EAD, especially in combination with Abeta42 and p-tau181 analysis.

A Systematic Review and Meta-Analysis of CSF Neurofilament Protein Levels as Biomarkers in Dementia

BACKGROUND

Loss of cortical neurons is a key pathological feature in neurodegenerative dementias. Cerebrospinal fluid (CSF) neurofilaments (Nf) are a biomarker for neuronal death and axonal loss.

OBJECTIVE

To perform a meta-analysis to investigate the value of CSF Nf levels for the laboratory-supported differential diagnosis of neurodegenerative dementias.

METHODS

A systematic review and meta-analysis of studies on CSF Nf heavy (NfH) and light (NfL) levels in patients with dementia. The dementia subgroups analysed were Alzheimer (AD), frontotemporal lobe dementia (FTLD), vascular dementia (SVD), minimal cognitive deficit (MCI).

RESULTS

We identified 12 studies on CSF NfH and NfL levels which met the inclusion criteria and 11 were of a quality good enough to be used in this meta-analysis. CSF data was available on 818 patients (306 AD, 106 SVD, 98 FTLD, 25 MCI, 283 controls). Overall CSF NfH and NfL levels were higher in patients with AD, FTLD and SVD when compared to controls. The size of the effect ranged from 0.71 to 1.38. The strongest effect was observed for the comparison of FTLD patients with controls, both for NfL (1.38) and NfH (0.74). CSF NfL were also able to separate patients with FTLD from those with AD.

CONCLUSION

At present we cannot recommend CSF NfH and NfL levels for use as a screening test in the diagnosis of dementia because of the rather small effect size. However, both neurofilament proteins may be of value for targeted investigation of some patients with FTLD, SVD and AD.

CSF neurofilaments in frontotemporal dementia compared with early onset Alzheimer's disease and controls

BACKGROUND

Frontotemporal dementia (FTD) is pathologically heterogeneous, sometimes revealing intraneuronal inclusions of neurofilaments. We therefore measured CSF neurofilament profiles in patients with FTD, patients with early onset Alzheimer's disease (EAD) and healthy control subjects to explore the discriminative potential of CSF neurofilaments compared with the existing CSF biomarkers amyloid-beta(1-42), tau and tau phosphorylated at threonine-181.

METHODS

CSF levels of light chain, heavy chain and hyperphosphorylated heavy chain neurofilaments (NfL, t-NfH and P-NfH) were compared between 17 subjects with FTD, 20 with EAD and 25 cognitively healthy controls.

RESULTS

A subgroup of FTD patients had remarkably high CSF levels of both NfL and NfH. The degree of NfH phosphorylation was increased in FTD compared to both other groups. The levels of CSF NfL were significantly higher in EAD compared to controls.

CONCLUSION

Differences in CSF biomarker profiles might reflect differential involvement of neurofilaments and tau in FTD and EAD. The subgroup of FTD patients with high CSF neurofilament levels may have a different neuropathological substrate and future studies addressing this specific issue are needed.

CSF neurofilament protein (NFL) — a marker of active HIV-related neurodegeneration

BACKGROUND AND METHODS

The light subunit of the neurofilament protein (NFL), a major structural component of myelinated axons, is a sensitive indicator of axonal injury in the central nervous system (CNS) in a variety of neurodegenerative disorders. Cerebrospinal fluid (CSF) NFL concentrations were measured by ELISA (normal < 250 ng/l) in archived samples from 210 HIV-infected patients not taking antiretroviral treatment: 55 with AIDS dementia complex (ADC), 44 with various CNS opportunistic infections/tumours (CNS OIs), 95 without neurological symptoms or signs, and 16 with primary HIV infection (PHI). The effect of highly active antiretroviral treatment (HAART) was studied by repeated CSF sampling in four of the ADC patients initiating treatment.

RESULTS

CSF NFL concentrations were significantly higher in patients with ADC (median 2590 ng/l, IQR 780-7360) and CNS OIs (2315 ng/l, 985-7390 ng/l) than in neuroasymptomatic patients (<250 ng/l, <250-300) or PHI (<250 ng/l, <250-280), p < 0.001. Among patients with ADC, those with more severe disease (stage 2-4) had higher levels than those with milder disease (stage 0.5-1), p < 0.01. CSF NFL declined during HAART to the limit of detection in parallel with virological response and neurological improvement in ADC.CSF NFL concentrations were higher in neuroasymptomatic patients with lower CD4-cell strata than higher, p < 0.001. This increase was less marked than in the ADC patients and noted in 26/58 neuroasymptomatic patients with CD4 counts <200/microl compared to 1/37 with CD4-cells > or =200/microl.

CONCLUSIONS

The findings of this study support the value of CSF NFL as a useful marker of ongoing CNS damage in HIV infection. Markedly elevated CSF NFL concentrations in patients without CNS OIs are associated with ADC, follow the grade of severity, and decrease after initiation of effective antiretroviral treatment. Nearly all previously suggested CSF markers of ADC relate to immune activation or HIV viral load that do not directly indicate brain injury. By contrast NFL is a sensitive marker of such injury, and should prove useful in evaluating the presence and activity of ongoing CNS injury in HIV infection.

In vitro assay of neurofilament light chain self-assembly using truncated mutants

Neurofilaments (NFs) are heteropolymers composed of light (NF-L), middle (NF-M), and heavy (NF-H) subunits, present in most neurons. NF-L polymerizes on its own to provide a scaffold on which regular NFs form via the cross-bridging of NF-M or NF-H. To clarify the mechanism of regulation of NF-L self-assembly, we developed an assay using truncated mutant NF-L fused to glutathione-S transferase (GST). Western immunoblotting data show that the GST-fused head-rod domains of NF-L are necessary and sufficient for detecting assembled NF-L. The levels of self-assembled NF-L subunits detected using GST fusion proteins were consistent with those detected by electron microscopy and turbidity assay. Our results collectively imply that GST-fused head-rod domains of NF-L are critical tools for analyzing NF-L self-assembly in vitro.

HIV and antiretroviral therapy in the brain: neuronal injury and repair

Approximately 40 million people worldwide are infected with human immunodeficiency virus (HIV). Despite HIV's known propensity to infect the CNS and cause neurological disease, HIV neurocognitive disorders remain under-recognized. Although combination antiretroviral therapy has improved the health of millions of those living with HIV, the penetration into the CNS of many such therapies is limited, and patients' quality of life continues to be diminished by milder, residual neurocognitive impairment. Synaptodendritic neuronal injury is emerging as an important mediator of such deficits in HIV. By carefully selecting specific antiretrovirals and supplementing them with neuroprotective agents, physicians might be able to facilitate innate CNS repair, promoting enhanced synaptodendritic plasticity, neural function and clinical neurological status.

The application of proteomics and genomics to the study of age-related neurodegeneration and neuroprotection

The present study aimed to acquire more information on aging-related alterations, using proteomic and genomic analyses of hippocampus from young (8 months) and old (27 months) rats. In the old rats, the proteomic analysis identified changes in proteins related to the iron-mediated oxidative stress (OS) pathway, including reduction in antioxidant enzymes (e.g., peroxiredoxin, cytochrome c oxidase) and induction of ferritin. Furthermore, the neurofilament light peptide, associated with neurodegenerative processes, was enhanced and binding/ chaperone proteins were altered in old vs. young rats. At the genes levels, significant molecular changes related to neurodegeneration were identified in aged rat hippocampus. Thus, the effects of the potent neuroprotective compounds, the anti-Parkinson drug, rasagiline and the anti-Alzheimer drug, ladostigil (1 mg/kg, for 30 days) on gene expression in the hippocampus were further investigated. Both drugs reversed the effect of aging on the expression of various mitochondrial and key regulator genes involved in neurodegeneration, cell survival, synaptogenesis, oxidation, and metabolism. These results support the hypothesis that OS and mitochondrial dysfunction may play a pivotal role in aging and age-associated neurodegenerative diseases, and can serve as potential clinical targets for future therapy.

Proteomic identification of biomarkers of traumatic brain injury

Traumatic brain injury (TBI) is a major national health problem without a US Food and Drug Administration-approved therapy. This review summarizes the importance of discovering relevant TBI protein biomarkers and presents logical rationale that neuroproteomic technologies are uniquely suited for the discovery of otherwise unnoticed TBI biomarkers. It highlights that one must make careful decisions when choosing which paradigm (human vs. animal models) and which biologic samples to use for such proteomic studies. It further outlines some of the desirable attributes of an ideal TBI biomarker and discusses how biomarkers discovered proteomically are complementary to those identified by traditional approaches. Lastly, the most important sequela of any proteomically identified TBI biomarker is validation in preclinical or clinical samples.

Normalisation of cerebrospinal fluid biomarkers parallels improvement of neurological symptoms following HAART in HIV dementia--case report

Background

Since the introduction of HAART the incidence of HIV dementia has declined and HAART seems to improve neurocognitive function in patients with HIV dementia. Currently, HIV dementia develops mainly in patients without effective treatment, though it has also been described in patients on HAART and milder HIV-associated neuropsychological impairment is still frequent among HIV-1 infected patients regardless of HAART. Elevated cerebrospinal fluid (CSF) levels of markers of neural injury and immune activation have been found in HIV dementia, but neither of those, nor CSF HIV-1 RNA levels have been proven useful as diagnostic or prognostic pseudomarkers in HIV dementia.

Case presentation

We report a case of HIV dementia (MSK stage 3) in a 57 year old antiretroviral naïve man who was introduced on zidovudine, lamivudine and ritonavir boosted indinavir, and followed with consecutive lumbar punctures before and after two and 15 months after initiation of HAART. Improvement of neurocognitive function was paralleled by normalisation of CSF neural markers (NFL, Tau and GFAP) levels and a decline in CSF and serum neopterin and CSF and plasma HIV-1 RNA levels.

Conclusion

The value of these CSF markers as prognostic pseudomarkers of the effect of HAART on neurocognitive impairment in HIV dementia ought to be evaluated in longitudinal studies.

Defining and evaluating HIV-related neurodegenerative disease and its treatment targets: a combinatorial approach to use of cerebrospinal fluid molecular biomarkers

There are a number of reasons that the accomplishments of clinical trials related to HIV-related neurodegenerative disease (HRND) and the AIDS dementia complex (ADC) have had such limited impact on clinical practice. These include: rapid evolution and progress in the treatment of systemic HIV infection that has quickly outpaced neurological efforts and has markedly reduced disease incidence; ethical constraints that (rightly) demand neurologically compromised patients receive the best available treatment before experimental therapeutics; complicated backgrounds and comorbidities of patients now most susceptible to HRND; and reluctance of general AIDS clinicians and drug companies to look beyond systemic or pivotal outcomes. However, the field has also been slow to adopt methods that better exploit advances in understanding of the pathogenesis of central nervous system (CNS) infection and brain injury, and that might circumvent some of these constraints. Using a simple model of pathogenesis, we propose an approach to characterizing patients, selecting treatment targets, and evaluating outcomes that emphasize a combination of cerebrospinal fluid (CSF) markers. This model begins by using three markers related to cardinal components of HRND: CNS HIV infection (measurement of CSF HIV RNA), intrathecal immunoactivation (CSF neopterin), and brain injury [CSF light chain neurofilament (NFL)]. Careful analysis of this and other marker combinations promises more rational trial design and more rapid progress in managing CNS HIV infection and HRND using both antiviral and adjuvant treatment approaches.

Cerebrospinal fluid levels of neurofilament light in chronic experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) induced by myelin oligodendrocyte glycoprotein (MOG) is a chronic relapsing-remitting animal model of multiple sclerosis (MS). Neurofilament light (NF-L), a structural protein expressed in neuronal cells can be used to quantify the amount of neuronal damage in MS patients. An immunoassay was used to measure levels of neurofilament light in cerebrospinal fluid (CSF) in rats with myelin oligodendrocyte glycoprotein-induced EAE. Significantly increased levels of neurofilament were found in the immunized animals compared to the controls, strengthening the similarities in the diseases and the progression pattern between the animal model and MS. The turnover of NF-L during this disease is increased since significantly elevated levels also were identified in the spinal cord of the diseased animals and immunohistochemistry gave support for this observation. Monitoring neurofilament levels in EAE can be used to follow disease progression and effects of therapy.

Antibody formation against beta-tubulin class III in response to brain trauma

Brain trauma typically leads to neuronal damage and loss. Assuming a transient autoimmune response to debris of the damaged neurones, we have monitored serum titres of IgG and IgM antibodies to beta-tubulin class III (betaTcIII), which is almost exclusively found in neuronal cytoskeletons. In 15 out of 18 patients, the peak of the IgG or IgM antibody titre appeared in the serum within 3 weeks of a brain trauma.

Neurofilament phosphoforms: surrogate markers for axonal injury, degeneration and loss

This review on the role of neurofilaments as surrogate markers for axonal degeneration in neurological diseases provides a brief background to protein synthesis, assembly, function and degeneration. Methodological techniques for quantification are described and a protein nomenclature is proposed. The relevance for recognising anti-neurofilament autoantibodies is noted. Pathological implications are discussed in view of immunocytochemical, cell-culture and genetic findings. With reference to the present symposium on multiple sclerosis, the current literature on body fluid levels of neurofilaments in demyelinating disease is summarised.

Cerebrospinal fluid signs of neuronal damage after antiretroviral treatment interruption in HIV-1 infection

Background

The neurofilament is a major structural component of myelinated axons. Increased cerebrospinal fluid (CSF) concentrations of the light chain of the neurofilament protein (NFL) can serve as a sensitive indicator of central nervous system (CNS) injury. To assess whether interrupting antiretroviral treatment of HIV infection might have a deleterious effect on the CNS, we measured NFL levels in HIV-infected subjects interrupting therapy.

We identified subjects who had CSF HIV RNA concentrations below 50 copies/mL at the time combination antiretroviral therapy was interrupted, and for whom CSF samples were available before and after the interruption.

Results

A total of 8 subjects were studied. The median (range) CSF NFL level at baseline was <125 (<125–220) ng/L (normal <250 ng/L). All 8 subjects exhibited an increase in CSF and plasma HIV RNA after stopping therapy, accompanied by intrathecal immunoactivation as evidenced by CSF lymphocytic pleocytosis (7/8 patients) and increased CSF neopterin concentration (5/6 patients). Three subjects showed a consistent increase in CSF NFL, rising from <125 ng/L to a maximum of 880 (at day 148), 1,010 (day 58) and 10,930 ng/L (day 101). None exhibited new neurological symptoms or signs, or experienced functional deterioration during the period off treatment; of 5 who underwent brief quantitative neurological testing, none showed worsening performance.

Conclusion

These findings suggest that resurgence of active HIV replication may result in measurable, albeit subclinical, CNS injury. Further studies are needed to define the frequency and pathobiological importance of the increase in CSF NFL.

Axonal pathology in subarachnoid and intracerebral hemorrhage

Electrically active axons degenerate in the presence of nitric oxide (NO) in vitro. High CSF NO concentrations have been observed in patients with hemorrhagic brain injury such as subarachnoid hemorrhage (SAH) and intracerebral hemorrhage (ICH). This study investigated the evidence for axonal injury in SAH and ICH and related this to CSF NO levels. In this study, neurofilament phosphoforms (NfH(SMI34), NfH(SMI35), NfH(SMI38), NfH(SMI310)), surrogate markers for axonal injury, and NO metabolites (nitrate, nitrite = NOx) were measured by ELISA in cerebrospinal fluid (CSF) from patients with SAH and ICH and from a group of controls. Injury severity was classified using the Glasgow Coma Scale, and survival was used as the outcome measure. Compared to the control group, a higher proportion of patients with SAH and ICH had elevated NfH(SMI34) levels from day 0 to day 6 (p < 0.001), elevated NfH(SMI35) levels from day 1 to 6 (p < 0.001), and elevated NfH(SMI310) levels at day 0, 1, 4, and 6 (p < 0.001). The NOx levels were higher in the SAH and ICH patients than in the controls (p < 0.05) and distinguished the non-survivors from the survivors (p < 0.05). No direct correlation was found for NOx with any of the NfH phosphoforms. This study provides evidence for primary and secondary axonal injury in patients with SAH and ICH, with non-survivors also having higher NOx levels. CSF NfH phosphoforms might emerge as a putative surrogate marker for monitoring the development for secondary axonal degeneration in neurocritical care and guiding targeted neuroprotective strategies.

Zinc induces neurofilament phosphorylation independent of p70 S6 kinase in N2a cells

Hyperphosphorylated neurofilaments are a part of neurofibrillary tangles in Alzheimer's disease brains. Zinc has been shown to be increased in the brain areas heavily affected by Alzheimer pathologies. Zinc could induce tau hyperphosphorylation in SH-SY5Y and N2a cells, and tau phosphorylation may be mediated by p70 S6 kinase activation. Many of the tau kinases can also phosphorylate neurofilaments, and in this study we wanted to see whether neurofilament phosphorylation is regulated by p70 S6 kinase in N2a cells. We found that zinc induces rapamycin-dependent p70 S6 kinase phosphorylation at Thr421/Ser424 and Thr389, and rapamycin-independent phosphorylation of neurofilaments at the SMI34 epitope. Although zinc could induce cell proliferation and cell growth, and increased phosphorylation of neurofilaments, only cell growth appeared to be related to p7056kinase activation.

Biological markers in CSF and blood for axonal degeneration in multiple sclerosis

Biomarkers in body fluids could help to predict and monitor neurological decline in people with multiple sclerosis (MS). We discuss markers for axonal damage in body fluids in people with MS. The most promising axonal marker for discriminating patients with MS from those with other neurological diseases is the neurofilament light chain in CSF. Antibodies against the heavy-chain isoform are associated with disease progression. Other studies have shown altered CSF concentrations of tau proteins, actin, tubulin, and 14-3-3 protein. Interestingly, the concentration of 24S-hydroxycholesterol was decreased in serum of patients with MS. No clear changes have been shown for the markers apolipoprotein E and neurospecific enolase. We describe three types of markers for axonal damage: markers that reflect processes in the CNS, those that reflect extraneural processes, and those that reflect whole-body changes. These concepts may be helpful for biomarker research in various neurodegenerative diseases.

An enzyme immunoassay to quantify neurofilament light chain in cerebrospinal fluid

Neurofilament light chain is a component of the axonal cytoskeleton. The concentration of the neurofilament light chain in cerebrospinal fluid may reflect axonal damage or the extent of white matter damage. In this study we describe a sensitive immunoassay for the detection of neurofilament light chain in cerebrospinal fluid using commercially available materials. The detection limit of the assay was 5 ng/l and the assay was linear up to 390 ng/l. Mean recovery was 91.5% and inter-assay and intra-assay coefficients of variation were below 18%. Strongly increased levels of neurofilament light chain were observed in patients with cerebrovascular accidents, subarachnoid hemorrhage and severe traumatic brain injury, suggesting the occurrence of axonal damage in these conditions.

Neuronal cytoskeletal alterations in an experimental model of depression

It has been proposed that depression is associated with hippocampal morphological changes. The apical dendrite atrophy of hippocampal CA3 pyramidal neurons has been described in experimental models of depression. The aim of the present study was to determine which cytoskeletal components are involved in the morphological changes previously described in the hippocampus of depressed animals. The expression of different neuronal cytoskeletal markers was analyzed by immunohistochemistry in rats exposed to a learned helplessness paradigm, an experimental model of depression. Rats were trained with 60 inescapable foot shocks (0.6 mA/15 s) and escape latencies and failures were tested 4 days after training. Animals in which learned helplessness behavior persisted for 21 days were included in the depressed group. No foot shocks were delivered to control rats. Microtubule-associated protein 2 (MAP-2) and light (NFL; 68 kDa), medium (NFM; 160 kDa) and heavy (NFH; 200 kDa) neurofilament subunit immunostainings were analyzed employing morphometric parameters. In the depressed group, NFL immunostaining decreased 55% (P<0.05) and 60% (P<0.001) in CA3 and dentate gyrus, respectively. In the same areas, MAP-2, NFM and NFH immunostainings did not differ between depressed and control animals. Since NFL is present in the core of mature neurofilament, it is proposed that hippocampal depression-associated plastic alterations may be due to changes in the dynamics of the neurofilament assembly.