Comparison of CSF biomarkers in Down syndrome and autosomal dominant Alzheimer's disease: a cross-sectional study.

BACKGROUND: Due to trisomy of chromosome 21 and the resultant extra copy of the amyloid precursor protein gene, nearly all adults with Down syndrome develop Alzheimer's disease pathology by the age of 40 years and are at high risk for dementia given their increased life expectancy compared with adults with Down syndrome in the past. We aimed to compare CSF biomarker patterns in Down syndrome with those of carriers of autosomal dominant Alzheimer's disease mutations to enhance our understanding of disease mechanisms in these two genetic groups at high risk for Alzheimer's disease. METHODS: We did a cross-sectional study using data from adults enrolled in the Alzheimer's Biomarker Consortium-Down Syndrome (ABC-DS) study, a multisite longitudinal study of Alzheimer's disease in Down syndrome, as well as a cohort of carriers of autosomal dominant Alzheimer's disease mutations and non-carrier sibling controls enrolled in the Dominantly Inherited Alzheimer Network (DIAN) study. For ABC-DS, participants with baseline CSF, available clinical diagnosis, and apolipoprotein E genotype as of Jan 31, 2019, were included in the analysis. DIAN participants with baseline CSF, available clinical diagnosis, and apolipoprotein E genotype as of June 30, 2018, were evaluated as comparator groups. CSF samples obtained from adults with Down syndrome, similarly aged carriers of autosomal dominant Alzheimer's disease mutations, and non-carrier siblings (aged 30-61 years) were analysed for markers of amyloid ß (Aß1-40, Aß1-42); tau phosphorylated at threonine 181-related processes; neuronal, axonal, or synaptic injury (total tau, visinin-like protein 1, neurofilament light chain [NfL], synaptosomal-associated protein 25); and astrogliosis and neuroinflammation (chitinase-3-like protein 1 [YKL-40]) via immunoassay. Biomarker concentrations were compared as a function of dementia status (asymptomatic or symptomatic), and linear regression was used to evaluate and compare the relationship between biomarker concentrations and age among groups. FINDINGS: We assessed CSF samples from 341 individuals (178 [52%] women, 163 [48%] men, aged 30-61 years). Participants were adults with Down syndrome (n=41), similarly aged carriers of autosomal dominant Alzheimer's disease mutations (n=192), and non-carrier siblings (n=108). Individuals with Down syndrome had patterns of Alzheimer's disease-related CSF biomarkers remarkably similar to carriers of autosomal dominant Alzheimer's disease mutations, including reductions (all p<0·0080) in Aß1-42 to Aß1-40 ratio and increases in markers of phosphorylated tau-related processes; neuronal, axonal, and synaptic injury (p<0·080); and astrogliosis and neuroinflammation, with greater degrees of abnormality in individuals with dementia. Differences included overall higher concentrations of Aß and YKL-40 (both p<0·0008) in Down syndrome and potential elevations in CSF tau (p<0·010) and NfL (p<0·0001) in the asymptomatic stage (ie, no dementia symptoms). FUNDING: National Institute on Aging, Eunice Kennedy Shriver National Institute of Child Health and Human Development, German Center for Neurodegenerative Diseases, and Japan Agency for Medical Research and Development.

Cerebrospinal fluid biomarkers link toxic astrogliosis and microglial activation to multiple sclerosis severity.

BACKGROUND: Once multiple sclerosis (MS) reaches the progressive stage, immunomodulatory treatments have limited efficacy. This suggests that processes other than activation of innate immunity may at least partially underlie disability progression during late stages of MS. Pathology identified these alternative processes as aberrant activation of astrocytes and microglia, and subsequent degeneration of oligodendrocytes and neurons. However, we mostly lack biomarkers that could measure central nervous system (CNS) cell-specific intrathecal processes in living subjects. This prevents differentiating pathogenic processes from an epiphenomenon. Therefore, we sought to develop biomarkers of CNS cell-specific processes and link them to disability progression in MS. METHODS: In a blinded manner, we measured over 1000 proteins in the cerebrospinal fluid (CSF) of 431 patients with neuroimmunological diseases and healthy volunteers using modified DNA-aptamers (SOMAscan®). We defined CNS cell type-enriched clusters using variable cluster analysis, combined with in vitro modeling. Differences between diagnostic categories were identified in the training cohort (n = 217) and their correlation to disability measures were assessed; results were validated in an independent validation cohort (n = 214). RESULTS: Astrocyte cluster 8 (MMP7, SERPINA3, GZMA and CLIC1) and microglial cluster 2 (DSG2 and TNFRSF25) were reproducibly elevated in MS and had a significant and reproducible correlation with MS severity suggesting their pathogenic role. In vitro studies demonstrated that proteins of astrocyte cluster 8 are noticeably released upon stimulation with proinflammatory stimuli and overlap with the phenotype of recently described neuro-toxic (A1) astrocytes. CONCLUSION: Microglial activation and toxic astrogliosis are associated with MS disease process and may partake in CNS tissue destruction. This hypothesis should be tested in new clinical trials.

Neurodegeneration, synaptic dysfunction, and gliosis are phenotypic of Alzheimer dementia.

OBJECTIVE: To test the hypothesis that cognitively unimpaired individuals with Alzheimer disease (AD) neuropathology differ from individuals with AD dementia on biomarkers of neurodegeneration, synaptic dysfunction, and glial activation. METHODS: In a cross-sectional study, adult participants >70 years old (n = 79, age 77.1 ± 5.3 years) underwent comprehensive cognitive evaluation and CSF collection, which was assayed for markers of amyloid, phosphorylated tau (p-tau), neurodegeneration (neurofilament light protein [NFL] and total tau), synaptic dysfunction (neurogranin), and glial activation (chitinase-3-like protein 1 [YKL-40]). Participants were divided into 3 groups based on diagnosis and p-tau/ß-amyloid42 (Aß42): those with low p-tau/Aß42 and unimpaired cognition were classified as controls (n = 25); those with high p-tau/Aß42 diagnosed with AD-dementia or AD-mild cognitive impairment were classified as AD-Dementia (n = 40); and those with high p-tau/Aß42 but unimpaired cognition were classified as mismatches (n = 14). A similar, secondary analysis was performed with no age exclusion criteria (n = 411). RESULTS: In both the primary and secondary analyses, biomarker levels between groups were compared with the use of analysis of covariance while controlling for age and demographic variables. Despite p-tau/Aß42 and Aß42/Aß40 levels comparable to those of the AD-Dementia group, mismatches had significantly lower levels of NFL and total tau. While not significantly lower than the AD-Dementia group on YKL-40 and neurogranin, mismatches were also not significantly different from controls. CONCLUSIONS: These results provide evidence that, in the absence of significant neurodegenerative processes, individuals who harbor AD neuropathology may remain cognitively unimpaired. This finding provides insight into the biological processes phenotypic of dementia and supports monitoring multiple biomarkers in individuals positive for AD neuropathology.

Blood Brain Barrier Impairment in HIV-Positive Naïve and Effectively Treated Patients: Immune Activation Versus Astrocytosis.

Blood brain barrier (BBB) damage is a common feature in central nervous system infections by HIV and it may persist despite effective antiretroviral therapy. Astrocyte involvement has not been studied in this setting. Patients were enrolled in an ongoing prospective study and subjects with central nervous system-affecting disorders were excluded. Patients were divided into two groups: treated subjects with cerebrospinal fluid (CSF) HIV RNA <50 copies/mL (CSF-controllers) and in late-presenters CD4+ T lymphocytes <100/uL. CSF biomarkers of neuronal or astrocyte damage were measured and compared to CSF serum-to-albumin ratio. 134 patients were included; 67 subjects in each group (50 %) with similar demographic characteristics (with the exception of older age in CSF controllers). CD4 (cells/uL), plasma and CSF HIV RNA (Log10 copies/mL) were 43 (20-96), 5.6 (5.2-6) and 3.9 (3.2-4.7) in LPs and 439 (245-615), <1.69 (9 patients <2.6) and <1.69 in CSFc. BBB impairment was observed in 17 late-presenters (25.4 %) and in 9 CSF-controllers (13.4 %). CSF biomarkers were similar but for higher CSF neopterin values in late-presenters (2.3 vs. 0.6 ng/mL, p < 0.001). CSARs were associated with CSF neopterin (rho = 0.31, p = 0.03) and HIV RNA (rho = 0.24, p = 0.05) in late-presenters and with CSF tau (rho = 0.51, p < 0.001), p-tau (rho = 0.47, p < 0.001) and S100beta (rho = 0.33, p = 0.009) in CSF-controllers. In HAART-treated subjects with suppressed CSF HIV RNA, BBB altered permeability was associated with markers of neuronal damage and astrocytosis. Additional treatment targeting astrocytosis and/or viral protein production might be needed in order to reduce HIV effects in the central nervous system.

Elevated glial fibrillary acidic protein levels in the cerebrospinal fluid of patients with narcolepsy.

Glial fibrillary acidic protein (GFAP) is an established indicator of astrogliosis. Therefore, variable cerebrospinal fluid (CSF) concentrations of this protein might reflect disease-specific pathologic profiles. In patients with narcolepsy, a loss of hypocretin-1 (hcrt-1) neurons in the brain and low concentrations of hcrt-1 in CSF have been reported. We performed a commercially available enzyme-linked immunosorbent assay to investigate if GFAP also is altered in the CSF of these patients. Here we detected significantly higher CSF levels of GFAP in patients with low hcrt-1 levels, of which the majority had a diagnosis of narcolepsy and cataplexy (NC); however, this finding was not observed in patients with hcrt-1 levels that were within reference range. In conclusion, GFAP may be useful as an additional disease biomarker in patients with narcolepsy, and this hypothesis should be investigated in larger studies.

Cerebrospinal fluid protein biomarker panel for assessment of neurotoxicity induced by kainic acid in rats.

Glutamate excitotoxicity plays a key role in the etiology of a variety of neurological, psychiatric, and neurodegenerative disorders. The goal of this study was to investigate spatiotemporal distribution in the brain and cerebrospinal fluid (CSF) concentrations of ubiquitin C-terminal hydrolase-1 (UCH-L1), glial fibrillary acidic protein (GFAP), αII-spectrin breakdown products (SBDP150, SBDP145, and SBDP120), and their relationship to neuropathology in an animal model of kainic acid (KA) excitotoxicity. Triple fluorescent labeling and Fluoro-Jade C staining revealed a reactive gliosis in brain and specific localization of degenerating neurons in hippocampus and entorhinal cortex of KA-treated rats. Immunohistochemistry showed upregulation of GFAP expression in hippocampus and cortex beginning 24h post KA injection and peaking at 48h. At these time points concurrent with extensive neurodegeneration all SBDPs were observed throughout the brain. At 24h post KA injection, a loss of structural integrity was observed in cellular distribution of UCH-L1 that correlated with an increase in immunopositive material in the extracellular matrix. CSF levels of UCH-L1, GFAP, and SBDPs were significantly increased in KA-treated animals compared with controls. The temporal increase in CSF biomarkers correlated with brain tissue distribution and neurodegeneration. This study provided evidence supporting the use of CSF levels of glial and neuronal protein biomarkers to assess neurotoxic damage in preclinical animal models that could prove potentially translational to the clinic. The molecular nature of these biomarkers can provide critical information on the underlying mechanisms of neurotoxicity that might facilitate the development of novel drugs and allow physicians to monitor drug safety.

Increased levels of inflammatory chemokines in amyotrophic lateral sclerosis.

BACKGROUND AND PURPOSE: Amyotrophic lateral sclerosis (ALS) is classically assumed to be a neurodegenerative disorder. Inflammation has been observed in CNS tissue in ALS patients. We investigated the expression and prognostic relevance of proinflammatory chemokines in ALS. METHODS: We analyzed nine chemokines, eotaxin, eotaxin-3, IL-8, IP-10, MCP-1, MCP-4, macrophage derived chemokine (MDC), macrophage inflammatory protein-1beta (MIP-1beta), and serum thymus and activation- regulated chemokine (TARC) in serum and cerebrospinal fluid (CSF) of 20 ALS- and 20 non-inflammatory neurological disease (NIND)-patients. RESULTS: MCP-1 and IL-8 levels in CSF in ALS were significantly higher than in NIND (1304 pg/ml vs. 1055 pg/ml, P = 0.013 and 22.7 pg/ml vs. 18.6 pg/ml, P = 0.035). The expression of MCP-1 and IL-8 were higher in CSF than in serum (P < 0.001). There was a trend towards higher MCP-1 CSF levels in ALS patients with shorter time between first symptoms and diagnosis (r = -0.407; P = 0.075). CONCLUSIONS: We confirmed previous findings of increased MCP-1 levels in CSF of ALS patients. Furthermore, increased levels of IL-8 in CSF suggest a stimulation of a proinflammatory cytokine cascade after microglia activation. We found a tendency for higher MCP-1 values in patients with a shorter diagnostic delay, who are known to have also a shorter survival. This may suggest an association of higher MCP-1 levels with rapidly progressing 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.

Astrocytic activation in relation to inflammatory markers during clinical exacerbation of relapsing-remitting multiple sclerosis.

The study aimed to assay the cerebrospinal fluid (CSF) levels of protein S100B, a biomarker of astrocyte activation in relation to kynurenic acid (KYNA) and nitric oxide (NO) metabolites, nitrate/nitrite (NOx) concentrations in acute relapse multiple sclerosis (MS) patients. Twenty relapsing-remitting MS (RR-MS) patients and 10 controls were enrolled. RR-MS patients were assessed on the expanded disability status scale (EDSS) and underwent lumbar puncture. The CSF KYNA, NOx and S100B levels were significantly higher in RR-MS group compared to controls (p = 0.01, 0.001, 0.04, respectively). There was a significant correlation between CSF S100B and KYNA (p = 0.01) but not NOx (p > 0.05) in RR-MS. CSF KYNA, NOx or S100B concentrations did not correlate with disease characteristics of MS patients. Our study suggests the activation of the kynurenine pathway leading to the increase of neuroprotective KYNA in the CSF of MS patients during acute relapse what contrasts with chronic phases of the disease.

Ketogenic diet fed rats have low levels of S100B in cerebrospinal fluid.

Ketogenic diets have been used to treat seizure disorders of children resistant to conventional anti-epileptic drug treatment. The mechanism of action of this diet, however, is unknown. Gliosis is a very common characteristic in tissues associated with epileptogenesis and glial cytokines may be involved in the pathology of seizure disorders. We investigate herein, whether ketogenic diet fed rats demonstrate changes in the immunocontent of S100B, an astrocyte-derived cytokine elevated in the temporal lobe of refractory epilepsy. Lower levels of S100B were observed in cerebrospinal fluid with no significant changes in S100B and GFAP content in brain tissue. Ketogenic fed rats presented a lower seizure severity induced by pentylenetetrazole and no change in cerebrospinal fluid S100B after pentylenetetrazole administration. These results support the concept that the ketogenic diet is neuroprotective in seizure disorders. Since S100B has an extracellular activity in neuronal excitability and synaptic plasticity, it would be reasonable to conceive that a decrease in the S100B could be involved in the mechanism of action of the ketogenic diet. However, it is not possible to establish a direct link between reduced CSF S100B and decreased severity of PTZ-induced attacks at present moment. Regardless of this, CSF S100B could be proposed as an index of efficacy of ketogenic diet for seizure disorders.

Reaction of mouse brain oligodendrocytes and their precursors, astrocytes and microglia, to proinflammatory mediators circulating in the cerebrospinal fluid.

The response of glial cells to the acute intracerebroventricular administration of interferon-gamma, and of this cytokine combined with the endotoxin lipopolysaccharide or with tumor necrosis factor-alpha, was investigated in the brain of adult mice over a time course of 1 week. Oligodendrocytes were identified by immunocytochemistry, using O4 to label their precursors and 2',3'-cyclic nucleotide 3'-phosphohydrolase as marker of mature cells. Astrocytes were labeled by glial fibrillary acidic protein immunoreactivity and microglial cells by tomato lectin histochemistry. Compared with ovalbumin-injected control cases, all cytokine treatments caused a marked decrease of immunostained mature oligodendrocytes in the brain since 1 day postinjection. O4+ oligodendrocyte precursors increased instead progressively from 2 to 7 days. Astrocytes, markedly activated by cytokine treatments, also exhibited a progressive quantitative increase from 2 days onward. Activation and proliferation of microglial cells were instead most evident at 24 h postinjection. Such glial responses to interferon-gamma injections were especially marked in the periventricular brain parenchyma and were enhanced by coadministration of lipopolysaccharide or tumor necrosis factor-alpha. The findings show that a pulse of proinflammatory mediators in the cerebrospinal fluid affects mature oligodendrocytes, concomitantly with the early appearance of activated microglia, and that such reactions are rapidly followed by an increase of oligodendrocyte precursors paralleled by astrocytic activation. The data, which allowed dissecting the events elicited in glial cell populations by inflammatory mediators via the cerebrospinal fluid, indicate that these molecules elicit in vivo a toxic effect on mature oligodendrocytes and a stimulation of their precursors in the adult brain.

Cerebrospinal fluid from patients with neurodegenerative and neuroinflammatory diseases: no evidence for rat glial activation in vitro.

To determine the possible contribution of glial cells via oxidative stress/cytokine secretion in the pathogenesis of Parkinson's disease (PD), Alzheimer disease (AD), amyotrophic lateral sclerosis (ALS) or multiple sclerosis (MS) the concentration of nitric oxide (NO) (by the Griess method) and Interleukin-6 (IL-6) (by enzyme-linked immunosorbent assay) were measured in resting rat microglial and astrocytic cell culture supernatants stimulated by cerebrospinal fluid (CSF) (dilution 1:4, 1:10) from patients with the aforementioned diseases. Neither the concentration of NO (optical density at 450 nm: control, 0.036+/-0.006; MS, 0.034+/-0.008; AD, 0.031+/-0.006; PD, 0.02+/-0.01; lipopolysaccharide (LPS), 0.26+/-0.018) nor the amount of IL-6 (ng/ml: control, 0.112+/-0.026; PD, 0.12+/-0.027; MS, 0.123+/-0.008; ALS, 0.137+/-0.01; LPS, 1.81+/-0.11) differed in any disease group from those of unaffected controls. These findings suggest that the stimuli for inflammatory activation of glia are quite localized and not present in sufficient concentrations in the CSF of affected patients.

CSF neurofilament and glial fibrillary acidic protein in normal pressure hydrocephalus.

We examined CSF levels of markers of neuronal degeneration and astrogliosis-the light subunit of the neurofilament triplet protein (NFL) and the glial fibrillary acidic protein (GFAP)-in 65 patients with normal pressure hydrocephalus (NPH). NFL was increased sixfold (864 +/- 1,538 [mean +/- SD] versus 156 +/- 81 ng/L; p < or = 0.001) and GFAP twofold (1,116 +/- 1,085 versus 637 +/- 295 ng/L; p < or = 0.01) in NPH patients compared with neurologically healthy age-matched controls. No correlation was found between any particular symptom or sign and GFAP levels in CSF. The levels of NFL, on the other hand, were higher in patients with severe symptoms compared with those with moderate or no symptoms. Furthermore, there was a correlation between a high level of NFL and gait disturbance, incontinence, psychometric incapability, and social dysfunction. A high preoperative NFL level was associated with favorable outcome after shunt surgery. This indicates that NFL is a marker of ongoing and possibly still-reversible axonal damage in NPH.

A sensitive ELISA for glial fibrillary acidic protein: application in CSF of adults.

The present study concerns an ELISA for glial fibrillary acidic protein (GFAP) in cerebrospinal fluid (CSF). The application of the method in CSF of children has previously been described in this journal. We have now adapted the technique to allow determination of the much higher GFAP concentrations found in normal and pathological CSF of adults. The assay range was extended to 16,000 pg/ml. CSF levels as high as 170,000 pg/ml could be assayed since dilution experiments indicated immunological identity between purified GFAP and GFAP in CSF. In normal controls the concentrations correlated significantly with age (P < 0.001, Spearman rank correlation test). The concentrations were less than 200 pg/ml before 20 years of age and increased to between 500 and 1300 pg/ml at approximately 75 years of age. This increase of CSF GFAP probably reflects formation of astroglial filaments in the CNS and it must be taken into consideration when determining the pathological CSF GFAP level. The method was validated using CSF samples from patients with either astrogliosis or acute tissue destruction in the CNS. Although augmented levels were observed in both groups it is quite clear that patients with acute tissue destruction may display very high CSF GFAP concentrations, whereas levels in patients with astrogliosis were only modestly increased if at all.

Acute parkinsonian syndrome with demyelinating leukoencephalopathy in bone marrow transplant recipients.

A syndrome of rigidity, bradykinesia, spasticity, and often myoclonus and dementia developed acutely in 5 patients who had undergone successful engraftment of bone marrow transplants for the treatment of various hematologic diseases. Magnetic resonance imaging demonstrated widespread changes in white matter; brain biopsy disclosed mild demyelination associated with active phagocytosis of myelin. One patient, who was not treated, remains severely demented. Patients treated with very high-dose methylprednisolone had complete clinical recovery.

Cytologic diagnosis of gliomatosis cerebri.

Malignant cells were found in the cerebrospinal fluid of an elderly woman with a clinically confusing neurologic disease that was recognized as gliomatosis cerebri at autopsy. The usefulness of cerebrospinal fluid cytology in the antemortem diagnosis of this unusual brain tumor is discussed.

Sites of origin in the central nervous system of monoamine metabolites measured in human cerebrospinal fluid.

The concentrations of homovanillic acid (HVA) and 5-hydroxyindole-acetic acid (5-HIAA) were measured in five cases with partial or complete block of CSF circulation, at various levels. Determinations were made in both a lumbar and a cisternal, or `mixed', sample obtained during pneumoencephalography. Most of the HVA appears to enter the ventricular system at the lateral ventricles, whereas much of the 5-HIAA in CSF originates in lower neuronal structures, including the spinal cord. The spinal contribution to the 5-HIAA content of lumbar CSF is of the order of 23-37%.