Gas6/TAM system as potential biomarker for multiple sclerosis prognosis.

Introduction: The protein growth arrest-specific 6 (Gas6) and its tyrosine kinase receptors Tyro-3, Axl, and Mer (TAM) are ubiquitous proteins involved in regulating inflammation and apoptotic body clearance. Multiple sclerosis (MS) is the most common inflammatory demyelinating disease of the central nervous system leading to progressive and irreversible disability if not diagnosed and treated promptly. Gas6 and TAM receptors have been associated with neuronal remyelination and stimulation of oligodendrocyte survival. However, few data are available regarding clinical correlation in MS patients. We aimed to evaluate soluble levels of these molecules in the cerebrospinal fluid (CSF) and serum at MS diagnosis and correlate them with short-term disease severity. Methods: In a prospective cohort study, we enrolled 64 patients with a diagnosis of clinical isolated syndrome (CIS), radiological isolated syndrome (RIS) and relapsing-remitting (RR) MS according to the McDonald 2017 Criteria. Before any treatment initiation, we sampled the serum and CSF, and collected clinical data: disease course, presence of gadolinium-enhancing lesions, and expanded disability status score (EDSS). At the last clinical follow-up, we assessed EDSS and calculated MS severity score (MSSS) and age-related MS severity (ARMSS). Gas6 and TAM receptors were determined using an ELISA kit (R&D Systems) and compared to neurofilament (NFLs) levels evaluated with SimplePlex™ fluorescence-based immunoassay. Results: At diagnosis, serum sAxl was higher in patients receiving none or low-efficacy disease-modifying treatments (DMTs) versus patients with high-efficacy DMTs (p = 0.04). Higher CSF Gas6 and serum sAXL were associated with an EDSS <3 at diagnosis (p = 0.04; p = 0.037). Serum Gas6 correlates to a lower MSSS (r2 = -0.32, p = 0.01). Serum and CSF NFLs were confirmed as disability biomarkers in our cohort according to EDSS (p = 0.005; p = 0.002) and MSSS (r2 = 0.27, p = 0.03; r2 = 0.39, p = 0.001). Results were corroborated using multivariate analysis. Conclusions: Our data suggest a protective role of Gas6 and its receptors in patients with MS and suitable severity disease biomarkers.

Orthologous proteins of experimental de- and remyelination are differentially regulated in the CSF proteome of multiple sclerosis subtypes.

OBJECTIVE: Here, we applied a multi-omics approach (i) to examine molecular pathways related to de- and remyelination in multiple sclerosis (MS) lesions; and (ii) to translate these findings to the CSF proteome in order to identify molecules that are differentially expressed among MS subtypes. METHODS: To relate differentially expressed genes in MS lesions to de- and remyelination, we compared transcriptome of MS lesions to transcriptome of cuprizone (CPZ)-induced de- and remyelination. Protein products of the overlapping orthologous genes were measured within the CSF by quantitative proteomics, parallel reaction monitoring (PRM). Differentially regulated proteins were correlated with molecular markers of inflammation by using MesoScale multiplex immunoassay. Expression kinetics of differentially regulated orthologous genes and proteins were examined in the CPZ model. RESULTS: In the demyelinated and remyelinated corpus callosum, we detected 1239 differentially expressed genes; 91 orthologues were also differentially expressed in MS lesions. Pathway analysis of these orthologues suggested that the TYROBP (DAP12)-TREM2 pathway, TNF-receptor 1, CYBA and the proteasome subunit PSMB9 were related to de- and remyelination. We designed 129 peptides representing 51 orthologous proteins, measured them by PRM in 97 individual CSF, and compared their levels between relapsing (n = 40) and progressive MS (n = 57). Four proteins were differentially regulated among relapsing and progressive MS: tyrosine protein kinase receptor UFO (UFO), TIMP-1, apolipoprotein C-II (APOC2), and beta-2-microglobulin (B2M). The orthologous genes/proteins in the mouse brain peaked during acute remyelination. UFO, TIMP-1 and B2M levels correlated inversely with inflammation in the CSF (IL-6, MCP-1/CCL2, TARC/CCL17). APOC2 showed positive correlation with IL-2, IL-16 and eotaxin-3/CCL26. CONCLUSIONS: Pathology-based multi-omics identified four CSF markers that were differentially expressed in MS subtypes. Upregulated TIMP-1, UFO and B2M orthologues in relapsing MS were associated with reduced inflammation and reflected reparatory processes, in contrast to the upregulated orthologue APOC2 in progressive MS that reflected changes in lipid metabolism associated with increased inflammation.

Lipocalin 2 in cerebrospinal fluid as a marker of acute bacterial meningitis.

BACKGROUND: Early differential diagnosis between acute bacterial and viral meningitis is problematic. We aimed to investigate whether the detection of lipocalin 2, a protein of the acute innate immunity response, may be used as a marker for acute bacterial meningitis. METHODS: Transgenic mice expressing the human transferrin were infected by intraperitoneal route and were imaged. Cerebrospinal fluid (CSF) was sampled up to 48hours post- infection to measure lipocalin 2. We also tested a collection of 90 and 44 human CSF with confirmed acute bacterial or acute viral meningitis respectively. RESULTS: Lipocalin 2 was detected after 5 h in CSF during experimental infection in mice. Lipocalin 2 levels were significantly higher (p < 0.0001) in patients with confirmed acute bacterial meningitis (mean 125 pg/mL, range 106-145 pg/mL) than in patients with acute viral meningitis (mean 2 pg/mL, range 0-6 pg/mL) with a sensitivity of 81%, a specificity of 93%, a positive predictive value of 96% and a negative predictive value of 71% in diagnosing acute bacterial meningitis. CONCLUSIONS: Increased levels of lipocalin 2 in cerebrospinal fluid may discriminate between acute bacterial and viral meningitis in patients with clinical syndrome of meningitis.

The role of neutrophil gelatinase-associated lipocalin (NGAL) in cerebrospinal fluids for screening of acute bacterial meningitis.

BACKGROUND: Acute bacterial meningitis is a rare but extremely severe disease. The aim of this study was to investigate whether neutrophil gelatinase-associated lipocalin (NGAL) is present and measurable in cerebrospinal fluid (CSF) and if its assessment may be useful for identifying patients with bacterial meningitis. METHODS: Eligible specimens were all consecutive CSFs of patients with suspect acute bacterial meningitis that were referred from the Unit of Infectious Diseases for routine chemical and morphological analysis over a three months period. CSF measurements consisted in NGAL, glucose, and total protein concentrations, along with cell count and differential. RESULTS: Eighty eight CSFs were received throughout the study period, 58 (66%) with CSF findings compatible with bacterial meningitis. The values of white blood cells (WBC), polymorphonuclear (PMN) and mononuclear (MONO) leukocytes, red blood cells (RBC), total proteins, and NGAL were significantly increased in positive CSFs, whereas that of glucose did not significantly differ. A significant correlation was found between CSF concentration of NGAL and CSF values of PMN, WBC, RBC and total proteins, but not with that of glucose and MONO. The concentration of NGAL in CSF showed an area under the curve (AUC) of 0.94 for identifying positive CSFs, with specificity and sensitivity of 1.00 and 0.741 at a diagnostic threshold of 13 ng/mL. CONCLUSIONS: NGAL is present in CSF of patients with bacterial meningitis and its measurement may be helpful for identifying positive CSFs.

CSF protein biomarkers predicting longitudinal reduction of CSF ß-amyloid42 in cognitively healthy elders.

ß-amyloid (Aß) plaque accumulation is a hallmark of Alzheimer's disease (AD). It is believed to start many years prior to symptoms and is reflected by reduced cerebrospinal fluid (CSF) levels of the peptide Aß1-42 (Aß42). Here we tested the hypothesis that baseline levels of CSF proteins involved in microglia activity, synaptic function and Aß metabolism predict the development of Aß plaques, assessed by longitudinal CSF Aß42 decrease in cognitively healthy people. Forty-six healthy people with three to four serial CSF samples were included (mean follow-up 3 years, range 2-4 years). There was an overall reduction in Aß42 from a mean concentration of 211-195 pg ml(-1) after 4 years. Linear mixed-effects models using longitudinal Aß42 as the response variable, and baseline proteins as explanatory variables (n=69 proteins potentially relevant for Aß metabolism, microglia or synaptic/neuronal function), identified 10 proteins with significant effects on longitudinal Aß42. The most significant proteins were angiotensin-converting enzyme (ACE, P=0.009), Chromogranin A (CgA, P=0.009) and Axl receptor tyrosine kinase (AXL, P=0.009). Receiver-operating characteristic analysis identified 11 proteins with significant effects on longitudinal Aß42 (largely overlapping with the proteins identified by linear mixed-effects models). Several proteins (including ACE, CgA and AXL) were associated with Aß42 reduction only in subjects with normal baseline Aß42, and not in subjects with reduced baseline Aß42. We conclude that baseline CSF proteins related to Aß metabolism, microglia activity or synapses predict longitudinal Aß42 reduction in cognitively healthy elders. The finding that some proteins only predict Aß42 reduction in subjects with normal baseline Aß42 suggest that they predict future development of the brain Aß pathology at the earliest stages of AD, prior to widespread development of Aß plaques.

Lipocalin 2: novel component of proinflammatory signaling in Alzheimer's disease.

Alzheimer's disease (AD) is associated with an altered immune response, resulting in chronic increased inflammatory cytokine production with a prominent role of TNF-α. TNF-α signals are mediated by two receptors: TNF receptor 1 (TNFR1) and TNF receptor 2 (TNFR2). Signaling through TNFR2 is associated with neuroprotection, whereas signaling through TNFR1 is generally proinflammatory and proapoptotic. Here, we have identified a TNF-α-induced proinflammatory agent, lipocalin 2 (Lcn2) via gene array in murine primary cortical neurons. Further investigation showed that Lcn2 protein production and secretion were activated solely upon TNFR1 stimulation when primary murine neurons, astrocytes, and microglia were treated with TNFR1 and TNFR2 agonistic antibodies. Lcn2 was found to be significantly decreased in CSF of human patients with mild cognitive impairment and AD and increased in brain regions associated with AD pathology in human postmortem brain tissue. Mechanistic studies in cultures of primary cortical neurons showed that Lcn2 sensitizes nerve cells to ß-amyloid toxicity. Moreover, Lcn2 silences a TNFR2-mediated protective neuronal signaling cascade in neurons, pivotal for TNF-α-mediated neuroprotection. The present study introduces Lcn2 as a molecular actor in neuroinflammation in early clinical stages of AD.

Genetic association of sequence variants near AGER/NOTCH4 and dementia.

We performed a survey of sequence variation in a series of 20 genes involved in inflammation-related pathways for association with dementia risk in twin and unrelated case-control samples consisting in total of 1462 Swedish dementia casesand 1929 controls. For a total of 218 tested genetic markers, strong evidence was obtained implicating a region near AGER and NOTCH4 on chromosome 6p with replication across both samples and maximum combined significance at marker rs1800625 (OR = 1.37, 95% CI 1.19­1.56, p = 1.36×10(­6)). Imputation of the associated genomic interval provided an improved signal atrs8365, near the 3UTR of AGER (p = 7.34×10(­7)). The associated region extends 120 kb encompassing 11 candidate genes.While AGER encodes a key receptor for amyloid-ß protein, an analysis of network context based upon genes now confirmed to contribute to dementia risk (AßPP, PSEN1, PSEN2, CR1, CLU, PICALM, and APOE) suggested strong functional coupling to NOTCH4, with no significant coupling to the remaining candidates. The implicated region occurs in the broad HLA locus on chromosome 6p, but associated markers were not in strong LD with known variants that regulate HLA gene function, suggesting that this may represent a signal distinct from immune-system pathways.

Urinary biomarkers predict brain tumor presence and response to therapy.

PURPOSE: A major difficulty in treating brain tumors is the lack of effective methods of identifying novel or recurrent disease. In this study, we have evaluated the efficacy of urinary matrix metalloproteinases (MMP) as diagnostic biomarkers for brain tumors. EXPERIMENTAL DESIGN: Urine, cerebrospinal fluid, and tissue specimens were collected from patients with brain tumors. Zymography, ELISA, and immunohistochemistry were used to characterize the presence of MMP-2, MMP-9, MMP-9/neutrophil gelatinase-associated lipocalin (NGAL), and vascular endothelial growth factor (VEGF). Results were compared between age- and sex-matched controls and subjected to univariate and multivariate statistical analyses. RESULTS: Evaluation of a specific panel of urinary biomarkers by ELISA showed significant elevations of MMP-2, MMP-9, MMP-9/NGAL, and VEGF (all P < 0.001) in samples from brain tumor patients compared with controls. Multiplexing MMP-2 and VEGF provided superior accuracy compared with any other combination or individual biomarker. Receiver-operating characteristics curves for MMP-2 and VEGF showed excellent discrimination. Immunohistochemistry identified these same proteins in the source tumor tissue. A subset of patients with longitudinal follow-up revealed subsequent clearing of biomarkers after tumor resection. CONCLUSION: We report, for the first time, the identification of a panel of urinary biomarkers that predicts the presence of brain tumors. These biomarkers correlate with presence of disease, decrease with treatment, and can be tracked from source tissue to urine. These data support the hypothesis that urinary MMPs and associated proteins are useful predictors of the presence of brain tumors and may provide a basis for a novel, noninvasive method to identify new brain tumors and monitor known tumors after treatment.