Clinical status of motoneuron disease does not correlate with serum neurotoxicity on cultured neurons

Serum biomarkers of neuroinflammation and blood-brain barrier leakage in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is an incurable and rapidly progressive neurological disorder. Biomarkers are critical to understanding disease causation, monitoring disease progression and assessing the efficacy of treatments. However, robust peripheral biomarkers are yet to be identified. Neuroinflammation and breakdown of the blood-brain barrier (BBB) are common to familial and sporadic ALS and may produce a unique biomarker signature in peripheral blood. Using cytometric bead array (n = 15 participants per group (ALS or control)) and proteome profiling (n = 6 participants per group (ALS or control)), we assessed a total of 106 serum cytokines, growth factors, and BBB breakdown markers in the serum of control and ALS participants. Further, primary human brain pericytes, which maintain the BBB, were used as a biosensor of inflammation following pre-treatment with ALS serum. Principal components analysis of all proteome profile data showed no clustering of control or ALS sera, and no individual serum proteins met the threshold for statistical difference between ALS and controls (adjusted P values). However, the 20 most changed proteins between control and ALS sera showed a medium effect size (Cohen’s d = 0.67) and cluster analysis of their levels together identified three sample subsets; control-only, mixed control-ALS, and ALS-only. These 20 proteins were predominantly pro-angiogenic and growth factors, including fractalkine, BDNF, EGF, PDGF, Dkk-1, MIF and angiopoietin-2. S100β, a protein highly concentrated in glial cells and therefore a marker of BBB leakage when found in blood, was unchanged in ALS serum, suggesting that serum protein profiles were reflective of peripheral rather than CNS biofluids. Finally, primary human brain pericytes remained proliferative and their secretome was unchanged by chronic exposure to ALS serum. Our exploratory study suggests that individual serum cytokine levels may not be robust biomarkers in small studies of ALS, but that larger studies using multiplexed analysis of pro-angiogenic and growth factors may identify a peripheral signature of ALS pathogenesis.

Cerebrospinal fluid from amyotrophic lateral sclerosis has no effect on intracellular free calcium in cultured cortical neurons

The data from the literature regarding the presence of a neurotoxic factor in amyotrophic lateral sclerosis (ALS) plasma or cerebrospinal fluid (CSF) remain controversial. As a new approach to this question, we have studied the effect of CSF from ALS patients on the temporal dynamics of the intracellular free calcium concentration ([Ca2+]i) of murine cortical neurons in cultures using Fura-2 fluorescence videomicroscopy and single-cell imaging. CSF from seven ALS patients and controls was added at dilutions up to 20% to cortical neuronal cultures. The in vitro inhibition of CSF on [3H]kainic acid binding showed that the CSF did not contain any substances other than glutamate itself in larger amounts. At the concentrations used, the CSF did not have any effect on [Ca2+]i or on the neuronal responsiveness as defined by the ability of the cells to respond with a transient increase in [Ca2+]i to depolarization induced by KCl. The disturbance of the intracellular calcium homeostasis is one of the key mechanisms of action of excitotoxic compounds mediating delayed neuronal cell death by stimulation of glutamate receptor subtypes. In this study, CSF from ALS patients did not induce immediate rises in [Ca2+]i or disturbances of the intracellular calcium homeostasis when measured over a period of 2 h.

Sporadic ALS/MND: a global neurodegeneration with retroviral involvement?

Sporadic amyotrophic lateral sclerosis may be an aetiologically heterogenous disease. We confirmed elevated circulating IgG immune complexes, and altered IgG seroreactivities against human retroviral antigens (HIV-2 and HTLV immunoblots) in overlapping subgroups of patients. Together with preliminary findings of a positive polymerase chain reactivity for human T-lymphotropic virus (HTLV.tax/rex) in blood leukocytes of 5 out of 14 sALS patients, we interpret this as evidence for a retroviral involvement in this relentlessly progressive, often asymmetrically spreading neurodegeneration. The possibility of a secondary phenomenon seems unlikely, yet cannot be completely ruled out.

Immunoglobulin-G isotype changes in human sporadic amyotrophic lateral sclerosis (ALS)

Out of 50 patients with sporadic amyotrophic lateral sclerosis (sALS), excluding 8 patients with recent immunosuppressive medication or low total IgG, we examined all available 92 sera of 11 women and 31 men nephelometrically for serum immunoglobulin concentrations including IgG isotypes IgG1-4. Mean serum levels of IgA and IgM remained within references in all cases. Isotypes IgG1 and IgG3 were the most frequently altered immunoglobulins. Without specific treatment, 34 out of 42 patients (= 80%) and 58 out of 92 sera (= 63%) demonstrated low IgG3 concentrations (< 0.41 g/l), while 14 patients (= 33%) and 20 sera (= 22%) demonstrated low IgG1 serum levels (< 4.22 g/l). In patients with normal total IgG, isotypes IgG1 and IgG2 often changed in a complementary way, and IgG1/IgG2 serum concentrations correlated significantly (rs = -0.518, P < 0.001). In four longitudinally monitored patients, the IgG3 isotype ranged from 1.3% to 8.2% of serum IgG and demonstrated a remarkable individual variability over time, corresponding to the relatively short half-life of IgG3. Since elevated circulating immune complexes may fluctuate rapidly, altered serum immunoglobulin isotypes could become more convenient parameters in a still enigmatic disease. To assess their role and relevance, their association with clinical course, cerebrospinal fluid and circulating immune complexes has to be examined.