Interleukin-6, S-Nitrosothiols, and Neurodegeneration in Different Central Nervous System Demyelinating Disorders: Is There a Relationship?

BACKGROUND AND PURPOSE: A few groups have suggested that activated cytokines and nitrosative stress are closely involved in the pathogenesis of different demyelinating disorders induced by the neuroinflammatory destruction of neurons. The purpose of this study was to elucidate the associations of cytokines and S-nitrosothiols (RSNO) with the severity of neurodegeneration during relapse in demyelinating disorders of the central nervous system. METHODS: We measured levels of interleukin-6 (IL-6), erythropoietin, RSNO, and phosphorylated neurofilament heavy chain (pNfh) in cerebrospinal fluid (CSF) samples obtained from patients with different demyelinating disorders: multiple sclerosis (MS, n=52), acute disseminated encephalomyelitis (ADEM, n=9), and neuromyelitis optica spectrum disorders (NMOSD) with aquaporin-4 immunoglobulin G (AQP4-IgG, n=12). We compared these levels with those measured in a control group (n=24). RESULTS: We found that IL-6 in CSF was elevated in NMOSD with AQP4-IgG and ADEM patients as well as in MS patients after the destruction of soluble IL-6. Erythropoietin levels were lower in MS, while RSNO levels were higher in NMOSD with AQP4-IgG and MS patients than in the control group. CSF pNfh levels were elevated in MS and ADEM patients. CONCLUSIONS: These results confirm that IL-6 is activated in different demyelinating disorders, with this elevation being more prominent in the CSF of NMOSD with AQP4-IgG and ADEM patients. Moreover, S-nitrosylation is activated in demyelinating disorders with spinal-cord injury and neurodegeneration in these patients. However, we found no correlation between these biochemical markers, and so we could not confirm whether IL-6-mediated nitric oxide production is involved in spinal-cord lesions.