Objective High-mobility group box 1 (HMGB1) acts as a proinflammatory mediator when released by cells. Recent studies implicate extracellular HMGB1 in the pathogenesis of various autoimmune diseases. Our main aim of this study is to determine whether HMGB1 is involved in the neuromyelitis optica (NMO) inflammatory process.

Methods Cerebrospinal fluid (CSF) and serum HMGB1 levels in 42 NMO patients were compared with those in 30 multiple sclerosis (MS) patients, and 30 patients with other noninflammatory neurological disorders (ONNDs). We also tested the possible correlation between CSF HMGB1 levels and the clinical and laboratory variables in NMO patients.

Results CSF HMGB1 levels in NMO patients were higher than those in MS and ONNDs patients (p<0.001), and these levels in MS patients were higher than those in ONNDs patients (p<0.001). After treatment, the CSF HMGB1 levels in NMO patients decreased to normal. In addition, CSF HMGB1 levels correlated with CSF cell counts, CSF protein levels, CSF interleukin-6 levels, CSF glial fibrillary acidic protein levels, and CSF/serum albumin ratio (p≤0.001). Serum HMGB1 levels in MS patients were significantly higher than those in ONNDs patients (p=0.002).

Conclusions HMGB1 could play a key role in central nervous system inflammation in NMO patients.