Increased plasma IL-6, IL-8, TNF-alpha, and G-CSF in Japanese narcolepsy

Narcolepsy is a chronic hypersomnia involving excessive daytime sleepiness and cataplexy. Some susceptibility genes and environmental factors suggest that post-infectious immunological alterations underlie its pathophysiology. To investigate the immunological alterations in narcolepsy patients, we examined cytokines. Nine healthy controls and twenty-one narcolepsy patients with cataplexy were studied. All subjects were positive for the HLA-DRB1(∗)1501-DQB1(∗)0602 allele. Age-, sex-, and body mass index -matched healthy controls were selected. Plasma samples were separated using EDTA-2K-coated blood collection tubes. Bioplex Pro Human Cytokine 17-Plex Assays were used to measure plasma cytokines. Elevations of interleukin (IL)-6, IL-8, granulocyte- colony stimulating factor (G-CSF), and tumor necrosis factor-alpha were found in the narcolepsy group compared with healthy controls (p<0.05). G-CSF values were significantly correlated with the disease duration in narcolepsy patients (r=0.426, p<0.05). IL-8 and G-CSF play major roles in neutrophil activation in respiratory diseases. Since environmental factors including infection are reportedly associated with narcolepsy onset, elevated IL-8 and G-CSF may be involved in the pathophysiology of narcolepsy.