Peroxiredoxins are involved in the pathogenesis of multiple sclerosis and neuromyelitis optica spectrum disorder

Abstract

Peroxiredoxins (PRXs) are intracellular anti-oxidative enzymes but work as inflammatory amplifiers under the extracellular condition. To date, the function of PRXs in the pathogenesis of multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) is not fully understood. The aim of this study was to investigate whether PRXs play a role in the pathogenesis of MS and NMOSD. We analyzed levels of PRXs (PRX1, PRX5 and PRX6) in the cerebrospinal fluid (CSF) and serum of 16 patients with MS, 16 patients with NMOSD and 15 patients with other neurological disorders (ONDs). We identified potential correlations between significantly elevated PRXs levels and the clinical variables in patients with MS and NMOSD. Additionally, pathological analyses of PRXs (PRX1-6) in the central nervous system (CNS) were performed using the experimental autoimmune encephalomyelitis (EAE), animal model of MS. We found that serum levels of PRX5 and PRX6 in patients with MS and NMOSD were higher compared with those in patients with ONDs (P < 0·05). Furthermore, high levels of PRX5 and PRX6 were partly associated with blood-brain barrier dysfunction and disease duration in NMOSD patients. No significant elevation was found in CSF PRXs levels of MS and NMOSD. Spinal cords from EAE mice showed remarkable PRX5 staining, especially in CD45⁺ infiltrating cells. In conclusion, PRX5 and PRX6 may play a role in the pathogeneses of MS and NMOSD.

Keywords: CD45; blood-brain barrier; experimental autoimmune encephalomyelitis; multiple sclerosis; neuromyelitis optica spectrum disorder; peroxiredoxin.

Fig. 1

Cerbrospinal fluid (CSF) and serum levels of peroxiredoxins (PRXs) in patients. No significant differences in the CSF levels of PRXs were identified among patients with multiple sclerosis (MS) (n = 16), neuromyelitis optica spectrum disorder (NMOSD) (n = 16) and other neurological disorders (ONDs) (n = 15). Serum PRX5 and PRX6 levels were significantly elevated in patients with MS (n = 10) and NMOSD (n = 10) compared with patients with ONDs (n = 10). Dashed lines indicate mean values. *P < 0·05; **P < 0·01.

Fig. 2

Pathological findings of the experimental autoimmune encephalomyelitis (EAE) spinal cords. Hematoxylin and eosin (H&E), Luxol fast blue (LFB), Klüver–Barrera (KB), glial fibrillary acidic protein (GFAP) and CD11b immunoreactivity in the spinal cords of normal (a) and EAE mice (at day 18) (b: lower magnification; c: higher magnification) were performed (n = 2 in each group; representative images are shown). Inflammation, demyelination, and CD11b positivity were remarkable in EAE mice but not in normal mice. Black blank squares indicate the area of high magnification. Bars indicate 100 μm.

Fig. 3

Immunohistochemical staining of peroxiredoxins (PRXs) in the EAE spinal cords. PRX immunostaining in the spinal cords of normal (a) and experimental autoimmune encephalomyelitis (EAE) mice (at day 18) (b: lower magnification; c: higher magnification) were performed (n = 2 in each group; representative images are shown). PRX5 staining was remarkable in EAE mice but not in normal mice. Black blank squares indicate the area of high magnification. Bars indicate 100 μm.

Fig. 4

Immunofluorescent staining of the experimental autoimmune encephalomyelitis (EAE) spinal cords. (a,b) Peroxiredoxin 5 (PRX5) (red), CD3/CD45 (green) and 4′,6‐diamidino‐2‐phenylindole (DAPI) (blue) staining of the spinal cords of EAE (representative images are shown). PRX5 and CD45⁺ cells were confirmed in EAE spinal cords but CD3‐positive cells were not identified. (c) Merged images of PRX5 and CD45 (yellow) and PRX5 and DAPI (purple). PRX5 was expressed in CD45⁺ cells. White blank squares indicate the area of high magnification. Bars indicate 100 μm.