Treatment with pertussis toxin does not induce a multiple sclerosis-like phenotype in cuprizone-treated mice

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the human. Two competing theories are proposed for demyelination: an “outside in” mechanism where peripheral factors breach the blood brain barrier (BBB) leading to CNS demyelination or an “inside-out” mechanism where demyelination causes BBB disruption leading to an autoimmune response. Oral ingestion of cuprizone (CPZ) in animals induces CNS demyelination and inflammatory responses; however, it does not evoke the recruitment of the peripheral immune system as the BBB remains intact. We hypothesise that disruption of the BBB might trigger autoimmune response in the presence of available myelin antigen in CPZ treated mice by treating C57Bl/6 male mice with CPZ for 5 weeks and injecting intraperitoneal pertussis toxin (PT) during weeks 1-2 of CPZ treatment. Motor behaviour responses, demyelination, protein changes, and inflammation were determined using rotarod, histology, 2D proteomics, and immunohistochemistry, respectively. Treatment with CPZ alone, or CPZ with PT, depleted oligodendrocytes and produced demyelination in the corpus callosum and cerebral cortex as well as activation of astrocytes and microglia in these regions. No synergistic effects of CPZ with PT were observed for oligodendrocyte loss, demyelination and glial activation. No motor changes (latency to fall) were found during treatment. Western blot analysis did not demonstrate the recruitment of peripheral (CD4 and 8) immune cells in the CNS at post-mortem. The complete proteomics analysis is currently underway targeting novel candidate proteins that might involve in different pathological and/or inflammatory process. The results suggest that combined treatment does not trigger an autoimmune response like that observed in human MS