Suppression of the Peripheral Immune System Limits the Central Immune Response Following Cuprizone-Feeding: Relevance to Modelling Multiple Sclerosis

Abstract

Cuprizone (CPZ) preferentially affects oligodendrocytes (OLG), resulting in demyelination. To investigate whether central oligodendrocytosis and gliosis triggered an adaptive immune response, the impact of combining a standard (0.2%) or low (0.1%) dose of ingested CPZ with disruption of the blood brain barrier (BBB), using pertussis toxin (PT), was assessed in mice. 0.2% CPZ(±PT) for 5 weeks produced oligodendrocytosis, demyelination and gliosis plus marked splenic atrophy (37%) and reduced levels of CD4 (44%) and CD8 (61%). Conversely, 0.1% CPZ(±PT) produced a similar oligodendrocytosis, demyelination and gliosis but a smaller reduction in splenic CD4 (11%) and CD8 (14%) levels and no splenic atrophy. Long-term feeding of 0.1% CPZ(±PT) for 12 weeks produced similar reductions in CD4 (27%) and CD8 (43%), as well as splenic atrophy (33%), as seen with 0.2% CPZ(±PT) for 5 weeks. Collectively, these results suggest that 0.1% CPZ for 5 weeks may be a more promising model to study the ‘inside-out’ theory of Multiple Sclerosis (MS). However, neither CD4 nor CD8 were detected in the brain in CPZ±PT groups, indicating that CPZ-mediated suppression of peripheral immune organs is a major impediment to studying the ‘inside-out’ role of the adaptive immune system in this model over long time periods. Notably, CPZ(±PT)-feeding induced changes in the brain proteome related to the suppression of immune function, cellular metabolism, synaptic function and cellular structure/organization, indicating that demyelinating conditions, such as MS, can be initiated in the absence of adaptive immune system involvement.

CD8 T-cell Recruitment Into the Central Nervous System of Cuprizone-Fed Mice: Relevance to Modeling the Etiology of Multiple Sclerosis

“…While there have been numerous reports of CPZ being used to study demyelination, these have not established the involvement of peripheral T-cells at the sites of CPZ-induced demyelination in the CNS (Remington et al, 2007;Partridge et al, 2016;Traka et al, 2016;Tejedor et al, 2017;Sen et al, 2019a). It was thought that as CPZ does not induce a breach of the blood-brain barrier (BBB), T-cells have no access to the CNS (Remington et al, 2007;Skripuletz et al, 2011;Tejedor et al, 2017).…”

“…It was thought that as CPZ does not induce a breach of the blood-brain barrier (BBB), T-cells have no access to the CNS (Remington et al, 2007;Skripuletz et al, 2011;Tejedor et al, 2017). However, even when the BBB was breached using pertussis toxin (PT), CPZ evoked marked CNS demyelination, gliosis and changes in the abundance of proteoforms involved in metabolism, immune and synaptic functions, without detectable T-cell infiltration (Sen et al, 2019a). Studies have indicated that the apparent failure to trigger a T-cell-mediated CNS immune response is due to CPZ-induced atrophy of the thymus (the organ responsible for T-cell maturation and differentiation) and spleen (the organ of T and B lymphocyte production; Solti et al, 2015;Martin et al, 2018;Sui et al, 2019;Sen et al, 2019a).…”

“…However, even when the BBB was breached using pertussis toxin (PT), CPZ evoked marked CNS demyelination, gliosis and changes in the abundance of proteoforms involved in metabolism, immune and synaptic functions, without detectable T-cell infiltration (Sen et al, 2019a). Studies have indicated that the apparent failure to trigger a T-cell-mediated CNS immune response is due to CPZ-induced atrophy of the thymus (the organ responsible for T-cell maturation and differentiation) and spleen (the organ of T and B lymphocyte production; Solti et al, 2015;Martin et al, 2018;Sui et al, 2019;Sen et al, 2019a). Two additional effects of CPZ on the integrity and function of the peripheral immune system include an increase in the abundance of splenic arginase-I (a protein expressed by myeloid-derived suppressor cells in spleen) and a decreased abundance of protein disulfide isomerize (a protein required for assembly of the major histocompatibility complex-I; Partridge et al, 2016).…”

“…A change in the abundance of these proteins results in suppressed T-cell function (Kang et al, 2009). Likewise, proteoforms of calcium/calmodulin-dependent protein kinase type II subunit-α and leukocyte elastase inhibitor A, involved in T-cell functions, decreased in abundance following CPZ-feeding (Sen et al, 2019a). Moreover, marked changes in the number of mitochondrial proteoforms are suggested to suppress T-cell function (Sen et al, 2019a).…”

Differential Expression of miRNAs and Behavioral Change in the Cuprizone-Induced Demyelination Mouse Model

“…The research includes using animal models to help understand the demyelination and remyelination mechanisms, facilitating the study of cellular responses taking place in this process, and providing a robust platform for elucidating putative therapeutic targets. However, there is the limitation that no current animal model faithfully replicates the myriad of symptoms seen in the clinical condition of MS [2,7].…”