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

Mohammed S M Almuslehi,Monokesh K Sen,David A Mahns,Jens R Coorssen,Peter J Shortland

doi:10.3389/fncel.2020.00043

Mohammed S M Almuslehi, Monokesh K Sen + Show 3 more

Open Access

https://doi.org/10.3389/fncel.2020.00043

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Abstract

Cuprizone (CPZ)-feeding in mice induces atrophy of peripheral immune organs (thymus and spleen) and suppresses T-cell levels, thereby limiting its use as a model for studying the effects of the immune system in demyelinating diseases such as Multiple Sclerosis (MS). To investigate whether castration (Cx) can protect the peripheral immune organs from CPZ-induced atrophy and enable T-cell recruitment into the central nervous system (CNS) following a breach of the blood-brain barrier (BBB), three related studies were carried out. In Study 1, Cx prevented the dose-dependent reductions (0.1% < 0.2% CPZ) in thymic and splenic weight, size of the thymic medulla and splenic white pulp, and CD4 and CD8 (CD4/8) levels remained comparable to gonadally intact (Gi) control males. Importantly, 0.1% and 0.2% CPZ were equipotent at inducing central demyelination and glial activation. In Study 2, combining Cx with 0.1% CPZ-feeding and BBB disruption with pertussis toxin (PT) enhanced CD8+ T-cell recruitment into the CNS. The increased CD8+ T-cell level observed in the parenchyma of the cerebrum, cerebellum, brainstem and spinal cord were confirmed by flow cytometry and western blot analyses of CNS tissue. In Study 3, PT+0.1% CPZ-feeding to Gi female mice resulted in similar effects on the peripheral immune organs, CNS demyelination, and gliosis comparable to Gi males, indicating that testosterone levels alone were not responsible for the immune response seen in Study 2. The combination of Cx+0.1% CPZ-feeding+PT indicates that CPZ-induced demyelination can trigger an “inside-out” immune response when the peripheral immune system is spared and may provide a better model to study the initiating events in demyelinating conditions such as MS.

Highlights

Multiple Sclerosis (MS) is a heterogeneous, inflammatory demyelinating disease of the human central nervous system (CNS) for which the early initiating events and underlying etiology remain unclear (Stys et al, 2012; Stys, 2013; Partridge et al, 2015)
In female mice (Study 3), combining CPZ-feeding with blood-brain barrier (BBB) disruption resulted in CNS demyelination and gliosis, but no CD8+ T-cell infiltration into the brain or spinal cord. These results indicate that CPZ-induced demyelination in the CNS can trigger a CD8+ T-cell-mediated central response when the peripheral immune system is preserved
The findings fully establish that feeding juvenile male mice with 0.1% or 0.2% CPZ for 2 weeks produced equivalent levels of demyelination and gliosis in the corpus callosum

Summary

Introduction

Multiple Sclerosis (MS) is a heterogeneous, inflammatory demyelinating disease of the human central nervous system (CNS) for which the early initiating events and underlying etiology remain unclear (Stys et al, 2012; Stys, 2013; Partridge et al, 2015). There are no effective treatments to prevent disease initiation and progression (Sriram and Steiner, 2005; Vargas and Tyor, 2017). Several animal models such as experimental autoimmune encephalomyelitis (EAE; Glatigny and Bettelli, 2018), Theiler’s murine encephalomyelitis virus (Carrillo-Salinas et al, 2017), and the diphtheria toxin model (Traka et al, 2016) mimic various clinical and pathological features of the disease but no single model replicates the full complexity of disease initiation and progression. The cuprizone (CPZ) model possesses many key characteristics of MS including demyelination and gliosis (reviewed in Sen et al, 2019b) According to these pathological features, the CPZ model was selected as the most appropriate tool to test the ‘‘inside-out’’ theory of disease initiation (Caprariello et al, 2018). Myelin antigen presentation by antigen-presenting cells attracts peripheral T- and B-cells into the CNS, triggering a secondary inflammatory reaction that leads to the progressive autoimmune response characterized clinically (Stys et al, 2012; Stys, 2013)

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