Activity of NaV1.2 promotes neurodegeneration in an animal model of multiple sclerosis
Benjamin Schattling, Walid Fazeli, Birgit Engeland, Yuanyuan Liu, Holger Lerche, Dirk Isbrandt, Manuel A. Friese
Benjamin Schattling, Walid Fazeli, Birgit Engeland, Yuanyuan Liu, Holger Lerche, Dirk Isbrandt, Manuel A. Friese
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Research Article Neuroscience

Activity of NaV1.2 promotes neurodegeneration in an animal model of multiple sclerosis

Abstract

Counteracting the progressive neurological disability caused by neuronal and axonal loss is the major unmet clinical need in multiple sclerosis therapy. However, the mechanisms underlying irreversible neuroaxonal degeneration in multiple sclerosis and its animal model experimental autoimmune encephalomyelitis (EAE) are not well understood. A long-standing hypothesis holds that the distribution of voltage-gated sodium channels along demyelinated axons contributes to neurodegeneration by increasing neuroaxonal sodium influx and energy demand during CNS inflammation. Here, we tested this hypothesis in vivo by inserting a human gain-of-function mutation in the mouse NaV1.2-encoding gene Scn2a that is known to increase NaV1.2-mediated persistent sodium currents. In mutant mice, CNS inflammation during EAE leads to elevated neuroaxonal degeneration and increased disability and lethality compared with wild-type littermate controls. Importantly, immune cell infiltrates were not different between mutant EAE mice and wild-type EAE mice. Thus, this study shows that increased neuronal NaV1.2 activity exacerbates inflammation-induced neurodegeneration irrespective of immune cell alterations and identifies NaV1.2 as a promising neuroprotective drug target in multiple sclerosis.

Authors

Benjamin Schattling, Walid Fazeli, Birgit Engeland, Yuanyuan Liu, Holger Lerche, Dirk Isbrandt, Manuel A. Friese

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Figure 2

Heterozygous Scn2aA263V mutation (M/+) leads to an exacerbated EAE disease course without altering immune responses.

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Heterozygous Scn2aA263V mutation (M/+) leads to an exacerbated EAE disea...
(A) Kaplan-Meier survival analysis of male EAE mice after immunization with MOG35–55 (wild-type: n = 9; M/+: n = 11; P = 0.02). (B) Clinical disability scores and (C) body weight changes of female EAE mice after immunization with MOG35–55 (wild-type: n = 13; M/+: n = 20; two independent experiments). (D–F) Representative histopathological stainings and quantifications of whole cervical spinal cord sections (D) or dorsal columns (E and F) of diseased mice 14 days (D14) or 30 days (D30) after immunization (n = 3–4 mice per group with 2–4 color-coded slices per animal). Sections were stained for cellular infiltration (D; H&E, sample images from D14), myelin (E; Luxol fast blue [LFB], sample images from D14), and astrocytes (F; glial fibrillary acidic protein [GFAP]). For each quantification, multiple replicates of data from individual animals were color coded (D–F). Scale bar: 100 μm. (G) Single-cell suspensions of draining lymph nodes were prepared 7 days after immunization from wild-type EAE (n = 3) and M/+ EAE (n = 3) mice, and restimulated with MOG35–55 peptide. T cell proliferation was assessed by incorporation of [methyl-3H]thymidine. CNS-infiltrating cells were isolated 15 days after immunization from wild-type EAE (n = 3) and M/+ EAE (n = 3) mice, and the total number of CD45+ leukocytes (H) and the leukocyte subsets (I) were analyzed by multicolor flow cytometry. All data are presented as mean ± SEM. Statistical analyses were performed by Gehan-Breslow-Wilcoxon test (A), Mann-Whitney test (B and C), 2-way analysis of variance with Sidak’s post-hoc test (G and I), or Student’s t test (D–F and H); *P < 0.05. Color coding has to be evaluated separately for each graph, i.e., each color represents one particular animal at one specific time point for one particular parameter.