BACKGROUND: The innate immune response in the CNS plays a critical role in disease progression in multiple
sclerosis (MS)/ experimental autoimmune encephalomyelitis (EAE). Astrocytes, microglia, and pro-inflammatory
monocytes actively promote neurodegeneration, demyelination and scar formation, but therapeutic strategies
targeting glial cells remain elusive. Reactive astrocytes in EAE (here called the “EAE-astrocytes” for short) in the
spinal cord secrete numerous pro-inflammatory factors, with inhibition of each factor individually being beneficial
in EAE. Whereas targeting pro-inflammatory factors individually may be beneficial, a more promising strategy
may be to target the pro-inflammatory secretome of EAE-astrocytes more broadly. This idea emerges from
published work with the oral MS drug and sphingosine-1-phosphate (S1P) receptor modulator, fingolimod, in
which it was shown that astrocyte activation in the presence of fingolimod, yields a secretome that is less pro-
inflammatory. Our lab recently showed pathological involvement of Sur1-Trpm4 in MS/ EAE. During the chronic
phase of EAE, Sur1-Trpm4 channels are robustly upregulated predominantly by reactive astrocytes (EAE-
astrocytes), with global suppression of SUR1 reducing secretion of several pro-inflammatory
cytokines/chemokines, and reducing clinical symptoms, demyelination and axonal loss. New experiments have
expanded on this work, revealing what may be a critical interaction between Sur1-Trpm4 and S1P signaling in
EAE-astrocytes. Preliminary data show that: (i) in EAE, Sur1-Trpm4, S1P1 and S1P3 receptors are highly co-
localized in EAE-astrocytes; (ii) in EAE, astrocyte-specific deletion of Abcc8, which encodes Sur1, yields a
secretome similar to that with fingolimod; (iii) in cultured astrocytes, Sur1-Trpm4 channels are downstream of,
and are required for, S1P signaling; (iv) in cultured astrocytes, Sur1-Trpm4 channels regulate the transcription
of numerous pro-inflammatory factors. Our central hypothesis is that Sur1-Trpm4 channels are required for the
S1P-mediated signaling that perpetuates the pro-inflammatory astrocytic secretome and contributes to disease
maintenance/progression in MS/ EAE.
DESCRIPTION: This project has three mechanistic aims, all focused on Sur1-Trpm4 in EAE. In Aim 1, we will
study myelin oligodendrocyte glycoprotein (MOG) 35–55 EAE in male and female mice with genetic deletion of
Sur1 in astrocytes, initiated at different times after EAE induction, to establish the role of astrocytic Sur1 at
different stages of EAE. In Aim 2, molecular and patch clamp experiments will be used to demonstrate the role
of Sur1-Trpm4 in S1P signaling that regulates the secretome of activated astrocytes. In Aim 3, molecular
experiments will be used to characterize the role of Sur1-Trpm4 in regulating nuclear factor of activated T-cell
(NFAT)-mediated transcription of cytokines/chemokines in activated astrocytes. These studies will contribute
new mechanistic insights into the molecular interactions between Sur1-Trpm4 and S1P signaling in astrocytes,
and thereby reveal new treatment targets for MS.