SignificanceMolecular mechanisms underlying distinct disabilities during neurological diseases may differ based on the neurological pathway involved. Multiple sclerosis (MS) is multifocal, characterized by distinct disabilities affecting walking, vision, cognition, and fatigue. Neuroprotective treatments tailored for each disability may be more effective than nonspecific treatments aiming to reduce a composite of disabilities in clinical trials. Here, we use the MS model to apply a cell-specific and region-specific gene expression approach to discover targets in distinct neuroanatomic regions. Altered cholesterol synthesis gene expression in astrocytes in spinal cord and optic nerve was identified as a potential target for walking and visual disabilities, respectively. This disability-specific discovery approach represents a strategy for finding neuroprotective treatments for multifocal neurodegenerative diseases.

Estrogen has well-documented neuroprotective effects in a variety of clinical and experimental disorders of the CNS, including autoimmune inflammation, traumatic injury, stroke, and neurodegenerative diseases. The beneficial effects of estrogens in CNS disorders include mitigation of clinical symptoms, as well as attenuation of histopathological signs of neurodegeneration and inflammation. The cellular mechanisms that underlie these CNS effects of estrogens are uncertain, because a number of different cell types express estrogen receptors in the peripheral immune system and the CNS. Here, we investigated the potential roles of two endogenous CNS cell types in estrogen-mediated neuroprotection. We selectively deleted estrogen receptor-α (ERα) from either neurons or astrocytes using well-characterized Cre-loxP systems for conditional gene knockout in mice, and studied the effects of these conditional gene deletions on ERα ligand-mediated neuroprotective effects in a wellcharacterized model of adoptive experimental autoimmune encephalomyelitis (EAE). We found that the pronounced and significant neuroprotective effects of systemic treatment with ERα ligand on clinical function, CNS inflammation, and axonal loss during EAE were completely prevented by conditional deletion of ERα from astrocytes, whereas conditional deletion of ERα from neurons had no significant effect. These findings show that signaling through ERα in astrocytes, but not through ERα in neurons, is essential for the beneficial effects of ERα ligand in EAE. Our findings reveal a unique cellular mechanism for estrogen-mediated CNS neuroprotective effects by signaling through astrocytes, and have implications for understanding the pathophysiology of sex hormone effects in diverse CNS disorders.multiple sclerosis | astrogliosis | conditional knockout T he female sex hormone, estrogen, is neuroprotective in many clinical and experimental CNS disorders, including autoimmune conditions such as multiple sclerosis (MS), neurodegenerative conditions such as Alzheimer's and Parkinson diseases, and traumatic injury and stroke (1-4). Estrogen treatment has been shown to ameliorate clinical disease and decrease neuropathology in these disease models (1-4). Pharmacological studies have suggested roles for different estrogen receptors, but the cell types that mediate neuroprotective effects of estrogen are not known for any experimental or clinical condition. Identifying cells that bear specific estrogen receptor subtypes and are essential for specific estrogen-mediated effects is fundamental to elucidating and therapeutically exploiting the mechanisms that underlie estrogen-mediated neuroprotection. Toward this end, we used a genetic loss-of-function strategy. We selectively deleted estrogen receptor-α (ERα) from two different CNS cell types, neurons and astrocytes, and then determined the effects of these conditional gene deletions on the ability of ERα-ligand treatment to ameliorate disease severity of experimental autoimmune encephalomyelitis (EAE) in mice.EAE i...

SummaryBackground Relapses of multiple sclerosis decrease during pregnancy, when the hormone estriol is increased. Estriol treatment is anti-infl ammatory and neuroprotective in preclinical studies. In a small single-arm study of people with multiple sclerosis estriol reduced gadolinium-enhancing lesions and was favourably immunomodulatory. We assessed whether estriol treatment reduces multiple sclerosis relapses in women.

Regional differences in neurons, astrocytes, oligodendrocytes, and microglia exist in the brain during health, and regional differences in the transcriptome may occur for each cell type during neurodegeneration. Multiple sclerosis (MS) is multifocal, and regional differences in the astrocyte transcriptome occur in experimental autoimmune encephalomyelitis (EAE), an MS model. MS and EAE are characterized by inflammation, demyelination, and axonal damage, with minimal remyelination. Here, RNA-sequencing analysis of MS tissues from six brain regions suggested a focus on oligodendrocyte lineage cells (OLCs) in corpus callosum. Olig1-RiboTag mice were used to determine the translatome of OLCs in vivo in corpus callosum during the remyelination phase of a chronic cuprizone model with axonal damage. Cholesterol-synthesis gene pathways dominated as the top up-regulated pathways in OLCs during remyelination. In EAE, remyelination was induced with estrogen receptor-β (ERβ) ligand treatment, and up-regulation of cholesterol-synthesis gene expression was again observed in OLCs. ERβ-ligand treatment in the cuprizone model further increased cholesterol synthesis gene expression and enhanced remyelination. Conditional KOs of ERβ in OLCs demonstrated that increased cholesterol-synthesis gene expression in OLCs was mediated by direct effects in both models. To address this direct effect, ChIP assays showed binding of ERβ to the putative estrogen-response element of a key cholesterol-synthesis gene (Fdps). As fetal OLCs are exposed in utero to high levels of estrogens in maternal blood, we discuss how remyelinating properties of estrogen treatment in adults during injury may recapitulate normal developmental myelination through targeting cholesterol homeostasis in OLCs.

Estrogens can signal through either estrogen receptor ␣ (ER␣) or ␤ (ER␤) to ameliorate experimental autoimmune encephalomyelitis (EAE), the most widely used mouse model of multiple sclerosis (MS). Cellular targets of estrogen-mediated neuroprotection are still being elucidated. Previously, we demonstrated that ER␣ on astrocytes, but not neurons, was critical for ER␣ ligand-mediated neuroprotection in EAE, including decreased T-cell and macrophage inflammation and decreased axonal loss. Here, we determined whether ER␤ on astrocytes or neurons could mediate neuroprotection in EAE, by selectively removing ER␤ from either of these cell types using Cre-loxP gene deletion. Our results demonstrated that, even though ER␤ ligand treatment was neuroprotective in EAE, this neuroprotection was not mediated through ER␤ on either astrocytes or neurons and did not involve a reduction in levels of CNS inflammation. Given the differential neuroprotective and anti-inflammatory effects mediated via ER␣ versus ER␤ on astrocytes, we looked for molecules within astrocytes that were affected by signaling through ER␣, but not ER␤. We found that ER␣ ligand treatment, but not ER␤ ligand treatment, decreased expression of the chemokines CCL2 and CCL7 by astrocytes in EAE. Together, our data show that neuroprotection in EAE mediated via ER␤ signaling does not require ER␤ on either astrocytes or neurons, whereas neuroprotection in EAE mediated via ER␣ signaling requires ER␣ on astrocytes and reduces astrocyte expression of proinflammatory chemokines. These findings reveal important cellular differences in the neuroprotective mechanisms of estrogen signaling through ER␣ and ER␤ in EAE.