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Astrocyte Deletion of alpha2-Na/K ATPase Triggers Episodic Motor Paralysis in Mice via a Metabolic Pathway

ABSTRACT: Familial hemiplegic migraine is an episodic neurological disorder characterized by transient sensory and motor symptoms and signs. Mutations of the ion pump alpha2-Na/K ATPase represent a key genetic cause of familial hemiplegic migraine, but the mechanisms by which alpha2-Na/K ATPase mutations lead to the migraine phenotype remain incompletely understood. Here, we unexpectedly find that mice in which alpha2-Na/K ATPase is conditionally deleted in astrocytes display episodic transient motor paralysis. Functional neuroimaging reveals that conditional knockout of alpha2-Na/K ATPase triggers spontaneous cortical spreading depression events that are associated with low voltage activity events upon EEG monitoring, which in turn correlate with transient motor impairment in these mice. Transcriptomic and metabolomic analyses show that loss of alpha2-Na/K ATPase alters metabolic gene expression in astrocytes in vivo with consequent elevation of serine and glycine in the brain. Strikingly, feeding alpha2-Na/K ATPase knockout mice a serine- and glycine-free diet reverses the phenotype of transient motor impairment. Together, our findings define a novel metabolic mechanism regulated by astrocytic alpha2-Na/K ATPase that triggers episodic transient motor paralysis in mice, laying the foundation for potential new treatment strategies for patients with familial hemiplegic migraine.

ORGANISM(S): Mus musculus

PROVIDER: GSE145102 | GEO | 2020/10/20

REPOSITORIES: GEO

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Project description:The Na/K-ATPase is the specific receptor for cardiotonic steroids (CTS) such as ouabain and digoxin. At pharmacological concentrations used in the treatment of cardiac conditions, CTS inhibit the ion-pumping function of Na/K-ATPase. At much lower concentrations, in the range of those reported for endogenous CTS in the blood, they stimulate hypertrophic growth of cultured cardiac myocytes through initiation of a Na/K-ATPase-mediated and reactive oxygen species (ROS)-dependent signaling. To examine a possible effect of endogenous concentrations of CTS on cardiac structure and function in vivo, we compared mice expressing the naturally resistant Na/K-ATPase α1 and age-matched mice genetically engineered to express a mutated Na/K-ATPase α1 with high affinity for CTS. In this model, total cardiac Na/K-ATPase activity, α1, α2 and β1 protein content remained unchanged, and the cardiac Na/K-ATPase dose-response curve to ouabain shifted to the left as expected. In males aged 3–6 months, increased α1 sensitivity to CTS resulted in a significant increase of cardiac carbonylated protein content, suggesting that ROS production was elevated. A moderate but significant increase of about 15% of the heart-weight-to-tibia-length ratio, accompanied by an increase of myocyte cross-sectional area was detected. Echocardiographic analyses did not reveal any change in cardiac function, and there was no fibrosis or re-expression of the fetal gene program. RNA sequencing analysis indicated that pathways related to energy metabolism were upregulated, while those related to extracellular matrix organization were downregulated. Consistent with a functional role of the latter, an angiotensin-II challenge that triggered fibrosis in the α1r/rα2s/s mouse failed to do so in the α1s/sα2s/s. Taken together, these results are indicative of a link between circulating CTS, Na/K-ATPase α1, ROS, and physiological cardiac hypertrophy in mice under baseline laboratory conditions.

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Astrocyte Deletion of alpha2-Na/K ATPase Triggers Episodic Motor Paralysis in Mice via a Metabolic Pathway

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