Astrocytic 2-Na⁺/K⁺ ATPase inhibition suppresses astrocyte reactivity and reduces neurodegeneration in a tauopathy mouse model

Alzheimer's disease (AD) is the most dominant form of dementia characterized by the deposition of extracellular amyloid plaques and intracellular neurofibrillary tau tangles (NFTs). In addition to these pathologies, an emerging pathophysiological mechanism that influences AD is neuroinflammation. Astrocytes are a vital type of glial cell that contribute to neuroinflammation, and reactive astrocytes, or astrogliosis, are a well-known pathological feature of AD. However, the mechanisms by which astrocytes contribute to the neurodegenerative process in AD have not been fully elucidated. Here, we showed that astrocytic alpha 2-Na+/K+ adenosine triphosphatase (alpha 2-NKA) is elevated in postmortem human brain tissue from AD and progressive nuclear palsy, a primary tauopathy. The increased astrocytic alpha 2-NKA was also recapitulated in a mouse model of tauopathy. Pharmacological inhibition of alpha 2-NKA robustly suppressed neuroinflammation and reduced brain atrophy. In addition, alpha 2-NKA knockdown in tauopathy mice halted the accumulation of tau pathology. We also demonstrated that alpha 2-NKA promoted tauopathy, in part, by regulating the proinflammatory protein lipocalin-2 (Lcn2). Overexpression of Lcn2 in tauopathy mice increased tau pathology, and prolonged Lcn2 exposure to primary neurons promoted tau uptake in vitro. These studies collectively highlight the contribution of reactive astrocytes to tau pathogenesis in mice and define alpha 2-NKA as a major regulator of astrocytic-dependent neuroinflammation.