Unique molecular characteristics and microglial origin of Kv1.3 channel-positive brain myeloid cells in Alzheimer's disease.

Abstract

Kv1.3 potassium channels, expressed by proinflammatory central nervous system mononuclear phagocytes (CNS-MPs), are promising therapeutic targets for modulating neuroinflammation in Alzheimer's disease (AD). The molecular characteristics of Kv1.3-high CNS-MPs and their cellular origin from microglia or CNS-infiltrating monocytes are unclear. While Kv1.3 blockade reduces amyloid beta (Aβ) burden in mouse models, the downstream immune effects on molecular profiles of CNS-MPs remain unknown. We show that functional Kv1.3 channels are selectively expressed by a subset of CD11b⁺CD45⁺ CNS-MPs acutely isolated from an Aβ mouse model (5xFAD) as well as fresh postmortem human AD brain. Transcriptomic profiling of purified CD11b⁺Kv1.3⁺ CNS-MPs, CD11b⁺CD45^int Kv1.3^neg microglia, and peripheral monocytes from 5xFAD mice revealed that Kv1.3-high CNS-MPs highly express canonical microglial markers (<i>Tmem119</i>, <i>P2ry12</i>) and are distinct from peripheral Ly6c^high/Ly6c^low monocytes. Unlike homeostatic microglia, Kv1.3-high CNS-MPs express relatively lower levels of homeostatic genes, higher levels of <i>CD11c</i>, and increased levels of glutamatergic transcripts, potentially representing phagocytic uptake of neuronal elements. Using irradiation bone marrow CD45.1/CD45.2 chimerism in 5xFAD mice, we show that Kv1.3⁺ CNS-MPs originate from microglia and not blood-derived monocytes. We show that Kv1.3 channels regulate membrane potential and early signaling events in microglia. Finally, in vivo blockade of Kv1.3 channels in 5xFAD mice by ShK-223 reduced Aβ burden, increased CD11c⁺ CNS-MPs, and expression of phagocytic genes while suppressing proinflammatory genes (<i>IL1b</i>). Our results confirm the microglial origin and identify unique molecular features of Kv1.3-expressing CNS-MPs. In addition, we provide evidence for CNS immunomodulation by Kv1.3 blockers in AD mouse models resulting in a prophagocytic phenotype.