Abstract

Microglia are key immune cells in the central nervous system, whose dysfunction contributes to neuroinflammation and neurological disorders. Astragali Radix (AR), the root of Astragalus membranaceus (Fisch.) Bge. var. mongholicus (Bge.) Hsiao, is known for neuroprotective effects, yet its active compounds remain underexplored. This study reports the first isolation of Millepurpan (MPP) from AR extract and reveals its potent anti-inflammatory effects in BV-2 microglial cells stimulated with lipopolysaccharide (LPS). Binding assays show MPP targets the ATPase head domain of structural maintenance of chromosomes 2 (SMC2), a condensin complex subunit, inducing steric hindrance that obstructs the ATP-binding pocket. LPS suppresses SMC2 nuclear translocation, causing p21-mediated G0/G1 arrest; MPP restores nuclear SMC2 and promotes G1/S transition. Seahorse metabolic analysis indicates MPP reverses LPS-induced glycolytic reprogramming, an effect abolished by Palbociclib co-treatment, highlighting cell cycle progression's role in metabolic regulation. In vivo, MPP crosses the blood-brain barrier, reduces microglial hyperactivation, and protects neurons in LPS-treated C57BL/6 mice. Immunofluorescence confirms MPP rescues nuclear SMC2 depleted by LPS, supporting its anti-neuroinflammatory action. Reanalysis of single-cell RNA sequencing datasets indicates dysregulation of SMC2 and downstream genes in Alzheimer's disease patients, suggesting SMC2 as a potential biomarker for neuroinflammation. Together, findings reveal an SMC2-mediated pathway whereby MPP binding promotes SMC2 nuclear translocation, mitigating neuroinflammation via regulation of microglial cell cycle and metabolic homeostasis. Given cell cycle regulation's importance in cellular homeostasis, SMC2 emerges as a promising therapeutic target, and MPP as a candidate agent for neuroinflammatory disorder treatment.