Critical role of high-dose Astragalus in Buyang Huanwu Decoction for enhancing neurovascular coupling in a Qi Deficiency and Blood Stasis animal model

Abstract Background Buyang Huanwu Decoction (BHD) is a classical Traditional Chinese Medicine (TCM) formula effective for treating Chronic Cerebral Ischemia with Qi Deficiency and Blood Stasis Syndrome (CCI QDBS ), which is known to alleviate neuronal damage and improve cerebral blood flow. The use of a high dose of Astragalus (Huangqi) has been clinically emphasized as crucial to BHD's efficacy, yet the pharmacological basis for this requirement remains unelucidated. Objective This study aimed to compare the therapeutic efficacy of BHD with a high dose of Astragalus (120 g, BHD HA ) versus a low dose (30 g, BHD LA ) in treating CCI QDBS and to investigate the underlying mechanisms. Methods A mouse model of CCI QDBS was established by combining systemic hypotension with bilateral common carotid artery occlusion and sleep deprivation. The necessity of high-dose Astragalus in BHD was evaluated by assessing syndrome-specific symptoms, cognitive performance, and brain functional connectivity via functional magnetic resonance imaging (fMRI). Neurovascular coupling (NVC) function was visualized in real-time using two-photon in vivo microscopy. RNA sequencing and immunofluorescence were employed to explore the molecular mechanisms by which BHD HA improves NVC and mitigates brain injury. Finally, the role of nuclear Factor IA (NFIA) was validated through targeted gene silencing using an AAV-shRNA vector (pAVV-U6-sh Nfia ). Results BHD HA demonstrated significantly superior therapeutic effects compared to BHD LA . It more effectively ameliorated CCI QDBS -induced deficits, including memory impairment and fatigue-like behaviors, and significantly enhanced brain functional connectivity. Mechanistically, BHD HA induced the morphological recovery of astrocytes, increased their perivascular coverage, and restored impaired NVC function. These beneficial effects were found to be dependent on the upregulation of NFIA. Silencing Nfia abolished the therapeutic advantages of BHD HA in improving NVC and cognitive function. Conclusion Our findings demonstrate that the high dose of Astragalus is essential for the therapeutic efficacy of BHD under the conditions of the present experimental model. BHD HA alleviates CCI QDBS by modulating NFIA to maintain the stability of the neurovascular unit (NUV), thereby improving neurovascular coupling, remodeling brain functional connectivity, and restoring cognitive function. This study provides a scientific basis for the high-dose application of Astragalus in this classical formula. This study provides a scientific basis for the high-dose application of Astragalus in the treatment of CCI QDBS using BHD.