Astragaloside IV Mitigates Subarachnoid Hemorrhage-Induced Brain Injury via Regulating Microglial Polarization and Neuroinflammation Mediated by cGAS/STING Pathway.

OBJECTIVE

To investigate the effects of astragaloside IV (AS-IV) on subarachnoid hemorrhage (SAH)-related brain injury and explore the underlying mechanisms.

METHODS

The effects of related signaling pathways on SAH were analyzed through stimulator of interferon gene (STING) knockout and RNA sequencing (RNA-seq) in mice. In vitro, mouse BV2 microglial cell line was stimulated with hemin to establish a model mimicking SAH. AS-IV was administered after SAH. Neurological deficits and the therapeutic effects of AS-IV in mice were assessed using modified Garcia scores. ELISA and Western blot were employed to measure the expressions of inflammatory factors and the cyclic GMP-AMP synthase (cGAS)/STING signaling pathway both in vivo and in vitro, respectively. TUNEL staining was used to evaluate neuronal apoptosis, Fluoro-Jade C (FJC) staining for neuronal degeneration, immunofluorescence for microglial activation and polarization, and flow cytometry for myeloid cell changes in peripheral blood.

RESULTS

The knockout of STING alleviated early brain injury following SAH (P<0.01). RNA-seq revealed the activation of the cGAS/STING and NF-κB related pathways following SAH. In vitro, hemin elevated cGAS-STING and inflammatory factor levels in microglial cells, while AS-IV significantly inhibited these effects (P<0.05 or P<0.01). SAH mice showed reduced neurological scores, obvious systemic inflammation, increased neuronal apoptosis and degeneration, with elevated cGAS-STING pathway and inflammatory factors in brain tissue (P<0.05 or P<0.01). AS-IV suppressed these effects and improved microglial activation and morphology (P<0.05 or P<0.01).

CONCLUSIONS

In the early stage of brain injury following SAH, AS-IV regulates microglial polarization through the cGAS/STING pathway, thus improving neurological outcomes and alleviating neuroinflammation. AS-IV may be an effective therapeutic agent for the pathology of neuroinflammation following SAH.