RIP1 Exacerbates BBB Disruption by Impairing Autophagy-Mediated A2 Astrocyte Polarization in Hypertension-Induced Cerebral Microhemorrhage in Mice.

Cerebral microhemorrhages (CMHs) contribute to cognitive decline and motor deficits. Inhibiting A1 astrocyte polarization can attenuate brain injury and promote recovery after experimental intracerebral hemorrhage. Despite RIP1 is a known mediator of neurological impairment in hemorrhage models, it is not known whether it regulates astrocytic phenotypic switching to influence CMH progression. Here, a mouse model of hypertension-induced CMHs was established by co-administration of Ang II and L-NAME. Following hypertension induction, daily neurological assessments showed progressively declining scores, indicating ongoing CMH development. RIP1 silencing delayed CMH onset, reduced cumulative incidence, and alleviated hypertension-induced deficits including gait abnormalities, impaired spatial learning and memory, blood-brain barrier (BBB) dysfunction, and A1 astrocyte polarization. In vitro, primary mouse astrocytes were exposed to hemoglobin to simulate the microhemorrhagic microenvironment. RIP1 silencing attenuated hemoglobin-induced A1 polarization and promoted a shift toward the A2 phenotype. Furthermore, RIP1 knockdown counteracted the detrimental effects of A1-polarized astrocytes on endothelial function, as evidenced by improved endothelial cell proliferation, migration, and tube formation. Mechanistically, RIP1 knockdown facilitated the transition from A1 to A2 astrocytic phenotype by activating autophagy and suppressing the NF-κB-NLRP3 inflammasome pathway, thereby mitigating hypertension-induced BBB disruption following CMHs. In conclusion, RIP1 silencing alleviates BBB disruption following hypertension-induced CMHs by promoting autophagy-mediated A2 astrocyte polarization.