Blockade of IRE1-XBP1 Signaling Pathway Ameliorates IL-6-dependent Nerve Damage and Neuron Pyroptosis after Subarachnoid Hemorrhage in Mice.

Subarachnoid hemorrhage (SAH) often results in severe neurological impairment. While spliced X-box binding protein 1 (XBP1s) has been implicated in brain injury, its specific role and mechanism in SAH-induced mice remain unclear. A murine SAH model was established to explore the function of XBP1 knockdown. Neurological function was evaluated through behavioral tests, brain edema measurement, and hematoxylin and eosin staining. Blood-brain barrier (BBB) integrity and neuronal pyroptosis were assessed using Evans blue extravasation, western blotting, immunofluorescence and LDH release assay. The direct interaction of IL-6 by XBP1s was confirmed using chromatin immunoprecipitation and luciferase reporter assays. Finally, the functional central to our hypothesis was verified by administering exogenous IL-6 or IL-6 blocking antibody to SAH mice. We found that XBP1s and p-IRE1 were significantly up-regulated after SAH. Knockdown of XBP1 ameliorated neurological deficits, preserved BBB integrity (as indicated by increased ZO-1/Occludin and reduced Evans blue leakage), and suppressed neuronal pyroptosis, evidenced by decreased levels of pyroptosis-related proteins and LDH release. Mechanistically, XBP1s was identified as a direct transcriptional enhancer of IL-6. In the mouse SAH model, the protective effects of XBP1 knockdown on the BBB and against pyroptosis were effectively abolished by the exogenous administration of IL-6 and were comparable to administration of the IL-6 blocking antibody. The IRE1-XBP1s signaling axis played an important role in SAH-induced neuronal damage and pyroptosis by directly up-regulating IL-6 expression. Inhibition of this axis represents a mechanistically grounded and promising strategy for SAH intervention.