Sphk1/S1P pathway promotes blood-brain barrier breakdown after intracerebral hemorrhage through inducing Nlrp3-mediated endothelial cell pyroptosis

Intracerebral hemorrhage (ICH) is a severe stroke subtype with high mortality and limited therapeutic options. The blood-brain barrier (BBB) breakdown post-ICH exacerbates secondary brain injury, highlighting the need for targeted therapies to preserve the BBB integrity. We aim to investigate the role of the Sphk1/S1P pathway in BBB breakdown following ICH and to evaluate the therapeutic potential of Sphk1 inhibition in mitigating this breakdown. Using a combination of human patient samples, mouse models of ICH, and in vitro cellular assays, we assessed the expression levels of Sphk1/S1P after ICH and changes of the BBB after ICH. The Sphk1 inhibitor PF543 and siRNAs were utilized to explore the pathway's impact on BBB integrity and the underlying mechanisms. The results indicate significant upregulation of Sphk1/S1P in the peri-hematomal brain tissue after ICH, which correlates with increased BBB leakage. Pharmacological inhibition of Sphk1 with PF543 attenuates BBB leakage, reduces hematoma volume, and improves neurological outcomes in mice. At the molecular and ultrastructural level, Sphk1 inhibition protects the BBB integrity by preserving tight junction proteins and suppressing endothelial transcytosis. Furthermore, mechanistic studies reveal that Sphk1 promotes Nlrp3-mediated pyroptosis of brain endothelial cells through the ERK1/2 signaling pathway. Taken together, the Sphk1/S1P pathway plays a critical role in ICH-induced BBB breakdown, and its inhibition represents a promising therapeutic strategy for ICH management.