Sphingosine-1-Phosphate Receptor 3 Mediated Neuroinflammation is Critically Involved in the Development of Brain...

Brain injury after cardiac arrest (CA) is a major cause of death and disability, with neuroinflammation increasingly recognized as a key driver. Although the sphingosine-1-phosphate receptor 3 (S1PR3)-a G protein-coupled receptor-has been linked to neurological disorders, its role in CA-induced brain injury remains unclear. We induced CA in mice via intravenous potassium chloride injection. S1PR3 expression and subcellular localization were assessed in cortex and hippocampus. Mice received intraperitoneal CAY10444 (a selective S1PR3 antagonist) alone or with Colivelin TFA (a Janus Kinase 2 (JAK2)/Signal Transducer and Activator of Transcription 3 (STAT3) agonist). Survival after return of spontaneous circulation (ROSC) was recorded. Neurological function was evaluated using neurological deficit score, rotarod, adhesive removal, and novel object recognition tests. Brain pathology was examined by H&E, Nissl, immunohistochemistry, and Golgi staining. Microglial and astrocyte activation were quantified by immunohistochemistry; IL-1β, TNF-α, and IL-6 mRNA levels were measured; and JAK2/STAT3 pathway activity was assessed by Western blot for p-JAK2 and p-STAT3. CA/CPR upregulated S1PR3 in the brain and increased its co-localization with neurons and glia. CAY10444 improved survival and all behavioral outcomes. It reduced neuronal loss, axonal damage, dendritic spine loss, and suppressed microglial and astrocytic activation in the hippocampus. CAY10444 also lowered IL-1β, TNF-α, and IL-6 expression and decreased CA-induced JAK2/STAT3 phosphorylation. Colivelin TFA partially reversed these benefits. CAY10444 confers neuroprotection after CA/CPR by inhibiting S1PR3 and downstream JAK2/STAT3 signaling, thereby dampening neuroinflammation and neuronal death. S1PR3 is therefore a promising therapeutic target for CA-induced brain injury.