Selective S1PR1 activation improves brain infarction, neurological outcome, and cerebrovascular endothelial health following experimental ischemic injury

Sphingosine-1-phosphate receptor 1 (S1PR1) is highly expressed in endothelial cells and receptor activation plays an important role in mediating endothelial function and health, thus showing promise as a pharmacologic target for acute ischemic stroke (AIS) treatment. Here, we examined the effect of a selective S1PR1 ligand, RP101075, on infarct volume and neurological outcome in adult male mice subjected to transient middle cerebral artery occlusion (tMCAO). Concomitantly, we examined S1PR1 expression profile in the ischemic mouse brain, as well as S1PR1 expression and impact of receptor activation on human brain microvascular endothelial cell (HBMEC) proliferation and survival following hypoxia plus glucose deprivation (HGD). We observed that RP101075 administration at onset of reperfusion reduced infarct volume and lessened neurological deficits in tMCAO mice and these responses were S1PR1 dependent. Additionally, we observed that tMCAO increased brain S1PR1 protein levels and flow cytometry revealed increases in S1PR1 levels are greatest in brain endothelial cells compared to other brain cell types (astrocyte, neuron, microglia). In cultured HBMECs, RP101075 increased cell proliferation and ozanimod, parent compound of RP1010175, increased live cell count during HGD; this response was S1PR1 dependent. In conclusion, S1PR1 activation improves neuroprotection/outcome post-stroke and preserves brain endothelial cell survival following ischemia-like injury.