S1PR3 Inactivation Aggravates Cerebrovascular Endothelial Cell Permeability Mediated by cPLA ₂ and STAT3 Phosphorylation Under Oxidative Stress

Sphingosine-1-phosphate receptor-3 (S1PR3) has been implicated in the maintenance of cerebrovascular integrity during cerebral ischemia. This study aimed to elucidate the impact of S1PR3 inactivation on oxidative stress-induced cerebrovascular endothelial cell permeability and to explore the potential mechanisms. In bEnd3 cells, blockade of S1PR3 exacerbated H₂O₂-induced endothelial hyperpermeability, ZO-1 redistribution, reactive oxygen species (ROS) accumulation and cell viability loss. A previous study indicated that the activation of p38 and extracellular signal-regulated kinase (ERK) pathway was essential for H₂O₂-mediated cytosolic phospholipase A₂ (cPLA₂) phosphorylation in bEnd3 cells. This study revealed that the activation of c-Jun N-terminal kinase (JNK) was crucial for H₂O₂-induced signal transducer and activator of transcription 3 (STAT3) phosphorylation. In bEnd3 monolayer, either blockade or genetic knockdown of S1PR3 further enhanced the phosphorylation level of p38, ERK, cPLA₂, JNK and STAT3 in response to H₂O₂ exposure. Furthermore, lentivirus-mediated knockdown of S1PR3 intensified H₂O₂-induced ZO-1 redistribution, paracellular hyperpermeability and ROS accumulation, while further compromising endothelial cell viability. Collectively, these results identified S1PR3 as a critical guardian of endothelial barrier integrity under oxidative stress, acting through cPLA₂- and STAT3-dependent signalling pathways.