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

ABSTRACT 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 H 2 O 2 ‐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 H 2 O 2 ‐mediated cytosolic phospholipase A 2 (cPLA 2 ) phosphorylation in bEnd3 cells. This study revealed that the activation of c‐Jun N‐terminal kinase (JNK) was crucial for H 2 O 2 ‐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, cPLA 2 , JNK and STAT3 in response to H 2 O 2 exposure. Furthermore, lentivirus‐mediated knockdown of S1PR3 intensified H 2 O 2 ‐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 cPLA 2 ‐ and STAT3‐dependent signalling pathways.