Abstract
<title>Abstract</title> <p> Vascular endothelial senescence is a pivotal driver of age-related pathologies. Metabolism plays a critical regulatory role in endothelial cell senescence. Our previous studies have shown that deficiency of DHCR24, a gene involved in lipid metabolism, promotes endothelial cell senescence. However, how DHCR24 participates in endothelial cell senescence through lipid metabolism remains unclear. Using endothelial-specific DHCR24 knockout mice and replicative senescent human umbilical vein endothelial cells (HUVECs), we demonstrate that DHCR24 depletion significantly reduces intracellular sphingosine-1-phosphate (S1P) levels. Mechanistically, DHCR24 loss downregulated sphingosine kinase 2 (SPHK2), impairing S1P synthesis, while concurrently upregulating the S1P transporter (SPNS2), enhancing S1P export. SPHK2 knockdown recapitulated SPNS2 upregulation and endothelial senescence, whereas pharmacological inhibition of SPNS2 with 16d attenuated SPHK2 knockdown-induced increases in p16, p53, and SA-β-gal activity, and restored eNOS expression and nitric oxide (NO) production. Critically, SPHK2 overexpression rescued senescence phenotypes in DHCR24-deficient cells. <italic>In vivo</italic> , endothelial-specific DHCR24 knockout increased circulating S1P levels, and plasma S1P was positively correlated with pulse wave velocity (PWV) in humans. Collectively, these findings establish the DHCR24-SPHK2/SPNS2-S1P axis as a central regulator of endothelial aging. </p>