Senescent endothelial dysfunction is attributed to the up-regulation of sphingosine-1-phosphate receptor-2 in aged rats.

Sphingosine-1-phosphate (S1P) regulates an array of biological activities in various cell types. Many S1P-regulated functions are mediated by S1P receptor subtypes. Previous studies have shown that the S1P receptor-2 (S1P(2) receptor) is involved in senescence of endothelial cells in vitro. However, the functional outcomes of S1P(2) receptor-mediated signaling pathways in a physiological environment are currently unknown. The main aim of this study was to explore the underlying mechanisms of senescent-associated impairments in pulmonary microvascular endothelial cells (PMECs) isolated from young and aged rats in vivo. The expression of S1P receptor subtypes in PMECs was detected using RT-PCR and Western blot analyses. The chemotaxis of PMECs was measured using the transwell migration assay. The endothelial morphogenesis assay was performed in three-dimensional Matrigel. The wound-healing assay was performed using a scratch wound model on primary PMEC monolayers. We observed that the S1P(2) receptor was markedly increased and S1P-regulated responses were significantly inhibited in PMECs isolated from aged rats. Furthermore, the senescent-associated impairments were revoked by the down-regulation of the S1P(2) receptor in senescent PMECs. These results indicate that the impaired functions (such as chemotactic, wound healing, and morphogenetic responses) in senescent PMECs in vivo are mediated by the S1P(2) receptor.