Up-regulating Sphingosine 1-Phosphate Receptor-2 Signaling Impairs Chemotactic, Wound-healing, and Morphogenetic Responses in Senescent Endothelial Cells

Qun Zeng,Harshini Sarojini,Chen-Yong Lin,Hongwei Lu,Steven P. Mathis,Eugenia Wang,Menq-Jer Lee,Timothy Hla,Christopher D. Kontos,Bodduluri Haribabu,Rosendo Estrada,Teresa Sanchez,Jen-Fu Lee

doi:10.1074/jbc.m804392200

Abstract

Vascular endothelial cells (ECs) have a finite lifespan when cultured in vitro and eventually enter an irreversible growth arrest state called "cellular senescence." It has been shown that sphingolipids may be involved in senescence; however, the molecular links involved are poorly understood. In this study, we investigated the signaling and functions of sphingosine 1-phosphate (S1P), a serum-borne bioactive sphingolipid, in ECs of different in vitro ages. We observed that S1P-regulated responses are significantly inhibited and the S1P(1-3) receptor subtypes are markedly increased in senescent ECs. Increased expression of S1P(1) and S1P(2) was also observed in the lesion regions of atherosclerotic endothelium, where senescent ECs have been identified in vivo. S1P-induced Akt and ERK1/2 activation were comparable between ECs of different in vitro ages; however, PTEN (phosphatase and tensin homolog deleted on chromosome 10) activity was significantly elevated and Rac activation was inhibited in senescent ECs. Rac activation and senescent-associated impairments were restored in senescent ECs by the expression of dominant-negative PTEN and by knocking down S1P(2) receptors. Furthermore, the senescent-associated impairments were induced in young ECs by the expression of S1P(2) to a level similar to that of in vitro senescence. These results indicate that the impairment of function in senescent ECs in culture is mediated by an increase in S1P signaling through S1P(2)-mediated activation of the lipid phosphatase PTEN.

Highlights

Ious cell types [1,2,3,4]
2 The abbreviations used are: S1P, sphingosine 1-phosphate; G-protein-coupled receptors (GPCRs), G-protein-coupled receptor; S1P1 and S1P2, two high affinity GPCRs for S1P; PTEN, phosphatase and tensin homolog deleted on chromosome 10; WT- and DN-PTEN, wild-type and dominant-negative PTEN
The signaling pathways regulated by the S1P1 and S1P3 receptors are required for the chemotaxis of endothelial cells, adherens junction assembly, endothelial morphogenesis, and angiogenic response in vitro and in vivo [7, 12,13]

Summary

Introduction

Ious cell types [1,2,3,4]. Most, if not all, of S1P-regulated functions are mediated by the S1P family of G-protein-coupled receptors (GPCRs) [5,6,7]. S1P2 vector ectopically express S1P2 receptors to a level similar to that attained by in vitro senescent ECs. Subsequently, young ECs were transduced with adenoviral particles carrying ␤-galactosidase, S1P1, or S1P2 vectors, and activation of integrin ␣v␤3 at cell migratory edges after S1P stimulation was examined

Results

Conclusion