Dataset Information

Oxidized LDL-induced angiogenesis involves sphingosine 1-phosphate: prevention by anti-S1P antibody.

ABSTRACT:

Background and purpose

Neovascularization occurring in atherosclerotic lesions may promote plaque expansion, intraplaque haemorrhage and rupture. Oxidized LDL (oxLDL) are atherogenic, but their angiogenic effect is controversial; both angiogenic and anti-angiogenic effects have been reported. The angiogenic mechanism of oxLDL is partly understood, but the role of the angiogenic sphingolipid, sphingosine 1-phosphate (S1P), in this process is not known. Thus, we investigated whether S1P is involved in the oxLDL-induced angiogenesis and whether an anti-S1P monoclonal antibody can prevent this effect.

Experimental approach

Angiogenesis was assessed by capillary tube formation by human microvascular endothelial cells (HMEC-1) cultured on Matrigel and in vivo by the Matrigel plug assay in C57BL/6 mice.

Key results

Human oxLDL exhibited a biphasic angiogenic effect on HMEC-1; low concentrations were angiogenic, higher concentrations were cytotoxic. The angiogenic response to oxLDL was blocked by the sphingosine kinase (SPHK) inhibitor, dimethylsphingosine, by SPHK1-siRNA and by an anti-S1P monoclonal antibody. Moreover, inhibition of oxLDL uptake and subsequent redox signalling by anti-CD36 and anti-LOX-1 receptor antibodies and by N-acetylcysteine, respectively, blocked SPHK1 activation and tube formation. In vivo, in the Matrigel plug assay, low concentrations of human oxLDL or murine oxVLDL also triggered angiogenesis, which was prevented by i.p. injection of the anti-S1P antibody.

Conclusion and implications

These data highlight the role of S1P in angiogenesis induced by oxLDL both in HMEC-1 cultured on Matrigel and in vivo in the Matrigel plug model in mice, and demonstrate that the anti-S1P antibody effectively blocks the angiogenic effect of oxLDL.

SUBMITTER: Camare C

PROVIDER: S-EPMC4280971 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Because sphingosine 1-phosphate (S1P) is a potent stimulator of angiogenesis, we hypothesized that the S1P pathway is activated to stimulate endometrial/placental angiogenesis during pregnancy. We initially localized S1P signaling pathway members in the gravid and nongravid uterine horns of unilaterally pregnant ewes. Sphingosine kinase-1 expression was greater in gravid compared to nongravid horns. In situ hybridization revealed elevated expression of sphingosine 1-phosphate phosphatase (SGPP1) in gravid interplacentomal endometrial stroma on Days 20 and 40 compared to the nongravid uterine horn, but expression increased in endometrium of the nongravid uterine horn between Days 40 and 120. SGPP1 expression increased in placentomes late in gestation. Sphingosine 1-phosphate lyase mRNA was modestly expressed at Day 20 and then decreased. In contrast, sphingosine 1-phosphate receptor 1 (S1PR1) mRNA increased in endometrium and caruncular stroma of the gravid uterine horn. Treatment with FTY720 and VPC23019, S1P receptor antagonists, blocked human and ovine endothelial cell invasion using an in vitro model of sprouting angiogenesis. Knockdown of S1PR1 with siRNA reduced invasion responses as well. We previously reported that delta-like 4 (DLL4) and A disintegrin and metalloproteinase with thrombospondin-like repeats 1 (ADAMTS1) participate in endothelial cell invasion stimulated by S1P and growth factors in vitro, and thus investigated whether their expression correlated with areas undergoing angiogenesis in vivo. DLL4 expression was similar to S1PR1, while ADAMTS1 mRNA was expressed by endometria of both nongravid and gravid horns, as well as conceptus and placentomes. These results establish that S1P signaling pathway members and S1P- and growth factor-regulated genes are prominent in uterine and placental tissue and in some cases are correlated with areas undergoing angiogenesis. Thus, S1P signaling may be crucial for proper fetal-placental development.