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Comment |
Follicular Fluid High-Density Lipoprotein (FF-HDL)-Associated Sphingosine 1-Phosphate (S1P) Promotes Human Granulosa Lutein Cell Migration via S1P Receptor Type 3 (S1PR3) and Small G Protein RAC1. Becker S et al. Coordinated migration and progesterone production by granulosa cells is critical to the development of corpus luteum, but the underlying mechanisms remain obscure. Sphingosine 1-phospate (S1P) associated with follicular fluid high-density lipoproteins (FF-HDL) was previously demonstrated to regulate ovarian angiogenesis. We here examined the effects of S1P and FF-HDL on the function of granulosa lutein cells. Both FF-HDL and S1P induced migration of primary human granulosa lutein cells (hGCs) and granulosa lutein cell line, HGL5. In addition, FF-HDL but not S1P promoted progesterone synthesis, and neither of two compounds stimulated proliferation of granulosa lutein cells. PCR and Western blot experiments demonstrated expression of S1P receptors type 1, 2, 3 and 5 but not type 4 in hGCs and HGL5 cells. FF-HDL- and S1P-induced granulosa lutein cell migration was emulated by FTY720, an agonist of S1P receptors 1, 3, 4, and 5 and by VPC24191, an agonist of S1P receptors 1 and 3, but not by SEW2871 and phytosphingosine-1-phosphate, agonists of S1P receptors 1 and 4, respectively. In addition, blockade of S1P receptor 3 with CAY1044, suramine or pertussis toxin inhibited hGCs and HGL5 cell migration towards FF-HDL or S1P, while blockade of S1P receptors 1 and 2 with W146 and JTE013, respectively, remained without effect. Both FF-HDL and S1P triggered activation of the small G protein RAC1 and the actin polymerization in granulosa cells and RAC1 inhibition with C. difficile toxin B or NSC23766 abolished FF-HDL- and S1P-induced migration. FF-HDL-associated S1P promotes granulosa lutein cell migration via S1PR3 and RAC1 activation. This may represent a novel mechanism contributing to the development of corpus luteum.
Follicular fluid high density lipoprotein (HDL) -associated sphingosine 1-phosphate is a novel mediator of ovarian angiogenesis von Otte S, et al .
Angiogenesis plays an important role in the development of the ovarian follicle and its subsequent transition into the corpus luteum. Accordingly, follicular fluid is a rich source of mitogenic and angiogenic factors such as bFGF and VEGF secreted by granulosa cells. In the present study we show that follicular fluid deprived of bFGF or VEGF by means of thermal denaturation or antibody neutralization retains its capacity to stimulate endothelial proliferation and angiogenesis. Mass spectrometric analysis of chromatographic fractions stimulating endothelial growth obtained from follicular fluid revealed that the heat-stable mitogenic activity is identical with the subfraction of follicular fluid high density lipoproteins (FF-HDL). Further investigations demonstrated that sphingosine 1-phosphate (S1P) - a lysophospholipid associated with FF-HDL - accounts for the capacity of this lipoprotein to stimulate endothelial growth and the formation of new vessels. Activation of mitogen-activated protein kinase (p42/44ERK1/2), protein kinase C (PKC) and protein kinase Akt represent signalling pathways utilized by FF-HDL and S1P to induce endothelial proliferation and angiogenesis. We conclude that HDL-associated S1P represents a novel mitogenic and angiogenic factor present in follicular fluid.
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