Failure of trophoblast invasion and remodelling of maternal blood vessels leads to the pregnancy complication pre-eclampsia (PE). Metabolomic profiling of placentas from such pregnancies has identified deranged sphingolipid metabolism as one of the pathways altered in PE. In other systems, the bioactive sphingolipid, sphingosine-1-phosphate (S1P) controls cell migration therefore this study aimed to determine its effect on extravillous trophoblast (EVT) function.
S1P (50 nM10 μM) attenuated migration of the EVT cell lines, Swan-71 and SGHPL-4 (P<0.05). QPCR and immunolocalisation demonstrated that these cells express S1P receptors 13. However S1PR2 was responsible for mediating S1Ps inhibitory effect as the specific S1PR2 inhibitor, JTE-013 (100 nM) abolished S1P-attenuated migration (P<0.05) whereas treatment with the S1R1/3 inhibitor, FTY720 (100 nM), had no effect. S1PR2 can associate with the G proteins Gα12/13, Gαq, or Gαi, however analysis of Swan-71 cell migration and actin cytoskeleton in the presence of S1P±the Rho kinase inhibitor, Y-27632 (10 μM; n=6) suggests preferential activation of Gα12/13. Recent studies of osteoclast suggest that S1PR2 is regulated by vitamin D thus we investigated whether vitamin D affects S1P signalling in trophoblast. QPCR analysis revealed a significant reduction (fourfold decrease; P<0.05) in S1PR2, but not R1 and R3, expression after treatment with 10 mM 1,25(OH)2D3 for 48 or 72 h. Moreover, S1P did not inhibit the migration of Swan-71 cells exposed to 10 nM 1,25(OH)2D3 (P<0.05).
This study demonstrates that although EVT express three S1P receptor isoforms, S1P predominantly signals through S1PR2/Gα12/13 to activate Rho and actin stress fibre formation and thereby acts as potent inhibitor of EVT migration. Importantly, expression of S1PR2, and therefore S1P function, can be down-regulated by vitamin D. Our data suggest that vitamin D deficiency, which is known to be associated with PE, may contribute to the impaired trophoblast migration that underlies this condition.