Aberrant sphingolipid metabolism in the human fallopian tube with ectopic pregnancy

Sphingosine 1-phosphate (S1P), a product of sphingomyelin metabolism, is generated via phosphorylation of sphingosine by sphingosine kinases (SphK). It acts via a family of G protein-coupled receptors or as an intracellular second messenger for agonists acting through the S1P receptors (S1P1-5). In our study, the expression of SphK1 and S1P1 was identified by immunohistochemistry and immunoblot. The concentration of S1P was measured using ELISA. The spontaneous contraction of isolated fallopian tube strips was determined by tension recording. Our results showed that SphK1 and S1P1 were localized in the fallopian tube epithelial cells. In addition, smooth muscle cells also contained S1P1. Compared with the intrauterine pregnancy group, SPHK1 and S1P1 were overexpressed in ectopic pregnancy. However, the S1P concentration within the human oviduct from ectopic pregnancy subjects was largely reduced than that from normal pregnancy subject. The results from tension recording indicated that exogenous and intracellularly generated S1P can regulate the spontaneous contraction of oviduct isolated from rats and human. In conclusion, the sphingolipid metabolism signal pathway functionally existed in the human fallopian tube. Aberrant sphingolipid metabolism in the human fallopian tube may be involved in ectopic pregnancy.