IL SISTEMA ADENILIL CICLASI/AMP CICLICO NELLA REGOLAZIONE DELLE FUNZIONI DEL TROFOBLASTO UMANO

Normal placentation requires a highly coordinated control of proliferation, migration and invasiveness of extravillous trophoblast (EVT) cells. Since prostaglandin E2 is a major prostanoid synthesized by intrauterine tissues and highly involved in pregnancy homeostasis, we examined the possibility that it modulates EVT cell functions. Here, we report the presence of both mRNAs and proteins for prostaglandin E2 (PGE2) EP2 and EP4 receptor isoforms in first-trimester human chorionic villi and in the human trophoblast-derived HTR-8/SVneo cells. Moreover, we found that the prostanoid consistently inhibits serum- or epidermal growth factor-induced cell proliferation and migration. An involvement of cAMP in the PGE2 antiproliferative action is suggested by the observation that the prostanoid greatly enhances cAMP level in HTR-8/SVneo cells and that forskolin inhibits cell proliferation and migration. Provided that our data are applicable to the trophoblast tissue in vivo, we suggest that PGE2 exerts an important control on EVT cell functions, preventing their excessive proliferation and migration. Moreover we have tested the hypothesis that human early trophoblast is a target for somatostatin (SRIF) regulatory actions. We report for the first time that SRIF receptor isoform SSTR2A and 2B transcripts and proteins are present in first-trimester human chorionic villi and HTR-8/SVneo cells. In this cell line, SRIF receptors are functional, since the peptide reduces PGE2- and forskolin-stimulated cAMP concentration. Moreover, SRIF enhanes HTR-8/SVneo cells proliferation and migration, supporting the idea that the peptide regulates early trophoblast functions mainly through an interaction with the receptor isoform SSTR2. Considering the fundamental role of cAMP in the regulation of early trophoblast functions, we also characterized the AC/cAMP system in HTR-8/SVneo cells, analysing the expression of the enzyme isoforms and G protein α subunits. We found the presence of AC3, AC5, AC6, AC7, AC9 isoforms, being AC6 the major isoform expressed. As for G proteins, Gαs and Gαq isoforms are much more expressed with respect to Gαi and Gαo. Our data on the role of cAMP in the modulation of trophoblast functions are in line with the expression level of both AC isoforms and G alfa proteins in the HTR-8/SVneo cells, considering their biochemical and functional properties In conclusion, provided that our data are applicable to the trophoblast tissue in vivo, we suggest an involvement of AC/cAMP pathway in mediating SRIF and PGE2 effects on proliferation and migration of the extravillous trophoblast cells.