RhoE Is Regulated by Cyclic AMP and Promotes Fusion of Human BeWo Choriocarcinoma Cells

Fusion of placental villous cytotrophoblasts with the overlying syncytiotrophoblast is essential for the maintenance of successful pregnancy, and disturbances in this process have been implicated in pathological conditions such as pre-eclampsia and intra-uterine growth retardation. In this study we examined the role of the Rho GTPase family member RhoE in trophoblast differentiation and fusion using the BeWo choriocarcinoma cell line, a model of villous cytotrophoblast fusion. Treatment of BeWo cells with the cell permeable cyclic AMP analogue dibutyryl cyclic AMP (dbcAMP) resulted in a strong upregulation of RhoE at 24h, coinciding with the onset of fusion. Using the protein kinase A (PKA)-specific cAMP analogue N6-phenyl-cAMP, and a specific inhibitor of PKA (14–22 amide, PKI), we found that upregulation of RhoE by cAMP was mediated through activation of PKA signalling. Silencing of RhoE expression by RNA interference resulted in a significant decrease in dbcAMP-induced fusion. However, expression of differentiation markers human chorionic gonadotrophin and placental alkaline phosphatase was unaffected by RhoE silencing. Finally, we found that RhoE upregulation by dbcAMP was significantly reduced under hypoxic conditions in which cell fusion is impaired. These results show that induction of RhoE by cAMP is mediated through PKA and promotes BeWo cell fusion but has no effect on functional differentiation, supporting evidence that these two processes may be controlled by separate or diverging pathways

Antiphospholipid antibodies: effects on trophoblast and endothelial cells

PROBLEM: Antiphospholipid syndrome (APS) may affect placental functions through several possible mechanisms. Interaction of antiphospholipid antibodies (aPL) with cells involved in the coagulation cascade is thought to produce a procoagulant state. Thrombotic placental pathology is however not specific for the APS. METHOD OF STUDY: An analysis of published data. RESULTS: It is now generally accepted that the clinically relevant aPL bind to proteins with affinity for phospholipids (PL), such as beta2-glycoprotein I (beta2-GPI). Following the attachment of beta2-GPI to trophoblast anionic PL, both molecules undergo conformational changes resulting in the exposure of cryptic epitopes within the structure of beta2-GPI. This may allow the subsequent binding of antibodies hence affecting trophoblast functions directly. Moreover anti-beta2-GPI antibodies induce the activation of endothelial cells (ECs), resulting in a proinflammatory state which favours the prothrombotic diathesis of the syndrome. CONCLUSION: Numerous ameliorations in the APS knowledge have been introduced in the last few years. To have clarified the mechanism of antibody mediated damage on trophoblast and ECs represents an important step to explain the cellular events leading to pregnancy complication