Placental corticotrophin releasing hormone (CRH) appears to play important physiological roles during pregnancy and labour. In the placenta, CRH appears to regulate diverse actions such as human trophoblast cell grown and invasion, tissue remodeling, direct modulation of the placental prostaglandin generation and bioavailability and control of placental vascular tone through regulation of endothelial NOS (NOSIII) expression and activation1. CRH actions are mediated through expression of both R1 and R2 CRH receptors (CRH-R) in human syncytiotrophoblasts. To characterize the signaling properties of syncytiotrophoblast CRH-R and identify the mechanisms regulating CRH-NOSIII interactions, we used the cytotrophoblast cell line (BeWo derived from choriocarcinoma) which responds to increased intracellular cAMP levels by differentiation into a multinucleated cell with a syncytiotrophoblast phenotype2. Results showed that syncytialization of BeWo cells by forskolin treatment for 24 h, increased by 3× CRH-R1 mRNA expression. Indirect confocal analysis identified strong CRH-R expression primarily around the plasma membrane and diffuse, low level specific staining throughout the cytoplasm. Analysis of the functional characteristics of CRH-R demonstrated that activation of CRH-R by CRH led to significant activation of ERK1/2 and p38MAPK through pathways involving EGF-R transactivation but not PI3-K activation. CRH-induced ERK1/2 and p38MAPK activation was transient (maximal response at 5 min) and confocal microscopy studies showed that activated ERK1/2 was primarily but not exclusively localized to the cytoplasm. Interestingly, cAMP studies suggested that the BeWo CRH-Rs are not coupled to the adenylyl cyclase/cAMP pathway. Moreover, CRH appears to activate the PKB/ Akt and this leads to downstream phosphorylation of NOSIII at serine 1177, a signaling event associated with NOSIII activation. We conclude that syncytialized BeWo cells express functional CRH-R that can regulate distinct signaling cascades generating messengers potentially important for placental biology.
1. Hillhouse EW & Grammatopoulos DK. Reproduction 2002 124 323329.
2. Wice B, et al. Exp Cell Res 1990 186 306316.
03 - 07 May 2008
European Society of Endocrinology