Human Placenta Expresses α2-Adrenergic Receptors and May Be Implicated in Pathogenesis of Preeclampsia and Fetal Growth Restriction.

α2-Adrenergic receptors (α2ARs) are G-protein-coupled receptors involved in catecholamine signaling by extracellular regulated protein kinase 1 and 2 (ERK1/2) pathways. We examined placental expression and function of α2AR subtypes in women with severe preeclampsia (sPE) with and without intrauterine growth restriction (IUGR). Placental biopsies were analyzed from 52 women with i) sPE (n = 8); ii) sPE + IUGR (n = 9); iii) idiopathic IUGR (n = 8); iv) idiopathic preterm birth (n = 16); and v) healthy term controls (n = 11). Expression of α2AR subtypes (α2A, α2B, α2C) and phospho-ERK1/2 (receptor activation marker) was investigated by immunohistochemistry and/or quantitative real-time RT-PCR. The effects of α2CAR knockdown on syncytialization (syncytin-1 and -2) and β-human chorionic gonadotropin secretion were examined in BeWo cells stimulated with forskolin. The effects of α2AR agonist UK 14,304 and specific α2CAR antagonist were tested, using a trophoblast migration assay. All three α2ARs were expressed and functionally active in human placenta with site-specific localization. Highest α2BAR and α2CAR mRNA expression was identified in sPE + IUGR. α2CAR knockdown increased expression of syncytin-1 and -2 but decreased secretion of β-human chorionic gonadotropin. UK 14,304 impaired trophoblast migration. The observed α2AR expression pattern suggests different function for each subtype. α2CAR modulates trophoblast syncytialization and migration and may carry pathogenic role in sPE + IUGR.