CRH acts on CRH-R1 and -R2 to differentially modulate the expression of large-conductance calcium-activated potassium channels in human pregnant myometrium

Abstract

CRH has been implicated to play a key role in the control of human pregnancy and parturition. Large-conductance potassium channels (BK Ca) play a pivotal role in the modulation of uterine contractility during pregnancy. The objectives of the present study were to investigate the effect of CRH on BK Ca expression in human pregnant myometrial cells. Myometrial tissues were collected at cesarean section from pregnantwomennot-in- labor (TNL) or in-labor (TL) at term, and myocytes were isolated and cultured. CRH was identified in human pregnant myometrium and mainly expressed in myometrial myocytes. Cultured myometrial cells were able to secrete CRH. In TNL myometrial cells, CRH treatment increased the expression of BK Ca α- and β-subunits. CRH receptor type 1 (CRH-R1) antagonist, antalarmin, decreased whereas CRH receptor type 2 (CRH-R2) antagonist, astressin2b, increased the expression of BK Ca. CRH-R2 small interfering RNA (siRNA) caused an increase, but CRH-R1 siRNA resulted in a decrease, in BK Ca expression. In contrast to TNL cells, CRH exhibited an opposite effect on BK Ca expression in TL myometrial cells, i.e. decreased BK Ca expression. Antalarmin enhanced but astressin2b reduced BK Ca expression. CRH-R2 siRNA decreased whereas CRH-R1 siRNA increased BKCa expression. 1,3-Dihydro-1-[2-hydroxy-5-(trifluoromethyl)phenyl]- 5- (trifluoromethyl)-2H-benzimidazol-2-one significantly inhibited the frequency of spontaneous contractions of myometrial strips, and this effect was significantly decreased in TL strips compared with TNL ones. Our data suggest that CRH-R1 and CRH-R2 show differential regulation of BK Caexpression. These effects mediated by CRH-R1 and CRH-R2 are changed after the onset of labor. This leads us to suggest that CRH may fine-tune myometrial contractility by modulating the expression of BK Ca during pregnancy and labor. Copyright © 2011 by The Endocrine Society.