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Pregnancy-adapted uterine artery endothelial cell Ca2+ signaling and its relationship with membrane potential.

ABSTRACT: Pregnancy-derived uterine artery endothelial cells (P-UAEC) express P2Y2 receptors and at high cell density show sustained and synchronous [Ca2+]i burst responses in response to ATP Bursts in turn require coupling of transient receptor potential canonical type3 channel (TRPC3) and inositol 1,4,5-triphosphate receptor type 2 (IP3R2), which is upregulated in P-UAEC in a manner dependent on connexin 43 (Cx43) gap junctions. While there is no known direct interaction of TRPC3 with Cx43, early descriptions of TRPC3 function showed it may also be influenced by altered membrane potential (V_m). Herein, we ask if enhanced TRPC3 Ca2+ bursting due to enhanced Cx43 coupling may be coupled via dynamic alterations in V_m in P-UAEC, as reported in some (HUVEC) but not all endothelial cells. Following basic electrical characterization of UAEC, we employed a high sensitivity cell imaging system to simultaneously monitor cell V_m and [Ca2+]i in real time in continuous monolayers of UAEC Our findings show that while acute and sustained phase [Ca2+]i bursting occur dose-dependently in response to ATP, V_m is not coregulated with any periodicity related to [Ca2+]i bursting. Only a small but significant progressive change in V_m is seen, and this is more closely related to overall mobilization of Ca2+. Surprisingly, this is also most apparent in NP-UAEC > P-UAEC In contrast [Ca2+]i bursting is more synchronous in P-UAEC and even achieves [Ca2+]i waves passing through the P-UAEC monolayer. The relevance of these findings to mechanisms of pregnancy adaptation and its failure in hypertensive pregnancy are discussed.

SUBMITTER: Alvarez RE

PROVIDER: S-EPMC5688774 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The pregnancy-augmented uterine vasodilation is linked to increased AT2R (angiotensin type-2 receptor) that mediates the vasodilatory effects of angiotensin II. However, the mechanisms controlling AT2R expression during pregnancy remain unclear. Estrogens are known to play a role in vascular adaptations during pregnancy. We hypothesized that estrogen stimulates uterine artery AT2R expression via ER (estrogen receptor)-β-dependent transcription in a pregnancy-specific endothelium-dependent manner. Plasma estradiol levels increased and peaked in late pregnancy and returned to prepregnant levels post-partum, correlating with uterine artery AT2R and ERβ upregulation. Estradiol stimulated AT2R mRNA expression in endothelium-intact but not endothelium-denuded late pregnant and nonpregnant rat uterine artery ex vivo. Consistently, estradiol stimulated AT2R mRNA expression in late pregnant but not nonpregnant primary human uterine artery endothelial cells in vitro, which was abolished by ER antagonist ICI 182,780. Higher ERα protein bound to ER-responsive elements in AT2R promoter in the nonpregnant arteries whereas higher ERβ bound in the pregnant state. ERα protein levels were similar but higher ERβ protein levels were expressed in pregnant versus nonpregnant human uterine artery endothelial cells. Estradiol stimulation recruited ERα to the AT2R promoter in the nonpregnant state and ERβ to the AT2R promoter in pregnancy; however, only ERβ recruitment mediated transactivation of the AT2R reporter gene in pregnant human uterine artery endothelial cells. Estradiol-induced AT2R expression was abolished by the specific ERβ (not ERα) antagonist 4-[2-Phenyl-5,7-bis(trifluoromethyl)pyrazolo[1,5-a]pyrimidin-3-yl]phenol (PHTPP) and mimicked by the specific ERβ (not ERα) agonist 2,3-bis(4-Hydroxyphenyl)-propionitrile (DPN) in pregnant human uterine artery endothelial cells in vitro. This study demonstrates a novel role of pregnancy-augmented ERβ in AT2R upregulation in the uterine artery and provides new insights into the mechanisms underlying uterine vascular adaptation to pregnancy.

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Pregnancy-adapted uterine artery endothelial cell Ca2+ signaling and its relationship with membrane potential.

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