Characterization of the Cyclic Adenosine Monophosphate Target Site in the Oxytocin Receptor Gene in Rabbit Amnion1

Abstract

Oxytocin (OXT) is a potent stimulator of prostaglandin E(2) (PGE(2)) synthesis by rabbit amnion cells obtained near the end of pregnancy. Coincident with a marked increase in sensitivity of PGE(2) synthesis to OXT, the concentration of OXT receptors (OXTRs) is abruptly upregulated about 200-fold at term. This increase can be mimicked in preterm amnion cells in primary culture by the synergistic action of agents that increase cAMP synthesis and by glucocorticoids. To elucidate the mechanism of cAMP action, we cloned the rabbit OXTR gene and isolated a 200-base pair (bp) forskolin-responsive region about 4.7 kilobase upstream from the transcriptional start site using transient transfection assays. This region corresponds to a DNase I-hypersensitive site that appears in amnion tissue only near the end of pregnancy, when OXTRs are upregulated. The effects of forskolin were mediated in part by cAMP response element binding protein (CREB), as coexpression of reporter constructs with dominant negative CREB inhibited reporter expression. In addition, CREB was cross-linked to sites in the 200-bp region only in chromatin isolated from cells near the end of pregnancy, as demonstrated by chromatin immunoprecipitation (ChIP). Because the transient transfection results are consistent with work using tissue extracts (DNase I hypersensitivity and ChIP), we conclude that cAMP, acting through a specific upstream CREB binding site, is critical for the physiological upregulation of OXTRs in the amnion at the end of gestation.

Nonsocial Functions of Hypothalamic Oxytocin

“…In fact, olfactory OXT does play a critical role in brain function. For instance, vaginocervical stimulation can promote olfactory social recognition memory in female rats through the release of OXT [153] where OXTR is also identified [8, 9]. Moreover, nasal application of OXT has been associated to improving lactation failure, autism, schizophrenia, and other aberrant social behaviors [154–156] bypassing the blood-brain barrier via multiple approaches [125].…”

“…In addition to the hypothalamic origin, OXT is also produced in extrahypothalamic regions and peripheral tissues, for example, the retina, adrenal medulla, thymus, the pancreas, adipocytes, placenta, amnion, corpus luteum, interstitial cells of Leydig in the testis, and heart [7]. In mammals, OXT receptor (OXTR) has been identified in a broad spectrum of tissues, including myoepithelium of the mammary gland, myometrium of the uterus, endometrium, decidua, ovary, testis, epididymis, vas deferens, kidney, heart, thymus, pancreas, and adipocytes as well as the brain and spinal cord [7–9]. Thus, OXT can function in extensive central and peripheral sites.…”

Up-regulation of oxytocin receptor gene and protein in the sheep anterior pituitary by a dopamine derivative (salsolinol)

“…Some data suggest that cAMP may induce the up-regulation of OTR gene expression. Treatment with forskolin, a compound that elevates the intracellular cAMP concentration, increases OT binding and OTR mRNA expression in rabbit amnion cells in vitro (Jeng and Soloff 2009). Additionally, dibutyryl-cAMP has been shown to increase OTR gene expression in vitro (Ivell et al 2001).…”

Dual Oxytocin Receptor-G Protein Signaling in the Autoregulation of Activities of Oxytocin Neurons

“…Moreover, pertussis toxin uncouples G i/o protein from OTR and reduces OT-stimulated increase in IP 3 level by 53% through an indirect effect of cAMP elevation [39, 98], indicating that activation of G i/o protein promotes the recovery of G αq -PLC-β signaling or the resensitization of G q -coupled OTR. In addition, OTR-G i/o-βγ -mediated coactivation of AC II [49] may also promote OTR production and recycling as shown in cultured human myometrial cells [99], wherein OT can cause sphingosine kinase activation and sphingosine 1-phosphate release [100]. These facts highlight the possibility that following activation of OTR-G q protein signaling, the (re)generation of lipid signals can promote OTR recycling with certain latency while OTR-G i/o protein signaling could also play a pivotal role.…”