Trophoblastic cells of the hydatidiform mole contain a beta 1-subtype adrenergic receptor

The placenta-brain-axis

All mammalian species depend on the placenta, a transient organ, for exchange of gases, nutrients, and waste between the mother and conceptus. Besides serving as a conduit for such exchanges, the placenta produces hormones and other factors that influence maternal physiology and fetal development. To meet all of these adaptations, the placenta has evolved to become the most structurally diverse organ within all mammalian taxa. However, commonalities exist as to how placental responses promote survival against in utero threats and can alter the trajectory of fetal development, in particular the brain. Increasing evidence suggests that reactions of the  placenta to various in utero stressors may lead to long-standing health outcomes, otherwise considered developmental origin of health and disease effects. Besides transferring nutrients and gases, the placenta produces neurotransmitters, including serotonin, dopamine, norepinephrine/epinephrine, that may circulate and influence brain development. Neurobehavioral disorders, such as autism spectrum disorders, likely trace their origins back to placental disturbances. This intimate relationship between the placenta and brain has led to coinage of the term, the placenta-brain-axis. This axis will be the focus herein, including how conceptus sex might influence it, and technologies employed to parse out the effects of placental-specific transcript expression changes on later neurobehavioral disorders. Ultimately, the placenta might provide a historical record of in utero threats the fetus confronted and a roadmap to understand how placenta responses to such encounters impacts the placental-brain-axis. Improved early diagnostic and preventative approaches may thereby be designed to mitigate such placental disruptions.

Extended Human G-Protein Coupled Receptor Network: Cell-Type-Specific Analysis of G-Protein Coupled Receptor Signaling Pathways

G-protein coupled receptors (GPCRs) mediate crucial physiological functions in humans, have been implicated in an array of diseases, and are therefore prime drug targets. GPCRs signal via a multitude of pathways, mainly through G-proteins and β-arrestins, to regulate effectors responsible for cellular responses. The limited number of transducers results in different GPCRs exerting control on the same pathway, while the availability of signaling proteins in a cell defines the result of GPCR activation. The aim of this study was to construct the extended human GPCR network (hGPCRnet) and examine the effect that cell-type specificity has on GPCR signaling pathways. To achieve this, protein-protein interaction data between GPCRs, G-protein coupled receptor kinases (GRKs), Gα subunits, β-arrestins, and effectors were combined with protein expression data in cell types. This resulted in the hGPCRnet, a very large interconnected network, and similar cell-type-specific networks in which, distinct GPCR signaling pathways were formed. Finally, a user friendly web application, hGPCRnet ( http://bioinformatics.biol.uoa.gr/hGPCRnet ), was created to allow for the visualization and exploration of these networks and of GPCR signaling pathways. This work, and the resulting application, can be useful in further studies of GPCR function and pharmacology.

Human trophoblast cultures: models for implantation and peri-implantation toxicology

Implantation is the process that leads from blastocyst attachment to its embedding in the uterine wall. It is widely believed that failure of implantation is a common cause of pregnancy loss. Toxic agents can interfere directly with the process of implantation and therefore may account for unexplained implantation failures. Our knowledge of human implantation remains limited, mainly due to the lack of adequate experimental models. Studies of mechanisms underlying implantation in humans are by nature and for ethical reasons restricted to in vitro models. The aim of this review is to provide a critical evaluation of various in vitro models of implantation in humans, as well as essential background knowledge required for application of these models to the assessment of peri-implantation toxicity. Particular attention has been devoted to cell-cell and cell-matrix interactions as possible endpoints in the screening of toxic agents.

Guanine nucleotide binding in human placental syncytiotrophoblast membranes and comparative regulation of adenylate cyclase in syncytiotrophoblast, turkey erythrocyte and bovine calf testes membranes by guanosine-5'-triphosphate

Guanosine-5'-triphosphate (GTP) binds specifically to syncytiotrophoblast plasma membranes and increases the production of cyclic AMP in these membranes. 1. In syncytiotrophoblast membranes, GTP alone caused a significant increase in the basal levels of cyclic AMP in a dose dependent manner. 2. GTP alone did not significantly stimulate cyclic AMP production in turkey erythrocyte or bovine calf testes membranes. 3. GTP decreased Gpp(NH)p-mediated cyclic AMP production while increasing NaF-mediated cyclic AMP production in placental, erythrocyte and testes membranes. 4. Since cyclic AMP has been reported to regulate the levels of placental hormones, and it is shown in this study that GTP increases cyclic AMP production in the placenta, this study suggests: (A) placental GTP levels may indirectly regulate placental hormone production, (B) placental beta adrenergic (BA) mediated adenylate cyclase activity may not be regulated in the same manner as the BA system of avian erythrocytes.

Distribution of adrenergic receptors does not explain regional differences in blood flow in the pregnant rabbit uterus

The increase in uterine blood flow during pregnancy is maximal at the placental implantation site, but the mechanisms of this increase are poorly understood. Adrenergic receptor activation may influence blood flow both directly and indirectly. We therefore asked whether distribution of myometrial adrenergic receptors within the rabbit uterus could explain the increased blood flow to smooth muscle under the placenta. alpha-Adrenergic and beta-adrenergic receptor concentrations and affinities were measured in myometrium from under the placenta and compared to myometrium between placentas and distant from the placentas. There were no differences in receptor concentrations or affinities in different parts of the uterus. We therefore conclude that the distribution of adrenergic receptors in the pregnant rabbit uterus cannot explain the preferential blood flow to myometrium at the placental implantation site.