No abstract

There was an error in the version of Development 139, 313-323 published on ePress on December 7th 2011.The first two authors should have been listed as having contributed equally to this work. The print and final online versions are correct.The authors apologise to readers for this mistake.

Homeostatic control of volume within the alveolar spaces of the mammary gland has been proposed to involve a feedback system mediated by serotonin signaling. In this article, we describe some of the mechanisms underlying this feedback based on studies of a human normal mammary epithelial cell line (MCF10A) and mouse mammary epithelium. Mammary serotonin was elevated during lactation and after injection of 5-hydroxytryptophan (5-HTP). The genes encoding the serotonin reuptake transporter (SERT) and the type 7 serotonin receptor (5-HT 7) were expressed in human and mouse mammary epithelial cells, and serotonin caused a concentration-dependent increase of cAMP in MCF10A cells. Mouse and human mammary epithelial cells formed polarized membranes, in which tight junction activity was monitored. Treatment of mammary epithelial membranes with serotonin receptor antagonists increased their transepithelial electrical resistance (TEER). Antagonist and agonist effects on TEER were mediated by receptors on the basolateral face of the membranes. Our results suggest a process in which serotonin accumulates in the interstitial fluid surrounding the mammary secretory epithelium and is detected by 5-HT7 receptors, whereupon milk secretion is inhibited. One mechanism responsible for this process is serotonin-mediated opening of tight junctions, which dissipates the transepithelial gradients necessary for milk secretion.lactation ͉ MCF10A ͉ milk protein ͉ serotonin receptor ͉ serotonin transporter

Endogenous bioelectrical signaling coordinates cell behaviors toward correct anatomical outcomes. Lack of a model explaining spatialized dynamics of bioelectric states has hindered the understanding of the etiology of some birth defects and the development of predictive interventions. Nicotine, a known neuroteratogen, induces serious defects in brain patterning and learning. Our bio-realistic computational model explains nicotine’s effects via the disruption of endogenous bioelectrical gradients and predicts that exogenous HCN2 ion channels would restore the endogenous bioelectric prepatterns necessary for brain patterning. Voltage mapping in vivo confirms these predictions, and exogenous expression of the HCN2 ion channel rescues nicotine-exposed embryos, resulting in normal brain morphology and molecular marker expression, with near-normal learning capacity. By combining molecular embryology, electrophysiology, and computational modeling, we delineate a biophysical mechanism of developmental brain damage and its functional rescue.

IntroductionThe breast microenvironment can either retard or accelerate the events associated with progression of latent cancers. However, the actions of local physiological mediators in the context of breast cancers are poorly understood. Serotonin (5-HT) is a critical local regulator of epithelial homeostasis in the breast and other organs. Herein, we report complex alterations in the intrinsic mammary gland serotonin system of human breast cancers.MethodsSerotonin biosynthetic capacity was analyzed in human breast tumor tissue microarrays using immunohistochemistry for tryptophan hydroxylase 1 (TPH1). Serotonin receptors (5-HT1-7) were analyzed in human breast tumors using the Oncomine database. Serotonin receptor expression, signal transduction, and 5-HT effects on breast cancer cell phenotype were compared in non-transformed and transformed human breast cells.ResultsIn the context of the normal mammary gland, 5-HT acts as a physiological regulator of lactation and involution, in part by favoring growth arrest and cell death. This tightly regulated 5-HT system is subverted in multiple ways in human breast cancers. Specifically, TPH1 expression undergoes a non-linear change during progression, with increased expression during malignant progression. Correspondingly, the tightly regulated pattern of 5-HT receptors becomes dysregulated in human breast cancer cells, resulting in both ectopic expression of some isoforms and suppression of others. The receptor expression change is accompanied by altered downstream signaling of 5-HT receptors in human breast cancer cells, resulting in resistance to 5-HT-induced apoptosis, and stimulated proliferation.ConclusionsOur data constitutes the first report of direct involvement of 5-HT in human breast cancer. Increased 5-HT biosynthetic capacity accompanied by multiple changes in 5-HT receptor expression and signaling favor malignant progression of human breast cancer cells (for example, stimulated proliferation, inappropriate cell survival). This occurs through uncoupling of serotonin from the homeostatic regulatory mechanisms of the normal mammary epithelium. The findings open a new avenue for identification of diagnostic and prognostic markers, and valuable new therapeutic targets for managing breast cancer.

Mammary gland homeostasis and the lactation-to-involution switch are regulated by serotonin (5-hydroxytryptamine (5-HT)). Mammary epithelial tight junctions are physiological targets of 5-HT, and their disruption marks an early stage of mammary gland involution. In these studies, we have identified signal transduction mechanism employed by 5-HT during regulation of mammary gland transepithelial resistance. Transepithelial electrical resistance and tight junction protein architecture were studied in cultures of MCF10A human mammary epithelial cells. Serotonin had biphasic effects on mammary epithelial resistance. At lower concentrations and earlier time points, 5-HT potentiated epithelial transmembrane resistance, whereas at higher concentrations and later time points, 5-HT decreased transepithelial electrical resistance and disrupted tight junctions. Both the early and delayed actions of 5-HT were mediated by the 5-HT7 receptor through activation of G s /cAMP. 5-HT induced the activities of both protein kinase A and p38 mitogen-activated protein kinase. Inhibition of p38 mitogen-activated protein kinase abrogated 5-HT-induced disruption of mammary epithelial tight junctions (the delayed effect). In contrast, inhibition of protein kinase A prevented the increased epithelial resistance in response to 5-HT (the transient effect). These studies imply an integrated set of mechanisms whereby transient, modest activation of 5-HT7 promotes tight junction integrity, and sustained 5-HT7 activation drives involution by disrupting tight junctions.The complex and specialized functions of mammary glands has evolved to meet the specific nutritional needs of the newborn. The rapid and extensive development of the mammary gland leading to establishment of the highly energy-consuming lactation stage is balanced by the massive tissue remodeling and disintegration of mammary epithelial tissue during the involution stage (1-3). Dysregulation of these events has severe consequences for maternal health and infant nutrition and health as well as from the practical perspective of dairy production.Under the influence of endocrine hormones like estrogen, progesterone, and prolactin, the mammary gland reaches the fully developed alveolar stage by the end of pregnancy. However, lactation (milk synthesis and secretion) is not established until parturition, characterized by a drop in systemic progesterone levels along with a surge in the levels of prolactin and glucocorticoids (4 -8). Isolation of the alveolar lumen from interstitial and vascular spaces by closure of tight junctions is a critical cellular event that regulates milk synthesis and secretion (9 -11). The importance of tight junction closure is displayed by the complex interplay between the endocrine hormones in regulating them and thus, in turn, regulating lactation (11-13).Each alveolar unit of a lactating mammary gland is independently regulated in an autocrine-paracrine manner through a feedback system of local factors (14 -16). Absence of a suckling stimulus results in accumu...

-neural region). Together, the local and long-range bioelectric signals create a binary control system capable of fine-tuning apoptosis and proliferation with the brain and spinal cord to achieve correct pattern and size control. Our data suggest a roadmap for utilizing bioelectric state as a diagnostic modality and convenient intervention parameter for birth defects and degenerative disease states of the CNS.

There was an error in the version of Development 139, 313-323 published on ePress on December 7th 2011.The first two authors should have been listed as having contributed equally to this work. The print and final online versions are correct.The authors apologise to readers for this mistake.