Descripción: The regulatory role of estrogen, bone morphogenetic protein-4 (BMP-4), and TGF-β has a strong impact on hormone secretion, gene transcription, and cellular growth of prolactin (PRL)-producing cells. In contrast to TGF-β, BMP-4 induces the secretion of PRL in GH3 cells. Therefore, we studied the mechanism of their transcriptional regulation. Both BMP-4 and TGF-β inhibited the transcriptional activity of the estrogen receptor (ER). Estrogens had no effect on TGF-β-specific Smad protein transcriptional activity but presented a stimulatory action on the transcriptional activity of the BMP-4-specific Smads. BMP-4/estrogen cross talk was observed both on PRL hormone secretion and on the PRL promoter. This cross talk was abolished by the expression of a dominant-negative form for Smad-1 and treatment with ICI 182780 but not by point mutagenesis of the estrogen response element site within the promoter, suggesting that Smad/ER interaction might be dependent on the ER and a Smad binding element. By serial deletions of the PRL promoter, we observed that indeed a region responsive to BMP-4 is located between -2000 and -1500 bp upstream of the transcriptional start site. Chromatin immunoprecipitation confirmed Smad-4 binding to this region, and by specific mutation and gel shift assay, a Smad binding element responsible site was characterized. These results demonstrate that the different transcriptional factors involved in the Smad/ER complexes regulate their transcriptional activity in differential ways and may account for the different regulatory roles of BMP-4, TGF-β, and estrogens in PRL-producing cells. Copyright © 2009 by The Endocrine Society.

Descripción: Two of the most potent cytokines that regulate anterior pituitary cell function are leukemia inhibitory factor and IL-6. These and others like IL-11 and ciliary neurotrophic factor are referred to as the gp130 cytokines because they share the gp130 glycoprotein as a common receptor initial signal transducer. We and others have shown that gp130 cytokines and their receptors are expressed and functional in normal and tumoral anterior pituitary cells. To study the role of gp130 cytokines in tumorigenic process, we generated gp130 cDNA gp130 sense and gp130 antisense (gp130-AS) transfected stable clones derived from lactosomatotroph GH3 cells. We examined hormone secretion and cell proliferation of these clones as well as their tumorigenic properties in athymic nude mice. Although gp130-AS clones, which have low gp130 levels and impaired signal transducer and activator of transcription 3 activity and suppressor of cytokine signaling-3 expression, showed reduced proliferation and hormone secretion (GH and prolactin) in response to gp130 cytokines, they had a normal response to gp130-independent stimuli. Moreover, gp130-AS clones showed a severely impaired in vivo tumor development. In contrast, the overexpressing gp130 clones (gp130 sense) showed no differences, compared with cells transfected with control vector. Thus, the present study provides new evidence supporting a link between gp130 and pituitary abnormal growth.

Descripción: Functional interaction between the immune and neuroendocrine systems is mediated by humoral mediators, neurotransmitters, and cytokines, including TRH and PRL. We examined the role of neuroendocrine changes, particularly TRH and PRL, during the T cell-dependent immune response. After immunization of rats with sheep red blood cells (SRBC, a T cell-dependent antigen), an increase of hypothalamic TRH messenger RNA (mRNA) was observed at 4-24 h post immunization, in contrast to the decrease observed after treatment with lipopolysaccharide (LPS). During the above period, with SRBC, there was an increase in pituitary TRH receptor mRNA and plasma PRL levels but no changes in TSH and GH. Also, in contrast to the early corticosterone peak induced by LPS, the activation of the hypothalamic-pituitary-adrenocortical suppressive response appears in a late phase, 5-7 days after SRBC. Intracerebroventricular injection of antisense oligonucleotide complementary to rat TRH mRNA in conscious freely-moving rats immunized with SRBC resulted in a significant inhibition of specific antibody production and a concomitant inability to produce the peak in plasma PRL levels. These studies demonstrate, for the first time, that the T cell-dependent immune response is critically dependent on the early activation of TRH and PRL and that the neuroendocrine changes occurring during it are profoundly different from those occurring during the T cell-independent and inflammatory responses (LPS model).

Descripción: The mammary epithelium undergoes cyclical periods of cellular proliferation, differentiation, and regression. During lactation, the signal transducer and activator of transcription factor (STAT)-5A and the glucocorticoid receptor (GR) synergize to induce milk protein expression and also act as survival factors. During involution, STAT3 activation mediates epithelial cell apoptosis and mammary gland remodeling. It has been shown that the administration of glucocorticoids at weaning prevents epithelial cell death, probably by extracellular matrix breakdown prevention. Our results show that the synthetic glucocorticoid dexamethasone (DEX) modulates STAT5A and STAT3 signaling and inhibits apoptosis induction in postlactating mouse mammary glands, only when administered within the first 48 h upon cessation of suckling. DEX administration right after weaning delayed STAT5A inactivation and degradation, preserving gene expression of target genes as β-casein (bcas) and prolactin induced protein (pip). Weaning-triggered GR down-regulation is also delayed by the hormone treatment. Moreover, DEX administration delayed STAT3 activation and translocation into epithelial cells nuclei. In particular, DEX treatment impaired the increment in gene expression of signal transducer subunit gp130, normally up-regulated from lactation to involution and responsible for STAT3 activation. Therefore, the data shown herein indicate that glucocorticoids are able to modulate early involution by controlling the strong cross talk that GR, STAT5, and STAT3 pathways maintains in the mammary epithelium. Copyright © 2010 by The Endocrine Society.

Descripción: The relationship between antidopaminergic drugs and glucose has not been extensively studied, even though chronic neuroleptic treatment causes hyperinsulinemia in normal subjects or is associated with diabetes in psychiatric patients. We sought to evaluate dopamine D2 receptor (D2R) participation in pancreatic function. Glucose homeostasis was studied in D2R knockout mice (Drd2-/-) mice and in isolated islets from wild-type and Drd2-/- mice, using different pharmacological tools. Pancreas immunohistochemistry was performed. Drd2-/- male mice exhibited an impairment of insulin response to glucose and high fasting glucose levels and were glucose intolerant. Glucose intolerance resulted from a blunted insulin secretory response, rather than insulin resistance, as shown by glucose-stimulated insulin secretion tests (GSIS) in vivo and in vitro and by a conserved insulin tolerance test in vivo. On the other hand, short-term treatment with cabergoline, a dopamine agonist, resulted in glucose intolerance and decreased insulin response to glucose in wild-type but not in Drd2 -/- mice; this effect was partially prevented by haloperidol, a D2R antagonist. In vitro results indicated that GSIS was impaired in islets from Drd2-/- mice and that only in wild-type islets did dopamine inhibit GSIS, an effect that was blocked by a D2R but not a D1R antagonist. Finally, immunohistochemistry showed a diminished pancreatic β-cell mass in Drd2-/-mice and decreasedβ-cell replication in 2-month-old Drd2-/- mice. Pancreatic D2Rs inhibit glucose-stimulated insulin release. Lack of dopaminergic inhibition throughout development may exert a gradual deteriorating effect on insulin homeostasis, so that eventually glucose intolerance develops. Copyright © 2010 by The Endocrine Society.

Descripción: Curcumin (diferuloylmethane) is the active ingredient of the spice plant Curcuma longa and has been shown to act anti-tumorigenic in different types of tumours. Therefore, we have studied its effect in pituitary tumour cell lines and adenomas. Proliferation of lactosomatotroph GH3 and somatotroph MtT/S rat pituitary cells as well as of corticotroph AtT20 mouse pituitary cells was inhibited by curcumin in monolayer cell culture and in colony formation assay in soft agar. Fluorescence-activated cell sorting (FACS) analysis demonstrated curcumin-induced cell cycle arrest at G2/M. Analysis of cell cycle proteins by immunoblotting showed reduction in cyclin D1, cyclin-dependent kinase 4 and no change in p27kip. FACS analysis with Annexin V-FITC/7-aminoactinomycin D staining demonstrated curcumin-induced early apoptosis after 3, 6, 12 and 24 h treatment and nearly no necrosis. Induction of DNA fragmentation, reduction of Bcl-2 and enhancement of cleaved caspase-3 further confirmed induction of apoptosis by curcumin. Growth of GH3 tumours in athymic nude mice was suppressed by curcumin in vivo. In endocrine pituitary tumour cell lines, GH, ACTH and prolactin production were inhibited by curcumin. Studies in 25 human pituitary adenoma cell cultures have confirmed the antitumorigenic and hormone-suppressive effects of curcumin. Altogether, the results described in this report suggest this natural compound as a good candidate for therapeutic use on pituitary tumours. © 2009 Society for Endocrinology Printed in Great Britain.