Bromocriptine improves glucose tolerance independent of circadian timing, prolactin, or the melanocortin-4 receptor

Bromocriptine, a dopamine D2 receptor agonist originally used for the treatment of hyperprolactinemia, is largely successful in reducing hyperglycemia and improving glucose tolerance in type 2 diabetics. However, the mechanism behind bromocriptine's effect on glucose intolerance is unclear. Here, we tested three hypotheses, that bromocriptine may exert its effects on glucose metabolism by 1) decreasing prolactin secretion, 2) indirectly increasing activity of key melanocortin receptors in the central nervous system, or 3) improving/restoring circadian rhythms. Using a diet-induced obese (DIO) mouse model, we established that a 2-wk treatment of bromocriptine is robustly effective at improving glucose tolerance. We then demonstrated that bromocriptine is effective at improving the glucose tolerance of both DIO prolactin-deficient and melanocortin-4 receptor (MC4R)-deficient mice, pointing to bromocriptine's ability to affect glucose tolerance independently of prolactin or MC4R signaling. Finally, we tested bromocriptine's dependence on the circadian system by testing its effectiveness in environmental (e.g., repeated shifts to the light-dark cycle) and genetic (e.g., the Clock mutant mouse) models of circadian disruption. In both models of circadian disruption, bromocriptine was effective at improving glucose tolerance, indicating that a functional or well-aligned endogenous clock is not necessary for bromocriptine's effects on glucose metabolism. Taken together, these results do not support the role of prolactin, MC4R, or the circadian clock as integral to bromocriptine's underlying mechanism. Instead, we find that bromocriptine is a robust diabetic treatment and resilient to genetically induced obesity, diabetes, and circadian disruption.

Generation of a lentiviral vector system to efficiently express bioactive recombinant human prolactin hormones

The contribution of the pleiotropic hormone Prolactin (PRL) to several physiological and pathological processes is still unknown. To clarify the role of PRL in these processes during the last decade, different human PRL antagonists have been produced to either partially or fully block the wild type hormone activity. In this work, we have cloned these wild type and antagonist sequences in lentivectors (LV) to express them as recombinant self-processing polypeptides by employing a P2A sequence (hPRL-P2A-GFP). We show that these LVs can efficiently transduce and express the hPRL proteins in different cell types and that the P2A sequence does not affect their activities. Additionally, we have tested their activities in paracrine and autocrine cell culture experiments. Our results demonstrate that these recombinant hPRL-P2A proteins are bioactive in both paracrine and autocrine modes, highlighting the potential usefulness of these hPRL-containing LVs for determining the contribution of hPRL to different biological processes.

Tobacco chemical-induced mouse lung adenocarcinoma cell lines pin the prolactin orthologue proliferin as a lung tumour promoter

Lung adenocarcinoma (LADC) is the leading cause of cancer death worldwide. Nevertheless, syngeneic mouse models of the disease are sparse, and cell lines suitable for transplantable and immunocompetent mouse models of LADC remain unmet needs. We established multiple mouse LADC cell lines by repeatedly exposing two mouse strains (FVB, Balb/c) to the tobacco carcinogens urethane or diethylnitrosamine and by culturing out the resulting lung tumours for prolonged periods of time. Characterization of the resulting cell lines (n = 7) showed that they were immortal and phenotypically stable in vitro, and oncogenic, metastatic and lethal in vivo. The primary tumours that gave rise to the cell lines, as well as secondary tumours generated by transplantation of the cell lines, displayed typical LADC features, such as glandular architecture and mucin and thyroid transcription factor 1 expression. Moreover, these cells exhibited marked molecular similarity with human smokers' LADC, including carcinogen-specific Kras point mutations (KrasQ61R in urethane- and KrasQ61H in diethylnitrosamine-triggered cell lines) and Trp53 deletions and displayed stemness features. Interestingly, all cell lines overexpressed proliferin, a murine prolactin orthologue, which functioned as a lung tumour promoter. Furthermore, prolactin was overexpressed and portended poor prognosis in human LADC. In conclusion, we report the first LADC cell lines derived from mice exposed to tobacco carcinogens. These cells closely resemble human LADC and provide a valuable tool for the functional investigation of the pathobiology of the disease.

Effects of high and low temperature on expression of GnIH, GnIH receptor, GH and PRL genes in the male grass puffer during breeding season

Gonadotropin-inhibitory hormone (GnIH) is a multifunctional hypophysiotropic neurohormone and has a stimulatory role in the control of reproduction in the grass puffer. To clarify the neuroendocrine mechanisms underlying the effect of changes in water temperature on reproduction in fish, we previously revealed that, in parallel to gonadal regression, both low and high temperature significantly decreased the expressions of the genes encoding kisspeptin (kiss2), kisspeptin receptor (kiss2r), gonadotropin-releasing hormone 1 (gnrh1) in the brain and gonadotropin (GTH) subunits (fshb and lhb) in the pituitary of sexually mature male grass puffer. In this study, we examined the changes in expression of gnih and GnIH receptor gene (gnihr) in the brain and pituitary along with the genes for growth hormone (gh) and prolactin (prl) in the pituitary of male grass puffer exposed to low temperature (14 °C), normal temperature (21 °C, as initial control) and high temperature (28 °C) conditions for 7 days. The levels of gnih and gnihr mRNAs were significantly decreased in both low and high temperature conditions compared to normal temperature in the brain and pituitary. Similarly, the gh mRNA levels were significantly decreased in both low and high temperature conditions. The prl mRNAs showed no significant changes at high temperature, whereas drastically decreased at low temperature possibly by dysfunctional cold stress. Taken together, the present results suggest that, in addition to the inhibitory effect of temperature changes on the Kiss2/GnRH1/GTH system, the suppression of GnIH/GH system may also be involved in the termination of reproduction by high temperature at the end of breeding season.

Arginine vasotocin (AVT)/mesotocin (MT) receptors in chickens: Evidence for the possible involvement of AVT-AVPR1 signaling in the regulation of oviposition and pituitary prolactin expression

Two structurally related peptides, arginine vasotocin (AVT) and mesotocin (MT), are reported to regulate many physiological processes, such as anti-diuresis and oviposition in birds, and their actions are likely mediated by four AVT/MT receptors (AVPR1A, AVPR1B, MTR and AVPR2b), which are orthologous/paralogous to human AVPR1A, AVPR1B, OXTR and AVPR2 respectively. However, our knowledge regarding the functions of these avian AVT/MT receptors has been limited. Here, we examined the functionality and expression of these receptors in chickens and investigated the roles of AVT in the anterior pituitary. Our results showed that 1) AVPR1A, AVPR1B and AVPR2b could be preferentially activated by AVT, monitored by cell-based luciferase reporter assays and/or Western blot, indicating that they are AVT-specific receptors (AVPR1A; AVPR1B) or AVT-preferring receptor (AVPR2b) functionally coupled to intracellular calcium, MAPK/ERK and cAMP/PKA signaling pathways. In contrast, MTR could be activated by AVT and MT with similar potencies, indicating that MTR is a receptor common for both peptides; 2) Using qPCR, differential expression of the four receptors was found in chicken tissues including the oviduct and anterior pituitary. In particular, only AVPR1A is abundantly expressed in the uterus, suggesting its involvement in mediating AVT-induced oviposition. 3) In cultured chick pituitary cells, AVT could stimulate ACTH and PRL expression and secretion, an action likely mediated by AVPR1B and/or AVPR1A abundantly expressed in anterior pituitary. Collectively, our data helps to elucidate the roles of AVT/MT in birds, such as the 'oxytocic action' of AVT, which induces uterine muscle contraction during oviposition.

The Pituitary Transcriptional Response Related to Feed Conversion in Pigs

Over the decades, pig breeding objectives have focused on improving the meat content in the carcass without taking into consideration the more effective fattening indicators that affect feed conversion. At present, pig growth traits associated particularly with animal feeding have become crucial due to their economic significance. This is especially evident in countries where pigs are maintained on large farms. The present study indicates that pituitary differentially expressed genes (DEGs) are activated in response to variable feed conversion (FC) in pigs. The experiment included two native Polish breeds: Puławska and Złotnicka White (ZW). The whole pituitary transcriptome was sequenced using next-generation sequencing (NGS) technology. The RNA-seq method identified over 500 and 300 DEGs in the pituitaries of the ZW and the Puławska pig populations, respectively, that were associated with hormonal regulation, notch signaling, and Wnt pathways. Lower FC in the ZW pigs favoured increased fat content in the body and significantly higher prolactin expression. The obtained results indicate that low FC values in pigs are related to slower growth or increased fat content, which suggests various pituitary responses. Therefore, the identified candidate genes were not directly associated with feed conversion values but with other factors. However, the present study delivers new insights into pituitary regulation in pigs.

Embryoid body-based RNA-seq analyses reveal a potential TBBPA multifaceted developmental toxicity

The frequent detection of tetrabromobisphenol A (TBBPA) in the human body, especially in umbilical cord serum and breast milk, has raised concerns about TBBPA potential effects on embryonic development. The differentiation of embryonic stem cells (ESCs) in vitro can serve as a model for the early stages of embryonic development. In this study, we differentiated mouse ESCs via 3D aggregates called embryoid bodies in presence of environment and human relevant TBPPA concentrations for 28 days. We collected samples at different time points and analyzed TBBPA-dependent global gene expression changes by RNA-seq. Our analyses revealed a potential TBBPA multifaceted developmental toxicity with effects on the nervous and cardiac/skeletal muscle systems. Mechanistically, our findings suggest TBBPA endocrine disrupting activities in part via prolactin signaling.

Polygenic risk for circulating reproductive hormone levels and their influence on hippocampal volume and depression susceptibility

Altered reproductive hormone levels have been associated with the pathophysiology of depressive disorders and this risk may be imparted by their modulatory effect upon hippocampal structure and function. Currently it is unclear whether altered levels of reproductive hormones are causally associated with hippocampal volume reductions and the risk of depressive disorders. Here, we utilize genome-wide association study (GWAS) summary statistics from a GWAS focusing on reproductive hormones, consisting of 2913 individuals. Using this data, we generated polygenic risk scores (PRS) for estradiol, progesterone, prolactin and testosterone in the European RADIANT cohort consisting of 176 postpartum depression (PPD) cases (100% female, mean age: 41.6 years old), 2772 major depressive disorder (MDD) cases (68.6% female, mean age: 46.9 years old) and 1588 control participants (62.5% female, mean age: 42.4 years old), for which there was also a neuroimaging subset of 111 individuals (60.4% female, mean age: 50.0 years old). Only the best-fit PRS for estradiol showed a significant negative association with hippocampal volume, as well as many of its individual subfields; including the molecular layer and granule cell layer of the dentate gyrus, subiculum, CA1, CA2/3 and CA4 regions. Interestingly, several of these subfields are implicated in adult hippocampal neurogenesis. When we tested the same estradiol PRS for association with case-control status for PPD or MDD there was no significant relationship observed. Here, we provide evidence that genetic risk for higher plasma estradiol is negatively associated with hippocampal volume, but this does not translate into an increased risk of MDD or PPD. This work suggests that the relationship between reproductive hormones, the hippocampus, and depression is complex, and that there may not be a clear-cut pathway for etiology or risk moderation.

Inhibition of epidermal growth factor receptor stimulates prolactin expression in primary culture of the mouse pituitary gland

The roles of epidermal growth factor (EGF) in the regulation of prolactin (PRL) gene expression in the normal pituitary gland remain poorly understood. In the present study, the effects of EGF and an inhibitor of the EGF receptor, erlotinib, on PRL gene expression were examined both in the pituitary tumour cell line GH3 and in a primary culture of the mouse pituitary gland under similar experimental conditions. The results showed that EGF stimulated PRL expression in GH3 cells, but not in normal cells. Erlotinib was found to counteract EGF in GH3 cells inhibiting the PRL expression enhanced by EGF. By contrast, erlotinib induced an elevation in the PRL mRNA levels in the primary culture of the adult pituitary gland and the initiation of PRL production in the culture of the foetal pituitary gland in which PRL production had not yet occurred. Western blot analyses showed that EGF induced and erlotinib inhibited the activation of extracellular regulated protein kinase equally in GH3 and normal cells. These results suggest that the consequences of EGF receptor activation in normal PRL cells contradict those in adenomatous PRL cells.

A role for kinesin-1 subunits KIF5B/KLC1 in regulating epithelial mesenchymal plasticity in breast tumorigenesis

Background

Epithelial mesenchymal plasticity (EMP) is deemed vital in breast cancer progression, metastasis, stemness and resistance to therapy. Therefore, characterizing molecular mechanisms contributing to EMP are in need enabling the development of more advanced therapeutics against breast cancer. While kinesin superfamily proteins (KIFs) are well known for their role in intracellular cargo movement, our knowledge of their function in breast tumorigenesis is still limited.

Methods

Various breast cancer cell lines representing different molecular subtypes were used to determine the role of kinesine-1 subunits KIF5B/KLC1 in regulation of EMP.

Findings

In breast cancer, we show that kinesin family member 5B (KIF5B) and its partner protein kinesin light chain 1 (KLC1), subunits of kinesin-1, to play differential roles in regulating EMP and tumorigenesis. Indeed, we found KIF5B to be expressed in triple negative (TN)-basal-like/claudin low breast cancer subtype and to be an inducer of epithelial-mesenchymal transition (EMT), stemness, invasiveness, tumor formation and metastatic colonization. Whereas, we found KLC1 to be expressed in epithelial/luminal breast cancer subtypes and to be a suppressor of EMT, invasion, metastasis and stem cell markers expression as well as to be an inducer of epithelial/luminal phenotype. Interestingly, in TN-basal-like/claudin low cells we found a novel nuclear accumulation of KIF5B and its interaction with the EMT transcriptional regulator Snail1 independent of KLC1. In addition, TGF-β mediated pro-invasive activity was found to be dependent on KIF5B expression. In contrast, the epithelial differentiation factor and EMT suppressor prolactin (PRL) was found to repress KIF5B gene expression and KIF5B-Snail1 nuclear accumulation, but enhanced KLC1 gene expression and KIF5B-KLC1 interaction.

Interpretation

Together, these results highlight a new paradigm for kinesin-1 function in breast tumorigenesis by regulating EMP programing and aggressiveness.

Fund

This work was supported by the Canadian Institutes of Health Research (operating grants #233437 and 233438) granted to Suhad Ali.

Disentangling juxtacrine from paracrine signalling in dynamic tissue

Prolactin is a major hormone product of the pituitary gland, the central endocrine regulator. Despite its physiological importance, the cell-level mechanisms of prolactin production are not well understood. Having significantly improved the resolution of real-time-single-cell-GFP-imaging, the authors recently revealed that prolactin gene transcription is highly dynamic and stochastic yet shows space-time coordination in an intact tissue slice. However, it still remains an open question as to what kind of cellular communication mediates the observed space-time organization. To determine the type of interaction between cells we developed a statistical model. The degree of similarity between two expression time series was studied in terms of two distance measures, Euclidean and geodesic, the latter being a network-theoretic distance defined to be the minimal number of edges between nodes, and this was used to discriminate between juxtacrine from paracrine signalling. The analysis presented here suggests that juxtacrine signalling dominates. To further determine whether the coupling is coordinating transcription or post-transcriptional activities we used stochastic switch modelling to infer the transcriptional profiles of cells and estimated their similarity measures to deduce that their spatial cellular coordination involves coupling of transcription via juxtacrine signalling. We developed a computational model that involves an inter-cell juxtacrine coupling, yielding simulation results that show space-time coordination in the transcription level that is in agreement with the above analysis. The developed model is expected to serve as the prototype for the further study of tissue-level organised gene expression for epigenetically regulated genes, such as prolactin.

Prolactin - a pleiotropic factor in health and disease

The principal role of prolactin in mammals is the regulation of lactation. Prolactin is a hormone that is mainly synthesized and secreted by lactotroph cells in the anterior pituitary gland. Prolactin signalling occurs via a unique transmembrane prolactin receptor (PRL-R). The structure of the PRL-R has now been elucidated and is similar to that of many biologically fundamental receptors of the class 1 haematopoietic cytokine receptor family such as the growth hormone receptor. The PRL-R is expressed in a wide array of tissues, and a growing number of biological processes continue to be attributed to prolactin. In this Review, we focus on the newly discovered roles of prolactin in human health and disease, particularly its involvement in metabolic homeostasis including body weight control, adipose tissue, skin and hair follicles, pancreas, bone, the adrenal response to stress, the control of lactotroph cell homeostasis and maternal behaviour. New data concerning the pathological states of hypoprolactinaemia and hyperprolactinaemia will also be presented and discussed.

A novel type of prolactin expressed in the bullfrog pituitary specifically during the larval period

Prolactin (PRL) is one of the major hormones that control amphibian metamorphosis. Recently, a PRL (PRL1B) gene that is different from the known PRL (PRL1A) gene has been found in the genomes of several amphibian species. In order to ascertain whether the PRL1B gene is expressed in the bullfrog (Rana catesbeiana) pituitary, cloning of cDNA encoding PRL1B in the pituitary of the premetamorphic bullfrog tadpole was attempted. The bullfrog PRL1B amino acid sequence predicted from the obtained cDNA showed 62% identity with those of Xenopus PRL1Bs that have been presumed from the genome sequences, whereas the sequence identity between bullfrog PRL1A and PRL1B was 48%. A molecular phylogenetic tree showed that bullfrog PRL1B is most appropriately grouped with amphibian PRL1Bs. Quantitative PCR analysis revealed that the mRNA expression levels of bullfrog PRL1B in the pituitary were high during pre- and prometamorphosis, sharply declined at metamorphic climax and became undetectable after metamorphosis. In contrast, PRL1A mRNA levels were relatively low during pre- and prometamorphosis, rose at climax and remained high after metamorphosis. Immunohistochemical study using antibodies against partial peptides of PRL1A and PRL1B revealed that most of the PRL1A- and PRL1B-immunoreactive cells in the larval pituitary were distributed separately, but that some of the cells immunoreactive with both antibodies were also present. Western blot analysis with the larval pituitary extract indicated that PRL1B-immunoreactive band appeared at the position of molecular weight ca. 22.1 kDa and PRL1A-immunoreactive band at the position of ca. 22.8 kDa. The results obtained in this experiment suggest the possibility that PRL1B plays as-yet-unknown role(s) during the pre-climactic period of metamorphosis. This is the first report on the existence of PRL1B as a protein in the amphibian larval pituitary.

Characterization of a Novel POU1F1 Mutation Identified on Screening 160 Growth Hormone Deficiency Patients

The objective of the study is the functional characterization of a novel POU1F1 c.605delC mutation in combined pituitary hormone deficiency (CPHD) and to report the clinical and genetic details of 160 growth hormone deficiency patients. Screening of GH1, GHRHR, POU1F1, PROP1, and HESX1 genes by Sanger sequencing was carried out in 160 trios and 100 controls followed by characterization of the POU1F1 c.605delC mutation by expression studies including site directed mutagenesis, co-transfection, protein degradation, and luciferase assays to compare the wild type and mutant POU1F1. In vitro studies showed that the POU1F1 c.605delC mutation codes for a truncated protein with reduced transactivation capacity on its downstream effectors, viz., growth hormone (GH) and prolactin (PRL) causing severe CPHD. Experiments using different protease inhibitors reveal rescue of the protein upon blockage of the lysosomal pathway that might be useful in novel drug designing using targeted approach thereby maintaining the milieu and preventing/delaying the disease. The study provides an insight into the disease causing mechanism of POU1F1 c.605delC mutation identified in a CPHD child with severe short stature and failure to thrive. It also shows mutation effect on the expression, function and turnover of protein and highlights mechanistic details by which these potent regulators may operate.

Role of kisspeptin and Kiss1R in the regulation of prolactin gene expression in rat somatolactotroph GH3 cells

Hypothalamic kisspeptin is a known principal activator of gonadotropin-releasing hormone neurons and governs the hypothalamic-pituitary-gonadal axis. Previous reports have shown that kisspeptin is also released into the hypophyseal portal circulation and directly affects the anterior pituitary. In this study, we examined the direct effect of kisspeptin on pituitary prolactin-producing cells. The rat pituitary somatolactotroph cell line GH3 expresses the kisspeptin receptor (Kiss1R); however, in these cells, kisspeptin failed to stimulate prolactin-promoter activity. When GH3 cells overexpressed Kiss1R, kisspeptin clearly increased prolactin-promoter activity, with a concomitant increase in extracellular signal-regulated kinase (ERK) and cAMP/protein kinase A (PKA) signaling pathways. In the experiments using GH3 cells overexpressing Kiss1R, kisspeptin did not potentiate thyrotropin-releasing hormone (TRH)-induced prolactin-promoter activity, but it potentiated the pituitary adenylate cyclase-activating polypeptide-induced prolactin-promoter activity, with a concomitant enhancement of ERK and PKA signaling pathways. Although the basal and TRH-induced prolactin-promoter activities were not modulated by increasing amounts of Kiss1R expression in GH3 cells, kisspeptin-stimulated prolactin-promoter activity was increased by the amount of Kiss1R overexpression. Endogenous Kiss1r mRNA expression in GH3 cells was significantly increased by treatment with estradiol (E2) but not by TRH. In addition, kisspeptin's ability to stimulate prolactin-promoter activity was restored after E2 treatment in non-transfected GH3 cells. Our current observations suggest that kisspeptin might have a direct effect on prolactin expression in the anterior pituitary prolactin-producing cells under the influence of E2, which may regulate Kiss1R expression and function.

The maternal hormone in the male brain: Sexually dimorphic distribution of prolactin signalling in the mouse brain

Research of the central actions of prolactin is highly focused on females, but this hormone has also documented roles in male physiology and behaviour. Here, we provide the first description of the pattern of prolactin-derived signalling in the male mouse brain, employing the immunostaining of phosphorylated signal transducer and activator of transcription 5 (pSTAT5) after exogenous prolactin administration. Next, we explore possible sexually dimorphic differences by comparing pSTAT5 immunoreactivity in prolactin-supplemented males and females. We also assess the role of testosterone in the regulation of central prolactin signalling in males by comparing intact with castrated prolactin-supplemented males. Prolactin-supplemented males displayed a widespread pattern of pSTAT5 immunoreactivity, restricted to brain centres showing expression of the prolactin receptor. Immunoreactivity for pSTAT5 was present in several nuclei of the preoptic, anterior and tuberal hypothalamus, as well as in the septofimbrial nucleus or posterodorsal medial amygdala of the telencephalon. Conversely, non-supplemented control males were virtually devoid of pSTAT5-immunoreactivity, suggesting that central prolactin actions in males are limited to situations concurrent with substantial hypophyseal prolactin release (e.g. stress or mating). Furthermore, comparison of prolactin-supplemented males and females revealed a significant, female-biased sexual dimorphism, supporting the view that prolactin has a preeminent role in female physiology and behaviour. Finally, in males, castration significantly reduced pSTAT5 immunoreactivity in some structures, including the paraventricular and ventromedial hypothalamic nuclei and the septofimbrial region, thus indicating a region-specific regulatory role of testosterone over central prolactin signalling.

Molecular evolution of prolactin in Chiroptera: Accelerated evolution and a large insertion in vespertilionid bats

Pituitary prolactin (PRL) shows an episodic pattern of evolution in mammals, with a slow underlying rate (near stasis) and periods of rapid change in some groups. PRL evolution in bats, the second most speciose mammalian order, has not previously been studied, and is examined here. Slow basal evolution of PRL is seen in some bats, particularly megabats, but in most microbat groups evolution of PRL is more rapid. Accelerated evolution of PRL is particularly notable in the family Vespertilionidae, where analysis of nonsynonymous and synonymous substitutions indicates that it reflects adaptive evolution/positive selection. Remarkably, vespertilionid bats also show a large sequence insertion, of variable length, into exon 4 of PRL, giving a protein sequence 18-60 amino acids longer than normal, with the longest insertions in bats of the genus Myotis. An equivalent insertion has not been reported in PRL of any other vertebrate group. In the 3-dimensional structure of the complex between PRL and the extracellular domain (ecd) of its receptor (PRL:PRLR₂) the inserted sequence is seen to be introduced in the short loop between helices 2 and 3 of PRL; it is far removed from the receptor-binding sites, and may not interfere with binding. The ecd of the receptor also shows variable rates of evolution, with a higher rate in the Vespertilionidae, but this is much less marked than for the hormone. The distribution of substitutions introduced into PRL during vespertilionid evolution appears to be non-random, and this and the evidence for positive selection suggests that the rapid evolution and insert sequence introduction were associated with a significant change in the biological properties of the hormone.

Pituitary somatolactotropes evade an oncogenic response to Ras

Distinct cell types have been shown to respond to activated Ras signaling in a cell-specific manner. In contrast to its pro-tumorigenic role in some human epithelial cancers, oncogenic Ras triggers differentiation of pheochromocytoma cells and medullary thyroid carcinoma cells. Furthermore, we have previously demonstrated that in pituitary somatolactotropes, activated Ras promotes differentiation and is not sufficient to drive tumorigenesis. These findings demonstrate that lactotrope cells have the ability to evade the tumorigenic fate that is often associated with persistent activation of Ras/ERK signaling, and suggest that there may be differential expression of inhibitory signaling molecules or negative cell cycle regulators that act as a brake to prevent the tumorigenic effects of sustained Ras signaling. Here we aim to gain further insight into the mechanisms that allow GH4T2 cells to evade an oncogenic response to Ras. We show that Ral, but likely not menin, plays a key role in directing Ras-mediated differentiation of somatolactotropes, which may allow these cells to escape the tumorigenic fate that is often associated with activated Ras signaling. We also show that dominant negative Ras expression results in reduced GH4T2 cell proliferation and transformation, but does not influence differentiation. Taken together, the data presented here begin to shed light on the mechanisms by which pituitary somatolactotropes evade an oncogenic response to persistently activated Ras signaling and suggest that the architecture of the Ras signaling cascade in some endocrine cell types may be distinct from that of cells that respond to Ras in an oncogenic manner.

High Mobility Group Box 1 Regulates Uterine Decidualization through Bone Morphogenetic Protein 2 and Plays a Role in Kruppel-Like Factor 5-Induced Stromal Differentiation

BACKGROUND/AIMS

High mobility group box 1 (Hmgb1) is associated with a variety of physiological processes including embryonic development, cell proliferation and differentiation, but little information is available regarding its biological role in decidualization.

METHODS

In situ hybridization, real-time PCR, RNA interference, gene overexpression and MTS assay were used to analyze the spatiotemporal expression of Hmgb1 in mouse uterus during the pre-implantation period, and explore its function and regulatory mechanisms during uterine decidualization.

RESULTS

Hmgb1 mRNA was obviously observed in uterine epithelium on day 2 and 3 of pregnancy, but its expression was scarcely detected on day 4 of pregnancy. With the onset of embryo implantation, abundant Hmgb1 expression was noted in the subluminal stromal cells around the implanting blastocyst at implantation sites. Meanwhile, the accumulation of Hmgb1 mRNA was visualized in the decidual cells. Hmgb1 advanced the proliferation of uterine stromal cells and induced the expression of prolactin family 8, subfamily a, member 2 (Prl8a2), a reliable differentiation marker for decidualization. In uterine stromal cells, cAMP analogue 8-Br-cAMP up-regulated the expression of Hmgb1, but the up-regulation was abrogated by protein kinase A (PKA) inhibitor H89. Silencing of Hmgb1 by specific siRNA impeded the induction of 8-Br-cAMP on Prl8a2. Further analysis evidenced that Hmgb1 was a critical mediator of Kruppel-like factor 5 (Klf5) function in stromal differentiation. Knockdown of bone morphogenetic protein 2 (Bmp2) prevented the up-regulation of Prl8a2 elicited by Hmgb1 overexpression, whereas addition of exogenous recombinant Bmp2 protein (rBmp2) reversed the repression of Hmgb1 siRNA on Prl8a2 expression.

CONCLUSION

Hmgb1 may play an important role during mouse uterine decidualization.

Evolution of the growth hormone, prolactin, prolactin 2 and somatolactin family

Growth hormone (GH), prolactin (PRL), prolactin 2 (PRL2) and somatolactin (SL) belong to the same hormone family and have a wide repertoire of effects including development, osmoregulation, metabolism and stimulation of growth. Both the hormone and the receptor family have been proposed to have expanded by gene duplications in early vertebrate evolution. A key question is how hormone-receptor preferences have arisen among the duplicates. The first step to address this is to determine the time window for these duplications. Specifically, we aimed to see if duplications resulted from the two basal vertebrate tetraploidizations (1R and 2R). GH family genes from a broad range of vertebrate genomes were investigated using a combination of sequence-based phylogenetic analyses and comparisons of synteny. We conclude that the PRL and PRL2 genes arose from a common ancestor in 1R/2R, as shown by neighboring gene families. No other gene duplicates were preserved from these tetraploidization events. The ancestral genes that would give rise to GH and PRL/PRL2 arose from an earlier duplication; most likely a local gene duplication as they are syntenic in several species. Likewise, some evidence suggests that SL arose from a local duplication of an ancestral GH/SL gene in the same time window, explaining the lack of similarity in chromosomal neighbors to GH, PRL or PRL2. Thus, the basic triplet of ancestral GH, PRL/PRL2 and SL genes appear to be unexpectedly ancient. Following 1R/2R, only SL was duplicated in the teleost-specific tetraploidization 3R, resulting in SLa and SLb. These time windows contrast with our recent report that the corresponding receptor genes GHR and PRLR arose through a local duplication in jawed vertebrates and that both receptor genes duplicated further in 3R, which reveals a surprising asynchrony in hormone and receptor gene duplications.

Prolactin selectively transported to cerebrospinal fluid from blood under hypoxic/ischemic conditions

Aim

The aim of this study was to determine and to verify the correlation between the amount of prolactin (PRL) levels in the blood and in the cerebrospinal fluid (CSF) by various causes of death as an indicator for acute hypoxia in autopsy cases. It is to confirm the cause of the change in prolactin level in CSF by in vitro system.

Materials and methods

In autopsy materials, the PRL levels in blood from the right heart ventricle and in the CSF were measured by chemiluminescent enzyme immunoassay, and changes in the percentage of PRL-positive cells in the pituitary gland were examined using an immunohistochemical method. Furthermore, an inverted culture method was used as an in vitro model of the blood-CSF barrier using epithelial cells of the human choroid plexus (HIBCPP cell line) and SDR-P-1D5 or MSH-P3 (PRL-secreting cell line derived from miniature swine hypophysis) under normoxic or hypoxic (5% oxygen) conditions, and as an index of cell activity, we used Vascular Endothelial Growth Factor (VEGF).

Results and discussion

Serum PRL levels were not significantly different between hypoxia/ischemia cases and other causes of death. However, PRL levels in CSF were three times higher in cases of hypoxia/ischemia than in those of the other causes of death. In the cultured cell under the hypoxia condition, PRL and VEGF showed a high concentration at 10 min. We established a brain-CSF barrier model to clarify the mechanism of PRL transport to CSF from blood, the PRL concentrations from blood to CSF increased under hypoxic conditions from 5 min. These results suggested that PRL moves in CSF through choroidal epithelium from blood within a short time. PRL is hypothesized to protect the hypoxic/ischemic brain, and this may be because of the increased transportation of the choroid plexus epithelial cells.

Highly deleterious variations in COX1, CYTB, SCG5, FK2, PRL and PGF genes are the potential adaptation of the immigrated African ostrich population

Because of variable inconvenient living conditions in some places around the world, it is difficult to collect reliable physiological data for ostriches. Therefore, this study aims to provide a comprehensive in silico insight for the nature of polymorphism of important genetic loci that are related to physiological and reproductive traits. Sixty-nine mature ostriches ranging over half of Iraq were screened. Six exonic genetic loci, including cytochrome c oxidase I (COX1), cytochrome b (CYTB), secretogranin V (SCG5), feather keratin 2-like (FK2), prolactin (PRL) and placenta growth factor (PGF) were genotyped by PCR-single stranded conformation polymorphism (SSCP). Thirty-six novel SNPs, including seventeen nonsynonymous (ns) SNPs, were observed. Several computational software programs were utilized to assess the extent of the nsSNPs on their corresponding proteins structure, function and stability. The results showed several deleterious functional and stability changes in almost all the proteins studied. The total severity of each missense mutation was evaluated and compared with other nsSNPs accumulatively. It is evident from the extensive cumulative in silico computation that both p.E34D and p.E60K in PGF have the highest deleterious effect. The cumulative predictions from the present study are an impressive guide for the genotypes of African ostriches, which bypassed the expensive protocols for wet laboratory screening, to identify the effects of variants. To the best of our knowledge, this is the first investigation of its kind on the analyses and prediction outcome of missense mutations in African ostrich populations. The highly deleterious nsSNPs in the placenta growth factor are possible adaptive mutations which might be associated with adaptation in extreme and new environments. The flow and protocol of the computational predictions can be extended for various wild animals to identify the molecular nature of adaptations.

Evolution of the POU1F1 transcription factor in mammals: Rapid change of the alternatively-spliced β-domain

The POU1F1 (Pit-1) transcription factor is important in regulating expression of growth hormone, prolactin and TSH β-subunit, and controlling development of the anterior pituitary cells in which these hormones are produced. POU1F1 is a conserved protein comprising three main domains, an N-terminal transcription activation domain (TAD), a POU-specific domain and a C-terminal homeodomain. Within the TAD, a β-domain can be inserted by alternative splicing, giving an extended 'β-variant' with altered properties. Here sequence data from over 100 species were used to assess the variability of POU1F1 in mammals. This showed that the POU-specific domain and homeodomain are very strongly conserved, and that the TAD is somewhat less conserved, as are linker and hinge regions between these main domains. On the other hand, the β-domain is very variable, apparently evolving at a rate not significantly different from that expected for unconstrained, neutral evolution. In several species stop and/or frameshift mutations within the β-domain would prevent expression of the β-variant as a functional protein. In most species expression of the β-variant is low (<5% of total POU1F1 expression). The rate of evolution of POU1F1 in mammals shows little variation, though the lineage leading to dog does show an episode of accelerated change. This comparative genomics study suggests that in most mammalian species POU1F1 variants produced by alternative splicing may have little physiological significance.

[CORRELATION BETWEEN HEAT PAIN THRESHOLD DEGREE AND TRPV1 RECEPTOR PROTEIN LEVEL OVER VARIOUS PHASES OF THE OVARIAN-MENSTRUAL CYCLE]

Numerous scientific studies demonstrating differences in pain sensitivity over various phases of the ovarian-menstrual cycle (OMC) in healthy women have been published in recent decades, but the basis for these differences is however still poorly understood. The aim of the current study was to assess the correlation between the heat pain threshold degree and the dynamics of TRPV1 (Transient receptor potential channeling subfamily V member1) receptor protein level, as well as aggression degree in healthy women in the follicular and luteal phases of OMC. An increased TRPV1 receptor protein level and a decreased thermal pain threshold were found in the luteal phase of the OMC. The study revealed a correlation of the progesterone level in the luteal phase with a degree of increase of TRPV1 level, as well as with the degree of decrease of heat pain threshold. The relationship between the degree of pain threshold, as well as TRPV1 level with follicle stimulating (FSH), luteinizing (LH) hormones and prolactin levels was not found. Also, there was no correlation between TRPV1 or heat pain threshold levels and aggression degree.

Vasoinhibin Suppresses the Neurotrophic Effects of VEGF and NGF in Newborn Rat Primary Sensory Neurons

BACKGROUND/AIMS

Studies on the biological actions of vasoinhibins have focused mainly on endothelial cells. However, there is incipient knowledge about how vasoinhibins affect the nervous system, even if the target cells and mechanisms of action involved in these effects are unknown.

METHODS

In order to determine if neurons are direct targets of vasoinhibins, we examined cellular outcomes and the intracellular pathways involved in the neuronal actions of vasoinhibins using newborn rat dorsal root ganglion (DRG) neurons as a model system.

RESULTS

Vascular endothelial growth factor (VEGF) or nerve growth factor (NGF) treatment for 48 h resulted in neurite outgrowth stimulation in both DRG cultured explants and isolated primary sensory neurons. Interestingly, a recombinant vasoinhibin containing the first 123 amino acids of human prolactin antagonized the VEGF- and NGF-induced stimulation of neurite outgrowth. Vasoinhibin significantly reduced the density of neurites in DRG explants and obliterated neuritogenesis in isolated DRG neurons in primary culture, supporting a direct neuronal effect of vasoinhibin. In cultures of isolated DRG cells, virtually all β3-tubulin-labeled cells express TrkA, and the majority of these cells also express VEGFR2. Short-term VEGF or NGF treatment of DRG explants resulted in increased ERK1/2 and AKT phosphorylation, whereas incubation of DRG with the combination of either VEGF or NGF together with vasoinhibin resulted in blunted VEGF- or NGF-induced phosphorylation of both ERK1/2 and AKT.

CONCLUSION

Our results show that primary sensory neurons are direct targets of vasoinhibin, and suggest that vasoinhibin inhibition of neurite outgrowth involves the disruption of ERK and AKT phosphorylation cascades.