Three mRNA transcripts of the proopiomelanocortin gene in human placenta at term

Energy Balance Regulating Neuropeptides Are Expressed through Pregnancy and Regulated by Interleukin-6 Deficiency in Mouse Placenta

The placenta produces a number of signaling molecules including metabolic and reproductive hormones as well as several inflammatory mediators. Among them, Interleukin-6 (IL-6), a well-known immune and metabolic regulator, acts peripherally modulating metabolic function and centrally increasing energy expenditure and reducing body fat. IL-6 interacts with key hypothalamic neuropeptidergic systems controlling energy homeostasis such as those producing the orexigenic/anabolic: neuropeptide Y (NPY) and agouti-related peptide (AgRP) and anorectic/catabolic neuropeptides: proopiomelanocortin (POMC) and cocaine and amphetamine regulated transcript (CART). Human and rat placenta have been identified as source of these neuropeptides, but their expression and regulation in murine placental tissues remain unknown. Therefore, placental mRNA levels of IL-6, NPY, AgRP, POMC, and CART at different pregnancy stages (gestational days 13, 15, and 18) were analyzed by real time PCR, as were the effect of IL-6 deficiency (IL-6 knockout mice) on their placental expression. Our results showed that placenta-derived neuropeptides were regulated by gestational age and IL-6 throughout the second half of mouse pregnancy. These data suggest that IL-6 may participate in the fine tune control of energy balance during pregnancy by extending its action as a metabolic signal to the main organ at the fetomaternal interface: the placenta.

Intermediate lobe immunoreactivity in a patient with suspected lymphocytic hypophysitis

Lymphocytic hypophysitis is an organ-specific autoimmune disease characterised by destruction of pituitary hormone-secreting cells due to attack by self-reactive T lymphocytes. The spectrum of pituitary autoantibodies characterised by indirect immunofluorescence (IF) in these patients has not been substantially defined. The purpose of this study was to determine the spectrum of pituitary autoantibodies in 16 lymphocytic hypophysitis patients. Pituitary sections were prepared from guinea pigs and sera from 16 lymphocytic hypophysitis patients (13 biopsy proven and 3 suspected cases) and 13 healthy controls were evaluated for immunoreactivity to the pituitary tissue by immunofluorescence. A single patient was found to have high titre pituitary autoantibodies against guinea pig pituitary tissue. Immunoreactivity was directed against cells of the intermediate lobe. We present the case report of the patient who is a 24 year old woman that presented with headaches, polyuria and polydipsia. A uniformly enlarged pituitary mass was visible on MRI and a diagnosis of suspected lymphocytic hypophysitis was made. Based on our IF study, we postulate this patient has an autoimmune process directed towards the major cell type in the intermediate lobe, the melanotroph. Pre-adsorption with peptides representing adrenocorticotropic hormone, α-melanocyte stimulating hormone or β-endorphin did not affect the IF signal suggesting our patient's pituitary autoantibodies may target some other product of Proopiomelanocortin (POMC) processing, such as corticotrophin-like intermediate peptide or γ-lipoprotein. Alternatively, the autoantibodies may target a peptide completely unrelated to POMC processing.

Effects of experimentally induced hyperthyroidism on central hypothalamic-pituitary-adrenal axis function in rats: in vitro and in situ studies

Hyperthyroidism is associated with hypercorticosteronemia, although the locus that is principally responsible for the hypercorticosteronism remains unclear. The purpose of this study was to assess the effects of hyperthyroidism on the functional integrity of the hypothalamic-pituitary-adrenal (HPA) axis, to identify the locus in the HPA axis that is principally affected, and address the time-dependent effects of alterations in thyroid status. The functional integrity of each component of the HPA axis was examined in vitro and in situ in sham-thyroidectomized male Sprague-Dawley rats given placebo or in thyroidectomized rats given pharmacological dose (50 μg) of thyroxin for 7 or 60 days. Basal plasma corticosterone and corticosterone binding globulin (CBG) concentrations were significantly increased in short- and long-term hyperthyroid rats, and by 60 days. Basal plasma ACTH levels were similar to controls. Both hypothalamic CRH content and the magnitude of KCL- and arginine vasopressin (AVP)-induced CRH release from hypothalamic culture were increased in long-term hyperthyroid rats. There was a significant increase in the content of both ACTH and β-endorphin in the anterior pituitaries of both short- and long-term hyperthyroid animals. Short-term hyperthyroid rats showed a significant increase in basal POMC mRNA expression in the anterior pituitary, and chronically hyperthyroid animals showed increased stress-induced POMC mRNA expression. Adrenal cultures taken from short-term hyperthyroid rats responded to exogenous ACTH with an exaggerated corticosterone response, while those taken from 60-day hyperthyroid animals showed responses similar to controls. The findings show that hyperthyroidism is associated with hypercorticosteronemia and HPA axis dysfunction that becomes more pronounced as the duration of hyperthyroidism increases. The evidence suggests that experimentally induced hyperthyroidism is associated with central hyperactivity of the HPA axis.

Growth hormone and proopiomelanocortin are targeted by autoantibodies in a patient with biopsy-proven IgG4-related hypophysitis

Hypophysitis is a chronic inflammation of the pituitary gland often caused by autoimmunity. Among the autoimmune diseases it is one of the few where the autoantigens remain to be identified. The goal of the paper was to characterize the antigenic profile in a previously reported patient with IgG4-related hypophysitis. Immunofluorescence and immunoblotting were performed to detect antibodies to human pituitary proteins. The proteins recognized by western blotting were then submitted to mass spectrometry for sequencing. The patient's autoantibodies recognized two unique bands around 40 and 30 kDa on immunoblotting. Sequencing revealed one peptide from proopiomelanocortin in the 40 kDa band and four peptides from growth hormone in the 30 kDa band. This work represents the first antigenic profile in IgG4-related hypophysitis, and the first recognition of proopiomelanocortin as a possible pituitary autoantigen. In addition, the work supports previous suggestions of growth hormone as a pituitary autoantigen. Further studies are needed to prove the pathogenicity and diagnostic utility of these two pituitary proteins.

Extrapituitary production of anterior pituitary hormones: an overview

Protein hormones from the anterior pituitary gland have well-established endocrine roles in their peripheral target glands. It is, however, now known that these proteins are also produced within many of their target tissues, in which they act as local autocrine or paracrine factors, with physiological and/or pathophysiological significance. This emerging concept is the focus of this brief review.

Effects of melanocortins on fetal development

Melanocortins, adrenocorticotropic hormone (ACTH) and α-, β-, and γ-melanocyte-stimulating hormone (MSH) are produced in the placenta and secreted into embryos/fetuses. ACTH concentrations are higher in fetal plasma than in maternal plasma and peak at mid-gestation in rats, whereas ACTH production starts in the anterior lobe of the fetal pituitary at later stages. Melanocortin receptors (MC1-5R), receptors for ACTH and α-, β- and γ-MSH, are expressed in various adult organs. The specific function of these receptors has been well examined in the hypothalamic-pituitary-adrenocortical (HPA) axis and the HPA axis-like network in the skin, and anti-inflammatory effects for white blood cells have also been investigated. MC2R and/or MC5R are also expressed in the testis, lung, kidney, adrenal, liver, pancreas, brain and blood cells at different stages in mouse and rat embryos/fetuses. Melanocortins in embryos and fetuses promote maturation of the HPA axis and also contribute to the development of lung, testis, brain and blood cells. Recently, a unique ACTH function was revealed in fetuses: placental ACTH, which is secreted by the maternal leukemia inhibitory factor (LIF), and induces LIF secretion from fetal nucleated red blood cells. Finally, the maternal LIF-placental ACTH-fetal LIF signal relay regulates the LIF level and promotes neurogenesis in fetuses, which suggests that ACTH acts as a signal transducer or effector for fetal development in the maternal-fetal signal pathway.

The effects of hydrotherapy on anxiety, pain, neuroendocrine responses, and contraction dynamics during labor

BACKGROUND

Hydrotherapy (immersion or bathing) is used worldwide to promote relaxation and decrease parturient anxiety and pain in labor, but the psychophysiological effects of this intervention remain obscure.

DESIGN

A pretest-posttest design with repeated measures was used to examine the effects of hydrotherapy on maternal anxiety and pain, neuroendocrine responses, plasma volume shift (PVS), and uterine contractions (CXs) during labor. Correlations among variables were examined at three time points (preimmersion and twice during hydrotherapy).

METHODS

Eleven term women (mean age 24.5 years) in spontaneous labor were immersed to the xiphoid in 37 degrees C water for 1 hr. Blood samples and measures of anxiety and pain were obtained under dry baseline conditions and repeated at 15 and 45 min of hydrotherapy. Uterine contractions were monitored telemetrically.

RESULTS

Hydrotherapy was associated with decreases in anxiety, vasopressin (V), and oxytocin (O) levels at 15 and 45 min (all ps < .05). There were no significant differences between preimmersion and immersion pain or cortisol (C) levels. Pain decreased more for women with high baseline pain than for women with low baseline levels at 15 and 45 min. Cortisol levels decreased twice as much at 15 min of hydrotherapy for women with high baseline pain as for those with low baseline pain. beta-endorphin (betaE) levels increased at 15 min but did not differ between baseline and 45 min. During immersion, CX frequency decreased. A positive PVS at 15 min was correlated with contraction duration.

CONCLUSIONS

Hydrotherapy during labor affects neuroendocrine responses that modify psychophysiological processes.

ACTH is a novel regulator of bone mass

Adrenocorticotropin (ACTH) is one of several peptide hormones derived from a larger molecule, proopiomelanocortin (POMC). ACTH is a classic endocrine hormone, processed and secreted from the pituitary to stimulate cortisol production from the fasciculata cells in the adrenal gland. However, ACTH is also produced by other cells, including macrophages, at many sites in the body. ACTH binds to a specific member of the melanocortin receptor family, the MC2R. MC2R is expressed in osteoblastic cells in vivo, as shown by in situ hybridization. MC2R expression is strongest at sites of active bone deposition, and thus ACTH response probably varies with osteoblastic activity or stage of osteoblast differentiation. In vitro ACTH stimulates proliferation of osteoblasts in a dose-dependent manner. ACTH at 10 nM increases collagen I mRNA in the osteoblastic cell line SaOs2, although at lower concentrations ACTH may oppose osteoblast differentiation. ACTH is thus, at high concentrations, anabolic for the osteoblast, and it is highly likely that the hormone has concentration-dependent effects on bone metabolism in vivo.

ACTH: cellular peptide hormone synthesis and secretory pathways

Adrenocorticotrophic hormone (ACTH) is derived from the prohormone, pro-opiomelanocortin (POMC). This precursor undergoes proteolytic cleavage to yield a number of different peptides which vary depending on the tissue. In the anterior pituitary, POMC is processed to ACTH by the prohormone convertase, PC1 and packaged in secretory granules ready for stimulated secretion. In response to stress, corticotrophin releasing hormone (CRH), stimulates release of ACTH from the pituitary cell which in turn causes release of glucocorticoids from the adrenal gland. In tissues, such as the hypothalamus and skin, ACTH is further processed intracellularly to alpha melanocyte stimulating hormone (alphaMSH) which has distinct roles in these tissues. The prohormone, POMC, is itself released from cells and found in the human circulation at concentrations greater than ACTH. While much is known about the tightly regulated synthesis of POMC, there is still a lot to learn about the mechanisms for differentiating secretion of POMC, and the POMC-derived peptides. Understanding what happens to the POMC released from cells will provide new insights into its function.

The tissue-specific processing of pro-opiomelanocortin

It is just over 30 years since the definitive identification of the adrenocorticotrophin (ACTH) precursor, pro-opiomelanocotin (POMC). Although first characterised in the anterior and intermediate lobes of the pituitary, POMC is also expressed in a number of both central and peripheral tissues including the skin, central nervous tissue and placenta. Following synthesis, POMC undergoes extensive post-translational processing producing not only ACTH, but also a number of other biologically active peptides. The extent and pattern of this processing is tissue-specific, the end result being the tissue dependent production of different combinations of peptides from the same precursor. These peptides have a diverse range of biological roles ranging from pigmentation to adrenal function to the regulation of feeding. This level of complexity has resulted in POMC becoming the archetypal model for prohormone processing, illustrating how a single protein combined with post-translational modification can have a diverse number of roles.

Food-intake-regulating-neuropeptides are expressed and regulated through pregnancy and following food restriction in rat placenta

BACKGROUND

Neuropeptide Y (NPY), agouti related peptide (AgRP), cocaine and amphetamine-regulated transcript (CART) and melanocortins, the products of the proopiomelanocortin (POMC), are hypothalamic peptides involved in feeding regulation and energy homeostasis. Recent evidence has demonstrated their expression in rat and human placenta.

METHODS

In the current study, we have investigated the expression of those neuropeptides in the rat placenta by real-time PCR using a model of maternal food restriction.

RESULTS

Our results showed that placental-derived neuropeptides were regulated through pregnancy and following food restriction.

CONCLUSION

These data could indicate that placental-derived neuropeptides represent a local regulatory circuit that may fine-tune control of energy balance during pregnancy.

Evaluation of proopiomelanocortin mRNA in the peripheral blood from patients with Cushing's syndrome of different origin

ACTH-dependent Cushing's syndrome is due to ACTH overproduction originating from a pituitary corticotroph adenoma (Cushing's disease) or from ectopic tumors (ectopic ACTH syndrome). Due to difficulties in the differential diagnosis between these two forms of hypercortisolism it would be important to have molecular tools able to discriminate the two conditions. It is known that proopiomelanocortin (POMC) gene transcription can originate messengers of different length. ACTHomas show the normal 1072 nucleotides (nt) transcript, whereas ectopic tumors seem to be associated with a longer mRNA form (1450 nt). In order to analyse the presence of different POMC transcripts, we extracted total RNA from peripheral lymphocytes of 10 patients with Cushing's disease, 10 with ectopic Cushing syndrome, and 20 controls as well as from pituitary tissues (2 ACTH-omas and a normal pituitary polyA+ sample). Northern blot analysis correctly revealed a 1072 nt mRNA molecule in pituitary ACTH-oma and in the normal pituitary polyA+ RNA samples, whereas neither this molecule nor other alternative transcripts were detected in blood samples from patients and controls. These data were confirmed by the more sensitive RT-PCR technique. This study further underlines the need for alternative approaches in the diagnosis of ACTH-dependent Cushing's syndrome.

Human placental protein/peptides stimulate melanin synthesis by enhancing tyrosinase gene expression

Placental protein/peptides as biological response modifier are well documented, but not much known about melanogenesis. We possibly for the first time, demonstrated melanogenesis in B16F10 mouse melanoma by a placental protein/peptide fraction (PPPF) prepared from a hydroalcoholic extract of fresh term human placenta. This study described the effect of PPPF on the induction of tyrosinase; the key enzyme of melanogenesis to investigate the basis of PPPF induced pigmentation in primary melanocyte and B16F10 melanoma. Tyrosinase induction by PPPF in B16F10 cells was found dose- and time dependent at the level of activity. Tyrosinase, at the level of transcription and protein expression when assessed by RT-PCR and Western blot analyses found to have considerable induction over untreated control. PPPF led to enhanced activation of tyrosinase promoter resulting higher transcription thus substantiating the role of PPPF as a stimulator of melanogenesis. Actinomycin D, the transcriptional inhibitor of protein synthesis, blocked the stimulatory action of PPPF since the induction of tyrosinase and melanin was markedly reduced in presence of this inhibitor. Thus the results suggested that PPPF mediated increase in tyrosinase expression occurred through transcriptional upregulation to stimulate melanogenesis in B16F10 cells and in primary melanocyte also.

Estrogen/hypothalamus-pituitary-adrenal axis interactions in the fetus: The interplay between placenta and fetal brain

OBJECTIVE

The hormonal interactions between the placenta and the fetal hypothalamus-pituitary-adrenal (HPA) axis are reviewed.

METHODS

This review addresses data obtained from the chronically catheterized fetal sheep, drawing relevant comparisons to human fetuses.

RESULTS

In the sheep, and perhaps in primate species, parturition is initiated by an increase in the activity of the HPA axis. The endogenous mechanisms underlying the increase in activity of the fetal HPA axis are incompletely understood but might involve an interplay between placenta and fetal hypothalamus and pituitary. Various hypotheses have been proposed, involving placental secretion of prostaglandins and various components of the fetal HPA axis. In the sheep, the influence of estradiol appears to be potent, and various experiments have suggested the possibility that, in late gestation, there exists a positive feedback relationship between placental estrogen secretion and pituitary adrenocorticotropin (ACTH) secretion. Estradiol circulates in concentrations known to stimulate fetal ACTH secretion. Additionally, estradiol circulates in the form of estradiol-3-sulfate, a molecular form that is taken up by the fetal brain and deconjugated by steroid sulfatase, which is expressed in the fetal brain. Recent evidence suggests that the interaction between estradiol and ACTH might involve production of paracrine or autocrine substances in the fetal brain. One candidate mediator is prostaglandin E2 (PGE2), highlighted by the action of estradiol on the expression of prostaglandin endoperoxide synthase-2 (PGHS-2 or COX-2) in brain regions known to be important for controlling HPA activity.

CONCLUSION

Estradiol, secreted by the placenta in increasing amounts in late gestation, is a potent stimulator of fetal ACTH secretion. The interactions between estradiol and the fetal HPA axis might function as a positive feedback loop that increases the concentrations of both hormones before birth.

Ontogenetic changes in the extra-pituitary expression of pro-opiomelanocortin in the developing ovine fetus

Previous studies performed in this laboratory have demonstrated that the fetal lung contains immunoreactive adrenocorticotropin (irACTH), and that the lung both clears and secretes irACTH under basal and stimulated conditions. Furthermore, we have demonstrated that the irACTH in fetal lung is accounted for by proopiomelanocortin (POMC), and that there is an evidence of post-translational processing that is distinct from the pattern of processing typical of the anterior pituitary. The present study was designed to test the hypothesis that POMC is synthesized in the fetal lung, and that there is decreased synthesis in the late-gestation ovine fetal lung. Lungs were collected from fetal sheep at 80, 100, 120, 130, and 145 days gestation (n=4/group; term=147 days). POMC mRNA was measured using reverse transcription and real-time polymerase chain reaction with probe and primers designed in this laboratory. The greatest abundance of POMC mRNA was in the 80-days fetal sheep, and the relative abundance decreased as a function of fetal gestational age. POMC protein was measured using immunoblot analysis in lungs from 80, 120, and 145-days fetal sheep. The pattern of POMC protein abundance was consistent with that of the mRNA (highest at 80 days, lowest at 145 days). The POMC immunoblot revealed specific staining of a peptide with molecular weight of 27 kDa and another peptide with a molecular weight slightly higher than that of native POMC (32 kDa). For comparison, we measured POMC mRNA in skeletal muscle and small intestine. We found POMC expression in both fetal tissues, but no statistically significant ontogenetic pattern of expression. We conclude that POMC is synthesized in the ovine fetal lung, and that the rate of synthesis decreases as the fetus matures in utero. We speculate that the decreasing abundance of POMC mRNA and protein reflects decreased release of POMC and POMC-related peptides into the fetal bloodstream.