Prolactin Production Research Articles

Prolactin releasing peptide (PrRP) stimulates luteinizing hormone (LH) and follicle stimulating hormone (FSH) via a hypothalamic mechanism in male rats.

Prolactin releasing peptide (PrRP) was originally isolated as an endogenous hypothalamic ligand for the hGR3 orphan receptor. It has been shown to release prolactin from dispersed pituitaries harvested from lactating female rats and only at very high doses in cycling females. PrRP is reported to have no effect on prolactin production from dispersed pituitary cells harvested from males. The CNS distribution of this peptide suggested a role for PrRP in the control of the hypothalamo-pituitary axis. The aim of this study was to examine the actions of PrRP (1-31) on circulating pituitary hormones following intracerebroventricular (ICV) injection in male rats and to investigate the mechanism of PrRP's effect by measurement of hypothalamic releasing factors in vitro. In our experiments, PrRP (1-31) did not release LH, FSH, TSH, growth hormone or prolactin directly from dispersed male pituitary cells in vitro. We have shown for the first time that following ICV injection of PrRP (1-31) 5 nmol there was a highly significant simulation of plasma LH that began at 10 minutes and was maintained over the course of the experiment (at 60 minutes PrRP 5 nmol 2.2 +/- 0.2 vs. saline 0.5 +/- 0.1 ng/ml, p<0.001). Plasma FSH increased at 20 minutes following ICV injection (PrRP 5nmol 10.8 +/- 2.0 ng/ml vs. saline 5.1 +/- 0.5, p<0.01). Total plasma testosterone increased at 60 minutes post injection (PrRP 5nmol 9.2 +/- 1.6 vs. saline 3.5 +/- 0.6 nmol/l, p<0.01). There was no significant alteration in plasma prolactin levels. PrRP significantly increased the release of LHRH from hypothalamic explants in vitro (PrRP 100nmol/l 180.5 +/- 34.5% of the basal secretion, p<0.05). PrRP (100nmol/l) also increased the following hypothalamic peptides involved in the control of pituitary hormone release, vasoactive intestinal peptide (VIP) 188.1 +/- 24.6% and galanin 153.8 +/- 13.0% (both p<0.001 vs. basal secretion) but had no effect on orexin A secretion. These results suggest a role for PrRP in the control of gonadotrophin secretion acting via a hypothalamic mechanism involving the release of LHRH.

Effect of activin on production and secretion of prolactin and growth hormone in cultured rat GH3 cells.

To evaluate the effect of the growth factor activin A on the secretion of prolactin (PRL) and GH in cultured GH3 cells. The concentrations of PRL and GH secreted from GH3 cells cultured in media with and without activin A were measured by RIA, and the expression of PRL mRNA and GH mRNA were analyzed using the Northern blot method. Activin A significantly inhibited PRL release from GH3 cells cultured for 48h in a dose-dependent manner (activin: 0.3-3nM). The inhibitory effects of 3nM activin A were observed in the culture from 12h to 48h (53.2% of control). Activin A (3nM) also significantly inhibited the expression of PRL mRNA at 24h (33.8% of control). In contrast, activin A significantly stimulated GH release from GH3 cells cultured for 48h in a dose-dependent manner (activin: 0.3-3nM). The stimulatory effect of 3nM activin A was observed in the culture for 48h (157.6% of control). Activin A (3nM) also significantly stimulated the expression of GH mRNA at 24h (183.6% of control). In spite of these significant changes in PRL and GH secretion, pit-1 mRNA levels were not significantly changed by activin A. These findings indicated that activin A modulates PRL and GH secretion through the regulation of PRL and GH gene transcription in GH3 cells, but that these effects are unrelated to pit-1 gene expression.

Corticotrophin-releasing hormone (CRH) interacts with inflammatory prostaglandins and interleukins and affects the decidualization of human endometrial stroma.

The hypothalamic neuropeptide, corticotrophin-releasing hormone (CRH), which is also produced by human endometrium, has been shown to induce its decidualization in vitro. This process, induced mainly by progesterone, has characteristics of an aseptic inflammatory reaction, and is modulated by locally produced pro-inflammatory factors. In humans, prostaglandin E(2) (PGE(2)) enhances while interleukin (IL)-1 inhibits the decidualizing effect of progesterone. The aim of the present work was to test the hypothesis that CRH might affect the decidualization of human endometrium interacting with these factors. Therefore, we studied its effects on the production of pro-inflammatory interleukins IL-1, IL-6 and of PGE(2) from human endometrial stromal cells in primary culture. The results strongly suggest that CRH decidualizes stromal cells, as judged by the appearance of cytokeratins and the production of prolactin, two established markers of decidualization. In parallel to its effect on decidualization, CRH also decreased the production of PGE(2), while it increased the production of IL-1 and IL-6. Exposure of endometrial stromal cells to IL-6 also caused decidualization. The data presented here suggest that endometrial CRH regulates the production of local modulators of decidualization, i.e. PGE(2), IL-1 and IL-6. We postulate that, through the regulation of these factors, CRH acts as a local fine-tuner of decidualization initiated by progesterone.

Elevated luteinizing hormone induces expression of its receptor and promotes steroidogenesis in the adrenal cortex.

Transgenic (TG) female mice expressing bLHbeta-CTP (a chimeric protein derived from the beta-subunit of bovine luteinizing hormone [LH] and a fragment of the beta-subunit of human chorionic gonadotropin [hCG]) exhibit elevated serum LH, infertility, polycystic ovaries, and ovarian tumors. In humans, increased LH secretion also occurs in infertility and polycystic ovarian syndrome, often concomitant with adrenocortical dysfunction. We therefore investigated adrenal function in LH overexpressing bLHbeta-CTP female mice. The size of their adrenals was increased by 80% with histological signs of cortical stimulation. Furthermore, adrenal steroid production was increased, with up to 14-fold elevated serum corticosterone. Primary adrenal cells from TG and control females responded similarly to ACTH stimulation, but, surprisingly, the TG adrenals responded to hCG with significantly increased cAMP, progesterone, and corticosterone production. LH receptor (LHR) expression and activity were also elevated in adrenals from female TG mice, but gonadectomized TG females showed no increase in corticosterone, suggesting that the dysfunctional ovaries of the intact TG females promote adrenocortical hyperfunction. We suggest that, in intact TG females, enhanced ovarian estrogen synthesis causes increased secretion of prolactin (PRL), which elevates LHR expression. Chronically elevated serum LH, augmented by enhanced PRL production, induces functional LHR expression in mouse adrenal cortex, leading to elevated, LH-dependent, corticosterone production. Thus, besides polycystic ovaries, the bLHbeta-CTP mice provide a useful model for studying human disorders related to elevated LH secretion and adrenocortical hyperfunction.

Mapping and Developmental Expression Analysis of the WD-Repeat Gene Preb

We have isolated from mouse a novel WD-motif-containing gene designated Preb. This gene encodes a predicted protein of 416 amino acids and has significant homology with other members of the WD-motif gene superfamily that play a role in cell fate determination. Preb maps to the proximal end of chromosome 5 in mouse, near the Hmx1 homeobox gene. Preb is detectable in early stage embryos in the peripheral nervous system, developing liver, and surface ectoderm. Later, Preb is expressed in the anterior portion of Rathke's pouch, which gives rise to the anterior pituitary, the organ responsible for the production of prolactin and other hormones. In midgestation embryos, the most extensive expression of Preb is observed in the perichondrium of the craniofacial, axial, and appendicular skeleton. The expression pattern of Preb in murine embryos suggests a potential role in the specification of multiple cell types, in particular, the fetal skeleton.

Plasma prolactin, blood metabolites and milk production in bromocryptine-treated crossbred goats

To determine the effect of bromocryptine on plasma prolactin, metabolites and milk production, six healthy crossbred goats in their second or third lactation were selected from the institute’s goat herd. The goats were injected with bromocryptine @ 5 mg per day intramuscularly for a period of 5 days during 55–60 days of lactation (period I) and treatment was repeated after 14 days for an additional 5 days (period II). Blood samples were collected for 5 consecutive days before, during and after administration of bromocryptine during both periods of the study. Milk samples were collected on days coinciding with the days of blood sampling. During period I, bromocryptine administration decreased ( P < 0.01) milk yields by 27.4%. After withdrawal of bromocryptine the yields increased ( P < 0.01); however, during period II, bromocryptine treatment did not decrease milk yields. During period I bromocryptine treatment suppressed prolactin level ( P < 0.01) which coincided with decrease in milk yield, but in period II such decreases in prolactin did not coincide with changes in milk yields. Fat content increased ( P < 0.01) after bromocryptine administration in both periods. A decrease ( P < 0.01) in protein and lactose content indicated a possible role of prolactin in the synthesis of these constituents by the mammary gland cell in goats. Blood glucose and NEFA were not affected by bromocryptine in period I but in period II an increase in blood glucose with a simultaneous decrease in NEFA was observed ( P < 0.01).From this study it is concluded that prolactin has a role in the maintenance of milk secretion through protein synthesis by the mammary gland. However, it does not seem to have any direct role on milk fat synthesis.

Rat Decidual Prolactin: IDENTIFICATION, MOLECULAR CLONING, AND CHARACTERIZATION

Establishment and maintenance of pregnancy require the activity of a highly specialized maternal tissue, the decidua. It is well established that the human decidua synthesizes and releases prolactin. However, in the rat, no study has been able to demonstrate the production of prolactin by the decidua. In this report, we established for the first time using Northern blot analysis and reverse transcription-polymerase chain reaction, Western blot analysis, immunocytochemistry, and enzyme-linked immunosorbent assay, that a defined cell population located in the rat antimesometrial decidua expresses prolactin mRNA, as well as synthesizes and secretes this hormone. By reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends, we cloned a full-length cDNA for rat decidua prolactin, whose sequence was identical to that of pituitary prolactin. Our results also showed that pituitary prolactin appeared to down-regulate decidual prolactin levels. Under these circumstances, inhibition of pituitary prolactin secretion led to a rise in both decidual prolactin mRNA and protein expression. Moreover, addition of exogenous prolactin to primary decidual cells in culture also caused a marked decrease in decidual prolactin mRNA expression. Finally, treatment of primary decidual cells with steroid hormones or 8-bromo-cAMP revealed a differential regulation of decidual prolactin expression from that of pituitary suggesting a tissue-specific regulation of prolactin gene expression, possibly through the use of an alternative promoter in rat decidua.

Absence of prolactin gene expression in colorectal cancer.

AIMS: Previous studies documenting hyperprolactinaemia in patients with colorectal cancer have suggested that the tumour is the source of hormone production. The aim of this study was to determine the...

Onapristone Suppresses Prolactin Production in Explant Cultures of Leiomyoma

Objective: To assess the action of onapristone, a type I antiprogestin, on prolactin (PRL) production by explant cultures of leiomyoma and myometrium. Design: Explant cultures of myometrium and leiomyomas from 3 premenopausal women undergoing hysterectomy in the proliferative phase of the menstrual cycle. Main Outcome Measures: PRL secretion measured by radioimmunoassay. Results: PRL secretion was decreased in leiomyomas by onapristone. There was no effect in the myometrium. There was no additional effect with the addition of the type II antiprogestin mifepristone (RU 486). Conclusion: PRL production is suppressed in leiomyomas but not in myometrium after treatment with onapristone in vitro. This suppression may serve as a marker for the clinical effectiveness of agents used in the treatment of leiomyomas.

Increased episodic release and disorderliness of prolactin secretion in both micro- and macroprolactinomas.

To quantify prolactin (PRL) secretion patterns, ten untreated (female) microprolactinoma patients and six (male) macroprolactinoma patients underwent repetitive blood sampling every 10 min over 24 h. PRL release activity was analyzed from plasma PRL concentration (immunofluorimetric assay) profiles via a model-independent discrete peak detection program (Cluster) and a waveform-independent deconvolution technique (Pulse). Diurnal variations were analyzed by cosinor analysis. The number of distinct PRL pulses (mean +/- S.E.M.) was increased in patients: microprolactinoma 18.6 +/- 0.6/24 h versus female controls 12.4 +/- 0.6 (P = 6.7 x 10-s), and macroprolactinoma 18.0 +/- 0.9 versus male controls 13.5 +/- 0.8/24 h (P = 0.003). In patients, PRL pulse height, amplitude, pulse area and interpeak nadir concentrations were each greatly elevated compared with gender-matched controls. By 2-component deconvolution analysis, the mean nadir PRL secretion rate in microprolactinoma patients was augmented 20-fold at 0.408 +/- 0.089 microgram/l per min versus in female controls 0.019 +/- 0.009 microgram/l per min (P < 0.001); and in macroprolactinoma by 130-fold at 2.067 +/- 0.693 micrograms/l per min versus male controls 0.016 +/- 0.001 microgram/l per min (P = 0.001). Corresponding 24 h mean PRL secretion rates were in women, 0.658 +/- 0.147 and 0.044 +/- 0.018 (P < 0.001), and in men, 3.309 +/- 1.156 and 0.035 +/- 0.010 micrograms/l per min (P = 0.001), being respectively 15- and 94-fold increased in tumors. The estimated PRL production per day was 160 +/- 15 and 187 +/- 20 micrograms in male and female controls respectively. PRL production was 2860 +/- 640 micrograms in female patients with microadenomas (P < 0.001), and 37,800 +/- 5900 micrograms in male macroadenoma patients (P = 0.001). Cosinor analysis of the plasma concentrations revealed a significant rhythm in nine of ten, patients with a microadenoma, and in five of six with a macroadenoma. The same method applied to pulse height and amplitude disclosed a significant rhythm for PRL pulse height, but not for pulse amplitude, suggesting preserved rhythmicity of baseline interpulse nadir PRL concentrations. Approximate entropy (ApEn), a scale- and model-independent regularity statistic, averaged 1.6559 +/- 0.028 in microprolactinoma patients versus 0.8128 +/- 0.079 in female controls (P = 1.7 x 10(-8)); ApEn in macroadenomas was 1.5674 +/- 0.054 versus male controls 0.8773 +/- 0.076 (P = 1.7 x 10(-5), signifying greater secretory irregularity in the patients. Compared with microadenomas, macroadenomas exhibited a higher mean plasma concentration, overall mean PRL secretion rate, nadir secretion rate and pulse area, but similar peak frequency. We conclude that PRL secretion by prolactinomas is characterized by increased plasma PRL episodicity of release, increased total (15- to 100-fold) and basal (20- to 130-fold) secretion rates, and increased disorderlines of minute-to-minute secretion. These abnormalities of secretory control are very similar to those for GH and ACTH identified earlier in acromegaly and Cushing's disease respectively, thus suggesting mechanistic generality of pituitary tumor secretory derangements, independent of the particular hormone.

Prolactin and its receptor in human endometrium.

Synthesis of prolactin (PRL) in human endometrium extends from the late luteal phase of the menstrual cycle throughout the pregnancy. We have studied the hormonal requirements for the sustained production of PRL and its receptor (PRL-R) in a long-term primary cell culture system. Progestin stimulates the production PRL and its receptor when stromal cells transform into decidual cells. The rise in PRL production rate correlates with an increase in steady-state PRL mRNA levels which are caused by increased transcription rate gene. Replacing progestin by the antiprogestin, RU 486, causes a transient superinduction of PRL production followed by reduction to basal level of expression. On the other hand, RU 486 exerts immediate inhibition of PRL-receptor mRNA expression. In addition, relaxin (RLX) enhances PRL synthesis. The transcription of the PRL gene in endometrium is dependent upon the promotor 6-kb upstream of the transcription start site in the pituitary. That biological functions of PRL and its receptor are critical to implantation and the maintenance of pregnancy is suggested by the impaired fertility of PRL and PRL-R knockout mice. PRL enhances endometrial cell growth at low concentrations and inhibits it at high concentrations. This dual action indicates an autocrine action of PRL-R-mediated signaling transduction pathways during reproductive cycles and pregnancy. During gestation, decidual-derived prolactin regulates the volume of amniotic and fetal extracellular fluid and electrolytes.

Effect of anticardiolipin antibodies on prolactin and insulin-like growth factor binding protein-1 production by human decidual cells.

The effect of anticardiolipin antibodies (ACAs) on basal- and growth factor-stimulated prolactin and insulin-like growth factor (IGF) binding protein (BP)-1 production by cultured human decidual cells was investigated. Decidual cells were cultured for 24, 48, or 96 hr in medium supplemented with 5% ACA-containing or 5% control serum and increasing concentrations of insulin (1-10 micrograms/mL) or IGF-1 (10-100 ng/mL). No significant increase in prolactin production was observed after addition of increasing doses of insulin and IGF-I in the presence of ACA-containing serum, while a dose-dependent stimulation was seen with control serum. Time-dependent prolactin accumulation was also reduced when cells were cultured in the former conditions. IGF BP-1 release was not affected by insulin and IGF-I in the presence of both sera. However, lower IGF BP-1 levels and a less pronounced time-dependent accumulation were observed in the presence of ACA-positive serum. Our data suggest that ACAs affect cellular transduction mechanisms regulating critical events, such as decidual cell differentiation. These cellular dysfunctions might be relevant in the induction of some obstetric disorders typical of this syndrome.

Regional Localization of Immunoreactive c-fos and Prolactin in Human Endometrium during the Normal Menstrual Cycle

The objective of the present study was to evaluate the cyclic changes and regional localization of immunoreactive c-fos and prolactin (PRL) in the human endometrium, using immunohistochemistry. Immunoreactive PRL was found in the epithelium of 9.1% of the proliferative specimens and in 55.6% of the secretory specimens (p < 0.05, Fisher’s exact test). In the endometrial stroma, immunoreactive PRL was present in 9.1 and 66.7% of the proliferative and secretory samples, respectively (p < 0.01). Immunoreactive c-fos predominated in the stroma and was identified in 54.5% of the specimens in the proliferative phase, but in only 7.1% of those in the secretory phase (p < 0.05). The progesterone/estradiol ratio was lower in the patients expressing immunoreactive c-fos (median = 13.1 ng/ml) compared to those who did not (median = 84.5 ng/ml, p < 0.05). We conclude that immunoreactive c-fos is found mostly in stromal cells during the proliferative phase of the menstrual cycle, and is sharply reduced during the secretory phase, when the endometrium is under progesterone stimulation – attested by PRL production.

Hormone secretion by cell culture of human GH-PRL secreting pituitary adenomas: effects of bromocriptine.

Dopamine agonists effectively reduce the secretion of prolactin (PRL) in the great majority of prolactinomas and reduce the bulk of the adenomas, as well as have partial therapeutic effect on some patients with acromegaly. The inhibitory effect of bromocriptine (BC), a dopamine agonist, on growth hormone (GH) and PRL secretion of dispersed cells from the pituitary adenomas of 16 cases of acromegaly, which secret GH and PRL simultaneously, were evaluated in vitro. The significant inhibitory effects of BC on PRL secretion were found in 12 cases. It was also found that PRL secretion was strongly inhibited when GH was suppressed; on the contrary, when GH secretion was not suppressed, the production of PRL was not or weakly inhibited. The exact mechanism of the effects is unclear so far. It is necessary to investigate, at molecular level, the etiology of GH-PRL adenomas and its response to therapeutic agents.

Marker genes of decidualization: activation of the decidual prolactin gene.

Decidualization of human endometrial stromal (ES) cells in vitro is induced by cAMP analogues and ligands that elevate cellular cAMP levels in a manner resembling the gonadotrophins, prostaglandin E2 and relaxin (RLX). This differentiation process is marked by the onset of decidual prolactin (PRL) production in the late luteal phase of the cycle. Using transfection assays and a primary ES cell culture system, we have demonstrated that decidual PRL gene transcription is driven by an alternative upstream promoter (dPRL), approximately 6 kb upstream of the pituitary transcription start site. In primary cell cultures, RLX not only acutely but also permanently elevated cellular cAMP levels and induced PRL secretion after 6 days. Northern and Western blot analyses revealed all regulatory subunit isoforms (RIalpha, RIbeta, RIIalpha, RIIbeta) and catalytic subunits Calpha and Cbeta of protein kinase A (PKA) in ES cells. Transcript levels of PKA subunit isoforms are not altered during decidualization, but in decidualized ES cells exposed to elevated cellular cAMP levels by stimulation with RLX for >6 days, RIalpha protein levels were significantly reduced, whereas levels of all other forms remained unchanged. Reducing the availability of R subunits changed the R:C subunit ratio in favour of C and increased kinase activity. In transient transfections of undifferentiated ES cells, the dPRL promoter was activated by 8-Br-cAMP and by C subunit (Cbeta) of PKA. This induction, and the differentiation-dependent activity of the dPRL promoter in transfected decidualized cells, was effectively abolished by the co-expression of protein kinase inhibitor (PKI). A fragment of 332 bp of 5'-flanking region of the dPRL transcription start site was sufficient to mediate full inducibility by cAMP. cAMP activation of the dPRL promoter in ES cells was biphasic as an initial weak induction within 12 hours was followed by a subsequent, much more intense induction after 12 hours. The secondary induction was not seen with a control construct driven by a consensus cAMP response element (CRE) linked to a minimal promoter. The early response of the dPRL promoter depended upon a non-palindromic CRE at position -12 and mutation of this sequence led to omission of the early, but not of the delayed, induction. The major activation of the dPRL promoter depended upon a different region between position -332 and -270 since its deletion significantly reduced inducibility by cAMP. Its action was probably indirect as its kinetics differed from classic CRE-mediated responses, and it was specific to ES cells.

Prolactin (PRL) and its receptor: actions, signal transduction pathways and phenotypes observed in PRL receptor knockout mice.

PRL is an anterior pituitary hormone that, along with GH and PLs, forms a family of hormones that probably resulted from the duplication of an ancestral gene. The PRLR is also a member of a larger family, known as the cytokine class-1 receptor superfamily, which currently has more than 20 different members. PRLRs or binding sites are widely distributed throughout the body. In fact, it is difficult to find a tissue that does not express any PRLR mRNA or protein. In agreement with this wide distribution of receptors is the fact that now more than 300 separate actions of PRL have been reported in various vertebrates, including effects on water and salt balance, growth and development, endocrinology and metabolism, brain and behavior, reproduction, and immune regulation and protection. Clearly, a large proportion of these actions are directly or indirectly associated with the process of reproduction, including many behavioral effects. PRL is also becoming well known as an important regulator of immune function. A number of disease states, including the growth of different forms of cancer as well as various autoimmune diseases, appear to be related to an overproduction of PRL, which may act in an endocrine, autocrine, or paracrine manner, or via an increased sensitivity to the hormone. The first step in the mechanism of action of PRL is the binding to a cell surface receptor. The ligand binds in a two-step process in which site 1 on PRL binds to one receptor molecule, after which a second receptor molecule binds to site 2 on the hormone, forming a homodimer consisting of one molecule of PRL and two molecules of receptor. The PRLR contains no intrinsic tyrosine kinase cytoplasmic domain but associates with a cytoplasmic tyrosine kinase, JAK2. Dimerization of the receptor induces tyrosine phosphorylation and activation of the JAK kinase followed by phosphorylation of the receptor. Other receptor-associated kinases of the Src family have also been shown to be activated by PRL. One major pathway of signaling involves phosphorylation of cytoplasmic State proteins, which themselves dimerize and translocate to nucleus and bind to specific promoter elements on PRL-responsive genes. In addition, the Ras/Raf/MAP kinase pathway is also activated by PRL and may be involved in the proliferative effects of the hormone. Finally, a number of other potential mediators have been identified, including IRS-1, PI-3 kinase, SHP-2, PLC gamma, PKC, and intracellular Ca2+. The technique of gene targeting in mice has been used to develop the first experimental model in which the effect of the complete absence of any lactogen or PRL-mediated effects can be studied. Heterozygous (+/-) females show almost complete failure to lactate after the first, but not subsequent, pregnancies. Homozygous (-/-) females are infertile due to multiple reproductive abnormalities, including ovulation of premeiotic oocytes, reduced fertilization of oocytes, reduced preimplantation oocyte development, lack of embryo implantation, and the absence of pseudopregnancy. Twenty per cent of the homozygous males showed delayed fertility. Other phenotypes, including effects on the immune system and bone, are currently being examined. It is clear that there are multiple actions associated with PRL. It will be important to correlate known effects with local production of PRL to differentiate classic endocrine from autocrine/paracrine effects. The fact that extrapituitary PRL can, under some circumstances, compensate for pituitary PRL raises the interesting possibility that there may be effects of PRL other than those originally observed in hypophysectomized rats. The PRLR knockout mouse model should be an interesting system by which to look for effects activated only by PRL or other lactogenic hormones. On the other hand, many of the effects reported in this review may be shared with other hormones, cytokines, or growth factors and thus will be more difficult to study. (ABSTRACT TRUNCATED)

Hypothalamic-pituitary-mediated immunomodulation: arginine vasopressin is a neuroendocrine immune mediator.

Organisms respond to a variety of environmental agents, such as those that cause inflammation, by mounting a coordinated complex series of adaptive responses involving the immune, nervous and endocrine systems. These adaptations are aimed at restoring the homeostatic balance and the return to the status quo ante. This interaction is facilitated by cytokines, hormones and neurotransmitters, as well as receptors that are endogenous to the neural, immune and endocrine systems. These shared ligands and receptors provide the molecular basis of this cross-talk. Studies of animal models of autoimmune diseases have shown that defects in the neuroendocrine immune communications contribute to the development of chronic inflammatory autoimmune disease. By analogy, similar observations have now been made in patients with inflammatory rheumatic disorders. For instance, patients with rheumatoid arthritis have abnormally low cortisol responses to inflammation, whilst the production of prolactin is excessive and dysregulated. Prolactin is a pro-inflammatory neuropeptide. This paper reviews the evidence to support the viewpoint that the neuropeptide arginine vasopressin, which is also produced by the hypothalamus, should be considered to be another neuroendocrine modulator of immune and inflammatory responses. It is also being hypothesized that the production of arginine vasopressin might be dysregulated and excessive in rheumatoid arthritis, and that this could be another additional neuroendocrine factor contributing to the pathophysiology of the disease.

Paraneoplastic hyperprolactinemia

A 38-year-old female patient, known to have widespread adenocarcinoma of an unknown primary, presented with galactorrhoea and amenorrhoea for a few months. The serum prolactin level was markedly elevated (more than 20-fold the upper normal limit). A pituitary C.T. Scan was normal. Other causes of marked hyperprolactinaemia were excluded. Ectopic Prolactin production is an interesting phenomenon, only four cases having been reported worldwide(1). The diagnosis of more cases of ectopic prolactin production may help to explain some aspects of osteoporosis and hypogonadism in patients with internal malignancy.

Prolactin is an autocrine growth factor for the Jurkat human T-leukemic cell line

Despite convincing evidence of cooperation between IL-2 and endogenous prolactin (PRL) during T cell activation, the individual role of PRL as a T-cell lineage cytokine remains to be defined. We have examined the production and function of PRL on the Jurkat human T-leukemic cell line, which does not constitutively produce IL-2. The majority of Jurkat cells expressed PRL receptor (R) under standard culture conditions, whereas appearance of the α chain of the IL-2-R required PHA–PMA stimulation, as did IL-2 synthesis. Western blotting revealed a predominant band at 23.5 kDa and a weaker band at 25.5 kDa in both Jurkat cell lysates and human (h) pituitary PRL. Metabolic labeling of the cell lysates with 35 S -methionine and immunoprecipitation with an antiserum against hPRL showed that both forms of PRL are actively synthesized by the Jurkat cell line. PRL released in the medium was biologically active in the rat Nb2 lymphoma mitogenic assay. Depletion of medium PRL with two polyclonal anti-hPRL antisera inhibited the growth of Jurkat cells in a dose-dependent manner, as evaluated by cell number and 3 H -TdR uptake. Purified pituitary or recombinant hPRL at a wide range of concentrations had no significant effect on their growth, but reversed the blocking activity of the anti-hPRL antibody. Recombinant IL-2 had no effect on the antibody-induced growth inhibition. Taken as a whole, these results demonstrate that PRL can act as an autocrine T cell growth factor independently of IL-2 and are the first evidence of its involvement in human leukemic growth and possibly in leukemic transformation.

TGF-B and Estrogen Regulate P27(Kip1) and Cyclin D(1) in Normal and Neoplastic Rat Pituitary Cells.

Pituitary hyperplasia and tumor growth are regulated by various hormones and growth factors. Estrogen (E(2)) stimulates pituitary cell proliferation and prolactin (PRL) production. Estrogen also regulates transforming growth factor-B (TGF-B) effects in the pituitary. IGF-B in turn regulates various cell cycle proteins including p15 and p27(Kip1) (p27). To better understand the regulatory role of growth factors and hormones in the cell cycle we analyzed cyclin D(1), cyclin E, and p27 expression in normal and neoplastic rat pituitary cells. An in vitro analysis using cultured normal pituitary cells and GH(3) tumor cells and an in vivo analysis of estrogen-treated normal pituitary and implanted GH(3) cells were performed. Semiquantitative RT-PCR was used to analyze mRNA expression for cyclin D(1) cyclin E, and p27 in cultured pituitary cells and E(2)-treated pituitaries in vivo, Cyclin D(1) and p27 were localized in the nuclei of normal pituitary cells by immunocytochemistry (ICC). Very weak or absent immunostaining for cyclin D(1) and p27 was present in GH(3) cells. Both normal pituitary and GH(3) cells had strong nuclear staining for cyclin E. Normal pituitary had a 20-fold greater amount of cyclin D mRNA and a 3-fold greater amount of p27 mRNA compared to GH cells, whereas GH cells had slightly (1.5-fold) more cyclin E than normal pituitary cells. Treatment in vivo stimulated cell proliferation and decreased cyclin D(1) mRNA levels in normal pituitary. GH(3) tumor cells, implanted subcutaneously in the same animal, showed increased proliferation after E(2) treatment, but there was no change in cyclin B(1) mRNA in GH(3) cells. Cyclin E and p27 mRNA levels did not change significantly in normal pituitary or in GH(3) cells after E(2) treatment in vivo. Treatment of normal pituitary cells with 10(-9)M TGF-B1 for 3 d in vitro led to significant decreases in cyclin B(1) and p27 mRNAs (p < 0.05 ), whereas cyclin E levels were unchanged. These results indicate that cyclin B(1) and p27 mRNAs are present at significantly higher levels in normal pituitary compared to GH(3) cells, and that both E(2) and TGF-B1 can down-regulate cyclin B(1) mRNA levels in normal pituitary cells, suggesting that these factors regulate G1 to S phase transition in pituitary cells. The lower levels of specific cell cycle regulators in GH cells may explain the decreased regulatory control by E(2) in GH(3) tumor cells.