Intrinsic pituitary interleukin-1 beta is induced by bacterial lipopolysaccharide

Human and murine pituitary expression of leukemia inhibitory factor. Novel intrapituitary regulation of adrenocorticotropin hormone synthesis and secretion

Leukemia inhibitory factor (LIF) gene expression was detected in human fetal pituitary tissue by expression of LIF mRNA transcripts, protein immunocytochemistry, and immunoelectron microscopy. Fetal LIF immunoreactivity colocalized with 30% of ACTH-expressing cells, approximately 20% of somatotrophs, and approximately 15% of non-hormone-expressing cells. LIF was also strongly expressed in normal adult pituitary and in four growth hormone-producing and two ACTH-producing adenomas, but not in eight nonfunctioning pituitary tumors. Culture of fetal cells expressing surface LIF-binding sites demonstrated predominance of in vitro ACTH secretion as compared with other pituitary hormones. In AtT-20 murine cells, LIF (ED50 10 pM) stimulated basal proopiomelanocortin mRNA levels by 40% and corticotropin-releasing hormone-induced ACTH secretion (two- to threefold), as did oncostatin M (ED50 30 pM), a related peptide. ACTH responses were not further enhanced by both cytokines together, which is consistent with their shared receptor. Anti-LIF antiserum neutralized basal and LIF-induced ACTH secretion, suggesting autocrine regulation of ACTH by LIF. The results show that human pituitary cells express the LIF gene and LIF-binding sites, predominantly in corticotrophs. Pituitary LIF expression and LIF regulation of proopiomelanocortin and ACTH reflect an intrapituitary role for LIF in modulating early embryonic determination of specific human pituitary cells and as a paracrine or autocrine regulator of mature ACTH.

Peripheral lipopolysaccharide stimulation induces interleukin-1 beta messenger RNA in rat brain microglial cells

The inflammatory cytokine interleukin-1 acts as an endogenous pyrogen in organisms affected by infectious diseases and has been shown to influence the activity of the central nervous system. Using in situ hybridization histochemistry, we have examined the cellular source of interleukin-1 beta in rat brain after peripheral stimulation with the bacterial lipopolysaccharide, a potent inducer of interleukin-1. Whereas no interleukin-1 beta messenger RNA could be detected in brains in unstimulated rats, lipopolysaccharide induced a transient, high and widespread expression of interleukin-1 beta messenger RNA in the entire brain. The highest levels of interleukin-1 beta messenger RNA were observed 6-8 h after stimulation with lipopolysaccharide. Using a combination of non-radioactive in situ hybridization and immunocytochemistry with the microglial-specific antibody OX-42, interleukin-1 beta messenger RNA-positive cells could be identified as microglia. We conclude that brain microglial cells are the major source of interleukin-1 beta messenger RNA after peripheral administration of lipopolysaccharide.

Interleukin-1 beta and tumour necrosis factor-alpha stimulate the mRNA expression of interleukin-1 receptors in mouse anterior pituitary AtT-20 cells

The RT-PCR technique was used to study IL-1 receptor mRNA levels in AtT-20 cells. IL-1 beta increased type I IL-1 receptor mRNA levels within 1 h, with elevated levels remaining after 24 h, whereas it induced a bell-shaped alteration of type II IL-1 receptor mRNA levels, with a peak after 6 h. Tumour necrosis factor-alpha (TNF alpha) similarly up-regulated type II IL-1 receptor mRNA levels, and type I IL-1 receptor mRNAs albeit to a lesser extent than IL-1 beta. Furthermore, IL-1 beta also induced increases in TNF alpha and c-fos mRNAs. The IL-1 receptor antagonist can fully block all the above effects of IL-1 beta. Up-regulation of type II IL-1R mRNA levels in AtT-20 cells could constitute an important way to modulate IL-1 actions, since type II IL-1R is believed to antagonize IL-1 effects.

Characterization of Interleukin-2 (IL-2) receptor expression and action of IL-2 and IL-6 on normal anterior pituitary cell growth

The pituitary gland is known to express cytokines and their receptors. Interleukin-2 (IL-2) and IL-2 receptor (IL-2R) transcripts and protein products in corticotrophic cells have been previously described. IL-2R were also observed in PRL and GH-producing cells. The synthesis of IL-1 and IL-6 and their receptors by pituitary cells has also been reported. We recently demonstrated that the cytokines in addition to their regulatory effects on anterior pituitary hormone secretion are involved in the autocrine or paracrine regulation of pituitary growth. In the present study we show in normal rat anterior pituitary cells: (a) expression of IL-2Rα chain mRNA, (b) the co-localization of IL-2Rα chain with TSH, FSH and LH-producing cells, (c) the percentage of co-localization of IL-2R with all types of anterior pituitary hormone producing cells: PRL> > > ACTH> > GH> TSH = FSH = LH. (d) that [(3)H]-thymidine is incorporated into the nucleus of all types of hormoneproducing cells without incorporation into other cell types, following IL-2 and IL-6 stimulation. Our results suggest that IL-2 acts on all types of anterior pituitary hormone-producing cells and, through specific functional receptors on the same or other cells, constitutes, as well as IL-6, an inter or intra-cellular factor involved in the coordinate regulation not only of hormone secretion but also of the proliferation of anterior pituitary hormone-producing cells.

Development and heterogeneity of prolactin cells

Prolactin (PRL) is synthesized in pituitary cells called mammotrophs (PRL cells). Ample evidence demonstrates that the PRL cell population consists of structurally and functionally heterogeneous PRL cells. Multiple variants of PRL molecules are found in various species. Prolactin cells may be divided into various subtypes in the rat and mouse. Secretory activities differ among the PRL cell population. These heterogeneities may reflect various phases of the maturation process of PRL cells, or the integrated outcome of various functional differences in PRL cells. To clarify the significance of heterogeneities among PRL cells, we present updated reports on the differentiation, proliferation, and development of PRL cells, and discuss factors responsible for the functional differences in PRL cell population. The age-related alteration in PRL secretion in the rat is summarized, because it is one of the most important aspects of the developmental changes in PRL cells. A mammosomatotroph, which secretes growth hormone and PRL, is found in various species. Prolactin cells and somatotrophs are derived from the same lineage. The possible relationship among PRL cells, somatotrophs, and mammosomatotrophs is discussed.

IL-1 is expressed in human adrenal gland in vivo. Possible role in a local immune-adrenal axis

IL-1 is an important mediator in the dialogue between the immune system and the hypothalamo-pituitary-adrenal axis. A direct influence of IL-1 upon adrenal steroidogenesis has been demonstrated in experimental animals. We therefore designed a study to see if IL-1 is expressed within the normal human adrenal gland. The combination of in situ hybridization and specific immunostaining to IL-1 beta was eminently suited to demonstrate both mRNA and protein production. The specific immunostaining of the different cells combined with in situ hybridization (IL-1) allowed us to identify the exact cellular source of IL-1. IL-1 mRNA occurred in the zona reticularis in 17 alpha-hydroxylase positive steroid cells surrounding the adrenomedullary cells. Some CD68+ macrophages in this zona showed a positive signal. A weak signal was seen to IL-1 mRNA in few chromaffin cells, while IL-1-like immunoreactivity was more frequent. We conclude that in the normal situation in man IL-1 is mainly expressed in specialized cortical cells. The occurrence of the major glucocorticoid inducing factor in the normal human adrenal gland itself provides evidence for an autocrine or paracrine reaction under physiological conditions.

Pituitary and ovarian interleukin-1 alpha content changes according to estrous cycle and acute stress exposure

A complex interaction between the immune and neuroendocrine systems has been established. In particular, cytokines are known to be one of the mediators of the stress response, and modulate hormone secretion by acting in the brain, pituitary and gonads. The aim of the present study is to investigate whether pituitary and ovarian interleukin-1 alpha (IL-1 alpha) content changes according to the estrous cycle. In addition, the possible pituitary and ovarian IL-1 alpha changes in rats exposed to acute (5 min) or chronic intermittent (twice a day for 4 days) cold swimming stress were studied. The IL-1 alpha content of ovarian and pituitary homogenates was measured by a sensitive and specific radioimmunoassay. Immunoreactive IL-1 alpha (irIL-1 alpha) was detectable only in ovaries collected in rats at proestrus and estrus while not in those collected at diestrus I and II. The highest values were found at proestrus. No significant changes were found in ovarian irIL-1 alpha content in rats exposed to acute or chronic intermittent stress in comparison to control rats. In the pituitary, no difference in IL-1 alpha content was found throughout the estrous cycle. Acute stress induced a significant increase in pituitary irIL-1 alpha content only at proestrus (p < 0.01), however, no significant differences were found in comparison to control rats after chronic intermittent stress. The proestrus-related changes of ovarian IL-1 alpha may constitute a hormone-dependent signal within the ovary that is involved in the ovulatory process.(ABSTRACT TRUNCATED AT 250 WORDS)

Hierarchical cortical control of neuroimmunomodulatory pathways

The central nervous system and the immune system are both stimulus response systems with sophisticated memories mediating defence and adaptation to external and internal threats. There is mounting evidence that these two systems share their information in a bidirectional flow of cytokines, steroids, and neuropeptides. This review examines the influence of higher cognitive centres on immunity and highlights the central role played by the hypothalamus in enabling these two systems to function as an integrated unit to maintain homeostasis. The search for novel compounds that are capable of enhancing immunity by regulating these brain-immune feedback loops offers one of the most exciting areas for future neurobiological research.

Regulation of interleukin-1 receptors and hypothalamic-pituitary-adrenal axis by lipopolysaccharide treatment in the mouse

We measured iodine-125-labeled recombinant human interleukin-1 alpha (125I-IL-1 alpha) binding in the hippocampus, pituitary, liver, spleen and testis, and plasma adrenocorticotropic hormone (ACTH) and corticosterone levels after i.p. injection of various dose and treatment regimens of the bacterial endotoxin, lipopolysaccharide (LPS). Plasma ACTH and corticosterone levels were significantly increased at 2 h after acute administration of LPS (60 or 300 micrograms/mouse). 125I-IL-1 alpha binding in all peripheral tissues examined was significantly and comparably decreased at 2 h after a single injection of 30 micrograms or 300 micrograms LPS/mouse. On the other hand, 125I-IL-1 alpha binding in hippocampus was significantly decreased only after high dose administration of LPS (300 micrograms/mouse). In order to evaluate if activation of IL-1 in brain resulting in the observed decrease in 125I-IL-1 alpha binding may require more sustained exposure to endotoxin, we compared the effects of a single injection (60 micrograms/mouse) and two injections of LPS (30 micrograms/mouse each at 0 and 12 h). A single injection of LPS (60 micrograms/mouse) decreased 125I-IL-1 alpha binding in the testis but not in the hippocampus, while two LPS injections (30 micrograms/mouse each at 0 and 12 h) caused dramatic reductions in 125I-IL-1 alpha binding in both the hippocampus and testis.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships between basal hypothalamic-pituitary-thyroid-axis activity and plasma haptoglobin levels in depression

The present study was carried out in investigate the relationship between basal hypothalamic-pituitary-thyroid (HPT)-axis function and the acute phase (AP) response in depression. Toward this end, the authors measured serum concentrations of basal thyroid-stimulating-hormone (TSH), free thyroxine (FT4) and free triiodothyronine (FT3), and plasma levels of an AP protein, i.e. haptoglobin (Hp) in 38 depressed in-patients and in 11 normal controls. In depression, basal TSH was significantly and negatively related to Hp values, whereas in normal controls a trend toward a positive correlation between both factors was found. Depressed patients with increased Hp levels (> or = 250 mg/dl) showed significantly lower basal TSH levels than patients with normal Hp levels. No significant correlations were found between Hp plasma levels and either FT4 or FT3 serum concentrations. The results support the hypothesis that lower TSH secretion in major depression may be related to the AP response in that illness, and may constitute an expression of a coordinated neuroendocrine-immune response to nonthyroidal illness.

Cytokines and the brain corticosteroid receptor balance: relevance to pathophysiology of neuroendocrine-immune communication

Interleukin-1 (IL-1) and interleukin-6 (IL-6), and their cognate receptors, are expressed in hippocampal neurons, which are targets for corticosteroid hormones. Corticosteroids bind to intracellular receptors, that is, mineralocorticoid (MRs) and glucocorticoid receptors (GRs). MRs respond to low concentrations of the steroid, while higher concentrations are needed for additional activation of GRs. MR occupation appears relevant in hippocampal neurons for stability of ongoing transmission, for basal activity and sensitivity of the stress response system, and for behavioural reactivity and response selection. Additional transient GR activation suppresses excitability, facilitates recovery from the stress response, and promotes information storage. Thus, the balance of MR- and GR-mediated effects appears critical for the long-term control exerted by corticosteroids over specific aspects of neuronal activity, stress responsiveness, and behavioural adaptation. Administration of IL-1 produces a long-lasting increase in corticosterone. IL-1 also influences MR function in hippocampus and causes a shift in the MR/GR balance, which may underlie prolonged activation of the HPA axis during an immune response.

Effects of lipopolysaccharide on hypothalamic-pituitary-adrenal axis in vitro

The possible involvement of lipopolysaccharide (LPS) and interleukin-1 beta (IL-1 beta) and their eventual interplay in CRH and ACTH release from cultured hypothalamic and pituitary cells respectively, have been studied. IL-1 beta was able to activate the hypothalamo-pituitary-adrenal axis at both hypothalamic and pituitary sites; LPS showed no direct action at hypothalamic level but it was able to inhibit basal and IL-1 beta-induced ACTH release: this could be responsible for a blunting of the adrenal cortex response that normally occurs in septic shock syndrome.

Bioactive peptides in anterior pituitary cells

The anterior pituitary (AP) has been shown to contain a wide variety of bioactive peptides: brain-gut peptides, growth factors, hypothalamic releasing factors, posterior lobe peptides, opioids, and various other peptides. The localization of most of these peptides was first established by immunocytochemical methods and some of the peptides were localized in identified cell types. Although intracellular localization of a peptide may be the consequence of internalization from the plasma compartment, there is evidence for local synthesis of most of these peptides in the AP based on the identification of their messenger-RNA (mRNA). In several cases the release of the peptide from the AP cell has been shown and regulation of synthesis, storage and release have also been described. Because the amount of most of the AP peptides is very low (except for POMC peptides and galanin), endocrine functions are not expected. There is more evidence for paracrine, autocrine, or intracrine roles in growth, differentiation, and regeneration, or in the control of hormone release. To demonstrate such functions, in vitro AP experiments have been designed to avoid the interference of hypothalamic or peripheral hormones. The strategy is first to show a direct effect of the peptide after adding it to the in vitro system and, secondly, to explore if the endogenous AP peptide has a similar action by using blockers of peptide receptors or antisera immunoneutralizing the peptide.

Activation of the hypothalamus-pituitary-adrenal axis by bacterial endotoxins: routes and intermediate signals

Peripheral administration of endotoxin induces brain-mediated responses, including activation of the hypothalamus-pituitary-adrenal (HPA) axis and changes in thermoregulation. This paper reviews the mechanisms by which endotoxin affects these responses. The effects on thermoregulation are complex and include macrophage-dependent hyperthermic and hypothermic responses. Low doses of endotoxin, given IP, activate peripheral macrophages to produce interleukin (IL)-1 beta, which enters the circulation and acts as a hormonal signal. IL-1 may pass fenestrated endothelium in the median eminence to stimulate corticotropin-releasing hormone (CRH) secretion from the CRH nerve-terminals. In addition, IL-1 may activate brain endothelial cells to produce IL-1, IL-6, prostaglandins, etc., and secrete these substances into the brain. By paracrine actions, these substances may affect neurons (e.g., CRH neurons) or act on microglial cells, which show IL-1-induced IL-1 production and therefore amplify and prolong the intracerebral IL-1 signal. In contrast, high doses of endotoxin given i.v. may directly stimulate endothelial cells to produce IL-1, IL-6, and prostaglandin-E2 (PGE2) and thereby activate the HPA axis in a macrophage-independent manner.

Cytokines and hypothalamic-pituitary function

Several cytokines are now known to affect the release of anterior pituitary hormones by an action on the hypothalamus and/or the pituitary gland. The major cytokines involved are IL-1, IL-2, IL-6, TNF-alpha and interferon-tau. Their predominant effects are to stimulate the hypothalamic-pituitary-adrenal axis and to suppress the hypothalamic-pituitary-thyroid and gonadal axes, and growth hormone release. The relative importance of systemically and locally produced cytokines in achieving these responses and their precise sites of action have not been fully established. There are indeed conflicting reports on the individual effects of each cytokine which need to be clarified. There is now cumulating evidence that there are important interactions between the immune and neuroendocrine systems which may explain in part, some of the effects on growth, thyroid, adrenal and reproductive functions which occur in acute and chronic disease. This article reviews the current knowledge of the effects of some cytokines on hypothalamic-pituitary function.

MIF is a pituitary-derived cytokine that potentiates lethal endotoxaemia

Cytokines are critical in the often fatal cascade of events that cause septic shock. One regulatory system that is likely to be important in controlling inflammatory responses is the neuroendocrine axis. The pituitary, for example, is ideally situated to integrate central and peripheral stimuli, and initiates the increase in systemic glucocorticoids that accompanies host stress responses. To assess further the contribution of the pituitary to systemic inflammatory processes, we examined the secretory profile of cultured pituitary cells and whole pituitaries in vivo after stimulation with bacterial lipopolysaccharide (LPS). Here we identify macrophage migration inhibitory factor (MIF) as a major secreted protein release by anterior pituitary cells in response to LPS stimulation. Serum analysis of control, hypophysectomized and T-cell-deficient (nude) mice suggests that pituitary-derived MIF contributes to circulating MIF present in the post-acute phase of endotoxaemia. Recombinant murine MIF greatly enhances lethality when co-injected with LPS and anti-MIF antibody confers full protection against lethal endotoxaemia. We conclude that MIF plays a central role in the toxic response to endotoxaemia and possibly septic shock.

Induction of tumor necrosis factor-alpha mRNA in the brain after peripheral endotoxin treatment: comparison with interleukin-1 family and interleukin-6

The constitutive expression of tumor necrosis factor-alpha (TNF alpha) mRNA and its induction (60 min later) by peripheral injection of Escherichia coli lipopolysaccharide (2 mg/kg i.p.) was demonstrated by polymerase chain reaction (PCR), in the pituitary and hypothalamus but not in the striatum or hippocampus of the rat. The pattern of TNF alpha mRNA induction is different from that observed for mRNAs of IL-1 alpha and IL-1 beta, IL-1ra and IL-6 respectively. This demonstration of the induction of TNF alpha in the brain may contribute to our understanding of the central effects of TNF alpha in fever and anorexia.

Neuroendocrine regulation of thyrotropin-releasing hormone (TRH) in the tuberoinfundibular system

[...] It is now required to list each part needed for mucous excretion. They are two ducts in the brain substance, then a thin portion of membrane shaped as the infundibulum, then the gland that receives the tip of this infundibulum and the ducts that drive the mucus (pituita) from this gland to the palate and nares. [...] and I said that one (duct) [...] from the middle of the common cavity (third ventricle) descends [...] into the brain substance, and the end of this duct is [...] the sinus of the gland where the brain mucus is collected [...].

Neuroimmunological regulation of α-MSH release in tilapia (Oreochromis mossambicus)

This study describes the effects of IL-1 (interleukin 1) and LPS (bacterial endotoxin lipopolysaccharide) on the release of α-MSH (alpha melanocyte stimulating hormone) from the neurointermediate lobe (NIL) of the teleost Oreochromis mossambicus (tilapia). In vivo treatment of tilapia with IL-1 for 8 days led to a 49% inhibition of basal α-MSH release, measured by means of an in vitro micro-superfusion technique. The treatment did not affect the sensitivity of the tissue to TRH. In vitro, the release of α-MSH was inhibited by LPS in a dose dependent manner. In addition to its effects on the unstimulated release of the hormone, LPS also blunted the response to a TRH stimulation. Together with recent results obtained by others demonstrating the effects of (neuro-)peptides on immune parameters and the presence of cytokines in fish, the present data establish the bidirectional character of the communication between the immune and the (neuro-)endocrine systems in teleosts.

Interleukin-1 beta measured by radioimmunoassay in the rat spleen and thymus is increased during chronic inflammatory stress

We have developed an extraction method and radioimmunoassay for the measurement of interleukin-1 beta (IL-1 beta) in rat tissues, using an antibody specific for IL-1 beta, IL-1 beta was detected in the spleen and thymus of control rats. Adrenalectomy (ADX) had no effect upon control levels of IL-1 beta. In animals with adjuvant-induced arthritis, IL-1 beta content in the spleen and thymus increased after 14 days. These increases in tissue IL-1 beta contents were not evident in ADX arthritic animals. We conclude that IL-1 beta synthesis is stimulated in tissues of the immune system following the development of adjuvant-induced arthritis. Failure to observe elevated levels of tissue IL-1 beta in ADX arthritic rats may be evidence for tissue depletion due to increased IL-1 beta release in the absence of circulating corticosteroids.

Molecular identification of two types of interleukin-1 receptors in the murine pituitary gland

The present study was carried out to characterize interleukin-1 (IL-1) receptors on murine pituitary cells. Receptor autoradiography confirmed the existence of binding sites for IL-1 alpha in the murine adenohypophysis, but not in the neural or intermediate lobes. Specific binding of IL-1 to isolated pituitary membranes revealed a Kd of 0.9 nM with a Bmax of 37 fmol/mg protein. To examine the possibility that the adenohypophysis synthesizes a receptor for IL-1, immunocytochemistry experiments with a specific monoclonal antibody against the type I receptor revealed the existence of this protein in only the adenohypophysis. Identity of the type I IL-1 receptor was similar to that found on T cells as determined by: 1) amplification of the predicted 619 bp fragment spanning the cytoplasmic, transmembrane and extracellular domains from RNA of pituitary and T cell origin, as well as clonal AtT-20 pituitary cells, and 2) restriction fragment analysis and sequencing of the amplified cDNAs. The pituitary gland and AtT-20 cells also expressed transcripts for the newly identified type II receptor for IL-1 as assessed by amplification of a specific 325 bp fragment, restriction fragment analysis and nucleotide sequencing, and these transcripts were similar to those found on B lymphocytes. These data identify two different forms of the IL-1 receptor in both normal and transformed pituitary cells and establish that these receptors are similar at the molecular level to those first identified on T and B lymphocytes.

Corticotropin-releasing hormone modulates cytokines release in cultured human peripheral blood mononuclear cells

Immune and neuroendocrine systems interact at various levels. In particular, either cytokines activate the hypothalamus-pituitary-adrenal axis (HPA) or corticotropin-releasing hormone (CRH) induces the release of beta-endorphin from peripheral human mononuclear cells. The aim of the present study was to investigate whether CRH may affect cytokine production and activity in human peripheral blood mononuclear cells (PBMC). Primary cultures of human PBMC and monocytes were used. They were incubated in presence of different doses of synthetic human CRH. Media were collected and interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) levels were measured by ELISA, while interferon-gamma (IFN-gamma) levels were measured by bioassay. In addition, phytohemoagglutinin-induced lymphocyte proliferation was evaluated by testing [3H]thymidine incorporation in the presence of various doses of CRH. CRH significantly increased IL-6 release from PBMC (p < 0.01). The addition of CRH to PBMC significantly decreased IFN-gamma levels, in a dose dependent manner (p < 0.01). No significant effect of CRH was observed on lymphocyte proliferation or IL-1 beta production. The present results suggest a role for CRH as a paracrine mediator for human immune cells, increasing the evidence of a clear correlation between immune and neuroendocrine system.

Interleukin-2 and interleukin-2 receptor expression in human corticotrophic adenoma and murine pituitary cell cultures

The production of IL-1 and IL-6 by pituitary cells has recently been demonstrated. In this study we investigated the expression of IL-2 and its receptor (IL-2R) by pituitary cells of different species. In Northern blots, a single hybridizing band of 1 kb, identical to that in normal stimulated lymphocytes, was obtained with specific IL-2 probes. In the mouse AT-20 pituitary tumor cell line, IL-2 mRNA expression was detected after stimulation with corticotropin-releasing hormone or phorbol myristate acetate. In human corticotrophic adenoma cells, basal IL-2 mRNA expression as well as IL-2 secretion were further stimulated by phorbol myristate acetate. Both adenoma and AtT-20 cells showed detectable amounts of IL-2R mRNA and by immunofluorescence, IL-2R membrane expression. In addition, dual immunofluorescence studies in rat anterior pituitary cells demonstrated colocalization of IL-2R with ACTH-positive cells and other cell types expressing the receptor. In addition to the action of lymphocyte-produced IL-2, this cytokine may have a paracrine or autocrine regulatory role within the pituitary. It remains to be established whether IL-2 production occurs in the normal pituitary or is intrinsic to the process of tumor development of these cells. IL-2 may be involved in the growth control of pituitary cells.

Interleukin-6 and corticotrophin-releasing hormone mRNA are modulated during differentiation of human neuroblastoma cells

Two cell clones [BE(2)-C and BE(2)-M17] derived from the human neuroblastoma cell line SK-N-BE(2) express corticotrophin-releasing hormone as well as interleukin-6 mRNA. Both genes are overexpressed, although with a different time course, following exposure to 5 microM retinoic acid, in parallel to the induction of neuroblastic differentiation. On the contrary, we are unable to detect interleukin-1 beta mRNA in these cell lines. Both cytokines are known to increase hypothalamic CRH mRNA. The production of cytokines and neuropeptides by neuroblastoma cells indicate a complex dialogue between tumour cells and anti-tumour immunity.

Pharmacokinetics, safety and immunomodulatory effects of human recombinant interleukin-1 receptor antagonist in healthy humans

A phase I study of human recombinant interleukin-1 receptor antagonist (IL-1ra) was conducted in healthy males between the ages of 18 and 30. Twenty-five volunteers received a single, 3 h continuous intravenous infusion of doses ranging between 1 mg/kg and 10 mg/kg IL-1ra. At 3 h into the infusion, plasma IL-1ra levels were 3.1 micrograms/ml and 29 micrograms/ml for the 1 mg/kg and 10 mg/kg doses, respectively. Post-infusion plasma IL-1ra levels declined rapidly, exhibiting an initial half-life of 21 min and a terminal half-life of 108 min. Clinical, hematological, biochemical, endocrinological and immunomodulatory effects were monitored over 72 h and compared to those of four subjects receiving a 3 h infusion of saline. There were no clinically significant differences between the drug and saline groups in symptoms, physical examinations, complete blood counts, mononuclear cell phenotypes, blood chemistry profiles, serum iron and serum cortisol levels. Peripheral blood mononuclear cells (PBMC) obtained after completion of the IL-1ra infusion synthesized significantly less interleukin 6 ex vivo than PBMC from saline-injected controls. These data suggest that transient blockade of interleukin 1 receptors is safe and does not significantly affect homeostasis.

Response of pituitary and spleen pro-opiomelanocortin mRNA, and spleen and thymus interleukin-1 beta mRNA to adjuvant arthritis in the rat

During development of adjuvant-induced arthritis (AA) in the rat, pituitary pro-opiomelanocortin (POMC) mRNA expression was increased. Pituitary POMC mRNA was much higher following adrenalectomy and AA. Spleen POMC mRNA also increased with a similar time kinetics, although the levels in the spleen were much lower than those in the pituitary. In control animals, spleen interleukin-1 beta (IL-1 beta mRNA) was undetectable, whereas AA led to the accumulation of IL-1 beta mRNA and the highest levels were seen in the adrenalectomised AA group. Thymic IL-1 beta expression was also increased in AA animals. These results suggest that AA leads to the activation of both the neuroendocrine and the immune systems and the interaction between these systems may play a role in this disease state.

Growth factors and the anterior pituitary

Normal growth and secretion in the pituitary gland are dependent upon the co-ordinated action of a large number of extracellular growth factors, neuropeptides and peripheral hormones acting on their respective cellular receptors and via complex intracellular signalling pathways. The pituitary and hypothalamus are exposed to a large number of growth factors, several of which have well-documented effects on secretory function and may act as physiological modulators of pituitary hormone synthesis and release. IGF-I, for example, almost certainly acts as a feedback regulator of GH secretion. Despite well-documented mitogenic effects in other tissues, little is known about the role of these growth factors in normal pituitary cell turnover, compensatory hyperplasia or adenoma formation. There is now good evidence, however, that at least some of the hypothalamic releasing peptides are mitogenic for their respective pituitary cell subpopulations. The aetiology of pituitary tumours remains poorly understood but some appear to develop as a result of somatic mutation. Such mutations could enhance growth by causing altered expression of growth factors or their receptors, or constitutive activation of proteins involved in the intracellular mitogenic signal. Abnormalities have been documented at each of these levels in human pituitary tumours. The identification of an activating point mutation in the alpha subunit of Gs, the stimulatory regulatory peptide of adenylyl cyclase, in a proportion of somatotroph adenomas represents a major advance in our understanding of pituitary tumour pathogenesis. This and other findings may ultimately lead to new therapeutic approaches to the management of pituitary disease.

Abnormal production of interleukin-1 by microglia from trisomy 16 mice

The production of interleukin-1 (IL-1) was examined in cultured CNS microglia obtained from trisomy 16 (Ts16) fetal mouse brain, a model system for studies relevant to Down syndrome (DS). When compared to microglia from their normal littermates, Ts16 microglia produced significantly higher levels of IL-1 activity both before and following stimulation with lipopolysaccharide (LPS). IL-1 release was stimulated by alpha/beta interferon (IFN) in the normal but not Ts16 microglial cultures. The overall level of IL-1 production in normal littermates, however, was still less than that seen in Ts16. Thus, microglia from Ts16 mice may function in an inappropriate manner and, if this abnormality occurs in vivo, may have wide ranging effects on a developing nervous system.

Host responses and neuroendocrinological changes in pyrexia in childhood

Host responses and neuroendocrinological changes during pyrexia in childhood were studied. Serum IL-1 beta could not be detected in most subjects either during pyrexia or in afebrile periods. IL-1 beta was detected in two cases, increasing during pyrexia and decreasing during the afebrile period. Plasma ACTH increased during pyrexia, but this was not statistically significant. Serum cortisol during pyrexia increased to around twice the normal value, and many subjects showed a high level of arginine vasopressin. The subjects, who did not develop dehydration, showed a decrease in serum osmolality and serum sodium during the pyrexia period. Serum Fe and Zn decreased, but serum Cu increased during both periods. It could not be confirmed that IL-1 activates the hypothalamic-pituitary-adrenal axis during pyrexia. It is concluded that AVP is important in the control of fever and the maintenance of homeostasis of body fluid during pyrexia.

Effects of interleukin-1 beta on secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) by cultured rat anterior pituitary cells

Interleukin-1 beta (IL-1 beta) at doses of 0.15 and 1.5 nM significantly inhibited FSH secretion and stimulated LH secretion by cultured rat pituitary cells after 24-72 hr incubation whereas 15 pM of IL-1 beta was not effective. Treatment with IL-1 beta for 12-48 hr did not affect intracellular content of FSH. However, treatment with 0.15 and 1.5 nM of IL-1 beta for 72 hr significantly suppressed intracellular content of FSH whereas various doses of IL-1 beta incubated with the cells for 12-72 hr showed no effect on the intracellular content of LH. Pretreatment with IL-1 beta for 48 hr inhibited both GnRH-mediated LH and FSH secretions by the pituitary. The secretion of FSH and LH mediated by an activator of protein kinase C, phorbol 12-myristate 13-acetate, was also significantly suppressed by pretreatment with IL-1 beta for 48 hr. These results suggest that (a) IL-1 beta has opposite effects on the secretion of LH and FSH and (b) pretreatment with IL-1 beta suppresses GnRH-mediated stimulation of LH and FSH by the pituitary and this suppressive effect of IL-1 beta may involve the suppression of a protein kinase C-dependent mechanism.

The neurophysiological regulation of growth hormone secretion

With the advent of genetic engineering, the importance of GH in the regulation of growth and metabolism in domestic species has been clearly demonstrated. Ample evidence of an integral role for GH in the processes of growth and lactation exists in dairy cattle (1,2), sheep (3), beef cattle (4) and swine (5). For example, circulating GH levels are high during the period of rapid growth in several species including cattle (6), swine (7) and poultry (8). Endogenous GH secretion is primarily controlled by the central nervous system (CNS) via two specific hypothalamic neurohormones, growth hormone-releasing factor (GRF) and somatostatin (SRIF), an inhibitor of GH release. The secretion of GRF and SRIF is governed by a host of neuropeptides and neurotransmitters which provide a functional link between higher CNS centers and hypophysiotropic neurons. This review will focus on the CNS regulation of GH secretion and circulating factors which feedback to either stimulate or inhibit its release.