Production of immunoreactive growth hormone by mononuclear leukocytes

The roles of prolactin, growth hormone, insulin-like growth factor-I, and thyroid hormones in lymphocyte development and function: insights from genetic models of hormone and hormone receptor deficiency

An extensive literature suggesting that PRL, GH, IGF-I, and thyroid hormones play an important role in immunity has evolved. Because the use of one or more of these hormones as immunostimulants in humans is being considered, it is of critical importance to resolve their precise role in immunity. This review addresses new experimental evidence from analysis of lymphocyte development and function in mice with genetic defects in expression of these hormones or their receptors that calls into question the presumed role played by some of these hormones and reveals unexpected effects of others. These recent findings from the mutant mouse models are integrated and placed in context of the wider literature on endocrine-immune system interactions. The hypothesis that will be developed is that, with the exception of a role for thyroid hormones in B cell development, PRL, GH, and IGF-I are not obligate immunoregulators. Instead, they apparently act as anabolic and stress-modulating hormones in most cells, including those of the immune system.

Effects of growth hormone-releasing hormone-related peptide on stem cell factor expression in cultured rat Sertoli cells

The growth hormone-releasing hormone (GHRH) gene produces a precursor molecule that contains GHRH and a carboxyl-terminal peptide that we have named GHRH-related peptide (GHRH-RP). This peptide, like GHRH, stimulates the expression of stem cell factor (SCF), an important reproductive and hematopoietic cytokine, in vitro and in vivo. In the present study, using primary cultures of rat Sertoli cells, we compared the time course of action and the level of SCF stimulation seen following treatment with GHRH-RP and GHRH. Additionally, we investigated the activity of a truncated peptide, p75-92NH2, whose sequence is contained within GHRH-RP. All three of these peptides were shown to stimulate the steady-state levels of SCF mRNA to a comparable degree. However, the time course of action for GHRH-RP differed markedly from that of GHRH. GHRH-RP and p75-92NH2, similar to GHRH, induce SCF expression, at least in part, via the activation of the protein kinase A/cyclic adenosine monophosphate intracellular signaling pathway.

Identification of SP3 as a negative regulatory transcription factor in the monocyte expression of growth hormone

A number of studies from different laboratories clearly show that cells of the immune system produce a GH molecule indistinguishable from that produced in the pituitary. A more recent finding from our studies suggests that monocytes use the same first exon and promoter sequence for the expression of lymphocyte GH as that reported for the expression of pituitary GH. In this report we have extended these results by determining that two members of the SP family of transcription factors, SP1 and SP3, bind to the region at -138/-133 bp containing a GGGAGG motif. Confirmation that this region of the monocyte GH promoter-bound SP1 and SP3 was accomplished using electrophoretic mobility shift assays with SP1 consensus and mutant probes as well as specific antibodies to SP1 and SP3. Selective mutation of the SP1/SP3 site increased basal transcription by 73%, indicating that this site is important in transcriptional inhibition. Overexpression of SP1 had no demonstrable effect on the GH promoter, whereas overexpression of SP3 caused inhibition of expression in P-388 monocyte cells. Cotransfection of P-388 cells with overexpression vectors for both SP1 and SP3 transcription factors also resulted in inhibition of basal expression. Transfection experiments in Drosophila SL-2 cells overexpressing SP1 and/or SP3 suggest that both factors repress the basal expression of GH promoter luciferase constructs and that the effect together was additive. Taken together, the results demonstrate that basal expression of monocyte GH may be negatively regulated by SP3.

Effect of insulin-like growth factor I on HIV type 1 long terminal repeat-driven chloramphenicol acetyltransferase expression

In this study, we have investigated the ability of insulin-like growth factor I (IGF-I) to inhibit HIV long terminal repeat (LTR)-driven gene expression. Using COS 7 cells cotransfected with tat and an HIV LTR linked to a chloramphenicol acetyltransferase (CAT) reporter, we observed that physiological levels of IGF-I (10(-9) M) significantly inhibited CAT expression in a concentration- and time-dependent manner. IGF-I did not inhibit CAT expression in COS 7 cells transfected with pSVCAT, and did not affect CAT expression in the absence of cotransfection with tat. Transfection of HIV-1 proviral DNA into COS 7 cells +/- IGF-I resulted in a significant decrease (p < 0.05) in infectious virion production. Both IGF-I and Ro24-7429 inhibited LTR-driven CAT expression, while TNF-alpha-enhanced CAT expression was not affected by IGF-I. On the other hand, a plasmid encoding parathyroid hormone-related peptide exhibited dramatic additivity of inhibition of CAT expression in COS 7 cells. Finally, we show that in Jurkat or U937 cells cotransfected with HIVLTRCAT/tat, IGF-I significantly inhibited CAT expression. Further, interleukin 4 showed in U937 cells inhibition of CAT expression that was not additive to IGF-I induced inhibition. Our data demonstrate that IGF-I can specifically inhibit HIVLTRCAT expression. This inhibition may occur at the level of the tat/TAR interaction. Finally, this IGF-I effect is seen in target cell lines and similar paths of inhibition may be involved in the various cell types employed.

Growth hormone in immune reconstitution

Immune cell death or dysfunction is induced by HIV infection and results in an immunocompromised state. Newer treatments are able to control viral replication to prevent massive cytoreduction. Attention must now focus on therapies that will rapidly reconstitute the immune system to provide defense against future HIV attacks as well as opportunistic infections. In addition to increasing the rate of differentiation of myeloid and lymphoid precursors from marrow stem cells, ideal therapies should improve thymic function as well. Growth hormone (GH), a member of the hematopoietic cytokine superfamily and its receptors, is expressed in multiple sites within the immune system. GH has been shown to have a stimulatory effect on the function of thymic cells, as well as other immune cell types. In this paper, we consider the use of GH to reconstitute the immune system following cytoreduction due to HIV infection.

Regulation of the hypothalamic-pituitary-adrenal axis by cytokines: actions and mechanisms of action

Glucocorticoids are hormone products of the adrenal gland, which have long been recognized to have a profound impact on immunologic processes. The communication between immune and neuroendocrine systems is, however, bidirectional. The endocrine and immune systems share a common "chemical language," with both systems possessing ligands and receptors of "classical" hormones and immunoregulatory mediators. Studies in the early to mid 1980s demonstrated that monocyte-derived or recombinant interleukin-1 (IL-1) causes secretion of hormones of the hypothalamic-pituitary-adrenal (HPA) axis, establishing that immunoregulators, known as cytokines, play a pivotal role in this bidirectional communication between the immune and neuroendocrine systems. The subsequent 10-15 years have witnessed demonstrations that numerous members of several cytokine families increase the secretory activity of the HPA axis. Because this neuroendocrine action of cytokines is mediated primarily at the level of the central nervous system, studies investigating the mechanisms of HPA activation produced by cytokines take on a more broad significance, with findings relevant to the more fundamental question of how cytokines signal the brain. This article reviews published findings that have documented which cytokines have been shown to influence hormone secretion from the HPA axis, determined under what physiological/pathophysiological circumstances endogenous cytokines regulate HPA axis activity, established the possible sites of cytokine action on HPA axis hormone secretion, and identified the potential neuroanatomic and pharmacological mechanisms by which cytokines signal the neuroendocrine hypothalamus.

Regulation of VIP production and secretion by murine lymphocytes

Vasoactive intestinal peptide (VIP) is a neuropeptide present in the lymphoid microenvironment with a multiplicity of actions. Two sources for VIP have been described in the immune system, the terminals present in central and peripheral lymphoid organs and the immune cells. Although VIP is synthesized by lymphocytes, there is no evidence demonstrating that VIP is released, and which stimuli are able to induce VIP production and secretion. In this study, we demonstrated for the first time, that agents that mediate important immune functions, such as proliferation and antigenic stimulation (Con A, LPS, and anti-TCR antibody), inflammation (LPS, TNFalpha, IL-6 and IL-1beta) or apoptosis (dexamethasone) induce the production and release of VIP to the lymphoid microenvironment. We conclude that VIP is produced and secreted by lymphocytes and propose that during an immune response, the timely release of VIP within the lymphoid organs and peritoneum should influence the differentiation and/or downregulation of the ongoing response.

Effects of insulin-like growth factor 1 on neutrophil and monocyte functions in normal and septic states

BACKGROUND

Insulin-like growth factor 1 (IGF-1) mediates anabolic actions in catabolic states and also influences the immune system. Endogenous IGF-1 production is suppressed in sepsis; replacement therapy is therefore a natural approach to obtain the protein anabolic and potentially immune-stimulating effects of IGF-1.

METHODS

Twenty-two piglets were randomized to three groups: an IGF-1 group (n = 8) receiving a continuous infusion of 1.3 mg/h of IGF-1, a nontreated septic control group (n = 8), and a nonseptic control group (n = 6) receiving saline. Phagocytosis and respiratory burst in porcine neutrophils were evaluated by flow cytometry (FCM); tumor necrosis factor (TNF) levels were measured in serum during the septic period. In addition, human neutrophils and monocytes were primed in vitro with IGF-1 and subsequently were stimulated with phorbol myristate acetate (PMA) or Escherichia coli; phagocytosis and respiratory burst were evaluated by FCM.

RESULTS

Under nonseptic conditions, pretreatment with IGF-1 suppressed the ability of neutrophils to ingest bacteria (ie, the level of phagocytosis) 43.4% +/- 2.7% (IGF-1-treated) vs 55.8% +/- 3.4% (nontreated septic controls) and 57.3% +/- 3.34% (nonseptic controls) (p = .01). When challenged by live E. coli infusion, phagocytosis increased in the IGF-1 group to the levels of the nontreated group. The respiratory burst showed a convincing priming effect of IGF-1. After 4 hours of sepsis, the mean fluorescence intensity was 63.1 +/- 6.9 in the IGF-1 group and 40.7 +/- 3.0 in nontreated septic controls. The serum levels of TNF-alpha in the nontreated septic control group were twice those in the IGF-1-treated group, ie, 65.7 +/- 13.1 pg/mL in the nontreated septic controls and 31.5 +/- 7.5 pg/mL in the IGF-1 group (p = .03). In vitro priming of human neutrophils and monocytes with IGF-1 and subsequent stimulation with PMA or E. coli demonstrated that IGF-1 enhanced both phagocytosis and respiratory burst.

CONCLUSIONS

IGF-1 serves as a priming agent for biologic functions of leukocytes.

Growth hormone. A paracrine growth factor?

A number of tissues, including the brain, pituitary, immune system, placenta, mammary gland, and testis, may be self-contained units of GH regulation, production, and action. The production of GH and GH-releasing factors outside the hypothalamo-pituitary axis complements, rather than replaces, the traditional endocrine interactions between GH-releasing factors, GH, and its target tissues.

Both pituitary and placental growth hormone transcripts are expressed in human peripheral blood mononuclear cells (PBMC)

The hGH-V gene codes for a variant of human pituitary growth hormone (hGH-N) named placental growth hormone (hPGH). hPGH shares 93% amino acid identity with hGH-N. Until now the hGH-V gene was considered to be exclusively expressed in human placenta, where it replaces maternal circulating hGH-N at the end of pregnancy. In this study we investigated by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis hGH-N, and hGH-V, gene expression in PBMC in men, women and pregnant women. We have demonstrated that hGH-N and hGH-V transcripts are simultaneously produced by PBMC in both men and women as well as pregnant women. The PBMC of a PIT-1-negative woman expressed only the hGH-V transcript, but not the hGH-N one as expected. In conclusion, hGH-V mRNA is expressed by cells other than the syncytiotrophoblast, is not regulated by PIT-1, and may be involved in immune regulation, as is pituitary GH.

Growth hormone and Pit-1 expression in bovine fetal lymphoid cells

Bovine fetal lymphoid cells were examined for growth hormone (GH) and the transcription factor Pit-1/GHF-1 mRNA. GH and Pit-1/GHF-1 transcripts were detected in thymocytes and splenocytes from fetuses at 60, 90, 120, and 270 d of gestation using reverse transcription-polymerase chain reaction (RT-PCR). Northern analysis indicated that the lymphoid GH mRNA was approximately 350 nucleotides larger than in the pituitary. RT-PCR analysis demonstrated that the coding regions as well as 3' untranslated region of the lymphocyte GH and pituitary transcripts were the same. Analysis of the 5'-untranslated region of the lymphocyte GH mRNA showed that transcription began upstream from the start site in the pituitary gland, suggesting differences in regulation in these tissues. Fetal thymocytes and splenocytes expressed Pit-1/GHF-1 mRNA; however, they contained only the 2.5-kb transcript. The GH and Pit-1/GHF-1 mRNA in fetal lymphoid cells supports the hypothesis that lymphocyte-derived GH may function as an autocrine and/or paracrine factor during the development and maturation of the bovine fetal immune system.

Effect of growth hormone on human alveolar macrophage oxidative metabolism

BACKGROUND

Growth hormone (GH) has diverse immunological actions and has been shown to augment oxidative metabolism in rat peritoneal and porcine alveolar macrophages and both human and animal neutrophils. A study was performed to determine the effects of GH on human alveolar macrophages in vitro.

METHODS

Macrophages were harvested from 10 patients undergoing bronchoalveolar lavage and incubated with 0, 10 and 100 nmol/ml GH for four hours. Oxidative metabolism was assessed by means of a fluorescent assay using FMLP and E coli as stimulants. Fluorescence was measured using flow cytometry.

RESULTS

No difference in basal or stimulated oxidative metabolism was found between the GH and control groups.

CONCLUSIONS

GH does not have a direct stimulatory action on human alveolar macrophages in vitro. However, this does not exclude an indirect effect in vivo. The results contrast with previous studies on animal alveolar macrophages.

Growth hormone expression in murine bone marrow cells is independent of the pituitary transcription factor Pit-1

GH has been shown to promote the development and function of leukocytes. The expression of both GH and GH-receptors in lymphoid cells has led to the hypothesis that GH acts in an autocrine or paracrine fashion. The described effects of GH on hematopoiesis and B cell development, led us to investigate GH expression in bone marrow cells. By immunocytochemistry, we show that bone marrow-derived granulocytes and macrophages contain immunoreactive GH. We found that 65 +/- 24% of the granulocytes were stained with anti-GH, whereas 5.8 +/- 1.5% of the granulocytes contained detectable amounts of GH mRNA as assessed by in situ hybridization. To address a possible alternative regulation mechanism in bone marrow and to establish whether locally derived GH might still play a role in pituitary-deficient dwarf mice, we also addressed GH expression in bone marrow from hypopituitary Snell dwarf mice. These mice have a mutated gene for the pituitary transcription factor Pit-1 that is deficient in DNA binding. Our finding that GH expression (immunoreactive protein and mRNA) in bone marrow cells from dwarf mice is similar to that in normal mice points to a Pit-1 independent regulation of GH in mouse bone marrow.

Characterization of rainbow trout (Oncorhynchus mykiss) growth hormone 1 gene and the promoter region of growth hormone 2 gene

Studies by Agellon et al. (Mol. Reprod. Dev. 1, 11-17) showed the presence of two growth hormone (rtGH1 and rtGH2) mRNA species in pituitary glands of adult rainbow trout (Oncorhynchus mykiss). In this study, we have detected rtGH1 and rtGH2 mRNAs in pituitary glands of rainbow trout from fry to 2 years of age. The level of rtGH1 mRNA is notably higher than that of rtGH2 mRNA in 10-day-old fry and 2-year-old females. These results suggest differential expression of rtGH1 and rtGH2 genes in different sexes and developmental stages. As a step toward elucidating the mechanism of differential expression of both GH genes, DNA fragments encoding rtGH1 gene and the promoter/regulatory region of rtGH2 gene were isolated and characterized. Rainbow trout GH genes span approximately 4.5 kb and are composed of six exons and five introns. The 5'-flanking region of both genes contain consensus sequences for TATA boxes and several Pit-1 binding sequences. Consensus sequences related to the cAMP response element, thyroid hormone response element, retinoic acid response element, estrogen response element (ERE), and glucocorticoid response element are present not only in the 5'-flanking region, but also in introns and exons in rtGH1 gene. These hormone response elements, except ERE, are also present in rtGH2 gene.

Regulation of interleukin (IL)-1alpha, IL-1beta, and IL-6 expression by growth hormone and prolactin in bovine thymic stromal cells

Growth hormone (GH) and prolactin (PRL) have been implicated in T-cell development, but relatively little is known about the mechanism(s) of their actions on the multiple cell types in this complex tissue. Here, we investigated the effects of GH and PRL on the expression of interleukin (IL)-1alpha, IL-1beta and IL-6 in thymic stromal cells (TSC). These cytokine mRNAs were increased by GH, PRL and placental lactogen (PL) in primary cultures prepared from mid-gestational fetuses in a dose-dependent manner. IL-1 receptor antagonist (IL-1ra) abolished the hormone-induced IL-6 expression, suggesting that the induction of IL-6 was secondary to IL-1 activity. To examine the effects of these hormones on an individual cell type and develop a system in which signalling mechanisms can be studied, we generated immortalized cell lines using a strategy of conditional transformation. In the cell line, TSC-936, which displayed vimentin-positive staining and morphological characteristics of mesenchymal cells, both GH and PRL increased levels of steady-state mRNAs for IL-1alpha and IL-1beta. Nuclear run-on analysis revealed that the transcription rate of the IL-1beta gene was significantly increased by GH and PRL at 30 and 60 min, respectively, but that for IL-1alpha was not significantly changed, suggesting the possibility of an alternative mechanism mediating this response. These data suggest that modulation of cytokine gene expression is one mechanism by which GH and PRL facilitate thymic development and T-cell maturation.

Evidence for a local action of growth hormone in embryonic tooth development in the rat

Studies in non-dental embryonic tissues have suggested that an interaction between growth hormone and its receptor may play a role in growth and development before the foetal pituitary gland is competent. This study reports the distribution of growth hormone, its receptor and binding protein in developing rat tooth germs from embryonic day 17 to 21 and postnatal day 0 using antibodies specific for each of these proteins. Four foetal rats were processed at each time point (E17, E18, E20/21 and postnatal day 0). Following routine fixation and paraffin embedding, sections were treated with antisera to rat growth hormone, rat growth hormone binding protein and growth hormone receptor. Localization of antibody/antigen complexes was subsequently visualized by addition of biotinylated IgG and reaction with streptavidin peroxidase and diaminobenzidine. Assessment of the level of staining was qualitative and based on a subjective rankings ranging from equivocal to very strong staining. Overall, growth hormone and its binding protein were located both in the cellular elements and throughout the extracellular matrix, whereas the growth hormone receptor showed an exclusively intra-cellular location. All three proteins were detectable in cells of the dental epithelium and mesenchyme at the primordial bud stage (E17) which occurs prior to expression of pituitary growth hormone. At the cap stage of odontogenesis (E18-19), numerous cells in both the dental epithelium and mesenchyme were intensely immunoreactive for growth hormone, its binding protein and receptor. In the succeeding early bell stage (E20-21), most of the mesenchymal cells in the dental pulp were mildly positive for these proteins, while the dental epithelium and adjacent mesenchyme were more immunoreactive. At the late bell stage (postnatal day 0), all three proteins were localized in dental epithelium, differentiating mesenchymal cells the cuspal surface facing the epithelial-mesenchymal interface, preodontoblasts, and odontoblasts forming dentine. From these observations, immunoreactive growth hormone, its receptor and binding protein appear to be expressed in odontogenic cells undergoing histodifferentiation, morphodifferentiation and dentinogenesis in a cell-type and stage-specific pattern throughout embryonic tooth development. This suggests the possibility that growth hormone, or a growth hormone-like protein, plays a paracrine/autocrine role in tooth development in utero.

Molecular characterization of immune derived proenkephalin mRNA and the involvement of the adrenergic system in its expression in rat lymphoid cells

Proenkephalin (PENK), a classically defined opioid gene, was originally thought to be expressed almost exclusively in the mature nervous and neuroendocrine systems. In the last few years, it was demonstrated, however, that significant levels of PENK mRNA and PENK-derived peptides are transiently expressed in cells of the immune system. Very little is known about the molecular mechanisms regulating this transient expression. In order to investigate those mechanisms, we examined the in vivo expression of PENK mRNA in mesenteric lymph nodes after exposing rats to lipopolysaccharide. In the present study we demonstrate that: (i) promoter usage and splicing of PENK mRNA function similarly in mesenteric lymph nodes as in neural cells; (2) PENK expression in mesenteric lymph nodes is modulated by adrenaline via adrenergic receptors; and (3) the adrenergic system participates in the modulation of the LPS induced PENK mRNA expression. These results provide more evidence for the involvement of opioids in neuro-immune interactions.

Monoclonal antibodies against recombinant human growth hormone as probes to study immune function

Monoclonal antibodies were raised against human recombinant growth hormone (rhGH) and those that did not cross-react with other human recombinant proteins like prolactin (PRL), interleukin 2 (IL-2), insulin, or bovine pituitary growth hormone were selected. The selected hybridoma supernatants were studied for their ability to influence T lymphocyte proliferation when induced either by a mitogen, such as phytohemagglutinin (PHA), or by alloantigen. All supernatants inhibited proliferation. Three MAbs were then purified by several passages on antimouse IgG (or IgM)-agarose columns, and characterized. These MAbs recognized three different epitopes, as revealed by competition study, although their inhibitory effect on PHA-induced T cell proliferation was quite similar. The data demonstrate that the MAbs were not cytolytic, that they did not interfere with the PHA binding to T cell membranes, and, as revealed by FACS analysis, did not bind to the membrane. Finally, these MAbs immunoprecipitated a 44-kDa molecule from PHA-activated T cell-concentrated supernatants. These data indicate that the MAbs recognized a soluble factor that plays a central role in T cell proliferation and that is probably the immune growth hormone.

Immunoregulatory properties of growth hormone and prolactin

Reciprocal communication between the neuroendocrine and immune systems is critical to the establishment of host homeostatic and defence mechanisms. The production and utilisation of common ligands and their receptors by cells of the immune and neuroendocrine systems constitutes a biochemical information circuit between and within the immune and neuroendocrine systems. Although the structures of the various signalling components appear to be similar in both systems, the regulation of their synthesis may be different. Growth hormone and prolactin have similar and marked influences on the function/activity of each of the major immune cell types, both in vitro and in vivo. The underlying molecular mechanisms are just beginning to be unravelled, and it is anticipated that further work in this rapidly developing field will establish abnormal pituitary and/or lymphocyte growth hormone and prolactin synthesis and function as a contributory factor to a number of pathologic situations, including leukaemia and autoimmunity.

Growth hormone activation of human monocytes for superoxide production but not tumor necrosis factor production, cell adherence, or action against Mycobacterium tuberculosis

We have previously demonstrated that growth hormone (GH) is a human macrophage-activating factor which primes monocytes for enhanced production of H2O2 in vitro. This report extends our observations to other monocyte functions relevant to infection. We find that GH also primes monocytes for O2- production, to a degree similar to the effect of gamma interferon. Neither macrophage-activating factor alone stimulates monocytes to release bioactive tumor necrosis factor. However, GH, unlike gamma interferon, does not synergize with endotoxin for enhanced tumor necrosis factor production. In further contrast, GH does not alter monocyte adherence or morphology, while phagocytosis and killing of Mycobacterium tuberculosis by GH-treated monocytes are also unaffected. Therefore, despite the multiplicity of the effects of GH on the immune system in vivo, its effects on human monocytes in vitro appear to be limited to priming for the release of reactive oxygen intermediates.

Expression of the growth hormone gene in immune tissues

It is well established that growth hormone (GH)-like proteins and mRNA are present in immune tissues, but it is not known whether this reflects ectopic transcription of the GH gene or the expression of a closely related gene. This possibility was, therefore, investigated. Immunoreactive (IR) GH-like proteins were readily measured by radioimmunoassay and immunoblotting in the spleen, bursa of Fabricius and thymus of immature White Leghorn chickens, in which IR-GH was similar in size and antigenicity to the major GH moieties present in the pituitary gland. RT-PCR of mRNA from these immune tissues, with oligonucleotide primers spanning the coding region of pituitary GH cDNA, also generated cDNA fragments identical in size (689 bp) to pituitary GH cDNA.BamHI andRsaI cleavage sites were located in these cDNA sequences in the same position as those in pituitary GH cDNA. These amplified cDNA sequences also contained sequences that hybridized, by Southern blotting, with a chicken pituitary GH cDNA probe, thus suggesting a high degree of homology between pituitary and immune GH transcripts. The nucleotide sequence of the PCR products generated from these immune tissues, determined by a modified cycle dideoxy chain termination method, were also identical to pituitary GH cDNA. This homology extended over 593 bp of the spleen cDNA (spanning nucleotides 70-663 of the pituitary GH cDNA and its coding region for amino acids 5-201), 613 bp of the bursa cDNA fragment (spanning nucleotides 63-676 of the pituitary GH cDNA and its coding region for amino acids 3-207) and 607 bp of the thymic cDNA fragment (spanning nucleotides 61-665 of pituitary GH cDNA and its coding region for amino acids 4-203). These results clearly establish that the GH mRNA is present in immune tissues, in which GH-IR proteins are present. The local production of GH within the immune system of the domestic fowl, therefore, suggests it has paracrine or autocrine roles in modulating immune function.

Vascular permeability to growth hormone in the rat central nervous system after focal spinal cord injury. Influence of a new anti-oxidant H 290/51 and age

Vascular permeability to the growth hormone (GH) across the blood-brain barrier (BBB) is unknown. This investigation was undertaken to examine vascular permeability to 125I-labelled rat growth hormone (rGH) in the central nervous system (CNS) of normal animals. Since age and spinal cord injury influences the metabolism of GH, these factors were also included. No statistically significant difference was seen regarding rGH permeability between young (aged 19-21 weeks) and old (age 38-42 weeks) animals. A focal trauma to the cord, produced by an incision into the right dorsal horn of the T10-11 segments in young animals, increased rGH permeability in several spinal cord segments at 0.5-5.0 h after injury. This permeability increase progressed over time. Similar trauma to old rats resulted in a significantly less increase in rGH permeability in the spinal cord 5 h after the trauma. This indicates that trauma-induced increased permeability of rGH is age-dependent. Pretreatment of normal young animals with a new antioxidant (H 290/51) did not influence the rGH permeability. However the drug prevented the trauma-induced increase of rGH permeability at 5 h after injury. This indicates that inhibition of lipid peroxidation has some protective effect on trauma-induced increase in rGH permeability.

Growth hormone alters lymphocyte sub-populations and antibody production in dwarf rats in vivo

Female dwarf rats at different ages were treated with recombinant porcine GH or with a potent sheep anti-rat GH serum. Body weight and spleen weight increased with GH and decreased with anti-GH treatment (p < 0.001). Neither GH nor anti-GH treatment resulted in a change in circulating WBCs, but GH decreased, while anti-GH increased, RBC counts (p < 0.001). Similarly, GH treatment tended to decrease the ratio of CD4+:CD8+ T-cells while anti-GH increased (p < 0.05) the ratio. Anti-GH treatment also enhanced the animals' ability to produce specific IgG in response to KLH injection. These results indicate that GH may have a physiological role in suppressing humoral immune function but may enhance cell-mediated immunity.

The influence of thyroxine, growth hormone and prolactin alone and in combination on the production of prolactin-like activity by splenocytes from Snell dwarf mice

The production of a prolactin (PRL)-like substance by mitogen-stimulated immunocompetent cells has been reported previously for a number of species. The Snell dwarf mouse has a deficiency in thyrotropin (TSH), growth hormone (GH) and prolactin (PRL) as a result of a defect in the pituitary Pit-1 promoter. Since the gene for PRL is present in the dwarf mouse pituitary but not activated it was of interest to determine whether a similar deficiency existed for splenocytes from the dwarf animal. Irradiated splenocytes from dwarfs and normal littermates were cocultured in synthetic AIM-V medium with Nb2 cells and stimulated with concanavalvin A (Con-A). The 3H thymidine incorporation into Nb2 cells in cocultures was quantitated by the addition of mouse PRL to Nb2 cells alone. Splenocytes from dwarf mice produced significantly less PRL-like activity (p < 0.02) than did splenocytes from normal animals. The administration of thyroxine (T4) to dwarf mice increased body weight (BW) gain and the number of splenocytes/g BW. The administration of recombinant bovine GH but not recombinant bPRL further increased body weight gain over T4 alone but neither pituitary hormone had any additional effect on the number of splenocytes/g BW over that noted for T4 alone. Prolactin and GH alone had no effect on splenocyte numbers/g BW. The decreased production of PRL-like activity in the dwarf mouse was not altered by either GH or PRL injection. The injection of T4 alone and in combination with pituitary hormones increased the production of PRL-like activity by dwarf splenocytes to values similar to that observed for normal animals.

Immunohistochemical localization of growth hormone receptor binding protein in the mammalian cerebellum

A panel of monoclonal antibodies to the growth hormone (GH) receptor/binding protein was used to demonstrate the existence and detail the expression of GH receptors in the cerebellum of 2, 10, 28 days old postnatal and adult rats and 10, 20 days old and adult rabbits by immunohistochemistry to define potential targets for endogenous GH action in the cerebellum. Receptors were localized in membrane and cytoplasmic components of neurons and glial cells and expression decreased with age. Intense immunoreactivity was observed in the cytoplasm and dendrites of Purkinje cells and in cells of the cerebellar nuclei. Glial cells also showed receptor expression. Strong immunoreactivity was observed with two monoclonal antibodies and lesser reactivity was seen with others, paralleling their affinities for the receptor. The cytoplasmic presence of this putatively plasma membrane located GH receptor is accounted for by the high receptor content of endoplasmic reticulum and the existence of a soluble form of the GH receptor, namely the GH binding protein (BP) derived from the membrane receptor by cleavage, and receptor localization reported here correlate well with the distribution of insulin-like growth factor 1 (IGF-1) mRNA and immunoreactivity in cerebellar Purkinje cells and glial cells. Primary localization of the receptor in the cerebellum is in direct contradiction to both classical GH action and the somatomedin hypothesis and supports and extends the theory of genetically regulated macroneuronal maturation.

Growth hormone inhibits normal B-cell differentiation and neutrophils' chemotaxis in vitro

In acromegalic patients we have previously described a low ability of B-lymphocytes to differentiate into plasma cells under PWM stimulation, and a decreased chemotaxis of polymorphonuclear leukocytes (PMN) towards N-formylmethionylphenilalanine (FMP). In this study we examined the effect of exogenous GH over these immune functions in normal cells. PMN were purified by dextran sedimentation, incubated with recombinant human GH (0 to 20 ng/ml) and subjected to stimulation with FMP. PBMC were cultured with or without PWM, in the presence of GH (between 0 and 100 ng/ml). Plasma cells were determined as hemolysis plaque forming cells and also by immunofluorescence. GH, in a dose-dependent way, decreased directed migration of PMN (5 ng/ml: 1.787 +/- 148 microns; 10 ng/ml: 1.581 +/- 221 microns; 20 ng/ml: 1.569 +/- 149 microns, all as mean +/- S.E.M.), when compared to similar values of untreated PMN (0 ng/ml 2.085 +/- 139 microns). GH treatment did not modify spontaneous migration. Net migration showed the same pattern as directed migration. GH decreased dose-dependently the PWM-driven differentiation of B-lymphocytes into plasma cells to 60% of the basal level. Although not significantly, GH tended to increase spontaneous B-cell differentiation. These results could account for the already described defect in B-cell differentiation and PWN chemotaxis in acromegaly, emphasizing the relationship between the endocrine and immune systems.

Neuroendocrine-immune interactions

The role of the neuroendocrine system in influencing both immune development and function has become an area of active research within many model systems, including the chicken. It is now clear that the neuroendocrine system can exert immediate feedback regulation on the immune system as well as control specific aspects of immune differentiation and development. The primary lymphoid organs of avian species (i.e., the thymus and the bursa of Fabricius) are also known to function as endocrine organs. These produce hormonal products that influence the development of lymphoid cells and that may feed back on the neuroendocrine system. In conjunction with the endocrine activities of the primary lymphoid organs, immune and accessory cells are known to produce a variety of secreted products or cytokines that have the potential not only for the regulation of immune function but also for mediating neuroendocrine activities. Finally, it has been demonstrated in a variety of species that leukocytes are capable of producing endocrine mediators previously believed to be produced only under the direct control of the hypothalamic-pituitary axis. Thus, there are numerous possibilities for bidirectional interactions between the immune and neuroendocrine systems. This discussion focuses primarily on these interactions with an emphasis on the means by which the hormonal mediators, growth hormone and thyroid hormone, may affect the thymus and the thymic microenvironment. The role of the adrenocorticoids and gonadal steroids in regulating immune function and their involvement in immune feedback circuits are also discussed.

Stimulatory effects of immunoreactive growth hormone on proliferation of a human lymphocyte cell line

Previous studies have indicated the secretion of a growth hormone-like molecule by the lymphocyte T-cell line, H9. We examined the autocrine growth-promoting effects of this T-cell derived factor. H9 conditioned medium stimulates proliferation of H9 cells themselves in a dose-dependent fashion. This growth stimulating effect could be blocked by anti-human growth hormone antiserum, but could not be simulated by addition of growth hormone only or interleukin 2 only, or a combination of both. Dexamethasone inhibited H9 growth in low nutrient culture conditions and seemed to somewhat offset the growth promoting effect of the hGH-like molecule. However, the exact role played by dexamethasone in H9 cell growth and death, as well as the exact mechanism by which the hGH-like molecule exerted its growth-promoting action, remain to be elucidated.

Vasoactive intestinal peptide (VIP) mRNA expression in rat T and B lymphocytes

Different evidence suggests that VIP has immunoregulatory functions and may be secreted by different cells involved in inflammatory and immune responses. In the present study, we demonstrate by reverse transcription (RT) and polymerase chain reaction (PCR) VIP gene expression in rat thymocytes and T and B cells derived from spleen and lymph nodes. We have obtained a specific VIP cDNA product of 458 bp identical in size to that obtained from cerebral cortex. These results have been confirmed by Southern blot analysis. VIP message has also been detected in the T-T hybridoma YH-1633 and in a non-immune cell line, the pheochromocytoma PC 12. VIP gene expression in central and peripheral lymphoid organs suggests that VIP may be a T and B cell-derived cytokine involved in T-cell differentiation and in cell immune responses.

Reduction in superoxide anion secretion and bactericidal activity of neutrophils from aged rats: reversal by the combination of gamma interferon and growth hormone

Polymorphonuclear neutrophils (PMN) from bone marrow of 24-month-old rats kill Escherichia coli less efficiently than PMN from 3-month-old rats. Secretion of O2- and killing of E. coli by PMN from both young and old rats can be significantly augmented by preincubation with either 250 U of gamma interferon (IFN-gamma) or 250 ng of growth hormone (GH) per ml. This priming is specific, because neutralizing monoclonal antibodies against either IFN-gamma or GH completely abrogate the enhanced O2- secretion by PMN from young rats. However, in contrast to PMN from young rats, PMN from aged rats are not primed to kill E. coli by 10-fold-lower concentrations of either IFN-gamma (25 U/ml) or GH (25 ng/ml). To explore the mechanism for the reduction in bacterial killing by PMN from old rats, a syngeneic GH-secreting pituitary cell line (GH3) was implanted in vivo. PMN from GH3-treated aged rats, but not control aged rats, could now be primed in vitro for O2- secretion by IFN-gamma (25 U/ml). Although PMN from aged rats do not respond to the lower doses of either IFN-gamma or GH, the combination of both reagents totally restores the ability of PMN to secrete O2- and to kill E. coli. This synergistic priming is observed with PMN from aged rats, but not with those from young rats, and can be detected when both reagents are added simultaneously or when they are added in either sequence. Furthermore, addition of a monoclonal antibody against either IFN-gamma or GH abrogates the synergism of these two molecules. Collectively, these data identify an important alteration in myeloid cells from aged rodents by showing that their PMN are intrinsically unable to respond to low concentrations of IFN-gamma by secreting O2- and killing bacteria. The results also define a previously unrecognized synergism in PMN from aged animals by showing that GH synergizes with IFN-gamma both in vivo and in vitro to restore these suppressed responses.

Effects of streptozotocin-induced diabetes on lymphocyte POMC and growth hormone gene expression in the rat

Diabetes in the rat is associated with a change in the profiles of several neuroendocrine hormones resulting in poor growth and decreased immune function. Since lymphocytes can also serve as a source of neuroendocrine hormones, we have examined whether the change in hormone profiles are accompanied by an impairment of lymphocyte GH and POMC gene expression in the immune system. Diabetes was induced by the administration of streptozotocin (STZ; 10 mg/100 g body weight) and 3 days later GH and ACTH protein and mRNA were determined. The results show a modest diminution of GH RNA in the spleen of diabetic animals whereas the expression of POMC mRNA and ACTH by the thymus was enhanced. The expression of POMC in the spleen appeared unaltered while the increase of POMC RNA in the thymus was evident after the first day of STZ treatment. STZ had no direct effect on GH or POMC expression in the spleen or thymus cells in vitro. Insulin does not appear to be involved in the expression of lymphocyte GH or POMC. The administration of insulin to the diabetic animals had no significant effect on the expression of GH or POMC by the immune cells. In addition, lymphocytes do not appear to serve as a source of insulin or are the expression of genes for lymphocyte GH or ACTH altered by insulin in vitro. Taken together, the findings are the first to report on the expression of neuroendocrine genes in lymphocytes during diabetes. The mechanism for the inhibition of GH and stimulation of POMC expression by lymphocytes in diabetic animals is unknown, but it is tempting to speculate an important role in the development of the autoimmunity that characterizes this complex disease.

Localization and ontogeny of growth hormone receptor gene expression in the central nervous system

There is literature evidence that both growth hormone (GH) and its mediator, insulin-like growth factor 1 (IGF-1), are able to act upon neuronal and glial cells in the brain. We report here the location of the GH receptor in the brain of the rat and rabbit. Receptor distribution was determined by immunohistochemistry with GH receptor/binding protein (BP) specific monoclonal antibodies and by in situ hybridization with a [35S]riboprobe. GH receptor/BP immunoreactivity in the rat was most prominent in the neonate and declined with postnatal age. Receptor immunoreactivity was generalised with variation in immunoreactivity in regional areas. In the rat, strongest immunoreactivity was seen in layers 2, 3, 5 and especially layer 6 of the cerebral cortex, in neurones of the thalamus and hypothalamus, in Purkinje cells of the cerebellum, in neurones of the trapezoid body of the brainstem, and in retinal ganglion cells. Glial cells, notably astrocytes were also strongly reactive, along with ependyma of the choroid plexus, ventricular lining and pia mater. In the neonatal rabbit, strongest immunoreactivity was evident in layers 2 and 3 of the cerebral cortex, in pyramidal cells of the hippocampus, and in neurones of the inferior and superior colliculi, brain stem reticular formation, dorsal thalamus and hypothalamus. A similar distribution of GH receptor mRNA was seen by in situ hybridization. The ontogeny of GH receptor/BP mRNA in whole rat brain was quantified by solution hybridization-RNAse protection assay. Contrary to its ontogeny in the liver (Endocrinology, 113 (1983) 1325-1329) receptor mRNA decreased with postnatal age.(ABSTRACT TRUNCATED AT 250 WORDS)

Polymorphonuclear neutrophil granulocyte chemotactic hyperresponsiveness in a case of canine acromegaly

Growth hormone (GH) has recently been shown to affect polymorphonuclear neutrophil granulocyte (PMN) function and to be secreted by mononuclear cells, indicating that the hormone may be active in an immunophysiologic network, acting as an endo- or paracrine priming agent. The purpose of the present study was to evaluate the chemotactic responsiveness of canine peripheral PMN in a dog with acromegaly, caused by spontaneous, progesterone-induced hypersecretion of GH and, secondary to this, a seven-fold increase in insulin-like growth factor I (IGF-I). The chemotactic responsiveness towards zymosan-activated serum (ZAS) and leukotriene B4 (LTB4) was evaluated at a time when the dog suffered from acromegaly and again 57 days after corrective surgery (ovariohysterectomy). The experiments showed that PMN from the patient exhibited enhanced chemotactic migration that appeared to be associated with the hypersomatotropic condition as judged from the reversibility of the phenomenon. The glucose intolerance and elevated serum alkaline phosphatase that were observed in the acromegalic dog were also shown to be reversible following surgery.

Syncytiotrophoblastic localization of the human growth hormone variant mRNA in the placenta

The hGH/hCS genes, clustered on chromosome 17 in the 5' to 3' order GH-N, CS-L, CS-A, GH-V and CS-B, show a high degree of sequence identity. The expression product of the GH-V gene is the placental growth hormone, which replaces pituitary GH in maternal blood throughout pregnancy. By means of mRNA competitive hybridization using 32P-labelled and unlabelled 30 bases long oligonucleotides, we first optimized specific hybridization conditions. In situ hybridization was then performed to locate the GH-V mRNA encoding placental growth hormone. The hGH-V gene appears expressed in the placental syncytiotrophoblast. Unlike the CS-A and CS-B genes (both encoding hPL) which are expressed uniformly in the syncytiotrophoblast, the GH-V mRNA is located in a few syncytiotrophoblast cells only.

TSH beta subunit gene expression in human lymphocytes

Production of neuroendocrine peptides by human lymphocytes is thought to facilitate control of the immune response. The presence of neuroendocrine peptide gene expression, specifically the TSH beta subunit gene, was studied in human lymphocytes using Northern blot analysis and polymerase chain reaction (PCR) techniques. Northern blot analysis of human lymphocyte RNA probed with a TSH beta cDNA probe failed to demonstrate TSH beta subunit steady state message levels. PCR amplification of lymphocyte-derived cDNA using TSH beta subunit complementary primers resulted in amplification of a .38 Kb DNA fragment, confirming expression and initial exonic splicing of TSH beta subunit gene exons 2 and 3 in human lymphocytes. Sequence analysis of this .38 Kb DNA fragment demonstrated conservation of exon borders after splicing (exons 2 and 3) and predicted an amino acid translation product similar, if not identical, to human TSH beta peptide sequence. Hybridization with a TSH beta subunit cDNA probe of PCR-amplified reverse-transcribed lymphocyte RNA suggested that: (1) the abundance of TSH beta subunit gene transcripts in human lymphocytes is less than the relative abundance in T3-treated pituitary; and (2) this messenger RNA may be modulated by the presence of certain thyromimetic compounds (T2, T3, TRIAC).

Humoral mediation of changing body composition during aging and chronic inflammation

A decline in lean body mass and an accompanying increase in fat mass are known to occur during aging. The consequences of these changes in body composition may include decreased strength and physical activity, altered energy metabolism, and impaired resistance to infection. The mechanisms behind these age-related events remain unknown, but they may include changes in some of the hormonal and cytokine mediators that seem to regulate body composition. The common inflammatory condition rheumatoid arthritis could provide a useful model of these phenomena dissociated from chronological aging. This article reviews changes in neuroendocrine and immune modulators of metabolism and their consequences during aging and chronic inflammation.

The production of growth hormone and insulin-like growth factor-I by the same subpopulation of rat mononuclear leukocytes

In the present study, we evaluated the subpopulation of lymphoid cells from normal and hypophysectomized rats producing GH and IGF-I in vitro. The data show that removal of the pituitary results in depression of GH production in spleen, thymus, and bone marrow and an increase in the peripheral blood leukocytes. The changes in the percentage of cells producing GH in hypophysectomized animals are not due to a single cell type but appears to influence the T-helper, T-cytotoxic, and B-cell subsets. Interestingly, no significant changes in the levels of GH RNA were detected between control and hypophysectomized animals after the in vitro culture. We also found that the increase in GH production in spleen cell cultures after mitogen stimulation could be accounted for by an increase in the percentage of T cells producing GH. Lastly, we demonstrated that the cells positive for GH production were also positive for IGF-I production. This later finding coupled with our previous results suggest that an autocrine regulatory circuit may be important for the production of leukocyte-derived irGH and irIGF-I within the immune system.

Immunoreactive growth hormone production by human lymphocyte cell lines

1. Two human lymphocyte cell lines, a T-cell line and a B-cell line, were shown to produce and secrete immunoreactive growth hormone (irGH). The irGH molecules secreted by the two cell lines appeared to be de novo synthesized and their molecular size was similar to that of pituitary GH as well as irGH secreted by peripheral blood lymphocytes. 2. Affinity-purified irGH molecules had human growth hormone (hGH)-like mitogenic activity on Nb2 cells. These findings indicate that the irGH molecules produced by H9 and IM9 were similar to hGH in structure. 3. However, the irGH messages could not be amplified by polymerase chain reaction (PCR) primers which had been demonstrated to be able to amplify reverse-transcribed hGH messenger RNA successfully, suggesting that the lymphocyte-derived irGH and pituitary hGH are not exactly identical molecules. 4. We conclude that the H9 and IM9 cells produce a growth hormone-related molecule whose structure is different from that in the anterior pituitary.

Case report: recurrent Salmonella typhi chest wall abscess associated with a pituitary macroadenoma

An unusual manifestation of a Salmonella typhi infection is presented in a patient with a growth hormone producing tumor. Growth hormone may effect cell mediated immunity and predispose to localized or disseminated intracellular infections.

Growth hormone augments superoxide anion secretion of human neutrophils by binding to the prolactin receptor

Recombinant human growth hormone (HuGH) and human prolactin (HuPRL), but not GH of bovine or porcine origin, prime human neutrophils for enhanced superoxide anion (O2-) secretion. Since HuGH, but not GH of other species, effectively binds to the HuPRL receptor (HuPRL-R), we used a group of HuGH variants created by site-directed mutagenesis to identify the receptor on human neutrophils responsible for HuGH priming. A monoclonal antibody (MAb) directed against the HuPRL-R completely abrogated O2- secretion by neutrophils incubated with either HuGH or HuPRL, whereas a MAb to the HuGH-R had no effect. The HuGH variant K172A/F176A, which has reduced affinity for both the HuGH-binding protein (BP) and the HuPRL-BP, was unable to prime human neutrophils. This indicates that priming is initiated by a ligand-receptor interaction, the affinity of which is near that defined for receptors for PRL and GH. Another HuGH variant, K168A/E174A, which has relatively low affinity for the HuPRL-BP but slightly increased affinity for the HuGH-BP, had much reduced ability to prime neutrophils. In contrast, HuGH variant E56D/R64M, which has a similar affinity as wild-type HuGH for the HuPRL-BP but a lower affinity for the HuGH-BP, primed neutrophils as effectively as the wild-type HuGH. Finally, binding of HuGH to the HuPRL-BP but not to the HuGH-BP has been shown to be zinc dependent, and priming of neutrophils by HuGH was also responsive to zinc. Collectively, these data directly couple the binding of HuGH to the HuPRL-R with one aspect of functional activation of human target cells.

Characterization of a novel mRNA expressed by neurons in mature brain

In previous studies, differential hybridization screening of an activated murine T-lymphocyte cDNA library identified an interleukin 2-responsive mRNA, designated F5, expressed in lymphoid tissues and brain only. We now report characterization of a full-length clone isolated from an adult mouse brain cDNA library. Neither the nucleic acid nor amino acid sequences demonstrated similarity to reported sequences. On Southern blotting, the protein coding sequence hybridized to genomic DNA from a variety of species. On Northern blotting, F5 mRNA was expressed in adult mouse brain, spinal cord, eye, and dorsal root ganglia but not in peripheral nerve. In situ hybridization studies demonstrated prominent expression by neurons in brain. F5 mRNA expression was undetectable in embryonic rat cerebral hemisphere and low until postnatal day 21. F5 is a novel mRNA selectively expressed by proliferating lymphocytes and mature neurons.

Inhibition of immunoreactive growth hormone secretion from lymphoid cell lines by dexamethasone

The regulation of irGH secretion by the immune system was examined using lymphoid cell lines, H9 and IM9. Using a highly sensitive immunoassay, irGH secretion by H9 was negatively regulated by dexamethasone, whereas many other regulators of hGH secretion, including hormones, monoamines, and second messenger, had no measurable effect on irGH secretion. Treatment of H9 cells with dexamethasone for 48 hours could cause as high as 70% reduction in irGH secretion without affecting either cell numbers or viability. Using IM9, neither growth hormone releasing hormone nor thyrotropin releasing hormone had significant effect on either irGH steady-state level transcripts or irGH secretion. These findings suggest that irGH secretion by lymphocytes was regulated in a different manner from that by pituitary cells.