Human cortical neurogenesis is altered via glucocorticoid-mediated regulation of ZBTB16 expression

Glucocorticoids are important for proper organ maturation, and their levels are tightly regulated during development. Here, we use human cerebral organoids and mice to study the cell-type-specific effects of glucocorticoids on neurogenesis. We show that glucocorticoids increase a specific type of basal progenitors (co-expressing PAX6 and EOMES) that has been shown to contribute to cortical expansion in gyrified species. This effect is mediated via the transcription factor ZBTB16 and leads to increased production of neurons. A phenome-wide Mendelian randomization analysis of an enhancer variant that moderates glucocorticoid-induced ZBTB16 levels reveals causal relationships with higher educational attainment and altered brain structure. The relationship with postnatal cognition is also supported by data from a prospective pregnancy cohort study. This work provides a cellular and molecular pathway for the effects of glucocorticoids on human neurogenesis that relates to lasting postnatal phenotypes.

High-throughput screening of glucocorticoid-induced enhancer activity reveals mechanisms of stress-related psychiatric disorders

Exposure to stressful life events increases the risk for psychiatric disorders. Mechanistic insight into the genetic factors moderating the impact of stress can increase our understanding of disease processes. Here, we test 3,662 single nucleotide polymorphisms (SNPs) from preselected expression quantitative trait loci in massively parallel reporter assays to identify genetic variants that modulate the activity of regulatory elements sensitive to glucocorticoids, important mediators of the stress response. Of the tested SNP sequences, 547 were located in glucocorticoid-responsive regulatory elements of which 233 showed allele-dependent activity. Transcripts regulated by these functional variants were enriched for those differentially expressed in psychiatric disorders in the postmortem brain. Phenome-wide Mendelian randomization analysis in 4,439 phenotypes revealed potentially causal associations specifically in neurobehavioral traits, including major depression and other psychiatric disorders. Finally, a functional gene score derived from these variants was significantly associated with differences in the physiological stress response, suggesting that these variants may alter disease risk by moderating the individual set point of the stress response.

TMEFF2 is an endogenous inhibitor of the CRH signal transduction pathway

TMEFF2 is a transmembrane protein with unknown function, containing an altered epidermal growth factor (EGF)-like motif, two follistatin-like domains, and a cytosolic tail with a putative G-protein-activating motif. TMEFF2 is predominantly expressed in brain and prostate and has been implicated in cell signaling, neuronal cell survival, and tumor suppression. We found that expression of TMEFF2 in pituitary corticotrope cells inhibits the effects of corticotropin-releasing hormone (CRH) on the production of intracellular cAMP, and CREB, and transcription of Pomc. Regulation of the activity of CRH by TMEFF2 requires neither the cytoplasmic tail nor the EGF domain, while deletion of the follistatin modules abolishes the inhibitory function of TMEFF2. Moreover, a soluble secreted protein containing the complete extracellular domain is sufficient for inhibition of CRH signaling. TMEFF2-induced inhibition depends on serum components. Furthermore, TMEFF2 regulates the non-canonical activin/BMP4 signaling, PI3K, and Ras/ERK1/2 pathways. Thus, TMEFF2 inhibits the CRH signaling pathway and the PI3K/AKT and Ras/ERK1/2 pathways, contributing to a significant inhibition of transcription of Pomc. We found that expression of TMEFF2 in human Cushing's adenoma is reduced when compared with normal human pituitary, which may indicate that TMEFF2 acts as a tumor suppressor in these adenomas. Furthermore, the overexpression of TMEFF2 decreased proliferation of corticotrope cells. Our results indicate a potential therapeutic use of TMEFF2 or factors that stimulate the activity of TMEFF2 for the treatment of corticotrope tumors in order to reduce their secretion of ACTH and proliferation.

Effect of SOM230 (pasireotide) on corticotropic cells: action in dogs with Cushing's disease

SOM230 (pasireotide) is a multiligand somatostatin (SRIF) analog able to bind to somatostatin receptor (SSTR) subtypes 1, 2, 3 and 5, and trigger antisecretory and antiproliferative signaling cascades. Canines have become in vivo models to test the pharmacological treatment of corticotropinomas because they frequently develop Cushing's disease in a spontaneous manner, due to adrenocorticotropic hormone (ACTH)-producing pituitary adenomas. Different levels of expression of SSTR2 and SSTR5 have been shown in both mouse AtT20 cells and canine tumoral corticotropinoma cells. The objective of this study was to evaluate whether SOM230 controls both tumor cell growth and hormone synthesis, therefore controlling the disease. SOM230 was tested in dogs suffering from Cushing's disease (10 animals were treated continuously during 6 months, and another 10 were treated with 3 cycles consisting of 2 months of treatment followed by a 2-month rest period). A significant decrease in ACTH, urinary cortisol creatinine ratio, adenoma size (magnetic nuclear resonance) and improvement of clinical signs were obtained, without side effects. AtT20 cells treated with SOM230 suppressed pro-opiomelanocortin (POMC) promoter activity through SSTR2, via the G(i) α-subunit, and reduced Nur77/Nurr1 transcriptional activity. We conclude that SOM230, in addition to its well-described antisecretory effects, inhibits, as shown in AtT20 cells, ACTH synthesis at the POMC transcriptional level, an effect mediated mainly through SSTR2, and limits tumor growth. The controlled Cushing's disease in the dogs that received the treatment indicates that SOM230 has a potential therapeutic use in humans suffering from Cushing's disease.

Pituitary tumors: cell type-specific roles for BMP-4

BMP-4 plays a crucial role not only in the formation of the anterior pituitary during embryo development but also in the pathogenesis of pituitary tumors in adults. In tumor cells, BMP-4 promotes prolactin secretion and lactotroph cell proliferation through a Smad-estrogen receptor crosstalk but it inhibits ACTH production and cell proliferation of corticotrophs. In addition, BMP-4 increases GH secretion in rat pituitary tumor somatolactotroph GH3 cells and FSHbeta subunit gene transcription in the murine gonadotroph cell line, LbetaT2. Therefore, BMP-4 has a differential role on different types of pituitary tumors: it promotes pituitary prolactinoma while it inhibits corticotroph pathogenesis in Cushing's disease. The modulation of BMP-4 also plays an important role in the therapeutic mechanism of action of bromocriptine, somatostatin analogs and retinoic acid.

Cytokines and genes in pituitary tumorigenesis: RSUME role in cell biology

Cytokines of the IL-6 or gp130 family regulate many cellular responses and play regulatory roles in numerous tissues, and are placed as auto-paracrine regulators of pituitary function acting in normal and tumoral anterior pituitary cells. Especially, IL-6 has a regulatory role in the hormone secretion and growth of the anterior pituitary and is involved in adenoma pathogenesis. Recently, IL-6 has been shown to mediate oncogene-induced senescence (OIS). IL-6 might participate in such a process in adenomas pituitary as well. From pituitary tumoral gp130 overexpressing cells, an unknown protein, RSUME, has been cloned. RSUME is induced by hypoxia in pituitary tumors and regulate pathways involved in angiogenic and tumorigenic processes (NF-kappaB/IkappaB and HIF-1alpha pathways). Thus, it could have an important role in the development of the pituitary tumors.

Molecular mechanisms of glucocorticoid receptor signaling

This review highlights the most recent findings on the molecular mechanisms of the glucocorticoid receptor (GR). Most effects of glucocorticoids are mediated by the intracellular GR which is present in almost every tissue and controls transcriptional activation via direct and indirect mechanisms. Nevertheless the glu-cocorticoid responses are tissue -and gene- specific. GR associates selectively with corticosteroid ligands produced in the adrenal gland in response to changes of humoral homeostasis. Ligand interaction with GR promotes either GR binding to genomic glucocorticoid response elements, in turn modulating gene transcription, or interaction of GR monomers with other transcription factors activated by other signalling pathways leading to transrepression. The GR regulates a broad spectrum of physiological functions, including cell differentiation, metabolism and inflammatory responses. Thus, disruption or dysregulation of GR function will result in severe impairments in the maintenance of homeostasis and the control of adaptation to stress.

NOD2 receptors in adenopituitary folliculostellate cells: expression and function

Folliculostellate cells (FS cells) are non-endocrine cells from the pituitary gland that respond to bacterial endotoxins by producing cytokines. In immune cells, an important component of bacterial recognition are the toll-like receptors (TLRs). Previously, we showed that FS cells express TLR4. The TLR4 ligand lipopolysaccharide (LPS) stimulates interleukin-6 (IL6) production through nuclear factor kappaB (NFKB) induction. Binding of IL6 to gp130 receptor activates signal transducer and activator of transcription 3 (STAT3), an important mediator of inflammatory response. Another family involved in innate immune response following bacterial infection is the nucleotide-binding oligomerisation domain (NOD) intracellular receptor family. Herein, we describe for the first time the expression and function of NOD receptors in human pituitary and FS TtT/GF cell line. The NOD2 agonist muramyl dipeptide (MDP) increased Nf kappa b1-transcriptional activity, -protein expression and IL6 secretion in TtT/GF cells. Furthermore, these effects were potentiated by the combination of MDP and LPS. Silencing NOD2 abolished the action of LPS on NFKB transcriptional activity and IL6 production, indicating that, in TtT/GF cells, TLR4 transduces its signal through NOD2 receptor. We show here that in TtT/GF cells, Nod2 overexpression or stimulation by MDP increased STAT3 transcriptional activity. Furthermore, silencing STAT3 inhibited basal, LPS and MDP stimulated NFKB protein expression and overexpression of protein inhibitor of activated STAT3 (Pias3) markedly decreased basal NFKB activity. These data suggest that in TtT/GF cells, STAT3 acting upstream to NFKB mediates NOD2 receptor signalling pathway. In conclusion, the present study demonstrates that NOD molecules play a modulatory role in the pituitary by regulating the function and activation of FS cells in response to bacterial components.

Potential of retinoic acid derivatives for the treatment of corticotroph pituitary adenomas

Cushing's disease is a severe clinical condition caused by hypersecretion of corticosteroids due to excessive ACTH secretion from a pituitary adenoma. This complex endocrine disorder still represents a major challenge for the physician in terms of efficient treatment. In the last years there was only little progress in elucidating the molecular mechanisms responsible for the constitutive and autonomous ACTH secretion of pituitary corticotrophinomas. As a consequence, no effective drug therapy is currently available, particularly if surgical excision is not successful. In the present article we examine recent studies that have investigated the therapeutic potential of retinoic acid receptors as nuclear receptor targets for the treatment of Cushing's disease. Retinoic acid is an efficient drug used for the treatment of different types of cancers and it proved to act in animal models of Cushing's disease. The efficiency of this treatment in patients with this disorder still needs to be tested in clinical trials.

Differential gene expression in models of pituitary prolactin-producing tumoral cells

Although several genes and signalling pathways have been identified as important effectors in the development of pituitary tumours, our understanding of pituitary tumorigenesis remains incomplete and is the focus of much current research. Use of the mRNA differential display technique in prolactinomas from D2-receptor knockout mice and in stable GH3 cell line clones with enhanced tumorigenicity in vivo has led to the identification of two genes that are involved in the pathogenic process--BMP-4 and RSUME. Bone morphogenetic protein-4 (BMP-4) has been found to have a crucial role in prolactinoma development and also in signalling crosstalk with oestrogens. In contrast, BMP-4 has an inhibitory role in corticotrophinomas. RSUME (RWD-containing sumoylation enhancer) was identified from a transformed lactosomatotrophic cell line that had increased tumorigenic and angiogenic potential. Expression of RSUME was induced under hypoxic conditions and it has a potential role during vascularization. The differential expression and action of BMP-4 in prolactinomas and corticotrophinomas highlights the importance of studying a gene with contrasting actions in two cell lineages of the same organ in order to understand the pituitary transformation process. Both BMP-4 and RSUME may be interesting targets for inhibiting steps involved in pituitary tumorigenesis.

Interferon-gamma inhibits cellular proliferation and ACTH production in corticotroph tumor cells through a novel janus kinases-signal transducer and activator of transcription 1/nuclear factor-kappa B inhibitory signaling pathway

Interferon-gamma (IFNG) is a cytokine that exerts potent antiproliferative and tumoricidal effects in a variety of cancers. Moreover, IFNG modulates normal pituitary hormone secretion, and was shown to inhibit the expression of the ACTH precursor POMC in murine ACTH-secreting AtT-2010/21/2008 tumor cells. We have studied the functional role of IFNG on pituitary tumor cells, focusing on the involvement of IFNG in the molecular events leading to the control of POMC transcriptional repression. Herein, it is shown that IFNG inhibits AtT-20 tumor cell proliferation without inducing apoptosis. Unexpectedly, an activated janus kinases-signal transducer and activator of transcription (JAK-STAT1) cascade is required for IFNG inhibitory action on POMC promoter activity. Factor-kappa B (NF-kappaB) is necessary for the inhibitory action of IFNG on Pomc transcription, since loss of NF-kappaB activity with IkappaB super-repressor abolishes this effect. In addition, 1 and 2 IFNG receptor immunoreactivity was detected in human corticotropinoma cells. Interestingly, IFNG inhibits ACTH production from these cells in primary cell culture, without affecting basal ACTH biosynthesis in normal non-tumoral pituitary cells. In conclusion, our data show for the first time that POMC transcription can be negatively regulated by a JAK-STAT1 and NF-kappaB-dependent pathway.

Pituitary action of cytokines: focus on BMP-4 and gp130 family

The anterior pituitary can develop benign tumors of different sizes, classified as micro- and macroadenomas, frequently associated with high levels of hormone production, leading to different associated syndromes like Cushing's disease, acromegaly or prolactinomas. Much work has been done in order to understand the signaling pathways and the factors and hormones involved in the pituitary tumorigenic process. In recent years, much evidence has been collected and it is now well documented that cytokines of the gp130 family, such as interleukin-6, that use gp130 as a common signaling protein stimulate not only the proliferation but also the hormone secretion of pituitary cells. Experiments in vivo have shown that the overexpression of the gp130 receptor resulted in pituitary abnormal growth. Moreover, it has been recently described that bone morphogenetic protein-4 (BMP-4), a member of the TGF-beta family, has a stimulatory role on lactosomatotropic cells promoting the development of prolactinomas but it has an inhibitory action on the corticotropic lineage. This inhibitory action prevents Cushing's disease progression. Furthermore, BMP-4 mediates the antiproliferative action of retinoic acid in these cells. The present review highlights the most recent work about gp130 and TGF-beta cytokine families and their role in pituitary tumorigenesis.

Retinoic acid as a novel medical therapy for Cushing's disease in dogs

Cushing's disease is almost always caused by an ACTH-secreting pituitary tumor, but effective medical therapy is currently limited. Because retinoic acid has been shown to be potentially useful in decreasing corticotroph secretion and proliferation in rodent models, we have studied its action in dogs with Cushing's disease. A randomized treatment with retinoic acid (n = 22) vs. ketoconazole (n = 20) in dogs with Cushing's disease was assigned for a period of 180 d. Clinical signs, plasma ACTH and alpha-MSH, the cortisol/creatinine urine ratio, and pituitary magnetic resonance imaging were assessed and compared at different time points. We recorded a significant reduction in plasma ACTH and alpha-MSH, and also in the cortisol/creatinine urine ratio, of the dogs treated with retinoic acid. Pituitary adenoma size was also significantly reduced at the end of retinoic acid treatment. Survival time and all the clinical signs evaluated showed an improvement in the retinoic-acid-treated dogs. No adverse events or signs of hepatotoxicity were observed, suggesting that the drug is not only effective but also safe. Retinoic acid treatment controls ACTH and cortisol hyperactivity and tumor size in dogs with ACTH-secreting tumors, leading to resolution of the clinical phenotype. This study highlights the possibility of using retinoic acid as a novel therapy in the treatment of ACTH-secreting tumors in humans with Cushing's disease.

Bone morphogenetic protein-4 inhibits corticotroph tumor cells: involvement in the retinoic acid inhibitory action

The molecular mechanisms governing the pathogenesis of ACTH-secreting pituitary adenomas are still obscure. Furthermore, the pharmacological treatment of these tumors is limited. In this study, we report that bone morphogenetic protein-4 (BMP-4) is expressed in the corticotrophs of human normal adenohypophysis and its expression is reduced in corticotrophinomas obtained from Cushing's patients compared with the normal pituitary. BMP-4 treatment of AtT-20 mouse corticotrophinoma cells has an inhibitory effect on ACTH secretion and cell proliferation. AtT-20 cells stably transfected with a dominant-negative form of the BMP-4 signal cotransducer Smad-4 or the BMP-4 inhibitor noggin have increased tumorigenicity in nude mice, showing that BMP-4 has an inhibitory role on corticotroph tumorigenesis in vivo. Because the activation of the retinoic acid receptor has an inhibitory action on Cushing's disease progression, we analyzed the putative interaction of these two pathways. Indeed, retinoic acid induces both BMP-4 transcription and expression and its antiproliferative action is blocked in Smad-4dn- and noggin-transfected Att-20 cells that do not respond to BMP-4. Therefore, retinoic acid induces BMP-4, which participates in the antiproliferative effects of retinoic acid. This new mechanism is a potential target for therapeutic approaches for Cushing's disease.

New Aspects in the Diagnosis and Treatment of Cushing Disease

Cushing disease, which is caused by the excessive production of ACTH, is a rare and complex endocrine disorder that still represents a major challenge for the physician in terms of accurate diagnosis and efficient treatment. Diagnosing Cushing syndrome and its etiology is an elaborate procedure and no single test is sensitive and specific enough to provide sufficient accuracy. Therefore, an ordered cascade of tests is necessary recommended by a consensus statement in 2002. The proposed diagnostic algorithm will be summarized in the following section. In the absence of efficient drug therapy, transsphenoidal resection of the pituitary adenoma is the treatment of choice for the reduction of ACTH secretion. However, not all patients can be cured by surgery. In the present article, we examine recent studies that have investigated the therapeutic potential of new generations of drugs for the treatment of Cushing disease such as cabergoline and SOM230. The role of nuclear receptors: retinoic acid receptors and peroxisome proliferator-activated receptor-gamma as new approaches for treating pituitary tumors is also discussed.

Bone Morphogenetic Protein-4 Control of Pituitary Pathophysiology

Bone morphogenetic protein-4 (BMP-4), a member of the transforming growth factor-Beta(TGF-Beta) family, is overexpressed in different prolactinoma models and induces the development of these lineage adenomas. SMAD proteins activated by growth factors of the TGF-Beta and BMP family interact with estrogen receptors to stimulate the proliferation of prolactin and growth hormone-secreting cells. Furthermore, BMP-4 presents differential expression in normal and adenomatous corticotropes and inhibitory action on corticotropinoma cell proliferation. Moreover, BMP-4 mediates the antiproliferative action of retinoic acid in these cells. The present review highlights not only the crucial and opposite role of BMP-4 in the progression of pituitary adenomas but also that BMP-4 and retinoic acid interaction might serve as a potential new mechanism target for therapeutic approaches for Cushing disease.

New perspectives in the treatment of Cushing's syndrome

Regardless of etiology, all cases of endogenous Cushing's syndrome are due to increased production of cortisol by the adrenal gland. Most are caused by adrenocorticotrophic hormone (ACTH)-secreting pituitary adenomas. Alternatively, the glucocorticoid excess may be due to adrenal neoplasia or to ectopic ACTH-secreting tumors. Cushing's syndrome is characterized by endocrine and metabolic alterations such as truncal obesity, hypertension, weakness, amenorrhea, hyperglycemia, osteoporosis and depression. Unless treated, the disease is associated with high morbidity, and ultimately, mortality. Depending on the etiology of Cushing's syndrome two different treatment modalities are possible: reduction of pituitary ACTH production or reduction of adrenocortical cortisol secretion. In the absence of efficient drug therapy, transsphenoidal resection of the pituitary adenoma is the primary treatment of choice for the reduction of ACTH secretion. In the last years there was much progress in understanding the molecular mechanisms that control the function of the hypothalamic-pituitary-adrenal axis. Thus, new insights made it possible to identify potential drug targets for the treatment of Cushing's syndrome. The present article reviews different drug targets and therapeutic options including drugs that control the central ACTH regulation, e.g. by modulating signaling pathways and transcriptional regulation of ACTH biosynthesis, corticotrophin releasing hormone (CRH) or glucocorticoid receptor antagonists, inhibitors of glucocorticoid synthesis, ketoconazole, somatostatin and dopamine analogs. Some of these substances might be useful for the treatment of Cushing's syndrome.

Nur77 induction and activation are necessary for interleukin-1 stimulation of proopiomelanocortin in AtT-20 corticotrophs

Nur77 and Nurr1 are critical for proopiomelanocortin (POMC) regulation by corticotrophin releasing hormone (CRH) in corticotrophs. We analyze the regulation and activity of Nur77 by interleukin (IL)-1 in AtT-20 corticotrophic cells and its consequences on POMC regulation. IL-1 induces Nur77 and not Nurr1 mRNA and shows an increased transcriptional activity on the NurRE site, an effect dependent of p38 protein kinase activity. A NurRE mutation abrogates POMC promoter transcription by IL-1 and a stable AtT-20 clone overexpressing a dominant negative form of Nur77 is unresponsive to IL-1-dependent POMC induction and adrenocorticotrophin (ACTH) secretion. These results demonstrate that Nur77 is essential for POMC stimulation by IL-1 in corticotrophs.

Migratory Activity and Functional Changes of Green Fluorescent Effector Cells before and during Experimental Autoimmune Encephalomyelitis

Homing behavior and function of autoimmune CD4+ T cells in vivo was analyzed before and during EAE, using MBP-specific T cells retrovirally engineered to express the gene of green fluorescent protein. The cells migrate from parathymic lymph nodes to blood and to the spleen. Preceding disease onset, large numbers of effector cells invade the CNS, with only negligible numbers left in the periphery. In early EAE, most (>90%) infiltrating CD4+ cells were effector cells. Migratory effector cells downregulate activation markers (CD25, OX-40) but upregulate several chemokine receptors and adsorb MHC class II on their membranes. Within the CNS, the effector cells are reactivated, with upregulated proinflammatory cytokines and downmodulated T cell receptor-associated structures, presumably reflecting autoantigen recognition in situ.

Transfection of immature murine bone marrow-derived dendritic cells with the granulocyte-macrophage colony-stimulating factor gene potently enhances their in vivo antigen-presenting capacity

Ag presentation by dendritic cells (DC) is crucial for induction of primary T cell-mediated immune responses in vivo. Because DC culture from blood or bone marrow-derived progenitors is now clinically applicable, this study investigated the effectiveness of in vitro-generated murine bone marrow-derived DC (Bm-DC) for in vivo immunization protocols. Previous studies demonstrated that GM-CSF is an essential growth and differentiation factor for DC in culture and that in vivo administration of GM-CSF augments primary immune responses, which renders GM-CSF an attractive candidate to further enhance the effectiveness of DC-based immunotherapy protocols. Therefore, immature Bm-DC were transiently transfected with the GM-CSF gene and tested for differentiation, migration, and Ag-presenting capacity in vitro and in vivo. In vitro, GM-CSF gene-transfected Bm-DC were largely unaltered with regard to MHC and costimulatory molecule expression as well as alloantigen or peptide Ag-presenting capacity. When used for in vivo immunizations, however, the Ag-presenting capacity of GM-CSF gene-transfected Bm-DC was greatly enhanced compared with mock-transfected or untransfected cells, as determined by their effectiveness to induce primary immune reactions against hapten, protein Ag, and tumor Ag, respectively. Increased effectiveness in vivo correlated with the better migratory capacity of GM-CSF gene-transfected Bm-DC. These results show that GM-CSF gene transfection significantly enhances the capacity of DC to induce primary immune responses in vivo, which might also improve DC-based vaccines currently under clinical investigation.

Transfection of Immature Murine Bone Marrow-Derived Dendritic Cells with the Granulocyte-Macrophage Colony-Stimulating Factor Gene Potently Enhances Their In Vivo Antigen-Presenting Capacity

Ag presentation by dendritic cells (DC) is crucial for induction of primary T cell-mediated immune responses in vivo. Because DC culture from blood or bone marrow-derived progenitors is now clinically applicable, this study investigated the effectiveness of in vitro-generated murine bone marrow-derived DC (Bm-DC) for in vivo immunization protocols. Previous studies demonstrated that GM-CSF is an essential growth and differentiation factor for DC in culture and that in vivo administration of GM-CSF augments primary immune responses, which renders GM-CSF an attractive candidate to further enhance the effectiveness of DC-based immunotherapy protocols. Therefore, immature Bm-DC were transiently transfected with the GM-CSF gene and tested for differentiation, migration, and Ag-presenting capacity in vitro and in vivo. In vitro, GM-CSF gene-transfected Bm-DC were largely unaltered with regard to MHC and costimulatory molecule expression as well as alloantigen or peptide Ag-presenting capacity. When used for in vivo immunizations, however, the Ag-presenting capacity of GM-CSF gene-transfected Bm-DC was greatly enhanced compared with mock-transfected or untransfected cells, as determined by their effectiveness to induce primary immune reactions against hapten, protein Ag, and tumor Ag, respectively. Increased effectiveness in vivo correlated with the better migratory capacity of GM-CSF gene-transfected Bm-DC. These results show that GM-CSF gene transfection significantly enhances the capacity of DC to induce primary immune responses in vivo, which might also improve DC-based vaccines currently under clinical investigation.

TRH receptor on immune cells: in vitro and in vivo stimulation of human lymphocyte and rat splenocyte DNA synthesis by TRH

This work examined whether (1) immune cells express thyrotrophin releasing hormone (TRH) receptor mRNA and (2) TRH modulates lymphocyte activation. By Northern blot of RNA extracted from human peripheral blood mononuclear cells (PBMC) and rat splenocytes, a single TRH receptor mRNA band of about 3.8 kb (identical to that obtained from pituitary cells) was obtained, under both basal and stimulated conditions. A significant increase in DNA synthesis was observed in phytohemagglutinin-stimulated PBMC and concanavalin A (Con A) stimulated splenocytes when TRH (10(-6) M-10(-12) M) was added. After 5, 30, 60, 180 min and 24 h of TRH administration in vivo, a significant increase in the rat splenocyte proliferative response to Con A was observed. In vivo administration of anti-rat TSH antibody (1/1000) blocked the increase observed after 30 min of TRH administration on the Con A stimulated splenocyte response. TRH possess immunostimulatory functions directly via its receptor and indirectly via release of other immunostimulatory factors such as thyrotrophin.

Glucocorticoids suppress interleukin-1 receptor antagonist synthesis following induction by endotoxin

Glucocorticoids, as part of their physiological role in the control of inflammatory and immune processes, suppress the expression of IL-1 and other cytokines. We have found a dose-dependent inhibition by dexamethasone (10 nM to 10 microM) of mRNA levels of the recently cloned IL-1 receptor antagonist (IL-1ra) in endotoxin-stimulated human monocytes. At the same concentrations, both dexamethasone and cortisol inhibited the secretion of IL-1ra. These inhibitory effects were reversed by blocking glucocorticoid receptors with the specific antagonist RU 38486, but not by adding exogenous IL-1, even up to 100 ng/ml, to the monocytes. A similar inhibition of IL-1ra mRNA and protein secretion was found in monocytes obtained after dexamethasone administration in vivo. In addition, we observed parallel increases in glucocorticoid and IL-1ra levels following endotoxin administration to normal volunteers. Our results show that glucocorticoids shut down not only IL-1 but also IL-1ra expression, ruling out induction of IL-1ra as part of the glucocorticoid antiinflammatory mechanism. The control of the delicate immunoregulatory balance of the IL-1/IL-1ra system during endotoxemia underscores the physiological importance of glucocorticoids in the final control of immune responses.

Lesions of the medial septal nucleus produce a long-lasting inhibition of T lymphocyte proliferation

The influence of the central cholinergic system on the immune system was studied in Wistar rats by lesioning the medial septal nucleus. This lesion inhibited T cell proliferation of splenocytes and thymocytes induced by the mitogens concanavalin A (Con A), phytohemagglutinin (PHA) and pokeweed mitogen (PWM) up to 25 days and did not affect proliferation at 40 days after lesioning. In contrast, the response to the B cell mitogen lipopolysaccharide from E. coli (LPS) was not affected at any time. These findings suggest a regulatory role of the cholinergic medial septal nucleus on T lymphocyte proliferation.