Lipopolysaccharide directly stimulates the intrapituitary interleukin-6 production by folliculostellate cells via specific receptors and the p38alpha mitogen-activated protein kinase/nuclear factor-kappaB pathway

The role of microbial metabolites in endocrine tumorigenesis: From the mechanistic insights to potential therapeutic biomarkers

Microbial metabolites have been indicated to communicate with the host's endocrine system, regulating hormone production, immune-endocrine communications, and interactions along the gut-brain axis, eventually affecting the occurrence of endocrine cancer. Furthermore, microbiota metabolites such as short-chain fatty acids (SCFAs) have been found to affect the tumor microenvironment and boost immunity against tumors. SCFAs, including butyrate and acetate, have been demonstrated to exert anti-proliferative and anti-protective activity on pancreatic cancer cells. The employing of microbial metabolic products in conjunction with radiation and chemotherapy has shown promising outcomes in terms of reducing treatment side effects and boosting effectiveness. Certain metabolites, such as valerate and butyrate, have been made known to improve the efficiency of CAR T-cell treatment, whilst others, such as indole-derived tryptophan metabolites, have been shown to inhibit tumor immunity. This review explores the intricate interplay between microbial metabolites and endocrine tumorigenesis, spanning mechanistic insights to the discovery of potential therapeutic biomarkers.

The impact of inflammatory stress on hypothalamic kisspeptin neurons: Mechanisms underlying inflammation-associated infertility in humans and domestic animals

Inflammatory diseases attenuate reproductive functions in humans and domestic animals. Lipopolysaccharide (LPS), an endotoxin released by bacteria, is known to disrupt female reproductive functions in various inflammatory diseases. LPS administration has been used to elucidate the impact of pathophysiological activation of the immune system on reproduction. Hypothalamic kisspeptin neurons are the master regulators of mammalian reproduction, mediating direct stimulation of hypothalamic gonadotropin-releasing hormone (GnRH) release and consequent release of gonadotropins, such as luteinizing hormone (LH) and follicle-stimulating hormone from the pituitary. The discovery of kisspeptin neurons in the mammalian hypothalamus has drastically advanced our understanding of how inflammatory stress causes reproductive dysfunction in both humans and domestic animals. Inflammation-induced ovarian dysfunction could be caused, at least partly, by aberrant GnRH and LH secretion, which is regulated by kisspeptin signaling. In this review, we focus on the effects of LPS on hypothalamic kisspeptin neurons to outline the impact of inflammatory stress on neuroendocrine regulation of mammalian reproductive systems. First, we summarize the attenuation of female reproduction by LPS during inflammation and the effects of LPS on ovarian and pituitary function. Second, we outline the inhibitory effects of LPS on pulsatile- and surge-mode GnRH/LH release. Third, we discuss the LPS-responsive hypothalamic-pituitary-adrenal axis and hypothalamic neural systems in terms of the cytokine-mediated pathway and the possible direct action of LPS via its hypothalamic receptors. This article describes the impact of LPS on hypothalamic kisspeptin neurons and the possible mechanisms underlying LPS-mediated disruption of LH pulses/surge via kisspeptin neurons.

Pituitary adenomas evade apoptosis via noxa deregulation in Cushing's disease

Sporadic pituitary adenomas occur in over 10% of the population. Hormone-secreting adenomas, including those causing Cushing’s disease (CD), cause severe morbidity and early mortality. Mechanistic studies of CD are hindered by a lack of in vitro models and control normal human pituitary glands. Here, we surgically annotate adenomas and adjacent normal glands in 25 of 34 patients. Using single-cell RNA sequencing (RNA-seq) analysis of 27594 cells, we identify CD adenoma transcriptomic signatures compared with adjacent normal cells, with validation by bulk RNA-seq, DNA methylation, qRT-PCR, and immunohistochemistry. CD adenoma cells include a subpopulation of proliferating, terminally differentiated corticotrophs. In CD adenomas, we find recurrent promoter hypomethylation and transcriptional upregulation of PMAIP1 (encoding pro-apoptotic BH3-only bcl-2 protein noxa) but paradoxical noxa downregulation. Using primary CD adenoma cell cultures and a corticotroph-enriched mouse cell line, we find that selective proteasomal inhibition with bortezomib stabilizes noxa and induces apoptosis, indicating its utility as an anti-tumor agent.

Asuzu et al. perform single-cell transcriptomic profiling in Cushing’s disease (CD) adenomas and find overexpression and DNA hypomethylation of PMAIP1, which encodes the pro-apoptotic protein noxa. Noxa is degraded by the proteasome. Proteasomal inhibition rescues noxa and induces apoptosis in CD.

Molecular Mechanisms of Lipopolysaccharide (LPS) Induced Inflammation in an Immortalized Ovine Luteal Endothelial Cell Line (OLENDO)

Escherichia coli (E. coli) is the most common Gram-negative bacterium causing infection of the uterus or mammary gland and is one of the major causes of infertility in livestock. In those animals affected by E. coli driven LPS-mediated infections, fertility problems occur in part due to disrupted follicular and luteal functionality. However, the molecular mechanisms by which LPS induces inflammation, and specifically, the role of LPS in the disruption of capillary morphogenesis and endothelial barrier function remain unclear. Here, we hypothesized that LPS may lead to alterations in luteal angiogenesis and vascular function by inducing inflammatory reactions in endothelial cells. Accordingly, OLENDO cells were treated with LPS followed by evaluation of the expression of selected representative proinflammatory cytokines: NF-kB, IL6, IL8, TNFα, and ICAM 1. While TNFα was not affected by treatment with LPS, transcripts of NF-kB, IL6, and IL8 were affected in a dosage-dependent manner. Additionally, the activity of TLR2 and TLR4 was blocked, resulting in suppression of the LPS-induced expression of ICAM 1, NF-kB, IL6, and IL8. Inhibition of the PKA or MAPK/ERK pathways suppressed the LPS-stimulated expression of NF-kB, IL6, and IL8, whereas blocking the PKC pathway had the opposite effect. Furthermore, LPS-induced phosphorylation of Erk1 and Erk2 was inhibited when the TLR4 or MAPK/ERK pathways were blocked. Finally, LPS seems to induce inflammatory processes in OLENDO cells via TLR2 and TLR4, utilizing different signaling pathways.

Macrophages are activated in the rat anterior pituitary under chronic inflammatory conditions

In the anterior lobe of the pituitary gland (AP), non-endocrine cells regulate hormone secretion by endocrine cells. However, the functions of non-endocrine cells in the AP during chronic pain are largely unclear. Here, we show that macrophages, but not folliculostellate (FS) cells, were selectively increased in the AP in the complete Freund's adjuvant (CFA)-induced chronic inflammatory pain model in rats. In addition, IL-1β expression was increased in the AP, and the IL-1β-immunopositive cells were identified as macrophages. On the other hand, increased macrophage density and IL-1β expression were not detected in a neuropathic pain model induced by partial sciatic nerve ligation (PSL). Furthermore, we found c-Fos expression specifically in the somatotrophs under the chronic inflammatory pain condition. Because IL-1β promotes growth hormone (GH) synthesis and release, our results suggest that AP macrophage contributes to GH release through IL-1βduring chronic inflammatory pain.　.

Pituitary Remodeling Throughout Life: Are Resident Stem Cells Involved?

The pituitary gland has the primordial ability to dynamically adapt its cell composition to changing hormonal needs of the organism throughout life. During the first weeks after birth, an impressive growth and maturation phase is occurring in the gland during which the distinct hormonal cell populations expand. During pubertal growth and development, growth hormone (GH) levels need to peak which requires an adaptive enterprise in the GH-producing somatotrope population. At aging, pituitary function wanes which is associated with organismal decay including the somatopause in which GH levels drop. In addition to these key time points of life, the pituitary's endocrine cell landscape plastically adapts during specific (patho-)physiological conditions such as lactation (need for PRL) and stress (engagement of ACTH). Particular resilience is witnessed after physical injury in the (murine) gland, culminating in regeneration of destroyed cell populations. In many other tissues, adaptive and regenerative processes involve the local stem cells. Over the last 15 years, evidence has accumulated that the pituitary gland houses a resident stem cell compartment. Recent studies propose their involvement in at least some of the cell remodeling processes that occur in the postnatal pituitary but support is still fragmentary and not unequivocal. Many questions remain unsolved such as whether the stem cells are key players in the vivid neonatal growth phase and whether the decline in pituitary function at old age is associated with decreased stem cell fitness. Furthermore, the underlying molecular mechanisms of pituitary plasticity, in particular the stem cell-linked ones, are still largely unknown. Pituitary research heavily relies on transgenic in vivo mouse models. While having proven their value, answers to pituitary stem cell-focused questions may more diligently come from a novel powerful in vitro research model, termed organoids, which grow from pituitary stem cells and recapitulate stem cell phenotype and activation status. In this review, we describe pituitary plasticity conditions and summarize what is known on the involvement and phenotype of pituitary stem cells during these pituitary remodeling events.

Pituitary miRNAs target GHRHR splice variants to regulate GH synthesis by mediating different intracellular signalling pathways

Growth hormone (GH), whose synthesis and release are mainly regulated by intracellular signals mediated by growth hormone-releasing hormone receptor (GHRHR), is one of the major pituitary hormones and critical regulators of organism growth, metabolism, and immunoregulation. Pig GHRHR splice variants (SVs) may activate different signalling pathways via the variable C-terminal by alternative splicing, and SVs have the potential to change microRNA (miRNA) binding sites. In this study, we first confirmed the existence of pig GHRHR SVs (i.e., GHRHR, GHRHR SV1 and SV2) and demonstrated the inhibitory effects of critical pituitary miRNAs (i.e., let-7e and miR-328-5p) on GH synthesis and cell proliferation of primary pituitary cells. The SVs of GHRHR targeted by let-7e and miR-328-5p were predicted via bioinformatics analysis and verified by performing dual-luciferase reporter assays and detecting the expression of target transcripts. The differential responses of let-7e, and miR-328-5p to GH-releasing hormone and the changes in signalling pathways mediated by GHRHR suggested that let-7e and miR-328-5p were involved in GH synthesis mediated by GHRHR SVs, indicating that the two miRNAs played different roles by different ways. Finally, results showed that the protein coded by the GHRHR transcript regulated GH through the NO/NOS signalling pathway, whereas that coded by SV1 and SV2 regulated GH through the PKA/CREB signalling pathway, which was confirmed by the changes in signalling pathways after transfecting the expression vectors of GHRHR SVs to GH3 cells. To the best of our knowledge, this paper is the first to report pituitary miRNAs regulate GH synthesis by targeting the different SVs of GHRHR.

Inflammation and LPS-Binding Protein Enable the Stimulatory Effect of Endotoxin on Prolactin Secretion in the Ovine Anterior Pituitary: Ex Vivo Study

Prolactin is a hormone that plays an important role in the regulation of many physiological processes including lactation, reproduction, fat metabolism, and immune response. The secretion of prolactin could be disturbed by an immune stress commonly accompanying infection. This study was designed to determine the influence of bacterial endotoxin—lipopolysaccharide (LPS)—on prolactin gene (PRL) expression and prolactin release from the ovine anterior pituitary (AP) explants collected from saline- and LPS-treated ewes in the follicular phase. The expressions of toll-like receptor 4 (TLR4) and proinflammatory cytokines interleukin- (IL-) 1β, IL-6, and tumor necrosis factor- (TNF-) α genes were also assayed. The results of the study showed that LPS stimulates prolactin secretion and IL-6 gene expression in the AP explants, but its action on lactotrophs depends on the immunological status of animal. It was demonstrated that an important role in enhancing the effect of LPS on the pituitary in the saline-treated ewes is played by LPS-binding protein (LBP)- “adapter molecule” for LPS binding to the cell surface receptor CD14 and then to TLR4. Also, it was found that bacterial endotoxin acting on the anterior pituitary cells may enhance prolactin secretion, and this effect of LPS could be mediated by IL-6 which is known as prolactin-releasing factor. Identification of the neuroendocrine and immune interactions in the regulation of prolactin secretion could be helpful in developing newer and more effective treatments for dysfunctions connected with disorders in this hormone secretion.

Intraurethral injection with LPS: an effective experimental model of prostatic inflammation

OBJECTIVE

Chronic inflammation has been recognized as having a prominent role pathogenesis of benign prostatic hyperplasia (BPH) and cancer. It is believed that chronic inflammation induces prostatic fibromuscular growth. This correlation has been clearly illustrated by both in vivo and in vitro studies; however, current experimental models of BPH require complex surgery or hormonal treatment. Therefore, the aim of the present study was to propose a new murine model of BPH/prostatitis induced by intraurethral injection of LPS.

METHODS

Male Swiss and C57Bl/6 mice were then sacrificed 3, 7, 10, and 14 days after intraurethral injection of LPS. The prostates were quickly dissected and fixed for morphological and immunohistochemical analyses.

RESULTS

The results showed that LPS played an important role in the cell proliferation of the prostate. Histological and ultrastructural analysis showed epithelial hyperplasia, clear stromal cells, little inflammatory infiltration, and heavy bleeding. Treatment with LPS also promoted the increase of growth factor (FGF-7 and TGF-β), α-actin, and proinflammatory cytokines (IL-1, IL-6, IL-17), both in the stroma and epithelium.

CONCLUSION

According to the present findings, it can be concluded that the intraurethral administration of LPS promotes tissue remodeling, as well as stimulating the pattern of pro-inflammatory cytokines, and therefore, constitutes an effective experimental model of BPH/inflammation.

Endotoxin-Induced Inflammation Suppresses the Effect of Melatonin on the Release of LH from the Ovine Pars Tuberalis Explants-Ex Vivo Study

The secretion of the hormone melatonin reliably reflects environmental light conditions. Among numerous actions, in seasonal breeders, melatonin may regulate the secretion of the gonadotropins acting via its corresponding receptors occurring in the Pars Tuberalis (PT). However, it was previously found that the secretory activity of the pituitary may be dependent on the immune status of the animal. Therefore, this study was designed to determine the role of melatonin in the modulation of luteinizing hormone (LH) secretion from the PT explants collected from saline- and endotoxin-treated ewes in the follicular phase of the oestrous cycle. Twelve Blackhead ewes were sacrificed 3 h after injection with lipopolysaccharide (LPS; 400 ng/kg) or saline, and the PTs were collected. Each PT was cut into 4 explants, which were then divided into 4 groups: I, incubated with 'pure' medium 199; II, treated with gonadotropin-releasing hormone (GnRH) (100 pg/mL); III, treated with melatonin (10 nmol/mL); and IV, incubated with GnRH and melatonin. Melatonin reduced (p < 0.05) GnRH-induced secretion of LH only in the PT from saline-treated ewes. Explants collected from LPS-treated ewes were characterized by lower (p < 0.05) GnRH-dependent response in LH release. It was also found that inflammation reduced the gene expression of the GnRH receptor and the MT1 melatonin receptors in the PT. Therefore, it was shown that inflammation affects the melatonin action on LH secretion from the PT, which may be one of the mechanisms via which immune/inflammatory challenges disturb reproduction processes in animals.

Pituitary dendritic cells communicate immune pathogenic signals

This study reveals the presence of dendritic cells (DCs) in the pituitary gland, which play a role in communicating immune activation to the hypothalamic pituitary adrenal (HPA) axis. Using enhanced yellow fluorescent protein (eyfp) expression as a reporter for CD11c, a marker of DCs, we demonstrate anatomically the presence of CD11c/eyfp+ cells throughout the pituitary. Flow cytometric analysis shows that the predominant cellular phenotype of pituitary CD11c/eyfp+ cells resembles that of non-lymphoid DCs. In vivo and in vitro immune challenge with lipopolysaccharide (LPS) stimulates these pituitary CD11c/eyfp+ DCs, but not eyfp(neg) cells, to increase levels of pro-inflammatory cytokines, IL-6, IL-1β, and TNF-α. In vivo analysis of plasma glucocorticoid (GC) and adrenocorticotropic hormone (ACTH) levels at this early phase of the immune response to LPS suggest that pro-inflammatory cytokine production by DCs within the pituitary may activate the release of GCs from the adrenals via ACTH. Pituitary CD11c/eyfp+ cells also express annexin A1 (ANXA1), indicating a role in GC signal attenuation. In summary, our data demonstrate that a resident DC population of the pituitary gland coordinates GC release in the early phase of systemic immune activation, thereby providing an essential immune signaling sentinel for the initial shaping of the systemic immune response to LPS.

Proton receptor GPR68 expression in dendritic-cell-like S100β-positive cells of rat anterior pituitary gland: GPR68 induces interleukin-6 gene expression in extracellular acidification

S100β-positive cells, which do not express the classical pituitary hormones, appear to possess multifunctional properties and are assumed to be heterogeneous in the anterior pituitary gland. The presence of several protein markers has shown that S100β-positive cells are composed of populations such as stem/progenitor cells, epithelial cells, astrocytes and dendritic cells. Recently, we succeeded in separating S100β-positive cells into round-cell (dendritic-cell-like) and process-cell types. We also found the characteristic expression of anti-inflammatory factors (interleukin-6, Il-6) and membrane receptors (integrin β-6) in the round type. Here, we further investigate the function of the subpopulation of S100β-positive cells. Since IL-6 is also a paracrine factor that regulates hormone producing-cells, we examine whether a correlation exists among extracellular acid stress, IL-6 and hormone production by using primary cultures of anterior pituitary cells. Dendritic-cell-like S100β-positive cells notably expressed Gpr68 (proton receptor) and Il-6. Furthermore, the expression of Il-6 and proopiomelanocortin (Pomc) was up-regulated by extracellular acidification. The functional role of IL-6 and GPR68 in the gene expression of Pomc during extracellular acidification was also examined. Small interfering RNA for Il-6 up-regulated Pomc expression and that for Gpr68 reversed the down-regulation of Il-6 and up-regulated Pomc expression by extracellular acidification. Thus, S100β-positive dendritic-like cells can sense an increase in extracellular protons via GPR68 and respond by the production of IL-6 in order to suppress the up-regulation of Pomc expression.

Activation of the inflammatory transcription factor nuclear factor interleukin-6 during inflammatory and psychological stress in the brain

BACKGROUND

The transcription factor nuclear factor interleukin 6 (NF-IL6) is known to be activated by various inflammatory stimuli in the brain. Interestingly, we recently detected NF-IL6-activation within the hypothalamus-pituitary-adrenal (HPA)-axis of rats after systemic lipopolysaccharide (LPS)-injection. Thus, the aim of the present study was to investigate whether NF-IL6 is activated during either, inflammatory, or psychological stress in the rat brain.

METHODS

Rats were challenged with either the inflammatory stimulus LPS (100 μg/kg, i.p.) or exposed to a novel environment. Core body temperature (Tb) and motor activity were monitored using telemetry, animals were killed at different time points, brains and blood removed, and primary cell cultures of the anterior pituitary lobe (AL) were investigated. Analyses were performed using immunohistochemistry, RT-PCR, and cytokine-specific bioassays.

RESULTS

Stress stimulation by a novel environment increased NF-IL6-immunoreactivity (IR) in the pituitary's perivascular macrophages and hypothalamic paraventricular cells and a rise in Tb lasting approximately 2 h. LPS stimulation lead to NF-IL6-IR in several additional cell types including ACTH-IR-positive corticotrope cells in vivo and in vitro. Two other proinflammatory transcription factors, namely signal transducer and activator of transcription (STAT)3 and NFκB, were significantly activated and partially colocalized with NF-IL6-IR in cells of the AL only after LPS-stimulation, but not following psychological stress. In vitro NF-IL6-activation was associated with induction and secretion of TNFα in folliculostellate cells, which could be antagonized by the JAK-STAT-inhibitor AG490.

CONCLUSIONS

We revealed, for the first time, that NF-IL6 activation occurs not only during inflammatory LPS stimulation, but also during psychological stress, that is, a novel environment. Both stressors were associated with time-dependent activation of NF-IL6 in different cell types of the brain and the pituitary. Moreover, while NF-IL6-IR was partially linked to STAT3 and NFκB activation, TNFα production, and ACTH-IR after LPS stimulation; this was not the case after exposure to a novel environment, suggesting distinct underlying signaling pathways. Overall, NF-IL6 can be used as a broad activation marker in the brain and might be of interest for therapeutic approaches not only during inflammatory but also psychological stress.

Anterior pituitary cell networks

Both endocrine and non-endocrine cells of the pituitary gland are organized into structural and functional networks which are formed during embryonic development but which may be modified throughout life. Structural mapping of the various endocrine cell types has highlighted the existence of distinct network motifs and relationships with the vasculature which may relate to temporal differences in their output. Functional characterization of the network activity of growth hormone and prolactin cells has revealed a role for cell organization in gene regulation, the plasticity of pituitary hormone output and remarkably the ability to memorize altered demand. As such, the description of these endocrine cell networks alters the concept of the pituitary from a gland which simply responds to external regulation to that of an oscillator which may memorize information and constantly adapt its coordinated networks' responses to the flow of hypothalamic inputs.

Melatonin attenuated mediators of neuroinflammation and alpha-7 nicotinic acetylcholine receptor mRNA expression in lipopolysaccharide (LPS) stimulated rat astrocytoma cells, C6

Melatonin has been known to affect a variety of astrocytes functions in many neurological disorders but its mechanism of action on neuroinflammatory cascade and alpha-7 nicotinic acetylcholine receptor (α7-nAChR) expression are still not properly understood. Present study demonstrated that treatment of C6 cells with melatonin for 24 hours significantly decreased lipopolysaccharide (LPS) induced nitrative and oxidative stress, expressions of cyclooxigenase-2 (COX-2), inducible nitric-oxide synthase (iNOS) and glial fibrillary acidic protein (GFAP). Melatonin also modulated LPS-induced mRNA expressions of α7-nAChR and inflammatory cytokine genes. Furthermore, melatonin reversed LPS-induced changes in C/EBP homologous protein 10 (CHOP), microsomal prostaglandin E synthase-1(mPGES-1) and phosphorylated p38 mitogen activated protein kinase (P-p38). Treatment with pyrrolidine dithiocarbamate (PDTC) inhibited α7-nAChR mRNA expression in LPS-induced C6 cells. Our findings explored anti-neuroinflammatory action of melatonin, which may suggests its beneficial roles in the neuroinflammation associated disorders.

Protein kinase A enhances lipopolysaccharide-induced IL-6, IL-8, and PGE₂ production by human gingival fibroblasts

OBJECTIVE

Periodontal disease is accompanied by inflammation of the gingiva and destruction of periodontal tissues, leading to alveolar bone loss in severe clinical cases. Interleukin (IL)-6, IL-8, and the chemical mediator prostaglandin E₂ (PGE₂) are known to play important roles in inflammatory responses and tissue degradation. Recently, we reported that the protein kinase A (PKA) inhibitor H-89 suppresses lipopolysaccharide (LPS)-induced IL-8 production by human gingival fibroblasts (HGFs). In the present study, the relevance of the PKA activity and two PKA-activating drugs, aminophylline and adrenaline, to LPS-induced inflammatory cytokines (IL-6 and IL-8) and PGE₂ by HGFs were examined.

METHODS

HGFs were treated with LPS from Porphyromonas gingivalis and H-89, the cAMP analog dibutyryl cyclic AMP (dbcAMP), aminophylline, or adrenaline. After 24 h, IL-6, IL-8, and PGE₂ levels were evaluated by ELISA.

RESULTS

H-89 did not affect LPS-induced IL-6 production, but suppressed IL-8 and PGE₂ production. In contrast, dbcAMP significantly increased LPS-induced IL-6, IL-8, and PGE₂ production. Up to 10 μg/ml of aminophylline did not affect LPS-induced IL-6, IL-8, or PGE₂ production, but they were significantly increased at 100 μg/ml. Similarly, 0.01 μg/ml of adrenaline did not affect LPS-induced IL-6, IL-8, or PGE₂ production, but they were significantly increased at concentrations of 0.1 and 1 μg/ml. In the absence of LPS, H-89, dbcAMP, aminophylline, and adrenaline had no relevance to IL-6, IL-8, or PGE₂ production.

CONCLUSION

These results suggest that the PKA pathway, and also PKA-activating drugs, enhance LPS-induced IL-6, IL-8, and PGE₂ production by HGFs. However, aminophylline may not have an effect on the production of these molecules at concentrations used in clinical settings (8 to 20 μg/ml in serum). These results suggest that aminophylline does not affect inflammatory responses in periodontal disease.

Cellular and molecular specificity of pituitary gland physiology

The anterior pituitary gland has the ability to respond to complex signals derived from central and peripheral systems. Perception of these signals and their integration are mediated by cell interactions and cross-talk of multiple signaling transduction pathways and transcriptional regulatory networks that cooperate for hormone secretion, cell plasticity, and ultimately specific pituitary responses that are essential for an appropriate physiological response. We discuss the physiopathological and molecular mechanisms related to this integrative regulatory system of the anterior pituitary gland and how it contributes to modulate the gland functions and impacts on body homeostasis.

Neutralization of LPS or blockage of TLR4 signaling prevents stress-triggered fetal loss in murine pregnancy

Maternal stress can cause loss of both histocompatible (syngeneic) and histoincompatible (semiallogeneic) embryos in pregnant mice. Stress increases abortogenic Th1 cytokines and reduces levels of anti-abortogenic Th2 cytokines, progesterone levels, and T regulatory cell activity. While physiological levels of interferon-γ promote vascular remodeling at the feto-maternal interface, an overshooting Th1 cytokine response requires a Toll-like receptor (TLR)-mediated "danger signal" such as lipopolysaccharide (LPS). Interestingly, stress can enhance permeability of mucosal membranes to entry of bacterial products and promote transmucosal migration of commensal bacteria. We hypothesized that bacterial component such as LPS may provide the danger signal through which stress triggers maternal immune activation, subsequently resulting in fetal rejection. Blocking the TLR4 receptor for LPS or neutralization of LPS using bactericidal permeability increasing protein abrogate fetal loss due to sonic stress challenge in DBA/2J-mated CBA/J mice. These treatments prevented stress-triggered immune responses in the decidua, upregulated Treg cells, and reduced the frequency of mature dendritic cells in uterine-draining lymph nodes but not in the uterus. Interestingly, anti-TLR4 treatment only partly ameliorated stress-induced endocrine responses, such as increased hypothalamic corticotropin releasing hormone and vasopressin mRNA expression but not decrease of serum progesterone. Galectin-1 knock-out mice were more susceptible to stress-triggered complete implantation failure rather than fetal loss, which was also abolished by LPS neutralization. Insights provided in this paper shed new light on the mechanisms by which stress affects pregnancy outcome and introduce microbial-derived LPS as a mediator within the cascade of stress-triggered immune and endocrine events during pregnancy.

[Delirium in the intensive care unit]

In recent years delirium in the intensive care unit (ICU) has internationally become a matter of rising concern for intensive care physicians. Due to the design of highly sophisticated ventilators the practice of deep sedation is nowadays mostly obsolete. To assess a ventilated ICU patient for delirium easy to handle bedside tests have been developed which permit a psychiatric scoring. The significance of ICU delirium is equivalent to organ failure and has been proven to be an independent prognostic factor for mortality and length of ICU and hospital stay. The pathophysiology and risk factors of ICU delirium are still insufficiently understood in detail. A certain constellation of pre-existing patient-related conditions, the current diagnosis and surgical procedure and administered medication entail a higher risk for the occurrence of ICU delirium. A favored hypothesis is that an imbalance of the neurotransmitters acetylcholine and dopamine serotonin results in an unpredictable neurotransmission. Currently, the administration of neuroleptics, enforced physiotherapy, re-orientation measures and appropriate pain treatment are the basis of the therapeutic approach.

Adenosine regulates thrombomodulin and endothelial protein C receptor expression in folliculostellate cells of the pituitary gland

Adenosine stimulates the release of interleukin 6 (IL-6) and vascular endothelial growth factor from folliculostellate cells of the anterior pituitary gland indicating that such cells are also involved in the communication between the immune and endocrine systems during stress and inflammation. In order to understand the precise actions of adenosine on folliculostellate cells, DNA microarray analysis was used to determine global changes in gene expression. Hierarchical clusters revealed, of the genes that had altered expression, the majority were suppressed and many, such as B cell translocation gene 2 and cyclin-dependent kinase inhibitor 2b were related to cell cycle arrest or inhibition of proliferation. Several of the up-regulated genes were associated with cytokine signalling or membrane receptor activity. The most notable of these being IL-6, sulfiredoxin 1, endothelial protein C receptor (EPCR) and thrombomodulin (THBD) which can all play a role in controlling inflammation. The EPCR and THBD pathway is well known in anti-coagulation but also has anti-inflammatory and anti-apoptotic properties. Up-regulation of EPCR and THBD in folliculostellate cells was confirmed by qRT-PCR and western blotting analysis and their expression were also demonstrated in many of the hormone-secreting cells of the anterior pituitary gland. Our findings suggest that adenosine can stimulate expression of stress and inflammation related genes from folliculostellate cells of the anterior pituitary gland. These genes include EPCR and THBD, neither of which has been previously identified in the pituitary gland.

In vivo Angiotensin II AT1 receptor blockade selectively inhibits LPS-induced innate immune response and ACTH release in rat pituitary gland

Systemic lipopolysaccharide (LPS) administration induces an innate immune response and stimulates the hypothalamic-pituitary-adrenal axis. We studied Angiotensin II AT(1) receptor participation in the LPS effects with focus on the pituitary gland. LPS (50 microg/kg, i.p.) enhanced, 3h after administration, gene expression of pituitary CD14 and that of Angiotensin II AT(1A) receptors in pituitary and hypothalamic paraventricular nucleus (PVN); stimulated ACTH and corticosterone release; decreased pituitary CRF(1) receptor mRNA and increased all plasma and pituitary pro-inflammatory factors studied. The AT(1) receptor blocker (ARB) candesartan (1mg/kg/day, s.c. daily for 3 days before LPS) blocked pituitary and PVN AT(1) receptors, inhibited LPS-induced ACTH but not corticosterone secretion and decreased LPS-induced release of TNF-alpha, IL-1beta and IL-6 to the circulation. The ARB reduced LPS-induced pituitary gene expression of IL-6, LIF, iNOS, COX-2 and IkappaB-alpha; and prevented LPS-induced increase of nNOS/eNOS activity. The ARB did not affect LPS-induced TNF-alpha and IL-1beta gene expression, IL-6 or IL-1beta protein content or LPS-induced decrease of CRF(1) receptors. When administered alone, the ARB increased basal plasma corticosterone levels and basal PGE(2) mRNA in pituitary. Our results demonstrate that the pituitary gland is a target for systemically administered LPS. AT(1) receptor activity is necessary for the complete pituitary response to LPS and is limited to specific pro-inflammatory pathways. There is a complementary and complex influence of the PVN and circulating cytokines on the initial pituitary response to LPS. Our findings support the proposal that ARBs may be considered for the treatment of inflammatory conditions.

Etiology and site of temporal lobe epilepsy influence postictal cytokine release

Inflammatory mechanisms are involved in the pathogenesis of epilepsy. Vice versa, immune functions are regulated by the brain. We measured postictal changes in serum levels of the immuno-modulating cytokines IL-1beta, IL-6 and TNFalpha in patients with well-defined temporal lobe epilepsy (TLE) and determined modifying factors. Serum levels of IL-1beta, IL-6 and TNFalpha were quantified by ELISA at baseline as well as immediately, 1h and 24h after a complex partial (CPS) or secondary generalized tonic-clonic seizure (GTCS) during video-EEG monitoring in 25 patients suffering from temporal epilepsy. IL-6 increased by 51% immediately after the seizure (p<0.01) and remained elevated for 24h. This increase lacked in patients with hippocampal sclerosis (HS; n=16, mean increase 28%, p>0.5, vs. 112%, p<0.01 in patients without HS). IL-6 levels were higher after right-sided seizures as compared to left-sided seizures 24h after the seizure (8.7pg/mL vs. 3.4pg/mL, p<0.05). In patients taking valproate (VPA, n=9), the levels of IL-1beta were higher as compared to patients not treated with VPA. The results suggest a relationship between the cytokine system and characteristics of TLE such as side and pathology.

Intrapituitary expression and regulation of the gp130 cytokine interleukin-6 and its implication in pituitary physiology and pathophysiology

Interleukin (IL)-6, a member of the gp130 cytokine family, is sometimes designated as an "endocrine" cytokine because of its strong regulatory influence on hormone production. Systemically acting IL-6 derived from immune cells is a potent stimulator of the hypothalamus-pituitary-adrenal axis and therefore plays an important role in modulating immune-neuroendocrine interactions during inflammatory or infectious processes. However, IL-6 is also produced within the anterior pituitary by so-called folliculostellate (FS) cells and is also synthesized in and released by tumor cells in pituitary adenomas. Growth factors (e.g., transforming growth factor-beta), neuropeptides (e.g., pituitary adenylate cyclase-activating polypeptide), or hormones (e.g., glucocorticoids) regulate IL-6 production both in FS and pituitary tumor cells. Interestingly, components of the innate immune system, such as toll-like receptor 4 and nucleotide-binding oligomerization domains (NODs), are expressed in FS and pituitary tumor cells. Therefore, cell-wall components of bacteria (lipopolysaccharide, muramyl dipeptide, diamino pimelic acid) stimulate IL-6 production in normal and tumoral pituitary. The intrinsic IL-6 production by FS cells in normal anterior pituitary may participate in immune-neuroendocrine interactions during inflammatory processes. In pituitary adenomas, IL-6 stimulates hormone secretion, tumor cell proliferation, and the production of angiogenic factors, such as vascular endothelial growth factor-A, suggesting an important role of IL-6 in the pathophysiology and progression of pituitary adenomas.

Immunological tolerance-related genes in a spontaneous tolerant model of rat liver transplantation explored by suppression subtractive hybridization

Natural immunological tolerance can be induced in certain types of allogeneic liver transplantation in rats. To screen for genes associated with the induction of tolerance, suppression subtractive hybridization was performed in the rat liver transplantation model between a DA donor and PVG recipient combination where spontaneous immunological tolerance is known to occur without any immunosuppressive treatment. As a result, 112 genes were cloned from a DA liver graft that survived for 20 days in the fully allogeneic PVG recipient. After confirmation of the expression intensity using an in-house manufactured DNA array with cDNAs from the DA graft, 36 genes were classified in the highly expressed group and 26 moderately expressed group. In the first group, there were 8 immunoglobulin-related genes and 6 MHC class II-related genes, suggesting the existence of an underlying rejection response. Among those genes, an antiapoptotic gene in the p38 MAP kinase pathway, heme oxygenase gene (HO-1), and a ras cascade gene, IQ motif containing GTPase activating protein 1 (Iqgapl), retained biological significance. The results suggested that the molecular response to a liver graft tends to be antiapoptotic and to terminate the rejection response. Unfortunately, there was no gene identified that qualified as a putative immunosuppressive protein, liver suppressor factor-1 (LSF-1). The panel of genes identified in the present work will be a useful panel of candidate genes to investigate the induction of spontaneous tolerance.

Toll‐like receptors in the gonads and reproductive tract: emerging roles in reproductive physiology and pathology

Interactions between the immune system and reproductive system have important consequences for fertility and reproductive health in general. There is increasing evidence that many of the interactions between the immune and reproductive systems involve the Toll-like receptors (TLRs). While there is no doubt that TLRs are important in providing protection against infection in the reproductive tract, there is increasing evidence for the involvement of TLRs in more basic pathology and physiology of reproduction. In the female, TLRs have been implicated in critical aspects of ovarian, endometrial and placental function, as well as in ovarian cancer, pelvic inflammatory disease, intrauterine growth restriction, pre-eclampsia and preterm birth. In the male, TLRs appear to play a role in the control of testicular steroidogenesis and spermatogenesis in disease and, potentially, during normal function, as well. Recent studies also have begun to highlight the role of various TLRs in the aetiology of prostatitis and prostatic cancer. Given the nascent state of knowledge concerning this important area, it is clear that more studies are needed, which should provide valuable new insights into the biology of the TLRs and reproductive function in general.

Post-translational modification plays an essential role in the translocation of annexin A1 from the cytoplasm to the cell surface

Annexin A1 (ANXA1) has an important role in cell-cell communication in the host defense and neuroendocrine systems. In both systems, its actions are exerted extracellularly via membrane-bound receptors on adjacent sites after translocation of the protein from the cytoplasm to the cell surface of adjacent cells. This study used molecular, microscopic, and pharmacological approaches to explore the mechanisms underlying the cellular exportation of ANXA1 in TtT/GF (pituitary folliculo-stellate) cells. LPS caused serine-phosphorylation of ANXA1 (ANXA1-S27-PO4) and translocation of the phosphorylated protein to the cell membrane. The fundamental requirement of phosphorylation for membrane translocation was confirmed by immunofluorescence microscopy on cells transfected with wild-type or mutated (S27/A) ANXA1 constructs tagged with enhanced green fluorescence protein. The trafficking of ANXA1-S27-PO4 to the cell surface was dependent on PI3-kinase and MAP-kinase. It also required HMG-coenzyme A and myristoylation. The effects of HMG-coenzyme A blockade were overcome by mevalonic acid (the product of HMG-coenzyme A) and farnesyl-pyrophosphate but not by geranyl-geranylpyrophosphate or cholesterol. Together, these results suggest that serine-27 phosphorylation is essential for the translocation of ANXA1 across the cell membrane and also identify a role for isoprenyl lipids. Such lipids could target consensus sequences in ANXA1. Alternatively, they may target other proteins in the signal transduction cascade (e.g., transporters).

Comparative proteomics analysis of human pituitary adenomas: current status and future perspectives

This article will review the published research on the elucidation of the mechanisms of pituitary adenoma formation. Mass spectrometry (MS) plays a key role in those studies. Comparative proteomics has been used with the long-term goal to locate, detect, and characterize the differentially expressed proteins (DEPs) in human pituitary adenomas; to identify tumor-related and -specific biomarkers; and to clarify the basic molecular mechanisms of pituitary adenoma formation. The methodology used for comparative proteomics, the current status of human pituitary proteomics studies, and future perspectives are reviewed. The methodologies that are used in comparative proteomics studies of human pituitary adenomas are readily exportable to other different areas of cancer research.

Immune modulation of the hypothalamic-pituitary-adrenal (HPA) axis during viral infection

Compelling data has been amassed indicating that soluble factors, or cytokines, emanating from the immune system can have profound effects on the neuroendocrine system, in particular the hypothalamic- pituitary-adrenal (HPA) axis. HPA activation by cytokines (via the release of glucocorticoids), in turn, has been found to play a critical role in restraining and shaping immune responses. Thus, cytokine-HPA interactions represent a fundamental consideration regarding the maintenance of homeostasis and the development of disease during viral infection. Although reviews exist that focus on the bi-directional communication between the immune system and the HPA axis during viral infection (188,235), others have focused on the immunomodulatory effects of glucocorticoids during viral infection (14,225). This review, however, concentrates on the other side of the bi-directional loop of neuroendocrine-immune interactions, namely, the characterization of HPA axis activity during viral infection and the mechanisms employed by cytokines to stimulate glucocorticoid release.

Science review: The brain in sepsis--culprit and victim

On one side, brain dysfunction is a poorly explored complication of sepsis. On the other side, brain dysfunction may actively contribute to the pathogenesis of sepsis. The current review aimed at summarizing the current knowledge about the reciprocal interaction between the immune and central nervous systems during sepsis. The immune-brain cross talk takes part in circumventricular organs that, being free from blood-brain-barrier, interface between brain and bloodstream, in autonomic nuclei including the vagus nerve, and finally through the damaged endothelium. Recent observations have confirmed that sepsis is associated with excessive brain inflammation and neuronal apoptosis which clinical relevance remains to be explored. In parallel, damage within autonomic nervous and neuroendocrine systems may contribute to sepsis induced organ dysfunction.

Macrophage migration inhibitory factor is released from pituitary folliculo-stellate-like cells by endotoxin and dexamethasone and attenuates the steroid-induced inhibition of interleukin 6 release

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine produced by peripheral immune cells and also by endocrine cells in the anterior pituitary gland. MIF exerts its proinflammatory actions in the host-defense system by blocking the inhibitory effects of glucocorticoids on the release of other proinflammatory cytokines (e.g. IL-1, IL-6, TNFalpha). Reports that pituitary folliculo-stellate (FS) cells share many characteristics with immune cells led us to propose that these cells may serve as an additional source of MIF in the pituitary and that pituitary-derived MIF may act in an autocrine or paracrine manner to modulate endotoxin-induced cytokine release from FS cells. In the present study we addressed this hypothesis by using 1) immunohistochemistry to localize MIF in primary pituitary tissue and 2) well-characterized FS (TtT/GF), corticotroph (AtT20), and macrophage/monocyte (RAW 264.7) cell lines to explore the effects of CRH, endotoxin, and dexamethasone on MIF release and to examine the effects of MIF on IL-6 release. Our immunohistochemical study showed that MIF is expressed in abundance in S100-positive FS cells and also in other pituitary cell types. All three cell lines expressed MIF protein and responded to endotoxin (10-1000 ng/ml, 24 h) and dexamethasone (100 pM to 10 nM, 24 h) with concentration-dependent increases in MIF release. CRH (10-100 nM) also stimulated MIF release from AtT20 cells but, unlike endotoxin and dexamethasone, it had no effect on MIF release from TtT/GF or RAW cells. Recombinant MIF did not affect the basal release of IL-6 from TtT/GF cells; however, it effectively reversed the inhibitory effects of dexamethasone (1 nM) on the endotoxin-induced release of IL-6 from these cells. The results suggest that the FS cells are both a source of and a target for MIF and raise the possibility that MIF serves as a paracrine/autocrine factor in the pituitary gland that contributes to the protective neuroendocrine response to endotoxin.

Estrogens sensitize anterior pituitary gland to apoptosis

Tissue homeostasis results from a balance between cell proliferation and cell death by apoptosis. Estradiol affects proliferation as well as apoptosis in hormone-dependent tissues. In the present study, we investigated the apoptotic response of the anterior pituitary gland to lipopolysaccharide (LPS) in cycling female rats, and the influence of estradiol in this response in ovariectomized (OVX) rats. The OVX rats were chronically estrogenized with implanted Silastic capsules containing 1 mg of 17beta-estradiol (E2). Cycling or OVX and E2-treated rats were injected with LPS (250 microg/rat ip). Apoptosis was determined by the terminal deoxynucleotidyl-mediated dUTP nick-end labeling (TUNEL) method in sections of the anterior pituitary gland and spleen. Chronic estrogenization induced apoptosis in the anterior pituitary gland. Acute endotoxemia triggered apoptosis of cells in the anterior pituitary gland of E2-treated rats but not of OVX rats. No differences were observed in the apoptotic response to LPS in spleen between OVX and E2-treated rats. The apoptotic response of the anterior pituitary to LPS was variable along the estrous cycle, being higher at proestrus than at estrus or diestrus I. Approximately 75% of the apoptotic cells were identified as lactotropes by immunofluorescence. In conclusion, our results indicate that estradiol induces apoptosis and enables the proapoptotic action of LPS in the anterior pituitary gland. Also, our study suggests that estrogens may be involved in anterior pituitary cell renewal during the estrous cycle, sensitizing lactotropes to proapoptotic stimuli.

Prolonged exposure to intermittent alcohol vapors decreases the ACTH as well as hypothalamic nitric oxide and cytokine responses to endotoxemia

BACKGROUND

Prolonged exposure to alcohol blunts the response of the hypothalamic-pituitary-adrenal (HPA) axis to various stressors, including the systemic injection of a lipopolysaccharide (LPS). We previously showed that decreased synthesis of the hypothalamic peptides corticotropin-releasing factor (CRF) and vasopressin (VP) played a central role in this phenomenon. However, the mechanisms that lead to decreased hypothalamic neuronal activity have not been identified. In the present work, we tested the hypothesis that alcohol decreased signals that are elicited by LPS and that stimulate hypothalamic CRF and VP synthesis, namely nitric oxide (NO) and the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6).

METHODS

Adult male rats were exposed to intermittent (5 hr/day) alcohol vapors for 5 days. Control animals were kept in comparable chambers but not exposed to the vapors. On day 6, the animals received an injection of LPS through permanent indwelling intravenous cannulae. The dependent variables were plasma ACTH levels measured by IRMA (immunoradiometric assay); pituitary and hypothalamic TNF-alpha and IL-6 mRNA levels measured by RNase protection assay; basal activity of neuronal NO synthase measured by conversion of [14C]arginine to [14C]citrulline, the constitutive enzyme that synthesizes NO and modulates the influence of this gas on LPS-induced HPA axis activity; and basal and LPS-induced levels of citrulline (an index of NO formation) in the hypothalamus, measured by immunocytochemistry.

RESULTS

After injection with LPS, rats that were pretreated with alcohol exhibited a significantly (p < 0.01) decreased release of ACTH, compared with controls. There was no difference in basal NO synthase activity or hypothalamic citrulline levels. In contrast, LPS-induced hypothalamic citrulline levels were significantly (p < 0.01) lower in alcohol-exposed rats, as were pituitary TNF-alpha and IL-6 transcripts. In the hypothalamus, the TNF-alpha but not IL-6 response to LPS was also reduced.

CONCLUSIONS

These results indicate that prolonged exposure to alcohol decreases the ACTH, hypothalamic NO and TNF-alpha, and pituitary TNF-alpha and IL-6 responses to LPS. This suggests that altered NO and proinflammatory cytokine levels in the brain may modulate the inhibitory influence exerted by alcohol on the HPA axis response to endotoxemia.

Expression of novel neurotrophin-1/B-cell stimulating factor-3 (NNT-1/BSF-3) in murine pituitary folliculostellate TtT/GF cells: pituitary adenylate cyclase-activating polypeptide and vasoactive intestinal peptide-induced stimulation of NNT-1/BSF-3 is mediated by protein kinase A, protein kinase C, and extracellular-signal-regulated kinase1/2 pathways

Novel neurotrophin-1/B cell stimulating factor-3 (NNT-1/BSF-3) is a gp130 cytokine potently stimulating corticotroph proopiomelanocortin gene expression and ACTH secretion by a Janus kinase-signal transducer and activator of transcription (JAK-STAT)-dependent mechanism. In the current study, we examined the regulation of NNT-1/BSF-3 mRNA expression in murine pituitary folliculostellate TtT/GF cells using Northern blot technique. A 5- to 9-fold and a 4- to 7-fold induction in NNT-1/BSF-3 mRNA expression was observed between 2 and 6 h stimulation with the protein kinase C (PKC) stimulus phorbol-12-myristate-13-acetate (100 nm) and the protein kinase A (PKA) stimulus Bu(2)cAMP (5 mm), respectively. Pituitary adenylate cyclase-activating polypeptide (PACAP-38, 50 nm) and vasoactive intestinal peptide (VIP, 50 nm) also stimulated NNT-1/BSF-3 mRNA expression 5- to 9-fold between 2 and 6 h. Preincubation with PKC and PKA inhibitors such as H-7 (20 microm), GF109203X (50 microm), and H-89 (50 microm) decreased the stimulatory effects of PACAP and VIP. Both PACAP-38 and VIP also rapidly induced ERK1/2 phosphorylation and their stimulatory effect on NNT-1/BSF-3 mRNA expression was reduced by the MAPK kinase/ERK kinase (MEK) inhibitor U0126 (10 microm). Dexamethasone (10(-7) m) was a potent inhibitor of phorbol-12-myristate-13-acetate-induced NNT-1/BSF-3 expression. RT-PCR analysis demonstrated TtT/GF cells to express the short and the hop variant but not the hip variant of the PACAP-1 receptor (PAC1-R). In addition, TtT/GF cells express the VIP/PACAP-2 receptor (VPAC2-R). In summary, NNT-1/BSF-3 is expressed in pituitary folliculostellate TtT/GF cells and induced by PKC-, PKA-, and ERK1/2-dependent mechanisms. The novel gp130 cytokine NNT-1/BSF-3 derived from folliculostellate cells might act as a paracrine neuroimmunoendocrine modulator of pituitary corticotroph function.

Adenosine-induced IL-6 expression in pituitary folliculostellate cells is mediated via A2b adenosine receptors coupled to PKC and p38 MAPK

Activation of adenosine receptors in folliculostellate (FS) cells of the pituitary gland leads to the secretion of IL-6 and vascular endothelial growth factor (VEGF). We investigated the action of adenosine A2 receptor agonists on IL-6 and VEGF secretion in two murine FS cell lines (TtT/GF and Tpit/F1), and demonstrated a rank order of potency, 5'-N-ethylcarboxamidoadenosine (NECA)>2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine>adenosine, suggesting mediation via the A2b receptor. NECA-mediated IL-6 release was inhibited by the PLC inhibitor 1-[6-((17beta-3-methoxyestra-1,3,5(10)-tiene-17-yl)amino)hexyl]-1H-pyrrole-2,5-dione, the PI3 kinase inhibitor wortmannin and the PKC inhibitors bisindolylmaleimide 1 and bisindolymaleimide X1 HCl (Ro-32-0432). NECA-mediated IL-6 release was attenuated (<50%) by the extracellular signal-regulated kinase MAPK inhibitor 2'-amino-3'-methoxyflavone, and completely (>95%) inhibited by the p38 MAPK inhibitor 4-(4-fluorophenyl)-2-(4-methylsulphinylphenyl)-5-(4-pyridyl)1H-imidazole. NECA stimulates p38 MAPK phosphorylation that is inhibited by Ro-32-0432 but not by wortmannin. Dexamethasone inhibits NECA-stimulated IL-6 and VEGF secretion. These findings indicate that adenosine can stimulate IL-6 secretion in FS cells via the A2b receptor coupled principally to PLC/PKC and p38 MAPK; such an action may be important in the modulation of inflammatory response processes in the pituitary gland.

Dexamethasone induces rapid serine-phosphorylation and membrane translocation of annexin 1 in a human folliculostellate cell line via a novel nongenomic mechanism involving the glucocorticoid receptor, protein kinase C, phosphatidylinositol 3-kinase, and mitogen-activated protein kinase

Our recent studies on rat pituitary tissue suggest that the annexin 1 (ANXA1)-dependent inhibitory actions of glucocorticoids on ACTH secretion are effected via a paracrine mechanism that involves protein kinase C (PKC)-dependent translocation of a serine-phosphorylated species of ANXA1 (Ser-P-ANXA1) to the plasma membrane of the nonsecretory folliculostellate cells. In the present study, we have used a human folliculostellate cell line (PDFS) to explore the signaling mechanisms that cause the translocation of Ser-P-ANXA1 to the membrane together with Western blot analysis and flow cytometry to detect the phosphorylated protein. Exposure of PDFS cells to dexamethasone caused time-dependent increases in the expression of ANXA1 mRNA and protein, which were first detected within 2 h of steroid contact. This genomic response was preceded by the appearance within 30 min of substantially increased amounts of Ser-P-ANXA1 and by translocation of the phosphorylated protein to the cell surface. The prompt membrane translocation of Ser-P-ANXA1 provoked by dexamethasone was inhibited by the glucocorticoid receptor, antagonist, mifepristone, but not by actinomycin D or cycloheximide, which effectively inhibit mRNA and protein synthesis respectively in our preparation. It was also inhibited by a nonselective PKC inhibitor (PKC(9-31)), by a selective inhibitor of Ca(2+)-dependent PKCs (Go 6976) and by annexin 5 (which sequesters PKC in other systems). In addition, blockade of phosphatidylinositiol 3-kinase (wortmannin) or MAPK pathways with PD 98059 or UO 126 (selective for MAPK kinse 1 and 2) prevented the steroid-induced translocation of Ser-P-ANXA1 to the cell surface. These results suggest that glucocorticoids induce rapid serine phosphorylation and membrane translocation of ANXA1 via a novel nongenomic, glucocorticoid receptor-dependent mechanism that requires MAPK, phosphatidylinositiol 3-kinase, and Ca(2+)-dependent PKC pathways.

NF kappa B activation in mouse pituitary: comparison of response to interleukin-1 beta and lipopolysaccharide

The mouse anterior pituitary contains both types of interleukin (IL)-1 receptors, IL-1 receptor type I (IL-1RI) and IL-1 receptor type II (IL-1RII). These receptors are expressed mainly on somatotroph cells. In the present study, the ability of the mouse pituitary to respond in vivo to IL-1 or to lipopolysaccharide (LPS) was demonstrated by measuring, with an electrophoretic mobility shift assay, the presence of an active NF kappa B complex in cell nuclei from pituitaries of mice injected intraperitoneally with recombinant rat-IL-1 beta or LPS. Using immunohistochemistry with an antibody directed against the p65 NF kappa B subunit, a rapid and transient NF kappa B response to LPS was observed. This response was present predominantly in the nuclei of glial fibrillary acidic protein (GFAP)-positive cells and F4/80-labelled cells of the posterior and the anterior pituitary 15 min after stimulation and became faint after 2 h. In comparison, the early and strong NF kappa B response to IL-1 beta treatment was localized into somatotroph cells, GFAP positive cells and F4/80-labelled cells of the posterior and anterior pituitary. Activation of NF kappa B in response to IL-1 beta was no longer apparent in IL-1RI knockout mice, confirming that this receptor is essential for the transduction of IL-1 signal in the pituitary, but remained after LPS treatment. In addition, we investigated the effect of IL-1 on target genes by measuring the mRNA and proteins synthesis of growth hormone (GH), IL-6 and IL-1ra in the pituitary and the plasma. IL-1 beta was shown to induce a rapid and strong synthesis of IL-6 and IL-1ra in the pituitary but failed to regulate GH contents or release. These data suggest that the pituitary is able to respond to a systemic infection via cytokine-mediated responses transduced by IL-1.

Rat anterior pituitary folliculostellate cells are targets of interleukin-1beta and a major source of intrapituitary follistatin

Folliculostellate cells of the anterior pituitary are postulated to be an important source of factors, such as follistatin, that regulate pituitary function by intercellular communication. To gain further insight into the function of this cell type, folliculostellate cells were enriched from cultured rat anterior pituitary cells, and an immortalized cell line designated FS/D1h was established and characterized. These FS/D1h cells express S100 immunoreactivity and produce IL-6 but not pituitary hormones such as GH, ACTH, FSH, and LH. Importantly, FS/D1h cells express large amounts of follistatin mRNA and secrete the protein, as quantified indirectly by the amount of [(125)I]activin A immunoprecipitated with a follistatin antiserum. The FS/D1h cells also express alpha, betaA, and betaB inhibin/activin subunit mRNAs, but whether they produce the corresponding activins and inhibins has not been determined. The response of FS/D1h cells to agents thought to modulate folliculostellate cell function was evaluated. IL-1beta (0.005-5 nM) stimulated the secretion of follistatin and increased mRNA expression. In parallel, IL-6 secretion was stimulated. Dexamethasone, pituitary adenylate cyclase-activating polypeptide(1-27), and lipopolysaccharide but not testosterone, 12-O-tetradecanoylphorbol-13-acetate, or forskolin also increased follistatin secretion. Surprisingly, activin had no effect on follistatin mRNA levels, despite the fact that FS/D1h cells express ActRII, ActRIIB, and ALK-4 (ActRIB). Activin, on the other hand, induced Smad7 mRNA accumulation and exerted an antiproliferative effect on FS/D1h cells. Altogether, these observations support the possibility that follistatin originating from folliculostellate cells participates in mediating the effects of IL-1beta, glucocorticoids, and other agents on the response of pituitary cells to activins.

Quercetin suppresses proinflammatory cytokines production through MAP kinases andNF-kappaB pathway in lipopolysaccharide-stimulated macrophage

Quercetin is a flavonoid molecule ubiquitous in nature and functions as an anti-oxidant and anti-inflammatory agent with little toxicity in vivo and in vitro. Dose- and time-dependent effect of quercetin has been investigated on proinflammatory cytokine expression and NO production, focusing on its effects on the MAP kinases and the NF-kappaB signal transduction pathways in LPS-stimulated RAW 264.7 cells by using RT-PCR and immunoblotting. Quercetin strongly reduced activation of phosphorylated ERK kinase and p38 MAP kinase but not JNK MAP kinase by LPS treatment. In addition, quercetin treatment inhibited NF-kappaB activation through stabilization of the NF-kappaB/IkappaB complex and IkappaB degradation and proinflammatory cytokines and NO/iNOS expression. Quercetin may exert its anti-inflammatory and immunomodulatory properties in the effect molecules such as proinflammatory cytokines and NO/iNOS by suppressing the activation of ERK and p38 MAP kinase, and NF-kappaB/IkappaB signal transduction pathways.