Interleukin-6 and ACTH act synergistically to stimulate the release of corticosterone from adrenal gland cells

Ketogenic diet promotes tumor ferroptosis but induces relative corticosterone deficiency that accelerates cachexia

Glucose dependency of cancer cells can be targeted with a high-fat, low-carbohydrate ketogenic diet (KD). However, in IL-6-producing cancers, suppression of the hepatic ketogenic potential hinders the utilization of KD as energy for the organism. In IL-6-associated murine models of cancer cachexia, we describe delayed tumor growth but accelerated cachexia onset and shortened survival in mice fed KD. Mechanistically, this uncoupling is a consequence of the biochemical interaction of two NADPH-dependent pathways. Within the tumor, increased lipid peroxidation and, consequently, saturation of the glutathione (GSH) system lead to the ferroptotic death of cancer cells. Systemically, redox imbalance and NADPH depletion impair corticosterone biosynthesis. Administration of dexamethasone, a potent glucocorticoid, increases food intake, normalizes glucose levels and utilization of nutritional substrates, delays cachexia onset, and extends the survival of tumor-bearing mice fed KD while preserving reduced tumor growth. Our study emphasizes the need to investigate the effects of systemic interventions on both the tumor and the host to accurately assess therapeutic potential. These findings may be relevant to clinical research efforts that investigate nutritional interventions such as KD in patients with cancer.

Ketogenic diet promotes tumor ferroptosis but induces relative corticosterone deficiency that accelerates cachexia

The dependency of cancer cells on glucose can be targeted with high-fat low-carbohydrate ketogenic diet (KD). However, hepatic ketogenesis is suppressed in IL-6 producing cancers, which prevents the utilization of this nutrient source as energy for the organism. In two IL-6 associated murine models of cancer cachexia we describe delayed tumor growth but accelerated onset of cancer cachexia and shortened survival when mice are fed KD. Mechanistically, we find this uncoupling is a consequence of the biochemical interaction of two simultaneously occurring NADPH-dependent pathways. Within the tumor, increased production of lipid peroxidation products (LPPs) and, consequently, saturation of the glutathione (GSH) system leads to ferroptotic death of cancer cells. Systemically, redox imbalance and NADPH depletion impairs the biosynthesis of corticosterone, the main regulator of metabolic stress, in the adrenal glands. Administration of dexamethasone, a potent glucocorticoid, improves food intake, normalizes glucose homeostasis and utilization of nutritional substrates, delays onset of cancer cachexia and extends survival of tumor-bearing mice fed KD, while preserving reduced tumor growth. Our study highlights that the outcome of systemic interventions cannot necessarily be extrapolated from the effect on the tumor alone, but that they have to be investigated for anti-cancer and host effects. These findings may be relevant to clinical research efforts that investigate nutritional interventions such as KD in patients with cancer.

The etiology of poststroke-depression: a hypothesis involving HPA axis

Approximately, one in three ischemic stroke survivors suffered from depression, namely, post-stroke depression (PSD). PSD affects functional rehabilitation and may lead to poor quality of life of patients. There are numerous explanations about the etiologies of PSD. Here, we speculated that PSD are likely to be the result of specific changes in brain pathology. We hypothesized that the stroke-induced hyperactivity of hypothalamic-pituitary-adrenal (HPA) axis plays an important role in PSD. Stroke initiates a complex sequence of events in neuroendocrine system including HPA axis. The HPA axis is involved in the pathophysiology of depression, especially, the overactivity of the HPA axis occurs in major depressive disorder. This review summarizes the possible etiologies of PSD, focusing on the stroke-induced activation of HPA axis, mainly including the stress followed by severe brain damage and the proinflammatory cytokines release. The role of hyperactive of HPA axis in PSD was discussed in detail, which includes the role of high level corticotropin-releasing hormone in PSD, the effects of glucocorticoids on the alterations in specific brain structures, the expression of enzymes, excitotoxicity, the change in intestinal permeability, and the activation of microglia. The relationship between neuroendocrine regulation and inflammation was also described. Finally, the therapy of PSD by regulating HPA axis, neuroendocrine, and immunity was discussed briefly. Nevertheless, the change of HPA axis and the occurring of PSD maybe interact and promote on each other, and future investigations should explore this hypothesis in more depth.

Interleukin-6 response to insulin-induced hypoglycemia is associated with hypothalamic-pituitary-adrenal axis activation

Increased plasma levels of interleukin-6 (IL-6) in response to acute hypoglycemia have been well documented. Aiming to study the interaction between IL-6 and counter-regulatory hormones during hypoglycemic stress we conducted an exploratory single center study involving 26 adult patients undergoing insulin tolerance test. Insulin-induced hypoglycemia elicited a significant dynamic response of IL-6, adrenaline, noradrenaline, GH, prolactin, ACTH and serum and salivary cortisol (P < 0.001 for all variables). Patients with insufficient HPA axis response had lower hypoglycemia-induced IL-6 increase (median: 0.88 pg/mL) compared with individuals with intact HPA axis response (2.03 pg/mL, P = 0.007). IL-6 maximal increase correlated with the maximal increase of serum cortisol (rs = 0.48; P = 0.013), salivary cortisol (rs = 0.66; P = 0.012), plasma ACTH (rs = 0.48; P = 0.013) and with the increase in procedure-related symptoms of anxiety and hypoglycemia (rs = 0.57; P = 0.003). In conclusion, hypoglycemic stress-induced IL-6 increase is associated with activation of the HPA axis, suggesting that IL-6 response to hypoglycemic stress may be regarded as part of the counter-regulatory response, possibly contributing to the maintenance of glucose homeostasis.

Recent Advances in Electrochemical and Optical Biosensors Designed for Detection of Interleukin 6

Interleukin 6 (IL-6), being a major component of homeostasis, immunomodulation, and hematopoiesis, manifests multiple pathological conditions when upregulated in response to viral, microbial, carcinogenic, or autoimmune stimuli. High fidelity immunosensors offer real-time monitoring of IL-6 and facilitate early prognosis of life-threatening diseases. Different approaches to augment robustness and enhance overall performance of biosensors have been demonstrated over the past few years. Electrochemical- and fluorescence-based detection methods with integrated electronics have been subjects of intensive research due to their ability to offer a better signal-to-noise ratio, high specificity, ultra-sensitivity, and wide dynamic range. In this review, the pleiotropic role of IL-6 and its clinical significance is discussed in detail, followed by detection schemes devised so far for their quantitative analysis. A critical review on underlying signal amplification strategies and performance of electrochemical and optical biosensors is presented. In conclusion, we discuss the reliability and feasibility of the proposed detection technologies for commercial applications.

Grading Distress of Different Animal Models for Gastrointestinal Diseases Based on Plasma Corticosterone Kinetics

Simple Summary

Animal welfare is an important aspect of biomedical research. Many regulations have been implemented to combine high quality of research with minimal harm to laboratory animals. These guidelines also demand a prospective severity assessment of each animal model. A comparison of distress between animal models could allow realistic harm and benefit analysis and an appropriate use of refinement methods. However, studies comparing distress between different animal models are still rare. One good parameter for analyzing distress is the concentration of the stress hormone corticosterone in the blood. Therefore, we compared the corticosterone kinetics of distinct gastrointestinal animal models. The aim of this study was to evaluate which parameter the highest corticosterone concentration or the duration of increased stress hormone level could be used to quantify distress. We observed a significant increase of corticosterone 30 min after stress induction in all animal models. However, the corticosterone kinetics differed between the distinct interventions. Both the absolute value and the duration of increased corticosterone level correlated directly with an assessed distress score. We conclude that both variables of corticosterone kinetics are valid parameters to compare distress between animal models.

Abstract

Comparative studies for evaluating distress in established animal models are still rare. However, this issue is becoming more important as a consequence of worldwide appreciation of animal welfare. One good parameter for evaluating distress is the quantification of corticosterone. We hypothesized that not just the absolute value but also the duration of increased corticosterone concentration in the blood is an important aspect for evaluating animal distress. Therefore, we analyzed plasma corticosterone concentrations 30, 60, 120, and 240 min after induction of pancreatitis by cerulein, liver damage by carbon tetrachloride, liver damage by bile duct ligation, and after orthotopic injection of pancreatic cancer cells. We also evaluated corticosterone kinetics after injection of distinct carrier substances. Compared to phosphate buffered saline, dimethyl sulfoxide leads to dose-dependent higher and longer-lasting circulating corticosterone concentrations. In all disease models, we observed significantly increased corticosterone concentration 30 min after stress induction. However, the corticosterone kinetics differed among the animal models. Both the absolute value of corticosterone concentration and the duration correlated positively with the quantification of animal distress by a score sheet. This suggests that both variables of corticosterone kinetics might provide a solid basis for comparing and grading distress of different animal models.

Developmental Trajectories of Early Life Stress and Trauma: A Narrative Review on Neurobiological Aspects Beyond Stress System Dysregulation

Early life stressors display a high universal prevalence and constitute a major public health problem. Prolonged psychoneurobiological alterations as sequelae of early life stress (ELS) could represent a developmental risk factor and mediate risk for disease, leading to higher physical and mental morbidity rates in later life. ELS could exert a programming effect on sensitive neuronal brain networks related to the stress response during critical periods of development and thus lead to enduring hyper- or hypo-activation of the stress system and altered glucocorticoid signaling. In addition, alterations in emotional and autonomic reactivity, circadian rhythm disruption, functional and structural changes in the brain, as well as immune and metabolic dysregulation have been lately identified as important risk factors for a chronically impaired homeostatic balance after ELS. Furthermore, human genetic background and epigenetic modifications through stress-related gene expression could interact with these alterations and explain inter-individual variation in vulnerability or resilience to stress. This narrative review presents relevant evidence from mainly human research on the ten most acknowledged neurobiological allostatic pathways exerting enduring adverse effects of ELS even decades later (hypothalamic-pituitary-adrenal axis, autonomic nervous system, immune system and inflammation, oxidative stress, cardiovascular system, gut microbiome, sleep and circadian system, genetics, epigenetics, structural, and functional brain correlates). Although most findings back a causal relation between ELS and psychobiological maladjustment in later life, the precise developmental trajectories and their temporal coincidence has not been elucidated as yet. Future studies should prospectively investigate putative mediators and their temporal sequence, while considering the potentially delayed time-frame for their phenotypical expression. Better screening strategies for ELS are needed for a better individual prevention and treatment.

Mechanisms of Mitochondrial Redox Signaling in Psychosocial Stress-Responsive Systems: New Insights into an Old Story

SIGNIFICANCE

Psychosocial stress is associated with alterations in serum glucocorticoids and cytokines, such as interleukin-6 (IL-6) and IL-1β, which functionally interact. However, the molecular mechanisms and physiological relationship between the two systems within the context of stress exposure are not well characterized. Recent Advances: Extracellular IL-6, which stimulates the release of cortisol from the zona fasciculata of the adrenal cortex, mediates its intracellular effects by tyrosine phosphorylation of the transcription factor signal transducer and activator of transcription 3 (STAT3). Mitochondrial electron transfer reactions are involved in both STAT3-driven ATP production in oxidative respiration and adrenocortical steroid biosynthesis.

CRITICAL ISSUES

The role of STAT3 in oxidative respiration and steroidogenesis suggests that it integrates both nuclear and mitochondrial actions, thereby preserving main steps of glucocorticoid biosynthesis in the adrenal gland under psychosocial stress. This review discusses the notion that these two pathways are together simultaneously involved in protection against chronic stressors.

FUTURE DIRECTIONS

Linking the function of cytokines and main components of the hypothalamic-pituitary-adrenal (HPA) axis to molecular mechanisms of mitochondrial redox signaling will be essential for a better understanding of the relevant stress-responsive systems engaged in stress vulnerability. Antioxid. Redox Signal. 28, 760-772.

Curcumin suppresses inflammatory cytokines and heat shock protein 70 release and improves metabolic parameters during experimental sepsis

CONTEXT

Curcumin has been reported to have anti-inflammatory, antioxidant and hypoglycaemic properties, besides reducing mortality in sepsis.

OBJECTIVE

This study evaluates the biological activities of a curcumin dispersion formulated by spray-drying in experimental sepsis.

MATERIALS AND METHODS

Male Wistar rats were subjected to sepsis by caecal ligation and puncture (CLP), controls were sham operated. The animals were treated with curcumin dispersion (100 mg/kg, p.o.) or water for 7 days prior to CLP and at 2 h after surgery. One group was used to analyze curcumin absorption through HPLC; another had the survival rate assessed during 48 h; and from a third group, blood was collected by decapitation to analyze metabolic and inflammatory parameters.

RESULTS

The plasma curcumin levels reached 2.5 ng/mL at 4 h, dropped significantly (p < 0.001) at 6 h (1.2 ng/mL), and were undetectable at 24 h in both groups. Curcumin temporarily increased the survival rate of the septic rats by 20%. Moreover, it attenuated glycaemia (p < 0.05) and volemia (p < 0.05) alterations typically observed during sepsis, and decreased the levels of the proinflammatory cytokines IL-1β and IL-6 in plasma (p < 0.001) and peritoneal lavage fluid (p < 0.05) of septic rats. Serum HSP70 levels were decreased (p < 0.01) at 24 h after CLP.

DISCUSSION AND CONCLUSION

Our results show that the curcumin dispersion dose employed was not detrimental to the septic rats. In fact, it temporarily increased their survival rate, improved important metabolic parameters, reduced proinflammatory cytokines and HSP70 production.

Interleukin-6 increases the expression of key proteins associated with steroidogenesis in human NCI-H295R adrenocortical cells

Mechanisms of interleukin-6 (IL-6)-induced cortisol release (CR) were investigated by exposing H295R cells to IL-6 and determining mRNA/protein expression (PCR/western blots) for steroidogenic enzymes (SE), steroidogenic acute regulatory protein (StAR), steroidogenic factor-1 (SF-1) (enhances SE/StAR expression), activator protein 1 (AP-1) (regulates SE/StAR expression) and adrenal hypoplasia congenita-like protein (DAX-1) (inhibits SE/StAR expression). Promoter activity of StAR (SPA) was measured by a luciferase-coupled promoter. Cortisol release was increased by 10ng/mL IL-6 (24h P<0.01). Proteins/mRNAs (StAR, cholesterol side chain cleavage enzyme, SF-1, AP-1) and SPA were increased by IL-6 (60min 1-50ng/mL IL-6; 5ng/mL IL-6 30-120min P<0.05). Four other SE proteins/mRNAs were also increased by 10ng/mL IL-6 (60min P<0.01). Protein/mRNA for DAX-1 was decreased by IL-6 (60min 1-50ng/mL IL-6; 5ng/mL IL-6 30-120min P<0.01). Phosphorylation of Janus kinase (JAK) and signal transducer and activator of transcription (STAT) was increased by IL-6 (JAK2 60min 1-50ng/mL IL-6; 10ng/mL IL-6 5-60min P<0.05; STAT1 and STAT3 60min 10ng/mL IL-6 P<0.01). Inhibition of JAK/STAT with AG490 (10μM) or piceatannol (50μM) blocked (P<0.01 10ng/mL IL-6vs. IL-6 plus AG490 or piceatannol) IL-6-induced increases in SPA and StAR mRNA. In summary, IL-6-induced CR may be facilitated by increased StAR and SE mediated by increased SF-1 and AP-1, decreased DAX-1, and increased phosphorylation of JAK/STAT.

Interleukin 6 increases the in vitro expression of key proteins associated with steroidogenesis in the bovine adrenal zona fasciculata

In this study, the in vitro effects of interleukin 6 (IL-6) on the messenger RNAs (mRNAs) and proteins for key steroidogenic factors in the bovine adrenal zona fasciculata (ZF) were determined. Bovine adrenal glands were obtained from an abattoir, and the ZF was isolated. Strips of ZF were then exposed to different concentration of murine IL-6 and/or adrenocorticotropic hormone (ACTH) for various intervals, the protein and mRNA extracted, and the mRNA and protein expression determined by real-time polymerase chain reaction and Western blots. Exposure (1 h) to IL-6 increased in a concentration-dependent manner (10-pg IL-6/mL, P < 0.05 vs control; 100-pg IL-6/mL, P < 0.01 vs control) the relative expression of the mRNAs and proteins for steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme (P450scc), 3β hydroxysteroid dehydrogenase type 2 (3β HSD), 17α-hydroxylase/17,20-lyase/17,20-desmolase (P450 17OH), steroid 21-hydroxylase (P450 21OH), steroid 11-β-hydroxylase type 1 (P450 11βOH), and steroidogenic factor 1 (SF-1), a nuclear factor that increases StAR and steroidogenic enzymes (SEs) expression. Similarly, IL-6 (10 pg/mL) increased the relative expression of proteins and mRNAs for StAR, P450scc, 3β HSD, P450 17OH, P450 21 OH, P450 11βOH, and SF-1 in a time-dependent manner (30 min, P < 0.05 vs control; 60, 120, and 240 min, P < 0.01 vs control). In contrast, IL-6 decreased in a concentration-dependent (P < 0.01 vs control for 1, 10, and 100 pg IL-6/mL) and time-dependent (P < 0.05 vs control for 30, 60,120, and 240 min of 10 pg IL-6/mL) manner the relative expression of the mRNA and protein for adrenal hypoplasia congenita-like protein (DAX-1), a nuclear factor that decreases expression of StAR and SEs. Incubation (1 h) of ZF with 100-nM ACTH increased (P < 0.05 vs control) the relative expression of StAR, P450scc, 3β HSD, P450 17OH, P450 21OH, P450 11βOH, and SF-1 and decreased (P < 0.01 vs control) the relative expression of DAX-1. Murine IL-6 (10 pg/mL) augmented (P < 0.05 vs ACTH) both the stimulatory and inhibitory effects of ACTH. Bovine IL-6 (100 pg/mL, 1-h incubation) also increased (P < 0.01 vs control) the relative expression of the proteins for StAR, P450scc, and SF-1 and decreased (P < 0.01 vs control) the relative expression of DAX-1. In summary, IL-6 increased ZF expression of StAR and 5 SEs, which may be mediated in part by decreasing DAX-1 expression and increasing SF-1 expression.

Hormonal control of T-cell development in health and disease

The physiology of the thymus, the primary lymphoid organ in which T cells are generated, is controlled by hormones. Data from animal models indicate that several peptide and nonpeptide hormones act pleiotropically within the thymus to modulate the proliferation, differentiation, migration and death by apoptosis of developing thymocytes. For example, growth hormone and prolactin can enhance thymocyte proliferation and migration, whereas glucocorticoids lead to the apoptosis of these developing cells. The thymus undergoes progressive age-dependent atrophy with a loss of cells being generated and exported, therefore, hormone-based therapies are being developed as an alternative strategy to rejuvenate the organ, as well as to augment thymocyte proliferation and the export of mature T cells to peripheral lymphoid organs. Some hormones (such as growth hormone and progonadoliberin-1) are also being used as therapeutic agents to treat immunodeficiency disorders associated with thymic atrophy, such as HIV infection. In this Review, we discuss the accumulating data that shows the thymus gland is under complex and multifaceted hormonal control that affects the process of T-cell development in health and disease.

A review on role of psychological factors in the etiopathogenesis of Pandu Roga with reference to iron deficiency anemia

“Pandu” Roga is a disease entity described in Ayurveda which has clinical features similar to that of various types of anemia, in which there develops a pale-yellow discoloration on the skin. Besides the various etiological factors, Acharya Charaka has specially described some psychological causative factors among which Chinta (excessive worry), Bhaya (fear) and Shoka (grief) are three main factors, which play an important role in the pathogenesis of Pandu Roga. This paper aims to explore the scientific explanations for the above stated factors in the causation of Pandu Roga (anemia). Hence, a thorough search was made on the internet using the keywords anemia, psychological stress, anger, fear and some scientific studies were found on the concerned topic. It reveal that these factors disturb the process of iron distribution within the body and affects the process of erythropoiesis causing iron deficiency anemia.

Interleukin-6 inhibits adrenal androgen release from bovine adrenal zona reticularis cells by inhibiting the expression of steroidogenic proteins

Interleukin-6 (IL-6) is secreted by adrenocortical cells and modifies cortisol secretion. In this study, the effects of IL-6 on adrenal androgen release were investigated. The zona reticularis (ZR) was generally isolated from bovine adrenal glands by dissection. In select experiments, the intact adrenal cortex (ie, all 3 adrenocortical zones) was dissected from the adrenal glands. For androgen release experiments, ZR and intact adrenocortical cubes were dispersed into isolated cells, the cells cultured and exposed to IL-6 and/or adrenocorticotropic hormone (ACTH), and androgen release determined by radioimmunoassay. Basal and ACTH-stimulated androgen release from the ZR was inhibited by IL-6 in a concentration-dependent (10-1000 pg/mL) and time-dependent (4-24 h) manner (P < 0.01 by 1-way analysis of variance and the Bonferroni test). In contrast, IL-6 increased basal and ACTH-stimulated androgen release from mixed adrenocortical cells (P < 0.01). The mechanism of IL-6 inhibition of androgen release was investigated by exposing ZR strips to IL-6 and measuring the expression of the messenger RNA (mRNA) and protein of steroidogenic factors. Basal and ACTH-stimulated expression of the mRNA and protein for steroidogenic acute regulatory protein, cholesterol side chain cleavage enzyme, 3-β-hydroxysteroid dehydrogenase type 2, steroid 17-α-hydroxylase/17,20 lyase/17,20 desmolase, and the nuclear factor steroidogenic factor 1 (SF-1), that stimulates steroidogenesis, were decreased by IL-6 (P < 0.01). In contrast IL-6 increased the mRNA and protein for dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1 (DAX-1), a nuclear factor that inhibits steroidogenesis (P < 0.01). In summary, IL-6 decreased androgen release and the expression of steroidogenic factors in the ZR, and this decrease may be mediated in part through increasing DAX-1 and decreasing SF-1.

Dynamic pituitary-adrenal interactions in response to cardiac surgery

OBJECTIVES

To characterize the dynamics of the pituitary-adrenal interaction during the course of coronary artery bypass grafting both on and off pump. Since our data pointed to a major change in adrenal responsiveness to adrenocorticotropic hormone, we used a reverse translation approach to investigate the molecular mechanisms underlying this change in a rat model of critical illness.

DESIGN

CLINICAL STUDIES

Prospective observational study.

ANIMAL STUDIES

Controlled experimental study.

SETTING

CLINICAL STUDIES

Cardiac surgery operating rooms and critical care units.

ANIMAL STUDIES

University research laboratory.

SUBJECTS

CLINICAL STUDIES

Twenty, male patients.

ANIMAL STUDIES

Adult, male Sprague-Dawley rats.

INTERVENTIONS

CLINICAL STUDIES

Coronary artery bypass graft-both on and off pump.

ANIMAL STUDIES

Injection of either lipopolysaccharide or saline (controls) via a jugular vein cannula.

MEASUREMENTS AND MAIN RESULTS

CLINICAL STUDIES

Blood samples were taken for 24 hours from placement of the first venous access. Cortisol and adrenocorticotropic hormone were measured every 10 and 60 minutes, respectively, and corticosteroid-binding globulin was measured at the beginning and end of the 24-hour period and at the end of operation. There was an initial rise in both levels of adrenocorticotropic hormone and cortisol to supranormal values at around the end of surgery. Adrenocorticotropic hormone levels then returned toward preoperative values. Ultradian pulsatility of both adrenocorticotropic hormone and cortisol was maintained throughout the perioperative period in all individuals. The sensitivity of the adrenal gland to adrenocorticotropic hormone increased markedly at around 8 hours after surgery maintaining very high levels of cortisol in the face of "basal" levels of adrenocorticotropic hormone. This sensitivity began to return toward preoperative values at the end of the 24-hour sampling period.

ANIMAL STUDIES

Adult, male Sprague-Dawley rats were given either lipopolysaccharide or sterile saline via a jugular vein cannula. Hourly blood samples were subsequently collected for adrenocorticotropic hormone and corticosterone measurement. Rats were killed 6 hours after the injection, and the adrenal glands were collected for measurement of steroidogenic acute regulatory protein, steroidogenic factor 1, and dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1 messenger RNAs and protein using real-time quantitative polymerase chain reaction and Western immunoblotting, respectively. Adrenal levels of the adrenocorticotropic hormone receptor (melanocortin type 2 receptor) messenger RNA and its accessory protein (melanocortin type 2 receptor accessory protein) were also measured by real-time quantitative polymerase chain reaction. In response to lipopolysaccharide, rats showed a pattern of adrenocorticotropic hormone and corticosterone that was similar to patients undergoing coronary artery bypass grafting. We were also able to demonstrate increased intra-adrenal corticosterone levels and an increase in steroidogenic acute regulatory protein, steroidogenic factor 1, and melanocortin type 2 receptor accessory protein messenger RNAs and steroidogenic acute regulatory protein, and a reduction in dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1 and melanocortin type 2 receptor messenger RNAs, 6 hours after lipopolysaccharide injection.

CONCLUSIONS

Severe inflammatory stimuli activate the hypothalamic-pituitary-adrenal axis resulting in increased steroidogenic activity in the adrenal cortex and an elevation of cortisol levels in the blood. Following coronary artery bypass grafting, there is a massive increase in both adrenocorticotropic hormone and cortisol secretion. Despite a subsequent fall of adrenocorticotropic hormone to basal levels, cortisol remains elevated and coordinated adrenocorticotropic hormone-cortisol pulsatility is maintained. This suggested that there is an increase in adrenal sensitivity to adrenocorticotropic hormone, which we confirmed in our animal model of immune activation of the hypothalamic-pituitary-adrenal axis. Using this model, we were able to show that this increased adrenal sensitivity results from changes in the regulation of both stimulatory and inhibitory intra-adrenal signaling pathways. Increased understanding of the dynamics of normal hypothalamic-pituitary-adrenal responses to major surgery will provide us with a more rational approach to glucocorticoid therapy in critically ill patients.

Repeated predictable stress causes resilience against colitis-induced behavioral changes in mice

Inflammatory bowel disease is associated with an increased risk of mental disorders and can be exacerbated by stress. In this study which was performed with male 10-week old C57Bl/6N mice, we used dextran sulfate sodium (DSS)-induced colitis to evaluate behavioral changes caused by intestinal inflammation, to assess the interaction between repeated psychological stress (water avoidance stress, WAS) and colitis in modifying behavior, and to analyze neurochemical correlates of this interaction. A 7-day treatment with DSS (2% in drinking water) decreased locomotion and enhanced anxiety-like behavior in the open field test and reduced social interaction. Repeated exposure to WAS for 7 days had little influence on behavior but prevented the DSS-induced behavioral disturbances in the open field and SI tests. In contrast, repeated WAS did not modify colon length, colonic myeloperoxidase content and circulating proinflammatory cytokines, parameters used to assess colitis severity. DSS-induced colitis was associated with an increase in circulating neuropeptide Y (NPY), a rise in the hypothalamic expression of cyclooxygenase-2 mRNA and a decrease in the hippocampal expression of NPY mRNA, brain-derived neurotrophic factor mRNA and mineralocorticoid receptor mRNA. Repeated WAS significantly decreased the relative expression of corticotropin-releasing factor mRNA in the hippocampus. The effect of repeated WAS to blunt the DSS-evoked behavioral disturbances was associated with a rise of circulating corticosterone and an increase in the expression of hypothalamic NPY mRNA. These results show that experimental colitis leads to a particular range of behavioral alterations which can be prevented by repeated WAS, a model of predictable chronic stress, while the severity of colitis remains unabated. We conclude that the mechanisms underlying the resilience effect of repeated WAS involves hypothalamic NPY and the hypothalamic-pituitary-adrenal axis.

Circadian rhythmicity, variability and correlation of interleukin-6 levels in plasma and cerebrospinal fluid of healthy men

BACKGROUND

Interleukin-6 (IL-6) is a cytokine with pleiotropic actions in both the periphery of the body and the central nervous system (CNS). Altered IL-6 secretion has been associated with inflammatory dysregulation and several adverse health consequences. However, little is known about the physiological circadian characteristics and dynamic inter-correlation between circulating and CNS IL-6 levels in humans, or their significance.

METHODS

Simultaneous assessment of plasma and cerebrospinal fluid (CSF) IL-6 levels was performed hourly in 11 healthy male volunteers over 24h, to characterize physiological IL-6 secretion levels in both compartments.

RESULTS

IL-6 levels showed considerable within- and between-subject variability in both plasma and CSF, with plasma/CSF ratios revealing consistently higher levels in the CSF. Both CSF and plasma IL-6 levels showed a distinctive circadian variation, with CSF IL-6 levels exhibiting a main 24h, and plasma a biphasic 12h, circadian component. Plasma peaks were roughly at 4 p.m. and 4 a.m., while the CSF peak was at around 7 p.m. There was no correlation between coincident CSF and plasma IL-6 values, but evidence for significant correlations at a negative 7-8h time lag.

CONCLUSIONS

This study provides evidence in humans for a circadian IL-6 rhythm in CSF and confirms prior observations reporting a plasma biphasic circadian pattern. Our results indicate differential IL-6 regulation across the two compartments and are consistent with local production of IL-6 in the CNS. Possible physiological significance is discussed and implications for further research are highlighted.

[Interaction between hypnotic agents and the hypothalamic-pituitary-adrenocorticotropic axis during surgery]

During stress, the relationship between the central nervous system and the immune system is essential to maintain homeostasis. The main neuroendocrine system involved in this interaction is the hypothalamic-pituitary-adrenal axis (HPA), which via the synthesis of glucocorticoids will modulate the intensity of the inflammatory response. Anaesthetic agents could be interacting with the HPA axis during surgery. Although etomidate currently remains in the center of the discussions, it seems, at least experimentally, that most hypnotics have the capacity to modulate the synthesis of adrenal steroids. Nevertheless, with the large literature on this subject, etomidate seems to be the most deleterious hypnotic agent on the HPA axis function. Its use should be limited when HPA axis is already altered.

Nutrition Monitoring in the PICU

The ideal set of variables for nutritional monitoring that may correlate with patient outcomes has not been identified. This is particularly difficult in the PICU patient because many of the standard modes of nutritional monitoring, although well described and available, are fraught with difficulties. Thus, repeated anthropometric and laboratory markers must be jointly analyzed but individually interpreted according to disease and metabolic changes, in order to modify and monitor the nutritional treatment. In addition, isotope techniques are neither clinically feasible nor compatible with the multiple measurements needed to follow progression. On the other hand, indirect alternatives exist but may have pitfalls, of which the clinician must be aware. Risks exist for both overfeeding and underfeeding of PICU patients so that an accurate monitoring of energy expenditure, using targeted indirect calorimetry, is necessary to avoid either extreme. This is very important, since the monitoring of the nutritional status of the critically ill child serves as a guide to early and effective nutritional intervention.

The effect of isoflurane anaesthesia and vasectomy on circulating corticosterone and ACTH in BALB/c mice

The use of blood corticosterone and faecal corticosterone metabolites as biomarkers of post-surgical stress and pain in laboratory animals has increased during the last decade. However, many aspects of their reliability in laboratory mice remain uninvestigated. This study investigated serum corticosterone and adrenocorticotropic hormone (ACTH) in mice subjected to isoflurane anaesthesia and vasectomy, and mice subjected to isoflurane anaesthesia without surgery. Serum levels of corticosterone and ACTH after pre-treatment with dexamethasone were analysed to provide further information about the stress hormone profiles. Vasectomy resulted in an increase in corticosterone for at least four hours after surgery with a peak 30min after the mice regained righting reflex. Mice subjected to isoflurane anaesthesia without surgery had the highest level of serum corticosterone 5min after regained righting reflex and the level returned to baseline levels four hours after the procedure. In vasectomised mice, treated with dexamethasone, high levels of corticosterone remained 30min after the procedure, whereas the anaesthetised mice, treated with dexamethasone, had significantly lower levels of corticosterone compared to anaesthetised mice not treated with dexamethasone. Thus, dexamethasone effectively inhibited the corticosterone response in the anaesthetised-only mice, but not in the mice subjected to surgery. In conclusion, both isoflurane anaesthesia and vasectomy during isoflurane anaesthesia resulted in an increase in serum glucocorticoids, but the negative feedback mechanism of newly operated mice, was altered. This may have consequences for the interpretation of glucocorticoids measurements as a biomarker of post-surgical stress in mice.

Cytokines, neurophysiology, neuropsychology, and psychiatric symptoms

Recent research has overcome the old paradigms of the brain as an immunologically privileged organ, and of the exclusive role of neurotransmitters and neuropeptides as signal transducers in the central nervous system. Growing evidence suggests that the signal proteins of the immune system - the cytokines - are also involved in modulation of behavior and induction of psychiatric symptoms. This article gives an overview on the nature of cytokines and the proposed mechanisms of immune-to-brain interaction. The role of cytokines in psychiatric symptoms, syndromes, and disorders like sickness behavior, major depression, and schizophrenia are discussed together with recent immunogenetic findings.

Adipokines and cardiovascular risk in Cushing's syndrome

Cushing's syndrome (CS) is associated with increased cardiovascular morbidity and mortality. Recent evidence also suggests that increased cardiovascular risk may persist even after long-term remission of CS. Increased central obesity, a typical feature of CS, is associated with altered production of adipokines, which contributes to the pathogenesis of several metabolic and cardiovascular complications observed in this condition. In vitro and in vivo studies have shown a relationship between cortisol and adipokines in several experimental settings. In patients with either active or 'cured' CS, an increase in leptin and resistin levels as well as the release of pro-inflammatory cytokines, such as tumor necrosis factor-α and interleukin-6, may be associated with increased cardiovascular risk. For other adipokines, including adiponectin, results are inconclusive. Studies are needed to further elucidate the interactions between clinical and subclinical increases in cortisol production and altered adipokine release in CS.

Expression of adiponectin receptors in mouse adrenal glands and the adrenocortical Y-1 cell line: adiponectin regulates steroidogenesis

Obesity is frequently associated with malfunctions of the hypothalamus-pituitary-adrenal (HPA) axis and hyperaldosteronism, but the mechanism underlying this association remains unclear. Since the adrenal glands are embedded in adipose tissue, direct cross-talk between adipose tissue and the adrenal gland has been proposed. A previous study found that adiponectin receptor mRNA was expressed in human adrenal glands and aldosterone-producing adenoma (APA). However, the expression of adiponectin receptors in adrenal glands has not been confirmed at the protein level or in other species. Furthermore, it is unclear whether adiponectin receptors expressed in adrenal cells are functional. We found, for the first time, that adiponectin receptor (AdipoR1 and AdipoR2) mRNA and protein were expressed in mouse adrenal and adrenocortical Y-1 cells. However, adiponectin itself was not expressed in mouse adrenal or Y-1 cells. Furthermore, adiponectin acutely reduced basal levels of corticosterone and aldosterone secretion. ACTH-induced steroid secretion was also inhibited by adiponectin, and this was accompanied by a parallel change in the expression of the key genes involved in steroidogenesis. These findings indicate that adiponectin may take part in the modulation of steroidogenesis. Thus, adiponectin is likely to have physiological and/or pathophysiological significance as an endocrine regulator of adrenocortical function.

Corticotropin-releasing hormone deficiency is associated with reduced local inflammation in a mouse model of experimental colitis

CRH, the hypothalamic component of the hypothalamic-pituitary adrenal axis, attenuates inflammation through stimulation of glucocorticoid release, whereas peripherally expressed CRH acts as a proinflammatory mediator. CRH is expressed in the intestine and up-regulated in patients with ulcerative colitis. However, its pathophysiological significance in intestinal inflammatory diseases has just started to emerge. In a mouse model of acute, trinitrobenzene sulfonic acid-induced experimental colitis, we demonstrate that, despite low glucocorticoid levels, CRH-deficient mice develop substantially reduced local inflammatory responses. These effects were shown by histological scoring of tissue damage and neutrophil infiltration. At the same time, CRH deficiency was found to be associated with higher serum leptin and IL-6 levels along with sustained anorexia and weight loss, although central CRH has been reported to be a strong appetite suppressor. Taken together, our results support an important proinflammatory role for CRH during mouse experimental colitis and possibly in inflammatory bowel disease in humans. Moreover, the results suggest that CRH is involved in homeostatic pathways that link inflammation and metabolism.

Psychological stress induces hypoferremia through the IL-6-hepcidin axis in rats

Anemia is a widespread public health problem. The psychological stress decreases serum iron level and inhibits erythropoiesis. However, the molecular mechanisms involved, leading to iron mal-regulation are not well known. We used a communication box paradigm to induce psychological stress and found that serum iron level decreased after 3d while liver iron storage increased after 7d. Moreover, psychological stress up-regulated expressions of interleukin-6 (IL-6) and hepcidin, while down-regulating ferroportin expression after 3d. These changes were blocked by the injection of IL-6 monoclonal antibody. In conclusion, the IL-6-hepcidin axis is up-regulated by psychological stress in rats, resulting in hypoferremia and increase of hepatic iron storage.

The immune-mediated alteration of serotonin and glutamate: towards an integrated view of depression

Beside the well-known deficiency in serotonergic neurotransmission as pathophysiological correlate of major depression (MD), recent evidence points to a pivotal role of increased glutamate receptor activation as well. However, cause and interaction of these neurotransmitter alterations are not understood. In this review, we present a hypothesis integrating current concepts of neurotransmission and hypothalamus-pituitary-adrenal (HPA) axis dysregulation with findings on immunological alterations and alterations in brain morphology in MD. An immune activation including increased production of proinflammatory cytokines has repeatedly been described in MD. Proinflammatory cytokines such as interleukin-2, interferon-gamma, or tumor necrosis factor-alpha activate the tryptophan- and serotonin-degrading enzyme indoleamine 2,3-dioxygenase (IDO). Depressive states during inflammatory somatic disorders are also associated with increased proinflammatory cytokines and increased consumption of tryptophan via activation of IDO. An enhanced consumption of serotonin and its precursor tryptophan through IDO activation could well explain the reduced availability of serotonergic neurotransmission in MD. An increased activation of IDO and its subsequent enzyme kynurenine monooxygenase by proinflammatory cytokines, moreover, leads to an enhanced production of quinolinic acid, a strong agonist of the glutamatergic N-methyl-D-aspartate receptor. In inflammatory states of the central nervous system, IDO is mainly activated in microglial cells, which preferentially metabolize tryptophan to the NMDA receptor agonist quinolinic acid, whereas astrocytes - counteracting this metabolism due to the lack of an enzyme of this metabolism - have been observed to be reduced in MD. Therefore the type 1/type 2 immune response imbalance, associated with an astrocyte/microglia imbalance, leads to serotonergic deficiency and glutamatergic overproduction. Astrocytes are further strongly involved in re-uptake and metabolic conversion of glutamate. The reduced number of astrocytes could contribute to both, a diminished counterregulation of IDO activity in microglia and an altered glutamatergic neurotransmission. Further search for antidepressant agents should take into account anti-inflammatory drugs, for example, cyclooxygenase-2 inhibitors, might exert antidepressant effects by acting on serotonergic deficiency, glutamatergic hyperfunction and antagonizing neurotoxic effects of quinolinic acid.

Consensus paper of the WFSBP Task Force on Biological Markers: biological markers in depression

Biological markers for depression are of great interest to aid in elucidating the causes of major depression. We assess currently available biological markers to query their validity for aiding in the diagnosis of major depression. We specifically focus on neurotrophic factors, serotonergic markers, biochemical markers, immunological markers, neuroimaging, neurophysiological findings, and neuropsychological markers. We delineate the most robust biological markers of major depression. These include decreased platelet imipramine binding, decreased 5-HT1A receptor expression, increase of soluble interleukin-2 receptor and interleukin-6 in serum, decreased brain-derived neurotrophic factor in serum, hypocholesterolemia, low blood folate levels, and impaired suppression of the dexamethasone suppression test. To date, however, none of these markers are sufficiently specific to contribute to the diagnosis of major depression. Thus, with regard to new diagnostic manuals such as DSM-V and ICD-11 which are currently assessing whether biological markers may be included in diagnostic criteria, no biological markers for major depression are currently available for inclusion in the diagnostic criteria.

Increased interleukin-6 receptor expression in the paraventricular nucleus of rats with heart failure

Activation of the hypothalamic-pituitary-adrenal (HPA) axis and augmented plasma and tissue levels of IL-6 are hallmarks of heart failure (HF). Within the forebrain, cardiovascular homeostasis is mediated in part by the paraventricular nucleus (PVN) of the hypothalamus. IL-6, via binding to the IL-6 receptor (IL-6R)/glycoprotein 130 (gp130) complex influences cellular and physiological responses. Thus, in the current study, we hypothesized that PVN IL-6R protein and gene expression are upregulated in HF vs. sham-operated rats, whereas gp130 levels in the same tissues remain stable. Six weeks after coronary ligation surgery, hemodynamic measurements were obtained, and HF rats were divided into moderate noncongestive and severe chronic congestive groups based on cardiac indices. Plasma IL-6 levels were determined and changes in gene and protein expression of IL-6R and gp130 between sham-operated and HF rats were determined via real-time PCR and Western blot analyses, respectively. Plasma levels of IL-6 were elevated in rats with severe, but not moderate, HF compared with sham-operated controls. In both moderate and severe HF rats, protein but not gene expression of IL-6R was significantly increased in PVN tissue but not in non-PVN tissue, compared with sham-operated controls. Gene and protein levels of the gp130 subunit were not altered by HF in either tissue analyzed. Collectively, these data suggest that within the brain of HF rats, IL-6R expression is not a global change. Rather the increased IL-6 levels characteristic of HF may alter PVN-mediated physiological responses via enhanced expression of the IL-6R.

Interleukin-8 synthesis, regulation, and steroidogenic role in H295R human adrenocortical cells

The adrenal gland secretes several cytokines, and cytokines modulate steroid secretion by this gland. In this study, a survey of cytokine production by H295R human adrenocortical cells demonstrated that these cells secreted IL-2, IL-4, IL-8, IL-10, IL-13, and TNFalpha but not IL-5, IL-12, or interferon-gamma. IL-8 was the IL secreted at higher concentration. IL-8 secretion, its regulation, and role in steroidogenesis were further studied. Secreted ILs and steroids were measured by ELISA in cell culture supernatant. IL-8 mRNA was quantified by real-time RT-PCR. H295R cells and human adrenal gland expressed IL-8 mRNA. Angiotensin II, potassium, endothelin-1, IL-1alpha, IL-1beta, TNFalpha, and Escherichia coli lipopolysaccharide dose-dependently increase IL-8 secretion by H295R cells after 24 h incubation. IL-6 had no effect on IL-8 secretion. Angiotensin II time-dependently increased IL-8 secretion by H295R cells up to 48 h. Angiotensin II caused a biphasic increase in IL-8 mRNA expression with a peak 6 h after stimulation. TNFalpha synergized angiotensin II, potassium, and IL-1alpha-mediated IL-8 secretion. IL-8 did not modify aldosterone or cortisol secretion by H295R cells under basal or stimulated (angiotensin II or potassium) conditions. In conclusion, it is demonstrated for the first time that human adrenal cells expressed and secreted IL-8 under the regulation of angiotensin II, potassium, endothelin-1, and immune peptides. Adrenal-secreted IL-8 is one point of convergence between the adrenal gland and the immune system and may have relevance in physiological and pathophysiological conditions associated with increased levels of aldosterone secretagogues and the immune system.

Paraadrenal Castleman disease presenting with adrenal hyperandrogenism

Castleman disease, or angiofollicular lymph node hyperplasia, is a rare benign lymphoproliferative disorder. We report an uncommon case of retroperitoneal Castleman syndrome associated with adrenal hyperandrogenism and with interleukin-6 as the possible link in the pathophysiology of both disturbances. Four years after surgical resection of the paraadrenal mass, the patient is free of signs of recurrence of Castleman disease and adrenal hyperandrogenism.

Interleukin-6 and Nitric Oxide Synthase Expression in the Vasopressin and Corticotrophin-releasing Factor Systems of the Rat Hypothalamus

Nitric oxide synthase (NOS) and interleukin-6 (IL-6) are constitutively expressed in hypothalamic cells. However, phenotypic and functional aspects of these cells remain unknown. We have studied the expression pattern of these two molecules in hypothalamic cells expressing corticotropin-releasing factor (CRF) and arginin-vasopressin (AVP), two major regulatory peptides in the hypothalamus-pituitary system, using immunofluorescence, intracerebroventricular injection of colchicine, and the study in parallel of the labeling pattern of axons in the median eminence. Within AVP cells, we distinguished two different populations: large, intensely stained AVP cells coexpressing IL-6; and large, intensely stained AVP cells coexpressing IL-6 and NOS. Within the CRF cells, we distinguished three different populations: large, intensely stained CRF cells immunonegative for AVP, NOS, and IL-6; large cells weakly stained for CRF and AVP, immunopositive for NOS and immunonegative for IL-6; and small cells intensely stained for CRF and AVP and immunonegative for IL-6 and NOS. In addition, we also found AVP cells containing IL-6 in the suprachiasmatic nucleus. These results suggest that neuronal NOS and IL-6 may be involved in different modulatory processes in hypophysiotropic and non-hypophysiotropic cells.

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.

Early menopause, low body mass index, and smoking are independent risk factors for developing giant cell arteritis

OBJECTIVE

To assess female sex hormone related variables in a group of women with biopsy positive giant cell arteritis and a control group.

METHODS

49 women with biopsy positive giant cell arteritis, aged 50 to 69 years at the time of diagnosis, answered a questionnaire on hormonal and reproductive factors. The same questions were answered by a large population of women from the same geographical area in connection with routine mammograms. The results were tested statistically, using logistic regression analysis of each variable adjusted for age, and a multivariate logistic regression analysis including age and the variables which differed significantly between giant cell arteritis and controls.

RESULTS

From the multivariate logistic regression analysis, three independent variables were associated with an increased risk of having giant cell arteritis: smoking and being an ex-smoker (odds ratio (OR) = 6.324 (95% confidence interval (CI), 3.503 to 11.418), p<0.0001); body mass index (a reduction of 1.0 kg/m2 increased the risk by 10% (OR = 0.898 (0.846 to 0.952), p = 0.0003); and menopause before the age of 43 (OR = 3.521 (1.717 to 7.220), p = 0.0006).

CONCLUSIONS

There was a significant association between hormonal and reproduction related factors and the risk of developing giant cell arteritis in women given the diagnosis before the age of 70. The results suggest a possible role of oestrogen deficiency in the pathogenesis of giant cell arteritis. To confirm the results, an extended study will be needed, including women older than 70.

Psychosocial factors and interleukin-6 among women with advanced ovarian cancer

BACKGROUND

Relations among psychological stress, depression, social support, and interleukin-6 (IL-6, a proinflammatory cytokine) have been documented in humans and animals. Because elevated IL-6 is associated with a poorer prognosis among ovarian cancer patients and has been implicated in the metastasis of ovarian cancer, the current study examined relations between psychosocial factors and IL-6 among women with advanced-stage ovarian cancer.

METHODS

Sixty-one ovarian cancer patients completed assessments of social support, distressed mood, and quality of life before surgery. Peripheral blood was drawn preoperatively, and the plasma was assayed for IL-6. Ascites samples were also assayed for IL-6 for a subset of patients.

RESULTS

Both IL-6 levels and distressed mood were elevated among patients. After statistically adjusting effects of age and disease stage, social attachment was associated with lower levels of IL-6 in peripheral blood (P = 0.03), whereas poorer health-related quality of life was associated with higher IL-6 (P values ranged from 0.01 to 0.03 on different measures). This pattern of relations was also found in the ascites. Moreover, IL-6 levels in peripheral blood plasma correlated significantly with IL-6 in the ascites (P < 0.001), suggesting that peripheral IL-6 reflects IL-6 levels at the site of the tumor.

CONCLUSIONS

Results suggest that social support may play a protective role with respect to IL-6 elevations, and IL-6 may be an independent marker of health-related quality of life among ovarian cancer patients. Processes involving IL-6 represent possible pathways by which behavioral factors may contribute to disease outcomes among women with ovarian cancer.

Mutant mouse models of depression: Candidate genes and current mouse lines

Depression is a multifactorial and multigenetic disease. At present, three main theories try to conceptualize its molecular and biochemical mechanisms, namely the monoamine-, the hypothalamus-pituitary-adrenal- (HPA-) system- and the neurotrophin-hypotheses. One way to explore, validate or falsify these hypotheses is to alter the expression of genes that are involved in these systems and study their respective role in animal behavior and neuroendocrinological parameters. Following an introduction in which we briefly describe each hypothesis, we review here the different mouse lines generated to study the respective molecular pathways. Among the many mutant lines generated, only a few can be regarded as genetic depression models or as models of predisposition for a depressive syndrome after stress exposure. However, this is likely to reflect the human situation where depressive syndromes are complex, can vary to a great extent with respect to their symptomatology, and may be influenced by a variety of environmental factors. Mice with mutations of candidate genes showing depression-like features on behavioral or neurochemical levels may help to define a complex molecular framework underlying depressive syndromes. Because it is conceivable that manipulation of one single genetic function may be necessary but not sufficient to cause complex behavioral alterations, strategies for improving genetic modeling of depression-like syndromes in animals possibly require a simultaneous targeted dysregulation of several genes involved in the pathogenesis of depression. This approach would correspond to the new concept of 'endophenotypes' in human depression research trying to identify behavioral traits which are thought to be encoded by a limited set of genes.

Characterization of an interleukin-6- and adrenocorticotropin-dependent, immune-to-adrenal pathway during viral infection

There has been longstanding interest in the capacity of the immune system to access immunomodulatory glucocorticoid responses without invoking upstream neuroendocrine secretagogues, including CRH and ACTH. Here, we investigate the role of CRH and ACTH in adrenal glucocorticoid responses to murine cytomegalovirus (MCMV). Mice infected with MCMV exhibit IL-6-dependent glucocorticoid responses that peak at 36 h post infection and protect against cytokine (TNFalpha)-mediated lethality. Acute administration of a CRH-antibody (Ab) completely eliminated ACTH responses to both low- and high-dose MCMV. However, corticosterone responses in CRH-Ab-treated animals remained apparent in mice infected with low-dose MCMV and were robust in mice infected with high-dose MCMV. CRH-knockout (KO) mice exhibited robust corticosterone responses to both MCMV doses, despite reduced baseline and MCMV-induced ACTH. Interestingly, robust corticosterone responses in CRH-Ab-treated and CRH-KO mice were associated with exaggerated IL-6 levels, and IL-6 and corticosterone concentrations in infected CRH-Ab-treated animals were significantly correlated. Neutralization of IL-6 responses in infected CRH-KO mice reduced corticosterone responses by approximately 70%. Finally, MCMV-infected mice deprived of ACTH by hypophysectomy failed to elicit glucocorticoid responses, despite elevated plasma IL-6 concentrations. Taken together, these results suggest that a greater than normal induction of IL-6 compensates for the absence of a normal CRH-dependent ACTH surge during viral infection. This enhanced IL-6 response, in turn, may mediate a direct immune-adrenal pathway that can become a predominant driving force for glucocorticoid induction in the absence of CRH. However, the presence of ACTH appears to serve as a necessary permissive factor, enabling direct cytokine actions on the adrenal gland.

Circadian rhythms on hypothalamic–pituitary–adrenal axis hormones and cytokines of collagen induced arthritis in rats

This study is designed to identify whether circadian rhythms of the hormones of the hypothalamic-pituitary-adrenal (HPA) axis are associated with corresponding circadian fluctuations in cytokines in a rat model of collagen-induced arthritis (CIA). CIA is induced in Wistar rats by an intradermal injection of bovine type II collagen emulsified with complete adjuvant at the left foot. On day 33, in both the CIA and the control rats, circulating adrenocorticotropin hormone (ACTH) and corticosterone, tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and IL-1beta were evaluated at 6 h intervals from 00:00 to 24:00, and analyzed by statistics and cosinor-rhythmometry. The results showed that plasma corticosterone in CIA rats had a trough at 18:00 and reached a peak at 06:00 significantly. While peak values were presented in TNF-alpha at 24:00 and in IL-6 from 06:00 and 18:00 to 24:00. CIA rats exhibit abnormal circadian rhythms, with degrading amplitudes of corticosterone and IL-6, elevating amplitude of TNF-alpha, and marked phase shifts in corticosterone and IL-6. Our investigation suggests that the disorders of HPA axis in CIA rats may be related to the influence of inflammation mediators on hypothalamic centers. The circadian rhythms of hormones and cytokines in CIA rats may be reset due to the defective function of the HPA axis.

Role of interleukin-6 in stress response in normal and tumorous adrenal cells and during chronic inflammation

Interleukin-6 (IL-6) is the end-product of a cytokine signaling cascade and is secreted by specialized immune cells during inflammation. It has a great influence on many functions, including differentiation, stimulation, and activation of immune cells, or other cells of neuroendocrine origin. Thus, IL-6 serves as a key messenger in its communication with the neuroendocrine system, and serves as a potent activator of the hypothalamic-pituitary-adrenal axis at all levels. Changes in the levels of expression of this cytokine and its receptor have been observed during chronic inflammatory disease, and have been associated with tumorigenesis. Therefore, we studied the effect of IL-6 on normal and adenomatous human adrenal cells in vitro. The expression of IL-6 receptor mRNA was quantified within the same tissue. IL-6 potently stimulated cortisol secretion from dispersed normal human adrenal cells. We found immunoreactivity for the IL-6 receptor on cultured cells and paraffin-embedded sections of adrenal tissues. Further, there was a more pronounced expression of IL-6 mRNA in adrenal adenomas of patients with Cushing's syndrome, compared to normal human adrenals. Despite this fact, the sensitivity of cells of adenomatous adrenal glands to IL-6 was significantly decreased relative to cells from normal controls. These results were confirmed employing the permanent adrenocortical cancer cell line model NCI-H295. We infer that the loss of responsivity of tumorous adrenal cells to IL-6, and in part corticotropin, is an important step in the process of adrenal tumorigenesis by which regulation by differentiating proteins is bypassed.