Immunoendocrine communication via the hypothalamo-pituitary-adrenal axis in autoimmune diseases

Trial watch: dexmedetomidine in cancer therapy

Dexmedetomidine (DEX) is a highly selective α2-adrenoceptor agonist that is widely used in intensive and anesthetic care for its sedative and anxiolytic properties. DEX has the capacity to alleviate inflammatory pain while limiting immunosuppressive glucocorticoid stress during major surgery, thus harboring therapeutic benefits for oncological procedures. Recently, the molecular mechanisms of DEX-mediated anticancer effects have been partially deciphered. Together with additional preclinical data, these mechanistic insights support the hypothesis that DEX-induced therapeutic benefits are mediated via the stimulation of adaptive anti-tumor immune responses. Similarly, published clinical trials including ancillary studies described an immunostimulatory role of DEX during the perioperative period of cancer surgery. The impact of DEX on long-term patient survival remains elusive. Nevertheless, DEX-mediated immunostimulation offers an interesting therapeutic option for onco-anesthesia. Our present review comprehensively summarizes data from preclinical and clinical studies as well as from ongoing trials with a distinct focus on the role of DEX in overcoming (tumor microenvironment (TME)-imposed) cancer therapy resistance. The objective of this update is to guide clinicians in their choice toward immunostimulatory onco-anesthetic agents that have the capacity to improve disease outcome.

Trial watch: beta-blockers in cancer therapy

Compelling evidence supports the hypothesis that stress negatively impacts cancer development and prognosis. Irrespective of its physical, biological or psychological source, stress triggers a physiological response that is mediated by the hypothalamic-pituitary-adrenal axis and the sympathetic adrenal medullary axis. The resulting release of glucocorticoids and catecholamines into the systemic circulation leads to neuroendocrine and metabolic adaptations that can affect immune homeostasis and immunosurveillance, thus impairing the detection and eradication of malignant cells. Moreover, catecholamines directly act on β-adrenoreceptors present on tumor cells, thereby stimulating survival, proliferation, and migration of nascent neoplasms. Numerous preclinical studies have shown that blocking adrenergic receptors slows tumor growth, suggesting potential clinical benefits of using β-blockers in cancer therapy. Much of these positive effects of β-blockade are mediated by improved immunosurveillance. The present trial watch summarizes current knowledge from preclinical and clinical studies investigating the anticancer effects of β-blockers either as standalone agents or in combination with conventional antineoplastic treatments or immunotherapy.

Strengthening the Immune System and Reducing Inflammation and Oxidative Stress through Diet and Nutrition: Considerations during the COVID-19 Crisis

The coronavirus-disease 2019 (COVID-19) was announced as a global pandemic by the World Health Organization. Challenges arise concerning how to optimally support the immune system in the general population, especially under self-confinement. An optimal immune response depends on an adequate diet and nutrition in order to keep infection at bay. For example, sufficient protein intake is crucial for optimal antibody production. Low micronutrient status, such as of vitamin A or zinc, has been associated with increased infection risk. Frequently, poor nutrient status is associated with inflammation and oxidative stress, which in turn can impact the immune system. Dietary constituents with especially high anti-inflammatory and antioxidant capacity include vitamin C, vitamin E, and phytochemicals such as carotenoids and polyphenols. Several of these can interact with transcription factors such as NF-kB and Nrf-2, related to anti-inflammatory and antioxidant effects, respectively. Vitamin D in particular may perturb viral cellular infection via interacting with cell entry receptors (angiotensin converting enzyme 2), ACE2. Dietary fiber, fermented by the gut microbiota into short-chain fatty acids, has also been shown to produce anti-inflammatory effects. In this review, we highlight the importance of an optimal status of relevant nutrients to effectively reduce inflammation and oxidative stress, thereby strengthening the immune system during the COVID-19 crisis.

Endogenous and exogenous glucocorticoids abolish the efficacy of immune-dependent cancer therapies

Glucocorticoids mediate potent anti-inflammatory and immunosuppressive effects. A chronic elevation of the endogenous glucocorticoid tonus subsequent to mental stress, as well as continuous treatment with exogenous glucocorticoids, activate an immunosuppressive transcription factor, TSC22D3, in dendritic cells, causing the subversion of cancer therapy-elicited antineoplastic immune responses and subsequent therapeutic failure.

Neonatal corticosterone mitigates autoimmune neuropsychiatric disorders associated with streptococcus in mice

Increased glucocorticoid concentrations have been shown to favor resilience towards autoimmune phenomena. Here, we addressed whether experimentally induced elevations in circulating glucocorticoids mitigate the abnormalities exhibited by an experimental model of Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcus (PANDAS). This is a pathogenic hypothesis linking repeated exposures to Group-A-beta-hemolytic streptococcus (GAS), autoantibodies targeting selected brain nuclei and neurobehavioral abnormalities. To persistently elevate glucocorticoid concentrations, we supplemented lactating SJL/J mice with corticosterone (CORT; 80 mg/L) in the drinking water. Starting in adolescence (postnatal day 28), developing offspring were exposed to four injections - at bi-weekly intervals - of a GAS homogenate and tested for behavioral, immunological, neurochemical and molecular alterations. GAS mice showed increased perseverative behavior, impaired sensorimotor gating, reduced reactivity to a serotonergic agonist and inflammatory infiltrates in the anterior diencephalon. Neonatal CORT persistently increased circulating glucocorticoids concentrations and counteracted these alterations. Additionally, neonatal CORT increased peripheral and CNS concentrations of the anti-inflammatory cytokine IL-9. Further, upstream regulator analysis of differentially expressed genes in the striatum showed that the regulatory effect of estradiol is inhibited in GAS-treated mice and activated in GAS-treated mice exposed to CORT. These data support the hypothesis that elevations in glucocorticoids may promote central immunomodulatory processes.

Premature ovarian failure

Premature ovarian failure (POF) is the term usually used to describe women aged younger than 40 years, who present with amenorrhoea, hypergonadotropic hypogonadism, and infertility. POF is a devastating diagnosis for reproductive-aged women. The clinical presentation is diverse, and several different disorders can lead to premature ovarian failure. POF has serious health consequences, including psychological distress, infertility, osteoporosis, autoimmune disorders, ischaemic heart disease, and increased risk of mortality. Hashimoto's disease is the most frequent autoimmune disorder associated with premature ovarian failure. Management should be initiated immediately to prevent long-term consequences. Oestrogen therapy is the mainstay of management. Hormone therapy should be provided to eliminate symptoms of oestrogen deficiency.

Neonatal corticosterone administration in rodents as a tool to investigate the maternal programming of emotional and immune domains

Neonatal experiences exert persistent influences on individual development. These influences encompass numerous domains including emotion, cognition, reactivity to external stressors and immunity. The comprehensive nature of the neonatal programming of individual phenotype is reverberated in the large amount of experimental data collected by many authors in several scientific fields: biomedicine, evolutionary and molecular biology. These data support the view that variations in precocious environmental conditions may calibrate the individual phenotype at many different levels. Environmental influences have been traditionally addressed through experimental paradigms entailing the modification of the neonatal environment and the multifactorial (e.g. behaviour, endocrinology, cellular and molecular biology) analysis of the developing individual's phenotype. These protocols suggested that the role of the mother in mediating the offspring's phenotype is often associated with the short-term effects of environmental manipulations on dam's physiology. Specifically, environmental manipulations may induce fluctuations in maternal corticosteroids (corticosterone in rodents) which, in turn, are translated to the offspring through lactation. Herein, I propose that this mother-offspring transfer mechanism can be leveraged to devise experimental protocols based on the exogenous administration of corticosterone during lactation. To support this proposition, I refer to a series of studies in which these protocols have been adopted to investigate the neonatal programming of individual phenotype at the level of emotional and immune regulations. While these paradigms cannot replace traditional studies, I suggest that they can be considered a valid complement.

Pediatric Autoimmune Disorders Associated with Streptococcal Infections and Tourette's Syndrome in Preclinical Studies

Accumulating evidence suggests that Tourette's Syndrome (TS) - a multifactorial pediatric disorder characterized by the recurrent exhibition of motor tics and/or vocal utterances - can partly depend on immune dysregulation provoked by early repeated streptococcal infections. The natural and adaptive antibody-mediated reaction to streptococcus has been proposed to potentially turn into a pathological autoimmune response in vulnerable individuals. Specifically, in conditions of increased permeability of the blood brain barrier (BBB), streptococcus-induced antibodies have been proposed to: (i) reach neuronal targets located in brain areas responsible for motion control; and (ii) contribute to the exhibition of symptoms. This theoretical framework is supported by indirect evidence indicating that a subset of TS patients exhibit elevated streptococcal antibody titers upon tic relapses. A systematic evaluation of this hypothesis entails preclinical studies providing a proof of concept of the aforementioned pathological sequelae. These studies shall rest upon individuals characterized by a vulnerable immune system, repeatedly exposed to streptococcus, and carefully screened for phenotypes isomorphic to the pathological signs of TS observed in patients. Preclinical animal models may thus constitute an informative, useful tool upon which conducting targeted, hypothesis-driven experiments. In the present review we discuss the available evidence in preclinical models in support of the link between TS and pediatric autoimmune neuropsychiatric disorders associated with streptococcus infections (PANDAS), and the existing gaps that future research shall bridge. Specifically, we report recent preclinical evidence indicating that the immune responses to repeated streptococcal immunizations relate to the occurrence of behavioral and neurological phenotypes reminiscent of TS. By the same token, we discuss the limitations of these studies: limited evidence of behavioral phenotypes isomorphic to tics and scarce knowledge about the immunological phenomena favoring the transition from natural adaptive immunity to pathological outcomes.

Circadian Clocks and the Interaction between Stress Axis and Adipose Function

Many physiological processes and most endocrine functions show fluctuations over the course of the day. These so-called circadian rhythms are governed by an endogenous network of cellular clocks and serve as an adaptation to daily and, thus, predictable changes in the organism's environment. Circadian clocks have been described in several tissues of the stress axis and in adipose cells where they regulate the rhythmic and stimulated release of stress hormones, such as glucocorticoids, and various adipokine factors. Recent work suggests that both adipose and stress axis clock systems reciprocally influence each other and adrenal-adipose rhythms may be key players in the development and therapy of metabolic disorders. In this review, we summarize our current understanding of adrenal and adipose tissue rhythms and clocks and how they might interact to regulate energy homoeostasis and stress responses under physiological conditions. Potential chronotherapeutic strategies for the treatment of metabolic and stress disorders are discussed.

Corticotropic axis drive of overnight cortisol secretion is suppressed in adolescents and young adults with type 1 diabetes mellitus

CONTEXT

Type 1 diabetes mellitus (T1DM) is a pro-inflammatory stress state, which, with its attendant hyperglycemia, likely disrupts hypothalamo-pituitary-adrenal (HPA) control, further dysregulating glucose homeostasis.

OBJECTIVE

To test the hypothesis that endogenous adrenocorticotropic hormone (ACTH)-cortisol dose-responsive drive, estimated analytically, is significantly accentuated in adolescents and young adults with T1DM compared with healthy individuals.

DESIGN, SETTING, PATIENTS, AND INTERVENTIONS

This was a pilot study of 11 volunteers with T1DM and 10 controls, ages 16-30 yr, at a medical center. Subjects underwent overnight frequent blood sampling (every 10 min for ACTH and cortisol and every 60 min for blood glucose) from 10 pm to 8 am. T1DM volunteers maintained their home insulin regimen.

MAIN OUTCOMES

Deconvolution analysis and dose-response estimates were the key outcomes.

RESULTS

Mean free cortisol, but not ACTH, concentrations were lower in the T1DM group compared with controls (p = 0.012). Non-invasive ACTH-cortisol dose-response estimates revealed that T1DM patients had reduced ACTH efficacy (maximal cortisol secretion, p = 0.009), reduced ACTH potency as quantified by greater EC50 (ACTH concentration driving half-maximal cortisol secretion, p = 0.04), and increased ACTH sensitivity (more positive ACTH-cortisol slope, p = 0.03). Post-hoc gender comparisons indicated that these differences were limited to females. Linear regression in women showed a strong correlation of both ACTH efficacy and EC50 with C-peptide levels (both p < 0.01).

CONCLUSION

Compared with healthy individuals, T1DM patients manifest decreased overnight adrenal responsiveness to endogenous ACTH leading to lower free cortisol concentrations. These findings suggest impaired stress-related adaptations of the HPA axis in T1DM.

Endocrine-immune interactions in pregnant non-human primates with intrauterine infection

Preterm birth remains the most common cause of perinatal mortality. Although the causes of preterm labor are multifactorial and vary according to gestational age, preterm labor and term labor share common cellular and molecular mechanisms, including stimulation of the fetal hypothalamic-pituitary-adrenal (HPA) axis and endocrine/immune system interactions. We have developed a non-human primate experimental model for intrauterine infection and preterm labor using chronically instrumented rhesus monkeys (Macaca mulatta) with timed gestations. We have documented the temporal and quantitative relationships among intrauterine infection, the synthesis and release of proinflammatory cytokines, prostaglandins, and fetal-placental steroid biosynthesis in this model. Infection-induced preterm parturition is characterized by significant elevations in amniotic fluid proinflammatory cytokines and by increases in fetal adrenal steroid biosynthesis, but not by corresponding increases in placental estrogen biosynthesis characteristic of spontaneous parturition. This suggests that activation of the fetal HPA axis by the stress of infection is accompanied by placental dysfunction and also that infection-induced preterm parturition is not dependent upon the increased estrogen biosynthesis observed in spontaneous parturition. These different endocrine and immune responses have important diagnostic and therapeutic implications in the management of preterm labor.

Dual roles for perivascular macrophages in immune-to-brain signaling

Cytokines produced during infection/inflammation activate adaptive central nervous system (CNS) responses, including acute stress responses mediated by the hypothalamo-pituitary-adrenal (HPA) axis. The mechanisms by which cytokines engage HPA control circuitry remain unclear, though stimulated release of prostanoids from neighboring vascular cells has been implicated in this regard. How specific vascular cell types, endothelial cells (ECs) versus perivascular cells (PVCs; a subset of brain-resident macrophages), participate in this response remains unsettled. We exploited the phagocytic activity of PVCs to deplete them in rats by central injection of a liposome-encapsulated proapoptotic drug. This manipulation abrogated CNS and hormonal indices of HPA activation under immune challenge conditions (interleukin-1) that activated prostanoid synthesis only in PVCs, while enhancing these responses to stimuli (lipopolysaccharide) that engaged prostanoid production by ECs as well. Thus, PVCs provide both prostanoid-mediated drive to the HPA axis and an anti-inflammatory action that constrains endothelial and overall CNS responses to inflammatory insults.

The stressed CNS: when glucocorticoids aggravate inflammation

Glucocorticoids (GCs) are hormones released during the stress response that are well known for their immunosuppressive and anti-inflammatory properties; however, recent advances have uncovered situations wherein they have effects in the opposite direction. The CNS is a particularly interesting example, both because of its unique immune environment, and because GCs affect immune responses differently in different brain regions. In this minireview we discuss the contexts wherein GCs increase CNS inflammation and point out directions for future investigation.

Glucocorticoid receptor-mediated expression of caldesmon regulates cell migration via the reorganization of the actin cytoskeleton

Glucocorticoids (GCs) play important roles in numerous cellular processes, including growth, development, homeostasis, inhibition of inflammation, and immunosuppression. Here we found that GC-treated human lung carcinoma A549 cells exhibited the enhanced formation of the thick stress fibers and focal adhesions, resulting in suppression of cell migration. In a screen for GC-responsive genes encoding actin-interacting proteins, we identified caldesmon (CaD), which is specifically up-regulated in response to GCs. CaD is a regulatory protein involved in actomyosin-based contraction and the stability of actin filaments. We further demonstrated that the up-regulation of CaD expression was controlled by glucocorticoid receptor (GR). An activated form of GR directly bound to the two glucocorticoid-response element-like sequences in the human CALD1 promoter and transactivated the CALD1 gene, thereby up-regulating the CaD protein. Forced expression of CaD, without GC treatment, also enhanced the formation of thick stress fibers and focal adhesions and suppressed cell migration. Conversely, depletion of CaD abrogated the GC-induced phenotypes. The results of this study suggest that the GR-dependent up-regulation of CaD plays a pivotal role in regulating cell migration via the reorganization of the actin cytoskeleton.

An inflammatory review of glucocorticoid actions in the CNS

In recent years, the classic view that glucocorticoids, the adrenal steroids secreted during stress, are universally anti-inflammatory has been challenged at a variety of levels. It was first observed that under some circumstances, acute GC exposure could have pro-inflammatory effects on the peripheral immune response. More recently, chronic exposure to GCs has been found to have pro-inflammatory effects on the specialized immune response to injury in the central nervous system. Here we review the evidence that in some cases, glucocorticoids can increase pro-inflammatory cell migration, cytokine production, and even transcription factor activity in the brain. We consider how these unexpected effects of glucocorticoids can co-exist with their well-established anti-inflammatory properties, as well as the considerable clinical implications of these findings.

Corticotrope hypersecretion coupled with cortisol hypo-responsiveness to stimuli is present in patients with autoimmune endocrine diseases: evidence for subclinical primary hypoadrenalism?

OBJECTIVE

In autoimmune polyglandular syndrome types 1, 2, and 4 primary adrenal insufficiency is present, but its diagnosis is often late. We investigated the function of the hypothalamic-pituitary-adrenal axis in a group of patients with autoimmune diseases (AP) without any symptoms and signs of hypoadrenalism.

DESIGN

In 10 AP and 12 normal subjects (NS), we studied cortisol (F), aldosterone (A), and DHEA responses to 0.06 microg adrenocorticotropin (ACTH) (1-24) followed by 250 microg, ACTH and F responses to human corticotropin-releasing hormone (hCRH; 100 microg) and insulin tolerance test (ITT) (0.1 UI/kg).

RESULTS

Basal F, A, DHEA, as well as urinary free cortisol and plasma renin activity levels in AP and NS were similar, whereas ACTH levels in AP were higher (P<0.05) than in NS. NS showed F, A, and DHEA response to both consecutive ACTH doses. In AP, the F, A, and DHEA responses to 250 microg ACTH were similar to those in NS, whereas the 0.06 microg ACTH dose did not elicit any significant response. The ACTH responses to hCRH and ITT in AP were higher (P<0.05) than in NS. The F response to hCRH in AP was lower (P<0.05) than in NS, whereas the F response to ITT in AP did not significantly differ from NS.

CONCLUSIONS

Enhancement of both basal and stimulated corticotrope secretion coupled with reduced adrenal sensitivity to low ACTH dose is present in AP patients without symptoms and signs of hypoadrenalism. This functional picture suggests that normal adrenal secretion is maintained due to corticotrope hyperfunction, suggesting the existence of some subclinical primary hypoadrenalism.

Proliferating brain cells are a target of neurotoxic CSF in systemic autoimmune disease

Brain atrophy, neurologic and psychiatric (NP) manifestations are common complications in the systemic autoimmune disease, lupus erythematosus (SLE). Here we show that the cerebrospinal fluid (CSF) from autoimmune MRL-lpr mice and a deceased NP-SLE patient reduce the viability of brain cells which proliferate in vitro. This detrimental effect was accompanied by periventricular neurodegeneration in the brains of autoimmune mice and profound in vivo neurotoxicity when their CSF was administered to the CNS of a rat. Multiple ionic responses with microfluorometry and protein peaks on electropherograms suggest more than one mechanism of cellular demise. Similar to the CSF from diseased MRL-lpr mice, the CSF from a deceased SLE patient with a history of psychosis, memory impairment, and seizures, reduced viability of the C17.2 neural stem cell line. Proposed mechanisms of cytotoxicity involve binding of intrathecally synthesized IgG autoantibodies to target(s) common to different mammalian species and neuronal populations. More importantly, these results indicate that the viability of proliferative neural cells can be compromised in systemic autoimmune disease. Antibody-mediated lesions of germinal layers may impair the regenerative capacity of the brain in NP-SLE and possibly, brain development and function in some forms of CNS disorders in which autoimmune phenomena have been documented.

Impaired response to amphetamine and neuronal degeneration in the nucleus accumbens of autoimmune MRL-lpr mice

Spontaneous development of lupus-like disease in MRL-lpr mice is accompanied by a constellation of behavioral deficits, including blunted responsiveness to sucrose. Although autoimmunity-induced damage of limbic areas is proposed to underlie this deficit, the systemic nature of the disease precludes inference of a causal relationship between CNS damage and functional loss. Based on the stimulatory effects of d-amphetamine sulfate (AMPH) on sucrose intake, the present study pharmacologically probes the functional status of central dopaminergic circuits involved in control of behavioral reward. The response rates were compared between diseased MRL-lpr mice and congenic MRL +/+ controls tested in the sucrose preference paradigm. Neuronal loss was assessed by Fluoro Jade B (FJB) staining of nucleus accumbens and the CA2/CA3 region. While control mice significantly increased intake of sucrose solutions 60 min after administration of AMPH (i.p., 0.5 mg/kg), the intake in drugged MRL-lpr mice was comparable to those given saline injection. Increased FJB staining was detected in the nucleus accumbens and hippocampus of diseased mice, and AMPH treatment neither altered this nor other measures of organ pathology. The results obtained are consistent with previously observed changes in the mesolimbic dopamine system of MRL-lpr mice and suggest that the lesion in the nucleus accumbens and deficits in dopamine release underlie impaired responsiveness to palatable stimulation during the progress of systemic autoimmune disease. As such, they point to a neurotransmitter-specific regional brain damage which may account for depressive behaviors in neuropsychiatric lupus erythematosus.

Hippocampal damage in mouse and human forms of systemic autoimmune disease

Systemic lupus erythematosus (SLE) is frequently accompanied by neuropsychiatric (NP) and cognitive deficits of unknown etiology. By using autoimmune MRL-lpr mice as an animal model of NP-SLE, we examine the relationship between autoimmunity, hippocampal damage, and behavioral dysfunction. Fluoro Jade B (FJB) staining and anti-ubiquitin (anti-Ub) immunocytochemistry were used to assess neuronal damage in young (asymptomatic) and aged (diseased) mice, while spontaneous alternation behavior (SAB) was used to estimate the severity of hippocampal dysfunction. The causal relationship between autoimmunity and neuropathology was tested by prolonged administration of the immunosuppressive drug cyclophosphamide (CY). In comparison to congenic MRL +/+ controls, SAB acquisition rates and performance in the "reversal" trial were impaired in diseased MRL-lpr mice, suggesting limited use of the spatial learning strategy. FJB-positive neurons and anti-Ub particles were frequent in the CA3 region. Conversely, CY treatment attenuated the SAB deficit and overall FJB staining. Similarly to mouse brain, the hippocampus from a patient who died from NP-SLE showed reduced neuronal density in the CA3 region and dentate gyrus, as well as increased FJB positivity in these regions. Gliosis and neuronal loss were observed in the gray matter, and T lymphocytes and stromal calcifications were common in the choroid plexus. Taken together, these results suggest that systemic autoimmunity induces significant hippocampal damage, which may underlie affective and cognitive deficits in NP-SLE.

Monocyte proinflammatory cytokine release is higher and glucocorticoid sensitivity is lower in middle aged men than in women independent of cardiovascular risk factors

OBJECTIVE

To investigate whether stimulated monocyte cytokine release and its inhibition by glucocorticoids differs between men and women.

DESIGN

In vitro monocyte interleukin 6 (IL-6) and tumour necrosis factor alpha (TNFalpha) release after lipopolysaccharide stimulation were assessed with and without co-incubation with increasing doses of dexamethasone and hydrocortisone separately. Glucocorticoid sensitivity was defined as the amount of a particular glucocorticoid required to inhibit lipopolysaccharide stimulated monocyte cytokine release by 50%. The established cardiovascular risk factors of age, body mass index, number of cigarettes smoked daily, low density cholesterol to high density cholesterol ratio, systolic and diastolic blood pressure, and haemoglobin A1c were used as covariates.

SETTING

Aircraft manufacturing plant in southern Germany.

PATIENTS

269 middle aged male and 36 middle aged female employees.

RESULTS

Release of monocyte IL-6 and TNFalpha (each p = 0.001) was higher in samples from men than in those from women. Inhibition of lipopolysaccharide stimulated IL-6 and TNFalpha release by either glucocorticoid was less pronounced in samples from men than in those from women (IL-6: dexamethasone p = 0.033, hydrocortisone p = 0.029; TNFalpha: dexamethasone p < 0.001, hydrocortisone p = 0.089).

CONCLUSIONS

The finding suggests that proinflammatory activity of circulating monocytes is higher in men than in women independent of cardiovascular risk factors, thereby providing one explanation for the relatively greater coronary risk in men.

Degranulation of mast cells located in median eminence in response to compound 48/80 evokes adrenocortical secretion via histamine and CRF in dogs

The effect of intracerebroventricular infusion of compound 48/80 (C48/80), a mast cell secretagogue, on adrenal cortisol secretion was investigated in dogs under pentobarbital sodium anesthesia. A marked increase in adrenal cortisol secretion was elicited by C48/80 along with a concomitant increase in the plasma levels of cortisol and immunoreactive ACTH, but neither arterial blood pressure and heart rate nor the plasma histamine level altered significantly. Pretreatment with either anti-CRF antiserum or pyrilamine maleate (H(1) histamine-receptor antagonist) significantly attenuated the C48/80-evoked increase in cortisol secretion, but pretreatment with metiamide (H(2)-receptor antagonist) significantly potentiated it. Significant attenuation of the C48/80-evoked increase in cortisol also occurred in dogs given ketotifen, a mast cell stabilizing drug, before pharmacologic challenge. In the pars tuberalis and median eminence (ME), mast cells were highly concentrated in close association with the primary plexus of the hypophysial portal system. Degranulated mast cells were extensively found in the ME of C48/80-treated animals. These results suggest that mast cells located in these regions liberated histamine within the brain as a result of degranulation induced by C48/80 and that this led to activation of the hypothalamic-pituitary-adrenocortical axis.

Exposure to a dysfunctional glucocorticoid receptor from early embryonic life programs the resistance to experimental autoimmune encephalomyelitis via nitric oxide-induced immunosuppression

Glucocorticoid (GC) hormones play a central role in the bidirectional communication between the neuroendocrine and the immune systems and exert, via GC receptors (GR), potent immunosuppressive and anti-inflammatory effects. In this study, we report that GR deficiency of transgenic mice expressing GR antisense RNA from early embryonic life has a dramatic impact in programming the susceptibility to experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. GR deficiency renders mice resistant to myelin oligodendrocyte glycoprotein-induced EAE, and such mice do not develop clinical or histological signs of disease compared with EAE-susceptible wild-type mice. Resistance to EAE in GR-deficient mice is associated not with endogenous GC levels, but with a significant reduction in spleen and lymph node cell proliferation. The use of NO inhibitors in vitro indicates that NO is the candidate immunosuppressor molecule. GR-deficient mice develop 3- to 6-fold higher nitrite levels in the periphery and are resistant to NO inhibition by GCs. Specific inhibition of NO production in vivo by treatment with the inducible NO synthase inhibitor, L-N(6)-(1-iminoethyl)-lysine, suppressed circulating nitrites, increased myelin oligodendrocyte glycoprotein-specific cell proliferation, and rendered GR-deficient mice susceptible to EAE. Thus, life-long GR deficiency triggers inducible NO synthase induction and NO generation with consequent down-regulation of effector cell proliferation. These findings identify a novel link among GR, NO, and EAE susceptibility and highlight NO as critical signaling molecule in bidirectional communication between the hypothalamic-pituitary-adrenocortical axis and the immune system.

Glucocorticoid production in the chicken bursa and thymus

Glucocorticoid (GC) hormones play an important role in thymic T cell selection and in the development of autoimmune diseases. Previous studies have shown that the mammalian thymus itself is able to produce GC. In order to assess the importance of these findings in terms of the evolutionary development of the immune system, we investigated the functional presence of steroidogenic enzymes in primary lymphoid organs of chickens, which represent one of the best studied non-mammalian species. To this end, we attempted to demonstrate enzyme activities of the whole set of steroidogenic enzymes for the synthesis of GC in the bursa of Fabricius and the thymus. We isolated steroidogenic organelles from primary lymphoid tissues, incubated these with radioactive (precursor) steroids in vitro and visualized the resulting products by thin-layer chromatography. Our results show that the chicken bursa as well as the chicken thymus possesses all enzymes and cofactors required for GC production. The observation of GC production in an organ responsible for B cell selection and maturation is a further step in uncovering the yet ill-defined mechanism of B cell selection. These results provide the biochemical basis for the in situ hormonal effects, and underline the general importance of GC hormones on T and B lymphocyte development and selection.

Neonatal dexamethasone treatment increases susceptibility to experimental autoimmune disease in adult rats

Major concern has emerged about the possible long term adverse effects of glucocorticoid treatment, which is frequently used for the prevention of chronic lung disease in preterm infants. Here we show that neonatal glucocorticoid treatment of rats increases the severity (p< or = 0.01) and incidence (p< or =0.01) of the inflammatory autoimmune disease experimental autoimmune encephalomyelitis in adult life. In search of possible mechanisms responsible for the increased susceptibility to experimental autoimmune encephalomyelitis, we investigated the reactivity of the hypothalamo-pituitary-adrenal axis and of immune cells in adult rats after neonatal glucocorticoid treatment. We observed that neonatal glucocorticoid treatment reduces the corticosterone response after an LPS challenge in adult rats (p< or =0.001). Interestingly, LPS-stimulated macrophages of glucocorticoid-treated rats produce less TNF-alpha and IL-1beta in adult life than control rats (p<0.05). In addition, splenocytes obtained from adult rats express increased mRNA levels of the proinflammatory cytokines IFN-gamma (p<0.01) and TNF-beta (p<0.05) after neonatal glucocorticoid treatment. Apparently, neonatal glucocorticoid treatment has permanent programming effects on endocrine as well as immune functioning in adult life. In view of the frequent clinical application of glucocorticoids to preterm infants, our data demonstrate that neonatal glucocorticoid treatment may be a risk factor for the development of (auto)immune disease in man.

Onset and severity of inflammation in rats exposed to the learned helplessness paradigm

OBJECTIVE

To test the hypothesis that there is an association between susceptibility to inflammation and a hyporesponsive hypothalamo-pituitary-adrenal (HPA) axis.

METHODS

Animals were separated on the basis of behaviour in the learned helplessness (LH) paradigm into groups of LH(+) (i.e. animals which did not escape footshock) and LH(-) animals. Adjuvant-induced arthritis (AA) was subsequently induced in the LH(+) and LH(-) animals.

RESULTS

Plasma corticosterone was significantly increased in response to the LH test in the LH(-) compared with the LH(+) rats. We observed an earlier onset and increased inflammation in the LH(-) rats in spite of the greater corticosterone response to the acute stress. We noted lower levels of plasma testosterone in the LH(-) animals suggesting a possible influence for this protective factor in AA.

CONCLUSION

These data suggest that increased onset and severity of inflammation in AA is not a simple consequence of an attenuated HPA axis response to stress as proposed in the Lewis rat. Indeed we have observed the converse. Together these data suggest that the balance of pro- and anti-inflammatory factors released in response to stress may influence the progress of AA.

On the adaptive significance of stress-induced immunosuppression

We approach the field of stress immunology from an ecological point of view and ask: why should a heavy physical workload, for example as a result of a high reproductive effort, compromise immune function? We argue that immunosuppression by neuroendocrine mechanisms, such as stress hormones, during heavy physical workload is adaptive, and consider two different ultimate explanations of such immunosuppression. First, several authors have suggested that the immune system is suppressed to reallocate resources to other metabolic demands. In our view, this hypothesis assumes that considerable amounts of energy or nutrients can be saved by suppressing the immune system; however, this assumption requires further investigation. Second, we suggest an alternative explanation based on the idea that the immune system is tightly regulated by neuroendocrine mechanisms to avoid hyperactivation and ensuing autoimmune responses. We hypothesize that the risk of autoimmune responses increases during heavy physical workload and that the immune system is suppressed to counteract this.

Evidence for an intramedullary prostaglandin-dependent mechanism in the activation of stress-related neuroendocrine circuitry by intravenous interleukin-1

We have provided evidence that the stimulatory effects of intravenous interleukin-1 (IL-1) on neurosecretory neurons in the paraventricular nucleus (PVH) that express corticotropin-releasing factor (CRF) depend specifically on the integrity of catecholaminergic projections originating in caudal medulla. Here we report on experiments designed to test alternative means by which circulating IL-1 might access medullary aminergic neurons, including mechanisms involving sensory components of the vagus, the area postrema, or perivascular cells bearing IL-1 receptors. Neither abdominal vagotomy nor area postrema lesions reliably altered Fos expression induced in the medulla or PVH in response to a moderately suprathreshold dose of IL-1beta. Cytokine-stimulated increases in CRF mRNA in the PVH were also unaffected by either ablation. By contrast, systemic administration of the cyclooxygenase inhibitor indomethacin resulted in parallel dose-related attenuations of IL-1 effects in hypothalamus and medulla. Microinjections of prostaglandin E2 (PGE2; >/=10 ng) in rostral ventrolateral medulla, the principal seat of IL-1-sensitive neurons that project to the PVH, provoked discrete patterns of cellular activation in hypothalamus and medulla that mimicked those seen in response to intravenous IL-1. We interpret these findings as supporting the hypothesis that paracrine effects of PGE2 released from perivascular cells in the medulla as a consequence of IL-1 stimulation and, acting through prostanoid receptors on or near local aminergic neurons that project to the PVH, contribute to the stimulatory effects of increased circulating IL-1 on neurons constituting the central limb of the hypothalamo-pituitary-adrenal axis.

Corticosterone responses of adult Lewis and Fischer rats

Indwelling catheters were implanted into the inferior vena cava of adult male and female Lewis/N and Fischer 344 rats. Each animal was exposed to ACTH, novelty stimulation, nicotine, lipopolysaccharide (LPS), and saline on 5 consecutive days. Blood was withdrawn before (baseline) and at several time points after the stimulus on each day. There were no differences in baseline corticosterone levels nor in responses to saline in any group. In general, responses to stimulation peaked at 15-30 min and returned to baseline by 60-90 min. Corticosterone responses to LPS showed a different time course; maximal responses occur at 1-2 h and return to baseline by 24 h. Fischer animals showed higher corticosterone levels than Lewis rats during the response to stimulation, but returned to baseline at the same times. Females of each strain showed higher corticosterone responses than males at 15, 30, and 45 min after ACTH, but the sexes did not differ in response to the other stimuli. For individual rats, the maximum response to ACTH was slightly correlated with the maximum response to novelty stimulation, nicotine, and saline but was not correlated with the response to LPS.

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

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