Cross-talk between Adrenal Medulla and Adrenal Cortex in Stress

Non-classical animal models for studying adrenal diseases: advantages, limitations, and implications for research

The study of adrenal disorders is a key component of scientific research, driven by the complex innervation, unique structure, and essential functions of the adrenal glands. This review explores the use of non-traditional animal models for studying congenital adrenal hyperplasia. It highlights the advantages, limitations, and relevance of these models, including domestic ferrets, dogs, guinea pigs, golden hamsters, pigs, and spiny mice. We provide a detailed analysis of the histological structure, steroidogenesis pathways, and genetic characteristics of these animal models. The morphological and functional similarities between the adrenal glands of spiny mice and humans highlight their potential as an important avenue for future research.

Asymmetries of Left and Right Adrenal Glands in Neural Innervation and Glucocorticoids Production

The adrenal gland is paired peripheral end organs of the neuroendocrine system and is responsible for producing crucial stress hormones from its two functional compartments, the adrenal cortex, and the adrenal medulla under stimuli. Left-right asymmetry in vertebrates exists from the central nervous system to peripheral paired endocrine glands. The sided difference in the cerebral cortex is extensively investigated, while the knowledge of asymmetry of paired endocrine glands is still poor. The present study aims to investigate the asymmetries of bilateral adrenal glands, which play important roles in stress adaptation and energy homeostasis via steroid hormones produced from the distinct functional zones. Left and right adrenal glands from male C57BL/6J mice were initially histologically analyzed, and high-throughput RNA sequencing was then used to detect the gene transcriptional difference between left and right adrenal glands. Subsequently, the enrichment of functional pathways and ceRNA regulatory work was validated. The results demonstrated that the left adrenal gland had higher tissue mass and levels of energy expenditure, whereas the right adrenal gland appeared to be more potent in glucocorticoid secretion. Further analysis of adrenal stem/progenitor cell markers predicted that Shh signaling might play an important role in the left-right asymmetry of adrenal glands. Of the hub miRNAs, miRNA-466i-5p was identified in the left-right differential innervation of the adrenal glands. Therefore, the present study provides evidence that there are asymmetries between the left and right adrenal glands in glucocorticoid production and neural innervation, in which Shh signaling and miRNA-466i-5p play an important role.

The Adrenal Gland of Squamata (Reptilia): A Comparative Overview

The adrenal gland is a complex endocrine organ composed of two components: a steroidogenic tissue, which produces steroid hormones, and a chromaffin tissue, which mainly produces norepinephrine and epinephrine. Through evolution, their relationships with each other changed. They begin as isolated chromaffin and steroidogenic cell aggregates, typical of fish, and end with the advanced compact gland, typical of mammals, which consists of an external steroidogenic cortical zone and an internal chromaffin medullary zone. The adrenal gland of reptiles is unique because, with few exceptions, it is near the gonads and genital ducts, and the chromaffin and steroidogenic tissues are closely associated. However, the degree of mixing is variable. For example, in Squamata, the mixing degree of chromaffin and steroidogenic tissues, their reciprocal position in the gland, and the relative quantities of norepinephrine and epinephrine secreted by the chromaffin cells are extremely variable. This variability could be related to the phylogenetic history of the species. After a brief discussion of the adrenal gland and its main functions in vertebrates, this overview will examine the general characteristics of the adrenal gland of squamates, the differences in morphology of the gland, and the possible relationships with the phylogeny of the different species.

Plasma-Metanephrines in Patients with Autoimmune Addison's Disease with and without Residual Adrenocortical Function

PURPOSE

Residual adrenocortical function, RAF, has recently been demonstrated in one-third of patients with autoimmune Addison's disease (AAD). Here, we set out to explore any influence of RAF on the levels of plasma metanephrines and any changes following stimulation with cosyntropin.

METHODS

We included 50 patients with verified RAF and 20 patients without RAF who served as controls upon cosyntropin stimulation testing. The patients had abstained from glucocorticoid and fludrocortisone replacement > 18 and 24 h, respectively, prior to morning blood sampling. The samples were obtained before and 30 and 60 min after cosyntropin stimulation and analyzed for serum cortisol, plasma metanephrine (MN), and normetanephrine (NMN) by liquid-chromatography tandem-mass pectrometry (LC-MS/MS).

RESULTS

Among the 70 patients with AAD, MN was detectable in 33%, 25%, and 26% at baseline, 30 min, and 60 min after cosyntropin stimulation, respectively. Patients with RAF were more likely to have detectable MN at baseline (p = 0.035) and at the time of 60 min (p = 0.048) compared to patients without RAF. There was a positive correlation between detectable MN and the level of cortisol at all time points (p = 0.02, p = 0.04, p < 0.001). No difference was noted for NMN levels, which remained within the normal reference ranges.

CONCLUSION

Even very small amounts of endogenous cortisol production affect MN levels in patients with AAD.

Experimental envenomation with honeybee venom melittin and phospholipase A2 induced multiple ultrastructural changes in adrenocortical mitochondria

Bee stings represent a public health subject, but the mechanisms involved in bee venom toxicity are not yet fully understood. To evaluate the reactions of adrenocortical cells, through which organisms respond to stress, two honeybee venom components: melittin (Mlt) and phospholipase A2 (PLA2) were tested as potential chemical stressors. Modifications were investigated with transmission electron microscopy and microanalysis. A single dose of Mlt (31 mg/kg) or PLA2 (9.3 mg/kg) was injected in rats of groups ML and PL; daily doses of Mlt (350 μg/kg) or PLA2 (105 μg/kg) were injected 30 days in rats of groups M30 and P30. Adrenocortical cells in ML group showed ultrastructural degenerative alterations of nuclei, endoplasmic reticulum, and mitochondria that exhibited lipid inclusions and mitochondrial cristae (MC) re-organized into mono- or multimembrane large vesicles, and whorls of membranes. Many MC were degenerated. In the M30 group, similar ultrastructural changes, but of lower amplitude were noted; lipid cytosolic droplets were heterogenous. MC diameters in Mlt groups (melittin treated groups) were significantly higher than in control (C) group. In PL group, mitochondria contained large lipid inclusions, vesicular MC of different sizes and multiple membranes, and debris, or whorl structures. In P30 group MC were tubular with increased diameters. In both PLA2 groups (PLA2 treated groups) MC were significantly larger than in C group. We concluded that Mlt and PLA2 were powerful stressors, toxic at the tested doses, cellular reactions concerning in all groups mainly mitochondria, but also other cellular compartments. Apart from degenerative regression of MC, the rearrangement of tubular MC occurred into one or multiple large multimembrane vesicular MC. Reactions to the high doses were more pronounced, with the highest amplitude in ML group, and the lowest in P30 group.

The neural addiction of cancer

The recently uncovered key role of the peripheral and central nervous systems in controlling tumorigenesis and metastasis has opened a new area of research to identify innovative approaches against cancer. Although the 'neural addiction' of cancer is only partially understood, in this Perspective we discuss the current knowledge and perspectives on peripheral and central nerve circuitries and brain areas that can support tumorigenesis and metastasis and the possible reciprocal influence that the brain and peripheral tumours exert on one another. Tumours can build up local autonomic and sensory nerve networks and are able to develop a long-distance relationship with the brain through circulating adipokines, inflammatory cytokines, neurotrophic factors or afferent nerve inputs, to promote cancer initiation, growth and dissemination. In turn, the central nervous system can affect tumour development and metastasis through the activation or dysregulation of specific central neural areas or circuits, as well as neuroendocrine, neuroimmune or neurovascular systems. Studying neural circuitries in the brain and tumours, as well as understanding how the brain communicates with the tumour or how intratumour nerves interplay with the tumour microenvironment, can reveal unrecognized mechanisms that promote cancer development and progression and open up opportunities for the development of novel therapeutic strategies. Targeting the dysregulated peripheral and central nervous systems might represent a novel strategy for next-generation cancer treatment that could, in part, be achieved through the repurposing of neuropsychiatric drugs in oncology.

The Adrenergic Nerve Network in Cancer

The central and autonomic nervous systems interact and converge to build up an adrenergic nerve network capable of promoting cancer. While a local adrenergic sympathetic innervation in peripheral solid tumors influences cancer and stromal cell behavior, the brain can participate to the development of cancer through an intermixed dysregulation of the sympathoadrenal system, adrenergic neurons, and the hypothalamo-pituitary-adrenal axis. A deeper understanding of the adrenergic nerve circuitry within the brain and tumors and its interactions with the microenvironment should enable elucidation of original mechanisms of cancer and novel therapeutic strategies.

Caloric Restriction in Group-Housed Mice: Littermate and Sex Influence on Behavioral and Hormonal Data

Much of the research done on aging, oxidative stress, anxiety, and cognitive and social behavior in rodents has focused on caloric restriction (CR). This often involves several days of single housing, which can cause numerous logistical problems, as well as cognitive and social dysfunctions. Previous results in our laboratory showed the viability of long-term CR in grouped rats. Our research has studied the possibility of CR in grouped female and male littermates and unrelated CB6F1/J (C57BL/6J × BALBc/J hybrid strain) mice, measuring: (i) possible differences in body mass proportions between mice in ad libitum and CR conditions (at 70% of ad libitum), (ii) aggressive behavior, using the number of pushes and chasing behavior time as an indicator and social behavior using the time under the feeder as indicator, and (iii) difference in serum adrenocorticotropic hormone (ACTH) concentrations (stress biomarker), under ad libitum and CR conditions. Results showed the impossibility of implementing CR in unrelated male mice. In all other groups, CR was possible, with a less aggressive behavior (measured only with the number of pushes) observed in the unrelated female mice under CR conditions. In that sense, the ACTH levels measured on the last day of CR showed no difference in stress levels. These results indicate that implementantion of long-term CR in mice can be optimized technically and also related to their well-being by grouping animals, in particular, related mice.

Cortisol, DHEA and DHEA-S during exposure therapy in patients with obsessive-compulsive disorder - secretion patterns and prediction of treatment response

The cortisol response in patients with obsessive-compulsive disorder (OCD) during exposure with response prevention (ERP), a stressful but very effective psychotherapeutic treatment, has shown contradictory findings in three prior studies with low sample sizes. In a larger cohort of 51 patients with OCD we repeatedly measured subjective units of distress (SUD) and the adrenocortical stress hormones cortisol, dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEA-S) in saliva during the very first session of ERP and on the day before. Expectedly, SUD were increased on the ERP day before the session and further rose during ERP, but salivary cortisol and DHEA were statistically indistinguishable from the comparison condition. Interestingly, DHEA-S was significantly elevated throughout the ERP versus the comparison day, but did not further increase in acute response to ERP. According to an explorative analysis in a subsample, hormone levels on the comparison or the ERP day did not predict anti-OCD treatment response one month later. These results corroborate our prior findings of cortisol non-response despite considerable subjective stress in ERP. The role of DHEA-S in anticipatory anxiety and the effects of augmentative cortisol therapy in ERP need further study.

Glucocorticoid Excess in Patients with Pheochromocytoma Compared with Paraganglioma and Other Forms of Hypertension

CONTEXT

Catecholamines and adrenocortical steroids are important regulators of blood pressure. Bidirectional relationships between adrenal steroids and catecholamines have been established but whether this is relevant to patients with pheochromocytoma is unclear.

OBJECTIVE

This study addresses the hypothesis that patients with pheochromocytoma and paraganglioma (PPGL) have altered steroid production compared with patients with primary hypertension.

DESIGN

Multicenter cross-sectional study.

SETTING

Twelve European referral centers.

PATIENTS

Subjects included 182 patients with pheochromocytoma, 36 with paraganglioma and 270 patients with primary hypertension. Patients with primary aldosteronism (n = 461) and Cushing syndrome (n = 124) were included for additional comparisons.

INTERVENTION

In patients with PPGLs, surgical resection of tumors.

OUTCOME MEASURES

Differences in mass spectrometry-based profiles of 15 adrenal steroids between groups and after surgical resection of PPGLs. Relationships of steroids to plasma and urinary metanephrines and urinary catecholamines.

RESULTS

Patients with pheochromocytoma had higher (P < .05) circulating concentrations of cortisol, 11-deoxycortisol, 11-deoxycorticosterone, and corticosterone than patients with primary hypertension. Concentrations of cortisol, 11-deoxycortisol, and corticosterone were also higher (P < .05) in patients with pheochromocytoma than with paraganglioma. These steroids correlated positively with plasma and urinary metanephrines and catecholamines in patients with pheochromocytoma, but not paraganglioma. After adrenalectomy, there were significant decreases in cortisol, 11-deoxycortisol, corticosterone, 11-deoxycorticosterone, aldosterone, and 18-oxocortisol.

CONCLUSIONS

This is the first large study in patients with PPGLs that supports in a clinical setting the concept of adrenal cortical-medullary interactions involving an influence of catecholamines on adrenal steroids. These findings could have implications for the cardiovascular complications of PPGLs and the clinical management of patients with the tumors.

Characterization of Group I Metabotropic Glutamate Receptors in Rat and Human Adrenal Glands

Glutamate and its receptors have been demonstrated to promote both basal and nicotine-evoked catecholamine release in bovine chromaffin cells. Multiple glutamate receptors, including metabotropic glutamate receptors (mGluRs), are found in the adrenal glands of several species, as well as in chromaffin cells. However, there is limited information available regarding the expression of glutamate metabotropic receptor (GRM)1-8 mRNAs and the detailed localization of group I mGluRs (mGluR1 and mGluR5) in the rat and human adrenal cortex and medulla. Therefore, we examined mRNA expression of GRM1-8 subunits using reverse transcription-polymerase chain reaction (RT-PCR) and the distribution of mGluR1 and mGluR5 by immunostaining. The results showed that the GRM1-8 mRNAs were expressed in both the cortex and medulla of rat and human adrenal glands with the exception of GRM1, which was not detectable in the rat adrenal cortex. Immunostaining of mGluR1 revealed that it was localized only in the adrenal medulla of rats but was present in both the adrenal cortex and medulla in humans. In the adrenal medulla, the central part of the adrenal glands, mGluR1 was detected in chromaffin cells but not in nerve fibers and ganglion cells. Immunoactivity of mGluR5 was visible in the capillary wall throughout the adrenal cortex and medulla in rat and human samples. Its immunoactivity was also observed in ganglion cells in the rat adrenal medulla. There was no mGluR5 immunoactivity detected in chromaffin cells and nerve fibers in the rat and human adrenal medulla. Using dissected rat adrenal medulla as a model, we found that treatment with a mGluR1 agonist activated extracellular signal-regulated kinase (ERK) 1/2 and increased the expression of tyrosine hydroxylase (TH), the rate-limiting enzyme of catecholamine synthesis. Moreover, these results showed that mGluR1 signaling was involved in hypoxia-induced upregulation of TH in the rat adrenal medulla. This study shows the expression of GRM1-8 mRNAs in rat and human adrenal glands and indicates that glutamate, through the activation of mGluRs, may play various physiological roles in the adrenal gland. Furthermore, mGluR1 may be involved in catecholamine biosynthesis by regulating TH, and mGluR5 may affect cortical and medullar hormone levels by regulating microvascular function.

Post-Mortem Immunohistochemical Evidence of β2-Adrenergic Receptor Expression in the Adrenal Gland

The evidence from post-mortem biochemical studies conducted on cortisol and catecholamines suggest that analysis of the adrenal gland could provide useful information about its role in human pathophysiology and the stress response. Authors designed an immunohistochemical study on the expression of the adrenal β2-adrenergic receptor (β2-AR), a receptor with high-affinity for catecholamines, with the aim to show which zones it is expressed in and how its expression differs in relation to the cause of death. The immunohistochemical study was performed on adrenal glands obtained from 48 forensic autopsies of subjects that died as a result of different pathogenic mechanisms using a mouse monoclonal β2-AR antibody. The results show that immunoreactivity for β2-AR was observed in all adrenal zones. Furthermore, immunoreactivity for β2-AR has shown variation in the localization and intensity of different patterns in relation to the original cause of death. To the best of our knowledge, this is the first study that demonstrates β2-AR expression in the human cortex and provides suggestions on the possible involvement of β2-AR in human cortex hormonal stimulation. In conclusion, the authors provide a possible explanation for the observed differences in expression in relation to the cause of death.

The adrenal gland in stress - Adaptation on a cellular level

Human individuals are constantly confronted to various kinds of stressors and the body's response and adaptation is essential for human health. The adrenal gland as the main producer of stress hormones plays a major role in the response to physiological challenges and is able to adapt to these physiological needs. Proper adaptation is of particular importance since dysregulation of the stress system is the cause of various human diseases including obesity, depression, Parkinson's disease, and post-traumatic stress disorder. Therefore, it is fundamental to understand the physiological, cellular, and molecular underpinnings of the stress adaptation in humans. Because of ethical reasons it is problematic to study the plasticity of the human gland in stress. Hence, various experimental models have been established for the analysis of the functional and cellular role of the adrenal gland adaptation on a translational approach. Here, we summarize the insights of stress-induced adrenal plasticity gained from these models and discuss their relevance to clinical observations.

Tyrosine-hydroxylase immunoreactivity in the mouse transparent brain and adrenal glands

Working on catecholamine systems for years, the neuropharmacologist Arvid Carlsson has made a number of important and pioneering discoveries, which have highlighted the key role of these neuronal and peripheral neurotransmitters in brain functions and adrenal regulations. Since then, major advances have been made concerning the distribution of the catecholaminergic systems in particular by studying their rate-limiting enzyme, tyrosine hydroxylase (TH). Recently new methods of tissue transparency coupled with in toto immununostaining and three-dimensional (3D) imaging technologies allow to precisely map TH immunoreactive pathways in the mouse brain and adrenal glands. High magnification images and movies obtained with combined technologies (iDISCO+ and light-sheet microscopy) are presented in this review dedicated to the pioneer work of Arvid Carlsson and his collaborators.

Cholesterol signaling in single cells: lessons from STAR and sm-FISH

Cholesterol is an important regulator of cell signaling, both through direct impacts on cell membranes and through oxy-metabolites that activate specific receptors (steroids, hydroxy-cholesterols, bile acids). Cholesterol moves slowly through and between cell membranes with the assistance of specific binding proteins and transfer processes. The prototype cholesterol regulator is the Steroidogenesis Acute Regulatory (STAR), which moves cholesterol into mitochondria, where steroid synthesis is initiated by cytochrome P450 11A1 in multiple endocrine cell types. CYP27A1 generates hydroxyl cholesterol metabolites that activate LXR nuclear receptors to control cholesterol homeostatic and transport mechanisms. LXR regulation of cholesterol transport and storage as cholesterol ester droplets is shared by both steroid-producing cells and macrophage. This cholesterol signaling is crucial to brain neuron regulation by astrocytes and microglial macrophage, mediated by ApoE and sensitive to disruption by β-amyloid plaques. sm-FISH delivers appreciable insights into signaling in single cells, by resolving single RNA molecules as mRNA and by quantifying pre-mRNA at gene loci. sm-FISH has been applied to problems in physiology, embryo development and cancer biology, where single cell features have critical impacts. sm-FISH identifies novel features of STAR transcription in adrenal and testis cells, including asymmetric expression at individual gene loci, delayed splicing and 1:1 association of mRNA with mitochondria. This may represent a functional unit for the translation-dependent cholesterol transfer directed by STAR, which integrates into mitochondrial fusion dynamics. Similar cholesterol dynamics repeat with different players in the cycling of cholesterol between astrocytes and neurons in the brain, which may be abnormal in neurodegenerative diseases.

Adrenal cortical and chromaffin stem cells: Is there a common progeny related to stress adaptation?

The adrenal gland is a highly plastic organ with the capacity to adapt the body homeostasis to different physiological needs. The existence of stem-like cells in the adrenal cortex has been revealed in many studies. Recently, we identified and characterized in mice a pool of glia-like multipotent Nestin-expressing progenitor cells, which contributes to the plasticity of the adrenal medulla. In addition, we found that these Nestin progenitors are actively involved in the stress response by giving rise to chromaffin cells. Interestingly, we also observed a Nestin-GFP-positive cell population located under the adrenal capsule and scattered through the cortex. In this article, we discuss the possibility of a common progenitor giving rise to subpopulations of cells both in the adrenal cortex and medulla, the isolation and characterization of this progenitor as well as its clinical potential in transplantation therapies and in pathophysiology.

Interleukin-6-mediated signaling in adrenal medullary chromaffin cells

The pro-inflammatory cytokines, tumor necrosis factor-α, and interleukin-1β/α modulate catecholamine secretion, and long-term gene regulation, in chromaffin cells of the adrenal medulla. Since interleukin-6 (IL6) also plays a key integrative role during inflammation, we have examined its ability to affect both tyrosine hydroxylase activity and adrenomedullary gene transcription in cultured bovine chromaffin cells. IL6 caused acute tyrosine/threonine phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), and serine/tyrosine phosphorylation of signal transducer and activator of transcription 3 (STAT3). Consistent with ERK1/2 activation, IL6 rapidly increased tyrosine hydroxylase phosphorylation (serine-31) and activity, as well as up-regulated genes, encoding secreted proteins including galanin, vasoactive intestinal peptide, gastrin-releasing peptide, and parathyroid hormone-like hormone. The effects of IL6 on the entire bovine chromaffin cell transcriptome were compared to those generated by G-protein-coupled receptor (GPCR) agonists (histamine and pituitary adenylate cyclase-activating polypeptide) and the cytokine receptor agonists (interferon-α and tumor necrosis factor-α). Of 90 genes up-regulated by IL6, only 16 are known targets of IL6 in the immune system. Those remaining likely represent a combination of novel IL6/STAT3 targets, ERK1/2 targets and, potentially, IL6-dependent genes activated by IL6-induced transcription factors, such as hypoxia-inducible factor 1α. Notably, genes induced by IL6 include both neuroendocrine-specific genes activated by GPCR agonists, and transcripts also activated by the cytokines. These results suggest an integrative role for IL6 in the fine-tuning of the chromaffin cell response to a wide range of physiological and paraphysiological stressors, particularly when immune and endocrine stimuli converge.

Intrastriatal Grafting of Chromospheres: Survival and Functional Effects in the 6-OHDA Rat Model of Parkinson's Disease

Cell replacement therapy in Parkinson’s disease (PD) aims at re-establishing dopamine neurotransmission in the striatum by grafting dopamine-releasing cells. Chromaffin cell (CC) grafts produce some transitory improvements of functional motor deficits in PD animal models, and have the advantage of allowing autologous transplantation. However, CC grafts have exhibited low survival, poor functional effects and dopamine release compared to other cell types. Recently, chromaffin progenitor-like cells were isolated from bovine and human adult adrenal medulla. Under low-attachment conditions, these cells aggregate and grow as spheres, named chromospheres. Here, we found that bovine-derived chromosphere-cell cultures exhibit a greater fraction of cells with a dopaminergic phenotype and higher dopamine release than CC. Chromospheres grafted in a rat model of PD survived in 57% of the total grafted animals. Behavioral tests showed that surviving chromosphere cells induce a reduction in motor alterations for at least 3 months after grafting. Finally, we found that compared with CC, chromosphere grafts survive more and produce more robust and consistent motor improvements. However, further experiments would be necessary to determine whether the functional benefits induced by chromosphere grafts can be improved, and also to elucidate the mechanisms underlying the functional effects of the grafts.

The effects of stress on brain and adrenal stem cells

The brain and adrenal are critical control centers that maintain body homeostasis under basal and stress conditions, and orchestrate the body's response to stress. It is noteworthy that patients with stress-related disorders exhibit increased vulnerability to mental illness, even years after the stress experience, which is able to generate long-term changes in the brain's architecture and function. High levels of glucocorticoids produced by the adrenal cortex of the stressed subject reduce neurogenesis, which contributes to the development of depression. In support of the brain-adrenal connection in stress, many (but not all) depressed patients have alterations in the components of the limbic-hypothalamic-pituitary-adrenal (LHPA) axis, with enlarged adrenal cortex and increased glucocorticoid levels. Other psychiatric disorders, such as post-traumatic stress disorder, bipolar disorder and depression, are also associated with abnormalities in hippocampal volume and hippocampal function. In addition, hippocampal lesions impair the regulation of the LHPA axis in stress response. Our knowledge of the functional connection between stress, brain function and adrenal has been further expanded by two recent, independent papers that elucidate the effects of stress on brain and adrenal stem cells, showing similarities in the way that the progenitor populations of these organs behave under stress, and shedding more light into the potential cellular and molecular mechanisms involved in the adaptation of tissues to stress.

Effect of a pre-exercise hydrocortisone dose on short-term physical performance in female patients with primary adrenal failure

OBJECTIVE

Many patients with primary adrenal insufficiency (Addison's disease) take extra doses of glucocorticoids during stressful events, but a benefit has not been demonstrated in controlled trials. Here, we investigated the effects of a pre-exercise hydrocortisone dose on cardiorespiratory, hormonal and metabolic parameters in response to short-term strenuous physical activity.

DESIGN

This was a randomized placebo-controlled, two-week cross-over clinical trial.

PARTICIPANTS

Ten women with Addison's disease and 10 age-matched healthy females participated in the study.

MEASUREMENTS

All women in the study underwent maximal incremental exercise testing. A stress dose of 10 mg hydrocortisone or placebo was given 1 h prior to exercise on two occasions. Blood samples were drawn before, and 0, 15 and 30 min post exercise. Oxygen uptake, maximal aerobic capacity, endocrine and metabolic responses to physical activity, as well as health status by questionnaires were evaluated.

RESULTS

Maximal aerobic capacity and duration of exercise were significantly lower in patients than in healthy subjects and did not improve with the treatment. After an extra hydrocortisone dose serum cortisol was significantly higher than in the healthy subjects (P<0.001). Post-exercise glucose and adrenaline levels were significantly lower and free fatty acids insignificantly higher in patients irrespective of stress dose. Stress dosing did not alter other metabolic or hormonal parameters or quality of life after the exercise.

CONCLUSIONS

The patients did not benefit from an extra dose of hydrocortisone in short strenuous exercise. Stress dosing may not be justified in this setting. Whether stress dosing is beneficial in other types of physical activity will have to be examined further.

Adrenocortical Gap Junctions and Their Functions

Adrenal cortical steroidogenesis and proliferation are thought to be modulated by gap junction-mediated direct cell-cell communication of regulatory molecules between cells. Such communication is regulated by the number of gap junction channels between contacting cells, the rate at which information flows between these channels, and the rate of channel turnover. Knowledge of the factors regulating gap junction-mediated communication and the turnover process are critical to an understanding of adrenal cortical cell functions, including development, hormonal response to adrenocorticotropin, and neoplastic dedifferentiation. Here, we review what is known about gap junctions in the adrenal gland, with particular attention to their role in adrenocortical cell steroidogenesis and proliferation. Information and insight gained from electrophysiological, molecular biological, and imaging (immunocytochemical, freeze fracture, transmission electron microscopic, and live cell) techniques will be provided.

Practical approaches for evaluating adrenal toxicity in nonclinical safety assessment

The adrenal gland has characteristic morphological and biochemical features that render it particularly susceptible to the actions of xenobiotics. As is the case with other endocrine organs, the adrenal gland is under the control of upstream organs (hypothalamic-pituitary system) in vivo, often making it difficult to elucidate the mode of toxicity of a test article. It is very important, especially for pharmaceuticals, to determine whether a test article-related change is caused by a direct effect or other associated factors. In addition, antemortem data, including clinical signs, body weight, food consumption and clinical pathology, and postmortem data, including gross pathology, organ weight and histopathologic examination of the adrenal glands and other related organs, should be carefully monitored and evaluated. During evaluation, the following should also be taken into account: (1) species, sex and age of animals used, (2) metabolic activation by a cytochrome P450 enzyme(s) and (3) physicochemical properties and the metabolic pathway of the test article. In this review, we describe the following crucial points for toxicologic pathologists to consider when evaluating adrenal toxicity: functional anatomy, blood supply, hormone production in each compartment, steroid biosynthesis, potential medulla-cortex interaction, and species and gender differences in anatomical features and other features of the adrenal gland which could affect vulnerability to toxic effects. Finally practical approaches for evaluating adrenal toxicity in nonclinical safety studies are discussed.

Chronic subordinate colony housing paradigm: a mouse model to characterize the consequences of insufficient glucocorticoid signaling

Chronic, in particular chronic psychosocial, stress is a burden of modern societies and known to be a risk factor for numerous somatic and affective disorders (in detail referenced below). However, based on the limited existence of appropriate, and clinically relevant, animal models for studying the effects of chronic stress, the detailed behavioral, physiological, neuronal, and immunological mechanisms linking stress and such disorders are insufficiently understood. To date, most chronic stress studies in animals employ intermittent exposure to the same (homotypic) or to different (heterotypic) stressors of varying duration and intensity. Such models are only of limited value, since they do not adequately reflect the chronic and continuous situation that humans typically experience. Furthermore, application of different physical or psychological stimuli renders comparisons to the mainly psychosocial stressors faced by humans, as well as between the different stress studies almost impossible. In contrast, rodent models of chronic psychosocial stress represent situations more akin to those faced by humans and consequently seem to hold more clinical relevance. Our laboratory has developed a model in which mice are exposed to social stress for 19 continuous days, namely the chronic subordinate colony housing (CSC) paradigm, to help bridge this gap. The main aim of the current review article is to provide a detailed summary of the behavioral, physiological, neuronal, and immunological consequences of the CSC paradigm, and wherever possible relate the findings to other stress models and to the human situation.

Lipoproteins and Hedgehog signalling--possible implications for the adrenal gland function

BACKGROUND

Metabolic syndrome is a common metabolic disorder that is associated with an increased risk of type 2 diabetes and cardiovascular diseases. Disturbances in adrenal steroid hormone production significantly contribute to the development of this disorder. Therefore, it is extremely important to fully understand the mechanisms governing adrenal gland function, both in physiological and pathological conditions.

RESULTS

Recently, Sonic hedgehog has emerged as an important regulator of adrenal development, with a possible role in adult gland homeostasis. Recent work of our group shows that lipoproteins are important regulators of Hedgehog signaling; they act as carriers for the spread of Hedgehog proteins, but also contain lipid(s) that inhibit the pathway.

CONCLUSIONS

We propose that lipoproteins may affect Sonic hedgehog signaling in the adult adrenal gland at multiple levels. Understanding the interplay between lipoprotein metabolism and adrenal Hedgehog signaling may improve our understanding of how adrenal gland disorders contribute to the metabolic syndrome.

Chronic psychosocial stress results in sensitization of the HPA axis to acute heterotypic stressors despite a reduction of adrenal in vitro ACTH responsiveness

Although chronic psychosocial stress is often accompanied by changes in basal hypothalamo-pituitary-adrenal (HPA) axis activity, it is vital for a chronically-stressed organism to mount adequate glucocorticoid (GC) responses when exposed to acute challenges. The main aim of the present study was to test whether this is true or not for the chronic subordinate colony housing (CSC, 19 days) paradigm, an established and clinically relevant mouse model of chronic psychosocial stress. As shown previously, CSC mice are characterized by unaffected morning and decreased evening plasma corticosterone (CORT) levels despite enlarged adrenals, suggesting a maladaptive breakdown of adrenal functioning. Plasma CORT levels, determined by repeated blood sampling via jugular vein catheters, as well as relative right adrenal CORT content were increased in CSC compared with single-housed control (SHC) mice in response to acute elevated platform (EPF, 5min) exposure. However, in vitro stimulation of adrenal explants with physiological and pharmacological doses of ACTH revealed an attenuated responsiveness of both the left and right adrenal glands following CSC, despite mRNA and/or protein expression of melanocortin 2 receptor (Mc2r), Mc2r accessory protein (MRAP), and key enzymes of steroidogenesis were not down-regulated. Taken together, we show that chronic psychosocial stressor exposure impairs in vitro ACTH responsiveness of both the left and right adrenal glands, whereas it increases adrenal responsiveness to an acute heterotypic stressor in vivo. This suggests that an additional factor present during acute stressor exposure in vivo rescues left and right adrenal ACTH sensitivity, or itself acts as CORT secretagogue in chronically stressed CSC mice.

Role of reactive oxygen species in the neural and hormonal regulation of the PNMT gene in PC12 cells

The stress hormone, epinephrine, is produced predominantly by adrenal chromaffin cells and its biosynthesis is regulated by the enzyme phenylethanolamine N-methyltransferase (PNMT). Studies have demonstrated that PNMT may be regulated hormonally via the hypothalamic-pituitary-adrenal axis and neurally via the stimulation of the splanchnic nerve. Additionally, hypoxia has been shown to play a key role in the regulation of PNMT. The purpose of this study was to examine the impact of reactive oxygen species (ROS) produced by the hypoxia mimetic agent CoCl₂, on the hormonal and neural stimulation of PNMT in an in vitro cell culture model, utilizing the rat pheochromocytoma (PC12) cell line. RT-PCR analyses show inductions of the PNMT intron-retaining and intronless mRNA splice variants by CoCl₂ (3.0- and 1.76-fold, respectively). Transient transfection assays of cells treated simultaneously with CoCl₂ and the synthetic glucocorticoid, dexamethasone, show increased promoter activity (18.5-fold), while mRNA levels of both splice variants do not demonstrate synergistic effects. Similar results were observed when investigating the effects of CoCl₂-induced ROS on the neural stimulation of PNMT via forskolin. Our findings demonstrate that CoCl₂-induced ROS have synergistic effects on hormonal and neural activation of the PNMT promoter.

Maternal perinatal undernutrition has long-term consequences on morphology, function and gene expression of the adrenal medulla in the adult male rat

Epidemiological studies suggest that maternal undernutrition sensitises to the development of chronic adult diseases, such as type 2 diabetes, hypertension and obesity. Although the physiological mechanisms involved in this 'perinatal programming' remain largely unknown, alterations of stress neuroendocrine systems such as the hypothalamic-pituitary-adrenal (HPA) and sympathoadrenal axes might play a crucial role. Despite recent reports showing that maternal perinatal undernutrition disturbs chromaffin cells organisation and activity in male rats at weaning, its long-term effects on adrenal medulla in adult animals are unknown. Using a rat model of maternal perinatal 50% food restriction (FR50) from the second week of gestation until weaning, histochemistry approaches revealed alterations in noradrenergic chromaffin cells aggregation and in cholinergic innervation in the adrenal medulla of 8-month-old FR50 rats. Electron microscopy showed that chromaffin cell granules exhibited ultrastructural changes in FR50 rats. These morphological changes were associated with reduced circulating levels and excretion of catecholamines. By contrast, catecholamine plasma levels were significantly increased after a 16 or 72 h of fasting, indicating that the responsiveness of the sympathoadrenal system to food deprivation was accentuated in FR50 adult rats. Among 384 pituitary adenylate cyclase-activating polypeptide-sensitive genes, we identified 129 genes (33.6%) that were under expressed (ratio < 0.7) in FR50 animals. A large number of these genes are involved in cytoskeleton remodelling and vesicle trafficking. Taken together, our results show that maternal perinatal undernutrition programmes adrenomedullary function and gene expression in adult male rats. Because catecholamines contribute to metabolic homeostasis, as well as arterial blood pressure regulation, the alterations observed in the adrenal medulla of adult male FR50 rats may participate in the programming of chronic adult diseases.

Gap junction-mediated intercellular communication in the adrenal medulla: an additional ingredient of stimulus-secretion coupling regulation

The traditional understanding of stimulus-secretion coupling in adrenal neuroendocrine chromaffin cells states that catecholamines are released upon trans-synaptic sympathetic stimulation mediated by acetylcholine released from the splanchnic nerve terminals. Although this statement remains largely true, it deserves to be tempered. In addition to its neurogenic control, catecholamine secretion also depends on a local gap junction-mediated communication between chromaffin cells. We review here the insights gained since the first description of gap junctions in the adrenal medullary tissue. Adrenal stimulus-secretion coupling now appears far more intricate than was previously envisioned and its deciphering represents a challenge for neurobiologists engaged in the study of the regulation of neuroendocrine secretion. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.

Adrenal responses to stress

Based on concepts proposed by Langley, Cannon, and Selye, adrenal responses to stress occur in a syndrome that reflects activation of the sympathoadrenal system and hypothalamic–pituitary–adrenocortical (HPA) axis; and a "stress syndrome" maintains homeostasis in emergencies such as "fight or flight" situations, but if the stress response is excessive or prolonged then any of a variety of clinical disorders can arise. The idea of a unitary sympathoadrenal system does not account for evidence that different stressors elicit different patterns of autonomic responses, with exposure to some stressors differentially affecting sympathetic noradrenergic and adrenomedullary hormonal activities. Instead, adrenomedullary responses to stressors are more closely tied to adrenocortical than to sympathetic noradrenergic responses. Distress involves concurrent activation of the HPA and adrenomedullary neuroendocrine systems.

Acetylation-mediated epigenetic regulation of glucocorticoid receptor activity: circadian rhythm-associated alterations of glucocorticoid actions in target tissues

Glucocorticoids influence organ functions through the glucocorticoid receptor, a protein acetylated and deacetylated by several histone acetyltransferases and deacetylases. We reported that the circadian rhythm-related transcription factor "Clock", a key component of the biological CLOCK with inherent histone acetyltransferase activity, acetylates glucocorticoid receptor lysines within its hinge region--a "lysine cluster" containing a KXKK motif--and represses its transcriptional activity. This Clock-induced repression of the glucocorticoid receptor activity is inversely phased to the diurnally circulating glucocorticoids and may act as a local counter regulatory mechanism to the actions of these hormones. Importantly, uncoupling of the central CLOCK-regulated hypothalamic-pituitary-adrenal axis and peripheral CLOCK-mediated alterations of glucocorticoid action, such as chronic stress and frequent trans-time zone travel or night-shift work, may cause functional hypercortisolism and contribute to various pathologies. Thus, acetylation-mediated epigenetic regulation of the glucocorticoid receptor may be essential for the maintenance of proper time-integrated glucocorticoid action, significantly influencing human well-being and longevity.

Adrenal gland responses to lipopolysaccharide after stress and ethanol administration in male rats

All forms of stress, including restraint stress (RS) and lipopolysaccharide (LPS) administration, activate the hypothalamic-pituitary-adrenal (HPA) axis. LPS binds to a recognition protein (CD14) and toll-like receptor 2/4 in different cells and tissues, including the adrenal gland, to induce the production of cytokines and cause upregulation of cyclooxygenase and nitric oxide synthase (NOS) enzymes. Acute ethanol exposure activates the HPA axis, but in some conditions prolonged administration can dampen this activation as well as decrease the inflammatory responses to LPS. Therefore, this study was designed to evaluate the adrenal response to a challenge dose of LPS (50 μg/kg) injected i.p., after submitting male rats to RS, twice a day (2 h each time) for 5 days and/or ethanol administration (3 g/kg) by gavage also for 5 days, twice daily. At the end of the experiment, plasma corticosterone concentrations and adrenal gland content of prostaglandin E (PGE) and NOS activity were measured as stress mediators. The results showed that repetitive ethanol administration attenuated the adrenal stress response to LPS challenge alone and after RS, by preventing the increase in plasma corticosterone concentrations and by decreasing the PGE content and NOS activity in the adrenal gland. Therefore, we conclude that moderate alcohol consumption could attenuate the effects of psychophysical stress and impair an inflammatory response.

Acute and chronic stress increase DHEAS concentrations in rhesus monkeys

Most studies on the stress-responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis have focused on glucocorticoids, while few studies have investigated the adrenal secretion of dehydroepiandrosterone sulfate (DHEAS), which is unique to primates. Monkeys were chair-restrained for 2h per day for seven consecutive days, and blood samples were collected upon placement in the chair, and at 15, 30, 60 and 120 min later. Like cortisol, DHEAS concentrations increased throughout the initial session of chair restraint (acute stress). Unlike the cortisol response, which decreased after repeated exposure to the stressor, the DHEAS response was sustained throughout the seventh session of restraint (chronic stress) and response to the seventh session of restraint did not differ from the DHEAS response to the initial session. Like cortisol, DHEAS concentrations showed a diurnal rhythm with higher concentrations in the morning compared to the evening and a decrease in response to dexamethasone (DEX) administration. After repeated exposure to the stressor, the suppression of DHEAS in response to dexamethasone was more complete, suggesting an increase in negative feedback sensitivity. These data show that DHEAS concentrations increase in response to both acute and chronic (repeated) stress and provide another measure of HPA activity that parallels cortisol during acute responses to stress but diverges in chronic or repeated stress.

Adrenomedullary function in patients with nonclassic congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is classified into three types based on disease severity: classic salt-wasting, classic simple virilizing, and nonclassic. Adrenomedullary dysplasia and epinephrine deficiency have been described in classic CAH, resulting in glucose dysregulation. Our objective was to investigate adrenomedullary function in nonclassic CAH and to evaluate adrenomedullary function according to disease severity. Adrenomedullary function was evaluated in response to a standardized cycle ergonometer test in 23 CAH patients (14 females, age 9-38 years; 6 salt-wasting, 7 simple virilizing, 5 nonclassic receiving glucocorticoid treatment, 5 nonclassic not receiving glucocorticoid), and 14 controls (7 females, age 12-38 years). Epinephrine, glucose, and cortisol were measured at baseline and peak exercise. CAH patients and controls were similar in age and anthropometric measures. Patients with nonclassic CAH who were not receiving glucocorticoid and controls experienced the expected stress-induced rise in epinephrine, glucose, and cortisol. Compared to controls, patients with all types of CAH receiving glucocorticoid had impaired exercise-induced changes in epinephrine (salt-wasting: p=0.01;simple virilizing: p=0.01; nonclassic: p=0.03), and cortisol (salt-wasting: p=0.004; simple virilizing: p=0.006; nonclassic: p=0.03). Salt-wasting patients displayed the most significant impairment, including impairment in glucose response relative to controls (p=0.03). Hydrocortisone dose was negatively correlated with epinephrine response (r=-0.58; p=0.007) and glucose response (r=-0.60; p=0.002). The present study demonstrates that untreated patients with nonclassic CAH have normal adrenomedullary function. The degree of epinephrine deficiency in patients with CAH is associated with the severity of adrenocortical dysfunction, as well as glucocorticoid therapy.

Effects of housing and short-term transportation on hormone and lymphocyte receptor concentrations in beef cattle

The experiment was designed to evaluate the effects of housing system and short-term transportation on the pituitary and adrenal response and on blood progesterone concentrations of beef cattle. Since the use of steroid hormones in farm animals has been banned in the EU (Council Directive 96/22/EC), it seems important to study the possible modifications in serum progesterone concentrations induced by stress in cattle. Thirty-two, 6 months old male Piedmontese beef cattle (16 reared in a littered loose house, Group A, and 16 housed in a littered tying stall barn, Group B) were blood sampled at T1 (6 months old), T2 (12 months old), T3 (18 months old, before transportation to the slaughterhouse) and T4 (after transportation to the slaughterhouse) in order to measure hormonal concentrations and lymphocyte glucocorticoid (GR) and β-adrenergic (β-AR) receptor concentrations. Circulating hormone concentrations were measured using commercial radioimmunoassay kits, whereas lymphocyte receptor density was determined through binding assays. In beef cattle housed in tie stall barn a significant increase in serum cortisol concentration was observed at T3, whereas there was no effect of the housing system on blood progesterone concentrations. Short-term transportation caused a significant increase in blood cortisol and catecholamine concentrations in both groups, whereas lymphocyte GR and β-AR significantly decreased in Group A. Our data confirm the activation of the hypothalamic-pituitary-adrenal axis and the catecholaminergic system in short-term transportation and suggest that the stress-induced increase in circulating progesterone concentrations does not exceed the limit established by pending legislation.

Tyrosine hydroxylase, chromogranin A, and steroidogenic acute regulator as markers for successful separation of human adrenal medulla

Progress in high throughput "-omic" techniques now allows the simultaneous measurement of expression levels of thousands of genes and promises the improved understanding of the molecular biology of diseases such as cancer. Detection of the dysfunction of molecular pathways in diseases requires healthy control tissue. This is difficult to obtain from pheochromocytomas (PHEOs), rare chromaffin tumors derived from adrenal medulla. The two options for obtaining adrenal tissue are: (1) whole organ removal post-mortem or during radical nephrectomy; (2) removal during PHEO surgery. Access to high quality normal adrenal tissue is limited. Removal of whole adrenals during nephrectomy is rare, because of improved surgical techniques. For adrenals removed post-mortem, the lag time to proper organ perfusion causes uncontrolled tissue degradation. Adjacent normal adrenal tissue can almost never be obtained from resected PHEOs, because they often replace the entire medulla or are well-encapsulated. If a margin of normal adrenal is attached to a resected PHEO, it seldom contains any medulla. The clean separation of medulla and cortex is further complicated, because their border is convoluted, and because adult adrenal consists of approximately 90% cortex. Thus, the quality of separation has to be evaluated with specific medullary and cortical markers. We describe the successful dissection of highly pure, medullary tissue from adrenals snap-frozen upon resection during radical nephrectomy or after brain death. Separation quality has been verified by quantitative reverse transcription with polymerase chain reaction for the medullary enzymes, tyrosine hydroxylase, and chromogranin A, and for the cortical enzyme, steroidogenic acute regulator.

Involvement of opioids and catecholamines in stress modulation of LH secretion in the male pig

The effects of different acute stressors on LH secretion and their possible interactions with opioidergic and catecholaminergic-modulation of LH secretion were investigated using gonadectomized male miniature pigs. Nose-snare (NS) or high intensity cracker blast (CB) or ACTH (1 iu/kg BW) was administered 3h after start of blood sampling. Animals also received either naloxone (Nal; 1 mg/kg BW) or propranolol-a beta-adrenergic antagonist (Pro; 0.5 mg/kg BW) or saline. Naloxone and propranolol were given 30 (Nal) or 15 min (Pro), before the application of stressor or ACTH. Blood samples were collected every 10 min for 6h. Neither the acute stress of NS nor CB altered the LH secretion. ACTH increased the mean plasma LH concentrations and the LH pulse amplitude (p< or =0.01) but not the pulse frequency. Naloxone elevated the mean LH values in controls, but had no effects on LH pulse frequency or pulse amplitude. Naloxone-induced increase in LH concentrations was attenuated by NS and ACTH. There was an increase in mean plasma LH values (p< or =0.05), LH pulse amplitude (p< or =0.01) and pulse frequency (p< or =0.05) after treatment with propranolol. Nose-snare caused a reduction in the propranolol-induced increase of LH pulse frequency and pulse amplitude. In conclusion, although, the transient painful stress of NS does not affect the LH values, it alters the opioidergic and catecholaminergic-modulation of LH secretion. The interference with opioid system is possibly mediated by ACTH.

Isolation of neural crest derived chromaffin progenitors from adult adrenal medulla

Chromaffin cells of the adrenal medulla are neural crest-derived cells of the sympathoadrenal lineage. Unlike the closely-related sympathetic neurons, a subpopulation of proliferation-competent cells exists even in the adult. Here, we describe the isolation, expansion, and in vitro characterization of proliferation-competent progenitor cells from the bovine adrenal medulla. Similar to neurospheres, these cells, when prevented from adherence to the culture dish, grew in spheres, which we named chromospheres. These chromospheres were devoid of mRNA specific for smooth muscle cells (MYH11) or endothelial cells (PECAM1). During sphere formation, markers for differentiated chromaffin cells, such as phenylethanolamine-N-methyl transferase, were downregulated while neural progenitor markers nestin, vimentin, musashi 1, and nerve growth factor receptor, as well as markers of neural crest progenitor cells such as Sox1 and Sox9, were upregulated. Clonal analysis and bromo-2'-deoxyuridine-incorporation analysis demonstrated the self-renewing capacity of chromosphere cells. Differentiation protocols using NGF and BMP4 or dexamethasone induced neuronal or endocrine differentiation, respectively. Electrophysiological analyses of neural cells derived from chromospheres revealed functional properties of mature nerve cells, such as tetrodotoxin-sensitive sodium channels and action potentials. Our study provides evidence that proliferation and differentiation competent chromaffin progenitor cells can be isolated from adult adrenal medulla and that these cells might harbor the potential for the treatment of neurodegenerative diseases, such as Parkinson's disease.