Mineralocorticoid and glucocorticoid receptors at the neuronal membrane, regulators of nongenomic corticosteroid signalling

Chronic stress induces behavioural changes through increased kynurenic acid by downregulation of kynurenine-3-monooxygenase with microglial decline

BACKGROUND AND PURPOSE

Alterations in tryptophan-kynurenine (TRP-KYN) pathway are implicated in major depressive disorder (MDD). α7 nicotinic acetylcholine (α7nACh) receptor regulates the hypothalamic-pituitary-adrenal (HPA) axis. We have shown that deficiency of kynurenine 3-monooxygenase (KMO) induces depression-like behaviour via kynurenic acid (KYNA; α7nACh antagonist). In this study, we investigated the involvement of the TRP-KYN pathway in stress-induced behavioural changes and the regulation of the HPA axis.

EXPERIMENTAL APPROACH

Mice were exposed to chronic unpredictable mild stress (CUMS) and subjected to behavioural tests. We measured TRP-KYN metabolites and the expression of their enzymes in the hippocampus. KMO heterozygous mice were used to investigate stress vulnerability. We also evaluated the effect of nicotine (s.c.) on CUMS-induced behavioural changes and an increase in serum corticosterone (CORT) concentration.

KEY RESULTS

CUMS decreased social interaction time but increased immobility time under tail suspension associated with increased serum corticosterone concentration. CUMS increased KYNA levels via KMO suppression with microglial decline in the hippocampus. Kmo+/- mice were vulnerable to stress: they exhibited social impairment and increased serum corticosterone concentration even after short-term CUMS. Nicotine attenuated CUMS-induced behavioural changes and increased serum corticosterone concentration by inhibiting the increase in corticotropin-releasing hormone. Methyllycaconitine (α7nACh antagonist) inhibited the attenuating effect of nicotine.

CONCLUSIONS AND IMPLICATIONS

CUMS-induced behavioural changes and the HPA axis dysregulation could be induced by the increased levels of KYNA via KMO suppression. KYNA plays an important role in the pathophysiology of MDD as an α7nACh antagonist. Therefore, α7nACh receptor is an attractive therapeutic target for MDD.

Hypothalamus-pituitary-adrenal and gut-brain axes in biological interaction pathway of the depression

The hypothalamus-pituitary-adrenal (HPA) and gut-brain axes are vital biological pathways in depression. The HPA axis regulates the body's stress response, and chronic stress can lead to overactivation of the HPA axis, resulting in elevated cortisol levels that contribute to neuronal damage, particularly in regions such as the hippocampus and prefrontal cortex, both of which are involved in mood regulation and mental disorders. In parallel, the gut-brain axis, a bidirectional communication network between the gut microbiota and the central nervous system, influences emotional and cognitive functions. Imbalances in gut microbiota can affect the HPA axis, promoting inflammation and increasing gut permeability. This allows endotoxins to enter the bloodstream, contributing to neuroinflammation and altering neurotransmitter production, including serotonin. Since the majority of serotonin is produced in the gut, disruptions in this pathway may be linked to depressive symptoms. This review explores the interplay between the HPA axis and the gut-brain axis in the context of depression.

Current Strategies and Future Directions of Wearable Biosensors for Measuring Stress Biochemical Markers for Neuropsychiatric Applications

Most wearable biosensors aimed at capturing psychological state target stress biomarkers in the form of physical symptoms that can correlate with dysfunction in the central nervous system (CNS). However, such markers lack the specificity needed for diagnostic or preventative applications. Wearable biochemical sensors (WBSs) have the potential to fill this gap, however, the technology is still in its infancy. Most WBSs proposed thus far target cortisol. Although cortisol detection is demonstrated as a viable method for approximating the extent and severity of psychological stress, the hormone also lacks specificity. Multiplex WBSs that simultaneously target cortisol alongside other viable stress-related biochemical markers (SBMs) can prove to be indispensable for understanding how psychological stress contributes to the pathophysiology of neuropsychiatric illnesses (NPIs) and, thus, lead to the discovery of new biomarkers and more objective clinical tools. However, none target more than one SBM implicated in NPIs. Till this review, cortisol's connection to dysfunctions in the CNS, to other SBMs, and their implication in various NPIs has not been discussed in the context of developing WBS technology. As such, this review is meant to inform the biosensing and neuropsychiatric communities of viable future directions and possible challenges for WBS technology for neuropsychiatric applications.

Caffeic acid differentially modulates behavior and neurochemicals in chronic unpredictable mild stress and dexamethasone induced models of depression

In the present study authors studied the effect of caffeic acid (CA) in chronic unpredictable mild stress (CUMS) and dexamethasone (DEXA) model of depression. CUMS (21 days) and DEXA (1.5 mg/kg × 21 days) was used for the induction of depression and anxiety related behavior. Locomotor activity was determined using actophotometer. Depression related behavior was determined using tail suspension test (TST) and forced swim test (FST) whereas for the determination of anxiety related behavior elevated plus maze (EPM) test was used. Following behavioral studies, mice were sacrificed by decapitation method. Hippocampus was dissected and was used for the neurochemical assays including 5-HT (serotonin), glutamate, nitrite and gamma-aminobutyric acid (GABA). The results obtained suggested that the CA (25-100 mg/kg, i.p.) did not affect the activity count in CUMS exposed and DEXA treated mice. CA (50 mg/kg) evoked anxiogenic reactions in CUMS model by increasing the hippocampal nitrite and glutamate level while CA (50 mg/kg) exerted anxiolysis in DEXA model by reducing the level of 5-HT. In CUMS model, CA exerted antidepressant like effect by increasing the hippocampal nitric oxide (NO) level, in DEXA model CA exerted antidepressant like effect by reducing the hippocampal glutamate level. CA failed to reverse DEXA mediated nNOS inhibition and therefore decreases hippocampal glutamate level to exert antidepressant like effect. Thus, CA modulate anxiety and depression related neurobehavioral alterations in both CUMS and DEXA models.

Mitogen-activated protein kinase dependent presynaptic potentiation in the lateral habenula mediates depressive-like behaviors in rats

Emerging evidence suggests that the enhanced activity of lateral habenula (LHb) is involved in depressive disorders. This abnormal potentiation of LHb neurons was shown to originate from presynaptic alterations; however, the mechanisms underlying this presynaptic enhancement and physiological consequences are yet to be elucidated. Previously, we reported that presynaptic transmission in the LHb is temporally rhythmic, showing greater activity in the afternoon than in the morning. Here, we used a learned helpless rodent model of depression to show that exposure to a stressor or incubation with the stress hormone, corticosterone, abolished the presynaptic temporal variation in the LHb. In addition, selective inhibition of mitogen-activated protein kinase (MAPK) kinase (MAPKK, MEK) activity in the LHb restored the presynaptic alteration even after stress exposure. Moreover, we observed a slight increase in phosphorylated synapsin I after stress exposure. Finally, we found that a blockade of MAPK signaling before stress exposure successfully prevented the depression-like behaviors, including behavioral despair and helplessness, in an acute learned helpless animal model of depression. Our study delineates the cellular and molecular mechanisms responsible for the abnormal presynaptic enhancement of the LHb in depression, which may mediate depressive behaviors.

Two Hits of EDCs Three Generations Apart: Evaluating Multigenerational Anxiety-Like Behavioral Phenotypes in Female Rats Exposed to Aroclor 1221 and Vinclozolin

BACKGROUND

Endocrine-disrupting chemicals (EDCs) are exogenous chemical compounds that interfere with the normal function of the endocrine system and are linked to direct and inherited adverse effects in both humans and wildlife. Legacy EDCs such as polychlorinated biphenyls (PCBs) are no longer used yet remain detectable in biological specimens around the world; concurrently, we are exposed to newer EDCs like the fungicide vinclozolin (VIN). This combination of individuals' direct environmental chemical exposures and any heritable changes caused by their ancestors' chemical exposures leads to a layered pattern of both direct and ancestrally inherited exposures that might have cumulative effects over generations.

OBJECTIVES

We assessed consequences of both direct and ancestral exposure to EDCs over six generations, examining anxiety-like behaviors in maternal and paternal lines of female rats. We used the "two hits, three generations apart" multigenerational exposure model to explore how two distinct EDCs-the weakly estrogenic PCB mixture Aroclor 1221 (A1221) and the antiandrogenic VIN-interact on behavior across generations. We also explored serum hormones as a potential mechanism.

METHODS

Rats were prenatally exposed to A1221, VIN, or vehicle (DMSO) in the F1 generation, and a second exposure (same or different) was administered to the F4 generation. Anxiety-like behavior was measured in the Open Field test, Light:Dark box, and Elevated Plus Maze in the F1, F3, F4, and F6 generations. Serum concentrations of estradiol and corticosterone were analyzed.

RESULTS

Behavioral effects were not detectable in the F1 generation but emerged and became more robust across generations. Rats with ancestral VIN exposure demonstrated less anxiety-like behavior in the F3 paternal line in comparison with controls. Rats exposed to ancestral then prenatal A1221/VIN and VIN/A1221 had more anxiety-like behavior in the F4 maternal line, and those with two ancestral hits of VIN/VIN had more anxiety in the F6 paternal line, in comparison with controls.

DISCUSSION

Our findings suggest that anxiety-like behavioral phenotypes can manifest in rats following germline exposure to EDCs and that subsequent exposures across generations can intensify these effects in a lineage-dependent manner. https://doi.org/10.1289/EHP15621.

Glucocorticoids induce HMGB1 release in primary cultured rat cortical microglia

Stress, a risk factor for major depressive disorder and Alzheimer disease, leads to the release of high-mobility group box-1 (HMGB1) protein, which in turn causes neuroinflammation. The mechanism underlying stress-induced HMGB1 release is unknown, but stress-associated glucocorticoids could be involved. Primary cultured rat cortical microglia and neurons were treated with corticosterone, a stress-associated glucocorticoid, and HMGB1 release was measured by ELISA and western blotting to test this hypothesis. With corticosterone treatment, significant HMGB1 was released in microglia but not in neuronal cell cultures. HMGB1 mRNA expression and HMGB1 protein expression in microglia were not affected by corticosterone treatment. Thus, the source of extracellular HMGB1 released into the medium is likely to be existing nuclear HMGB1 rather than newly synthesized HMGB1. Corticosterone-induced HMGB1 release in microglia culture was significantly attenuated by blocking glucocorticoid receptors but not mineralocorticoid receptors. Dexamethasone, a selective glucocorticoid receptor agonist, and dexamethasone-bovine serum albumin (BSA), a membrane-impermeable glucocorticoid receptor agonist used to confirm the membrane receptor-mediated effects of glucocorticoids, increased the release of HMGB1. Immunocytochemistry showed that HMGB1 translocated from the nucleus to the cytoplasm following dexamethasone or dexamethasone-BSA treatment through glucocorticoid receptors. The present findings suggest that glucocorticoids stimulate microglial membrane glucocorticoid receptors and trigger cytoplasmic translocation and extracellular release of nuclear HMGB1. Thus, under stress conditions, glucocorticoids induce microglial HMGB1 release, leading to a neuroinflammatory state that could mediate neurological disorders.

Altered Steroidome in Women with Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) mainly afflicting young women. Various steroids can influence the onset and development of the disease or, on the contrary, mitigate its course; however, a systematic review of steroidomic changes in MS patients is lacking. Based on the gas chromatography tandem mass spectrometry (GC-MS/MS) platform and, in the case of estradiol, also using immunoassay, this study performed a comprehensive steroidomic analysis in 25 female MS patients aged 39(32, 49) years compared to 15 female age-matched controls aged 38(31, 46) years. A significant trend towards higher ratios of conjugated steroids to their unconjugated counterparts was found in patients, which is of particular interest in terms of the balance between excitatory and inhibitory steroid modulators of ionotropic receptors. Patients showed altered metabolic pathway to cortisol with decreased conversion of pregnenolone to 17-hydroxypregnenolone and 17-hydroxypregnenolone to 17-hydroxyprogesterone and increased conversion of 17-hydroxypregnenolone to dehydroepiandrosterone (DHEA), resulting in lower levels of 17-hydroxyprogesterone, as well as indications of impaired conversion of 11-deoxy-steroids to 11β-hydroxy-steroids but reduced conversion of cortisol to cortisone. Due to over-activation of hypothalamic-pituitary-adrenal axis (HPAA), however, cortisol and cortisone levels were higher in patients with indications of depleted cortisol synthesizing enzymes. Patients showed lower conversion of DHEA to androstenedione, androstenedione to testosterone, androstenedione to estradiol in the major pathway, and testosterone to estradiol in the minor pathway for estradiol synthesis at increased conversion of androstenedione to testosterone. They also showed lower conversion of immunoprotective Δ5 androstanes to their more potent 7α/β-hydroxy metabolites and had lower circulating allopregnanolone and higher ratio 3β-hydroxy-steroids to their neuroprotective 3α-hydroxy-counterparts.

Mechanistic insights regarding neuropsychiatric and neuropathologic impacts of air pollution

Air pollution is a significant environmental health risk for urban areas and developing countries. Air pollution may contribute to the incidence of cardiopulmonary and metabolic diseases. Evidence also points to the role of air pollution in worsening or developing neurological and neuropsychiatric conditions. Inhaled pollutants include compositionally differing mixtures of respirable gaseous and particulate components of varied sizes, solubilities, and chemistry. Inhalation of combustibles and volatile organic compounds (VOCs) or other irritant particulate matter (PM) may trigger lung sensory afferents which initiate a sympathetic stress response via activation of the hypothalamic-pituitary-adrenal (HPA) and sympathetic-adrenal-medullary (SAM) axes. Activation of SAM and HPA axes are associated with selective inhibition of hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary-thyroid (HPT) axes following exposure. Regarding chronic exposure in susceptible hosts, these changes may become pathological by causing neuroinflammation, neurotransmitter, and neuroendocrine imbalances. Soluble PM, such as metals and nano-size particles may translocate across the olfactory, trigeminal, or vagal nerves through retrograde axonal transport, or through systemic circulation which may disrupt the blood-brain barrier (BBB) and deposit in neural tissue. Neuronal deposition of metallic components can have a negative impact through multiple molecular mechanisms. In addition to systemic translocation, the release of pituitary and stress hormones, altered metabolic hormonal status and resultant circulating metabolic milieu, and sympathetically and HPA-mediated changes in immune markers, may secondarily impact the brain through a variety of regulatory adrenal hormone-dependent mechanisms. Several reviews covering air pollution as a risk factor for neuropsychiatric disorders have been published, but no reviews discuss the in-depth intersection between molecular and stress-related neuroendocrine mechanisms, thereby addressing adaptation and susceptibility variations and link to peripheral tissue effects. The purpose of this review is to discuss evidence regarding neurochemical, neuroendocrine, and molecular mechanisms which may contribute to neuropathology from air pollution exposure. This review also covers bi-directional neural and systemic interactions which may raise the risk for air pollution-related systemic illness.

Molecular and Genetics Perspectives on Primary Adrenocortical Hyperfunction Disorders

Adrenocortical disorders encompass a broad spectrum of conditions ranging from benign hyperplasia to malignant tumors, significantly disrupting hormone balance and causing a variety of clinical manifestations. By leveraging next-generation sequencing and in silico analyses, recent studies have uncovered the genetic and molecular pathways implicated in these transitions. In this review, we explored the molecular and genetic alterations in adrenocortical disorders, with a particular focus on the transitions from normal adrenal function to hyperfunction. The insights gained are intended to enhance diagnostic and therapeutic strategies, offering up-to-date knowledge for managing these complex conditions effectively.

Looking Back to Move Forward: Research in Stress, Behavior, and Immune Function

BACKGROUND

From the original studies investigating the effects of adrenal gland secretion to modern high-throughput multidimensional analyses, stress research has been a topic of scientific interest spanning just over a century.

SUMMARY

The objective of this review was to provide historical context for influential discoveries, surprising findings, and preclinical models in stress-related neuroimmune research. Furthermore, we summarize this work and present a current understanding of the stress pathways and their effects on the immune system and behavior. We focus on recent work demonstrating stress-induced immune changes within the brain and highlight studies investigating stress effects on microglia. Lastly, we conclude with potential areas for future investigation concerning microglia heterogeneity, bone marrow niches, and sex differences.

KEY MESSAGES

Stress is a phenomenon that ties together not only the central and peripheral nervous system, but the immune system as well. The cumulative effects of stress can enhance or suppress immune function, based on the intensity and duration of the stressor. These stress-induced immune alterations are associated with neurobiological changes, including structural remodeling of neurons and decreased neurogenesis, and these contribute to the development of behavioral and cognitive deficits. As such, research in this field has revealed important insights into neuroimmune communication as well as molecular and cellular mediators of complex behaviors relevant to psychiatric disorders.

From Young to Old: Mimicking Neuronal Aging in Directly Converted Neurons from Young Donors

A substantial challenge in human brain aging is to find a suitable model to mimic neuronal aging in vitro as accurately as possible. Using directly converted neurons (iNs) from human fibroblasts is considered a promising tool in human aging since it retains the aging-associated mitochondrial donor signature. Still, using iNs from aged donors can pose certain restrictions due to their lower reprogramming and conversion efficacy than those from younger individuals. To overcome these limitations, our study aimed to establish an in vitro neuronal aging model mirroring features of in vivo aging by acute exposure on young iNs to either human stress hormone cortisol or the mitochondrial stressor rotenone, considering stress as a trigger of in vivo aging. The impact of rotenone was evident in mitochondrial bioenergetic properties by showing aging-associated deficits in mitochondrial respiration, cellular ATP, and MMP and a rise in glycolysis, mitochondrial superoxide, and mitochondrial ROS; meanwhile, cortisol only partially induced an aging-associated mitochondrial dysfunction. To replicate the in vivo aging-associated mitochondrial dysfunctions, using rotenone, a mitochondrial complex I inhibitor, proved to be superior to the cortisol model. This work is the first to use stress on young iNs to recreate aging-related mitochondrial impairments.

Effects of stress-related neuromodulators on amygdala and hippocampus resting state functional connectivity

BACKGROUND

The human stress response is characterized by increases in neuromodulators, including norepinephrine (NE) and cortisol. Both neuromodulators can enter the brain and affect neurofunctional responses. Two brain areas associated with stress are the amygdala and the hippocampus. The precise influence of NE and cortisol on the amygdala and hippocampal resting state functional connectivity (RSFC) is poorly understood.

AIMS

To investigate the influence of NE and cortisol on the amygdala and hippocampal RSFC.

METHODS

We recruited 165 participants who received 10 mg yohimbine and/or 10 mg hydrocortisone in a randomized, placebo-controlled design. With seed-based analyses, we compared RSFC of the hippocampus and amygdala separately between the three groups that received medication versus placebo.

RESULTS

We found no differences between yohimbine and placebo condition or between hydrocortisone and placebo condition regarding amygdala or hippocampal FC. Compared with placebo, the yohimbine/hydrocortisone condition showed increased amygdala and hippocampal RSFC with the cerebellum. Also, they had increased hippocampal RSFC with the amygdala and cerebral white matter.

DISCUSSION

The group with elevated NE and cortisol showed significantly increased RSFC between the amygdala, hippocampus, and cerebellum compared to placebo. These three brain areas are involved in associative learning and emotional memory, suggesting a critical role for this network in the human stress response. Our results show that NE and cortisol together may influence the strength of this association. Compared to placebo, we found no differences in the groups receiving only one medication, suggesting that increasing one neuromodulator alone may not induce differences in neurofunctional responses. The study procedure has been registered at clinicaltrials.gov (ID: NCT04359147).

Glucocorticoid effects on the brain: from adaptive developmental plasticity to allostatic overload

Exposure to stress during early life may alter the developmental trajectory of an animal by a mechanism known as adaptive plasticity. For example, to enhance reproductive success in an adverse environment, it is known that animals accelerate their growth during development. However, these short-term fitness benefits are often associated with reduced longevity, a phenomenon known as the growth rate-lifespan trade-off. In humans, early life stress exposure compromises health later in life and increases disease susceptibility. Glucocorticoids (GCs) are major stress hormones implicated in these processes. This Review discusses the evidence for GC-mediated adaptive plasticity in development, leading to allostatic overload in later life. We focus on GC-induced effects on brain structure and function, including neurogenesis; highlight the need for longitudinal studies; and discuss approaches to identify molecular mechanisms mediating GC-induced alteration of the brain developmental trajectory leading to adult dysfunctions. Further understanding of how stress and GC exposure can alter developmental trajectories at the molecular and cellular level is of critical importance to reduce the burden of mental and physical ill health across the life course.

Is the efficacy of oxytocin for autism diminished at higher dosages or repeated doses?: Potential mechanisms and candidate solutions

No approved pharmacological intervention currently exists to address the core symptoms of autism spectrum disorder, a prevalent neurodevelopmental condition. However, there is a growing body of empirical evidence highlighting oxytocin's modulatory effects on social and communicative behaviors. Numerous single-dose trials have consistently demonstrated the efficacy of oxytocin in ameliorating behavioral and neural measurements associated with the core symptoms of autism spectrum disorder. Nevertheless, prior investigations involving the repeated administration of oxytocin have yielded disparate findings concerning its effectiveness, particularly in relation to clinical measures of the core symptoms of autism spectrum disorder. Recent studies have also raised the possibility of diminishing efficacy of oxytocin over time, particularly when higher or recurrent dosages of oxytocin are administered. This review article aims to provide an overview of previous studies examining this issue. Furthermore, it aims to discuss the potential mechanisms underlying these effects, including the interaction between oxytocin and vasopressin, as well as potential strategies for addressing the challenges mentioned. This review's overall objective is to provide insights into the potential development of innovative therapeutics to mitigate the core symptoms of autism spectrum disorder, representing potential breakthroughs in the treatment of this complex neurodevelopmental condition.

The cortisol switch between vulnerability and resilience

In concert with neuropeptides and transmitters, the end products of the hypothalamus-pituitary-adrenal (HPA) axis, the glucocorticoid hormones cortisol and corticosterone (CORT), promote resilience: i.e., the ability to cope with threats, adversity, and trauma. To exert this protective action, CORT activates mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) that operate in a complementary manner -as an on/off switch- to coordinate circadian events, stress-coping, and adaptation. The evolutionary older limbic MR facilitates contextual memory retrieval and supports an on-switch in the selection of stress-coping styles at a low cost. The rise in circulating CORT concentration after stress subsequently activates a GR-mediated off-switch underlying recovery of homeostasis by providing the energy for restraining the primary stress reactions and promoting cognitive control over emotional reactivity. GR activation facilitates contextual memory storage of the experience to enable future stress-coping. Such complementary MR-GR-mediated actions involve rapid non-genomic and slower gene-mediated mechanisms; they are time-dependent, conditional, and sexually dimorphic, and depend on genetic background and prior experience. If coping fails, GR activation impairs cognitive control and promotes emotional arousal which eventually may compromise resilience. Such breakdown of resilience involves a transition to a chronic stress construct, where information processing is crashed; it leads to an imbalanced MR-GR switch and hence increased vulnerability. Novel MR-GR modulators are becoming available that may reset a dysregulated stress response system to reinstate the cognitive flexibility required for resilience.

Glucocorticoid feedback paradox: a homage to Mary Dallman

As the end product of the hypothalamus-pituitary-adrenal (HPA) axis, the glucocorticoid hormones cortisol and corticosterone coordinate circadian activities, stress-coping, and adaptation to change. For this purpose, the hormone promotes energy metabolism and controls defense reactions in the body and brain. This life-sustaining action exerted by glucocorticoids occurs in concert with the autonomic nervous and immune systems, transmitters, growth factors/cytokines, and neuropeptides. The current contribution will focus on the glucocorticoid feedback paradox in the HPA-axis: the phenomenon that stress responsivity remains resilient if preceded by stress-induced secretion of glucocorticoid hormone, but not if this hormone is previously administered. Furthermore, in animal studies, the mixed progesterone/glucocorticoid antagonist RU486 or mifepristone switches to an apparent partial agonist upon repeated administration. To address these enigmas several interesting phenomena are highlighted. These include the conditional nature of the excitation/inhibition balance in feedback regulation, the role of glucose as a determinant of stress responsivity, and the potential of glucocorticoids in resetting the stress response system. The analysis of the feedback paradox provides also a golden opportunity to review the progress in understanding the role of glucocorticoid hormone in resilience and vulnerability during stress, the science that was burned deeply in Mary Dallman's emotions.

The Effect of Potassium Canrenoate (Mineralocorticoid Receptor Antagonist) on the Markers of Inflammation in the Treatment of COVID-19 Pneumonia and Fibrosis-A Secondary Analysis of Randomized Placebo-Controlled Clinical Trial

In March 2020, the World Health Organization (WHO) announced a global pandemic of coronavirus disease 2019 (COVID-19) that presented mainly as an acute infection of the lower respiratory tract (pneumonia), with multiple long-term consequences, including lung fibrosis. The aim of this study was to evaluate the influence of potassium canrenoate on inflammatory markers in the treatment of COVID-19 pneumonia. A randomized clinical trial (RCT) of intravenous potassium canrenoate vs. placebo was performed between December 2020 and November 2021. This study is a secondary analysis of that RCT. In the final analysis, a total of 49 hospitalized patients were included (24 allocated to the potassium canrenoate group and 25 to the placebo group). Patients were assessed by serum testing and blood cell cytometry on day 1 and day 7 of the intervention. Age, sex, and body mass index were not significantly different between the placebo group and intervention group. Although there was a significantly higher rate of ischemic heart disease in the placebo group, rates of other preexisting comorbidities were not significantly different. There were no significant differences in the inflammatory parameters between the potassium canrenoate and placebo groups on day 1 and day 7. However, the intragroup comparisons using Wilcoxon's test showed significant differences between day 1 and day 7. The CD3% for potassium canrenoate increased significantly between day 1 and day 7 (12.85 ± 9.46; 11.55 vs. 20.50 ± 14.40; 17.80; p = 0.022), while the change in the placebo group was not significant (15.66 ± 11.39; 12.65 vs. 21.16 ± 15.37; 16.40; p = 0.181). The IL-1ß total count [%] increased over time for both potassium canrenoate (0.68 ± 0.58; 0.45 vs. 1.27 ± 0.83; 1.20; p = 0.004) and placebo (0.61 ± 0.59; 0.40 vs. 1.16 ± 0.91; 1.00; p = 0.016). The TNF-α total count (%) decreased significantly between day 1 and day 7 for potassium canrenoate (0.54 ± 0.45; 0.40 vs. 0.25 ± 0.23; 0.10; p = 0.031), but not for placebo (0.53 ± 0.47; 0.35 vs. 0.26 ± 0.31; 0.20; p = 0.056). Interleukin-6 (pg/mL) showed a significant decrease between day 1 and day 7 for potassium canrenoate (64.97 ± 72.52; 41.00 vs. 24.20 ± 69.38; 5.30; p = 0.006), but not the placebo group. This RCT has shown that the administration of potassium canrenoate to patients with COVID-19-induced pneumonia may be associated with significant changes in certain inflammatory markers (interleukin-6, CD3%, TNF-α), potentially related to pulmonary fibrosis. Although some positive trends were observed in the potassium canrenoate group, none of these observations reached statistical significance. Any possible benefits from the use of potassium canrenoate as an anti-inflammatory or antifibrotic drug in COVID-19 patients require further investigation.

Glucocorticoids and Their Receptor Isoforms: Roles in Female Reproduction, Pregnancy, and Foetal Development

Alterations in the hypothalamic-pituitary-adrenal (HPA) axis and associated changes in circulating levels of glucocorticoids are integral to an organism's response to stressful stimuli. Glucocorticoids acting via glucocorticoid receptors (GRs) play a role in fertility, reproduction, placental function, and foetal development. GRs are ubiquitously expressed throughout the female reproductive system and regulate normal reproductive function. Stress-induced glucocorticoids have been shown to inhibit reproduction and affect female gonadal function by suppressing the hypothalamic-pituitary-gonadal (HPG) axis at each level. Furthermore, during pregnancy, a mother's exposure to prenatal stress or external glucocorticoids can result in long-lasting alterations to the foetal HPA and neuroendocrine function. Several GR isoforms generated via alternative splicing or translation initiation from the GR gene have been identified in the mammalian ovary and uterus. The GR isoforms identified include the splice variants, GRα and GRβ, and GRγ and GR-P. Glucocorticoids can exert both stimulatory and inhibitory effects and both pro- and anti-inflammatory functions in the ovary, in vitro. In the placenta, thirteen GR isoforms have been identified in humans, guinea pigs, sheep, rats, and mice, indicating they are conserved across species and may be important in mediating a differential response to stress. Distinctive responses to glucocorticoids, differential birth outcomes in pregnancy complications, and sex-based variations in the response to stress could all potentially be dependent on a particular GR expression pattern. This comprehensive review provides an overview of the structure and function of the GR in relation to female fertility and reproduction and discusses the changes in the GR and glucocorticoid signalling during pregnancy. To generate this overview, an extensive non-systematic literature search was conducted across multiple databases, including PubMed, Web of Science, and Google Scholar, with a focus on original research articles, meta-analyses, and previous review papers addressing the subject. This review integrates the current understanding of GR variants and their roles in glucocorticoid signalling, reproduction, placental function, and foetal growth.

Glucocorticoid Treatment in Acute Respiratory Distress Syndrome: An Overview on Mechanistic Insights and Clinical Benefit

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS), triggered by various pathogenic factors inside and outside the lungs, leads to diffuse lung injury and can result in respiratory failure and death, which are typical clinical critical emergencies. Severe acute pancreatitis (SAP), which has a poor clinical prognosis, is one of the most common diseases that induces ARDS. When SAP causes the body to produce a storm of inflammatory factors and even causes sepsis, clinicians will face a two-way choice between anti-inflammatory and anti-infection objectives while considering the damaged intestinal barrier and respiratory failure, which undoubtedly increases the difficulty of the diagnosis and treatment of SAP-ALI/ARDS. For a long time, many studies have been devoted to applying glucocorticoids (GCs) to control the inflammatory response and prevent and treat sepsis and ALI/ARDS. However, the specific mechanism is not precise, the clinical efficacy is uneven, and the corresponding side effects are endless. This review discusses the mechanism of action, current clinical application status, effectiveness assessment, and side effects of GCs in the treatment of ALI/ARDS (especially the subtype caused by SAP).

The human glucocorticoid receptor

Glucocorticoids are members of steroid hormones that are biosynthesized in the intermediate cellular zone of the adrenal cortex (zona fasciculata) and released into the peripheral blood as final products of the hypothalamic-pituitary-adrenal (HPA) axis, as well as under the control of the circadian biologic system. These molecules regulate every physiologic function of the organism as they bind to an almost ubiquitous hormone-activated transcription factor, the glucocorticoid receptor (GR), which influences the rate of transcription of a huge number of target genes amounting to up to 20% of the mammalian genome. The evolving progress of cellular, molecular and computational-structural biology and the implication of epigenetics in every-day clinical practice have enabled us a deeper and ever-increasing understanding of how target tissues respond to natural and synthetic glucocorticoids. In this chapter, we summarize the current knowledge on the structure, expression, function and signaling of the human glucocorticoid receptor in normal and pathologic conditions.

Translation of Experimental Findings from Animal to Human Biology: Identification of Neuronal Mineralocorticoid and Glucocorticoid Receptors in a Sectioned Main Nerve Trunk of the Leg

The activation of the mineralocorticoid (MR) and glucocorticoid (GR) receptors on peripheral sensory neurons seems to modify pain perception through both direct non-genomic and indirect genomic pathways. These distinct subpopulations of sensory neurons are not known for peripheral human nerves. Therefore, we examined MR and GR on subpopulations of sensory neurons in sectioned human and rat peripheral nerves. Real-time PCR (RT-PCR) and double immunofluorescence confocal analysis of MR and GR with the neuronal markers PGP9.5, neurofilament 200 (NF200), and the potential pain signaling molecules CGRP, Nav1.8, and TRPV1 were performed in human and rat nerve tissue. We evaluated mechanical hyperalgesia after intrathecal administration of GR and MR agonists. We isolated MR- and GR-specific mRNA from human peripheral nerves using RT-PCR. Our double immunofluorescence analysis showed that the majority of GR colocalized with NF200 positive, myelinated, mechanoreceptive A-fibers and, to a lesser extent, with peripheral peptidergic CGRP-immunoreactive sensory nerve fibers in humans and rats. However, the majority of MR colocalized with CGRP in rat as well as human nerve tissue. Importantly, there was an abundant colocalization of MR with the pain signaling molecules TRPV1, CGRP, and Nav1.8 in human as well as rat nerve tissue. The intrathecal application of the GR agonist reduced, and intrathecal administration of an MR agonist increased, mechanical hyperalgesia in rats. Altogether, these findings support a translational approach in mammals that aims to explain the modulation of sensory information through MR and GR activation. Our findings show a significant overlap between humans and rats in MR and GR expression in peripheral sensory neurons.

Stress, a Brief Update

Stress is fundamental for health and adaptation; it is an evolutionarily conserved response that involves several systems in the organism. The study of the stress response could be traced back to the end of the nineteenth century with George Beard's or Claude Bernard's work and, from that moment on, several studies that have allowed the elucidation of its neurobiology and the consequences of suffering from it were consolidated. In this theoretical review, we discuss the most relevant researches to our knowledge on the study of stress response, from the concept of stress, its neurobiology, the hormonal response during stress, as well as its regulation, the effects of acute and chronic stress, stress from cognition, the different stress responses during life, as well as its relationship with different psychiatric disorders. Taken together, the reviewed research updates the classic perspective on stress, increasing the factors that should be considered in research to explore the effects of stress on health.

Glucocorticoids improve the balance of M1/M2 macrophage polarization in experimental autoimmune uveitis through the P38MAPK-MEF2C axis

Uveitis is a common ocular disease that can induce serious complications and sequelae. It is one of the major causes of blindness. Currently, mounting evidence suggests that glucocorticoids (GCs) can suppress ocular inflammation and promote the healing of damaged ocular tissues, but the underlying mechanism remains unclear. The present study aimed to elucidate the mechanism by which GCs modulate the homeostasis of M1/M2 macrophage polarization in experimental autoimmune uveitis (EAU) through the p38MAPK-MEF2C axis. Female Lewis rats were randomly divided into four groups: a normal control (NC) group, an EAU group, an EAU + glucocorticoid (EAU + GC) group, and an EAU + p38MAPK inhibitor (EAU + SB) group. The EAU model was induced in EAU, EAU + GC, and EAU + SB groups, followed by the treatments of normal saline, GC (predisione), and SB203580, respectively. The findings demonstrated that the rats in GC and SB groups had much less ocular inflammation, and the clinical and pathological scores decreased. Further research revealed that GC and SB treatment could inhibit iNOS and CD86 expression while promoting Arg-1 and CD206 secretion in IRBP-induced uveitis rats. Moreover, we found that the role of GC was similar to the results of SB203580, but the role of GC was masked by the C16-PAF (a p38MAPK activator) treatment. Molecular docking and western blot results confirmed that GC's therapeutic action against EAU is mediated via the p38MAPK-MEF2C axis. It regulates macrophage polarization by encouraging M1 to M2 transition and releasing anti-inflammatory factors.

Circadian glucocorticoids throughout development

Glucocorticoids (GCs) are essential drivers of mammalian tissue growth and maturation during one of the most critical developmental windows, the perinatal period. The developing circadian clock is shaped by maternal GCs. GC deficits, excess, or exposure at the wrong time of day leads to persisting effects later in life. During adulthood, GCs are one of the main hormonal outputs of the circadian system, peaking at the beginning of the active phase (i.e., the morning in humans and the evening in nocturnal rodents) and contributing to the coordination of complex functions such as energy metabolism and behavior, across the day. Our article discusses the current knowledge on the development of the circadian system with a focus on the role of GC rhythm. We explore the bidirectional interaction between GCs and clocks at the molecular and systemic levels, discuss the evidence of GC influence on the master clock in the suprachiasmatic nuclei (SCN) of the hypothalamus during development and in the adult system.

From Ligands to Behavioral Outcomes: Understanding the Role of Mineralocorticoid Receptors in Brain Function

Stress is a normal response to situational pressures or demands. Exposure to stress activates the hypothalamic-pituitary-adrenal (HPA) axis and leads to the release of corticosteroids, which act in the brain via two distinct receptors: mineralocorticoid receptors (MR) and glucocorticoid receptors (GR). Persistent HPA axis overactivation or dysregulation can disrupt an individual's homeostasis, thereby contributing to an increased risk for mental illness. On the other hand, successful coping with stressful events involves adaptive and cognitive processes in the brain that render individuals more resilient to similar stressors in the future. Here we review the role of the MR in these processes, starting with an overview of the physiological structure, ligand binding, and expression of MR, and further summarizing its role in the brain, its relevance to psychiatric disorders, and related rodent studies. Given the central role of MR in cognitive and emotional functioning, and its importance as a target for promoting resilience, future research should investigate how MR modulation can be used to alleviate disturbances in emotion and behavior, as well as cognitive impairment, in patients with stress-related psychiatric disorders.

Transcriptional substrates of brain structural and functional impairments in drug-naive first-episode patients with major depressive disorder

BACKGROUND

Despite remarkable success in identifying genetic risk factors for depression, there are still open questions about the exact genetic mechanisms underlying certain disease phenotypes, such as brain structural and functional impairments.

METHODS

Comprehensive multi-modal neuroimaging meta-analyses were conducted to examine changes in brain structure and function in drug-naive first-episode patients with major depressive disorder (DF-MDD). Combined with the Allen Human Brain Atlas, transcriptome-neuroimaging spatial association analyses were performed to identify genes whose expression related to these brain structural and functional changes, followed by a range of gene functional signature analyses.

RESULTS

Meta-analyses revealed gray matter atrophy in the insula, temporal pole, cerebellum and postcentral gyrus, and a complex pattern of hyper-function in the temporal pole and hypo-function in the cuneus/precuneus, angular gyrus and lingual gyrus in DF-MDD. Moreover, these brain structural and functional changes were spatially associated with the expression of 1194 and 1733 genes, respectively. Importantly, there were commonalities and differences in the two gene sets and their functional signatures including functional enrichment, specific expression, behavioral relevance, and constructed protein-protein interaction networks.

LIMITATIONS

The results merit further verification using a large sample of DF-MDD.

CONCLUSIONS

Our findings not only corroborate the polygenic nature of depression, but also suggest common and distinct genetic modulations of brain structural and functional impairments in this disorder.

Molecular mechanisms of glucocorticoid resistance

BACKGROUND

As a powerful anti-inflammatory, immunosuppressive, and antiproliferative drug, glucocorticoid (GC) plays an important role in the treatment of various diseases. However, some patients may experience glucocorticoid resistance (GCR) in clinical, and its molecular mechanism have not been determined.

METHODS

The authors performed a review of the literature on GCR focusing on mutations in the NR3C1 gene and impaired glucocorticoid receptor (GR) signalling, using METSTR (2000 through May 2022) to identify original articles and reviews on this topic. The search terms included 'glucocorticoid resistance/insensitive', 'steroid resistance/insensitive', 'NR3C1', and 'glucocorticoid receptor'.

RESULTS

Primary GCR is mainly caused by NR3C1 gene mutation, and 31 NR3C1 gene mutations have been reported so far. Secondary GCR is caused by impaired GC signalling pathways, including decreased expression of GR, impaired nuclear translocation of GR, and impaired binding of GR to GC and GR to target genes. However, the current research is more on the expression level of GR, and there are relatively few studies on other mechanisms. In addition, methods for improving GC sensitivity are rarely reported.

CONCLUSION

The molecular mechanisms of GCR are complex and may differ in different diseases or different patients. In future studies, when exploring the mechanism of GCR, methods to improve GC sensitivity should also be investigated.

Can scale cortisol concentration be quantified non-lethally in wild fish species?

Cortisol, the primary glucocorticoid in fishes, is secreted into the bloodstream in response to stress. Circulating cortisol accumulates in scales, a durable calcified structure that can be easily sampled from many fish species. As such, the use of scale cortisol concentration (SCC) is currently being explored as a means of chronic stress biomonitoring in wild fishes. Scales serve an important role in fish physiology and thus the number of scales required for reliable cortisol analysis is a limiting factor in the non-lethal collection of such samples. To date, scale cortisol quantification has also only been performed non-lethally in captive fishes and due to differences in stress responsiveness SCCs likely differ in wild species. As such, this study aimed to (1) apply our fish scale processing and analysis protocol to wild fish species and (2) apply it to five north temperate fish species to provide information useful to future non-lethal scale sampling regimes. Cortisol was successfully measured in scales collected from wild northern pike (Esox lucius), walleye (Sander vitreus), whitefish (Coregonus clupeaformis), white sucker (Catostomus commersonii) and captive rainbow trout (Oncorhynchus mykiss). SCCs were significantly different between species and thus the sample mass required for reliable cortisol analysis differed as well. In addition to the size of the fish and the mass of their scales this is an important consideration for future scale cortisol analyses as these factors could make SCC an attainable non-lethal sample matrix in some species of fish but impractical in others.

Cortisol Interaction with Aquaporin-2 Modulates Its Water Permeability: Perspectives for Non-Genomic Effects of Corticosteroids

Aquaporins (AQPs) are water channels widely distributed in living organisms and involved in many pathophysiologies as well as in cell volume regulations (CVR). In the present study, based on the structural homology existing between mineralocorticoid receptors (MRs), glucocorticoid receptors (GRs), cholesterol consensus motif (CCM) and the extra-cellular vestibules of AQPs, we investigated the binding of corticosteroids on the AQP family through in silico molecular dynamics simulations of AQP2 interactions with cortisol. We propose, for the first time, a putative AQPs corticosteroid binding site (ACBS) and discussed its conservation through structural alignment. Corticosteroids can mediate non-genomic effects; nonetheless, the transduction pathways involved are still misunderstood. Moreover, a growing body of evidence is pointing toward the existence of a novel membrane receptor mediating part of these rapid corticosteroids' effects. Our results suggest that the naturally produced glucocorticoid cortisol inhibits channel water permeability. Based on these results, we propose a detailed description of a putative underlying molecular mechanism. In this process, we also bring new insights on the regulatory function of AQPs extra-cellular loops and on the role of ions in tuning the water permeability. Altogether, this work brings new insights into the non-genomic effects of corticosteroids through the proposition of AQPs as the membrane receptor of this family of regulatory molecules. This original result is the starting point for future investigations to define more in-depth and in vivo the validity of this functional model.

Effects of neuromodulation on cognitive and emotional responses to psychosocial stressors in healthy humans

Physiological and psychological stressors can exert wide-ranging effects on the human brain and behavior. Research has improved understanding of how the sympatho-adreno-medullary (SAM) and hypothalamic-pituitary-adrenocortical (HPA) axes respond to stressors and the differential responses that occur depending on stressor type. Although the physiological function of SAM and HPA responses is to promote survival and safety, exaggerated psychobiological reactivity can occur in psychiatric disorders. Exaggerated reactivity may occur more for certain types of stressors, specifically, psychosocial stressors. Understanding stressor effects and how the body regulates these responses can provide insight into ways that psychobiological reactivity can be modulated. Non-invasive neuromodulation is one way that responding to stressors may be altered; research into these interventions may provide further insights into the brain circuits that modulate stress reactivity. This review focuses on the effects of acute psychosocial stressors and how neuromodulation might be effective in altering stress reactivity. Although considerable research into stress interventions focuses on treating pathology, it is imperative to first understand these mechanisms in non-clinical populations; therefore, this review will emphasize populations with no known pathology and consider how these results may translate to those with psychiatric pathologies.

Exposure to antenatal corticosteroids and infant cortisol regulation

Administration of antenatal corticosteroids (AC) is the standard of care during pregnancy for women who are at risk of early delivery. Evidence indicates that AC improve survival and reduce morbidity for preterm infants. However, research suggests that infants whose mothers receive AC have an altered hypothalamic-pituitary-axis (HPA) response to stressors in early life. Results are mixed regarding the nature of these effects, with studies showing both suppressed and augmented HPA activity. In addition, research is very limited beyond the 4th month of life. The purpose of this study was to determine if AC exposure was associated with infant cortisol levels in a resting state or in response to a stressor at 1, 6 and 12 months postnatal. We also evaluated the moderating role of preterm birth in this association. 181 women and their infants participated in the study. Women were recruited during the 3rd trimester of pregnancy; at this time, they completed the Perceived Stress Scale and provided 8 salivary samples over a 2-day period for cortisol assay. They provided these data again at 6 and 12 months postnatal. At 1, 6, and 12 months postnatal, salivary samples were collected from infants to examine their cortisol levels before and after participation in a 'stressor protocol'. Data were extracted from the medical record on AC exposure, gestational age, maternal obstetric risk, and neonatal morbidity. Mixed effects multilevel regression modeling was used to examine the aims. Infants whose mothers received AC had significantly lower resting state (B = -2.47, CI: -3.691, -0.0484) and post-stressor (B = -2.51, CI: -4.283, -0.4276) cortisol levels across the first year of life than infants whose mothers did not receive AC. There was no moderating effect of preterm birth on the relationship between AC exposure and cortisol. Results indicate a state of dampened HPA activation and cortisol hypo-arousal that persists across the first year of life among infants who were exposed to corticosteroids in utero. Further research is needed to examine mechanisms responsible for any alterations that occur during development of the fetal HPA axis, including epigenetic and biochemical factors that control hormonal secretion, negative feedback, and glucocorticoid receptor function throughout the HPA axis. Findings warrant careful consideration by obstetric clinicians of the benefits and risks of prescribing AC.

Dexamethasone and potassium canrenoate alleviate hyperalgesia by competitively regulating IL-6/JAK2/STAT3 signaling pathway during inflammatory pain in vivo and in vitro

BACKGROUND

Dexamethasone (Dexa) and potassium canrenoate (Cane) modulate nociceptive behavior via glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) by two mechanisms (genomic and nongenomic pathways). This study was designed to investigate the Dexa- or Cane-mediated nongenomic and genomic effects on mechanical nociception and inflammation-induced changes in interleukin-6 (IL-6) mediated signaling pathway in rats.

METHODS

Freund's complete adjuvant (FCA) was used to trigger an inflammation of the right hind paw in male Sprague-Dawley rats. First, the mechanical nociceptive behavioral changes were examined following intraplantar administration of GR agonist Dexa and/or MR antagonist Cane in vivo. Subsequently, the protein levels of IL-6, IL-6Rα, JAK2, pJAK2, STAT3, pSTAT3Ser727 , migration inhibitory factor, and cyclooxygenase-2 were assessed by Western blot following intraplantar injection of Dexa or Cane or the combination. Moreover, the molecular docking studies determined the interaction between Dexa, Cane, and IL-6. The competition binding assay was carried out using enzyme-linked immunosorbent assays (ELISA).

RESULTS

Administration of Dexa and Cane dose-dependently attenuated FCA-induced inflammatory pain. The sub-additive effect of Dexa/Cane combination was elucidated by isobologram analysis, accompanied by decrease in the spinal levels of IL-6, pJAK2, and pSTAT3Ser727 . The molecular docking study demonstrated that both Dexa and Cane displayed a firm interaction with THR138 binding site of IL-6 via a strong hydrogen bond. ELISA revealed that Dexa has a higher affinity to IL-6 than Cane.

CONCLUSIONS

There was no additive or negative effect of Dexa and Cane, and they modulate the IL-6/JAK2/STAT3 signaling pathway through competitive binding with IL-6 and relieves hypersensitivity during inflammatory pain.

Tricyclic antidepressants target FKBP51 SUMOylation to restore glucocorticoid receptor activity

FKBP51 is an important inhibitor of the glucocorticoid receptor (GR) signaling. High FKBP51 levels are associated to stress-related disorders, which are linked to GR resistance. SUMO conjugation to FKBP51 is necessary for FKBP51's inhibitory action on GR. The GR/FKBP51 pathway is target of antidepressant action. Thus we investigated if these drugs could inhibit FKBP51 SUMOylation and therefore restore GR activity. Screening cells using Ni²⁺ affinity and in vitro SUMOylation assays revealed that tricyclic antidepressants- particularly clomipramine- inhibited FKBP51 SUMOylation. Our data show that clomipramine binds to FKBP51 inhibiting its interaction with PIAS4 and therefore hindering its SUMOylation. The inhibition of FKBP51 SUMOylation decreased its binding to Hsp90 and GR facilitating FKBP52 recruitment, and enhancing GR activity. Reduction of PIAS4 expression in rat primary astrocytes impaired FKBP51 interaction with GR, while clomipramine could no longer exert its inhibitory action. This mechanism was verified in vivo in mice treated with clomipramine. These results describe the action of antidepressants as repressors of FKBP51 SUMOylation as a molecular switch for restoring GR sensitivity, thereby providing new potential routes of antidepressant intervention.

Brain Mineralocorticoid receptor in health and disease: from molecular signaling to cognitive and emotional function

Brain mineralocorticoid receptors (MR) mediate effects of glucocorticoid hormones in stress adaptation, as well as the effects of aldosterone itself in relation to salt homeostasis. Brain stem MRs respond to aldosterone, whereas forebrain MRs mediate rapid and delayed glucocorticoid effects in conjunction with the glucocorticoid receptor (GR). MR‐mediated effects depend on age, gender, genetic variations, and environmental influences. Disturbed MR activity through chronic stress, certain (endocrine) diseases or during glucocorticoid therapy can cause deleterious effects on affective state, cognitive and behavioural function in susceptible individuals. Considering the important role MR plays in cognition and emotional function in health and disease, MR modulation by pharmacological intervention could relieve stress‐ and endocrine‐related symptoms. Here, we discuss recent pharmacological interventions in the clinic and genetic developments in the molecular underpinnings of MR signalling. Further understanding of MR‐dependent pathways may help to improve psychiatric symptoms in a diversity of settings.

Non-genomic steroid signaling through the mineralocorticoid receptor: Involvement of a membrane-associated receptor?

Corticosteroid receptors in the mammalian brain mediate genomic as well as non-genomic actions. Although receptors mediating genomic actions were already cloned 35 years ago, it remains unclear whether the same molecules are responsible for the non-genomic actions or that the latter involve a separate class of receptors. Here we focus on one type of corticosteroid receptors, i.e. the mineralocorticoid receptor (MR). We summarize some of the known properties and the current insight in the localization of the MR in peripheral cells and neurons, especially in relation to non-genomic signaling. Previous studies from our own and other labs provided evidence that MRs mediating non-genomic actions are identical to the ones involved in genomic signaling, but may be translocated to the plasma cell membrane instead of the nucleus. With fixed cell imaging and live cell imaging techniques we tried to visualize these presumed membrane-associated MRs, using antibodies or overexpression of MR-GFP in COS7 and hippocampal cultured neurons. Despite the physiological evidence for MR location in or close to the cell membrane, we could not convincingly visualize membrane localization of endogenous MRs or GFP-MR molecules. However, we did find punctae of labeled antibodies intracellularly, which might indicate transactivating spots of MR near the membrane. We also found some evidence for trafficking of MR via beta-arrestins. In beta-arrestin knockout mice, we didn't observe metaplasticity in the basolateral amygdala anymore, indicating that internalization of MRs could play a role during corticosterone activation. Furthermore, we speculate that membrane-associated MRs could act indirectly via activating other membrane located structures like e.g. GPER and/or receptor tyrosine kinases.

High Sensitivity of the Circadian Clock in the Hippocampal Dentate Gyrus to Glucocorticoid- and GSK3-Beta-Dependent Signals

AIMS

Circadian clocks in the hippocampus (HPC) align memory processing with appropriate time of day. Our study was aimed at ascertaining the specificity of glycogen synthase kinase 3-beta (GSK3β)- and glucocorticoid (GC)-dependent pathways in the entrainment of clocks in individual HPC regions, CA1-3, and dentate gyrus (DG).

METHODS

The role of GCs was addressed in vivo by comparing the effects of adrenalectomy (ADX) and subsequent dexamethasone (DEX) supplementation on clock gene expression profiles (Per1, Per2, Nr1d1, and Bmal1). In vitro the effects of DEX and the GSK3β inhibitor, CHIR-99021, were assessed from recordings of bioluminescence rhythms in HPC organotypic explants of mPER2Luc mice.

RESULTS

Circadian rhythms of clock gene expression in all HPC regions were abolished by ADX, and DEX injections to the rats rescued those rhythms in DG. The DEX treatment of the HPC explants significantly lengthened periods of the bioluminescence rhythms in all HPC regions with the most significant effect in DG. In contrast to DEX, CHIR-99021 significantly shortened the period of bioluminescence rhythm. Again, the effect was most significant in DG which lacks the endogenously inactivated (phosphorylated) form of GSK3β. Co-treatment of the explants with CHIR-99021 and DEX produced the CHIR-99021 response. Therefore, the GSK3β-mediated pathway had dominant effect on the clocks.

CONCLUSION

GSK3β- and GC-dependent pathways entrain the clock in individual HPC regions by modulating their periods in an opposite manner. The results provide novel insights into the mechanisms connecting the arousal state-relevant signals with temporal control of HPC-dependent memory and cognitive functions.

Corticosteroids in Immunosuppression

Corticosteroids have been utilized as mainstay pharmacological intervention for successful organ transplantation since the beginning. Several challenges exist in establishing a balance between achieving a tolerant atmosphere in the host immune system while minimizing the long-term impact of steroids on the body. Corticosteroids are used early in all solid organ transplantation but there is wide variability across various organs and centers in the duration of use and protocols of planned steroid wean. The adverse event profile of steroids is exhaustive and across many organ systems.

Cortisol and Dexamethasone Mediate Glucocorticoid Actions in the Lesser Spotted Catshark (Scyliorhinus canicula)

Simple Summary

For the first time, glucocorticoid actions of corticosteroids are evidenced in vivo and ex vivo in sharks, highlighting the importance of carbohydrate metabolism in situations of high-energy expenditure in this taxonomical group. Long-term (7 days) in vivo administration of dexamethasone (DEX, a synthetic glucocorticoid) decreased 1α-hydroxycorticosterone (1α-OHB, the main corticosteroid hormone in sharks), while also modified carbohydrates metabolism in liver and white muscle. Short-term (1 to 5 h) ex vivo incubation of liver and muscle explants with cortisol (corticosteroid not present in sharks) and DEX revealed glucose secretion mediated by glucocorticoid receptors (GR), as seen by the employment of mifepristone (a GR inhibitor).

Abstract

Corticosteroids are hormones produced in vertebrates exerting gluco- and mineralocorticoid actions (GC and MC) mediated by specific receptors (GR and MR, respectively). In elasmobranchs, the major circulating corticosteroid is the 1α-hydroxycorticosterone (1α-OHB). This hormone acts as a MC, but to date its role as a GC has not been established. As there is no 1α-OHB standard available, here we employed a set of in vivo and ex vivo approaches to test GC actions of other corticosteroids in the lesser spotted catshark (Scyliorhinus canicula). Dexamethasone (DEX, a synthetic corticosteroid) slow-release implants decreased plasma 1α-OHB levels after 7 days, and modified carbohydrates metabolism in liver and white muscle (energy stores and metabolic enzymes). In addition, ex vivo culture of liver and white muscle explants confirmed GC actions of corticosteroids not naturally present in sharks (cortisol and DEX) by increasing glucose secretion from these tissues. Dose–response curves induced by cortisol and DEX, altogether with the use of specific GR inhibitor mifepristone, confirmed the involvement of GR mediating glucose secretion. This study highlights the influence of corticosteroids in the glucose balance of S. canicula, though the role of 1α-OHB as a GC hormone in sharks should be further confirmed.

Genetic Architecture Underlying Differential Resting-state Functional Connectivity of Subregions Within the Human Visual Cortex

The human visual cortex is a heterogeneous entity that has multiple subregions showing substantial variability in their functions and connections. We aimed to identify genes associated with resting-state functional connectivity (rsFC) of visual subregions using transcriptome-neuroimaging spatial correlations in discovery and validation datasets. Results showed that rsFC of eight visual subregions were associated with expression measures of eight gene sets, which were specifically expressed in brain tissue and showed the strongest correlations with visual behavioral processes. Moreover, there was a significant divergence in these gene sets and their functional features between medial and lateral visual subregions. Relative to those associated with lateral subregions, more genes associated with medial subregions were found to be enriched for neuropsychiatric diseases and more diverse biological functions and pathways, and to be specifically expressed in multiple types of neurons and immune cells and during the middle and late stages of cortical development. In addition to shared behavioral processes, lateral subregion associated genes were uniquely correlated with high-order cognition. These findings of commonalities and differences in the identified rsFC-related genes and their functional features across visual subregions may improve our understanding of the functional heterogeneity of the visual cortex from the perspective of underlying genetic architecture.

Glucocorticoid Signaling and Epigenetic Alterations in Stress-Related Disorders

Stress is defined as a state of threatened or perceived as threatened homeostasis. The well-tuned coordination of the stress response system is necessary for an organism to respond to external or internal stressors and re-establish homeostasis. Glucocorticoid hormones are the main effectors of stress response and aberrant glucocorticoid signaling has been associated with an increased risk for psychiatric and mood disorders, including schizophrenia, post-traumatic stress disorder and depression. Emerging evidence suggests that life-stress experiences can alter the epigenetic landscape and impact the function of genes involved in the regulation of stress response. More importantly, epigenetic changes induced by stressors persist over time, leading to increased susceptibility for a number of stress-related disorders. In this review, we discuss the role of glucocorticoids in the regulation of stress response, the mechanism through which stressful experiences can become biologically embedded through epigenetic alterations, and we underline potential associations between epigenetic changes and the development of stress-related disorders.

Effect of acute heat stress on cognitive performance of chickens in a feed-related discriminant task

Little is known about immediate and long-lasting effect of acute heat stress on chicken cognition. Thirty-five, 9-week-old birds were trained to differentiate two cone colours; white (rewarded, R; with feed underneath) and black (unrewarded, UR; empty). The sixteen birds that learnt the task were randomly assigned to three temperature regimens (TR: 22-24 °C (control), 30-32 and 36-38 °C for 3h/day) for three consecutive days during which rectal (RT), wing (WT) and eye (ET) temperatures were monitored. After the 3 h of exposure, birds were allowed to rest for 1 h before the commencement of the discriminant task. The latencies to open the cones (R and UR) and proportion of cones opened were recorded. A long-lasting effect was tested a week after exposure to TR. TR had a significant effect on RT, WT and ET. The motivation to turn over R cones was weaker in birds exposed to 36-38 °C than birds exposed to 22-24 °C. Also, the proportion of R cones opened were fewer in birds that experienced TR of 36-38 °C compared to birds exposed to 22-24 °C and 30-32 °C specifically on two out of the three cognitive test days (Days 1 and 3). Latency and proportion of UR cones opened was not affected by TR. RT, WT and ET were all negatively and significantly correlated with latency to open the UR cones. Previous exposure of birds to three TR had no effect on the latency to open both cones but the proportion of R cones opened was greater in birds exposed to 30-32 °C compared to the 22-24 °C birds. In conclusion, an immediate (36-38 °C) and long-lasting effect (30-32 °C) of acute heat stress was associated with a weak motivation to perform feed related discrimination task.

Activation of the glucocorticoid receptor rapidly triggers calcium-dependent serotonin release in vitro

Aims

Glucocorticoids rapidly provoke serotonin (5‐HT) release in vivo. We aimed to investigate molecular mechanisms of glucocorticoid receptor (GR)‐triggered 5‐HT release.

Methods

Employing 1C11 cells to model 5‐HT neurotransmission, immunofluorescence and Pearson's Correlation Coefficient were used to analyze colocalization of GR, 5‐HT, vesicle membrane protein synaptotagmin 1 and vesicle dye FM4‐64FX. FFN511 and FM4‐64FX dyes as well as calcium imaging were used to visualize vesicular 5‐HT release upon application of GR agonist dexamethasone, GR antagonist mifepristone and voltage‐gated calcium channel (VGCC) inhibitors.

Results

GR, 5‐HT, synaptotagmin 1 and FM4‐64FX showed overlapping staining patterns, with Pearson's Correlation Coefficient indicating colocalization. Similarly to potassium chloride, dexamethasone caused a release of FFN511 and uptake of FM4‐64FX, indicating vesicular 5‐HT release. Mifepristone, calcium depletion and inhibition of L‐type VGCC significantly diminished dexamethasone‐induced vesicular 5‐HT release.

Conclusions

In close proximity to 5‐HT releasing sites, activated GR rapidly triggers L‐type VGCC‐dependent vesicular 5‐HT release. These findings provide a better understanding of the interrelationship between glucocorticoids and 5‐HT release.

Cortisol promotes the cognitive regulation of high intensive emotions independent of timing

Failures to cognitively downregulate negative emotions are a crucial risk factor for mental disorders. Previous studies provide evidence for a stress-induced improvement of cognitive emotion regulation possibly mediated via glucocorticoid actions. Cortisol can initialize immediate non-genomic as well as delayed genomic effects on cognitive control functioning, but its distinct effects on emotion regulation processes remain to be shown. Here, we sought to characterize time-dependent effects of oral cortisol administration on cognitive emotion regulation outcomes. We expected cortisol to improve emotion regulation success. Possible interactions with the delay between cortisol treatment and emotion regulation, strategy use and intensity of the emotional stimuli were examined. Eighty-five healthy men received either 10 mg hydrocortisone or a placebo in a double-blind, randomized design 30 or 90 min prior to an emotion regulation paradigm, in which they were asked to downregulate their emotional responses towards low and high intensive negative pictures via reappraisal or distraction. Affective ratings and pupil dilation served as outcome measures. Reduced arousal, enhanced valence ratings as well as increases in pupil dilations indexing the cognitive regulatory effort indicated successful downregulation of negative emotions evoked by high intensive but not low intensive negative pictures. Cortisol significantly reduced arousal ratings when downregulating high intensive negative emotions via distraction and (at a trend level) via reappraisal, independent of timing, demonstrating a beneficial effect of cortisol on subjective regulatory outcomes. Taken together, this study provides initial evidence suggesting that cortisol promotes the cognitive control of high intensive negative emotions both, 30 and 90 min after treatment.

Corticosterone-induced Hippocampal 5-HT Responses were Muted in Depressive-like State

Interactions between the hypothalamic-pituitary-adrenal axis and the central 5-HT system in the depressive state remain largely unknown. The present study investigated corticosterone (CORT) regulations of extracellular 5-HT in the hippocampal CA3 in a mouse model of depression. Basal dialysate 5-HT, true extracellular 5-HT, 5-HT reuptake efficiency, and time courses of dialysate 5-HT following CORT injections at 10, 20, and 40 mg/kg were determined at baseline, depressive-like state and after subsequent fluoxetine (FLX) treatment using in vivo microdialysis in male C57BL/6 mice. Behavioral tests were used to determine behavioral phenotypes and therapeutic responses to FLX. Depressed mice showed decreased extracellular 5-HT, increased 5-HT reuptake efficiency, and absence of the increase in dialysate 5-HT response to CORT injections, which were all reversed in FLX-responsive mice. Surprisingly, the FLX nonresponsive mice continued to worsen behaviorally and exhibited lower extracellular 5-HT and higher 5-HT reuptake efficiency. Our study indicates that abolished-CORT induced 5-HT response, decreased extracellular 5-HT, and increased 5-HT reuptake efficiency might be the signature features associated with depressive-like state. Increased 5-HT reuptake efficiency was one of the underlying mechanisms, with target effectors remaining to be explored. The findings in the FLX nonresponsive mice suggest distinct neuromechanisms, which might be genetically predetermined.

Delayed effects of acute stress on cognitive emotion regulation

Acute stress has been shown to modulate cognitive emotion regulation. Besides interactions with strategy use or sex, another critical modulating factor appears to be stress timing. Exposure to acute stress initiates immediate and delayed glucocorticoid effects on cognitive control functions. Previous studies indicated a delayed increase in prefrontal activity after stress and cortisol elevations, which might also improve the ability to cognitively regulate emotions when the acute stress state has subsided. In this study, we investigated the delayed impact of acute stress on the two emotion regulation strategies reappraisal and distraction. Eighty-one healthy males and free-cycling females were exposed to the Trier Social Stress Test or a control condition 90 min before they were tested in an emotion regulation paradigm, which required them to up- and downregulate their emotional responses towards negative pictures. Affective ratings served to measure emotion regulation success, whereas pupil dilation was included to additionally assess the cognitive effort required to deliberately regulate emotions. Stress affected neither arousal, valence or success ratings nor pupil dilation. However, cortisol increases were significantly associated with reduced arousal and enhanced valence ratings when regulating negative emotions via distraction. Exploratory mediation analyses revealed an indirect effect of stress on arousal and valence ratings for distraction that was mediated by cortisol increase. Our findings thereby provide further evidence that cortisol is positively related to emotion regulation success, which might be driven by a glucocorticoid-mediated mechanism facilitating attentional shifting.

Glucocorticoid-mediated mechanisms of hippocampal damage: Contribution of subgranular neurogenesis

A comprehensive overview of the interplay between glucocorticoids (GCs) and adult hippocampal neurogenesis (AHN) is presented, particularly, in the context of a diseased brain. The effectors of GCs in the dentate gyrus neurogenic niche of the hippocampal are reviewed, and the consequences of the GC signaling on the generation and integration of new neurons are discussed. Recent findings demonstrating how GC signaling mediates impairments of the AHN in various brain pathologies are overviewed. GC-mediated effects on the generation and integration of adult-born neurons in the hippocampal dentate gyrus depend on the nature, severity, and duration of the acting stress factor. GCs realize their effects on the AHN primarily via specific glucocorticoid and mineralocorticoid receptors. Disruption of the reciprocal regulation between the hypothalamic-pituitary-adrenal (HPA) axis and the generation of the adult-born granular neurons is currently considered to be a key mechanism implicating the AHN into the pathogenesis of numerous brain diseases, including those without a direct hippocampal damage. These alterations vary from reduced proliferation of stem and progenitor cells to increased cell death and abnormalities in morphology, connectivity, and localization of young neurons. Although the involvement of the mutual regulation between the HPA axis and the AHN in the pathogenesis of cognitive deficits and mood impairments is evident, several unresolved critical issues are stated. Understanding the details of GC-mediated mechanisms involved in the alterations in AHN could enable the identification of molecular targets for ameliorating pathology-induced imbalance in the HPA axis/AHN mutual regulation to conquer cognitive and psychiatric disturbances.

Molecular cloning, characterization, and gene expression behavior of glucocorticoid and mineralocorticoid receptors from the Chinese alligator (Alligator sinensis)

The Chinese alligator is an endemic crocodilian species in China. We isolated and obtained the glucocorticoid and mineralocorticoid receptor genes coding from the kidney of Alligator sinensis by nested polymerase chain reaction (PCR) and rapid amplification of cDNA ends (RACE). The glucocorticoid receptor (GR) gene has 2343 base pairs encoding 780 amino acids, while the mineralocorticoid receptor (MR) gene is 2958 bp in length encoding 985 amino acids. Quantitative real-time PCR was used to detect the distribution of messenger RNA (mRNA) levels. The maximum mRNA expressions were observed in the ovary and kidney, suggesting that these receptors may be involved in basic cellular functions or stress response of alligators. Besides this, RT-qPCR was performed to analyze the abundance of GR and MR mRNA transcripts in early embryonic development of the Chinese alligator in the kidney, liver, and heart. The mRNA levels of GR and MR at earlier stages in kidney, liver, and heart indicates that they might involve in the transcriptional regulation of early embryos and activate many precise developmental effects in fetal tissues. We also measured the protein expression in the liver embryonic developmental stages and found that the GR and MR proteins were restricted to both the nuclei and cytoplasm. The protein expression levels in the liver at different embryonic developmental stages have extremely prominent differences. Taken together, our results showed the full coding regions of GR and MR, their characteristics, and embryonic developmental mRNA and protein expressions of both genes in A. sinensis. This study could provide the necessary information for further investigating the diverse functions of GR and MR in A. sinensis.

The Simplified Science of Corticosteroids for Clinicians

Clinicians should be aware of the differences in corticosteroid formulations as these differences dictate which agent is best in various clinical situations. Corticosteroids work primarily by modulating transcriptional, post-transcriptional, and post-translational mechanisms within cellular nuclei to decrease the production of inflammatory mediators. Because this process requires change at the cellular level, clinical effects typically take days. The main consideration when selecting a corticosteroid is solubility. Less-soluble agents have a longer onset of action and a longer duration. However, they can have negative side effects on soft-tissue structures. They are ideal for intra-articular use. More-soluble agents have a faster onset of action but are rapidly cleared. They are ideal for extra-articular soft-tissue structures. Fluorinated compounds have decreased solubility, which further increases duration of action, but they have been shown to be associated with tendon rupture and atrophy.