Elevated Glucocorticoid Levels Research Articles

Abstract C004: Glucocorticoids establish a metastatic-promoting tumor microenvironment in a PDAC mouse model

Abstract Disseminated cancer cells (DCCs) arriving to a new organ may either proliferate and form metastasis, get eliminated by immune cells, or enter a quiescent stage. The factors that determine the DCCs’ fate, including getting quiescent DCCs to re-initiate proliferation and successfully evade the immune system, remain poorly understood, in part due to the lack of robust mouse models. We established a pancreatic ductal adenocarcinoma (PDAC) mouse model of dormant DCCs in the liver. An “immunization protocol” was used to mimic PDAC resection in patients: KPC1199 PDAC cells were injected to establish primary tumors and allow an adaptive immune response to develop against the cancer cells; the tumors were surgically resected; and new KPC1199 cells were intrasplenically injected to establish experimental liver metastases. The overwhelming majority of the KPC1199 cells were eliminated. No metastases spontaneously formed during 20 months of observation, but about 3-8 sporadic, single DCCs were found per liver cross section, and 94% of these DCCs were negative for proliferation markers. Although the model is based on entraining an adaptive immune response, T cell depletion resulted in only 25-30% of mice developing just 1-3 metastases each. This suggests that T cell depletion results in metastasis from the small percentage of DCCs that were proliferating. The DCC-hosting mice therefore represents of model to identify factors that can trigger further DCC proliferation and metastatic recurrence. Patients with PDAC often experience significant stress, leading to excess of endogenous glucocorticoids (GCs). Additionally, synthetic GCs are used during e.g., chemotherapy to manage side effects. To mimic elevated GC levels in patients, we treated DCC-hosting mice with synthetic GCs resulting in an increased percentage of proliferating DCCs (increasing from <6% of the examined cells in control mice to about 36%). Yet, no metastases formed. GC treatment also decreased T cell and increased neutrophil liver infiltration. Neutrophils can form protease-containing neutrophil extracellular traps (NETs), which we previously showed trigger DCC proliferation by proteolytic remodeling of the extracellular matrix protein laminin. We found that neutrophils from GC-treated mice spontaneously formed more NETs, and additionally, NET-generated laminin remodeling was observed in the liver metastasis. Together, the data suggest, that GC treatment drive quiescent DCCs to proliferate via neutrophils but alone this is insufficient to cause metastases. Consistent with this interpretation, T cell depletion combined with GC treatment resulted in multiple metastases in all mice examined. Of note, deleting the GC receptor in the DCCs did not reduce metastases, supporting that GCs act on the host and not the cancer cells. In conclusion, our data suggest that for quiescent DCCs to form metastases, they need signals that trigger proliferation and simultaneously, they must overcome immune surveillance. Elevated GC levels or GC treatment in immune suppressed individuals represents such a scenario. Citation Format: Xiao Han, Xueyan He, Yuan Gao, Sicheng Pan, Mikala Egeblad. Glucocorticoids establish a metastatic-promoting tumor microenvironment in a PDAC mouse model [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C004.

Decreased Brain pH Underlies Behavioral and Brain Abnormalities Induced by Chronic Exposure to Glucocorticoids in Mice.

Depressed patients may exhibit glucocorticoid hypersecretion, suggesting that elevated levels of glucocorticoids may play an important role in the pathophysiology of depression. Some postmortem brain studies have shown decreased pH and increased lactate levels in psychiatric patients, implying involvement of these factors in the pathogenesis. To investigate the effects of glucocorticoids on brain pH and lactate levels, and their roles in depressive symptoms, brain pH and lactate were examined in mice treated with corticosterone (CORT), the major bioactive glucocorticoid in rodents. A single administration of CORT decreased hippocampal pH after 24 h. Three weeks of CORT treatment decreased pH in the prefrontal cortex (PFC), striatum, and hippocampus (HC), whereas intake of pH 9.0 drinking water increased pH in these brain regions. pH and lactate levels were correlated in the PFC and HC of mice treated with CORT for 3 weeks. The suppression of body weight gain and decrease in adrenal weight observed after 3 weeks of CORT treatment were not alleviated by pH 9.0 water. However, an increase in immobility time in the forced swim test and a decrease in neurogenesis in the hippocampus were alleviated. The decrease in brain pH and increase in immobility time in the forced swim test and a decrease in neurogenesis in the hippocampus induced by CORT treatment were abolished by co-treatment with the glucocorticoid receptor (GR) antagonist mifepristone. These findings indicate that decreased brain pH via GRs may be related to glucocorticoid-induced depression-like behavior and decreased hippocampal neurogenesis.

Synthesis of Carborane–Thiazole Conjugates as Tyrosinase and 11β-Hydroxysteroid Dehydrogenase Inhibitors: Antiproliferative Activity and Molecular Docking Studies

The presented study depicts the synthesis of 11 carborane–thiazole conjugates with anticancer activity, as well as an evaluation of their biological activity as inhibitors of two enzymes: tyrosinase and 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). The overexpression of tyrosinase results in the intracellular accumulation of melanin and can be observed in melanoma. The overexpression of 11β-HSD1 results in an elevation of glucocorticoid levels and has been associated with the aggravation of metabolic disorders such as type II diabetes mellitus and obesity. Recently, as the comorbidity of melanomas and metabolic disorders is being recognized as an important issue, the search for new therapeutic options has intensified. This study demonstrates that carborane–thiazole derivatives inhibit both enzymes, exerting beneficial effects. The antiproliferative action of all newly synthesized compounds was evaluated using three cancer cell lines, namely A172 (human brain glioblastoma), B16F10 (murine melanoma) and MDA-MB-231 (human breast adenocarcinoma), as well as a healthy control cell line of HUVEC (human umbilical vein endothelial cells). The results show that 9 out of 11 newly synthesized compounds demonstrated similar antiproliferative action against the B16F10 cell line to the reference drug, and three of these compounds surpassed it. To the best of our knowledge, this study is the first to demonstrate dual inhibitory action of carborane–thiazole derivatives against both tyrosinase and 11β-HSD1. Therefore, it represents the first step towards the simultaneous treatment of melanoma and comorbid diseases such as type II diabetes mellitus.

Systemic immunostimulation induces glucocorticoid-mediated thymic involution succeeded by rebound hyperplasia which is impaired in aged recipients.

The thymus is the central organ involved with T-cell development and the production of naïve T cells. During normal aging, the thymus undergoes marked involution, reducing naïve T-cell output and resulting in a predominance of long-lived memory T cells in the periphery. Outside of aging, systemic stress responses that induce corticosteroids (CS), or other insults such as radiation exposure, induce thymocyte apoptosis, resulting in a transient acute thymic involution with subsequent recovery occurring after cessation of the stimulus. Despite the increasing utilization of immunostimulatory regimens in cancer, effects on the thymus and naïve T cell output have not been well characterized. Using both mouse and human systems, the thymic effects of systemic immunostimulatory regimens, such as high dose IL-2 (HD IL-2) with or without agonistic anti-CD40 mAbs and acute primary viral infection, were investigated. These regimens produced a marked acute thymic involution in mice, which correlated with elevated serum glucocorticoid levels and a diminishment of naïve T cells in the periphery. This effect was transient and followed with a rapid thymic "rebound" effect, in which an even greater quantity of thymocytes was observed compared to controls. Similar results were observed in humans, as patients receiving HD IL-2 treatment for cancer demonstrated significantly increased cortisol levels, accompanied by decreased peripheral blood naïve T cells and reduced T-cell receptor excision circles (TRECs), a marker indicative of recent thymic emigrants. Mice adrenalectomized prior to receiving immunotherapy or viral infection demonstrated protection from this glucocorticoid-mediated thymic involution, despite experiencing a substantially higher inflammatory cytokine response and increased immunopathology. Investigation into the effects of immunostimulation on middle aged (7-12 months) and advance aged (22-24 months) mice, which had already undergone significant thymic involution and had a diminished naïve T cell population in the periphery at baseline, revealed that even further involution was incurred. Thymic rebound hyperplasia, however, only occurred in young and middle-aged recipients, while advance aged not only lacked this rebound hyperplasia, but were entirely absent of any indication of thymic restoration. This coincided with prolonged deficits in naïve T cell numbers in advanced aged recipients, further skewing the already memory dominant T cell pool. These results demonstrate that, in both mice and humans, systemic immunostimulatory cancer therapies, as well as immune challenges like subacute viral infections, have the potential to induce profound, but transient, glucocorticoid-mediated thymic involution and substantially reduced thymic output, resulting in the reduction of peripheral naive T cells. This can then be followed by a marked rebound effect with naïve T cell restoration, events that were shown not to occur in advanced-aged mice.

Early-life glucocorticoids accelerate lymphocyte count senescence in roe deer

Immunosenescence corresponds to the progressive decline of immune functions with increasing age. Although it is critical to understand what modulates such a decline, the ecological and physiological drivers of immunosenescence remain poorly understood in the wild. Among them, the level of glucocorticoids (GCs) during early life are good candidates to modulate immunosenescence patterns because these hormones can have long-term consequences on individual physiology. Indeed, GCs act as regulators of energy allocation to ensure allostasis, are part of the stress response triggered by unpredictable events and have immunosuppressive effects when chronically elevated. We used longitudinal data collected over two decades in two populations of roe deer (Capreolus capreolus) to test whether higher baseline GC levels measured within the first year of life were associated with a more pronounced immunosenescence and parasite susceptibility. We first assessed immunosenescence trajectories in these populations facing contrasting environmental conditions. Then, we found that juvenile GC levels can modulate lymphocyte trajectory. Lymphocyte depletion was accelerated late in life when GCs were elevated early in life. Although the exact mechanism remains to be elucidated, it could involve a role of GCs on thymic characteristics. In addition, elevated GC levels in juveniles were associated with a higher abundance of lung parasites during adulthood for individuals born during bad years, suggesting short-term negative effects of GCs on juvenile immunity, having in turn long-lasting consequences on adult parasite load, depending on juvenile environmental conditions. These findings offer promising research directions in assessing the carry-over consequences of GCs on life-history traits in the wild.

Moderate intensity aerobic exercise prevents myopathic consequences of glucocorticoid administration in aged female mice

Elevated glucocorticoids induce a myopathy characterized by the loss of muscle mass and increased muscle fatiguability. The elderly is highly susceptible to the myopathic effects as they are more likely to experience elevated glucocorticoid levels. Aerobic exercise can prevent glucocorticoid-induced loss of muscle in younger rodents; however, it is unknown whether aerobic exercise can influence glucocorticoid myopathic features in aged muscle. Therefore, the purpose of this study was to define the extent to which moderate intensity aerobic exercise influenced glucocorticoid myopathy in aged muscle. 24-month-old female C57BL/6 mice were randomized into 4 groups of equal bodyweights. Two groups remained sedentary while the other 2 groups began treadmill aerobic exercise performed 5x/week at 10 m/min for 30 min at 5% grade. At the end of the first week of exercise, one group of sedentary mice and one group of exercising mice began receiving once daily subcutaneous injections of dexamethasone (1 mg/kg; DEX). The other group of sedentary mice and group of exercising mice began receiving once daily subcutaneous injections of saline only. All treatments (sedentary/exercise or DEX/saline) continued for an additional 2 weeks. At the end of week 3, the contractile properties of the triceps surae muscle complex were assessed in situ via electrical stimulation of the sciatic nerve. Specific measures included twitch force, sub tetanic force (60 Hz stimulation frequency), tetanic force (125 Hz stimulation frequency), and a fatigue protocol consisting of 60 high force contractions, with each contraction separated by 4 seconds. After testing, muscles of the triceps surae complex were extracted and weighed. Total protein content of the gastrocnemius was determined by the Bradford method. DEX lowered muscle mass, lowered gastrocnemius total protein content, and enhanced fatigue, with aerobic exercise preventing those changes. Interestingly, main effects were noted for DEX to increase twitch and 60 Hz absolute force, normalized force, and RFD in both sedentary and exercise trained mice. Neither DEX nor exercise altered half-relaxation time at any stimulation frequency, nor did they alter tetanic force at the 125 Hz stimulation. These data show that the detrimental effects of elevated glucocorticoids to skeletal muscle morphology and contractile function in aged muscle can be mitigated by moderate intensity aerobic exercise training. They also indicate that there may be some positive benefits to submaximal force generating capacity following a clinically relevant dose of glucocorticoids in aged females. This work was supported by a Doctoral grant from the American College of Sports Medicine (GRL) and NIH R03AG073445 (BSG). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Seasonal Hair Glucocorticoid Fluctuations in Wild Mice (Phyllotis darwini) within a Semi-Arid Landscape in North-Central Chile.

Mammals in drylands face environmental challenges exacerbated by climate change. Currently, human activity significantly impacts these environments, and its effects on the energy demands experienced by individuals have not yet been determined. Energy demand in organisms is managed through elevations in glucocorticoid levels, which also vary with developmental and health states. Here, we assessed how anthropization, individual characteristics, and seasonality influence hair glucocorticoid concentration in the Darwin's leaf-eared mouse (Phyllotis darwini) inhabiting two areas with contrasting anthropogenic intervention in a semi-arid ecosystem of northern Chile. Hair samples were collected (n = 199) to quantify hair corticosterone concentration (HCC) using enzyme immunoassays; additionally, sex, body condition, and ectoparasite load were recorded. There were no differences in HCC between anthropized areas and areas protected from human disturbance; however, higher concentrations were recorded in females, and seasonal fluctuations were experienced by males. The results indicate that animals inhabiting semi-arid ecosystems are differentially stressed depending on their sex. Additionally, sex and season have a greater impact on corticosterone concentration than anthropogenic perturbation, possibly including temporal factors, precipitation, and primary production. The influence of sex and seasonality on HCC in P. darwini make it necessary to include these variables in future stress assessments of this species.

Associations between glucocorticoids and habitat selection reflect daily and seasonal energy requirements

BackgroundGlucocorticoids are often associated with stressful environments, but they are also thought to drive the best strategies to improve fitness in stressful environments. Glucocorticoids improve fitness in part by regulating foraging behaviours in response to daily and seasonal energy requirements. However, many studies demonstrating relationships between foraging behaviour and glucocorticoids are experimental, and few observational studies conducted under natural conditions have tested whether changing glucocorticoid levels are related to daily and seasonal changes in energy requirements.MethodsWe integrated glucocorticoids into habitat selection models to test for relationships between foraging behaviour and glucocorticoid levels in elk (Cervus canadensis) as their daily and seasonal energy requirements changed. Using integrated step selection analysis, we tested whether elevated glucocorticoid levels were related to foraging habitat selection on a daily scale and whether that relationship became stronger during lactation, one of the greatest seasonal periods of energy requirement for female mammals.ResultsWe found stronger selection of foraging habitat by female elk with elevated glucocorticoids (eß = 1.44 95% CI 1.01, 2.04). We found no difference in overall glucocorticoid levels after calving, nor a significant change in the relationship between glucocorticoids and foraging habitat selection at the time of calving. However, we found a gradual increase in the relationship between glucocorticoids and habitat selection by female elk as their calves grew over the next few months (eß = 1.01, 95% CI 1.00, 1.02), suggesting a potentially stronger physiological effect of glucocorticoids for elk with increasing energy requirements.ConclusionsWe suggest glucocorticoid-integrated habitat selection models demonstrate the role of glucocorticoids in regulating foraging responses to daily and seasonal energy requirements. Ultimately, this integration will help elucidate the implications of elevated glucocorticoids under natural conditions.

Baseline and stress-induced steroid plasma levels and immune function vary annually and are associated with vocal activity in male toads (Rhinella icterica)

Theoretical models predict that elevated androgen and glucocorticoid levels in males during the reproductive season promote immunosuppression. However, some studies report decreased stress response during this season. This study investigated annual variation in plasma corticosterone and testosterone levels, plasma bacterial killing ability (BKA), and neutrophil to lymphocyte ratio (NLR) in free-living male toads (Rhinella icterica). Toads were sampled in the field (baseline) and 1 h-post restraint over five months, and we considered the occurrence of vocal activity. Baseline corticosterone, testosterone, and BKA showed higher values during the reproductive period, specifically in calling male toads. The NLR was similar throughout the year, but higher values were observed in calling toads. Moreover, baseline NLR and BKA were positively correlated with both testosterone and corticosterone, suggesting higher steroid levels during reproduction are associated with enhanced cellular and humoral immunity. Despite fluctuation of baseline values, post-restraint corticosterone levels remained uniform over the year, indicating that toads reached similar maximum values throughout the year. Testosterone levels decreased following restraint before one specific reproductive period but increased in response to restraint during and after this period. Meanwhile, BKA decreased due to restraint only after the reproductive period, indicating immune protection and resilience to immunosuppression by stressors associated with steroid hormones during reproduction. Our results show that baseline and stress-induced hormonal and immune regulation varies throughout the year and are associated with vocal activity in R. icterica males, indicating a possible compromise between steroids and immune function in anuran males.

Effect of ACEA 1021 on Neurotoxicity Induced by Dexamethasone — Initial Behavioral Study

Considerable evidence suggests that glucocorticoids (GCs) play an important role in neurodegeneration. Chronic elevated levels of GCs can result in neuronal degeneration of the hippocampal piramidal neurons, which are paralleled by cognitive deficits. Moreover, GCs potentiate stress or ischemia-induced accumulation of excitatory amino acids (EAA) in the extracellular space of hippocampus. ACEA 1021 (licostinel), a selective antagonist of the N-methyl-D-aspartate (NMDA) receptor, has been reported to prevent the excitotoxic action of high extracellular glutamate levels. The aim of this study was to investigate the effect of ACEA 1021 on neurotoxic effect of dexamethasone (DEX - a synthetic GCs receptor agonist). The experiments were carried out on Albino Swiss mice (25-30 g). ACEA 1021, at the doses: 1.25 and 2.5 mg/kg/day, ip, was administered 15 min before DEX (16 mg/kg/day, ip). The long-term memory acquisition (passive avoidance test) and the motor performance (“chimney” test) were evaluated 14 days after the drugs administration. The prolongation of climbing time in the “chimney” test and decrease of the retention time in the memory task of mice treated with DEX for 14 days. In mice treated with DEX for 14 days, ACEA 1021 at the both doses reduced the climbing time in the “chimney” test, at the dose of 1.25 mg/kg improved memory acquisition. The above findings suggest that ACEA 1021 could prevent the neurotoxic effects induced by DEX, but further study needs to be carried out to explain this effect.

Epigenetic Mechanisms Modulated by Glucocorticoids With a Focus on Cushing Syndrome.

In Cushing syndrome (CS), prolonged exposure to high cortisol levels results in a wide range of devastating effects causing multisystem morbidity. Despite the efficacy of treatment leading to disease remission and clinical improvement, hypercortisolism-induced complications may persist. Since glucocorticoids use the epigenetic machinery as a mechanism of action to modulate gene expression, the persistence of some comorbidities may be mediated by hypercortisolism-induced long-lasting epigenetic changes. Additionally, glucocorticoids influence microRNA expression, which is an important epigenetic regulator as it modulates gene expression without changing the DNA sequence. Evidence suggests that chronically elevated glucocorticoid levels may induce aberrant microRNA expression which may impact several cellular processes resulting in cardiometabolic disorders. The present article reviews the evidence on epigenetic changes induced by (long-term) glucocorticoid exposure. Key aspects of some glucocorticoid-target genes and their implications in the context of CS are described. Lastly, the effects of epigenetic drugs influencing glucocorticoid effects are discussed for their ability to be potentially used as adjunctive therapy in CS.

Intermittent Fasting-Improved Glucose Homeostasis Is Not Entirely Dependent on Caloric Restriction in db/db Male Mice.

Intermittent fasting (IF), which involves prolonged fasting intervals accompanied by caloric restriction, is an effective dietary treatment for obesity and diabetes. Although IF offers many benefits, it is difficult to determine whether these benefits are the consequences of caloric restriction. Every-other-day feeding (EODF) is a commonly used IF research model. This study was designed to identify other effectors of EODF, in addition to caloric restriction, and the possible underlying mechanisms. Diabetic db/db mice were divided into three groups: ad libitum (AL), meal-feeding (MF) and EODF. The MF model was employed to attain a level of caloric restriction comparable to EODF, with food distribution evenly divided between 10 AM and 6 PM, thereby minimizing the fasting interval. EODF yielded greater improvements in glucose homeostasis than MF in db/db mice by reducing fasting glucose levels and enhancing glucose tolerance. However, these effects on glucose metabolism were less pronounced in lean mice. Furthermore, ubiquitination of the liverspecific glucocorticoid receptor (GR) facilitated its degradation, and downregulating Kruppel-like factor 9 (KLF9), which ultimately suppressed liver gluconeogenesis in diabetic EODF mice. Although GR and KLF9 might mediate the metabolic benefits of EODF, the potential benefits of EODF might be limited by elevated serum glucocorticoid (GC) levels in diabetic EODF mice. Overall, this study suggests that the metabolic benefits of EODF in improving glucose homeostasis are independent of caloric restriction, possibly due to the downstream effects of liver-specific GR degradation.

Glucocorticoid stress hormones stimulate vesicle-free Tau secretion and spreading in the brain

Chronic stress and elevated levels of glucocorticoids (GCs), the main stress hormones, accelerate Alzheimer’s disease (AD) onset and progression. A major driver of AD progression is the spreading of pathogenic Tau protein between brain regions, precipitated by neuronal Tau secretion. While stress and high GC levels are known to induce intraneuronal Tau pathology (i.e. hyperphosphorylation, oligomerization) in animal models, their role in trans-neuronal Tau spreading is unexplored. Here, we find that GCs promote secretion of full-length, primarily vesicle-free, phosphorylated Tau from murine hippocampal neurons and ex vivo brain slices. This process requires neuronal activity and the kinase GSK3β. GCs also dramatically enhance trans-neuronal Tau spreading in vivo, and this effect is blocked by an inhibitor of Tau oligomerization and type 1 unconventional protein secretion. These findings uncover a potential mechanism by which stress/GCs stimulate Tau propagation in AD.

Avian extraembryonic membranes respond to yolk corticosterone early in development.

During times of maternal stress, developing embryos can be exposed to elevated levels of glucocorticoids, which can affect development and permanently alter offspring phenotype. In placental species, the placenta mediates fetal exposure to maternal glucocorticoids via metabolism, yet the placenta itself responds to glucocorticoids to regulate offspring growth and development. In oviparous species, maternal glucocorticoids can be deposited into the egg yolk and are metabolized early in development. This metabolism is mediated by the extraembryonic membranes, but it is unknown if the extraembryonic membranes also respond to maternal glucocorticoids in a way comparable to the placenta. In this study, we quantified the expression of acyl-CoA thioesterase 13 (Acot13) as an initial marker of the membrane's response to corticosterone in chicken (Gallus gallus) eggs. Acot13 regulates fatty acid processing in the embryo, to potentially regulate resource availability during development. We addressed the following questions using Acot13 expression: 1) Do the extraembryonic membranes respond to yolk corticosterone early in development? 2) Is the response to corticosterone dependent on the dose of corticosterone? 3) What is the duration of the response to corticosterone? 4) Does a metabolite of corticosterone (5β-corticosterone) elicit the same response as corticosterone? We found that corticosterone significantly induces the expression of Acot13 on day four of development and that expression of Acot13 increases with the dose of corticosterone. Further, we found expression of Acot13 is significantly elevated by corticosterone on days four and six of development compared to oil treated eggs, but not on days eight and ten. Although this response is transient, it occurs during a critical period of development and could initiate a cascade of events that ultimately alter offspring phenotype. Finally, we found that 5β-corticosterone does not increase the expression of Acot13, indicating that metabolism inactivates corticosterone. Ultimately, this study provides insight into the mechanisms underlying how maternally deposited glucocorticoids can affect embryonic development.

Glucocorticoid receptor antagonist CORT113176 attenuates motor and neuropathological symptoms of Huntington's disease in R6/2 mice

Huntington's Disease (HD) is a progressive neurodegenerative disease caused by a mutation in the huntingtin gene. The mutation leads to a toxic gain of function of the mutant huntingtin (mHtt) protein resulting in cellular malfunction, aberrant huntingtin aggregation and eventually neuronal cell death. Patients with HD show impaired motor functions and cognitive decline. Elevated levels of glucocorticoids have been found in HD patients and in HD mouse models, and there is a positive correlation between increased glucocorticoid levels and the progression of HD. Therefore, antagonism of the glucocorticoid receptor (GR) may be an interesting strategy for the treatment of HD. In this study, we evaluated the efficacy of the selective GR antagonist CORT113176 in the commonly used R6/2 mouse model. In male mice, CORT113176 treatment significantly delayed the loss of grip strength, the development of hindlimb clasping, gait abnormalities, and the occurrence of epileptic seizures. CORT113176 treatment delayed loss of DARPP-32 immunoreactivity in the dorsolateral striatum. It also restored HD-related parameters including astrocyte markers in both the dorsolateral striatum and the hippocampus, and microglia markers in the hippocampus. This suggests that CORT113176 has both cell-type and brain region-specific effects. CORT113176 delayed the formation of mHtt aggregates in the striatum and the hippocampus. In female mice, we did not observe major effects of CORT113176 treatment on HD-related symptoms, with the exception of the anti-epileptic effects. We conclude that CORT113176 effectively delays several key symptoms related to the HD phenotype in male R6/2 mice and believe that GR antagonism may be a possible treatment option.

Contribution of changes in the orexin system and energy sensors in the brain in depressive disorder - a study in an animal model

BackgroundMaternal elevated glucocorticoid levels during pregnancy can affect the developing fetus, permanently altering the structure and function of its brain throughout life. Excessive action of these hormones is known to contribute to psychiatric disorders, including depression.MaterialsThe study was performed in a rat model of depression based on prenatal administration of dexamethasone (DEX) in late pregnancy (0.1 mg/kg, days 14–21). We evaluated the effects of prenatal DEX treatment on the cognition and bioenergetic signaling pathways in the brain of adult male rats, in the frontal cortex and hippocampus, and in response to stress in adulthood, using behavioral and biochemical test batteries.ResultsWe revealed cognitive deficits in rats prenatally treated with DEX. At the molecular level, a decrease in the orexin A and orexin B levels and downregulation of the AMPK-SIRT1-PGC1α transduction pathway in the frontal cortex of these animals were observed. In the hippocampus, a decreased expression of orexin B was found and changes in the MR/GR ratio were demonstrated. Furthermore, an increase in HDAC5 level triggered by the prenatal DEX treatment in both brain structures and a decrease in MeCP2 level in the hippocampus were reported.ConclusionsOur study demonstrated that prenatal DEX treatment is associated with cognitive dysfunction and alterations in various proteins leading to metabolic changes in the frontal cortex, while in the hippocampus adaptation mechanisms were activated. The presented results imply that different pathophysiological metabolic processes may be involved in depression development, which may be useful in the search for novel therapies.

A frog in hot water: the effect of temperature elevation on the adrenal stress response of an African amphibian.

Amphibians, with their unique physiology and habitat requirements, are especially vulnerable to changes in environmental temperatures. While the activation of the physiological stress response can help to mitigate the impact of such habitat alteration, chronic production of elevated glucocorticoid levels can be deleterious in nature. There is no empirical evidence indicating the physiological response of African amphibians to temperature changes, where individuals are unable to emigrate away from potential stressors. To rectify this, we used the edible bullfrog (Pyxicephalus edulis) as a model species to determine the effect of elevated temperature on the adrenocortical response of the species using a recently established matrix. While a control group was kept at a constant temperature (25 °C) throughout the study period, an experimental group was exposed to control (25 °C) and elevated temperatures (30 °C). Mucous swabs were collected throughout the study period to determine dermal glucocorticoid (dGC) concentrations, as a proxy for physiological stress. In addition to this, individual body mass measurements were collected. The results showed that individuals within the experimental group who experienced increased temperatures had significantly elevated dGC levels compared to the control animals. Furthermore, there was a significant difference in the percentage mass change between experimental and control animals . These findings indicate the physiological sensitivity of the edible bullfrog to a thermal stressor in captivity. While this study shows the importance of proper amphibian management within the captive environment, it also highlights the coming danger of global climate change to this and similar amphibian species.

Extraembryonic metabolism of corticosterone protects against effects of exposure

When females experience stress during reproduction, developing embryos can be exposed to elevated levels of glucocorticoids, which can permanently affect offspring development, physiology, and behavior. However, the embryo can regulate exposure to glucocorticoids. In placental species, the placenta regulates embryonic exposure to maternal steroids via metabolism. In a comparable way, recent evidence has shown the extraembryonic membranes of avian species also regulate embryonic exposure to a number of maternal steroids deposited in the yolk via metabolism early in development. However, despite the known effects of embryonic exposure to glucocorticoids, it is not yet understood how glucocorticoids are metabolized early in development. To address this knowledge gap, we injected corticosterone into freshly laid chicken (Gallus gallus) eggs and identified corticosterone metabolites, located metabolomic enzyme transcript expression, tracked metabolomic enzyme transcript expression during the first six days of development, and determined the effect of corticosterone and metabolites on embryonic survival. We found that yolk corticosterone was metabolized before day four of development into two metabolites: 5β-corticosterone and 20β-corticosterone. The enzymes, AKR1D1 and CBR1 respectively, were expressed in the extraembryonic membranes. Expression was dynamic during early development, peaking on day two of development. Finally, we found that corticosterone exposure is lethal to the embryos, yet exposure to the metabolites is not, suggesting that metabolism protects the embryo. Ultimately, we show that the extraembryonic membranes of avian species actively regulate their endocrine environment very early in development.

Post-stress expression of genes involved in neuroplasticity in the hippocampus and blood of rats with different level of nervous system excitability

The causes and mechanisms of most mental disorders remain unclear. While stress is known to trigger depressive and anxiety disorders, the role of genetically determined individual differences in forming vulnerability to post-stress neurochemical disorders, including those that affect neuroplasticity, remains unresolved. Early studies suggest that acute and chronic stress lead to elevated glucocorticoid levels in the bloodstream and alter the expression of glucocorticoid and mineralocorticoid receptors. Additionally, both forms of stress can decrease the levels of brain-derived neurotrophic factor (BDNF), which plays a role in neuronal growth, development, and synapse building [1]. However, current studies insufficiently explain the complete mechanism of the stress response as they only explore variations in post-stress alteration of gene expression for proteins related to differing nervous system functional characteristics. The strains of rats from the Biocollection of the Pavlov Institute of Physiology, RAS, are a convenient model for studying the impact of genetically determined nervous system features on stress reactivity. The strains, selected based on the threshold of nervous system excitability [2], include HT (high threshold of excitability, low excitability) and LT (low threshold of excitability, high excitability) strains. These strains display contrasting responses to extended emotional and painful stress and exhibit unique changes in brain structures implicated in emotional regulation and stress reactivity at the molecular, cellular, and epigenetic levels [2]. The aim of this study is to examine the mRNA levels of genes encoding glucocorticoid and mineralocorticoid receptors (NR3C1, NR3C2) and brain-derived neurotrophic factor (BDNF) in the hippocampus and blood of rat strains that exhibit contrasting nervous system excitability. The study investigates interstrain variations in animals under non-stressful conditions and changes in response to prolonged exposure to emotional and painful stimuli. The experiment utilized 96 animals, with 6 animals in both the control and experimental groups at each time point. The stress model utilized was long-term emotional and painful stress as per K. Gecht [2]. The study assessed the expression of genes for glucocorticoid receptors and neurotrophic factor by isolating RNA from the hippocampus and blood of rats of two strains decapitated at 1, 7, 24, and 60 days post-stress. Gene expression analysis was conducted through real-time PCR and underwent further data processing using the ΔΔCt method. The statistical tests employed included the Kruskal–Wallis and Mann–Whitney tests. The analysis of the expression of the observed genes in intact animals demonstrates that highly excitable LT rats have a significantly lower level of expression of the nr3c2 gene, which encodes the mineralocorticoid receptor in the hippocampus, when compared to the low excitable HT strain. When studying the short-term and long-term effects of stress on the expression of the observed genes (nr3c1, nr3c2, bdnf), a decline was observed in the level of bdnf mRNA in the hippocampus of the LT strain 60 days after stress. The study suggests that the genetically determined characteristics of highly excitable animals affect the weakened adaptive abilities of their nervous system. One of the markers of this weakening is the reduced level of mRNA for the nr3c2 gene in the hippocampus under normal conditions, as well as a decrease in the expression of the bdnf gene in response to stress.

Acute or Chronic Exposure to Corticosterone Promotes Wakefulness in Mice.

Elevated glucocorticoid levels triggered by stress potentially contribute to sleep disturbances in stress-induced depression. However, sleep changes in response to elevated corticosterone (CORT), the major glucocorticoid in rodents, remain unclear. Here, we investigated the effects of acute or chronic CORT administration on sleep using electroencephalogram (EEG) and electromyography (EMG) recordings in freely moving mice. Acute CORT exposure rapidly promoted wakefulness, marked by increased episodes and enhanced EEG delta power, while simultaneously suppressing rapid eye movement (REM) and non-rapid eye movement (NREM) sleep, with the latter marked by decreased mean duration and reduced delta power. Prolonged 28-day CORT exposure led to excessive wakefulness and REM sleep, characterized by higher episodes, and decreased NREM sleep, characterized by higher episodes and reduced mean duration. EEG theta activity during REM sleep and delta activity during NREM sleep were attenuated following 28-day CORT exposure. These effects persisted, except for REM sleep amounts, even 7 days after the drug withdrawal. Elevated plasma CORT levels and depressive phenotypes were identified and correlated with observed sleep changes during and after administration. Fos expression significantly increased in the lateral habenula, lateral hypothalamus, and ventral tegmental area following acute or chronic CORT treatment. Our findings demonstrate that CORT exposure enhanced wakefulness, suppressed and fragmented NREM sleep, and altered EEG activity across all stages. This study illuminates sleep alterations during short or extended periods of heightened CORT levels in mice, providing a neural link connecting insomnia and depression.