Posttraumatic stress disorder (PTSD) is a psychological disorder that develops following exposure to perceived life-threatening trauma. Characteristic features include behavioral changes caused by... Show morePosttraumatic stress disorder (PTSD) is a psychological disorder that develops following exposure to perceived life-threatening trauma. Characteristic features include behavioral changes caused by heightened arousal, including fear and anxiety. Glucocorticoid receptor (GR) hypersensitivity, as defined by strong negative feedback, has been one of the most robust findings of altered HPA axis function in PTSD. In this thesis, we evaluated GR-related changes that were exposed to the three consecutive stressors of the single prolonged stress (SPS) animal model for PTSD. We tested the potential of the GR antagonist RU486 treatment in reversing these stress-induced effects. We found that GR antagonism can normalize some stress-induced parameters. We demonstrated that varying the timing of RU486 administration and evaluation gave different behavioral results and dynamics of gene expression, that revealed complex interactions between stress and RU486 over time. We also tested the GR sensitivity after administered the exogenous corticosterone. Our data suggest the enhanced stress responsiveness after SPS to moderate but not mild stressors and a sensitization of brain GR signaling that extends beyond direct negative feedback regulation. Lastly, we provide evidence for a role of β-arrestin-2 as a modulator of regulating amygdala activity in response to fear/anxious memory of PTSD. Show less
Gentenaar, M.; Meulmeester, F.L.; Burg, X.R. van der; Hoekstra, A.T.; Hunt, H.; Kroon, J.; ... ; Meijer, O.C. 2024
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)... Show moreHuntington'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 regionspecific 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. Show less
What we collectively call “stress” is how we experience our body’s reaction to a stressor. This response is aimed to deal with the current stressor and to prepare for recurrences in the future. The... Show moreWhat we collectively call “stress” is how we experience our body’s reaction to a stressor. This response is aimed to deal with the current stressor and to prepare for recurrences in the future. The stress response is for an important part dependent on glucocorticoid hormones. By and large, the acute response to glucocorticoids is beneficial, but chronic exposure often becomes maladaptive. To improve prevention and treatment of disorders we can develop due to stress, it is important to better understand the effects and working mechanisms of glucocorticoids. While we already possess extensive knowledge regarding glucocorticoids and glucocorticoid receptor signaling, we introduced and studied five “aspects of context”, which we felt address important current misconceptions or gaps of knowledge. Corticosterone was at the center of all the studies we performed, yet the eventual outcome of glucocorticoid receptor activation differed extensively in all experiments. Thus, the context in which corticosterone exerts its effects matters, and it is to researcher to be aware of this when designing new studies and interpreting available data. Whilst our research merely addressed some specific processes, the lessons learned from these experiments can be applied much broader to the biology of glucocorticoid signaling and other nuclear family members. Show less
Stress, obesity and (stress-related) mood disorders such as depression and anxiety disorders are highly prevalent in modern society. These diseases often coincide. This may be because they trigger... Show moreStress, obesity and (stress-related) mood disorders such as depression and anxiety disorders are highly prevalent in modern society. These diseases often coincide. This may be because they trigger and reinforce each other, creating a vicious cycle. Social and psychological factors play a role in this cycle, but in this thesis we focused on the underlying biological mechanisms. We identified new obesity-related factors that likely affect fear and discovered new sites of action in the brain for factors that are already known to regulate fear. We also applied three novel drug treatment strategies. Each of these target (different) components of the stress system and were shown to alleviate stress- or diet-induced metabolic disease in mice. Certain strategies reduced obesity, while others seemed to prevent or even cure fatty liver disease in mice. This thesis thus represents a step towards breaking the vicious cycle between stress, obesity and (stress-related) mood disorders. Show less
Objective: Carbonyl reductase 1 (Cbr1), a recently discovered contributor to tissue glucocorticoid metabolism converting corticosterone to 2013dihydrocorticosterone (2013-DHB), is upregulated in... Show moreObjective: Carbonyl reductase 1 (Cbr1), a recently discovered contributor to tissue glucocorticoid metabolism converting corticosterone to 2013dihydrocorticosterone (2013-DHB), is upregulated in adipose tissue of obese humans and mice and may contribute to cardiometabolic complications of obesity. This study tested the hypothesis that Cbr1-mediated glucocorticoid metabolism influences glucocorticoid and mineralocorticoid receptor activation in adipose tissue and impacts glucose homeostasis in lean and obese states. Methods: The actions of 2013-DHB on corticosteroid receptors in adipose tissue were investigated first using a combination of in silico, in vitro, and transcriptomic techniques and then in vivo administration in combination with receptor antagonists. Mice lacking one Cbr1 allele and mice overexpressing Cbr1 in their adipose tissue underwent metabolic phenotyping before and after induction of obesity with high-fat feeding. Results: 2013-DHB activated both the glucocorticoid and mineralocorticoid receptor in adipose tissue and systemic administration to wild-type mice induced glucose intolerance, an effect that was ameliorated by both glucocorticoid and mineralocorticoid receptor antagonism. Cbr1 haploinsufficient lean male mice had lower fasting glucose and improved glucose tolerance compared with littermate controls, a difference that was abolished by administration of 2013-DHB and absent in female mice with higher baseline adipose 2013-DHB concentrations than male mice. Conversely, overexpression of Cbr1 in adipose tissue resulted in worsened glucose tolerance and higher fasting glucose in lean male and female mice. However, neither Cbr1 haploinsfficiency nor adipose overexpression affected glucose dyshomeostasis induced by high-fat feeding. Conclusions: Carbonyl reductase 1 is a novel regulator of glucocorticoid and mineralocorticoid receptor activation in adipose tissue that influences glucose homeostasis in lean mice. (c) 2021 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Show less
Glucocorticoids mediate numerous essential processes in the human body via binding to the glucocorticoid receptor (GR). Excessive GR signaling can cause disease, and GR antagonists can be used to... Show moreGlucocorticoids mediate numerous essential processes in the human body via binding to the glucocorticoid receptor (GR). Excessive GR signaling can cause disease, and GR antagonists can be used to treat many symptoms of glucocorticoid-induced pathology. The purpose of this study was to characterize the tissue-specific properties of the selective GR antagonist CORT125281. We evaluated the antagonistic effects of CORT125281 upon acute and subchronic corticosterone exposure in mice. In the acute corticosterone setting, hypothalamus-pituitary-adrenal-axis activity was investigated by measurement of basal- and stress-induced corticosterone levels, adrenocorticotropic hormone levels and pituitary proopiomelanocortin expression. GR signaling was evaluated by RT-PCR analysis of GR-responsive transcripts in liver, muscle, brown adipose tissue (BAT), white adipose tissue (WAT) and hippocampus. Pretreatment with a high dose of CORT125281 antagonized GR activity in a tissue-dependent manner. We observed complete inhibition of GR-induced target gene expression in the liver, partial blockade in muscle and BAT and no antagonism in WAT and hippocampus. Tissue distribution only partially explained the lack of effective antagonism. CORT125281 treatment did not disinhibit the hypothalamus-pituitary-adrenal neuroendocrine axis. In the subchronic corticosterone setting, CORT125281 partially prevented corticosterone-induced hyperinsulinemia, but not hyperlipidemia and immune suppression. In conclusion, CORT125281 antagonizes GR transcriptional activity in a tissue-dependent manner and improves corticosterone-induced hyperinsulinemia. Tailored dosing of CORT125281 may allow tissue-specific inhibition of GR transcriptional activity. Show less
Kroon, J.; Schilperoort, M.; Panhuis, W.I.H.; Berg, R. van den; Doeselaar, L. van; Verzijl, C.R.C.; ... ; Kooijman, S. 2020
Objective: Brown adipose tissue (BAT) displays a strong circadian rhythm in metabolic activity, but it is unclear how this rhythm is regulated. As circulating levels of corticosterone coincide with... Show moreObjective: Brown adipose tissue (BAT) displays a strong circadian rhythm in metabolic activity, but it is unclear how this rhythm is regulated. As circulating levels of corticosterone coincide with the rhythm of triglyceride-derived fatty acid (FA) uptake by BAT, we investigated whether corticosterone regulates BAT circadian rhythm.Methods: Corticosterone levels were flattened by implanting mice with subcutaneous corticosterone-releasing pellets, resulting in constant circulating corticosterone levels.Results: Flattened corticosterone rhythm caused a complete loss of circadian rhythm in triglyceride-derived fatty acid uptake by BAT. This effect was independent of glucocorticoid receptor expression in (brown) adipocytes and was not caused by deregulation of clock gene expression or overexposure to glucocorticoids, but rather seemed mediated by reduced sympathetic innervation of BAT. In a mouse model of hyperlipidemia and metabolic syndrome, long-term experimental flattening of corticosterone -and thus rhythm in BAT function -resulted in adiposity.Conclusions: This study highlights that a physiological rhythm in glucocorticoids is an important regulator of BAT function and essential for the maintenance of metabolic health.(c) 2021 The Author(s). Published by Elsevier GmbH. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Show less
Today__s Western society and work promotes a sedentary lifestyle. This, coupled with high caloric food availability has increased obesity followed by an increased prevalence of the metabolic... Show moreToday__s Western society and work promotes a sedentary lifestyle. This, coupled with high caloric food availability has increased obesity followed by an increased prevalence of the metabolic syndrome (MetS), type 2 diabetes (T2D) and cardiovascular diseases (CVD). Epidemiological data show a clear association between increased cortisol plasma levels, CVD and obesity, but animal models of the MetS are inconclusive with respect to whether the hypothalamus-pituitary-adrenal (HPA) axis is activated or not. It has remained unknown if, and to what extent HPA axis activity plays a pathogenic role in MetS development, and if the development of MetS changes it. In this thesis, we investigate high fat diet (HFD)-effect on the basal HPA axis activity and the effect of chronically elevated, exogenuously administered, corticosterone on MetS features as well as atherosclerosis development in spesific mouse models. From these studies we concluded that HFD reduces HPA axis activity where supraphysiological corticosterone levels worsen the features of MetS and the metabolic adaptations to a period of corticosterone excess in mice are long-lasting and may not completely recover to restore homeostasis. Futher more corticosteroid excess has both beneficial and harmful effects on cardiovascular risk factors that can be explained by their immunosuppressive and metabolic properties. Show less
Chronic stress is considered a vulnerability factor for depression. A key symptom is anhedonia; a reduced response to positive stimuli. Drugs are effective for only 20-40% of the patients and new... Show moreChronic stress is considered a vulnerability factor for depression. A key symptom is anhedonia; a reduced response to positive stimuli. Drugs are effective for only 20-40% of the patients and new drugs are urgently needed. The objective of the research was to develop a mouse model of depression that would express anhedonia, induced by chronic stress. Mice were repeatedly exposed to the non-physical presence of a rat. Alterations in stress system activity were measured. Anhedonia was assessed by studying the behavioral response to positive stimuli. As a potential therapeutical approach we assessed reward expectation, and studied the effect of repeated administration of mifepristone (glucocorticoid receptor antagonist), directly targeting stress system regulation. Our model induced changes in the sensitivity of the reward system that contributed to cognitive impairments underlying anhedonia. The effects could partially be restored by additional reward. Mifepristone in na_ve mice suppressed stress system activity, which could indicate a similar direction of effects in stressed mice if provided. Concluding, our chronic stress mouse model induces anhedonia. The new methodology to reduce stress by either providing additional positive stimuli or mifepristone, increases the well being of the mice and may prove a new drug target to treat depression in humans. Show less
Horst, J.P. ter; Mark, M.H. van der; Arp, M.; Berger, S.; Kloet, E.R. de; Oitzl, M.S. 2012
Corticosteroid effects on cognitive abilities during behavioral adaptation to stress are mediated by two types of receptors. While the glucocorticoid receptor (GR) is mainly involved in the... Show moreCorticosteroid effects on cognitive abilities during behavioral adaptation to stress are mediated by two types of receptors. While the glucocorticoid receptor (GR) is mainly involved in the consolidation of memory, the mineralocorticoid receptor (MR) mediates appraisal and initial responses to novelty. Recent findings in humans and mice suggest that under stress, the MR might be involved in the use of different learning strategies. Here, we used male mice lacking the MR in the forebrain (MRCaMKCre), which were subjected to 5-10 min acute restraint stress, followed 30 min later by training trials on the circular hole board. Mice had to locate an exit hole using extra- and intra-maze cues. We assessed performance and the use of spatial and stimulus-response strategies. Non-stressed MRCaMKCre mice showed delayed learning as compared to control littermates. Prior stress impaired performance in controls, but did not further deteriorate learning in MRCamKCre mice. When stressed, 20-30% of both MRCaMKCre and control mice switched from a spatial to a stimulus-response strategy, which rescued performance in MRCaMKCre mice. Furthermore, MRCaMKCre mice showed increased GR mRNA expression in all CA areas of the hippocampus and an altered basal and stress-induced corticosterone secretion, which supports their role in the modulation of neuroendocrine activity. In conclusion, our data provide evidence for the critical role of MR in the fast formation of spatial memory. In the absence of forebrain MR spatial learning performance was under basal circumstances impaired, while after stress further deterioration of performance was rescued by switching behavior increasingly to a stimulus-response strategy. (C) 2012 Elsevier Inc. All rights reserved. Show less
Adrenal corticosterone secretion of newborn mice rapidly desensitizes to repeated maternal absence. The present study investigated the effects of novelty exposure, maternal care and genotype on... Show moreAdrenal corticosterone secretion of newborn mice rapidly desensitizes to repeated maternal absence. The present study investigated the effects of novelty exposure, maternal care and genotype on this phenomenon. Maternal separation (MS) took place on postnatal days (pnd) 3-5. In Wistar rats, the degree of novelty in the MS-environment was varied by exposing pups to: (i) "home separation": pups remained in the home cage: (ii) "novel separation": pups were placed individually in a novel cage. Maternal care was recorded on pnd 1 to 4. To investigate the effect of genotype, we also examined Long Evans in the "home separation" condition. Basal and stress-induced ACTH and corticosterone levels were measured. Adrenal tyrosine hydroxylase (TH) and melanocortin receptor-2 (MCR-2) proteins served as markers for adrenal function.We show, in both rat strains, that the rise in plasma corticosterone induced by a single 8 h-MS on pnd 5 was abolished, when this separation procedure had also been performed on pnd 3 and 4. Habituation to maternal absence occurred irrespective of housing conditions. However, pups in the "home separation" condition received less maternal care upon reunion than those placed in the "novel separation". These "home separation" pups appeared more responsive to a subsequent acute novelty-stressor, and their adrenal TH and MCR-2 were higher. Long Evans rats appeared more stress responsive than the Wistars, in the home separation condition.In conclusion, separation environment, maternal care and genotype do not affect adrenal desensitization to repeated 8 h-MS itself, but may modulate the adrenal stress-responsiveness of separated pups. (C) 2011 Elsevier Inc. All rights reserved. Show less
An adverse early life event is considered a risk factor for stress-related psychiatric disorders in genetically predisposed individuals, probably because of its lasting effect on susceptibility to... Show moreAn adverse early life event is considered a risk factor for stress-related psychiatric disorders in genetically predisposed individuals, probably because of its lasting effect on susceptibility to stress. The objective of this thesis research was to examine in the mouse CD1 strain the immediate and permanent effects of an adverse early experience on the neuroendocrine stress system. For this purpose the hypothalamic-pituitary-adrenal (HPA) axis was examined of mouse pups that were refrained from maternal care, a laboratory model for neglect mimicking aspects of abuse. The data show that the infants__ stress response system readily adapts to daily repeated 8 hours of maternal separation, but that it continues to respond to a novelty stressor. The rapid adaptation to repeated maternal absence seems rather due to the ability to predict return of the mother than to adjust metabolism to episodic food deprivation. If maternal separation was extended to a single episode of 24 hours the immediate outcome was more profound but transient, although subtle effects on stress reactions and cognitive performance did persist. The findings demonstrate the amazing plasticity of the newborn brain and provide a basis to study the mechanistic underpinning of vulnerability or resilience to psychopathology. Show less
