Mechanisms of Brain Glucocorticoid Resistance in Stress-Induced Psychopathologies

Complement C5a Receptor Signaling Alters Stress Responsiveness and Modulates Microglia Following Chronic Stress Exposure

Background

Accumulating evidence underscores the pivotal role of heightened inflammation in the pathophysiology of stress-related diseases, but the underlying mechanisms remain elusive. The complement system, a key effector of the innate immune system, produces the C5-cleaved activation product C5a upon activation, initiating inflammatory responses through the canonical C5a receptor 1 (C5aR1). While C5aR1 is expressed in stress-responsive brain regions, its role in stress responsiveness remains unknown.

Methods

To investigate C5a-C5aR1 signaling in stress responses, mice underwent acute and chronic stress paradigms. Circulating C5a levels and messenger RNA expression of C5aR1 in the hippocampus and adrenal gland were measured. C5aR1-deficient mice were used to elucidate the effects of disrupted C5a-C5aR1 signaling across behavioral, hormonal, metabolic, and inflammation parameters.

Results

Chronic restraint stress elevated circulating C5a levels while reducing C5aR1 messenger RNA expression in the hippocampus and adrenal gland. Notably, the absence of C5aR1 signaling enhanced adrenal sensitivity to adrenocorticotropic hormone, concurrently reducing pituitary adrenocorticotropic hormone production and enhancing the response to acute stress. C5aR1-deficient mice exhibited attenuated reductions in locomotor activity and body weight under chronic stress. Additionally, these mice displayed increased glucocorticoid receptor sensitivity and disrupted glucose and insulin homeostasis. Chronic stress induced an increase in C5aR1-expressing microglia in the hippocampus, a response mitigated in C5aR1-deficient mice.

Conclusions

C5a-C5aR1 signaling emerges as a key metabolic regulator during stress, suggesting that complement activation and dysfunctional C5aR1 signaling may contribute to neuroinflammatory phenotypes in stress-related disorders. The results advocate for further exploration of complement C5aR1 as a potential therapeutic target for stress-related conditions.

Blood mRNA expression levels of glucocorticoid receptors and FKBP5 are associated with depressive disorder and altered HPA axis

BACKGROUND

While depression has been associated with alterations in the hypothalamic-pituitary adrenal (HPA) axis function, there is still controversy regarding the nature and extent of the dysfunction, such as in the debate about hypercortisolism vs. hypocortisolism. It may therefore be necessary to understand whether and how HPA axis function in depression is linked to mRNA expression of key genes regulating this system.

METHODS

We studied 163 depressed outpatients, most of whom were chronically ill, and 181 healthy controls. Blood mRNA expression levels of NR3C1 (including GRα, GRβ, and GR-P isoforms), FKBP4, and FKBP5 were measured at baseline. HPA axis feedback sensitivity was measured by the dexamethasone (Dex)/corticotropin-releasing hormone (CRH) test. The association between mRNA expression levels and HPA axis feedback sensitivity was examined.

RESULTS

Compared to controls, patients showed significantly higher expression of GRα and lower expression of FKBP5, and higher post-Dex cortisol levels, even after controlling for age and sex. FKBP5 expression was significantly positively correlated with cortisol levels in patients, while GRα expression was significantly negatively correlated with cortisol levels in controls.

LIMITATIONS

Most patients were taking psychotropic medications. The large number of correlation tests may have caused type I errors.

CONCLUSIONS

The tripartite relationship between depression, mRNA expression of GR and FKBP5, and HPA axis function suggests that the altered gene expression affects HPA axis dysregulation and, as a result, impacts the development and/or illness course of depressive disorder. The combination of increased GRα expression and decreased FKBP5 expression may serve as a biomarker for chronic depression.

Early Life Stress and Major Depressive Disorder-An Update on Molecular Mechanisms and Synaptic Impairments

Early life stress (ELS), characterized as abuse, neglect, and abandonment, can cause several adverse consequences in the lives of affected individuals. ELS experiences can affect an individual's development in variable ways, persisting in the long term and promoting lasting impacts, considering that early exposure to stressors can be biologically incorporated, as prolonged stimulation of stress response systems affects the development of the brain structure and other body systems, increasing the risk of diseases associated with stress and cognitive impairment. This type of stress increases the risk of developing major depressive disorder (MDD) in a severe form that does not respond adequately to traditional antidepressant treatments. Several alterations are studied as mechanisms that relate ELS with MDD, such as epigenetic alterations, neurotransmitters, and neuronal signaling. This review discusses research that brings evidence about the ELS mechanisms involved in synaptic impairments and MDD. The processes involved in epigenetic changes and the HPA axis are highlighted, as well as changes in neurotransmitters and neuronal signaling mechanisms.

Th17 Cells, Glucocorticoid Resistance, and Depression

Depression is a severe mental disorder that disrupts mood and social behavior and is one of the most common neuropsychological symptoms of other somatic diseases. During the study of the disease, a number of theories were put forward (monoamine, inflammatory, vascular theories, etc.), but none of those theories fully explain the pathogenesis of the disease. Steroid resistance is a characteristic feature of depression and can affect not only brain cells but also immune cells. T-helper cells 17 type (Th17) are known for their resistance to the inhibitory effects of glucocorticoids. Unlike the inhibitory effect on other subpopulations of T-helper cells, glucocorticoids can enhance the differentiation of Th17 lymphocytes, their migration to the inflammation, and the production of IL-17A, IL-21, and IL-23 in GC-resistant disease. According to the latest data, in depression, especially the treatment-resistant type, the number of Th17 cells in the blood and the production of IL-17A is increased, which correlates with the severity of the disease. However, there is still a significant gap in knowledge regarding the exact mechanisms by which Th17 cells can influence neuroinflammation in depression. In this review, we discuss the mutual effect of glucocorticoid resistance and Th17 lymphocytes on the pathogenesis of depression.

Stress circuitry: mechanisms behind nervous and immune system communication that influence behavior

Inflammatory processes are increased by stress and contribute to the pathology of mood disorders. Stress is thought to primarily induce inflammation through peripheral and central noradrenergic neurotransmission. In healthy individuals, these pro-inflammatory effects are countered by glucocorticoid signaling, which is also activated by stress. In chronically stressed individuals, the anti-inflammatory effects of glucocorticoids are impaired, allowing pro-inflammatory effects to go unchecked. Mechanisms underlying this glucocorticoid resistance are well understood, but the precise circuits and molecular mechanisms by which stress increases inflammation are not as well known. In this narrative review, we summarize the mechanisms by which chronic stress increases inflammation and contributes to the onset and development of stress-related mood disorders. We focus on the neural substrates and molecular mechanisms, especially those regulated by noradrenergic signaling, that increase inflammatory processes in stressed individuals. We also discuss key knowledge gaps in our understanding of the communication between nervous and immune systems during stress and considerations for future therapeutic strategies. Here we highlight the mechanisms by which noradrenergic signaling contributes to inflammatory processes during stress and how this inflammation can contribute to the pathology of stress-related mood disorders. Understanding the mechanisms underlying crosstalk between the nervous and immune systems may lead to novel therapeutic strategies for mood disorders and/or provide important considerations for treating immune-related diseases in individuals suffering from stress-related disorders.

Hormonal contraceptives, stress, and the brain: The critical need for animal models

Hormonal contraceptives are among the most important health and economic developments in the 20thCentury, providing unprecedented reproductive control and a range of health benefits including decreased premenstrual symptoms and protections against various cancers. Hormonal contraceptives modulate neural function and stress responsivity. These changes are usually innocuous or even beneficial, including their effects onmood. However, in approximately 4-10% of users, or up to 30 million people at any given time, hormonal contraceptives trigger depression or anxiety symptoms. How hormonal contraceptives contribute to these responses and who is at risk for adverse outcomes remain unknown. In this paper, we discussstudies of hormonal contraceptive use in humans and describe the ways in which laboratory animal models of contraceptive hormone exposure will be an essential tool for expanding findings to understand the precise mechanisms by which hormonal contraceptives influence the brain, stress responses, and depression risk.

Sex- and age-dependent effects of chronic corticosterone exposure on depressive-like, anxiety-like, and fear-related behavior: Role of amygdala glutamate receptors in the rat

Persistent glucocorticoid elevation consistent with chronic stress exposure can lead to psychopathology, including mood and anxiety disorders. Women and stress-exposed adolescents are more likely to be diagnosed with mood disorders, suggesting that sex and age are important factors in determining vulnerability, though much remains to be determined regarding the mechanisms underlying this risk. Thus, the aim of the present experiments was to use the chronic corticosterone (CORT) exposure paradigm, a model of depression-like behavior that has previously been established primarily in adult males, to determine the mood-related effects of CORT in female and adolescent rats. Depression- and anxiety-like effects in adulthood were determined using the sucrose preference (SPT), the forced swim test (FST), the elevated plus maze, and fear conditioning. Basolateral amygdala (BLA) and medial prefrontal cortex (mPFC) glutamate receptor subunit levels were then measured. In a subsequent experiment, adult male and female rats were tested for the effects of pharmacological activation (via AMPA) or inhibition (via NBQX) of AMPA receptors in the BLA on behavior in the FST. Overall, females showed reduced anxiety- and depressive-like behaviors relative to males. However, females treated with CORT in adolescence, but not adulthood, had increased immobility in the FST, indicative of depression-like behavior. In contrast, CORT did not alter behavior in adolescent-treated males, though the previously reported depression-like effect of adult CORT exposure was observed. Control females had higher expression of the AMPA receptor subunits GluA1 and GluA2/3 selectively in the BLA relative to males. Adolescent CORT treatment, however, decreased BLA GluA1 and GluA2/3 expression in females, but increased expression in males, consistent with the direction of depression-like behavioral effects. Male and female rats also demonstrated opposing patterns of response to BLA AMPA receptor modulation in the FST, with AMPA infusion magnifying the sex difference of decreased immobility in females. Overall, these experiments show that increased glutamate receptor function in the BLA may decrease the risk of developing depressive-like behavior, further supporting efforts to target glutamatergic receptors for the treatment of stress-related psychiatric disorders. These findings also support further focus on sex as a biological variable in neuropsychiatric research.

Central and Peripheral Immune Dysregulation in Posttraumatic Stress Disorder: Convergent Multi-Omics Evidence

Posttraumatic stress disorder (PTSD) is a chronic and multifactorial disorder with a prevalence ranging between 6–10% in the general population and ~35% in individuals with high lifetime trauma exposure. Growing evidence indicates that the immune system may contribute to the etiology of PTSD, suggesting the inflammatory dysregulation as a hallmark feature of PTSD. However, the potential interplay between the central and peripheral immune system, as well as the biological mechanisms underlying this dysregulation remain poorly understood. The activation of the HPA axis after trauma exposure and the subsequent activation of the inflammatory system mediated by glucocorticoids is the most common mechanism that orchestrates an exacerbated immunological response in PTSD. Recent high-throughput analyses in peripheral and brain tissue from both humans with and animal models of PTSD have found that changes in gene regulation via epigenetic alterations may participate in the impaired inflammatory signaling in PTSD. The goal of this review is to assess the role of the inflammatory system in PTSD across tissue and species, with a particular focus on the genomics, transcriptomics, epigenomics, and proteomics domains. We conducted an integrative multi-omics approach identifying TNF (Tumor Necrosis Factor) signaling, interleukins, chemokines, Toll-like receptors and glucocorticoids among the common dysregulated pathways in both central and peripheral immune systems in PTSD and propose potential novel drug targets for PTSD treatment.

Brain-immune axis regulation is responsive to cognitive behavioral therapy and mindfulness intervention: Observations from a randomized controlled trial in patients with Crohn's disease

Background and aims

Crohn's disease (CD) is a chronic inflammatory bowel disease associated with psychological stress that is regulated primarily by the hypothalamus-pituitary-adrenal (HPA) axis. Here, we determined whether the psychological characteristics of CD patients associate with their inflammatory state, and whether a 3-month trial of cognitive-behavioral and mindfulness-based stress reduction (COBMINDEX) impacts their inflammatory process.

Methods

Circulating inflammatory markers and a wide range of psychological parameters related to stress and well-being were measured in CD patients before and after COBMINDEX. Inflammatory markers in CD patients were also compared to age- and sex-matched healthy controls (HCs).

Results

CD patients exhibited increased peripheral low-grade inflammation compared with HCs, demonstrated by interconnected inflammatory modules represented by IL-6, TNFα, IL-17, MCP-1 and IL-18. Notably, higher IL-18 levels correlated with higher score of stress and a lower score of wellbeing in CD patients. COBMINDEX was accompanied by changes in inflammatory markers that coincided with changes in cortisol: changes in serum levels of cortisol correlated positively with those of IL-10 and IFNα and negatively with those of MCP-1. Furthermore, inflammatory markers of CD patients at baseline predicted COBMINDEX efficacy, as higher levels of distinct cytokines and cortisol at baseline, correlated negatively with changes in disease activity (by Harvey-Bradshaw Index) and psychological distress (global severity index measure) following COBMINDEX.

Conclusion

CD patients have a characteristic immunological profile that correlates with psychological stress, and disease severity. We suggest that COBMINDEX induces stress resilience in CD patients, which impacts their well-being, and their disease-associated inflammatory process.

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Patients with Crohn's disease exhibit distinct inflammatory and psychological modules.

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IL-18 correlates with clinical and psychological features of patients with Crohn's disease.

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COBMINDEX treatment strengthens resilience and recovers stress-induced inflammation among Crohn's disease patients.

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Both inflammatory and psychological measures predict COBMINDEX efficacy.

Glucocorticoid Receptor Antagonist Alters Corticosterone and Receptor-sensitive mRNAs in the Hypoxic Neonatal Rat

Hypoxia, a common stressor with preterm birth, increases morbidity and mortality associated with prematurity. Glucocorticoids (GCs) are administered to the preterm infant to improve oxygenation; prolonged use of GCs remains controversial. We evaluated a selective glucocorticoid receptor (GR) antagonist (CORT113176) in our neonatal rat model of human prematurity to assess how fasting and hypoxia-induced increases in neonatal corticosterone affects endogenous hormones and endocrine pancreas function. Neonatal rat pups at postnatal day (PD) 2, PD8, and PD15 were pretreated with CORT113176 and, after 60 minutes of separation and fasting, exposed to hypoxia (8% O2) or control (normoxia) for 30 or 60 minutes while fasting was continued. Plasma corticosterone, ACTH, glucose, and insulin were measured and fasting Homeostatic Model Assessment of Insulin Resistance was calculated. Glucocorticoid and insulin receptor-sensitive gene mRNAs were analyzed in liver, muscle, and adipose to evaluate target tissue biomarkers. CORT113176 pretreatment augmented baseline and hypoxia-induced increases in corticosterone and attenuated hypoxia-induced increases in insulin resistance at PD2. Normoxic and hypoxic stress increased the hepatic GR-sensitive gene mRNAs, Gilz and Per1; this was eliminated by pretreatment with CORT113176. CORT113176 pretreatment decreased baseline insulin receptor-sensitive gene mRNAs Akt2, Irs1, Pik3r1, and Srebp1c at PD2. We show that CORT113176 variably augments the stress-induced increases in corticosterone concentrations (attenuation of negative feedback) and that GR is critical for hepatic responses to stress in the hypoxic neonate. We also propose that measurement of Gilz and Per1 mRNA expression may be useful to evaluate the effectiveness of GR antagonism.

Hypothalamic Regulation of Corticotropin-Releasing Factor under Stress and Stress Resilience

This review addresses the molecular mechanisms of corticotropin-releasing factor (CRF) regulation in the hypothalamus under stress and stress resilience. CRF in the hypothalamus plays a central role in regulating the stress response. CRF stimulates adrenocorticotropic hormone (ACTH) release from the anterior pituitary. ACTH stimulates glucocorticoid secretion from the adrenal glands. Glucocorticoids are essential for stress coping, stress resilience, and homeostasis. The activated hypothalamic-pituitary-adrenal axis is suppressed by the negative feedback from glucocorticoids. Glucocorticoid-dependent repression of cAMP-stimulated Crf promoter activity is mediated by both the negative glucocorticoid response element and the serum response element. Conversely, the inducible cAMP-early repressor can suppress the stress response via inhibition of the cAMP-dependent Crf gene, as can the suppressor of cytokine signaling-3 in the hypothalamus. CRF receptor type 1 is mainly involved in a stress response, depression, anorexia, and seizure, while CRF receptor type 2 mediates “stress coping” mechanisms such as anxiolysis in the brain. Differential effects of FK506-binding immunophilins, FKBP4 and FKBP5, contribute to the efficiency of glucocorticoids under stress resilience. Together, a variety of factors contribute to stress resilience. All these factors would have the differential roles under stress resilience.

Glucocorticoid-Dependent Mechanisms of Brain Tolerance to Hypoxia

Adaptation of organisms to stressors is coordinated by the hypothalamic-pituitary-adrenal axis (HPA), which involves glucocorticoids (GCs) and glucocorticoid receptors (GRs). Although the effects of GCs are well characterized, their impact on brain adaptation to hypoxia/ischemia is still understudied. The brain is not only the most susceptible to hypoxic injury, but also vulnerable to GC-induced damage, which makes studying the mechanisms of brain hypoxic tolerance and resistance to stress-related elevation of GCs of great importance. Cross-talk between the molecular mechanisms activated in neuronal cells by hypoxia and GCs provides a platform for developing the most effective and safe means for prevention and treatment of hypoxia-induced brain damage, including hypoxic pre- and post-conditioning. Taking into account that hypoxia- and GC-induced reprogramming significantly affects the development of organisms during embryogenesis, studies of the effects of prenatal and neonatal hypoxia on health in later life are of particular interest. This mini review discusses the accumulated data on the dynamics of the HPA activation in injurious and non-injurious hypoxia, the role of the brain GRs in these processes, interaction of GCs and hypoxia-inducible factor HIF-1, as well as cross-talk between GC and hypoxic signaling. It also identifies underdeveloped areas and suggests directions for further prospective studies.

Glucocorticoids: Dr. Jekyll and Mr. Hyde of Hippocampal Neuroinflammation

Glucocorticoids (GCs) are an important component of adaptive response of an organism to stressogenic stimuli, a typical stress response being accompanied by elevation of GC levels in blood. Anti-inflammatory effects of GCs are widely used in clinical practice, while pro-inflammatory effects of GCs are believed to underlie neurodegeneration. This is particularly critical for the hippocampus, brain region controlling both cognitive function and emotions/affective behavior, and selectively vulnerable to neuroinflammation and neurodegeneration. The hippocampus is believed to be the main target of GCs since it has the highest density of GC receptors potentially underlying high sensitivity of hippocampal cells to severe stress. In this review, we analyzed the results of studies on pro- and anti-inflammatory effects of GCs in the hippocampus in different models of stress and stress-related pathologies. The available data form a sophisticated, though often quite phenomenological, picture of a modulatory role of GCs in hippocampal neuroinflammation. Understanding the dual nature of GC-mediated effects as well as causes and mechanisms of switching can provide us with effective approaches and tools to avert hippocampal neuroinflammatory events and as a result to prevent and treat brain diseases, both neurological and psychiatric. In the framework of a mechanistic view, we propose a new hypothesis describing how the anti-inflammatory effects of GCs may transform into the pro-inflammatory ones. According to it, long-term elevation of GC level or preliminary treatment with GC triggers accumulation of FKBP51 protein that suppresses activity of GC receptors and activates pro-inflammatory cascades, which, finally, leads to enhanced neuroinflammation.

Differential Effects of Fkbp4 and Fkbp5 on Regulation of the Proopiomelanocortin Gene in Murine AtT-20 Corticotroph Cells

The hypothalamic-pituitary-adrenal axis is stimulated in response to stress. When activated, it is suppressed by the negative feedback effect of glucocorticoids. Glucocorticoids directly inhibit proopiomelanocortin (Pomc) gene expression in the pituitary. Glucocorticoid signaling is mediated via glucocorticoid receptors, 11β-hydroxysteroid dehydrogenases, and the FK506-binding immunophilins, Fkbp4 and Fkbp5. Fkbp4 and Fkbp5 differentially regulate dynein interaction and nuclear translocation of the glucocorticoid receptor, resulting in modulation of the glucocorticoid action. Here, we explored the regulation of Fkbp4 and Fkbp5 genes and their proteins with dexamethasone, a major synthetic glucocorticoid drug, in murine AtT-20 corticotroph cells. To elucidate further roles of Fkbp4 and Fkbp5, we examined their effects on Pomc mRNA levels in corticotroph cells. Dexamethasone decreased Pomc mRNA levels as well as Fkpb4 mRNA levels in mouse corticotroph cells. Dexamethasone tended to decrease Fkbp4 protein levels, while it increased Fkpb5 mRNA and its protein levels. The dexamethasone-induced decreases in Pomc mRNA levels were partially canceled by Fkbp4 knockdown. Alternatively, Pomc mRNA levels were further decreased by Fkbp5 knockdown. Thus, Fkbp4 contributes to the negative feedback of glucocorticoids, and Fkbp5 reduces the efficiency of the glucocorticoid effect on Pomc gene expression in pituitary corticotroph cells.

Concepts of Neuroinflammation and Their Relationship With Impaired Mitochondrial Functions in Bipolar Disorder

Bipolar disorder (BD) is a chronic psychiatric disease, characterized by frequent behavioral episodes of depression and mania, and neurologically by dysregulated neurotransmission, neuroplasticity, growth factor signaling, and metabolism, as well as oxidative stress, and neuronal apoptosis, contributing to chronic neuroinflammation. These abnormalities result from complex interactions between multiple susceptibility genes and environmental factors such as stress. The neurocellular abnormalities of BD can result in gross morphological changes, such as reduced prefrontal and hippocampal volume, and circuit reorganization resulting in cognitive and emotional deficits. The term "neuroprogression" is used to denote the progressive changes from early to late stages, as BD severity and loss of treatment response correlate with the number of past episodes. In addition to circuit and cellular abnormalities, BD is associated with dysfunctional mitochondria, leading to severe metabolic disruption in high energy-demanding neurons and glia. Indeed, mitochondrial dysfunction involving electron transport chain (ETC) disruption is considered the primary cause of chronic oxidative stress in BD. The ensuing damage to membrane lipids, proteins, and DNA further perpetuates oxidative stress and neuroinflammation, creating a perpetuating pathogenic cycle. A deeper understanding of BD pathophysiology and identification of associated biomarkers of neuroinflammation are needed to facilitate early diagnosis and treatment of this debilitating disorder.

Hypothalamic Inflammation as a Potential Pathophysiologic Basis for the Heterogeneity of Clinical, Hormonal, and Metabolic Presentation in PCOS

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder among women of reproductive age. It is a heterogeneous condition characterized by reproductive, endocrine, metabolic, and psychiatric abnormalities. More than one pathogenic mechanism is involved in its development. On the other hand, the hypothalamus plays a crucial role in many important functions of the body, including weight balance, food intake, and reproduction. A high-fat diet with a large amount of long-chain saturated fatty acids can induce inflammation in the hypothalamus. Hypothalamic neurons can sense extracellular glucose concentrations and participate, with a feedback mechanism, in the regulation of whole-body glucose homeostasis. When consumed nutrients are rich in fat and sugar, and these regulatory mechanisms can trigger inflammatory pathways resulting in hypothalamic inflammation. The latter has been correlated with metabolic diseases, obesity, and depression. In this review, we explore whether the pattern and the expansion of hypothalamic inflammation, as a result of a high-fat and -sugar diet, may contribute to the heterogeneity of the clinical, hormonal, and metabolic presentation in PCOS via pathophysiologic mechanisms affecting specific areas of the hypothalamus. These mechanisms could be potential targets for the development of effective therapies for the treatment of PCOS.

Delivery room skin-to-skin contact in preterm infants affects long-term expression of stress response genes

Premature birth is a traumatic event that puts mother and child at risk for subsequent psychopathology. Skin-to-skin contact in the form of intermittent kangaroo mother care has been shown to positively affect the infant's stress response and cognitive development, but underlying mechanisms remain unclear. Moreover, first skin-to-skin contact is usually delayed for days after birth. In the delivery room skin-to-skin study (DR-SSC), a prospective randomized controlled trial conducted from 2/2012 to 7/2015, we set out to assess the effect of delivery room skin-to-skin contact on the infant's mRNA expression of six key molecules involved in stress response and neurobehavioral development at hospital discharge. 88 firstborn, singleton preterm infants (born at 25-32 weeks of gestational age) were included. In the delivery room after initial stabilization, infants were randomized to either 60 min of skin-to-skin or 5 min of visual contact with their mother. In this explorative add-on study on the original DR-SSC study, we determined the expression of six important stress response genes (CRHR1 and CRHR2, AVP, NR3C1, HTR2A, and SLC6A4) in peripheral white blood cells of infants during routine blood sampling upon hospital discharge (corrected gestational age of 40 weeks). Infants were followed up to six months corrected age. Relative mRNA expression of the corticotropin releasing hormone receptor 2 (CRH R2), the glucocorticoid receptor gene (NR3C1), and the serotonin transporter gene (SLC6A4) was significantly reduced in the delivery room SSC infants. Additionally, gene expression of CRH R2 showed a correlation with HPA axis reactivity and parameters of mother-child interaction at six months corrected age. Our results highlight the importance of delivery room mother-child skin-to-skin contact and underline the urgent need for in-depth studies on the underlying molecular mechanisms.

Low glucocorticoids in stress-related disorders: the role of inflammation

There is evidence that plasma cortisol concentration can be either increased or decreased in patients with depression and related anxiety and stress-related disorders; the exact pathophysiological mechanisms of this state are not almost clear. Several distinct theories were proposed and mechanisms, which could lead to decreased glucocorticoid signaling and/or levels, were described. However, there is a possible drawback in almost all the theories proposed: insufficient attention to the inflammatory process, which is undoubtedly present in several stress-related disorders, including post-traumatic stress disorder (PTSD). Previous studies only briefly mentioned the presence of an inflammatory reaction's signs in PTSD, without giving it due importance, although recognizing that it can affect the course of the disease. With that, the state of biochemical changes, characterized by the low glucocorticoids, glucocorticoid receptor's resistance and the signs of the persistent inflammation (with the high levels of circulating cytokines) might be observed not only in PTSD but in coronary heart diseases and systemic chronic inflammatory diseases (rheumatoid arthritis) as well. That is why the present review aims to depict the pathophysiological mechanisms, which lead to a decrease in glucocorticoids in PTSD due to the action of inflammatory stimuli. We described changes in the glucocorticoid system and inflammatory reaction as parts of an integral system, where glucocorticoids and the glucocorticoid receptor reside at the apex of a regulatory network that blocks several inflammatory pathways, while decreased glucocorticoid signaling and/or level leads to unchecked inflammatory reactions to promote pathologies such as PTSD. LAY SUMMARY This review emphasizes the importance of inflammatory reaction in the development of puzzling conditions sometimes observed in severe diseases including post-traumatic stress disorder - the decreased levels of glucocorticoids in the blood. Following the classical concepts, one would expect an increase in glucocorticoid hormones, since they are part of the feedback mechanism in the immune system, which reduces stress and inflammation. However, low levels of glucocorticoid hormones are also observed. Thus, this review describes potential mechanisms, which can lead to the development of such a state.

Chronic stress and endothelial dysfunction: mechanisms, experimental challenges, and the way ahead

Although chronic stress is an important risk factor for cardiovascular diseases (CVD) onset, the underlying mechanisms driving such pathophysiological complications remain relatively unknown. Here, dysregulation of innate stress response systems and the effects of downstream mediators are strongly implicated, with the vascular endothelium emerging as a primary target of excessive glucocorticoid and catecholamine action. Therefore, this review article explores the development of stress-related endothelial dysfunction by focusing on the following: 1) assessing the phenomenon of stress and complexities surrounding this notion, 2) discussing mechanistic links between chronic stress and endothelial dysfunction, and 3) evaluating the utility of various preclinical models currently employed to study mechanisms underlying the onset of stress-mediated complications such as endothelial dysfunction. The data reveal that preclinical models play an important role in our efforts to gain an increased understanding of mechanisms underlying stress-mediated endothelial dysfunction. It is our understanding that this provides a good foundation going forward, and we propose that further efforts should be made to 1) more clearly define the concept of stress and 2) standardize protocols of animal models with specific guidelines to better indicate the mental complications that are simulated.

Associations of FKBP4 and FKBP5 gene polymorphisms with disease susceptibility, glucocorticoid efficacy, anxiety, depression, and health-related quality of life in systemic lupus erythematosus patients

OBJECTIVES

To explore the associations of FKBP4 and FKBP5 gene polymorphisms with disease susceptibility, glucocorticoid (GC) efficacy, anxiety, depression, and health-related quality of life (HRQOL) in systemic lupus erythematosus (SLE) patients.

METHODS

All subjects were collected from the First and the Second Affiliated Hospital of Anhui Medical University in Hefei, China, during 2011 to 2015. In the case-control study, 541 SLE patients and 543 controls were recruited. In the follow-up study, 466 patients completed the 12-week follow-up and then were divided into GC-sensitive and GC-insensitive groups. Genotyping was determined using Multiplex SNaPshot technique. Data were analyzed using chi-square test and univariate and multivariate logistic regression analyses.

RESULTS

rs4713904, rs9368878, and rs7757037 of FKBP5 were associated with depression in SLE patients (rs4713904, P_BH = 0.037; rs9368878, P_BH = 0.001; rs7757037, P_BH = 0.003). Moreover, rs4713904 was associated with GC efficacy in males with SLE (P_BH = 0.011). The rs755658 of FKBP5 was associated with improvement in social function (P_BH = 0.022) and mental component summary (P_BH = 0.028). The rs4713907 of FKBP5 was related to improvement in total score of SF-36, bodily pain, and mental component summary score (all P_BH = 0.018). Furthermore, the rs12582595 of FKBP4 was correlated with general health improvement (P_BH = 0.033). No associations were seen between FKBP4/FKBP5 gene polymorphisms and SLE susceptibility and anxiety.

CONCLUSIONS

FKBP5 gene polymorphisms may be associated with depression and GC efficacy of SLE patients. Meanwhile, the genetic polymorphisms of FKBP4 and FKBP5 genes may be associated with HRQOL improvement in SLE patients. Key Points • FKBP5 gene polymorphisms were associated with depression of SLE patients. • FKBP5 gene polymorphisms were associated with GC efficacy of SLE patients. • FKBP5 gene polymorphisms were associated with HRQOL improvement in SLE patients. • FKBP4 gene polymorphisms were associated with HRQOL improvement in SLE patients.

Metabolites and metabolic pathways associated with glucocorticoid resistance in pregnant African-American women

Glucocorticoid resistance (GR) is associated with exposure to chronic stress and an increased risk of metabolic and inflammatory disorders in both animal and human populations. Studies on ethnic disparities highlight the African-American (AA) population as having a high propensity to both GR and chronic stress exposure. Glucocorticoids and inflammation play a very important role in pregnancy outcome and fetal development. To date, however, the metabolites and metabolic pathways associated with GR during pregnancy have not been identified, obscuring the mechanisms by which adverse health consequences arise, and thus impeding targeted therapeutic intervention. The objective of this study was to perform untargeted high-resolution metabolomics (HRM) profiling on 273 pregnant AA women, to identify metabolites and metabolic pathways associated with GR during the first trimester of pregnancy and to evaluate their cross-sectional association with birth outcomes and psychosocial variables related to chronic stress exposure. For this study, GR was determined by the concentration of dexamethasone required for 50% inhibition (Dex IC50) of the cytokine tumor-necrosis factor alpha (TNF-alpha) release in vitro in response to a standard dose of lipopolysaccharide. The results for Metabolome-Wide Association Studies (MWAS) and pathway enrichment analysis for serum metabolic associations with Dex IC50, showed energy (nicotinamide and TCA cycle), amino acid, and glycosphingolipid metabolism as top altered pathways. Bioinformatic analysis showed that GR, as indicated by elevated Dex IC50 in the pregnant women, was associated with increased inflammatory metabolites, oxidative stress related metabolites, increased demand for functional amino acids to support growth and development, and disruption in energy-related metabolites. If confirmed in future studies, targeting these physiologically significant metabolites and metabolic pathways may lead to future assessment and intervention strategies to prevent inflammatory and metabolic complications observed in pregnant populations.

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GR is associated with chronic stress and is a risk factor for adverse health outcomes, especially among African Americans.

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Metabolites and metabolic pathways associated with GR relate to energy production, amino acid metabolism, and inflammation.

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Findings provide a foundation for future studies investigating risk factors in this health disparity population.

Neuroinflammation and depressive disorder: The role of the hypothalamus

Data accumulated over the last two decades has demonstrated that hypothalamic inflammation plays an important role in the etiopathogenesis of the most prevalent diseases, such as cardiovascular diseases, metabolic syndrome, and even cancer. Recent findings indicate that hypothalamic inflammation is also associated with stress exposure and certain psychiatric diseases, such as depressive disorder. Mechanistic studies have shown that intense and/or chronic stress exposure is accompanied by the synthesis of inflammatory molecules in the hypothalamus, altered hypothalamic-pituitary-adrenal axis activity, and development of glucocorticoid resistance. Consequently, these factors might play a role in the etiopathogenesis of psychiatric disorders. We propose that hypothalamic inflammation represents an interconnection between somatic diseases and depressive disorder. These assumptions are discussed in this mini-review in the light of available data from studies focusing on hypothalamic inflammation.

Susceptibility Variations in Air Pollution Health Effects: Incorporating Neuroendocrine Activation

Diverse host factors/phenotypes may exacerbate or diminish biological responses induced by air pollutant exposure. We lack an understanding of biological indicators of environmental exposures that culminate in a physiological response versus those that lead to adversity. Variations in response phenotype might arise centrally and/or at the local tissue level. In addition to genetic differences, the current evidence supports the roles of preexisting cardiopulmonary diseases, diabetes, diet, adverse prenatal environments, neurobehavioral disorders, childhood infections, microbiome, sex, and psychosocial stressors in modifying the susceptibility to air pollutant exposures. Animal models of human diseases, obesity, nutritional inadequacies, and neurobehavioral conditions have been compared with healthy controls to understand the causes of variations in susceptibility. Although psychosocial stressors have been associated with increased susceptibility to air pollutant effects, the contribution of neuroendocrine stress pathways in mediating these effects is just emerging. The new findings of neuroendocrine activation leading to systemic metabolic and immunological effects of air pollutants, and the potential contribution to allostatic load, emphasize the consideration of these mechanisms into susceptibility. Variations in susceptibility to air pollution health effects are likely to underlie host genetic and physiological conditions in concert with disrupted neuroendocrine circuitry that alters physiological stability under the influence of stressors.

Epigenetic Modifications in Stress Response Genes Associated With Childhood Trauma

Adverse childhood experiences (ACEs) may be referred to by other terms (e.g., early life adversity or stress and childhood trauma) and have a lifelong impact on mental and physical health. For example, childhood trauma has been associated with posttraumatic stress disorder (PTSD), anxiety, depression, bipolar disorder, diabetes, and cardiovascular disease. The heritability of ACE-related phenotypes such as PTSD, depression, and resilience is low to moderate, and, moreover, is very variable for a given phenotype, which implies that gene by environment interactions (such as through epigenetic modifications) may be involved in the onset of these phenotypes. Currently, there is increasing interest in the investigation of epigenetic contributions to ACE-induced differential health outcomes. Although there are a number of studies in this field, there are still research gaps. In this review, the basic concepts of epigenetic modifications (such as methylation) and the function of the hypothalamic-pituitary-adrenal (HPA) axis in the stress response are outlined. Examples of specific genes undergoing methylation in association with ACE-induced differential health outcomes are provided. Limitations in this field, e.g., uncertain clinical diagnosis, conceptual inconsistencies, and technical drawbacks, are reviewed, with suggestions for advances using new technologies and novel research directions. We thereby provide a platform on which the field of ACE-induced phenotypes in mental health may build.

Natural Selection Equally Supports the Human Tendencies in Subordination and Domination: A Genome-Wide Study With in silico Confirmation and in vivo Validation in Mice

We proposed the following heuristic decision-making rule: "IF {an excess of a protein relating to the nervous system is an experimentally known physiological marker of low pain sensitivity, fast postinjury recovery, or aggressive, risk/novelty-seeking, anesthetic-like, or similar agonistic-intolerant behavior} AND IF {a single nucleotide polymorphism (SNP) causes overexpression of the gene encoding this protein} THEN {this SNP can be a SNP marker of the tendency in dominance} WHILE {underexpression corresponds to subordination} AND vice versa." Using this decision-making rule, we analyzed 231 human genes of neuropeptidergic, non-neuropeptidergic, and neurotrophinergic systems that encode neurotrophic and growth factors, interleukins, neurotransmitters, receptors, transporters, and enzymes. These proteins are known as key factors of human social behavior. We analyzed all the 5,052 SNPs within the 70 bp promoter region upstream of the position where the protein-coding transcript starts, which were retrieved from databases Ensembl and dbSNP using our previously created public Web service SNP_TATA_Comparator (http://beehive.bionet.nsc.ru/cgi-bin/mgs/tatascan/start.pl). This definition of the promoter region includes all TATA-binding protein (TBP)-binding sites. A total of 556 and 552 candidate SNP markers contributing to the dominance and the subordination, respectively, were uncovered. On this basis, we determined that 231 human genes under study are subject to natural selection against underexpression (significance p < 0.0005), which equally supports the human tendencies in domination and subordination such as the norm of a reaction (plasticity) of the human social hierarchy. These findings explain vertical transmission of domination and subordination traits previously observed in rodent models. Thus, the results of this study equally support both sides of the century-old unsettled scientific debate on whether both aggressiveness and the social hierarchy among humans are inherited (as suggested by Freud and Lorenz) or are due to non-genetic social education, when the children are influenced by older individuals across generations (as proposed by Berkowitz and Fromm).

Cannabidiol regulates the expression of hypothalamus-pituitary-adrenal axis-related genes in response to acute restraint stress

BACKGROUND

Research interest has grown around the potential therapeutic use of cannabidiol in mood-related disorders, due to its anxiolytic and antidepressant-like effects. These have been partially attributed to its action as an allosteric modulator of 5-HTR1A. However, the exact mechanism supporting cannabidiol properties remains unclear.

AIMS

To assess the effects of cannabidiol on different targets of the hypothalamus-pituitary-adrenal axis under baseline and stress conditions.

METHODS

We administered cannabidiol (5 mg/kg, 15 mg/kg or 30 mg/kg, intraperitoneally) or vehicle to male C57BL/6J mice 90 min before single restraint stress exposure (20 min). Using real-time polymerase chain reaction analysis, we measured alterations in the relative gene expression of corticotropin-releasing factor in the paraventricular nucleus, pro-opiomelanocortin in the arcuate nucleus of the hypothalamus, glucocorticoid receptor in the hippocampus, and serotonin 5-HTR1A receptor in the hippocampus and amygdala.

RESULTS

Under baseline conditions, cannabidiol did not modify any element of the hypothalamus-pituitary-adrenal axis. In contrast, all doses induced alterations in 5-HTR1A in the amygdala and hippocampus. Interestingly, cannabidiol at low (5 mg/kg) and intermediate doses (15 mg/kg) successfully blocked the effects induced by acute stress on corticotropin-releasing factor, pro-opiomelanocortin and glucocorticoid receptor gene expression. Also, restraint stress induced the opposite effects in 5-HTR1A gene expression in the hippocampus and amygdala, an effect not seen in mice treated with cannabidiol at low doses.

CONCLUSIONS

Taken together, these data suggest the ability of cannabidiol to regulate acute stress hypothalamus-pituitary-adrenal axis activation might be explained, at least in part, by its action on 5-HTR1A receptors.

Disease- and treatment-associated acquired glucocorticoid resistance

The development of resistance to glucocorticoids (GCs) in therapeutic regimens poses a major threat. Generally, GC resistance is congenital or acquired over time as a result of disease progression, prolonged GC treatment or, in some cases, both. Essentially, disruptions in the function and/or pool of the glucocorticoid receptor α (GRα) underlie this resistance. Many studies have detailed how alterations in GRα function lead to diminished GC sensitivity; however, the current review highlights the wealth of data concerning reductions in the GRα pool, mediated by disease-associated and treatment-associated effects, which contribute to a significant decrease in GC sensitivity. Additionally, the current understanding of the molecular mechanisms involved in driving reductions in the GRα pool is discussed. After highlighting the importance of maintaining the level of the GRα pool to combat GC resistance, we present current strategies and argue that future strategies to prevent GC resistance should involve biased ligands with a predisposition for reduced GR dimerization, a strategy originally proposed as the SEMOGRAM-SEDIGRAM concept to reduce the side-effect profile of GCs.

Consequences of early life stress on genomic landscape of H3K4me3 in prefrontal cortex of adult mice

Background

Maternal separation models in rodents are widely used to establish molecular mechanisms underlying prolonged effects of early life adversity on neurobiological and behavioral outcomes in adulthood. However, global epigenetic signatures following early life stress in these models remain unclear.

Results

In this study, we carried out a ChIP-seq analysis of H3K4 trimethylation profile in the prefrontal cortex of adult male mice with a history of early life stress. Two types of stress were used: prolonged separation of pups from their mothers (for 3 h once a day, maternal separation, MS) and brief separation (for 15 min once a day, handling, HD). Adult offspring in the MS group demonstrated reduced locomotor activity in the open field test accompanied by reduced exploratory activity, while the HD group showed decreased anxiety-like behavior only. In a group of maternal separation, we have found a small number (45) of slightly up-regulated peaks, corresponding to promoters of 70 genes, while no changes were observed in a group of handling. Among the genes whose promoters have differential enrichment of H3K4me3, the most relevant ones participate in gene expression regulation, modulation of chromatin structure and mRNA processing. For two genes, Ddias and Pip4k2a, increased H3K4me3 levels were associated with the increased mRNA expression in MS group.

Conclusion

The distribution of H3K4me3 in prefrontal cortex showed relatively low variability across all individuals, and only some subtle changes were revealed in mice with a history of early life stress. It is possible that the observed long-lasting behavioral alterations induced by maternal separation are mediated by other epigenetic mechanisms, or other brain structures are responsible for these effects.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4479-2) contains supplementary material, which is available to authorized users.

Molecular Mechanisms of Neuroplasticity: An Expanding Universe

Biochemical processes in synapses and other neuronal compartments underlie neuroplasticity (functional and structural alterations in the brain enabling adaptation to the environment, learning, memory, as well as rehabilitation after brain injury). This basic molecular level of brain plasticity covers numerous specific proteins (enzymes, receptors, structural proteins, etc.) participating in many coordinated and interacting signal and metabolic processes, their modulation forming a molecular basis for brain plasticity. The articles in this issue are focused on different "hot points" in the research area of biochemical mechanisms supporting neuroplasticity.