A Comprehensive Overview on Stress Neurobiology: Basic Concepts and Clinical Implications

Stress Influences the Effect of Obsessive-Compulsive Symptoms on Emotion Regulation

Obsessive-compulsive disorder (OCD) is associated with emotion regulation impairments, namely the frequent use of maladaptive strategies such as suppression and the decreased use of reappraisal strategies. Additionally, these patients exhibit elevated stress levels. Since stress exposure affects emotion regulation abilities, stress might influence the relationship between obsessive-compulsive symptoms and emotion regulation. In this study, we explored the effects of stress and obsessive-compulsive symptoms on emotion regulation in a sample of healthy and OCD individuals. We used self-reported psychometric scales to measure stress levels, obsessive-compulsive symptoms, and emotion reappraisal and suppression skills. We applied multiple regression and mediation analyses. Our results demonstrated that increased reappraisal scores were associated with higher suppression scores. Additionally, elevated stress values predicted increased scores for suppression and decreased scores for reappraisal. Furthermore, the reappraisal abilities resulted from a combination of a direct effect of obsessive-compulsive symptoms and an indirect effect of obsessive-compulsive symptoms mediated by stress. The reliance on suppression strategies and the difficulty in using reappraisal approaches are explained by stress levels and are not directly explained by obsessive-compulsive symptoms. This study highlights the necessity of targeting stress in current therapy-based treatments for OCD.

Connectivity differences between Gulf War Illness (GWI) phenotypes during a test of attention

One quarter of veterans returning from the 1990–1991 Persian Gulf War have developed Gulf War Illness (GWI) with chronic pain, fatigue, cognitive and gastrointestinal dysfunction. Exertion leads to characteristic, delayed onset exacerbations that are not relieved by sleep. We have modeled exertional exhaustion by comparing magnetic resonance images from before and after submaximal exercise. One third of the 27 GWI participants had brain stem atrophy and developed postural tachycardia after exercise (START: Stress Test Activated Reversible Tachycardia). The remainder activated basal ganglia and anterior insulae during a cognitive task (STOPP: Stress Test Originated Phantom Perception). Here, the role of attention in cognitive dysfunction was assessed by seed region correlations during a simple 0-back stimulus matching task (“see a letter, push a button”) performed before exercise. Analysis was analogous to resting state, but different from psychophysiological interactions (PPI). The patterns of correlations between nodes in task and default networks were significantly different for START (n = 9), STOPP (n = 18) and control (n = 8) subjects. Edges shared by the 3 groups may represent co-activation caused by the 0-back task. Controls had a task network of right dorsolateral and left ventrolateral prefrontal cortex, dorsal anterior cingulate cortex, posterior insulae and frontal eye fields (dorsal attention network). START had a large task module centered on the dorsal anterior cingulate cortex with direct links to basal ganglia, anterior insulae, and right dorsolateral prefrontal cortex nodes, and through dorsal attention network (intraparietal sulci and frontal eye fields) nodes to a default module. STOPP had 2 task submodules of basal ganglia–anterior insulae, and dorsolateral prefrontal executive control regions. Dorsal attention and posterior insulae nodes were embedded in the default module and were distant from the task networks. These three unique connectivity patterns during an attention task support the concept of Gulf War Disease with recognizable, objective patterns of cognitive dysfunction.

Experimental colitis reduces microglial cell activation in the mouse brain without affecting microglial cell numbers

Inflammatory bowel disease (IBD) patients frequently suffer from anxiety disorders and depression, indicating that altered gut-brain axis signalling during gastrointestinal inflammation is a risk factor for psychiatric disease. Microglia, immune cells of the brain, is thought to be involved in a number of mental disorders, but their role in IBD is largely unknown. In the current work, we investigated whether colitis induced by dextran sulphate sodium (DSS), a murine model of IBD, alters microglial phenotypes in the brain. We found that colitis caused a reduction of Iba-1 and CD68 immunoreactivity, microglial activation markers, in specific brain regions of the limbic system such as the medial prefrontal cortex (mPFC), while other areas remained unaffected. Flow cytometry showed an increase of monocyte-derived macrophages during colitis and gene expression analysis in the mPFC showed pronounced changes of microglial markers including cluster of differentiation 86 (CD86), tumour necrosis factor-α, nitric oxide synthase 2, CD206 and chitinase-like protein 3 consistent with both M1 and M2 activation. Taken together, these findings suggest that experimental colitis-induced inflammation is propagated to the brain altering microglial function.

Work-Related Stress, Physio-Pathological Mechanisms, and the Influence of Environmental Genetic Factors

Work-related stress is a growing health problem in modern society. The stress response is characterized by numerous neurochemicals, neuroendocrine and immune modifications that involve various neurological systems and circuits, and regulation of the gene expression of the different receptors. In this regard, a lot of research has focused the attention on the role played by the environment in influencing gene expression, which in turn can control the stress response. In particular, genetic factors can moderate the sensitivities of specific types of neural cells or circuits mediating the imprinting of the environment on different biological systems. In this current review, we wish to analyze systematic reviews and recent experimental research on the physio-pathological mechanisms that underline stress-related responses. In particular, we analyze the relationship between genetic and epigenetic factors in the stress response.

Biomarkers in Stress Related Diseases/Disorders: Diagnostic, Prognostic, and Therapeutic Values

Various internal and external factors negatively affect the homeostatic equilibrium of organisms at the molecular to the whole-body level, inducing the so-called state of stress. Stress affects an organism's welfare status and induces energy-consuming mechanisms to combat the subsequent ill effects; thus, the individual may be immunocompromised, making them vulnerable to pathogens. The information presented here has been extensively reviewed, compiled, and analyzed from authenticated published resources available on Medline, PubMed, PubMed Central, Science Direct, and other scientific databases. Stress levels can be monitored by the quantitative and qualitative measurement of biomarkers. Potential markers of stress include thermal stress markers, such as heat shock proteins (HSPs), innate immune markers, such as Acute Phase Proteins (APPs), oxidative stress markers, and chemical secretions in the saliva and urine. In addition, stress biomarkers also play critical roles in the prognosis of stress-related diseases and disorders, and therapy guidance. Moreover, different components have been identified as potent mediators of cardiovascular, central nervous system, hepatic, and nephrological disorders, which can also be employed to evaluate these conditions precisely, but with stringent validation and specificity. Considerable scientific advances have been made in the detection, quantitation, and application of these biomarkers. The present review describes the current progress of identifying biomarkers, their prognostic, and therapeutic values.

Biomarkers in Stress Related Diseases/Disorders: Diagnostic, Prognostic, and Therapeutic Values

Various internal and external factors negatively affect the homeostatic equilibrium of organisms at the molecular to the whole-body level, inducing the so-called state of stress. Stress affects an organism's welfare status and induces energy-consuming mechanisms to combat the subsequent ill effects; thus, the individual may be immunocompromised, making them vulnerable to pathogens. The information presented here has been extensively reviewed, compiled, and analyzed from authenticated published resources available on Medline, PubMed, PubMed Central, Science Direct, and other scientific databases. Stress levels can be monitored by the quantitative and qualitative measurement of biomarkers. Potential markers of stress include thermal stress markers, such as heat shock proteins (HSPs), innate immune markers, such as Acute Phase Proteins (APPs), oxidative stress markers, and chemical secretions in the saliva and urine. In addition, stress biomarkers also play critical roles in the prognosis of stress-related diseases and disorders, and therapy guidance. Moreover, different components have been identified as potent mediators of cardiovascular, central nervous system, hepatic, and nephrological disorders, which can also be employed to evaluate these conditions precisely, but with stringent validation and specificity. Considerable scientific advances have been made in the detection, quantitation, and application of these biomarkers. The present review describes the current progress of identifying biomarkers, their prognostic, and therapeutic values.

Chronic Stress, Inflammation, and Colon Cancer: A CRH System-Driven Molecular Crosstalk

Chronic stress is thought to be involved in the occurrence and progression of multiple diseases, via mechanisms that still remain largely unknown. Interestingly, key regulators of the stress response, such as members of the corticotropin-releasing-hormone (CRH) family of neuropeptides and receptors, are now known to be implicated in the regulation of chronic inflammation, one of the predisposing factors for oncogenesis and disease progression. However, an interrelationship between stress, inflammation, and malignancy, at least at the molecular level, still remains unclear. Here, we attempt to summarize the current knowledge that supports the inseparable link between chronic stress, inflammation, and colorectal cancer (CRC), by modulation of a cascade of molecular signaling pathways, which are under the regulation of CRH-family members expressed in the brain and periphery. The understanding of the molecular basis of the link among these processes may provide a step forward towards personalized medicine in terms of CRC diagnosis, prognosis and therapeutic targeting.

BDNF and Cortisol integrative system - Plasticity vs. degeneration: Implications of the Val66Met polymorphism

BDNF is the neurotrophin mediating pro-neuronal survival and plasticity. Cortisol (COR), in turn, is engaged in the coordination of several processes in the brain homeostasis. Stress-responsive, both factors show an integrative role through their receptor's dynamics in neurophysiology. Furthermore, the Val66Met BDNF polymorphism may play a role in this mechanism.

AIM

to investigate BDNF-COR interaction in the human neurophysiology context.

METHODS

We collected all papers containing BDNF and COR parameters or showing COR analyses in genotyped individuals in a PubMed search - full description available on PROSPERO - CRD42016050206.

DISCUSSION

BDNF and COR perform distinct roles in the physiology of the brain whose systems are integrated by glucocorticoid receptors dynamics. The BDNF polymorphism appears to have an influence on individual COR responsivity to stress. BDNF and COR play complementary roles in the nervous system where COR is a regulator of positive/negative effects. Exercise positively regulates both factors, regardless of BDNF polymorphism.

High perceived stress in women is linked to oxidation, inflammation and immunosenescence

Chronic stress situations lead to an impairment of immune response and higher oxidative and inflammatory stress, which are important underlying mechanisms of the ageing process. However, given that the physiological stress response depends on the subjective appraisal of a given stressor, the aim of the study was to investigate the effect that different degrees of perceived stress have, regardless of their type, on immune functions, oxidative and inflammatory stress and ageing rate of women (30-50 years old). For that purpose, a group of 49 women was classified, according to their scores obtained in the perceived stress scale (PSS), into low (n = 23), moderate (n = 14) and high (n = 12) degree of perceived stress. The immune functions studied were: neutrophil and lymphocyte chemotaxis, neutrophil phagocytic capacity, natural killer activity, lymphoproliferation and LPS-stimulated cytokine release. Basal cytokine release was studied as an inflammatory stress marker. Antioxidant (superoxide dismutase, glutathione peroxidase and reductase activities, and reduced glutathione) and oxidant compounds (oxidized glutathione and malondialdehyde) were also investigated in whole blood as markers of oxidative stress. The results show that, in general, women with a moderate or high degree of perceived stress have a worse immune functionality and higher oxidative and inflammatory stress compared to women with low stress perception. In addition, a positive correlation was found between PSS scores and the biological age of each woman (P ≤ 0.001). In conclusion, high levels of perceived stress in women are associated with a higher oxidative and inflammatory stress and immunosenescence, which seem to accelerate their ageing rate.

Melanin-concentrating hormone in the Locus Coeruleus aggravates helpless behavior in stressed rats

Animal studies have shown that antagonists of receptor 1 of Melanin-Concentrating Hormone (MCH-R1) elicit antidepressive-like behavior, suggesting that MCH-R1 might be a novel target for the treatment of depression and supports the hypothesis that MCHergic signaling regulates depressive-like behaviors. Consistent with the evidence that MCHergic neurons send projections to dorsal and median raphe nuclei, we have previously demonstrated that MCH microinjections in both nuclei induced a depressive-like behavior. Even though MCH neurons also project to Locus Coeruleus (LC), only a few studies have reported the behavioral and neurochemical effect of MCH into the LC. We studied the effects of MCH (100 and 200 ng) into the LC on coping-stress related behaviors associated with depression, using two different behavioral tests: the forced swimming test (FST) and the learned helplessness (LH). To characterize the functional interaction between MCH and the noradrenergic LC system, we also evaluated the neurochemical effects of MCH (100 ng) on the extracellular levels of noradrenaline (NA) in the medial prefrontal cortex (mPFC), an important LC terminal region involved in emotional processing. MCH administration into the LC elicited a depressive-like behavior evidenced in both paradigms. Interestingly, in the LH, MCH (100) elicited a significant increase in escape failures only in stressed animals. A significant decrease in prefrontal levels of NA was observed after MCH microinjection into the LC. Our results demonstrate that increased MCH signaling into the LC triggers depressive-like behaviors, especially in stressed animals. These data further corroborate the important role of MCH in the neurobiology of depression.

Chronic restraint stress induces esophageal fibrosis with enhanced oxidative stress in a murine model

Although the underlying mechanism of stress remains unknown, it has been associated with the pathophysiology of gastroesophageal reflux diseases, the development of which appear to be accelerated by oxidative stress and fibrosis. The aim of the current study was to investigate the effect of chronic restraint stress on esophageal oxidative stress and fibrosis, as well as the impact of oxidative stress in a murine model whereby 8-week old C57BL/6J male mice were subjected to intermittent chronic restraint stress for a two-week period. The current study demonstrated that chronic restraint stress significantly reduced the body weight of mice compared with the control group. Although chronic restraint stress did not significantly alter the levels of triglycerides or cholesterol, free fatty acid concentration was significantly increased compared with the control group. Furthermore, chronic restraint stress significantly upregulated the expression levels of several fibrotic biomarkers including collagen type I, transforming growth factor β-1, α-smooth muscle actin and SMAD-3 compared with the control group. In addition, the expression levels of the reactive oxygen species (ROS) NADPH oxidase-4 and malondialdehyde were significantly increased, while the expression levels of nuclear factor erythroid 2-related factor 2 and heme oxygenase-1 were significantly decreased in esophageal tissue from mice in the chronic restraint stress group compared with the control group. In conclusion, chronic restraint stress may induce esophageal fibrosis by accumulating ROS and increasing fibrotic gene expression in a murine model.

Mental illness and well-being: an affect regulation perspective

Mental health crucially depends upon affective states such as emotions, stress responses, impulses and moods. These states shape how we think, feel and behave. Often, they support adaptive functioning. At other times, however, they can become detrimental to mental health via maladaptive affect generation processes and/or maladaptive affect regulation processes. Here, we present an integrative framework for considering the role of affect generation and regulation in mental illness and well-being. Our model views affect generation as an iterative cycle of attending to, appraising and responding to situations. It views affect regulation as an iterative series of decisions aimed at altering affect generation. Affect regulation decisions include identifying what, if anything, should be changed about affect, selecting where to intervene in the affect generation cycle, choosing how to implement this intervention, and monitoring the regulation attempt to decide whether to maintain, switch or stop it. Difficulties with these decisions, often arising from biased inputs to them, can contribute to manifestations of mental illness such as clinical symptoms, syndromes and disorders. The model has a number of implications for clinical assessment and treatment. Specifically, it offers a common set of concepts for characterizing different affective states; it highlights interactions between affect generation and affect regulation; it identifies assessment and treatment targets among the component processes of affect regulation; and it is applicable to prevention and treatment of mental illness as well as to promotion and restoration of psychological well-being.

Neuroinflammation caused by mental stress: the effect of chronic restraint stress and acute repeated social defeat stress in mice

Objectives: Cerebrovascular disease (CVD) is the leading cause of permanent disability worldwide. Inflammation has been reported to play an important role in the progression of CVD. Neuropsychiatric disorders such as depression are associated with increased incidence of CVD epidemiologically, although the mechanisms underlying this association are not clear. In this study, we assessed the effect of the acute repeated social defeat stress (RSDS) and chronic restraint stress (CRS) on neuroinflammation in mice. Methods: A total of 40 6-week-old male C57BL/6J mice were divided into RSDS, CRS, and corresponding control groups. In the RSDS group, male C57BL/6J mice were repeatedly subjected to bouts of social defeat by a larger CD-1 mouse for 10 min daily for 10 consecutive days. In the CRS group, the mice were exposed to restraint stress for 6 h per day for 28 consecutive days. Depressive behavior was evaluated by conducting sucrose preference test over 24 h. Peripheral blood serum and brain tissues were collected for measurement of corticosterone (CORT), epinephrine (EPI), and inflammatory factors (TNF-α and IL-6) using ELISA or real-time PCR 24 h after the sucrose preference test. Results: Both RSDS and CRS decreased the sucrose preference ratio. The acute stress increased serum CORT and EPI, while the chronic stress did not significantly influence them. Both stress models induced an inflammatory response in peripheral serum and the brain. Conclusions: RSDS and CRS are two effective models of depressive behavior, and both models cause neuroinflammation, which may be responsible for the increased risk of CVD seen in patients with depression.

Hyperthermia-induced seizures followed by repetitive stress are associated with age-dependent changes in specific aspects of the mouse stress system

Stress is among the most frequently self-reported factors provoking epileptic seizures in children and adults. It is still unclear, however, why some people display stress-sensitive seizures and others do not. Recently, we showed that young epilepsy patients with stress-sensitive seizures exhibit a dysregulated hypothalamic-pituitary-adrenal (HPA)-axis. Most likely, this dysregulation gradually develops, and is triggered by stressors occurring early in life (early-life stress [ELS]). ELS may be particularly impactful when overlapping with the period of epileptogenesis. To examine this in a controlled and prospective manner, the present study investigated the effect of repetitive variable stressors or control treatment between postnatal day (PND) 12 and 24 in male mice exposed on PND10 to hyperthermia (HT)-induced prolonged seizures (control: normothermia). A number of peripheral and central indices of HPA-axis activity were evaluated at pre-adolescent and young adult age (ie, at PND25 and 90, respectively). At PND25 but not at PND90, body weight gain and absolute as well as relative (to body weight) thymus weight were reduced by ELS (vs control), whereas relative adrenal weight was enhanced, confirming the effectiveness of the stress treatment. Basal and stress-induced corticosterone levels were unaffected, though, by ELS at both ages. HT by itself did not affect any of these peripheral markers of HPA-axis activity, nor did it interact with ELS. However, centrally we did observe age-specific interaction effects of HT and ELS with regard to hippocampal glucocorticoid receptor mRNA expression, neurogenesis with the immature neurone marker doublecortin and the number of hilar (ectopic) granule cells using Prox1 staining. This lends some support to the notion that exposure to repetitive stress after HT-induced seizures may dysregulate central components of the stress system in an age-dependent manner. Such dysregulation could be one of the mechanisms conferring higher vulnerability of individuals with epilepsy to develop seizures in the face of stress.

In the face of stress: Interpreting individual differences in stress-induced facial expressions

Stress is an inevitable part of life that can profoundly impact social and emotional functioning, contributing to the development of psychiatric disease. One key component of emotion and social processing is facial expressions, which humans can readily detect and react to even without conscious awareness. Facial expressions have been the focus of philosophic and scientific interest for centuries. Historically, facial expressions have been relegated to peripheral indices of fixed emotion states. More recently, affective neuroscience has undergone a conceptual revolution, resulting in novel interpretations of these muscle movements. Here, we review the role of facial expressions according to the leading affective neuroscience theories, including constructed emotion and social-motivation accounts. We specifically highlight recent data (Mayo et al, 2018) demonstrating the way in which stress shapes facial expressions and how this is influenced by individual factors. In particular, we focus on the consequence of genetic variation within the endocannabinoid system, a neuromodulatory system implicated in stress and emotion, and its impact on stress-induced facial muscle activity. In a re-analysis of this dataset, we highlight how gender may also influence these processes, conceptualized as variation in the "fight-or-flight" or "tend-and-befriend" behavioral responses to stress. We speculate on how these interpretations may contribute to a broader understanding of facial expressions, discuss the potential use of facial expressions as a trans-diagnostic marker of psychiatric disease, and suggest future work necessary to resolve outstanding questions.

Immunostimulatory effect of kumquat (Fortunella crassifolia) and its constituents, β-cryptoxanthin andR-limonene

The active constituents of kumquat in NK cell activation and anti-stress effects are β-cryptoxanthin andR-limonene.

Non-trauma-focused meditation versus exposure therapy in veterans with post-traumatic stress disorder: a randomised controlled trial

BACKGROUND

Post-traumatic stress disorder (PTSD) is a complex and difficult-to-treat disorder, affecting 10-20% of military veterans. Previous research has raised the question of whether a non-trauma-focused treatment can be as effective as trauma exposure therapy in reducing PTSD symptoms. This study aimed to compare the non-trauma-focused practice of Transcendental Meditation (TM) with prolonged exposure therapy (PE) in a non-inferiority clinical trial, and to compare both therapies with a control of PTSD health education (HE).

METHODS

We did a randomised controlled trial at the Department of Veterans Affairs San Diego Healthcare System in CA, USA. We included 203 veterans with a current diagnosis of PTSD resulting from active military service randomly assigned to a TM or PE group, or an active control group of HE, using stratified block randomisation. Each treatment provided 12 sessions over 12 weeks, with daily home practice. TM and HE were mainly given in a group setting and PE was given individually. The primary outcome was change in PTSD symptom severity over 3 months, assessed by the Clinician-Administered PTSD Scale (CAPS). Analysis was by intention to treat. We hypothesised that TM would show non-inferiority to PE in improvement of CAPS score (Δ=10), with TM and PE superior to PTSD HE. This study is registered with ClinicalTrials.gov, number NCT01865123.

FINDINGS

Between June 10, 2013, and Oct 7, 2016, 203 veterans were randomly assigned to an intervention group (68 to the TM group, 68 to the PE group, and 67 to the PTSD HE group). TM was significantly non-inferior to PE on change in CAPS score from baseline to 3-month post-test (difference between groups in mean change -5·9, 95% CI -14·3 to 2·4, p=0·0002). In standard superiority comparisons, significant reductions in CAPS scores were found for TM versus PTSD HE (-14·6 95% CI, -23·3 to -5·9, p=0·0009), and PE versus PTSD HE (-8·7 95% CI, -17·0 to -0·32, p=0·041). 61% of those receiving TM, 42% of those receiving PE, and 32% of those receiving HE showed clinically significant improvements on the CAPS score.

INTERPRETATION

A non-trauma-focused-therapy, TM, might be a viable option for decreasing the severity of PTSD symptoms in veterans and represents an efficacious alternative for veterans who prefer not to receive or who do not respond to traditional exposure-based treatments of PTSD.

FUNDING

Department of Defense, US Army Medical Research.

Positive metacognitions about alcohol mediate the relationship between FKBP5 variability and problematic drinking in a sample of young women

BACKGROUND

Previous research has shown that polymorphisms in the FKBP5 gene are related to some psychiatric conditions, including alcohol dependence. These relationships are moderated by the level of adverse childhood experiences that one has undergone. Maladaptive metacognition, associated with symptoms of psychiatric disorders and disturbed emotional self-regulation, is also a strong predictor of problematic alcohol use. Recent studies suggest that maladaptive metacognitions may be part of the developmental pathway from childhood abuse to drinking problems. This study attempted to identify relationships between FKBP5 polymorphisms and metacognitions about the positive effects of alcohol use and problematic drinking in a group differing in levels of childhood trauma.

METHODS

The sample studied was composed of 502 female participants aged 18-25 years (M=21.78; SD=1.84). Positive metacognitions about alcohol use were measured with the Positive Alcohol Metacognitions Scale (PAMS) and problematic drinking was gauged using the WHO Alcohol Use Disorders Identification Test. Levels of childhood adverse experiences were determined with the use of the Childhood Questionnaire. A total of 18 single-nucleotide polymorphisms (SNPs) in the FKBP5 gene were genotyped.

RESULTS

We did not find any interaction between the gene and childhood trauma on problematic drinking or metacognitions. However we identified a strong main effect of two SNPs of the FKBP5 gene - rs755658 and rs1334894 - on the PAMS subscale measuring positive metacognitive beliefs about emotional self-regulation. We also found nominally significant relations of several other SNPs with metacognitions and problematic drinking. Additionally, we showed that positive alcohol metacognitions mediate the relationship between problematic drinking and both rs755658 and rs1334894.

CONCLUSION

Our results may shed some light on the biological underpinnings of the developmental pathway leading to problematic drinking through maladaptive metacognitions.