Stress-induced remodeling of lymphoid innervation

Social isolation and loneliness: Undervalued risk factors for disease states and mortality

Social isolation and loneliness are two common but undervalued conditions associated with a poor quality of life, decreased overall health and mortality. In this review, we aim to discuss the health consequences of social isolation and loneliness. We first provide the potential causes of these two conditions. Then, we explain the pathophysiological processes underlying the effects of social isolation and loneliness in disease states. Afterwards, we explain the important associations between these conditions and different non-communicable diseases, as well as the impact of social isolation and loneliness on health-related behaviours. Finally, we discuss the current and novel potential management strategies for these conditions. Healthcare professionals who attend to socially isolated and/or lonely patients should be fully competent in these conditions and assess their patients thoroughly to detect and properly understand the effects of isolation and loneliness. Patients should be offered education and treatment alternatives through shared decision-making. Future studies are needed to understand the underlying mechanisms better and to improve the treatment strategies for both social isolation and loneliness.

Variation in infant rhesus monkeys' (Macaca mulatta) neutrophil-to-lymphocyte ratio is associated with environmental conditions, emotionality, and cortisol concentrations, and predicts disease-related outcomes

The neutrophil-to-lymphocyte ratio (NLR) is a predictor of morbidity for a variety of medical conditions, but little is known about how variation in NLR arises. We examined variation in this measure in a sample of 4577 infant rhesus monkeys (54.8 % female), who participated in the BioBehavioral Assessment program at the California National Primate Research Center at 3-4 months of age. Lower values for NLR were seen for animals reared indoors, for animals that were raised to be free of specific pathogens, and for males. In addition lower NLR was associated with higher stress values of cortisol and with greater emotionality in response to an acute stressor. Finally, lower NLR in infancy was associated with greater risk for developing airways hyperresponsiveness (a hallmark of asthma); with display of diarrhea up to 3.97 years later; and with greater viral load when infected with the simian immunodeficiency virus at a mean of 6.1 years of age. Infant NLR was a better predictor of viral load than was a contemporaneously obtained measure of NLR. Infant and adult values of NLR were only modestly correlated; one reason may be that the infant measure was obtained during stressful conditions and the adult measure was obtained under baseline conditions. We propose that NLR is an integrated outcome measure reflecting organization and interaction of stress-response and immune systems. As such, assessment of NLR under conditions of stress may be a particularly useful marker of individual differences in morbidity, especially for conditions in which stress plays an important role, as in asthma, diarrhea/colitis, and AIDS.

Stress-induced biological aging: A review and guide for research priorities

Exposure to chronic adverse conditions, and the resultant activation of the neurobiological response cascade, has been associated with an increased risk of early onset of age-related disease and, recently, with an older biological age. This body of research has led to the hypothesis that exposure to stressful life experiences, when occurring repeatedly or over a prolonged period, may accelerate the rate at which the body ages. The mechanisms through which chronic psychosocial stress influences distinct biological aging pathways to alter rates of aging likely involve multiple layers in the physiological-molecular network. In this review, we integrate research using animal, human, and in vitro models to begin to delineate the distinct pathways through which chronic psychosocial stress may impact biological aging, as well as the neuroendocrine mediators (i.e., norepinephrine, epinephrine, and glucocorticoids) that may drive these effects. Findings highlight key connections between stress and aging, namely cellular metabolic activity, DNA damage, telomere length, cellular senescence, and inflammatory response patterns. We conclude with a guiding framework and conceptual model that outlines the most promising biological pathways by which chronic adverse conditions could accelerate aging and point to key missing gaps in knowledge where future research could best answer these pressing questions.

Chronic stress increases transcriptomic indicators of biological aging in mouse bone marrow leukocytes

Research with animals and humans has demonstrated that chronic stress exposure can impact key biological aging pathways such as inflammation and DNA damage, suggesting a mechanism through which stress may increase risk for age-related disease. However, it is less clear whether these effects extend to other hallmarks of the aging process, such as cellular senescence. Male SCID mice were exposed to 14 days of restraint stress, with (n ​= ​6) or without (n ​= ​10) propranolol administration, or a non-stress control condition (n ​= ​10). Normal femoral bone marrow leukocytes were isolated from engrafted leukemia cells that had been injected prior to the stressor, as the mice were also under a cancer challenge. We performed whole genome transcriptional profiling to assess indicators of biological aging: cell stress, DNA damage repair, cellular senescence markers p16^INK4a and p21, and the pro-inflammatory senescence-associated secretory phenotype (SASP). ANCOVAs that adjusted for tumor load and Fisher's pairwise comparisons revealed that stressed mice had enhanced p16^INK4a (p ​= ​.02) and p21 (p ​= ​.004), lower DNA damage repair (p ​< ​.001), and higher SASP (p ​= ​.03) gene expression than control mice. Stressed mice also showed up-regulated beta-adrenergic (CREB) and inflammatory (NF-кB, AP-1) and down-regulated cell stress (Nrf2) transcription factor activity relative to control mice (ps ​< ​.01). Propranolol reversed CREB and Nrf2 activity (ps ​< ​.03). Findings suggest that chronic stress exposure can impact several key biological aging pathways within bone marrow leukocytes and these effects may be partially mediated by sympathetic beta-adrenergic receptor activation.

Neural control of immune cell trafficking

Leukocyte trafficking between blood and tissues is an essential function of the immune system that facilitates humoral and cellular immune responses. Within tissues, leukocytes perform surveillance and effector functions via cell motility and migration toward sites of tissue damage, infection, or inflammation. Neurotransmitters that are produced by the nervous system influence leukocyte trafficking around the body and the interstitial migration of immune cells in tissues. Neural regulation of leukocyte dynamics is influenced by circadian rhythms and altered by stress and disease. This review examines current knowledge of neuro–immune interactions that regulate leukocyte migration and consequences for protective immunity against infections and cancer.

Risky family climates presage increased cellular aging in young adulthood

A scientific consensus is emerging that children reared in risky family climates are prone to chronic diseases and premature death later in life. Few prospective data, however, are available to inform the mechanisms of these relationships. In a prospective study involving 323 Black families, we sought to determine whether, and how, childhood risky family climates are linked to a potential risk factor for later-life disease: increases in cellular aging (indexed by epigenetic aging). As hypothesized, risky family climates were associated with greater outflows of the stress hormones epinephrine and norepinephrine at ages 19 and 20 years; this, in turn, led to increases in cellular aging across ages 20-27 years. If sustained, these tendencies may place children from risky family climates on a trajectory toward the chronic diseases of aging.

Sympathetic improvement of cancer vaccine efficacy

The link between stress, other psychological factors and response to cancer, or even the cancer incidence and metastasis, is well established. The inhibition of β-Adrenergic receptors (β-AR) using β-blockers was demonstrated to have an inhibitory effect on cancer recurrence. Direct effects on the stress-induced suppression of anti-tumor immune responses were also shown. In a recent issue of Cancer Immunology Research, Daher and colleagues studied the molecular mechanism behind this protective effect in the context of cancer vaccination. They provided evidence that the β-AR signaling affected the priming of naïve CD8 + T cells in their myeloma model, rather than effector CD8 + T cells which downregulated the expression of β-AR after activation and became insensitive to such signaling. Blocking the β-adrenergic signaling during vaccination led to increased expansion and effector functions of antigen-specific CD8 + T cells and reduced tumor growth. This has implications for the clinical use of β-blockers as adjuvants to enhance cancer vaccination and other types of immunotherapy.

Externalizing trajectories predict elevated inflammation among adolescents exposed to early institutional rearing: A randomized clinical trial

BACKGROUND

There has been mounting interest in the pathophysiological relation between inflammation and psychopathology. In this paper, we examined associations between internalizing and externalizing psychopathology and inflammation in adolescents with a history of severe psychosocial deprivation and children reared in typical family contexts.

METHOD

The Bucharest Early Intervention Project is a longitudinal randomized trial of high-quality foster care as an alternative to institutional care. This report is based on 56 institutionalized children randomized to care as usual, 59 institutionalized children randomized to foster care, and 101 never institutionalized children who were recruited as an in-country comparison sample. Externalizing and internalizing behaviors were reported by parents and teachers at ages 8, 12, and 16. At age 16, C-reactive protein (CRP) was derived from blood spots in a subset of participants (n = 127). Multiple-group latent growth curve models were used to examine externalizing and internalizing trajectories and their associations with CRP.

RESULTS

Among children assigned to care as usual, higher levels of externalizing behaviors at age 8, as well as smaller decreases in these behaviors from 8 to 16 years predicted higher levels of CRP at age 16. In the same group of children, higher internalizing behaviors at age 8, but not the rate of change in these behaviors, also predicted higher levels of CRP. In contrast, these relations were not observed in the children assigned to foster care and never institutionalized controls.

CONCLUSIONS

Early institutional rearing is associated with a coupling of psychopathology and inflammation, whereas early placement into foster care buffers against these risks. These findings have implications for promoting healthy mental and physical development amongst institutionalized children.

Stress, inflammation, and eicosanoids: an emerging perspective

Clinical and experimental studies support the notion that adrenergic stimulation and chronic stress affect inflammation, metabolism, and tumor growth. Eicosanoids are also known to heavily influence inflammation while regulating certain stress responses. However, additional work is needed to understand the full extent of interactions between the stress-related pathways and eicosanoids. Here, we review the potential influences that stress, inflammation, and metabolic pathways have on each other, in the context of eicosanoids. Understanding the intricacies of such interactions could provide insights on how systemic metabolic effects mediated by the stress pathways can be translated into therapies for cancer and other diseases.

Loneliness, Social Isolation, and Cardiovascular Health

SIGNIFICANCE

Social and demographic changes have led to an increased prevalence of loneliness and social isolation in modern society. Recent Advances: Population-based studies have demonstrated that both objective social isolation and the perception of social isolation (loneliness) are correlated with a higher risk of mortality and that both are clearly risk factors for cardiovascular disease (CVD). Lonely individuals have increased peripheral vascular resistance and elevated blood pressure. Socially isolated animals develop more atherosclerosis than those housed in groups.

CRITICAL ISSUES

Molecular mechanisms responsible for the increased cardiovascular risk are poorly understood. In recent reports, loneliness and social stress were associated with activation of the hypothalamic-pituitary-adrenocortical axis and the sympathetic nervous system. Repeated and chronic social stress leads to glucocorticoid resistance, enhanced myelopoiesis, upregulated proinflammatory gene expression, and oxidative stress. However, the causal role of these mechanisms in the development of loneliness-associated CVD remains unclear.

FUTURE DIRECTIONS

Elucidation of the molecular mechanisms of how CVD is induced by loneliness and social isolation requires additional studies. Understanding of the pathomechanisms is essential for the development of therapeutic strategies to prevent the detrimental effects of social stress on health. Antioxid. Redox Signal. 28, 837-851.

The theory of constructed emotion: an active inference account of interoception and categorization

The science of emotion has been using folk psychology categories derived from philosophy to search for the brain basis of emotion. The last two decades of neuroscience research have brought us to the brink of a paradigm shift in understanding the workings of the brain, however, setting the stage to revolutionize our understanding of what emotions are and how they work. In this article, we begin with the structure and function of the brain, and from there deduce what the biological basis of emotions might be. The answer is a brain-based, computational account called the theory of constructed emotion.

Laboratory rhesus macaque social housing and social changes: Implications for research

Macaque species, specifically rhesus (Macaca mulatta), are the most common nonhuman primates (NHPs) used in biomedical research due to their suitability as a model of high priority diseases (e.g., HIV, obesity, cognitive aging), cost effective breeding and housing compared to most other NHPs, and close evolutionary relationship to humans. With this close evolutionary relationship, however, is a shared adaptation for a socially stimulating environment, without which both their welfare and suitability as a research model are compromised. While outdoor social group housing provides the best approximation of a social environment that matches the macaque behavioral biology in the wild, this is not always possible at all facilities, where animals may be housed indoors in small groups, in pairs, or alone. Further, animals may experience many housing changes in their lifetime depending on project needs, changes in social status, management needs, or health concerns. Here, we review the evidence for the physiological and health effects of social housing changes and the potential impacts on research outcomes for studies using macaques, particularly rhesus. We situate our review in the context of increasing regulatory pressure for research facilities to both house NHPs socially and mitigate trauma from social aggression. To meet these regulatory requirements and further refine the macaque model for research, significant advances must be made in our understanding and management of rhesus macaque social housing, particularly pair-housing since it is the most common social housing configuration for macaques while on research projects. Because most NHPs are adapted for sociality, a social context is likely important for improving repeatability, reproducibility, and external validity of primate biomedical research. Am. J. Primatol. 79:e22528, 2017. © 2016 Wiley Periodicals, Inc.

Structural Remodeling of Sympathetic Innervation in Atherosclerotic Blood Vessels: Role of Atherosclerotic Disease Progression and Chronic Social Stress

OBJECTIVE

The sympathetic nervous system (SNS) can undergo dramatic structural plasticity in response to behavioral factors and/or the presence of disease, leading to SNS hyperinnervation of peripheral tissues. The SNS has been proposed as an important mediator between stressful behavior and the progression of atherosclerosis in the vasculature. The present study examined whether structural remodeling of the SNS occurs in the vasculature in a genetically hyperlipidemic animal model of atherosclerosis, the Watanabe heritable hyperlipidemic rabbit (WHHL; relative to normolipidemic New Zealand white rabbits [NZW]), and whether SNS plasticity is driven by the progression of disease and/or by stressful social behavior.

METHODS

WHHL and NZW rabbits were assigned to an unstable or stable social environment for 4 months. Aortic atherosclerosis was assessed and SNS aortic innervation quantified using immunofluorescent microscopy.

RESULTS

Numerous SNS varicosities were observed throughout the aorta in WHHLs and NZWs, extending into the vascular media and intima, an innervation pattern not previously reported. WHHLs exhibited significantly greater innervation than NZWs (F(1,41) = 55.3, p < .001), with extensive innervation of the atherosclerotic neointima. The innervation density was highly correlated with the extent of disease in the WHHLs (r(21) = 0.855, p < .001). Social environment did not influence innervation in NZWs (aortic arch: p = .078, thoracic aorta: p = .34) or WHHLs (arch: p = .97, thoracic: p = .61).

CONCLUSIONS

The findings suggest that hyperinnervation is driven largely by the progression of disease rather than social environment. SNS innervation patterns observed in atherosclerotic human and mouse aortas were consistent with the rabbit, suggesting that SNS hyperinnervation of the diseased vessel wall is a general feature across mammalian species.

An active inference theory of allostasis and interoception in depression

In this paper, we integrate recent theoretical and empirical developments in predictive coding and active inference accounts of interoception (including the Embodied Predictive Interoception Coding model) with working hypotheses from the theory of constructed emotion to propose a biologically plausible unified theory of the mind that places metabolism and energy regulation (i.e. allostasis), as well as the sensory consequences of that regulation (i.e. interoception), at its core. We then consider the implications of this approach for understanding depression. We speculate that depression is a disorder of allostasis, whose myriad symptoms result from a 'locked in' brain that is relatively insensitive to its sensory context. We conclude with a brief discussion of the ways our approach might reveal new insights for the treatment of depression.This article is part of the themed issue 'Interoception beyond homeostasis: affect, cognition and mental health'.

Association of serum interleukin-6 with mental health problems in children exposed to perinatal complications and social disadvantage

There is consistent evidence that inflammation is involved in mental disorders pathogenesis. Herein, using data from the High Risk Cohort Study for Psychiatric Disorders, we investigated the relationship between parental mood disorders (PMD), environmental factors, serum interleukin-6 (IL6) and mental health problems in children aged 6-12. We measured the serum levels of IL6 in 567 children. Information related to socio-demographic characteristics, mental health problems and multiple risk factors, as well as parent's psychiatric diagnosis, was captured. We evaluated two groups of environmental risk factors (i.e. perinatal complications and social disadvantage) using a cumulative risk model. Results showed that higher serum levels of IL6 were associated with PMD (RR=1.072, p=0.001), perinatal complications (RR=1.022, p=0.013) and social disadvantage (RR=1.024, p=0.021). There was an interaction between PMD and social disadvantage (RR=1.141, p=0.021), as the effect of PMD on IL6 was significantly higher in children exposed to higher levels of social disadvantage. Moreover, there was a positive correlation between IL6 and mental health problems (RR=1.099, p=0.026), which was moderated by exposure to perinatal complications or social disadvantage (RR=1.273, p=0.015 and RR=1.179, p=0.048, respectively). In conclusions, there is evidence of a differential inflammatory activation in children with PMD and exposure to environmental risk factors, when compared to matched peers. Systemic inflammation may be involved in the pathway linking familial risk and mental health problems.

Sympathetic nervous system regulation of the tumour microenvironment

The peripheral autonomic nervous system (ANS) is known to regulate gene expression in primary tumours and their surrounding microenvironment. Activation of the sympathetic division of the ANS in particular modulates gene expression programmes that promote metastasis of solid tumours by stimulating macrophage infiltration, inflammation, angiogenesis, epithelial-mesenchymal transition and tumour invasion, and by inhibiting cellular immune responses and programmed cell death. Haematological cancers are modulated by sympathetic nervous system (SNS) regulation of stem cell biology and haematopoietic differentiation programmes. In addition to identifying a molecular basis for physiologic stress effects on cancer, these findings have also identified new pharmacological strategies to inhibit cancer progression in vivo.

Sympathoadrenergic modulation of hematopoiesis: a review of available evidence and of therapeutic perspectives

Innervation of the bone marrow (BM) has been described more than one century ago, however the first in vivo evidence that sympathoadrenergic fibers have a role in hematopoiesis dates back to less than 25 years ago. Evidence has since increased showing that adrenergic nerves in the BM release noradrenaline and possibly also dopamine, which act on adrenoceptors and dopaminergic receptors (DR) expressed on hematopoietic cells and affect cell survival, proliferation, migration and engraftment ability. Remarkably, dysregulation of adrenergic fibers to the BM is associated with hematopoietic disturbances and myeloproliferative disease. Several adrenergic and dopaminergic agents are already in clinical use for non-hematological indications and with a usually favorable risk-benefit profile, and are therefore potential candidates for non-conventional modulation of hematopoiesis.

Monocyte trafficking to the brain with stress and inflammation: a novel axis of immune-to-brain communication that influences mood and behavior

HIGHLIGHTSPsychological stress activates neuroendocrine pathways that alter immune responses.Stress-induced alterations in microglia phenotype and monocyte priming leads to aberrant peripheral and central inflammation.Elevated pro-inflammatory cytokine levels caused by microglia activation and recruitment of monocytes to the brain contribute to development and persistent anxiety-like behavior.Mechanisms that mediate interactions between microglia, endothelial cells, and macrophages and how these contribute to changes in behavior are discussed.Sensitization of microglia and re-distribution of primed monocytes are implicated in re-establishment of anxiety-like behavior. Psychological stress causes physiological, immunological, and behavioral alterations in humans and rodents that can be maladaptive and negatively affect quality of life. Several lines of evidence indicate that psychological stress disrupts key functional interactions between the immune system and brain that ultimately affects mood and behavior. For example, activation of microglia, the resident innate immune cells of the brain, has been implicated as a key regulator of mood and behavior in the context of prolonged exposure to psychological stress. Emerging evidence implicates a novel neuroimmune circuit involving microglia activation and sympathetic outflow to the peripheral immune system that further reinforces stress-related behaviors by facilitating the recruitment of inflammatory monocytes to the brain. Evidence from various rodent models, including repeated social defeat (RSD), revealed that trafficking of monocytes to the brain promoted the establishment of anxiety-like behaviors following prolonged stress exposure. In addition, new evidence implicates monocyte trafficking from the spleen to the brain as key regulator of recurring anxiety following exposure to prolonged stress. The purpose of this review is to discuss mechanisms that cause stress-induced monocyte re-distribution in the brain and how dynamic interactions between microglia, endothelial cells, and brain macrophages lead to maladaptive behavioral responses.

The neuroendocrinology of social isolation

Social isolation has been recognized as a major risk factor for morbidity and mortality in humans for more than a quarter of a century. Although the focus of research has been on objective social roles and health behavior, the brain is the key organ for forming, monitoring, maintaining, repairing, and replacing salutary connections with others. Accordingly, population-based longitudinal research indicates that perceived social isolation (loneliness) is a risk factor for morbidity and mortality independent of objective social isolation and health behavior. Human and animal investigations of neuroendocrine stress mechanisms that may be involved suggest that (a) chronic social isolation increases the activation of the hypothalamic pituitary adrenocortical axis, and (b) these effects are more dependent on the disruption of a social bond between a significant pair than objective isolation per se. The relational factors and neuroendocrine, neurobiological, and genetic mechanisms that may contribute to the association between perceived isolation and mortality are reviewed.

Human social genomics

A growing literature in human social genomics has begun to analyze how everyday life circumstances influence human gene expression. Social-environmental conditions such as urbanity, low socioeconomic status, social isolation, social threat, and low or unstable social status have been found to associate with differential expression of hundreds of gene transcripts in leukocytes and diseased tissues such as metastatic cancers. In leukocytes, diverse types of social adversity evoke a common conserved transcriptional response to adversity (CTRA) characterized by increased expression of proinflammatory genes and decreased expression of genes involved in innate antiviral responses and antibody synthesis. Mechanistic analyses have mapped the neural "social signal transduction" pathways that stimulate CTRA gene expression in response to social threat and may contribute to social gradients in health. Research has also begun to analyze the functional genomics of optimal health and thriving. Two emerging opportunities now stand to revolutionize our understanding of the everyday life of the human genome: network genomics analyses examining how systems-level capabilities emerge from groups of individual socially sensitive genomes and near-real-time transcriptional biofeedback to empirically optimize individual well-being in the context of the unique genetic, geographic, historical, developmental, and social contexts that jointly shape the transcriptional realization of our innate human genomic potential for thriving.

Close interactions between sympathetic neural fibres and follicular dendritic cells network are not altered in Peyer's patches and spleen of C57BL/6 mice during the preclinical stage of 139A scrapie infection

During preclinical stage of prion diseases, secondary lymphoid organs seem to play an important role in prion amplification prior the invasion of the associated peripheral nervous system. In mice, it was shown that the relative positioning of follicular dendritic cells (FDC) and sympathetic nervous system (SNS) affects the velocity of neuroinvasion following scrapie inoculation. In this study, we checked if scrapie infection, by oral or intraperitoneal route, could influence this neuroimmune interface between FDC and tyrosine hydroxylase (TH) positive neural fibres within Peyer's patches (PP) and spleen of the C57BL/6 mouse strain. We concluded that, in vivo, scrapie 139A and ME7 strains do not modify FDC-SNS neuroimmune interface. However, age seems to alter this neuroimmune interface and thus could influence the neuroinvasion in prion pathogenesis.

Prevention moderates associations between family risks and youth catecholamine levels

OBJECTIVE

The purpose of this study was to establish, using a quasi-experimental design, whether 2 family risk factors, parental psychological dysfunction and nonsupportive parenting, during preadolescence could longitudinally predict elevated sympathetic nervous system (SNS) activity 9 years later, and to determine whether participation in an efficacious family centered prevention program could moderate these associations if they emerged.

METHOD

Rural African American preadolescents (N = 476) were assigned randomly to the Strong African American Families (SAAF) program or to a control condition. When youths were 11 years of age (M = 11.2 years), primary caregivers provided data on their own depressive symptoms and self-esteem, and youths provided data on their receipt of nonsupportive parenting. When the youths were 20 years of age, indicators of SNS activity, the catecholamines epinephrine and norepinephrine, were assayed from their overnight urine voids.

RESULTS

Parental psychological dysfunction and nonsupportive parenting forecast elevated catecholamine levels for youths in the control condition, but not for those in the SAAF condition.

CONCLUSIONS

The demonstration that a prevention program can induce reduction of catecholamine levels is important from both theoretical and public health perspectives, because it shows that the developmental progression from family risk factors to heightened sympathetic nervous system activity is not immutable.

Stress induced neuroendocrine-immune plasticity: A role for the spleen in peripheral inflammatory disease and inflammaging?

Research over the past decade has revealed close interaction between the nervous and immune systems in regulation of peripheral inflammation linking psychosocial stress with chronic somatic disease and aging. Moreover emerging data suggests that chronic inflammations lead to a pro-inflammatory status underlying premature aging called inflammaging. In this context, the spleen can be seen as a switch board monitoring peripherally derived neuroendocrine-immune mediators in the blood and keeping up a close communication with the central stress response via its mainly sympathetic innervation. The effect aims at balanced and well-timed stress axis activation and immune adaptation in acute peripheral inflammatory events. Constant adjustment to the needs generated by environmental and endogenous challenges is provided by neuroendocrine-immune plasticity. However, maladaptive plasticity induced e.g., by chronic stress-axis activation and excessive non-neuronal derived neuroendocrine mediators may be at the heart of the observed stress sensitivity promote inflammaging under chronic inflammatory conditions. We here review the role of neurotransmitters, neuropeptides and neurotrophins as stress mediators modulating the immune response in the spleen and their potential role in inflammaging.

The circadian clock in cancer development and therapy

Most aspects of mammalian function display circadian rhythms driven by an endogenous clock. The circadian clock is operated by genes and comprises a central clock in the brain that responds to environmental cues and controls subordinate clocks in peripheral tissues via circadian output pathways. The central and peripheral clocks coordinately generate rhythmic gene expression in a tissue-specific manner in vivo to couple diverse physiological and behavioral processes to periodic changes in the environment. However, with the industrialization of the world, activities that disrupt endogenous homeostasis with external circadian cues have increased. This change in lifestyle has been linked to an increased risk of diseases in all aspects of human health, including cancer. Studies in humans and animal models have revealed that cancer development in vivo is closely associated with the loss of circadian homeostasis in energy balance, immune function, and aging, which are supported by cellular functions important for tumor suppression including cell proliferation, senescence, metabolism, and DNA damage response. The clock controls these cellular functions both locally in cells of peripheral tissues and at the organismal level via extracellular signaling. Thus, the hierarchical mammalian circadian clock provides a unique system to study carcinogenesis as a deregulated physiological process in vivo. The asynchrony between host and malignant tissues in cell proliferation and metabolism also provides new and exciting options for novel anticancer therapies.

Brain-gut interactions in inflammatory bowel disease

Psycho-neuro-endocrine-immune modulation through the brain-gut axis likely has a key role in the pathogenesis of inflammatory bowel disease (IBD). The brain-gut axis involves interactions among the neural components, including (1) the autonomic nervous system, (2) the central nervous system, (3) the stress system (hypothalamic-pituitary-adrenal axis), (4) the (gastrointestinal) corticotropin-releasing factor system, and (5) the intestinal response (including the intestinal barrier, the luminal microbiota, and the intestinal immune response). Animal models suggest that the cholinergic anti-inflammatory pathway through an anti-tumor necrosis factor effect of the efferent vagus nerve could be a therapeutic target in IBD through a pharmacologic, nutritional, or neurostimulation approach. In addition, the psychophysiological vulnerability of patients with IBD, secondary to the potential presence of any mood disorders, distress, increased perceived stress, or maladaptive coping strategies, underscores the psychological needs of patients with IBD. Clinicians need to address these issues with patients because there is emerging evidence that stress or other negative psychological attributes may have an effect on the disease course. Future research may include exploration of markers of brain-gut interactions, including serum/salivary cortisol (as a marker of the hypothalamic-pituitary-adrenal axis), heart rate variability (as a marker of the sympathovagal balance), or brain imaging studies. The widespread use and potential impact of complementary and alternative medicine and the positive response to placebo (in clinical trials) is further evidence that exploring other psycho-interventions may be important therapeutic adjuncts to the conventional therapeutic approach in IBD.

Clustering of depression and inflammation in adolescents previously exposed to childhood adversity

BACKGROUND

There is mounting interest in the hypothesis that inflammation contributes to the pathogenesis of depression and underlies depressed patients' vulnerability to comorbid medical conditions. However, research on depression and inflammation has yielded conflicting findings, fostering speculation that these conditions associate only in certain subgroups, such as patients exposed to childhood adversity.

METHODS

We studied 147 female adolescents. All were in good health at baseline but at high risk for depression because of family history or cognitive vulnerability. Subjects were assessed every 6 months for 2.5 years, undergoing diagnostic interviews and venipuncture for measurement of two inflammatory biomarkers, C-reactive protein (CRP) and interleukin-6 (IL-6). Childhood adversity was indexed by parental separation, low socioeconomic status, and familial psychopathology.

RESULTS

Multilevel models indicated that childhood adversity promotes clustering of depression and inflammation. Among subjects exposed to high childhood adversity, the transition to depression was accompanied by increases in both CRP and IL-6. Higher CRP remained evident 6 months later, even after depressive symptoms had abated. These lingering effects were bidirectional, such that among subjects with childhood adversity, high IL-6 forecasted depression 6 months later, even after concurrent inflammation was considered. This coupling of depression and inflammation was not apparent in subjects without childhood adversity.

CONCLUSIONS

These findings suggest that childhood adversity promotes the formation of a neuroimmune pipeline in which inflammatory signaling between the brain and periphery is amplified. Once established, this pipeline leads to a coupling of depression and inflammation, which may contribute to later affective difficulties and biomedical complications.

Adrenergic modulation of immune cells: an update

Sympathoadrenergic pathways are crucial to the communication between the nervous system and the immune system. The present review addresses emerging issues in the adrenergic modulation of immune cells, including: the specific pattern of adrenoceptor expression on immune cells and their role and changes upon cell differentiation and activation; the production and utilization of noradrenaline and adrenaline by immune cells themselves; the dysregulation of adrenergic immune mechanisms in disease and their potential as novel therapeutic targets. A wide array of sympathoadrenergic therapeutics is currently used for non-immune indications, and could represent an attractive source of non-conventional immunomodulating agents.

Psychoneuroimmunology of infection: implications for occupational therapy

Background: Psychoneuroimmunology is the study of the interactive relationships between the mind and immune system. This article looks at psychological factors influencing infection susceptibility. A thorough review of the research evidence on this topic is beyond the scope of this article. Recent infection-specific psychoneuroimmunology literature is therefore highlighted and possible underlying mechanisms are summarized.

Content: Current evidence shows that susceptibility to infections and allergies can be increased by chronic stress through suppression of the T-helper 1 immune response in favour of a T-helper 2 immune response.

Conclusions: Holistic interventions such as stress management, lifestyle changes, and career management could be considered to reduce susceptibility to infection. Further research however is required in this area to contribute to an evidence base underpinning psychosocial interventions for preventative health care.

Stress, atopy and allergy: A re-evaluation from a psychoneuroimmunologic persepective

Since the early days of psychosomatic thinking, atopic disease was considered exemplary. In the 70s and 80s numerous reports stated increased anxiety, depression or ill stresscoping in atopics in correlation with enhanced disease activity. Employed patient groups however were small and diverse and controls rare. Therefore, the question remained, whether psychopathological findings in atopics were of pathogenetic relevance or an epiphenomenon of chronic inflammatory disease. Recently, the discussion has been revived and refocused by psychoneuroimmunological findings. We now know that atopic disease is characterized by an imbalance of the classical stress-axis response along the hypothalamus-pituitary-adrenal axis (HPA) and the sympathetic axis (SA). This imbalance can be found shoulder-to-shoulder with enhanced expression of newly emerging neuroendocrine stress mediators such as substance P (SP) and nerve growth factor that form up to a third stress axis (neurotrophin neuropeptide axis: NNA). Together they can alter the inflammatory as well as the neuroendocrine stress-response on several levels. In skin, the immediate inflammatory response to stress involves neuropeptide release and mast cell degranulation, in short neurogenic inflammation. Systemically, antigen-presentation and TH2 cytokine bias are promoted under the influence of cortisol and neuropeptides. Imbalanced stress-responsiveness may therefore be at the core of exacerbated allergic disease and deserves re-evaluation of therapeutic options such as neutralization of SP-signaling by antagonists against its receptor NK1, cortisol treatment as supplementation and relaxation techniques to balance the stress-response.

The mechanosensory role of primary cilia in vascular hypertension

Local regulation of vascular tone plays an important role in cardiovascular control of blood pressure. Aside from chemical or hormonal regulations, this local homeostasis is highly regulated by fluid-shear stress. It was previously unclear how vascular endothelial cells were able to sense fluid-shear stress. The cellular functions of mechanosensory cilia within vascular system have emerged recently. In particular, hypertension is insidious and remains a continuous problem that evolves during the course of polycystic kidney disease (PKD). The basic and clinical perspectives on primary cilia are discussed with regard to the pathogenesis of hypertension in PKD.

Social isolation is associated with elevated tumor norepinephrine in ovarian carcinoma patients

Noradrenergic pathways have been implicated in growth and progression of ovarian cancer. Intratumoral norepinephrine (NE) has been shown to increase with stress in an animal cancer model, but little is known regarding how tumor NE varies with disease stage and with biobehavioral factors in ovarian cancer patients. This study examined relationships between pre-surgical measures of social support, depressed mood, perceived stress, anxiety, tumor histology and tumor catecholamine (NE and epinephrine [E]) levels among 68 ovarian cancer patients. We also examined whether associations observed between biobehavioral measures and tumor catecholamines extended to other compartments. Higher NE levels were found in advanced stage (p=0.006) and higher grade (p=0.001) tumors. Adjusting for stage, grade, and peri-surgical beta blockers, patients with a perceived lack of social support had significantly higher tumor NE (β=-0.29, p=0.012). A similar trend was seen for social support and ascites NE (adjusting for stage, peri-surgical beta blockers and caffeine: β=-0.50, p=0.075), but not for plasma NE. Other biobehavioral factors were not related to tumor, ascites, or plasma NE (p values >0.21). Tumor E was undetectable in the majority of tumors and thus E was not further analyzed. In summary, these results suggest that tumor NE provides distinct information from circulating plasma concentrations. Tumor NE levels were elevated in relationship to tumor grade and stage. Low subjective social support was associated with elevated intratumoral NE. As beta-adrenergic signaling is related to key biological pathways involved in tumor growth, these findings may have implications for patient outcomes in ovarian cancer.

Immune and nervous systems: more than just a superficial similarity?

Strong evidence is emerging that the nervous and immune systems share mechanisms of gene regulation, signaling, cell communication, and supracellular organization. This brings to the fore many questions, not least of which is the developmental and evolutionary origin of the commonalities between the two systems. By providing answers to these questions, immunologists and neurobiologists increasingly expose the mechanistic and conceptual affinities of their respective fields and facilitate the understanding of fundamental principles that govern the organization of complex cellular systems. The current essay and reviews in Immunity and Neuron attempt to communicate to the wider scientific community a series of examples relating to commonalities between the immune and nervous system and enhance the dialog and exchange of ideas between the two fields.

Divergent effects of norepinephrine, dopamine and substance P on the activation, differentiation and effector functions of human cytotoxic T lymphocytes

Background

Neurotransmitters are important regulators of the immune system, with very distinct and varying effects on different leukocyte subsets. So far little is known about the impact of signals mediated by neurotransmitters on the function of CD8⁺ T lymphocytes. Therefore, we investigated the influence of norepinephrine, dopamine and substance P on the key tasks of CD8⁺ T lymphocytes: activation, migration, extravasation and cytotoxicity.

Results

The activation of naïve CD8⁺ T lymphocytes by CD3/CD28 cross-linking was inhibited by norepinephrine and dopamine, which was caused by a downregulation of interleukin (IL)-2 expression via Erk1/2 and NF-κB inhibition. Furthermore, all of the investigated neurotransmitters increased the spontaneous migratory activity of naïve CD8⁺ T lymphocytes with dopamine being the strongest inducer. In contrast, activated CD8⁺ T lymphocytes showed a reduced migratory activity in the presence of norepinephrine and substance P. With regard to extravasation we found norepinephrine to induce adhesion of activated CD8⁺ T cells: norepinephrine increased the interleukin-8 release from endothelium, which in turn had effect on the activated CXCR1⁺ CD8⁺ T cells. At last, release of cytotoxic granules from activated cells in response to CD3 cross-linking was not influenced by any of the investigated neurotransmitters, as we have analyzed by measuring the β-hexosamidase release.

Conclusion

Neurotransmitters are specific modulators of CD8⁺ T lymphocytes not by inducing any new functions, but by fine-tuning their key tasks. The effect can be either stimulatory or suppressive depending on the activation status of the cells.

Social stress desensitizes lymphocytes to regulation by endogenous glucocorticoids: insights from in vivo cell trafficking dynamics in rhesus macaques

OBJECTIVE

To determine whether chronic social stress can desensitize leukocytes to normal physiologic regulation by endogenous glucocorticoids.

METHODS

We analyzed the longitudinal relationship between plasma cortisol levels and peripheral blood lymphocyte counts over 16 monthly assessments in 18 rhesus macaques randomized to recurrent social encounters with a stable set of conspecifics or continually varying social partners (unstable socialization).

RESULTS

Animals socialized under stable conditions showed the expected inverse relationship between plasma cortisol concentrations and circulating lymphocyte frequencies. That relationship was significantly attenuated in animals subject to unstable social conditions. Differences in leukocyte redistributional sensitivity to endogenous glucocorticoids emerged within the first week of differential socialization, persisted throughout the 60-week study period, and were correlated with other measures of glucocorticoid desensitization (blunted hypothalamic-pituitary-adrenal (HPA) axis response to acute stress and redistributional response to dexamethasone challenge). Effects of unstable social conditions on leukocyte sensitivity to cortisol regulation were not related to physical aggression.

CONCLUSION

Chronic social stress can impair normal physiologic regulation of leukocyte function by the HPA axis in ways that may contribute to the increased physical health risks associated with social adversity.

Health psychology: developing biologically plausible models linking the social world and physical health

Research over the past several decades has documented psychosocial influences on the development and progression of several major medical illnesses. The field is now increasingly focused on identifying the biological and behavioral mechanisms underlying these effects. This review takes stock of the knowledge accumulated in the biological arena to date and highlights conceptual and methodological approaches that have proven especially productive. It emphasizes the value of a disease-centered approach that "reverse engineers" adverse health outcomes into their specific biological determinants and then identifies psychologically modulated neuroendocrine and immunologic dynamics that modulate those pathological processes at the cellular and molecular levels.

Depression, social support, and beta-adrenergic transcription control in human ovarian cancer

Motivated by previous indications that beta-adrenergic signaling can regulate tumor cell gene expression in model systems, we sought to determine whether similar dynamics occur in primary human ovarian cancer. DNA microarray analyses of 10 ovarian carcinomas identified 266 human transcripts that were differentially expressed in tumors from patients with elevated biobehavioral risk factors (high depressive symptoms and low social support) relative to grade- and stage-matched tumors from low-risk patients. Promoter-based bioinformatic analyses indicated increased activity of several beta-adrenergically-linked transcription control pathways, including CREB/ATF, NF-kappaB/Rel, STAT, and Ets family transcription factors. Consistent with increased beta-adrenergic signaling, high biobehavioral risk patients also showed increased intra-tumor concentrations of norepinephrine (but no difference in plasma norepinephrine). These data show that genome-wide transcriptional profiles are significantly altered in tumors from patients with high behavioral risk profiles, and they identify beta-adrenergic signal transduction as a likely mediator of those effects.

Catecholamines can mediate stress-related effects on tumor progression

Studies have implicated behavior as a factor that can influence several aspects of health and have described the complex bidirectional interactions among the CNS, the endocrine system and the immune system that are involved. There is evidence that psychological factors can affect the incidence and progression of some cancers in humans. The hypothesis that stress could be a cofactor is supported by data obtained from animal models. Catecholamines, norepinephrine in particular, have been shown to directly affect various aspects of tumor development that is separate from the well-characterized effects on the cellular immune response to immunogenic tumors. Studies have shown that norepinephrine can directly affect tumor cell behavior and gene expression, further suggesting another mechanism for stress-related modulation of tumor progression. This line of research further suggests that interventions targeting components of the activated sympathetic-adrenal-medullary axis, or the utilization of β-adrenergic receptor-blocking agents, may represent new strategies for slowing down the progression of malignant disease and improving cancer patients' quality of life.

Social regulation of leukocyte homeostasis: the role of glucocorticoid sensitivity

Recent small-scale genomics analyses suggest that physiologic regulation of pro-inflammatory gene expression by endogenous glucocorticoids may be compromised in individuals who experience chronic social isolation. The present study assessed the relationship between leukocyte distributional sensitivity to glucocorticoid regulation and subjective social isolation in a large population-based sample of older adults. Initial analyses confirmed that circulating neutrophil percentages were elevated, and circulating lymphocyte and monocyte percentages were suppressed, in direct proportion to circulating cortisol levels. However, leukocyte distributional sensitivity to endogenous glucocorticoids was abrogated in individuals reporting either occasional or frequent experiences of subjective social isolation. This finding held in both non-parametric univariate analyses and in multivariate linear models controlling for a variety of biological, social, behavioral, and psychological confounders. The present results suggest that social factors may alter immune cell sensitivity to physiologic regulation by the hypothalamic-pituitary-adrenal axis in ways that could ultimately contribute to the increased physical health risks associated with social isolation.

Social temperament and lymph node innervation

Socially inhibited individuals show increased vulnerability to viral infections, and this has been linked to increased activity of the sympathetic nervous system (SNS). To determine whether structural alterations in SNS innervation of lymphoid tissue might contribute to these effects, we assayed the density of catecholaminergic nerve fibers in 13 lymph nodes from seven healthy adult rhesus macaques that showed stable individual differences in propensity to socially affiliate (Sociability). Tissues from Low Sociable animals showed a 2.8-fold greater density of catecholaminergic innervation relative to tissues from High Sociable animals, and this was associated with a 2.3-fold greater expression of nerve growth factor (NGF) mRNA, suggesting a molecular mechanism for observed differences. Low Sociable animals also showed alterations in lymph node expression of the immunoregulatory cytokine genes IFNG and IL4, and lower secondary IgG responses to tetanus vaccination. These findings are consistent with the hypothesis that structural differences in lymphoid tissue innervation might potentially contribute to relationships between social temperament and immunobiology.