Chronic stress, social support, and persistent alterations in the natural killer cell response to cytokines in older adults

Making "Good" Choices: Social Isolation in Mice Exacerbates the Effects of Chronic Stress on Decision Making

Chronic stress can impact decision-making and lead to a preference for immediate rewards rather than long-term payoffs. Factors that may influence these effects of chronic stress on decision-making are under-explored. Here we used a mouse model to investigate the changes in decision-making caused by the experience of chronic stress and the role of social isolation in exaggerating these changes. To test decision-making, mice were trained to perform a Cost-Benefit Conflict (CBC) task on a T-maze, in which they could choose between a high-reward, high-risk alternative and a low-reward, low-risk alternative. Mice were either housed in groups or alone throughout the experiment. Both groups of mice underwent a seven-day period of repeated immobilization to induce chronic stress. Stress levels were confirmed using behavioral (open field test) and physiological (urine corticosterone ELISA) measures. We found a significant increase in frequency of high-risk decisions after exposure to chronic stress among both socially- and individually-housed mice. Crucially, socially-housed mice showed a significantly smaller increase in high-risk decision-making compared to singly-housed mice. These findings suggest that chronic stress leads to an increase in high-risk decision-making in mice, and that lack of social interaction may exacerbate this stress effect.

Is episodic memory performance more vulnerable to depressive affect in older adulthood?

This study examined how age, depressive symptoms, demographic variables, frailty, and health factors jointly influence episodic memory across the lifespan in two large, diverse samples. Hierarchical regression analyses from both samples showed that depressive symptoms negatively impacted episodic memory performance with the effect being more pronounced for older adults. Health and frailty tended not to be associated with episodic memory. However, the main effect of depressive symptoms tended to remain significant over and above other predictors, while the interaction with age was weakened with the addition of demographic variables. The unique contribution of this study is demonstrating that the relationship between depressive symptoms and episodic memory is moderated by age across relatively large non-clinical lifespan samples of adults. The findings indicate the importance of measuring and studying depressive symptoms during the course of aging in order to better understand the complex relationship between age, affect, physical functioning, and memory.

Social environment is associated with gene regulatory variation in the rhesus macaque immune system

Variation in the social environment is a fundamental component of many vertebrate societies. In humans and other primates, adverse social environments often translate into lasting physiological costs. The biological mechanisms associated with these effects are therefore of great interest, both for understanding the evolutionary impacts of social behavior and in the context of human health. However, large gaps remain in our understanding of the mechanisms that mediate these effects at the molecular level. Here we addressed these questions by leveraging the power of an experimental system that consisted of 10 social groups of female macaques, in which each individual's social status (i.e., dominance rank) could be experimentally controlled. Using this paradigm, we show that dominance rank results in a widespread, yet plastic, imprint on gene regulation, such that peripheral blood mononuclear cell gene expression data alone predict social status with 80% accuracy. We investigated the mechanistic basis of these effects using cell type-specific gene expression profiling and glucocorticoid resistance assays, which together contributed to rank effects on gene expression levels for 694 (70%) of the 987 rank-related genes. We also explored the possible contribution of DNA methylation levels to these effects, and identified global associations between dominance rank and methylation profiles that suggest epigenetic flexibility in response to status-related behavioral cues. Together, these results illuminate the importance of the molecular response to social conditions, particularly in the immune system, and demonstrate a key role for gene regulation in linking the social environment to individual physiology.

Do experiences of racial discrimination predict cardiovascular disease among African American men? The moderating role of internalized negative racial group attitudes

Studies examining associations between racial discrimination and cardiovascular health outcomes have been inconsistent, with some studies finding the highest risk of hypertension among African Americans who report no discrimination. A potential explanation of the latter is that hypertension and other cardiovascular problems are fostered by internalization and denial of racial discrimination. To explore this hypothesis, the current study examines the role of internalized negative racial group attitudes in linking experiences of racial discrimination and history of cardiovascular disease among African American men. We predicted a significant interaction between reported discrimination and internalized negative racial group attitudes in predicting cardiovascular disease. Weighted logistic regression analyses were conducted among 1216 African American men from the National Survey of American Life (NSAL; 2001-2003). We found no main effect of racial discrimination in predicting history of cardiovascular disease. However, agreeing with negative beliefs about Blacks was positively associated with cardiovascular disease history, and also moderated the effect of racial discrimination. Reporting racial discrimination was associated with higher risk of cardiovascular disease among African American men who disagreed with negative beliefs about Blacks. However, among African American men who endorsed negative beliefs about Blacks, the risk of cardiovascular disease was greatest among those reporting no discrimination. Findings suggest that racial discrimination and the internalization of negative racial group attitudes are both risk factors for cardiovascular disease among African American men. Furthermore, the combination of internalizing negative beliefs about Blacks and the absence of reported racial discrimination appear to be associated with particularly poor cardiovascular health. Steps to address racial discrimination as well as programs aimed at developing a positive racial group identity may help to improve cardiovascular health among African American men.

Racial discrimination and racial identity attitudes in relation to self-rated health and physical pain and impairment among two-spirit American Indians/Alaska Natives

OBJECTIVES

We examined associations between racial discrimination and actualization, defined as the degree of positive integration between self-identity and racial group identity, and self-rated health and physical pain and impairment.

METHODS

We used logistic regressions to analyze data from 447 gay, lesbian, bisexual, and other sexual-minority American Indians/Alaska Natives.

RESULTS

Greater self-reported discrimination was associated with higher odds of physical pain and impairment (odds ratio [OR] = 1.42; 95% confidence interval [CI] = 1.13, 1.78); high levels of actualization were associated with lower odds of physical pain and impairment (OR = 0.59; 95% CI = 0.35, 0.99) and self-rated fair or poor health (OR = 0.54; 95% CI = 0.32, 0.90). Actualization also moderated the influence of discrimination on self-rated health (t = -2.33; P = .020). Discrimination was positively associated with fair or poor health among participants with low levels of actualization, but this association was weak among those with high levels of actualization.

CONCLUSIONS

Among two-spirit American Indians/Alaska Natives, discrimination may be a risk factor for physical pain and impairment and for fair or poor self-rated health among those with low levels of actualization. Actualization may protect against physical pain and impairment and poor self-rated health and buffer the negative influence of discrimination.

Immune response, depression and fatigue in relation to support intervention in mammary cancer patients

GOAL OF WORK

To study the effect of support intervention on immune function in breast cancer patients.

MATERIALS AND METHODS

Breast cancer patients from an ongoing prospective randomised quality-of -life study were chosen for assaying immune functions in relation to a support-group intervention program running on a residential basis. Twenty-one women received adjuvant-combined radio-chemotherapy (CT-RT) and 20 women radiotherapy (RT). Eleven CT-RT and ten RT patients were randomised to support-group intervention, the rest served as controls. Immune tests for NK cells and NK-cell cytotoxicity, as well as lymphocyte subpopulations and response to antigen were performed before intervention, 2, 6, and 12 months later, in parallel to controls and healthy volunteers (n = 11). Depression, anxiety and fatigue were evaluated by the Hospital Anxiety and Depression (HAD) and the Norwegian Fatigue questionnaire. The density of NK cell receptors and in vitro quantitation of functional NK cytotoxicity against K562 cell line were evaluated. Four-colour flow cytometry was used to detect signal transduction molecules and cytokine expression. T-cell proliferate response to purified protein derivate (PPD) antigen was evaluated.

RESULTS

No significant immune effect of support intervention could be found. The immune variables were severely disarranged compared to healthy volunteers but showed a statistically significant improvement over time. The majority of patients suffered from fatigue but had low scores for depression and anxiety.

CONCLUSION

No effect on immune parameters could be detected from support intervention. The long-lasting immune suppression might override a putative effect of the intervention. Low depression scores may contribute to the absence of a detectable effect.

Impaired natural killer cell lysis in breast cancer patients with high levels of psychological stress is associated with altered expression of killer immunoglobin-like receptors

BACKGROUND

We previously reported that cancer-related psychological stress is associated with reduced natural killer (NK) cell lysis. We hypothesized that reduced NK cell cytotoxicity in patients with increased levels of stress would correlate with alterations in the expression of inhibitory NK cell receptors (killer immunoglobulin-like receptors, or KIRs). The specific aim of this study was to examine KIR expression in patients with high or low levels of psychologic stress and correlate alterations in KIR expression with NK cell function.

MATERIALS AND METHODS

Two hundred twenty-seven patients underwent baseline evaluation of cancer-related psychological stress and were randomized to psychosocial intervention versus observation. From this population, two groups were defined based on pretreatment measurements of NK lytic activity, stress levels, and the availability of cryopreserved peripheral blood mononuclear cells (PBMC). Group I (n=9) had low stress by the Impact of Events Scale (IES), and high NK cell lysis at the 50:1 effector: target ratio (NK(50)=52-89%). Group II (n=8) had high stress and low NK(50) (27-52%). Lymphokine activated killer (LAK) activity, antibody dependent cellular cytotoxicity (ADCC), and expression of cytokine receptors, adhesion molecules, and killer immunoglobulin-like receptors (KIRs) were assessed in PBMC.

RESULTS

Incubation of PBMC with NK-stimulatory cytokines (IL-2, IL-12, or IL-15) led to significant increases in cytotoxic activity regardless of IES/NK(50) scores. There were no significant group differences in NK cell surface expression of the IL-2 receptor components CD25 and CD122, antibody-dependent lysis of HER2/neu-positive SKBr3 cells treated with an anti-HER2/neu monoclonal antibody, expression of adhesion molecules (CD2, CD11a, CD18) and markers of activation (CD69), or expression of the KIRs CD158a, NKG2a, NKB1, and CD161. However, levels of CD158b were significantly higher in Group I after incubation in media alone or with IL-2, and CD94 expression was significantly lower in Group I after incubation with IL-2.

CONCLUSIONS

In this study of a small subset of breast cancer patients chosen from a previous clinical trial of psychosocial intervention for breast cancer, impaired NK lysis in breast cancer patients with high levels of psychological stress was associated with alterations in surface expression of killer immunoglobulin-like receptors. However, immune effectors retained the ability to lyse antibody-coated targets and to initiate lymphokine-activated killer activity, irrespective of stress levels or baseline NK(50).

Stress induces substance P in vagal sensory neurons innervating the mouse airways

BACKGROUND

Tachykinins-like substance P (SP) have been shown to play an important role in initiating and perpetuating airway inflammation. Furthermore, they are supposed to be released into tissues in response to stress.

OBJECTIVE

The aim of this study was to investigate the effects of stress alone or in combination with allergic airway inflammation on SP expression in sensory neurons innervating the mouse airways.

METHODS

Balb/c mice were systemically sensitized to ovalbumin (OVA), followed by allergen aerosol exposure, and compared with non-sensitized controls. Additionally, OVA-sensitized and -challenged and non-sensitized mice were exposed to sound stress. SP expression in airway-specific and overall vagal sensory neurons of the jugular and nodose ganglion complex was analysed using retrograde neuronal tracing in combination with immunohistochemistry. Preprotachykinin A (PPT-A) mRNA, the precursor for SP, was quantified in lung tissue by real-time PCR. Bronchoalveolar lavage (BAL) fluid was obtained, and cell numbers and differentiation were determined.

RESULTS

Stress and/or allergic airway inflammation significantly increased SP expression in retrograde-labelled vagal sensory neurons from the mouse lower airways compared with controls [stress: 15.7+/-0.8% (% of retrograde-labelled neurons, mean+/-SEM); allergen: 17.9+/-0.4%; allergen/stress: 13.1+/-0.7% vs. controls: 6.3+/-0.3%]. Similarly, SP expression increased in overall vagal sensory neurons identified by the neuronal marker protein gene product (PGP) 9.5 [stress: 9.3+/-0.6% (% of PGP 9.5-positive neurons, means+/-SEM); allergen: 12.5+/-0.4%; allergen/stress: 10.2+/-0.4% vs. controls: 5.1+/-0.3%]. Furthermore, stress significantly increased PPT-A mRNA expression in lung tissue from OVA-sensitized and -challenged animals, and immune cells were identified as an additional source of SP in the lung by immunohistochemistry. Associated with enhanced neuronal SP expression, a significantly higher number of leucocytes were found in the BAL following allergen exposure. Further, stress significantly increased allergen-induced airway inflammation identified by increased leucocyte numbers in BAL fluids.

CONCLUSION

The central event of sound stress leads to the stimulation of SP expression in airway-specific neurons. However, in sensitized stressed mice an additional local source of SP (probably inflammatory cells) might enhance allergic airway inflammation.

Exaggerated Plasma Fibrin Formation (D-Dimer) in Elderly Alzheimer Caregivers as Compared to Noncaregiving Controls

BACKGROUND

The chronic stress of providing care for a spouse suffering from Alzheimer's disease has been associated with an increased risk for coronary artery disease and overall mortality. Procoagulant changes are kindled by mental stress, and they are prospectively associated with atherothrombotic events.

OBJECTIVE

To examine whether dementia caregivers would show greater coagulation activity and less fibrinolytic capacity than noncaregiving controls.

METHODS

Subjects were 48 (30 female and 18 male) elderly (mean age +/- SD, 72 +/- 9 years) community-dwelling spousal Alzheimer caregivers and 20 noncaregiving age- and gender-matched controls. Plasma levels of thrombin-antithrombin III, fibrin D-dimer, von Willebrand factor, tissue-type plasminogen activator, and plasminogen activator inhibitor 1 were measured.

RESULTS

D-dimer, a marker of fibrin formation and degradation, was significantly higher in caregivers than in controls (688 +/- 575 vs. 406 +/- 157 ng/ml, p = 0.021). Plasma levels of the four other hemostasis variables were not significantly different between the two groups. Controlling for the classic cardiovascular risk factors body mass index, hypertension status, smoking status, hypercholesterolemia, type II diabetes, and medication potentially affecting hemostasis did not change results.

CONCLUSION

The findings suggest that Alzheimer caregivers have an increased fibrin turnover as compared to noncaregiving controls independent of common confounders of hemostasis. Such an elevated clotting diathesis might contribute to increased cardiovascular risk and overall mortality with dementia caregiving strain.

Modulation of Immune Functions by Foods

Evidence is rapidly accumulating as to the beneficial effects of foods. However, it is not always clear whether the information is based on data evaluated impartially in a scientific fashion. Human research into whether foods modulate immune functions in either intervention studies or randomized controlled trials can be classified into three categories according to the physical state of subjects enrolled for investigation: (i) studies examining the effect of foods in healthy individuals; (ii) studies analyzing the effect of foods on patients with hypersensitivity; and (iii) studies checking the effect of foods on immunocompromized subjects, including patients who had undergone surgical resection of cancer and newborns. The systematization of reported studies has made it reasonable to conclude that foods are able to modulate immune functions manifesting as either innate immunity (phagocytic activity, NK cell activity) or acquired immunity (T cell response, antibody production). Moreover, improvement of immune functions by foods can normalize the physical state of allergic patients or cancer patients, and may reduce the risk of diseases in healthy individuals. Therefore, it is valuable to assess the immune-modulating abilities of foods by measuring at least one parameter of either innate or acquired immunity.

Stress and immune responses after surgical treatment for regional breast cancer

BACKGROUND

Adults who undergo chronic stress, such as the diagnosis and surgical treatment of breast cancer, often experience adjustment difficulties and important biologic effects. This stress can affect the immune system, possibly reducing the ability of individuals with cancer to resist disease progression and metastatic spread. We examined whether stress influences cellular immune responses in patients following breast cancer diagnosis and surgery.

METHODS

We studied 116 patients recently treated surgically for invasive breast cancer. Before beginning their adjuvant therapy, all subjects completed a validated questionnaire assessing the stress of being cancer patients. A 60-mL blood sample taken from each patient was subjected to a panel of natural killer (NK) cell and T-lymphocyte assays. We then developed multiple regression models to test the contribution of psychologic stress in predicting immune function. All regression equations controlled for variables that might exert short- or long-term effects on these responses, and we also ruled out other potentially confounding variables.

RESULTS

We found, reproducibly between and within assays, the following: 1) Stress level significantly predicted lower NK cell lysis, 2) stress level significantly predicted diminished response of NK cells to recombinant interferon gamma, and 3) stress level significantly predicted decreased proliferative response of peripheral blood lymphocytes to plant lectins and to a monoclonal antibody directed against the T-cell receptor.

CONCLUSIONS

The data show that the physiologic effects of stress inhibit cellular immune responses that are relevant to cancer prognosis, including NK cell toxicity and T-cell responses. Additional, longitudinal studies are needed to determine the duration of these effects, their health consequences, and their biologic and/or behavioral mechanisms.

Chronic stress alters the immune response to influenza virus vaccine in older adults

To determine whether a chronic stressor (caregiving for a spouse with a progressive dementia) is associated with an impaired immune response to influenza virus vaccination, we compared 32 caregivers' vaccine responses with those of 32 sex-, age-, and socioeconomically matched control subjects. Caregivers showed a poorer antibody response following vaccination relative to control subjects as assessed by two independent methods, ELISA and hemagglutination inhibition. Caregivers also had lower levels of in vitro virus-specific-induced interleukin 2 levels and interleukin 1beta; interleukin 6 did not differ between groups. These data demonstrate that down-regulation of the immune response to influenza virus vaccination is associated with a chronic stressor in the elderly. These results could have implications for vulnerability to infection among older adults.

Health psychology: psychological factors and physical disease from the perspective of human psychoneuroimmunology

This review addresses the importance of studies of human psychoneuroimmunology in understanding the role of psychological factors in physical illness. First, it provides psychologically and biologically plausible explanations for how psychological factors might influence immunity and immune system-mediated disease. Second, it covers substantial evidence that factors such as stress, negative affect, clinical depression, social support, and repression/denial can influence both cellular and humoral indicators of immune status and function. Third, at least in the case of the less serious infectious diseases (colds, influenza, herpes), it considers consistent and convincing evidence of links between stress and negative affect and disease onset and progression. Although still early in its development, research also suggests a role of psychological factors in autoimmune diseases. Evidence for effects of stress, depression, and repression/denial on onset and progression of AIDs and cancer is less consistent and inconclusive, possibly owing to methodological limitations inherent in studying these complex illnesses, or because psychological influences on immunity are not of the magnitude or type necessary to alter the body's response in these cases. What is missing in this literature, however, is strong evidence that the associations between psychological factors and disease that do exist are attributable to immune changes.

A biobehavioral model of cancer stress and disease course

Approximately 1 million Americans are diagnosed with cancer each year and must cope with the disease and treatments. Many studies have documented the deteriorations in quality of life that occur. These data suggest that the adjustment process is burdensome and lengthy. There is ample evidence showing that adults experiencing other long-term stressors experience not only high rates of adjustment difficulties (e.g., syndromal depression) but important biologic effects, such as persistent downregulation of elements of the immune system, and adverse health outcomes, such as higher rates of respiratory tract infections. Thus, deteriorations in quality of life with cancer are underscored if they have implications for biological processes, such as the immune system, relating to disease progression and spread. Considering these and other data, a biobehavioral model of adjustment to the stresses of cancer is offered, and mechanisms by which psychological and behavioral responses may influence biological processes and, perhaps, health outcomes are proposed. Finally, strategies for testing the model via experiments testing psychological interventions are offered.

A biobehavioral model of cancer stress and disease course

Approximately 1 million Americans are diagnosed with cancer each year and must cope with the disease and treatments. Many studies have documented the deteriorations in quality of life that occur. These data suggest that the adjustment process is burdensome and lengthy. There is ample evidence showing that adults experiencing other long-term stressors experience not only high rates of adjustment difficulties (e.g., syndromal depression) but important biologic effects, such as persistent downregulation of elements of the immune system, and adverse health outcomes, such as higher rates of respiratory tract infections. Thus, deteriorations in quality of life with cancer are underscored if they have implications for biological processes, such as the immune system, relating to disease progression and spread. Considering these and other data, a biobehavioral model of adjustment to the stresses of cancer is offered, and mechanisms by which psychological and behavioral responses may influence biological processes and, perhaps, health outcomes are proposed. Finally, strategies for testing the model via experiments testing psychological interventions are offered.